[core] Never write hook_received eagerly on the lazy resume path - #3794

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VaguelySerious merged 3 commits into
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peter/lazy-only-hook-resume
Aug 26, 2026
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[core] Never write hook_received eagerly on the lazy resume path#3794
VaguelySerious merged 3 commits into
mainfrom
peter/lazy-only-hook-resume

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@VaguelySerious

@VaguelySeriousVaguelySerious commented Aug 25, 2026•
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Makes resumeHook() never create hook_received itself. It only publishes the queue message and returns; the consumer materializes the event from hookInput before it replays.

The queue message becomes the single point of durability, which it is supposed to be anyway.

Note there's an existing edge case: run goes terminal, swallows a hook_received first (can't do any work in response to the hook_received), despite the resumeHook call returning success.

Now, this edge case has a wider race window, since we don't even check at resumeHook time whether the run is terminal. The race is thus 100ms-1s wider than before.

Also, we keep around an eager-only specifically for the AbortController, because that needs an immediate confirmed hook_received insert (instead of an eventual insert).

OTEL changes: ResumedHook.resilientResume and the workflow.hook.resilient_resume span attribute are retained on the type but never set, since there is no partial outcome to report. workflow.hook.resume_strategy reports lazy (was parallel); consumers still accept parallel from producers that predate this.

@VaguelySerious
[core] Never write hook_received eagerly on the lazy resume path
7907553
resumeHook() raced its own `hook_received` write against the queue
publish, and the consumer re-ensured the same event from `hookInput`
before replay. Both sides wrote; a `(runId, resumeId)` constraint
collapsed them onto one.
Drop the producer's write. On the lazy path resumeHook() publishes one
message and nothing else, so a resume costs one round trip and the event
is created once, by the side about to replay it. The dedup constraint
still covers repeated deliveries of that message.
Two consequences:
- A failed publish now fails the resume outright: the message carries
both the trigger and the only copy of the payload, so there is nothing
persisted for a later delivery to recover.
- A resume against an ended run resolves instead of throwing
HookNotFoundError, whenever it also skipped reading the run (the
common case: the hook lookup returns the resume context inline).
Nothing resumes either way. Run-fallback resumes and the sequential
path keep their terminal checks.
`ResumedHook.resilientResume` and the `workflow.hook.resilient_resume`
span attribute are retained but never set. The resume span reports
`resume_strategy: lazy`; consumers still accept `parallel` from older
producers.
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changeset-botBot commented Aug 25, 2026•
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🦋 Changeset detected

Latest commit: 2db81fd

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 20 packages
NameType
@workflow/corePatch
@workflow/vitestPatch
@workflow/worldPatch
@workflow/buildersPatch
@workflow/cliPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/web-sharedPatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/world-localPatch
@workflow/world-postgresPatch
@workflow/world-vercelPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch

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example-nextjs-workflow-turbopackReadyReadyPreview, v0Aug 25, 2026 11:25pm
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🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

python-node (8 failed):

  • promiseAllWorkflow | wrun_41M0XKW8620GVT2WRP55HYPZSC | 🔍 observability
  • sleepingWorkflow | wrun_41M0XKWVH40GV71GF8BPKP0T9J | 🔍 observability
  • parallelSleepWorkflow | wrun_41M0XKWYC70GPJA4V38D59N3E2 | 🔍 observability
  • nullByteWorkflow | wrun_41M0XKX4SQ0GP6HZD95DV47PKN | 🔍 observability
  • cancelRun - cancelling a running workflow | wrun_41M0XKZDMG0GSB2G7GCDRQ2NQ9 | 🔍 observability
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XKZFR00GZRXDDEPFZ1HPY1 | 🔍 observability
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XKZPB90GJV2V6KE0BCPM3C | 🔍 observability
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XM069J0GPFSMSB5XV2DXAV | 🔍 observability

🌐 Cross-language Conformance (9 failed)

python (9 failed):

  • deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M0XM2RVN13GZTK3JMW2QWTAX
  • promiseAllWorkflow | wrun_41M0XKW8620GVT2WRP55HYPZSC
  • sleepingWorkflow | wrun_41M0XKWVH40GV71GF8BPKP0T9J
  • parallelSleepWorkflow | wrun_41M0XKWYC70GPJA4V38D59N3E2
  • nullByteWorkflow | wrun_41M0XKX4SQ0GP6HZD95DV47PKN
  • cancelRun - cancelling a running workflow | wrun_41M0XKZDMG0GSB2G7GCDRQ2NQ9
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XKZFR00GZRXDDEPFZ1HPY1
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XKZPB90GJV2V6KE0BCPM3C
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XM069J0GPFSMSB5XV2DXAV

⚠️ 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.

  • cancelRun via CLI - cancelling a running workflow (express)
  • cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
  • hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-turbopack)
  • hookGetConflictWorkflow - awaiting hook.getConflict() registers hook without payload (nitro)
  • hookTokenReuseLoopWorkflow - same run recreates a hook with the same token after dispose() (nuxt)
  • hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (tanstack-start)
  • hookWorkflow (tanstack-start)

🛠 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.

42 infra events
  • cold-start-warmup · suite warmup (python) · at 23:25:36Z · abandoned wrun_41M0XKS15H0GKRGMPXB3BRH801 · (+7 more)
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:25:52Z · abandoned wrun_41M0XKWP1K0GQE7ZMWK3QVV9WH
  • run-pickup-stall · nullByteWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1V0GN48M281TQWYKXD
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1R0GX4XSJKEQFHDDP4
  • run-pickup-stall · sleepingWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1R0GX4XSJKEQFHDDP3
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWPG60GSQ5YTBCAT0R7QB
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:26:26Z · abandoned wrun_41M0XKXP4D0GT11GP7CXZJERSH
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHRM0GRK595NF7QZ7VMV
  • run-pickup-stall · sleepingWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHRT0GWH385E6D5A1WY0
  • run-pickup-stall · nullByteWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHN60GP60BDTSGJHE2N5
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYJ310GPM1BBQ5ZB1HMS9
  • run-pickup-stall · instanceMethodStepWorkflow - instance methods with "use step" directive (nest) · at 23:27:01Z · abandoned wrun_41M0XKYQJ10GMHHQ9ZPEHX3WYV
  • run-pickup-stall · cancelRun - cancelling a running workflow (fastify) · at 23:27:04Z · abandoned wrun_41M0XKYVQV0GVFJEC0SVC71Y0P
  • run-pickup-stall · sleepWithSequentialStepsWorkflow - sequential steps work with concurrent sleep (control) (hono) · at 23:27:05Z · abandoned wrun_41M0XKYX620GM8Q9H32MMS55CF
  • run-pickup-stall · hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nitro) · at 23:27:05Z · abandoned wrun_41M0XKYX700GR9A3EQ51EYPKNA
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (nitro) · at 23:27:07Z · abandoned wrun_41M0XKYY5Z0GGNC8DK7M443GQ1
  • run-pickup-stall · hookSupersedeOwnerWorkflow - duplicate cancels the owner and claims the released token (nextjs-turbopack) · at 23:27:09Z · abandoned wrun_41M0XKZ0WC0GTXDYDZ02VTEM6Z
  • run-pickup-stall · abortAfterCompletionWorkflow: abort after step completes is a no-op (sveltekit) · at 23:27:10Z · abandoned wrun_41M0XKZ1Z70GTY5V3QSAH2H2RZ
  • run-pickup-stall · distributedAbortController - TTL expiration triggers signal (express) · at 23:27:14Z · abandoned wrun_41M0XKZ5M00GN1VZFNF6C3CY49
  • cold-start-warmup · suite warmup (tanstack-start) · at 23:27:15Z · abandoned wrun_01M0XKYVF0HS6PN1CC3S1FJA0N
  • cold-start-warmup · suite warmup (python) · at 23:27:41Z · abandoned wrun_01M0XKWTDZ34YVV9AMNV48892H · (+7 more)
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:27:44Z · abandoned wrun_41M0XKYNRC0GYVYJ14M2MVD0CR
  • run-pickup-stall · sleepingWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJPKHME0N782V18DW0W
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJG4G0H79RQPBWJHFE5
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJH5ZZGDY3RXKG8B6FJ
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJRRY8G09YF6PBYEGZX
  • run-pickup-stall · nullByteWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJTBEF2HGZ4XCD1FFVD
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6DYNY7ZPWTK3MRJDVB
  • run-pickup-stall · sleepingWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6FXEBKATKVRZQ3QWH8
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6KSC1A1D6SYR5MX28S
  • run-pickup-stall · nullByteWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6MK5FWT49R55M5892A
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6H2D5X39KWWRGAHQ08
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:29:27Z · abandoned wrun_41M0XM1DMW0GVYCY0X56JYVMVX
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:29:27Z · abandoned wrun_41M0XM0KXT0GXVKC45119RZFCC
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:29:56Z · abandoned wrun_01M0XM44T1HC37KPH38V1MX2KJ
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:29:56Z · abandoned wrun_01M0XM44T41428VQNKEWD0046K
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:29:56Z · abandoned wrun_01M0XM44TBYBWXSGH5CB7M1FVS
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:30:26Z · abandoned wrun_01M0XM525V7VCQ8PZYC6KW0XF0
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:30:26Z · abandoned wrun_01M0XM525T3K8J0CFCNXJRQ7FH
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:30:56Z · abandoned wrun_01M0XM5ZDEGXBD0YNDMSARKHV5
  • run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 23:31:07Z · abandoned wrun_01M0XM6ARE8E5B3NCYNWQ7RS3A
  • run-pickup-stall · concurrent hook token conflict - two workflows cannot use the same hook token simultaneously (nextjs-webpack) · at 23:31:12Z · abandoned wrun_01M0XM6FE4SE79KFHSYPFWAYW5

E2E Test Summary

Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production357087424320
✅ 💻 Local Development392205584480
✅ 📦 Local Production392205584480
✅ 🐘 Local Postgres392205584480
✅ 🪟 Windows32000320
❌ 🌐 Cross-language Conformance09132141
✅ vercel-http-transport8170143960
✅ vercel-multi-region270027
✅ vercel-ws-transport553087640
Total1705317277819848
Details by Category

❌ ▲ Vercel Production

AppPassedFailedSkipped
✅ astro-node132028
✅ astro-quickjs132028
✅ example-node132028
✅ example-quickjs132028
✅ express-node132028
✅ express-quickjs132028
✅ fastify-node132028
✅ fastify-quickjs132028
✅ hono-node132028
✅ hono-quickjs132028
✅ nest-node132028
✅ nest-quickjs132028
✅ nextjs-turbopack-node15703
✅ nextjs-turbopack-quickjs15703
✅ nextjs-webpack-node15703
✅ nextjs-webpack-quickjs15703
✅ nitro-node132028
✅ nitro-quickjs132028
✅ nuxt-node132028
✅ nuxt-quickjs132028
❌ python-node08152
✅ sveltekit-node15109
✅ sveltekit-quickjs15109
✅ tanstack-start-node132028
✅ tanstack-start-quickjs132028
✅ vite-node132028
✅ vite-quickjs132028

✅ 💻 Local Development

AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026

✅ 📦 Local Production

AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026

✅ 🐘 Local Postgres

AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026

✅ 🪟 Windows

AppPassedFailedSkipped
✅ nextjs-turbopack-node16000
✅ nextjs-turbopack-quickjs16000

❌ 🌐 Cross-language Conformance

AppPassedFailedSkipped
❌ python09132

✅ vercel-http-transport

AppPassedFailedSkipped
✅ example132028
✅ express132028
✅ hono132028
✅ nextjs-turbopack15703
✅ nitro132028
✅ vite132028

✅ vercel-multi-region

AppPassedFailedSkipped
✅ nextjs-turbopack2700

✅ vercel-ws-transport

AppPassedFailedSkipped
✅ example132028
✅ express132028
✅ nextjs-turbopack15703
✅ vite132028

📋 View full workflow run

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📊 Workflow Benchmarks

commit 2db81fd · Tue, 25 Aug 2026 23:39:23 GMT · run logs

Backend: vercel · app: nextjs-turbopack

MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1207 (+75%) 🔻1295 🔴 (+25%) 🔻1325 🔴 (+26%) 🔻1467 🔴 (+28%) 🔻30
TTFSstream256 (+16%) 🔻1255 🔴 (+16%) 🔻1290 🔴 (+13%)1345 🔴 (+11%)30
TTFShook + stream1483 (+180%) 🔻1623 🔴 (+23%) 🔻1647 🔴 (+21%) 🔻2052 🔴 (+24%) 🔻30
Fan-out TTFSPromise.all(100 steps)547 (-5.0%)765 (-52%) 💚1903 (+9.4%)2019 (+12%)10
Fan-out TTLSPromise.all(100 steps)1838 (-7.9%)4757 (+17%) 🔻5109 (-30%) 💚8120 (-97%) 💚10
STSO1020 steps (inline)100 (+3.1%)121 (-12%)140 (-11%)189 (-16%) 💚1019
WO1020 steps121258 (-9.6%)121258 (-9.6%)121258 (-9.6%)121258 (-9.6%)1
CRTTfirst chunk (pooled)86 (-22%) 💚122 (-41%) 💚171 (-51%) 💚452 (+22%) 🔻28

Streams

ScenarioCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)102 (-24%)122 (-40%)176 (-38%)328 (-62%)101 (-67%)10
size sweep (100/s, 160B-12KB)102 (-30%)164 (-10%)439 (+36%)980 (+68%)118 (-41%)10
replay gateway-gpt-5.4-nano-2000t (1x)126 (-42%)111 (-33%)151 (-30%)270 (-37%)243 (-32%)3
replay eve-gpt-5.6-sol-2000t (1x)142 (-1%)116 (-29%)155 (-26%)299 (-15%)469 (+26%)2
replay eve-gpt-5.6-sol-2000t (2x)97 (-59%)146 (-39%)194 (-50%)363 (-55%)233 (-50%)3
📈 STSO distribution vs main (inline / queue-hop histograms)

1020 steps (inline)

Cumulative STSO time: main 133929ms → this run 121089ms (Δ -12840ms, -10%)

 50-100 ms ┃ main 2 this 0 -2
100-150 ms ██████████████████████░┃ main 875 this 972 +97
150-200 ms ┃██ main 121 this 38 -83
200-250 ms ┃ main 12 this 6 -6
250-300 ms ┃ main 6 this 2 -4
300-350 ms ┃ main 2 this 1 -1
350-400 ms ┃ main 1 this 0 -1
📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······██▁···· 104.1 (-36%) 100 (-28%) 176 (-38%) 328 (-62%) 3000
sweep ······▆█▂▁··· 157.9 (-2%) 106 (-23%) 439 (+36%) 980 (+68%) 3000
gw 1x ·····▁█▆▁···· 101.7 (-29%) 96 (-27%) 151 (-30%) 270 (-37%) 5295
eve 1x ·····▁█▅▁▁··· 100.3 (-27%) 90 (-26%) 155 (-26%) 299 (-15%) 5186
eve 2x ·····▁▅█▂···· 126.1 (-38%) 115 (-30%) 194 (-50%) 363 (-55%) 7779

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

control ▃▂▆▂█▇▆▁▃▁ 98–114ms
sweep ▅█▄▂▃▂▂▄▁▂ 130–219ms
gw 1x ▃▃▁▂▃█▄▄▅▅ 92–117ms
eve 1x ▃▁▂▅▄▄▆█▆▁ 87–118ms
eve 2x ▄▁▂▂▁▄▅█▅▁ 108–162ms

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

sweep ▃▆█▆▄▂▁ 156–161ms

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

control ▁▅▄▅██▆▅▇▄ 24–36ms
sweep ▆▁▂▅█▂▆▂▃▅ 39–73ms
gw 1x ▃▅▁▁▃█▃▆▆▄ 24–35ms
eve 1x ▂▂▁▅▃▃▅▇█▂ 19–26ms
eve 2x ▇▃▁▃▆▆█▂▅▆ 17–23ms
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-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041

🔴 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.

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Sim World

Simulated world deterministic testing for races. Traces

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

fence=per-spec

scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0

Full trace: world-sim.txt

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FrameworkFlow routeStep reg.Framework output
hono200.9 KiB (±0)40.3 KiB (-214 B)1.76 MiB (-135 B)
nextjs-turbopack206.3 KiB (±0)439 B (±0)762.7 KiB (-442 B)
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.

2db81fd · run

@VaguelySerious
Handle the resume-visibility consequence of the lazy path
18b5306
`resumeHook()` returning no longer implies `hook_received` is in the log:
the consuming invocation writes it. A caller that reads the run back
immediately can see a log without it.
hook-token-reuse's first test was such a caller. It picked the next hook
to resume by "has no hook_received yet", so after the eager write went
away it was handed back the hook it had just resumed, delivered a second
payload to it, and starved the round waiting for its own. The eager
write had been acting as its barrier.
`waitForHook()` grows a `notHookId` option to express "the next hook,
not the one I just resumed", and its doc says why the old predicate is
not sufficient on its own.
Also narrows the ended-run claim: the by-token lookup still validates
that a hook holds the token, so the silent case needs the hook to
outlive its run (minimum retention, or before the token is released).
@VaguelySerious
VaguelySerious marked this pull request as ready for review August 25, 2026 23:13
@VaguelySerious
Keep a durable resume for the step-abort ordering barrier
2db81fd
The abort path's own comment states the invariant: a step that aborts a
shared AbortController resumes a hook to record the abort, and that
write must be committed before the step completes, or the continuation
`step_completed` enqueues dispatches the next step with a stale,
non-aborted signal. It routes the resume to `preCompletionOps` for
exactly that reason.
Awaiting a lazy `resumeHook()` no longer supplies it: it resolves when
the resume is published, leaving the write to the consumer. So
preCompletionOps kept its ordering while the thing being ordered moved
out from under it, and `abortFromStepWorkflow` started failing with
stepSawAborted=false alongside workflowAborted=true — the stale-signal
dispatch, exactly as described.
Add `resumeHookDurable()`, which forces the sequential path, and use it
there. The gate checks it first so the span reads
`resume_fallback_reason: durable_required` rather than naming whichever
other condition happened to fail. The round trip it costs is the right
price for an internal barrier; the lazy path is for the external resume
it was written for.
abort-controller-step.test.ts mocks the two entry points separately, so
a regression to the lazy one shows up as the durable mock going
uncalled.
karthikscale3
karthikscale3 approved these changes Aug 26, 2026
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Approved.

Checked the lazy-resume producer/consumer flow and its fallbacks: queue-publish failure, redelivery and idempotent deduplication, reusable-hook multiple resumes, terminal runs, oversized/legacy/unsupported fallbacks, and the AbortController durable-write ordering barrier.

Validation:

  • Built the affected workspace packages.
  • Ran focused core and world-local suites: 34 tests passed.
  • Started the local Next.js workflow stack and confirmed the workflow manifest was reachable.

No blocking issues found.

@VaguelySerious
VaguelySerious merged commit d9e0777 into mainAug 26, 2026
182 of 184 checks passed
@VaguelySerious
VaguelySerious deleted the peter/lazy-only-hook-resume branch August 26, 2026 16:14
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No backport to stable for d9e0777 (AI decision).

