fix(core): make dynamic start() refusals fatal

[alangenfeld]

Summary & Motivation

Every deterministic refusal start() makes before writing anything threw a plain WorkflowRuntimeError, which the step executor retries — so a step calling start() with dynamic source burned its whole retry budget on the opt-in being off, then reported retry exhaustion instead of the refusal. A World's validateRunExecutionContext throw becomes a fresh fatal error carrying the World's message with the original as cause, since that object may be frozen, shared, or not an Error. A start whose current deployment could not be determined stays retryable; only a confirmed mismatch is fatal.

Known limit: when workflow code calls start() directly (start is itself a step), the fatal marker does not survive the step boundary, so FatalError.is() is false on the error the workflow catches — the step still fails without retrying.

Test Plan

Unit tests added in start.test.ts.

[changeset-bot]

🦋 Changeset detected

Latest commit: 33c64ee

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

This PR includes changesets to release 17 packages

Name	Type
@workflow/core	Patch
@workflow/builders	Patch
@workflow/cli	Patch
@workflow/next	Patch
@workflow/nitro	Patch
@workflow/vitest	Patch
@workflow/web-shared	Patch
@workflow/web	Patch
workflow	Patch
@workflow/world-testing	Patch
@workflow/astro	Patch
@workflow/nest	Patch
@workflow/rollup	Patch
@workflow/sveltekit	Patch
@workflow/vite	Patch
@workflow/nuxt	Patch
@workflow/world-vercel	Patch

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

[vercel]

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

Project	Deployment	Actions	Updated
example-nextjs-workflow-turbopack	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
example-nextjs-workflow-webpack	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
example-workflow	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
workbench-astro-workflow	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
workbench-express-workflow	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
workbench-fastify-workflow	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
workbench-hono-workflow	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
workbench-nestjs-workflow	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
workbench-nitro-workflow	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
workbench-nuxt-workflow	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
workbench-python-workflow	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
workbench-sveltekit-workflow	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
workbench-tanstack-start-workflow	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
workbench-vite-workflow	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
workflow-docs	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
workflow-swc-playground	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
workflow-tarballs	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC
workflow-web	Ready	Preview, v0	Sep 30, 2026 10:00pm UTC

[github-actions]

📊 Workflow Benchmarks

commit 33c64ee · Wed, 30 Sep 2026 22:23:05 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	2488 (+241%) 🔻	2650 🔴 (+143%) 🔻	2696 🔴 (+142%) 🔻	2908 🔴 (+142%) 🔻	30
TTFS	stream	2417 (+999%) 🔻	2539 🔴 (+142%) 🔻	2575 🔴 (+135%) 🔻	2654 🔴 (+86%) 🔻	30
TTFS	hook + stream	2824 (+222%) 🔻	3012 🔴 (+127%) 🔻	3045 🔴 (+117%) 🔻	3079 🔴 (+97%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	577 (-34%) 💚	831 (-51%) 💚	849 (-52%) 💚	2998 (+60%) 🔻	10
Fan-out TTLS	Promise.all(100 steps)	2125 (-7.3%)	3611 (-0.5%)	3701 (-2.0%)	11327 (+57%) 🔻	10
STSO	1020 steps (inline)	172 (+72%) 🔻	217 (+67%) 🔻	236 (+53%) 🔻	318 (+57%) 🔻	1019
WO	1020 steps	213233 (+62%) 🔻	213233 (+62%) 🔻	213233 (+62%) 🔻	213233 (+62%) 🔻	1
CRTT	first chunk (pooled)	87 (+21%) 🔻	114 (-20%) 💚	126 (-41%) 💚	130 (-63%) 💚	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	101 (+3%)	179 (-7%)	233 (-23%)	574 (+17%)	150 (-33%)	10
size sweep (100/s, 160B-12KB)	99.5 (-4%)	172 (-24%)	214 (-39%)	303 (-52%)	143 (-32%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	98 (-28%)	150 (-21%)	182 (-43%)	286 (-50%)	194 (-56%)	3
replay eve-gpt-5.6-sol-2000t (1x)	128 (+22%)	166 (-16%)	201 (-34%)	294 (-47%)	214 (-53%)	2
replay eve-gpt-5.6-sol-2000t (2x)	98 (-31%)	237 (-28%)	301 (-38%)	498 (-47%)	194 (-59%)	3

