[core] Add the wake-loop scenario to the event log race repro

[VaguelySerious]

Scenario

wake-loop: one sequential loop that races a reusable hook read (iterator.next() carried across heartbeat wins) against a heartbeat sleep, with a four-step cycle (verify, drain, verify, sync) per fresh wake or heartbeat, a verify before every heartbeat is re-armed, stale wakes that emit no step, and occasional back-to-back cycles decided by the drain step's result. Nothing in the workflow fans out; every bit of concurrency comes from the driver, which sends single wakes at a short cadence, bursts of near-simultaneous wakes, and wakes aimed at the heartbeat deadline so a hook_received commits right next to a wait_completed.

This is the shape of a production run on 5.0.0-beta.46 that failed CORRUPTED_EVENT_LOG with Replay could not consume event: eventType=wait_created. Its persisted log is self-consistent (a faithful offline replay of all 633 slots is clean, and no correlation ordinal is bound to two entities), yet from the moment one wait_completed landed, replays of the same immutable prefix stalled at the same wait_created intermittently: 16 stalled passes against dozens of clean ones over three minutes, each queuing a recovery replay that usually succeeded, until four consecutive stalls exhausted the budget. The only replay that reproduces the exact message offline is one that observes a hook payload ahead of an earlier wait_completed: it runs a wake cycle where the log recorded a heartbeat, and its next drain draws the ordinal the log holds for the heartbeat's wait_created.

Knobs (EVENT_LOG_RACE_REPRO_WAKE_LOOP_*): attempts, fresh wakes per run, heartbeat, drain duration and spread, step payload size (so replays pay real hydration), continue-every, fresh/burst/idle ratios, burst size, gap range, max cycles. Defaults live in the harness only, as for the other scenarios; three of them are exposed as workflow_dispatch inputs (GitHub caps a workflow at 25). The result JSON carries pressure.wakeLoop (fresh/stale/bursts/idles sent; cycles/heartbeats/stale consumed reported by the run) and the return-value ledger is cross-checked for internal consistency.

Results

The scenario reproduces the class on the release the incident happened on and is clean on main. Same dispatch (48 wake-loop runs, concurrency 12) on this branch and on the scenario cherry-picked onto workflow@5.0.0-beta.46 (peter/repro-wake-loop-beta46):

Lane	main	beta.46
vercel	47 completed, 0 corrupt, 1 slow run cancelled at runTimeoutMs	41 completed, 6 CORRUPTED_EVENT_LOG
world-local	48 completed	38 completed, 9 CORRUPTED_EVENT_LOG, 1 stuck
world-postgres	48 completed, 0 divergence WARNs	48 completed, 397 divergence WARNs (all recovered)

Of the 6 corrupted Vercel-lane logs on beta.46, 3 hold a step bound to the ordinal a sibling gave a wait (a flipped replay committed) and 3 are self-consistent logs where the flipped replays only diverged, the incident's shape. Details in the comment below. Locally on world-postgres (this branch) 38 runs were clean as well.

🤖 Generated with Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: 9386ce1

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[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated
example-nextjs-workflow-turbopack	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
example-nextjs-workflow-webpack	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
example-workflow	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
workbench-astro-workflow	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
workbench-express-workflow	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
workbench-fastify-workflow	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
workbench-hono-workflow	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
workbench-nestjs-workflow	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
workbench-nitro-workflow	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
workbench-nuxt-workflow	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
workbench-python-workflow	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
workbench-sveltekit-workflow	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
workbench-tanstack-start-workflow	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
workbench-vite-workflow	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
workflow-docs	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
workflow-swc-playground	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
workflow-tarballs	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC
workflow-web	Ready	Preview, v0	Sep 8, 2026 7:24pm UTC

[github-actions]

