fix(runtime): stop estimating context fit; the provider decides, the Maka window is a user target

[Joob1n]

Summary

The runtime no longer estimates whether a request fits a context window. Every "does it fit" question is answered by a provider; every trigger is a real number. This is the remaining step after #4486, which removed the fabricated capacity and the two terminal gates but kept the chars/4 delta estimate, the 32,000-token fallback history budget, and a per-step JSON.stringify of the whole request as a payload ruler. Design and discussion: #4559 (this PR), #4458 (history).

What decides now

• The conversation provider's own context-length rejection is recovered by one compact-and-retry; a second rejection surfaces as the provider's error (context_overflow), and the user's message stays editable.
• The summarizer's provider decides whether compaction input fits: input_too_large retreats the fold by half, and the loop exits through no_safe_completed_span when even the smallest legal span is refused.
• Proactive compaction has one trigger: the previous accepted request's real inputTokens + outputTokens, as the provider counted them, compared with the context window the user declared for the model (a model-facts pin or a relay profile). Reasoning tokens are counted whole on purpose — high is the safe direction for a trigger that can only ask for a compaction.
• A reply the provider cut at its output limit (finishReason: length) folds once before the next request.

What is gone: estimateNextRequestTokens, exceedsHighWater, midTurnRequestPayloadChars, the final-request rescue re-entry, maxHistoryEstimatedTokens and its five consumers, the quarter-window / 16,384 reserve, the 32,000 fallback, the replacement_not_smaller and prefix_over_budget replay gates, size-based replay selection, the estimated input fit before summarizer calls, and the chars/4 summary-size floor.

Notes for the user (four new system_note kinds): context_provider_dropping when an append-only step's usage did not grow (a provider evicting or rewriting context), and context_window_suggestion when a rejection lands at a proven-fit total, carrying the number the user can declare.

Refs #4559 — the issue closes when the whole series (#4574, #4575, #4576) has landed and the remaining items are triaged there.
Refs #4458, #4486

Follow-up PRs (stacked on this one)

The user-facing surfaces are deliberately split out so this PR stays the atomic runtime change and the UI pieces can be reviewed in parallel. Both are open as drafts on top of this branch and will be rebased and undrafted once this merges:

• feat(desktop): show the model's reported context window beside the declared setting #4575 — Desktop settings: the model's reported window shown beside the declared setting with a one-click apply. Without it, a user who has never declared a window gets no proactive compaction and no in-app pointer to the number they could set; the context_window_suggestion note from this PR is the runtime-side half of that pointer.
• feat(desktop): show context usage beside the model controls #4576 — Desktop composer: read-only context-usage indicator fed by the persisted lastRequestAnchor this PR introduces (percentage with a declared window, absolute tokens without one, a dash when the provider reports no usage).

Not in this series, defined and tracked on #4623 (the degraded modes when the provider does not speak): PR D applies the provider-dropping rule at the turn boundary, PR E adds a "compact and retry" action for provider rejections the error classifier does not recognise. Neither reopens a path this PR touches.

Behaviour changes to review

1. No declared window means no proactive compaction. The first time such a session fills up costs one provider round trip and possibly one cut reply; the context_window_suggestion note then offers the last accepted total as the value to declare. This is the "Maka does not decide for the user" principle; the trade-off is stated in Context budget: stop estimating fit; the provider decides, the Maka window is a user target #4559.
2. A /models report or models.dev metadata is no longer a threshold on its own.resolveDeclaredContextWindow (runtime) and declaredContextWindow (core, single owner of the rule) count only a facts pin or a relay profile. resolveSelectedModelContextWindow keeps its old meaning for display and contextRemaining.
3. token_usage.lastRequestAnchor is now { inputTokens, outputTokens? }. The retired payloadChars key still decodes, so sessions written by 0.2.0 keep loading; sessions written by this build do not open in 0.2.0 (the closed-allowlist cost already noted in CHANGELOG.md).
4. Summaries are capped at 8,000 output tokens (DEFAULT_HISTORY_COMPACT_MAX_OUTPUT_TOKENS; the summarizer's maxOutputTokens option was declared and never passed). A length finish gets one shorter retry, then fails open. The too-small-for-fold floor reads the summarizer call's real usage; a producer that reports none is not floored.
5. Checkpoint replay is structural: a source-matched checkpoint replays as [block, everything after the boundary]. No local size gate stands between a materializable fold and dispatch.
6. ContextBudgetDiagnostic.maxHistoryEstimatedTokens is retired (decode-only). HistoryCompactionPolicy.midTurn loses reserveTokens. buildDefaultContextBudgetPolicy drops its connection parameter.
7. Every OpenAI-compatible Chat request now asks for stream usage (stream_options.include_usage), unless the registry opts a provider out. Found live: only two providers opted in, so a local Ollama and every plain OpenAI-compatible relay — the connection type behind Context budget: an undeclared window fabricates a capacity that kills live turns #4458 — returned no usage, and the baseline, the eviction check and the indicator all stayed dark for them.
8. Summary requests close with a user instruction. Found live: a chat-template model handed a conversation ending on its own turn emits end-of-sequence and nothing else (Ollama qwen2.5, both sizes: finish stop, one output token, empty text), so history compaction never succeeded against a local model. Existing message-shape tests gained the trailing user:text.
9. The trigger reserves the model's declared output limit and fires on >= (review). baseline + outputLimit >= declaredWindow, where the limit is connection.models[].maxOutputTokens or generated metadata — a provider fact — and 0 when none is declared. Without it a window declared at the provider's real size could never be crossed by an accepted request. The window itself remains the user's declaration (see the reply on the review for why the metadata window stays a hint).
10. A context-length rejection from the summarizer's provider is input_too_large again (review), so the planner's retreat-by-half has a producer; the same classification is applied to the Codex compaction call.
11. The window suggestion note is written only when the turn surfaces the rejection (review): after the one fold is spent or when there is no seam, naming the last accepted total, which a fold does not clear.
12. The size floor judges an initial fold only (review): on a roll-forward the summarizer's input is the increment, not the covered span, so the floor stands down there and the fold context carries usage only. The eviction check compares input against input, since reasoning is not resent on every wire.

On dropping the signed delta

#4486 kept a signed chars/4 delta so step 0 could fold before a large new message or image went out. I dropped it: the delta prices an image at a constant and under-reads CJK by about half, so the round trip it saves is the one it is most likely to misjudge; large text results are already capped by the byte-based tool-result archive before they go out; and removing it takes the whole payload ruler and the per-step JSON.stringify(messages) with it. Happy to be argued back.

Test coverage removed

Thirty-seven tests encoded the estimate, the reserve, the payload ruler, the fit gates, or the pre-turn estimate gate; each is either re-pointed at a real-usage observable or removed with the mechanism. Re-pointed: the usage baseline is the last request's INPUT tokens → input plus output; compacts over the high water → compacts after provider usage crosses the declared window; keeps user_stop when stopping an oversized pre-turn summary → keeps user_stop when stopping while a usage-triggered fold is summarizing; persists the LAST request as the anchor → persists the last request input and output as the anchor; replays a durable pre_turn checkpoint below the current high water → without a local size gate; rejects a paragraph-sized summary for a large folded span → when usage says it is too small. Removed outright (the mechanism is gone): the three manual compactHistory … exceeds current limits / makes the full replay larger cases, the three reserve-derivation cases, anchors on real provider usage plus a tail char/4 delta, credits a SIGNED negative payload delta, falls back to whole-projection char/4 on cold start, high-water crosses at contextWindow minus reserve, a fold that cannot shrink the real payload is refused, a runaway summary is rejected as replacement_not_smaller, bounds the oldest oversized tool result before dispatch, fails with input_too_large before dispatch, charges the summarization instructions against the input budget, a summary at exactly the floor is accepted under ceil-based token estimates, the capacity verdict measures the steering payload, the anchor a finalization step writes excludes the tool schemas it cleared, dispatches a pre-turn Compaction recipe without projecting history and keeps a transiently unavailable automatic Compaction checkpoint recoverable (both exercised the deleted pre-turn gate; memory extraction from a hook-triggered fold stays covered), applies max-history overrides to checkpoint replay validation, accepts a complete checkpoint above legacy block limits when the full replay fits, compacts one oversized prior turn before an unknown-model request, compacts an oversized latest turn when an older turn is also retained, dispatches an oversized prior turn when its summary fails, after trying once, never runs a pointless summarizer on a small-window model, a usage object without usable input tokens falls back to cold start, a last-request anchor is only valid as a complete positive pair, a half-written anchor fails the whole token_usage message decode (replaced by the new-shape and retired-key cases).

New coverage: the declared-window rule for pin / relay / reported / metadata sources; baseline = input + output, > not >=, cleared after a fold, seeded from the previous turn, discarded across a model switch; a /models window is not a declaration; pendingLengthFold; the summarizer output cap, shorten retry, and output_length after two cuts; usage-based size floor; retreat by half and its give-up exit; structural replay; both notes, including the non-firing cases (pruned step, step 0, declaration already crossed); the retired payloadChars key decodes and an unknown key still fails.

Live verification against a real provider (Ollama)

Driven through the real AiSdkBackend with getAIModel against a local Ollama (qwen2.5:0.5b / qwen2.5:1.5b, default num_ctx 4096), five turns of ~740 tokens each, the previous turn's ledger and run header fed back as prior context.

Scenario	Observed
Declared window 1,500, qwen2.5:1.5b	Turns 1–3: anchors {745,10}, {1481,10}, {2217,10} persisted; baseline 1,491 at turn 3 is < 1,500, no fold. Turn 4: baseline 2,227 > 1,500 → pre_turn fold; summary malformed twice → failedOpen[malformed_summary_missing_section], request dispatched, end_turn. Turn 5: fold again, repair produces a 1,737-char checkpoint → replaced; the request's provider-counted input drops 2,954 → 1,222.
Same, before the two fixes above	No token_usage event at all (Ollama returned no usage because it was never asked); once usage flowed, the summarizer returned empty text every time. Both fixed in this PR.
No declared window, 8 turns	Never folds, never terminates; every turn end_turn. Usage grows 745 → 3,700 and then plateaus at 3,716 for turns 6–8 while ~740 tokens are appended per turn: Ollama truncates silently at num_ctx with no error.

Known limitation, stated plainly: the silent-truncation plateau above happens between turns, and context_provider_dropping only fires within a turn (step ≥ 1, on an input count that did not grow), because at step 0 a user edit can shrink the input legitimately. A provider that truncates instead of rejecting therefore gives an undeclared-window user no signal today; declaring the window is the protection. Detecting the cross-turn plateau without an estimate needs a ledger-shape check on the anchor (did anything before the anchored request change?) — a follow-up, tracked on #4559. Closing that gap is PR D on #4623.

Verification

Rebased on main@148f8eb29 (after #4578 landed, so this PR no longer carries the dependency bump); the Runtime Host compatibility epoch moves 104 → 105 for the two new note kinds and the reshaped anchor. Locally: npm --workspace @maka/{core,storage,runtime,runtime-host,mcp,ui} run build, npm run typecheck (all workspaces), npm run lint, npm run format:check, npm run check:asf-headers, node scripts/protocol-epoch-check.mjs --base origin/main — all clean. Targeted suites: 425/425 across usage-record-last-request-anchor, context-budget-mid-turn-policy, context-budget-model-facts, history-compaction, history-compact-checkpoint, history-compact-summarizer, mid-turn-capacity-backend, overflow-reactive-recovery, ai-sdk-backend; core suite 760/760; provider-conformance 24/24, history-compact-summarizer 53/53, execution-model-composition 28/28 and the CLI pi-transcript suites after the review fixes. Not run locally: the full npm test matrix (the Electron/OpenSSL and owned-Host timing cases fail on this machine independently of the branch) — relying on CI for those.

Self-review

• The core rule declaredContextWindow was implemented twice (runtime and chat-model-choice) in an earlier draft; consolidated into @maka/core/model-thinking with runtime delegating. One owner for the one rule the design turns on.
• The user-stop-during-summary obligation had lost its test when the pre-turn gate went; re-pointed at the hook-triggered fold. The test also records that one request is still attempted after the stop and is rejected by the transport on its already-aborted signal — pre-existing behaviour, now pinned.
• An earlier draft regenerated the Astryx theme with a stale local @astryxdesign/core@0.5.0; that artifact is not in this PR.
• memory-extraction.ts and session-recap.ts keep their own bounded-request budgets; they are auxiliary calls, not history compaction, and are out of scope here.
• Diagnostics (estimatedTokensBefore/After on compaction decisions) still use the chars/4 estimator. They are recorded numbers, not decisions, and are kept so existing telemetry consumers do not break.

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Claude Code — design discussion, implementation, tests, and review; verified by the author.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No

https://claude.ai/code/session_014ajaRxC4jydavY9nYUFj5J

[Astro-Han]

The direction is the one from #4458 and I still hold it: fit is the provider's answer, the trigger is a real number, and the only irreversible outcome is the provider's rejection. The reduction is real, every symbol in "What is gone" is gone from docs and desktop too, and all six workspace suites, typecheck, lint and format pass locally on 372c1de9, and the three commits since (148326eb) touch none of the files cited below. What stops me approving is not the code, it is three places where the design as implemented does not do what the design says. Line-level fixes are inline.

The proactive trigger cannot fire against a correctly declared window. The trigger is baseline > declaredWindow, and the baseline is a request the provider accepted. If the user declares the provider's real window, no accepted request can exceed it, the fold never runs, and every session goes through rejection first. It fires only when the user declares something smaller, which is the retired reserve reintroduced as a number the user has to guess without being told. This is open point 2 of #4559, and I would settle it the other way: resolve the window as declared > relay profile > models.dev > /models, none only when all are absent; trigger on baseline > window − reserve; make the reserve a real number, the model's output limit plus the tool-result archive cap times pending tool calls, with a fraction of the window as the floor. Those are provider facts and Maka's own content policy, so the "real numbers only" principle holds. A default is not Maka deciding for the user, it is a default the user can override, and the alternative is that out of the box every fill costs a rejection and possibly a cut reply, which CLI users get without even the hint, because pi-transcript.ts drops the two new note kinds. The per-step check already gives mid-turn triggering; only the window and the threshold change.

The summarizer's provider does not get to decide. The design names four deciders, and one of them, "the summarizer's provider decides whether compaction input fits, input_too_large retreats the fold by half", has no producer. Only fitHistoryCompactMessages throws input_too_large, this PR removes that call from history-compact-summarizer.ts and openai-codex-history-compactor.ts, and both catches wrap every provider error as provider_error. So a session whose fold prefix is too large for the summarizer fails open on the first rejection, /compact included, and has no in-app way back under the window. That is worse than main, which at least estimated. The fix is small, classify ContextLength in both catches, but the regression must use a fake provider that rejects above N tokens; all five current input_too_large tests throw the error from a fixture, which is why this was invisible.

The compatibility contract. Two new system_note kinds and the new lastRequestAnchor shape land in packages/core closed allowlists, the same class of change #4486 bumped the epoch for, and the epoch is unchanged. A merge-base client handshakes fine (host-kernel.ts admits on strict equality) and fails decodeStoredMessage on the first transcript carrying a new note. main is on 96 now: rebase, take 97, and put back the three CHANGELOG sentences from #4486 that are still true (see inline).

One consequence of the first point that lives outside the diff: settings-provider-copy.ts still says "when empty, built-in metadata decides", and /context and the inspector still divide by resolveSelectedModelContextWindow, so an undeclared user sees 70% of 200k and never gets a fold. Whichever way the window question settles, the copy and the denominator have to follow the same rule.

On the test claim: five re-pointed tests pass unchanged on main's built sources (the no-size-gate replay, the two size-floor cases, the no-usage case, fails open after repeated input-too-large retreat), and two rules lost their only coverage with the deletions while still existing, the memory gate's unavailable outcome and the rule that a synthetic /compact usage row must not shadow the real anchor. The remaining persisted-anchor test uses an anchor below the window, so it passes regardless of the run-header check.

Evidence boundary: static read against main61224f51; all suites run locally; new tests also run against main's built sources in a scratch copy; no live provider.

AI-assisted review: drafted with Maka; I verified the trigger arithmetic, the input_too_large producers, the epoch state and the size-floor inputs myself.

简体中文

方向就是 #4458 上讨论定下的，我仍然支持：放不放得下由 provider 回答，压缩触发用真实数字，唯一不可逆的结果是 provider 的拒绝。删得也干净，「What is gone」里的每个符号在 docs 和 desktop 里都没有残留，本地六个 workspace 的测试、typecheck、lint、format 全绿；之后的三个提交（148326eb）没有碰到下面引用的任何文件。让我暂时不 approve 的不是代码本身，而是三处实现和设计说的不是一回事。能局部修的都放在行内评论里。

主动触发对着正确声明的窗口永远打不响。 触发条件是「上次请求的 input+output 大于声明窗口」，而上次请求是 provider 已经接受的。如果用户把窗口声明成 provider 的真实大小，任何被接受的请求都不可能超过它，主动压缩一次也不会触发，每个会话都要先撞一次拒绝。只有用户把窗口声明得比真实值小它才触发，这等于把删掉的 reserve 变成了一个要用户自己猜、又不告诉他的数字。这是 #4559 的 open point 2，我的意见相反：窗口按「用户声明 > relay profile > models.dev 元数据 > /models 报告」解析，全都没有才算无；触发条件改成「上次用量 > 窗口 − reserve」；reserve 用真实数字：模型的 output limit（下一步回复最多这么大）加上工具结果归档上限乘以待处理的工具调用数，再用窗口的固定比例兜底。这些都是 provider 的事实和 Maka 自己的内容策略，「只用真实数字」的原则不受影响。给一个默认值不是替用户决定，用户随时可以覆盖；不给的后果是开箱用户每次填满都要付一次拒绝、可能还拿到被截断的回复，CLI 用户连提示都看不到，因为 pi-transcript.ts 把两个新 note kind 丢掉了。turn 内每一步都检查的逻辑已经有了，只需要改窗口和阈值。

summarizer 的 provider 并没有拿到决定权。 设计列了四个决定者，其中「summarizer 的 provider 决定压缩输入放不放得下，input_too_large 就把范围退半」这一条没有产生者。全仓只有 fitHistoryCompactMessages 会抛 input_too_large，本 PR 把它从 history-compact-summarizer.ts 和 openai-codex-history-compactor.ts 里删掉了，两处的 catch 又把所有 provider 错误一律包成 provider_error。于是一个长会话的折叠前缀如果对 summarizer 也太大，第一次拒绝就整体放弃，/compact 走同一条路也一样，会话在 app 内没有回到窗口内的办法，比 main 还差，main 至少还估算一下。修法很小，两个 catch 里判断 ContextLength 再抛，但回归测试必须用「输入超过 N tokens 就拒绝」的假 provider；现在五个相关测试全是 fixture 手抛这个错误，所以这个洞看不见。

兼容契约。 两个新的 system_note kind 和新的 lastRequestAnchor 形状都进了 packages/core 的闭合 allowlist，和 #4486 推 epoch 的那次是同一类改动，但 epoch 没动。merge-base 上的旧 client 握手能通过（host-kernel.ts 按严格相等准入），然后在第一条带新 note 的 transcript 上解码失败。main 现在已经是 96：rebase 取 97，并把 #4486 写的、仍然成立的三句 CHANGELOG 加回来（见行内）。

第一点在 diff 之外的一个后果：settings-provider-copy.ts 的帮助文案「留空跟随内置元数据」现在不成立，/context 和 inspector 的分母也还是 resolveSelectedModelContextWindow，未声明的用户会看到「已用 70% / 200k」却永远等不到压缩。窗口问题无论怎么定，文案和分母都要跟同一条规则。

关于测试的说法：五条 re-pointed 测试在 main 的构建产物上原样通过（无 size gate 的 replay、两条体量下限、无 usage、退半后 fail open）；两条规则随删测试失去了唯一覆盖但仍然存在：memory gate 返回 unavailable 的处理，以及手动 /compact 写的合成 usage 行不得遮蔽真实 anchor。剩下那条持久 anchor 测试的 anchor 低于窗口，不管 run header 合不合法都过。

[Astro-Han]

baselineTokens is a request the provider accepted, so with the window declared at the provider's real size this is never true; the fold only runs when the user declares something smaller. That is the reserve in disguise. baseline > window − reserve, with the reserve from output limit plus the tool-result cap, is what makes this fire before the rejection. First point in the main comment.

[Astro-Han]

Dead branch: nothing throws input_too_large any more. fitHistoryCompactMessages was its only producer and both summarizer catches now wrap provider errors as provider_error. Classify ContextLength with classifyError in history-compact-summarizer.ts and openai-codex-history-compactor.ts so this retreat has a producer, and test it with a fake provider that rejects above N tokens.

[Astro-Han]

Baseline includes last step's reasoning; on wires that do not resend it (gpt-5.x), next input ≈ previous input + tool call + result, which is below input + output whenever reasoning exceeded the appended content, the normal case. Compare against last step's input alone; keep input + output for the trigger.

[Astro-Han]

Written before recoverFromOverflowError runs, so a send that overflows once, folds and completes still tells the user the provider refused. #4559 places this under "already folded". Move it after the recovery verdict; overflow-reactive-recovery.test.ts:1834 (tool, overflow, done) currently pins the wrong order. And suggestedContextWindow: baselineTokens sits on the strict > boundary, so a user who applies it still needs one more rejection.

[Astro-Han]

On a roll-forward the summarizer is sent previous summary + new events, so inputTokens is the increment while the checkpoint replaces the whole covered span; in steady state this floor never trips and a fifty-token summary after a small increment is persisted. The new test passes on main because the stub's usage is unrelated to the messages. Feed it a span-sized real number (previous checkpoint's compactCallInputTokens plus this increment) or drop the floor openly.

[Astro-Han]

The comment above says this re-runs the size floor, but no summarizerUsage is passed so the floor is skipped, and coveredRuntimeEvents is now required and unread by the validator. Same for the external-producer branch in history-compaction.ts. Either pass a real number or delete the field, the three constructions and the comment.

[Astro-Han]

Three sentences from #4486 were dropped and are still true: sessions from this build do not open in earlier releases and the runtime.sqlite copy must be taken before upgrading; context_budget_exhausted is no longer produced but still decodes; the epoch line (97 after rebase). The body says the allowlist cost is "already noted in CHANGELOG.md", and it no longer is.

[Joob1n]

Thanks for the read — every finding was real. Fixes are in 38b2d837 (one commit, each item with a test that fails on the previous commit), plus two live-provider findings in the commits before it.

Trigger arithmetic. You are right that baseline > declaredWindow could never fire against a window declared at the provider's real size. Fixed the way you suggested for the reserve, with one narrowing: the reserve is the model's declared output limit only (connection.models[].maxOutputTokens or generated metadata; 0 when none is declared), and the trigger is baseline + limit >= window. I did not add the tool-result cap × pending calls term: the active prune already bounds each result before it goes out, and a second constant on the trigger side is the kind of number the design is trying not to own. Live on Ollama (qwen2.5:1.5b, declared 1,500) the fold now fires at 2,227 with the previous usage as the only input, folds to a 1,737-char checkpoint after one repair, and the next request's provider-counted input drops 2,954 → 1,222.

Window source — kept as declared-only, deliberately. This is the one point where I did not take the suggestion, and it is the issue author's call rather than mine: the Maka window is a target the user chooses to stay under, not a fact about the model, so the model's reported window is shown beside the setting with one click to apply (#4575) but never becomes the threshold on its own. The cost you name is real and stated in the description: with nothing declared, the first fill costs one rejection and possibly one cut reply. The context_window_suggestion note then offers the last accepted total; it is now written only when the turn actually surfaces the error, and the CLI transcript renders both new note kinds.

input_too_large producer. Correct — I removed the only producer. Both summarizer catches now classify ContextLength as input_too_large, with a fake provider that rejects above N characters as the regression.

Epoch and CHANGELOG. Bumped to 97 on rebase and the three sentences are back.

Inline items: eviction check compares input with input; the size floor applies to the initial fold only (the roll-forward input is the increment, as you say) and CheckpointSummaryFoldContext carries usage only, so the builder/copy seams validate structure and truncation; the suggestion note moves after recovery and names the fold-proof last accepted total; the run-header test's anchor now sits above the window so the header check decides; the synthetic /compact row test is restored; the roll-forward floor test now asserts both directions.

Two things I left as they were, with reasons. The Host's runComposition.contextWindow stays the model's reported window: it is a protocol fact clients already display, and the declared window gets its own surface in the composer indicator (#4576) rather than a changed meaning for an existing field. And the memory-gate unavailable outcome is still exercised by the mid-turn fixture's extraction path (remember returns unavailable there, asserted at the fold that dispatches extraction); if you meant a different obligation, tell me which and I will pin it.

[Joob1n]

Rebased on main@8ea3c4f05 now that #4578 has landed, so the dependency bump is no longer carried here (6 commits). main moved the compatibility epoch to 98 in the meantime (#4561 / #4568), so this PR's bump is now 98 → 99; the CHANGELOG line and the epoch comment follow. No other changes since a65076258.

[likun666661]

方向我赞成：把“请求是否 fit”的裁决权完全交给 provider，把本地侧收缩为“真实 usage + 用户目标只触发可逆 fold”，比多把估算尺同时参与决策更干净。PR 的主要因果链也基本成立。不过在 approve 前，我认为还有下面几个点需要收口：

1. [P1] compatibility epoch 与最新 main 撞号。 当前 main@898b86d 已经把 RUNTIME_HOST_COMPATIBILITY_EPOCH 升到 99，用于 ScheduledTask 的 Connection identity；本 PR 也独立使用 99 表示两个新 system note 和 lastRequestAnchor shape。两边是不同的不兼容协议变化。rebase 后不能只解决文本冲突并继续保留 99，需要把合并结果升到 100，同步注释、CHANGELOG 和 epoch test；否则能力不同的 client/host 可能错误通过严格相等握手。

2. [P2] repair 请求里的 ContextLength 会被吞成初次格式错误。history-compact-summarizer.ts:206-243 中，初次 summary malformed 后，repair 使用更长的 system prompt。如果初次调用刚好 fit、repair 因新增 instruction 被 provider 拒绝，内层 catch 会把该错误包装成初次的 malformed_summary_*；外层看到它已经是 HistoryCompactSummarizerError 后直接重抛，不会再分类为 input_too_large。planner 因此不会执行 halve-and-retry，和“summarizer provider decides”不一致。建议在 repair catch 中保留 ContextLength 分类，并补一个“initial malformed, repair overflow”的回归测试。

3. [P2] 架构文档仍描述修复前的 trigger。 中英文文档目前都写成“上次 inputTokens + outputTokens 超过用户窗口时触发”；实现已经是 baseline + model.maxOutputTokens >= declaredWindow（ai-sdk-compaction.ts:896-908）。这是核心规则，应同步两份文档，避免后续实现和测试重新漂移。

4. Issue closure 建议调整。#4559 的 proposal 还包含 missing-usage hint、unclassified overflow 的 compact-and-retry action、metadata window 一键采用和 composer indicator。本 PR 没有 missing-usage note，unclassified action 明确留在系列之外，UI 又拆到 #4575/#4576。拆 PR 没问题，但此时 Closes #4559 会让完整验收范围过早关闭；建议改成 Refs #4559，或先明确把 #4559 收缩为 runtime-only。

从 Occam 的角度，我的判断是：架构方向已收敛，问题定义尚未完全收敛。 最小因果主线已经很清楚：

history grows
→ user target may request a reversible fold
→ provider outcome decides actual fit
→ canonical history is never rejected or mutated by an estimate

但“provider decides”尚未覆盖 provider 沉默的情况：PR 自己的 Ollama 实测已经显示跨 turn usage plateau / silent truncation，而当前 dropping note 只检查同 turn 的 step ≥ 1。建议把无 usage、无法分类以及 silent eviction 明确定义成可见的 degraded mode；否则“未声明 window 时系统提供什么保证”仍是开放语义。

另外，includeUsage ?? true 现在会给所有 OpenAI-compatible Chat server 发送 stream_options.include_usage。现有 conformance test 只覆盖支持该字段的 fake server；最好再补一个严格 relay 拒绝该字段时的契约测试，明确 fail、fallback 或 opt-out 行为。

CI 当前是绿的，diff check 也干净；上面第 1 项是基于最新 main 的当前 merge blocker，第 2 项是静态可达的 provider-boundary bug。修完这些，我认为核心 runtime 改动可以继续推进。

[Joob1n]

Thanks — the first three are real and are fixed in 6c5e53ddd / ba14a706c; the fourth is done in the PR body.

1. Epoch.main moved again while this was open (#4321 → 99, #4508 → 100), so the rebase now lands this PR's bump as 100 → 101; comment, CHANGELOG and the epoch check follow. The protocol tests assert against the exported constant, not a literal, so nothing else pins the number.

2. Repair-path ContextLength. Confirmed: the repair catch wrapped every failure under the initial defect, so a context-length rejection of the longer repair prompt never reached the planner as input_too_large. The catch now classifies before wrapping; regression test "a context-length rejection of the repair request stays the input_too_large signal" (initial malformed → repair rejected → input_too_large, two provider calls) fails on the previous commit.

3. Docs. Both llm-compaction-events-log-projection-draft documents now state the implemented trigger: previous accepted inputTokens + outputTokensplus the reply reserve (the model's declared maxOutputTokens, zero when unknown) reaching the declared window.

4. Issue closure. Changed to Refs #4559; the issue closes when #4574/#4575/#4576 have all landed and the remaining proposal items are triaged there.

On the two broader points:

• Degraded modes (no usage, unclassified rejection, cross-turn plateau). Agreed that these deserve names. They are deliberately outside this PR: the dropping note is scoped to a single send because within one send Maka knows it only appended, while across turns the user may have edited or branched and a lower inputTokens is legitimate. Opened context: define the degraded modes when the provider does not speak (no usage, unclassified rejection, silent eviction) #4623 with the three modes, the signal each one gives today, and the two small follow-ups: PR D applies the same dropping rule at the turn boundary (first request's inputTokens below the persisted anchor with no fold or prune before the send → note), PR E adds "compact and retry" on an unclassified provider error. Both are notes/actions on top of this PR's paths, so they can land right after it without reopening it.

• stream_options on strict relays. Decided and pinned in 6ce7d7332: a relay that rejects the field fails with the provider's own 400 text and the runtime does not resend without it — the conformance test asserts one request, the stream_options body field, and the provider message reaching the stream's error part. Rationale: a connection that cannot report usage has no context baseline, so a silent fallback would hide exactly the degraded mode above; the error names the field, and a per-adapter includeUsage: false is the one-line opt-out if a real relay needs it. The field has been part of the Chat Completions API since 2024-05 and the Kimi OpenAI path in this repo has sent it since feat(runtime): support Kimi OpenAI protocol #1462.

[Joob1n]

Rebased on main@b1ec28989. main took epoch 101 in the meantime (#4608), so this PR's bump is now 101 → 102; comment, CHANGELOG and the epoch check follow. The strict-relay contract test is e10dd49a4's head commit (was 6ce7d7332 before the rebase). No other changes.

[likun666661]

复查了最新 head e10dd49a4。上一轮的主要项都已正确落地：epoch 102 对应 merge base 101；repair-path ContextLength 保留为 input_too_large 且有回归；两份文档的 trigger 公式已更新；PR body 改成了 Refs #4559；strict relay 的一次 400 / 不静默重试契约也已固定。CI 当前是绿的，PR 可干净合并。

还有两个行为/scope 问题和一个文档漂移需要收口：

1. [P1] #4559 仍会被 closing keyword 关闭。 PR body 虽然已经改成 Refs #4559，但首个 commit 20f01b862 的 message body 仍然包含 Closes #4559。本仓库只允许 squash merge，并配置为 squash_merge_commit_message: COMMIT_MESSAGES；因此这个 closing keyword 会进入 default-branch 的 squash commit，仍会关闭 issue。既然约定是整个 #4574/#4575/#4576 系列落地并完成剩余 triage 后再关闭，请把该 commit message amend 为 Refs #4559（或确保最终 squash message 中完全没有 closing keyword），而不只是修改 PR body。

2. [P2] provider-dropping 实现检测的是“严格下降”，对外契约写的是“没有增长”。packages/runtime/src/ai-sdk-backend.ts:2170-2182 当前条件是：

   stepUsage.inputTokens<lastStepInputTokens

   但 PR summary、commit message、CLI/UI copy 和新开的 #4623 都把信号定义为 usage “did not grow / stops growing or drops”。本 PR 自己的 Ollama 证据正是输入在 3,716 持平 plateau；严格 < 不会对这个案例写 note。当前测试也只有 100 → 50 的 decrease，没有 equal-usage case。

   如果 observable contract 确实是“append-only request 的 input 没增长”，这里应使用 <= 并补一个 equal-usage regression。#4623 的 PR D 也不应只定义成 “below persisted anchor”，否则同一个跨-turn plateau 仍不会被检测。若等值被刻意排除，则应反过来收窄 PR、copy 和 #4623 的声明，并说明为什么 plateau 不是可靠信号；现在代码和承诺二者只能有一个成立。

3. [P3] 中文架构文档仍有两处旧的 size-policy 语义。docs/architecture/llm-compaction-events-log-projection-draft.zh-CN.md:88-93 的公式仍写 current context budget，而英文已改成 user-declared capacity and provider outcome；同文档 :121-130 仍把 checkpoint 的必要问题写成“它在当前 token policy 下仍然能否进入 prompt？”，英文已改为 source/provider-state identity。后文已经明确删除 replay size verdict，因此这两处应与英文及最终实现同步。

除了以上三项，上一轮要求的修复我没有再发现回归。前两项处理后，我认为这轮可以进入 approve。

[Joob1n]

All three are fixed on 2cbc332af.

1. Closing keyword in the commit body. You are right that the PR body is not where this is decided under squash merge with COMMIT_MESSAGES. 20f01b862 is reworded to Refs #4559 (now 3ed669070 after the rebase); no commit on the branch carries a closing keyword any more.

2. < vs <=. Fixed to <=, with the copy as the authority rather than the other way round. Your reading of the evidence is the right one: the live Ollama run plateaus at 3,716 input tokens and never drops, so the strict comparison would have missed the exact case the PR cites. An equal input count after an append-only step (no fold, no prune, no image omission) is already impossible without provider-side eviction or rewriting, so equality is signal, not noise. New regression "records provider context dropping when an append-only step reports the same usage" (100 → 100 across the step) fails on the previous commit; the existing decrease and prune-explains-it tests still pass.

#4623 is updated to match: PR D's rule is "at or below the persisted anchor", not "below", for the same reason.

3. Chinese document drift. Both passages are synced with the English text: the materialization inputs now read 用户声明的 capacity 与 provider 结果, and the checkpoint's replay question is source/provider-state identity rather than the retired token policy.

One note on scope: both documents still ask "which high-water decision produced it" in that same list. It is stale in both languages equally, so I left it rather than widening this PR's document diff; say the word and I will fold it in here, otherwise it goes with the #4623 documentation pass.

[me2seeks]

Reviewing with real edge cases in mind, grounded in production data from a kimi-coding-plan/k3-256k workspace (see also #4634 — this PR fixes its root causes 1 and 2; items 3 and 4 there remain open).

Overall the direction is sound: every trigger is now a provider-reported number, and I live-verified the new summarizer request shape against k3-256k (details inline on the summarizer change). My concerns are about the paths where the provider never speaks: silent over-window acceptance, output-limit cuts caused by our own maxOutputTokens, and unrecognized error shapes.

[me2seeks]

Real edge case from live data: kimi-coding-plan/k3-256k accepts requests beyond its fetched window without rejecting or truncating — observed a session accepted at 322K input tokens against a fetched contextWindow of 262,144, with usage still growing monotonically (305K → 322K). On such a provider every signal this design reads stays dark for an undeclared window:

• no rejection → reactive fold never fires;
• usage never plateaus → context_provider_dropping never fires (and it is mid-turn only anyway);
• context_window_suggestion only fires on a surfaced rejection → never written;
• a fetched /models window is not a declaration → the proactive trigger below never arms.

Net effect: an undeclared kimi session degrades silently and indefinitely (this is exactly the data behind #4634). I agree with "Maka does not decide for the user" as a principle, but for providers observed to accept over-window requests, could the fetched window seed a default declaration (user-overridable), or should the cross-turn plateau check (#4623 PR D) be a blocker rather than a follow-up?

[me2seeks]

pendingLengthFold is set on anylength finish with no size or cause guard. Two real cases where the fold is useless or harmful:

1. The cut came from our own configured maxOutputTokens, not the window: maka sends maxOutputTokens: 131072 on kimi-coding-plan main requests (from lookupModelMetadata). A reply cut at that cap is not helped by folding history at all — the next request carries the same cap. If the model keeps wanting more output (long reasoning at effort=max, large file generation), this turn folds every step, repeatedly shrinking history while never addressing the constraint.
2. A user who declares a small output limit for cost control gets routine length finishes → folds at a few K tokens of context, paying a summarizer call each time.

Suggest gating the length fold on baseline + replyReserve >= capacity (i.e. plausibly window-caused), or capping length-folds per turn.

[me2seeks]

For k3-256k, declaredModelOutputLimit resolves to 131,072 from bundled metadata — half of its 262,144 window. A user who pins the full window gets proactive folding at baseline >= 131,072, i.e. ~50% utilization, which is far earlier than "stay under your declared window" suggests. Reserving the output limit is right in principle (without it a real-size declaration is never crossed), but when the declared output limit is a large fraction of the window the reserve dominates. Consider capping it, e.g. min(outputLimit, capacity / 4) or a fixed bound.

[me2seeks]

The per-send latch and the fingerprint circuit still only cover malformed-summary reasons. After a provider_error / output_length fail-open, baselineTokens stays set, so overWindow remains true and every subsequent step retries the summarizer. Observed live on kimi-coding-plan (which reports failures as HTTP 200 + error body): 15 consecutive failed summarizer calls over ~47 minutes, each 30–45 s, before the main request. Suggest latching any summarizer failure for the rest of the send, with the same fail-open diagnostic. (#4634 item 3)

[me2seeks]

Defaulting includeUsage on for every non-opted-out OpenAI-compatible server is the right call for usage coverage, but a strict relay/proxy that rejects unknown fields (older vLLM, some gateways) will 400 every streaming request after upgrade, and opting out requires a registry code change. Consider a one-time fallback: on a 400 whose error text mentions stream_options/include_usage, retry without it and remember that for the connection.

[me2seeks]

Two false-positive paths for the dropping note:

1. Finalization steps remove all tool schemas (resolveDispatch returns [] for the child-summary / sandbox-boundary finalization step), which legitimately drops the next request's input by several K tokens with no fold/prune/image-omit — this condition doesn't exclude that case, so a routine turn end can report "provider is dropping context".
2. No hysteresis: a 1-token decrease fires the note. Cache accounting or tokenizer drift between calls can produce tiny legitimate decreases. A small relative threshold (e.g. drop > 1–2% or > N tokens) would keep the note meaningful.

[me2seeks]

Confirming this fixes the kimi-coding-plan failure mode from #4634 — I live-tested this exact request shape (system template + trailing user instruction) against k3-256k on both wires: it now returns a fully compliant sectioned summary, where the system-prompt-only shape returned content: null (7 tokens) or continued the conversation as the assistant.

One follow-up worth noting (not blocking): the summarizer request still opens with a different system prompt than the main loop, so it shares no prefix cache with it — the first fold of a session pays a full uncached pass over the folded span (observed 39–88 s on 155–253K inputs). Moving the whole instruction into the trailing user message would let the summarizer reuse the main loop's cached prefix (~99% hits); keeping the template in system is also fine if that's load-bearing for other providers, but the cache cost is real at high context.

[Joob1n]

Thank you for the production data. Every path you named is real, and four of them are fixed on 1faabac55. The evidence for each is your k3-256k workspace, so I have quoted your numbers in the commit message rather than restating them here.

Summarizer retry storm (#4634 item 3). Fixed. The per-send latch recorded only malformed reasons, and the baseline that fired the trigger survives a fail-open, so a provider_error re-armed the same condition on every later step. Every fail-open reason now latches for the rest of the send. Regression: "bounds a provider-error summarizer failure across later steps in the same turn" (one summarizer call, failOpenReason: provider_error, no checkpoint), failing on the previous commit.

pendingLengthFold with no cause guard. Fixed, and your first case is the discriminator: the reply's own outputTokens says which limit cut it. A reply that stopped at the maxOutputTokens Maka sends was cut by Maka's budget, and the next request carries the same budget, so the fold is marked only when the reply stopped below it. That covers your cost-control case too, since a small declared output limit is reached exactly. No new constant, and both numbers are provider-reported. Regression: "does not fold when the reply was cut by the output budget Maka itself sends".

Dropping-note false positives. The finalization case is fixed: the note is suppressed when the step's own active tool set shrank, which is Maka reshaping the request rather than the provider evicting anything. Regression: "does not report provider dropping when the step dropped its tool schemas". On hysteresis I would rather not add a threshold, and I think the <= change (this PR now treats a plateau as the signal, per @likun666661's review) makes the case: after an append-only step, an input count that merely failed to grow already means the appended content was not counted, so a one-token decrease is not a weaker signal than equality but a marginally stronger one. normalizeAiSdkUsage sums no-cache, cache-read and cache-write, so cache accounting does not move the total. If you have a case where drift moves it anyway, that is worth a threshold and I will add one.

stream_options on strict relays. Adopted your suggestion over my earlier position, which @likun666661 also questioned: the deciding argument is that opting out needs a registry code change, so a strict relay has no user-facing recovery. A 400 whose body names the field now triggers one retry without it, remembered per base URL for the process. The connection then simply reports no usage, which the composer indicator (#4576) shows as a dash. Contract test asserts the three requests: asked, retried without, and never asked again.

Providers that accept beyond their fetched window. This one I have not changed, and I want to be explicit about why, because you are right that every signal stays dark. A cross-turn plateau check (PR D on #4623) does not rescue it either: your session's usage grows monotonically to 322K, so there is no plateau to detect. The only thing that arms anything is a declaration. Two options I can see:

1. A note when accepted usage exceeds the model's reported window while nothing is declared. That is two real numbers and no decision on the user's behalf, and it is the same shape as the existing context_window_suggestion. It fits this design and I would be glad to add it, here or as PR D's sibling.
2. Seeding a default declaration from the fetched window, which is the thing Context budget: stop estimating fit; the provider decides, the Maka window is a user target #4559 deliberately removed: a fetched number is a hint, and a session that compacts because of a number the user never chose is the failure this PR exists to end.

My preference is 1. Say which you would rather review and I will follow.

Prefix cache on the summarizer request. Noted as a follow-up, not forgotten: your 39–88 s uncached first attempts are a strong argument for moving the whole instruction into the trailing user message now that the trailing message exists. I have left the system template in place here because it is load-bearing for the providers the current tests cover, and changing both the shape and the cache behaviour in the same PR would make the k3-256k regression hard to attribute. It belongs on #4634.

Thanks also for live-testing the summarizer request shape; that is the part of this PR I could only verify against Ollama and fake providers.

[Joob1n]

Follow-up on the two open items from your review, both now on 77590471e.

The reply reserve is no longer the model's output limit. Your k3-256k arithmetic was the deciding case: reserving 131,072 against a 262,144 declaration folds at half the window a user deliberately chose. It is now twice the last reply the model actually wrote, bounded at 8,000 tokens. Both halves are provider-reported, the margin tracks the session's own behaviour rather than a catalog maximum, and no previous reply means no reserve at all. On your numbers a session answering in 2–3K tokens now folds at roughly 256K of 262K instead of 131K. The old test that asserted the output limit is rewritten around the new rule (a 900-token anchor with a 60-token reply folds against a 1,000 window, the same anchor with a 5-token reply does not, and the model's 600-token output limit is irrelevant to both).

A reserve measured from a smaller previous reply can still be too small, so that case is now reported rather than silent: when an accepted request's own input plus its reply exceed the declared window, the transcript carries one context_window_overrun note per send with both numbers. It is the honest reading of "the reply needed more room than was left", it uses only provider-reported numbers, and it tells a user who wants whole replies to raise the declaration. The next request folds anyway because the baseline now exceeds the window; the note explains why rather than changing what happens.

That makes three note kinds in this PR, all in the same epoch move (now 103 → 104 after the latest rebase).

Still yours to choose: the undeclared-window case on a provider that accepts past its reported window. My preference remains a note when accepted usage exceeds the model's reported window while nothing is declared, rather than seeding a declaration from a fetched number. Say which you would rather review.

[Joob1n]

Added, on 0d0a32dce: with nothing declared, a request the provider accepts past the window its own catalog entry reports now writes one context_reported_window_exceeded note per send, naming what the exchange used and what the model reports. It changes nothing on its own — a reported window stays a hint, and Maka still declares nothing on the user's behalf — but the case you found is no longer invisible. With a declaration in place the overrun note already owns that ground, and a test pins that the two never fire for the same fact.

That is the fourth note kind in this PR, all within the same epoch move (103 → 104 after the latest rebase). Local gates are green; the mid-turn suite is 73/73.

[me2seeks]

Thanks — verified 1faabac55 and 77590471e on the diff. The cutByOwnBudget discriminator is a better fix than the proximity gate I suggested: it distinguishes the two length causes with two provider-reported numbers, and my cost-control case falls out of it for free. The behaviour-measured reply reserve (2× last reply, ≤8K) fixes the k3-256k half-window arithmetic, and context_window_overrun is the right honest reporting for a reply that outgrew a reserve measured from smaller ones.

Undeclared window on a provider that accepts past its reported window: I choose option 1 — a note when accepted usage exceeds the model's reported window while nothing is declared. Two reasons beyond the ones you gave:

1. Coverage differs by surface. TUI has a real-time ctx indicator (I have a PR open adding one, with colour) so a TUI user can transiently see 322K > 262K; Desktop has nothing. A persisted note in the transcript is the only durable signal on Desktop, and the only one that survives the moment on TUI.
2. The note closes the loop with feat(desktop): show the model's reported context window beside the declared setting #4575. The number it should name is the reported window the user could adopt, and the natural call to action is the settings surface with the one-click apply from feat(desktop): show the model's reported context window beside the declared setting #4575.

One constraint from the k3-256k data: on such providers usage crosses the reported window gradually and keeps growing (305K → 322K), so the note should fire once per session when the crossing is first observed (the accepted total first exceeds the reported window), not per send — otherwise it spams on every step past the line.

On hysteresis for the dropping note: your <= argument and the normalizeAiSdkUsage sum hold; I have no live case where drift moves the total, so I withdraw that suggestion.

I will take the summarizer prefix-cache item back to #4634 as agreed.

[Joob1n]

Adopted the once-per-crossing constraint on 8c88243ca. The note now fires on the transition rather than per send: the previous accepted total was still inside the reported window and this one is not. That previous total comes from the persisted anchor, so a resumed session does not repeat a crossing it already reported, and a session that is already past the line stays quiet. Test "does not repeat the reported-window note once the session is already past the line" (a 320-token anchor against a reported 100) fails without the guard.

Your two reasons are both in the code's favour: the note is the durable Desktop signal, and it names the reported window, which is the number #4575 offers to apply in one click. Noted on the withdrawn hysteresis and on taking the prefix-cache item to #4634.

[Joob1n]

Correction on the previous push: a rebase of mine stopped on a conflict and the branch was pushed mid-rebase, so 8c88243ca briefly showed this PR with 5 of its 13 commits. The head is now 1283c874c, rebased on main@148f8eb29 with all 13 commits and every local gate green. Nothing in the content changed; main also took epoch 104 in the meantime, so this PR's bump is now 104 → 105 and the comment, CHANGELOG and commit message follow.

[Joob1n]

Closing this in favour of a smaller series. Not because anything here was wrong: it is green and every review item on it is either fixed or deliberately carried forward. The reason is that the design converged past what this PR's shape can carry, and a reviewer arriving now would have to reconstruct it from four rounds of comments.

Two things changed after the last round, both simplifications, and both invalidate part of this PR rather than adding to it:

1. The compaction module runs at most once per send. The proactive and reactive folds were two independent latches here. A fold already covers everything except the live head, so a second one buys a little tail and costs the most recent verbatim context. When a request is still rejected after a fold, the honest diagnosis is that the new message itself is too large, and that is what the user should be told.
2. A finishReason: length no longer triggers a fold. A reply cut below the maxOutputTokens Maka sends can mean the provider ran out of window room, or that the provider has its own lower output cap. Those are indistinguishable from the outside, and an indistinguishable signal should not drive an action. This removes the cutByOwnBudget discriminator @me2seeks and I converged on, one level up: the discriminator was right for the question asked, but the question should not have been asked.

A third change is larger and belongs on its own review: when a fold is rejected as too large, retreat to the span the last accepted request's input covered, rather than halving the covered range. That boundary was accepted by this exact model on this exact connection, so it is provably within capacity, where halving is a guess. The last reply's own span is folded separately when it exceeds 24,000 tokens.

The full design is written up on #4559 as three modules (judge / send / compact) with the call bounds.

Where each review finding goes

Finding	Reviewer	Lands in
Trigger arithmetic needs a reply reserve	@Astro-Han	PR 1
input_too_large must have a real producer	@Astro-Han	PR 2
Eviction check must compare input against input	@Astro-Han	PR 1
Window-suggestion note timing (after recovery, not before)	@Astro-Han	PR 1
Size floor only on the initial fold, not on roll-forward	@Astro-Han	PR 2
Fold-context cleanup, CHANGELOG, CLI note kinds, epoch	@Astro-Han	PR 1
Epoch collision with main	@likun666661	PR 1
Repair request's context-length rejection swallowed as a format defect	@likun666661	PR 2
Architecture documents describing the pre-fix trigger	@likun666661	PR 1
Closing keyword in the commit body, not just the PR body	@likun666661	PR 1
Dropping note must fire on a plateau (<=), not only a decrease	@likun666661	PR 1
Summarizer retry storm: latch every failure, not only malformed ones	@me2seeks	PR 2
Reply reserve must not be the model's output limit	@me2seeks	PR 1
Dropping note false positive on tool-schema shrink	@me2seeks	PR 1
stream_options retreat for strict relays	@me2seeks	PR 1
Undeclared window on a provider that accepts past its reported window	@me2seeks	PR 1
Reported-window note once per crossing, not per send	@me2seeks	PR 1
Length-fold cause guard	@me2seeks	superseded, see 2 above
Summarizer prefix-cache cost	@me2seeks	#4634

The series

• PR 1 — send module: trigger, reply reserve, persisted anchor, one compaction per send, "this message is too large", stream-usage collection with the strict-relay retreat, and all four system notes. One epoch move.
• PR 2 — compaction module: summarizer request shape, output cap and retries, failure latch, and the retreat to the last accepted input boundary.
• feat(desktop): show the model's reported context window beside the declared setting #4575, feat(desktop): show context usage beside the model controls #4576 — unchanged, rebased onto PR 1 when it lands.
• PR 5 — "compact and retry" for a rejection the classifier does not recognise (context: define the degraded modes when the provider does not speak (no usage, unclassified rejection, silent eviction) #4623).

Thank you all for the four rounds; the findings are carried, not discarded.

[Joob1n]

The replacement is #4653: the send module, with the two simplifications described above and the same review findings carried. The compaction module's retreat boundary follows in a second PR.

