fix(world-local,core): stop re-executing in-flight inline steps on redelivery

[VaguelySerious]

closes #3909

Problem

Since #3255 (@workflow/world-local@5.0.0-beta.33), world-local's queue gives each delivery a 30s undici headersTimeout/bodyTimeout. A delivery runs inline steps before it responds, so any "use step" longer than 30s had its live delivery declared failed and redelivered after a 5s backoff. That redelivery keeps x-vqs-message-attempt: 1, so the runtime re-enters turbo, skips the event log, and runs the same lazy inline step body again, concurrently. With the optimistic start, the body runs before the create-claim settles, so the losing claim discards only the result, not the side effects. The effect is one extra execution per ~35s of step runtime, and on world-local it leaves no trace in the durable log. I re-checked on main at 873b70b5c and both halves are still there.

Fix

Two independent changes. Either one alone closes the report.

1. world-local: no delivery deadline by default. DEFAULT_HEADERS_TIMEOUT_MS and DEFAULT_BODY_TIMEOUT_MS go from 30_000 to 0, matching what fix(world-postgres): remove implicit queue HTTP deadlines #4114 did for world-postgres. WORKFLOW_LOCAL_HEADERS_TIMEOUT_MS and WORKFLOW_LOCAL_BODY_TIMEOUT_MS still work, now as opt-in, and the docs warn that setting one below your longest inline step brings the duplication back.
2. core: every inline execution goes through runStepSingleFlight. Before, runtime.ts sent only owned-recovery steps through the in-process single-flight. Lazy and pre-claimed steps ran directly, on the assumption that their create-claim was the exactly-once gate. quickjs-entrypoint.ts already sends every inline candidate through the single-flight, so this change makes the node:vm path match it. Fresh claims log at debug, as they do in QuickJS. This covers any world whose transport can redeliver a live message, not just world-local.

Tests

• New workbench/vitest/test/inline-step-ownership.test.ts case (Local world: 30s undici transport timeout redelivers a live queue message and re-executes an in-flight lazy-inline step #3909): it re-sends the run's start message 500ms into a 1.5s inline step and asserts the body is entered exactly once. Without the core change it fails (expected ['entered', 'entered'] to have a length of 1). With the change it passes.
• queue.test.ts now asserts the defaults are 0. The tests for a stalled handler and a stalled body already set their deadlines explicitly, so they now cover the opt-in path and I only renamed them.
• pnpm --filter @workflow/core test: 2622 passed. pnpm --filter @workflow/world-local test: 592 passed. workbench/vitest: 44 passed. Typecheck is clean.

Not addressed

Turbo still treats metadata.attempt === 1 as proof that this is the first delivery (see the NOTE at runtime.ts:1237). With (2) in place the duplicate body is absorbed, but a redelivery still replays against an empty log. That deserves a separate decision: either count transport-failure redeliveries as attempts, or stop using the attempt number as that proof.

🤖 Generated with Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: 2d2b2ab

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 10:53pm UTC
example-nextjs-workflow-webpack	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC
example-workflow	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC
workbench-astro-workflow	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC
workbench-express-workflow	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC
workbench-fastify-workflow	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC
workbench-hono-workflow	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC
workbench-nestjs-workflow	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC
workbench-nitro-workflow	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC
workbench-nuxt-workflow	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC
workbench-python-workflow	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC
workbench-sveltekit-workflow	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC
workbench-tanstack-start-workflow	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC
workbench-vite-workflow	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC
workflow-docs	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC
workflow-swc-playground	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC
workflow-tarballs	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC
workflow-web	Ready	Preview, v0	Sep 30, 2026 10:53pm UTC

[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.

• 'hookGetConflictWithPriorStepWorkflow' - hook.getConflict() does not block step execution (nuxt · local-dev / local / node / 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 · runs app-generated source against a registered step (tanstack-start) · at 22:52:38Z · abandoned wrun_01M3T89QDP6Q5XVBM1SSW6YDEH
• cold-start-warmup · suite warmup (tanstack-start) · at 22:52:45Z · abandoned wrun_01M3T89QCMEWDCYC918BFPMPFK
• run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 23:00:47Z · abandoned wrun_01M3T8RNAHJ8KMPN3C1Q8CYT46

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]

📊 Workflow Benchmarks

commit 2d2b2ab · Wed, 30 Sep 2026 23:15:56 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	420 (-42%) 💚	2395 🔴 (+119%) 🔻	2445 🔴 (+119%) 🔻	2980 🔴 (+148%) 🔻	30
TTFS	stream	424 (+93%) 🔻	2439 🔴 (+132%) 🔻	2534 🔴 (+131%) 🔻	3135 🔴 (+120%) 🔻	30
TTFS	hook + stream	627 (-29%) 💚	3316 🔴 (+150%) 🔻	3340 🔴 (+138%) 🔻	3974 🔴 (+155%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	531 (-39%) 💚	835 (-51%) 💚	878 (-51%) 💚	2916 (+56%) 🔻	10
Fan-out TTLS	Promise.all(100 steps)	1312 (-43%) 💚	4816 (+33%) 🔻	6207 (+64%) 🔻	6810 (-5.7%)	10
STSO	1020 steps (inline)	142 (+42%) 🔻	197 (+52%) 🔻	220 (+43%) 🔻	322 (+59%) 🔻	1019
WO	1020 steps	192217 (+46%) 🔻	192217 (+46%) 🔻	192217 (+46%) 🔻	192217 (+46%) 🔻	1
CRTT	first chunk (pooled)	65 (-9.7%)	121 (-15%)	133 (-37%) 💚	164 (-54%) 💚	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	117 (+18%)	163 (-15%)	207 (-31%)	325 (-34%)	174 (-22%)	10
size sweep (100/s, 160B-12KB)	93 (-10%)	162 (-28%)	213 (-40%)	385 (-39%)	158 (-25%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	104 (-24%)	145 (-24%)	176 (-45%)	499 (-13%)	300 (-31%)	3
replay eve-gpt-5.6-sol-2000t (1x)	117 (+11%)	146 (-26%)	186 (-39%)	357 (-35%)	292 (-36%)	2
replay eve-gpt-5.6-sol-2000t (2x)	111 (-22%)	188 (-43%)	254 (-48%)	839 (-11%)	480 (+2%)	3