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

1020 steps (inline)

Cumulative STSO time: main 131526ms → this run 212681ms (Δ +81155ms, +62%)

100-150 ms  ┃███████████████████████  main 899  this   0  -899
150-200 ms  ███░░░░░░░░┃              main 108  this 446  +338
200-250 ms  █░░░░░░░░░░░░┃            main   8  this 509  +501
250-300 ms  ┃                         main   2  this  49   +47
300-350 ms  ┃                         main   0  this   9    +9
350-400 ms  ┃                         main   1  this   4    +3
400-450 ms  ┃                         main   1  this   0    -1
450-500 ms  ┃                         main   0  this   1    +1
500-550 ms  ┃                         main   0  this   1    +1

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

variant  RTT 1ms→5s+             avg         p50         p90         p99     n
control  ······▁█▂▁···   151.4 (-4%)   140 (+1%)  233 (-23%)  574 (+17%)  3000
sweep    ······▁█▁····  149.1 (-15%)   144 (-7%)  214 (-39%)  303 (-52%)  3000
gw 1x    ······▂█▁····  132.1 (-17%)   129 (-5%)  182 (-43%)  286 (-50%)  5295
eve 1x   ······▂█▁····  140.1 (-14%)   131 (-3%)  201 (-34%)  294 (-47%)  5186
eve 2x   ······▁█▄▁···    178 (-23%)  161 (-25%)  301 (-38%)  498 (-47%)  7779

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

control  ▁▅█▂▃▁▃▄▂▃  140–176ms
sweep    ▄▁▃▄▃█▅█▄▄  143–155ms
gw 1x    ▁▃▂▂▂▂▃▅▃█  127–144ms
eve 1x   ▃▄█▃▁▄▆▃▃▂  127–161ms
eve 2x   ▂▁▄▁▁▂▅█▄▄  153–230ms

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

sweep  ▁▅█▅▄▅▃  148–150ms

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

control  ▂█▁▃▄▅▂▇▅▆  37–49ms
sweep    ▂▃█▇▄▆▆▅▂▁  54–67ms
gw 1x    ▄▄▄▁▅▅▅█▅█  33–44ms
eve 1x   ▇██▆▄▇▅▃▁▄  22–28ms
eve 2x   ▅▄▃▃▄▂▃▁▄█  20–37ms

📜 Previous results (2)

2e9ba36

Wed, 30 Sep 2026 21:19:32 GMT · run logs

vercel / nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	710 (-2.6%)	2541 🔴 (+133%) 🔻	2611 🔴 (+134%) 🔻	2764 🔴 (+130%) 🔻	30
TTFS	stream	2248 (+922%) 🔻	2611 🔴 (+148%) 🔻	2655 🔴 (+142%) 🔻	3004 🔴 (+111%) 🔻	30
TTFS	hook + stream	2886 (+229%) 🔻	3164 🔴 (+138%) 🔻	3254 🔴 (+132%) 🔻	5307 🔴 (+240%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	628 (-28%) 💚	1036 (-39%) 💚	1162 (-35%) 💚	3024 (+62%) 🔻	10
Fan-out TTLS	Promise.all(100 steps)	2120 (-7.5%)	3510 (-3.3%)	3836 (+1.6%)	11688 (+62%) 🔻	10
STSO	1020 steps (inline)	171 (+71%) 🔻	209 (+61%) 🔻	226 (+47%) 🔻	298 (+47%) 🔻	1019
WO	1020 steps	207532 (+58%) 🔻	207532 (+58%) 🔻	207532 (+58%) 🔻	207532 (+58%) 🔻	1
CRTT	first chunk (pooled)	88 (+22%) 🔻	112 (-21%) 💚	134 (-37%) 💚	153 (-57%) 💚	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	101 (+2%)	174 (-9%)	215 (-29%)	312 (-37%)	133 (-41%)	10
size sweep (100/s, 160B-12KB)	100 (-3%)	173 (-23%)	236 (-33%)	314 (-50%)	141 (-34%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	96 (-30%)	163 (-14%)	193 (-40%)	263 (-54%)	177 (-59%)	3
replay eve-gpt-5.6-sol-2000t (1x)	121 (+15%)	168 (-15%)	199 (-35%)	308 (-44%)	248 (-46%)	2
replay eve-gpt-5.6-sol-2000t (2x)	131 (-8%)	211 (-35%)	260 (-47%)	419 (-55%)	193 (-59%)	3