[Joob1n]

Summary

The runtime no longer estimates whether a request fits a context window. Every "does it fit" question is answered by a provider; every trigger is a real number. This is the remaining step after #4486, which removed the fabricated capacity and the two terminal gates but kept the chars/4 delta estimate, the 32,000-token fallback history budget, and a per-step JSON.stringify of the whole request as a payload ruler. Design and discussion: #4559 (this PR), #4458 (history).

What decides now

• The conversation provider's own context-length rejection is recovered by one compact-and-retry; a second rejection surfaces as the provider's error (context_overflow), and the user's message stays editable.
• The summarizer's provider decides whether compaction input fits: input_too_large retreats the fold by half, and the loop exits through no_safe_completed_span when even the smallest legal span is refused.
• Proactive compaction has one trigger: the previous accepted request's real inputTokens + outputTokens, as the provider counted them, compared with the context window the user declared for the model (a model-facts pin or a relay profile). Reasoning tokens are counted whole on purpose — high is the safe direction for a trigger that can only ask for a compaction.
• A reply the provider cut at its output limit (finishReason: length) folds once before the next request.

What is gone: estimateNextRequestTokens, exceedsHighWater, midTurnRequestPayloadChars, the final-request rescue re-entry, maxHistoryEstimatedTokens and its five consumers, the quarter-window / 16,384 reserve, the 32,000 fallback, the replacement_not_smaller and prefix_over_budget replay gates, size-based replay selection, the estimated input fit before summarizer calls, and the chars/4 summary-size floor.

Notes for the user (four new system_note kinds): context_provider_dropping when an append-only step's usage did not grow (a provider evicting or rewriting context), and context_window_suggestion when a rejection lands at a proven-fit total, carrying the number the user can declare.

Refs #4559 — the issue closes when the whole series (#4574, #4575, #4576) has landed and the remaining items are triaged there.
Refs #4458, #4486

Follow-up PRs (stacked on this one)

The user-facing surfaces are deliberately split out so this PR stays the atomic runtime change and the UI pieces can be reviewed in parallel. Both are open as drafts on top of this branch and will be rebased and undrafted once this merges:

• feat(desktop): show the model's reported context window beside the declared setting #4575 — Desktop settings: the model's reported window shown beside the declared setting with a one-click apply. Without it, a user who has never declared a window gets no proactive compaction and no in-app pointer to the number they could set; the context_window_suggestion note from this PR is the runtime-side half of that pointer.
• feat(desktop): show context usage beside the model controls #4576 — Desktop composer: read-only context-usage indicator fed by the persisted lastRequestAnchor this PR introduces (percentage with a declared window, absolute tokens without one, a dash when the provider reports no usage).

Not in this series, defined and tracked on #4623 (the degraded modes when the provider does not speak): PR D applies the provider-dropping rule at the turn boundary, PR E adds a "compact and retry" action for provider rejections the error classifier does not recognise. Neither reopens a path this PR touches.

Behaviour changes to review

1. No declared window means no proactive compaction. The first time such a session fills up costs one provider round trip and possibly one cut reply; the context_window_suggestion note then offers the last accepted total as the value to declare. This is the "Maka does not decide for the user" principle; the trade-off is stated in Context budget: stop estimating fit; the provider decides, the Maka window is a user target #4559.
2. A /models report or models.dev metadata is no longer a threshold on its own.resolveDeclaredContextWindow (runtime) and declaredContextWindow (core, single owner of the rule) count only a facts pin or a relay profile. resolveSelectedModelContextWindow keeps its old meaning for display and contextRemaining.
3. token_usage.lastRequestAnchor is now { inputTokens, outputTokens? }. The retired payloadChars key still decodes, so sessions written by 0.2.0 keep loading; sessions written by this build do not open in 0.2.0 (the closed-allowlist cost already noted in CHANGELOG.md).
4. Summaries are capped at 8,000 output tokens (DEFAULT_HISTORY_COMPACT_MAX_OUTPUT_TOKENS; the summarizer's maxOutputTokens option was declared and never passed). A length finish gets one shorter retry, then fails open. The too-small-for-fold floor reads the summarizer call's real usage; a producer that reports none is not floored.
5. Checkpoint replay is structural: a source-matched checkpoint replays as [block, everything after the boundary]. No local size gate stands between a materializable fold and dispatch.
6. ContextBudgetDiagnostic.maxHistoryEstimatedTokens is retired (decode-only). HistoryCompactionPolicy.midTurn loses reserveTokens. buildDefaultContextBudgetPolicy drops its connection parameter.
7. Every OpenAI-compatible Chat request now asks for stream usage (stream_options.include_usage), unless the registry opts a provider out. Found live: only two providers opted in, so a local Ollama and every plain OpenAI-compatible relay — the connection type behind Context budget: an undeclared window fabricates a capacity that kills live turns #4458 — returned no usage, and the baseline, the eviction check and the indicator all stayed dark for them.
8. Summary requests close with a user instruction. Found live: a chat-template model handed a conversation ending on its own turn emits end-of-sequence and nothing else (Ollama qwen2.5, both sizes: finish stop, one output token, empty text), so history compaction never succeeded against a local model. Existing message-shape tests gained the trailing user:text.
9. The trigger reserves the model's declared output limit and fires on >= (review). baseline + outputLimit >= declaredWindow, where the limit is connection.models[].maxOutputTokens or generated metadata — a provider fact — and 0 when none is declared. Without it a window declared at the provider's real size could never be crossed by an accepted request. The window itself remains the user's declaration (see the reply on the review for why the metadata window stays a hint).
10. A context-length rejection from the summarizer's provider is input_too_large again (review), so the planner's retreat-by-half has a producer; the same classification is applied to the Codex compaction call.
11. The window suggestion note is written only when the turn surfaces the rejection (review): after the one fold is spent or when there is no seam, naming the last accepted total, which a fold does not clear.
12. The size floor judges an initial fold only (review): on a roll-forward the summarizer's input is the increment, not the covered span, so the floor stands down there and the fold context carries usage only. The eviction check compares input against input, since reasoning is not resent on every wire.

On dropping the signed delta

#4486 kept a signed chars/4 delta so step 0 could fold before a large new message or image went out. I dropped it: the delta prices an image at a constant and under-reads CJK by about half, so the round trip it saves is the one it is most likely to misjudge; large text results are already capped by the byte-based tool-result archive before they go out; and removing it takes the whole payload ruler and the per-step JSON.stringify(messages) with it. Happy to be argued back.

Test coverage removed

Thirty-seven tests encoded the estimate, the reserve, the payload ruler, the fit gates, or the pre-turn estimate gate; each is either re-pointed at a real-usage observable or removed with the mechanism. Re-pointed: the usage baseline is the last request's INPUT tokens → input plus output; compacts over the high water → compacts after provider usage crosses the declared window; keeps user_stop when stopping an oversized pre-turn summary → keeps user_stop when stopping while a usage-triggered fold is summarizing; persists the LAST request as the anchor → persists the last request input and output as the anchor; replays a durable pre_turn checkpoint below the current high water → without a local size gate; rejects a paragraph-sized summary for a large folded span → when usage says it is too small. Removed outright (the mechanism is gone): the three manual compactHistory … exceeds current limits / makes the full replay larger cases, the three reserve-derivation cases, anchors on real provider usage plus a tail char/4 delta, credits a SIGNED negative payload delta, falls back to whole-projection char/4 on cold start, high-water crosses at contextWindow minus reserve, a fold that cannot shrink the real payload is refused, a runaway summary is rejected as replacement_not_smaller, bounds the oldest oversized tool result before dispatch, fails with input_too_large before dispatch, charges the summarization instructions against the input budget, a summary at exactly the floor is accepted under ceil-based token estimates, the capacity verdict measures the steering payload, the anchor a finalization step writes excludes the tool schemas it cleared, dispatches a pre-turn Compaction recipe without projecting history and keeps a transiently unavailable automatic Compaction checkpoint recoverable (both exercised the deleted pre-turn gate; memory extraction from a hook-triggered fold stays covered), applies max-history overrides to checkpoint replay validation, accepts a complete checkpoint above legacy block limits when the full replay fits, compacts one oversized prior turn before an unknown-model request, compacts an oversized latest turn when an older turn is also retained, dispatches an oversized prior turn when its summary fails, after trying once, never runs a pointless summarizer on a small-window model, a usage object without usable input tokens falls back to cold start, a last-request anchor is only valid as a complete positive pair, a half-written anchor fails the whole token_usage message decode (replaced by the new-shape and retired-key cases).

New coverage: the declared-window rule for pin / relay / reported / metadata sources; baseline = input + output, > not >=, cleared after a fold, seeded from the previous turn, discarded across a model switch; a /models window is not a declaration; pendingLengthFold; the summarizer output cap, shorten retry, and output_length after two cuts; usage-based size floor; retreat by half and its give-up exit; structural replay; both notes, including the non-firing cases (pruned step, step 0, declaration already crossed); the retired payloadChars key decodes and an unknown key still fails.

Live verification against a real provider (Ollama)

Driven through the real AiSdkBackend with getAIModel against a local Ollama (qwen2.5:0.5b / qwen2.5:1.5b, default num_ctx 4096), five turns of ~740 tokens each, the previous turn's ledger and run header fed back as prior context.

Scenario	Observed
Declared window 1,500, qwen2.5:1.5b	Turns 1–3: anchors {745,10}, {1481,10}, {2217,10} persisted; baseline 1,491 at turn 3 is < 1,500, no fold. Turn 4: baseline 2,227 > 1,500 → pre_turn fold; summary malformed twice → failedOpen[malformed_summary_missing_section], request dispatched, end_turn. Turn 5: fold again, repair produces a 1,737-char checkpoint → replaced; the request's provider-counted input drops 2,954 → 1,222.
Same, before the two fixes above	No token_usage event at all (Ollama returned no usage because it was never asked); once usage flowed, the summarizer returned empty text every time. Both fixed in this PR.
No declared window, 8 turns	Never folds, never terminates; every turn end_turn. Usage grows 745 → 3,700 and then plateaus at 3,716 for turns 6–8 while ~740 tokens are appended per turn: Ollama truncates silently at num_ctx with no error.

Known limitation, stated plainly: the silent-truncation plateau above happens between turns, and context_provider_dropping only fires within a turn (step ≥ 1, on an input count that did not grow), because at step 0 a user edit can shrink the input legitimately. A provider that truncates instead of rejecting therefore gives an undeclared-window user no signal today; declaring the window is the protection. Detecting the cross-turn plateau without an estimate needs a ledger-shape check on the anchor (did anything before the anchored request change?) — a follow-up, tracked on #4559. Closing that gap is PR D on #4623.

Verification

Rebased on main@148f8eb29 (after #4578 landed, so this PR no longer carries the dependency bump); the Runtime Host compatibility epoch moves 104 → 105 for the two new note kinds and the reshaped anchor. Locally: npm --workspace @maka/{core,storage,runtime,runtime-host,mcp,ui} run build, npm run typecheck (all workspaces), npm run lint, npm run format:check, npm run check:asf-headers, node scripts/protocol-epoch-check.mjs --base origin/main — all clean. Targeted suites: 425/425 across usage-record-last-request-anchor, context-budget-mid-turn-policy, context-budget-model-facts, history-compaction, history-compact-checkpoint, history-compact-summarizer, mid-turn-capacity-backend, overflow-reactive-recovery, ai-sdk-backend; core suite 760/760; provider-conformance 24/24, history-compact-summarizer 53/53, execution-model-composition 28/28 and the CLI pi-transcript suites after the review fixes. Not run locally: the full npm test matrix (the Electron/OpenSSL and owned-Host timing cases fail on this machine independently of the branch) — relying on CI for those.

Self-review

• The core rule declaredContextWindow was implemented twice (runtime and chat-model-choice) in an earlier draft; consolidated into @maka/core/model-thinking with runtime delegating. One owner for the one rule the design turns on.
• The user-stop-during-summary obligation had lost its test when the pre-turn gate went; re-pointed at the hook-triggered fold. The test also records that one request is still attempted after the stop and is rejected by the transport on its already-aborted signal — pre-existing behaviour, now pinned.
• An earlier draft regenerated the Astryx theme with a stale local @astryxdesign/core@0.5.0; that artifact is not in this PR.
• memory-extraction.ts and session-recap.ts keep their own bounded-request budgets; they are auxiliary calls, not history compaction, and are out of scope here.
• Diagnostics (estimatedTokensBefore/After on compaction decisions) still use the chars/4 estimator. They are recorded numbers, not decisions, and are kept so existing telemetry consumers do not break.

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Claude Code — design discussion, implementation, tests, and review; verified by the author.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No

https://claude.ai/code/session_014ajaRxC4jydavY9nYUFj5J

[Astro-Han]

The direction is the one from #4458 and I still hold it: fit is the provider's answer, the trigger is a real number, and the only irreversible outcome is the provider's rejection. The reduction is real, every symbol in "What is gone" is gone from docs and desktop too, and all six workspace suites, typecheck, lint and format pass locally on 372c1de9, and the three commits since (148326eb) touch none of the files cited below. What stops me approving is not the code, it is three places where the design as implemented does not do what the design says. Line-level fixes are inline.

The proactive trigger cannot fire against a correctly declared window. The trigger is baseline > declaredWindow, and the baseline is a request the provider accepted. If the user declares the provider's real window, no accepted request can exceed it, the fold never runs, and every session goes through rejection first. It fires only when the user declares something smaller, which is the retired reserve reintroduced as a number the user has to guess without being told. This is open point 2 of #4559, and I would settle it the other way: resolve the window as declared > relay profile > models.dev > /models, none only when all are absent; trigger on baseline > window − reserve; make the reserve a real number, the model's output limit plus the tool-result archive cap times pending tool calls, with a fraction of the window as the floor. Those are provider facts and Maka's own content policy, so the "real numbers only" principle holds. A default is not Maka deciding for the user, it is a default the user can override, and the alternative is that out of the box every fill costs a rejection and possibly a cut reply, which CLI users get without even the hint, because pi-transcript.ts drops the two new note kinds. The per-step check already gives mid-turn triggering; only the window and the threshold change.

The summarizer's provider does not get to decide. The design names four deciders, and one of them, "the summarizer's provider decides whether compaction input fits, input_too_large retreats the fold by half", has no producer. Only fitHistoryCompactMessages throws input_too_large, this PR removes that call from history-compact-summarizer.ts and openai-codex-history-compactor.ts, and both catches wrap every provider error as provider_error. So a session whose fold prefix is too large for the summarizer fails open on the first rejection, /compact included, and has no in-app way back under the window. That is worse than main, which at least estimated. The fix is small, classify ContextLength in both catches, but the regression must use a fake provider that rejects above N tokens; all five current input_too_large tests throw the error from a fixture, which is why this was invisible.

The compatibility contract. Two new system_note kinds and the new lastRequestAnchor shape land in packages/core closed allowlists, the same class of change #4486 bumped the epoch for, and the epoch is unchanged. A merge-base client handshakes fine (host-kernel.ts admits on strict equality) and fails decodeStoredMessage on the first transcript carrying a new note. main is on 96 now: rebase, take 97, and put back the three CHANGELOG sentences from #4486 that are still true (see inline).

One consequence of the first point that lives outside the diff: settings-provider-copy.ts still says "when empty, built-in metadata decides", and /context and the inspector still divide by resolveSelectedModelContextWindow, so an undeclared user sees 70% of 200k and never gets a fold. Whichever way the window question settles, the copy and the denominator have to follow the same rule.

On the test claim: five re-pointed tests pass unchanged on main's built sources (the no-size-gate replay, the two size-floor cases, the no-usage case, fails open after repeated input-too-large retreat), and two rules lost their only coverage with the deletions while still existing, the memory gate's unavailable outcome and the rule that a synthetic /compact usage row must not shadow the real anchor. The remaining persisted-anchor test uses an anchor below the window, so it passes regardless of the run-header check.

Evidence boundary: static read against main61224f51; all suites run locally; new tests also run against main's built sources in a scratch copy; no live provider.

AI-assisted review: drafted with Maka; I verified the trigger arithmetic, the input_too_large producers, the epoch state and the size-floor inputs myself.

简体中文

方向就是 #4458 上讨论定下的，我仍然支持：放不放得下由 provider 回答，压缩触发用真实数字，唯一不可逆的结果是 provider 的拒绝。删得也干净，「What is gone」里的每个符号在 docs 和 desktop 里都没有残留，本地六个 workspace 的测试、typecheck、lint、format 全绿；之后的三个提交（148326eb）没有碰到下面引用的任何文件。让我暂时不 approve 的不是代码本身，而是三处实现和设计说的不是一回事。能局部修的都放在行内评论里。

主动触发对着正确声明的窗口永远打不响。 触发条件是「上次请求的 input+output 大于声明窗口」，而上次请求是 provider 已经接受的。如果用户把窗口声明成 provider 的真实大小，任何被接受的请求都不可能超过它，主动压缩一次也不会触发，每个会话都要先撞一次拒绝。只有用户把窗口声明得比真实值小它才触发，这等于把删掉的 reserve 变成了一个要用户自己猜、又不告诉他的数字。这是 #4559 的 open point 2，我的意见相反：窗口按「用户声明 > relay profile > models.dev 元数据 > /models 报告」解析，全都没有才算无；触发条件改成「上次用量 > 窗口 − reserve」；reserve 用真实数字：模型的 output limit（下一步回复最多这么大）加上工具结果归档上限乘以待处理的工具调用数，再用窗口的固定比例兜底。这些都是 provider 的事实和 Maka 自己的内容策略，「只用真实数字」的原则不受影响。给一个默认值不是替用户决定，用户随时可以覆盖；不给的后果是开箱用户每次填满都要付一次拒绝、可能还拿到被截断的回复，CLI 用户连提示都看不到，因为 pi-transcript.ts 把两个新 note kind 丢掉了。turn 内每一步都检查的逻辑已经有了，只需要改窗口和阈值。

summarizer 的 provider 并没有拿到决定权。 设计列了四个决定者，其中「summarizer 的 provider 决定压缩输入放不放得下，input_too_large 就把范围退半」这一条没有产生者。全仓只有 fitHistoryCompactMessages 会抛 input_too_large，本 PR 把它从 history-compact-summarizer.ts 和 openai-codex-history-compactor.ts 里删掉了，两处的 catch 又把所有 provider 错误一律包成 provider_error。于是一个长会话的折叠前缀如果对 summarizer 也太大，第一次拒绝就整体放弃，/compact 走同一条路也一样，会话在 app 内没有回到窗口内的办法，比 main 还差，main 至少还估算一下。修法很小，两个 catch 里判断 ContextLength 再抛，但回归测试必须用「输入超过 N tokens 就拒绝」的假 provider；现在五个相关测试全是 fixture 手抛这个错误，所以这个洞看不见。

兼容契约。 两个新的 system_note kind 和新的 lastRequestAnchor 形状都进了 packages/core 的闭合 allowlist，和 #4486 推 epoch 的那次是同一类改动，但 epoch 没动。merge-base 上的旧 client 握手能通过（host-kernel.ts 按严格相等准入），然后在第一条带新 note 的 transcript 上解码失败。main 现在已经是 96：rebase 取 97，并把 #4486 写的、仍然成立的三句 CHANGELOG 加回来（见行内）。

第一点在 diff 之外的一个后果：settings-provider-copy.ts 的帮助文案「留空跟随内置元数据」现在不成立，/context 和 inspector 的分母也还是 resolveSelectedModelContextWindow，未声明的用户会看到「已用 70% / 200k」却永远等不到压缩。窗口问题无论怎么定，文案和分母都要跟同一条规则。

关于测试的说法：五条 re-pointed 测试在 main 的构建产物上原样通过（无 size gate 的 replay、两条体量下限、无 usage、退半后 fail open）；两条规则随删测试失去了唯一覆盖但仍然存在：memory gate 返回 unavailable 的处理，以及手动 /compact 写的合成 usage 行不得遮蔽真实 anchor。剩下那条持久 anchor 测试的 anchor 低于窗口，不管 run header 合不合法都过。

[Astro-Han]

baselineTokens is a request the provider accepted, so with the window declared at the provider's real size this is never true; the fold only runs when the user declares something smaller. That is the reserve in disguise. baseline > window − reserve, with the reserve from output limit plus the tool-result cap, is what makes this fire before the rejection. First point in the main comment.

[Astro-Han]

Dead branch: nothing throws input_too_large any more. fitHistoryCompactMessages was its only producer and both summarizer catches now wrap provider errors as provider_error. Classify ContextLength with classifyError in history-compact-summarizer.ts and openai-codex-history-compactor.ts so this retreat has a producer, and test it with a fake provider that rejects above N tokens.

[Astro-Han]

Baseline includes last step's reasoning; on wires that do not resend it (gpt-5.x), next input ≈ previous input + tool call + result, which is below input + output whenever reasoning exceeded the appended content, the normal case. Compare against last step's input alone; keep input + output for the trigger.

[Astro-Han]

Written before recoverFromOverflowError runs, so a send that overflows once, folds and completes still tells the user the provider refused. #4559 places this under "already folded". Move it after the recovery verdict; overflow-reactive-recovery.test.ts:1834 (tool, overflow, done) currently pins the wrong order. And suggestedContextWindow: baselineTokens sits on the strict > boundary, so a user who applies it still needs one more rejection.

[Astro-Han]

On a roll-forward the summarizer is sent previous summary + new events, so inputTokens is the increment while the checkpoint replaces the whole covered span; in steady state this floor never trips and a fifty-token summary after a small increment is persisted. The new test passes on main because the stub's usage is unrelated to the messages. Feed it a span-sized real number (previous checkpoint's compactCallInputTokens plus this increment) or drop the floor openly.

[Astro-Han]

The comment above says this re-runs the size floor, but no summarizerUsage is passed so the floor is skipped, and coveredRuntimeEvents is now required and unread by the validator. Same for the external-producer branch in history-compaction.ts. Either pass a real number or delete the field, the three constructions and the comment.

[Astro-Han]

Three sentences from #4486 were dropped and are still true: sessions from this build do not open in earlier releases and the runtime.sqlite copy must be taken before upgrading; context_budget_exhausted is no longer produced but still decodes; the epoch line (97 after rebase). The body says the allowlist cost is "already noted in CHANGELOG.md", and it no longer is.

[Joob1n]

Thanks for the read — every finding was real. Fixes are in 38b2d837 (one commit, each item with a test that fails on the previous commit), plus two live-provider findings in the commits before it.

Trigger arithmetic. You are right that baseline > declaredWindow could never fire against a window declared at the provider's real size. Fixed the way you suggested for the reserve, with one narrowing: the reserve is the model's declared output limit only (connection.models[].maxOutputTokens or generated metadata; 0 when none is declared), and the trigger is baseline + limit >= window. I did not add the tool-result cap × pending calls term: the active prune already bounds each result before it goes out, and a second constant on the trigger side is the kind of number the design is trying not to own. Live on Ollama (qwen2.5:1.5b, declared 1,500) the fold now fires at 2,227 with the previous usage as the only input, folds to a 1,737-char checkpoint after one repair, and the next request's provider-counted input drops 2,954 → 1,222.

Window source — kept as declared-only, deliberately. This is the one point where I did not take the suggestion, and it is the issue author's call rather than mine: the Maka window is a target the user chooses to stay under, not a fact about the model, so the model's reported window is shown beside the setting with one click to apply (#4575) but never becomes the threshold on its own. The cost you name is real and stated in the description: with nothing declared, the first fill costs one rejection and possibly one cut reply. The context_window_suggestion note then offers the last accepted total; it is now written only when the turn actually surfaces the error, and the CLI transcript renders both new note kinds.

input_too_large producer. Correct — I removed the only producer. Both summarizer catches now classify ContextLength as input_too_large, with a fake provider that rejects above N characters as the regression.

Epoch and CHANGELOG. Bumped to 97 on rebase and the three sentences are back.

Inline items: eviction check compares input with input; the size floor applies to the initial fold only (the roll-forward input is the increment, as you say) and CheckpointSummaryFoldContext carries usage only, so the builder/copy seams validate structure and truncation; the suggestion note moves after recovery and names the fold-proof last accepted total; the run-header test's anchor now sits above the window so the header check decides; the synthetic /compact row test is restored; the roll-forward floor test now asserts both directions.

Two things I left as they were, with reasons. The Host's runComposition.contextWindow stays the model's reported window: it is a protocol fact clients already display, and the declared window gets its own surface in the composer indicator (#4576) rather than a changed meaning for an existing field. And the memory-gate unavailable outcome is still exercised by the mid-turn fixture's extraction path (remember returns unavailable there, asserted at the fold that dispatches extraction); if you meant a different obligation, tell me which and I will pin it.

[Joob1n]

Rebased on main@8ea3c4f05 now that #4578 has landed, so the dependency bump is no longer carried here (6 commits). main moved the compatibility epoch to 98 in the meantime (#4561 / #4568), so this PR's bump is now 98 → 99; the CHANGELOG line and the epoch comment follow. No other changes since a65076258.

[likun666661]

方向我赞成：把“请求是否 fit”的裁决权完全交给 provider，把本地侧收缩为“真实 usage + 用户目标只触发可逆 fold”，比多把估算尺同时参与决策更干净。PR 的主要因果链也基本成立。不过在 approve 前，我认为还有下面几个点需要收口：

1. [P1] compatibility epoch 与最新 main 撞号。 当前 main@898b86d 已经把 RUNTIME_HOST_COMPATIBILITY_EPOCH 升到 99，用于 ScheduledTask 的 Connection identity；本 PR 也独立使用 99 表示两个新 system note 和 lastRequestAnchor shape。两边是不同的不兼容协议变化。rebase 后不能只解决文本冲突并继续保留 99，需要把合并结果升到 100，同步注释、CHANGELOG 和 epoch test；否则能力不同的 client/host 可能错误通过严格相等握手。

2. [P2] repair 请求里的 ContextLength 会被吞成初次格式错误。history-compact-summarizer.ts:206-243 中，初次 summary malformed 后，repair 使用更长的 system prompt。如果初次调用刚好 fit、repair 因新增 instruction 被 provider 拒绝，内层 catch 会把该错误包装成初次的 malformed_summary_*；外层看到它已经是 HistoryCompactSummarizerError 后直接重抛，不会再分类为 input_too_large。planner 因此不会执行 halve-and-retry，和“summarizer provider decides”不一致。建议在 repair catch 中保留 ContextLength 分类，并补一个“initial malformed, repair overflow”的回归测试。

3. [P2] 架构文档仍描述修复前的 trigger。 中英文文档目前都写成“上次 inputTokens + outputTokens 超过用户窗口时触发”；实现已经是 baseline + model.maxOutputTokens >= declaredWindow（ai-sdk-compaction.ts:896-908）。这是核心规则，应同步两份文档，避免后续实现和测试重新漂移。

4. Issue closure 建议调整。#4559 的 proposal 还包含 missing-usage hint、unclassified overflow 的 compact-and-retry action、metadata window 一键采用和 composer indicator。本 PR 没有 missing-usage note，unclassified action 明确留在系列之外，UI 又拆到 #4575/#4576。拆 PR 没问题，但此时 Closes #4559 会让完整验收范围过早关闭；建议改成 Refs #4559，或先明确把 #4559 收缩为 runtime-only。

从 Occam 的角度，我的判断是：架构方向已收敛，问题定义尚未完全收敛。 最小因果主线已经很清楚：

history grows
→ user target may request a reversible fold
→ provider outcome decides actual fit
→ canonical history is never rejected or mutated by an estimate

但“provider decides”尚未覆盖 provider 沉默的情况：PR 自己的 Ollama 实测已经显示跨 turn usage plateau / silent truncation，而当前 dropping note 只检查同 turn 的 step ≥ 1。建议把无 usage、无法分类以及 silent eviction 明确定义成可见的 degraded mode；否则“未声明 window 时系统提供什么保证”仍是开放语义。

另外，includeUsage ?? true 现在会给所有 OpenAI-compatible Chat server 发送 stream_options.include_usage。现有 conformance test 只覆盖支持该字段的 fake server；最好再补一个严格 relay 拒绝该字段时的契约测试，明确 fail、fallback 或 opt-out 行为。

CI 当前是绿的，diff check 也干净；上面第 1 项是基于最新 main 的当前 merge blocker，第 2 项是静态可达的 provider-boundary bug。修完这些，我认为核心 runtime 改动可以继续推进。

[Joob1n]

Thanks — the first three are real and are fixed in 6c5e53ddd / ba14a706c; the fourth is done in the PR body.

1. Epoch.main moved again while this was open (#4321 → 99, #4508 → 100), so the rebase now lands this PR's bump as 100 → 101; comment, CHANGELOG and the epoch check follow. The protocol tests assert against the exported constant, not a literal, so nothing else pins the number.

2. Repair-path ContextLength. Confirmed: the repair catch wrapped every failure under the initial defect, so a context-length rejection of the longer repair prompt never reached the planner as input_too_large. The catch now classifies before wrapping; regression test "a context-length rejection of the repair request stays the input_too_large signal" (initial malformed → repair rejected → input_too_large, two provider calls) fails on the previous commit.

3. Docs. Both llm-compaction-events-log-projection-draft documents now state the implemented trigger: previous accepted inputTokens + outputTokensplus the reply reserve (the model's declared maxOutputTokens, zero when unknown) reaching the declared window.

4. Issue closure. Changed to Refs #4559; the issue closes when #4574/#4575/#4576 have all landed and the remaining proposal items are triaged there.

On the two broader points:

• Degraded modes (no usage, unclassified rejection, cross-turn plateau). Agreed that these deserve names. They are deliberately outside this PR: the dropping note is scoped to a single send because within one send Maka knows it only appended, while across turns the user may have edited or branched and a lower inputTokens is legitimate. Opened context: define the degraded modes when the provider does not speak (no usage, unclassified rejection, silent eviction) #4623 with the three modes, the signal each one gives today, and the two small follow-ups: PR D applies the same dropping rule at the turn boundary (first request's inputTokens below the persisted anchor with no fold or prune before the send → note), PR E adds "compact and retry" on an unclassified provider error. Both are notes/actions on top of this PR's paths, so they can land right after it without reopening it.

• stream_options on strict relays. Decided and pinned in 6ce7d7332: a relay that rejects the field fails with the provider's own 400 text and the runtime does not resend without it — the conformance test asserts one request, the stream_options body field, and the provider message reaching the stream's error part. Rationale: a connection that cannot report usage has no context baseline, so a silent fallback would hide exactly the degraded mode above; the error names the field, and a per-adapter includeUsage: false is the one-line opt-out if a real relay needs it. The field has been part of the Chat Completions API since 2024-05 and the Kimi OpenAI path in this repo has sent it since feat(runtime): support Kimi OpenAI protocol #1462.

[Joob1n]

Rebased on main@b1ec28989. main took epoch 101 in the meantime (#4608), so this PR's bump is now 101 → 102; comment, CHANGELOG and the epoch check follow. The strict-relay contract test is e10dd49a4's head commit (was 6ce7d7332 before the rebase). No other changes.

[likun666661]

复查了最新 head e10dd49a4。上一轮的主要项都已正确落地：epoch 102 对应 merge base 101；repair-path ContextLength 保留为 input_too_large 且有回归；两份文档的 trigger 公式已更新；PR body 改成了 Refs #4559；strict relay 的一次 400 / 不静默重试契约也已固定。CI 当前是绿的，PR 可干净合并。

还有两个行为/scope 问题和一个文档漂移需要收口：

1. [P1] #4559 仍会被 closing keyword 关闭。 PR body 虽然已经改成 Refs #4559，但首个 commit 20f01b862 的 message body 仍然包含 Closes #4559。本仓库只允许 squash merge，并配置为 squash_merge_commit_message: COMMIT_MESSAGES；因此这个 closing keyword 会进入 default-branch 的 squash commit，仍会关闭 issue。既然约定是整个 #4574/#4575/#4576 系列落地并完成剩余 triage 后再关闭，请把该 commit message amend 为 Refs #4559（或确保最终 squash message 中完全没有 closing keyword），而不只是修改 PR body。

2. [P2] provider-dropping 实现检测的是“严格下降”，对外契约写的是“没有增长”。packages/runtime/src/ai-sdk-backend.ts:2170-2182 当前条件是：

   stepUsage.inputTokens<lastStepInputTokens

   但 PR summary、commit message、CLI/UI copy 和新开的 #4623 都把信号定义为 usage “did not grow / stops growing or drops”。本 PR 自己的 Ollama 证据正是输入在 3,716 持平 plateau；严格 < 不会对这个案例写 note。当前测试也只有 100 → 50 的 decrease，没有 equal-usage case。

   如果 observable contract 确实是“append-only request 的 input 没增长”，这里应使用 <= 并补一个 equal-usage regression。#4623 的 PR D 也不应只定义成 “below persisted anchor”，否则同一个跨-turn plateau 仍不会被检测。若等值被刻意排除，则应反过来收窄 PR、copy 和 #4623 的声明，并说明为什么 plateau 不是可靠信号；现在代码和承诺二者只能有一个成立。

3. [P3] 中文架构文档仍有两处旧的 size-policy 语义。docs/architecture/llm-compaction-events-log-projection-draft.zh-CN.md:88-93 的公式仍写 current context budget，而英文已改成 user-declared capacity and provider outcome；同文档 :121-130 仍把 checkpoint 的必要问题写成“它在当前 token policy 下仍然能否进入 prompt？”，英文已改为 source/provider-state identity。后文已经明确删除 replay size verdict，因此这两处应与英文及最终实现同步。

除了以上三项，上一轮要求的修复我没有再发现回归。前两项处理后，我认为这轮可以进入 approve。

[Joob1n]

All three are fixed on 2cbc332af.

1. Closing keyword in the commit body. You are right that the PR body is not where this is decided under squash merge with COMMIT_MESSAGES. 20f01b862 is reworded to Refs #4559 (now 3ed669070 after the rebase); no commit on the branch carries a closing keyword any more.

2. < vs <=. Fixed to <=, with the copy as the authority rather than the other way round. Your reading of the evidence is the right one: the live Ollama run plateaus at 3,716 input tokens and never drops, so the strict comparison would have missed the exact case the PR cites. An equal input count after an append-only step (no fold, no prune, no image omission) is already impossible without provider-side eviction or rewriting, so equality is signal, not noise. New regression "records provider context dropping when an append-only step reports the same usage" (100 → 100 across the step) fails on the previous commit; the existing decrease and prune-explains-it tests still pass.

#4623 is updated to match: PR D's rule is "at or below the persisted anchor", not "below", for the same reason.

3. Chinese document drift. Both passages are synced with the English text: the materialization inputs now read 用户声明的 capacity 与 provider 结果, and the checkpoint's replay question is source/provider-state identity rather than the retired token policy.

One note on scope: both documents still ask "which high-water decision produced it" in that same list. It is stale in both languages equally, so I left it rather than widening this PR's document diff; say the word and I will fold it in here, otherwise it goes with the #4623 documentation pass.

[me2seeks]

Reviewing with real edge cases in mind, grounded in production data from a kimi-coding-plan/k3-256k workspace (see also #4634 — this PR fixes its root causes 1 and 2; items 3 and 4 there remain open).

Overall the direction is sound: every trigger is now a provider-reported number, and I live-verified the new summarizer request shape against k3-256k (details inline on the summarizer change). My concerns are about the paths where the provider never speaks: silent over-window acceptance, output-limit cuts caused by our own maxOutputTokens, and unrecognized error shapes.

[me2seeks]

Real edge case from live data: kimi-coding-plan/k3-256k accepts requests beyond its fetched window without rejecting or truncating — observed a session accepted at 322K input tokens against a fetched contextWindow of 262,144, with usage still growing monotonically (305K → 322K). On such a provider every signal this design reads stays dark for an undeclared window:

• no rejection → reactive fold never fires;
• usage never plateaus → context_provider_dropping never fires (and it is mid-turn only anyway);
• context_window_suggestion only fires on a surfaced rejection → never written;
• a fetched /models window is not a declaration → the proactive trigger below never arms.

Net effect: an undeclared kimi session degrades silently and indefinitely (this is exactly the data behind #4634). I agree with "Maka does not decide for the user" as a principle, but for providers observed to accept over-window requests, could the fetched window seed a default declaration (user-overridable), or should the cross-turn plateau check (#4623 PR D) be a blocker rather than a follow-up?

[me2seeks]

pendingLengthFold is set on anylength finish with no size or cause guard. Two real cases where the fold is useless or harmful:

1. The cut came from our own configured maxOutputTokens, not the window: maka sends maxOutputTokens: 131072 on kimi-coding-plan main requests (from lookupModelMetadata). A reply cut at that cap is not helped by folding history at all — the next request carries the same cap. If the model keeps wanting more output (long reasoning at effort=max, large file generation), this turn folds every step, repeatedly shrinking history while never addressing the constraint.
2. A user who declares a small output limit for cost control gets routine length finishes → folds at a few K tokens of context, paying a summarizer call each time.

Suggest gating the length fold on baseline + replyReserve >= capacity (i.e. plausibly window-caused), or capping length-folds per turn.

[me2seeks]

For k3-256k, declaredModelOutputLimit resolves to 131,072 from bundled metadata — half of its 262,144 window. A user who pins the full window gets proactive folding at baseline >= 131,072, i.e. ~50% utilization, which is far earlier than "stay under your declared window" suggests. Reserving the output limit is right in principle (without it a real-size declaration is never crossed), but when the declared output limit is a large fraction of the window the reserve dominates. Consider capping it, e.g. min(outputLimit, capacity / 4) or a fixed bound.

[me2seeks]

The per-send latch and the fingerprint circuit still only cover malformed-summary reasons. After a provider_error / output_length fail-open, baselineTokens stays set, so overWindow remains true and every subsequent step retries the summarizer. Observed live on kimi-coding-plan (which reports failures as HTTP 200 + error body): 15 consecutive failed summarizer calls over ~47 minutes, each 30–45 s, before the main request. Suggest latching any summarizer failure for the rest of the send, with the same fail-open diagnostic. (#4634 item 3)

[me2seeks]

Defaulting includeUsage on for every non-opted-out OpenAI-compatible server is the right call for usage coverage, but a strict relay/proxy that rejects unknown fields (older vLLM, some gateways) will 400 every streaming request after upgrade, and opting out requires a registry code change. Consider a one-time fallback: on a 400 whose error text mentions stream_options/include_usage, retry without it and remember that for the connection.

[me2seeks]

Two false-positive paths for the dropping note:

1. Finalization steps remove all tool schemas (resolveDispatch returns [] for the child-summary / sandbox-boundary finalization step), which legitimately drops the next request's input by several K tokens with no fold/prune/image-omit — this condition doesn't exclude that case, so a routine turn end can report "provider is dropping context".
2. No hysteresis: a 1-token decrease fires the note. Cache accounting or tokenizer drift between calls can produce tiny legitimate decreases. A small relative threshold (e.g. drop > 1–2% or > N tokens) would keep the note meaningful.

[me2seeks]

Confirming this fixes the kimi-coding-plan failure mode from #4634 — I live-tested this exact request shape (system template + trailing user instruction) against k3-256k on both wires: it now returns a fully compliant sectioned summary, where the system-prompt-only shape returned content: null (7 tokens) or continued the conversation as the assistant.

One follow-up worth noting (not blocking): the summarizer request still opens with a different system prompt than the main loop, so it shares no prefix cache with it — the first fold of a session pays a full uncached pass over the folded span (observed 39–88 s on 155–253K inputs). Moving the whole instruction into the trailing user message would let the summarizer reuse the main loop's cached prefix (~99% hits); keeping the template in system is also fine if that's load-bearing for other providers, but the cache cost is real at high context.

[Joob1n]

Thank you for the production data. Every path you named is real, and four of them are fixed on 1faabac55. The evidence for each is your k3-256k workspace, so I have quoted your numbers in the commit message rather than restating them here.

Summarizer retry storm (#4634 item 3). Fixed. The per-send latch recorded only malformed reasons, and the baseline that fired the trigger survives a fail-open, so a provider_error re-armed the same condition on every later step. Every fail-open reason now latches for the rest of the send. Regression: "bounds a provider-error summarizer failure across later steps in the same turn" (one summarizer call, failOpenReason: provider_error, no checkpoint), failing on the previous commit.

pendingLengthFold with no cause guard. Fixed, and your first case is the discriminator: the reply's own outputTokens says which limit cut it. A reply that stopped at the maxOutputTokens Maka sends was cut by Maka's budget, and the next request carries the same budget, so the fold is marked only when the reply stopped below it. That covers your cost-control case too, since a small declared output limit is reached exactly. No new constant, and both numbers are provider-reported. Regression: "does not fold when the reply was cut by the output budget Maka itself sends".

Dropping-note false positives. The finalization case is fixed: the note is suppressed when the step's own active tool set shrank, which is Maka reshaping the request rather than the provider evicting anything. Regression: "does not report provider dropping when the step dropped its tool schemas". On hysteresis I would rather not add a threshold, and I think the <= change (this PR now treats a plateau as the signal, per @likun666661's review) makes the case: after an append-only step, an input count that merely failed to grow already means the appended content was not counted, so a one-token decrease is not a weaker signal than equality but a marginally stronger one. normalizeAiSdkUsage sums no-cache, cache-read and cache-write, so cache accounting does not move the total. If you have a case where drift moves it anyway, that is worth a threshold and I will add one.

stream_options on strict relays. Adopted your suggestion over my earlier position, which @likun666661 also questioned: the deciding argument is that opting out needs a registry code change, so a strict relay has no user-facing recovery. A 400 whose body names the field now triggers one retry without it, remembered per base URL for the process. The connection then simply reports no usage, which the composer indicator (#4576) shows as a dash. Contract test asserts the three requests: asked, retried without, and never asked again.

Providers that accept beyond their fetched window. This one I have not changed, and I want to be explicit about why, because you are right that every signal stays dark. A cross-turn plateau check (PR D on #4623) does not rescue it either: your session's usage grows monotonically to 322K, so there is no plateau to detect. The only thing that arms anything is a declaration. Two options I can see:

1. A note when accepted usage exceeds the model's reported window while nothing is declared. That is two real numbers and no decision on the user's behalf, and it is the same shape as the existing context_window_suggestion. It fits this design and I would be glad to add it, here or as PR D's sibling.
2. Seeding a default declaration from the fetched window, which is the thing Context budget: stop estimating fit; the provider decides, the Maka window is a user target #4559 deliberately removed: a fetched number is a hint, and a session that compacts because of a number the user never chose is the failure this PR exists to end.

My preference is 1. Say which you would rather review and I will follow.

Prefix cache on the summarizer request. Noted as a follow-up, not forgotten: your 39–88 s uncached first attempts are a strong argument for moving the whole instruction into the trailing user message now that the trailing message exists. I have left the system template in place here because it is load-bearing for the providers the current tests cover, and changing both the shape and the cache behaviour in the same PR would make the k3-256k regression hard to attribute. It belongs on #4634.

Thanks also for live-testing the summarizer request shape; that is the part of this PR I could only verify against Ollama and fake providers.

[Joob1n]

Follow-up on the two open items from your review, both now on 77590471e.

The reply reserve is no longer the model's output limit. Your k3-256k arithmetic was the deciding case: reserving 131,072 against a 262,144 declaration folds at half the window a user deliberately chose. It is now twice the last reply the model actually wrote, bounded at 8,000 tokens. Both halves are provider-reported, the margin tracks the session's own behaviour rather than a catalog maximum, and no previous reply means no reserve at all. On your numbers a session answering in 2–3K tokens now folds at roughly 256K of 262K instead of 131K. The old test that asserted the output limit is rewritten around the new rule (a 900-token anchor with a 60-token reply folds against a 1,000 window, the same anchor with a 5-token reply does not, and the model's 600-token output limit is irrelevant to both).

A reserve measured from a smaller previous reply can still be too small, so that case is now reported rather than silent: when an accepted request's own input plus its reply exceed the declared window, the transcript carries one context_window_overrun note per send with both numbers. It is the honest reading of "the reply needed more room than was left", it uses only provider-reported numbers, and it tells a user who wants whole replies to raise the declaration. The next request folds anyway because the baseline now exceeds the window; the note explains why rather than changing what happens.

That makes three note kinds in this PR, all in the same epoch move (now 103 → 104 after the latest rebase).

Still yours to choose: the undeclared-window case on a provider that accepts past its reported window. My preference remains a note when accepted usage exceeds the model's reported window while nothing is declared, rather than seeding a declaration from a fetched number. Say which you would rather review.

[Joob1n]

Added, on 0d0a32dce: with nothing declared, a request the provider accepts past the window its own catalog entry reports now writes one context_reported_window_exceeded note per send, naming what the exchange used and what the model reports. It changes nothing on its own — a reported window stays a hint, and Maka still declares nothing on the user's behalf — but the case you found is no longer invisible. With a declaration in place the overrun note already owns that ground, and a test pins that the two never fire for the same fact.

That is the fourth note kind in this PR, all within the same epoch move (103 → 104 after the latest rebase). Local gates are green; the mid-turn suite is 73/73.

[me2seeks]

Thanks — verified 1faabac55 and 77590471e on the diff. The cutByOwnBudget discriminator is a better fix than the proximity gate I suggested: it distinguishes the two length causes with two provider-reported numbers, and my cost-control case falls out of it for free. The behaviour-measured reply reserve (2× last reply, ≤8K) fixes the k3-256k half-window arithmetic, and context_window_overrun is the right honest reporting for a reply that outgrew a reserve measured from smaller ones.

Undeclared window on a provider that accepts past its reported window: I choose option 1 — a note when accepted usage exceeds the model's reported window while nothing is declared. Two reasons beyond the ones you gave:

1. Coverage differs by surface. TUI has a real-time ctx indicator (I have a PR open adding one, with colour) so a TUI user can transiently see 322K > 262K; Desktop has nothing. A persisted note in the transcript is the only durable signal on Desktop, and the only one that survives the moment on TUI.
2. The note closes the loop with feat(desktop): show the model's reported context window beside the declared setting #4575. The number it should name is the reported window the user could adopt, and the natural call to action is the settings surface with the one-click apply from feat(desktop): show the model's reported context window beside the declared setting #4575.

One constraint from the k3-256k data: on such providers usage crosses the reported window gradually and keeps growing (305K → 322K), so the note should fire once per session when the crossing is first observed (the accepted total first exceeds the reported window), not per send — otherwise it spams on every step past the line.

On hysteresis for the dropping note: your <= argument and the normalizeAiSdkUsage sum hold; I have no live case where drift moves the total, so I withdraw that suggestion.

I will take the summarizer prefix-cache item back to #4634 as agreed.

[Joob1n]

Adopted the once-per-crossing constraint on 8c88243ca. The note now fires on the transition rather than per send: the previous accepted total was still inside the reported window and this one is not. That previous total comes from the persisted anchor, so a resumed session does not repeat a crossing it already reported, and a session that is already past the line stays quiet. Test "does not repeat the reported-window note once the session is already past the line" (a 320-token anchor against a reported 100) fails without the guard.

Your two reasons are both in the code's favour: the note is the durable Desktop signal, and it names the reported window, which is the number #4575 offers to apply in one click. Noted on the withdrawn hysteresis and on taking the prefix-cache item to #4634.

[Joob1n]

Correction on the previous push: a rebase of mine stopped on a conflict and the branch was pushed mid-rebase, so 8c88243ca briefly showed this PR with 5 of its 13 commits. The head is now 1283c874c, rebased on main@148f8eb29 with all 13 commits and every local gate green. Nothing in the content changed; main also took epoch 104 in the meantime, so this PR's bump is now 104 → 105 and the comment, CHANGELOG and commit message follow.

[Joob1n]

Closing this in favour of a smaller series. Not because anything here was wrong: it is green and every review item on it is either fixed or deliberately carried forward. The reason is that the design converged past what this PR's shape can carry, and a reviewer arriving now would have to reconstruct it from four rounds of comments.

Two things changed after the last round, both simplifications, and both invalidate part of this PR rather than adding to it:

1. The compaction module runs at most once per send. The proactive and reactive folds were two independent latches here. A fold already covers everything except the live head, so a second one buys a little tail and costs the most recent verbatim context. When a request is still rejected after a fold, the honest diagnosis is that the new message itself is too large, and that is what the user should be told.
2. A finishReason: length no longer triggers a fold. A reply cut below the maxOutputTokens Maka sends can mean the provider ran out of window room, or that the provider has its own lower output cap. Those are indistinguishable from the outside, and an indistinguishable signal should not drive an action. This removes the cutByOwnBudget discriminator @me2seeks and I converged on, one level up: the discriminator was right for the question asked, but the question should not have been asked.

A third change is larger and belongs on its own review: when a fold is rejected as too large, retreat to the span the last accepted request's input covered, rather than halving the covered range. That boundary was accepted by this exact model on this exact connection, so it is provably within capacity, where halving is a guess. The last reply's own span is folded separately when it exceeds 24,000 tokens.

The full design is written up on #4559 as three modules (judge / send / compact) with the call bounds.

Where each review finding goes

Finding	Reviewer	Lands in
Trigger arithmetic needs a reply reserve	@Astro-Han	PR 1
input_too_large must have a real producer	@Astro-Han	PR 2
Eviction check must compare input against input	@Astro-Han	PR 1
Window-suggestion note timing (after recovery, not before)	@Astro-Han	PR 1
Size floor only on the initial fold, not on roll-forward	@Astro-Han	PR 2
Fold-context cleanup, CHANGELOG, CLI note kinds, epoch	@Astro-Han	PR 1
Epoch collision with main	@likun666661	PR 1
Repair request's context-length rejection swallowed as a format defect	@likun666661	PR 2
Architecture documents describing the pre-fix trigger	@likun666661	PR 1
Closing keyword in the commit body, not just the PR body	@likun666661	PR 1
Dropping note must fire on a plateau (<=), not only a decrease	@likun666661	PR 1
Summarizer retry storm: latch every failure, not only malformed ones	@me2seeks	PR 2
Reply reserve must not be the model's output limit	@me2seeks	PR 1
Dropping note false positive on tool-schema shrink	@me2seeks	PR 1
stream_options retreat for strict relays	@me2seeks	PR 1
Undeclared window on a provider that accepts past its reported window	@me2seeks	PR 1
Reported-window note once per crossing, not per send	@me2seeks	PR 1
Length-fold cause guard	@me2seeks	superseded, see 2 above
Summarizer prefix-cache cost	@me2seeks	#4634

The series

• PR 1 — send module: trigger, reply reserve, persisted anchor, one compaction per send, "this message is too large", stream-usage collection with the strict-relay retreat, and all four system notes. One epoch move.
• PR 2 — compaction module: summarizer request shape, output cap and retries, failure latch, and the retreat to the last accepted input boundary.
• feat(desktop): show the model's reported context window beside the declared setting #4575, feat(desktop): show context usage beside the model controls #4576 — unchanged, rebased onto PR 1 when it lands.
• PR 5 — "compact and retry" for a rejection the classifier does not recognise (context: define the degraded modes when the provider does not speak (no usage, unclassified rejection, silent eviction) #4623).

Thank you all for the four rounds; the findings are carried, not discarded.

[Joob1n]

The replacement is #4653: the send module, with the two simplifications described above and the same review findings carried. The compaction module's retreat boundary follows in a second PR.

