[world-vercel] Decode chunked event frames without repeated copies

[NathanColosimo]

Summary

• collect partial network chunks before growing the frame buffer
• concatenate buffered bytes once per requested frame field instead of once per incoming chunk
• preserve frame ordering, arbitrary chunk boundaries, owned payload bytes, and early stream cancellation

Performance

Local Node microbenchmark, one 8 MB frame:

Input chunks	Before	After
64 KB	~31 ms	~0.6 ms
16 KB	~93 ms	~0.9 ms

The benchmark is synthetic, but it directly exercises the removed repeated-copy behavior.

Validation

• pnpm --filter @workflow/world-vercel... build
• pnpm --filter @workflow/world-vercel test — 513 tests passed
• pnpm --filter @workflow/world-vercel typecheck
• Biome and git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: 116cb19

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

This PR includes changesets to release 17 packages

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

[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.

• getTailIndex returns -1 before any chunks are written (nextjs-webpack)
• webhookWorkflow (nest)

🛠 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 · addTenWorkflow (astro) · at 22:36:22Z · abandoned wrun_01M08XWAEDYKQYJ181QR4M9RQK
• run-pickup-stall · addTenWorkflow (tanstack-start) · at 22:36:30Z · abandoned wrun_01M08XWJ552M3XT6YC4SX8FWQD

E2E Test Summary

Summary

	Passed	Failed	Skipped	Total
✅ ▲ Vercel Production	3474	0	738	4212
✅ 💻 Local Development	3810	0	558	4368
✅ 📦 Local Production	3810	0	558	4368
✅ 🐘 Local Postgres	3810	0	558	4368
✅ 🪟 Windows	312	0	0	312
✅ 🌐 Cross-language Conformance	9	0	128	137
✅ vercel-multi-region	27	0	0	27
Total	15252	0	2540	17792

Details by Category

✅ ▲ Vercel Production

App	Passed	Failed	Skipped
✅ astro-node	128	0	28
✅ astro-quickjs	128	0	28
✅ example-node	128	0	28
✅ example-quickjs	128	0	28
✅ express-node	128	0	28
✅ express-quickjs	128	0	28
✅ fastify-node	128	0	28
✅ fastify-quickjs	128	0	28
✅ hono-node	128	0	28
✅ hono-quickjs	128	0	28
✅ nest-node	128	0	28
✅ nest-quickjs	128	0	28
✅ nextjs-turbopack-node	153	0	3
✅ nextjs-turbopack-quickjs	153	0	3
✅ nextjs-webpack-node	153	0	3
✅ nextjs-webpack-quickjs	153	0	3
✅ nitro-node	128	0	28
✅ nitro-quickjs	128	0	28
✅ nuxt-node	128	0	28
✅ nuxt-quickjs	128	0	28
✅ python-node	8	0	148
✅ sveltekit-node	147	0	9
✅ sveltekit-quickjs	147	0	9
✅ tanstack-start-node	128	0	28
✅ tanstack-start-quickjs	128	0	28
✅ vite-node	128	0	28
✅ vite-quickjs	128	0	28

✅ 💻 Local Development

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 📦 Local Production

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 🪟 Windows

App	Passed	Failed	Skipped
✅ nextjs-turbopack-node	156	0	0
✅ nextjs-turbopack-quickjs	156	0	0

✅ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
✅ python	9	0	128

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

---

📋 View full workflow run

[vercel]

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

Project	Deployment	Actions	Updated (UTC)
example-nextjs-workflow-turbopack	Ready	Preview	Aug 17, 2026 10:34pm
example-nextjs-workflow-webpack	Ready	Preview	Aug 17, 2026 10:34pm
example-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-astro-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-express-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-fastify-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-hono-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nestjs-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nitro-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nuxt-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-python-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-sveltekit-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-tanstack-start-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-vite-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workflow-docs	Ready	Preview, v0	Aug 17, 2026 10:34pm
workflow-swc-playground	Ready	Preview	Aug 17, 2026 10:34pm
workflow-tarballs	Ready	Preview	Aug 17, 2026 10:34pm
workflow-web	Ready	Preview	Aug 17, 2026 10:34pm

[github-actions]

Sim World

Simulated world deterministic testing for races. Traces

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

fence=per-spec

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

Full trace: world-sim.txt

[github-actions]

📊 Workflow Benchmarks

commit 15a90ed · Mon, 17 Aug 2026 22:51:56 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	247 (+9.8%)	1520 🔴 (+34%) 🔻	1530 🔴 (+29%) 🔻	1933 🔴 (+18%) 🔻	30
TTFS	stream	239 (+5.3%)	1422 🔴 (+20%) 🔻	1463 🔴 (+21%) 🔻	1541 🔴 (-18%) 💚	30
TTFS	hook + stream	500 (+31%) 🔻	1760 🔴 (+29%) 🔻	1903 🔴 (+36%) 🔻	1972 🔴 (+36%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	1273 (+1.4%)	2373 (-0.9%)	2578 (±0%)	2684 (±0%)	10
Fan-out TTLS	Promise.all(100 steps)	6502 (-6.3%)	7915 (-7.7%)	8675 (-1.8%)	9838 (+10%)	10
STSO	1020 steps (inline)	149 (-6.9%)	259 (-11%)	290 (-15%) 💚	443 (-11%)	1019
WO	1020 steps	249616 (-10%)	249616 (-10%)	249616 (-10%)	249616 (-10%)	1
CRTT	first chunk (pooled)	95 (+1.1%)	179 (+25%) 🔻	288 (+51%) 🔻	1222 (+224%) 🔻	28

Streams

Scenario	wr c/s	rd c/s	wr KiB/s	rd KiB/s	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	100 (±0%)	102 (+5%)	5 (±0%)	5.1 (+5%)	116 (-5%)	256 (+15%)	302 (-38%)	1285 (+1%)	211 (-7%)	10
size sweep (100/s, 160B-12KB)	100 (±0%)	101 (+3%)	334 (±0%)	337 (+3%)	141 (-2%)	378 (+49%)	460 (-33%)	1222 (-1%)	178 (-59%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	89.2 (±0%)	89.2 (±0%)	16.2 (±0%)	16.2 (-1%)	170 (+40%)	173 (-31%)	278 (-88%)	792 (-79%)	761 (-5%)	3
replay eve-gpt-5.6-sol-2000t (1x)	54.7 (±0%)	54.7 (-4%)	355 (±0%)	355 (-4%)	269 (+105%)	158 (-27%)	220 (-67%)	410 (-92%)	398 (-87%)	2
replay eve-gpt-5.6-sol-2000t (2x)	109 (±0%)	110 (±0%)	710 (±0%)	712 (±0%)	118 (-2%)	258 (+10%)	373 (+11%)	539 (-17%)	343 (-8%)	3

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

1020 steps (inline)

Cumulative STSO time: main 277417ms → this run 248241ms (Δ -29176ms, -11%)

 100-150 ms ┃ main 0 this 1 +1
150-200 ms ██░┃ main 47 this 93 +46
200-250 ms ███████████████░░░░░░░░┃ main 357 this 589 +232
250-300 ms █████████┃██████ main 397 this 255 -142
300-350 ms █┃███ main 126 this 47 -79
350-400 ms ┃█ main 50 this 19 -31
400-450 ms ┃ main 23 this 6 -17
450-500 ms ┃ main 9 this 3 -6
500-550 ms ┃ main 4 this 3 -1
550-600 ms ┃ main 2 this 0 -2
600-650 ms ┃ main 2 this 0 -2
700-750 ms ┃ main 1 this 1 +0
850-900 ms ┃ main 1 this 1 +0
1100-1150 ms ┃ main 0 this 1 +1

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

variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▃▁▁·· 182 (-6%) 142 (-1%) 302 (-38%) 1285 (+1%) 3000
sweep ······▂█▅▁▁·· 215.7 (+1%) 158 (+10%) 460 (-33%) 1222 (-1%) 3000
gw 1x ·····▁▄█▂▁··· 150.2 (-49%) 121 (-20%) 278 (-88%) 792 (-79%) 5295
eve 1x ·····▁▄█▂▁··· 136.5 (-60%) 119 (-14%) 220 (-67%) 410 (-92%) 5186
eve 2x ·····▁▂█▅▁··· 190.7 (-4%) 157 (-11%) 373 (+11%) 539 (-17%) 7779

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

control ▂▁▃▇▂▂▁█▂▂ 151–250ms
sweep ▆█▄▅▃▃▄▁▂▁ 171–288ms
gw 1x ▂▃█▂▁█▁▂▂▄ 120–212ms
eve 1x █▂▄█▃▂▃▇▄▁ 118–159ms
eve 2x ▁▃▅▃▃▂▅█▄▂ 147–257ms

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

sweep ▁▁▂█▄▅▅ 213–220ms

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

control ▂▅▇▄▃▁▁█▂▂ 31–76ms
sweep ▄▅▁▂█▆▆▁▄▅ 36–74ms
gw 1x ▄██▃▃▆▁▆▂█ 36–48ms
eve 1x ▇▂▃█▄▄▂▃▁▂ 26–34ms
eve 2x ▆▆▅▆▄▄▇▁▄█ 26–35ms

📜 Previous results (1)

116cb19

Mon, 17 Aug 2026 18:06:05 GMT · run logs

vercel / nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	271 (+22%) 🔻	1469 🔴 (+35%) 🔻	1498 🔴 (+30%) 🔻	1552 🔴 (+2.8%)	30
TTFS	stream	1319 (+511%) 🔻	1479 🔴 (+40%) 🔻	1500 🔴 (+39%) 🔻	1532 🔴 (+39%) 🔻	30
TTFS	hook + stream	1434 (+259%) 🔻	1752 🔴 (+27%) 🔻	1821 🔴 (+29%) 🔻	2043 🔴 (+33%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	1158 (-9.7%)	1411 (-43%) 💚	2580 (+3.8%)	2893 (-11%)	10
Fan-out TTLS	Promise.all(100 steps)	6310 (-42%) 💚	11678 (-5.9%)	13221 (+2.5%)	16265 (-5.8%)	10
STSO	1020 steps (inline)	134 (-13%)	233 (-53%) 💚	263 (-52%) 💚	372 (-50%) 💚	1019
WO	1020 steps	225600 (-50%) 💚	225600 (-50%) 💚	225600 (-50%) 💚	225600 (-50%) 💚	1
CRTT	first chunk (pooled)	83 (-12%)	114 (-17%) 💚	121 (-44%) 💚	341 (+46%) 🔻	28

Streams

Scenario	wr c/s	rd c/s	wr KiB/s	rd KiB/s	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	100 (±0%)	100 (+1%)	5 (±0%)	5 (±0%)	110 (-1%)	122 (-50%)	269 (-22%)	391 (-60%)	113 (-49%)	10
size sweep (100/s, 160B-12KB)	100 (±0%)	100 (-1%)	334 (±0%)	334 (-1%)	97 (-19%)	133 (-26%)	248 (+6%)	1119 (+110%)	111 (-39%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	89.2 (±0%)	89 (±0%)	16.2 (±0%)	16.2 (±0%)	97 (-29%)	249 (+38%)	599 (+122%)	899 (-21%)	439 (-47%)	3
replay eve-gpt-5.6-sol-2000t (1x)	54.7 (±0%)	54.7 (±0%)	355 (±0%)	355 (±0%)	107 (-31%)	110 (-33%)	136 (-49%)	389 (-78%)	300 (-65%)	2
replay eve-gpt-5.6-sol-2000t (2x)	109 (±0%)	109 (±0%)	710 (±0%)	709 (±0%)	114 (-9%)	152 (-36%)	201 (-49%)	407 (-46%)	256 (-55%)	3

ℹ️ Metric definitions & methodology

_{Streams: writer/reader sustained rates (steady window, 10% trimmed each side), 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.}

[github-actions]

No backport to stable for 52526e1 (AI decision).

This is a pure performance optimization of decodeFrames in packages/world-vercel/src/frames.ts — it replaces per-chunk buffer reallocation with a single concatenation, carrying a patch changeset but no user-visible defect fix. The prior behavior was merely slower (~31ms vs ~0.6ms for an 8 MB frame), not a correctness, hang, or unbounded-memory problem, so it does not meet the stability bar for the maintenance line. It also slightly tightens assumptions about chunk values (dropping the !value guard), which is added risk with no fix to justify it.

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

52526e14aaa848dc24eaeebfbf91ccc9ca0df89a

[pranaygp]

This appears to have broken all vercel-world e2e lanes on main (encrypted frame payloads corrupted; WS transport jobs hung at the 30m ceiling) — bisect and mechanism in #3650, which reverts it. Root cause looks like deferred chunk concatenation stashing yielded views across awaits, letting the stream reuse their backing buffers before the copy.

