emrg: daemon — invalidate usage anchor on mid-session model/provider switch

Agent.md

@@ -119,7 +119,7 @@ Community needs voiced in HN agent-UI discussions map directly to EMRG's design:
 pkill -f "emrg.server"; rm -f ~/.emrg/emrgd.token; python -m emrg
 ```
 
-Python: `uv run pytest tests/ -v` (1102) — import check: `uv run python -c "from emrg.client.app import run_client"`
+Python: `uv run pytest tests/ -v` (1106) — import check: `uv run python -c "from emrg.client.app import run_client"`
 GUI: `cd emrg/gui && npm test` (265: 45 daemon_client + 20 conn-manager + 22 app-commands + 132 renderer smoke + 15 i18n + 8 integration + 3 commands + 8 build-config + 7 gui-state + 2 tool-group + 3 preload-api) — syntax: `node --check main.js preload.js daemon_client.js renderer/js/*.js`; renderer React suite: `cd emrg/gui/renderer && npm run typecheck && npm test` (168 vitest: 5 snapshot-store + 9 utils + 3 ErrorBoundary + 2 App smoke + 11 commands + 4 copywriting + 11 i18n + 11 markdown + 15 transcript + 7 TranscriptView + 15 history + 22 composer + 14 Composer + 12 sidebar + 10 Sidebar + 9 fileTree + 8 FileTree) + `npm run build` → `renderer/dist/`
 CI: `uv run pytest` (ubuntu + **windows-2025 matrix** — Windows pytest 回归在 PR CI 即失败，v0.2.29 教训 #725) + GUI tests + **actionlint workflow lint** (`rhysd/actionlint@v1.7.12` gate, #444 — workflow 解析错误在 PR CI 即失败，如 `if:` secrets 上下文)
 Re-trigger: `scripts/re-trigger-ci.sh [branch]` (workflow_dispatch, #527 — 替代空 commit 重触发：Actions outage 会整段丢弃 push 事件，dispatch 走 API 路径不受影响)

emrg/server/daemon.py

@@ -250,6 +250,11 @@ def __init__(self, llm_config: LlmConfig) -> None:
  # (warn once per session, no per-round spam).
  self._usage_anchor_dropped_by_compact: set[str] = set()
  self._warned_missing_usage_anchor: set[str] = set()
+ # Community feedback 2026-08-26T18:21:30 (Dev.to comment 3dh3g):
+ # sessions whose usage anchor was deliberately invalidated by a
+ # mid-session model/provider switch — the next anchor-less round is a
+ # legitimate re-anchor round, not a silent provider usage-loss.
+ self._usage_anchor_dropped_by_switch: set[str] = set()
  # Community feedback 2026-08-26T07:18:29: session_id ->
  # (estimated_tokens, iso_ts) at anchor-loss warning time, so the
  # estimator drift of the anchor-less window can be measured when
@@ -2965,6 +2970,24 @@ def _count_chars_for_tokens(text: str) -> int:
  ascii_chars += 1
  return (cjk // 2) + (ascii_chars // 4)
 
+ def _invalidate_usage_anchors_on_switch(self) -> None:
+ """Drop every usage anchor when the active model/provider changes.
+
+ Community feedback 2026-08-26T18:21:30 (Dev.to comment 3dh3g): the
+ anchor is keyed by session_id only, so a mid-session model switch
+ would project the OLD provider's real prompt_tokens + the NEW
+ estimate delta — a mixed base that can silently miss the auto-compact
+ gate across providers (the #946 failure mode). Invalidate anchors and
+ any pending drift window, and mark sessions so the fail-LOUD
+ missing-anchor warning treats the switch round as a legitimate
+ re-anchor round (the next response re-anchors from the new
+ provider's real prompt_tokens).
+ """
+ switched = set(self._usage_anchors)
+ self._usage_anchors.clear()
+ self._missing_anchor_est.clear()
+ self._usage_anchor_dropped_by_switch.update(switched)
+
  def _warn_missing_usage_anchor(
  self, session, messages: list[dict], estimated: int
  ) -> None:
@@ -2989,6 +3012,13 @@ def _warn_missing_usage_anchor(
  if session.session_id in self._usage_anchor_dropped_by_compact:
  self._usage_anchor_dropped_by_compact.discard(session.session_id)
  return
+ # Model/provider switch round: anchor deliberately invalidated by
+ # _invalidate_usage_anchors_on_switch (Dev.to 3dh3g) — consume the
+ # marker so the NEXT anchor-less round warns if the new provider is
+ # also silent.