This is a latency optimization plus deliberate contract change to resumeHook(): the producer no longer writes hook_received, so a resolved resume no longer implies the event is visible, and a resume against an ended run now resolves instead of throwing HookNotFoundError. It also adds new API surface (resumeHookDurable, a notHookId option on @workflow/vitest's waitForHook()) and a new lazy telemetry strategy value. None of that fixes a defect on stable; it widens an existing race window and changes observable behavior of an existing API, which is exactly what a maintenance line should not absorb.

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

d9e0777eb8b1ce5f3be3fe865bc5a17fdbdb9d5d

@github-actionsgithub-actionsBot mentioned this pull request Aug 26, 2026
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@karthikscale3karthikscale3karthikscale3 approved these changes
@msullivanmsullivanAwaiting requested review from msullivan
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@VaguelySerious@karthikscale3
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

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[core] Never write hook_received eagerly on the lazy resume path - #3794
Merged
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peter/lazy-only-hook-resume
Aug 26, 2026
Merged
[core] Never write hook_received eagerly on the lazy resume path#3794
VaguelySerious merged 3 commits into
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@VaguelySerious
@VaguelySeriousVaguelySerious
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Aug 25, 2026•

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Makes resumeHook() never create hook_received itself. It only publishes the queue message and returns; the consumer materializes the event from hookInput before it replays.
The queue message becomes the single point of durability, which it is supposed to be anyway.
Note there's an existing edge case: run goes terminal, swallows a hook_received first (can't do any work in response to the hook_received), despite the resumeHook call returning success.
Now, this edge case has a wider race window, since we don't even check at resumeHook time whether the run is terminal. The race is thus 100ms-1s wider than before.
Also, we keep around an eager-only specifically for the AbortController, because that needs an immediate confirmed hook_received insert (instead of an eventual insert).
OTEL changes: ResumedHook.resilientResume and the workflow.hook.resilient_resume span attribute are retained on the type but never set, since there is no partial outcome to report. workflow.hook.resume_strategy reports lazy (was parallel); consumers still accept parallel from producers that predate this.
@VaguelySerious
[core] Never write hook_received eagerly on the lazy resume path
7907553
resumeHook() raced its own `hook_received` write against the queue
publish, and the consumer re-ensured the same event from `hookInput`
before replay. Both sides wrote; a `(runId, resumeId)` constraint
collapsed them onto one.
Drop the producer's write. On the lazy path resumeHook() publishes one
message and nothing else, so a resume costs one round trip and the event
is created once, by the side about to replay it. The dedup constraint
still covers repeated deliveries of that message.
Two consequences:
- A failed publish now fails the resume outright: the message carries
both the trigger and the only copy of the payload, so there is nothing
persisted for a later delivery to recover.
- A resume against an ended run resolves instead of throwing
HookNotFoundError, whenever it also skipped reading the run (the
common case: the hook lookup returns the resume context inline).
Nothing resumes either way. Run-fallback resumes and the sequential
path keep their terminal checks.
`ResumedHook.resilientResume` and the `workflow.hook.resilient_resume`
span attribute are retained but never set. The resume span reports
`resume_strategy: lazy`; consumers still accept `parallel` from older
producers.
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🦋 Changeset detected
Latest commit: 2db81fd
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 20 packages
NameType
@workflow/corePatch
@workflow/vitestPatch
@workflow/worldPatch
@workflow/buildersPatch
@workflow/cliPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/web-sharedPatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/world-localPatch
@workflow/world-postgresPatch
@workflow/world-vercelPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
Not sure what this means? Click here to learn what changesets are.
Click here if you're a maintainer who wants to add another changeset to this PR
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (8 failed)
python-node (8 failed):
  • promiseAllWorkflow | wrun_41M0XKW8620GVT2WRP55HYPZSC | 🔍 observability
  • sleepingWorkflow | wrun_41M0XKWVH40GV71GF8BPKP0T9J | 🔍 observability
  • parallelSleepWorkflow | wrun_41M0XKWYC70GPJA4V38D59N3E2 | 🔍 observability
  • nullByteWorkflow | wrun_41M0XKX4SQ0GP6HZD95DV47PKN | 🔍 observability
  • cancelRun - cancelling a running workflow | wrun_41M0XKZDMG0GSB2G7GCDRQ2NQ9 | 🔍 observability
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XKZFR00GZRXDDEPFZ1HPY1 | 🔍 observability
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XKZPB90GJV2V6KE0BCPM3C | 🔍 observability
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XM069J0GPFSMSB5XV2DXAV | 🔍 observability
🌐 Cross-language Conformance (9 failed)
python (9 failed):
  • deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M0XM2RVN13GZTK3JMW2QWTAX
  • promiseAllWorkflow | wrun_41M0XKW8620GVT2WRP55HYPZSC
  • sleepingWorkflow | wrun_41M0XKWVH40GV71GF8BPKP0T9J
  • parallelSleepWorkflow | wrun_41M0XKWYC70GPJA4V38D59N3E2
  • nullByteWorkflow | wrun_41M0XKX4SQ0GP6HZD95DV47PKN
  • cancelRun - cancelling a running workflow | wrun_41M0XKZDMG0GSB2G7GCDRQ2NQ9
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XKZFR00GZRXDDEPFZ1HPY1
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XKZPB90GJV2V6KE0BCPM3C
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XM069J0GPFSMSB5XV2DXAV
⚠️ 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.
  • cancelRun via CLI - cancelling a running workflow (express)
  • cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
  • hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-turbopack)
  • hookGetConflictWorkflow - awaiting hook.getConflict() registers hook without payload (nitro)
  • hookTokenReuseLoopWorkflow - same run recreates a hook with the same token after dispose() (nuxt)
  • hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (tanstack-start)
  • hookWorkflow (tanstack-start)
🛠 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.
42 infra events
  • cold-start-warmup · suite warmup (python) · at 23:25:36Z · abandoned wrun_41M0XKS15H0GKRGMPXB3BRH801 · (+7 more)
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:25:52Z · abandoned wrun_41M0XKWP1K0GQE7ZMWK3QVV9WH
  • run-pickup-stall · nullByteWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1V0GN48M281TQWYKXD
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1R0GX4XSJKEQFHDDP4
  • run-pickup-stall · sleepingWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1R0GX4XSJKEQFHDDP3
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWPG60GSQ5YTBCAT0R7QB
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:26:26Z · abandoned wrun_41M0XKXP4D0GT11GP7CXZJERSH
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHRM0GRK595NF7QZ7VMV
  • run-pickup-stall · sleepingWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHRT0GWH385E6D5A1WY0
  • run-pickup-stall · nullByteWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHN60GP60BDTSGJHE2N5
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYJ310GPM1BBQ5ZB1HMS9
  • run-pickup-stall · instanceMethodStepWorkflow - instance methods with "use step" directive (nest) · at 23:27:01Z · abandoned wrun_41M0XKYQJ10GMHHQ9ZPEHX3WYV
  • run-pickup-stall · cancelRun - cancelling a running workflow (fastify) · at 23:27:04Z · abandoned wrun_41M0XKYVQV0GVFJEC0SVC71Y0P
  • run-pickup-stall · sleepWithSequentialStepsWorkflow - sequential steps work with concurrent sleep (control) (hono) · at 23:27:05Z · abandoned wrun_41M0XKYX620GM8Q9H32MMS55CF
  • run-pickup-stall · hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nitro) · at 23:27:05Z · abandoned wrun_41M0XKYX700GR9A3EQ51EYPKNA
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (nitro) · at 23:27:07Z · abandoned wrun_41M0XKYY5Z0GGNC8DK7M443GQ1
  • run-pickup-stall · hookSupersedeOwnerWorkflow - duplicate cancels the owner and claims the released token (nextjs-turbopack) · at 23:27:09Z · abandoned wrun_41M0XKZ0WC0GTXDYDZ02VTEM6Z
  • run-pickup-stall · abortAfterCompletionWorkflow: abort after step completes is a no-op (sveltekit) · at 23:27:10Z · abandoned wrun_41M0XKZ1Z70GTY5V3QSAH2H2RZ
  • run-pickup-stall · distributedAbortController - TTL expiration triggers signal (express) · at 23:27:14Z · abandoned wrun_41M0XKZ5M00GN1VZFNF6C3CY49
  • cold-start-warmup · suite warmup (tanstack-start) · at 23:27:15Z · abandoned wrun_01M0XKYVF0HS6PN1CC3S1FJA0N
  • cold-start-warmup · suite warmup (python) · at 23:27:41Z · abandoned wrun_01M0XKWTDZ34YVV9AMNV48892H · (+7 more)
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:27:44Z · abandoned wrun_41M0XKYNRC0GYVYJ14M2MVD0CR
  • run-pickup-stall · sleepingWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJPKHME0N782V18DW0W
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJG4G0H79RQPBWJHFE5
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJH5ZZGDY3RXKG8B6FJ
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJRRY8G09YF6PBYEGZX
  • run-pickup-stall · nullByteWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJTBEF2HGZ4XCD1FFVD
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6DYNY7ZPWTK3MRJDVB
  • run-pickup-stall · sleepingWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6FXEBKATKVRZQ3QWH8
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6KSC1A1D6SYR5MX28S
  • run-pickup-stall · nullByteWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6MK5FWT49R55M5892A
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6H2D5X39KWWRGAHQ08
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:29:27Z · abandoned wrun_41M0XM1DMW0GVYCY0X56JYVMVX
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:29:27Z · abandoned wrun_41M0XM0KXT0GXVKC45119RZFCC
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:29:56Z · abandoned wrun_01M0XM44T1HC37KPH38V1MX2KJ
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:29:56Z · abandoned wrun_01M0XM44T41428VQNKEWD0046K
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:29:56Z · abandoned wrun_01M0XM44TBYBWXSGH5CB7M1FVS
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:30:26Z · abandoned wrun_01M0XM525V7VCQ8PZYC6KW0XF0
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:30:26Z · abandoned wrun_01M0XM525T3K8J0CFCNXJRQ7FH
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:30:56Z · abandoned wrun_01M0XM5ZDEGXBD0YNDMSARKHV5
  • run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 23:31:07Z · abandoned wrun_01M0XM6ARE8E5B3NCYNWQ7RS3A
  • run-pickup-stall · concurrent hook token conflict - two workflows cannot use the same hook token simultaneously (nextjs-webpack) · at 23:31:12Z · abandoned wrun_01M0XM6FE4SE79KFHSYPFWAYW5
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production357087424320
✅ 💻 Local Development392205584480
✅ 📦 Local Production392205584480
✅ 🐘 Local Postgres392205584480
✅ 🪟 Windows32000320
❌ 🌐 Cross-language Conformance09132141
✅ vercel-http-transport8170143960
✅ vercel-multi-region270027
✅ vercel-ws-transport553087640
Total1705317277819848
Details by Category
❌ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro-node132028
✅ astro-quickjs132028
✅ example-node132028
✅ example-quickjs132028
✅ express-node132028
✅ express-quickjs132028
✅ fastify-node132028
✅ fastify-quickjs132028
✅ hono-node132028
✅ hono-quickjs132028
✅ nest-node132028
✅ nest-quickjs132028
✅ nextjs-turbopack-node15703
✅ nextjs-turbopack-quickjs15703
✅ nextjs-webpack-node15703
✅ nextjs-webpack-quickjs15703
✅ nitro-node132028
✅ nitro-quickjs132028
✅ nuxt-node132028
✅ nuxt-quickjs132028
❌ python-node08152
✅ sveltekit-node15109
✅ sveltekit-quickjs15109
✅ tanstack-start-node132028
✅ tanstack-start-quickjs132028
✅ vite-node132028
✅ vite-quickjs132028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node16000
✅ nextjs-turbopack-quickjs16000
❌ 🌐 Cross-language Conformance
AppPassedFailedSkipped
❌ python09132
✅ vercel-http-transport
AppPassedFailedSkipped
✅ example132028
✅ express132028
✅ hono132028
✅ nextjs-turbopack15703
✅ nitro132028
✅ vite132028
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
✅ vercel-ws-transport
AppPassedFailedSkipped
✅ example132028
✅ express132028
✅ nextjs-turbopack15703
✅ vite132028
📋 View full workflow run
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📊 Workflow Benchmarks
commit 2db81fd · Tue, 25 Aug 2026 23:39:23 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1207 (+75%) 🔻1295 🔴 (+25%) 🔻1325 🔴 (+26%) 🔻1467 🔴 (+28%) 🔻30
TTFSstream256 (+16%) 🔻1255 🔴 (+16%) 🔻1290 🔴 (+13%)1345 🔴 (+11%)30
TTFShook + stream1483 (+180%) 🔻1623 🔴 (+23%) 🔻1647 🔴 (+21%) 🔻2052 🔴 (+24%) 🔻30
Fan-out TTFSPromise.all(100 steps)547 (-5.0%)765 (-52%) 💚1903 (+9.4%)2019 (+12%)10
Fan-out TTLSPromise.all(100 steps)1838 (-7.9%)4757 (+17%) 🔻5109 (-30%) 💚8120 (-97%) 💚10
STSO1020 steps (inline)100 (+3.1%)121 (-12%)140 (-11%)189 (-16%) 💚1019
WO1020 steps121258 (-9.6%)121258 (-9.6%)121258 (-9.6%)121258 (-9.6%)1
CRTTfirst chunk (pooled)86 (-22%) 💚122 (-41%) 💚171 (-51%) 💚452 (+22%) 🔻28
Streams
ScenarioCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)102 (-24%)122 (-40%)176 (-38%)328 (-62%)101 (-67%)10
size sweep (100/s, 160B-12KB)102 (-30%)164 (-10%)439 (+36%)980 (+68%)118 (-41%)10
replay gateway-gpt-5.4-nano-2000t (1x)126 (-42%)111 (-33%)151 (-30%)270 (-37%)243 (-32%)3
replay eve-gpt-5.6-sol-2000t (1x)142 (-1%)116 (-29%)155 (-26%)299 (-15%)469 (+26%)2
replay eve-gpt-5.6-sol-2000t (2x)97 (-59%)146 (-39%)194 (-50%)363 (-55%)233 (-50%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 133929ms → this run 121089ms (Δ -12840ms, -10%)
 50-100 ms ┃ main 2 this 0 -2
100-150 ms ██████████████████████░┃ main 875 this 972 +97
150-200 ms ┃██ main 121 this 38 -83
200-250 ms ┃ main 12 this 6 -6
250-300 ms ┃ main 6 this 2 -4
300-350 ms ┃ main 2 this 1 -1
350-400 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······██▁···· 104.1 (-36%) 100 (-28%) 176 (-38%) 328 (-62%) 3000
sweep ······▆█▂▁··· 157.9 (-2%) 106 (-23%) 439 (+36%) 980 (+68%) 3000
gw 1x ·····▁█▆▁···· 101.7 (-29%) 96 (-27%) 151 (-30%) 270 (-37%) 5295
eve 1x ·····▁█▅▁▁··· 100.3 (-27%) 90 (-26%) 155 (-26%) 299 (-15%) 5186
eve 2x ·····▁▅█▂···· 126.1 (-38%) 115 (-30%) 194 (-50%) 363 (-55%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control ▃▂▆▂█▇▆▁▃▁ 98–114ms
sweep ▅█▄▂▃▂▂▄▁▂ 130–219ms
gw 1x ▃▃▁▂▃█▄▄▅▅ 92–117ms
eve 1x ▃▁▂▅▄▄▆█▆▁ 87–118ms
eve 2x ▄▁▂▂▁▄▅█▅▁ 108–162ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▃▆█▆▄▂▁ 156–161ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▅▄▅██▆▅▇▄ 24–36ms
sweep ▆▁▂▅█▂▆▂▃▅ 39–73ms
gw 1x ▃▅▁▁▃█▃▆▆▄ 24–35ms
eve 1x ▂▂▁▅▃▃▅▇█▂ 19–26ms
eve 2x ▇▃▁▃▆▆█▂▅▆ 17–23ms

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-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 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.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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FrameworkFlow routeStep reg.Framework output
hono200.9 KiB (±0)40.3 KiB (-214 B)1.76 MiB (-135 B)
nextjs-turbopack206.3 KiB (±0)439 B (±0)762.7 KiB (-442 B)
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.
2db81fd · run
@VaguelySerious
Handle the resume-visibility consequence of the lazy path
18b5306
`resumeHook()` returning no longer implies `hook_received` is in the log:
the consuming invocation writes it. A caller that reads the run back
immediately can see a log without it.
hook-token-reuse's first test was such a caller. It picked the next hook
to resume by "has no hook_received yet", so after the eager write went
away it was handed back the hook it had just resumed, delivered a second
payload to it, and starved the round waiting for its own. The eager
write had been acting as its barrier.
`waitForHook()` grows a `notHookId` option to express "the next hook,
not the one I just resumed", and its doc says why the old predicate is
not sufficient on its own.
Also narrows the ended-run claim: the by-token lookup still validates
that a hook holds the token, so the silent case needs the hook to
outlive its run (minimum retention, or before the token is released).
@VaguelySerious
VaguelySerious
marked this pull request as ready for review
August 25, 2026 23:13
@VaguelySerious
Keep a durable resume for the step-abort ordering barrier
2db81fd
The abort path's own comment states the invariant: a step that aborts a
shared AbortController resumes a hook to record the abort, and that
write must be committed before the step completes, or the continuation
`step_completed` enqueues dispatches the next step with a stale,
non-aborted signal. It routes the resume to `preCompletionOps` for
exactly that reason.
Awaiting a lazy `resumeHook()` no longer supplies it: it resolves when
the resume is published, leaving the write to the consumer. So
preCompletionOps kept its ordering while the thing being ordered moved
out from under it, and `abortFromStepWorkflow` started failing with
stepSawAborted=false alongside workflowAborted=true — the stale-signal
dispatch, exactly as described.
Add `resumeHookDurable()`, which forces the sequential path, and use it
there. The gate checks it first so the span reads
`resume_fallback_reason: durable_required` rather than naming whichever
other condition happened to fail. The round trip it costs is the right
price for an internal barrier; the lazy path is for the external resume
it was written for.
abort-controller-step.test.ts mocks the two entry points separately, so
a regression to the lazy one shows up as the durable mock going
uncalled.
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Approved.
Checked the lazy-resume producer/consumer flow and its fallbacks: queue-publish failure, redelivery and idempotent deduplication, reusable-hook multiple resumes, terminal runs, oversized/legacy/unsupported fallbacks, and the AbortController durable-write ordering barrier.
Validation:
  • Built the affected workspace packages.
  • Ran focused core and world-local suites: 34 tests passed.
  • Started the local Next.js workflow stack and confirmed the workflow manifest was reachable.
No blocking issues found.
@VaguelySerious
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No backport to stable for d9e0777 (AI decision).
This is a latency optimization plus deliberate contract change to resumeHook(): the producer no longer writes hook_received, so a resolved resume no longer implies the event is visible, and a resume against an ended run now resolves instead of throwing HookNotFoundError. It also adds new API surface (resumeHookDurable, a notHookId option on @workflow/vitest's waitForHook()) and a new lazy telemetry strategy value. None of that fixes a defect on stable; it widens an existing race window and changes observable behavior of an existing API, which is exactly what a maintenance line should not absorb.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
d9e0777eb8b1ce5f3be3fe865bc5a17fdbdb9d5d