🤖 Generated with Claude Code

[NathanColosimo]

Summary

• collect partial network chunks before growing the frame buffer
• concatenate buffered bytes once per requested frame field instead of once per incoming chunk
• preserve frame ordering, arbitrary chunk boundaries, owned payload bytes, and early stream cancellation

Performance

Local Node microbenchmark, one 8 MB frame:

Input chunks	Before	After
64 KB	~31 ms	~0.6 ms
16 KB	~93 ms	~0.9 ms

The benchmark is synthetic, but it directly exercises the removed repeated-copy behavior.

Validation

• pnpm --filter @workflow/world-vercel... build
• pnpm --filter @workflow/world-vercel test — 513 tests passed
• pnpm --filter @workflow/world-vercel typecheck
• Biome and git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: 116cb19

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

This PR includes changesets to release 17 packages

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

[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.

• getTailIndex returns -1 before any chunks are written (nextjs-webpack)
• webhookWorkflow (nest)

🛠 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 · addTenWorkflow (astro) · at 22:36:22Z · abandoned wrun_01M08XWAEDYKQYJ181QR4M9RQK
• run-pickup-stall · addTenWorkflow (tanstack-start) · at 22:36:30Z · abandoned wrun_01M08XWJ552M3XT6YC4SX8FWQD

E2E Test Summary

Summary

	Passed	Failed	Skipped	Total
✅ ▲ Vercel Production	3474	0	738	4212
✅ 💻 Local Development	3810	0	558	4368
✅ 📦 Local Production	3810	0	558	4368
✅ 🐘 Local Postgres	3810	0	558	4368
✅ 🪟 Windows	312	0	0	312
✅ 🌐 Cross-language Conformance	9	0	128	137
✅ vercel-multi-region	27	0	0	27
Total	15252	0	2540	17792

Details by Category

✅ ▲ Vercel Production

App	Passed	Failed	Skipped
✅ astro-node	128	0	28
✅ astro-quickjs	128	0	28
✅ example-node	128	0	28
✅ example-quickjs	128	0	28
✅ express-node	128	0	28
✅ express-quickjs	128	0	28
✅ fastify-node	128	0	28
✅ fastify-quickjs	128	0	28
✅ hono-node	128	0	28
✅ hono-quickjs	128	0	28
✅ nest-node	128	0	28
✅ nest-quickjs	128	0	28
✅ nextjs-turbopack-node	153	0	3
✅ nextjs-turbopack-quickjs	153	0	3
✅ nextjs-webpack-node	153	0	3
✅ nextjs-webpack-quickjs	153	0	3
✅ nitro-node	128	0	28
✅ nitro-quickjs	128	0	28
✅ nuxt-node	128	0	28
✅ nuxt-quickjs	128	0	28
✅ python-node	8	0	148
✅ sveltekit-node	147	0	9
✅ sveltekit-quickjs	147	0	9
✅ tanstack-start-node	128	0	28
✅ tanstack-start-quickjs	128	0	28
✅ vite-node	128	0	28
✅ vite-quickjs	128	0	28

✅ 💻 Local Development

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 📦 Local Production

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 🪟 Windows

App	Passed	Failed	Skipped
✅ nextjs-turbopack-node	156	0	0
✅ nextjs-turbopack-quickjs	156	0	0

✅ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
✅ python	9	0	128

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

---

📋 View full workflow run

[vercel]

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

Project	Deployment	Actions	Updated (UTC)
example-nextjs-workflow-turbopack	Ready	Preview	Aug 17, 2026 10:34pm
example-nextjs-workflow-webpack	Ready	Preview	Aug 17, 2026 10:34pm
example-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-astro-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-express-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-fastify-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-hono-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nestjs-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nitro-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nuxt-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-python-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-sveltekit-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-tanstack-start-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-vite-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workflow-docs	Ready	Preview, v0	Aug 17, 2026 10:34pm
workflow-swc-playground	Ready	Preview	Aug 17, 2026 10:34pm
workflow-tarballs	Ready	Preview	Aug 17, 2026 10:34pm
workflow-web	Ready	Preview	Aug 17, 2026 10:34pm

[github-actions]

Sim World

Simulated world deterministic testing for races. Traces

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

fence=per-spec

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

Full trace: world-sim.txt

[github-actions]

📊 Workflow Benchmarks

commit 15a90ed · Mon, 17 Aug 2026 22:51:56 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	247 (+9.8%)	1520 🔴 (+34%) 🔻	1530 🔴 (+29%) 🔻	1933 🔴 (+18%) 🔻	30
TTFS	stream	239 (+5.3%)	1422 🔴 (+20%) 🔻	1463 🔴 (+21%) 🔻	1541 🔴 (-18%) 💚	30
TTFS	hook + stream	500 (+31%) 🔻	1760 🔴 (+29%) 🔻	1903 🔴 (+36%) 🔻	1972 🔴 (+36%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	1273 (+1.4%)	2373 (-0.9%)	2578 (±0%)	2684 (±0%)	10
Fan-out TTLS	Promise.all(100 steps)	6502 (-6.3%)	7915 (-7.7%)	8675 (-1.8%)	9838 (+10%)	10
STSO	1020 steps (inline)	149 (-6.9%)	259 (-11%)	290 (-15%) 💚	443 (-11%)	1019
WO	1020 steps	249616 (-10%)	249616 (-10%)	249616 (-10%)	249616 (-10%)	1
CRTT	first chunk (pooled)	95 (+1.1%)	179 (+25%) 🔻	288 (+51%) 🔻	1222 (+224%) 🔻	28

Streams

Scenario	wr c/s	rd c/s	wr KiB/s	rd KiB/s	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	100 (±0%)	102 (+5%)	5 (±0%)	5.1 (+5%)	116 (-5%)	256 (+15%)	302 (-38%)	1285 (+1%)	211 (-7%)	10
size sweep (100/s, 160B-12KB)	100 (±0%)	101 (+3%)	334 (±0%)	337 (+3%)	141 (-2%)	378 (+49%)	460 (-33%)	1222 (-1%)	178 (-59%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	89.2 (±0%)	89.2 (±0%)	16.2 (±0%)	16.2 (-1%)	170 (+40%)	173 (-31%)	278 (-88%)	792 (-79%)	761 (-5%)	3
replay eve-gpt-5.6-sol-2000t (1x)	54.7 (±0%)	54.7 (-4%)	355 (±0%)	355 (-4%)	269 (+105%)	158 (-27%)	220 (-67%)	410 (-92%)	398 (-87%)	2
replay eve-gpt-5.6-sol-2000t (2x)	109 (±0%)	110 (±0%)	710 (±0%)	712 (±0%)	118 (-2%)	258 (+10%)	373 (+11%)	539 (-17%)	343 (-8%)	3

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

1020 steps (inline)

Cumulative STSO time: main 277417ms → this run 248241ms (Δ -29176ms, -11%)

 100-150 ms ┃ main 0 this 1 +1
150-200 ms ██░┃ main 47 this 93 +46
200-250 ms ███████████████░░░░░░░░┃ main 357 this 589 +232
250-300 ms █████████┃██████ main 397 this 255 -142
300-350 ms █┃███ main 126 this 47 -79
350-400 ms ┃█ main 50 this 19 -31
400-450 ms ┃ main 23 this 6 -17
450-500 ms ┃ main 9 this 3 -6
500-550 ms ┃ main 4 this 3 -1
550-600 ms ┃ main 2 this 0 -2
600-650 ms ┃ main 2 this 0 -2
700-750 ms ┃ main 1 this 1 +0
850-900 ms ┃ main 1 this 1 +0
1100-1150 ms ┃ main 0 this 1 +1

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

variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▃▁▁·· 182 (-6%) 142 (-1%) 302 (-38%) 1285 (+1%) 3000
sweep ······▂█▅▁▁·· 215.7 (+1%) 158 (+10%) 460 (-33%) 1222 (-1%) 3000
gw 1x ·····▁▄█▂▁··· 150.2 (-49%) 121 (-20%) 278 (-88%) 792 (-79%) 5295
eve 1x ·····▁▄█▂▁··· 136.5 (-60%) 119 (-14%) 220 (-67%) 410 (-92%) 5186
eve 2x ·····▁▂█▅▁··· 190.7 (-4%) 157 (-11%) 373 (+11%) 539 (-17%) 7779

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

control ▂▁▃▇▂▂▁█▂▂ 151–250ms
sweep ▆█▄▅▃▃▄▁▂▁ 171–288ms
gw 1x ▂▃█▂▁█▁▂▂▄ 120–212ms
eve 1x █▂▄█▃▂▃▇▄▁ 118–159ms
eve 2x ▁▃▅▃▃▂▅█▄▂ 147–257ms

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

sweep ▁▁▂█▄▅▅ 213–220ms

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

control ▂▅▇▄▃▁▁█▂▂ 31–76ms
sweep ▄▅▁▂█▆▆▁▄▅ 36–74ms
gw 1x ▄██▃▃▆▁▆▂█ 36–48ms
eve 1x ▇▂▃█▄▄▂▃▁▂ 26–34ms
eve 2x ▆▆▅▆▄▄▇▁▄█ 26–35ms

📜 Previous results (1)

116cb19

Mon, 17 Aug 2026 18:06:05 GMT · run logs

vercel / nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	271 (+22%) 🔻	1469 🔴 (+35%) 🔻	1498 🔴 (+30%) 🔻	1552 🔴 (+2.8%)	30
TTFS	stream	1319 (+511%) 🔻	1479 🔴 (+40%) 🔻	1500 🔴 (+39%) 🔻	1532 🔴 (+39%) 🔻	30
TTFS	hook + stream	1434 (+259%) 🔻	1752 🔴 (+27%) 🔻	1821 🔴 (+29%) 🔻	2043 🔴 (+33%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	1158 (-9.7%)	1411 (-43%) 💚	2580 (+3.8%)	2893 (-11%)	10
Fan-out TTLS	Promise.all(100 steps)	6310 (-42%) 💚	11678 (-5.9%)	13221 (+2.5%)	16265 (-5.8%)	10
STSO	1020 steps (inline)	134 (-13%)	233 (-53%) 💚	263 (-52%) 💚	372 (-50%) 💚	1019
WO	1020 steps	225600 (-50%) 💚	225600 (-50%) 💚	225600 (-50%) 💚	225600 (-50%) 💚	1
CRTT	first chunk (pooled)	83 (-12%)	114 (-17%) 💚	121 (-44%) 💚	341 (+46%) 🔻	28

Streams

Scenario	wr c/s	rd c/s	wr KiB/s	rd KiB/s	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	100 (±0%)	100 (+1%)	5 (±0%)	5 (±0%)	110 (-1%)	122 (-50%)	269 (-22%)	391 (-60%)	113 (-49%)	10
size sweep (100/s, 160B-12KB)	100 (±0%)	100 (-1%)	334 (±0%)	334 (-1%)	97 (-19%)	133 (-26%)	248 (+6%)	1119 (+110%)	111 (-39%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	89.2 (±0%)	89 (±0%)	16.2 (±0%)	16.2 (±0%)	97 (-29%)	249 (+38%)	599 (+122%)	899 (-21%)	439 (-47%)	3
replay eve-gpt-5.6-sol-2000t (1x)	54.7 (±0%)	54.7 (±0%)	355 (±0%)	355 (±0%)	107 (-31%)	110 (-33%)	136 (-49%)	389 (-78%)	300 (-65%)	2
replay eve-gpt-5.6-sol-2000t (2x)	109 (±0%)	109 (±0%)	710 (±0%)	709 (±0%)	114 (-9%)	152 (-36%)	201 (-49%)	407 (-46%)	256 (-55%)	3

ℹ️ Metric definitions & methodology

_{Streams: writer/reader sustained rates (steady window, 10% trimmed each side), 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.}

[github-actions]

No backport to stable for 52526e1 (AI decision).

This is a pure performance optimization of decodeFrames in packages/world-vercel/src/frames.ts — it replaces per-chunk buffer reallocation with a single concatenation, carrying a patch changeset but no user-visible defect fix. The prior behavior was merely slower (~31ms vs ~0.6ms for an 8 MB frame), not a correctness, hang, or unbounded-memory problem, so it does not meet the stability bar for the maintenance line. It also slightly tightens assumptions about chunk values (dropping the !value guard), which is added risk with no fix to justify it.

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

52526e14aaa848dc24eaeebfbf91ccc9ca0df89a

[pranaygp]

This appears to have broken all vercel-world e2e lanes on main (encrypted frame payloads corrupted; WS transport jobs hung at the 30m ceiling) — bisect and mechanism in #3650, which reverts it. Root cause looks like deferred chunk concatenation stashing yielded views across awaits, letting the stream reuse their backing buffers before the copy.

🤖 Generated with Claude Code

[NathanColosimo]

Summary

• collect partial network chunks before growing the frame buffer
• concatenate buffered bytes once per requested frame field instead of once per incoming chunk
• preserve frame ordering, arbitrary chunk boundaries, owned payload bytes, and early stream cancellation

Performance

Local Node microbenchmark, one 8 MB frame:

Input chunks	Before	After
64 KB	~31 ms	~0.6 ms
16 KB	~93 ms	~0.9 ms

The benchmark is synthetic, but it directly exercises the removed repeated-copy behavior.