📊 Workflow Benchmarks

commit 9386ce1 · Tue, 08 Sep 2026 19:51:34 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	162 (-18%) 💚	374 🔴 (-65%) 💚	795 🔴 (-27%) 💚	1285 🔴 (+7.2%)	30
TTFS	stream	166 (-5.7%)	466 🔴 (-54%) 💚	1230 🔴 (+20%) 🔻	1507 🔴 (+45%) 🔻	30
TTFS	hook + stream	368 (-66%) 💚	1480 🔴 (+25%) 🔻	1677 🔴 (+31%) 🔻	1796 🔴 (-9.3%)	30
Fan-out TTFS	Promise.all(100 steps)	473 (-20%) 💚	1831 (+6.3%)	1901 (+8.6%)	1901 (+3.5%)	10
Fan-out TTLS	Promise.all(100 steps)	1687 (+6.8%)	3319 (-13%)	3503 (-11%)	3854 (-64%) 💚	10
STSO	1020 steps (inline)	79 (-23%) 💚	128 (-9.9%)	144 (-13%)	238 (-22%) 💚	1019
WO	1020 steps	130163 (-12%)	130163 (-12%)	130163 (-12%)	130163 (-12%)	1
CRTT	first chunk (pooled)	58 (-11%)	84 (-37%) 💚	135 (-25%) 💚	203 (-26%) 💚	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	81.5 (-6%)	151 (-3%)	260 (+17%)	497 (+25%)	141 (-11%)	10
size sweep (100/s, 160B-12KB)	82.5 (-15%)	170 (-36%)	214 (-57%)	359 (-62%)	135 (-45%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	80 (-22%)	125 (-30%)	197 (-42%)	478 (-28%)	235 (-28%)	3
replay eve-gpt-5.6-sol-2000t (1x)	72 (-57%)	126 (-17%)	154 (-23%)	483 (+17%)	433 (+11%)	2
replay eve-gpt-5.6-sol-2000t (2x)	69 (-50%)	180 (-27%)	307 (-12%)	1224 (+142%)	281 (-24%)	3

📈 STSO distribution vs main (inline / queue-hop histograms)

1020 steps (inline)

Cumulative STSO time: main 147324ms → this run 128659ms (Δ -18665ms, -13%)

   50-100 ms  ┃                         main   0  this   1    +1
  100-150 ms  █████████████████████░░┃  main 819  this 942  +123
  150-200 ms  ┃███                      main 159  this  58  -101
  200-250 ms  ┃                         main  23  this  10   -13
  250-300 ms  ┃                         main   7  this   0    -7
  300-350 ms  ┃                         main   4  this   4    +0
  350-400 ms  ┃                         main   2  this   2    +0
  400-450 ms  ┃                         main   1  this   1    +0
  450-500 ms  ┃                         main   2  this   0    -2
  500-550 ms  ┃                         main   1  this   0    -1
  650-700 ms  ┃                         main   0  this   1    +1
3750-3800 ms  ┃                         main   1  this   0    -1

📈 CRTT drill-down vs main (RTT distributions & profiles)

variant  RTT 1ms→5s+             avg         p50         p90           p99     n
control  ······▄█▁▁···   127.5 (-1%)   118 (-3%)  260 (+17%)    497 (+25%)  3000
sweep    ······▅█▂····  126.3 (-30%)  115 (-15%)  214 (-57%)    359 (-62%)  3000
gw 1x    ·····▁██▁▁···  113.6 (-23%)  101 (-20%)  197 (-42%)    478 (-28%)  5295
eve 1x   ·····▁██▁▁···  110.5 (-16%)   99 (-15%)  154 (-23%)    483 (+17%)  5186
eve 2x   ·····▁▄█▃▁▁··  160.8 (-16%)  126 (-26%)  307 (-12%)  1224 (+142%)  7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):

control  █▆▃▂▂▃▃▂▁▂  111–166ms
sweep    █▄▃▂▁▁▂▂▇▄  110–157ms
gw 1x    █▄▄▄▄▃▁▇▄▂  95–137ms
eve 1x   ▁▂▂▁▁▂█▃▂▁  100–153ms
eve 2x   ▁█▄▃▁▅▆▇▄▂  109–226ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):

sweep  ▆█▇▄▁▁▃  125–128ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):

control  █▄▁▆▃▂▃▃▁▂  34–46ms
sweep    ▄▄▅█▄▃▁▃▂▃  38–50ms
gw 1x    ▆▅▃▁▅▅▃▇█▃  28–35ms
eve 1x   ▄▆▁▂▅▆█▄▂▇  19–25ms
eve 2x   ▄█▃▆▅▇█▁▄▆  19–27ms

ℹ️ Metric definitions & methodology

_{Streams: first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.}

_{The collapsed STSO distribution section above buckets every step gap, split inline (same warm process — pure framework overhead) vs queue-hop (fresh process — dispatch, reinit, replay). █ = main, ┃ = this run, ░ = fill.}

_{The collapsed CRTT drill-down: per-variant RTT histograms (fixed log bins, · = empty) and mean RTT/positive-CDV profile lines over stream progress and chunk size. Histograms, avgs, and profiles merge exactly across runs; p50–p99 are percentile-of-percentiles. Per-index rows live in the artifacts.}

