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[core] Drop pre-slot event ID support and preconditionGuard capability - #3519
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… resilient dispatch by default Three removals that stand on their own, split out of the v5 API switch. **Pre-slot event ids.** `maxEventSlot`, `findEventSlotGap`, and the step executor's slot observer went through a lenient decoder that answered "no position" for an id that is not a slot. That leniency *was* the pre-slot support, and it is the wrong shape now: a write whose `eventCount` is absent is indistinguishable, to a World, from one that honestly loaded nothing. They call `requireEventSlot` and throw. Skew protection is what makes it safe on Vercel — a run executes on the deployment that created it, so a build carrying this never replays a run created before slot ids. **The `preconditionGuard` capability.** Every World is now assumed to be able to refuse a stale replay-context write, so the three behaviors that keyed on the flag apply unconditionally: the per-step inline event-log delta stays enabled while the run has an open hook, an inline step's `step_started` claim is awaited before the body runs, and resilient dispatch stops consulting it. Before this only world-vercel declared it, so for world-local and world-postgres this is a behavior change rather than a no-op — they now pay the await-then-run claim while a hook is open, and get the inline delta in that same case. **`WORKFLOW_RESILIENT_STEP_DISPATCH`.** Off by default, `=1` to opt in. The publish races the create's verdict: a World that refuses the `step_created` sends the runtime back to replay while the payload-carrying message is already out, and nothing orders the refusal before the consumer's redelivery re-ensure. It was gated on the capability that no longer exists, and was already off for world-vercel, which declared it. `@workflow/world-sim` moves to slot ids with the runtime, since it drives the real one. The book's mint-ordered count goes 35/6/6 to 38/3/3 and append-only stays 41/0/0: four of the six reds staged a read missing an event the log already held, which under slots is a gap the runtime re-reads past. Also deletes `.changeset/windows-preload-timeout.md`, committed here by mistake. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
🦋 Changeset detectedLatest commit: 1ca4d70 The changes in this PR will be included in the next version bump. This PR includes changesets to release 20 packages
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🧪 E2E Test Results✅ All tests passed E2E Test SummarySummary
Details by Category✅ ▲ Vercel Production
✅ 💻 Local Development
✅ 📦 Local Production
✅ 🐘 Local Postgres
✅ 🪟 Windows
✅ vercel-multi-region
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📊 Workflow Benchmarks❌ The benchmark run for Partial results from the failed run: commit Backend:
📈 STSO distribution vs main (inline / queue-hop histograms)1020 steps (inline) Cumulative STSO time: main 228513ms → this run 190800ms (Δ -37713ms, -17%) 📜 Previous results (2)88553f8Thu, 13 Aug 2026 21:32:46 GMT · run logs
392953fThu, 13 Aug 2026 02:02:54 GMT · run logs
ℹ️ Metric definitions & methodologyThe collapsed STSO distribution section above buckets every step gap of the sequential-steps run (not a sampled window), split by whether the step ending the gap ran inline — in the same warm process as the step before it, so the gap is pure framework overhead — or after a queue-hop — the first step of a fresh process, which pays queue dispatch, client reinit and event-log replay. Bars overlay the two runs: Best/P75/P90/P99 deltas compare against the most recent benchmark run on Metrics — TTFS: time to first step body (in-deployment start() → first step body, deployment clocks) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · SL: stream latency (in-deployment write → read propagation, readAt - writtenAt) · SO: stream overhead (end-to-end write+consume time beyond the modelled generation window) Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out · stream latency: parallel reader/writer steps on a dedicated stream; SL is the in-deployment write->read propagation (readAt - writtenAt) · stream overhead (text): writer streams 300 variable-length text token deltas paced at 100/s for 3s (a haiku-size LLM's token throughput) while a parallel reader drains the whole stream; SO is the end-to-end write+consume time beyond the 3s generation window (overhead/backpressure) · stream overhead (structured): same workload as stream overhead (text), but each delta is an AI-SDK-style structured object ({ type: 'text-delta', id, text }) instead of a raw string, so the SO gap vs the text scenario is the added serialization cost 🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600 · SL 50/60/125 · SO 250/500/1000 All metrics are measured from deployment-side timestamps only. Runs are triggered by an in-deployment route that stamps the anchor ( Cold starts are kept in the numbers on purpose — they are part of real bursty-workload latency. The workbench deployment cold-starts the |
Sim WorldSimulated world deterministic testing for races. Traces 🟠 Mint-ordered log — 3 fail of 41 total
Full trace: 🟢 Append-only log — 0 fail of 41 total
Full trace: |
Event Log Race Repro1 of 14 latest repro runs hit event-log regressions. Run History
Latest Scenario Breakdown
Latest Non-Completed Runs
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pranaygp
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Reviewed the full diff, verified the sim-book baselines locally (mint-ordered 38/3/3, append-only 41/0/0, --no-fence 5), and re-ran the affected suites on the current head — all green. 88553f8 addressed every should-fix from the first review round (the #3404 doc revert, the 412-fence safety-argument framing, the latent null-runId mint in the sim facade, the stale scenario descriptions, and the world-vercel changeset). Two non-blocking threads remain open: the building-a-world capabilities paragraph should state slot allocation as a hard requirement of the v5 World contract (and the v5 GA docs PR should call out the breaking change for custom-world maintainers), and the pre-slot-run story for self-hosted worlds deserves a line in the release notes. The new world-local/world-postgres repro lanes added in 7d214db will give this PR's delta-with-open-hooks change its first storm datapoints on the worlds it actually affects.