Validation

• pnpm --filter @workflow/world-vercel... build
• pnpm --filter @workflow/world-vercel test — 513 tests passed
• pnpm --filter @workflow/world-vercel typecheck
• Biome and git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: 116cb19

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

This PR includes changesets to release 17 packages

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

[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.

• getTailIndex returns -1 before any chunks are written (nextjs-webpack)
• webhookWorkflow (nest)

🛠 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 · addTenWorkflow (astro) · at 22:36:22Z · abandoned wrun_01M08XWAEDYKQYJ181QR4M9RQK
• run-pickup-stall · addTenWorkflow (tanstack-start) · at 22:36:30Z · abandoned wrun_01M08XWJ552M3XT6YC4SX8FWQD

E2E Test Summary

Summary

	Passed	Failed	Skipped	Total
✅ ▲ Vercel Production	3474	0	738	4212
✅ 💻 Local Development	3810	0	558	4368
✅ 📦 Local Production	3810	0	558	4368
✅ 🐘 Local Postgres	3810	0	558	4368
✅ 🪟 Windows	312	0	0	312
✅ 🌐 Cross-language Conformance	9	0	128	137
✅ vercel-multi-region	27	0	0	27
Total	15252	0	2540	17792

Details by Category

✅ ▲ Vercel Production

App	Passed	Failed	Skipped
✅ astro-node	128	0	28
✅ astro-quickjs	128	0	28
✅ example-node	128	0	28
✅ example-quickjs	128	0	28
✅ express-node	128	0	28
✅ express-quickjs	128	0	28
✅ fastify-node	128	0	28
✅ fastify-quickjs	128	0	28
✅ hono-node	128	0	28
✅ hono-quickjs	128	0	28
✅ nest-node	128	0	28
✅ nest-quickjs	128	0	28
✅ nextjs-turbopack-node	153	0	3
✅ nextjs-turbopack-quickjs	153	0	3
✅ nextjs-webpack-node	153	0	3
✅ nextjs-webpack-quickjs	153	0	3
✅ nitro-node	128	0	28
✅ nitro-quickjs	128	0	28
✅ nuxt-node	128	0	28
✅ nuxt-quickjs	128	0	28
✅ python-node	8	0	148
✅ sveltekit-node	147	0	9
✅ sveltekit-quickjs	147	0	9
✅ tanstack-start-node	128	0	28
✅ tanstack-start-quickjs	128	0	28
✅ vite-node	128	0	28
✅ vite-quickjs	128	0	28

✅ 💻 Local Development

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 📦 Local Production

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 🪟 Windows

App	Passed	Failed	Skipped
✅ nextjs-turbopack-node	156	0	0
✅ nextjs-turbopack-quickjs	156	0	0

✅ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
✅ python	9	0	128

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

---

📋 View full workflow run

[vercel]

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

Project	Deployment	Actions	Updated (UTC)
example-nextjs-workflow-turbopack	Ready	Preview	Aug 17, 2026 10:34pm
example-nextjs-workflow-webpack	Ready	Preview	Aug 17, 2026 10:34pm
example-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-astro-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-express-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-fastify-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-hono-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nestjs-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nitro-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nuxt-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-python-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-sveltekit-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-tanstack-start-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-vite-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workflow-docs	Ready	Preview, v0	Aug 17, 2026 10:34pm
workflow-swc-playground	Ready	Preview	Aug 17, 2026 10:34pm
workflow-tarballs	Ready	Preview	Aug 17, 2026 10:34pm
workflow-web	Ready	Preview	Aug 17, 2026 10:34pm

[github-actions]

Sim World

Simulated world deterministic testing for races. Traces

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

fence=per-spec

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

Full trace: world-sim.txt

[github-actions]

📊 Workflow Benchmarks

commit 15a90ed · Mon, 17 Aug 2026 22:51:56 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	247 (+9.8%)	1520 🔴 (+34%) 🔻	1530 🔴 (+29%) 🔻	1933 🔴 (+18%) 🔻	30
TTFS	stream	239 (+5.3%)	1422 🔴 (+20%) 🔻	1463 🔴 (+21%) 🔻	1541 🔴 (-18%) 💚	30
TTFS	hook + stream	500 (+31%) 🔻	1760 🔴 (+29%) 🔻	1903 🔴 (+36%) 🔻	1972 🔴 (+36%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	1273 (+1.4%)	2373 (-0.9%)	2578 (±0%)	2684 (±0%)	10
Fan-out TTLS	Promise.all(100 steps)	6502 (-6.3%)	7915 (-7.7%)	8675 (-1.8%)	9838 (+10%)	10
STSO	1020 steps (inline)	149 (-6.9%)	259 (-11%)	290 (-15%) 💚	443 (-11%)	1019
WO	1020 steps	249616 (-10%)	249616 (-10%)	249616 (-10%)	249616 (-10%)	1
CRTT	first chunk (pooled)	95 (+1.1%)	179 (+25%) 🔻	288 (+51%) 🔻	1222 (+224%) 🔻	28

Streams

Scenario	wr c/s	rd c/s	wr KiB/s	rd KiB/s	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	100 (±0%)	102 (+5%)	5 (±0%)	5.1 (+5%)	116 (-5%)	256 (+15%)	302 (-38%)	1285 (+1%)	211 (-7%)	10
size sweep (100/s, 160B-12KB)	100 (±0%)	101 (+3%)	334 (±0%)	337 (+3%)	141 (-2%)	378 (+49%)	460 (-33%)	1222 (-1%)	178 (-59%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	89.2 (±0%)	89.2 (±0%)	16.2 (±0%)	16.2 (-1%)	170 (+40%)	173 (-31%)	278 (-88%)	792 (-79%)	761 (-5%)	3
replay eve-gpt-5.6-sol-2000t (1x)	54.7 (±0%)	54.7 (-4%)	355 (±0%)	355 (-4%)	269 (+105%)	158 (-27%)	220 (-67%)	410 (-92%)	398 (-87%)	2
replay eve-gpt-5.6-sol-2000t (2x)	109 (±0%)	110 (±0%)	710 (±0%)	712 (±0%)	118 (-2%)	258 (+10%)	373 (+11%)	539 (-17%)	343 (-8%)	3

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

1020 steps (inline)

Cumulative STSO time: main 277417ms → this run 248241ms (Δ -29176ms, -11%)

 100-150 ms ┃ main 0 this 1 +1
150-200 ms ██░┃ main 47 this 93 +46
200-250 ms ███████████████░░░░░░░░┃ main 357 this 589 +232
250-300 ms █████████┃██████ main 397 this 255 -142
300-350 ms █┃███ main 126 this 47 -79
350-400 ms ┃█ main 50 this 19 -31
400-450 ms ┃ main 23 this 6 -17
450-500 ms ┃ main 9 this 3 -6
500-550 ms ┃ main 4 this 3 -1
550-600 ms ┃ main 2 this 0 -2
600-650 ms ┃ main 2 this 0 -2
700-750 ms ┃ main 1 this 1 +0
850-900 ms ┃ main 1 this 1 +0
1100-1150 ms ┃ main 0 this 1 +1

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

variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▃▁▁·· 182 (-6%) 142 (-1%) 302 (-38%) 1285 (+1%) 3000
sweep ······▂█▅▁▁·· 215.7 (+1%) 158 (+10%) 460 (-33%) 1222 (-1%) 3000
gw 1x ·····▁▄█▂▁··· 150.2 (-49%) 121 (-20%) 278 (-88%) 792 (-79%) 5295
eve 1x ·····▁▄█▂▁··· 136.5 (-60%) 119 (-14%) 220 (-67%) 410 (-92%) 5186
eve 2x ·····▁▂█▅▁··· 190.7 (-4%) 157 (-11%) 373 (+11%) 539 (-17%) 7779

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

control ▂▁▃▇▂▂▁█▂▂ 151–250ms
sweep ▆█▄▅▃▃▄▁▂▁ 171–288ms
gw 1x ▂▃█▂▁█▁▂▂▄ 120–212ms
eve 1x █▂▄█▃▂▃▇▄▁ 118–159ms
eve 2x ▁▃▅▃▃▂▅█▄▂ 147–257ms

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

sweep ▁▁▂█▄▅▅ 213–220ms

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

control ▂▅▇▄▃▁▁█▂▂ 31–76ms
sweep ▄▅▁▂█▆▆▁▄▅ 36–74ms
gw 1x ▄██▃▃▆▁▆▂█ 36–48ms
eve 1x ▇▂▃█▄▄▂▃▁▂ 26–34ms
eve 2x ▆▆▅▆▄▄▇▁▄█ 26–35ms

📜 Previous results (1)

116cb19

Mon, 17 Aug 2026 18:06:05 GMT · run logs

vercel / nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	271 (+22%) 🔻	1469 🔴 (+35%) 🔻	1498 🔴 (+30%) 🔻	1552 🔴 (+2.8%)	30
TTFS	stream	1319 (+511%) 🔻	1479 🔴 (+40%) 🔻	1500 🔴 (+39%) 🔻	1532 🔴 (+39%) 🔻	30
TTFS	hook + stream	1434 (+259%) 🔻	1752 🔴 (+27%) 🔻	1821 🔴 (+29%) 🔻	2043 🔴 (+33%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	1158 (-9.7%)	1411 (-43%) 💚	2580 (+3.8%)	2893 (-11%)	10
Fan-out TTLS	Promise.all(100 steps)	6310 (-42%) 💚	11678 (-5.9%)	13221 (+2.5%)	16265 (-5.8%)	10
STSO	1020 steps (inline)	134 (-13%)	233 (-53%) 💚	263 (-52%) 💚	372 (-50%) 💚	1019
WO	1020 steps	225600 (-50%) 💚	225600 (-50%) 💚	225600 (-50%) 💚	225600 (-50%) 💚	1
CRTT	first chunk (pooled)	83 (-12%)	114 (-17%) 💚	121 (-44%) 💚	341 (+46%) 🔻	28

Streams

Scenario	wr c/s	rd c/s	wr KiB/s	rd KiB/s	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	100 (±0%)	100 (+1%)	5 (±0%)	5 (±0%)	110 (-1%)	122 (-50%)	269 (-22%)	391 (-60%)	113 (-49%)	10
size sweep (100/s, 160B-12KB)	100 (±0%)	100 (-1%)	334 (±0%)	334 (-1%)	97 (-19%)	133 (-26%)	248 (+6%)	1119 (+110%)	111 (-39%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	89.2 (±0%)	89 (±0%)	16.2 (±0%)	16.2 (±0%)	97 (-29%)	249 (+38%)	599 (+122%)	899 (-21%)	439 (-47%)	3
replay eve-gpt-5.6-sol-2000t (1x)	54.7 (±0%)	54.7 (±0%)	355 (±0%)	355 (±0%)	107 (-31%)	110 (-33%)	136 (-49%)	389 (-78%)	300 (-65%)	2
replay eve-gpt-5.6-sol-2000t (2x)	109 (±0%)	109 (±0%)	710 (±0%)	709 (±0%)	114 (-9%)	152 (-36%)	201 (-49%)	407 (-46%)	256 (-55%)	3

ℹ️ Metric definitions & methodology

_{Streams: writer/reader sustained rates (steady window, 10% trimmed each side), 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.}

[github-actions]

No backport to stable for 52526e1 (AI decision).

This is a pure performance optimization of decodeFrames in packages/world-vercel/src/frames.ts — it replaces per-chunk buffer reallocation with a single concatenation, carrying a patch changeset but no user-visible defect fix. The prior behavior was merely slower (~31ms vs ~0.6ms for an 8 MB frame), not a correctness, hang, or unbounded-memory problem, so it does not meet the stability bar for the maintenance line. It also slightly tightens assumptions about chunk values (dropping the !value guard), which is added risk with no fix to justify it.

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

52526e14aaa848dc24eaeebfbf91ccc9ca0df89a

[pranaygp]

This appears to have broken all vercel-world e2e lanes on main (encrypted frame payloads corrupted; WS transport jobs hung at the 30m ceiling) — bisect and mechanism in #3650, which reverts it. Root cause looks like deferred chunk concatenation stashing yielded views across awaits, letting the stream reuse their backing buffers before the copy.

🤖 Generated with Claude Code

[NathanColosimo]

Summary

• collect partial network chunks before growing the frame buffer
• concatenate buffered bytes once per requested frame field instead of once per incoming chunk
• preserve frame ordering, arbitrary chunk boundaries, owned payload bytes, and early stream cancellation

Performance

Local Node microbenchmark, one 8 MB frame:

Input chunks	Before	After
64 KB	~31 ms	~0.6 ms
16 KB	~93 ms	~0.9 ms

The benchmark is synthetic, but it directly exercises the removed repeated-copy behavior.