92925a4

Wed, 30 Sep 2026 20:19:04 GMT · run logs

vercel / nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	2438 (+234%) 🔻	2618 🔴 (+140%) 🔻	2659 🔴 (+139%) 🔻	2914 🔴 (+142%) 🔻	30
TTFS	stream	2450 (+1014%) 🔻	2600 🔴 (+147%) 🔻	2659 🔴 (+142%) 🔻	2768 🔴 (+94%) 🔻	30
TTFS	hook + stream	2701 (+208%) 🔻	2912 🔴 (+119%) 🔻	2936 🔴 (+109%) 🔻	3247 🔴 (+108%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	623 (-28%) 💚	2964 (+73%) 🔻	3022 (+69%) 🔻	3173 (+69%) 🔻	10
Fan-out TTLS	Promise.all(100 steps)	2166 (-5.5%)	5593 (+54%) 🔻	6906 (+83%) 🔻	10491 (+45%) 🔻	10
STSO	1020 steps (inline)	129 (+29%) 🔻	205 (+58%) 🔻	243 (+58%) 🔻	481 (+137%) 🔻	1019
WO	1020 steps	218846 (+66%) 🔻	218846 (+66%) 🔻	218846 (+66%) 🔻	218846 (+66%) 🔻	1
CRTT	first chunk (pooled)	69 (-4.2%)	110 (-23%) 💚	334 (+58%) 🔻	415 (+17%) 🔻	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	99.5 (+1%)	156 (-19%)	241 (-20%)	4418 (+798%)	116 (-49%)	10
size sweep (100/s, 160B-12KB)	90 (-13%)	224 (-1%)	368 (+4%)	571 (-10%)	159 (-25%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	103 (-25%)	153 (-19%)	191 (-41%)	581 (+1%)	332 (-24%)	3
replay eve-gpt-5.6-sol-2000t (1x)	254 (+143%)	154 (-22%)	187 (-39%)	318 (-42%)	431 (-5%)	2
replay eve-gpt-5.6-sol-2000t (2x)	94 (-34%)	202 (-38%)	341 (-30%)	713 (-24%)	388 (-17%)	3

ℹ️ Metric definitions & methodology

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

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

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

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

_{Metrics — TTFS: time to first step body (in-deployment start() → first step body) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)}

_{Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles}

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

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

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

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

[github-actions]

🧪 E2E Test Results

✅ All tests passed

⚠️ Flaky E2E Tests (passed on retry)

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

• a run can take over its own earlier hook (astro · local-dev / local / node / stable)
• hookTokenReuseLoopWorkflow - same run recreates a hook with the same token after dispose() (nuxt · local-dev / local / quickjs / stable)

🛠 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.