[Joob1n]

Summary

The runtime no longer estimates whether a request fits a context window. Every "does it fit" question is answered by a provider; every trigger is a real number. This is the remaining step after #4486, which removed the fabricated capacity and the two terminal gates but kept the chars/4 delta estimate, the 32,000-token fallback history budget, and a per-step JSON.stringify of the whole request as a payload ruler. Design and discussion: #4559 (this PR), #4458 (history).

What decides now

• The conversation provider's own context-length rejection is recovered by one compact-and-retry; a second rejection surfaces as the provider's error (context_overflow), and the user's message stays editable.
• The summarizer's provider decides whether compaction input fits: input_too_large retreats the fold by half, and the loop exits through no_safe_completed_span when even the smallest legal span is refused.
• Proactive compaction has one trigger: the previous accepted request's real inputTokens + outputTokens, as the provider counted them, compared with the context window the user declared for the model (a model-facts pin or a relay profile). Reasoning tokens are counted whole on purpose — high is the safe direction for a trigger that can only ask for a compaction.
• A reply the provider cut at its output limit (finishReason: length) folds once before the next request.

What is gone: estimateNextRequestTokens, exceedsHighWater, midTurnRequestPayloadChars, the final-request rescue re-entry, maxHistoryEstimatedTokens and its five consumers, the quarter-window / 16,384 reserve, the 32,000 fallback, the replacement_not_smaller and prefix_over_budget replay gates, size-based replay selection, the estimated input fit before summarizer calls, and the chars/4 summary-size floor.

Notes for the user (four new system_note kinds): context_provider_dropping when an append-only step's usage did not grow (a provider evicting or rewriting context), and context_window_suggestion when a rejection lands at a proven-fit total, carrying the number the user can declare.

Refs #4559 — the issue closes when the whole series (#4574, #4575, #4576) has landed and the remaining items are triaged there.
Refs #4458, #4486

Follow-up PRs (stacked on this one)

The user-facing surfaces are deliberately split out so this PR stays the atomic runtime change and the UI pieces can be reviewed in parallel. Both are open as drafts on top of this branch and will be rebased and undrafted once this merges:

• feat(desktop): show the model's reported context window beside the declared setting #4575 — Desktop settings: the model's reported window shown beside the declared setting with a one-click apply. Without it, a user who has never declared a window gets no proactive compaction and no in-app pointer to the number they could set; the context_window_suggestion note from this PR is the runtime-side half of that pointer.
• feat(desktop): show context usage beside the model controls #4576 — Desktop composer: read-only context-usage indicator fed by the persisted lastRequestAnchor this PR introduces (percentage with a declared window, absolute tokens without one, a dash when the provider reports no usage).

Not in this series, defined and tracked on #4623 (the degraded modes when the provider does not speak): PR D applies the provider-dropping rule at the turn boundary, PR E adds a "compact and retry" action for provider rejections the error classifier does not recognise. Neither reopens a path this PR touches.

Behaviour changes to review

1. No declared window means no proactive compaction. The first time such a session fills up costs one provider round trip and possibly one cut reply; the context_window_suggestion note then offers the last accepted total as the value to declare. This is the "Maka does not decide for the user" principle; the trade-off is stated in Context budget: stop estimating fit; the provider decides, the Maka window is a user target #4559.
2. A /models report or models.dev metadata is no longer a threshold on its own.resolveDeclaredContextWindow (runtime) and declaredContextWindow (core, single owner of the rule) count only a facts pin or a relay profile. resolveSelectedModelContextWindow keeps its old meaning for display and contextRemaining.
3. token_usage.lastRequestAnchor is now { inputTokens, outputTokens? }. The retired payloadChars key still decodes, so sessions written by 0.2.0 keep loading; sessions written by this build do not open in 0.2.0 (the closed-allowlist cost already noted in CHANGELOG.md).
4. Summaries are capped at 8,000 output tokens (DEFAULT_HISTORY_COMPACT_MAX_OUTPUT_TOKENS; the summarizer's maxOutputTokens option was declared and never passed). A length finish gets one shorter retry, then fails open. The too-small-for-fold floor reads the summarizer call's real usage; a producer that reports none is not floored.
5. Checkpoint replay is structural: a source-matched checkpoint replays as [block, everything after the boundary]. No local size gate stands between a materializable fold and dispatch.
6. ContextBudgetDiagnostic.maxHistoryEstimatedTokens is retired (decode-only). HistoryCompactionPolicy.midTurn loses reserveTokens. buildDefaultContextBudgetPolicy drops its connection parameter.
7. Every OpenAI-compatible Chat request now asks for stream usage (stream_options.include_usage), unless the registry opts a provider out. Found live: only two providers opted in, so a local Ollama and every plain OpenAI-compatible relay — the connection type behind Context budget: an undeclared window fabricates a capacity that kills live turns #4458 — returned no usage, and the baseline, the eviction check and the indicator all stayed dark for them.
8. Summary requests close with a user instruction. Found live: a chat-template model handed a conversation ending on its own turn emits end-of-sequence and nothing else (Ollama qwen2.5, both sizes: finish stop, one output token, empty text), so history compaction never succeeded against a local model. Existing message-shape tests gained the trailing user:text.
9. The trigger reserves the model's declared output limit and fires on >= (review). baseline + outputLimit >= declaredWindow, where the limit is connection.models[].maxOutputTokens or generated metadata — a provider fact — and 0 when none is declared. Without it a window declared at the provider's real size could never be crossed by an accepted request. The window itself remains the user's declaration (see the reply on the review for why the metadata window stays a hint).
10. A context-length rejection from the summarizer's provider is input_too_large again (review), so the planner's retreat-by-half has a producer; the same classification is applied to the Codex compaction call.
11. The window suggestion note is written only when the turn surfaces the rejection (review): after the one fold is spent or when there is no seam, naming the last accepted total, which a fold does not clear.
12. The size floor judges an initial fold only (review): on a roll-forward the summarizer's input is the increment, not the covered span, so the floor stands down there and the fold context carries usage only. The eviction check compares input against input, since reasoning is not resent on every wire.

On dropping the signed delta

#4486 kept a signed chars/4 delta so step 0 could fold before a large new message or image went out. I dropped it: the delta prices an image at a constant and under-reads CJK by about half, so the round trip it saves is the one it is most likely to misjudge; large text results are already capped by the byte-based tool-result archive before they go out; and removing it takes the whole payload ruler and the per-step JSON.stringify(messages) with it. Happy to be argued back.

Test coverage removed

Thirty-seven tests encoded the estimate, the reserve, the payload ruler, the fit gates, or the pre-turn estimate gate; each is either re-pointed at a real-usage observable or removed with the mechanism. Re-pointed: the usage baseline is the last request's INPUT tokens → input plus output; compacts over the high water → compacts after provider usage crosses the declared window; keeps user_stop when stopping an oversized pre-turn summary → keeps user_stop when stopping while a usage-triggered fold is summarizing; persists the LAST request as the anchor → persists the last request input and output as the anchor; replays a durable pre_turn checkpoint below the current high water → without a local size gate; rejects a paragraph-sized summary for a large folded span → when usage says it is too small. Removed outright (the mechanism is gone): the three manual compactHistory … exceeds current limits / makes the full replay larger cases, the three reserve-derivation cases, anchors on real provider usage plus a tail char/4 delta, credits a SIGNED negative payload delta, falls back to whole-projection char/4 on cold start, high-water crosses at contextWindow minus reserve, a fold that cannot shrink the real payload is refused, a runaway summary is rejected as replacement_not_smaller, bounds the oldest oversized tool result before dispatch, fails with input_too_large before dispatch, charges the summarization instructions against the input budget, a summary at exactly the floor is accepted under ceil-based token estimates, the capacity verdict measures the steering payload, the anchor a finalization step writes excludes the tool schemas it cleared, dispatches a pre-turn Compaction recipe without projecting history and keeps a transiently unavailable automatic Compaction checkpoint recoverable (both exercised the deleted pre-turn gate; memory extraction from a hook-triggered fold stays covered), applies max-history overrides to checkpoint replay validation, accepts a complete checkpoint above legacy block limits when the full replay fits, compacts one oversized prior turn before an unknown-model request, compacts an oversized latest turn when an older turn is also retained, dispatches an oversized prior turn when its summary fails, after trying once, never runs a pointless summarizer on a small-window model, a usage object without usable input tokens falls back to cold start, a last-request anchor is only valid as a complete positive pair, a half-written anchor fails the whole token_usage message decode (replaced by the new-shape and retired-key cases).

New coverage: the declared-window rule for pin / relay / reported / metadata sources; baseline = input + output, > not >=, cleared after a fold, seeded from the previous turn, discarded across a model switch; a /models window is not a declaration; pendingLengthFold; the summarizer output cap, shorten retry, and output_length after two cuts; usage-based size floor; retreat by half and its give-up exit; structural replay; both notes, including the non-firing cases (pruned step, step 0, declaration already crossed); the retired payloadChars key decodes and an unknown key still fails.

Live verification against a real provider (Ollama)

Driven through the real AiSdkBackend with getAIModel against a local Ollama (qwen2.5:0.5b / qwen2.5:1.5b, default num_ctx 4096), five turns of ~740 tokens each, the previous turn's ledger and run header fed back as prior context.

Scenario	Observed
Declared window 1,500, qwen2.5:1.5b	Turns 1–3: anchors {745,10}, {1481,10}, {2217,10} persisted; baseline 1,491 at turn 3 is < 1,500, no fold. Turn 4: baseline 2,227 > 1,500 → pre_turn fold; summary malformed twice → failedOpen[malformed_summary_missing_section], request dispatched, end_turn. Turn 5: fold again, repair produces a 1,737-char checkpoint → replaced; the request's provider-counted input drops 2,954 → 1,222.
Same, before the two fixes above	No token_usage event at all (Ollama returned no usage because it was never asked); once usage flowed, the summarizer returned empty text every time. Both fixed in this PR.
No declared window, 8 turns	Never folds, never terminates; every turn end_turn. Usage grows 745 → 3,700 and then plateaus at 3,716 for turns 6–8 while ~740 tokens are appended per turn: Ollama truncates silently at num_ctx with no error.

Known limitation, stated plainly: the silent-truncation plateau above happens between turns, and context_provider_dropping only fires within a turn (step ≥ 1, on an input count that did not grow), because at step 0 a user edit can shrink the input legitimately. A provider that truncates instead of rejecting therefore gives an undeclared-window user no signal today; declaring the window is the protection. Detecting the cross-turn plateau without an estimate needs a ledger-shape check on the anchor (did anything before the anchored request change?) — a follow-up, tracked on #4559. Closing that gap is PR D on #4623.

Verification

Rebased on main@148f8eb29 (after #4578 landed, so this PR no longer carries the dependency bump); the Runtime Host compatibility epoch moves 104 → 105 for the two new note kinds and the reshaped anchor. Locally: npm --workspace @maka/{core,storage,runtime,runtime-host,mcp,ui} run build, npm run typecheck (all workspaces), npm run lint, npm run format:check, npm run check:asf-headers, node scripts/protocol-epoch-check.mjs --base origin/main — all clean. Targeted suites: 425/425 across usage-record-last-request-anchor, context-budget-mid-turn-policy, context-budget-model-facts, history-compaction, history-compact-checkpoint, history-compact-summarizer, mid-turn-capacity-backend, overflow-reactive-recovery, ai-sdk-backend; core suite 760/760; provider-conformance 24/24, history-compact-summarizer 53/53, execution-model-composition 28/28 and the CLI pi-transcript suites after the review fixes. Not run locally: the full npm test matrix (the Electron/OpenSSL and owned-Host timing cases fail on this machine independently of the branch) — relying on CI for those.

Self-review

• The core rule declaredContextWindow was implemented twice (runtime and chat-model-choice) in an earlier draft; consolidated into @maka/core/model-thinking with runtime delegating. One owner for the one rule the design turns on.
• The user-stop-during-summary obligation had lost its test when the pre-turn gate went; re-pointed at the hook-triggered fold. The test also records that one request is still attempted after the stop and is rejected by the transport on its already-aborted signal — pre-existing behaviour, now pinned.
• An earlier draft regenerated the Astryx theme with a stale local @astryxdesign/core@0.5.0; that artifact is not in this PR.
• memory-extraction.ts and session-recap.ts keep their own bounded-request budgets; they are auxiliary calls, not history compaction, and are out of scope here.
• Diagnostics (estimatedTokensBefore/After on compaction decisions) still use the chars/4 estimator. They are recorded numbers, not decisions, and are kept so existing telemetry consumers do not break.

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Claude Code — design discussion, implementation, tests, and review; verified by the author.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No

https://claude.ai/code/session_014ajaRxC4jydavY9nYUFj5J

[Astro-Han]

The direction is the one from #4458 and I still hold it: fit is the provider's answer, the trigger is a real number, and the only irreversible outcome is the provider's rejection. The reduction is real, every symbol in "What is gone" is gone from docs and desktop too, and all six workspace suites, typecheck, lint and format pass locally on 372c1de9, and the three commits since (148326eb) touch none of the files cited below. What stops me approving is not the code, it is three places where the design as implemented does not do what the design says. Line-level fixes are inline.

The proactive trigger cannot fire against a correctly declared window. The trigger is baseline > declaredWindow, and the baseline is a request the provider accepted. If the user declares the provider's real window, no accepted request can exceed it, the fold never runs, and every session goes through rejection first. It fires only when the user declares something smaller, which is the retired reserve reintroduced as a number the user has to guess without being told. This is open point 2 of #4559, and I would settle it the other way: resolve the window as declared > relay profile > models.dev > /models, none only when all are absent; trigger on baseline > window − reserve; make the reserve a real number, the model's output limit plus the tool-result archive cap times pending tool calls, with a fraction of the window as the floor. Those are provider facts and Maka's own content policy, so the "real numbers only" principle holds. A default is not Maka deciding for the user, it is a default the user can override, and the alternative is that out of the box every fill costs a rejection and possibly a cut reply, which CLI users get without even the hint, because pi-transcript.ts drops the two new note kinds. The per-step check already gives mid-turn triggering; only the window and the threshold change.

The summarizer's provider does not get to decide. The design names four deciders, and one of them, "the summarizer's provider decides whether compaction input fits, input_too_large retreats the fold by half", has no producer. Only fitHistoryCompactMessages throws input_too_large, this PR removes that call from history-compact-summarizer.ts and openai-codex-history-compactor.ts, and both catches wrap every provider error as provider_error. So a session whose fold prefix is too large for the summarizer fails open on the first rejection, /compact included, and has no in-app way back under the window. That is worse than main, which at least estimated. The fix is small, classify ContextLength in both catches, but the regression must use a fake provider that rejects above N tokens; all five current input_too_large tests throw the error from a fixture, which is why this was invisible.

The compatibility contract. Two new system_note kinds and the new lastRequestAnchor shape land in packages/core closed allowlists, the same class of change #4486 bumped the epoch for, and the epoch is unchanged. A merge-base client handshakes fine (host-kernel.ts admits on strict equality) and fails decodeStoredMessage on the first transcript carrying a new note. main is on 96 now: rebase, take 97, and put back the three CHANGELOG sentences from #4486 that are still true (see inline).

One consequence of the first point that lives outside the diff: settings-provider-copy.ts still says "when empty, built-in metadata decides", and /context and the inspector still divide by resolveSelectedModelContextWindow, so an undeclared user sees 70% of 200k and never gets a fold. Whichever way the window question settles, the copy and the denominator have to follow the same rule.

On the test claim: five re-pointed tests pass unchanged on main's built sources (the no-size-gate replay, the two size-floor cases, the no-usage case, fails open after repeated input-too-large retreat), and two rules lost their only coverage with the deletions while still existing, the memory gate's unavailable outcome and the rule that a synthetic /compact usage row must not shadow the real anchor. The remaining persisted-anchor test uses an anchor below the window, so it passes regardless of the run-header check.

Evidence boundary: static read against main61224f51; all suites run locally; new tests also run against main's built sources in a scratch copy; no live provider.

AI-assisted review: drafted with Maka; I verified the trigger arithmetic, the input_too_large producers, the epoch state and the size-floor inputs myself.

简体中文

方向就是 #4458 上讨论定下的，我仍然支持：放不放得下由 provider 回答，压缩触发用真实数字，唯一不可逆的结果是 provider 的拒绝。删得也干净，「What is gone」里的每个符号在 docs 和 desktop 里都没有残留，本地六个 workspace 的测试、typecheck、lint、format 全绿；之后的三个提交（148326eb）没有碰到下面引用的任何文件。让我暂时不 approve 的不是代码本身，而是三处实现和设计说的不是一回事。能局部修的都放在行内评论里。

主动触发对着正确声明的窗口永远打不响。 触发条件是「上次请求的 input+output 大于声明窗口」，而上次请求是 provider 已经接受的。如果用户把窗口声明成 provider 的真实大小，任何被接受的请求都不可能超过它，主动压缩一次也不会触发，每个会话都要先撞一次拒绝。只有用户把窗口声明得比真实值小它才触发，这等于把删掉的 reserve 变成了一个要用户自己猜、又不告诉他的数字。这是 #4559 的 open point 2，我的意见相反：窗口按「用户声明 > relay profile > models.dev 元数据 > /models 报告」解析，全都没有才算无；触发条件改成「上次用量 > 窗口 − reserve」；reserve 用真实数字：模型的 output limit（下一步回复最多这么大）加上工具结果归档上限乘以待处理的工具调用数，再用窗口的固定比例兜底。这些都是 provider 的事实和 Maka 自己的内容策略，「只用真实数字」的原则不受影响。给一个默认值不是替用户决定，用户随时可以覆盖；不给的后果是开箱用户每次填满都要付一次拒绝、可能还拿到被截断的回复，CLI 用户连提示都看不到，因为 pi-transcript.ts 把两个新 note kind 丢掉了。turn 内每一步都检查的逻辑已经有了，只需要改窗口和阈值。

summarizer 的 provider 并没有拿到决定权。 设计列了四个决定者，其中「summarizer 的 provider 决定压缩输入放不放得下，input_too_large 就把范围退半」这一条没有产生者。全仓只有 fitHistoryCompactMessages 会抛 input_too_large，本 PR 把它从 history-compact-summarizer.ts 和 openai-codex-history-compactor.ts 里删掉了，两处的 catch 又把所有 provider 错误一律包成 provider_error。于是一个长会话的折叠前缀如果对 summarizer 也太大，第一次拒绝就整体放弃，/compact 走同一条路也一样，会话在 app 内没有回到窗口内的办法，比 main 还差，main 至少还估算一下。修法很小，两个 catch 里判断 ContextLength 再抛，但回归测试必须用「输入超过 N tokens 就拒绝」的假 provider；现在五个相关测试全是 fixture 手抛这个错误，所以这个洞看不见。

兼容契约。 两个新的 system_note kind 和新的 lastRequestAnchor 形状都进了 packages/core 的闭合 allowlist，和 #4486 推 epoch 的那次是同一类改动，但 epoch 没动。merge-base 上的旧 client 握手能通过（host-kernel.ts 按严格相等准入），然后在第一条带新 note 的 transcript 上解码失败。main 现在已经是 96：rebase 取 97，并把 #4486 写的、仍然成立的三句 CHANGELOG 加回来（见行内）。

第一点在 diff 之外的一个后果：settings-provider-copy.ts 的帮助文案「留空跟随内置元数据」现在不成立，/context 和 inspector 的分母也还是 resolveSelectedModelContextWindow，未声明的用户会看到「已用 70% / 200k」却永远等不到压缩。窗口问题无论怎么定，文案和分母都要跟同一条规则。

关于测试的说法：五条 re-pointed 测试在 main 的构建产物上原样通过（无 size gate 的 replay、两条体量下限、无 usage、退半后 fail open）；两条规则随删测试失去了唯一覆盖但仍然存在：memory gate 返回 unavailable 的处理，以及手动 /compact 写的合成 usage 行不得遮蔽真实 anchor。剩下那条持久 anchor 测试的 anchor 低于窗口，不管 run header 合不合法都过。

[Astro-Han]

baselineTokens is a request the provider accepted, so with the window declared at the provider's real size this is never true; the fold only runs when the user declares something smaller. That is the reserve in disguise. baseline > window − reserve, with the reserve from output limit plus the tool-result cap, is what makes this fire before the rejection. First point in the main comment.

[Astro-Han]

Dead branch: nothing throws input_too_large any more. fitHistoryCompactMessages was its only producer and both summarizer catches now wrap provider errors as provider_error. Classify ContextLength with classifyError in history-compact-summarizer.ts and openai-codex-history-compactor.ts so this retreat has a producer, and test it with a fake provider that rejects above N tokens.

[Astro-Han]

Baseline includes last step's reasoning; on wires that do not resend it (gpt-5.x), next input ≈ previous input + tool call + result, which is below input + output whenever reasoning exceeded the appended content, the normal case. Compare against last step's input alone; keep input + output for the trigger.

[Astro-Han]

Written before recoverFromOverflowError runs, so a send that overflows once, folds and completes still tells the user the provider refused. #4559 places this under "already folded". Move it after the recovery verdict; overflow-reactive-recovery.test.ts:1834 (tool, overflow, done) currently pins the wrong order. And suggestedContextWindow: baselineTokens sits on the strict > boundary, so a user who applies it still needs one more rejection.

[Astro-Han]

On a roll-forward the summarizer is sent previous summary + new events, so inputTokens is the increment while the checkpoint replaces the whole covered span; in steady state this floor never trips and a fifty-token summary after a small increment is persisted. The new test passes on main because the stub's usage is unrelated to the messages. Feed it a span-sized real number (previous checkpoint's compactCallInputTokens plus this increment) or drop the floor openly.

[Astro-Han]

The comment above says this re-runs the size floor, but no summarizerUsage is passed so the floor is skipped, and coveredRuntimeEvents is now required and unread by the validator. Same for the external-producer branch in history-compaction.ts. Either pass a real number or delete the field, the three constructions and the comment.

[Astro-Han]

Three sentences from #4486 were dropped and are still true: sessions from this build do not open in earlier releases and the runtime.sqlite copy must be taken before upgrading; context_budget_exhausted is no longer produced but still decodes; the epoch line (97 after rebase). The body says the allowlist cost is "already noted in CHANGELOG.md", and it no longer is.

[Joob1n]

Thanks for the read — every finding was real. Fixes are in 38b2d837 (one commit, each item with a test that fails on the previous commit), plus two live-provider findings in the commits before it.

Trigger arithmetic. You are right that baseline > declaredWindow could never fire against a window declared at the provider's real size. Fixed the way you suggested for the reserve, with one narrowing: the reserve is the model's declared output limit only (connection.models[].maxOutputTokens or generated metadata; 0 when none is declared), and the trigger is baseline + limit >= window. I did not add the tool-result cap × pending calls term: the active prune already bounds each result before it goes out, and a second constant on the trigger side is the kind of number the design is trying not to own. Live on Ollama (qwen2.5:1.5b, declared 1,500) the fold now fires at 2,227 with the previous usage as the only input, folds to a 1,737-char checkpoint after one repair, and the next request's provider-counted input drops 2,954 → 1,222.

Window source — kept as declared-only, deliberately. This is the one point where I did not take the suggestion, and it is the issue author's call rather than mine: the Maka window is a target the user chooses to stay under, not a fact about the model, so the model's reported window is shown beside the setting with one click to apply (#4575) but never becomes the threshold on its own. The cost you name is real and stated in the description: with nothing declared, the first fill costs one rejection and possibly one cut reply. The context_window_suggestion note then offers the last accepted total; it is now written only when the turn actually surfaces the error, and the CLI transcript renders both new note kinds.

input_too_large producer. Correct — I removed the only producer. Both summarizer catches now classify ContextLength as input_too_large, with a fake provider that rejects above N characters as the regression.

Epoch and CHANGELOG. Bumped to 97 on rebase and the three sentences are back.

Inline items: eviction check compares input with input; the size floor applies to the initial fold only (the roll-forward input is the increment, as you say) and CheckpointSummaryFoldContext carries usage only, so the builder/copy seams validate structure and truncation; the suggestion note moves after recovery and names the fold-proof last accepted total; the run-header test's anchor now sits above the window so the header check decides; the synthetic /compact row test is restored; the roll-forward floor test now asserts both directions.

Two things I left as they were, with reasons. The Host's runComposition.contextWindow stays the model's reported window: it is a protocol fact clients already display, and the declared window gets its own surface in the composer indicator (#4576) rather than a changed meaning for an existing field. And the memory-gate unavailable outcome is still exercised by the mid-turn fixture's extraction path (remember returns unavailable there, asserted at the fold that dispatches extraction); if you meant a different obligation, tell me which and I will pin it.

[Joob1n]

Rebased on main@8ea3c4f05 now that #4578 has landed, so the dependency bump is no longer carried here (6 commits). main moved the compatibility epoch to 98 in the meantime (#4561 / #4568), so this PR's bump is now 98 → 99; the CHANGELOG line and the epoch comment follow. No other changes since a65076258.

[likun666661]

方向我赞成：把“请求是否 fit”的裁决权完全交给 provider，把本地侧收缩为“真实 usage + 用户目标只触发可逆 fold”，比多把估算尺同时参与决策更干净。PR 的主要因果链也基本成立。不过在 approve 前，我认为还有下面几个点需要收口：

1. [P1] compatibility epoch 与最新 main 撞号。 当前 main@898b86d 已经把 RUNTIME_HOST_COMPATIBILITY_EPOCH 升到 99，用于 ScheduledTask 的 Connection identity；本 PR 也独立使用 99 表示两个新 system note 和 lastRequestAnchor shape。两边是不同的不兼容协议变化。rebase 后不能只解决文本冲突并继续保留 99，需要把合并结果升到 100，同步注释、CHANGELOG 和 epoch test；否则能力不同的 client/host 可能错误通过严格相等握手。

2. [P2] repair 请求里的 ContextLength 会被吞成初次格式错误。history-compact-summarizer.ts:206-243 中，初次 summary malformed 后，repair 使用更长的 system prompt。如果初次调用刚好 fit、repair 因新增 instruction 被 provider 拒绝，内层 catch 会把该错误包装成初次的 malformed_summary_*；外层看到它已经是 HistoryCompactSummarizerError 后直接重抛，不会再分类为 input_too_large。planner 因此不会执行 halve-and-retry，和“summarizer provider decides”不一致。建议在 repair catch 中保留 ContextLength 分类，并补一个“initial malformed, repair overflow”的回归测试。

3. [P2] 架构文档仍描述修复前的 trigger。 中英文文档目前都写成“上次 inputTokens + outputTokens 超过用户窗口时触发”；实现已经是 baseline + model.maxOutputTokens >= declaredWindow（ai-sdk-compaction.ts:896-908）。这是核心规则，应同步两份文档，避免后续实现和测试重新漂移。

4. Issue closure 建议调整。#4559 的 proposal 还包含 missing-usage hint、unclassified overflow 的 compact-and-retry action、metadata window 一键采用和 composer indicator。本 PR 没有 missing-usage note，unclassified action 明确留在系列之外，UI 又拆到 #4575/#4576。拆 PR 没问题，但此时 Closes #4559 会让完整验收范围过早关闭；建议改成 Refs #4559，或先明确把 #4559 收缩为 runtime-only。

从 Occam 的角度，我的判断是：架构方向已收敛，问题定义尚未完全收敛。 最小因果主线已经很清楚：

history grows
→ user target may request a reversible fold
→ provider outcome decides actual fit
→ canonical history is never rejected or mutated by an estimate

但“provider decides”尚未覆盖 provider 沉默的情况：PR 自己的 Ollama 实测已经显示跨 turn usage plateau / silent truncation，而当前 dropping note 只检查同 turn 的 step ≥ 1。建议把无 usage、无法分类以及 silent eviction 明确定义成可见的 degraded mode；否则“未声明 window 时系统提供什么保证”仍是开放语义。

另外，includeUsage ?? true 现在会给所有 OpenAI-compatible Chat server 发送 stream_options.include_usage。现有 conformance test 只覆盖支持该字段的 fake server；最好再补一个严格 relay 拒绝该字段时的契约测试，明确 fail、fallback 或 opt-out 行为。

CI 当前是绿的，diff check 也干净；上面第 1 项是基于最新 main 的当前 merge blocker，第 2 项是静态可达的 provider-boundary bug。修完这些，我认为核心 runtime 改动可以继续推进。

[Joob1n]

Thanks — the first three are real and are fixed in 6c5e53ddd / ba14a706c; the fourth is done in the PR body.

1. Epoch.main moved again while this was open (#4321 → 99, #4508 → 100), so the rebase now lands this PR's bump as 100 → 101; comment, CHANGELOG and the epoch check follow. The protocol tests assert against the exported constant, not a literal, so nothing else pins the number.

2. Repair-path ContextLength. Confirmed: the repair catch wrapped every failure under the initial defect, so a context-length rejection of the longer repair prompt never reached the planner as input_too_large. The catch now classifies before wrapping; regression test "a context-length rejection of the repair request stays the input_too_large signal" (initial malformed → repair rejected → input_too_large, two provider calls) fails on the previous commit.

3. Docs. Both llm-compaction-events-log-projection-draft documents now state the implemented trigger: previous accepted inputTokens + outputTokensplus the reply reserve (the model's declared maxOutputTokens, zero when unknown) reaching the declared window.

4. Issue closure. Changed to Refs #4559; the issue closes when #4574/#4575/#4576 have all landed and the remaining proposal items are triaged there.

On the two broader points:

• Degraded modes (no usage, unclassified rejection, cross-turn plateau). Agreed that these deserve names. They are deliberately outside this PR: the dropping note is scoped to a single send because within one send Maka knows it only appended, while across turns the user may have edited or branched and a lower inputTokens is legitimate. Opened context: define the degraded modes when the provider does not speak (no usage, unclassified rejection, silent eviction) #4623 with the three modes, the signal each one gives today, and the two small follow-ups: PR D applies the same dropping rule at the turn boundary (first request's inputTokens below the persisted anchor with no fold or prune before the send → note), PR E adds "compact and retry" on an unclassified provider error. Both are notes/actions on top of this PR's paths, so they can land right after it without reopening it.

• stream_options on strict relays. Decided and pinned in 6ce7d7332: a relay that rejects the field fails with the provider's own 400 text and the runtime does not resend without it — the conformance test asserts one request, the stream_options body field, and the provider message reaching the stream's error part. Rationale: a connection that cannot report usage has no context baseline, so a silent fallback would hide exactly the degraded mode above; the error names the field, and a per-adapter includeUsage: false is the one-line opt-out if a real relay needs it. The field has been part of the Chat Completions API since 2024-05 and the Kimi OpenAI path in this repo has sent it since feat(runtime): support Kimi OpenAI protocol #1462.

[Joob1n]

Rebased on main@b1ec28989. main took epoch 101 in the meantime (#4608), so this PR's bump is now 101 → 102; comment, CHANGELOG and the epoch check follow. The strict-relay contract test is e10dd49a4's head commit (was 6ce7d7332 before the rebase). No other changes.

[likun666661]

复查了最新 head e10dd49a4。上一轮的主要项都已正确落地：epoch 102 对应 merge base 101；repair-path ContextLength 保留为 input_too_large 且有回归；两份文档的 trigger 公式已更新；PR body 改成了 Refs #4559；strict relay 的一次 400 / 不静默重试契约也已固定。CI 当前是绿的，PR 可干净合并。

还有两个行为/scope 问题和一个文档漂移需要收口：

1. [P1] #4559 仍会被 closing keyword 关闭。 PR body 虽然已经改成 Refs #4559，但首个 commit 20f01b862 的 message body 仍然包含 Closes #4559。本仓库只允许 squash merge，并配置为 squash_merge_commit_message: COMMIT_MESSAGES；因此这个 closing keyword 会进入 default-branch 的 squash commit，仍会关闭 issue。既然约定是整个 #4574/#4575/#4576 系列落地并完成剩余 triage 后再关闭，请把该 commit message amend 为 Refs #4559（或确保最终 squash message 中完全没有 closing keyword），而不只是修改 PR body。

2. [P2] provider-dropping 实现检测的是“严格下降”，对外契约写的是“没有增长”。packages/runtime/src/ai-sdk-backend.ts:2170-2182 当前条件是：

   stepUsage.inputTokens<lastStepInputTokens

   但 PR summary、commit message、CLI/UI copy 和新开的 #4623 都把信号定义为 usage “did not grow / stops growing or drops”。本 PR 自己的 Ollama 证据正是输入在 3,716 持平 plateau；严格 < 不会对这个案例写 note。当前测试也只有 100 → 50 的 decrease，没有 equal-usage case。

   如果 observable contract 确实是“append-only request 的 input 没增长”，这里应使用 <= 并补一个 equal-usage regression。#4623 的 PR D 也不应只定义成 “below persisted anchor”，否则同一个跨-turn plateau 仍不会被检测。若等值被刻意排除，则应反过来收窄 PR、copy 和 #4623 的声明，并说明为什么 plateau 不是可靠信号；现在代码和承诺二者只能有一个成立。

3. [P3] 中文架构文档仍有两处旧的 size-policy 语义。docs/architecture/llm-compaction-events-log-projection-draft.zh-CN.md:88-93 的公式仍写 current context budget，而英文已改成 user-declared capacity and provider outcome；同文档 :121-130 仍把 checkpoint 的必要问题写成“它在当前 token policy 下仍然能否进入 prompt？”，英文已改为 source/provider-state identity。后文已经明确删除 replay size verdict，因此这两处应与英文及最终实现同步。

除了以上三项，上一轮要求的修复我没有再发现回归。前两项处理后，我认为这轮可以进入 approve。

[Joob1n]

All three are fixed on 2cbc332af.

1. Closing keyword in the commit body. You are right that the PR body is not where this is decided under squash merge with COMMIT_MESSAGES. 20f01b862 is reworded to Refs #4559 (now 3ed669070 after the rebase); no commit on the branch carries a closing keyword any more.

2. < vs <=. Fixed to <=, with the copy as the authority rather than the other way round. Your reading of the evidence is the right one: the live Ollama run plateaus at 3,716 input tokens and never drops, so the strict comparison would have missed the exact case the PR cites. An equal input count after an append-only step (no fold, no prune, no image omission) is already impossible without provider-side eviction or rewriting, so equality is signal, not noise. New regression "records provider context dropping when an append-only step reports the same usage" (100 → 100 across the step) fails on the previous commit; the existing decrease and prune-explains-it tests still pass.

#4623 is updated to match: PR D's rule is "at or below the persisted anchor", not "below", for the same reason.

3. Chinese document drift. Both passages are synced with the English text: the materialization inputs now read 用户声明的 capacity 与 provider 结果, and the checkpoint's replay question is source/provider-state identity rather than the retired token policy.

One note on scope: both documents still ask "which high-water decision produced it" in that same list. It is stale in both languages equally, so I left it rather than widening this PR's document diff; say the word and I will fold it in here, otherwise it goes with the #4623 documentation pass.

[me2seeks]

Reviewing with real edge cases in mind, grounded in production data from a kimi-coding-plan/k3-256k workspace (see also #4634 — this PR fixes its root causes 1 and 2; items 3 and 4 there remain open).

Overall the direction is sound: every trigger is now a provider-reported number, and I live-verified the new summarizer request shape against k3-256k (details inline on the summarizer change). My concerns are about the paths where the provider never speaks: silent over-window acceptance, output-limit cuts caused by our own maxOutputTokens, and unrecognized error shapes.

[me2seeks]

Real edge case from live data: kimi-coding-plan/k3-256k accepts requests beyond its fetched window without rejecting or truncating — observed a session accepted at 322K input tokens against a fetched contextWindow of 262,144, with usage still growing monotonically (305K → 322K). On such a provider every signal this design reads stays dark for an undeclared window:

• no rejection → reactive fold never fires;
• usage never plateaus → context_provider_dropping never fires (and it is mid-turn only anyway);
• context_window_suggestion only fires on a surfaced rejection → never written;
• a fetched /models window is not a declaration → the proactive trigger below never arms.

Net effect: an undeclared kimi session degrades silently and indefinitely (this is exactly the data behind #4634). I agree with "Maka does not decide for the user" as a principle, but for providers observed to accept over-window requests, could the fetched window seed a default declaration (user-overridable), or should the cross-turn plateau check (#4623 PR D) be a blocker rather than a follow-up?

[me2seeks]

pendingLengthFold is set on anylength finish with no size or cause guard. Two real cases where the fold is useless or harmful:

1. The cut came from our own configured maxOutputTokens, not the window: maka sends maxOutputTokens: 131072 on kimi-coding-plan main requests (from lookupModelMetadata). A reply cut at that cap is not helped by folding history at all — the next request carries the same cap. If the model keeps wanting more output (long reasoning at effort=max, large file generation), this turn folds every step, repeatedly shrinking history while never addressing the constraint.
2. A user who declares a small output limit for cost control gets routine length finishes → folds at a few K tokens of context, paying a summarizer call each time.

Suggest gating the length fold on baseline + replyReserve >= capacity (i.e. plausibly window-caused), or capping length-folds per turn.

[me2seeks]

For k3-256k, declaredModelOutputLimit resolves to 131,072 from bundled metadata — half of its 262,144 window. A user who pins the full window gets proactive folding at baseline >= 131,072, i.e. ~50% utilization, which is far earlier than "stay under your declared window" suggests. Reserving the output limit is right in principle (without it a real-size declaration is never crossed), but when the declared output limit is a large fraction of the window the reserve dominates. Consider capping it, e.g. min(outputLimit, capacity / 4) or a fixed bound.

[me2seeks]

The per-send latch and the fingerprint circuit still only cover malformed-summary reasons. After a provider_error / output_length fail-open, baselineTokens stays set, so overWindow remains true and every subsequent step retries the summarizer. Observed live on kimi-coding-plan (which reports failures as HTTP 200 + error body): 15 consecutive failed summarizer calls over ~47 minutes, each 30–45 s, before the main request. Suggest latching any summarizer failure for the rest of the send, with the same fail-open diagnostic. (#4634 item 3)

[me2seeks]

Defaulting includeUsage on for every non-opted-out OpenAI-compatible server is the right call for usage coverage, but a strict relay/proxy that rejects unknown fields (older vLLM, some gateways) will 400 every streaming request after upgrade, and opting out requires a registry code change. Consider a one-time fallback: on a 400 whose error text mentions stream_options/include_usage, retry without it and remember that for the connection.

[me2seeks]

Two false-positive paths for the dropping note:

1. Finalization steps remove all tool schemas (resolveDispatch returns [] for the child-summary / sandbox-boundary finalization step), which legitimately drops the next request's input by several K tokens with no fold/prune/image-omit — this condition doesn't exclude that case, so a routine turn end can report "provider is dropping context".
2. No hysteresis: a 1-token decrease fires the note. Cache accounting or tokenizer drift between calls can produce tiny legitimate decreases. A small relative threshold (e.g. drop > 1–2% or > N tokens) would keep the note meaningful.

[me2seeks]

Confirming this fixes the kimi-coding-plan failure mode from #4634 — I live-tested this exact request shape (system template + trailing user instruction) against k3-256k on both wires: it now returns a fully compliant sectioned summary, where the system-prompt-only shape returned content: null (7 tokens) or continued the conversation as the assistant.

One follow-up worth noting (not blocking): the summarizer request still opens with a different system prompt than the main loop, so it shares no prefix cache with it — the first fold of a session pays a full uncached pass over the folded span (observed 39–88 s on 155–253K inputs). Moving the whole instruction into the trailing user message would let the summarizer reuse the main loop's cached prefix (~99% hits); keeping the template in system is also fine if that's load-bearing for other providers, but the cache cost is real at high context.

[Joob1n]

Thank you for the production data. Every path you named is real, and four of them are fixed on 1faabac55. The evidence for each is your k3-256k workspace, so I have quoted your numbers in the commit message rather than restating them here.

Summarizer retry storm (#4634 item 3). Fixed. The per-send latch recorded only malformed reasons, and the baseline that fired the trigger survives a fail-open, so a provider_error re-armed the same condition on every later step. Every fail-open reason now latches for the rest of the send. Regression: "bounds a provider-error summarizer failure across later steps in the same turn" (one summarizer call, failOpenReason: provider_error, no checkpoint), failing on the previous commit.

pendingLengthFold with no cause guard. Fixed, and your first case is the discriminator: the reply's own outputTokens says which limit cut it. A reply that stopped at the maxOutputTokens Maka sends was cut by Maka's budget, and the next request carries the same budget, so the fold is marked only when the reply stopped below it. That covers your cost-control case too, since a small declared output limit is reached exactly. No new constant, and both numbers are provider-reported. Regression: "does not fold when the reply was cut by the output budget Maka itself sends".

Dropping-note false positives. The finalization case is fixed: the note is suppressed when the step's own active tool set shrank, which is Maka reshaping the request rather than the provider evicting anything. Regression: "does not report provider dropping when the step dropped its tool schemas". On hysteresis I would rather not add a threshold, and I think the <= change (this PR now treats a plateau as the signal, per @likun666661's review) makes the case: after an append-only step, an input count that merely failed to grow already means the appended content was not counted, so a one-token decrease is not a weaker signal than equality but a marginally stronger one. normalizeAiSdkUsage sums no-cache, cache-read and cache-write, so cache accounting does not move the total. If you have a case where drift moves it anyway, that is worth a threshold and I will add one.

stream_options on strict relays. Adopted your suggestion over my earlier position, which @likun666661 also questioned: the deciding argument is that opting out needs a registry code change, so a strict relay has no user-facing recovery. A 400 whose body names the field now triggers one retry without it, remembered per base URL for the process. The connection then simply reports no usage, which the composer indicator (#4576) shows as a dash. Contract test asserts the three requests: asked, retried without, and never asked again.

Providers that accept beyond their fetched window. This one I have not changed, and I want to be explicit about why, because you are right that every signal stays dark. A cross-turn plateau check (PR D on #4623) does not rescue it either: your session's usage grows monotonically to 322K, so there is no plateau to detect. The only thing that arms anything is a declaration. Two options I can see:

1. A note when accepted usage exceeds the model's reported window while nothing is declared. That is two real numbers and no decision on the user's behalf, and it is the same shape as the existing context_window_suggestion. It fits this design and I would be glad to add it, here or as PR D's sibling.
2. Seeding a default declaration from the fetched window, which is the thing Context budget: stop estimating fit; the provider decides, the Maka window is a user target #4559 deliberately removed: a fetched number is a hint, and a session that compacts because of a number the user never chose is the failure this PR exists to end.

My preference is 1. Say which you would rather review and I will follow.

Prefix cache on the summarizer request. Noted as a follow-up, not forgotten: your 39–88 s uncached first attempts are a strong argument for moving the whole instruction into the trailing user message now that the trailing message exists. I have left the system template in place here because it is load-bearing for the providers the current tests cover, and changing both the shape and the cache behaviour in the same PR would make the k3-256k regression hard to attribute. It belongs on #4634.

Thanks also for live-testing the summarizer request shape; that is the part of this PR I could only verify against Ollama and fake providers.

[Joob1n]

Follow-up on the two open items from your review, both now on 77590471e.

The reply reserve is no longer the model's output limit. Your k3-256k arithmetic was the deciding case: reserving 131,072 against a 262,144 declaration folds at half the window a user deliberately chose. It is now twice the last reply the model actually wrote, bounded at 8,000 tokens. Both halves are provider-reported, the margin tracks the session's own behaviour rather than a catalog maximum, and no previous reply means no reserve at all. On your numbers a session answering in 2–3K tokens now folds at roughly 256K of 262K instead of 131K. The old test that asserted the output limit is rewritten around the new rule (a 900-token anchor with a 60-token reply folds against a 1,000 window, the same anchor with a 5-token reply does not, and the model's 600-token output limit is irrelevant to both).

A reserve measured from a smaller previous reply can still be too small, so that case is now reported rather than silent: when an accepted request's own input plus its reply exceed the declared window, the transcript carries one context_window_overrun note per send with both numbers. It is the honest reading of "the reply needed more room than was left", it uses only provider-reported numbers, and it tells a user who wants whole replies to raise the declaration. The next request folds anyway because the baseline now exceeds the window; the note explains why rather than changing what happens.

That makes three note kinds in this PR, all in the same epoch move (now 103 → 104 after the latest rebase).

Still yours to choose: the undeclared-window case on a provider that accepts past its reported window. My preference remains a note when accepted usage exceeds the model's reported window while nothing is declared, rather than seeding a declaration from a fetched number. Say which you would rather review.

[Joob1n]

Added, on 0d0a32dce: with nothing declared, a request the provider accepts past the window its own catalog entry reports now writes one context_reported_window_exceeded note per send, naming what the exchange used and what the model reports. It changes nothing on its own — a reported window stays a hint, and Maka still declares nothing on the user's behalf — but the case you found is no longer invisible. With a declaration in place the overrun note already owns that ground, and a test pins that the two never fire for the same fact.

That is the fourth note kind in this PR, all within the same epoch move (103 → 104 after the latest rebase). Local gates are green; the mid-turn suite is 73/73.

[me2seeks]

Thanks — verified 1faabac55 and 77590471e on the diff. The cutByOwnBudget discriminator is a better fix than the proximity gate I suggested: it distinguishes the two length causes with two provider-reported numbers, and my cost-control case falls out of it for free. The behaviour-measured reply reserve (2× last reply, ≤8K) fixes the k3-256k half-window arithmetic, and context_window_overrun is the right honest reporting for a reply that outgrew a reserve measured from smaller ones.

Undeclared window on a provider that accepts past its reported window: I choose option 1 — a note when accepted usage exceeds the model's reported window while nothing is declared. Two reasons beyond the ones you gave:

1. Coverage differs by surface. TUI has a real-time ctx indicator (I have a PR open adding one, with colour) so a TUI user can transiently see 322K > 262K; Desktop has nothing. A persisted note in the transcript is the only durable signal on Desktop, and the only one that survives the moment on TUI.
2. The note closes the loop with feat(desktop): show the model's reported context window beside the declared setting #4575. The number it should name is the reported window the user could adopt, and the natural call to action is the settings surface with the one-click apply from feat(desktop): show the model's reported context window beside the declared setting #4575.

One constraint from the k3-256k data: on such providers usage crosses the reported window gradually and keeps growing (305K → 322K), so the note should fire once per session when the crossing is first observed (the accepted total first exceeds the reported window), not per send — otherwise it spams on every step past the line.

On hysteresis for the dropping note: your <= argument and the normalizeAiSdkUsage sum hold; I have no live case where drift moves the total, so I withdraw that suggestion.

I will take the summarizer prefix-cache item back to #4634 as agreed.

[Joob1n]

Adopted the once-per-crossing constraint on 8c88243ca. The note now fires on the transition rather than per send: the previous accepted total was still inside the reported window and this one is not. That previous total comes from the persisted anchor, so a resumed session does not repeat a crossing it already reported, and a session that is already past the line stays quiet. Test "does not repeat the reported-window note once the session is already past the line" (a 320-token anchor against a reported 100) fails without the guard.

Your two reasons are both in the code's favour: the note is the durable Desktop signal, and it names the reported window, which is the number #4575 offers to apply in one click. Noted on the withdrawn hysteresis and on taking the prefix-cache item to #4634.

[Joob1n]

Correction on the previous push: a rebase of mine stopped on a conflict and the branch was pushed mid-rebase, so 8c88243ca briefly showed this PR with 5 of its 13 commits. The head is now 1283c874c, rebased on main@148f8eb29 with all 13 commits and every local gate green. Nothing in the content changed; main also took epoch 104 in the meantime, so this PR's bump is now 104 → 105 and the comment, CHANGELOG and commit message follow.

[Joob1n]

Closing this in favour of a smaller series. Not because anything here was wrong: it is green and every review item on it is either fixed or deliberately carried forward. The reason is that the design converged past what this PR's shape can carry, and a reviewer arriving now would have to reconstruct it from four rounds of comments.

Two things changed after the last round, both simplifications, and both invalidate part of this PR rather than adding to it:

1. The compaction module runs at most once per send. The proactive and reactive folds were two independent latches here. A fold already covers everything except the live head, so a second one buys a little tail and costs the most recent verbatim context. When a request is still rejected after a fold, the honest diagnosis is that the new message itself is too large, and that is what the user should be told.
2. A finishReason: length no longer triggers a fold. A reply cut below the maxOutputTokens Maka sends can mean the provider ran out of window room, or that the provider has its own lower output cap. Those are indistinguishable from the outside, and an indistinguishable signal should not drive an action. This removes the cutByOwnBudget discriminator @me2seeks and I converged on, one level up: the discriminator was right for the question asked, but the question should not have been asked.

A third change is larger and belongs on its own review: when a fold is rejected as too large, retreat to the span the last accepted request's input covered, rather than halving the covered range. That boundary was accepted by this exact model on this exact connection, so it is provably within capacity, where halving is a guess. The last reply's own span is folded separately when it exceeds 24,000 tokens.

The full design is written up on #4559 as three modules (judge / send / compact) with the call bounds.

Where each review finding goes

Finding	Reviewer	Lands in
Trigger arithmetic needs a reply reserve	@Astro-Han	PR 1
input_too_large must have a real producer	@Astro-Han	PR 2
Eviction check must compare input against input	@Astro-Han	PR 1
Window-suggestion note timing (after recovery, not before)	@Astro-Han	PR 1
Size floor only on the initial fold, not on roll-forward	@Astro-Han	PR 2
Fold-context cleanup, CHANGELOG, CLI note kinds, epoch	@Astro-Han	PR 1
Epoch collision with main	@likun666661	PR 1
Repair request's context-length rejection swallowed as a format defect	@likun666661	PR 2
Architecture documents describing the pre-fix trigger	@likun666661	PR 1
Closing keyword in the commit body, not just the PR body	@likun666661	PR 1
Dropping note must fire on a plateau (<=), not only a decrease	@likun666661	PR 1
Summarizer retry storm: latch every failure, not only malformed ones	@me2seeks	PR 2
Reply reserve must not be the model's output limit	@me2seeks	PR 1
Dropping note false positive on tool-schema shrink	@me2seeks	PR 1
stream_options retreat for strict relays	@me2seeks	PR 1
Undeclared window on a provider that accepts past its reported window	@me2seeks	PR 1
Reported-window note once per crossing, not per send	@me2seeks	PR 1
Length-fold cause guard	@me2seeks	superseded, see 2 above
Summarizer prefix-cache cost	@me2seeks	#4634

The series

• PR 1 — send module: trigger, reply reserve, persisted anchor, one compaction per send, "this message is too large", stream-usage collection with the strict-relay retreat, and all four system notes. One epoch move.
• PR 2 — compaction module: summarizer request shape, output cap and retries, failure latch, and the retreat to the last accepted input boundary.
• feat(desktop): show the model's reported context window beside the declared setting #4575, feat(desktop): show context usage beside the model controls #4576 — unchanged, rebased onto PR 1 when it lands.
• PR 5 — "compact and retry" for a rejection the classifier does not recognise (context: define the degraded modes when the provider does not speak (no usage, unclassified rejection, silent eviction) #4623).

Thank you all for the four rounds; the findings are carried, not discarded.

[Joob1n]

The replacement is #4653: the send module, with the two simplifications described above and the same review findings carried. The compaction module's retreat boundary follows in a second PR.