Validation

• pnpm --filter @workflow/world-vercel... build
• pnpm --filter @workflow/world-vercel test — 513 tests passed
• pnpm --filter @workflow/world-vercel typecheck
• Biome and git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: 116cb19

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

This PR includes changesets to release 17 packages

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

[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.

• getTailIndex returns -1 before any chunks are written (nextjs-webpack)
• webhookWorkflow (nest)

🛠 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 · addTenWorkflow (astro) · at 22:36:22Z · abandoned wrun_01M08XWAEDYKQYJ181QR4M9RQK
• run-pickup-stall · addTenWorkflow (tanstack-start) · at 22:36:30Z · abandoned wrun_01M08XWJ552M3XT6YC4SX8FWQD

E2E Test Summary

Summary

	Passed	Failed	Skipped	Total
✅ ▲ Vercel Production	3474	0	738	4212
✅ 💻 Local Development	3810	0	558	4368
✅ 📦 Local Production	3810	0	558	4368
✅ 🐘 Local Postgres	3810	0	558	4368
✅ 🪟 Windows	312	0	0	312
✅ 🌐 Cross-language Conformance	9	0	128	137
✅ vercel-multi-region	27	0	0	27
Total	15252	0	2540	17792

Details by Category

✅ ▲ Vercel Production

App	Passed	Failed	Skipped
✅ astro-node	128	0	28
✅ astro-quickjs	128	0	28
✅ example-node	128	0	28
✅ example-quickjs	128	0	28
✅ express-node	128	0	28
✅ express-quickjs	128	0	28
✅ fastify-node	128	0	28
✅ fastify-quickjs	128	0	28
✅ hono-node	128	0	28
✅ hono-quickjs	128	0	28
✅ nest-node	128	0	28
✅ nest-quickjs	128	0	28
✅ nextjs-turbopack-node	153	0	3
✅ nextjs-turbopack-quickjs	153	0	3
✅ nextjs-webpack-node	153	0	3
✅ nextjs-webpack-quickjs	153	0	3
✅ nitro-node	128	0	28
✅ nitro-quickjs	128	0	28
✅ nuxt-node	128	0	28
✅ nuxt-quickjs	128	0	28
✅ python-node	8	0	148
✅ sveltekit-node	147	0	9
✅ sveltekit-quickjs	147	0	9
✅ tanstack-start-node	128	0	28
✅ tanstack-start-quickjs	128	0	28
✅ vite-node	128	0	28
✅ vite-quickjs	128	0	28

✅ 💻 Local Development

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 📦 Local Production

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 🪟 Windows

App	Passed	Failed	Skipped
✅ nextjs-turbopack-node	156	0	0
✅ nextjs-turbopack-quickjs	156	0	0

✅ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
✅ python	9	0	128

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

---

📋 View full workflow run

[vercel]

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

Project	Deployment	Actions	Updated (UTC)
example-nextjs-workflow-turbopack	Ready	Preview	Aug 17, 2026 10:34pm
example-nextjs-workflow-webpack	Ready	Preview	Aug 17, 2026 10:34pm
example-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-astro-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-express-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-fastify-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-hono-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nestjs-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nitro-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nuxt-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-python-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-sveltekit-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-tanstack-start-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-vite-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workflow-docs	Ready	Preview, v0	Aug 17, 2026 10:34pm
workflow-swc-playground	Ready	Preview	Aug 17, 2026 10:34pm
workflow-tarballs	Ready	Preview	Aug 17, 2026 10:34pm
workflow-web	Ready	Preview	Aug 17, 2026 10:34pm

[github-actions]

Sim World

Simulated world deterministic testing for races. Traces

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

fence=per-spec

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

Full trace: world-sim.txt

[github-actions]

📊 Workflow Benchmarks

commit 15a90ed · Mon, 17 Aug 2026 22:51:56 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	247 (+9.8%)	1520 🔴 (+34%) 🔻	1530 🔴 (+29%) 🔻	1933 🔴 (+18%) 🔻	30
TTFS	stream	239 (+5.3%)	1422 🔴 (+20%) 🔻	1463 🔴 (+21%) 🔻	1541 🔴 (-18%) 💚	30
TTFS	hook + stream	500 (+31%) 🔻	1760 🔴 (+29%) 🔻	1903 🔴 (+36%) 🔻	1972 🔴 (+36%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	1273 (+1.4%)	2373 (-0.9%)	2578 (±0%)	2684 (±0%)	10
Fan-out TTLS	Promise.all(100 steps)	6502 (-6.3%)	7915 (-7.7%)	8675 (-1.8%)	9838 (+10%)	10
STSO	1020 steps (inline)	149 (-6.9%)	259 (-11%)	290 (-15%) 💚	443 (-11%)	1019
WO	1020 steps	249616 (-10%)	249616 (-10%)	249616 (-10%)	249616 (-10%)	1
CRTT	first chunk (pooled)	95 (+1.1%)	179 (+25%) 🔻	288 (+51%) 🔻	1222 (+224%) 🔻	28

Streams

Scenario	wr c/s	rd c/s	wr KiB/s	rd KiB/s	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	100 (±0%)	102 (+5%)	5 (±0%)	5.1 (+5%)	116 (-5%)	256 (+15%)	302 (-38%)	1285 (+1%)	211 (-7%)	10
size sweep (100/s, 160B-12KB)	100 (±0%)	101 (+3%)	334 (±0%)	337 (+3%)	141 (-2%)	378 (+49%)	460 (-33%)	1222 (-1%)	178 (-59%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	89.2 (±0%)	89.2 (±0%)	16.2 (±0%)	16.2 (-1%)	170 (+40%)	173 (-31%)	278 (-88%)	792 (-79%)	761 (-5%)	3
replay eve-gpt-5.6-sol-2000t (1x)	54.7 (±0%)	54.7 (-4%)	355 (±0%)	355 (-4%)	269 (+105%)	158 (-27%)	220 (-67%)	410 (-92%)	398 (-87%)	2
replay eve-gpt-5.6-sol-2000t (2x)	109 (±0%)	110 (±0%)	710 (±0%)	712 (±0%)	118 (-2%)	258 (+10%)	373 (+11%)	539 (-17%)	343 (-8%)	3

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

1020 steps (inline)

Cumulative STSO time: main 277417ms → this run 248241ms (Δ -29176ms, -11%)

 100-150 ms ┃ main 0 this 1 +1
150-200 ms ██░┃ main 47 this 93 +46
200-250 ms ███████████████░░░░░░░░┃ main 357 this 589 +232
250-300 ms █████████┃██████ main 397 this 255 -142
300-350 ms █┃███ main 126 this 47 -79
350-400 ms ┃█ main 50 this 19 -31
400-450 ms ┃ main 23 this 6 -17
450-500 ms ┃ main 9 this 3 -6
500-550 ms ┃ main 4 this 3 -1
550-600 ms ┃ main 2 this 0 -2
600-650 ms ┃ main 2 this 0 -2
700-750 ms ┃ main 1 this 1 +0
850-900 ms ┃ main 1 this 1 +0
1100-1150 ms ┃ main 0 this 1 +1

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

variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▃▁▁·· 182 (-6%) 142 (-1%) 302 (-38%) 1285 (+1%) 3000
sweep ······▂█▅▁▁·· 215.7 (+1%) 158 (+10%) 460 (-33%) 1222 (-1%) 3000
gw 1x ·····▁▄█▂▁··· 150.2 (-49%) 121 (-20%) 278 (-88%) 792 (-79%) 5295
eve 1x ·····▁▄█▂▁··· 136.5 (-60%) 119 (-14%) 220 (-67%) 410 (-92%) 5186
eve 2x ·····▁▂█▅▁··· 190.7 (-4%) 157 (-11%) 373 (+11%) 539 (-17%) 7779

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

control ▂▁▃▇▂▂▁█▂▂ 151–250ms
sweep ▆█▄▅▃▃▄▁▂▁ 171–288ms
gw 1x ▂▃█▂▁█▁▂▂▄ 120–212ms
eve 1x █▂▄█▃▂▃▇▄▁ 118–159ms
eve 2x ▁▃▅▃▃▂▅█▄▂ 147–257ms

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

sweep ▁▁▂█▄▅▅ 213–220ms

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

control ▂▅▇▄▃▁▁█▂▂ 31–76ms
sweep ▄▅▁▂█▆▆▁▄▅ 36–74ms
gw 1x ▄██▃▃▆▁▆▂█ 36–48ms
eve 1x ▇▂▃█▄▄▂▃▁▂ 26–34ms
eve 2x ▆▆▅▆▄▄▇▁▄█ 26–35ms

📜 Previous results (1)

116cb19

Mon, 17 Aug 2026 18:06:05 GMT · run logs

vercel / nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	271 (+22%) 🔻	1469 🔴 (+35%) 🔻	1498 🔴 (+30%) 🔻	1552 🔴 (+2.8%)	30
TTFS	stream	1319 (+511%) 🔻	1479 🔴 (+40%) 🔻	1500 🔴 (+39%) 🔻	1532 🔴 (+39%) 🔻	30
TTFS	hook + stream	1434 (+259%) 🔻	1752 🔴 (+27%) 🔻	1821 🔴 (+29%) 🔻	2043 🔴 (+33%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	1158 (-9.7%)	1411 (-43%) 💚	2580 (+3.8%)	2893 (-11%)	10
Fan-out TTLS	Promise.all(100 steps)	6310 (-42%) 💚	11678 (-5.9%)	13221 (+2.5%)	16265 (-5.8%)	10
STSO	1020 steps (inline)	134 (-13%)	233 (-53%) 💚	263 (-52%) 💚	372 (-50%) 💚	1019
WO	1020 steps	225600 (-50%) 💚	225600 (-50%) 💚	225600 (-50%) 💚	225600 (-50%) 💚	1
CRTT	first chunk (pooled)	83 (-12%)	114 (-17%) 💚	121 (-44%) 💚	341 (+46%) 🔻	28

Streams

Scenario	wr c/s	rd c/s	wr KiB/s	rd KiB/s	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	100 (±0%)	100 (+1%)	5 (±0%)	5 (±0%)	110 (-1%)	122 (-50%)	269 (-22%)	391 (-60%)	113 (-49%)	10
size sweep (100/s, 160B-12KB)	100 (±0%)	100 (-1%)	334 (±0%)	334 (-1%)	97 (-19%)	133 (-26%)	248 (+6%)	1119 (+110%)	111 (-39%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	89.2 (±0%)	89 (±0%)	16.2 (±0%)	16.2 (±0%)	97 (-29%)	249 (+38%)	599 (+122%)	899 (-21%)	439 (-47%)	3
replay eve-gpt-5.6-sol-2000t (1x)	54.7 (±0%)	54.7 (±0%)	355 (±0%)	355 (±0%)	107 (-31%)	110 (-33%)	136 (-49%)	389 (-78%)	300 (-65%)	2
replay eve-gpt-5.6-sol-2000t (2x)	109 (±0%)	109 (±0%)	710 (±0%)	709 (±0%)	114 (-9%)	152 (-36%)	201 (-49%)	407 (-46%)	256 (-55%)	3

ℹ️ Metric definitions & methodology

_{Streams: writer/reader sustained rates (steady window, 10% trimmed each side), 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.}

[github-actions]

No backport to stable for 52526e1 (AI decision).

This is a pure performance optimization of decodeFrames in packages/world-vercel/src/frames.ts — it replaces per-chunk buffer reallocation with a single concatenation, carrying a patch changeset but no user-visible defect fix. The prior behavior was merely slower (~31ms vs ~0.6ms for an 8 MB frame), not a correctness, hang, or unbounded-memory problem, so it does not meet the stability bar for the maintenance line. It also slightly tightens assumptions about chunk values (dropping the !value guard), which is added risk with no fix to justify it.

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

52526e14aaa848dc24eaeebfbf91ccc9ca0df89a

[pranaygp]

This appears to have broken all vercel-world e2e lanes on main (encrypted frame payloads corrupted; WS transport jobs hung at the 30m ceiling) — bisect and mechanism in #3650, which reverts it. Root cause looks like deferred chunk concatenation stashing yielded views across awaits, letting the stream reuse their backing buffers before the copy.

🤖 Generated with Claude Code

[NathanColosimo]

Summary

• collect partial network chunks before growing the frame buffer
• concatenate buffered bytes once per requested frame field instead of once per incoming chunk
• preserve frame ordering, arbitrary chunk boundaries, owned payload bytes, and early stream cancellation

Performance

Local Node microbenchmark, one 8 MB frame:

Input chunks	Before	After
64 KB	~31 ms	~0.6 ms
16 KB	~93 ms	~0.9 ms

The benchmark is synthetic, but it directly exercises the removed repeated-copy behavior.

Validation

• pnpm --filter @workflow/world-vercel... build
• pnpm --filter @workflow/world-vercel test — 513 tests passed
• pnpm --filter @workflow/world-vercel typecheck
• Biome and git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: 116cb19

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

This PR includes changesets to release 17 packages

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

[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.