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[core] Never write hook_received eagerly on the lazy resume path - #3794
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Aug 26, 2026
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[core] Never write hook_received eagerly on the lazy resume path#3794
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Makes resumeHook() never create hook_received itself. It only publishes the queue message and returns; the consumer materializes the event from hookInput before it replays.
The queue message becomes the single point of durability, which it is supposed to be anyway.
Note there's an existing edge case: run goes terminal, swallows a hook_received first (can't do any work in response to the hook_received), despite the resumeHook call returning success.
Now, this edge case has a wider race window, since we don't even check at resumeHook time whether the run is terminal. The race is thus 100ms-1s wider than before.
Also, we keep around an eager-only specifically for the AbortController, because that needs an immediate confirmed hook_received insert (instead of an eventual insert).
OTEL changes: ResumedHook.resilientResume and the workflow.hook.resilient_resume span attribute are retained on the type but never set, since there is no partial outcome to report. workflow.hook.resume_strategy reports lazy (was parallel); consumers still accept parallel from producers that predate this.
@VaguelySerious
[core] Never write hook_received eagerly on the lazy resume path
7907553
resumeHook() raced its own `hook_received` write against the queue
publish, and the consumer re-ensured the same event from `hookInput`
before replay. Both sides wrote; a `(runId, resumeId)` constraint
collapsed them onto one.
Drop the producer's write. On the lazy path resumeHook() publishes one
message and nothing else, so a resume costs one round trip and the event
is created once, by the side about to replay it. The dedup constraint
still covers repeated deliveries of that message.
Two consequences:
- A failed publish now fails the resume outright: the message carries
both the trigger and the only copy of the payload, so there is nothing
persisted for a later delivery to recover.
- A resume against an ended run resolves instead of throwing
HookNotFoundError, whenever it also skipped reading the run (the
common case: the hook lookup returns the resume context inline).
Nothing resumes either way. Run-fallback resumes and the sequential
path keep their terminal checks.
`ResumedHook.resilientResume` and the `workflow.hook.resilient_resume`
span attribute are retained but never set. The resume span reports
`resume_strategy: lazy`; consumers still accept `parallel` from older
producers.
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🦋 Changeset detected
Latest commit: 2db81fd
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 20 packages
NameType
@workflow/corePatch
@workflow/vitestPatch
@workflow/worldPatch
@workflow/buildersPatch
@workflow/cliPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/web-sharedPatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/world-localPatch
@workflow/world-postgresPatch
@workflow/world-vercelPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
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Click here if you're a maintainer who wants to add another changeset to this PR
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (8 failed)
python-node (8 failed):
  • promiseAllWorkflow | wrun_41M0XKW8620GVT2WRP55HYPZSC | 🔍 observability
  • sleepingWorkflow | wrun_41M0XKWVH40GV71GF8BPKP0T9J | 🔍 observability
  • parallelSleepWorkflow | wrun_41M0XKWYC70GPJA4V38D59N3E2 | 🔍 observability
  • nullByteWorkflow | wrun_41M0XKX4SQ0GP6HZD95DV47PKN | 🔍 observability
  • cancelRun - cancelling a running workflow | wrun_41M0XKZDMG0GSB2G7GCDRQ2NQ9 | 🔍 observability
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XKZFR00GZRXDDEPFZ1HPY1 | 🔍 observability
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XKZPB90GJV2V6KE0BCPM3C | 🔍 observability
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XM069J0GPFSMSB5XV2DXAV | 🔍 observability
🌐 Cross-language Conformance (9 failed)
python (9 failed):
  • deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M0XM2RVN13GZTK3JMW2QWTAX
  • promiseAllWorkflow | wrun_41M0XKW8620GVT2WRP55HYPZSC
  • sleepingWorkflow | wrun_41M0XKWVH40GV71GF8BPKP0T9J
  • parallelSleepWorkflow | wrun_41M0XKWYC70GPJA4V38D59N3E2
  • nullByteWorkflow | wrun_41M0XKX4SQ0GP6HZD95DV47PKN
  • cancelRun - cancelling a running workflow | wrun_41M0XKZDMG0GSB2G7GCDRQ2NQ9
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XKZFR00GZRXDDEPFZ1HPY1
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XKZPB90GJV2V6KE0BCPM3C
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XM069J0GPFSMSB5XV2DXAV
⚠️ 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.
  • cancelRun via CLI - cancelling a running workflow (express)
  • cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
  • hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-turbopack)
  • hookGetConflictWorkflow - awaiting hook.getConflict() registers hook without payload (nitro)
  • hookTokenReuseLoopWorkflow - same run recreates a hook with the same token after dispose() (nuxt)
  • hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (tanstack-start)
  • hookWorkflow (tanstack-start)
🛠 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.
42 infra events
  • cold-start-warmup · suite warmup (python) · at 23:25:36Z · abandoned wrun_41M0XKS15H0GKRGMPXB3BRH801 · (+7 more)
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:25:52Z · abandoned wrun_41M0XKWP1K0GQE7ZMWK3QVV9WH
  • run-pickup-stall · nullByteWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1V0GN48M281TQWYKXD
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1R0GX4XSJKEQFHDDP4
  • run-pickup-stall · sleepingWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1R0GX4XSJKEQFHDDP3
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWPG60GSQ5YTBCAT0R7QB
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:26:26Z · abandoned wrun_41M0XKXP4D0GT11GP7CXZJERSH
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHRM0GRK595NF7QZ7VMV
  • run-pickup-stall · sleepingWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHRT0GWH385E6D5A1WY0
  • run-pickup-stall · nullByteWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHN60GP60BDTSGJHE2N5
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYJ310GPM1BBQ5ZB1HMS9
  • run-pickup-stall · instanceMethodStepWorkflow - instance methods with "use step" directive (nest) · at 23:27:01Z · abandoned wrun_41M0XKYQJ10GMHHQ9ZPEHX3WYV
  • run-pickup-stall · cancelRun - cancelling a running workflow (fastify) · at 23:27:04Z · abandoned wrun_41M0XKYVQV0GVFJEC0SVC71Y0P
  • run-pickup-stall · sleepWithSequentialStepsWorkflow - sequential steps work with concurrent sleep (control) (hono) · at 23:27:05Z · abandoned wrun_41M0XKYX620GM8Q9H32MMS55CF
  • run-pickup-stall · hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nitro) · at 23:27:05Z · abandoned wrun_41M0XKYX700GR9A3EQ51EYPKNA
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (nitro) · at 23:27:07Z · abandoned wrun_41M0XKYY5Z0GGNC8DK7M443GQ1
  • run-pickup-stall · hookSupersedeOwnerWorkflow - duplicate cancels the owner and claims the released token (nextjs-turbopack) · at 23:27:09Z · abandoned wrun_41M0XKZ0WC0GTXDYDZ02VTEM6Z
  • run-pickup-stall · abortAfterCompletionWorkflow: abort after step completes is a no-op (sveltekit) · at 23:27:10Z · abandoned wrun_41M0XKZ1Z70GTY5V3QSAH2H2RZ
  • run-pickup-stall · distributedAbortController - TTL expiration triggers signal (express) · at 23:27:14Z · abandoned wrun_41M0XKZ5M00GN1VZFNF6C3CY49
  • cold-start-warmup · suite warmup (tanstack-start) · at 23:27:15Z · abandoned wrun_01M0XKYVF0HS6PN1CC3S1FJA0N
  • cold-start-warmup · suite warmup (python) · at 23:27:41Z · abandoned wrun_01M0XKWTDZ34YVV9AMNV48892H · (+7 more)
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:27:44Z · abandoned wrun_41M0XKYNRC0GYVYJ14M2MVD0CR
  • run-pickup-stall · sleepingWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJPKHME0N782V18DW0W
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJG4G0H79RQPBWJHFE5
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJH5ZZGDY3RXKG8B6FJ
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJRRY8G09YF6PBYEGZX
  • run-pickup-stall · nullByteWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJTBEF2HGZ4XCD1FFVD
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6DYNY7ZPWTK3MRJDVB
  • run-pickup-stall · sleepingWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6FXEBKATKVRZQ3QWH8
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6KSC1A1D6SYR5MX28S
  • run-pickup-stall · nullByteWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6MK5FWT49R55M5892A
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6H2D5X39KWWRGAHQ08
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:29:27Z · abandoned wrun_41M0XM1DMW0GVYCY0X56JYVMVX
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:29:27Z · abandoned wrun_41M0XM0KXT0GXVKC45119RZFCC
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:29:56Z · abandoned wrun_01M0XM44T1HC37KPH38V1MX2KJ
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:29:56Z · abandoned wrun_01M0XM44T41428VQNKEWD0046K
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:29:56Z · abandoned wrun_01M0XM44TBYBWXSGH5CB7M1FVS
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:30:26Z · abandoned wrun_01M0XM525V7VCQ8PZYC6KW0XF0
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:30:26Z · abandoned wrun_01M0XM525T3K8J0CFCNXJRQ7FH
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:30:56Z · abandoned wrun_01M0XM5ZDEGXBD0YNDMSARKHV5
  • run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 23:31:07Z · abandoned wrun_01M0XM6ARE8E5B3NCYNWQ7RS3A
  • run-pickup-stall · concurrent hook token conflict - two workflows cannot use the same hook token simultaneously (nextjs-webpack) · at 23:31:12Z · abandoned wrun_01M0XM6FE4SE79KFHSYPFWAYW5
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production357087424320
✅ 💻 Local Development392205584480
✅ 📦 Local Production392205584480
✅ 🐘 Local Postgres392205584480
✅ 🪟 Windows32000320
❌ 🌐 Cross-language Conformance09132141
✅ vercel-http-transport8170143960
✅ vercel-multi-region270027
✅ vercel-ws-transport553087640
Total1705317277819848
Details by Category
❌ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro-node132028
✅ astro-quickjs132028
✅ example-node132028
✅ example-quickjs132028
✅ express-node132028
✅ express-quickjs132028
✅ fastify-node132028
✅ fastify-quickjs132028
✅ hono-node132028
✅ hono-quickjs132028
✅ nest-node132028
✅ nest-quickjs132028
✅ nextjs-turbopack-node15703
✅ nextjs-turbopack-quickjs15703
✅ nextjs-webpack-node15703
✅ nextjs-webpack-quickjs15703
✅ nitro-node132028
✅ nitro-quickjs132028
✅ nuxt-node132028
✅ nuxt-quickjs132028
❌ python-node08152
✅ sveltekit-node15109
✅ sveltekit-quickjs15109
✅ tanstack-start-node132028
✅ tanstack-start-quickjs132028
✅ vite-node132028
✅ vite-quickjs132028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node16000
✅ nextjs-turbopack-quickjs16000
❌ 🌐 Cross-language Conformance
AppPassedFailedSkipped
❌ python09132
✅ vercel-http-transport
AppPassedFailedSkipped
✅ example132028
✅ express132028
✅ hono132028
✅ nextjs-turbopack15703
✅ nitro132028
✅ vite132028
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
✅ vercel-ws-transport
AppPassedFailedSkipped
✅ example132028
✅ express132028
✅ nextjs-turbopack15703
✅ vite132028
📋 View full workflow run
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📊 Workflow Benchmarks
commit 2db81fd · Tue, 25 Aug 2026 23:39:23 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1207 (+75%) 🔻1295 🔴 (+25%) 🔻1325 🔴 (+26%) 🔻1467 🔴 (+28%) 🔻30
TTFSstream256 (+16%) 🔻1255 🔴 (+16%) 🔻1290 🔴 (+13%)1345 🔴 (+11%)30
TTFShook + stream1483 (+180%) 🔻1623 🔴 (+23%) 🔻1647 🔴 (+21%) 🔻2052 🔴 (+24%) 🔻30
Fan-out TTFSPromise.all(100 steps)547 (-5.0%)765 (-52%) 💚1903 (+9.4%)2019 (+12%)10
Fan-out TTLSPromise.all(100 steps)1838 (-7.9%)4757 (+17%) 🔻5109 (-30%) 💚8120 (-97%) 💚10
STSO1020 steps (inline)100 (+3.1%)121 (-12%)140 (-11%)189 (-16%) 💚1019
WO1020 steps121258 (-9.6%)121258 (-9.6%)121258 (-9.6%)121258 (-9.6%)1
CRTTfirst chunk (pooled)86 (-22%) 💚122 (-41%) 💚171 (-51%) 💚452 (+22%) 🔻28
Streams
ScenarioCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)102 (-24%)122 (-40%)176 (-38%)328 (-62%)101 (-67%)10
size sweep (100/s, 160B-12KB)102 (-30%)164 (-10%)439 (+36%)980 (+68%)118 (-41%)10
replay gateway-gpt-5.4-nano-2000t (1x)126 (-42%)111 (-33%)151 (-30%)270 (-37%)243 (-32%)3
replay eve-gpt-5.6-sol-2000t (1x)142 (-1%)116 (-29%)155 (-26%)299 (-15%)469 (+26%)2
replay eve-gpt-5.6-sol-2000t (2x)97 (-59%)146 (-39%)194 (-50%)363 (-55%)233 (-50%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 133929ms → this run 121089ms (Δ -12840ms, -10%)
 50-100 ms ┃ main 2 this 0 -2
100-150 ms ██████████████████████░┃ main 875 this 972 +97
150-200 ms ┃██ main 121 this 38 -83
200-250 ms ┃ main 12 this 6 -6
250-300 ms ┃ main 6 this 2 -4
300-350 ms ┃ main 2 this 1 -1
350-400 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······██▁···· 104.1 (-36%) 100 (-28%) 176 (-38%) 328 (-62%) 3000
sweep ······▆█▂▁··· 157.9 (-2%) 106 (-23%) 439 (+36%) 980 (+68%) 3000
gw 1x ·····▁█▆▁···· 101.7 (-29%) 96 (-27%) 151 (-30%) 270 (-37%) 5295
eve 1x ·····▁█▅▁▁··· 100.3 (-27%) 90 (-26%) 155 (-26%) 299 (-15%) 5186
eve 2x ·····▁▅█▂···· 126.1 (-38%) 115 (-30%) 194 (-50%) 363 (-55%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control ▃▂▆▂█▇▆▁▃▁ 98–114ms
sweep ▅█▄▂▃▂▂▄▁▂ 130–219ms
gw 1x ▃▃▁▂▃█▄▄▅▅ 92–117ms
eve 1x ▃▁▂▅▄▄▆█▆▁ 87–118ms
eve 2x ▄▁▂▂▁▄▅█▅▁ 108–162ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▃▆█▆▄▂▁ 156–161ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▅▄▅██▆▅▇▄ 24–36ms
sweep ▆▁▂▅█▂▆▂▃▅ 39–73ms
gw 1x ▃▅▁▁▃█▃▆▆▄ 24–35ms
eve 1x ▂▂▁▅▃▃▅▇█▂ 19–26ms
eve 2x ▇▃▁▃▆▆█▂▅▆ 17–23ms

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-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 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.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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FrameworkFlow routeStep reg.Framework output
hono200.9 KiB (±0)40.3 KiB (-214 B)1.76 MiB (-135 B)
nextjs-turbopack206.3 KiB (±0)439 B (±0)762.7 KiB (-442 B)
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.
2db81fd · run
@VaguelySerious
Handle the resume-visibility consequence of the lazy path
18b5306
`resumeHook()` returning no longer implies `hook_received` is in the log:
the consuming invocation writes it. A caller that reads the run back
immediately can see a log without it.
hook-token-reuse's first test was such a caller. It picked the next hook
to resume by "has no hook_received yet", so after the eager write went
away it was handed back the hook it had just resumed, delivered a second
payload to it, and starved the round waiting for its own. The eager
write had been acting as its barrier.
`waitForHook()` grows a `notHookId` option to express "the next hook,
not the one I just resumed", and its doc says why the old predicate is
not sufficient on its own.
Also narrows the ended-run claim: the by-token lookup still validates
that a hook holds the token, so the silent case needs the hook to
outlive its run (minimum retention, or before the token is released).
@VaguelySerious
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marked this pull request as ready for review
August 25, 2026 23:13
@VaguelySerious
Keep a durable resume for the step-abort ordering barrier
2db81fd
The abort path's own comment states the invariant: a step that aborts a
shared AbortController resumes a hook to record the abort, and that
write must be committed before the step completes, or the continuation
`step_completed` enqueues dispatches the next step with a stale,
non-aborted signal. It routes the resume to `preCompletionOps` for
exactly that reason.
Awaiting a lazy `resumeHook()` no longer supplies it: it resolves when
the resume is published, leaving the write to the consumer. So
preCompletionOps kept its ordering while the thing being ordered moved
out from under it, and `abortFromStepWorkflow` started failing with
stepSawAborted=false alongside workflowAborted=true — the stale-signal
dispatch, exactly as described.
Add `resumeHookDurable()`, which forces the sequential path, and use it
there. The gate checks it first so the span reads
`resume_fallback_reason: durable_required` rather than naming whichever
other condition happened to fail. The round trip it costs is the right
price for an internal barrier; the lazy path is for the external resume
it was written for.
abort-controller-step.test.ts mocks the two entry points separately, so
a regression to the lazy one shows up as the durable mock going
uncalled.
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Approved.
Checked the lazy-resume producer/consumer flow and its fallbacks: queue-publish failure, redelivery and idempotent deduplication, reusable-hook multiple resumes, terminal runs, oversized/legacy/unsupported fallbacks, and the AbortController durable-write ordering barrier.
Validation:
  • Built the affected workspace packages.
  • Ran focused core and world-local suites: 34 tests passed.
  • Started the local Next.js workflow stack and confirmed the workflow manifest was reachable.
No blocking issues found.
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No backport to stable for d9e0777 (AI decision).
This is a latency optimization plus deliberate contract change to resumeHook(): the producer no longer writes hook_received, so a resolved resume no longer implies the event is visible, and a resume against an ended run now resolves instead of throwing HookNotFoundError. It also adds new API surface (resumeHookDurable, a notHookId option on @workflow/vitest's waitForHook()) and a new lazy telemetry strategy value. None of that fixes a defect on stable; it widens an existing race window and changes observable behavior of an existing API, which is exactly what a maintenance line should not absorb.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
d9e0777eb8b1ce5f3be3fe865bc5a17fdbdb9d5d

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@VaguelySerious@karthikscale3