_{Best/P75/P90/P99 deltas compare against the most recent benchmark run on main at the time of this run. 🔻 flags a delta worse than +15%, 💚 one better than −15%.}

_{Metrics — TTFS: time to first step body (in-deployment start() → first step body) · 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) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)}

_{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 · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles}

_{Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000t eaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t 6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041}

_{🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600}

_{All timestamps are deployment-side; runs are triggered in-deployment, so the CI runner and api.vercel.com sit outside every measured window. TTFS = start() → first step body (includes dispatch + any cold start); Fan-out TTFS/TTLS = first/last step completion of one Promise.all from the same anchor (the gap is the runtime’s fan-out spread); STSO/WO between step bodies; CRTT inside the workflow (excludes the api.vercel.com read path).}

_{Cold starts stay in the numbers (real bursty-workload latency, inflates P75+); Best is the warm floor.}

[github-actions]

🧪 E2E Test Results

✅ All tests passed

⚠️ Flaky E2E Tests (passed on retry)

These tests failed at least once and passed on a retry. A recurring entry here is a real race worth investigating.

• addTenWorkflow (express)
• addTenWorkflow (vite)
• cancelRun via CLI - cancelling a running workflow (sveltekit)

🛠 Infra Events (absorbed by the harness)

Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.

• cold-start-warmup · suite warmup (tanstack-start) · at 19:30:11Z · abandoned wrun_01M217YTS98XAKHF67ABFJ75M3
• run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 19:34:32Z · abandoned wrun_01M21875S157GCTB1QXH89NRQQ

E2E Test Summary

Summary

	Passed	Failed	Skipped	Total
✅ ▲ Vercel Production	3636	0	684	4320
✅ 💻 Local Development	3922	0	558	4480
✅ 📦 Local Production	3922	0	558	4480
✅ 🐘 Local Postgres	3922	0	558	4480
✅ 🪟 Windows	320	0	0	320
✅ 🌐 Cross-language Conformance	68	0	73	141
✅ vercel-http-transport	817	0	143	960
✅ vercel-multi-region	27	0	0	27
✅ vercel-ws-transport	553	0	87	640
Total	17187	0	2661	19848

Details by Category

✅ ▲ Vercel Production

App	Passed	Failed	Skipped
✅ astro-node	132	0	28
✅ astro-quickjs	132	0	28
✅ example-node	132	0	28
✅ example-quickjs	132	0	28
✅ express-node	132	0	28
✅ express-quickjs	132	0	28
✅ fastify-node	132	0	28
✅ fastify-quickjs	132	0	28
✅ hono-node	132	0	28
✅ hono-quickjs	132	0	28
✅ nest-node	132	0	28
✅ nest-quickjs	132	0	28
✅ nextjs-turbopack-node	157	0	3
✅ nextjs-turbopack-quickjs	157	0	3
✅ nextjs-webpack-node	157	0	3
✅ nextjs-webpack-quickjs	157	0	3
✅ nitro-node	132	0	28
✅ nitro-quickjs	132	0	28
✅ nuxt-node	132	0	28
✅ nuxt-quickjs	132	0	28
✅ python-node	66	0	94
✅ sveltekit-node	151	0	9
✅ sveltekit-quickjs	151	0	9
✅ tanstack-start-node	132	0	28
✅ tanstack-start-quickjs	132	0	28
✅ vite-node	132	0	28
✅ vite-quickjs	132	0	28

✅ 💻 Local Development

App	Passed	Failed	Skipped
✅ astro-stable-node	134	0	26
✅ astro-stable-quickjs	134	0	26
✅ express-stable-node	134	0	26
✅ express-stable-quickjs	134	0	26
✅ fastify-stable-node	134	0	26
✅ fastify-stable-quickjs	134	0	26
✅ hono-stable-node	134	0	26
✅ hono-stable-quickjs	134	0	26
✅ nest-stable-node	134	0	26
✅ nest-stable-quickjs	134	0	26
✅ nextjs-turbopack-canary-node	141	0	19
✅ nextjs-turbopack-canary-quickjs	141	0	19
✅ nextjs-turbopack-stable-node	160	0	0
✅ nextjs-turbopack-stable-quickjs	160	0	0
✅ nextjs-webpack-canary-node	141	0	19
✅ nextjs-webpack-canary-quickjs	141	0	19
✅ nextjs-webpack-stable-node	160	0	0
✅ nextjs-webpack-stable-quickjs	160	0	0
✅ nitro-stable-node	134	0	26
✅ nitro-stable-quickjs	134	0	26
✅ nuxt-stable-node	134	0	26
✅ nuxt-stable-quickjs	134	0	26
✅ sveltekit-stable-node	153	0	7
✅ sveltekit-stable-quickjs	153	0	7
✅ tanstack-start-node	134	0	26
✅ tanstack-start-quickjs	134	0	26
✅ vite-stable-node	134	0	26
✅ vite-stable-quickjs	134	0	26