• getTailIndex returns -1 before any chunks are written (nextjs-webpack)
• webhookWorkflow (nest)

🛠 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 · addTenWorkflow (astro) · at 22:36:22Z · abandoned wrun_01M08XWAEDYKQYJ181QR4M9RQK
• run-pickup-stall · addTenWorkflow (tanstack-start) · at 22:36:30Z · abandoned wrun_01M08XWJ552M3XT6YC4SX8FWQD

E2E Test Summary

Summary

	Passed	Failed	Skipped	Total
✅ ▲ Vercel Production	3474	0	738	4212
✅ 💻 Local Development	3810	0	558	4368
✅ 📦 Local Production	3810	0	558	4368
✅ 🐘 Local Postgres	3810	0	558	4368
✅ 🪟 Windows	312	0	0	312
✅ 🌐 Cross-language Conformance	9	0	128	137
✅ vercel-multi-region	27	0	0	27
Total	15252	0	2540	17792

Details by Category

✅ ▲ Vercel Production

App	Passed	Failed	Skipped
✅ astro-node	128	0	28
✅ astro-quickjs	128	0	28
✅ example-node	128	0	28
✅ example-quickjs	128	0	28
✅ express-node	128	0	28
✅ express-quickjs	128	0	28
✅ fastify-node	128	0	28
✅ fastify-quickjs	128	0	28
✅ hono-node	128	0	28
✅ hono-quickjs	128	0	28
✅ nest-node	128	0	28
✅ nest-quickjs	128	0	28
✅ nextjs-turbopack-node	153	0	3
✅ nextjs-turbopack-quickjs	153	0	3
✅ nextjs-webpack-node	153	0	3
✅ nextjs-webpack-quickjs	153	0	3
✅ nitro-node	128	0	28
✅ nitro-quickjs	128	0	28
✅ nuxt-node	128	0	28
✅ nuxt-quickjs	128	0	28
✅ python-node	8	0	148
✅ sveltekit-node	147	0	9
✅ sveltekit-quickjs	147	0	9
✅ tanstack-start-node	128	0	28
✅ tanstack-start-quickjs	128	0	28
✅ vite-node	128	0	28
✅ vite-quickjs	128	0	28

✅ 💻 Local Development

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 📦 Local Production

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 🪟 Windows

App	Passed	Failed	Skipped
✅ nextjs-turbopack-node	156	0	0
✅ nextjs-turbopack-quickjs	156	0	0

✅ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
✅ python	9	0	128

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

---

📋 View full workflow run

[vercel]

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

Project	Deployment	Actions	Updated (UTC)
example-nextjs-workflow-turbopack	Ready	Preview	Aug 17, 2026 10:34pm
example-nextjs-workflow-webpack	Ready	Preview	Aug 17, 2026 10:34pm
example-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-astro-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-express-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-fastify-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-hono-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nestjs-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nitro-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nuxt-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-python-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-sveltekit-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-tanstack-start-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-vite-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workflow-docs	Ready	Preview, v0	Aug 17, 2026 10:34pm
workflow-swc-playground	Ready	Preview	Aug 17, 2026 10:34pm
workflow-tarballs	Ready	Preview	Aug 17, 2026 10:34pm
workflow-web	Ready	Preview	Aug 17, 2026 10:34pm

[github-actions]

Sim World

Simulated world deterministic testing for races. Traces

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

fence=per-spec

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

Full trace: world-sim.txt

[github-actions]

📊 Workflow Benchmarks

commit 15a90ed · Mon, 17 Aug 2026 22:51:56 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	247 (+9.8%)	1520 🔴 (+34%) 🔻	1530 🔴 (+29%) 🔻	1933 🔴 (+18%) 🔻	30
TTFS	stream	239 (+5.3%)	1422 🔴 (+20%) 🔻	1463 🔴 (+21%) 🔻	1541 🔴 (-18%) 💚	30
TTFS	hook + stream	500 (+31%) 🔻	1760 🔴 (+29%) 🔻	1903 🔴 (+36%) 🔻	1972 🔴 (+36%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	1273 (+1.4%)	2373 (-0.9%)	2578 (±0%)	2684 (±0%)	10
Fan-out TTLS	Promise.all(100 steps)	6502 (-6.3%)	7915 (-7.7%)	8675 (-1.8%)	9838 (+10%)	10
STSO	1020 steps (inline)	149 (-6.9%)	259 (-11%)	290 (-15%) 💚	443 (-11%)	1019
WO	1020 steps	249616 (-10%)	249616 (-10%)	249616 (-10%)	249616 (-10%)	1
CRTT	first chunk (pooled)	95 (+1.1%)	179 (+25%) 🔻	288 (+51%) 🔻	1222 (+224%) 🔻	28

Streams

Scenario	wr c/s	rd c/s	wr KiB/s	rd KiB/s	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	100 (±0%)	102 (+5%)	5 (±0%)	5.1 (+5%)	116 (-5%)	256 (+15%)	302 (-38%)	1285 (+1%)	211 (-7%)	10
size sweep (100/s, 160B-12KB)	100 (±0%)	101 (+3%)	334 (±0%)	337 (+3%)	141 (-2%)	378 (+49%)	460 (-33%)	1222 (-1%)	178 (-59%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	89.2 (±0%)	89.2 (±0%)	16.2 (±0%)	16.2 (-1%)	170 (+40%)	173 (-31%)	278 (-88%)	792 (-79%)	761 (-5%)	3
replay eve-gpt-5.6-sol-2000t (1x)	54.7 (±0%)	54.7 (-4%)	355 (±0%)	355 (-4%)	269 (+105%)	158 (-27%)	220 (-67%)	410 (-92%)	398 (-87%)	2
replay eve-gpt-5.6-sol-2000t (2x)	109 (±0%)	110 (±0%)	710 (±0%)	712 (±0%)	118 (-2%)	258 (+10%)	373 (+11%)	539 (-17%)	343 (-8%)	3

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

1020 steps (inline)

Cumulative STSO time: main 277417ms → this run 248241ms (Δ -29176ms, -11%)

 100-150 ms ┃ main 0 this 1 +1
150-200 ms ██░┃ main 47 this 93 +46
200-250 ms ███████████████░░░░░░░░┃ main 357 this 589 +232
250-300 ms █████████┃██████ main 397 this 255 -142
300-350 ms █┃███ main 126 this 47 -79
350-400 ms ┃█ main 50 this 19 -31
400-450 ms ┃ main 23 this 6 -17
450-500 ms ┃ main 9 this 3 -6
500-550 ms ┃ main 4 this 3 -1
550-600 ms ┃ main 2 this 0 -2
600-650 ms ┃ main 2 this 0 -2
700-750 ms ┃ main 1 this 1 +0
850-900 ms ┃ main 1 this 1 +0
1100-1150 ms ┃ main 0 this 1 +1

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

variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▃▁▁·· 182 (-6%) 142 (-1%) 302 (-38%) 1285 (+1%) 3000
sweep ······▂█▅▁▁·· 215.7 (+1%) 158 (+10%) 460 (-33%) 1222 (-1%) 3000
gw 1x ·····▁▄█▂▁··· 150.2 (-49%) 121 (-20%) 278 (-88%) 792 (-79%) 5295
eve 1x ·····▁▄█▂▁··· 136.5 (-60%) 119 (-14%) 220 (-67%) 410 (-92%) 5186
eve 2x ·····▁▂█▅▁··· 190.7 (-4%) 157 (-11%) 373 (+11%) 539 (-17%) 7779

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

control ▂▁▃▇▂▂▁█▂▂ 151–250ms
sweep ▆█▄▅▃▃▄▁▂▁ 171–288ms
gw 1x ▂▃█▂▁█▁▂▂▄ 120–212ms
eve 1x █▂▄█▃▂▃▇▄▁ 118–159ms
eve 2x ▁▃▅▃▃▂▅█▄▂ 147–257ms

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

sweep ▁▁▂█▄▅▅ 213–220ms

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

control ▂▅▇▄▃▁▁█▂▂ 31–76ms
sweep ▄▅▁▂█▆▆▁▄▅ 36–74ms
gw 1x ▄██▃▃▆▁▆▂█ 36–48ms
eve 1x ▇▂▃█▄▄▂▃▁▂ 26–34ms
eve 2x ▆▆▅▆▄▄▇▁▄█ 26–35ms

📜 Previous results (1)

116cb19

Mon, 17 Aug 2026 18:06:05 GMT · run logs

vercel / nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	271 (+22%) 🔻	1469 🔴 (+35%) 🔻	1498 🔴 (+30%) 🔻	1552 🔴 (+2.8%)	30
TTFS	stream	1319 (+511%) 🔻	1479 🔴 (+40%) 🔻	1500 🔴 (+39%) 🔻	1532 🔴 (+39%) 🔻	30
TTFS	hook + stream	1434 (+259%) 🔻	1752 🔴 (+27%) 🔻	1821 🔴 (+29%) 🔻	2043 🔴 (+33%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	1158 (-9.7%)	1411 (-43%) 💚	2580 (+3.8%)	2893 (-11%)	10
Fan-out TTLS	Promise.all(100 steps)	6310 (-42%) 💚	11678 (-5.9%)	13221 (+2.5%)	16265 (-5.8%)	10
STSO	1020 steps (inline)	134 (-13%)	233 (-53%) 💚	263 (-52%) 💚	372 (-50%) 💚	1019
WO	1020 steps	225600 (-50%) 💚	225600 (-50%) 💚	225600 (-50%) 💚	225600 (-50%) 💚	1
CRTT	first chunk (pooled)	83 (-12%)	114 (-17%) 💚	121 (-44%) 💚	341 (+46%) 🔻	28

Streams

Scenario	wr c/s	rd c/s	wr KiB/s	rd KiB/s	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	100 (±0%)	100 (+1%)	5 (±0%)	5 (±0%)	110 (-1%)	122 (-50%)	269 (-22%)	391 (-60%)	113 (-49%)	10
size sweep (100/s, 160B-12KB)	100 (±0%)	100 (-1%)	334 (±0%)	334 (-1%)	97 (-19%)	133 (-26%)	248 (+6%)	1119 (+110%)	111 (-39%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	89.2 (±0%)	89 (±0%)	16.2 (±0%)	16.2 (±0%)	97 (-29%)	249 (+38%)	599 (+122%)	899 (-21%)	439 (-47%)	3
replay eve-gpt-5.6-sol-2000t (1x)	54.7 (±0%)	54.7 (±0%)	355 (±0%)	355 (±0%)	107 (-31%)	110 (-33%)	136 (-49%)	389 (-78%)	300 (-65%)	2
replay eve-gpt-5.6-sol-2000t (2x)	109 (±0%)	109 (±0%)	710 (±0%)	709 (±0%)	114 (-9%)	152 (-36%)	201 (-49%)	407 (-46%)	256 (-55%)	3

ℹ️ Metric definitions & methodology

_{Streams: writer/reader sustained rates (steady window, 10% trimmed each side), 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.}

[github-actions]

No backport to stable for 52526e1 (AI decision).

This is a pure performance optimization of decodeFrames in packages/world-vercel/src/frames.ts — it replaces per-chunk buffer reallocation with a single concatenation, carrying a patch changeset but no user-visible defect fix. The prior behavior was merely slower (~31ms vs ~0.6ms for an 8 MB frame), not a correctness, hang, or unbounded-memory problem, so it does not meet the stability bar for the maintenance line. It also slightly tightens assumptions about chunk values (dropping the !value guard), which is added risk with no fix to justify it.

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

52526e14aaa848dc24eaeebfbf91ccc9ca0df89a

[pranaygp]

This appears to have broken all vercel-world e2e lanes on main (encrypted frame payloads corrupted; WS transport jobs hung at the 30m ceiling) — bisect and mechanism in #3650, which reverts it. Root cause looks like deferred chunk concatenation stashing yielded views across awaits, letting the stream reuse their backing buffers before the copy.

🤖 Generated with Claude Code

[NathanColosimo]

Summary

• collect partial network chunks before growing the frame buffer
• concatenate buffered bytes once per requested frame field instead of once per incoming chunk
• preserve frame ordering, arbitrary chunk boundaries, owned payload bytes, and early stream cancellation

Performance

Local Node microbenchmark, one 8 MB frame:

Input chunks	Before	After
64 KB	~31 ms	~0.6 ms
16 KB	~93 ms	~0.9 ms

The benchmark is synthetic, but it directly exercises the removed repeated-copy behavior.

Validation

• pnpm --filter @workflow/world-vercel... build
• pnpm --filter @workflow/world-vercel test — 513 tests passed
• pnpm --filter @workflow/world-vercel typecheck
• Biome and git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: 116cb19

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

This PR includes changesets to release 17 packages

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

[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.