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

1020 steps (inline)

Cumulative STSO time: main 131526ms → this run 191485ms (Δ +59959ms, +46%)

100-150 ms  ┃███████████████████████  main 899  this  11  -888
150-200 ms  ███░░░░░░░░░░░░░░░░░┃     main 108  this 784  +676
200-250 ms  █░░░┃                     main   8  this 171  +163
250-300 ms  ┃                         main   2  this  37   +35
300-350 ms  ┃                         main   0  this  11   +11
350-400 ms  ┃                         main   1  this   1    +0
400-450 ms  ┃                         main   1  this   4    +3

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

variant  RTT 1ms→5s+             avg         p50         p90         p99     n
control  ······▂█▁····    138 (-13%)   131 (-5%)  207 (-31%)  325 (-34%)  3000
sweep    ······▂█▁····  136.3 (-23%)  128 (-17%)  213 (-40%)  385 (-39%)  3000
gw 1x    ·····▁▃█▁▁···  130.4 (-18%)  123 (-10%)  176 (-45%)  499 (-13%)  5295
eve 1x   ·····▁▄█▁····  127.4 (-22%)  116 (-14%)  186 (-39%)  357 (-35%)  5186
eve 2x   ·····▁▂█▃▁▁··  167.6 (-27%)  149 (-31%)  254 (-48%)  839 (-11%)  7779

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

control  █▄▂▃▄▄▃▄▃▁  123–165ms
sweep    ▆▃▃▂▄▃▅█▄▁  123–156ms
gw 1x    █▁▃▄▁▁▃▁▃▃  123–149ms
eve 1x   ▂▁▆▃▁▄█▄█▅  114–143ms
eve 2x   ▃▄▂▂▁▂▄▆█▃  136–230ms

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

sweep  ▆█▄▄▁▁▃  134–139ms

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

control  █▂▃▆▁▅█▅▆▂  38–51ms
sweep    ▃▆▁▇▆▄▅█▄▁  49–68ms
gw 1x    ▃▅▆▁▁█▆▇▅▆  36–42ms
eve 1x   ▁▃▅▆▂█▆▄▂█  21–30ms
eve 2x   █▅▃▃▅▄▄▁▅▆  17–37ms

📜 Previous results (1)

5f56f85

Wed, 23 Sep 2026 19:35:42 GMT · run logs

vercel / nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	2186 (+946%) 🔻	2322 🔴 (+124%) 🔻	2378 🔴 (+40%) 🔻	2561 🔴 (+47%) 🔻	30
TTFS	stream	273 (+33%) 🔻	2280 🔴 (+35%) 🔻	2328 🔴 (+34%) 🔻	2382 🔴 (+18%) 🔻	30
TTFS	hook + stream	2463 (+376%) 🔻	2636 🔴 (+26%) 🔻	2694 🔴 (+28%) 🔻	7200 🔴 (+230%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	539 (-3.1%)	781 (-67%) 💚	829 (-69%) 💚	3189 (+18%) 🔻	10
Fan-out TTLS	Promise.all(100 steps)	2036 (+24%) 🔻	5546 (±0%)	5909 (-38%) 💚	10746 (+9.6%)	10
STSO	1020 steps (inline)	120 (-4.8%)	148 (-6.9%)	168 (-5.1%)	713 (+136%) 🔻	1019
WO	1020 steps	158982 (±0%)	158982 (±0%)	158982 (±0%)	158982 (±0%)	1
CRTT	first chunk (pooled)	73 (-9.9%)	122 (-1.6%)	221 (+45%) 🔻	597 (+162%) 🔻	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	115 (+8%)	224 (-35%)	299 (-36%)	485 (-39%)	175 (-41%)	10
size sweep (100/s, 160B-12KB)	95.5 (-15%)	207 (-21%)	284 (-44%)	626 (-51%)	171 (-6%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	101 (-25%)	164 (-41%)	206 (-46%)	380 (-58%)	299 (-40%)	3
replay eve-gpt-5.6-sol-2000t (1x)	128 (+19%)	168 (-66%)	206 (-70%)	481 (-50%)	280 (-45%)	2
replay eve-gpt-5.6-sol-2000t (2x)	278 (+187%)	259 (-59%)	371 (-62%)	661 (-58%)	326 (-58%)	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]

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)	97.2 KiB (±0)	1.98 MiB (+12 B)
nextjs-turbopack	273.3 KiB (±0)	426 B (±0)	979.6 KiB (+4 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.

2d2b2ab · run

[karthikscale3]

Reviewed the current diff. The single-flight change is focused, the regression test directly covers the duplicate inline-step execution race, and I found no blocking issues.

[github-actions]

No backport to stable for 0e64f7b (AI decision).

This is a genuine correctness fix (duplicate side effects from re-executing an in-flight inline step on redelivery), but it patches machinery that exists only on main: git show origin/stable:packages/core/src/runtime.ts is 1089 lines and contains no runStepSingleFlight, inFlightOwnedSteps, lazyStepInput, preclaimedStart, or any turbo/inline-step code at all. The defect being fixed therefore cannot occur on stable, and the change has no applicable target there.

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

0e64f7bc25b9159a39485c5ff5b2c8025bf2745a