[Joob1n]

Summary

The runtime no longer estimates whether a request fits a context window. Every "does it fit" question is answered by a provider; every trigger is a real number. This is the remaining step after #4486, which removed the fabricated capacity and the two terminal gates but kept the chars/4 delta estimate, the 32,000-token fallback history budget, and a per-step JSON.stringify of the whole request as a payload ruler. Design and discussion: #4559 (this PR), #4458 (history).

What decides now

• The conversation provider's own context-length rejection is recovered by one compact-and-retry; a second rejection surfaces as the provider's error (context_overflow), and the user's message stays editable.
• The summarizer's provider decides whether compaction input fits: input_too_large retreats the fold by half, and the loop exits through no_safe_completed_span when even the smallest legal span is refused.
• Proactive compaction has one trigger: the previous accepted request's real inputTokens + outputTokens, as the provider counted them, compared with the context window the user declared for the model (a model-facts pin or a relay profile). Reasoning tokens are counted whole on purpose — high is the safe direction for a trigger that can only ask for a compaction.
• A reply the provider cut at its output limit (finishReason: length) folds once before the next request.

What is gone: estimateNextRequestTokens, exceedsHighWater, midTurnRequestPayloadChars, the final-request rescue re-entry, maxHistoryEstimatedTokens and its five consumers, the quarter-window / 16,384 reserve, the 32,000 fallback, the replacement_not_smaller and prefix_over_budget replay gates, size-based replay selection, the estimated input fit before summarizer calls, and the chars/4 summary-size floor.

Notes for the user (four new system_note kinds): context_provider_dropping when an append-only step's usage did not grow (a provider evicting or rewriting context), and context_window_suggestion when a rejection lands at a proven-fit total, carrying the number the user can declare.

Refs #4559 — the issue closes when the whole series (#4574, #4575, #4576) has landed and the remaining items are triaged there.
Refs #4458, #4486

Follow-up PRs (stacked on this one)

The user-facing surfaces are deliberately split out so this PR stays the atomic runtime change and the UI pieces can be reviewed in parallel. Both are open as drafts on top of this branch and will be rebased and undrafted once this merges:

• feat(desktop): show the model's reported context window beside the declared setting #4575 — Desktop settings: the model's reported window shown beside the declared setting with a one-click apply. Without it, a user who has never declared a window gets no proactive compaction and no in-app pointer to the number they could set; the context_window_suggestion note from this PR is the runtime-side half of that pointer.
• feat(desktop): show context usage beside the model controls #4576 — Desktop composer: read-only context-usage indicator fed by the persisted lastRequestAnchor this PR introduces (percentage with a declared window, absolute tokens without one, a dash when the provider reports no usage).

Not in this series, defined and tracked on #4623 (the degraded modes when the provider does not speak): PR D applies the provider-dropping rule at the turn boundary, PR E adds a "compact and retry" action for provider rejections the error classifier does not recognise. Neither reopens a path this PR touches.

Behaviour changes to review

1. No declared window means no proactive compaction. The first time such a session fills up costs one provider round trip and possibly one cut reply; the context_window_suggestion note then offers the last accepted total as the value to declare. This is the "Maka does not decide for the user" principle; the trade-off is stated in Context budget: stop estimating fit; the provider decides, the Maka window is a user target #4559.
2. A /models report or models.dev metadata is no longer a threshold on its own.resolveDeclaredContextWindow (runtime) and declaredContextWindow (core, single owner of the rule) count only a facts pin or a relay profile. resolveSelectedModelContextWindow keeps its old meaning for display and contextRemaining.
3. token_usage.lastRequestAnchor is now { inputTokens, outputTokens? }. The retired payloadChars key still decodes, so sessions written by 0.2.0 keep loading; sessions written by this build do not open in 0.2.0 (the closed-allowlist cost already noted in CHANGELOG.md).
4. Summaries are capped at 8,000 output tokens (DEFAULT_HISTORY_COMPACT_MAX_OUTPUT_TOKENS; the summarizer's maxOutputTokens option was declared and never passed). A length finish gets one shorter retry, then fails open. The too-small-for-fold floor reads the summarizer call's real usage; a producer that reports none is not floored.
5. Checkpoint replay is structural: a source-matched checkpoint replays as [block, everything after the boundary]. No local size gate stands between a materializable fold and dispatch.
6. ContextBudgetDiagnostic.maxHistoryEstimatedTokens is retired (decode-only). HistoryCompactionPolicy.midTurn loses reserveTokens. buildDefaultContextBudgetPolicy drops its connection parameter.
7. Every OpenAI-compatible Chat request now asks for stream usage (stream_options.include_usage), unless the registry opts a provider out. Found live: only two providers opted in, so a local Ollama and every plain OpenAI-compatible relay — the connection type behind Context budget: an undeclared window fabricates a capacity that kills live turns #4458 — returned no usage, and the baseline, the eviction check and the indicator all stayed dark for them.
8. Summary requests close with a user instruction. Found live: a chat-template model handed a conversation ending on its own turn emits end-of-sequence and nothing else (Ollama qwen2.5, both sizes: finish stop, one output token, empty text), so history compaction never succeeded against a local model. Existing message-shape tests gained the trailing user:text.
9. The trigger reserves the model's declared output limit and fires on >= (review). baseline + outputLimit >= declaredWindow, where the limit is connection.models[].maxOutputTokens or generated metadata — a provider fact — and 0 when none is declared. Without it a window declared at the provider's real size could never be crossed by an accepted request. The window itself remains the user's declaration (see the reply on the review for why the metadata window stays a hint).
10. A context-length rejection from the summarizer's provider is input_too_large again (review), so the planner's retreat-by-half has a producer; the same classification is applied to the Codex compaction call.
11. The window suggestion note is written only when the turn surfaces the rejection (review): after the one fold is spent or when there is no seam, naming the last accepted total, which a fold does not clear.
12. The size floor judges an initial fold only (review): on a roll-forward the summarizer's input is the increment, not the covered span, so the floor stands down there and the fold context carries usage only. The eviction check compares input against input, since reasoning is not resent on every wire.

On dropping the signed delta

#4486 kept a signed chars/4 delta so step 0 could fold before a large new message or image went out. I dropped it: the delta prices an image at a constant and under-reads CJK by about half, so the round trip it saves is the one it is most likely to misjudge; large text results are already capped by the byte-based tool-result archive before they go out; and removing it takes the whole payload ruler and the per-step JSON.stringify(messages) with it. Happy to be argued back.

Test coverage removed

Thirty-seven tests encoded the estimate, the reserve, the payload ruler, the fit gates, or the pre-turn estimate gate; each is either re-pointed at a real-usage observable or removed with the mechanism. Re-pointed: the usage baseline is the last request's INPUT tokens → input plus output; compacts over the high water → compacts after provider usage crosses the declared window; keeps user_stop when stopping an oversized pre-turn summary → keeps user_stop when stopping while a usage-triggered fold is summarizing; persists the LAST request as the anchor → persists the last request input and output as the anchor; replays a durable pre_turn checkpoint below the current high water → without a local size gate; rejects a paragraph-sized summary for a large folded span → when usage says it is too small. Removed outright (the mechanism is gone): the three manual compactHistory … exceeds current limits / makes the full replay larger cases, the three reserve-derivation cases, anchors on real provider usage plus a tail char/4 delta, credits a SIGNED negative payload delta, falls back to whole-projection char/4 on cold start, high-water crosses at contextWindow minus reserve, a fold that cannot shrink the real payload is refused, a runaway summary is rejected as replacement_not_smaller, bounds the oldest oversized tool result before dispatch, fails with input_too_large before dispatch, charges the summarization instructions against the input budget, a summary at exactly the floor is accepted under ceil-based token estimates, the capacity verdict measures the steering payload, the anchor a finalization step writes excludes the tool schemas it cleared, dispatches a pre-turn Compaction recipe without projecting history and keeps a transiently unavailable automatic Compaction checkpoint recoverable (both exercised the deleted pre-turn gate; memory extraction from a hook-triggered fold stays covered), applies max-history overrides to checkpoint replay validation, accepts a complete checkpoint above legacy block limits when the full replay fits, compacts one oversized prior turn before an unknown-model request, compacts an oversized latest turn when an older turn is also retained, dispatches an oversized prior turn when its summary fails, after trying once, never runs a pointless summarizer on a small-window model, a usage object without usable input tokens falls back to cold start, a last-request anchor is only valid as a complete positive pair, a half-written anchor fails the whole token_usage message decode (replaced by the new-shape and retired-key cases).

New coverage: the declared-window rule for pin / relay / reported / metadata sources; baseline = input + output, > not >=, cleared after a fold, seeded from the previous turn, discarded across a model switch; a /models window is not a declaration; pendingLengthFold; the summarizer output cap, shorten retry, and output_length after two cuts; usage-based size floor; retreat by half and its give-up exit; structural replay; both notes, including the non-firing cases (pruned step, step 0, declaration already crossed); the retired payloadChars key decodes and an unknown key still fails.

Live verification against a real provider (Ollama)

Driven through the real AiSdkBackend with getAIModel against a local Ollama (qwen2.5:0.5b / qwen2.5:1.5b, default num_ctx 4096), five turns of ~740 tokens each, the previous turn's ledger and run header fed back as prior context.

Scenario	Observed
Declared window 1,500, qwen2.5:1.5b	Turns 1–3: anchors {745,10}, {1481,10}, {2217,10} persisted; baseline 1,491 at turn 3 is < 1,500, no fold. Turn 4: baseline 2,227 > 1,500 → pre_turn fold; summary malformed twice → failedOpen[malformed_summary_missing_section], request dispatched, end_turn. Turn 5: fold again, repair produces a 1,737-char checkpoint → replaced; the request's provider-counted input drops 2,954 → 1,222.
Same, before the two fixes above	No token_usage event at all (Ollama returned no usage because it was never asked); once usage flowed, the summarizer returned empty text every time. Both fixed in this PR.
No declared window, 8 turns	Never folds, never terminates; every turn end_turn. Usage grows 745 → 3,700 and then plateaus at 3,716 for turns 6–8 while ~740 tokens are appended per turn: Ollama truncates silently at num_ctx with no error.

Known limitation, stated plainly: the silent-truncation plateau above happens between turns, and context_provider_dropping only fires within a turn (step ≥ 1, on an input count that did not grow), because at step 0 a user edit can shrink the input legitimately. A provider that truncates instead of rejecting therefore gives an undeclared-window user no signal today; declaring the window is the protection. Detecting the cross-turn plateau without an estimate needs a ledger-shape check on the anchor (did anything before the anchored request change?) — a follow-up, tracked on #4559. Closing that gap is PR D on #4623.

Verification

Rebased on main@148f8eb29 (after #4578 landed, so this PR no longer carries the dependency bump); the Runtime Host compatibility epoch moves 104 → 105 for the two new note kinds and the reshaped anchor. Locally: npm --workspace @maka/{core,storage,runtime,runtime-host,mcp,ui} run build, npm run typecheck (all workspaces), npm run lint, npm run format:check, npm run check:asf-headers, node scripts/protocol-epoch-check.mjs --base origin/main — all clean. Targeted suites: 425/425 across usage-record-last-request-anchor, context-budget-mid-turn-policy, context-budget-model-facts, history-compaction, history-compact-checkpoint, history-compact-summarizer, mid-turn-capacity-backend, overflow-reactive-recovery, ai-sdk-backend; core suite 760/760; provider-conformance 24/24, history-compact-summarizer 53/53, execution-model-composition 28/28 and the CLI pi-transcript suites after the review fixes. Not run locally: the full npm test matrix (the Electron/OpenSSL and owned-Host timing cases fail on this machine independently of the branch) — relying on CI for those.

Self-review

• The core rule declaredContextWindow was implemented twice (runtime and chat-model-choice) in an earlier draft; consolidated into @maka/core/model-thinking with runtime delegating. One owner for the one rule the design turns on.
• The user-stop-during-summary obligation had lost its test when the pre-turn gate went; re-pointed at the hook-triggered fold. The test also records that one request is still attempted after the stop and is rejected by the transport on its already-aborted signal — pre-existing behaviour, now pinned.
• An earlier draft regenerated the Astryx theme with a stale local @astryxdesign/core@0.5.0; that artifact is not in this PR.
• memory-extraction.ts and session-recap.ts keep their own bounded-request budgets; they are auxiliary calls, not history compaction, and are out of scope here.
• Diagnostics (estimatedTokensBefore/After on compaction decisions) still use the chars/4 estimator. They are recorded numbers, not decisions, and are kept so existing telemetry consumers do not break.

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Claude Code — design discussion, implementation, tests, and review; verified by the author.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No

https://claude.ai/code/session_014ajaRxC4jydavY9nYUFj5J

[Astro-Han]

The direction is the one from #4458 and I still hold it: fit is the provider's answer, the trigger is a real number, and the only irreversible outcome is the provider's rejection. The reduction is real, every symbol in "What is gone" is gone from docs and desktop too, and all six workspace suites, typecheck, lint and format pass locally on 372c1de9, and the three commits since (148326eb) touch none of the files cited below. What stops me approving is not the code, it is three places where the design as implemented does not do what the design says. Line-level fixes are inline.

The proactive trigger cannot fire against a correctly declared window. The trigger is baseline > declaredWindow, and the baseline is a request the provider accepted. If the user declares the provider's real window, no accepted request can exceed it, the fold never runs, and every session goes through rejection first. It fires only when the user declares something smaller, which is the retired reserve reintroduced as a number the user has to guess without being told. This is open point 2 of #4559, and I would settle it the other way: resolve the window as declared > relay profile > models.dev > /models, none only when all are absent; trigger on baseline > window − reserve; make the reserve a real number, the model's output limit plus the tool-result archive cap times pending tool calls, with a fraction of the window as the floor. Those are provider facts and Maka's own content policy, so the "real numbers only" principle holds. A default is not Maka deciding for the user, it is a default the user can override, and the alternative is that out of the box every fill costs a rejection and possibly a cut reply, which CLI users get without even the hint, because pi-transcript.ts drops the two new note kinds. The per-step check already gives mid-turn triggering; only the window and the threshold change.

The summarizer's provider does not get to decide. The design names four deciders, and one of them, "the summarizer's provider decides whether compaction input fits, input_too_large retreats the fold by half", has no producer. Only fitHistoryCompactMessages throws input_too_large, this PR removes that call from history-compact-summarizer.ts and openai-codex-history-compactor.ts, and both catches wrap every provider error as provider_error. So a session whose fold prefix is too large for the summarizer fails open on the first rejection, /compact included, and has no in-app way back under the window. That is worse than main, which at least estimated. The fix is small, classify ContextLength in both catches, but the regression must use a fake provider that rejects above N tokens; all five current input_too_large tests throw the error from a fixture, which is why this was invisible.

The compatibility contract. Two new system_note kinds and the new lastRequestAnchor shape land in packages/core closed allowlists, the same class of change #4486 bumped the epoch for, and the epoch is unchanged. A merge-base client handshakes fine (host-kernel.ts admits on strict equality) and fails decodeStoredMessage on the first transcript carrying a new note. main is on 96 now: rebase, take 97, and put back the three CHANGELOG sentences from #4486 that are still true (see inline).

One consequence of the first point that lives outside the diff: settings-provider-copy.ts still says "when empty, built-in metadata decides", and /context and the inspector still divide by resolveSelectedModelContextWindow, so an undeclared user sees 70% of 200k and never gets a fold. Whichever way the window question settles, the copy and the denominator have to follow the same rule.

On the test claim: five re-pointed tests pass unchanged on main's built sources (the no-size-gate replay, the two size-floor cases, the no-usage case, fails open after repeated input-too-large retreat), and two rules lost their only coverage with the deletions while still existing, the memory gate's unavailable outcome and the rule that a synthetic /compact usage row must not shadow the real anchor. The remaining persisted-anchor test uses an anchor below the window, so it passes regardless of the run-header check.

Evidence boundary: static read against main61224f51; all suites run locally; new tests also run against main's built sources in a scratch copy; no live provider.

AI-assisted review: drafted with Maka; I verified the trigger arithmetic, the input_too_large producers, the epoch state and the size-floor inputs myself.

简体中文

方向就是 #4458 上讨论定下的，我仍然支持：放不放得下由 provider 回答，压缩触发用真实数字，唯一不可逆的结果是 provider 的拒绝。删得也干净，「What is gone」里的每个符号在 docs 和 desktop 里都没有残留，本地六个 workspace 的测试、typecheck、lint、format 全绿；之后的三个提交（148326eb）没有碰到下面引用的任何文件。让我暂时不 approve 的不是代码本身，而是三处实现和设计说的不是一回事。能局部修的都放在行内评论里。

主动触发对着正确声明的窗口永远打不响。 触发条件是「上次请求的 input+output 大于声明窗口」，而上次请求是 provider 已经接受的。如果用户把窗口声明成 provider 的真实大小，任何被接受的请求都不可能超过它，主动压缩一次也不会触发，每个会话都要先撞一次拒绝。只有用户把窗口声明得比真实值小它才触发，这等于把删掉的 reserve 变成了一个要用户自己猜、又不告诉他的数字。这是 #4559 的 open point 2，我的意见相反：窗口按「用户声明 > relay profile > models.dev 元数据 > /models 报告」解析，全都没有才算无；触发条件改成「上次用量 > 窗口 − reserve」；reserve 用真实数字：模型的 output limit（下一步回复最多这么大）加上工具结果归档上限乘以待处理的工具调用数，再用窗口的固定比例兜底。这些都是 provider 的事实和 Maka 自己的内容策略，「只用真实数字」的原则不受影响。给一个默认值不是替用户决定，用户随时可以覆盖；不给的后果是开箱用户每次填满都要付一次拒绝、可能还拿到被截断的回复，CLI 用户连提示都看不到，因为 pi-transcript.ts 把两个新 note kind 丢掉了。turn 内每一步都检查的逻辑已经有了，只需要改窗口和阈值。

summarizer 的 provider 并没有拿到决定权。 设计列了四个决定者，其中「summarizer 的 provider 决定压缩输入放不放得下，input_too_large 就把范围退半」这一条没有产生者。全仓只有 fitHistoryCompactMessages 会抛 input_too_large，本 PR 把它从 history-compact-summarizer.ts 和 openai-codex-history-compactor.ts 里删掉了，两处的 catch 又把所有 provider 错误一律包成 provider_error。于是一个长会话的折叠前缀如果对 summarizer 也太大，第一次拒绝就整体放弃，/compact 走同一条路也一样，会话在 app 内没有回到窗口内的办法，比 main 还差，main 至少还估算一下。修法很小，两个 catch 里判断 ContextLength 再抛，但回归测试必须用「输入超过 N tokens 就拒绝」的假 provider；现在五个相关测试全是 fixture 手抛这个错误，所以这个洞看不见。

兼容契约。 两个新的 system_note kind 和新的 lastRequestAnchor 形状都进了 packages/core 的闭合 allowlist，和 #4486 推 epoch 的那次是同一类改动，但 epoch 没动。merge-base 上的旧 client 握手能通过（host-kernel.ts 按严格相等准入），然后在第一条带新 note 的 transcript 上解码失败。main 现在已经是 96：rebase 取 97，并把 #4486 写的、仍然成立的三句 CHANGELOG 加回来（见行内）。

第一点在 diff 之外的一个后果：settings-provider-copy.ts 的帮助文案「留空跟随内置元数据」现在不成立，/context 和 inspector 的分母也还是 resolveSelectedModelContextWindow，未声明的用户会看到「已用 70% / 200k」却永远等不到压缩。窗口问题无论怎么定，文案和分母都要跟同一条规则。

关于测试的说法：五条 re-pointed 测试在 main 的构建产物上原样通过（无 size gate 的 replay、两条体量下限、无 usage、退半后 fail open）；两条规则随删测试失去了唯一覆盖但仍然存在：memory gate 返回 unavailable 的处理，以及手动 /compact 写的合成 usage 行不得遮蔽真实 anchor。剩下那条持久 anchor 测试的 anchor 低于窗口，不管 run header 合不合法都过。

[Astro-Han]

baselineTokens is a request the provider accepted, so with the window declared at the provider's real size this is never true; the fold only runs when the user declares something smaller. That is the reserve in disguise. baseline > window − reserve, with the reserve from output limit plus the tool-result cap, is what makes this fire before the rejection. First point in the main comment.

[Astro-Han]

Dead branch: nothing throws input_too_large any more. fitHistoryCompactMessages was its only producer and both summarizer catches now wrap provider errors as provider_error. Classify ContextLength with classifyError in history-compact-summarizer.ts and openai-codex-history-compactor.ts so this retreat has a producer, and test it with a fake provider that rejects above N tokens.

[Astro-Han]

Baseline includes last step's reasoning; on wires that do not resend it (gpt-5.x), next input ≈ previous input + tool call + result, which is below input + output whenever reasoning exceeded the appended content, the normal case. Compare against last step's input alone; keep input + output for the trigger.

[Astro-Han]

Written before recoverFromOverflowError runs, so a send that overflows once, folds and completes still tells the user the provider refused. #4559 places this under "already folded". Move it after the recovery verdict; overflow-reactive-recovery.test.ts:1834 (tool, overflow, done) currently pins the wrong order. And suggestedContextWindow: baselineTokens sits on the strict > boundary, so a user who applies it still needs one more rejection.

[Astro-Han]

On a roll-forward the summarizer is sent previous summary + new events, so inputTokens is the increment while the checkpoint replaces the whole covered span; in steady state this floor never trips and a fifty-token summary after a small increment is persisted. The new test passes on main because the stub's usage is unrelated to the messages. Feed it a span-sized real number (previous checkpoint's compactCallInputTokens plus this increment) or drop the floor openly.

[Astro-Han]

The comment above says this re-runs the size floor, but no summarizerUsage is passed so the floor is skipped, and coveredRuntimeEvents is now required and unread by the validator. Same for the external-producer branch in history-compaction.ts. Either pass a real number or delete the field, the three constructions and the comment.

[Astro-Han]

Three sentences from #4486 were dropped and are still true: sessions from this build do not open in earlier releases and the runtime.sqlite copy must be taken before upgrading; context_budget_exhausted is no longer produced but still decodes; the epoch line (97 after rebase). The body says the allowlist cost is "already noted in CHANGELOG.md", and it no longer is.

[Joob1n]

Thanks for the read — every finding was real. Fixes are in 38b2d837 (one commit, each item with a test that fails on the previous commit), plus two live-provider findings in the commits before it.

Trigger arithmetic. You are right that baseline > declaredWindow could never fire against a window declared at the provider's real size. Fixed the way you suggested for the reserve, with one narrowing: the reserve is the model's declared output limit only (connection.models[].maxOutputTokens or generated metadata; 0 when none is declared), and the trigger is baseline + limit >= window. I did not add the tool-result cap × pending calls term: the active prune already bounds each result before it goes out, and a second constant on the trigger side is the kind of number the design is trying not to own. Live on Ollama (qwen2.5:1.5b, declared 1,500) the fold now fires at 2,227 with the previous usage as the only input, folds to a 1,737-char checkpoint after one repair, and the next request's provider-counted input drops 2,954 → 1,222.

Window source — kept as declared-only, deliberately. This is the one point where I did not take the suggestion, and it is the issue author's call rather than mine: the Maka window is a target the user chooses to stay under, not a fact about the model, so the model's reported window is shown beside the setting with one click to apply (#4575) but never becomes the threshold on its own. The cost you name is real and stated in the description: with nothing declared, the first fill costs one rejection and possibly one cut reply. The context_window_suggestion note then offers the last accepted total; it is now written only when the turn actually surfaces the error, and the CLI transcript renders both new note kinds.

input_too_large producer. Correct — I removed the only producer. Both summarizer catches now classify ContextLength as input_too_large, with a fake provider that rejects above N characters as the regression.

Epoch and CHANGELOG. Bumped to 97 on rebase and the three sentences are back.

Inline items: eviction check compares input with input; the size floor applies to the initial fold only (the roll-forward input is the increment, as you say) and CheckpointSummaryFoldContext carries usage only, so the builder/copy seams validate structure and truncation; the suggestion note moves after recovery and names the fold-proof last accepted total; the run-header test's anchor now sits above the window so the header check decides; the synthetic /compact row test is restored; the roll-forward floor test now asserts both directions.

Two things I left as they were, with reasons. The Host's runComposition.contextWindow stays the model's reported window: it is a protocol fact clients already display, and the declared window gets its own surface in the composer indicator (#4576) rather than a changed meaning for an existing field. And the memory-gate unavailable outcome is still exercised by the mid-turn fixture's extraction path (remember returns unavailable there, asserted at the fold that dispatches extraction); if you meant a different obligation, tell me which and I will pin it.

[Joob1n]

Rebased on main@8ea3c4f05 now that #4578 has landed, so the dependency bump is no longer carried here (6 commits). main moved the compatibility epoch to 98 in the meantime (#4561 / #4568), so this PR's bump is now 98 → 99; the CHANGELOG line and the epoch comment follow. No other changes since a65076258.

[likun666661]

方向我赞成：把“请求是否 fit”的裁决权完全交给 provider，把本地侧收缩为“真实 usage + 用户目标只触发可逆 fold”，比多把估算尺同时参与决策更干净。PR 的主要因果链也基本成立。不过在 approve 前，我认为还有下面几个点需要收口：

1. [P1] compatibility epoch 与最新 main 撞号。 当前 main@898b86d 已经把 RUNTIME_HOST_COMPATIBILITY_EPOCH 升到 99，用于 ScheduledTask 的 Connection identity；本 PR 也独立使用 99 表示两个新 system note 和 lastRequestAnchor shape。两边是不同的不兼容协议变化。rebase 后不能只解决文本冲突并继续保留 99，需要把合并结果升到 100，同步注释、CHANGELOG 和 epoch test；否则能力不同的 client/host 可能错误通过严格相等握手。

2. [P2] repair 请求里的 ContextLength 会被吞成初次格式错误。history-compact-summarizer.ts:206-243 中，初次 summary malformed 后，repair 使用更长的 system prompt。如果初次调用刚好 fit、repair 因新增 instruction 被 provider 拒绝，内层 catch 会把该错误包装成初次的 malformed_summary_*；外层看到它已经是 HistoryCompactSummarizerError 后直接重抛，不会再分类为 input_too_large。planner 因此不会执行 halve-and-retry，和“summarizer provider decides”不一致。建议在 repair catch 中保留 ContextLength 分类，并补一个“initial malformed, repair overflow”的回归测试。

3. [P2] 架构文档仍描述修复前的 trigger。 中英文文档目前都写成“上次 inputTokens + outputTokens 超过用户窗口时触发”；实现已经是 baseline + model.maxOutputTokens >= declaredWindow（ai-sdk-compaction.ts:896-908）。这是核心规则，应同步两份文档，避免后续实现和测试重新漂移。

4. Issue closure 建议调整。#4559 的 proposal 还包含 missing-usage hint、unclassified overflow 的 compact-and-retry action、metadata window 一键采用和 composer indicator。本 PR 没有 missing-usage note，unclassified action 明确留在系列之外，UI 又拆到 #4575/#4576。拆 PR 没问题，但此时 Closes #4559 会让完整验收范围过早关闭；建议改成 Refs #4559，或先明确把 #4559 收缩为 runtime-only。

从 Occam 的角度，我的判断是：架构方向已收敛，问题定义尚未完全收敛。 最小因果主线已经很清楚：

history grows
→ user target may request a reversible fold
→ provider outcome decides actual fit
→ canonical history is never rejected or mutated by an estimate

但“provider decides”尚未覆盖 provider 沉默的情况：PR 自己的 Ollama 实测已经显示跨 turn usage plateau / silent truncation，而当前 dropping note 只检查同 turn 的 step ≥ 1。建议把无 usage、无法分类以及 silent eviction 明确定义成可见的 degraded mode；否则“未声明 window 时系统提供什么保证”仍是开放语义。

另外，includeUsage ?? true 现在会给所有 OpenAI-compatible Chat server 发送 stream_options.include_usage。现有 conformance test 只覆盖支持该字段的 fake server；最好再补一个严格 relay 拒绝该字段时的契约测试，明确 fail、fallback 或 opt-out 行为。

CI 当前是绿的，diff check 也干净；上面第 1 项是基于最新 main 的当前 merge blocker，第 2 项是静态可达的 provider-boundary bug。修完这些，我认为核心 runtime 改动可以继续推进。

[Joob1n]

Thanks — the first three are real and are fixed in 6c5e53ddd / ba14a706c; the fourth is done in the PR body.

1. Epoch.main moved again while this was open (#4321 → 99, #4508 → 100), so the rebase now lands this PR's bump as 100 → 101; comment, CHANGELOG and the epoch check follow. The protocol tests assert against the exported constant, not a literal, so nothing else pins the number.

2. Repair-path ContextLength. Confirmed: the repair catch wrapped every failure under the initial defect, so a context-length rejection of the longer repair prompt never reached the planner as input_too_large. The catch now classifies before wrapping; regression test "a context-length rejection of the repair request stays the input_too_large signal" (initial malformed → repair rejected → input_too_large, two provider calls) fails on the previous commit.

3. Docs. Both llm-compaction-events-log-projection-draft documents now state the implemented trigger: previous accepted inputTokens + outputTokensplus the reply reserve (the model's declared maxOutputTokens, zero when unknown) reaching the declared window.

4. Issue closure. Changed to Refs #4559; the issue closes when #4574/#4575/#4576 have all landed and the remaining proposal items are triaged there.

On the two broader points:

• Degraded modes (no usage, unclassified rejection, cross-turn plateau). Agreed that these deserve names. They are deliberately outside this PR: the dropping note is scoped to a single send because within one send Maka knows it only appended, while across turns the user may have edited or branched and a lower inputTokens is legitimate. Opened context: define the degraded modes when the provider does not speak (no usage, unclassified rejection, silent eviction) #4623 with the three modes, the signal each one gives today, and the two small follow-ups: PR D applies the same dropping rule at the turn boundary (first request's inputTokens below the persisted anchor with no fold or prune before the send → note), PR E adds "compact and retry" on an unclassified provider error. Both are notes/actions on top of this PR's paths, so they can land right after it without reopening it.

• stream_options on strict relays. Decided and pinned in 6ce7d7332: a relay that rejects the field fails with the provider's own 400 text and the runtime does not resend without it — the conformance test asserts one request, the stream_options body field, and the provider message reaching the stream's error part. Rationale: a connection that cannot report usage has no context baseline, so a silent fallback would hide exactly the degraded mode above; the error names the field, and a per-adapter includeUsage: false is the one-line opt-out if a real relay needs it. The field has been part of the Chat Completions API since 2024-05 and the Kimi OpenAI path in this repo has sent it since feat(runtime): support Kimi OpenAI protocol #1462.

[Joob1n]

Rebased on main@b1ec28989. main took epoch 101 in the meantime (#4608), so this PR's bump is now 101 → 102; comment, CHANGELOG and the epoch check follow. The strict-relay contract test is e10dd49a4's head commit (was 6ce7d7332 before the rebase). No other changes.

[likun666661]

复查了最新 head e10dd49a4。上一轮的主要项都已正确落地：epoch 102 对应 merge base 101；repair-path ContextLength 保留为 input_too_large 且有回归；两份文档的 trigger 公式已更新；PR body 改成了 Refs #4559；strict relay 的一次 400 / 不静默重试契约也已固定。CI 当前是绿的，PR 可干净合并。

还有两个行为/scope 问题和一个文档漂移需要收口：

1. [P1] #4559 仍会被 closing keyword 关闭。 PR body 虽然已经改成 Refs #4559，但首个 commit 20f01b862 的 message body 仍然包含 Closes #4559。本仓库只允许 squash merge，并配置为 squash_merge_commit_message: COMMIT_MESSAGES；因此这个 closing keyword 会进入 default-branch 的 squash commit，仍会关闭 issue。既然约定是整个 #4574/#4575/#4576 系列落地并完成剩余 triage 后再关闭，请把该 commit message amend 为 Refs #4559（或确保最终 squash message 中完全没有 closing keyword），而不只是修改 PR body。

2. [P2] provider-dropping 实现检测的是“严格下降”，对外契约写的是“没有增长”。packages/runtime/src/ai-sdk-backend.ts:2170-2182 当前条件是：

   stepUsage.inputTokens<lastStepInputTokens

   但 PR summary、commit message、CLI/UI copy 和新开的 #4623 都把信号定义为 usage “did not grow / stops growing or drops”。本 PR 自己的 Ollama 证据正是输入在 3,716 持平 plateau；严格 < 不会对这个案例写 note。当前测试也只有 100 → 50 的 decrease，没有 equal-usage case。

   如果 observable contract 确实是“append-only request 的 input 没增长”，这里应使用 <= 并补一个 equal-usage regression。#4623 的 PR D 也不应只定义成 “below persisted anchor”，否则同一个跨-turn plateau 仍不会被检测。若等值被刻意排除，则应反过来收窄 PR、copy 和 #4623 的声明，并说明为什么 plateau 不是可靠信号；现在代码和承诺二者只能有一个成立。

3. [P3] 中文架构文档仍有两处旧的 size-policy 语义。docs/architecture/llm-compaction-events-log-projection-draft.zh-CN.md:88-93 的公式仍写 current context budget，而英文已改成 user-declared capacity and provider outcome；同文档 :121-130 仍把 checkpoint 的必要问题写成“它在当前 token policy 下仍然能否进入 prompt？”，英文已改为 source/provider-state identity。后文已经明确删除 replay size verdict，因此这两处应与英文及最终实现同步。

除了以上三项，上一轮要求的修复我没有再发现回归。前两项处理后，我认为这轮可以进入 approve。

[Joob1n]

All three are fixed on 2cbc332af.

1. Closing keyword in the commit body. You are right that the PR body is not where this is decided under squash merge with COMMIT_MESSAGES. 20f01b862 is reworded to Refs #4559 (now 3ed669070 after the rebase); no commit on the branch carries a closing keyword any more.

2. < vs <=. Fixed to <=, with the copy as the authority rather than the other way round. Your reading of the evidence is the right one: the live Ollama run plateaus at 3,716 input tokens and never drops, so the strict comparison would have missed the exact case the PR cites. An equal input count after an append-only step (no fold, no prune, no image omission) is already impossible without provider-side eviction or rewriting, so equality is signal, not noise. New regression "records provider context dropping when an append-only step reports the same usage" (100 → 100 across the step) fails on the previous commit; the existing decrease and prune-explains-it tests still pass.

#4623 is updated to match: PR D's rule is "at or below the persisted anchor", not "below", for the same reason.

3. Chinese document drift. Both passages are synced with the English text: the materialization inputs now read 用户声明的 capacity 与 provider 结果, and the checkpoint's replay question is source/provider-state identity rather than the retired token policy.

One note on scope: both documents still ask "which high-water decision produced it" in that same list. It is stale in both languages equally, so I left it rather than widening this PR's document diff; say the word and I will fold it in here, otherwise it goes with the #4623 documentation pass.

[me2seeks]

Reviewing with real edge cases in mind, grounded in production data from a kimi-coding-plan/k3-256k workspace (see also #4634 — this PR fixes its root causes 1 and 2; items 3 and 4 there remain open).

Overall the direction is sound: every trigger is now a provider-reported number, and I live-verified the new summarizer request shape against k3-256k (details inline on the summarizer change). My concerns are about the paths where the provider never speaks: silent over-window acceptance, output-limit cuts caused by our own maxOutputTokens, and unrecognized error shapes.

[me2seeks]

Real edge case from live data: kimi-coding-plan/k3-256k accepts requests beyond its fetched window without rejecting or truncating — observed a session accepted at 322K input tokens against a fetched contextWindow of 262,144, with usage still growing monotonically (305K → 322K). On such a provider every signal this design reads stays dark for an undeclared window:

• no rejection → reactive fold never fires;
• usage never plateaus → context_provider_dropping never fires (and it is mid-turn only anyway);
• context_window_suggestion only fires on a surfaced rejection → never written;
• a fetched /models window is not a declaration → the proactive trigger below never arms.

Net effect: an undeclared kimi session degrades silently and indefinitely (this is exactly the data behind #4634). I agree with "Maka does not decide for the user" as a principle, but for providers observed to accept over-window requests, could the fetched window seed a default declaration (user-overridable), or should the cross-turn plateau check (#4623 PR D) be a blocker rather than a follow-up?

[me2seeks]

pendingLengthFold is set on anylength finish with no size or cause guard. Two real cases where the fold is useless or harmful:

1. The cut came from our own configured maxOutputTokens, not the window: maka sends maxOutputTokens: 131072 on kimi-coding-plan main requests (from lookupModelMetadata). A reply cut at that cap is not helped by folding history at all — the next request carries the same cap. If the model keeps wanting more output (long reasoning at effort=max, large file generation), this turn folds every step, repeatedly shrinking history while never addressing the constraint.
2. A user who declares a small output limit for cost control gets routine length finishes → folds at a few K tokens of context, paying a summarizer call each time.

Suggest gating the length fold on baseline + replyReserve >= capacity (i.e. plausibly window-caused), or capping length-folds per turn.

[me2seeks]

For k3-256k, declaredModelOutputLimit resolves to 131,072 from bundled metadata — half of its 262,144 window. A user who pins the full window gets proactive folding at baseline >= 131,072, i.e. ~50% utilization, which is far earlier than "stay under your declared window" suggests. Reserving the output limit is right in principle (without it a real-size declaration is never crossed), but when the declared output limit is a large fraction of the window the reserve dominates. Consider capping it, e.g. min(outputLimit, capacity / 4) or a fixed bound.

[me2seeks]

The per-send latch and the fingerprint circuit still only cover malformed-summary reasons. After a provider_error / output_length fail-open, baselineTokens stays set, so overWindow remains true and every subsequent step retries the summarizer. Observed live on kimi-coding-plan (which reports failures as HTTP 200 + error body): 15 consecutive failed summarizer calls over ~47 minutes, each 30–45 s, before the main request. Suggest latching any summarizer failure for the rest of the send, with the same fail-open diagnostic. (#4634 item 3)

[me2seeks]

Defaulting includeUsage on for every non-opted-out OpenAI-compatible server is the right call for usage coverage, but a strict relay/proxy that rejects unknown fields (older vLLM, some gateways) will 400 every streaming request after upgrade, and opting out requires a registry code change. Consider a one-time fallback: on a 400 whose error text mentions stream_options/include_usage, retry without it and remember that for the connection.

[me2seeks]

Two false-positive paths for the dropping note:

1. Finalization steps remove all tool schemas (resolveDispatch returns [] for the child-summary / sandbox-boundary finalization step), which legitimately drops the next request's input by several K tokens with no fold/prune/image-omit — this condition doesn't exclude that case, so a routine turn end can report "provider is dropping context".
2. No hysteresis: a 1-token decrease fires the note. Cache accounting or tokenizer drift between calls can produce tiny legitimate decreases. A small relative threshold (e.g. drop > 1–2% or > N tokens) would keep the note meaningful.

[me2seeks]

Confirming this fixes the kimi-coding-plan failure mode from #4634 — I live-tested this exact request shape (system template + trailing user instruction) against k3-256k on both wires: it now returns a fully compliant sectioned summary, where the system-prompt-only shape returned content: null (7 tokens) or continued the conversation as the assistant.

One follow-up worth noting (not blocking): the summarizer request still opens with a different system prompt than the main loop, so it shares no prefix cache with it — the first fold of a session pays a full uncached pass over the folded span (observed 39–88 s on 155–253K inputs). Moving the whole instruction into the trailing user message would let the summarizer reuse the main loop's cached prefix (~99% hits); keeping the template in system is also fine if that's load-bearing for other providers, but the cache cost is real at high context.

[Joob1n]

Thank you for the production data. Every path you named is real, and four of them are fixed on 1faabac55. The evidence for each is your k3-256k workspace, so I have quoted your numbers in the commit message rather than restating them here.

Summarizer retry storm (#4634 item 3). Fixed. The per-send latch recorded only malformed reasons, and the baseline that fired the trigger survives a fail-open, so a provider_error re-armed the same condition on every later step. Every fail-open reason now latches for the rest of the send. Regression: "bounds a provider-error summarizer failure across later steps in the same turn" (one summarizer call, failOpenReason: provider_error, no checkpoint), failing on the previous commit.

pendingLengthFold with no cause guard. Fixed, and your first case is the discriminator: the reply's own outputTokens says which limit cut it. A reply that stopped at the maxOutputTokens Maka sends was cut by Maka's budget, and the next request carries the same budget, so the fold is marked only when the reply stopped below it. That covers your cost-control case too, since a small declared output limit is reached exactly. No new constant, and both numbers are provider-reported. Regression: "does not fold when the reply was cut by the output budget Maka itself sends".

Dropping-note false positives. The finalization case is fixed: the note is suppressed when the step's own active tool set shrank, which is Maka reshaping the request rather than the provider evicting anything. Regression: "does not report provider dropping when the step dropped its tool schemas". On hysteresis I would rather not add a threshold, and I think the <= change (this PR now treats a plateau as the signal, per @likun666661's review) makes the case: after an append-only step, an input count that merely failed to grow already means the appended content was not counted, so a one-token decrease is not a weaker signal than equality but a marginally stronger one. normalizeAiSdkUsage sums no-cache, cache-read and cache-write, so cache accounting does not move the total. If you have a case where drift moves it anyway, that is worth a threshold and I will add one.

stream_options on strict relays. Adopted your suggestion over my earlier position, which @likun666661 also questioned: the deciding argument is that opting out needs a registry code change, so a strict relay has no user-facing recovery. A 400 whose body names the field now triggers one retry without it, remembered per base URL for the process. The connection then simply reports no usage, which the composer indicator (#4576) shows as a dash. Contract test asserts the three requests: asked, retried without, and never asked again.

Providers that accept beyond their fetched window. This one I have not changed, and I want to be explicit about why, because you are right that every signal stays dark. A cross-turn plateau check (PR D on #4623) does not rescue it either: your session's usage grows monotonically to 322K, so there is no plateau to detect. The only thing that arms anything is a declaration. Two options I can see:

1. A note when accepted usage exceeds the model's reported window while nothing is declared. That is two real numbers and no decision on the user's behalf, and it is the same shape as the existing context_window_suggestion. It fits this design and I would be glad to add it, here or as PR D's sibling.
2. Seeding a default declaration from the fetched window, which is the thing Context budget: stop estimating fit; the provider decides, the Maka window is a user target #4559 deliberately removed: a fetched number is a hint, and a session that compacts because of a number the user never chose is the failure this PR exists to end.

My preference is 1. Say which you would rather review and I will follow.

Prefix cache on the summarizer request. Noted as a follow-up, not forgotten: your 39–88 s uncached first attempts are a strong argument for moving the whole instruction into the trailing user message now that the trailing message exists. I have left the system template in place here because it is load-bearing for the providers the current tests cover, and changing both the shape and the cache behaviour in the same PR would make the k3-256k regression hard to attribute. It belongs on #4634.

Thanks also for live-testing the summarizer request shape; that is the part of this PR I could only verify against Ollama and fake providers.

[Joob1n]

Follow-up on the two open items from your review, both now on 77590471e.

The reply reserve is no longer the model's output limit. Your k3-256k arithmetic was the deciding case: reserving 131,072 against a 262,144 declaration folds at half the window a user deliberately chose. It is now twice the last reply the model actually wrote, bounded at 8,000 tokens. Both halves are provider-reported, the margin tracks the session's own behaviour rather than a catalog maximum, and no previous reply means no reserve at all. On your numbers a session answering in 2–3K tokens now folds at roughly 256K of 262K instead of 131K. The old test that asserted the output limit is rewritten around the new rule (a 900-token anchor with a 60-token reply folds against a 1,000 window, the same anchor with a 5-token reply does not, and the model's 600-token output limit is irrelevant to both).

A reserve measured from a smaller previous reply can still be too small, so that case is now reported rather than silent: when an accepted request's own input plus its reply exceed the declared window, the transcript carries one context_window_overrun note per send with both numbers. It is the honest reading of "the reply needed more room than was left", it uses only provider-reported numbers, and it tells a user who wants whole replies to raise the declaration. The next request folds anyway because the baseline now exceeds the window; the note explains why rather than changing what happens.

That makes three note kinds in this PR, all in the same epoch move (now 103 → 104 after the latest rebase).

Still yours to choose: the undeclared-window case on a provider that accepts past its reported window. My preference remains a note when accepted usage exceeds the model's reported window while nothing is declared, rather than seeding a declaration from a fetched number. Say which you would rather review.

[Joob1n]

Added, on 0d0a32dce: with nothing declared, a request the provider accepts past the window its own catalog entry reports now writes one context_reported_window_exceeded note per send, naming what the exchange used and what the model reports. It changes nothing on its own — a reported window stays a hint, and Maka still declares nothing on the user's behalf — but the case you found is no longer invisible. With a declaration in place the overrun note already owns that ground, and a test pins that the two never fire for the same fact.

That is the fourth note kind in this PR, all within the same epoch move (103 → 104 after the latest rebase). Local gates are green; the mid-turn suite is 73/73.

[me2seeks]

Thanks — verified 1faabac55 and 77590471e on the diff. The cutByOwnBudget discriminator is a better fix than the proximity gate I suggested: it distinguishes the two length causes with two provider-reported numbers, and my cost-control case falls out of it for free. The behaviour-measured reply reserve (2× last reply, ≤8K) fixes the k3-256k half-window arithmetic, and context_window_overrun is the right honest reporting for a reply that outgrew a reserve measured from smaller ones.

Undeclared window on a provider that accepts past its reported window: I choose option 1 — a note when accepted usage exceeds the model's reported window while nothing is declared. Two reasons beyond the ones you gave:

1. Coverage differs by surface. TUI has a real-time ctx indicator (I have a PR open adding one, with colour) so a TUI user can transiently see 322K > 262K; Desktop has nothing. A persisted note in the transcript is the only durable signal on Desktop, and the only one that survives the moment on TUI.
2. The note closes the loop with feat(desktop): show the model's reported context window beside the declared setting #4575. The number it should name is the reported window the user could adopt, and the natural call to action is the settings surface with the one-click apply from feat(desktop): show the model's reported context window beside the declared setting #4575.

One constraint from the k3-256k data: on such providers usage crosses the reported window gradually and keeps growing (305K → 322K), so the note should fire once per session when the crossing is first observed (the accepted total first exceeds the reported window), not per send — otherwise it spams on every step past the line.

On hysteresis for the dropping note: your <= argument and the normalizeAiSdkUsage sum hold; I have no live case where drift moves the total, so I withdraw that suggestion.

I will take the summarizer prefix-cache item back to #4634 as agreed.

[Joob1n]

Adopted the once-per-crossing constraint on 8c88243ca. The note now fires on the transition rather than per send: the previous accepted total was still inside the reported window and this one is not. That previous total comes from the persisted anchor, so a resumed session does not repeat a crossing it already reported, and a session that is already past the line stays quiet. Test "does not repeat the reported-window note once the session is already past the line" (a 320-token anchor against a reported 100) fails without the guard.

Your two reasons are both in the code's favour: the note is the durable Desktop signal, and it names the reported window, which is the number #4575 offers to apply in one click. Noted on the withdrawn hysteresis and on taking the prefix-cache item to #4634.

[Joob1n]

Correction on the previous push: a rebase of mine stopped on a conflict and the branch was pushed mid-rebase, so 8c88243ca briefly showed this PR with 5 of its 13 commits. The head is now 1283c874c, rebased on main@148f8eb29 with all 13 commits and every local gate green. Nothing in the content changed; main also took epoch 104 in the meantime, so this PR's bump is now 104 → 105 and the comment, CHANGELOG and commit message follow.

[Joob1n]

Closing this in favour of a smaller series. Not because anything here was wrong: it is green and every review item on it is either fixed or deliberately carried forward. The reason is that the design converged past what this PR's shape can carry, and a reviewer arriving now would have to reconstruct it from four rounds of comments.

Two things changed after the last round, both simplifications, and both invalidate part of this PR rather than adding to it:

1. The compaction module runs at most once per send. The proactive and reactive folds were two independent latches here. A fold already covers everything except the live head, so a second one buys a little tail and costs the most recent verbatim context. When a request is still rejected after a fold, the honest diagnosis is that the new message itself is too large, and that is what the user should be told.
2. A finishReason: length no longer triggers a fold. A reply cut below the maxOutputTokens Maka sends can mean the provider ran out of window room, or that the provider has its own lower output cap. Those are indistinguishable from the outside, and an indistinguishable signal should not drive an action. This removes the cutByOwnBudget discriminator @me2seeks and I converged on, one level up: the discriminator was right for the question asked, but the question should not have been asked.

A third change is larger and belongs on its own review: when a fold is rejected as too large, retreat to the span the last accepted request's input covered, rather than halving the covered range. That boundary was accepted by this exact model on this exact connection, so it is provably within capacity, where halving is a guess. The last reply's own span is folded separately when it exceeds 24,000 tokens.

The full design is written up on #4559 as three modules (judge / send / compact) with the call bounds.

Where each review finding goes

Finding	Reviewer	Lands in
Trigger arithmetic needs a reply reserve	@Astro-Han	PR 1
input_too_large must have a real producer	@Astro-Han	PR 2
Eviction check must compare input against input	@Astro-Han	PR 1
Window-suggestion note timing (after recovery, not before)	@Astro-Han	PR 1
Size floor only on the initial fold, not on roll-forward	@Astro-Han	PR 2
Fold-context cleanup, CHANGELOG, CLI note kinds, epoch	@Astro-Han	PR 1
Epoch collision with main	@likun666661	PR 1
Repair request's context-length rejection swallowed as a format defect	@likun666661	PR 2
Architecture documents describing the pre-fix trigger	@likun666661	PR 1
Closing keyword in the commit body, not just the PR body	@likun666661	PR 1
Dropping note must fire on a plateau (<=), not only a decrease	@likun666661	PR 1
Summarizer retry storm: latch every failure, not only malformed ones	@me2seeks	PR 2
Reply reserve must not be the model's output limit	@me2seeks	PR 1
Dropping note false positive on tool-schema shrink	@me2seeks	PR 1
stream_options retreat for strict relays	@me2seeks	PR 1
Undeclared window on a provider that accepts past its reported window	@me2seeks	PR 1
Reported-window note once per crossing, not per send	@me2seeks	PR 1
Length-fold cause guard	@me2seeks	superseded, see 2 above
Summarizer prefix-cache cost	@me2seeks	#4634

The series

• PR 1 — send module: trigger, reply reserve, persisted anchor, one compaction per send, "this message is too large", stream-usage collection with the strict-relay retreat, and all four system notes. One epoch move.
• PR 2 — compaction module: summarizer request shape, output cap and retries, failure latch, and the retreat to the last accepted input boundary.
• feat(desktop): show the model's reported context window beside the declared setting #4575, feat(desktop): show context usage beside the model controls #4576 — unchanged, rebased onto PR 1 when it lands.
• PR 5 — "compact and retry" for a rejection the classifier does not recognise (context: define the degraded modes when the provider does not speak (no usage, unclassified rejection, silent eviction) #4623).

Thank you all for the four rounds; the findings are carried, not discarded.

[Joob1n]

The replacement is #4653: the send module, with the two simplifications described above and the same review findings carried. The compaction module's retreat boundary follows in a second PR.