• getTailIndex returns -1 before any chunks are written (nextjs-webpack)
• webhookWorkflow (nest)

🛠 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 · addTenWorkflow (astro) · at 22:36:22Z · abandoned wrun_01M08XWAEDYKQYJ181QR4M9RQK
• run-pickup-stall · addTenWorkflow (tanstack-start) · at 22:36:30Z · abandoned wrun_01M08XWJ552M3XT6YC4SX8FWQD

E2E Test Summary

Summary

	Passed	Failed	Skipped	Total
✅ ▲ Vercel Production	3474	0	738	4212
✅ 💻 Local Development	3810	0	558	4368
✅ 📦 Local Production	3810	0	558	4368
✅ 🐘 Local Postgres	3810	0	558	4368
✅ 🪟 Windows	312	0	0	312
✅ 🌐 Cross-language Conformance	9	0	128	137
✅ vercel-multi-region	27	0	0	27
Total	15252	0	2540	17792

Details by Category

✅ ▲ Vercel Production

App	Passed	Failed	Skipped
✅ astro-node	128	0	28
✅ astro-quickjs	128	0	28
✅ example-node	128	0	28
✅ example-quickjs	128	0	28
✅ express-node	128	0	28
✅ express-quickjs	128	0	28
✅ fastify-node	128	0	28
✅ fastify-quickjs	128	0	28
✅ hono-node	128	0	28
✅ hono-quickjs	128	0	28
✅ nest-node	128	0	28
✅ nest-quickjs	128	0	28
✅ nextjs-turbopack-node	153	0	3
✅ nextjs-turbopack-quickjs	153	0	3
✅ nextjs-webpack-node	153	0	3
✅ nextjs-webpack-quickjs	153	0	3
✅ nitro-node	128	0	28
✅ nitro-quickjs	128	0	28
✅ nuxt-node	128	0	28
✅ nuxt-quickjs	128	0	28
✅ python-node	8	0	148
✅ sveltekit-node	147	0	9
✅ sveltekit-quickjs	147	0	9
✅ tanstack-start-node	128	0	28
✅ tanstack-start-quickjs	128	0	28
✅ vite-node	128	0	28
✅ vite-quickjs	128	0	28

✅ 💻 Local Development

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 📦 Local Production

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 🪟 Windows

App	Passed	Failed	Skipped
✅ nextjs-turbopack-node	156	0	0
✅ nextjs-turbopack-quickjs	156	0	0

✅ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
✅ python	9	0	128

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

---

📋 View full workflow run

[vercel]

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

Project	Deployment	Actions	Updated (UTC)
example-nextjs-workflow-turbopack	Ready	Preview	Aug 17, 2026 10:34pm
example-nextjs-workflow-webpack	Ready	Preview	Aug 17, 2026 10:34pm
example-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-astro-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-express-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-fastify-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-hono-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nestjs-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nitro-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nuxt-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-python-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-sveltekit-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-tanstack-start-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-vite-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workflow-docs	Ready	Preview, v0	Aug 17, 2026 10:34pm
workflow-swc-playground	Ready	Preview	Aug 17, 2026 10:34pm
workflow-tarballs	Ready	Preview	Aug 17, 2026 10:34pm
workflow-web	Ready	Preview	Aug 17, 2026 10:34pm

[github-actions]

Sim World

Simulated world deterministic testing for races. Traces

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

fence=per-spec

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

Full trace: world-sim.txt

[github-actions]

📊 Workflow Benchmarks

commit 15a90ed · Mon, 17 Aug 2026 22:51:56 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	247 (+9.8%)	1520 🔴 (+34%) 🔻	1530 🔴 (+29%) 🔻	1933 🔴 (+18%) 🔻	30
TTFS	stream	239 (+5.3%)	1422 🔴 (+20%) 🔻	1463 🔴 (+21%) 🔻	1541 🔴 (-18%) 💚	30
TTFS	hook + stream	500 (+31%) 🔻	1760 🔴 (+29%) 🔻	1903 🔴 (+36%) 🔻	1972 🔴 (+36%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	1273 (+1.4%)	2373 (-0.9%)	2578 (±0%)	2684 (±0%)	10
Fan-out TTLS	Promise.all(100 steps)	6502 (-6.3%)	7915 (-7.7%)	8675 (-1.8%)	9838 (+10%)	10
STSO	1020 steps (inline)	149 (-6.9%)	259 (-11%)	290 (-15%) 💚	443 (-11%)	1019
WO	1020 steps	249616 (-10%)	249616 (-10%)	249616 (-10%)	249616 (-10%)	1
CRTT	first chunk (pooled)	95 (+1.1%)	179 (+25%) 🔻	288 (+51%) 🔻	1222 (+224%) 🔻	28

Streams

Scenario	wr c/s	rd c/s	wr KiB/s	rd KiB/s	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	100 (±0%)	102 (+5%)	5 (±0%)	5.1 (+5%)	116 (-5%)	256 (+15%)	302 (-38%)	1285 (+1%)	211 (-7%)	10
size sweep (100/s, 160B-12KB)	100 (±0%)	101 (+3%)	334 (±0%)	337 (+3%)	141 (-2%)	378 (+49%)	460 (-33%)	1222 (-1%)	178 (-59%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	89.2 (±0%)	89.2 (±0%)	16.2 (±0%)	16.2 (-1%)	170 (+40%)	173 (-31%)	278 (-88%)	792 (-79%)	761 (-5%)	3
replay eve-gpt-5.6-sol-2000t (1x)	54.7 (±0%)	54.7 (-4%)	355 (±0%)	355 (-4%)	269 (+105%)	158 (-27%)	220 (-67%)	410 (-92%)	398 (-87%)	2
replay eve-gpt-5.6-sol-2000t (2x)	109 (±0%)	110 (±0%)	710 (±0%)	712 (±0%)	118 (-2%)	258 (+10%)	373 (+11%)	539 (-17%)	343 (-8%)	3

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

1020 steps (inline)

Cumulative STSO time: main 277417ms → this run 248241ms (Δ -29176ms, -11%)

 100-150 ms ┃ main 0 this 1 +1
150-200 ms ██░┃ main 47 this 93 +46
200-250 ms ███████████████░░░░░░░░┃ main 357 this 589 +232
250-300 ms █████████┃██████ main 397 this 255 -142
300-350 ms █┃███ main 126 this 47 -79
350-400 ms ┃█ main 50 this 19 -31
400-450 ms ┃ main 23 this 6 -17
450-500 ms ┃ main 9 this 3 -6
500-550 ms ┃ main 4 this 3 -1
550-600 ms ┃ main 2 this 0 -2
600-650 ms ┃ main 2 this 0 -2
700-750 ms ┃ main 1 this 1 +0
850-900 ms ┃ main 1 this 1 +0
1100-1150 ms ┃ main 0 this 1 +1

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

variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▃▁▁·· 182 (-6%) 142 (-1%) 302 (-38%) 1285 (+1%) 3000
sweep ······▂█▅▁▁·· 215.7 (+1%) 158 (+10%) 460 (-33%) 1222 (-1%) 3000
gw 1x ·····▁▄█▂▁··· 150.2 (-49%) 121 (-20%) 278 (-88%) 792 (-79%) 5295
eve 1x ·····▁▄█▂▁··· 136.5 (-60%) 119 (-14%) 220 (-67%) 410 (-92%) 5186
eve 2x ·····▁▂█▅▁··· 190.7 (-4%) 157 (-11%) 373 (+11%) 539 (-17%) 7779

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

control ▂▁▃▇▂▂▁█▂▂ 151–250ms
sweep ▆█▄▅▃▃▄▁▂▁ 171–288ms
gw 1x ▂▃█▂▁█▁▂▂▄ 120–212ms
eve 1x █▂▄█▃▂▃▇▄▁ 118–159ms
eve 2x ▁▃▅▃▃▂▅█▄▂ 147–257ms

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

sweep ▁▁▂█▄▅▅ 213–220ms

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

control ▂▅▇▄▃▁▁█▂▂ 31–76ms
sweep ▄▅▁▂█▆▆▁▄▅ 36–74ms
gw 1x ▄██▃▃▆▁▆▂█ 36–48ms
eve 1x ▇▂▃█▄▄▂▃▁▂ 26–34ms
eve 2x ▆▆▅▆▄▄▇▁▄█ 26–35ms

📜 Previous results (1)

116cb19

Mon, 17 Aug 2026 18:06:05 GMT · run logs

vercel / nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	271 (+22%) 🔻	1469 🔴 (+35%) 🔻	1498 🔴 (+30%) 🔻	1552 🔴 (+2.8%)	30
TTFS	stream	1319 (+511%) 🔻	1479 🔴 (+40%) 🔻	1500 🔴 (+39%) 🔻	1532 🔴 (+39%) 🔻	30
TTFS	hook + stream	1434 (+259%) 🔻	1752 🔴 (+27%) 🔻	1821 🔴 (+29%) 🔻	2043 🔴 (+33%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	1158 (-9.7%)	1411 (-43%) 💚	2580 (+3.8%)	2893 (-11%)	10
Fan-out TTLS	Promise.all(100 steps)	6310 (-42%) 💚	11678 (-5.9%)	13221 (+2.5%)	16265 (-5.8%)	10
STSO	1020 steps (inline)	134 (-13%)	233 (-53%) 💚	263 (-52%) 💚	372 (-50%) 💚	1019
WO	1020 steps	225600 (-50%) 💚	225600 (-50%) 💚	225600 (-50%) 💚	225600 (-50%) 💚	1
CRTT	first chunk (pooled)	83 (-12%)	114 (-17%) 💚	121 (-44%) 💚	341 (+46%) 🔻	28

Streams

Scenario	wr c/s	rd c/s	wr KiB/s	rd KiB/s	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	100 (±0%)	100 (+1%)	5 (±0%)	5 (±0%)	110 (-1%)	122 (-50%)	269 (-22%)	391 (-60%)	113 (-49%)	10
size sweep (100/s, 160B-12KB)	100 (±0%)	100 (-1%)	334 (±0%)	334 (-1%)	97 (-19%)	133 (-26%)	248 (+6%)	1119 (+110%)	111 (-39%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	89.2 (±0%)	89 (±0%)	16.2 (±0%)	16.2 (±0%)	97 (-29%)	249 (+38%)	599 (+122%)	899 (-21%)	439 (-47%)	3
replay eve-gpt-5.6-sol-2000t (1x)	54.7 (±0%)	54.7 (±0%)	355 (±0%)	355 (±0%)	107 (-31%)	110 (-33%)	136 (-49%)	389 (-78%)	300 (-65%)	2
replay eve-gpt-5.6-sol-2000t (2x)	109 (±0%)	109 (±0%)	710 (±0%)	709 (±0%)	114 (-9%)	152 (-36%)	201 (-49%)	407 (-46%)	256 (-55%)	3

ℹ️ Metric definitions & methodology

_{Streams: writer/reader sustained rates (steady window, 10% trimmed each side), 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.}

[github-actions]

No backport to stable for 52526e1 (AI decision).

This is a pure performance optimization of decodeFrames in packages/world-vercel/src/frames.ts — it replaces per-chunk buffer reallocation with a single concatenation, carrying a patch changeset but no user-visible defect fix. The prior behavior was merely slower (~31ms vs ~0.6ms for an 8 MB frame), not a correctness, hang, or unbounded-memory problem, so it does not meet the stability bar for the maintenance line. It also slightly tightens assumptions about chunk values (dropping the !value guard), which is added risk with no fix to justify it.

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

52526e14aaa848dc24eaeebfbf91ccc9ca0df89a

[pranaygp]

This appears to have broken all vercel-world e2e lanes on main (encrypted frame payloads corrupted; WS transport jobs hung at the 30m ceiling) — bisect and mechanism in #3650, which reverts it. Root cause looks like deferred chunk concatenation stashing yielded views across awaits, letting the stream reuse their backing buffers before the copy.

🤖 Generated with Claude Code

[NathanColosimo]

Summary

• collect partial network chunks before growing the frame buffer
• concatenate buffered bytes once per requested frame field instead of once per incoming chunk
• preserve frame ordering, arbitrary chunk boundaries, owned payload bytes, and early stream cancellation

Performance

Local Node microbenchmark, one 8 MB frame:

Input chunks	Before	After
64 KB	~31 ms	~0.6 ms
16 KB	~93 ms	~0.9 ms

The benchmark is synthetic, but it directly exercises the removed repeated-copy behavior.

Validation

• pnpm --filter @workflow/world-vercel... build
• pnpm --filter @workflow/world-vercel test — 513 tests passed
• pnpm --filter @workflow/world-vercel typecheck
• Biome and git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: 116cb19

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

This PR includes changesets to release 17 packages

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

[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.