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[core] Never write hook_received eagerly on the lazy resume path - #3794
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Aug 26, 2026
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[core] Never write hook_received eagerly on the lazy resume path#3794
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Makes resumeHook() never create hook_received itself. It only publishes the queue message and returns; the consumer materializes the event from hookInput before it replays.
The queue message becomes the single point of durability, which it is supposed to be anyway.
Note there's an existing edge case: run goes terminal, swallows a hook_received first (can't do any work in response to the hook_received), despite the resumeHook call returning success.
Now, this edge case has a wider race window, since we don't even check at resumeHook time whether the run is terminal. The race is thus 100ms-1s wider than before.
Also, we keep around an eager-only specifically for the AbortController, because that needs an immediate confirmed hook_received insert (instead of an eventual insert).
OTEL changes: ResumedHook.resilientResume and the workflow.hook.resilient_resume span attribute are retained on the type but never set, since there is no partial outcome to report. workflow.hook.resume_strategy reports lazy (was parallel); consumers still accept parallel from producers that predate this.
@VaguelySerious
[core] Never write hook_received eagerly on the lazy resume path
7907553
resumeHook() raced its own `hook_received` write against the queue
publish, and the consumer re-ensured the same event from `hookInput`
before replay. Both sides wrote; a `(runId, resumeId)` constraint
collapsed them onto one.
Drop the producer's write. On the lazy path resumeHook() publishes one
message and nothing else, so a resume costs one round trip and the event
is created once, by the side about to replay it. The dedup constraint
still covers repeated deliveries of that message.
Two consequences:
- A failed publish now fails the resume outright: the message carries
both the trigger and the only copy of the payload, so there is nothing
persisted for a later delivery to recover.
- A resume against an ended run resolves instead of throwing
HookNotFoundError, whenever it also skipped reading the run (the
common case: the hook lookup returns the resume context inline).
Nothing resumes either way. Run-fallback resumes and the sequential
path keep their terminal checks.
`ResumedHook.resilientResume` and the `workflow.hook.resilient_resume`
span attribute are retained but never set. The resume span reports
`resume_strategy: lazy`; consumers still accept `parallel` from older
producers.
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🦋 Changeset detected
Latest commit: 2db81fd
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 20 packages
NameType
@workflow/corePatch
@workflow/vitestPatch
@workflow/worldPatch
@workflow/buildersPatch
@workflow/cliPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/web-sharedPatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/world-localPatch
@workflow/world-postgresPatch
@workflow/world-vercelPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
Not sure what this means? Click here to learn what changesets are.
Click here if you're a maintainer who wants to add another changeset to this PR
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (8 failed)
python-node (8 failed):
  • promiseAllWorkflow | wrun_41M0XKW8620GVT2WRP55HYPZSC | 🔍 observability
  • sleepingWorkflow | wrun_41M0XKWVH40GV71GF8BPKP0T9J | 🔍 observability
  • parallelSleepWorkflow | wrun_41M0XKWYC70GPJA4V38D59N3E2 | 🔍 observability
  • nullByteWorkflow | wrun_41M0XKX4SQ0GP6HZD95DV47PKN | 🔍 observability
  • cancelRun - cancelling a running workflow | wrun_41M0XKZDMG0GSB2G7GCDRQ2NQ9 | 🔍 observability
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XKZFR00GZRXDDEPFZ1HPY1 | 🔍 observability
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XKZPB90GJV2V6KE0BCPM3C | 🔍 observability
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XM069J0GPFSMSB5XV2DXAV | 🔍 observability
🌐 Cross-language Conformance (9 failed)
python (9 failed):
  • deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M0XM2RVN13GZTK3JMW2QWTAX
  • promiseAllWorkflow | wrun_41M0XKW8620GVT2WRP55HYPZSC
  • sleepingWorkflow | wrun_41M0XKWVH40GV71GF8BPKP0T9J
  • parallelSleepWorkflow | wrun_41M0XKWYC70GPJA4V38D59N3E2
  • nullByteWorkflow | wrun_41M0XKX4SQ0GP6HZD95DV47PKN
  • cancelRun - cancelling a running workflow | wrun_41M0XKZDMG0GSB2G7GCDRQ2NQ9
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XKZFR00GZRXDDEPFZ1HPY1
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XKZPB90GJV2V6KE0BCPM3C
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XM069J0GPFSMSB5XV2DXAV
⚠️ 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.
  • cancelRun via CLI - cancelling a running workflow (express)
  • cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
  • hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-turbopack)
  • hookGetConflictWorkflow - awaiting hook.getConflict() registers hook without payload (nitro)
  • hookTokenReuseLoopWorkflow - same run recreates a hook with the same token after dispose() (nuxt)
  • hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (tanstack-start)
  • hookWorkflow (tanstack-start)
🛠 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.
42 infra events
  • cold-start-warmup · suite warmup (python) · at 23:25:36Z · abandoned wrun_41M0XKS15H0GKRGMPXB3BRH801 · (+7 more)
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:25:52Z · abandoned wrun_41M0XKWP1K0GQE7ZMWK3QVV9WH
  • run-pickup-stall · nullByteWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1V0GN48M281TQWYKXD
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1R0GX4XSJKEQFHDDP4
  • run-pickup-stall · sleepingWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1R0GX4XSJKEQFHDDP3
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWPG60GSQ5YTBCAT0R7QB
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:26:26Z · abandoned wrun_41M0XKXP4D0GT11GP7CXZJERSH
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHRM0GRK595NF7QZ7VMV
  • run-pickup-stall · sleepingWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHRT0GWH385E6D5A1WY0
  • run-pickup-stall · nullByteWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHN60GP60BDTSGJHE2N5
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYJ310GPM1BBQ5ZB1HMS9
  • run-pickup-stall · instanceMethodStepWorkflow - instance methods with "use step" directive (nest) · at 23:27:01Z · abandoned wrun_41M0XKYQJ10GMHHQ9ZPEHX3WYV
  • run-pickup-stall · cancelRun - cancelling a running workflow (fastify) · at 23:27:04Z · abandoned wrun_41M0XKYVQV0GVFJEC0SVC71Y0P
  • run-pickup-stall · sleepWithSequentialStepsWorkflow - sequential steps work with concurrent sleep (control) (hono) · at 23:27:05Z · abandoned wrun_41M0XKYX620GM8Q9H32MMS55CF
  • run-pickup-stall · hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nitro) · at 23:27:05Z · abandoned wrun_41M0XKYX700GR9A3EQ51EYPKNA
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (nitro) · at 23:27:07Z · abandoned wrun_41M0XKYY5Z0GGNC8DK7M443GQ1
  • run-pickup-stall · hookSupersedeOwnerWorkflow - duplicate cancels the owner and claims the released token (nextjs-turbopack) · at 23:27:09Z · abandoned wrun_41M0XKZ0WC0GTXDYDZ02VTEM6Z
  • run-pickup-stall · abortAfterCompletionWorkflow: abort after step completes is a no-op (sveltekit) · at 23:27:10Z · abandoned wrun_41M0XKZ1Z70GTY5V3QSAH2H2RZ
  • run-pickup-stall · distributedAbortController - TTL expiration triggers signal (express) · at 23:27:14Z · abandoned wrun_41M0XKZ5M00GN1VZFNF6C3CY49
  • cold-start-warmup · suite warmup (tanstack-start) · at 23:27:15Z · abandoned wrun_01M0XKYVF0HS6PN1CC3S1FJA0N
  • cold-start-warmup · suite warmup (python) · at 23:27:41Z · abandoned wrun_01M0XKWTDZ34YVV9AMNV48892H · (+7 more)
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:27:44Z · abandoned wrun_41M0XKYNRC0GYVYJ14M2MVD0CR
  • run-pickup-stall · sleepingWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJPKHME0N782V18DW0W
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJG4G0H79RQPBWJHFE5
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJH5ZZGDY3RXKG8B6FJ
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJRRY8G09YF6PBYEGZX
  • run-pickup-stall · nullByteWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJTBEF2HGZ4XCD1FFVD
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6DYNY7ZPWTK3MRJDVB
  • run-pickup-stall · sleepingWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6FXEBKATKVRZQ3QWH8
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6KSC1A1D6SYR5MX28S
  • run-pickup-stall · nullByteWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6MK5FWT49R55M5892A
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6H2D5X39KWWRGAHQ08
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:29:27Z · abandoned wrun_41M0XM1DMW0GVYCY0X56JYVMVX
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:29:27Z · abandoned wrun_41M0XM0KXT0GXVKC45119RZFCC
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:29:56Z · abandoned wrun_01M0XM44T1HC37KPH38V1MX2KJ
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:29:56Z · abandoned wrun_01M0XM44T41428VQNKEWD0046K
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:29:56Z · abandoned wrun_01M0XM44TBYBWXSGH5CB7M1FVS
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:30:26Z · abandoned wrun_01M0XM525V7VCQ8PZYC6KW0XF0
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:30:26Z · abandoned wrun_01M0XM525T3K8J0CFCNXJRQ7FH
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:30:56Z · abandoned wrun_01M0XM5ZDEGXBD0YNDMSARKHV5
  • run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 23:31:07Z · abandoned wrun_01M0XM6ARE8E5B3NCYNWQ7RS3A
  • run-pickup-stall · concurrent hook token conflict - two workflows cannot use the same hook token simultaneously (nextjs-webpack) · at 23:31:12Z · abandoned wrun_01M0XM6FE4SE79KFHSYPFWAYW5
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production357087424320
✅ 💻 Local Development392205584480
✅ 📦 Local Production392205584480
✅ 🐘 Local Postgres392205584480
✅ 🪟 Windows32000320
❌ 🌐 Cross-language Conformance09132141
✅ vercel-http-transport8170143960
✅ vercel-multi-region270027
✅ vercel-ws-transport553087640
Total1705317277819848
Details by Category
❌ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro-node132028
✅ astro-quickjs132028
✅ example-node132028
✅ example-quickjs132028
✅ express-node132028
✅ express-quickjs132028
✅ fastify-node132028
✅ fastify-quickjs132028
✅ hono-node132028
✅ hono-quickjs132028
✅ nest-node132028
✅ nest-quickjs132028
✅ nextjs-turbopack-node15703
✅ nextjs-turbopack-quickjs15703
✅ nextjs-webpack-node15703
✅ nextjs-webpack-quickjs15703
✅ nitro-node132028
✅ nitro-quickjs132028
✅ nuxt-node132028
✅ nuxt-quickjs132028
❌ python-node08152
✅ sveltekit-node15109
✅ sveltekit-quickjs15109
✅ tanstack-start-node132028
✅ tanstack-start-quickjs132028
✅ vite-node132028
✅ vite-quickjs132028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node16000
✅ nextjs-turbopack-quickjs16000
❌ 🌐 Cross-language Conformance
AppPassedFailedSkipped
❌ python09132
✅ vercel-http-transport
AppPassedFailedSkipped
✅ example132028
✅ express132028
✅ hono132028
✅ nextjs-turbopack15703
✅ nitro132028
✅ vite132028
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
✅ vercel-ws-transport
AppPassedFailedSkipped
✅ example132028
✅ express132028
✅ nextjs-turbopack15703
✅ vite132028
📋 View full workflow run
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📊 Workflow Benchmarks
commit 2db81fd · Tue, 25 Aug 2026 23:39:23 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1207 (+75%) 🔻1295 🔴 (+25%) 🔻1325 🔴 (+26%) 🔻1467 🔴 (+28%) 🔻30
TTFSstream256 (+16%) 🔻1255 🔴 (+16%) 🔻1290 🔴 (+13%)1345 🔴 (+11%)30
TTFShook + stream1483 (+180%) 🔻1623 🔴 (+23%) 🔻1647 🔴 (+21%) 🔻2052 🔴 (+24%) 🔻30
Fan-out TTFSPromise.all(100 steps)547 (-5.0%)765 (-52%) 💚1903 (+9.4%)2019 (+12%)10
Fan-out TTLSPromise.all(100 steps)1838 (-7.9%)4757 (+17%) 🔻5109 (-30%) 💚8120 (-97%) 💚10
STSO1020 steps (inline)100 (+3.1%)121 (-12%)140 (-11%)189 (-16%) 💚1019
WO1020 steps121258 (-9.6%)121258 (-9.6%)121258 (-9.6%)121258 (-9.6%)1
CRTTfirst chunk (pooled)86 (-22%) 💚122 (-41%) 💚171 (-51%) 💚452 (+22%) 🔻28
Streams
ScenarioCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)102 (-24%)122 (-40%)176 (-38%)328 (-62%)101 (-67%)10
size sweep (100/s, 160B-12KB)102 (-30%)164 (-10%)439 (+36%)980 (+68%)118 (-41%)10
replay gateway-gpt-5.4-nano-2000t (1x)126 (-42%)111 (-33%)151 (-30%)270 (-37%)243 (-32%)3
replay eve-gpt-5.6-sol-2000t (1x)142 (-1%)116 (-29%)155 (-26%)299 (-15%)469 (+26%)2
replay eve-gpt-5.6-sol-2000t (2x)97 (-59%)146 (-39%)194 (-50%)363 (-55%)233 (-50%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 133929ms → this run 121089ms (Δ -12840ms, -10%)
 50-100 ms ┃ main 2 this 0 -2
100-150 ms ██████████████████████░┃ main 875 this 972 +97
150-200 ms ┃██ main 121 this 38 -83
200-250 ms ┃ main 12 this 6 -6
250-300 ms ┃ main 6 this 2 -4
300-350 ms ┃ main 2 this 1 -1
350-400 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······██▁···· 104.1 (-36%) 100 (-28%) 176 (-38%) 328 (-62%) 3000
sweep ······▆█▂▁··· 157.9 (-2%) 106 (-23%) 439 (+36%) 980 (+68%) 3000
gw 1x ·····▁█▆▁···· 101.7 (-29%) 96 (-27%) 151 (-30%) 270 (-37%) 5295
eve 1x ·····▁█▅▁▁··· 100.3 (-27%) 90 (-26%) 155 (-26%) 299 (-15%) 5186
eve 2x ·····▁▅█▂···· 126.1 (-38%) 115 (-30%) 194 (-50%) 363 (-55%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control ▃▂▆▂█▇▆▁▃▁ 98–114ms
sweep ▅█▄▂▃▂▂▄▁▂ 130–219ms
gw 1x ▃▃▁▂▃█▄▄▅▅ 92–117ms
eve 1x ▃▁▂▅▄▄▆█▆▁ 87–118ms
eve 2x ▄▁▂▂▁▄▅█▅▁ 108–162ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▃▆█▆▄▂▁ 156–161ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▅▄▅██▆▅▇▄ 24–36ms
sweep ▆▁▂▅█▂▆▂▃▅ 39–73ms
gw 1x ▃▅▁▁▃█▃▆▆▄ 24–35ms
eve 1x ▂▂▁▅▃▃▅▇█▂ 19–26ms
eve 2x ▇▃▁▃▆▆█▂▅▆ 17–23ms

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-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 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.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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FrameworkFlow routeStep reg.Framework output
hono200.9 KiB (±0)40.3 KiB (-214 B)1.76 MiB (-135 B)
nextjs-turbopack206.3 KiB (±0)439 B (±0)762.7 KiB (-442 B)
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.
2db81fd · run
@VaguelySerious
Handle the resume-visibility consequence of the lazy path
18b5306
`resumeHook()` returning no longer implies `hook_received` is in the log:
the consuming invocation writes it. A caller that reads the run back
immediately can see a log without it.
hook-token-reuse's first test was such a caller. It picked the next hook
to resume by "has no hook_received yet", so after the eager write went
away it was handed back the hook it had just resumed, delivered a second
payload to it, and starved the round waiting for its own. The eager
write had been acting as its barrier.
`waitForHook()` grows a `notHookId` option to express "the next hook,
not the one I just resumed", and its doc says why the old predicate is
not sufficient on its own.
Also narrows the ended-run claim: the by-token lookup still validates
that a hook holds the token, so the silent case needs the hook to
outlive its run (minimum retention, or before the token is released).
@VaguelySerious
VaguelySerious
marked this pull request as ready for review
August 25, 2026 23:13
@VaguelySerious
Keep a durable resume for the step-abort ordering barrier
2db81fd
The abort path's own comment states the invariant: a step that aborts a
shared AbortController resumes a hook to record the abort, and that
write must be committed before the step completes, or the continuation
`step_completed` enqueues dispatches the next step with a stale,
non-aborted signal. It routes the resume to `preCompletionOps` for
exactly that reason.
Awaiting a lazy `resumeHook()` no longer supplies it: it resolves when
the resume is published, leaving the write to the consumer. So
preCompletionOps kept its ordering while the thing being ordered moved
out from under it, and `abortFromStepWorkflow` started failing with
stepSawAborted=false alongside workflowAborted=true — the stale-signal
dispatch, exactly as described.
Add `resumeHookDurable()`, which forces the sequential path, and use it
there. The gate checks it first so the span reads
`resume_fallback_reason: durable_required` rather than naming whichever
other condition happened to fail. The round trip it costs is the right
price for an internal barrier; the lazy path is for the external resume
it was written for.
abort-controller-step.test.ts mocks the two entry points separately, so
a regression to the lazy one shows up as the durable mock going
uncalled.
karthikscale3
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Approved.
Checked the lazy-resume producer/consumer flow and its fallbacks: queue-publish failure, redelivery and idempotent deduplication, reusable-hook multiple resumes, terminal runs, oversized/legacy/unsupported fallbacks, and the AbortController durable-write ordering barrier.
Validation:
  • Built the affected workspace packages.
  • Ran focused core and world-local suites: 34 tests passed.
  • Started the local Next.js workflow stack and confirmed the workflow manifest was reachable.
No blocking issues found.
@VaguelySerious
VaguelySerious
merged commit d9e0777
into
mainAug 26, 2026

182 of 184 checks passed

@VaguelySerious
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deleted the

peter/lazy-only-hook-resume

branch
August 26, 2026 16:14
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No backport to stable for d9e0777 (AI decision).
This is a latency optimization plus deliberate contract change to resumeHook(): the producer no longer writes hook_received, so a resolved resume no longer implies the event is visible, and a resume against an ended run now resolves instead of throwing HookNotFoundError. It also adds new API surface (resumeHookDurable, a notHookId option on @workflow/vitest's waitForHook()) and a new lazy telemetry strategy value. None of that fixes a defect on stable; it widens an existing race window and changes observable behavior of an existing API, which is exactly what a maintenance line should not absorb.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
d9e0777eb8b1ce5f3be3fe865bc5a17fdbdb9d5d

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@VaguelySerious@karthikscale3

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

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[core] Never write hook_received eagerly on the lazy resume path - #3794
Merged
VaguelySerious merged 3 commits into
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peter/lazy-only-hook-resume
Aug 26, 2026
Merged
[core] Never write hook_received eagerly on the lazy resume path#3794
VaguelySerious merged 3 commits into
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peter/lazy-only-hook-resume
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@VaguelySerious
@VaguelySeriousVaguelySerious
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Aug 25, 2026•