[Joob1n]

Summary

The runtime no longer estimates whether a request fits a context window. Every "does it fit" question is answered by a provider; every trigger is a real number. This is the remaining step after #4486, which removed the fabricated capacity and the two terminal gates but kept the chars/4 delta estimate, the 32,000-token fallback history budget, and a per-step JSON.stringify of the whole request as a payload ruler. Design and discussion: #4559 (this PR), #4458 (history).

What decides now

• The conversation provider's own context-length rejection is recovered by one compact-and-retry; a second rejection surfaces as the provider's error (context_overflow), and the user's message stays editable.
• The summarizer's provider decides whether compaction input fits: input_too_large retreats the fold by half, and the loop exits through no_safe_completed_span when even the smallest legal span is refused.
• Proactive compaction has one trigger: the previous accepted request's real inputTokens + outputTokens, as the provider counted them, compared with the context window the user declared for the model (a model-facts pin or a relay profile). Reasoning tokens are counted whole on purpose — high is the safe direction for a trigger that can only ask for a compaction.
• A reply the provider cut at its output limit (finishReason: length) folds once before the next request.

What is gone: estimateNextRequestTokens, exceedsHighWater, midTurnRequestPayloadChars, the final-request rescue re-entry, maxHistoryEstimatedTokens and its five consumers, the quarter-window / 16,384 reserve, the 32,000 fallback, the replacement_not_smaller and prefix_over_budget replay gates, size-based replay selection, the estimated input fit before summarizer calls, and the chars/4 summary-size floor.

Notes for the user (four new system_note kinds): context_provider_dropping when an append-only step's usage did not grow (a provider evicting or rewriting context), and context_window_suggestion when a rejection lands at a proven-fit total, carrying the number the user can declare.

Refs #4559 — the issue closes when the whole series (#4574, #4575, #4576) has landed and the remaining items are triaged there.
Refs #4458, #4486

Follow-up PRs (stacked on this one)

The user-facing surfaces are deliberately split out so this PR stays the atomic runtime change and the UI pieces can be reviewed in parallel. Both are open as drafts on top of this branch and will be rebased and undrafted once this merges:

• feat(desktop): show the model's reported context window beside the declared setting #4575 — Desktop settings: the model's reported window shown beside the declared setting with a one-click apply. Without it, a user who has never declared a window gets no proactive compaction and no in-app pointer to the number they could set; the context_window_suggestion note from this PR is the runtime-side half of that pointer.
• feat(desktop): show context usage beside the model controls #4576 — Desktop composer: read-only context-usage indicator fed by the persisted lastRequestAnchor this PR introduces (percentage with a declared window, absolute tokens without one, a dash when the provider reports no usage).

Not in this series, defined and tracked on #4623 (the degraded modes when the provider does not speak): PR D applies the provider-dropping rule at the turn boundary, PR E adds a "compact and retry" action for provider rejections the error classifier does not recognise. Neither reopens a path this PR touches.

Behaviour changes to review

1. No declared window means no proactive compaction. The first time such a session fills up costs one provider round trip and possibly one cut reply; the context_window_suggestion note then offers the last accepted total as the value to declare. This is the "Maka does not decide for the user" principle; the trade-off is stated in Context budget: stop estimating fit; the provider decides, the Maka window is a user target #4559.
2. A /models report or models.dev metadata is no longer a threshold on its own.resolveDeclaredContextWindow (runtime) and declaredContextWindow (core, single owner of the rule) count only a facts pin or a relay profile. resolveSelectedModelContextWindow keeps its old meaning for display and contextRemaining.
3. token_usage.lastRequestAnchor is now { inputTokens, outputTokens? }. The retired payloadChars key still decodes, so sessions written by 0.2.0 keep loading; sessions written by this build do not open in 0.2.0 (the closed-allowlist cost already noted in CHANGELOG.md).
4. Summaries are capped at 8,000 output tokens (DEFAULT_HISTORY_COMPACT_MAX_OUTPUT_TOKENS; the summarizer's maxOutputTokens option was declared and never passed). A length finish gets one shorter retry, then fails open. The too-small-for-fold floor reads the summarizer call's real usage; a producer that reports none is not floored.
5. Checkpoint replay is structural: a source-matched checkpoint replays as [block, everything after the boundary]. No local size gate stands between a materializable fold and dispatch.
6. ContextBudgetDiagnostic.maxHistoryEstimatedTokens is retired (decode-only). HistoryCompactionPolicy.midTurn loses reserveTokens. buildDefaultContextBudgetPolicy drops its connection parameter.
7. Every OpenAI-compatible Chat request now asks for stream usage (stream_options.include_usage), unless the registry opts a provider out. Found live: only two providers opted in, so a local Ollama and every plain OpenAI-compatible relay — the connection type behind Context budget: an undeclared window fabricates a capacity that kills live turns #4458 — returned no usage, and the baseline, the eviction check and the indicator all stayed dark for them.
8. Summary requests close with a user instruction. Found live: a chat-template model handed a conversation ending on its own turn emits end-of-sequence and nothing else (Ollama qwen2.5, both sizes: finish stop, one output token, empty text), so history compaction never succeeded against a local model. Existing message-shape tests gained the trailing user:text.
9. The trigger reserves the model's declared output limit and fires on >= (review). baseline + outputLimit >= declaredWindow, where the limit is connection.models[].maxOutputTokens or generated metadata — a provider fact — and 0 when none is declared. Without it a window declared at the provider's real size could never be crossed by an accepted request. The window itself remains the user's declaration (see the reply on the review for why the metadata window stays a hint).
10. A context-length rejection from the summarizer's provider is input_too_large again (review), so the planner's retreat-by-half has a producer; the same classification is applied to the Codex compaction call.
11. The window suggestion note is written only when the turn surfaces the rejection (review): after the one fold is spent or when there is no seam, naming the last accepted total, which a fold does not clear.
12. The size floor judges an initial fold only (review): on a roll-forward the summarizer's input is the increment, not the covered span, so the floor stands down there and the fold context carries usage only. The eviction check compares input against input, since reasoning is not resent on every wire.

On dropping the signed delta

#4486 kept a signed chars/4 delta so step 0 could fold before a large new message or image went out. I dropped it: the delta prices an image at a constant and under-reads CJK by about half, so the round trip it saves is the one it is most likely to misjudge; large text results are already capped by the byte-based tool-result archive before they go out; and removing it takes the whole payload ruler and the per-step JSON.stringify(messages) with it. Happy to be argued back.

Test coverage removed

Thirty-seven tests encoded the estimate, the reserve, the payload ruler, the fit gates, or the pre-turn estimate gate; each is either re-pointed at a real-usage observable or removed with the mechanism. Re-pointed: the usage baseline is the last request's INPUT tokens → input plus output; compacts over the high water → compacts after provider usage crosses the declared window; keeps user_stop when stopping an oversized pre-turn summary → keeps user_stop when stopping while a usage-triggered fold is summarizing; persists the LAST request as the anchor → persists the last request input and output as the anchor; replays a durable pre_turn checkpoint below the current high water → without a local size gate; rejects a paragraph-sized summary for a large folded span → when usage says it is too small. Removed outright (the mechanism is gone): the three manual compactHistory … exceeds current limits / makes the full replay larger cases, the three reserve-derivation cases, anchors on real provider usage plus a tail char/4 delta, credits a SIGNED negative payload delta, falls back to whole-projection char/4 on cold start, high-water crosses at contextWindow minus reserve, a fold that cannot shrink the real payload is refused, a runaway summary is rejected as replacement_not_smaller, bounds the oldest oversized tool result before dispatch, fails with input_too_large before dispatch, charges the summarization instructions against the input budget, a summary at exactly the floor is accepted under ceil-based token estimates, the capacity verdict measures the steering payload, the anchor a finalization step writes excludes the tool schemas it cleared, dispatches a pre-turn Compaction recipe without projecting history and keeps a transiently unavailable automatic Compaction checkpoint recoverable (both exercised the deleted pre-turn gate; memory extraction from a hook-triggered fold stays covered), applies max-history overrides to checkpoint replay validation, accepts a complete checkpoint above legacy block limits when the full replay fits, compacts one oversized prior turn before an unknown-model request, compacts an oversized latest turn when an older turn is also retained, dispatches an oversized prior turn when its summary fails, after trying once, never runs a pointless summarizer on a small-window model, a usage object without usable input tokens falls back to cold start, a last-request anchor is only valid as a complete positive pair, a half-written anchor fails the whole token_usage message decode (replaced by the new-shape and retired-key cases).

New coverage: the declared-window rule for pin / relay / reported / metadata sources; baseline = input + output, > not >=, cleared after a fold, seeded from the previous turn, discarded across a model switch; a /models window is not a declaration; pendingLengthFold; the summarizer output cap, shorten retry, and output_length after two cuts; usage-based size floor; retreat by half and its give-up exit; structural replay; both notes, including the non-firing cases (pruned step, step 0, declaration already crossed); the retired payloadChars key decodes and an unknown key still fails.

Live verification against a real provider (Ollama)

Driven through the real AiSdkBackend with getAIModel against a local Ollama (qwen2.5:0.5b / qwen2.5:1.5b, default num_ctx 4096), five turns of ~740 tokens each, the previous turn's ledger and run header fed back as prior context.

Scenario	Observed
Declared window 1,500, qwen2.5:1.5b	Turns 1–3: anchors {745,10}, {1481,10}, {2217,10} persisted; baseline 1,491 at turn 3 is < 1,500, no fold. Turn 4: baseline 2,227 > 1,500 → pre_turn fold; summary malformed twice → failedOpen[malformed_summary_missing_section], request dispatched, end_turn. Turn 5: fold again, repair produces a 1,737-char checkpoint → replaced; the request's provider-counted input drops 2,954 → 1,222.
Same, before the two fixes above	No token_usage event at all (Ollama returned no usage because it was never asked); once usage flowed, the summarizer returned empty text every time. Both fixed in this PR.
No declared window, 8 turns	Never folds, never terminates; every turn end_turn. Usage grows 745 → 3,700 and then plateaus at 3,716 for turns 6–8 while ~740 tokens are appended per turn: Ollama truncates silently at num_ctx with no error.

Known limitation, stated plainly: the silent-truncation plateau above happens between turns, and context_provider_dropping only fires within a turn (step ≥ 1, on an input count that did not grow), because at step 0 a user edit can shrink the input legitimately. A provider that truncates instead of rejecting therefore gives an undeclared-window user no signal today; declaring the window is the protection. Detecting the cross-turn plateau without an estimate needs a ledger-shape check on the anchor (did anything before the anchored request change?) — a follow-up, tracked on #4559. Closing that gap is PR D on #4623.

Verification

Rebased on main@148f8eb29 (after #4578 landed, so this PR no longer carries the dependency bump); the Runtime Host compatibility epoch moves 104 → 105 for the two new note kinds and the reshaped anchor. Locally: npm --workspace @maka/{core,storage,runtime,runtime-host,mcp,ui} run build, npm run typecheck (all workspaces), npm run lint, npm run format:check, npm run check:asf-headers, node scripts/protocol-epoch-check.mjs --base origin/main — all clean. Targeted suites: 425/425 across usage-record-last-request-anchor, context-budget-mid-turn-policy, context-budget-model-facts, history-compaction, history-compact-checkpoint, history-compact-summarizer, mid-turn-capacity-backend, overflow-reactive-recovery, ai-sdk-backend; core suite 760/760; provider-conformance 24/24, history-compact-summarizer 53/53, execution-model-composition 28/28 and the CLI pi-transcript suites after the review fixes. Not run locally: the full npm test matrix (the Electron/OpenSSL and owned-Host timing cases fail on this machine independently of the branch) — relying on CI for those.

Self-review

• The core rule declaredContextWindow was implemented twice (runtime and chat-model-choice) in an earlier draft; consolidated into @maka/core/model-thinking with runtime delegating. One owner for the one rule the design turns on.
• The user-stop-during-summary obligation had lost its test when the pre-turn gate went; re-pointed at the hook-triggered fold. The test also records that one request is still attempted after the stop and is rejected by the transport on its already-aborted signal — pre-existing behaviour, now pinned.
• An earlier draft regenerated the Astryx theme with a stale local @astryxdesign/core@0.5.0; that artifact is not in this PR.
• memory-extraction.ts and session-recap.ts keep their own bounded-request budgets; they are auxiliary calls, not history compaction, and are out of scope here.
• Diagnostics (estimatedTokensBefore/After on compaction decisions) still use the chars/4 estimator. They are recorded numbers, not decisions, and are kept so existing telemetry consumers do not break.

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Claude Code — design discussion, implementation, tests, and review; verified by the author.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No

https://claude.ai/code/session_014ajaRxC4jydavY9nYUFj5J

[Astro-Han]

The direction is the one from #4458 and I still hold it: fit is the provider's answer, the trigger is a real number, and the only irreversible outcome is the provider's rejection. The reduction is real, every symbol in "What is gone" is gone from docs and desktop too, and all six workspace suites, typecheck, lint and format pass locally on 372c1de9, and the three commits since (148326eb) touch none of the files cited below. What stops me approving is not the code, it is three places where the design as implemented does not do what the design says. Line-level fixes are inline.

The proactive trigger cannot fire against a correctly declared window. The trigger is baseline > declaredWindow, and the baseline is a request the provider accepted. If the user declares the provider's real window, no accepted request can exceed it, the fold never runs, and every session goes through rejection first. It fires only when the user declares something smaller, which is the retired reserve reintroduced as a number the user has to guess without being told. This is open point 2 of #4559, and I would settle it the other way: resolve the window as declared > relay profile > models.dev > /models, none only when all are absent; trigger on baseline > window − reserve; make the reserve a real number, the model's output limit plus the tool-result archive cap times pending tool calls, with a fraction of the window as the floor. Those are provider facts and Maka's own content policy, so the "real numbers only" principle holds. A default is not Maka deciding for the user, it is a default the user can override, and the alternative is that out of the box every fill costs a rejection and possibly a cut reply, which CLI users get without even the hint, because pi-transcript.ts drops the two new note kinds. The per-step check already gives mid-turn triggering; only the window and the threshold change.

The summarizer's provider does not get to decide. The design names four deciders, and one of them, "the summarizer's provider decides whether compaction input fits, input_too_large retreats the fold by half", has no producer. Only fitHistoryCompactMessages throws input_too_large, this PR removes that call from history-compact-summarizer.ts and openai-codex-history-compactor.ts, and both catches wrap every provider error as provider_error. So a session whose fold prefix is too large for the summarizer fails open on the first rejection, /compact included, and has no in-app way back under the window. That is worse than main, which at least estimated. The fix is small, classify ContextLength in both catches, but the regression must use a fake provider that rejects above N tokens; all five current input_too_large tests throw the error from a fixture, which is why this was invisible.

The compatibility contract. Two new system_note kinds and the new lastRequestAnchor shape land in packages/core closed allowlists, the same class of change #4486 bumped the epoch for, and the epoch is unchanged. A merge-base client handshakes fine (host-kernel.ts admits on strict equality) and fails decodeStoredMessage on the first transcript carrying a new note. main is on 96 now: rebase, take 97, and put back the three CHANGELOG sentences from #4486 that are still true (see inline).

One consequence of the first point that lives outside the diff: settings-provider-copy.ts still says "when empty, built-in metadata decides", and /context and the inspector still divide by resolveSelectedModelContextWindow, so an undeclared user sees 70% of 200k and never gets a fold. Whichever way the window question settles, the copy and the denominator have to follow the same rule.

On the test claim: five re-pointed tests pass unchanged on main's built sources (the no-size-gate replay, the two size-floor cases, the no-usage case, fails open after repeated input-too-large retreat), and two rules lost their only coverage with the deletions while still existing, the memory gate's unavailable outcome and the rule that a synthetic /compact usage row must not shadow the real anchor. The remaining persisted-anchor test uses an anchor below the window, so it passes regardless of the run-header check.

Evidence boundary: static read against main61224f51; all suites run locally; new tests also run against main's built sources in a scratch copy; no live provider.

AI-assisted review: drafted with Maka; I verified the trigger arithmetic, the input_too_large producers, the epoch state and the size-floor inputs myself.

简体中文

方向就是 #4458 上讨论定下的，我仍然支持：放不放得下由 provider 回答，压缩触发用真实数字，唯一不可逆的结果是 provider 的拒绝。删得也干净，「What is gone」里的每个符号在 docs 和 desktop 里都没有残留，本地六个 workspace 的测试、typecheck、lint、format 全绿；之后的三个提交（148326eb）没有碰到下面引用的任何文件。让我暂时不 approve 的不是代码本身，而是三处实现和设计说的不是一回事。能局部修的都放在行内评论里。

主动触发对着正确声明的窗口永远打不响。 触发条件是「上次请求的 input+output 大于声明窗口」，而上次请求是 provider 已经接受的。如果用户把窗口声明成 provider 的真实大小，任何被接受的请求都不可能超过它，主动压缩一次也不会触发，每个会话都要先撞一次拒绝。只有用户把窗口声明得比真实值小它才触发，这等于把删掉的 reserve 变成了一个要用户自己猜、又不告诉他的数字。这是 #4559 的 open point 2，我的意见相反：窗口按「用户声明 > relay profile > models.dev 元数据 > /models 报告」解析，全都没有才算无；触发条件改成「上次用量 > 窗口 − reserve」；reserve 用真实数字：模型的 output limit（下一步回复最多这么大）加上工具结果归档上限乘以待处理的工具调用数，再用窗口的固定比例兜底。这些都是 provider 的事实和 Maka 自己的内容策略，「只用真实数字」的原则不受影响。给一个默认值不是替用户决定，用户随时可以覆盖；不给的后果是开箱用户每次填满都要付一次拒绝、可能还拿到被截断的回复，CLI 用户连提示都看不到，因为 pi-transcript.ts 把两个新 note kind 丢掉了。turn 内每一步都检查的逻辑已经有了，只需要改窗口和阈值。

summarizer 的 provider 并没有拿到决定权。 设计列了四个决定者，其中「summarizer 的 provider 决定压缩输入放不放得下，input_too_large 就把范围退半」这一条没有产生者。全仓只有 fitHistoryCompactMessages 会抛 input_too_large，本 PR 把它从 history-compact-summarizer.ts 和 openai-codex-history-compactor.ts 里删掉了，两处的 catch 又把所有 provider 错误一律包成 provider_error。于是一个长会话的折叠前缀如果对 summarizer 也太大，第一次拒绝就整体放弃，/compact 走同一条路也一样，会话在 app 内没有回到窗口内的办法，比 main 还差，main 至少还估算一下。修法很小，两个 catch 里判断 ContextLength 再抛，但回归测试必须用「输入超过 N tokens 就拒绝」的假 provider；现在五个相关测试全是 fixture 手抛这个错误，所以这个洞看不见。

兼容契约。 两个新的 system_note kind 和新的 lastRequestAnchor 形状都进了 packages/core 的闭合 allowlist，和 #4486 推 epoch 的那次是同一类改动，但 epoch 没动。merge-base 上的旧 client 握手能通过（host-kernel.ts 按严格相等准入），然后在第一条带新 note 的 transcript 上解码失败。main 现在已经是 96：rebase 取 97，并把 #4486 写的、仍然成立的三句 CHANGELOG 加回来（见行内）。

第一点在 diff 之外的一个后果：settings-provider-copy.ts 的帮助文案「留空跟随内置元数据」现在不成立，/context 和 inspector 的分母也还是 resolveSelectedModelContextWindow，未声明的用户会看到「已用 70% / 200k」却永远等不到压缩。窗口问题无论怎么定，文案和分母都要跟同一条规则。

关于测试的说法：五条 re-pointed 测试在 main 的构建产物上原样通过（无 size gate 的 replay、两条体量下限、无 usage、退半后 fail open）；两条规则随删测试失去了唯一覆盖但仍然存在：memory gate 返回 unavailable 的处理，以及手动 /compact 写的合成 usage 行不得遮蔽真实 anchor。剩下那条持久 anchor 测试的 anchor 低于窗口，不管 run header 合不合法都过。

[Astro-Han]

baselineTokens is a request the provider accepted, so with the window declared at the provider's real size this is never true; the fold only runs when the user declares something smaller. That is the reserve in disguise. baseline > window − reserve, with the reserve from output limit plus the tool-result cap, is what makes this fire before the rejection. First point in the main comment.

[Astro-Han]

Dead branch: nothing throws input_too_large any more. fitHistoryCompactMessages was its only producer and both summarizer catches now wrap provider errors as provider_error. Classify ContextLength with classifyError in history-compact-summarizer.ts and openai-codex-history-compactor.ts so this retreat has a producer, and test it with a fake provider that rejects above N tokens.

[Astro-Han]

Baseline includes last step's reasoning; on wires that do not resend it (gpt-5.x), next input ≈ previous input + tool call + result, which is below input + output whenever reasoning exceeded the appended content, the normal case. Compare against last step's input alone; keep input + output for the trigger.

[Astro-Han]

Written before recoverFromOverflowError runs, so a send that overflows once, folds and completes still tells the user the provider refused. #4559 places this under "already folded". Move it after the recovery verdict; overflow-reactive-recovery.test.ts:1834 (tool, overflow, done) currently pins the wrong order. And suggestedContextWindow: baselineTokens sits on the strict > boundary, so a user who applies it still needs one more rejection.

[Astro-Han]

On a roll-forward the summarizer is sent previous summary + new events, so inputTokens is the increment while the checkpoint replaces the whole covered span; in steady state this floor never trips and a fifty-token summary after a small increment is persisted. The new test passes on main because the stub's usage is unrelated to the messages. Feed it a span-sized real number (previous checkpoint's compactCallInputTokens plus this increment) or drop the floor openly.

[Astro-Han]

The comment above says this re-runs the size floor, but no summarizerUsage is passed so the floor is skipped, and coveredRuntimeEvents is now required and unread by the validator. Same for the external-producer branch in history-compaction.ts. Either pass a real number or delete the field, the three constructions and the comment.

[Astro-Han]

Three sentences from #4486 were dropped and are still true: sessions from this build do not open in earlier releases and the runtime.sqlite copy must be taken before upgrading; context_budget_exhausted is no longer produced but still decodes; the epoch line (97 after rebase). The body says the allowlist cost is "already noted in CHANGELOG.md", and it no longer is.

[Joob1n]

Thanks for the read — every finding was real. Fixes are in 38b2d837 (one commit, each item with a test that fails on the previous commit), plus two live-provider findings in the commits before it.

Trigger arithmetic. You are right that baseline > declaredWindow could never fire against a window declared at the provider's real size. Fixed the way you suggested for the reserve, with one narrowing: the reserve is the model's declared output limit only (connection.models[].maxOutputTokens or generated metadata; 0 when none is declared), and the trigger is baseline + limit >= window. I did not add the tool-result cap × pending calls term: the active prune already bounds each result before it goes out, and a second constant on the trigger side is the kind of number the design is trying not to own. Live on Ollama (qwen2.5:1.5b, declared 1,500) the fold now fires at 2,227 with the previous usage as the only input, folds to a 1,737-char checkpoint after one repair, and the next request's provider-counted input drops 2,954 → 1,222.

Window source — kept as declared-only, deliberately. This is the one point where I did not take the suggestion, and it is the issue author's call rather than mine: the Maka window is a target the user chooses to stay under, not a fact about the model, so the model's reported window is shown beside the setting with one click to apply (#4575) but never becomes the threshold on its own. The cost you name is real and stated in the description: with nothing declared, the first fill costs one rejection and possibly one cut reply. The context_window_suggestion note then offers the last accepted total; it is now written only when the turn actually surfaces the error, and the CLI transcript renders both new note kinds.

input_too_large producer. Correct — I removed the only producer. Both summarizer catches now classify ContextLength as input_too_large, with a fake provider that rejects above N characters as the regression.

Epoch and CHANGELOG. Bumped to 97 on rebase and the three sentences are back.

Inline items: eviction check compares input with input; the size floor applies to the initial fold only (the roll-forward input is the increment, as you say) and CheckpointSummaryFoldContext carries usage only, so the builder/copy seams validate structure and truncation; the suggestion note moves after recovery and names the fold-proof last accepted total; the run-header test's anchor now sits above the window so the header check decides; the synthetic /compact row test is restored; the roll-forward floor test now asserts both directions.

Two things I left as they were, with reasons. The Host's runComposition.contextWindow stays the model's reported window: it is a protocol fact clients already display, and the declared window gets its own surface in the composer indicator (#4576) rather than a changed meaning for an existing field. And the memory-gate unavailable outcome is still exercised by the mid-turn fixture's extraction path (remember returns unavailable there, asserted at the fold that dispatches extraction); if you meant a different obligation, tell me which and I will pin it.

[Joob1n]

Rebased on main@8ea3c4f05 now that #4578 has landed, so the dependency bump is no longer carried here (6 commits). main moved the compatibility epoch to 98 in the meantime (#4561 / #4568), so this PR's bump is now 98 → 99; the CHANGELOG line and the epoch comment follow. No other changes since a65076258.

[likun666661]

方向我赞成：把“请求是否 fit”的裁决权完全交给 provider，把本地侧收缩为“真实 usage + 用户目标只触发可逆 fold”，比多把估算尺同时参与决策更干净。PR 的主要因果链也基本成立。不过在 approve 前，我认为还有下面几个点需要收口：

1. [P1] compatibility epoch 与最新 main 撞号。 当前 main@898b86d 已经把 RUNTIME_HOST_COMPATIBILITY_EPOCH 升到 99，用于 ScheduledTask 的 Connection identity；本 PR 也独立使用 99 表示两个新 system note 和 lastRequestAnchor shape。两边是不同的不兼容协议变化。rebase 后不能只解决文本冲突并继续保留 99，需要把合并结果升到 100，同步注释、CHANGELOG 和 epoch test；否则能力不同的 client/host 可能错误通过严格相等握手。

2. [P2] repair 请求里的 ContextLength 会被吞成初次格式错误。history-compact-summarizer.ts:206-243 中，初次 summary malformed 后，repair 使用更长的 system prompt。如果初次调用刚好 fit、repair 因新增 instruction 被 provider 拒绝，内层 catch 会把该错误包装成初次的 malformed_summary_*；外层看到它已经是 HistoryCompactSummarizerError 后直接重抛，不会再分类为 input_too_large。planner 因此不会执行 halve-and-retry，和“summarizer provider decides”不一致。建议在 repair catch 中保留 ContextLength 分类，并补一个“initial malformed, repair overflow”的回归测试。

3. [P2] 架构文档仍描述修复前的 trigger。 中英文文档目前都写成“上次 inputTokens + outputTokens 超过用户窗口时触发”；实现已经是 baseline + model.maxOutputTokens >= declaredWindow（ai-sdk-compaction.ts:896-908）。这是核心规则，应同步两份文档，避免后续实现和测试重新漂移。

4. Issue closure 建议调整。#4559 的 proposal 还包含 missing-usage hint、unclassified overflow 的 compact-and-retry action、metadata window 一键采用和 composer indicator。本 PR 没有 missing-usage note，unclassified action 明确留在系列之外，UI 又拆到 #4575/#4576。拆 PR 没问题，但此时 Closes #4559 会让完整验收范围过早关闭；建议改成 Refs #4559，或先明确把 #4559 收缩为 runtime-only。

从 Occam 的角度，我的判断是：架构方向已收敛，问题定义尚未完全收敛。 最小因果主线已经很清楚：

history grows
→ user target may request a reversible fold
→ provider outcome decides actual fit
→ canonical history is never rejected or mutated by an estimate

但“provider decides”尚未覆盖 provider 沉默的情况：PR 自己的 Ollama 实测已经显示跨 turn usage plateau / silent truncation，而当前 dropping note 只检查同 turn 的 step ≥ 1。建议把无 usage、无法分类以及 silent eviction 明确定义成可见的 degraded mode；否则“未声明 window 时系统提供什么保证”仍是开放语义。

另外，includeUsage ?? true 现在会给所有 OpenAI-compatible Chat server 发送 stream_options.include_usage。现有 conformance test 只覆盖支持该字段的 fake server；最好再补一个严格 relay 拒绝该字段时的契约测试，明确 fail、fallback 或 opt-out 行为。

CI 当前是绿的，diff check 也干净；上面第 1 项是基于最新 main 的当前 merge blocker，第 2 项是静态可达的 provider-boundary bug。修完这些，我认为核心 runtime 改动可以继续推进。

[Joob1n]

Thanks — the first three are real and are fixed in 6c5e53ddd / ba14a706c; the fourth is done in the PR body.

1. Epoch.main moved again while this was open (#4321 → 99, #4508 → 100), so the rebase now lands this PR's bump as 100 → 101; comment, CHANGELOG and the epoch check follow. The protocol tests assert against the exported constant, not a literal, so nothing else pins the number.

2. Repair-path ContextLength. Confirmed: the repair catch wrapped every failure under the initial defect, so a context-length rejection of the longer repair prompt never reached the planner as input_too_large. The catch now classifies before wrapping; regression test "a context-length rejection of the repair request stays the input_too_large signal" (initial malformed → repair rejected → input_too_large, two provider calls) fails on the previous commit.

3. Docs. Both llm-compaction-events-log-projection-draft documents now state the implemented trigger: previous accepted inputTokens + outputTokensplus the reply reserve (the model's declared maxOutputTokens, zero when unknown) reaching the declared window.

4. Issue closure. Changed to Refs #4559; the issue closes when #4574/#4575/#4576 have all landed and the remaining proposal items are triaged there.

On the two broader points:

• Degraded modes (no usage, unclassified rejection, cross-turn plateau). Agreed that these deserve names. They are deliberately outside this PR: the dropping note is scoped to a single send because within one send Maka knows it only appended, while across turns the user may have edited or branched and a lower inputTokens is legitimate. Opened context: define the degraded modes when the provider does not speak (no usage, unclassified rejection, silent eviction) #4623 with the three modes, the signal each one gives today, and the two small follow-ups: PR D applies the same dropping rule at the turn boundary (first request's inputTokens below the persisted anchor with no fold or prune before the send → note), PR E adds "compact and retry" on an unclassified provider error. Both are notes/actions on top of this PR's paths, so they can land right after it without reopening it.

• stream_options on strict relays. Decided and pinned in 6ce7d7332: a relay that rejects the field fails with the provider's own 400 text and the runtime does not resend without it — the conformance test asserts one request, the stream_options body field, and the provider message reaching the stream's error part. Rationale: a connection that cannot report usage has no context baseline, so a silent fallback would hide exactly the degraded mode above; the error names the field, and a per-adapter includeUsage: false is the one-line opt-out if a real relay needs it. The field has been part of the Chat Completions API since 2024-05 and the Kimi OpenAI path in this repo has sent it since feat(runtime): support Kimi OpenAI protocol #1462.

[Joob1n]

Rebased on main@b1ec28989. main took epoch 101 in the meantime (#4608), so this PR's bump is now 101 → 102; comment, CHANGELOG and the epoch check follow. The strict-relay contract test is e10dd49a4's head commit (was 6ce7d7332 before the rebase). No other changes.

[likun666661]

复查了最新 head e10dd49a4。上一轮的主要项都已正确落地：epoch 102 对应 merge base 101；repair-path ContextLength 保留为 input_too_large 且有回归；两份文档的 trigger 公式已更新；PR body 改成了 Refs #4559；strict relay 的一次 400 / 不静默重试契约也已固定。CI 当前是绿的，PR 可干净合并。

还有两个行为/scope 问题和一个文档漂移需要收口：

1. [P1] #4559 仍会被 closing keyword 关闭。 PR body 虽然已经改成 Refs #4559，但首个 commit 20f01b862 的 message body 仍然包含 Closes #4559。本仓库只允许 squash merge，并配置为 squash_merge_commit_message: COMMIT_MESSAGES；因此这个 closing keyword 会进入 default-branch 的 squash commit，仍会关闭 issue。既然约定是整个 #4574/#4575/#4576 系列落地并完成剩余 triage 后再关闭，请把该 commit message amend 为 Refs #4559（或确保最终 squash message 中完全没有 closing keyword），而不只是修改 PR body。

2. [P2] provider-dropping 实现检测的是“严格下降”，对外契约写的是“没有增长”。packages/runtime/src/ai-sdk-backend.ts:2170-2182 当前条件是：

   stepUsage.inputTokens<lastStepInputTokens

   但 PR summary、commit message、CLI/UI copy 和新开的 #4623 都把信号定义为 usage “did not grow / stops growing or drops”。本 PR 自己的 Ollama 证据正是输入在 3,716 持平 plateau；严格 < 不会对这个案例写 note。当前测试也只有 100 → 50 的 decrease，没有 equal-usage case。

   如果 observable contract 确实是“append-only request 的 input 没增长”，这里应使用 <= 并补一个 equal-usage regression。#4623 的 PR D 也不应只定义成 “below persisted anchor”，否则同一个跨-turn plateau 仍不会被检测。若等值被刻意排除，则应反过来收窄 PR、copy 和 #4623 的声明，并说明为什么 plateau 不是可靠信号；现在代码和承诺二者只能有一个成立。

3. [P3] 中文架构文档仍有两处旧的 size-policy 语义。docs/architecture/llm-compaction-events-log-projection-draft.zh-CN.md:88-93 的公式仍写 current context budget，而英文已改成 user-declared capacity and provider outcome；同文档 :121-130 仍把 checkpoint 的必要问题写成“它在当前 token policy 下仍然能否进入 prompt？”，英文已改为 source/provider-state identity。后文已经明确删除 replay size verdict，因此这两处应与英文及最终实现同步。

除了以上三项，上一轮要求的修复我没有再发现回归。前两项处理后，我认为这轮可以进入 approve。

[Joob1n]

All three are fixed on 2cbc332af.

1. Closing keyword in the commit body. You are right that the PR body is not where this is decided under squash merge with COMMIT_MESSAGES. 20f01b862 is reworded to Refs #4559 (now 3ed669070 after the rebase); no commit on the branch carries a closing keyword any more.

2. < vs <=. Fixed to <=, with the copy as the authority rather than the other way round. Your reading of the evidence is the right one: the live Ollama run plateaus at 3,716 input tokens and never drops, so the strict comparison would have missed the exact case the PR cites. An equal input count after an append-only step (no fold, no prune, no image omission) is already impossible without provider-side eviction or rewriting, so equality is signal, not noise. New regression "records provider context dropping when an append-only step reports the same usage" (100 → 100 across the step) fails on the previous commit; the existing decrease and prune-explains-it tests still pass.

#4623 is updated to match: PR D's rule is "at or below the persisted anchor", not "below", for the same reason.

3. Chinese document drift. Both passages are synced with the English text: the materialization inputs now read 用户声明的 capacity 与 provider 结果, and the checkpoint's replay question is source/provider-state identity rather than the retired token policy.

One note on scope: both documents still ask "which high-water decision produced it" in that same list. It is stale in both languages equally, so I left it rather than widening this PR's document diff; say the word and I will fold it in here, otherwise it goes with the #4623 documentation pass.

[me2seeks]

Reviewing with real edge cases in mind, grounded in production data from a kimi-coding-plan/k3-256k workspace (see also #4634 — this PR fixes its root causes 1 and 2; items 3 and 4 there remain open).

Overall the direction is sound: every trigger is now a provider-reported number, and I live-verified the new summarizer request shape against k3-256k (details inline on the summarizer change). My concerns are about the paths where the provider never speaks: silent over-window acceptance, output-limit cuts caused by our own maxOutputTokens, and unrecognized error shapes.

[me2seeks]

Real edge case from live data: kimi-coding-plan/k3-256k accepts requests beyond its fetched window without rejecting or truncating — observed a session accepted at 322K input tokens against a fetched contextWindow of 262,144, with usage still growing monotonically (305K → 322K). On such a provider every signal this design reads stays dark for an undeclared window:

• no rejection → reactive fold never fires;
• usage never plateaus → context_provider_dropping never fires (and it is mid-turn only anyway);
• context_window_suggestion only fires on a surfaced rejection → never written;
• a fetched /models window is not a declaration → the proactive trigger below never arms.

Net effect: an undeclared kimi session degrades silently and indefinitely (this is exactly the data behind #4634). I agree with "Maka does not decide for the user" as a principle, but for providers observed to accept over-window requests, could the fetched window seed a default declaration (user-overridable), or should the cross-turn plateau check (#4623 PR D) be a blocker rather than a follow-up?

[me2seeks]

pendingLengthFold is set on anylength finish with no size or cause guard. Two real cases where the fold is useless or harmful:

1. The cut came from our own configured maxOutputTokens, not the window: maka sends maxOutputTokens: 131072 on kimi-coding-plan main requests (from lookupModelMetadata). A reply cut at that cap is not helped by folding history at all — the next request carries the same cap. If the model keeps wanting more output (long reasoning at effort=max, large file generation), this turn folds every step, repeatedly shrinking history while never addressing the constraint.
2. A user who declares a small output limit for cost control gets routine length finishes → folds at a few K tokens of context, paying a summarizer call each time.

Suggest gating the length fold on baseline + replyReserve >= capacity (i.e. plausibly window-caused), or capping length-folds per turn.

[me2seeks]

For k3-256k, declaredModelOutputLimit resolves to 131,072 from bundled metadata — half of its 262,144 window. A user who pins the full window gets proactive folding at baseline >= 131,072, i.e. ~50% utilization, which is far earlier than "stay under your declared window" suggests. Reserving the output limit is right in principle (without it a real-size declaration is never crossed), but when the declared output limit is a large fraction of the window the reserve dominates. Consider capping it, e.g. min(outputLimit, capacity / 4) or a fixed bound.

[me2seeks]

The per-send latch and the fingerprint circuit still only cover malformed-summary reasons. After a provider_error / output_length fail-open, baselineTokens stays set, so overWindow remains true and every subsequent step retries the summarizer. Observed live on kimi-coding-plan (which reports failures as HTTP 200 + error body): 15 consecutive failed summarizer calls over ~47 minutes, each 30–45 s, before the main request. Suggest latching any summarizer failure for the rest of the send, with the same fail-open diagnostic. (#4634 item 3)

[me2seeks]

Defaulting includeUsage on for every non-opted-out OpenAI-compatible server is the right call for usage coverage, but a strict relay/proxy that rejects unknown fields (older vLLM, some gateways) will 400 every streaming request after upgrade, and opting out requires a registry code change. Consider a one-time fallback: on a 400 whose error text mentions stream_options/include_usage, retry without it and remember that for the connection.

[me2seeks]

Two false-positive paths for the dropping note:

1. Finalization steps remove all tool schemas (resolveDispatch returns [] for the child-summary / sandbox-boundary finalization step), which legitimately drops the next request's input by several K tokens with no fold/prune/image-omit — this condition doesn't exclude that case, so a routine turn end can report "provider is dropping context".
2. No hysteresis: a 1-token decrease fires the note. Cache accounting or tokenizer drift between calls can produce tiny legitimate decreases. A small relative threshold (e.g. drop > 1–2% or > N tokens) would keep the note meaningful.

[me2seeks]

Confirming this fixes the kimi-coding-plan failure mode from #4634 — I live-tested this exact request shape (system template + trailing user instruction) against k3-256k on both wires: it now returns a fully compliant sectioned summary, where the system-prompt-only shape returned content: null (7 tokens) or continued the conversation as the assistant.

One follow-up worth noting (not blocking): the summarizer request still opens with a different system prompt than the main loop, so it shares no prefix cache with it — the first fold of a session pays a full uncached pass over the folded span (observed 39–88 s on 155–253K inputs). Moving the whole instruction into the trailing user message would let the summarizer reuse the main loop's cached prefix (~99% hits); keeping the template in system is also fine if that's load-bearing for other providers, but the cache cost is real at high context.

[Joob1n]

Thank you for the production data. Every path you named is real, and four of them are fixed on 1faabac55. The evidence for each is your k3-256k workspace, so I have quoted your numbers in the commit message rather than restating them here.

Summarizer retry storm (#4634 item 3). Fixed. The per-send latch recorded only malformed reasons, and the baseline that fired the trigger survives a fail-open, so a provider_error re-armed the same condition on every later step. Every fail-open reason now latches for the rest of the send. Regression: "bounds a provider-error summarizer failure across later steps in the same turn" (one summarizer call, failOpenReason: provider_error, no checkpoint), failing on the previous commit.

pendingLengthFold with no cause guard. Fixed, and your first case is the discriminator: the reply's own outputTokens says which limit cut it. A reply that stopped at the maxOutputTokens Maka sends was cut by Maka's budget, and the next request carries the same budget, so the fold is marked only when the reply stopped below it. That covers your cost-control case too, since a small declared output limit is reached exactly. No new constant, and both numbers are provider-reported. Regression: "does not fold when the reply was cut by the output budget Maka itself sends".

Dropping-note false positives. The finalization case is fixed: the note is suppressed when the step's own active tool set shrank, which is Maka reshaping the request rather than the provider evicting anything. Regression: "does not report provider dropping when the step dropped its tool schemas". On hysteresis I would rather not add a threshold, and I think the <= change (this PR now treats a plateau as the signal, per @likun666661's review) makes the case: after an append-only step, an input count that merely failed to grow already means the appended content was not counted, so a one-token decrease is not a weaker signal than equality but a marginally stronger one. normalizeAiSdkUsage sums no-cache, cache-read and cache-write, so cache accounting does not move the total. If you have a case where drift moves it anyway, that is worth a threshold and I will add one.

stream_options on strict relays. Adopted your suggestion over my earlier position, which @likun666661 also questioned: the deciding argument is that opting out needs a registry code change, so a strict relay has no user-facing recovery. A 400 whose body names the field now triggers one retry without it, remembered per base URL for the process. The connection then simply reports no usage, which the composer indicator (#4576) shows as a dash. Contract test asserts the three requests: asked, retried without, and never asked again.

Providers that accept beyond their fetched window. This one I have not changed, and I want to be explicit about why, because you are right that every signal stays dark. A cross-turn plateau check (PR D on #4623) does not rescue it either: your session's usage grows monotonically to 322K, so there is no plateau to detect. The only thing that arms anything is a declaration. Two options I can see:

1. A note when accepted usage exceeds the model's reported window while nothing is declared. That is two real numbers and no decision on the user's behalf, and it is the same shape as the existing context_window_suggestion. It fits this design and I would be glad to add it, here or as PR D's sibling.
2. Seeding a default declaration from the fetched window, which is the thing Context budget: stop estimating fit; the provider decides, the Maka window is a user target #4559 deliberately removed: a fetched number is a hint, and a session that compacts because of a number the user never chose is the failure this PR exists to end.

My preference is 1. Say which you would rather review and I will follow.

Prefix cache on the summarizer request. Noted as a follow-up, not forgotten: your 39–88 s uncached first attempts are a strong argument for moving the whole instruction into the trailing user message now that the trailing message exists. I have left the system template in place here because it is load-bearing for the providers the current tests cover, and changing both the shape and the cache behaviour in the same PR would make the k3-256k regression hard to attribute. It belongs on #4634.

Thanks also for live-testing the summarizer request shape; that is the part of this PR I could only verify against Ollama and fake providers.

[Joob1n]

Follow-up on the two open items from your review, both now on 77590471e.

The reply reserve is no longer the model's output limit. Your k3-256k arithmetic was the deciding case: reserving 131,072 against a 262,144 declaration folds at half the window a user deliberately chose. It is now twice the last reply the model actually wrote, bounded at 8,000 tokens. Both halves are provider-reported, the margin tracks the session's own behaviour rather than a catalog maximum, and no previous reply means no reserve at all. On your numbers a session answering in 2–3K tokens now folds at roughly 256K of 262K instead of 131K. The old test that asserted the output limit is rewritten around the new rule (a 900-token anchor with a 60-token reply folds against a 1,000 window, the same anchor with a 5-token reply does not, and the model's 600-token output limit is irrelevant to both).

A reserve measured from a smaller previous reply can still be too small, so that case is now reported rather than silent: when an accepted request's own input plus its reply exceed the declared window, the transcript carries one context_window_overrun note per send with both numbers. It is the honest reading of "the reply needed more room than was left", it uses only provider-reported numbers, and it tells a user who wants whole replies to raise the declaration. The next request folds anyway because the baseline now exceeds the window; the note explains why rather than changing what happens.

That makes three note kinds in this PR, all in the same epoch move (now 103 → 104 after the latest rebase).

Still yours to choose: the undeclared-window case on a provider that accepts past its reported window. My preference remains a note when accepted usage exceeds the model's reported window while nothing is declared, rather than seeding a declaration from a fetched number. Say which you would rather review.

[Joob1n]

Added, on 0d0a32dce: with nothing declared, a request the provider accepts past the window its own catalog entry reports now writes one context_reported_window_exceeded note per send, naming what the exchange used and what the model reports. It changes nothing on its own — a reported window stays a hint, and Maka still declares nothing on the user's behalf — but the case you found is no longer invisible. With a declaration in place the overrun note already owns that ground, and a test pins that the two never fire for the same fact.

That is the fourth note kind in this PR, all within the same epoch move (103 → 104 after the latest rebase). Local gates are green; the mid-turn suite is 73/73.

[me2seeks]

Thanks — verified 1faabac55 and 77590471e on the diff. The cutByOwnBudget discriminator is a better fix than the proximity gate I suggested: it distinguishes the two length causes with two provider-reported numbers, and my cost-control case falls out of it for free. The behaviour-measured reply reserve (2× last reply, ≤8K) fixes the k3-256k half-window arithmetic, and context_window_overrun is the right honest reporting for a reply that outgrew a reserve measured from smaller ones.

Undeclared window on a provider that accepts past its reported window: I choose option 1 — a note when accepted usage exceeds the model's reported window while nothing is declared. Two reasons beyond the ones you gave:

1. Coverage differs by surface. TUI has a real-time ctx indicator (I have a PR open adding one, with colour) so a TUI user can transiently see 322K > 262K; Desktop has nothing. A persisted note in the transcript is the only durable signal on Desktop, and the only one that survives the moment on TUI.
2. The note closes the loop with feat(desktop): show the model's reported context window beside the declared setting #4575. The number it should name is the reported window the user could adopt, and the natural call to action is the settings surface with the one-click apply from feat(desktop): show the model's reported context window beside the declared setting #4575.

One constraint from the k3-256k data: on such providers usage crosses the reported window gradually and keeps growing (305K → 322K), so the note should fire once per session when the crossing is first observed (the accepted total first exceeds the reported window), not per send — otherwise it spams on every step past the line.

On hysteresis for the dropping note: your <= argument and the normalizeAiSdkUsage sum hold; I have no live case where drift moves the total, so I withdraw that suggestion.

I will take the summarizer prefix-cache item back to #4634 as agreed.

[Joob1n]

Adopted the once-per-crossing constraint on 8c88243ca. The note now fires on the transition rather than per send: the previous accepted total was still inside the reported window and this one is not. That previous total comes from the persisted anchor, so a resumed session does not repeat a crossing it already reported, and a session that is already past the line stays quiet. Test "does not repeat the reported-window note once the session is already past the line" (a 320-token anchor against a reported 100) fails without the guard.

Your two reasons are both in the code's favour: the note is the durable Desktop signal, and it names the reported window, which is the number #4575 offers to apply in one click. Noted on the withdrawn hysteresis and on taking the prefix-cache item to #4634.

[Joob1n]

Correction on the previous push: a rebase of mine stopped on a conflict and the branch was pushed mid-rebase, so 8c88243ca briefly showed this PR with 5 of its 13 commits. The head is now 1283c874c, rebased on main@148f8eb29 with all 13 commits and every local gate green. Nothing in the content changed; main also took epoch 104 in the meantime, so this PR's bump is now 104 → 105 and the comment, CHANGELOG and commit message follow.

[Joob1n]

Closing this in favour of a smaller series. Not because anything here was wrong: it is green and every review item on it is either fixed or deliberately carried forward. The reason is that the design converged past what this PR's shape can carry, and a reviewer arriving now would have to reconstruct it from four rounds of comments.

Two things changed after the last round, both simplifications, and both invalidate part of this PR rather than adding to it:

1. The compaction module runs at most once per send. The proactive and reactive folds were two independent latches here. A fold already covers everything except the live head, so a second one buys a little tail and costs the most recent verbatim context. When a request is still rejected after a fold, the honest diagnosis is that the new message itself is too large, and that is what the user should be told.
2. A finishReason: length no longer triggers a fold. A reply cut below the maxOutputTokens Maka sends can mean the provider ran out of window room, or that the provider has its own lower output cap. Those are indistinguishable from the outside, and an indistinguishable signal should not drive an action. This removes the cutByOwnBudget discriminator @me2seeks and I converged on, one level up: the discriminator was right for the question asked, but the question should not have been asked.

A third change is larger and belongs on its own review: when a fold is rejected as too large, retreat to the span the last accepted request's input covered, rather than halving the covered range. That boundary was accepted by this exact model on this exact connection, so it is provably within capacity, where halving is a guess. The last reply's own span is folded separately when it exceeds 24,000 tokens.

The full design is written up on #4559 as three modules (judge / send / compact) with the call bounds.

Where each review finding goes

Finding	Reviewer	Lands in
Trigger arithmetic needs a reply reserve	@Astro-Han	PR 1
input_too_large must have a real producer	@Astro-Han	PR 2
Eviction check must compare input against input	@Astro-Han	PR 1
Window-suggestion note timing (after recovery, not before)	@Astro-Han	PR 1
Size floor only on the initial fold, not on roll-forward	@Astro-Han	PR 2
Fold-context cleanup, CHANGELOG, CLI note kinds, epoch	@Astro-Han	PR 1
Epoch collision with main	@likun666661	PR 1
Repair request's context-length rejection swallowed as a format defect	@likun666661	PR 2
Architecture documents describing the pre-fix trigger	@likun666661	PR 1
Closing keyword in the commit body, not just the PR body	@likun666661	PR 1
Dropping note must fire on a plateau (<=), not only a decrease	@likun666661	PR 1
Summarizer retry storm: latch every failure, not only malformed ones	@me2seeks	PR 2
Reply reserve must not be the model's output limit	@me2seeks	PR 1
Dropping note false positive on tool-schema shrink	@me2seeks	PR 1
stream_options retreat for strict relays	@me2seeks	PR 1
Undeclared window on a provider that accepts past its reported window	@me2seeks	PR 1
Reported-window note once per crossing, not per send	@me2seeks	PR 1
Length-fold cause guard	@me2seeks	superseded, see 2 above
Summarizer prefix-cache cost	@me2seeks	#4634

The series

• PR 1 — send module: trigger, reply reserve, persisted anchor, one compaction per send, "this message is too large", stream-usage collection with the strict-relay retreat, and all four system notes. One epoch move.
• PR 2 — compaction module: summarizer request shape, output cap and retries, failure latch, and the retreat to the last accepted input boundary.
• feat(desktop): show the model's reported context window beside the declared setting #4575, feat(desktop): show context usage beside the model controls #4576 — unchanged, rebased onto PR 1 when it lands.
• PR 5 — "compact and retry" for a rejection the classifier does not recognise (context: define the degraded modes when the provider does not speak (no usage, unclassified rejection, silent eviction) #4623).

Thank you all for the four rounds; the findings are carried, not discarded.

[Joob1n]

The replacement is #4653: the send module, with the two simplifications described above and the same review findings carried. The compaction module's retreat boundary follows in a second PR.