• run-pickup-stall · maxRetries=0 disables retries (nextjs-turbopack) · at 22:00:12Z · abandoned wrun_41M3T59P220GHNV5W50AK0N2DC
• run-pickup-stall · runs app-generated source against a registered step (tanstack-start) · at 22:01:05Z · abandoned wrun_01M3T5BBAWRBZ5KGPAGPGW26JK
• cold-start-warmup · suite warmup (tanstack-start) · at 22:01:13Z · abandoned wrun_01M3T5BBBDMSMFWQQTMJPP850G
• run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 22:06:07Z · abandoned wrun_01M3T5MHPDXXPS0M4JCKXX11B3

E2E Test Summary

Summary

	Passed	Failed	Skipped	Total
✅ ▲ Vercel Production	3904	0	875	4779
✅ 💻 Local Development	4406	0	550	4956
✅ 📦 Local Production	4406	0	550	4956
✅ 🐘 Local Postgres	4406	0	550	4956
✅ 🪟 Windows	342	0	12	354
✅ 🌐 Cross-language Conformance	68	0	84	152
✅ dynamic-runs	0	0	0	0
✅ vercel-http-transport	879	0	183	1062
✅ vercel-multi-region	27	0	0	27
✅ vercel-ws-transport	595	0	113	708
Total	19033	0	2917	21950

Details by Category

✅ ▲ Vercel Production

App	Passed	Failed	Skipped
✅ astro-node	142	0	35
✅ astro-quickjs	142	0	35
✅ example-node	142	0	35
✅ example-quickjs	142	0	35
✅ express-node	142	0	35
✅ express-quickjs	142	0	35
✅ fastify-node	142	0	35
✅ fastify-quickjs	142	0	35
✅ hono-node	142	0	35
✅ hono-quickjs	142	0	35
✅ nest-node	142	0	35
✅ nest-quickjs	142	0	35
✅ nextjs-turbopack-node	169	0	8
✅ nextjs-turbopack-quickjs	169	0	8
✅ nextjs-webpack-node	169	0	8
✅ nextjs-webpack-quickjs	169	0	8
✅ nitro-node	142	0	35
✅ nitro-quickjs	142	0	35
✅ nuxt-node	142	0	35
✅ nuxt-quickjs	142	0	35
✅ python-node	66	0	111
✅ sveltekit-node	161	0	16
✅ sveltekit-quickjs	161	0	16
✅ tanstack-start-node	142	0	35
✅ tanstack-start-quickjs	142	0	35
✅ vite-node	142	0	35
✅ vite-quickjs	142	0	35

✅ 💻 Local Development

App	Passed	Failed	Skipped
✅ astro-stable-node	148	0	29
✅ astro-stable-quickjs	148	0	29
✅ express-stable-node	148	0	29
✅ express-stable-quickjs	148	0	29
✅ fastify-stable-node	148	0	29
✅ fastify-stable-quickjs	148	0	29
✅ hono-stable-node	148	0	29
✅ hono-stable-quickjs	148	0	29
✅ nest-stable-node	148	0	29
✅ nest-stable-quickjs	148	0	29
✅ nextjs-turbopack-canary-node	176	0	1
✅ nextjs-turbopack-canary-quickjs	176	0	1
✅ nextjs-turbopack-stable-node	176	0	1
✅ nextjs-turbopack-stable-quickjs	176	0	1
✅ nextjs-webpack-canary-node	176	0	1
✅ nextjs-webpack-canary-quickjs	176	0	1
✅ nextjs-webpack-stable-node	176	0	1
✅ nextjs-webpack-stable-quickjs	176	0	1
✅ nitro-stable-node	148	0	29
✅ nitro-stable-quickjs	148	0	29
✅ nuxt-stable-node	148	0	29
✅ nuxt-stable-quickjs	148	0	29
✅ sveltekit-stable-node	167	0	10
✅ sveltekit-stable-quickjs	167	0	10
✅ tanstack-start-node	148	0	29
✅ tanstack-start-quickjs	148	0	29
✅ vite-stable-node	148	0	29
✅ vite-stable-quickjs	148	0	29