• getTailIndex returns -1 before any chunks are written (nextjs-webpack)
• webhookWorkflow (nest)

🛠 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 · addTenWorkflow (astro) · at 22:36:22Z · abandoned wrun_01M08XWAEDYKQYJ181QR4M9RQK
• run-pickup-stall · addTenWorkflow (tanstack-start) · at 22:36:30Z · abandoned wrun_01M08XWJ552M3XT6YC4SX8FWQD

E2E Test Summary

Summary

	Passed	Failed	Skipped	Total
✅ ▲ Vercel Production	3474	0	738	4212
✅ 💻 Local Development	3810	0	558	4368
✅ 📦 Local Production	3810	0	558	4368
✅ 🐘 Local Postgres	3810	0	558	4368
✅ 🪟 Windows	312	0	0	312
✅ 🌐 Cross-language Conformance	9	0	128	137
✅ vercel-multi-region	27	0	0	27
Total	15252	0	2540	17792

Details by Category

✅ ▲ Vercel Production

App	Passed	Failed	Skipped
✅ astro-node	128	0	28
✅ astro-quickjs	128	0	28
✅ example-node	128	0	28
✅ example-quickjs	128	0	28
✅ express-node	128	0	28
✅ express-quickjs	128	0	28
✅ fastify-node	128	0	28
✅ fastify-quickjs	128	0	28
✅ hono-node	128	0	28
✅ hono-quickjs	128	0	28
✅ nest-node	128	0	28
✅ nest-quickjs	128	0	28
✅ nextjs-turbopack-node	153	0	3
✅ nextjs-turbopack-quickjs	153	0	3
✅ nextjs-webpack-node	153	0	3
✅ nextjs-webpack-quickjs	153	0	3
✅ nitro-node	128	0	28
✅ nitro-quickjs	128	0	28
✅ nuxt-node	128	0	28
✅ nuxt-quickjs	128	0	28
✅ python-node	8	0	148
✅ sveltekit-node	147	0	9
✅ sveltekit-quickjs	147	0	9
✅ tanstack-start-node	128	0	28
✅ tanstack-start-quickjs	128	0	28
✅ vite-node	128	0	28
✅ vite-quickjs	128	0	28

✅ 💻 Local Development

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 📦 Local Production

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 🪟 Windows

App	Passed	Failed	Skipped
✅ nextjs-turbopack-node	156	0	0
✅ nextjs-turbopack-quickjs	156	0	0

✅ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
✅ python	9	0	128

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

---

📋 View full workflow run

[vercel]

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

Project	Deployment	Actions	Updated (UTC)
example-nextjs-workflow-turbopack	Ready	Preview	Aug 17, 2026 10:34pm
example-nextjs-workflow-webpack	Ready	Preview	Aug 17, 2026 10:34pm
example-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-astro-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-express-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-fastify-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-hono-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nestjs-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nitro-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nuxt-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-python-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-sveltekit-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-tanstack-start-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-vite-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workflow-docs	Ready	Preview, v0	Aug 17, 2026 10:34pm
workflow-swc-playground	Ready	Preview	Aug 17, 2026 10:34pm
workflow-tarballs	Ready	Preview	Aug 17, 2026 10:34pm
workflow-web	Ready	Preview	Aug 17, 2026 10:34pm

[github-actions]

Sim World

Simulated world deterministic testing for races. Traces

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

fence=per-spec

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

Full trace: world-sim.txt

[github-actions]

📊 Workflow Benchmarks

commit 15a90ed · Mon, 17 Aug 2026 22:51:56 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	247 (+9.8%)	1520 🔴 (+34%) 🔻	1530 🔴 (+29%) 🔻	1933 🔴 (+18%) 🔻	30
TTFS	stream	239 (+5.3%)	1422 🔴 (+20%) 🔻	1463 🔴 (+21%) 🔻	1541 🔴 (-18%) 💚	30
TTFS	hook + stream	500 (+31%) 🔻	1760 🔴 (+29%) 🔻	1903 🔴 (+36%) 🔻	1972 🔴 (+36%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	1273 (+1.4%)	2373 (-0.9%)	2578 (±0%)	2684 (±0%)	10
Fan-out TTLS	Promise.all(100 steps)	6502 (-6.3%)	7915 (-7.7%)	8675 (-1.8%)	9838 (+10%)	10
STSO	1020 steps (inline)	149 (-6.9%)	259 (-11%)	290 (-15%) 💚	443 (-11%)	1019
WO	1020 steps	249616 (-10%)	249616 (-10%)	249616 (-10%)	249616 (-10%)	1
CRTT	first chunk (pooled)	95 (+1.1%)	179 (+25%) 🔻	288 (+51%) 🔻	1222 (+224%) 🔻	28

Streams

Scenario	wr c/s	rd c/s	wr KiB/s	rd KiB/s	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	100 (±0%)	102 (+5%)	5 (±0%)	5.1 (+5%)	116 (-5%)	256 (+15%)	302 (-38%)	1285 (+1%)	211 (-7%)	10
size sweep (100/s, 160B-12KB)	100 (±0%)	101 (+3%)	334 (±0%)	337 (+3%)	141 (-2%)	378 (+49%)	460 (-33%)	1222 (-1%)	178 (-59%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	89.2 (±0%)	89.2 (±0%)	16.2 (±0%)	16.2 (-1%)	170 (+40%)	173 (-31%)	278 (-88%)	792 (-79%)	761 (-5%)	3
replay eve-gpt-5.6-sol-2000t (1x)	54.7 (±0%)	54.7 (-4%)	355 (±0%)	355 (-4%)	269 (+105%)	158 (-27%)	220 (-67%)	410 (-92%)	398 (-87%)	2
replay eve-gpt-5.6-sol-2000t (2x)	109 (±0%)	110 (±0%)	710 (±0%)	712 (±0%)	118 (-2%)	258 (+10%)	373 (+11%)	539 (-17%)	343 (-8%)	3

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

1020 steps (inline)

Cumulative STSO time: main 277417ms → this run 248241ms (Δ -29176ms, -11%)

 100-150 ms ┃ main 0 this 1 +1
150-200 ms ██░┃ main 47 this 93 +46
200-250 ms ███████████████░░░░░░░░┃ main 357 this 589 +232
250-300 ms █████████┃██████ main 397 this 255 -142
300-350 ms █┃███ main 126 this 47 -79
350-400 ms ┃█ main 50 this 19 -31
400-450 ms ┃ main 23 this 6 -17
450-500 ms ┃ main 9 this 3 -6
500-550 ms ┃ main 4 this 3 -1
550-600 ms ┃ main 2 this 0 -2
600-650 ms ┃ main 2 this 0 -2
700-750 ms ┃ main 1 this 1 +0
850-900 ms ┃ main 1 this 1 +0
1100-1150 ms ┃ main 0 this 1 +1

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

variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▃▁▁·· 182 (-6%) 142 (-1%) 302 (-38%) 1285 (+1%) 3000
sweep ······▂█▅▁▁·· 215.7 (+1%) 158 (+10%) 460 (-33%) 1222 (-1%) 3000
gw 1x ·····▁▄█▂▁··· 150.2 (-49%) 121 (-20%) 278 (-88%) 792 (-79%) 5295
eve 1x ·····▁▄█▂▁··· 136.5 (-60%) 119 (-14%) 220 (-67%) 410 (-92%) 5186
eve 2x ·····▁▂█▅▁··· 190.7 (-4%) 157 (-11%) 373 (+11%) 539 (-17%) 7779

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

control ▂▁▃▇▂▂▁█▂▂ 151–250ms
sweep ▆█▄▅▃▃▄▁▂▁ 171–288ms
gw 1x ▂▃█▂▁█▁▂▂▄ 120–212ms
eve 1x █▂▄█▃▂▃▇▄▁ 118–159ms
eve 2x ▁▃▅▃▃▂▅█▄▂ 147–257ms

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

sweep ▁▁▂█▄▅▅ 213–220ms

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

control ▂▅▇▄▃▁▁█▂▂ 31–76ms
sweep ▄▅▁▂█▆▆▁▄▅ 36–74ms
gw 1x ▄██▃▃▆▁▆▂█ 36–48ms
eve 1x ▇▂▃█▄▄▂▃▁▂ 26–34ms
eve 2x ▆▆▅▆▄▄▇▁▄█ 26–35ms

📜 Previous results (1)

116cb19

Mon, 17 Aug 2026 18:06:05 GMT · run logs

vercel / nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	271 (+22%) 🔻	1469 🔴 (+35%) 🔻	1498 🔴 (+30%) 🔻	1552 🔴 (+2.8%)	30
TTFS	stream	1319 (+511%) 🔻	1479 🔴 (+40%) 🔻	1500 🔴 (+39%) 🔻	1532 🔴 (+39%) 🔻	30
TTFS	hook + stream	1434 (+259%) 🔻	1752 🔴 (+27%) 🔻	1821 🔴 (+29%) 🔻	2043 🔴 (+33%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	1158 (-9.7%)	1411 (-43%) 💚	2580 (+3.8%)	2893 (-11%)	10
Fan-out TTLS	Promise.all(100 steps)	6310 (-42%) 💚	11678 (-5.9%)	13221 (+2.5%)	16265 (-5.8%)	10
STSO	1020 steps (inline)	134 (-13%)	233 (-53%) 💚	263 (-52%) 💚	372 (-50%) 💚	1019
WO	1020 steps	225600 (-50%) 💚	225600 (-50%) 💚	225600 (-50%) 💚	225600 (-50%) 💚	1
CRTT	first chunk (pooled)	83 (-12%)	114 (-17%) 💚	121 (-44%) 💚	341 (+46%) 🔻	28

Streams

Scenario	wr c/s	rd c/s	wr KiB/s	rd KiB/s	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	100 (±0%)	100 (+1%)	5 (±0%)	5 (±0%)	110 (-1%)	122 (-50%)	269 (-22%)	391 (-60%)	113 (-49%)	10
size sweep (100/s, 160B-12KB)	100 (±0%)	100 (-1%)	334 (±0%)	334 (-1%)	97 (-19%)	133 (-26%)	248 (+6%)	1119 (+110%)	111 (-39%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	89.2 (±0%)	89 (±0%)	16.2 (±0%)	16.2 (±0%)	97 (-29%)	249 (+38%)	599 (+122%)	899 (-21%)	439 (-47%)	3
replay eve-gpt-5.6-sol-2000t (1x)	54.7 (±0%)	54.7 (±0%)	355 (±0%)	355 (±0%)	107 (-31%)	110 (-33%)	136 (-49%)	389 (-78%)	300 (-65%)	2
replay eve-gpt-5.6-sol-2000t (2x)	109 (±0%)	109 (±0%)	710 (±0%)	709 (±0%)	114 (-9%)	152 (-36%)	201 (-49%)	407 (-46%)	256 (-55%)	3

ℹ️ Metric definitions & methodology

_{Streams: writer/reader sustained rates (steady window, 10% trimmed each side), 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.}

[github-actions]

No backport to stable for 52526e1 (AI decision).

This is a pure performance optimization of decodeFrames in packages/world-vercel/src/frames.ts — it replaces per-chunk buffer reallocation with a single concatenation, carrying a patch changeset but no user-visible defect fix. The prior behavior was merely slower (~31ms vs ~0.6ms for an 8 MB frame), not a correctness, hang, or unbounded-memory problem, so it does not meet the stability bar for the maintenance line. It also slightly tightens assumptions about chunk values (dropping the !value guard), which is added risk with no fix to justify it.

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

52526e14aaa848dc24eaeebfbf91ccc9ca0df89a

[pranaygp]

This appears to have broken all vercel-world e2e lanes on main (encrypted frame payloads corrupted; WS transport jobs hung at the 30m ceiling) — bisect and mechanism in #3650, which reverts it. Root cause looks like deferred chunk concatenation stashing yielded views across awaits, letting the stream reuse their backing buffers before the copy.

🤖 Generated with Claude Code

[NathanColosimo]

Summary

• collect partial network chunks before growing the frame buffer
• concatenate buffered bytes once per requested frame field instead of once per incoming chunk
• preserve frame ordering, arbitrary chunk boundaries, owned payload bytes, and early stream cancellation

Performance

Local Node microbenchmark, one 8 MB frame:

Input chunks	Before	After
64 KB	~31 ms	~0.6 ms
16 KB	~93 ms	~0.9 ms

The benchmark is synthetic, but it directly exercises the removed repeated-copy behavior.

Validation

• pnpm --filter @workflow/world-vercel... build
• pnpm --filter @workflow/world-vercel test — 513 tests passed
• pnpm --filter @workflow/world-vercel typecheck
• Biome and git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: 116cb19

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

This PR includes changesets to release 17 packages

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

[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.