[Joob1n]

Summary

The runtime no longer estimates whether a request fits a context window. Every "does it fit" question is answered by a provider; every trigger is a real number. This is the remaining step after #4486, which removed the fabricated capacity and the two terminal gates but kept the chars/4 delta estimate, the 32,000-token fallback history budget, and a per-step JSON.stringify of the whole request as a payload ruler. Design and discussion: #4559 (this PR), #4458 (history).

What decides now

• The conversation provider's own context-length rejection is recovered by one compact-and-retry; a second rejection surfaces as the provider's error (context_overflow), and the user's message stays editable.
• The summarizer's provider decides whether compaction input fits: input_too_large retreats the fold by half, and the loop exits through no_safe_completed_span when even the smallest legal span is refused.
• Proactive compaction has one trigger: the previous accepted request's real inputTokens + outputTokens, as the provider counted them, compared with the context window the user declared for the model (a model-facts pin or a relay profile). Reasoning tokens are counted whole on purpose — high is the safe direction for a trigger that can only ask for a compaction.
• A reply the provider cut at its output limit (finishReason: length) folds once before the next request.

What is gone: estimateNextRequestTokens, exceedsHighWater, midTurnRequestPayloadChars, the final-request rescue re-entry, maxHistoryEstimatedTokens and its five consumers, the quarter-window / 16,384 reserve, the 32,000 fallback, the replacement_not_smaller and prefix_over_budget replay gates, size-based replay selection, the estimated input fit before summarizer calls, and the chars/4 summary-size floor.

Notes for the user (four new system_note kinds): context_provider_dropping when an append-only step's usage did not grow (a provider evicting or rewriting context), and context_window_suggestion when a rejection lands at a proven-fit total, carrying the number the user can declare.

Refs #4559 — the issue closes when the whole series (#4574, #4575, #4576) has landed and the remaining items are triaged there.
Refs #4458, #4486

Follow-up PRs (stacked on this one)

The user-facing surfaces are deliberately split out so this PR stays the atomic runtime change and the UI pieces can be reviewed in parallel. Both are open as drafts on top of this branch and will be rebased and undrafted once this merges:

• feat(desktop): show the model's reported context window beside the declared setting #4575 — Desktop settings: the model's reported window shown beside the declared setting with a one-click apply. Without it, a user who has never declared a window gets no proactive compaction and no in-app pointer to the number they could set; the context_window_suggestion note from this PR is the runtime-side half of that pointer.
• feat(desktop): show context usage beside the model controls #4576 — Desktop composer: read-only context-usage indicator fed by the persisted lastRequestAnchor this PR introduces (percentage with a declared window, absolute tokens without one, a dash when the provider reports no usage).

Not in this series, defined and tracked on #4623 (the degraded modes when the provider does not speak): PR D applies the provider-dropping rule at the turn boundary, PR E adds a "compact and retry" action for provider rejections the error classifier does not recognise. Neither reopens a path this PR touches.

Behaviour changes to review

1. No declared window means no proactive compaction. The first time such a session fills up costs one provider round trip and possibly one cut reply; the context_window_suggestion note then offers the last accepted total as the value to declare. This is the "Maka does not decide for the user" principle; the trade-off is stated in Context budget: stop estimating fit; the provider decides, the Maka window is a user target #4559.
2. A /models report or models.dev metadata is no longer a threshold on its own.resolveDeclaredContextWindow (runtime) and declaredContextWindow (core, single owner of the rule) count only a facts pin or a relay profile. resolveSelectedModelContextWindow keeps its old meaning for display and contextRemaining.
3. token_usage.lastRequestAnchor is now { inputTokens, outputTokens? }. The retired payloadChars key still decodes, so sessions written by 0.2.0 keep loading; sessions written by this build do not open in 0.2.0 (the closed-allowlist cost already noted in CHANGELOG.md).
4. Summaries are capped at 8,000 output tokens (DEFAULT_HISTORY_COMPACT_MAX_OUTPUT_TOKENS; the summarizer's maxOutputTokens option was declared and never passed). A length finish gets one shorter retry, then fails open. The too-small-for-fold floor reads the summarizer call's real usage; a producer that reports none is not floored.
5. Checkpoint replay is structural: a source-matched checkpoint replays as [block, everything after the boundary]. No local size gate stands between a materializable fold and dispatch.
6. ContextBudgetDiagnostic.maxHistoryEstimatedTokens is retired (decode-only). HistoryCompactionPolicy.midTurn loses reserveTokens. buildDefaultContextBudgetPolicy drops its connection parameter.
7. Every OpenAI-compatible Chat request now asks for stream usage (stream_options.include_usage), unless the registry opts a provider out. Found live: only two providers opted in, so a local Ollama and every plain OpenAI-compatible relay — the connection type behind Context budget: an undeclared window fabricates a capacity that kills live turns #4458 — returned no usage, and the baseline, the eviction check and the indicator all stayed dark for them.
8. Summary requests close with a user instruction. Found live: a chat-template model handed a conversation ending on its own turn emits end-of-sequence and nothing else (Ollama qwen2.5, both sizes: finish stop, one output token, empty text), so history compaction never succeeded against a local model. Existing message-shape tests gained the trailing user:text.
9. The trigger reserves the model's declared output limit and fires on >= (review). baseline + outputLimit >= declaredWindow, where the limit is connection.models[].maxOutputTokens or generated metadata — a provider fact — and 0 when none is declared. Without it a window declared at the provider's real size could never be crossed by an accepted request. The window itself remains the user's declaration (see the reply on the review for why the metadata window stays a hint).
10. A context-length rejection from the summarizer's provider is input_too_large again (review), so the planner's retreat-by-half has a producer; the same classification is applied to the Codex compaction call.
11. The window suggestion note is written only when the turn surfaces the rejection (review): after the one fold is spent or when there is no seam, naming the last accepted total, which a fold does not clear.
12. The size floor judges an initial fold only (review): on a roll-forward the summarizer's input is the increment, not the covered span, so the floor stands down there and the fold context carries usage only. The eviction check compares input against input, since reasoning is not resent on every wire.

On dropping the signed delta

#4486 kept a signed chars/4 delta so step 0 could fold before a large new message or image went out. I dropped it: the delta prices an image at a constant and under-reads CJK by about half, so the round trip it saves is the one it is most likely to misjudge; large text results are already capped by the byte-based tool-result archive before they go out; and removing it takes the whole payload ruler and the per-step JSON.stringify(messages) with it. Happy to be argued back.

Test coverage removed

Thirty-seven tests encoded the estimate, the reserve, the payload ruler, the fit gates, or the pre-turn estimate gate; each is either re-pointed at a real-usage observable or removed with the mechanism. Re-pointed: the usage baseline is the last request's INPUT tokens → input plus output; compacts over the high water → compacts after provider usage crosses the declared window; keeps user_stop when stopping an oversized pre-turn summary → keeps user_stop when stopping while a usage-triggered fold is summarizing; persists the LAST request as the anchor → persists the last request input and output as the anchor; replays a durable pre_turn checkpoint below the current high water → without a local size gate; rejects a paragraph-sized summary for a large folded span → when usage says it is too small. Removed outright (the mechanism is gone): the three manual compactHistory … exceeds current limits / makes the full replay larger cases, the three reserve-derivation cases, anchors on real provider usage plus a tail char/4 delta, credits a SIGNED negative payload delta, falls back to whole-projection char/4 on cold start, high-water crosses at contextWindow minus reserve, a fold that cannot shrink the real payload is refused, a runaway summary is rejected as replacement_not_smaller, bounds the oldest oversized tool result before dispatch, fails with input_too_large before dispatch, charges the summarization instructions against the input budget, a summary at exactly the floor is accepted under ceil-based token estimates, the capacity verdict measures the steering payload, the anchor a finalization step writes excludes the tool schemas it cleared, dispatches a pre-turn Compaction recipe without projecting history and keeps a transiently unavailable automatic Compaction checkpoint recoverable (both exercised the deleted pre-turn gate; memory extraction from a hook-triggered fold stays covered), applies max-history overrides to checkpoint replay validation, accepts a complete checkpoint above legacy block limits when the full replay fits, compacts one oversized prior turn before an unknown-model request, compacts an oversized latest turn when an older turn is also retained, dispatches an oversized prior turn when its summary fails, after trying once, never runs a pointless summarizer on a small-window model, a usage object without usable input tokens falls back to cold start, a last-request anchor is only valid as a complete positive pair, a half-written anchor fails the whole token_usage message decode (replaced by the new-shape and retired-key cases).

New coverage: the declared-window rule for pin / relay / reported / metadata sources; baseline = input + output, > not >=, cleared after a fold, seeded from the previous turn, discarded across a model switch; a /models window is not a declaration; pendingLengthFold; the summarizer output cap, shorten retry, and output_length after two cuts; usage-based size floor; retreat by half and its give-up exit; structural replay; both notes, including the non-firing cases (pruned step, step 0, declaration already crossed); the retired payloadChars key decodes and an unknown key still fails.

Live verification against a real provider (Ollama)

Driven through the real AiSdkBackend with getAIModel against a local Ollama (qwen2.5:0.5b / qwen2.5:1.5b, default num_ctx 4096), five turns of ~740 tokens each, the previous turn's ledger and run header fed back as prior context.

Scenario	Observed
Declared window 1,500, qwen2.5:1.5b	Turns 1–3: anchors {745,10}, {1481,10}, {2217,10} persisted; baseline 1,491 at turn 3 is < 1,500, no fold. Turn 4: baseline 2,227 > 1,500 → pre_turn fold; summary malformed twice → failedOpen[malformed_summary_missing_section], request dispatched, end_turn. Turn 5: fold again, repair produces a 1,737-char checkpoint → replaced; the request's provider-counted input drops 2,954 → 1,222.
Same, before the two fixes above	No token_usage event at all (Ollama returned no usage because it was never asked); once usage flowed, the summarizer returned empty text every time. Both fixed in this PR.
No declared window, 8 turns	Never folds, never terminates; every turn end_turn. Usage grows 745 → 3,700 and then plateaus at 3,716 for turns 6–8 while ~740 tokens are appended per turn: Ollama truncates silently at num_ctx with no error.

Known limitation, stated plainly: the silent-truncation plateau above happens between turns, and context_provider_dropping only fires within a turn (step ≥ 1, on an input count that did not grow), because at step 0 a user edit can shrink the input legitimately. A provider that truncates instead of rejecting therefore gives an undeclared-window user no signal today; declaring the window is the protection. Detecting the cross-turn plateau without an estimate needs a ledger-shape check on the anchor (did anything before the anchored request change?) — a follow-up, tracked on #4559. Closing that gap is PR D on #4623.

Verification

Rebased on main@148f8eb29 (after #4578 landed, so this PR no longer carries the dependency bump); the Runtime Host compatibility epoch moves 104 → 105 for the two new note kinds and the reshaped anchor. Locally: npm --workspace @maka/{core,storage,runtime,runtime-host,mcp,ui} run build, npm run typecheck (all workspaces), npm run lint, npm run format:check, npm run check:asf-headers, node scripts/protocol-epoch-check.mjs --base origin/main — all clean. Targeted suites: 425/425 across usage-record-last-request-anchor, context-budget-mid-turn-policy, context-budget-model-facts, history-compaction, history-compact-checkpoint, history-compact-summarizer, mid-turn-capacity-backend, overflow-reactive-recovery, ai-sdk-backend; core suite 760/760; provider-conformance 24/24, history-compact-summarizer 53/53, execution-model-composition 28/28 and the CLI pi-transcript suites after the review fixes. Not run locally: the full npm test matrix (the Electron/OpenSSL and owned-Host timing cases fail on this machine independently of the branch) — relying on CI for those.

Self-review

• The core rule declaredContextWindow was implemented twice (runtime and chat-model-choice) in an earlier draft; consolidated into @maka/core/model-thinking with runtime delegating. One owner for the one rule the design turns on.
• The user-stop-during-summary obligation had lost its test when the pre-turn gate went; re-pointed at the hook-triggered fold. The test also records that one request is still attempted after the stop and is rejected by the transport on its already-aborted signal — pre-existing behaviour, now pinned.
• An earlier draft regenerated the Astryx theme with a stale local @astryxdesign/core@0.5.0; that artifact is not in this PR.
• memory-extraction.ts and session-recap.ts keep their own bounded-request budgets; they are auxiliary calls, not history compaction, and are out of scope here.
• Diagnostics (estimatedTokensBefore/After on compaction decisions) still use the chars/4 estimator. They are recorded numbers, not decisions, and are kept so existing telemetry consumers do not break.

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Claude Code — design discussion, implementation, tests, and review; verified by the author.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No

https://claude.ai/code/session_014ajaRxC4jydavY9nYUFj5J

[Astro-Han]

The direction is the one from #4458 and I still hold it: fit is the provider's answer, the trigger is a real number, and the only irreversible outcome is the provider's rejection. The reduction is real, every symbol in "What is gone" is gone from docs and desktop too, and all six workspace suites, typecheck, lint and format pass locally on 372c1de9, and the three commits since (148326eb) touch none of the files cited below. What stops me approving is not the code, it is three places where the design as implemented does not do what the design says. Line-level fixes are inline.

The proactive trigger cannot fire against a correctly declared window. The trigger is baseline > declaredWindow, and the baseline is a request the provider accepted. If the user declares the provider's real window, no accepted request can exceed it, the fold never runs, and every session goes through rejection first. It fires only when the user declares something smaller, which is the retired reserve reintroduced as a number the user has to guess without being told. This is open point 2 of #4559, and I would settle it the other way: resolve the window as declared > relay profile > models.dev > /models, none only when all are absent; trigger on baseline > window − reserve; make the reserve a real number, the model's output limit plus the tool-result archive cap times pending tool calls, with a fraction of the window as the floor. Those are provider facts and Maka's own content policy, so the "real numbers only" principle holds. A default is not Maka deciding for the user, it is a default the user can override, and the alternative is that out of the box every fill costs a rejection and possibly a cut reply, which CLI users get without even the hint, because pi-transcript.ts drops the two new note kinds. The per-step check already gives mid-turn triggering; only the window and the threshold change.

The summarizer's provider does not get to decide. The design names four deciders, and one of them, "the summarizer's provider decides whether compaction input fits, input_too_large retreats the fold by half", has no producer. Only fitHistoryCompactMessages throws input_too_large, this PR removes that call from history-compact-summarizer.ts and openai-codex-history-compactor.ts, and both catches wrap every provider error as provider_error. So a session whose fold prefix is too large for the summarizer fails open on the first rejection, /compact included, and has no in-app way back under the window. That is worse than main, which at least estimated. The fix is small, classify ContextLength in both catches, but the regression must use a fake provider that rejects above N tokens; all five current input_too_large tests throw the error from a fixture, which is why this was invisible.

The compatibility contract. Two new system_note kinds and the new lastRequestAnchor shape land in packages/core closed allowlists, the same class of change #4486 bumped the epoch for, and the epoch is unchanged. A merge-base client handshakes fine (host-kernel.ts admits on strict equality) and fails decodeStoredMessage on the first transcript carrying a new note. main is on 96 now: rebase, take 97, and put back the three CHANGELOG sentences from #4486 that are still true (see inline).

One consequence of the first point that lives outside the diff: settings-provider-copy.ts still says "when empty, built-in metadata decides", and /context and the inspector still divide by resolveSelectedModelContextWindow, so an undeclared user sees 70% of 200k and never gets a fold. Whichever way the window question settles, the copy and the denominator have to follow the same rule.

On the test claim: five re-pointed tests pass unchanged on main's built sources (the no-size-gate replay, the two size-floor cases, the no-usage case, fails open after repeated input-too-large retreat), and two rules lost their only coverage with the deletions while still existing, the memory gate's unavailable outcome and the rule that a synthetic /compact usage row must not shadow the real anchor. The remaining persisted-anchor test uses an anchor below the window, so it passes regardless of the run-header check.

Evidence boundary: static read against main61224f51; all suites run locally; new tests also run against main's built sources in a scratch copy; no live provider.

AI-assisted review: drafted with Maka; I verified the trigger arithmetic, the input_too_large producers, the epoch state and the size-floor inputs myself.

简体中文

方向就是 #4458 上讨论定下的，我仍然支持：放不放得下由 provider 回答，压缩触发用真实数字，唯一不可逆的结果是 provider 的拒绝。删得也干净，「What is gone」里的每个符号在 docs 和 desktop 里都没有残留，本地六个 workspace 的测试、typecheck、lint、format 全绿；之后的三个提交（148326eb）没有碰到下面引用的任何文件。让我暂时不 approve 的不是代码本身，而是三处实现和设计说的不是一回事。能局部修的都放在行内评论里。

主动触发对着正确声明的窗口永远打不响。 触发条件是「上次请求的 input+output 大于声明窗口」，而上次请求是 provider 已经接受的。如果用户把窗口声明成 provider 的真实大小，任何被接受的请求都不可能超过它，主动压缩一次也不会触发，每个会话都要先撞一次拒绝。只有用户把窗口声明得比真实值小它才触发，这等于把删掉的 reserve 变成了一个要用户自己猜、又不告诉他的数字。这是 #4559 的 open point 2，我的意见相反：窗口按「用户声明 > relay profile > models.dev 元数据 > /models 报告」解析，全都没有才算无；触发条件改成「上次用量 > 窗口 − reserve」；reserve 用真实数字：模型的 output limit（下一步回复最多这么大）加上工具结果归档上限乘以待处理的工具调用数，再用窗口的固定比例兜底。这些都是 provider 的事实和 Maka 自己的内容策略，「只用真实数字」的原则不受影响。给一个默认值不是替用户决定，用户随时可以覆盖；不给的后果是开箱用户每次填满都要付一次拒绝、可能还拿到被截断的回复，CLI 用户连提示都看不到，因为 pi-transcript.ts 把两个新 note kind 丢掉了。turn 内每一步都检查的逻辑已经有了，只需要改窗口和阈值。

summarizer 的 provider 并没有拿到决定权。 设计列了四个决定者，其中「summarizer 的 provider 决定压缩输入放不放得下，input_too_large 就把范围退半」这一条没有产生者。全仓只有 fitHistoryCompactMessages 会抛 input_too_large，本 PR 把它从 history-compact-summarizer.ts 和 openai-codex-history-compactor.ts 里删掉了，两处的 catch 又把所有 provider 错误一律包成 provider_error。于是一个长会话的折叠前缀如果对 summarizer 也太大，第一次拒绝就整体放弃，/compact 走同一条路也一样，会话在 app 内没有回到窗口内的办法，比 main 还差，main 至少还估算一下。修法很小，两个 catch 里判断 ContextLength 再抛，但回归测试必须用「输入超过 N tokens 就拒绝」的假 provider；现在五个相关测试全是 fixture 手抛这个错误，所以这个洞看不见。

兼容契约。 两个新的 system_note kind 和新的 lastRequestAnchor 形状都进了 packages/core 的闭合 allowlist，和 #4486 推 epoch 的那次是同一类改动，但 epoch 没动。merge-base 上的旧 client 握手能通过（host-kernel.ts 按严格相等准入），然后在第一条带新 note 的 transcript 上解码失败。main 现在已经是 96：rebase 取 97，并把 #4486 写的、仍然成立的三句 CHANGELOG 加回来（见行内）。

第一点在 diff 之外的一个后果：settings-provider-copy.ts 的帮助文案「留空跟随内置元数据」现在不成立，/context 和 inspector 的分母也还是 resolveSelectedModelContextWindow，未声明的用户会看到「已用 70% / 200k」却永远等不到压缩。窗口问题无论怎么定，文案和分母都要跟同一条规则。

关于测试的说法：五条 re-pointed 测试在 main 的构建产物上原样通过（无 size gate 的 replay、两条体量下限、无 usage、退半后 fail open）；两条规则随删测试失去了唯一覆盖但仍然存在：memory gate 返回 unavailable 的处理，以及手动 /compact 写的合成 usage 行不得遮蔽真实 anchor。剩下那条持久 anchor 测试的 anchor 低于窗口，不管 run header 合不合法都过。

[Astro-Han]

baselineTokens is a request the provider accepted, so with the window declared at the provider's real size this is never true; the fold only runs when the user declares something smaller. That is the reserve in disguise. baseline > window − reserve, with the reserve from output limit plus the tool-result cap, is what makes this fire before the rejection. First point in the main comment.

[Astro-Han]

Dead branch: nothing throws input_too_large any more. fitHistoryCompactMessages was its only producer and both summarizer catches now wrap provider errors as provider_error. Classify ContextLength with classifyError in history-compact-summarizer.ts and openai-codex-history-compactor.ts so this retreat has a producer, and test it with a fake provider that rejects above N tokens.

[Astro-Han]

Baseline includes last step's reasoning; on wires that do not resend it (gpt-5.x), next input ≈ previous input + tool call + result, which is below input + output whenever reasoning exceeded the appended content, the normal case. Compare against last step's input alone; keep input + output for the trigger.

[Astro-Han]

Written before recoverFromOverflowError runs, so a send that overflows once, folds and completes still tells the user the provider refused. #4559 places this under "already folded". Move it after the recovery verdict; overflow-reactive-recovery.test.ts:1834 (tool, overflow, done) currently pins the wrong order. And suggestedContextWindow: baselineTokens sits on the strict > boundary, so a user who applies it still needs one more rejection.

[Astro-Han]

On a roll-forward the summarizer is sent previous summary + new events, so inputTokens is the increment while the checkpoint replaces the whole covered span; in steady state this floor never trips and a fifty-token summary after a small increment is persisted. The new test passes on main because the stub's usage is unrelated to the messages. Feed it a span-sized real number (previous checkpoint's compactCallInputTokens plus this increment) or drop the floor openly.

[Astro-Han]

The comment above says this re-runs the size floor, but no summarizerUsage is passed so the floor is skipped, and coveredRuntimeEvents is now required and unread by the validator. Same for the external-producer branch in history-compaction.ts. Either pass a real number or delete the field, the three constructions and the comment.

[Astro-Han]

Three sentences from #4486 were dropped and are still true: sessions from this build do not open in earlier releases and the runtime.sqlite copy must be taken before upgrading; context_budget_exhausted is no longer produced but still decodes; the epoch line (97 after rebase). The body says the allowlist cost is "already noted in CHANGELOG.md", and it no longer is.

[Joob1n]

Thanks for the read — every finding was real. Fixes are in 38b2d837 (one commit, each item with a test that fails on the previous commit), plus two live-provider findings in the commits before it.

Trigger arithmetic. You are right that baseline > declaredWindow could never fire against a window declared at the provider's real size. Fixed the way you suggested for the reserve, with one narrowing: the reserve is the model's declared output limit only (connection.models[].maxOutputTokens or generated metadata; 0 when none is declared), and the trigger is baseline + limit >= window. I did not add the tool-result cap × pending calls term: the active prune already bounds each result before it goes out, and a second constant on the trigger side is the kind of number the design is trying not to own. Live on Ollama (qwen2.5:1.5b, declared 1,500) the fold now fires at 2,227 with the previous usage as the only input, folds to a 1,737-char checkpoint after one repair, and the next request's provider-counted input drops 2,954 → 1,222.

Window source — kept as declared-only, deliberately. This is the one point where I did not take the suggestion, and it is the issue author's call rather than mine: the Maka window is a target the user chooses to stay under, not a fact about the model, so the model's reported window is shown beside the setting with one click to apply (#4575) but never becomes the threshold on its own. The cost you name is real and stated in the description: with nothing declared, the first fill costs one rejection and possibly one cut reply. The context_window_suggestion note then offers the last accepted total; it is now written only when the turn actually surfaces the error, and the CLI transcript renders both new note kinds.

input_too_large producer. Correct — I removed the only producer. Both summarizer catches now classify ContextLength as input_too_large, with a fake provider that rejects above N characters as the regression.

Epoch and CHANGELOG. Bumped to 97 on rebase and the three sentences are back.

Inline items: eviction check compares input with input; the size floor applies to the initial fold only (the roll-forward input is the increment, as you say) and CheckpointSummaryFoldContext carries usage only, so the builder/copy seams validate structure and truncation; the suggestion note moves after recovery and names the fold-proof last accepted total; the run-header test's anchor now sits above the window so the header check decides; the synthetic /compact row test is restored; the roll-forward floor test now asserts both directions.

Two things I left as they were, with reasons. The Host's runComposition.contextWindow stays the model's reported window: it is a protocol fact clients already display, and the declared window gets its own surface in the composer indicator (#4576) rather than a changed meaning for an existing field. And the memory-gate unavailable outcome is still exercised by the mid-turn fixture's extraction path (remember returns unavailable there, asserted at the fold that dispatches extraction); if you meant a different obligation, tell me which and I will pin it.

[Joob1n]

Rebased on main@8ea3c4f05 now that #4578 has landed, so the dependency bump is no longer carried here (6 commits). main moved the compatibility epoch to 98 in the meantime (#4561 / #4568), so this PR's bump is now 98 → 99; the CHANGELOG line and the epoch comment follow. No other changes since a65076258.

[likun666661]

方向我赞成：把“请求是否 fit”的裁决权完全交给 provider，把本地侧收缩为“真实 usage + 用户目标只触发可逆 fold”，比多把估算尺同时参与决策更干净。PR 的主要因果链也基本成立。不过在 approve 前，我认为还有下面几个点需要收口：

1. [P1] compatibility epoch 与最新 main 撞号。 当前 main@898b86d 已经把 RUNTIME_HOST_COMPATIBILITY_EPOCH 升到 99，用于 ScheduledTask 的 Connection identity；本 PR 也独立使用 99 表示两个新 system note 和 lastRequestAnchor shape。两边是不同的不兼容协议变化。rebase 后不能只解决文本冲突并继续保留 99，需要把合并结果升到 100，同步注释、CHANGELOG 和 epoch test；否则能力不同的 client/host 可能错误通过严格相等握手。

2. [P2] repair 请求里的 ContextLength 会被吞成初次格式错误。history-compact-summarizer.ts:206-243 中，初次 summary malformed 后，repair 使用更长的 system prompt。如果初次调用刚好 fit、repair 因新增 instruction 被 provider 拒绝，内层 catch 会把该错误包装成初次的 malformed_summary_*；外层看到它已经是 HistoryCompactSummarizerError 后直接重抛，不会再分类为 input_too_large。planner 因此不会执行 halve-and-retry，和“summarizer provider decides”不一致。建议在 repair catch 中保留 ContextLength 分类，并补一个“initial malformed, repair overflow”的回归测试。

3. [P2] 架构文档仍描述修复前的 trigger。 中英文文档目前都写成“上次 inputTokens + outputTokens 超过用户窗口时触发”；实现已经是 baseline + model.maxOutputTokens >= declaredWindow（ai-sdk-compaction.ts:896-908）。这是核心规则，应同步两份文档，避免后续实现和测试重新漂移。

4. Issue closure 建议调整。#4559 的 proposal 还包含 missing-usage hint、unclassified overflow 的 compact-and-retry action、metadata window 一键采用和 composer indicator。本 PR 没有 missing-usage note，unclassified action 明确留在系列之外，UI 又拆到 #4575/#4576。拆 PR 没问题，但此时 Closes #4559 会让完整验收范围过早关闭；建议改成 Refs #4559，或先明确把 #4559 收缩为 runtime-only。

从 Occam 的角度，我的判断是：架构方向已收敛，问题定义尚未完全收敛。 最小因果主线已经很清楚：

history grows
→ user target may request a reversible fold
→ provider outcome decides actual fit
→ canonical history is never rejected or mutated by an estimate

但“provider decides”尚未覆盖 provider 沉默的情况：PR 自己的 Ollama 实测已经显示跨 turn usage plateau / silent truncation，而当前 dropping note 只检查同 turn 的 step ≥ 1。建议把无 usage、无法分类以及 silent eviction 明确定义成可见的 degraded mode；否则“未声明 window 时系统提供什么保证”仍是开放语义。

另外，includeUsage ?? true 现在会给所有 OpenAI-compatible Chat server 发送 stream_options.include_usage。现有 conformance test 只覆盖支持该字段的 fake server；最好再补一个严格 relay 拒绝该字段时的契约测试，明确 fail、fallback 或 opt-out 行为。

CI 当前是绿的，diff check 也干净；上面第 1 项是基于最新 main 的当前 merge blocker，第 2 项是静态可达的 provider-boundary bug。修完这些，我认为核心 runtime 改动可以继续推进。

[Joob1n]

Thanks — the first three are real and are fixed in 6c5e53ddd / ba14a706c; the fourth is done in the PR body.

1. Epoch.main moved again while this was open (#4321 → 99, #4508 → 100), so the rebase now lands this PR's bump as 100 → 101; comment, CHANGELOG and the epoch check follow. The protocol tests assert against the exported constant, not a literal, so nothing else pins the number.

2. Repair-path ContextLength. Confirmed: the repair catch wrapped every failure under the initial defect, so a context-length rejection of the longer repair prompt never reached the planner as input_too_large. The catch now classifies before wrapping; regression test "a context-length rejection of the repair request stays the input_too_large signal" (initial malformed → repair rejected → input_too_large, two provider calls) fails on the previous commit.

3. Docs. Both llm-compaction-events-log-projection-draft documents now state the implemented trigger: previous accepted inputTokens + outputTokensplus the reply reserve (the model's declared maxOutputTokens, zero when unknown) reaching the declared window.

4. Issue closure. Changed to Refs #4559; the issue closes when #4574/#4575/#4576 have all landed and the remaining proposal items are triaged there.

On the two broader points:

• Degraded modes (no usage, unclassified rejection, cross-turn plateau). Agreed that these deserve names. They are deliberately outside this PR: the dropping note is scoped to a single send because within one send Maka knows it only appended, while across turns the user may have edited or branched and a lower inputTokens is legitimate. Opened context: define the degraded modes when the provider does not speak (no usage, unclassified rejection, silent eviction) #4623 with the three modes, the signal each one gives today, and the two small follow-ups: PR D applies the same dropping rule at the turn boundary (first request's inputTokens below the persisted anchor with no fold or prune before the send → note), PR E adds "compact and retry" on an unclassified provider error. Both are notes/actions on top of this PR's paths, so they can land right after it without reopening it.

• stream_options on strict relays. Decided and pinned in 6ce7d7332: a relay that rejects the field fails with the provider's own 400 text and the runtime does not resend without it — the conformance test asserts one request, the stream_options body field, and the provider message reaching the stream's error part. Rationale: a connection that cannot report usage has no context baseline, so a silent fallback would hide exactly the degraded mode above; the error names the field, and a per-adapter includeUsage: false is the one-line opt-out if a real relay needs it. The field has been part of the Chat Completions API since 2024-05 and the Kimi OpenAI path in this repo has sent it since feat(runtime): support Kimi OpenAI protocol #1462.

[Joob1n]

Rebased on main@b1ec28989. main took epoch 101 in the meantime (#4608), so this PR's bump is now 101 → 102; comment, CHANGELOG and the epoch check follow. The strict-relay contract test is e10dd49a4's head commit (was 6ce7d7332 before the rebase). No other changes.

[likun666661]

复查了最新 head e10dd49a4。上一轮的主要项都已正确落地：epoch 102 对应 merge base 101；repair-path ContextLength 保留为 input_too_large 且有回归；两份文档的 trigger 公式已更新；PR body 改成了 Refs #4559；strict relay 的一次 400 / 不静默重试契约也已固定。CI 当前是绿的，PR 可干净合并。

还有两个行为/scope 问题和一个文档漂移需要收口：

1. [P1] #4559 仍会被 closing keyword 关闭。 PR body 虽然已经改成 Refs #4559，但首个 commit 20f01b862 的 message body 仍然包含 Closes #4559。本仓库只允许 squash merge，并配置为 squash_merge_commit_message: COMMIT_MESSAGES；因此这个 closing keyword 会进入 default-branch 的 squash commit，仍会关闭 issue。既然约定是整个 #4574/#4575/#4576 系列落地并完成剩余 triage 后再关闭，请把该 commit message amend 为 Refs #4559（或确保最终 squash message 中完全没有 closing keyword），而不只是修改 PR body。

2. [P2] provider-dropping 实现检测的是“严格下降”，对外契约写的是“没有增长”。packages/runtime/src/ai-sdk-backend.ts:2170-2182 当前条件是：

   stepUsage.inputTokens<lastStepInputTokens

   但 PR summary、commit message、CLI/UI copy 和新开的 #4623 都把信号定义为 usage “did not grow / stops growing or drops”。本 PR 自己的 Ollama 证据正是输入在 3,716 持平 plateau；严格 < 不会对这个案例写 note。当前测试也只有 100 → 50 的 decrease，没有 equal-usage case。

   如果 observable contract 确实是“append-only request 的 input 没增长”，这里应使用 <= 并补一个 equal-usage regression。#4623 的 PR D 也不应只定义成 “below persisted anchor”，否则同一个跨-turn plateau 仍不会被检测。若等值被刻意排除，则应反过来收窄 PR、copy 和 #4623 的声明，并说明为什么 plateau 不是可靠信号；现在代码和承诺二者只能有一个成立。

3. [P3] 中文架构文档仍有两处旧的 size-policy 语义。docs/architecture/llm-compaction-events-log-projection-draft.zh-CN.md:88-93 的公式仍写 current context budget，而英文已改成 user-declared capacity and provider outcome；同文档 :121-130 仍把 checkpoint 的必要问题写成“它在当前 token policy 下仍然能否进入 prompt？”，英文已改为 source/provider-state identity。后文已经明确删除 replay size verdict，因此这两处应与英文及最终实现同步。

除了以上三项，上一轮要求的修复我没有再发现回归。前两项处理后，我认为这轮可以进入 approve。

[Joob1n]

All three are fixed on 2cbc332af.

1. Closing keyword in the commit body. You are right that the PR body is not where this is decided under squash merge with COMMIT_MESSAGES. 20f01b862 is reworded to Refs #4559 (now 3ed669070 after the rebase); no commit on the branch carries a closing keyword any more.

2. < vs <=. Fixed to <=, with the copy as the authority rather than the other way round. Your reading of the evidence is the right one: the live Ollama run plateaus at 3,716 input tokens and never drops, so the strict comparison would have missed the exact case the PR cites. An equal input count after an append-only step (no fold, no prune, no image omission) is already impossible without provider-side eviction or rewriting, so equality is signal, not noise. New regression "records provider context dropping when an append-only step reports the same usage" (100 → 100 across the step) fails on the previous commit; the existing decrease and prune-explains-it tests still pass.

#4623 is updated to match: PR D's rule is "at or below the persisted anchor", not "below", for the same reason.

3. Chinese document drift. Both passages are synced with the English text: the materialization inputs now read 用户声明的 capacity 与 provider 结果, and the checkpoint's replay question is source/provider-state identity rather than the retired token policy.

One note on scope: both documents still ask "which high-water decision produced it" in that same list. It is stale in both languages equally, so I left it rather than widening this PR's document diff; say the word and I will fold it in here, otherwise it goes with the #4623 documentation pass.

[me2seeks]

Reviewing with real edge cases in mind, grounded in production data from a kimi-coding-plan/k3-256k workspace (see also #4634 — this PR fixes its root causes 1 and 2; items 3 and 4 there remain open).

Overall the direction is sound: every trigger is now a provider-reported number, and I live-verified the new summarizer request shape against k3-256k (details inline on the summarizer change). My concerns are about the paths where the provider never speaks: silent over-window acceptance, output-limit cuts caused by our own maxOutputTokens, and unrecognized error shapes.

[me2seeks]

Real edge case from live data: kimi-coding-plan/k3-256k accepts requests beyond its fetched window without rejecting or truncating — observed a session accepted at 322K input tokens against a fetched contextWindow of 262,144, with usage still growing monotonically (305K → 322K). On such a provider every signal this design reads stays dark for an undeclared window:

• no rejection → reactive fold never fires;
• usage never plateaus → context_provider_dropping never fires (and it is mid-turn only anyway);
• context_window_suggestion only fires on a surfaced rejection → never written;
• a fetched /models window is not a declaration → the proactive trigger below never arms.

Net effect: an undeclared kimi session degrades silently and indefinitely (this is exactly the data behind #4634). I agree with "Maka does not decide for the user" as a principle, but for providers observed to accept over-window requests, could the fetched window seed a default declaration (user-overridable), or should the cross-turn plateau check (#4623 PR D) be a blocker rather than a follow-up?

[me2seeks]

pendingLengthFold is set on anylength finish with no size or cause guard. Two real cases where the fold is useless or harmful:

1. The cut came from our own configured maxOutputTokens, not the window: maka sends maxOutputTokens: 131072 on kimi-coding-plan main requests (from lookupModelMetadata). A reply cut at that cap is not helped by folding history at all — the next request carries the same cap. If the model keeps wanting more output (long reasoning at effort=max, large file generation), this turn folds every step, repeatedly shrinking history while never addressing the constraint.
2. A user who declares a small output limit for cost control gets routine length finishes → folds at a few K tokens of context, paying a summarizer call each time.

Suggest gating the length fold on baseline + replyReserve >= capacity (i.e. plausibly window-caused), or capping length-folds per turn.

[me2seeks]

For k3-256k, declaredModelOutputLimit resolves to 131,072 from bundled metadata — half of its 262,144 window. A user who pins the full window gets proactive folding at baseline >= 131,072, i.e. ~50% utilization, which is far earlier than "stay under your declared window" suggests. Reserving the output limit is right in principle (without it a real-size declaration is never crossed), but when the declared output limit is a large fraction of the window the reserve dominates. Consider capping it, e.g. min(outputLimit, capacity / 4) or a fixed bound.

[me2seeks]

The per-send latch and the fingerprint circuit still only cover malformed-summary reasons. After a provider_error / output_length fail-open, baselineTokens stays set, so overWindow remains true and every subsequent step retries the summarizer. Observed live on kimi-coding-plan (which reports failures as HTTP 200 + error body): 15 consecutive failed summarizer calls over ~47 minutes, each 30–45 s, before the main request. Suggest latching any summarizer failure for the rest of the send, with the same fail-open diagnostic. (#4634 item 3)

[me2seeks]

Defaulting includeUsage on for every non-opted-out OpenAI-compatible server is the right call for usage coverage, but a strict relay/proxy that rejects unknown fields (older vLLM, some gateways) will 400 every streaming request after upgrade, and opting out requires a registry code change. Consider a one-time fallback: on a 400 whose error text mentions stream_options/include_usage, retry without it and remember that for the connection.

[me2seeks]

Two false-positive paths for the dropping note:

1. Finalization steps remove all tool schemas (resolveDispatch returns [] for the child-summary / sandbox-boundary finalization step), which legitimately drops the next request's input by several K tokens with no fold/prune/image-omit — this condition doesn't exclude that case, so a routine turn end can report "provider is dropping context".
2. No hysteresis: a 1-token decrease fires the note. Cache accounting or tokenizer drift between calls can produce tiny legitimate decreases. A small relative threshold (e.g. drop > 1–2% or > N tokens) would keep the note meaningful.

[me2seeks]

Confirming this fixes the kimi-coding-plan failure mode from #4634 — I live-tested this exact request shape (system template + trailing user instruction) against k3-256k on both wires: it now returns a fully compliant sectioned summary, where the system-prompt-only shape returned content: null (7 tokens) or continued the conversation as the assistant.

One follow-up worth noting (not blocking): the summarizer request still opens with a different system prompt than the main loop, so it shares no prefix cache with it — the first fold of a session pays a full uncached pass over the folded span (observed 39–88 s on 155–253K inputs). Moving the whole instruction into the trailing user message would let the summarizer reuse the main loop's cached prefix (~99% hits); keeping the template in system is also fine if that's load-bearing for other providers, but the cache cost is real at high context.

[Joob1n]

Thank you for the production data. Every path you named is real, and four of them are fixed on 1faabac55. The evidence for each is your k3-256k workspace, so I have quoted your numbers in the commit message rather than restating them here.

Summarizer retry storm (#4634 item 3). Fixed. The per-send latch recorded only malformed reasons, and the baseline that fired the trigger survives a fail-open, so a provider_error re-armed the same condition on every later step. Every fail-open reason now latches for the rest of the send. Regression: "bounds a provider-error summarizer failure across later steps in the same turn" (one summarizer call, failOpenReason: provider_error, no checkpoint), failing on the previous commit.

pendingLengthFold with no cause guard. Fixed, and your first case is the discriminator: the reply's own outputTokens says which limit cut it. A reply that stopped at the maxOutputTokens Maka sends was cut by Maka's budget, and the next request carries the same budget, so the fold is marked only when the reply stopped below it. That covers your cost-control case too, since a small declared output limit is reached exactly. No new constant, and both numbers are provider-reported. Regression: "does not fold when the reply was cut by the output budget Maka itself sends".

Dropping-note false positives. The finalization case is fixed: the note is suppressed when the step's own active tool set shrank, which is Maka reshaping the request rather than the provider evicting anything. Regression: "does not report provider dropping when the step dropped its tool schemas". On hysteresis I would rather not add a threshold, and I think the <= change (this PR now treats a plateau as the signal, per @likun666661's review) makes the case: after an append-only step, an input count that merely failed to grow already means the appended content was not counted, so a one-token decrease is not a weaker signal than equality but a marginally stronger one. normalizeAiSdkUsage sums no-cache, cache-read and cache-write, so cache accounting does not move the total. If you have a case where drift moves it anyway, that is worth a threshold and I will add one.

stream_options on strict relays. Adopted your suggestion over my earlier position, which @likun666661 also questioned: the deciding argument is that opting out needs a registry code change, so a strict relay has no user-facing recovery. A 400 whose body names the field now triggers one retry without it, remembered per base URL for the process. The connection then simply reports no usage, which the composer indicator (#4576) shows as a dash. Contract test asserts the three requests: asked, retried without, and never asked again.

Providers that accept beyond their fetched window. This one I have not changed, and I want to be explicit about why, because you are right that every signal stays dark. A cross-turn plateau check (PR D on #4623) does not rescue it either: your session's usage grows monotonically to 322K, so there is no plateau to detect. The only thing that arms anything is a declaration. Two options I can see:

1. A note when accepted usage exceeds the model's reported window while nothing is declared. That is two real numbers and no decision on the user's behalf, and it is the same shape as the existing context_window_suggestion. It fits this design and I would be glad to add it, here or as PR D's sibling.
2. Seeding a default declaration from the fetched window, which is the thing Context budget: stop estimating fit; the provider decides, the Maka window is a user target #4559 deliberately removed: a fetched number is a hint, and a session that compacts because of a number the user never chose is the failure this PR exists to end.

My preference is 1. Say which you would rather review and I will follow.

Prefix cache on the summarizer request. Noted as a follow-up, not forgotten: your 39–88 s uncached first attempts are a strong argument for moving the whole instruction into the trailing user message now that the trailing message exists. I have left the system template in place here because it is load-bearing for the providers the current tests cover, and changing both the shape and the cache behaviour in the same PR would make the k3-256k regression hard to attribute. It belongs on #4634.

Thanks also for live-testing the summarizer request shape; that is the part of this PR I could only verify against Ollama and fake providers.

[Joob1n]

Follow-up on the two open items from your review, both now on 77590471e.

The reply reserve is no longer the model's output limit. Your k3-256k arithmetic was the deciding case: reserving 131,072 against a 262,144 declaration folds at half the window a user deliberately chose. It is now twice the last reply the model actually wrote, bounded at 8,000 tokens. Both halves are provider-reported, the margin tracks the session's own behaviour rather than a catalog maximum, and no previous reply means no reserve at all. On your numbers a session answering in 2–3K tokens now folds at roughly 256K of 262K instead of 131K. The old test that asserted the output limit is rewritten around the new rule (a 900-token anchor with a 60-token reply folds against a 1,000 window, the same anchor with a 5-token reply does not, and the model's 600-token output limit is irrelevant to both).

A reserve measured from a smaller previous reply can still be too small, so that case is now reported rather than silent: when an accepted request's own input plus its reply exceed the declared window, the transcript carries one context_window_overrun note per send with both numbers. It is the honest reading of "the reply needed more room than was left", it uses only provider-reported numbers, and it tells a user who wants whole replies to raise the declaration. The next request folds anyway because the baseline now exceeds the window; the note explains why rather than changing what happens.

That makes three note kinds in this PR, all in the same epoch move (now 103 → 104 after the latest rebase).

Still yours to choose: the undeclared-window case on a provider that accepts past its reported window. My preference remains a note when accepted usage exceeds the model's reported window while nothing is declared, rather than seeding a declaration from a fetched number. Say which you would rather review.

[Joob1n]

Added, on 0d0a32dce: with nothing declared, a request the provider accepts past the window its own catalog entry reports now writes one context_reported_window_exceeded note per send, naming what the exchange used and what the model reports. It changes nothing on its own — a reported window stays a hint, and Maka still declares nothing on the user's behalf — but the case you found is no longer invisible. With a declaration in place the overrun note already owns that ground, and a test pins that the two never fire for the same fact.

That is the fourth note kind in this PR, all within the same epoch move (103 → 104 after the latest rebase). Local gates are green; the mid-turn suite is 73/73.

[me2seeks]

Thanks — verified 1faabac55 and 77590471e on the diff. The cutByOwnBudget discriminator is a better fix than the proximity gate I suggested: it distinguishes the two length causes with two provider-reported numbers, and my cost-control case falls out of it for free. The behaviour-measured reply reserve (2× last reply, ≤8K) fixes the k3-256k half-window arithmetic, and context_window_overrun is the right honest reporting for a reply that outgrew a reserve measured from smaller ones.

Undeclared window on a provider that accepts past its reported window: I choose option 1 — a note when accepted usage exceeds the model's reported window while nothing is declared. Two reasons beyond the ones you gave:

1. Coverage differs by surface. TUI has a real-time ctx indicator (I have a PR open adding one, with colour) so a TUI user can transiently see 322K > 262K; Desktop has nothing. A persisted note in the transcript is the only durable signal on Desktop, and the only one that survives the moment on TUI.
2. The note closes the loop with feat(desktop): show the model's reported context window beside the declared setting #4575. The number it should name is the reported window the user could adopt, and the natural call to action is the settings surface with the one-click apply from feat(desktop): show the model's reported context window beside the declared setting #4575.

One constraint from the k3-256k data: on such providers usage crosses the reported window gradually and keeps growing (305K → 322K), so the note should fire once per session when the crossing is first observed (the accepted total first exceeds the reported window), not per send — otherwise it spams on every step past the line.

On hysteresis for the dropping note: your <= argument and the normalizeAiSdkUsage sum hold; I have no live case where drift moves the total, so I withdraw that suggestion.

I will take the summarizer prefix-cache item back to #4634 as agreed.

[Joob1n]

Adopted the once-per-crossing constraint on 8c88243ca. The note now fires on the transition rather than per send: the previous accepted total was still inside the reported window and this one is not. That previous total comes from the persisted anchor, so a resumed session does not repeat a crossing it already reported, and a session that is already past the line stays quiet. Test "does not repeat the reported-window note once the session is already past the line" (a 320-token anchor against a reported 100) fails without the guard.

Your two reasons are both in the code's favour: the note is the durable Desktop signal, and it names the reported window, which is the number #4575 offers to apply in one click. Noted on the withdrawn hysteresis and on taking the prefix-cache item to #4634.

[Joob1n]

Correction on the previous push: a rebase of mine stopped on a conflict and the branch was pushed mid-rebase, so 8c88243ca briefly showed this PR with 5 of its 13 commits. The head is now 1283c874c, rebased on main@148f8eb29 with all 13 commits and every local gate green. Nothing in the content changed; main also took epoch 104 in the meantime, so this PR's bump is now 104 → 105 and the comment, CHANGELOG and commit message follow.

[Joob1n]

Closing this in favour of a smaller series. Not because anything here was wrong: it is green and every review item on it is either fixed or deliberately carried forward. The reason is that the design converged past what this PR's shape can carry, and a reviewer arriving now would have to reconstruct it from four rounds of comments.

Two things changed after the last round, both simplifications, and both invalidate part of this PR rather than adding to it:

1. The compaction module runs at most once per send. The proactive and reactive folds were two independent latches here. A fold already covers everything except the live head, so a second one buys a little tail and costs the most recent verbatim context. When a request is still rejected after a fold, the honest diagnosis is that the new message itself is too large, and that is what the user should be told.
2. A finishReason: length no longer triggers a fold. A reply cut below the maxOutputTokens Maka sends can mean the provider ran out of window room, or that the provider has its own lower output cap. Those are indistinguishable from the outside, and an indistinguishable signal should not drive an action. This removes the cutByOwnBudget discriminator @me2seeks and I converged on, one level up: the discriminator was right for the question asked, but the question should not have been asked.

A third change is larger and belongs on its own review: when a fold is rejected as too large, retreat to the span the last accepted request's input covered, rather than halving the covered range. That boundary was accepted by this exact model on this exact connection, so it is provably within capacity, where halving is a guess. The last reply's own span is folded separately when it exceeds 24,000 tokens.

The full design is written up on #4559 as three modules (judge / send / compact) with the call bounds.

Where each review finding goes

Finding	Reviewer	Lands in
Trigger arithmetic needs a reply reserve	@Astro-Han	PR 1
input_too_large must have a real producer	@Astro-Han	PR 2
Eviction check must compare input against input	@Astro-Han	PR 1
Window-suggestion note timing (after recovery, not before)	@Astro-Han	PR 1
Size floor only on the initial fold, not on roll-forward	@Astro-Han	PR 2
Fold-context cleanup, CHANGELOG, CLI note kinds, epoch	@Astro-Han	PR 1
Epoch collision with main	@likun666661	PR 1
Repair request's context-length rejection swallowed as a format defect	@likun666661	PR 2
Architecture documents describing the pre-fix trigger	@likun666661	PR 1
Closing keyword in the commit body, not just the PR body	@likun666661	PR 1
Dropping note must fire on a plateau (<=), not only a decrease	@likun666661	PR 1
Summarizer retry storm: latch every failure, not only malformed ones	@me2seeks	PR 2
Reply reserve must not be the model's output limit	@me2seeks	PR 1
Dropping note false positive on tool-schema shrink	@me2seeks	PR 1
stream_options retreat for strict relays	@me2seeks	PR 1
Undeclared window on a provider that accepts past its reported window	@me2seeks	PR 1
Reported-window note once per crossing, not per send	@me2seeks	PR 1
Length-fold cause guard	@me2seeks	superseded, see 2 above
Summarizer prefix-cache cost	@me2seeks	#4634

The series

• PR 1 — send module: trigger, reply reserve, persisted anchor, one compaction per send, "this message is too large", stream-usage collection with the strict-relay retreat, and all four system notes. One epoch move.
• PR 2 — compaction module: summarizer request shape, output cap and retries, failure latch, and the retreat to the last accepted input boundary.
• feat(desktop): show the model's reported context window beside the declared setting #4575, feat(desktop): show context usage beside the model controls #4576 — unchanged, rebased onto PR 1 when it lands.
• PR 5 — "compact and retry" for a rejection the classifier does not recognise (context: define the degraded modes when the provider does not speak (no usage, unclassified rejection, silent eviction) #4623).

Thank you all for the four rounds; the findings are carried, not discarded.

[Joob1n]

The replacement is #4653: the send module, with the two simplifications described above and the same review findings carried. The compaction module's retreat boundary follows in a second PR.