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Makes resumeHook() never create hook_received itself. It only publishes the queue message and returns; the consumer materializes the event from hookInput before it replays.
The queue message becomes the single point of durability, which it is supposed to be anyway.
Note there's an existing edge case: run goes terminal, swallows a hook_received first (can't do any work in response to the hook_received), despite the resumeHook call returning success.
Now, this edge case has a wider race window, since we don't even check at resumeHook time whether the run is terminal. The race is thus 100ms-1s wider than before.
Also, we keep around an eager-only specifically for the AbortController, because that needs an immediate confirmed hook_received insert (instead of an eventual insert).
OTEL changes: ResumedHook.resilientResume and the workflow.hook.resilient_resume span attribute are retained on the type but never set, since there is no partial outcome to report. workflow.hook.resume_strategy reports lazy (was parallel); consumers still accept parallel from producers that predate this.
@VaguelySerious
[core] Never write hook_received eagerly on the lazy resume path
7907553
resumeHook() raced its own `hook_received` write against the queue
publish, and the consumer re-ensured the same event from `hookInput`
before replay. Both sides wrote; a `(runId, resumeId)` constraint
collapsed them onto one.
Drop the producer's write. On the lazy path resumeHook() publishes one
message and nothing else, so a resume costs one round trip and the event
is created once, by the side about to replay it. The dedup constraint
still covers repeated deliveries of that message.
Two consequences:
- A failed publish now fails the resume outright: the message carries
both the trigger and the only copy of the payload, so there is nothing
persisted for a later delivery to recover.
- A resume against an ended run resolves instead of throwing
HookNotFoundError, whenever it also skipped reading the run (the
common case: the hook lookup returns the resume context inline).
Nothing resumes either way. Run-fallback resumes and the sequential
path keep their terminal checks.
`ResumedHook.resilientResume` and the `workflow.hook.resilient_resume`
span attribute are retained but never set. The resume span reports
`resume_strategy: lazy`; consumers still accept `parallel` from older
producers.
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🦋 Changeset detected
Latest commit: 2db81fd
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 20 packages
NameType
@workflow/corePatch
@workflow/vitestPatch
@workflow/worldPatch
@workflow/buildersPatch
@workflow/cliPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/web-sharedPatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/world-localPatch
@workflow/world-postgresPatch
@workflow/world-vercelPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
Not sure what this means? Click here to learn what changesets are.
Click here if you're a maintainer who wants to add another changeset to this PR
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (8 failed)
python-node (8 failed):
  • promiseAllWorkflow | wrun_41M0XKW8620GVT2WRP55HYPZSC | 🔍 observability
  • sleepingWorkflow | wrun_41M0XKWVH40GV71GF8BPKP0T9J | 🔍 observability
  • parallelSleepWorkflow | wrun_41M0XKWYC70GPJA4V38D59N3E2 | 🔍 observability
  • nullByteWorkflow | wrun_41M0XKX4SQ0GP6HZD95DV47PKN | 🔍 observability
  • cancelRun - cancelling a running workflow | wrun_41M0XKZDMG0GSB2G7GCDRQ2NQ9 | 🔍 observability
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XKZFR00GZRXDDEPFZ1HPY1 | 🔍 observability
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XKZPB90GJV2V6KE0BCPM3C | 🔍 observability
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XM069J0GPFSMSB5XV2DXAV | 🔍 observability
🌐 Cross-language Conformance (9 failed)
python (9 failed):
  • deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M0XM2RVN13GZTK3JMW2QWTAX
  • promiseAllWorkflow | wrun_41M0XKW8620GVT2WRP55HYPZSC
  • sleepingWorkflow | wrun_41M0XKWVH40GV71GF8BPKP0T9J
  • parallelSleepWorkflow | wrun_41M0XKWYC70GPJA4V38D59N3E2
  • nullByteWorkflow | wrun_41M0XKX4SQ0GP6HZD95DV47PKN
  • cancelRun - cancelling a running workflow | wrun_41M0XKZDMG0GSB2G7GCDRQ2NQ9
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XKZFR00GZRXDDEPFZ1HPY1
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XKZPB90GJV2V6KE0BCPM3C
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XM069J0GPFSMSB5XV2DXAV
⚠️ 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.
  • cancelRun via CLI - cancelling a running workflow (express)
  • cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
  • hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-turbopack)
  • hookGetConflictWorkflow - awaiting hook.getConflict() registers hook without payload (nitro)
  • hookTokenReuseLoopWorkflow - same run recreates a hook with the same token after dispose() (nuxt)
  • hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (tanstack-start)
  • hookWorkflow (tanstack-start)
🛠 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.
42 infra events
  • cold-start-warmup · suite warmup (python) · at 23:25:36Z · abandoned wrun_41M0XKS15H0GKRGMPXB3BRH801 · (+7 more)
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:25:52Z · abandoned wrun_41M0XKWP1K0GQE7ZMWK3QVV9WH
  • run-pickup-stall · nullByteWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1V0GN48M281TQWYKXD
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1R0GX4XSJKEQFHDDP4
  • run-pickup-stall · sleepingWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1R0GX4XSJKEQFHDDP3
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWPG60GSQ5YTBCAT0R7QB
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:26:26Z · abandoned wrun_41M0XKXP4D0GT11GP7CXZJERSH
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHRM0GRK595NF7QZ7VMV
  • run-pickup-stall · sleepingWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHRT0GWH385E6D5A1WY0
  • run-pickup-stall · nullByteWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHN60GP60BDTSGJHE2N5
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYJ310GPM1BBQ5ZB1HMS9
  • run-pickup-stall · instanceMethodStepWorkflow - instance methods with "use step" directive (nest) · at 23:27:01Z · abandoned wrun_41M0XKYQJ10GMHHQ9ZPEHX3WYV
  • run-pickup-stall · cancelRun - cancelling a running workflow (fastify) · at 23:27:04Z · abandoned wrun_41M0XKYVQV0GVFJEC0SVC71Y0P
  • run-pickup-stall · sleepWithSequentialStepsWorkflow - sequential steps work with concurrent sleep (control) (hono) · at 23:27:05Z · abandoned wrun_41M0XKYX620GM8Q9H32MMS55CF
  • run-pickup-stall · hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nitro) · at 23:27:05Z · abandoned wrun_41M0XKYX700GR9A3EQ51EYPKNA
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (nitro) · at 23:27:07Z · abandoned wrun_41M0XKYY5Z0GGNC8DK7M443GQ1
  • run-pickup-stall · hookSupersedeOwnerWorkflow - duplicate cancels the owner and claims the released token (nextjs-turbopack) · at 23:27:09Z · abandoned wrun_41M0XKZ0WC0GTXDYDZ02VTEM6Z
  • run-pickup-stall · abortAfterCompletionWorkflow: abort after step completes is a no-op (sveltekit) · at 23:27:10Z · abandoned wrun_41M0XKZ1Z70GTY5V3QSAH2H2RZ
  • run-pickup-stall · distributedAbortController - TTL expiration triggers signal (express) · at 23:27:14Z · abandoned wrun_41M0XKZ5M00GN1VZFNF6C3CY49
  • cold-start-warmup · suite warmup (tanstack-start) · at 23:27:15Z · abandoned wrun_01M0XKYVF0HS6PN1CC3S1FJA0N
  • cold-start-warmup · suite warmup (python) · at 23:27:41Z · abandoned wrun_01M0XKWTDZ34YVV9AMNV48892H · (+7 more)
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:27:44Z · abandoned wrun_41M0XKYNRC0GYVYJ14M2MVD0CR
  • run-pickup-stall · sleepingWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJPKHME0N782V18DW0W
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJG4G0H79RQPBWJHFE5
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJH5ZZGDY3RXKG8B6FJ
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJRRY8G09YF6PBYEGZX
  • run-pickup-stall · nullByteWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJTBEF2HGZ4XCD1FFVD
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6DYNY7ZPWTK3MRJDVB
  • run-pickup-stall · sleepingWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6FXEBKATKVRZQ3QWH8
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6KSC1A1D6SYR5MX28S
  • run-pickup-stall · nullByteWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6MK5FWT49R55M5892A
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6H2D5X39KWWRGAHQ08
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:29:27Z · abandoned wrun_41M0XM1DMW0GVYCY0X56JYVMVX
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:29:27Z · abandoned wrun_41M0XM0KXT0GXVKC45119RZFCC
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:29:56Z · abandoned wrun_01M0XM44T1HC37KPH38V1MX2KJ
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:29:56Z · abandoned wrun_01M0XM44T41428VQNKEWD0046K
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:29:56Z · abandoned wrun_01M0XM44TBYBWXSGH5CB7M1FVS
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:30:26Z · abandoned wrun_01M0XM525V7VCQ8PZYC6KW0XF0
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:30:26Z · abandoned wrun_01M0XM525T3K8J0CFCNXJRQ7FH
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:30:56Z · abandoned wrun_01M0XM5ZDEGXBD0YNDMSARKHV5
  • run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 23:31:07Z · abandoned wrun_01M0XM6ARE8E5B3NCYNWQ7RS3A
  • run-pickup-stall · concurrent hook token conflict - two workflows cannot use the same hook token simultaneously (nextjs-webpack) · at 23:31:12Z · abandoned wrun_01M0XM6FE4SE79KFHSYPFWAYW5
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production357087424320
✅ 💻 Local Development392205584480
✅ 📦 Local Production392205584480
✅ 🐘 Local Postgres392205584480
✅ 🪟 Windows32000320
❌ 🌐 Cross-language Conformance09132141
✅ vercel-http-transport8170143960
✅ vercel-multi-region270027
✅ vercel-ws-transport553087640
Total1705317277819848
Details by Category
❌ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro-node132028
✅ astro-quickjs132028
✅ example-node132028
✅ example-quickjs132028
✅ express-node132028
✅ express-quickjs132028
✅ fastify-node132028
✅ fastify-quickjs132028
✅ hono-node132028
✅ hono-quickjs132028
✅ nest-node132028
✅ nest-quickjs132028
✅ nextjs-turbopack-node15703
✅ nextjs-turbopack-quickjs15703
✅ nextjs-webpack-node15703
✅ nextjs-webpack-quickjs15703
✅ nitro-node132028
✅ nitro-quickjs132028
✅ nuxt-node132028
✅ nuxt-quickjs132028
❌ python-node08152
✅ sveltekit-node15109
✅ sveltekit-quickjs15109
✅ tanstack-start-node132028
✅ tanstack-start-quickjs132028
✅ vite-node132028
✅ vite-quickjs132028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node134026
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✅ nextjs-turbopack-canary-quickjs141019
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✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
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📋 View full workflow run
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📊 Workflow Benchmarks
commit 2db81fd · Tue, 25 Aug 2026 23:39:23 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1207 (+75%) 🔻1295 🔴 (+25%) 🔻1325 🔴 (+26%) 🔻1467 🔴 (+28%) 🔻30
TTFSstream256 (+16%) 🔻1255 🔴 (+16%) 🔻1290 🔴 (+13%)1345 🔴 (+11%)30
TTFShook + stream1483 (+180%) 🔻1623 🔴 (+23%) 🔻1647 🔴 (+21%) 🔻2052 🔴 (+24%) 🔻30
Fan-out TTFSPromise.all(100 steps)547 (-5.0%)765 (-52%) 💚1903 (+9.4%)2019 (+12%)10
Fan-out TTLSPromise.all(100 steps)1838 (-7.9%)4757 (+17%) 🔻5109 (-30%) 💚8120 (-97%) 💚10
STSO1020 steps (inline)100 (+3.1%)121 (-12%)140 (-11%)189 (-16%) 💚1019
WO1020 steps121258 (-9.6%)121258 (-9.6%)121258 (-9.6%)121258 (-9.6%)1
CRTTfirst chunk (pooled)86 (-22%) 💚122 (-41%) 💚171 (-51%) 💚452 (+22%) 🔻28
Streams
ScenarioCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)102 (-24%)122 (-40%)176 (-38%)328 (-62%)101 (-67%)10
size sweep (100/s, 160B-12KB)102 (-30%)164 (-10%)439 (+36%)980 (+68%)118 (-41%)10
replay gateway-gpt-5.4-nano-2000t (1x)126 (-42%)111 (-33%)151 (-30%)270 (-37%)243 (-32%)3
replay eve-gpt-5.6-sol-2000t (1x)142 (-1%)116 (-29%)155 (-26%)299 (-15%)469 (+26%)2
replay eve-gpt-5.6-sol-2000t (2x)97 (-59%)146 (-39%)194 (-50%)363 (-55%)233 (-50%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 133929ms → this run 121089ms (Δ -12840ms, -10%)
 50-100 ms ┃ main 2 this 0 -2
100-150 ms ██████████████████████░┃ main 875 this 972 +97
150-200 ms ┃██ main 121 this 38 -83
200-250 ms ┃ main 12 this 6 -6
250-300 ms ┃ main 6 this 2 -4
300-350 ms ┃ main 2 this 1 -1
350-400 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······██▁···· 104.1 (-36%) 100 (-28%) 176 (-38%) 328 (-62%) 3000
sweep ······▆█▂▁··· 157.9 (-2%) 106 (-23%) 439 (+36%) 980 (+68%) 3000
gw 1x ·····▁█▆▁···· 101.7 (-29%) 96 (-27%) 151 (-30%) 270 (-37%) 5295
eve 1x ·····▁█▅▁▁··· 100.3 (-27%) 90 (-26%) 155 (-26%) 299 (-15%) 5186
eve 2x ·····▁▅█▂···· 126.1 (-38%) 115 (-30%) 194 (-50%) 363 (-55%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control ▃▂▆▂█▇▆▁▃▁ 98–114ms
sweep ▅█▄▂▃▂▂▄▁▂ 130–219ms
gw 1x ▃▃▁▂▃█▄▄▅▅ 92–117ms
eve 1x ▃▁▂▅▄▄▆█▆▁ 87–118ms
eve 2x ▄▁▂▂▁▄▅█▅▁ 108–162ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▃▆█▆▄▂▁ 156–161ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▅▄▅██▆▅▇▄ 24–36ms
sweep ▆▁▂▅█▂▆▂▃▅ 39–73ms
gw 1x ▃▅▁▁▃█▃▆▆▄ 24–35ms
eve 1x ▂▂▁▅▃▃▅▇█▂ 19–26ms
eve 2x ▇▃▁▃▆▆█▂▅▆ 17–23ms

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-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 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.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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FrameworkFlow routeStep reg.Framework output
hono200.9 KiB (±0)40.3 KiB (-214 B)1.76 MiB (-135 B)
nextjs-turbopack206.3 KiB (±0)439 B (±0)762.7 KiB (-442 B)
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.
2db81fd · run
@VaguelySerious
Handle the resume-visibility consequence of the lazy path
18b5306
`resumeHook()` returning no longer implies `hook_received` is in the log:
the consuming invocation writes it. A caller that reads the run back
immediately can see a log without it.
hook-token-reuse's first test was such a caller. It picked the next hook
to resume by "has no hook_received yet", so after the eager write went
away it was handed back the hook it had just resumed, delivered a second
payload to it, and starved the round waiting for its own. The eager
write had been acting as its barrier.
`waitForHook()` grows a `notHookId` option to express "the next hook,
not the one I just resumed", and its doc says why the old predicate is
not sufficient on its own.
Also narrows the ended-run claim: the by-token lookup still validates
that a hook holds the token, so the silent case needs the hook to
outlive its run (minimum retention, or before the token is released).
@VaguelySerious
VaguelySerious
marked this pull request as ready for review
August 25, 2026 23:13
@VaguelySerious
Keep a durable resume for the step-abort ordering barrier
2db81fd
The abort path's own comment states the invariant: a step that aborts a
shared AbortController resumes a hook to record the abort, and that
write must be committed before the step completes, or the continuation
`step_completed` enqueues dispatches the next step with a stale,
non-aborted signal. It routes the resume to `preCompletionOps` for
exactly that reason.
Awaiting a lazy `resumeHook()` no longer supplies it: it resolves when
the resume is published, leaving the write to the consumer. So
preCompletionOps kept its ordering while the thing being ordered moved
out from under it, and `abortFromStepWorkflow` started failing with
stepSawAborted=false alongside workflowAborted=true — the stale-signal
dispatch, exactly as described.
Add `resumeHookDurable()`, which forces the sequential path, and use it
there. The gate checks it first so the span reads
`resume_fallback_reason: durable_required` rather than naming whichever
other condition happened to fail. The round trip it costs is the right
price for an internal barrier; the lazy path is for the external resume
it was written for.
abort-controller-step.test.ts mocks the two entry points separately, so
a regression to the lazy one shows up as the durable mock going
uncalled.
karthikscale3
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Approved.
Checked the lazy-resume producer/consumer flow and its fallbacks: queue-publish failure, redelivery and idempotent deduplication, reusable-hook multiple resumes, terminal runs, oversized/legacy/unsupported fallbacks, and the AbortController durable-write ordering barrier.
Validation:
  • Built the affected workspace packages.
  • Ran focused core and world-local suites: 34 tests passed.
  • Started the local Next.js workflow stack and confirmed the workflow manifest was reachable.
No blocking issues found.
@VaguelySerious
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merged commit d9e0777
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August 26, 2026 16:14
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No backport to stable for d9e0777 (AI decision).
This is a latency optimization plus deliberate contract change to resumeHook(): the producer no longer writes hook_received, so a resolved resume no longer implies the event is visible, and a resume against an ended run now resolves instead of throwing HookNotFoundError. It also adds new API surface (resumeHookDurable, a notHookId option on @workflow/vitest's waitForHook()) and a new lazy telemetry strategy value. None of that fixes a defect on stable; it widens an existing race window and changes observable behavior of an existing API, which is exactly what a maintenance line should not absorb.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
d9e0777eb8b1ce5f3be3fe865bc5a17fdbdb9d5d

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@karthikscale3karthikscale3karthikscale3 approved these changes
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@VaguelySerious@karthikscale3