✅ 📦 Local Production

App	Passed	Failed	Skipped
✅ astro-stable-node	148	0	29
✅ astro-stable-quickjs	148	0	29
✅ express-stable-node	148	0	29
✅ express-stable-quickjs	148	0	29
✅ fastify-stable-node	148	0	29
✅ fastify-stable-quickjs	148	0	29
✅ hono-stable-node	148	0	29
✅ hono-stable-quickjs	148	0	29
✅ nest-stable-node	148	0	29
✅ nest-stable-quickjs	148	0	29
✅ nextjs-turbopack-canary-node	176	0	1
✅ nextjs-turbopack-canary-quickjs	176	0	1
✅ nextjs-turbopack-stable-node	176	0	1
✅ nextjs-turbopack-stable-quickjs	176	0	1
✅ nextjs-webpack-canary-node	176	0	1
✅ nextjs-webpack-canary-quickjs	176	0	1
✅ nextjs-webpack-stable-node	176	0	1
✅ nextjs-webpack-stable-quickjs	176	0	1
✅ nitro-stable-node	148	0	29
✅ nitro-stable-quickjs	148	0	29
✅ nuxt-stable-node	148	0	29
✅ nuxt-stable-quickjs	148	0	29
✅ sveltekit-stable-node	167	0	10
✅ sveltekit-stable-quickjs	167	0	10
✅ tanstack-start-node	148	0	29
✅ tanstack-start-quickjs	148	0	29
✅ vite-stable-node	148	0	29
✅ vite-stable-quickjs	148	0	29

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	148	0	29
✅ astro-stable-quickjs	148	0	29
✅ express-stable-node	148	0	29
✅ express-stable-quickjs	148	0	29
✅ fastify-stable-node	148	0	29
✅ fastify-stable-quickjs	148	0	29
✅ hono-stable-node	148	0	29
✅ hono-stable-quickjs	148	0	29
✅ nest-stable-node	148	0	29
✅ nest-stable-quickjs	148	0	29
✅ nextjs-turbopack-canary-node	176	0	1
✅ nextjs-turbopack-canary-quickjs	176	0	1
✅ nextjs-turbopack-stable-node	176	0	1
✅ nextjs-turbopack-stable-quickjs	176	0	1
✅ nextjs-webpack-canary-node	176	0	1
✅ nextjs-webpack-canary-quickjs	176	0	1
✅ nextjs-webpack-stable-node	176	0	1
✅ nextjs-webpack-stable-quickjs	176	0	1
✅ nitro-stable-node	148	0	29
✅ nitro-stable-quickjs	148	0	29
✅ nuxt-stable-node	148	0	29
✅ nuxt-stable-quickjs	148	0	29
✅ sveltekit-stable-node	167	0	10
✅ sveltekit-stable-quickjs	167	0	10
✅ tanstack-start-node	148	0	29
✅ tanstack-start-quickjs	148	0	29
✅ vite-stable-node	148	0	29
✅ vite-stable-quickjs	148	0	29

✅ 🪟 Windows

App	Passed	Failed	Skipped
✅ nextjs-turbopack-node	171	0	6
✅ nextjs-turbopack-quickjs	171	0	6

✅ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
✅ python	68	0	84

✅ dynamic-runs

App	Passed	Failed	Skipped
✅ astro-vercel	0	0	0
✅ example-vercel	0	0	0
✅ express-vercel	0	0	0
✅ fastify-vercel	0	0	0
✅ hono-vercel	0	0	0
✅ nest-vercel	0	0	0
✅ nextjs-turbopack-vercel	0	0	0
✅ nextjs-webpack-vercel	0	0	0
✅ nitro-vercel	0	0	0
✅ nuxt-vercel	0	0	0
✅ sveltekit-vercel	0	0	0
✅ tanstack-start-vercel	0	0	0
✅ vite-vercel	0	0	0

✅ vercel-http-transport

App	Passed	Failed	Skipped
✅ example	142	0	35
✅ express	142	0	35
✅ hono	142	0	35
✅ nextjs-turbopack	169	0	8
✅ nitro	142	0	35
✅ vite	142	0	35

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

✅ vercel-ws-transport

App	Passed	Failed	Skipped
✅ example	142	0	35
✅ express	142	0	35
✅ nextjs-turbopack	169	0	8
✅ vite	142	0	35

---

📋 View full workflow run

[github-actions]