[Joob1n]

Summary

The runtime no longer estimates whether a request fits a context window. Every "does it fit" question is answered by a provider; every trigger is a real number. This is the remaining step after #4486, which removed the fabricated capacity and the two terminal gates but kept the chars/4 delta estimate, the 32,000-token fallback history budget, and a per-step JSON.stringify of the whole request as a payload ruler. Design and discussion: #4559 (this PR), #4458 (history).

What decides now

• The conversation provider's own context-length rejection is recovered by one compact-and-retry; a second rejection surfaces as the provider's error (context_overflow), and the user's message stays editable.
• The summarizer's provider decides whether compaction input fits: input_too_large retreats the fold by half, and the loop exits through no_safe_completed_span when even the smallest legal span is refused.
• Proactive compaction has one trigger: the previous accepted request's real inputTokens + outputTokens, as the provider counted them, compared with the context window the user declared for the model (a model-facts pin or a relay profile). Reasoning tokens are counted whole on purpose — high is the safe direction for a trigger that can only ask for a compaction.
• A reply the provider cut at its output limit (finishReason: length) folds once before the next request.

What is gone: estimateNextRequestTokens, exceedsHighWater, midTurnRequestPayloadChars, the final-request rescue re-entry, maxHistoryEstimatedTokens and its five consumers, the quarter-window / 16,384 reserve, the 32,000 fallback, the replacement_not_smaller and prefix_over_budget replay gates, size-based replay selection, the estimated input fit before summarizer calls, and the chars/4 summary-size floor.

Notes for the user (four new system_note kinds): context_provider_dropping when an append-only step's usage did not grow (a provider evicting or rewriting context), and context_window_suggestion when a rejection lands at a proven-fit total, carrying the number the user can declare.

Refs #4559 — the issue closes when the whole series (#4574, #4575, #4576) has landed and the remaining items are triaged there.
Refs #4458, #4486

Follow-up PRs (stacked on this one)

The user-facing surfaces are deliberately split out so this PR stays the atomic runtime change and the UI pieces can be reviewed in parallel. Both are open as drafts on top of this branch and will be rebased and undrafted once this merges:

• feat(desktop): show the model's reported context window beside the declared setting #4575 — Desktop settings: the model's reported window shown beside the declared setting with a one-click apply. Without it, a user who has never declared a window gets no proactive compaction and no in-app pointer to the number they could set; the context_window_suggestion note from this PR is the runtime-side half of that pointer.
• feat(desktop): show context usage beside the model controls #4576 — Desktop composer: read-only context-usage indicator fed by the persisted lastRequestAnchor this PR introduces (percentage with a declared window, absolute tokens without one, a dash when the provider reports no usage).

Not in this series, defined and tracked on #4623 (the degraded modes when the provider does not speak): PR D applies the provider-dropping rule at the turn boundary, PR E adds a "compact and retry" action for provider rejections the error classifier does not recognise. Neither reopens a path this PR touches.

Behaviour changes to review

1. No declared window means no proactive compaction. The first time such a session fills up costs one provider round trip and possibly one cut reply; the context_window_suggestion note then offers the last accepted total as the value to declare. This is the "Maka does not decide for the user" principle; the trade-off is stated in Context budget: stop estimating fit; the provider decides, the Maka window is a user target #4559.
2. A /models report or models.dev metadata is no longer a threshold on its own.resolveDeclaredContextWindow (runtime) and declaredContextWindow (core, single owner of the rule) count only a facts pin or a relay profile. resolveSelectedModelContextWindow keeps its old meaning for display and contextRemaining.
3. token_usage.lastRequestAnchor is now { inputTokens, outputTokens? }. The retired payloadChars key still decodes, so sessions written by 0.2.0 keep loading; sessions written by this build do not open in 0.2.0 (the closed-allowlist cost already noted in CHANGELOG.md).
4. Summaries are capped at 8,000 output tokens (DEFAULT_HISTORY_COMPACT_MAX_OUTPUT_TOKENS; the summarizer's maxOutputTokens option was declared and never passed). A length finish gets one shorter retry, then fails open. The too-small-for-fold floor reads the summarizer call's real usage; a producer that reports none is not floored.
5. Checkpoint replay is structural: a source-matched checkpoint replays as [block, everything after the boundary]. No local size gate stands between a materializable fold and dispatch.
6. ContextBudgetDiagnostic.maxHistoryEstimatedTokens is retired (decode-only). HistoryCompactionPolicy.midTurn loses reserveTokens. buildDefaultContextBudgetPolicy drops its connection parameter.
7. Every OpenAI-compatible Chat request now asks for stream usage (stream_options.include_usage), unless the registry opts a provider out. Found live: only two providers opted in, so a local Ollama and every plain OpenAI-compatible relay — the connection type behind Context budget: an undeclared window fabricates a capacity that kills live turns #4458 — returned no usage, and the baseline, the eviction check and the indicator all stayed dark for them.
8. Summary requests close with a user instruction. Found live: a chat-template model handed a conversation ending on its own turn emits end-of-sequence and nothing else (Ollama qwen2.5, both sizes: finish stop, one output token, empty text), so history compaction never succeeded against a local model. Existing message-shape tests gained the trailing user:text.
9. The trigger reserves the model's declared output limit and fires on >= (review). baseline + outputLimit >= declaredWindow, where the limit is connection.models[].maxOutputTokens or generated metadata — a provider fact — and 0 when none is declared. Without it a window declared at the provider's real size could never be crossed by an accepted request. The window itself remains the user's declaration (see the reply on the review for why the metadata window stays a hint).
10. A context-length rejection from the summarizer's provider is input_too_large again (review), so the planner's retreat-by-half has a producer; the same classification is applied to the Codex compaction call.
11. The window suggestion note is written only when the turn surfaces the rejection (review): after the one fold is spent or when there is no seam, naming the last accepted total, which a fold does not clear.
12. The size floor judges an initial fold only (review): on a roll-forward the summarizer's input is the increment, not the covered span, so the floor stands down there and the fold context carries usage only. The eviction check compares input against input, since reasoning is not resent on every wire.

On dropping the signed delta

#4486 kept a signed chars/4 delta so step 0 could fold before a large new message or image went out. I dropped it: the delta prices an image at a constant and under-reads CJK by about half, so the round trip it saves is the one it is most likely to misjudge; large text results are already capped by the byte-based tool-result archive before they go out; and removing it takes the whole payload ruler and the per-step JSON.stringify(messages) with it. Happy to be argued back.

Test coverage removed

Thirty-seven tests encoded the estimate, the reserve, the payload ruler, the fit gates, or the pre-turn estimate gate; each is either re-pointed at a real-usage observable or removed with the mechanism. Re-pointed: the usage baseline is the last request's INPUT tokens → input plus output; compacts over the high water → compacts after provider usage crosses the declared window; keeps user_stop when stopping an oversized pre-turn summary → keeps user_stop when stopping while a usage-triggered fold is summarizing; persists the LAST request as the anchor → persists the last request input and output as the anchor; replays a durable pre_turn checkpoint below the current high water → without a local size gate; rejects a paragraph-sized summary for a large folded span → when usage says it is too small. Removed outright (the mechanism is gone): the three manual compactHistory … exceeds current limits / makes the full replay larger cases, the three reserve-derivation cases, anchors on real provider usage plus a tail char/4 delta, credits a SIGNED negative payload delta, falls back to whole-projection char/4 on cold start, high-water crosses at contextWindow minus reserve, a fold that cannot shrink the real payload is refused, a runaway summary is rejected as replacement_not_smaller, bounds the oldest oversized tool result before dispatch, fails with input_too_large before dispatch, charges the summarization instructions against the input budget, a summary at exactly the floor is accepted under ceil-based token estimates, the capacity verdict measures the steering payload, the anchor a finalization step writes excludes the tool schemas it cleared, dispatches a pre-turn Compaction recipe without projecting history and keeps a transiently unavailable automatic Compaction checkpoint recoverable (both exercised the deleted pre-turn gate; memory extraction from a hook-triggered fold stays covered), applies max-history overrides to checkpoint replay validation, accepts a complete checkpoint above legacy block limits when the full replay fits, compacts one oversized prior turn before an unknown-model request, compacts an oversized latest turn when an older turn is also retained, dispatches an oversized prior turn when its summary fails, after trying once, never runs a pointless summarizer on a small-window model, a usage object without usable input tokens falls back to cold start, a last-request anchor is only valid as a complete positive pair, a half-written anchor fails the whole token_usage message decode (replaced by the new-shape and retired-key cases).

New coverage: the declared-window rule for pin / relay / reported / metadata sources; baseline = input + output, > not >=, cleared after a fold, seeded from the previous turn, discarded across a model switch; a /models window is not a declaration; pendingLengthFold; the summarizer output cap, shorten retry, and output_length after two cuts; usage-based size floor; retreat by half and its give-up exit; structural replay; both notes, including the non-firing cases (pruned step, step 0, declaration already crossed); the retired payloadChars key decodes and an unknown key still fails.

Live verification against a real provider (Ollama)

Driven through the real AiSdkBackend with getAIModel against a local Ollama (qwen2.5:0.5b / qwen2.5:1.5b, default num_ctx 4096), five turns of ~740 tokens each, the previous turn's ledger and run header fed back as prior context.

Scenario	Observed
Declared window 1,500, qwen2.5:1.5b	Turns 1–3: anchors {745,10}, {1481,10}, {2217,10} persisted; baseline 1,491 at turn 3 is < 1,500, no fold. Turn 4: baseline 2,227 > 1,500 → pre_turn fold; summary malformed twice → failedOpen[malformed_summary_missing_section], request dispatched, end_turn. Turn 5: fold again, repair produces a 1,737-char checkpoint → replaced; the request's provider-counted input drops 2,954 → 1,222.
Same, before the two fixes above	No token_usage event at all (Ollama returned no usage because it was never asked); once usage flowed, the summarizer returned empty text every time. Both fixed in this PR.
No declared window, 8 turns	Never folds, never terminates; every turn end_turn. Usage grows 745 → 3,700 and then plateaus at 3,716 for turns 6–8 while ~740 tokens are appended per turn: Ollama truncates silently at num_ctx with no error.

Known limitation, stated plainly: the silent-truncation plateau above happens between turns, and context_provider_dropping only fires within a turn (step ≥ 1, on an input count that did not grow), because at step 0 a user edit can shrink the input legitimately. A provider that truncates instead of rejecting therefore gives an undeclared-window user no signal today; declaring the window is the protection. Detecting the cross-turn plateau without an estimate needs a ledger-shape check on the anchor (did anything before the anchored request change?) — a follow-up, tracked on #4559. Closing that gap is PR D on #4623.

Verification

Rebased on main@148f8eb29 (after #4578 landed, so this PR no longer carries the dependency bump); the Runtime Host compatibility epoch moves 104 → 105 for the two new note kinds and the reshaped anchor. Locally: npm --workspace @maka/{core,storage,runtime,runtime-host,mcp,ui} run build, npm run typecheck (all workspaces), npm run lint, npm run format:check, npm run check:asf-headers, node scripts/protocol-epoch-check.mjs --base origin/main — all clean. Targeted suites: 425/425 across usage-record-last-request-anchor, context-budget-mid-turn-policy, context-budget-model-facts, history-compaction, history-compact-checkpoint, history-compact-summarizer, mid-turn-capacity-backend, overflow-reactive-recovery, ai-sdk-backend; core suite 760/760; provider-conformance 24/24, history-compact-summarizer 53/53, execution-model-composition 28/28 and the CLI pi-transcript suites after the review fixes. Not run locally: the full npm test matrix (the Electron/OpenSSL and owned-Host timing cases fail on this machine independently of the branch) — relying on CI for those.

Self-review

• The core rule declaredContextWindow was implemented twice (runtime and chat-model-choice) in an earlier draft; consolidated into @maka/core/model-thinking with runtime delegating. One owner for the one rule the design turns on.
• The user-stop-during-summary obligation had lost its test when the pre-turn gate went; re-pointed at the hook-triggered fold. The test also records that one request is still attempted after the stop and is rejected by the transport on its already-aborted signal — pre-existing behaviour, now pinned.
• An earlier draft regenerated the Astryx theme with a stale local @astryxdesign/core@0.5.0; that artifact is not in this PR.
• memory-extraction.ts and session-recap.ts keep their own bounded-request budgets; they are auxiliary calls, not history compaction, and are out of scope here.
• Diagnostics (estimatedTokensBefore/After on compaction decisions) still use the chars/4 estimator. They are recorded numbers, not decisions, and are kept so existing telemetry consumers do not break.

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Claude Code — design discussion, implementation, tests, and review; verified by the author.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No

https://claude.ai/code/session_014ajaRxC4jydavY9nYUFj5J

[Astro-Han]

The direction is the one from #4458 and I still hold it: fit is the provider's answer, the trigger is a real number, and the only irreversible outcome is the provider's rejection. The reduction is real, every symbol in "What is gone" is gone from docs and desktop too, and all six workspace suites, typecheck, lint and format pass locally on 372c1de9, and the three commits since (148326eb) touch none of the files cited below. What stops me approving is not the code, it is three places where the design as implemented does not do what the design says. Line-level fixes are inline.

The proactive trigger cannot fire against a correctly declared window. The trigger is baseline > declaredWindow, and the baseline is a request the provider accepted. If the user declares the provider's real window, no accepted request can exceed it, the fold never runs, and every session goes through rejection first. It fires only when the user declares something smaller, which is the retired reserve reintroduced as a number the user has to guess without being told. This is open point 2 of #4559, and I would settle it the other way: resolve the window as declared > relay profile > models.dev > /models, none only when all are absent; trigger on baseline > window − reserve; make the reserve a real number, the model's output limit plus the tool-result archive cap times pending tool calls, with a fraction of the window as the floor. Those are provider facts and Maka's own content policy, so the "real numbers only" principle holds. A default is not Maka deciding for the user, it is a default the user can override, and the alternative is that out of the box every fill costs a rejection and possibly a cut reply, which CLI users get without even the hint, because pi-transcript.ts drops the two new note kinds. The per-step check already gives mid-turn triggering; only the window and the threshold change.

The summarizer's provider does not get to decide. The design names four deciders, and one of them, "the summarizer's provider decides whether compaction input fits, input_too_large retreats the fold by half", has no producer. Only fitHistoryCompactMessages throws input_too_large, this PR removes that call from history-compact-summarizer.ts and openai-codex-history-compactor.ts, and both catches wrap every provider error as provider_error. So a session whose fold prefix is too large for the summarizer fails open on the first rejection, /compact included, and has no in-app way back under the window. That is worse than main, which at least estimated. The fix is small, classify ContextLength in both catches, but the regression must use a fake provider that rejects above N tokens; all five current input_too_large tests throw the error from a fixture, which is why this was invisible.

The compatibility contract. Two new system_note kinds and the new lastRequestAnchor shape land in packages/core closed allowlists, the same class of change #4486 bumped the epoch for, and the epoch is unchanged. A merge-base client handshakes fine (host-kernel.ts admits on strict equality) and fails decodeStoredMessage on the first transcript carrying a new note. main is on 96 now: rebase, take 97, and put back the three CHANGELOG sentences from #4486 that are still true (see inline).

One consequence of the first point that lives outside the diff: settings-provider-copy.ts still says "when empty, built-in metadata decides", and /context and the inspector still divide by resolveSelectedModelContextWindow, so an undeclared user sees 70% of 200k and never gets a fold. Whichever way the window question settles, the copy and the denominator have to follow the same rule.

On the test claim: five re-pointed tests pass unchanged on main's built sources (the no-size-gate replay, the two size-floor cases, the no-usage case, fails open after repeated input-too-large retreat), and two rules lost their only coverage with the deletions while still existing, the memory gate's unavailable outcome and the rule that a synthetic /compact usage row must not shadow the real anchor. The remaining persisted-anchor test uses an anchor below the window, so it passes regardless of the run-header check.

Evidence boundary: static read against main61224f51; all suites run locally; new tests also run against main's built sources in a scratch copy; no live provider.

AI-assisted review: drafted with Maka; I verified the trigger arithmetic, the input_too_large producers, the epoch state and the size-floor inputs myself.

简体中文

方向就是 #4458 上讨论定下的，我仍然支持：放不放得下由 provider 回答，压缩触发用真实数字，唯一不可逆的结果是 provider 的拒绝。删得也干净，「What is gone」里的每个符号在 docs 和 desktop 里都没有残留，本地六个 workspace 的测试、typecheck、lint、format 全绿；之后的三个提交（148326eb）没有碰到下面引用的任何文件。让我暂时不 approve 的不是代码本身，而是三处实现和设计说的不是一回事。能局部修的都放在行内评论里。

主动触发对着正确声明的窗口永远打不响。 触发条件是「上次请求的 input+output 大于声明窗口」，而上次请求是 provider 已经接受的。如果用户把窗口声明成 provider 的真实大小，任何被接受的请求都不可能超过它，主动压缩一次也不会触发，每个会话都要先撞一次拒绝。只有用户把窗口声明得比真实值小它才触发，这等于把删掉的 reserve 变成了一个要用户自己猜、又不告诉他的数字。这是 #4559 的 open point 2，我的意见相反：窗口按「用户声明 > relay profile > models.dev 元数据 > /models 报告」解析，全都没有才算无；触发条件改成「上次用量 > 窗口 − reserve」；reserve 用真实数字：模型的 output limit（下一步回复最多这么大）加上工具结果归档上限乘以待处理的工具调用数，再用窗口的固定比例兜底。这些都是 provider 的事实和 Maka 自己的内容策略，「只用真实数字」的原则不受影响。给一个默认值不是替用户决定，用户随时可以覆盖；不给的后果是开箱用户每次填满都要付一次拒绝、可能还拿到被截断的回复，CLI 用户连提示都看不到，因为 pi-transcript.ts 把两个新 note kind 丢掉了。turn 内每一步都检查的逻辑已经有了，只需要改窗口和阈值。

summarizer 的 provider 并没有拿到决定权。 设计列了四个决定者，其中「summarizer 的 provider 决定压缩输入放不放得下，input_too_large 就把范围退半」这一条没有产生者。全仓只有 fitHistoryCompactMessages 会抛 input_too_large，本 PR 把它从 history-compact-summarizer.ts 和 openai-codex-history-compactor.ts 里删掉了，两处的 catch 又把所有 provider 错误一律包成 provider_error。于是一个长会话的折叠前缀如果对 summarizer 也太大，第一次拒绝就整体放弃，/compact 走同一条路也一样，会话在 app 内没有回到窗口内的办法，比 main 还差，main 至少还估算一下。修法很小，两个 catch 里判断 ContextLength 再抛，但回归测试必须用「输入超过 N tokens 就拒绝」的假 provider；现在五个相关测试全是 fixture 手抛这个错误，所以这个洞看不见。

兼容契约。 两个新的 system_note kind 和新的 lastRequestAnchor 形状都进了 packages/core 的闭合 allowlist，和 #4486 推 epoch 的那次是同一类改动，但 epoch 没动。merge-base 上的旧 client 握手能通过（host-kernel.ts 按严格相等准入），然后在第一条带新 note 的 transcript 上解码失败。main 现在已经是 96：rebase 取 97，并把 #4486 写的、仍然成立的三句 CHANGELOG 加回来（见行内）。

第一点在 diff 之外的一个后果：settings-provider-copy.ts 的帮助文案「留空跟随内置元数据」现在不成立，/context 和 inspector 的分母也还是 resolveSelectedModelContextWindow，未声明的用户会看到「已用 70% / 200k」却永远等不到压缩。窗口问题无论怎么定，文案和分母都要跟同一条规则。

关于测试的说法：五条 re-pointed 测试在 main 的构建产物上原样通过（无 size gate 的 replay、两条体量下限、无 usage、退半后 fail open）；两条规则随删测试失去了唯一覆盖但仍然存在：memory gate 返回 unavailable 的处理，以及手动 /compact 写的合成 usage 行不得遮蔽真实 anchor。剩下那条持久 anchor 测试的 anchor 低于窗口，不管 run header 合不合法都过。

[Astro-Han]

baselineTokens is a request the provider accepted, so with the window declared at the provider's real size this is never true; the fold only runs when the user declares something smaller. That is the reserve in disguise. baseline > window − reserve, with the reserve from output limit plus the tool-result cap, is what makes this fire before the rejection. First point in the main comment.

[Astro-Han]

Dead branch: nothing throws input_too_large any more. fitHistoryCompactMessages was its only producer and both summarizer catches now wrap provider errors as provider_error. Classify ContextLength with classifyError in history-compact-summarizer.ts and openai-codex-history-compactor.ts so this retreat has a producer, and test it with a fake provider that rejects above N tokens.

[Astro-Han]

Baseline includes last step's reasoning; on wires that do not resend it (gpt-5.x), next input ≈ previous input + tool call + result, which is below input + output whenever reasoning exceeded the appended content, the normal case. Compare against last step's input alone; keep input + output for the trigger.

[Astro-Han]

Written before recoverFromOverflowError runs, so a send that overflows once, folds and completes still tells the user the provider refused. #4559 places this under "already folded". Move it after the recovery verdict; overflow-reactive-recovery.test.ts:1834 (tool, overflow, done) currently pins the wrong order. And suggestedContextWindow: baselineTokens sits on the strict > boundary, so a user who applies it still needs one more rejection.

[Astro-Han]

On a roll-forward the summarizer is sent previous summary + new events, so inputTokens is the increment while the checkpoint replaces the whole covered span; in steady state this floor never trips and a fifty-token summary after a small increment is persisted. The new test passes on main because the stub's usage is unrelated to the messages. Feed it a span-sized real number (previous checkpoint's compactCallInputTokens plus this increment) or drop the floor openly.

[Astro-Han]

The comment above says this re-runs the size floor, but no summarizerUsage is passed so the floor is skipped, and coveredRuntimeEvents is now required and unread by the validator. Same for the external-producer branch in history-compaction.ts. Either pass a real number or delete the field, the three constructions and the comment.

[Astro-Han]

Three sentences from #4486 were dropped and are still true: sessions from this build do not open in earlier releases and the runtime.sqlite copy must be taken before upgrading; context_budget_exhausted is no longer produced but still decodes; the epoch line (97 after rebase). The body says the allowlist cost is "already noted in CHANGELOG.md", and it no longer is.

[Joob1n]

Thanks for the read — every finding was real. Fixes are in 38b2d837 (one commit, each item with a test that fails on the previous commit), plus two live-provider findings in the commits before it.

Trigger arithmetic. You are right that baseline > declaredWindow could never fire against a window declared at the provider's real size. Fixed the way you suggested for the reserve, with one narrowing: the reserve is the model's declared output limit only (connection.models[].maxOutputTokens or generated metadata; 0 when none is declared), and the trigger is baseline + limit >= window. I did not add the tool-result cap × pending calls term: the active prune already bounds each result before it goes out, and a second constant on the trigger side is the kind of number the design is trying not to own. Live on Ollama (qwen2.5:1.5b, declared 1,500) the fold now fires at 2,227 with the previous usage as the only input, folds to a 1,737-char checkpoint after one repair, and the next request's provider-counted input drops 2,954 → 1,222.

Window source — kept as declared-only, deliberately. This is the one point where I did not take the suggestion, and it is the issue author's call rather than mine: the Maka window is a target the user chooses to stay under, not a fact about the model, so the model's reported window is shown beside the setting with one click to apply (#4575) but never becomes the threshold on its own. The cost you name is real and stated in the description: with nothing declared, the first fill costs one rejection and possibly one cut reply. The context_window_suggestion note then offers the last accepted total; it is now written only when the turn actually surfaces the error, and the CLI transcript renders both new note kinds.

input_too_large producer. Correct — I removed the only producer. Both summarizer catches now classify ContextLength as input_too_large, with a fake provider that rejects above N characters as the regression.

Epoch and CHANGELOG. Bumped to 97 on rebase and the three sentences are back.

Inline items: eviction check compares input with input; the size floor applies to the initial fold only (the roll-forward input is the increment, as you say) and CheckpointSummaryFoldContext carries usage only, so the builder/copy seams validate structure and truncation; the suggestion note moves after recovery and names the fold-proof last accepted total; the run-header test's anchor now sits above the window so the header check decides; the synthetic /compact row test is restored; the roll-forward floor test now asserts both directions.

Two things I left as they were, with reasons. The Host's runComposition.contextWindow stays the model's reported window: it is a protocol fact clients already display, and the declared window gets its own surface in the composer indicator (#4576) rather than a changed meaning for an existing field. And the memory-gate unavailable outcome is still exercised by the mid-turn fixture's extraction path (remember returns unavailable there, asserted at the fold that dispatches extraction); if you meant a different obligation, tell me which and I will pin it.

[Joob1n]

Rebased on main@8ea3c4f05 now that #4578 has landed, so the dependency bump is no longer carried here (6 commits). main moved the compatibility epoch to 98 in the meantime (#4561 / #4568), so this PR's bump is now 98 → 99; the CHANGELOG line and the epoch comment follow. No other changes since a65076258.

[likun666661]

方向我赞成：把“请求是否 fit”的裁决权完全交给 provider，把本地侧收缩为“真实 usage + 用户目标只触发可逆 fold”，比多把估算尺同时参与决策更干净。PR 的主要因果链也基本成立。不过在 approve 前，我认为还有下面几个点需要收口：

1. [P1] compatibility epoch 与最新 main 撞号。 当前 main@898b86d 已经把 RUNTIME_HOST_COMPATIBILITY_EPOCH 升到 99，用于 ScheduledTask 的 Connection identity；本 PR 也独立使用 99 表示两个新 system note 和 lastRequestAnchor shape。两边是不同的不兼容协议变化。rebase 后不能只解决文本冲突并继续保留 99，需要把合并结果升到 100，同步注释、CHANGELOG 和 epoch test；否则能力不同的 client/host 可能错误通过严格相等握手。

2. [P2] repair 请求里的 ContextLength 会被吞成初次格式错误。history-compact-summarizer.ts:206-243 中，初次 summary malformed 后，repair 使用更长的 system prompt。如果初次调用刚好 fit、repair 因新增 instruction 被 provider 拒绝，内层 catch 会把该错误包装成初次的 malformed_summary_*；外层看到它已经是 HistoryCompactSummarizerError 后直接重抛，不会再分类为 input_too_large。planner 因此不会执行 halve-and-retry，和“summarizer provider decides”不一致。建议在 repair catch 中保留 ContextLength 分类，并补一个“initial malformed, repair overflow”的回归测试。

3. [P2] 架构文档仍描述修复前的 trigger。 中英文文档目前都写成“上次 inputTokens + outputTokens 超过用户窗口时触发”；实现已经是 baseline + model.maxOutputTokens >= declaredWindow（ai-sdk-compaction.ts:896-908）。这是核心规则，应同步两份文档，避免后续实现和测试重新漂移。

4. Issue closure 建议调整。#4559 的 proposal 还包含 missing-usage hint、unclassified overflow 的 compact-and-retry action、metadata window 一键采用和 composer indicator。本 PR 没有 missing-usage note，unclassified action 明确留在系列之外，UI 又拆到 #4575/#4576。拆 PR 没问题，但此时 Closes #4559 会让完整验收范围过早关闭；建议改成 Refs #4559，或先明确把 #4559 收缩为 runtime-only。

从 Occam 的角度，我的判断是：架构方向已收敛，问题定义尚未完全收敛。 最小因果主线已经很清楚：

history grows
→ user target may request a reversible fold
→ provider outcome decides actual fit
→ canonical history is never rejected or mutated by an estimate

但“provider decides”尚未覆盖 provider 沉默的情况：PR 自己的 Ollama 实测已经显示跨 turn usage plateau / silent truncation，而当前 dropping note 只检查同 turn 的 step ≥ 1。建议把无 usage、无法分类以及 silent eviction 明确定义成可见的 degraded mode；否则“未声明 window 时系统提供什么保证”仍是开放语义。

另外，includeUsage ?? true 现在会给所有 OpenAI-compatible Chat server 发送 stream_options.include_usage。现有 conformance test 只覆盖支持该字段的 fake server；最好再补一个严格 relay 拒绝该字段时的契约测试，明确 fail、fallback 或 opt-out 行为。

CI 当前是绿的，diff check 也干净；上面第 1 项是基于最新 main 的当前 merge blocker，第 2 项是静态可达的 provider-boundary bug。修完这些，我认为核心 runtime 改动可以继续推进。

[Joob1n]

Thanks — the first three are real and are fixed in 6c5e53ddd / ba14a706c; the fourth is done in the PR body.

1. Epoch.main moved again while this was open (#4321 → 99, #4508 → 100), so the rebase now lands this PR's bump as 100 → 101; comment, CHANGELOG and the epoch check follow. The protocol tests assert against the exported constant, not a literal, so nothing else pins the number.

2. Repair-path ContextLength. Confirmed: the repair catch wrapped every failure under the initial defect, so a context-length rejection of the longer repair prompt never reached the planner as input_too_large. The catch now classifies before wrapping; regression test "a context-length rejection of the repair request stays the input_too_large signal" (initial malformed → repair rejected → input_too_large, two provider calls) fails on the previous commit.

3. Docs. Both llm-compaction-events-log-projection-draft documents now state the implemented trigger: previous accepted inputTokens + outputTokensplus the reply reserve (the model's declared maxOutputTokens, zero when unknown) reaching the declared window.

4. Issue closure. Changed to Refs #4559; the issue closes when #4574/#4575/#4576 have all landed and the remaining proposal items are triaged there.

On the two broader points:

• Degraded modes (no usage, unclassified rejection, cross-turn plateau). Agreed that these deserve names. They are deliberately outside this PR: the dropping note is scoped to a single send because within one send Maka knows it only appended, while across turns the user may have edited or branched and a lower inputTokens is legitimate. Opened context: define the degraded modes when the provider does not speak (no usage, unclassified rejection, silent eviction) #4623 with the three modes, the signal each one gives today, and the two small follow-ups: PR D applies the same dropping rule at the turn boundary (first request's inputTokens below the persisted anchor with no fold or prune before the send → note), PR E adds "compact and retry" on an unclassified provider error. Both are notes/actions on top of this PR's paths, so they can land right after it without reopening it.

• stream_options on strict relays. Decided and pinned in 6ce7d7332: a relay that rejects the field fails with the provider's own 400 text and the runtime does not resend without it — the conformance test asserts one request, the stream_options body field, and the provider message reaching the stream's error part. Rationale: a connection that cannot report usage has no context baseline, so a silent fallback would hide exactly the degraded mode above; the error names the field, and a per-adapter includeUsage: false is the one-line opt-out if a real relay needs it. The field has been part of the Chat Completions API since 2024-05 and the Kimi OpenAI path in this repo has sent it since feat(runtime): support Kimi OpenAI protocol #1462.

[Joob1n]

Rebased on main@b1ec28989. main took epoch 101 in the meantime (#4608), so this PR's bump is now 101 → 102; comment, CHANGELOG and the epoch check follow. The strict-relay contract test is e10dd49a4's head commit (was 6ce7d7332 before the rebase). No other changes.

[likun666661]

复查了最新 head e10dd49a4。上一轮的主要项都已正确落地：epoch 102 对应 merge base 101；repair-path ContextLength 保留为 input_too_large 且有回归；两份文档的 trigger 公式已更新；PR body 改成了 Refs #4559；strict relay 的一次 400 / 不静默重试契约也已固定。CI 当前是绿的，PR 可干净合并。

还有两个行为/scope 问题和一个文档漂移需要收口：

1. [P1] #4559 仍会被 closing keyword 关闭。 PR body 虽然已经改成 Refs #4559，但首个 commit 20f01b862 的 message body 仍然包含 Closes #4559。本仓库只允许 squash merge，并配置为 squash_merge_commit_message: COMMIT_MESSAGES；因此这个 closing keyword 会进入 default-branch 的 squash commit，仍会关闭 issue。既然约定是整个 #4574/#4575/#4576 系列落地并完成剩余 triage 后再关闭，请把该 commit message amend 为 Refs #4559（或确保最终 squash message 中完全没有 closing keyword），而不只是修改 PR body。

2. [P2] provider-dropping 实现检测的是“严格下降”，对外契约写的是“没有增长”。packages/runtime/src/ai-sdk-backend.ts:2170-2182 当前条件是：

   stepUsage.inputTokens<lastStepInputTokens

   但 PR summary、commit message、CLI/UI copy 和新开的 #4623 都把信号定义为 usage “did not grow / stops growing or drops”。本 PR 自己的 Ollama 证据正是输入在 3,716 持平 plateau；严格 < 不会对这个案例写 note。当前测试也只有 100 → 50 的 decrease，没有 equal-usage case。

   如果 observable contract 确实是“append-only request 的 input 没增长”，这里应使用 <= 并补一个 equal-usage regression。#4623 的 PR D 也不应只定义成 “below persisted anchor”，否则同一个跨-turn plateau 仍不会被检测。若等值被刻意排除，则应反过来收窄 PR、copy 和 #4623 的声明，并说明为什么 plateau 不是可靠信号；现在代码和承诺二者只能有一个成立。

3. [P3] 中文架构文档仍有两处旧的 size-policy 语义。docs/architecture/llm-compaction-events-log-projection-draft.zh-CN.md:88-93 的公式仍写 current context budget，而英文已改成 user-declared capacity and provider outcome；同文档 :121-130 仍把 checkpoint 的必要问题写成“它在当前 token policy 下仍然能否进入 prompt？”，英文已改为 source/provider-state identity。后文已经明确删除 replay size verdict，因此这两处应与英文及最终实现同步。

除了以上三项，上一轮要求的修复我没有再发现回归。前两项处理后，我认为这轮可以进入 approve。

[Joob1n]

All three are fixed on 2cbc332af.

1. Closing keyword in the commit body. You are right that the PR body is not where this is decided under squash merge with COMMIT_MESSAGES. 20f01b862 is reworded to Refs #4559 (now 3ed669070 after the rebase); no commit on the branch carries a closing keyword any more.

2. < vs <=. Fixed to <=, with the copy as the authority rather than the other way round. Your reading of the evidence is the right one: the live Ollama run plateaus at 3,716 input tokens and never drops, so the strict comparison would have missed the exact case the PR cites. An equal input count after an append-only step (no fold, no prune, no image omission) is already impossible without provider-side eviction or rewriting, so equality is signal, not noise. New regression "records provider context dropping when an append-only step reports the same usage" (100 → 100 across the step) fails on the previous commit; the existing decrease and prune-explains-it tests still pass.

#4623 is updated to match: PR D's rule is "at or below the persisted anchor", not "below", for the same reason.

3. Chinese document drift. Both passages are synced with the English text: the materialization inputs now read 用户声明的 capacity 与 provider 结果, and the checkpoint's replay question is source/provider-state identity rather than the retired token policy.

One note on scope: both documents still ask "which high-water decision produced it" in that same list. It is stale in both languages equally, so I left it rather than widening this PR's document diff; say the word and I will fold it in here, otherwise it goes with the #4623 documentation pass.

[me2seeks]

Reviewing with real edge cases in mind, grounded in production data from a kimi-coding-plan/k3-256k workspace (see also #4634 — this PR fixes its root causes 1 and 2; items 3 and 4 there remain open).

Overall the direction is sound: every trigger is now a provider-reported number, and I live-verified the new summarizer request shape against k3-256k (details inline on the summarizer change). My concerns are about the paths where the provider never speaks: silent over-window acceptance, output-limit cuts caused by our own maxOutputTokens, and unrecognized error shapes.

[me2seeks]

Real edge case from live data: kimi-coding-plan/k3-256k accepts requests beyond its fetched window without rejecting or truncating — observed a session accepted at 322K input tokens against a fetched contextWindow of 262,144, with usage still growing monotonically (305K → 322K). On such a provider every signal this design reads stays dark for an undeclared window:

• no rejection → reactive fold never fires;
• usage never plateaus → context_provider_dropping never fires (and it is mid-turn only anyway);
• context_window_suggestion only fires on a surfaced rejection → never written;
• a fetched /models window is not a declaration → the proactive trigger below never arms.

Net effect: an undeclared kimi session degrades silently and indefinitely (this is exactly the data behind #4634). I agree with "Maka does not decide for the user" as a principle, but for providers observed to accept over-window requests, could the fetched window seed a default declaration (user-overridable), or should the cross-turn plateau check (#4623 PR D) be a blocker rather than a follow-up?

[me2seeks]

pendingLengthFold is set on anylength finish with no size or cause guard. Two real cases where the fold is useless or harmful:

1. The cut came from our own configured maxOutputTokens, not the window: maka sends maxOutputTokens: 131072 on kimi-coding-plan main requests (from lookupModelMetadata). A reply cut at that cap is not helped by folding history at all — the next request carries the same cap. If the model keeps wanting more output (long reasoning at effort=max, large file generation), this turn folds every step, repeatedly shrinking history while never addressing the constraint.
2. A user who declares a small output limit for cost control gets routine length finishes → folds at a few K tokens of context, paying a summarizer call each time.

Suggest gating the length fold on baseline + replyReserve >= capacity (i.e. plausibly window-caused), or capping length-folds per turn.

[me2seeks]

For k3-256k, declaredModelOutputLimit resolves to 131,072 from bundled metadata — half of its 262,144 window. A user who pins the full window gets proactive folding at baseline >= 131,072, i.e. ~50% utilization, which is far earlier than "stay under your declared window" suggests. Reserving the output limit is right in principle (without it a real-size declaration is never crossed), but when the declared output limit is a large fraction of the window the reserve dominates. Consider capping it, e.g. min(outputLimit, capacity / 4) or a fixed bound.

[me2seeks]

The per-send latch and the fingerprint circuit still only cover malformed-summary reasons. After a provider_error / output_length fail-open, baselineTokens stays set, so overWindow remains true and every subsequent step retries the summarizer. Observed live on kimi-coding-plan (which reports failures as HTTP 200 + error body): 15 consecutive failed summarizer calls over ~47 minutes, each 30–45 s, before the main request. Suggest latching any summarizer failure for the rest of the send, with the same fail-open diagnostic. (#4634 item 3)

[me2seeks]

Defaulting includeUsage on for every non-opted-out OpenAI-compatible server is the right call for usage coverage, but a strict relay/proxy that rejects unknown fields (older vLLM, some gateways) will 400 every streaming request after upgrade, and opting out requires a registry code change. Consider a one-time fallback: on a 400 whose error text mentions stream_options/include_usage, retry without it and remember that for the connection.

[me2seeks]

Two false-positive paths for the dropping note:

1. Finalization steps remove all tool schemas (resolveDispatch returns [] for the child-summary / sandbox-boundary finalization step), which legitimately drops the next request's input by several K tokens with no fold/prune/image-omit — this condition doesn't exclude that case, so a routine turn end can report "provider is dropping context".
2. No hysteresis: a 1-token decrease fires the note. Cache accounting or tokenizer drift between calls can produce tiny legitimate decreases. A small relative threshold (e.g. drop > 1–2% or > N tokens) would keep the note meaningful.

[me2seeks]

Confirming this fixes the kimi-coding-plan failure mode from #4634 — I live-tested this exact request shape (system template + trailing user instruction) against k3-256k on both wires: it now returns a fully compliant sectioned summary, where the system-prompt-only shape returned content: null (7 tokens) or continued the conversation as the assistant.

One follow-up worth noting (not blocking): the summarizer request still opens with a different system prompt than the main loop, so it shares no prefix cache with it — the first fold of a session pays a full uncached pass over the folded span (observed 39–88 s on 155–253K inputs). Moving the whole instruction into the trailing user message would let the summarizer reuse the main loop's cached prefix (~99% hits); keeping the template in system is also fine if that's load-bearing for other providers, but the cache cost is real at high context.

[Joob1n]

Thank you for the production data. Every path you named is real, and four of them are fixed on 1faabac55. The evidence for each is your k3-256k workspace, so I have quoted your numbers in the commit message rather than restating them here.

Summarizer retry storm (#4634 item 3). Fixed. The per-send latch recorded only malformed reasons, and the baseline that fired the trigger survives a fail-open, so a provider_error re-armed the same condition on every later step. Every fail-open reason now latches for the rest of the send. Regression: "bounds a provider-error summarizer failure across later steps in the same turn" (one summarizer call, failOpenReason: provider_error, no checkpoint), failing on the previous commit.

pendingLengthFold with no cause guard. Fixed, and your first case is the discriminator: the reply's own outputTokens says which limit cut it. A reply that stopped at the maxOutputTokens Maka sends was cut by Maka's budget, and the next request carries the same budget, so the fold is marked only when the reply stopped below it. That covers your cost-control case too, since a small declared output limit is reached exactly. No new constant, and both numbers are provider-reported. Regression: "does not fold when the reply was cut by the output budget Maka itself sends".

Dropping-note false positives. The finalization case is fixed: the note is suppressed when the step's own active tool set shrank, which is Maka reshaping the request rather than the provider evicting anything. Regression: "does not report provider dropping when the step dropped its tool schemas". On hysteresis I would rather not add a threshold, and I think the <= change (this PR now treats a plateau as the signal, per @likun666661's review) makes the case: after an append-only step, an input count that merely failed to grow already means the appended content was not counted, so a one-token decrease is not a weaker signal than equality but a marginally stronger one. normalizeAiSdkUsage sums no-cache, cache-read and cache-write, so cache accounting does not move the total. If you have a case where drift moves it anyway, that is worth a threshold and I will add one.

stream_options on strict relays. Adopted your suggestion over my earlier position, which @likun666661 also questioned: the deciding argument is that opting out needs a registry code change, so a strict relay has no user-facing recovery. A 400 whose body names the field now triggers one retry without it, remembered per base URL for the process. The connection then simply reports no usage, which the composer indicator (#4576) shows as a dash. Contract test asserts the three requests: asked, retried without, and never asked again.

Providers that accept beyond their fetched window. This one I have not changed, and I want to be explicit about why, because you are right that every signal stays dark. A cross-turn plateau check (PR D on #4623) does not rescue it either: your session's usage grows monotonically to 322K, so there is no plateau to detect. The only thing that arms anything is a declaration. Two options I can see:

1. A note when accepted usage exceeds the model's reported window while nothing is declared. That is two real numbers and no decision on the user's behalf, and it is the same shape as the existing context_window_suggestion. It fits this design and I would be glad to add it, here or as PR D's sibling.
2. Seeding a default declaration from the fetched window, which is the thing Context budget: stop estimating fit; the provider decides, the Maka window is a user target #4559 deliberately removed: a fetched number is a hint, and a session that compacts because of a number the user never chose is the failure this PR exists to end.

My preference is 1. Say which you would rather review and I will follow.

Prefix cache on the summarizer request. Noted as a follow-up, not forgotten: your 39–88 s uncached first attempts are a strong argument for moving the whole instruction into the trailing user message now that the trailing message exists. I have left the system template in place here because it is load-bearing for the providers the current tests cover, and changing both the shape and the cache behaviour in the same PR would make the k3-256k regression hard to attribute. It belongs on #4634.

Thanks also for live-testing the summarizer request shape; that is the part of this PR I could only verify against Ollama and fake providers.

[Joob1n]

Follow-up on the two open items from your review, both now on 77590471e.

The reply reserve is no longer the model's output limit. Your k3-256k arithmetic was the deciding case: reserving 131,072 against a 262,144 declaration folds at half the window a user deliberately chose. It is now twice the last reply the model actually wrote, bounded at 8,000 tokens. Both halves are provider-reported, the margin tracks the session's own behaviour rather than a catalog maximum, and no previous reply means no reserve at all. On your numbers a session answering in 2–3K tokens now folds at roughly 256K of 262K instead of 131K. The old test that asserted the output limit is rewritten around the new rule (a 900-token anchor with a 60-token reply folds against a 1,000 window, the same anchor with a 5-token reply does not, and the model's 600-token output limit is irrelevant to both).

A reserve measured from a smaller previous reply can still be too small, so that case is now reported rather than silent: when an accepted request's own input plus its reply exceed the declared window, the transcript carries one context_window_overrun note per send with both numbers. It is the honest reading of "the reply needed more room than was left", it uses only provider-reported numbers, and it tells a user who wants whole replies to raise the declaration. The next request folds anyway because the baseline now exceeds the window; the note explains why rather than changing what happens.

That makes three note kinds in this PR, all in the same epoch move (now 103 → 104 after the latest rebase).

Still yours to choose: the undeclared-window case on a provider that accepts past its reported window. My preference remains a note when accepted usage exceeds the model's reported window while nothing is declared, rather than seeding a declaration from a fetched number. Say which you would rather review.

[Joob1n]

Added, on 0d0a32dce: with nothing declared, a request the provider accepts past the window its own catalog entry reports now writes one context_reported_window_exceeded note per send, naming what the exchange used and what the model reports. It changes nothing on its own — a reported window stays a hint, and Maka still declares nothing on the user's behalf — but the case you found is no longer invisible. With a declaration in place the overrun note already owns that ground, and a test pins that the two never fire for the same fact.

That is the fourth note kind in this PR, all within the same epoch move (103 → 104 after the latest rebase). Local gates are green; the mid-turn suite is 73/73.

[me2seeks]

Thanks — verified 1faabac55 and 77590471e on the diff. The cutByOwnBudget discriminator is a better fix than the proximity gate I suggested: it distinguishes the two length causes with two provider-reported numbers, and my cost-control case falls out of it for free. The behaviour-measured reply reserve (2× last reply, ≤8K) fixes the k3-256k half-window arithmetic, and context_window_overrun is the right honest reporting for a reply that outgrew a reserve measured from smaller ones.

Undeclared window on a provider that accepts past its reported window: I choose option 1 — a note when accepted usage exceeds the model's reported window while nothing is declared. Two reasons beyond the ones you gave:

1. Coverage differs by surface. TUI has a real-time ctx indicator (I have a PR open adding one, with colour) so a TUI user can transiently see 322K > 262K; Desktop has nothing. A persisted note in the transcript is the only durable signal on Desktop, and the only one that survives the moment on TUI.
2. The note closes the loop with feat(desktop): show the model's reported context window beside the declared setting #4575. The number it should name is the reported window the user could adopt, and the natural call to action is the settings surface with the one-click apply from feat(desktop): show the model's reported context window beside the declared setting #4575.

One constraint from the k3-256k data: on such providers usage crosses the reported window gradually and keeps growing (305K → 322K), so the note should fire once per session when the crossing is first observed (the accepted total first exceeds the reported window), not per send — otherwise it spams on every step past the line.

On hysteresis for the dropping note: your <= argument and the normalizeAiSdkUsage sum hold; I have no live case where drift moves the total, so I withdraw that suggestion.

I will take the summarizer prefix-cache item back to #4634 as agreed.

[Joob1n]

Adopted the once-per-crossing constraint on 8c88243ca. The note now fires on the transition rather than per send: the previous accepted total was still inside the reported window and this one is not. That previous total comes from the persisted anchor, so a resumed session does not repeat a crossing it already reported, and a session that is already past the line stays quiet. Test "does not repeat the reported-window note once the session is already past the line" (a 320-token anchor against a reported 100) fails without the guard.

Your two reasons are both in the code's favour: the note is the durable Desktop signal, and it names the reported window, which is the number #4575 offers to apply in one click. Noted on the withdrawn hysteresis and on taking the prefix-cache item to #4634.

[Joob1n]

Correction on the previous push: a rebase of mine stopped on a conflict and the branch was pushed mid-rebase, so 8c88243ca briefly showed this PR with 5 of its 13 commits. The head is now 1283c874c, rebased on main@148f8eb29 with all 13 commits and every local gate green. Nothing in the content changed; main also took epoch 104 in the meantime, so this PR's bump is now 104 → 105 and the comment, CHANGELOG and commit message follow.

[Joob1n]

Closing this in favour of a smaller series. Not because anything here was wrong: it is green and every review item on it is either fixed or deliberately carried forward. The reason is that the design converged past what this PR's shape can carry, and a reviewer arriving now would have to reconstruct it from four rounds of comments.

Two things changed after the last round, both simplifications, and both invalidate part of this PR rather than adding to it:

1. The compaction module runs at most once per send. The proactive and reactive folds were two independent latches here. A fold already covers everything except the live head, so a second one buys a little tail and costs the most recent verbatim context. When a request is still rejected after a fold, the honest diagnosis is that the new message itself is too large, and that is what the user should be told.
2. A finishReason: length no longer triggers a fold. A reply cut below the maxOutputTokens Maka sends can mean the provider ran out of window room, or that the provider has its own lower output cap. Those are indistinguishable from the outside, and an indistinguishable signal should not drive an action. This removes the cutByOwnBudget discriminator @me2seeks and I converged on, one level up: the discriminator was right for the question asked, but the question should not have been asked.

A third change is larger and belongs on its own review: when a fold is rejected as too large, retreat to the span the last accepted request's input covered, rather than halving the covered range. That boundary was accepted by this exact model on this exact connection, so it is provably within capacity, where halving is a guess. The last reply's own span is folded separately when it exceeds 24,000 tokens.

The full design is written up on #4559 as three modules (judge / send / compact) with the call bounds.

Where each review finding goes

Finding	Reviewer	Lands in
Trigger arithmetic needs a reply reserve	@Astro-Han	PR 1
input_too_large must have a real producer	@Astro-Han	PR 2
Eviction check must compare input against input	@Astro-Han	PR 1
Window-suggestion note timing (after recovery, not before)	@Astro-Han	PR 1
Size floor only on the initial fold, not on roll-forward	@Astro-Han	PR 2
Fold-context cleanup, CHANGELOG, CLI note kinds, epoch	@Astro-Han	PR 1
Epoch collision with main	@likun666661	PR 1
Repair request's context-length rejection swallowed as a format defect	@likun666661	PR 2
Architecture documents describing the pre-fix trigger	@likun666661	PR 1
Closing keyword in the commit body, not just the PR body	@likun666661	PR 1
Dropping note must fire on a plateau (<=), not only a decrease	@likun666661	PR 1
Summarizer retry storm: latch every failure, not only malformed ones	@me2seeks	PR 2
Reply reserve must not be the model's output limit	@me2seeks	PR 1
Dropping note false positive on tool-schema shrink	@me2seeks	PR 1
stream_options retreat for strict relays	@me2seeks	PR 1
Undeclared window on a provider that accepts past its reported window	@me2seeks	PR 1
Reported-window note once per crossing, not per send	@me2seeks	PR 1
Length-fold cause guard	@me2seeks	superseded, see 2 above
Summarizer prefix-cache cost	@me2seeks	#4634

The series

• PR 1 — send module: trigger, reply reserve, persisted anchor, one compaction per send, "this message is too large", stream-usage collection with the strict-relay retreat, and all four system notes. One epoch move.
• PR 2 — compaction module: summarizer request shape, output cap and retries, failure latch, and the retreat to the last accepted input boundary.
• feat(desktop): show the model's reported context window beside the declared setting #4575, feat(desktop): show context usage beside the model controls #4576 — unchanged, rebased onto PR 1 when it lands.
• PR 5 — "compact and retry" for a rejection the classifier does not recognise (context: define the degraded modes when the provider does not speak (no usage, unclassified rejection, silent eviction) #4623).

Thank you all for the four rounds; the findings are carried, not discarded.

[Joob1n]

The replacement is #4653: the send module, with the two simplifications described above and the same review findings carried. The compaction module's retreat boundary follows in a second PR.