• getTailIndex returns -1 before any chunks are written (nextjs-webpack)
• webhookWorkflow (nest)

🛠 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 · addTenWorkflow (astro) · at 22:36:22Z · abandoned wrun_01M08XWAEDYKQYJ181QR4M9RQK
• run-pickup-stall · addTenWorkflow (tanstack-start) · at 22:36:30Z · abandoned wrun_01M08XWJ552M3XT6YC4SX8FWQD

E2E Test Summary

Summary

	Passed	Failed	Skipped	Total
✅ ▲ Vercel Production	3474	0	738	4212
✅ 💻 Local Development	3810	0	558	4368
✅ 📦 Local Production	3810	0	558	4368
✅ 🐘 Local Postgres	3810	0	558	4368
✅ 🪟 Windows	312	0	0	312
✅ 🌐 Cross-language Conformance	9	0	128	137
✅ vercel-multi-region	27	0	0	27
Total	15252	0	2540	17792

Details by Category

✅ ▲ Vercel Production

App	Passed	Failed	Skipped
✅ astro-node	128	0	28
✅ astro-quickjs	128	0	28
✅ example-node	128	0	28
✅ example-quickjs	128	0	28
✅ express-node	128	0	28
✅ express-quickjs	128	0	28
✅ fastify-node	128	0	28
✅ fastify-quickjs	128	0	28
✅ hono-node	128	0	28
✅ hono-quickjs	128	0	28
✅ nest-node	128	0	28
✅ nest-quickjs	128	0	28
✅ nextjs-turbopack-node	153	0	3
✅ nextjs-turbopack-quickjs	153	0	3
✅ nextjs-webpack-node	153	0	3
✅ nextjs-webpack-quickjs	153	0	3
✅ nitro-node	128	0	28
✅ nitro-quickjs	128	0	28
✅ nuxt-node	128	0	28
✅ nuxt-quickjs	128	0	28
✅ python-node	8	0	148
✅ sveltekit-node	147	0	9
✅ sveltekit-quickjs	147	0	9
✅ tanstack-start-node	128	0	28
✅ tanstack-start-quickjs	128	0	28
✅ vite-node	128	0	28
✅ vite-quickjs	128	0	28

✅ 💻 Local Development

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 📦 Local Production

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	130	0	26
✅ astro-stable-quickjs	130	0	26
✅ express-stable-node	130	0	26
✅ express-stable-quickjs	130	0	26
✅ fastify-stable-node	130	0	26
✅ fastify-stable-quickjs	130	0	26
✅ hono-stable-node	130	0	26
✅ hono-stable-quickjs	130	0	26
✅ nest-stable-node	130	0	26
✅ nest-stable-quickjs	130	0	26
✅ nextjs-turbopack-canary-node	137	0	19
✅ nextjs-turbopack-canary-quickjs	137	0	19
✅ nextjs-turbopack-stable-node	156	0	0
✅ nextjs-turbopack-stable-quickjs	156	0	0
✅ nextjs-webpack-canary-node	137	0	19
✅ nextjs-webpack-canary-quickjs	137	0	19
✅ nextjs-webpack-stable-node	156	0	0
✅ nextjs-webpack-stable-quickjs	156	0	0
✅ nitro-stable-node	130	0	26
✅ nitro-stable-quickjs	130	0	26
✅ nuxt-stable-node	130	0	26
✅ nuxt-stable-quickjs	130	0	26
✅ sveltekit-stable-node	149	0	7
✅ sveltekit-stable-quickjs	149	0	7
✅ tanstack-start-node	130	0	26
✅ tanstack-start-quickjs	130	0	26
✅ vite-stable-node	130	0	26
✅ vite-stable-quickjs	130	0	26

✅ 🪟 Windows

App	Passed	Failed	Skipped
✅ nextjs-turbopack-node	156	0	0
✅ nextjs-turbopack-quickjs	156	0	0

✅ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
✅ python	9	0	128

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

---

📋 View full workflow run

[vercel]

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

Project	Deployment	Actions	Updated (UTC)
example-nextjs-workflow-turbopack	Ready	Preview	Aug 17, 2026 10:34pm
example-nextjs-workflow-webpack	Ready	Preview	Aug 17, 2026 10:34pm
example-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-astro-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-express-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-fastify-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-hono-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nestjs-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nitro-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-nuxt-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-python-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-sveltekit-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-tanstack-start-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workbench-vite-workflow	Ready	Preview	Aug 17, 2026 10:34pm
workflow-docs	Ready	Preview, v0	Aug 17, 2026 10:34pm
workflow-swc-playground	Ready	Preview	Aug 17, 2026 10:34pm
workflow-tarballs	Ready	Preview	Aug 17, 2026 10:34pm
workflow-web	Ready	Preview	Aug 17, 2026 10:34pm

[github-actions]

Sim World

Simulated world deterministic testing for races. Traces

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

fence=per-spec

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

Full trace: world-sim.txt

[github-actions]

📊 Workflow Benchmarks

commit 15a90ed · Mon, 17 Aug 2026 22:51:56 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	247 (+9.8%)	1520 🔴 (+34%) 🔻	1530 🔴 (+29%) 🔻	1933 🔴 (+18%) 🔻	30
TTFS	stream	239 (+5.3%)	1422 🔴 (+20%) 🔻	1463 🔴 (+21%) 🔻	1541 🔴 (-18%) 💚	30
TTFS	hook + stream	500 (+31%) 🔻	1760 🔴 (+29%) 🔻	1903 🔴 (+36%) 🔻	1972 🔴 (+36%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	1273 (+1.4%)	2373 (-0.9%)	2578 (±0%)	2684 (±0%)	10
Fan-out TTLS	Promise.all(100 steps)	6502 (-6.3%)	7915 (-7.7%)	8675 (-1.8%)	9838 (+10%)	10
STSO	1020 steps (inline)	149 (-6.9%)	259 (-11%)	290 (-15%) 💚	443 (-11%)	1019
WO	1020 steps	249616 (-10%)	249616 (-10%)	249616 (-10%)	249616 (-10%)	1
CRTT	first chunk (pooled)	95 (+1.1%)	179 (+25%) 🔻	288 (+51%) 🔻	1222 (+224%) 🔻	28

Streams

Scenario	wr c/s	rd c/s	wr KiB/s	rd KiB/s	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	100 (±0%)	102 (+5%)	5 (±0%)	5.1 (+5%)	116 (-5%)	256 (+15%)	302 (-38%)	1285 (+1%)	211 (-7%)	10
size sweep (100/s, 160B-12KB)	100 (±0%)	101 (+3%)	334 (±0%)	337 (+3%)	141 (-2%)	378 (+49%)	460 (-33%)	1222 (-1%)	178 (-59%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	89.2 (±0%)	89.2 (±0%)	16.2 (±0%)	16.2 (-1%)	170 (+40%)	173 (-31%)	278 (-88%)	792 (-79%)	761 (-5%)	3
replay eve-gpt-5.6-sol-2000t (1x)	54.7 (±0%)	54.7 (-4%)	355 (±0%)	355 (-4%)	269 (+105%)	158 (-27%)	220 (-67%)	410 (-92%)	398 (-87%)	2
replay eve-gpt-5.6-sol-2000t (2x)	109 (±0%)	110 (±0%)	710 (±0%)	712 (±0%)	118 (-2%)	258 (+10%)	373 (+11%)	539 (-17%)	343 (-8%)	3

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

1020 steps (inline)

Cumulative STSO time: main 277417ms → this run 248241ms (Δ -29176ms, -11%)

 100-150 ms ┃ main 0 this 1 +1
150-200 ms ██░┃ main 47 this 93 +46
200-250 ms ███████████████░░░░░░░░┃ main 357 this 589 +232
250-300 ms █████████┃██████ main 397 this 255 -142
300-350 ms █┃███ main 126 this 47 -79
350-400 ms ┃█ main 50 this 19 -31
400-450 ms ┃ main 23 this 6 -17
450-500 ms ┃ main 9 this 3 -6
500-550 ms ┃ main 4 this 3 -1
550-600 ms ┃ main 2 this 0 -2
600-650 ms ┃ main 2 this 0 -2
700-750 ms ┃ main 1 this 1 +0
850-900 ms ┃ main 1 this 1 +0
1100-1150 ms ┃ main 0 this 1 +1

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

variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▃▁▁·· 182 (-6%) 142 (-1%) 302 (-38%) 1285 (+1%) 3000
sweep ······▂█▅▁▁·· 215.7 (+1%) 158 (+10%) 460 (-33%) 1222 (-1%) 3000
gw 1x ·····▁▄█▂▁··· 150.2 (-49%) 121 (-20%) 278 (-88%) 792 (-79%) 5295
eve 1x ·····▁▄█▂▁··· 136.5 (-60%) 119 (-14%) 220 (-67%) 410 (-92%) 5186
eve 2x ·····▁▂█▅▁··· 190.7 (-4%) 157 (-11%) 373 (+11%) 539 (-17%) 7779

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

control ▂▁▃▇▂▂▁█▂▂ 151–250ms
sweep ▆█▄▅▃▃▄▁▂▁ 171–288ms
gw 1x ▂▃█▂▁█▁▂▂▄ 120–212ms
eve 1x █▂▄█▃▂▃▇▄▁ 118–159ms
eve 2x ▁▃▅▃▃▂▅█▄▂ 147–257ms

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

sweep ▁▁▂█▄▅▅ 213–220ms

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

control ▂▅▇▄▃▁▁█▂▂ 31–76ms
sweep ▄▅▁▂█▆▆▁▄▅ 36–74ms
gw 1x ▄██▃▃▆▁▆▂█ 36–48ms
eve 1x ▇▂▃█▄▄▂▃▁▂ 26–34ms
eve 2x ▆▆▅▆▄▄▇▁▄█ 26–35ms

📜 Previous results (1)

116cb19

Mon, 17 Aug 2026 18:06:05 GMT · run logs

vercel / nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	271 (+22%) 🔻	1469 🔴 (+35%) 🔻	1498 🔴 (+30%) 🔻	1552 🔴 (+2.8%)	30
TTFS	stream	1319 (+511%) 🔻	1479 🔴 (+40%) 🔻	1500 🔴 (+39%) 🔻	1532 🔴 (+39%) 🔻	30
TTFS	hook + stream	1434 (+259%) 🔻	1752 🔴 (+27%) 🔻	1821 🔴 (+29%) 🔻	2043 🔴 (+33%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	1158 (-9.7%)	1411 (-43%) 💚	2580 (+3.8%)	2893 (-11%)	10
Fan-out TTLS	Promise.all(100 steps)	6310 (-42%) 💚	11678 (-5.9%)	13221 (+2.5%)	16265 (-5.8%)	10
STSO	1020 steps (inline)	134 (-13%)	233 (-53%) 💚	263 (-52%) 💚	372 (-50%) 💚	1019
WO	1020 steps	225600 (-50%) 💚	225600 (-50%) 💚	225600 (-50%) 💚	225600 (-50%) 💚	1
CRTT	first chunk (pooled)	83 (-12%)	114 (-17%) 💚	121 (-44%) 💚	341 (+46%) 🔻	28

Streams

Scenario	wr c/s	rd c/s	wr KiB/s	rd KiB/s	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	100 (±0%)	100 (+1%)	5 (±0%)	5 (±0%)	110 (-1%)	122 (-50%)	269 (-22%)	391 (-60%)	113 (-49%)	10
size sweep (100/s, 160B-12KB)	100 (±0%)	100 (-1%)	334 (±0%)	334 (-1%)	97 (-19%)	133 (-26%)	248 (+6%)	1119 (+110%)	111 (-39%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	89.2 (±0%)	89 (±0%)	16.2 (±0%)	16.2 (±0%)	97 (-29%)	249 (+38%)	599 (+122%)	899 (-21%)	439 (-47%)	3
replay eve-gpt-5.6-sol-2000t (1x)	54.7 (±0%)	54.7 (±0%)	355 (±0%)	355 (±0%)	107 (-31%)	110 (-33%)	136 (-49%)	389 (-78%)	300 (-65%)	2
replay eve-gpt-5.6-sol-2000t (2x)	109 (±0%)	109 (±0%)	710 (±0%)	709 (±0%)	114 (-9%)	152 (-36%)	201 (-49%)	407 (-46%)	256 (-55%)	3

ℹ️ Metric definitions & methodology

_{Streams: writer/reader sustained rates (steady window, 10% trimmed each side), 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.}

[github-actions]

No backport to stable for 52526e1 (AI decision).

This is a pure performance optimization of decodeFrames in packages/world-vercel/src/frames.ts — it replaces per-chunk buffer reallocation with a single concatenation, carrying a patch changeset but no user-visible defect fix. The prior behavior was merely slower (~31ms vs ~0.6ms for an 8 MB frame), not a correctness, hang, or unbounded-memory problem, so it does not meet the stability bar for the maintenance line. It also slightly tightens assumptions about chunk values (dropping the !value guard), which is added risk with no fix to justify it.

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

52526e14aaa848dc24eaeebfbf91ccc9ca0df89a

[pranaygp]

This appears to have broken all vercel-world e2e lanes on main (encrypted frame payloads corrupted; WS transport jobs hung at the 30m ceiling) — bisect and mechanism in #3650, which reverts it. Root cause looks like deferred chunk concatenation stashing yielded views across awaits, letting the stream reuse their backing buffers before the copy.

🤖 Generated with Claude Code