Review feedback: `slotEventIds` could no longer read as an optional extra. The runtime reads a position out of every event id it loads and fails the run when it cannot, so a World that does not allocate slots cannot replay a single workflow — the flag was the only optional part, not the allocation. So the flag is gone, the same way `preconditionGuard` went: nothing consumed it (three Worlds declared it and two doc comments mentioned it), and a flag describing something mandatory only invites a World to leave it off and wonder why replay fails. The substance moves to `Storage.events`, which is what a World implements, and says which two properties the runtime actually relies on: density, and bump-and-report. It also now states the part that was implicit — allocate the position *at the commit*, because that is what makes a reader's log a prefix rather than a prefix with a hole in it. The guide says it as a requirement in both places it comes up: the capabilities paragraph, which now points out what is deliberately not a capability, and the Event ID Allocation section, which opens with a warning callout naming the failure a World author would otherwise meet at replay time. And `@workflow/world-testing` asserts it, which is the reviewer's point that a World written against earlier guidance passes conformance today and fails every replay later. The new case checks that every id decodes to a slot, that the run is dense from 1, and that ids are in canonical form — a World padding to a different width sorts its own log wrongly past ten events. Verified by breaking the expectation on purpose: red on world-local, then green again, and green on world-postgres. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Event Log Race Repro (world-local)6 of 14 latest repro runs hit event-log regressions. Run History
Latest Scenario Breakdown
Latest Non-Completed Runs
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No backport to This is a deliberate contract/API change rather than a stability fix: it removes the To override, re-run the Backport to stable workflow manually via |
Three removals split out of #3512, which needed all of them but is about something else (the v5 event API). Nothing here depends on v5.
slotEventIdsis removed along with the dead code. Nothing consumed it, and a flag describing something mandatory only invites a World to leave it off and then fail every replay. The substance moves toStorage.events: density, bump-and-report, and allocate the position at the commit, which is what makes a reader's log a prefix rather than a prefix with a hole in it@workflow/world-testingasserts it:numbers events by positionchecks every id decodes to a slot, that the run is dense from 1, and that ids are canonical (a World padding to a different width sorts its own log wrongly past ten events). Verified it can fail, not just passEvent id is not slot-numbered. It now fails in the suite instead. The GA docs need an explicit migration note; that is not in this PRmaxEventSlot,findEventSlotGapand the step executor's slot observer went through a lenient decoder that answered "no position" for an id that is not a slot. That leniency was the pre-slot support: a write whoseeventCountis absent is indistinguishable, to a World, from one that honestly loaded nothingrequireEventSlot(new, in@workflow/world), which throwspackages/coremove from hand-written ULIDs toslotToEventId(n)preconditionGuardcapability removedstep_startedclaim is awaited before the body runs (optimistic start suppressed on stale-sensitive batches)WORKFLOW_RESILIENT_STEP_DISPATCHoff by default=1to opt in, where it used to be=0to opt outcapabilities.preconditionGuard, which no longer exists, and already off for world-vercel, which declared itstep_createdsends the runtime back to replay while the payload-carrying message is already out, and nothing orders the refusal before the consumer's redelivery re-ensure.changeset/windows-preload-timeout.md(committed here by mistake)@workflow/world-simmoves to slot ids alongside the runtime, since it drives the real one. Its book goes 35/6/6 to 38/3/3 mint-ordered and stays 41/0/0 append-only: four of the six reds staged a read missing an event the log already held, which under ULIDs was indistinguishable from a complete read and under slots is a gap the runtime re-reads past. Baselines updated in the workflow header, DESIGN.md and the workbench README.#3512 is now stacked on this.