[Joob1n]

Summary

The runtime no longer estimates whether a request fits a context window. Every "does it fit" question is answered by a provider; every trigger is a real number. This is the remaining step after #4486, which removed the fabricated capacity and the two terminal gates but kept the chars/4 delta estimate, the 32,000-token fallback history budget, and a per-step JSON.stringify of the whole request as a payload ruler. Design and discussion: #4559 (this PR), #4458 (history).

What decides now

• The conversation provider's own context-length rejection is recovered by one compact-and-retry; a second rejection surfaces as the provider's error (context_overflow), and the user's message stays editable.
• The summarizer's provider decides whether compaction input fits: input_too_large retreats the fold by half, and the loop exits through no_safe_completed_span when even the smallest legal span is refused.
• Proactive compaction has one trigger: the previous accepted request's real inputTokens + outputTokens, as the provider counted them, compared with the context window the user declared for the model (a model-facts pin or a relay profile). Reasoning tokens are counted whole on purpose — high is the safe direction for a trigger that can only ask for a compaction.
• A reply the provider cut at its output limit (finishReason: length) folds once before the next request.

What is gone: estimateNextRequestTokens, exceedsHighWater, midTurnRequestPayloadChars, the final-request rescue re-entry, maxHistoryEstimatedTokens and its five consumers, the quarter-window / 16,384 reserve, the 32,000 fallback, the replacement_not_smaller and prefix_over_budget replay gates, size-based replay selection, the estimated input fit before summarizer calls, and the chars/4 summary-size floor.

Notes for the user (four new system_note kinds): context_provider_dropping when an append-only step's usage did not grow (a provider evicting or rewriting context), and context_window_suggestion when a rejection lands at a proven-fit total, carrying the number the user can declare.

Refs #4559 — the issue closes when the whole series (#4574, #4575, #4576) has landed and the remaining items are triaged there.
Refs #4458, #4486

Follow-up PRs (stacked on this one)

The user-facing surfaces are deliberately split out so this PR stays the atomic runtime change and the UI pieces can be reviewed in parallel. Both are open as drafts on top of this branch and will be rebased and undrafted once this merges:

• feat(desktop): show the model's reported context window beside the declared setting #4575 — Desktop settings: the model's reported window shown beside the declared setting with a one-click apply. Without it, a user who has never declared a window gets no proactive compaction and no in-app pointer to the number they could set; the context_window_suggestion note from this PR is the runtime-side half of that pointer.
• feat(desktop): show context usage beside the model controls #4576 — Desktop composer: read-only context-usage indicator fed by the persisted lastRequestAnchor this PR introduces (percentage with a declared window, absolute tokens without one, a dash when the provider reports no usage).

Not in this series, defined and tracked on #4623 (the degraded modes when the provider does not speak): PR D applies the provider-dropping rule at the turn boundary, PR E adds a "compact and retry" action for provider rejections the error classifier does not recognise. Neither reopens a path this PR touches.

Behaviour changes to review

1. No declared window means no proactive compaction. The first time such a session fills up costs one provider round trip and possibly one cut reply; the context_window_suggestion note then offers the last accepted total as the value to declare. This is the "Maka does not decide for the user" principle; the trade-off is stated in Context budget: stop estimating fit; the provider decides, the Maka window is a user target #4559.
2. A /models report or models.dev metadata is no longer a threshold on its own.resolveDeclaredContextWindow (runtime) and declaredContextWindow (core, single owner of the rule) count only a facts pin or a relay profile. resolveSelectedModelContextWindow keeps its old meaning for display and contextRemaining.
3. token_usage.lastRequestAnchor is now { inputTokens, outputTokens? }. The retired payloadChars key still decodes, so sessions written by 0.2.0 keep loading; sessions written by this build do not open in 0.2.0 (the closed-allowlist cost already noted in CHANGELOG.md).
4. Summaries are capped at 8,000 output tokens (DEFAULT_HISTORY_COMPACT_MAX_OUTPUT_TOKENS; the summarizer's maxOutputTokens option was declared and never passed). A length finish gets one shorter retry, then fails open. The too-small-for-fold floor reads the summarizer call's real usage; a producer that reports none is not floored.
5. Checkpoint replay is structural: a source-matched checkpoint replays as [block, everything after the boundary]. No local size gate stands between a materializable fold and dispatch.
6. ContextBudgetDiagnostic.maxHistoryEstimatedTokens is retired (decode-only). HistoryCompactionPolicy.midTurn loses reserveTokens. buildDefaultContextBudgetPolicy drops its connection parameter.
7. Every OpenAI-compatible Chat request now asks for stream usage (stream_options.include_usage), unless the registry opts a provider out. Found live: only two providers opted in, so a local Ollama and every plain OpenAI-compatible relay — the connection type behind Context budget: an undeclared window fabricates a capacity that kills live turns #4458 — returned no usage, and the baseline, the eviction check and the indicator all stayed dark for them.
8. Summary requests close with a user instruction. Found live: a chat-template model handed a conversation ending on its own turn emits end-of-sequence and nothing else (Ollama qwen2.5, both sizes: finish stop, one output token, empty text), so history compaction never succeeded against a local model. Existing message-shape tests gained the trailing user:text.
9. The trigger reserves the model's declared output limit and fires on >= (review). baseline + outputLimit >= declaredWindow, where the limit is connection.models[].maxOutputTokens or generated metadata — a provider fact — and 0 when none is declared. Without it a window declared at the provider's real size could never be crossed by an accepted request. The window itself remains the user's declaration (see the reply on the review for why the metadata window stays a hint).
10. A context-length rejection from the summarizer's provider is input_too_large again (review), so the planner's retreat-by-half has a producer; the same classification is applied to the Codex compaction call.
11. The window suggestion note is written only when the turn surfaces the rejection (review): after the one fold is spent or when there is no seam, naming the last accepted total, which a fold does not clear.
12. The size floor judges an initial fold only (review): on a roll-forward the summarizer's input is the increment, not the covered span, so the floor stands down there and the fold context carries usage only. The eviction check compares input against input, since reasoning is not resent on every wire.

On dropping the signed delta

#4486 kept a signed chars/4 delta so step 0 could fold before a large new message or image went out. I dropped it: the delta prices an image at a constant and under-reads CJK by about half, so the round trip it saves is the one it is most likely to misjudge; large text results are already capped by the byte-based tool-result archive before they go out; and removing it takes the whole payload ruler and the per-step JSON.stringify(messages) with it. Happy to be argued back.

Test coverage removed

Thirty-seven tests encoded the estimate, the reserve, the payload ruler, the fit gates, or the pre-turn estimate gate; each is either re-pointed at a real-usage observable or removed with the mechanism. Re-pointed: the usage baseline is the last request's INPUT tokens → input plus output; compacts over the high water → compacts after provider usage crosses the declared window; keeps user_stop when stopping an oversized pre-turn summary → keeps user_stop when stopping while a usage-triggered fold is summarizing; persists the LAST request as the anchor → persists the last request input and output as the anchor; replays a durable pre_turn checkpoint below the current high water → without a local size gate; rejects a paragraph-sized summary for a large folded span → when usage says it is too small. Removed outright (the mechanism is gone): the three manual compactHistory … exceeds current limits / makes the full replay larger cases, the three reserve-derivation cases, anchors on real provider usage plus a tail char/4 delta, credits a SIGNED negative payload delta, falls back to whole-projection char/4 on cold start, high-water crosses at contextWindow minus reserve, a fold that cannot shrink the real payload is refused, a runaway summary is rejected as replacement_not_smaller, bounds the oldest oversized tool result before dispatch, fails with input_too_large before dispatch, charges the summarization instructions against the input budget, a summary at exactly the floor is accepted under ceil-based token estimates, the capacity verdict measures the steering payload, the anchor a finalization step writes excludes the tool schemas it cleared, dispatches a pre-turn Compaction recipe without projecting history and keeps a transiently unavailable automatic Compaction checkpoint recoverable (both exercised the deleted pre-turn gate; memory extraction from a hook-triggered fold stays covered), applies max-history overrides to checkpoint replay validation, accepts a complete checkpoint above legacy block limits when the full replay fits, compacts one oversized prior turn before an unknown-model request, compacts an oversized latest turn when an older turn is also retained, dispatches an oversized prior turn when its summary fails, after trying once, never runs a pointless summarizer on a small-window model, a usage object without usable input tokens falls back to cold start, a last-request anchor is only valid as a complete positive pair, a half-written anchor fails the whole token_usage message decode (replaced by the new-shape and retired-key cases).

New coverage: the declared-window rule for pin / relay / reported / metadata sources; baseline = input + output, > not >=, cleared after a fold, seeded from the previous turn, discarded across a model switch; a /models window is not a declaration; pendingLengthFold; the summarizer output cap, shorten retry, and output_length after two cuts; usage-based size floor; retreat by half and its give-up exit; structural replay; both notes, including the non-firing cases (pruned step, step 0, declaration already crossed); the retired payloadChars key decodes and an unknown key still fails.

Live verification against a real provider (Ollama)

Driven through the real AiSdkBackend with getAIModel against a local Ollama (qwen2.5:0.5b / qwen2.5:1.5b, default num_ctx 4096), five turns of ~740 tokens each, the previous turn's ledger and run header fed back as prior context.

Scenario	Observed
Declared window 1,500, qwen2.5:1.5b	Turns 1–3: anchors {745,10}, {1481,10}, {2217,10} persisted; baseline 1,491 at turn 3 is < 1,500, no fold. Turn 4: baseline 2,227 > 1,500 → pre_turn fold; summary malformed twice → failedOpen[malformed_summary_missing_section], request dispatched, end_turn. Turn 5: fold again, repair produces a 1,737-char checkpoint → replaced; the request's provider-counted input drops 2,954 → 1,222.
Same, before the two fixes above	No token_usage event at all (Ollama returned no usage because it was never asked); once usage flowed, the summarizer returned empty text every time. Both fixed in this PR.
No declared window, 8 turns	Never folds, never terminates; every turn end_turn. Usage grows 745 → 3,700 and then plateaus at 3,716 for turns 6–8 while ~740 tokens are appended per turn: Ollama truncates silently at num_ctx with no error.

Known limitation, stated plainly: the silent-truncation plateau above happens between turns, and context_provider_dropping only fires within a turn (step ≥ 1, on an input count that did not grow), because at step 0 a user edit can shrink the input legitimately. A provider that truncates instead of rejecting therefore gives an undeclared-window user no signal today; declaring the window is the protection. Detecting the cross-turn plateau without an estimate needs a ledger-shape check on the anchor (did anything before the anchored request change?) — a follow-up, tracked on #4559. Closing that gap is PR D on #4623.

Verification

Rebased on main@148f8eb29 (after #4578 landed, so this PR no longer carries the dependency bump); the Runtime Host compatibility epoch moves 104 → 105 for the two new note kinds and the reshaped anchor. Locally: npm --workspace @maka/{core,storage,runtime,runtime-host,mcp,ui} run build, npm run typecheck (all workspaces), npm run lint, npm run format:check, npm run check:asf-headers, node scripts/protocol-epoch-check.mjs --base origin/main — all clean. Targeted suites: 425/425 across usage-record-last-request-anchor, context-budget-mid-turn-policy, context-budget-model-facts, history-compaction, history-compact-checkpoint, history-compact-summarizer, mid-turn-capacity-backend, overflow-reactive-recovery, ai-sdk-backend; core suite 760/760; provider-conformance 24/24, history-compact-summarizer 53/53, execution-model-composition 28/28 and the CLI pi-transcript suites after the review fixes. Not run locally: the full npm test matrix (the Electron/OpenSSL and owned-Host timing cases fail on this machine independently of the branch) — relying on CI for those.

Self-review

• The core rule declaredContextWindow was implemented twice (runtime and chat-model-choice) in an earlier draft; consolidated into @maka/core/model-thinking with runtime delegating. One owner for the one rule the design turns on.
• The user-stop-during-summary obligation had lost its test when the pre-turn gate went; re-pointed at the hook-triggered fold. The test also records that one request is still attempted after the stop and is rejected by the transport on its already-aborted signal — pre-existing behaviour, now pinned.
• An earlier draft regenerated the Astryx theme with a stale local @astryxdesign/core@0.5.0; that artifact is not in this PR.
• memory-extraction.ts and session-recap.ts keep their own bounded-request budgets; they are auxiliary calls, not history compaction, and are out of scope here.
• Diagnostics (estimatedTokensBefore/After on compaction decisions) still use the chars/4 estimator. They are recorded numbers, not decisions, and are kept so existing telemetry consumers do not break.

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Claude Code — design discussion, implementation, tests, and review; verified by the author.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No

https://claude.ai/code/session_014ajaRxC4jydavY9nYUFj5J

[Astro-Han]

The direction is the one from #4458 and I still hold it: fit is the provider's answer, the trigger is a real number, and the only irreversible outcome is the provider's rejection. The reduction is real, every symbol in "What is gone" is gone from docs and desktop too, and all six workspace suites, typecheck, lint and format pass locally on 372c1de9, and the three commits since (148326eb) touch none of the files cited below. What stops me approving is not the code, it is three places where the design as implemented does not do what the design says. Line-level fixes are inline.

The proactive trigger cannot fire against a correctly declared window. The trigger is baseline > declaredWindow, and the baseline is a request the provider accepted. If the user declares the provider's real window, no accepted request can exceed it, the fold never runs, and every session goes through rejection first. It fires only when the user declares something smaller, which is the retired reserve reintroduced as a number the user has to guess without being told. This is open point 2 of #4559, and I would settle it the other way: resolve the window as declared > relay profile > models.dev > /models, none only when all are absent; trigger on baseline > window − reserve; make the reserve a real number, the model's output limit plus the tool-result archive cap times pending tool calls, with a fraction of the window as the floor. Those are provider facts and Maka's own content policy, so the "real numbers only" principle holds. A default is not Maka deciding for the user, it is a default the user can override, and the alternative is that out of the box every fill costs a rejection and possibly a cut reply, which CLI users get without even the hint, because pi-transcript.ts drops the two new note kinds. The per-step check already gives mid-turn triggering; only the window and the threshold change.

The summarizer's provider does not get to decide. The design names four deciders, and one of them, "the summarizer's provider decides whether compaction input fits, input_too_large retreats the fold by half", has no producer. Only fitHistoryCompactMessages throws input_too_large, this PR removes that call from history-compact-summarizer.ts and openai-codex-history-compactor.ts, and both catches wrap every provider error as provider_error. So a session whose fold prefix is too large for the summarizer fails open on the first rejection, /compact included, and has no in-app way back under the window. That is worse than main, which at least estimated. The fix is small, classify ContextLength in both catches, but the regression must use a fake provider that rejects above N tokens; all five current input_too_large tests throw the error from a fixture, which is why this was invisible.

The compatibility contract. Two new system_note kinds and the new lastRequestAnchor shape land in packages/core closed allowlists, the same class of change #4486 bumped the epoch for, and the epoch is unchanged. A merge-base client handshakes fine (host-kernel.ts admits on strict equality) and fails decodeStoredMessage on the first transcript carrying a new note. main is on 96 now: rebase, take 97, and put back the three CHANGELOG sentences from #4486 that are still true (see inline).

One consequence of the first point that lives outside the diff: settings-provider-copy.ts still says "when empty, built-in metadata decides", and /context and the inspector still divide by resolveSelectedModelContextWindow, so an undeclared user sees 70% of 200k and never gets a fold. Whichever way the window question settles, the copy and the denominator have to follow the same rule.

On the test claim: five re-pointed tests pass unchanged on main's built sources (the no-size-gate replay, the two size-floor cases, the no-usage case, fails open after repeated input-too-large retreat), and two rules lost their only coverage with the deletions while still existing, the memory gate's unavailable outcome and the rule that a synthetic /compact usage row must not shadow the real anchor. The remaining persisted-anchor test uses an anchor below the window, so it passes regardless of the run-header check.

Evidence boundary: static read against main61224f51; all suites run locally; new tests also run against main's built sources in a scratch copy; no live provider.

AI-assisted review: drafted with Maka; I verified the trigger arithmetic, the input_too_large producers, the epoch state and the size-floor inputs myself.

简体中文

方向就是 #4458 上讨论定下的，我仍然支持：放不放得下由 provider 回答，压缩触发用真实数字，唯一不可逆的结果是 provider 的拒绝。删得也干净，「What is gone」里的每个符号在 docs 和 desktop 里都没有残留，本地六个 workspace 的测试、typecheck、lint、format 全绿；之后的三个提交（148326eb）没有碰到下面引用的任何文件。让我暂时不 approve 的不是代码本身，而是三处实现和设计说的不是一回事。能局部修的都放在行内评论里。

主动触发对着正确声明的窗口永远打不响。 触发条件是「上次请求的 input+output 大于声明窗口」，而上次请求是 provider 已经接受的。如果用户把窗口声明成 provider 的真实大小，任何被接受的请求都不可能超过它，主动压缩一次也不会触发，每个会话都要先撞一次拒绝。只有用户把窗口声明得比真实值小它才触发，这等于把删掉的 reserve 变成了一个要用户自己猜、又不告诉他的数字。这是 #4559 的 open point 2，我的意见相反：窗口按「用户声明 > relay profile > models.dev 元数据 > /models 报告」解析，全都没有才算无；触发条件改成「上次用量 > 窗口 − reserve」；reserve 用真实数字：模型的 output limit（下一步回复最多这么大）加上工具结果归档上限乘以待处理的工具调用数，再用窗口的固定比例兜底。这些都是 provider 的事实和 Maka 自己的内容策略，「只用真实数字」的原则不受影响。给一个默认值不是替用户决定，用户随时可以覆盖；不给的后果是开箱用户每次填满都要付一次拒绝、可能还拿到被截断的回复，CLI 用户连提示都看不到，因为 pi-transcript.ts 把两个新 note kind 丢掉了。turn 内每一步都检查的逻辑已经有了，只需要改窗口和阈值。

summarizer 的 provider 并没有拿到决定权。 设计列了四个决定者，其中「summarizer 的 provider 决定压缩输入放不放得下，input_too_large 就把范围退半」这一条没有产生者。全仓只有 fitHistoryCompactMessages 会抛 input_too_large，本 PR 把它从 history-compact-summarizer.ts 和 openai-codex-history-compactor.ts 里删掉了，两处的 catch 又把所有 provider 错误一律包成 provider_error。于是一个长会话的折叠前缀如果对 summarizer 也太大，第一次拒绝就整体放弃，/compact 走同一条路也一样，会话在 app 内没有回到窗口内的办法，比 main 还差，main 至少还估算一下。修法很小，两个 catch 里判断 ContextLength 再抛，但回归测试必须用「输入超过 N tokens 就拒绝」的假 provider；现在五个相关测试全是 fixture 手抛这个错误，所以这个洞看不见。

兼容契约。 两个新的 system_note kind 和新的 lastRequestAnchor 形状都进了 packages/core 的闭合 allowlist，和 #4486 推 epoch 的那次是同一类改动，但 epoch 没动。merge-base 上的旧 client 握手能通过（host-kernel.ts 按严格相等准入），然后在第一条带新 note 的 transcript 上解码失败。main 现在已经是 96：rebase 取 97，并把 #4486 写的、仍然成立的三句 CHANGELOG 加回来（见行内）。

第一点在 diff 之外的一个后果：settings-provider-copy.ts 的帮助文案「留空跟随内置元数据」现在不成立，/context 和 inspector 的分母也还是 resolveSelectedModelContextWindow，未声明的用户会看到「已用 70% / 200k」却永远等不到压缩。窗口问题无论怎么定，文案和分母都要跟同一条规则。

关于测试的说法：五条 re-pointed 测试在 main 的构建产物上原样通过（无 size gate 的 replay、两条体量下限、无 usage、退半后 fail open）；两条规则随删测试失去了唯一覆盖但仍然存在：memory gate 返回 unavailable 的处理，以及手动 /compact 写的合成 usage 行不得遮蔽真实 anchor。剩下那条持久 anchor 测试的 anchor 低于窗口，不管 run header 合不合法都过。

[Astro-Han]

baselineTokens is a request the provider accepted, so with the window declared at the provider's real size this is never true; the fold only runs when the user declares something smaller. That is the reserve in disguise. baseline > window − reserve, with the reserve from output limit plus the tool-result cap, is what makes this fire before the rejection. First point in the main comment.

[Astro-Han]

Dead branch: nothing throws input_too_large any more. fitHistoryCompactMessages was its only producer and both summarizer catches now wrap provider errors as provider_error. Classify ContextLength with classifyError in history-compact-summarizer.ts and openai-codex-history-compactor.ts so this retreat has a producer, and test it with a fake provider that rejects above N tokens.

[Astro-Han]

Baseline includes last step's reasoning; on wires that do not resend it (gpt-5.x), next input ≈ previous input + tool call + result, which is below input + output whenever reasoning exceeded the appended content, the normal case. Compare against last step's input alone; keep input + output for the trigger.

[Astro-Han]

Written before recoverFromOverflowError runs, so a send that overflows once, folds and completes still tells the user the provider refused. #4559 places this under "already folded". Move it after the recovery verdict; overflow-reactive-recovery.test.ts:1834 (tool, overflow, done) currently pins the wrong order. And suggestedContextWindow: baselineTokens sits on the strict > boundary, so a user who applies it still needs one more rejection.

[Astro-Han]

On a roll-forward the summarizer is sent previous summary + new events, so inputTokens is the increment while the checkpoint replaces the whole covered span; in steady state this floor never trips and a fifty-token summary after a small increment is persisted. The new test passes on main because the stub's usage is unrelated to the messages. Feed it a span-sized real number (previous checkpoint's compactCallInputTokens plus this increment) or drop the floor openly.

[Astro-Han]

The comment above says this re-runs the size floor, but no summarizerUsage is passed so the floor is skipped, and coveredRuntimeEvents is now required and unread by the validator. Same for the external-producer branch in history-compaction.ts. Either pass a real number or delete the field, the three constructions and the comment.

[Astro-Han]

Three sentences from #4486 were dropped and are still true: sessions from this build do not open in earlier releases and the runtime.sqlite copy must be taken before upgrading; context_budget_exhausted is no longer produced but still decodes; the epoch line (97 after rebase). The body says the allowlist cost is "already noted in CHANGELOG.md", and it no longer is.

[Joob1n]

Thanks for the read — every finding was real. Fixes are in 38b2d837 (one commit, each item with a test that fails on the previous commit), plus two live-provider findings in the commits before it.

Trigger arithmetic. You are right that baseline > declaredWindow could never fire against a window declared at the provider's real size. Fixed the way you suggested for the reserve, with one narrowing: the reserve is the model's declared output limit only (connection.models[].maxOutputTokens or generated metadata; 0 when none is declared), and the trigger is baseline + limit >= window. I did not add the tool-result cap × pending calls term: the active prune already bounds each result before it goes out, and a second constant on the trigger side is the kind of number the design is trying not to own. Live on Ollama (qwen2.5:1.5b, declared 1,500) the fold now fires at 2,227 with the previous usage as the only input, folds to a 1,737-char checkpoint after one repair, and the next request's provider-counted input drops 2,954 → 1,222.

Window source — kept as declared-only, deliberately. This is the one point where I did not take the suggestion, and it is the issue author's call rather than mine: the Maka window is a target the user chooses to stay under, not a fact about the model, so the model's reported window is shown beside the setting with one click to apply (#4575) but never becomes the threshold on its own. The cost you name is real and stated in the description: with nothing declared, the first fill costs one rejection and possibly one cut reply. The context_window_suggestion note then offers the last accepted total; it is now written only when the turn actually surfaces the error, and the CLI transcript renders both new note kinds.

input_too_large producer. Correct — I removed the only producer. Both summarizer catches now classify ContextLength as input_too_large, with a fake provider that rejects above N characters as the regression.

Epoch and CHANGELOG. Bumped to 97 on rebase and the three sentences are back.

Inline items: eviction check compares input with input; the size floor applies to the initial fold only (the roll-forward input is the increment, as you say) and CheckpointSummaryFoldContext carries usage only, so the builder/copy seams validate structure and truncation; the suggestion note moves after recovery and names the fold-proof last accepted total; the run-header test's anchor now sits above the window so the header check decides; the synthetic /compact row test is restored; the roll-forward floor test now asserts both directions.

Two things I left as they were, with reasons. The Host's runComposition.contextWindow stays the model's reported window: it is a protocol fact clients already display, and the declared window gets its own surface in the composer indicator (#4576) rather than a changed meaning for an existing field. And the memory-gate unavailable outcome is still exercised by the mid-turn fixture's extraction path (remember returns unavailable there, asserted at the fold that dispatches extraction); if you meant a different obligation, tell me which and I will pin it.

[Joob1n]

Rebased on main@8ea3c4f05 now that #4578 has landed, so the dependency bump is no longer carried here (6 commits). main moved the compatibility epoch to 98 in the meantime (#4561 / #4568), so this PR's bump is now 98 → 99; the CHANGELOG line and the epoch comment follow. No other changes since a65076258.

[likun666661]

方向我赞成：把“请求是否 fit”的裁决权完全交给 provider，把本地侧收缩为“真实 usage + 用户目标只触发可逆 fold”，比多把估算尺同时参与决策更干净。PR 的主要因果链也基本成立。不过在 approve 前，我认为还有下面几个点需要收口：

1. [P1] compatibility epoch 与最新 main 撞号。 当前 main@898b86d 已经把 RUNTIME_HOST_COMPATIBILITY_EPOCH 升到 99，用于 ScheduledTask 的 Connection identity；本 PR 也独立使用 99 表示两个新 system note 和 lastRequestAnchor shape。两边是不同的不兼容协议变化。rebase 后不能只解决文本冲突并继续保留 99，需要把合并结果升到 100，同步注释、CHANGELOG 和 epoch test；否则能力不同的 client/host 可能错误通过严格相等握手。

2. [P2] repair 请求里的 ContextLength 会被吞成初次格式错误。history-compact-summarizer.ts:206-243 中，初次 summary malformed 后，repair 使用更长的 system prompt。如果初次调用刚好 fit、repair 因新增 instruction 被 provider 拒绝，内层 catch 会把该错误包装成初次的 malformed_summary_*；外层看到它已经是 HistoryCompactSummarizerError 后直接重抛，不会再分类为 input_too_large。planner 因此不会执行 halve-and-retry，和“summarizer provider decides”不一致。建议在 repair catch 中保留 ContextLength 分类，并补一个“initial malformed, repair overflow”的回归测试。

3. [P2] 架构文档仍描述修复前的 trigger。 中英文文档目前都写成“上次 inputTokens + outputTokens 超过用户窗口时触发”；实现已经是 baseline + model.maxOutputTokens >= declaredWindow（ai-sdk-compaction.ts:896-908）。这是核心规则，应同步两份文档，避免后续实现和测试重新漂移。

4. Issue closure 建议调整。#4559 的 proposal 还包含 missing-usage hint、unclassified overflow 的 compact-and-retry action、metadata window 一键采用和 composer indicator。本 PR 没有 missing-usage note，unclassified action 明确留在系列之外，UI 又拆到 #4575/#4576。拆 PR 没问题，但此时 Closes #4559 会让完整验收范围过早关闭；建议改成 Refs #4559，或先明确把 #4559 收缩为 runtime-only。

从 Occam 的角度，我的判断是：架构方向已收敛，问题定义尚未完全收敛。 最小因果主线已经很清楚：

history grows
→ user target may request a reversible fold
→ provider outcome decides actual fit
→ canonical history is never rejected or mutated by an estimate

但“provider decides”尚未覆盖 provider 沉默的情况：PR 自己的 Ollama 实测已经显示跨 turn usage plateau / silent truncation，而当前 dropping note 只检查同 turn 的 step ≥ 1。建议把无 usage、无法分类以及 silent eviction 明确定义成可见的 degraded mode；否则“未声明 window 时系统提供什么保证”仍是开放语义。

另外，includeUsage ?? true 现在会给所有 OpenAI-compatible Chat server 发送 stream_options.include_usage。现有 conformance test 只覆盖支持该字段的 fake server；最好再补一个严格 relay 拒绝该字段时的契约测试，明确 fail、fallback 或 opt-out 行为。

CI 当前是绿的，diff check 也干净；上面第 1 项是基于最新 main 的当前 merge blocker，第 2 项是静态可达的 provider-boundary bug。修完这些，我认为核心 runtime 改动可以继续推进。

[Joob1n]

Thanks — the first three are real and are fixed in 6c5e53ddd / ba14a706c; the fourth is done in the PR body.

1. Epoch.main moved again while this was open (#4321 → 99, #4508 → 100), so the rebase now lands this PR's bump as 100 → 101; comment, CHANGELOG and the epoch check follow. The protocol tests assert against the exported constant, not a literal, so nothing else pins the number.

2. Repair-path ContextLength. Confirmed: the repair catch wrapped every failure under the initial defect, so a context-length rejection of the longer repair prompt never reached the planner as input_too_large. The catch now classifies before wrapping; regression test "a context-length rejection of the repair request stays the input_too_large signal" (initial malformed → repair rejected → input_too_large, two provider calls) fails on the previous commit.

3. Docs. Both llm-compaction-events-log-projection-draft documents now state the implemented trigger: previous accepted inputTokens + outputTokensplus the reply reserve (the model's declared maxOutputTokens, zero when unknown) reaching the declared window.

4. Issue closure. Changed to Refs #4559; the issue closes when #4574/#4575/#4576 have all landed and the remaining proposal items are triaged there.

On the two broader points:

• Degraded modes (no usage, unclassified rejection, cross-turn plateau). Agreed that these deserve names. They are deliberately outside this PR: the dropping note is scoped to a single send because within one send Maka knows it only appended, while across turns the user may have edited or branched and a lower inputTokens is legitimate. Opened context: define the degraded modes when the provider does not speak (no usage, unclassified rejection, silent eviction) #4623 with the three modes, the signal each one gives today, and the two small follow-ups: PR D applies the same dropping rule at the turn boundary (first request's inputTokens below the persisted anchor with no fold or prune before the send → note), PR E adds "compact and retry" on an unclassified provider error. Both are notes/actions on top of this PR's paths, so they can land right after it without reopening it.

• stream_options on strict relays. Decided and pinned in 6ce7d7332: a relay that rejects the field fails with the provider's own 400 text and the runtime does not resend without it — the conformance test asserts one request, the stream_options body field, and the provider message reaching the stream's error part. Rationale: a connection that cannot report usage has no context baseline, so a silent fallback would hide exactly the degraded mode above; the error names the field, and a per-adapter includeUsage: false is the one-line opt-out if a real relay needs it. The field has been part of the Chat Completions API since 2024-05 and the Kimi OpenAI path in this repo has sent it since feat(runtime): support Kimi OpenAI protocol #1462.

[Joob1n]

Rebased on main@b1ec28989. main took epoch 101 in the meantime (#4608), so this PR's bump is now 101 → 102; comment, CHANGELOG and the epoch check follow. The strict-relay contract test is e10dd49a4's head commit (was 6ce7d7332 before the rebase). No other changes.

[likun666661]

复查了最新 head e10dd49a4。上一轮的主要项都已正确落地：epoch 102 对应 merge base 101；repair-path ContextLength 保留为 input_too_large 且有回归；两份文档的 trigger 公式已更新；PR body 改成了 Refs #4559；strict relay 的一次 400 / 不静默重试契约也已固定。CI 当前是绿的，PR 可干净合并。

还有两个行为/scope 问题和一个文档漂移需要收口：

1. [P1] #4559 仍会被 closing keyword 关闭。 PR body 虽然已经改成 Refs #4559，但首个 commit 20f01b862 的 message body 仍然包含 Closes #4559。本仓库只允许 squash merge，并配置为 squash_merge_commit_message: COMMIT_MESSAGES；因此这个 closing keyword 会进入 default-branch 的 squash commit，仍会关闭 issue。既然约定是整个 #4574/#4575/#4576 系列落地并完成剩余 triage 后再关闭，请把该 commit message amend 为 Refs #4559（或确保最终 squash message 中完全没有 closing keyword），而不只是修改 PR body。

2. [P2] provider-dropping 实现检测的是“严格下降”，对外契约写的是“没有增长”。packages/runtime/src/ai-sdk-backend.ts:2170-2182 当前条件是：

   stepUsage.inputTokens<lastStepInputTokens

   但 PR summary、commit message、CLI/UI copy 和新开的 #4623 都把信号定义为 usage “did not grow / stops growing or drops”。本 PR 自己的 Ollama 证据正是输入在 3,716 持平 plateau；严格 < 不会对这个案例写 note。当前测试也只有 100 → 50 的 decrease，没有 equal-usage case。

   如果 observable contract 确实是“append-only request 的 input 没增长”，这里应使用 <= 并补一个 equal-usage regression。#4623 的 PR D 也不应只定义成 “below persisted anchor”，否则同一个跨-turn plateau 仍不会被检测。若等值被刻意排除，则应反过来收窄 PR、copy 和 #4623 的声明，并说明为什么 plateau 不是可靠信号；现在代码和承诺二者只能有一个成立。

3. [P3] 中文架构文档仍有两处旧的 size-policy 语义。docs/architecture/llm-compaction-events-log-projection-draft.zh-CN.md:88-93 的公式仍写 current context budget，而英文已改成 user-declared capacity and provider outcome；同文档 :121-130 仍把 checkpoint 的必要问题写成“它在当前 token policy 下仍然能否进入 prompt？”，英文已改为 source/provider-state identity。后文已经明确删除 replay size verdict，因此这两处应与英文及最终实现同步。

除了以上三项，上一轮要求的修复我没有再发现回归。前两项处理后，我认为这轮可以进入 approve。

[Joob1n]

All three are fixed on 2cbc332af.

1. Closing keyword in the commit body. You are right that the PR body is not where this is decided under squash merge with COMMIT_MESSAGES. 20f01b862 is reworded to Refs #4559 (now 3ed669070 after the rebase); no commit on the branch carries a closing keyword any more.

2. < vs <=. Fixed to <=, with the copy as the authority rather than the other way round. Your reading of the evidence is the right one: the live Ollama run plateaus at 3,716 input tokens and never drops, so the strict comparison would have missed the exact case the PR cites. An equal input count after an append-only step (no fold, no prune, no image omission) is already impossible without provider-side eviction or rewriting, so equality is signal, not noise. New regression "records provider context dropping when an append-only step reports the same usage" (100 → 100 across the step) fails on the previous commit; the existing decrease and prune-explains-it tests still pass.

#4623 is updated to match: PR D's rule is "at or below the persisted anchor", not "below", for the same reason.

3. Chinese document drift. Both passages are synced with the English text: the materialization inputs now read 用户声明的 capacity 与 provider 结果, and the checkpoint's replay question is source/provider-state identity rather than the retired token policy.

One note on scope: both documents still ask "which high-water decision produced it" in that same list. It is stale in both languages equally, so I left it rather than widening this PR's document diff; say the word and I will fold it in here, otherwise it goes with the #4623 documentation pass.

[me2seeks]

Reviewing with real edge cases in mind, grounded in production data from a kimi-coding-plan/k3-256k workspace (see also #4634 — this PR fixes its root causes 1 and 2; items 3 and 4 there remain open).

Overall the direction is sound: every trigger is now a provider-reported number, and I live-verified the new summarizer request shape against k3-256k (details inline on the summarizer change). My concerns are about the paths where the provider never speaks: silent over-window acceptance, output-limit cuts caused by our own maxOutputTokens, and unrecognized error shapes.

[me2seeks]

Real edge case from live data: kimi-coding-plan/k3-256k accepts requests beyond its fetched window without rejecting or truncating — observed a session accepted at 322K input tokens against a fetched contextWindow of 262,144, with usage still growing monotonically (305K → 322K). On such a provider every signal this design reads stays dark for an undeclared window:

• no rejection → reactive fold never fires;
• usage never plateaus → context_provider_dropping never fires (and it is mid-turn only anyway);
• context_window_suggestion only fires on a surfaced rejection → never written;
• a fetched /models window is not a declaration → the proactive trigger below never arms.

Net effect: an undeclared kimi session degrades silently and indefinitely (this is exactly the data behind #4634). I agree with "Maka does not decide for the user" as a principle, but for providers observed to accept over-window requests, could the fetched window seed a default declaration (user-overridable), or should the cross-turn plateau check (#4623 PR D) be a blocker rather than a follow-up?

[me2seeks]

pendingLengthFold is set on anylength finish with no size or cause guard. Two real cases where the fold is useless or harmful:

1. The cut came from our own configured maxOutputTokens, not the window: maka sends maxOutputTokens: 131072 on kimi-coding-plan main requests (from lookupModelMetadata). A reply cut at that cap is not helped by folding history at all — the next request carries the same cap. If the model keeps wanting more output (long reasoning at effort=max, large file generation), this turn folds every step, repeatedly shrinking history while never addressing the constraint.
2. A user who declares a small output limit for cost control gets routine length finishes → folds at a few K tokens of context, paying a summarizer call each time.

Suggest gating the length fold on baseline + replyReserve >= capacity (i.e. plausibly window-caused), or capping length-folds per turn.

[me2seeks]

For k3-256k, declaredModelOutputLimit resolves to 131,072 from bundled metadata — half of its 262,144 window. A user who pins the full window gets proactive folding at baseline >= 131,072, i.e. ~50% utilization, which is far earlier than "stay under your declared window" suggests. Reserving the output limit is right in principle (without it a real-size declaration is never crossed), but when the declared output limit is a large fraction of the window the reserve dominates. Consider capping it, e.g. min(outputLimit, capacity / 4) or a fixed bound.

[me2seeks]

The per-send latch and the fingerprint circuit still only cover malformed-summary reasons. After a provider_error / output_length fail-open, baselineTokens stays set, so overWindow remains true and every subsequent step retries the summarizer. Observed live on kimi-coding-plan (which reports failures as HTTP 200 + error body): 15 consecutive failed summarizer calls over ~47 minutes, each 30–45 s, before the main request. Suggest latching any summarizer failure for the rest of the send, with the same fail-open diagnostic. (#4634 item 3)

[me2seeks]

Defaulting includeUsage on for every non-opted-out OpenAI-compatible server is the right call for usage coverage, but a strict relay/proxy that rejects unknown fields (older vLLM, some gateways) will 400 every streaming request after upgrade, and opting out requires a registry code change. Consider a one-time fallback: on a 400 whose error text mentions stream_options/include_usage, retry without it and remember that for the connection.

[me2seeks]

Two false-positive paths for the dropping note:

1. Finalization steps remove all tool schemas (resolveDispatch returns [] for the child-summary / sandbox-boundary finalization step), which legitimately drops the next request's input by several K tokens with no fold/prune/image-omit — this condition doesn't exclude that case, so a routine turn end can report "provider is dropping context".
2. No hysteresis: a 1-token decrease fires the note. Cache accounting or tokenizer drift between calls can produce tiny legitimate decreases. A small relative threshold (e.g. drop > 1–2% or > N tokens) would keep the note meaningful.

[me2seeks]

Confirming this fixes the kimi-coding-plan failure mode from #4634 — I live-tested this exact request shape (system template + trailing user instruction) against k3-256k on both wires: it now returns a fully compliant sectioned summary, where the system-prompt-only shape returned content: null (7 tokens) or continued the conversation as the assistant.

One follow-up worth noting (not blocking): the summarizer request still opens with a different system prompt than the main loop, so it shares no prefix cache with it — the first fold of a session pays a full uncached pass over the folded span (observed 39–88 s on 155–253K inputs). Moving the whole instruction into the trailing user message would let the summarizer reuse the main loop's cached prefix (~99% hits); keeping the template in system is also fine if that's load-bearing for other providers, but the cache cost is real at high context.

[Joob1n]

Thank you for the production data. Every path you named is real, and four of them are fixed on 1faabac55. The evidence for each is your k3-256k workspace, so I have quoted your numbers in the commit message rather than restating them here.

Summarizer retry storm (#4634 item 3). Fixed. The per-send latch recorded only malformed reasons, and the baseline that fired the trigger survives a fail-open, so a provider_error re-armed the same condition on every later step. Every fail-open reason now latches for the rest of the send. Regression: "bounds a provider-error summarizer failure across later steps in the same turn" (one summarizer call, failOpenReason: provider_error, no checkpoint), failing on the previous commit.

pendingLengthFold with no cause guard. Fixed, and your first case is the discriminator: the reply's own outputTokens says which limit cut it. A reply that stopped at the maxOutputTokens Maka sends was cut by Maka's budget, and the next request carries the same budget, so the fold is marked only when the reply stopped below it. That covers your cost-control case too, since a small declared output limit is reached exactly. No new constant, and both numbers are provider-reported. Regression: "does not fold when the reply was cut by the output budget Maka itself sends".

Dropping-note false positives. The finalization case is fixed: the note is suppressed when the step's own active tool set shrank, which is Maka reshaping the request rather than the provider evicting anything. Regression: "does not report provider dropping when the step dropped its tool schemas". On hysteresis I would rather not add a threshold, and I think the <= change (this PR now treats a plateau as the signal, per @likun666661's review) makes the case: after an append-only step, an input count that merely failed to grow already means the appended content was not counted, so a one-token decrease is not a weaker signal than equality but a marginally stronger one. normalizeAiSdkUsage sums no-cache, cache-read and cache-write, so cache accounting does not move the total. If you have a case where drift moves it anyway, that is worth a threshold and I will add one.

stream_options on strict relays. Adopted your suggestion over my earlier position, which @likun666661 also questioned: the deciding argument is that opting out needs a registry code change, so a strict relay has no user-facing recovery. A 400 whose body names the field now triggers one retry without it, remembered per base URL for the process. The connection then simply reports no usage, which the composer indicator (#4576) shows as a dash. Contract test asserts the three requests: asked, retried without, and never asked again.

Providers that accept beyond their fetched window. This one I have not changed, and I want to be explicit about why, because you are right that every signal stays dark. A cross-turn plateau check (PR D on #4623) does not rescue it either: your session's usage grows monotonically to 322K, so there is no plateau to detect. The only thing that arms anything is a declaration. Two options I can see:

1. A note when accepted usage exceeds the model's reported window while nothing is declared. That is two real numbers and no decision on the user's behalf, and it is the same shape as the existing context_window_suggestion. It fits this design and I would be glad to add it, here or as PR D's sibling.
2. Seeding a default declaration from the fetched window, which is the thing Context budget: stop estimating fit; the provider decides, the Maka window is a user target #4559 deliberately removed: a fetched number is a hint, and a session that compacts because of a number the user never chose is the failure this PR exists to end.

My preference is 1. Say which you would rather review and I will follow.

Prefix cache on the summarizer request. Noted as a follow-up, not forgotten: your 39–88 s uncached first attempts are a strong argument for moving the whole instruction into the trailing user message now that the trailing message exists. I have left the system template in place here because it is load-bearing for the providers the current tests cover, and changing both the shape and the cache behaviour in the same PR would make the k3-256k regression hard to attribute. It belongs on #4634.

Thanks also for live-testing the summarizer request shape; that is the part of this PR I could only verify against Ollama and fake providers.

[Joob1n]

Follow-up on the two open items from your review, both now on 77590471e.

The reply reserve is no longer the model's output limit. Your k3-256k arithmetic was the deciding case: reserving 131,072 against a 262,144 declaration folds at half the window a user deliberately chose. It is now twice the last reply the model actually wrote, bounded at 8,000 tokens. Both halves are provider-reported, the margin tracks the session's own behaviour rather than a catalog maximum, and no previous reply means no reserve at all. On your numbers a session answering in 2–3K tokens now folds at roughly 256K of 262K instead of 131K. The old test that asserted the output limit is rewritten around the new rule (a 900-token anchor with a 60-token reply folds against a 1,000 window, the same anchor with a 5-token reply does not, and the model's 600-token output limit is irrelevant to both).

A reserve measured from a smaller previous reply can still be too small, so that case is now reported rather than silent: when an accepted request's own input plus its reply exceed the declared window, the transcript carries one context_window_overrun note per send with both numbers. It is the honest reading of "the reply needed more room than was left", it uses only provider-reported numbers, and it tells a user who wants whole replies to raise the declaration. The next request folds anyway because the baseline now exceeds the window; the note explains why rather than changing what happens.

That makes three note kinds in this PR, all in the same epoch move (now 103 → 104 after the latest rebase).

Still yours to choose: the undeclared-window case on a provider that accepts past its reported window. My preference remains a note when accepted usage exceeds the model's reported window while nothing is declared, rather than seeding a declaration from a fetched number. Say which you would rather review.

[Joob1n]

Added, on 0d0a32dce: with nothing declared, a request the provider accepts past the window its own catalog entry reports now writes one context_reported_window_exceeded note per send, naming what the exchange used and what the model reports. It changes nothing on its own — a reported window stays a hint, and Maka still declares nothing on the user's behalf — but the case you found is no longer invisible. With a declaration in place the overrun note already owns that ground, and a test pins that the two never fire for the same fact.

That is the fourth note kind in this PR, all within the same epoch move (103 → 104 after the latest rebase). Local gates are green; the mid-turn suite is 73/73.

[me2seeks]

Thanks — verified 1faabac55 and 77590471e on the diff. The cutByOwnBudget discriminator is a better fix than the proximity gate I suggested: it distinguishes the two length causes with two provider-reported numbers, and my cost-control case falls out of it for free. The behaviour-measured reply reserve (2× last reply, ≤8K) fixes the k3-256k half-window arithmetic, and context_window_overrun is the right honest reporting for a reply that outgrew a reserve measured from smaller ones.

Undeclared window on a provider that accepts past its reported window: I choose option 1 — a note when accepted usage exceeds the model's reported window while nothing is declared. Two reasons beyond the ones you gave:

1. Coverage differs by surface. TUI has a real-time ctx indicator (I have a PR open adding one, with colour) so a TUI user can transiently see 322K > 262K; Desktop has nothing. A persisted note in the transcript is the only durable signal on Desktop, and the only one that survives the moment on TUI.
2. The note closes the loop with feat(desktop): show the model's reported context window beside the declared setting #4575. The number it should name is the reported window the user could adopt, and the natural call to action is the settings surface with the one-click apply from feat(desktop): show the model's reported context window beside the declared setting #4575.

One constraint from the k3-256k data: on such providers usage crosses the reported window gradually and keeps growing (305K → 322K), so the note should fire once per session when the crossing is first observed (the accepted total first exceeds the reported window), not per send — otherwise it spams on every step past the line.

On hysteresis for the dropping note: your <= argument and the normalizeAiSdkUsage sum hold; I have no live case where drift moves the total, so I withdraw that suggestion.

I will take the summarizer prefix-cache item back to #4634 as agreed.

[Joob1n]

Adopted the once-per-crossing constraint on 8c88243ca. The note now fires on the transition rather than per send: the previous accepted total was still inside the reported window and this one is not. That previous total comes from the persisted anchor, so a resumed session does not repeat a crossing it already reported, and a session that is already past the line stays quiet. Test "does not repeat the reported-window note once the session is already past the line" (a 320-token anchor against a reported 100) fails without the guard.

Your two reasons are both in the code's favour: the note is the durable Desktop signal, and it names the reported window, which is the number #4575 offers to apply in one click. Noted on the withdrawn hysteresis and on taking the prefix-cache item to #4634.

[Joob1n]

Correction on the previous push: a rebase of mine stopped on a conflict and the branch was pushed mid-rebase, so 8c88243ca briefly showed this PR with 5 of its 13 commits. The head is now 1283c874c, rebased on main@148f8eb29 with all 13 commits and every local gate green. Nothing in the content changed; main also took epoch 104 in the meantime, so this PR's bump is now 104 → 105 and the comment, CHANGELOG and commit message follow.

[Joob1n]

Closing this in favour of a smaller series. Not because anything here was wrong: it is green and every review item on it is either fixed or deliberately carried forward. The reason is that the design converged past what this PR's shape can carry, and a reviewer arriving now would have to reconstruct it from four rounds of comments.

Two things changed after the last round, both simplifications, and both invalidate part of this PR rather than adding to it:

1. The compaction module runs at most once per send. The proactive and reactive folds were two independent latches here. A fold already covers everything except the live head, so a second one buys a little tail and costs the most recent verbatim context. When a request is still rejected after a fold, the honest diagnosis is that the new message itself is too large, and that is what the user should be told.
2. A finishReason: length no longer triggers a fold. A reply cut below the maxOutputTokens Maka sends can mean the provider ran out of window room, or that the provider has its own lower output cap. Those are indistinguishable from the outside, and an indistinguishable signal should not drive an action. This removes the cutByOwnBudget discriminator @me2seeks and I converged on, one level up: the discriminator was right for the question asked, but the question should not have been asked.

A third change is larger and belongs on its own review: when a fold is rejected as too large, retreat to the span the last accepted request's input covered, rather than halving the covered range. That boundary was accepted by this exact model on this exact connection, so it is provably within capacity, where halving is a guess. The last reply's own span is folded separately when it exceeds 24,000 tokens.

The full design is written up on #4559 as three modules (judge / send / compact) with the call bounds.

Where each review finding goes

Finding	Reviewer	Lands in
Trigger arithmetic needs a reply reserve	@Astro-Han	PR 1
input_too_large must have a real producer	@Astro-Han	PR 2
Eviction check must compare input against input	@Astro-Han	PR 1
Window-suggestion note timing (after recovery, not before)	@Astro-Han	PR 1
Size floor only on the initial fold, not on roll-forward	@Astro-Han	PR 2
Fold-context cleanup, CHANGELOG, CLI note kinds, epoch	@Astro-Han	PR 1
Epoch collision with main	@likun666661	PR 1
Repair request's context-length rejection swallowed as a format defect	@likun666661	PR 2
Architecture documents describing the pre-fix trigger	@likun666661	PR 1
Closing keyword in the commit body, not just the PR body	@likun666661	PR 1
Dropping note must fire on a plateau (<=), not only a decrease	@likun666661	PR 1
Summarizer retry storm: latch every failure, not only malformed ones	@me2seeks	PR 2
Reply reserve must not be the model's output limit	@me2seeks	PR 1
Dropping note false positive on tool-schema shrink	@me2seeks	PR 1
stream_options retreat for strict relays	@me2seeks	PR 1
Undeclared window on a provider that accepts past its reported window	@me2seeks	PR 1
Reported-window note once per crossing, not per send	@me2seeks	PR 1
Length-fold cause guard	@me2seeks	superseded, see 2 above
Summarizer prefix-cache cost	@me2seeks	#4634

The series

• PR 1 — send module: trigger, reply reserve, persisted anchor, one compaction per send, "this message is too large", stream-usage collection with the strict-relay retreat, and all four system notes. One epoch move.
• PR 2 — compaction module: summarizer request shape, output cap and retries, failure latch, and the retreat to the last accepted input boundary.
• feat(desktop): show the model's reported context window beside the declared setting #4575, feat(desktop): show context usage beside the model controls #4576 — unchanged, rebased onto PR 1 when it lands.
• PR 5 — "compact and retry" for a rejection the classifier does not recognise (context: define the degraded modes when the provider does not speak (no usage, unclassified rejection, silent eviction) #4623).

Thank you all for the four rounds; the findings are carried, not discarded.

[Joob1n]

The replacement is #4653: the send module, with the two simplifications described above and the same review findings carried. The compaction module's retreat boundary follows in a second PR.