✅ 📦 Local Production

App	Passed	Failed	Skipped
✅ astro-stable-node	134	0	26
✅ astro-stable-quickjs	134	0	26
✅ express-stable-node	134	0	26
✅ express-stable-quickjs	134	0	26
✅ fastify-stable-node	134	0	26
✅ fastify-stable-quickjs	134	0	26
✅ hono-stable-node	134	0	26
✅ hono-stable-quickjs	134	0	26
✅ nest-stable-node	134	0	26
✅ nest-stable-quickjs	134	0	26
✅ nextjs-turbopack-canary-node	141	0	19
✅ nextjs-turbopack-canary-quickjs	141	0	19
✅ nextjs-turbopack-stable-node	160	0	0
✅ nextjs-turbopack-stable-quickjs	160	0	0
✅ nextjs-webpack-canary-node	141	0	19
✅ nextjs-webpack-canary-quickjs	141	0	19
✅ nextjs-webpack-stable-node	160	0	0
✅ nextjs-webpack-stable-quickjs	160	0	0
✅ nitro-stable-node	134	0	26
✅ nitro-stable-quickjs	134	0	26
✅ nuxt-stable-node	134	0	26
✅ nuxt-stable-quickjs	134	0	26
✅ sveltekit-stable-node	153	0	7
✅ sveltekit-stable-quickjs	153	0	7
✅ tanstack-start-node	134	0	26
✅ tanstack-start-quickjs	134	0	26
✅ vite-stable-node	134	0	26
✅ vite-stable-quickjs	134	0	26

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	134	0	26
✅ astro-stable-quickjs	134	0	26
✅ express-stable-node	134	0	26
✅ express-stable-quickjs	134	0	26
✅ fastify-stable-node	134	0	26
✅ fastify-stable-quickjs	134	0	26
✅ hono-stable-node	134	0	26
✅ hono-stable-quickjs	134	0	26
✅ nest-stable-node	134	0	26
✅ nest-stable-quickjs	134	0	26
✅ nextjs-turbopack-canary-node	141	0	19
✅ nextjs-turbopack-canary-quickjs	141	0	19
✅ nextjs-turbopack-stable-node	160	0	0
✅ nextjs-turbopack-stable-quickjs	160	0	0
✅ nextjs-webpack-canary-node	141	0	19
✅ nextjs-webpack-canary-quickjs	141	0	19
✅ nextjs-webpack-stable-node	160	0	0
✅ nextjs-webpack-stable-quickjs	160	0	0
✅ nitro-stable-node	134	0	26
✅ nitro-stable-quickjs	134	0	26
✅ nuxt-stable-node	134	0	26
✅ nuxt-stable-quickjs	134	0	26
✅ sveltekit-stable-node	153	0	7
✅ sveltekit-stable-quickjs	153	0	7
✅ tanstack-start-node	134	0	26
✅ tanstack-start-quickjs	134	0	26
✅ vite-stable-node	134	0	26
✅ vite-stable-quickjs	134	0	26

✅ 🪟 Windows

App	Passed	Failed	Skipped
✅ nextjs-turbopack-node	160	0	0
✅ nextjs-turbopack-quickjs	160	0	0

✅ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
✅ python	68	0	73

✅ vercel-http-transport

App	Passed	Failed	Skipped
✅ example	132	0	28
✅ express	132	0	28
✅ hono	132	0	28
✅ nextjs-turbopack	157	0	3
✅ nitro	132	0	28
✅ vite	132	0	28

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

✅ vercel-ws-transport

App	Passed	Failed	Skipped
✅ example	132	0	28
✅ express	132	0	28
✅ nextjs-turbopack	157	0	3
✅ vite	132	0	28

---

📋 View full workflow run

[github-actions]