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if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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[core] Never write hook_received eagerly on the lazy resume path - #3794
Merged
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peter/lazy-only-hook-resume
Aug 26, 2026
Merged
[core] Never write hook_received eagerly on the lazy resume path#3794
VaguelySerious merged 3 commits into
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@VaguelySerious
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Makes resumeHook() never create hook_received itself. It only publishes the queue message and returns; the consumer materializes the event from hookInput before it replays.
The queue message becomes the single point of durability, which it is supposed to be anyway.
Note there's an existing edge case: run goes terminal, swallows a hook_received first (can't do any work in response to the hook_received), despite the resumeHook call returning success.
Now, this edge case has a wider race window, since we don't even check at resumeHook time whether the run is terminal. The race is thus 100ms-1s wider than before.
Also, we keep around an eager-only specifically for the AbortController, because that needs an immediate confirmed hook_received insert (instead of an eventual insert).
OTEL changes: ResumedHook.resilientResume and the workflow.hook.resilient_resume span attribute are retained on the type but never set, since there is no partial outcome to report. workflow.hook.resume_strategy reports lazy (was parallel); consumers still accept parallel from producers that predate this.
@VaguelySerious
[core] Never write hook_received eagerly on the lazy resume path
7907553
resumeHook() raced its own `hook_received` write against the queue
publish, and the consumer re-ensured the same event from `hookInput`
before replay. Both sides wrote; a `(runId, resumeId)` constraint
collapsed them onto one.
Drop the producer's write. On the lazy path resumeHook() publishes one
message and nothing else, so a resume costs one round trip and the event
is created once, by the side about to replay it. The dedup constraint
still covers repeated deliveries of that message.
Two consequences:
- A failed publish now fails the resume outright: the message carries
both the trigger and the only copy of the payload, so there is nothing
persisted for a later delivery to recover.
- A resume against an ended run resolves instead of throwing
HookNotFoundError, whenever it also skipped reading the run (the
common case: the hook lookup returns the resume context inline).
Nothing resumes either way. Run-fallback resumes and the sequential
path keep their terminal checks.
`ResumedHook.resilientResume` and the `workflow.hook.resilient_resume`
span attribute are retained but never set. The resume span reports
`resume_strategy: lazy`; consumers still accept `parallel` from older
producers.
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🦋 Changeset detected
Latest commit: 2db81fd
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 20 packages
NameType
@workflow/corePatch
@workflow/vitestPatch
@workflow/worldPatch
@workflow/buildersPatch
@workflow/cliPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/web-sharedPatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/world-localPatch
@workflow/world-postgresPatch
@workflow/world-vercelPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
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example-nextjs-workflow-turbopackReadyReadyPreview, v0Aug 25, 2026 11:25pm
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (8 failed)
python-node (8 failed):
  • promiseAllWorkflow | wrun_41M0XKW8620GVT2WRP55HYPZSC | 🔍 observability
  • sleepingWorkflow | wrun_41M0XKWVH40GV71GF8BPKP0T9J | 🔍 observability
  • parallelSleepWorkflow | wrun_41M0XKWYC70GPJA4V38D59N3E2 | 🔍 observability
  • nullByteWorkflow | wrun_41M0XKX4SQ0GP6HZD95DV47PKN | 🔍 observability
  • cancelRun - cancelling a running workflow | wrun_41M0XKZDMG0GSB2G7GCDRQ2NQ9 | 🔍 observability
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XKZFR00GZRXDDEPFZ1HPY1 | 🔍 observability
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XKZPB90GJV2V6KE0BCPM3C | 🔍 observability
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XM069J0GPFSMSB5XV2DXAV | 🔍 observability
🌐 Cross-language Conformance (9 failed)
python (9 failed):
  • deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M0XM2RVN13GZTK3JMW2QWTAX
  • promiseAllWorkflow | wrun_41M0XKW8620GVT2WRP55HYPZSC
  • sleepingWorkflow | wrun_41M0XKWVH40GV71GF8BPKP0T9J
  • parallelSleepWorkflow | wrun_41M0XKWYC70GPJA4V38D59N3E2
  • nullByteWorkflow | wrun_41M0XKX4SQ0GP6HZD95DV47PKN
  • cancelRun - cancelling a running workflow | wrun_41M0XKZDMG0GSB2G7GCDRQ2NQ9
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XKZFR00GZRXDDEPFZ1HPY1
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XKZPB90GJV2V6KE0BCPM3C
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XM069J0GPFSMSB5XV2DXAV
⚠️ 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.
  • cancelRun via CLI - cancelling a running workflow (express)
  • cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
  • hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-turbopack)
  • hookGetConflictWorkflow - awaiting hook.getConflict() registers hook without payload (nitro)
  • hookTokenReuseLoopWorkflow - same run recreates a hook with the same token after dispose() (nuxt)
  • hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (tanstack-start)
  • hookWorkflow (tanstack-start)
🛠 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.
42 infra events
  • cold-start-warmup · suite warmup (python) · at 23:25:36Z · abandoned wrun_41M0XKS15H0GKRGMPXB3BRH801 · (+7 more)
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:25:52Z · abandoned wrun_41M0XKWP1K0GQE7ZMWK3QVV9WH
  • run-pickup-stall · nullByteWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1V0GN48M281TQWYKXD
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1R0GX4XSJKEQFHDDP4
  • run-pickup-stall · sleepingWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1R0GX4XSJKEQFHDDP3
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWPG60GSQ5YTBCAT0R7QB
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:26:26Z · abandoned wrun_41M0XKXP4D0GT11GP7CXZJERSH
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHRM0GRK595NF7QZ7VMV
  • run-pickup-stall · sleepingWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHRT0GWH385E6D5A1WY0
  • run-pickup-stall · nullByteWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHN60GP60BDTSGJHE2N5
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYJ310GPM1BBQ5ZB1HMS9
  • run-pickup-stall · instanceMethodStepWorkflow - instance methods with "use step" directive (nest) · at 23:27:01Z · abandoned wrun_41M0XKYQJ10GMHHQ9ZPEHX3WYV
  • run-pickup-stall · cancelRun - cancelling a running workflow (fastify) · at 23:27:04Z · abandoned wrun_41M0XKYVQV0GVFJEC0SVC71Y0P
  • run-pickup-stall · sleepWithSequentialStepsWorkflow - sequential steps work with concurrent sleep (control) (hono) · at 23:27:05Z · abandoned wrun_41M0XKYX620GM8Q9H32MMS55CF
  • run-pickup-stall · hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nitro) · at 23:27:05Z · abandoned wrun_41M0XKYX700GR9A3EQ51EYPKNA
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (nitro) · at 23:27:07Z · abandoned wrun_41M0XKYY5Z0GGNC8DK7M443GQ1
  • run-pickup-stall · hookSupersedeOwnerWorkflow - duplicate cancels the owner and claims the released token (nextjs-turbopack) · at 23:27:09Z · abandoned wrun_41M0XKZ0WC0GTXDYDZ02VTEM6Z
  • run-pickup-stall · abortAfterCompletionWorkflow: abort after step completes is a no-op (sveltekit) · at 23:27:10Z · abandoned wrun_41M0XKZ1Z70GTY5V3QSAH2H2RZ
  • run-pickup-stall · distributedAbortController - TTL expiration triggers signal (express) · at 23:27:14Z · abandoned wrun_41M0XKZ5M00GN1VZFNF6C3CY49
  • cold-start-warmup · suite warmup (tanstack-start) · at 23:27:15Z · abandoned wrun_01M0XKYVF0HS6PN1CC3S1FJA0N
  • cold-start-warmup · suite warmup (python) · at 23:27:41Z · abandoned wrun_01M0XKWTDZ34YVV9AMNV48892H · (+7 more)
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:27:44Z · abandoned wrun_41M0XKYNRC0GYVYJ14M2MVD0CR
  • run-pickup-stall · sleepingWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJPKHME0N782V18DW0W
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJG4G0H79RQPBWJHFE5
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJH5ZZGDY3RXKG8B6FJ
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJRRY8G09YF6PBYEGZX
  • run-pickup-stall · nullByteWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJTBEF2HGZ4XCD1FFVD
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6DYNY7ZPWTK3MRJDVB
  • run-pickup-stall · sleepingWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6FXEBKATKVRZQ3QWH8
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6KSC1A1D6SYR5MX28S
  • run-pickup-stall · nullByteWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6MK5FWT49R55M5892A
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6H2D5X39KWWRGAHQ08
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:29:27Z · abandoned wrun_41M0XM1DMW0GVYCY0X56JYVMVX
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:29:27Z · abandoned wrun_41M0XM0KXT0GXVKC45119RZFCC
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:29:56Z · abandoned wrun_01M0XM44T1HC37KPH38V1MX2KJ
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:29:56Z · abandoned wrun_01M0XM44T41428VQNKEWD0046K
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:29:56Z · abandoned wrun_01M0XM44TBYBWXSGH5CB7M1FVS
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:30:26Z · abandoned wrun_01M0XM525V7VCQ8PZYC6KW0XF0
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:30:26Z · abandoned wrun_01M0XM525T3K8J0CFCNXJRQ7FH
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:30:56Z · abandoned wrun_01M0XM5ZDEGXBD0YNDMSARKHV5
  • run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 23:31:07Z · abandoned wrun_01M0XM6ARE8E5B3NCYNWQ7RS3A
  • run-pickup-stall · concurrent hook token conflict - two workflows cannot use the same hook token simultaneously (nextjs-webpack) · at 23:31:12Z · abandoned wrun_01M0XM6FE4SE79KFHSYPFWAYW5
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production357087424320
✅ 💻 Local Development392205584480
✅ 📦 Local Production392205584480
✅ 🐘 Local Postgres392205584480
✅ 🪟 Windows32000320
❌ 🌐 Cross-language Conformance09132141
✅ vercel-http-transport8170143960
✅ vercel-multi-region270027
✅ vercel-ws-transport553087640
Total1705317277819848
Details by Category
❌ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro-node132028
✅ astro-quickjs132028
✅ example-node132028
✅ example-quickjs132028
✅ express-node132028
✅ express-quickjs132028
✅ fastify-node132028
✅ fastify-quickjs132028
✅ hono-node132028
✅ hono-quickjs132028
✅ nest-node132028
✅ nest-quickjs132028
✅ nextjs-turbopack-node15703
✅ nextjs-turbopack-quickjs15703
✅ nextjs-webpack-node15703
✅ nextjs-webpack-quickjs15703
✅ nitro-node132028
✅ nitro-quickjs132028
✅ nuxt-node132028
✅ nuxt-quickjs132028
❌ python-node08152
✅ sveltekit-node15109
✅ sveltekit-quickjs15109
✅ tanstack-start-node132028
✅ tanstack-start-quickjs132028
✅ vite-node132028
✅ vite-quickjs132028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node16000
✅ nextjs-turbopack-quickjs16000
❌ 🌐 Cross-language Conformance
AppPassedFailedSkipped
❌ python09132
✅ vercel-http-transport
AppPassedFailedSkipped
✅ example132028
✅ express132028
✅ hono132028
✅ nextjs-turbopack15703
✅ nitro132028
✅ vite132028
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
✅ vercel-ws-transport
AppPassedFailedSkipped
✅ example132028
✅ express132028
✅ nextjs-turbopack15703
✅ vite132028
📋 View full workflow run
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📊 Workflow Benchmarks
commit 2db81fd · Tue, 25 Aug 2026 23:39:23 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1207 (+75%) 🔻1295 🔴 (+25%) 🔻1325 🔴 (+26%) 🔻1467 🔴 (+28%) 🔻30
TTFSstream256 (+16%) 🔻1255 🔴 (+16%) 🔻1290 🔴 (+13%)1345 🔴 (+11%)30
TTFShook + stream1483 (+180%) 🔻1623 🔴 (+23%) 🔻1647 🔴 (+21%) 🔻2052 🔴 (+24%) 🔻30
Fan-out TTFSPromise.all(100 steps)547 (-5.0%)765 (-52%) 💚1903 (+9.4%)2019 (+12%)10
Fan-out TTLSPromise.all(100 steps)1838 (-7.9%)4757 (+17%) 🔻5109 (-30%) 💚8120 (-97%) 💚10
STSO1020 steps (inline)100 (+3.1%)121 (-12%)140 (-11%)189 (-16%) 💚1019
WO1020 steps121258 (-9.6%)121258 (-9.6%)121258 (-9.6%)121258 (-9.6%)1
CRTTfirst chunk (pooled)86 (-22%) 💚122 (-41%) 💚171 (-51%) 💚452 (+22%) 🔻28
Streams
ScenarioCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)102 (-24%)122 (-40%)176 (-38%)328 (-62%)101 (-67%)10
size sweep (100/s, 160B-12KB)102 (-30%)164 (-10%)439 (+36%)980 (+68%)118 (-41%)10
replay gateway-gpt-5.4-nano-2000t (1x)126 (-42%)111 (-33%)151 (-30%)270 (-37%)243 (-32%)3
replay eve-gpt-5.6-sol-2000t (1x)142 (-1%)116 (-29%)155 (-26%)299 (-15%)469 (+26%)2
replay eve-gpt-5.6-sol-2000t (2x)97 (-59%)146 (-39%)194 (-50%)363 (-55%)233 (-50%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 133929ms → this run 121089ms (Δ -12840ms, -10%)
 50-100 ms ┃ main 2 this 0 -2
100-150 ms ██████████████████████░┃ main 875 this 972 +97
150-200 ms ┃██ main 121 this 38 -83
200-250 ms ┃ main 12 this 6 -6
250-300 ms ┃ main 6 this 2 -4
300-350 ms ┃ main 2 this 1 -1
350-400 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······██▁···· 104.1 (-36%) 100 (-28%) 176 (-38%) 328 (-62%) 3000
sweep ······▆█▂▁··· 157.9 (-2%) 106 (-23%) 439 (+36%) 980 (+68%) 3000
gw 1x ·····▁█▆▁···· 101.7 (-29%) 96 (-27%) 151 (-30%) 270 (-37%) 5295
eve 1x ·····▁█▅▁▁··· 100.3 (-27%) 90 (-26%) 155 (-26%) 299 (-15%) 5186
eve 2x ·····▁▅█▂···· 126.1 (-38%) 115 (-30%) 194 (-50%) 363 (-55%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control ▃▂▆▂█▇▆▁▃▁ 98–114ms
sweep ▅█▄▂▃▂▂▄▁▂ 130–219ms
gw 1x ▃▃▁▂▃█▄▄▅▅ 92–117ms
eve 1x ▃▁▂▅▄▄▆█▆▁ 87–118ms
eve 2x ▄▁▂▂▁▄▅█▅▁ 108–162ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▃▆█▆▄▂▁ 156–161ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▅▄▅██▆▅▇▄ 24–36ms
sweep ▆▁▂▅█▂▆▂▃▅ 39–73ms
gw 1x ▃▅▁▁▃█▃▆▆▄ 24–35ms
eve 1x ▂▂▁▅▃▃▅▇█▂ 19–26ms
eve 2x ▇▃▁▃▆▆█▂▅▆ 17–23ms

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-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 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.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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FrameworkFlow routeStep reg.Framework output
hono200.9 KiB (±0)40.3 KiB (-214 B)1.76 MiB (-135 B)
nextjs-turbopack206.3 KiB (±0)439 B (±0)762.7 KiB (-442 B)
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.
2db81fd · run
@VaguelySerious
Handle the resume-visibility consequence of the lazy path
18b5306
`resumeHook()` returning no longer implies `hook_received` is in the log:
the consuming invocation writes it. A caller that reads the run back
immediately can see a log without it.
hook-token-reuse's first test was such a caller. It picked the next hook
to resume by "has no hook_received yet", so after the eager write went
away it was handed back the hook it had just resumed, delivered a second
payload to it, and starved the round waiting for its own. The eager
write had been acting as its barrier.
`waitForHook()` grows a `notHookId` option to express "the next hook,
not the one I just resumed", and its doc says why the old predicate is
not sufficient on its own.
Also narrows the ended-run claim: the by-token lookup still validates
that a hook holds the token, so the silent case needs the hook to
outlive its run (minimum retention, or before the token is released).
@VaguelySerious
VaguelySerious
marked this pull request as ready for review
August 25, 2026 23:13
@VaguelySerious
Keep a durable resume for the step-abort ordering barrier
2db81fd
The abort path's own comment states the invariant: a step that aborts a
shared AbortController resumes a hook to record the abort, and that
write must be committed before the step completes, or the continuation
`step_completed` enqueues dispatches the next step with a stale,
non-aborted signal. It routes the resume to `preCompletionOps` for
exactly that reason.
Awaiting a lazy `resumeHook()` no longer supplies it: it resolves when
the resume is published, leaving the write to the consumer. So
preCompletionOps kept its ordering while the thing being ordered moved
out from under it, and `abortFromStepWorkflow` started failing with
stepSawAborted=false alongside workflowAborted=true — the stale-signal
dispatch, exactly as described.
Add `resumeHookDurable()`, which forces the sequential path, and use it
there. The gate checks it first so the span reads
`resume_fallback_reason: durable_required` rather than naming whichever
other condition happened to fail. The round trip it costs is the right
price for an internal barrier; the lazy path is for the external resume
it was written for.
abort-controller-step.test.ts mocks the two entry points separately, so
a regression to the lazy one shows up as the durable mock going
uncalled.
karthikscale3
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Approved.
Checked the lazy-resume producer/consumer flow and its fallbacks: queue-publish failure, redelivery and idempotent deduplication, reusable-hook multiple resumes, terminal runs, oversized/legacy/unsupported fallbacks, and the AbortController durable-write ordering barrier.
Validation:
  • Built the affected workspace packages.
  • Ran focused core and world-local suites: 34 tests passed.
  • Started the local Next.js workflow stack and confirmed the workflow manifest was reachable.
No blocking issues found.
@VaguelySerious
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No backport to stable for d9e0777 (AI decision).
This is a latency optimization plus deliberate contract change to resumeHook(): the producer no longer writes hook_received, so a resolved resume no longer implies the event is visible, and a resume against an ended run now resolves instead of throwing HookNotFoundError. It also adds new API surface (resumeHookDurable, a notHookId option on @workflow/vitest's waitForHook()) and a new lazy telemetry strategy value. None of that fixes a defect on stable; it widens an existing race window and changes observable behavior of an existing API, which is exactly what a maintenance line should not absorb.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
d9e0777eb8b1ce5f3be3fe865bc5a17fdbdb9d5d

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@VaguelySerious@karthikscale3