Sim World

Simulated world deterministic testing for races. Traces

🟠 world-sim scenario book — 1 fail of 42 total

fence=per-spec

scenario	outcome	events	virt	replay	violations
✅ smoke-no-steps	completed	3	0ms	ok	0
✅ smoke-one-step	completed	6	0ms	ok	0
✅ hook-at-step-started	completed	12	0ms	ok	0
✅ hook-at-step-completed	completed	12	0ms	ok	0
✅ hook-at-hook-created	completed	12	0ms	ok	0
✅ deadline-hook-wins	completed	7	1.0h	ok	0
✅ deadline-expires	completed	7	1.0h	ok	0
✅ step-vs-timer-early-settlement	completed	8	1.0h	ok	0
✅ long-sleep	completed	11	30.0d	ok	0
✅ hook-never-arrives	stalled	3	0ms	skipped	0
✅ step-retries-twice	completed	10	2.0s	ok	0
✅ parallel-steps	completed	9	0ms	ok	0
✅ hook-on-execution-state	completed	12	0ms	ok	0
✅ peek-hook-before-branch	completed	12	0ms	ok	0
✅ peek-hook-after-branch	completed	12	0ms	ok	0
✅ peek-hook-at-registration	completed	12	0ms	ok	0
✅ race-hook-before-probe	completed	12	0ms	ok	0
✅ race-hook-after-probe	completed	12	0ms	ok	0
✅ race-duplicate-delivery	completed	13	0ms	ok	0
✅ attr-hook-before-step	completed	11	0ms	ok	0
✅ attr-hook-after-step	completed	11	0ms	ok	0
✅ attr-from-step-body	completed	13	0ms	ok	0
✅ fork-hook-after-timeout	completed	14	1.0m	ok	0
✅ fork-hook-before-timeout	completed	14	1.0m	ok	0
✅ count-hook-after-timeout	completed	17	1.0m	ok	0
✅ count-hook-before-timeout	completed	20	1.0m	ok	0
✅ stale-read-step-count-fork	completed	20	1.0m	ok	0
✅ stale-read-equal-step-counts	completed	14	1.0m	ok	0
✅ step-vs-step-fork	completed	12	0ms	ok	0
✅ step-vs-step-fork-fenced	completed	12	0ms	ok	0
✅ fence-catches-benign-direction	completed	12	5ms	ok	0
✅ in-flight-before-decision	completed	17	1.0m	ok	0
❌ in-flight-before-decision-counted	completed	17	1.0m	ok	0
✅ in-flight-after-decision	completed	19	2.0m	ok	0
✅ stale-read-step-count-fork-fenced	completed	20	1.0m	ok	0
✅ fork-hook-wins	completed	13	1.0m	ok	0
✅ fork-timeout-wins	completed	13	1.0m	ok	0
✅ unclaimed-payload-under-fork	completed	17	1.0m	ok	0
✅ claimed-payload-under-fork	completed	17	1.0m	ok	0
✅ writers-independent-step-bodies	completed	12	0ms	ok	0
✅ writers-scripted-tempo	completed	12	0ms	ok	0
✅ cancel-mid-step	cancelled	7	0ms	skipped	0

Full trace: world-sim.txt

[github-actions]

Framework	Flow route	Step reg.	Framework output
hono	265.9 KiB (±0)	97.3 KiB (+47 B)	1.98 MiB (+1.0 KiB)
nextjs-turbopack	273.3 KiB (±0)	426 B (±0)	979.7 KiB (+75 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.

33c64ee · run

[github-actions]

No backport to stable for 14dbfdc (AI decision).

This fixes retry behavior for dynamic start() refusals, but the dynamic-workflows feature does not exist on stable: packages/core/src/runtime/dynamic-workflow.ts is absent there (git ls-tree origin/stable) and stable's start.ts contains no experimental_dynamic/dynamicWorkflow code at all. The change therefore fixes main-only functionality and has nothing to correct on the maintenance line.

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

14dbfdc1f52e838854b6ee70398b742e4850e891