Sim World

Simulated world deterministic testing for races. Traces

🟠 world-sim scenario book — 1 fail of 41 total

fence=per-spec

scenario	outcome	events	virt	replay	violations
✅ smoke-no-steps	completed	3	0ms	ok	0
✅ smoke-one-step	completed	6	0ms	ok	0
✅ hook-at-step-started	completed	12	0ms	ok	0
✅ hook-at-step-completed	completed	12	0ms	ok	0
✅ hook-at-hook-created	completed	12	0ms	ok	0
✅ deadline-hook-wins	completed	7	1.0h	ok	0
✅ deadline-expires	completed	7	1.0h	ok	0
✅ long-sleep	completed	11	30.0d	ok	0
✅ hook-never-arrives	stalled	3	0ms	skipped	0
✅ step-retries-twice	completed	10	2.0s	ok	0
✅ parallel-steps	completed	9	0ms	ok	0
✅ hook-on-execution-state	completed	12	0ms	ok	0
✅ peek-hook-before-branch	completed	12	0ms	ok	0
✅ peek-hook-after-branch	completed	12	0ms	ok	0
✅ peek-hook-at-registration	completed	12	0ms	ok	0
✅ race-hook-before-probe	completed	12	0ms	ok	0
✅ race-hook-after-probe	completed	12	0ms	ok	0
✅ race-duplicate-delivery	completed	13	0ms	ok	0
✅ attr-hook-before-step	completed	11	0ms	ok	0
✅ attr-hook-after-step	completed	11	0ms	ok	0
✅ attr-from-step-body	completed	13	0ms	ok	0
✅ fork-hook-after-timeout	completed	14	1.0m	ok	0
✅ fork-hook-before-timeout	completed	14	1.0m	ok	0
✅ count-hook-after-timeout	completed	17	1.0m	ok	0
✅ count-hook-before-timeout	completed	20	1.0m	ok	0
✅ stale-read-step-count-fork	completed	20	1.0m	ok	0
✅ stale-read-equal-step-counts	completed	14	1.0m	ok	0
✅ step-vs-step-fork	completed	12	0ms	ok	0
✅ step-vs-step-fork-fenced	completed	12	0ms	ok	0
✅ fence-catches-benign-direction	completed	12	5ms	ok	0
✅ in-flight-before-decision	completed	17	1.0m	ok	0
❌ in-flight-before-decision-counted	completed	17	1.0m	ok	0
✅ in-flight-after-decision	completed	19	2.0m	ok	0
✅ stale-read-step-count-fork-fenced	completed	20	1.0m	ok	0
✅ fork-hook-wins	completed	13	1.0m	ok	0
✅ fork-timeout-wins	completed	13	1.0m	ok	0
✅ unclaimed-payload-under-fork	completed	17	1.0m	ok	0
✅ claimed-payload-under-fork	completed	17	1.0m	ok	0
✅ writers-independent-step-bodies	completed	12	0ms	ok	0
✅ writers-scripted-tempo	completed	12	0ms	ok	0
✅ cancel-mid-step	cancelled	7	0ms	skipped	0

Full trace: world-sim.txt

[github-actions]

Framework	Flow route	Step reg.	Framework output
hono	201.6 KiB (±0)	40.8 KiB (±0)	1.77 MiB (±0)
nextjs-turbopack	207.8 KiB (+780 B)	439 B (±0)	769.8 KiB (+1.1 KiB)

About these numbers

Sizes are gzip; parentheses show the change against main.
Flow route and Step reg. gate this job, on raw bytes rather than the gzip shown, at max(2%, 50.0 KiB). Framework output is informational.

9386ce1 · run

[github-actions]

Event Log Race Repro

• vercel clean, 26 runs
• local clean, 26 runs
• postgres clean, 26 runs

Run History

Run	Lane	Total	Complete	Corrupt	Stuck	Other
09-08 19:15	vercel	26	26	0	0	0
	local	26	26	0	0	0
	postgres	26	26	0	0	0
09-08 19:34	vercel	26	26	0	0	0
	local	26	26	0	0	0
	postgres	26	26	0	0	0

Config

vercel: 26 runs / step-storm 6, hook-storm 6, blocked-branch 6, wake-loop 6, hook-sleep 2 / c8 / 6x8 / watchdog 2500ms / step 2200±250ms / stagger 400ms / heartbeat 4000ms / burst 4000+1200ms / poke 750ms / poke budget 64 then /8 / timeout 240000ms

local, postgres: 26 runs / step-storm 6, hook-storm 6, blocked-branch 6, wake-loop 6, hook-sleep 2 / c8 / 6x8 / watchdog 2500ms / step 2200±250ms / stagger 400ms / heartbeat 4000ms / burst 4000+1200ms / poke 750ms / poke budget 64 then /8 / timeout 480000ms

[VaguelySerious]

A/B: this branch (main) vs the same scenario on workflow@5.0.0-beta.46

Both dispatched with wake_loop_attempts=48, other scenarios 0, concurrency=12, budget_ms=900000.