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[core] Never write hook_received eagerly on the lazy resume path - #3794
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peter/lazy-only-hook-resume
Aug 26, 2026
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[core] Never write hook_received eagerly on the lazy resume path#3794
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Makes resumeHook() never create hook_received itself. It only publishes the queue message and returns; the consumer materializes the event from hookInput before it replays.
The queue message becomes the single point of durability, which it is supposed to be anyway.
Note there's an existing edge case: run goes terminal, swallows a hook_received first (can't do any work in response to the hook_received), despite the resumeHook call returning success.
Now, this edge case has a wider race window, since we don't even check at resumeHook time whether the run is terminal. The race is thus 100ms-1s wider than before.
Also, we keep around an eager-only specifically for the AbortController, because that needs an immediate confirmed hook_received insert (instead of an eventual insert).
OTEL changes: ResumedHook.resilientResume and the workflow.hook.resilient_resume span attribute are retained on the type but never set, since there is no partial outcome to report. workflow.hook.resume_strategy reports lazy (was parallel); consumers still accept parallel from producers that predate this.
@VaguelySerious
[core] Never write hook_received eagerly on the lazy resume path
7907553
resumeHook() raced its own `hook_received` write against the queue
publish, and the consumer re-ensured the same event from `hookInput`
before replay. Both sides wrote; a `(runId, resumeId)` constraint
collapsed them onto one.
Drop the producer's write. On the lazy path resumeHook() publishes one
message and nothing else, so a resume costs one round trip and the event
is created once, by the side about to replay it. The dedup constraint
still covers repeated deliveries of that message.
Two consequences:
- A failed publish now fails the resume outright: the message carries
both the trigger and the only copy of the payload, so there is nothing
persisted for a later delivery to recover.
- A resume against an ended run resolves instead of throwing
HookNotFoundError, whenever it also skipped reading the run (the
common case: the hook lookup returns the resume context inline).
Nothing resumes either way. Run-fallback resumes and the sequential
path keep their terminal checks.
`ResumedHook.resilientResume` and the `workflow.hook.resilient_resume`
span attribute are retained but never set. The resume span reports
`resume_strategy: lazy`; consumers still accept `parallel` from older
producers.
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🦋 Changeset detected
Latest commit: 2db81fd
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 20 packages
NameType
@workflow/corePatch
@workflow/vitestPatch
@workflow/worldPatch
@workflow/buildersPatch
@workflow/cliPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/web-sharedPatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/world-localPatch
@workflow/world-postgresPatch
@workflow/world-vercelPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
Not sure what this means? Click here to learn what changesets are.
Click here if you're a maintainer who wants to add another changeset to this PR
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The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (8 failed)
python-node (8 failed):
  • promiseAllWorkflow | wrun_41M0XKW8620GVT2WRP55HYPZSC | 🔍 observability
  • sleepingWorkflow | wrun_41M0XKWVH40GV71GF8BPKP0T9J | 🔍 observability
  • parallelSleepWorkflow | wrun_41M0XKWYC70GPJA4V38D59N3E2 | 🔍 observability
  • nullByteWorkflow | wrun_41M0XKX4SQ0GP6HZD95DV47PKN | 🔍 observability
  • cancelRun - cancelling a running workflow | wrun_41M0XKZDMG0GSB2G7GCDRQ2NQ9 | 🔍 observability
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XKZFR00GZRXDDEPFZ1HPY1 | 🔍 observability
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XKZPB90GJV2V6KE0BCPM3C | 🔍 observability
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XM069J0GPFSMSB5XV2DXAV | 🔍 observability
🌐 Cross-language Conformance (9 failed)
python (9 failed):
  • deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M0XM2RVN13GZTK3JMW2QWTAX
  • promiseAllWorkflow | wrun_41M0XKW8620GVT2WRP55HYPZSC
  • sleepingWorkflow | wrun_41M0XKWVH40GV71GF8BPKP0T9J
  • parallelSleepWorkflow | wrun_41M0XKWYC70GPJA4V38D59N3E2
  • nullByteWorkflow | wrun_41M0XKX4SQ0GP6HZD95DV47PKN
  • cancelRun - cancelling a running workflow | wrun_41M0XKZDMG0GSB2G7GCDRQ2NQ9
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XKZFR00GZRXDDEPFZ1HPY1
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XKZPB90GJV2V6KE0BCPM3C
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XM069J0GPFSMSB5XV2DXAV
⚠️ 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.
  • cancelRun via CLI - cancelling a running workflow (express)
  • cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
  • hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-turbopack)
  • hookGetConflictWorkflow - awaiting hook.getConflict() registers hook without payload (nitro)
  • hookTokenReuseLoopWorkflow - same run recreates a hook with the same token after dispose() (nuxt)
  • hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (tanstack-start)
  • hookWorkflow (tanstack-start)
🛠 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.
42 infra events
  • cold-start-warmup · suite warmup (python) · at 23:25:36Z · abandoned wrun_41M0XKS15H0GKRGMPXB3BRH801 · (+7 more)
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:25:52Z · abandoned wrun_41M0XKWP1K0GQE7ZMWK3QVV9WH
  • run-pickup-stall · nullByteWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1V0GN48M281TQWYKXD
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1R0GX4XSJKEQFHDDP4
  • run-pickup-stall · sleepingWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1R0GX4XSJKEQFHDDP3
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWPG60GSQ5YTBCAT0R7QB
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:26:26Z · abandoned wrun_41M0XKXP4D0GT11GP7CXZJERSH
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHRM0GRK595NF7QZ7VMV
  • run-pickup-stall · sleepingWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHRT0GWH385E6D5A1WY0
  • run-pickup-stall · nullByteWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHN60GP60BDTSGJHE2N5
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYJ310GPM1BBQ5ZB1HMS9
  • run-pickup-stall · instanceMethodStepWorkflow - instance methods with "use step" directive (nest) · at 23:27:01Z · abandoned wrun_41M0XKYQJ10GMHHQ9ZPEHX3WYV
  • run-pickup-stall · cancelRun - cancelling a running workflow (fastify) · at 23:27:04Z · abandoned wrun_41M0XKYVQV0GVFJEC0SVC71Y0P
  • run-pickup-stall · sleepWithSequentialStepsWorkflow - sequential steps work with concurrent sleep (control) (hono) · at 23:27:05Z · abandoned wrun_41M0XKYX620GM8Q9H32MMS55CF
  • run-pickup-stall · hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nitro) · at 23:27:05Z · abandoned wrun_41M0XKYX700GR9A3EQ51EYPKNA
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (nitro) · at 23:27:07Z · abandoned wrun_41M0XKYY5Z0GGNC8DK7M443GQ1
  • run-pickup-stall · hookSupersedeOwnerWorkflow - duplicate cancels the owner and claims the released token (nextjs-turbopack) · at 23:27:09Z · abandoned wrun_41M0XKZ0WC0GTXDYDZ02VTEM6Z
  • run-pickup-stall · abortAfterCompletionWorkflow: abort after step completes is a no-op (sveltekit) · at 23:27:10Z · abandoned wrun_41M0XKZ1Z70GTY5V3QSAH2H2RZ
  • run-pickup-stall · distributedAbortController - TTL expiration triggers signal (express) · at 23:27:14Z · abandoned wrun_41M0XKZ5M00GN1VZFNF6C3CY49
  • cold-start-warmup · suite warmup (tanstack-start) · at 23:27:15Z · abandoned wrun_01M0XKYVF0HS6PN1CC3S1FJA0N
  • cold-start-warmup · suite warmup (python) · at 23:27:41Z · abandoned wrun_01M0XKWTDZ34YVV9AMNV48892H · (+7 more)
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:27:44Z · abandoned wrun_41M0XKYNRC0GYVYJ14M2MVD0CR
  • run-pickup-stall · sleepingWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJPKHME0N782V18DW0W
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJG4G0H79RQPBWJHFE5
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJH5ZZGDY3RXKG8B6FJ
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJRRY8G09YF6PBYEGZX
  • run-pickup-stall · nullByteWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJTBEF2HGZ4XCD1FFVD
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6DYNY7ZPWTK3MRJDVB
  • run-pickup-stall · sleepingWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6FXEBKATKVRZQ3QWH8
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6KSC1A1D6SYR5MX28S
  • run-pickup-stall · nullByteWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6MK5FWT49R55M5892A
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6H2D5X39KWWRGAHQ08
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:29:27Z · abandoned wrun_41M0XM1DMW0GVYCY0X56JYVMVX
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:29:27Z · abandoned wrun_41M0XM0KXT0GXVKC45119RZFCC
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:29:56Z · abandoned wrun_01M0XM44T1HC37KPH38V1MX2KJ
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:29:56Z · abandoned wrun_01M0XM44T41428VQNKEWD0046K
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:29:56Z · abandoned wrun_01M0XM44TBYBWXSGH5CB7M1FVS
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:30:26Z · abandoned wrun_01M0XM525V7VCQ8PZYC6KW0XF0
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:30:26Z · abandoned wrun_01M0XM525T3K8J0CFCNXJRQ7FH
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:30:56Z · abandoned wrun_01M0XM5ZDEGXBD0YNDMSARKHV5
  • run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 23:31:07Z · abandoned wrun_01M0XM6ARE8E5B3NCYNWQ7RS3A
  • run-pickup-stall · concurrent hook token conflict - two workflows cannot use the same hook token simultaneously (nextjs-webpack) · at 23:31:12Z · abandoned wrun_01M0XM6FE4SE79KFHSYPFWAYW5
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production357087424320
✅ 💻 Local Development392205584480
✅ 📦 Local Production392205584480
✅ 🐘 Local Postgres392205584480
✅ 🪟 Windows32000320
❌ 🌐 Cross-language Conformance09132141
✅ vercel-http-transport8170143960
✅ vercel-multi-region270027
✅ vercel-ws-transport553087640
Total1705317277819848
Details by Category
❌ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro-node132028
✅ astro-quickjs132028
✅ example-node132028
✅ example-quickjs132028
✅ express-node132028
✅ express-quickjs132028
✅ fastify-node132028
✅ fastify-quickjs132028
✅ hono-node132028
✅ hono-quickjs132028
✅ nest-node132028
✅ nest-quickjs132028
✅ nextjs-turbopack-node15703
✅ nextjs-turbopack-quickjs15703
✅ nextjs-webpack-node15703
✅ nextjs-webpack-quickjs15703
✅ nitro-node132028
✅ nitro-quickjs132028
✅ nuxt-node132028
✅ nuxt-quickjs132028
❌ python-node08152
✅ sveltekit-node15109
✅ sveltekit-quickjs15109
✅ tanstack-start-node132028
✅ tanstack-start-quickjs132028
✅ vite-node132028
✅ vite-quickjs132028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node16000
✅ nextjs-turbopack-quickjs16000
❌ 🌐 Cross-language Conformance
AppPassedFailedSkipped
❌ python09132
✅ vercel-http-transport
AppPassedFailedSkipped
✅ example132028
✅ express132028
✅ hono132028
✅ nextjs-turbopack15703
✅ nitro132028
✅ vite132028
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
✅ vercel-ws-transport
AppPassedFailedSkipped
✅ example132028
✅ express132028
✅ nextjs-turbopack15703
✅ vite132028
📋 View full workflow run
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📊 Workflow Benchmarks
commit 2db81fd · Tue, 25 Aug 2026 23:39:23 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1207 (+75%) 🔻1295 🔴 (+25%) 🔻1325 🔴 (+26%) 🔻1467 🔴 (+28%) 🔻30
TTFSstream256 (+16%) 🔻1255 🔴 (+16%) 🔻1290 🔴 (+13%)1345 🔴 (+11%)30
TTFShook + stream1483 (+180%) 🔻1623 🔴 (+23%) 🔻1647 🔴 (+21%) 🔻2052 🔴 (+24%) 🔻30
Fan-out TTFSPromise.all(100 steps)547 (-5.0%)765 (-52%) 💚1903 (+9.4%)2019 (+12%)10
Fan-out TTLSPromise.all(100 steps)1838 (-7.9%)4757 (+17%) 🔻5109 (-30%) 💚8120 (-97%) 💚10
STSO1020 steps (inline)100 (+3.1%)121 (-12%)140 (-11%)189 (-16%) 💚1019
WO1020 steps121258 (-9.6%)121258 (-9.6%)121258 (-9.6%)121258 (-9.6%)1
CRTTfirst chunk (pooled)86 (-22%) 💚122 (-41%) 💚171 (-51%) 💚452 (+22%) 🔻28
Streams
ScenarioCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)102 (-24%)122 (-40%)176 (-38%)328 (-62%)101 (-67%)10
size sweep (100/s, 160B-12KB)102 (-30%)164 (-10%)439 (+36%)980 (+68%)118 (-41%)10
replay gateway-gpt-5.4-nano-2000t (1x)126 (-42%)111 (-33%)151 (-30%)270 (-37%)243 (-32%)3
replay eve-gpt-5.6-sol-2000t (1x)142 (-1%)116 (-29%)155 (-26%)299 (-15%)469 (+26%)2
replay eve-gpt-5.6-sol-2000t (2x)97 (-59%)146 (-39%)194 (-50%)363 (-55%)233 (-50%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 133929ms → this run 121089ms (Δ -12840ms, -10%)
 50-100 ms ┃ main 2 this 0 -2
100-150 ms ██████████████████████░┃ main 875 this 972 +97
150-200 ms ┃██ main 121 this 38 -83
200-250 ms ┃ main 12 this 6 -6
250-300 ms ┃ main 6 this 2 -4
300-350 ms ┃ main 2 this 1 -1
350-400 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······██▁···· 104.1 (-36%) 100 (-28%) 176 (-38%) 328 (-62%) 3000
sweep ······▆█▂▁··· 157.9 (-2%) 106 (-23%) 439 (+36%) 980 (+68%) 3000
gw 1x ·····▁█▆▁···· 101.7 (-29%) 96 (-27%) 151 (-30%) 270 (-37%) 5295
eve 1x ·····▁█▅▁▁··· 100.3 (-27%) 90 (-26%) 155 (-26%) 299 (-15%) 5186
eve 2x ·····▁▅█▂···· 126.1 (-38%) 115 (-30%) 194 (-50%) 363 (-55%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control ▃▂▆▂█▇▆▁▃▁ 98–114ms
sweep ▅█▄▂▃▂▂▄▁▂ 130–219ms
gw 1x ▃▃▁▂▃█▄▄▅▅ 92–117ms
eve 1x ▃▁▂▅▄▄▆█▆▁ 87–118ms
eve 2x ▄▁▂▂▁▄▅█▅▁ 108–162ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▃▆█▆▄▂▁ 156–161ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▅▄▅██▆▅▇▄ 24–36ms
sweep ▆▁▂▅█▂▆▂▃▅ 39–73ms
gw 1x ▃▅▁▁▃█▃▆▆▄ 24–35ms
eve 1x ▂▂▁▅▃▃▅▇█▂ 19–26ms
eve 2x ▇▃▁▃▆▆█▂▅▆ 17–23ms

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-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 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.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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FrameworkFlow routeStep reg.Framework output
hono200.9 KiB (±0)40.3 KiB (-214 B)1.76 MiB (-135 B)
nextjs-turbopack206.3 KiB (±0)439 B (±0)762.7 KiB (-442 B)
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.
2db81fd · run
@VaguelySerious
Handle the resume-visibility consequence of the lazy path
18b5306
`resumeHook()` returning no longer implies `hook_received` is in the log:
the consuming invocation writes it. A caller that reads the run back
immediately can see a log without it.
hook-token-reuse's first test was such a caller. It picked the next hook
to resume by "has no hook_received yet", so after the eager write went
away it was handed back the hook it had just resumed, delivered a second
payload to it, and starved the round waiting for its own. The eager
write had been acting as its barrier.
`waitForHook()` grows a `notHookId` option to express "the next hook,
not the one I just resumed", and its doc says why the old predicate is
not sufficient on its own.
Also narrows the ended-run claim: the by-token lookup still validates
that a hook holds the token, so the silent case needs the hook to
outlive its run (minimum retention, or before the token is released).
@VaguelySerious
VaguelySerious
marked this pull request as ready for review
August 25, 2026 23:13
@VaguelySerious
Keep a durable resume for the step-abort ordering barrier
2db81fd
The abort path's own comment states the invariant: a step that aborts a
shared AbortController resumes a hook to record the abort, and that
write must be committed before the step completes, or the continuation
`step_completed` enqueues dispatches the next step with a stale,
non-aborted signal. It routes the resume to `preCompletionOps` for
exactly that reason.
Awaiting a lazy `resumeHook()` no longer supplies it: it resolves when
the resume is published, leaving the write to the consumer. So
preCompletionOps kept its ordering while the thing being ordered moved
out from under it, and `abortFromStepWorkflow` started failing with
stepSawAborted=false alongside workflowAborted=true — the stale-signal
dispatch, exactly as described.
Add `resumeHookDurable()`, which forces the sequential path, and use it
there. The gate checks it first so the span reads
`resume_fallback_reason: durable_required` rather than naming whichever
other condition happened to fail. The round trip it costs is the right
price for an internal barrier; the lazy path is for the external resume
it was written for.
abort-controller-step.test.ts mocks the two entry points separately, so
a regression to the lazy one shows up as the durable mock going
uncalled.
karthikscale3
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approved these changes
Aug 26, 2026
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Approved.
Checked the lazy-resume producer/consumer flow and its fallbacks: queue-publish failure, redelivery and idempotent deduplication, reusable-hook multiple resumes, terminal runs, oversized/legacy/unsupported fallbacks, and the AbortController durable-write ordering barrier.
Validation:
  • Built the affected workspace packages.
  • Ran focused core and world-local suites: 34 tests passed.
  • Started the local Next.js workflow stack and confirmed the workflow manifest was reachable.
No blocking issues found.
@VaguelySerious
VaguelySerious
merged commit d9e0777
into
mainAug 26, 2026

182 of 184 checks passed

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deleted the

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August 26, 2026 16:14
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No backport to stable for d9e0777 (AI decision).
This is a latency optimization plus deliberate contract change to resumeHook(): the producer no longer writes hook_received, so a resolved resume no longer implies the event is visible, and a resume against an ended run now resolves instead of throwing HookNotFoundError. It also adds new API surface (resumeHookDurable, a notHookId option on @workflow/vitest's waitForHook()) and a new lazy telemetry strategy value. None of that fixes a defect on stable; it widens an existing race window and changes observable behavior of an existing API, which is exactly what a maintenance line should not absorb.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
d9e0777eb8b1ce5f3be3fe865bc5a17fdbdb9d5d

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@karthikscale3karthikscale3karthikscale3 approved these changes
@msullivanmsullivanAwaiting requested review from msullivan
@fantixfantixAwaiting requested review from fantix