+ if session.session_id in self._usage_anchor_dropped_by_switch:
+ self._usage_anchor_dropped_by_switch.discard(session.session_id)
+ return
  if session.session_id in self._warned_missing_usage_anchor:
  return # already warned once for this session
  self._warned_missing_usage_anchor.add(session.session_id)
@@ -3516,6 +3546,12 @@ async def _handle_set_model(
  break
 
  self.llm.config.model = api_model
+ if api_model != old_model:
+ # Community feedback 2026-08-26T18:21:30 (Dev.to 3dh3g): a real
+ # API model change invalidates every usage anchor — the base held
+ # the previous provider's real prompt_tokens, which would mix
+ # with the new estimate delta on the next auto-compact projection.
+ self._invalidate_usage_anchors_on_switch()
  if new_ctx is not None:
  self.llm.config.context_window = new_ctx
  if new_vision is not None:

tests/test_daemon.py

@@ -602,6 +602,86 @@ def test_manual_compact_drop_marks_anchor(caplog):
  assert sid not in server._usage_anchor_dropped_by_compact # consumed
 
 
+# ── model/provider switch invalidates anchors (Dev.to comment 3dh3g) ──
+
+
+def test_invalidate_usage_anchors_on_switch():
+ """A mid-session model switch must drop every usage anchor: the anchor
+ holds the OLD provider's real prompt_tokens; projecting old base + new
+ estimate delta mixes bases and can silently miss the auto-compact gate
+ (community feedback 2026-08-26T18:21:30, Dev.to comment 3dh3g)."""
+ server = _make_server()
+ server._usage_anchors["s1"] = (222_000, 148_000)
+ server._usage_anchors["s2"] = (100_000, 60_000)
+ server._missing_anchor_est["s1"] = (150_000, "2026-08-26T00:00:00+08:00")
+
+ server._invalidate_usage_anchors_on_switch()
+
+ assert server._usage_anchors == {}
+ assert server._missing_anchor_est == {}
+ # Only sessions that held an anchor are marked for the re-anchor pass
+ assert server._usage_anchor_dropped_by_switch == {"s1", "s2"}
+
+
+def test_switch_round_does_not_warn_false_positive(caplog):
+ """The anchor-less round right after a model switch is legitimate — the
+ fail-LOUD warning must stay silent, and the marker is consumed so a
+ SECOND consecutive anchor-less round (new provider also silent) warns."""
+ server = _make_server()
+ sid = "switch-test"
+ server._usage_anchors[sid] = (222_000, 148_000)
+ messages = [
+ {"role": "assistant", "content": "x"},
+ {"role": "user", "content": "y"},
+ ]
+ server._invalidate_usage_anchors_on_switch()
+ assert server._usage_anchors == {}
+ assert sid in server._usage_anchor_dropped_by_switch
+
+ with caplog.at_level("WARNING", logger="emrg.server.daemon"):
+ server._warn_missing_usage_anchor(_SidSession(sid), messages, 100)
+ assert "usage anchor missing" not in caplog.text
+ assert sid not in server._usage_anchor_dropped_by_switch # consumed
+
+ # New provider still silent -> the next anchor-less round now warns
+ caplog.clear()
+ with caplog.at_level("WARNING", logger="emrg.server.daemon"):
+ server._warn_missing_usage_anchor(_SidSession(sid), messages, 200)
+ assert "usage anchor missing for established session" in caplog.text
+
+
+def test_handle_set_model_invalidates_usage_anchors():
+ """set_model with a REAL api-model change must invalidate usage anchors —
+ a mid-session switch must not project the old provider's base with the
+ new estimate delta (Dev.to comment 3dh3g)."""
+ import asyncio
+ server = _make_server()
+ server._usage_anchors["s1"] = (222_000, 148_000)
+ server._usage_anchors["s2"] = (100_000, 60_000)
+ writer = _FakeWriter()
+ new_name = server.llm.config.model + "-switched"
+
+ asyncio.run(server._handle_set_model(new_name, writer))
+
+ assert server._usage_anchors == {}
+ assert server._usage_anchor_dropped_by_switch == {"s1", "s2"}
+
+
+def test_handle_set_model_same_api_model_keeps_anchors():
+ """Re-selecting the SAME api model (e.g. display alias) must NOT
+ invalidate anchors — the provider/tokenizer is unchanged."""
+ import asyncio
+ server = _make_server()
+ server._usage_anchors["s1"] = (222_000, 148_000)
+ writer = _FakeWriter()
+ same = server.llm.config.model
+
+ asyncio.run(server._handle_set_model(same, writer))
+
+ assert server._usage_anchors == {"s1": (222_000, 148_000)}
+ assert server._usage_anchor_dropped_by_switch == set()
+
+
 # ── usage-anchor countable stats (community feedback 2026-08-26T07:18:29) ──