Lane	main (run)	beta.46 (run, branch peter/repro-wake-loop-beta46)
vercel	47 completed, 0 corrupt, 1 stuck (slow tail: still writing steps 3s before the 240s cancel; p50 119s, p90 166s at c12)	41 completed, 6 CORRUPTED_EVENT_LOG, 1 infra
world-local	48 completed	38 completed, 9 CORRUPTED_EVENT_LOG, 1 stuck
world-postgres	48 completed, 0 divergence WARNs in the app log	48 completed, 397 divergence WARNs in the app log (every episode recovered within the 3-retry budget)

So the scenario reproduces the class on the release the incident happened on, and is clean on main across 48+48+48 runs and 6+26+26 more at the default scale (three lanes, PR runs). On beta.46 the corrupted Vercel-lane logs split the same way the analysis predicted: 3 of 6 hold a step bound to the ordinal a sibling writer gave a wait (a flipped replay got to commit), 3 of 6 are self-consistent logs where the flipped replays only diverged, which is the incident's shape.

Two harness notes from the soak:

• The app log on world-postgres shows the divergence rate even when every run completes. The harness's outcome-only view is blind to recovered episodes; counting the Workflow replay diverged WARNs per lane would make the local lanes a rate signal. Follow-up.
• At concurrency=12 the wake-loop's slow tail brushes runTimeoutMs on the Vercel lane. The default scale (c8, 6 attempts) ran 95-140s.

🤖 Generated with Claude Code

[github-actions]

No backport to stable for 8a91d18 (AI decision).

This commit adds a brand-new wake-loop scenario (workflow shape, driver, knobs, CI dispatch inputs, docs) to the event-log race repro harness — additive investigative tooling rather than a fix for a defect or a flaky test, and the PR notes the shape is already clean on main. It also builds on main-only files: workbench/nextjs-turbopack/workflows/103_event_log_corruption_repro.ts and scripts/event-log-race-repro-local.sh are both absent on stable (verified via git ls-tree origin/stable), so the scenario has no host workflow to run against there. If a real fix later lands for the class this scenario reproduces, that fix (and any harness coverage it needs) can be backported on its own.

To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:

8a91d18d0dfdb142c68b0635bc7e5446a5b08403

[VaguelySerious]

Bisect: the fix is #3879 (fix(core): re-arm late-claimed hook deliveries)

Same wake_loop_attempts=48 concurrency=12 dispatch, scenario cherry-picked onto workflow@5.0.0-beta.46 plus exactly one of the two candidate fixes from beta.47:

beta.46 +	vercel	world-local	world-postgres
#3879 only (run)	48 completed, 0 corrupt	48 completed, 0 divergence WARNs	48 completed, 0 divergence WARNs
#3841 only (run)	44 completed, 4 corrupt	40 completed, 4 corrupt, 4 stuck, 187 WARNs	43 completed, 5 corrupt, 941 WARNs

Locally (world-postgres, 16 runs at c12 with 40 worker slots and 8 busy-loop processes to approximate a 4-core runner; the laptop is otherwise too fast to hit the window): beta.46 baseline 3 corrupt / 37 WARNs, +#3841 0 corrupt / 6 WARNs, +#3879 0 corrupt / 0 WARNs.

Mechanism, consistent with #3879's description and with the flip this scenario was built around: a buffered hook payload registers an unarmed delivery barrier; the idle safety net may retire it while the payload and its claim() closure stay alive in a retained VM. Before #3879, a later iterator.next() that claimed it called arm() on the retired entry, which changed nothing in the registry, so the runtime saw no committed delivery: isDeliveryIdle could report idle and the pass could suspend while the claim was still resolving, and later deliveries (a wait_completed appended on resume) had nothing at that index to order behind. The parked body then took the hook branch out of log order. In this shape that means a wake cycle where the log recorded a heartbeat, and the next drain draws the ordinal the log holds for the heartbeat's wait_created, which is exactly Replay could not consume event: eventType=wait_created. #3879 reinstalls an armed entry on a late claim, so the claim is visible to both the idle check and the ordering gates.

Branches for reruns: peter/repro-wake-loop-beta46, peter/bisect-b46-3879, peter/bisect-b46-3841.

🤖 Generated with Claude Code