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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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[core] Never write hook_received eagerly on the lazy resume path - #3794
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VaguelySerious merged 3 commits into
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peter/lazy-only-hook-resume
Aug 26, 2026
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[core] Never write hook_received eagerly on the lazy resume path#3794
VaguelySerious merged 3 commits into
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peter/lazy-only-hook-resume
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@VaguelySeriousVaguelySerious
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Makes resumeHook() never create hook_received itself. It only publishes the queue message and returns; the consumer materializes the event from hookInput before it replays.
The queue message becomes the single point of durability, which it is supposed to be anyway.
Note there's an existing edge case: run goes terminal, swallows a hook_received first (can't do any work in response to the hook_received), despite the resumeHook call returning success.
Now, this edge case has a wider race window, since we don't even check at resumeHook time whether the run is terminal. The race is thus 100ms-1s wider than before.
Also, we keep around an eager-only specifically for the AbortController, because that needs an immediate confirmed hook_received insert (instead of an eventual insert).
OTEL changes: ResumedHook.resilientResume and the workflow.hook.resilient_resume span attribute are retained on the type but never set, since there is no partial outcome to report. workflow.hook.resume_strategy reports lazy (was parallel); consumers still accept parallel from producers that predate this.
@VaguelySerious
[core] Never write hook_received eagerly on the lazy resume path
7907553
resumeHook() raced its own `hook_received` write against the queue
publish, and the consumer re-ensured the same event from `hookInput`
before replay. Both sides wrote; a `(runId, resumeId)` constraint
collapsed them onto one.
Drop the producer's write. On the lazy path resumeHook() publishes one
message and nothing else, so a resume costs one round trip and the event
is created once, by the side about to replay it. The dedup constraint
still covers repeated deliveries of that message.
Two consequences:
- A failed publish now fails the resume outright: the message carries
both the trigger and the only copy of the payload, so there is nothing
persisted for a later delivery to recover.
- A resume against an ended run resolves instead of throwing
HookNotFoundError, whenever it also skipped reading the run (the
common case: the hook lookup returns the resume context inline).
Nothing resumes either way. Run-fallback resumes and the sequential
path keep their terminal checks.
`ResumedHook.resilientResume` and the `workflow.hook.resilient_resume`
span attribute are retained but never set. The resume span reports
`resume_strategy: lazy`; consumers still accept `parallel` from older
producers.
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🦋 Changeset detected
Latest commit: 2db81fd
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 20 packages
NameType
@workflow/corePatch
@workflow/vitestPatch
@workflow/worldPatch
@workflow/buildersPatch
@workflow/cliPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/web-sharedPatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/world-localPatch
@workflow/world-postgresPatch
@workflow/world-vercelPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
Not sure what this means? Click here to learn what changesets are.
Click here if you're a maintainer who wants to add another changeset to this PR
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ProjectDeploymentActionsUpdated (UTC)
example-nextjs-workflow-turbopackReadyReadyPreview, v0Aug 25, 2026 11:25pm
example-nextjs-workflow-webpackReadyReadyPreview, v0Aug 25, 2026 11:25pm
example-workflowReadyReadyPreview, v0Aug 25, 2026 11:25pm
workbench-astro-workflowReadyReadyPreview, v0Aug 25, 2026 11:25pm
workbench-express-workflowReadyReadyPreview, v0Aug 25, 2026 11:25pm
workbench-fastify-workflowReadyReadyPreview, v0Aug 25, 2026 11:25pm
workbench-hono-workflowReadyReadyPreview, v0Aug 25, 2026 11:25pm
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workflow-webReadyReadyPreview, v0Aug 25, 2026 11:25pm
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (8 failed)
python-node (8 failed):
  • promiseAllWorkflow | wrun_41M0XKW8620GVT2WRP55HYPZSC | 🔍 observability
  • sleepingWorkflow | wrun_41M0XKWVH40GV71GF8BPKP0T9J | 🔍 observability
  • parallelSleepWorkflow | wrun_41M0XKWYC70GPJA4V38D59N3E2 | 🔍 observability
  • nullByteWorkflow | wrun_41M0XKX4SQ0GP6HZD95DV47PKN | 🔍 observability
  • cancelRun - cancelling a running workflow | wrun_41M0XKZDMG0GSB2G7GCDRQ2NQ9 | 🔍 observability
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XKZFR00GZRXDDEPFZ1HPY1 | 🔍 observability
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XKZPB90GJV2V6KE0BCPM3C | 🔍 observability
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XM069J0GPFSMSB5XV2DXAV | 🔍 observability
🌐 Cross-language Conformance (9 failed)
python (9 failed):
  • deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M0XM2RVN13GZTK3JMW2QWTAX
  • promiseAllWorkflow | wrun_41M0XKW8620GVT2WRP55HYPZSC
  • sleepingWorkflow | wrun_41M0XKWVH40GV71GF8BPKP0T9J
  • parallelSleepWorkflow | wrun_41M0XKWYC70GPJA4V38D59N3E2
  • nullByteWorkflow | wrun_41M0XKX4SQ0GP6HZD95DV47PKN
  • cancelRun - cancelling a running workflow | wrun_41M0XKZDMG0GSB2G7GCDRQ2NQ9
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XKZFR00GZRXDDEPFZ1HPY1
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XKZPB90GJV2V6KE0BCPM3C
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XM069J0GPFSMSB5XV2DXAV
⚠️ 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.
  • cancelRun via CLI - cancelling a running workflow (express)
  • cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
  • hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-turbopack)
  • hookGetConflictWorkflow - awaiting hook.getConflict() registers hook without payload (nitro)
  • hookTokenReuseLoopWorkflow - same run recreates a hook with the same token after dispose() (nuxt)
  • hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (tanstack-start)
  • hookWorkflow (tanstack-start)
🛠 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.
42 infra events
  • cold-start-warmup · suite warmup (python) · at 23:25:36Z · abandoned wrun_41M0XKS15H0GKRGMPXB3BRH801 · (+7 more)
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:25:52Z · abandoned wrun_41M0XKWP1K0GQE7ZMWK3QVV9WH
  • run-pickup-stall · nullByteWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1V0GN48M281TQWYKXD
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1R0GX4XSJKEQFHDDP4
  • run-pickup-stall · sleepingWorkflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWP1R0GX4XSJKEQFHDDP3
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:25:53Z · abandoned wrun_41M0XKWPG60GSQ5YTBCAT0R7QB
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:26:26Z · abandoned wrun_41M0XKXP4D0GT11GP7CXZJERSH
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHRM0GRK595NF7QZ7VMV
  • run-pickup-stall · sleepingWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHRT0GWH385E6D5A1WY0
  • run-pickup-stall · nullByteWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYHN60GP60BDTSGJHE2N5
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:26:54Z · abandoned wrun_41M0XKYJ310GPM1BBQ5ZB1HMS9
  • run-pickup-stall · instanceMethodStepWorkflow - instance methods with "use step" directive (nest) · at 23:27:01Z · abandoned wrun_41M0XKYQJ10GMHHQ9ZPEHX3WYV
  • run-pickup-stall · cancelRun - cancelling a running workflow (fastify) · at 23:27:04Z · abandoned wrun_41M0XKYVQV0GVFJEC0SVC71Y0P
  • run-pickup-stall · sleepWithSequentialStepsWorkflow - sequential steps work with concurrent sleep (control) (hono) · at 23:27:05Z · abandoned wrun_41M0XKYX620GM8Q9H32MMS55CF
  • run-pickup-stall · hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nitro) · at 23:27:05Z · abandoned wrun_41M0XKYX700GR9A3EQ51EYPKNA
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (nitro) · at 23:27:07Z · abandoned wrun_41M0XKYY5Z0GGNC8DK7M443GQ1
  • run-pickup-stall · hookSupersedeOwnerWorkflow - duplicate cancels the owner and claims the released token (nextjs-turbopack) · at 23:27:09Z · abandoned wrun_41M0XKZ0WC0GTXDYDZ02VTEM6Z
  • run-pickup-stall · abortAfterCompletionWorkflow: abort after step completes is a no-op (sveltekit) · at 23:27:10Z · abandoned wrun_41M0XKZ1Z70GTY5V3QSAH2H2RZ
  • run-pickup-stall · distributedAbortController - TTL expiration triggers signal (express) · at 23:27:14Z · abandoned wrun_41M0XKZ5M00GN1VZFNF6C3CY49
  • cold-start-warmup · suite warmup (tanstack-start) · at 23:27:15Z · abandoned wrun_01M0XKYVF0HS6PN1CC3S1FJA0N
  • cold-start-warmup · suite warmup (python) · at 23:27:41Z · abandoned wrun_01M0XKWTDZ34YVV9AMNV48892H · (+7 more)
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:27:44Z · abandoned wrun_41M0XKYNRC0GYVYJ14M2MVD0CR
  • run-pickup-stall · sleepingWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJPKHME0N782V18DW0W
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJG4G0H79RQPBWJHFE5
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJH5ZZGDY3RXKG8B6FJ
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJRRY8G09YF6PBYEGZX
  • run-pickup-stall · nullByteWorkflow (python) · at 23:27:56Z · abandoned wrun_01M0XM0FJTBEF2HGZ4XCD1FFVD
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6DYNY7ZPWTK3MRJDVB
  • run-pickup-stall · sleepingWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6FXEBKATKVRZQ3QWH8
  • run-pickup-stall · parallelSleepWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6KSC1A1D6SYR5MX28S
  • run-pickup-stall · nullByteWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6MK5FWT49R55M5892A
  • run-pickup-stall · promiseAllWorkflow (python) · at 23:28:56Z · abandoned wrun_01M0XM2A6H2D5X39KWWRGAHQ08
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:29:27Z · abandoned wrun_41M0XM1DMW0GVYCY0X56JYVMVX
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:29:27Z · abandoned wrun_41M0XM0KXT0GXVKC45119RZFCC
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:29:56Z · abandoned wrun_01M0XM44T1HC37KPH38V1MX2KJ
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:29:56Z · abandoned wrun_01M0XM44T41428VQNKEWD0046K
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:29:56Z · abandoned wrun_01M0XM44TBYBWXSGH5CB7M1FVS
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 23:30:26Z · abandoned wrun_01M0XM525V7VCQ8PZYC6KW0XF0
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 23:30:26Z · abandoned wrun_01M0XM525T3K8J0CFCNXJRQ7FH
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 23:30:56Z · abandoned wrun_01M0XM5ZDEGXBD0YNDMSARKHV5
  • run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 23:31:07Z · abandoned wrun_01M0XM6ARE8E5B3NCYNWQ7RS3A
  • run-pickup-stall · concurrent hook token conflict - two workflows cannot use the same hook token simultaneously (nextjs-webpack) · at 23:31:12Z · abandoned wrun_01M0XM6FE4SE79KFHSYPFWAYW5
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production357087424320
✅ 💻 Local Development392205584480
✅ 📦 Local Production392205584480
✅ 🐘 Local Postgres392205584480
✅ 🪟 Windows32000320
❌ 🌐 Cross-language Conformance09132141
✅ vercel-http-transport8170143960
✅ vercel-multi-region270027
✅ vercel-ws-transport553087640
Total1705317277819848
Details by Category
❌ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro-node132028
✅ astro-quickjs132028
✅ example-node132028
✅ example-quickjs132028
✅ express-node132028
✅ express-quickjs132028
✅ fastify-node132028
✅ fastify-quickjs132028
✅ hono-node132028
✅ hono-quickjs132028
✅ nest-node132028
✅ nest-quickjs132028
✅ nextjs-turbopack-node15703
✅ nextjs-turbopack-quickjs15703
✅ nextjs-webpack-node15703
✅ nextjs-webpack-quickjs15703
✅ nitro-node132028
✅ nitro-quickjs132028
✅ nuxt-node132028
✅ nuxt-quickjs132028
❌ python-node08152
✅ sveltekit-node15109
✅ sveltekit-quickjs15109
✅ tanstack-start-node132028
✅ tanstack-start-quickjs132028
✅ vite-node132028
✅ vite-quickjs132028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node134026
✅ astro-stable-quickjs134026
✅ express-stable-node134026
✅ express-stable-quickjs134026
✅ fastify-stable-node134026
✅ fastify-stable-quickjs134026
✅ hono-stable-node134026
✅ hono-stable-quickjs134026
✅ nest-stable-node134026
✅ nest-stable-quickjs134026
✅ nextjs-turbopack-canary-node141019
✅ nextjs-turbopack-canary-quickjs141019
✅ nextjs-turbopack-stable-node16000
✅ nextjs-turbopack-stable-quickjs16000
✅ nextjs-webpack-canary-node141019
✅ nextjs-webpack-canary-quickjs141019
✅ nextjs-webpack-stable-node16000
✅ nextjs-webpack-stable-quickjs16000
✅ nitro-stable-node134026
✅ nitro-stable-quickjs134026
✅ nuxt-stable-node134026
✅ nuxt-stable-quickjs134026
✅ sveltekit-stable-node15307
✅ sveltekit-stable-quickjs15307
✅ tanstack-start-node134026
✅ tanstack-start-quickjs134026
✅ vite-stable-node134026
✅ vite-stable-quickjs134026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node16000
✅ nextjs-turbopack-quickjs16000
❌ 🌐 Cross-language Conformance
AppPassedFailedSkipped
❌ python09132
✅ vercel-http-transport
AppPassedFailedSkipped
✅ example132028
✅ express132028
✅ hono132028
✅ nextjs-turbopack15703
✅ nitro132028
✅ vite132028
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
✅ vercel-ws-transport
AppPassedFailedSkipped
✅ example132028
✅ express132028
✅ nextjs-turbopack15703
✅ vite132028
📋 View full workflow run
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📊 Workflow Benchmarks
commit 2db81fd · Tue, 25 Aug 2026 23:39:23 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1207 (+75%) 🔻1295 🔴 (+25%) 🔻1325 🔴 (+26%) 🔻1467 🔴 (+28%) 🔻30
TTFSstream256 (+16%) 🔻1255 🔴 (+16%) 🔻1290 🔴 (+13%)1345 🔴 (+11%)30
TTFShook + stream1483 (+180%) 🔻1623 🔴 (+23%) 🔻1647 🔴 (+21%) 🔻2052 🔴 (+24%) 🔻30
Fan-out TTFSPromise.all(100 steps)547 (-5.0%)765 (-52%) 💚1903 (+9.4%)2019 (+12%)10
Fan-out TTLSPromise.all(100 steps)1838 (-7.9%)4757 (+17%) 🔻5109 (-30%) 💚8120 (-97%) 💚10
STSO1020 steps (inline)100 (+3.1%)121 (-12%)140 (-11%)189 (-16%) 💚1019
WO1020 steps121258 (-9.6%)121258 (-9.6%)121258 (-9.6%)121258 (-9.6%)1
CRTTfirst chunk (pooled)86 (-22%) 💚122 (-41%) 💚171 (-51%) 💚452 (+22%) 🔻28
Streams
ScenarioCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)102 (-24%)122 (-40%)176 (-38%)328 (-62%)101 (-67%)10
size sweep (100/s, 160B-12KB)102 (-30%)164 (-10%)439 (+36%)980 (+68%)118 (-41%)10
replay gateway-gpt-5.4-nano-2000t (1x)126 (-42%)111 (-33%)151 (-30%)270 (-37%)243 (-32%)3
replay eve-gpt-5.6-sol-2000t (1x)142 (-1%)116 (-29%)155 (-26%)299 (-15%)469 (+26%)2
replay eve-gpt-5.6-sol-2000t (2x)97 (-59%)146 (-39%)194 (-50%)363 (-55%)233 (-50%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 133929ms → this run 121089ms (Δ -12840ms, -10%)
 50-100 ms ┃ main 2 this 0 -2
100-150 ms ██████████████████████░┃ main 875 this 972 +97
150-200 ms ┃██ main 121 this 38 -83
200-250 ms ┃ main 12 this 6 -6
250-300 ms ┃ main 6 this 2 -4
300-350 ms ┃ main 2 this 1 -1
350-400 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······██▁···· 104.1 (-36%) 100 (-28%) 176 (-38%) 328 (-62%) 3000
sweep ······▆█▂▁··· 157.9 (-2%) 106 (-23%) 439 (+36%) 980 (+68%) 3000
gw 1x ·····▁█▆▁···· 101.7 (-29%) 96 (-27%) 151 (-30%) 270 (-37%) 5295
eve 1x ·····▁█▅▁▁··· 100.3 (-27%) 90 (-26%) 155 (-26%) 299 (-15%) 5186
eve 2x ·····▁▅█▂···· 126.1 (-38%) 115 (-30%) 194 (-50%) 363 (-55%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control ▃▂▆▂█▇▆▁▃▁ 98–114ms
sweep ▅█▄▂▃▂▂▄▁▂ 130–219ms
gw 1x ▃▃▁▂▃█▄▄▅▅ 92–117ms
eve 1x ▃▁▂▅▄▄▆█▆▁ 87–118ms
eve 2x ▄▁▂▂▁▄▅█▅▁ 108–162ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▃▆█▆▄▂▁ 156–161ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▅▄▅██▆▅▇▄ 24–36ms
sweep ▆▁▂▅█▂▆▂▃▅ 39–73ms
gw 1x ▃▅▁▁▃█▃▆▆▄ 24–35ms
eve 1x ▂▂▁▅▃▃▅▇█▂ 19–26ms
eve 2x ▇▃▁▃▆▆█▂▅▆ 17–23ms

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-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 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.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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FrameworkFlow routeStep reg.Framework output
hono200.9 KiB (±0)40.3 KiB (-214 B)1.76 MiB (-135 B)
nextjs-turbopack206.3 KiB (±0)439 B (±0)762.7 KiB (-442 B)
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.
2db81fd · run
@VaguelySerious
Handle the resume-visibility consequence of the lazy path
18b5306
`resumeHook()` returning no longer implies `hook_received` is in the log:
the consuming invocation writes it. A caller that reads the run back
immediately can see a log without it.
hook-token-reuse's first test was such a caller. It picked the next hook
to resume by "has no hook_received yet", so after the eager write went
away it was handed back the hook it had just resumed, delivered a second
payload to it, and starved the round waiting for its own. The eager
write had been acting as its barrier.
`waitForHook()` grows a `notHookId` option to express "the next hook,
not the one I just resumed", and its doc says why the old predicate is
not sufficient on its own.
Also narrows the ended-run claim: the by-token lookup still validates
that a hook holds the token, so the silent case needs the hook to
outlive its run (minimum retention, or before the token is released).
@VaguelySerious
VaguelySerious
marked this pull request as ready for review
August 25, 2026 23:13
@VaguelySerious
Keep a durable resume for the step-abort ordering barrier
2db81fd
The abort path's own comment states the invariant: a step that aborts a
shared AbortController resumes a hook to record the abort, and that
write must be committed before the step completes, or the continuation
`step_completed` enqueues dispatches the next step with a stale,
non-aborted signal. It routes the resume to `preCompletionOps` for
exactly that reason.
Awaiting a lazy `resumeHook()` no longer supplies it: it resolves when
the resume is published, leaving the write to the consumer. So
preCompletionOps kept its ordering while the thing being ordered moved
out from under it, and `abortFromStepWorkflow` started failing with
stepSawAborted=false alongside workflowAborted=true — the stale-signal
dispatch, exactly as described.
Add `resumeHookDurable()`, which forces the sequential path, and use it
there. The gate checks it first so the span reads
`resume_fallback_reason: durable_required` rather than naming whichever
other condition happened to fail. The round trip it costs is the right
price for an internal barrier; the lazy path is for the external resume
it was written for.
abort-controller-step.test.ts mocks the two entry points separately, so
a regression to the lazy one shows up as the durable mock going
uncalled.
karthikscale3
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Aug 26, 2026
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Approved.
Checked the lazy-resume producer/consumer flow and its fallbacks: queue-publish failure, redelivery and idempotent deduplication, reusable-hook multiple resumes, terminal runs, oversized/legacy/unsupported fallbacks, and the AbortController durable-write ordering barrier.
Validation:
  • Built the affected workspace packages.
  • Ran focused core and world-local suites: 34 tests passed.
  • Started the local Next.js workflow stack and confirmed the workflow manifest was reachable.
No blocking issues found.
@VaguelySerious
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merged commit d9e0777
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mainAug 26, 2026

182 of 184 checks passed

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peter/lazy-only-hook-resume

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August 26, 2026 16:14
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No backport to stable for d9e0777 (AI decision).
This is a latency optimization plus deliberate contract change to resumeHook(): the producer no longer writes hook_received, so a resolved resume no longer implies the event is visible, and a resume against an ended run now resolves instead of throwing HookNotFoundError. It also adds new API surface (resumeHookDurable, a notHookId option on @workflow/vitest's waitForHook()) and a new lazy telemetry strategy value. None of that fixes a defect on stable; it widens an existing race window and changes observable behavior of an existing API, which is exactly what a maintenance line should not absorb.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
d9e0777eb8b1ce5f3be3fe865bc5a17fdbdb9d5d

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Aug 26, 2026
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@karthikscale3karthikscale3karthikscale3 approved these changes
@msullivanmsullivanAwaiting requested review from msullivan
@fantixfantixAwaiting requested review from fantix

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@VaguelySerious@karthikscale3