fix(core): re-arm late-claimed hook deliveries by NathanColosimo · Pull Request #3879 · vercel/workflow

NathanColosimo · 2026-08-28T03:21:43Z

Summary

reinstall an armed delivery barrier when a retained reusable-hook claim closure runs after the original unarmed barrier was retired
keep arm() and markDelivered() terminal and idempotent after actual delivery
add a behavior-level regression through the real hook API plus a patch changeset

Root cause

A buffered hook payload registers an unarmed barrier because no workflow consumer has claimed it yet. The idle safety net may legitimately retire that barrier. In a retained VM, however, the payload and its claim() closure can survive into a later execution turn. Calling arm() then only mutated the already-retired entry, so the runtime still saw no committed delivery and could suspend before the payload reached workflow code.

The fix reinstalls the barrier as armed when that late claim occurs. The delivery chain then removes it normally after handing the payload to the workflow.

This addresses the retained-VM failure investigated from vercel/eve#2611.

Verification

pnpm vitest run src/async-deserialization-ordering.test.ts -t "should restore delivery protection when a buffered hook payload is claimed after its barrier retires"
related delivery-barrier, hook/sleep, and retained-VM suites: 86 passed
full @workflow/core suite: 2,284 passed, 3 expected failures, 1 skipped
cd packages/core && pnpm typecheck
Biome check: clean except the pre-existing cognitive-complexity warning in quiesceEarlierCascades
autoreview: clean, no actionable findings

changeset-bot · 2026-08-28T03:21:47Z

🦋 Changeset detected

Latest commit: dd087fa

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

This PR includes changesets to release 16 packages

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

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

vercel · 2026-08-28T03:21:49Z

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

Project	Deployment	Actions	Updated (UTC)
example-nextjs-workflow-turbopack	Ready	Preview, v0	Aug 28, 2026 4:22am
example-nextjs-workflow-webpack	Ready	Preview, v0	Aug 28, 2026 4:22am
example-workflow	Ready	Preview, v0	Aug 28, 2026 4:22am
workbench-astro-workflow	Ready	Preview, v0	Aug 28, 2026 4:22am
workbench-express-workflow	Ready	Preview, v0	Aug 28, 2026 4:22am
workbench-fastify-workflow	Ready	Preview, v0	Aug 28, 2026 4:22am
workbench-hono-workflow	Ready	Preview, v0	Aug 28, 2026 4:22am
workbench-nestjs-workflow	Ready	Preview, v0	Aug 28, 2026 4:22am
workbench-nitro-workflow	Ready	Preview, v0	Aug 28, 2026 4:22am
workbench-nuxt-workflow	Ready	Preview, v0	Aug 28, 2026 4:22am
workbench-python-workflow	Ready	Preview, v0	Aug 28, 2026 4:22am
workbench-sveltekit-workflow	Ready	Preview, v0	Aug 28, 2026 4:22am
workbench-tanstack-start-workflow	Ready	Preview, v0	Aug 28, 2026 4:22am
workbench-vite-workflow	Ready	Preview, v0	Aug 28, 2026 4:22am
workflow-docs	Ready	Preview, v0	Aug 28, 2026 4:22am
workflow-swc-playground	Ready	Preview, v0	Aug 28, 2026 4:22am
workflow-tarballs	Ready	Preview, v0	Aug 28, 2026 4:22am
workflow-web	Ready	Preview, v0	Aug 28, 2026 4:22am

github-actions · 2026-08-28T03:22:02Z

🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

python-node (8 failed):

promiseAllWorkflow | wrun_41M139HV1Z0GR7JMCM52NT1FEY | 🔍 observability
sleepingWorkflow | wrun_41M139JGEH0GQ9GGMY7S5EWDQD | 🔍 observability
parallelSleepWorkflow | wrun_41M139JGXC0GHSJWB73NA72NCH | 🔍 observability
nullByteWorkflow | wrun_41M139JS580GG64FT4QA6GEXX6 | 🔍 observability
cancelRun - cancelling a running workflow | wrun_41M139PQDF0GZ67TKMTXJE9CPD | 🔍 observability
cancelRun via CLI - cancelling a running workflow | wrun_41M139PRWP0GY2Z9XSPG0DTEAS | 🔍 observability
sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M139PWRT0GW5NE8SDEC7VJPA | 🔍 observability
resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M139QD490GZXPM70G2KCFXVV | 🔍 observability

🌐 Cross-language Conformance (9 failed)

python (9 failed):

deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M139WVMSZEERCVMWX6JTVKFN
promiseAllWorkflow | wrun_41M139HV1Z0GR7JMCM52NT1FEY
sleepingWorkflow | wrun_41M139JGEH0GQ9GGMY7S5EWDQD
parallelSleepWorkflow | wrun_41M139JGXC0GHSJWB73NA72NCH
nullByteWorkflow | wrun_41M139JS580GG64FT4QA6GEXX6
cancelRun - cancelling a running workflow | wrun_41M139PQDF0GZ67TKMTXJE9CPD
cancelRun via CLI - cancelling a running workflow | wrun_41M139PRWP0GY2Z9XSPG0DTEAS
sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M139PWRT0GW5NE8SDEC7VJPA
resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M139QD490GZXPM70G2KCFXVV

⚠️ Flaky E2E Tests (passed on retry)

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

addTenWorkflow (vite)
cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
hookWithSleepFinalStepWorkflow - step only on final payload (nextjs-webpack)
hookWorkflow (tanstack-start)

🛠 Infra Events (absorbed by the harness)

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

33 infra events

cold-start-warmup · suite warmup (python) · at 04:22:01Z · abandoned wrun_41M139H7C20GN0AEE852DC9FAE · (+6 more)
run-pickup-stall · nullByteWorkflow (python) · at 04:22:17Z · abandoned wrun_41M139MVQJ0GRE3AZTDY9TDCF0
run-pickup-stall · promiseAllWorkflow (python) · at 04:22:17Z · abandoned wrun_41M139MVQ70GNXRY3N5FNY45QX
run-pickup-stall · sleepingWorkflow (python) · at 04:22:17Z · abandoned wrun_41M139MVQE0GQ38D9JM3J13C9F
run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 04:22:17Z · abandoned wrun_41M139MW2M0GH96E7VS5M70SGP
run-pickup-stall · parallelSleepWorkflow (python) · at 04:22:17Z · abandoned wrun_41M139MVQE0GQ38D9JM3J13C9G
run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 04:22:50Z · abandoned wrun_41M139NVJT0GT0FQZ3DQX2TXG6
run-pickup-stall · promiseAllWorkflow (python) · at 04:23:18Z · abandoned wrun_41M139PQ430GN8F7VPPNFFQTE0
run-pickup-stall · parallelSleepWorkflow (python) · at 04:23:18Z · abandoned wrun_41M139PQ5K0GGXY5HR08DH0BS8
run-pickup-stall · sleepingWorkflow (python) · at 04:23:18Z · abandoned wrun_41M139PQ4J0GZJ9W8ZAJZHWDDY
run-pickup-stall · nullByteWorkflow (python) · at 04:23:18Z · abandoned wrun_41M139PQ380GJECJCPYBEDVEXJ
run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 04:23:58Z · abandoned wrun_41M139PTSZ0GSW1G2SE90DZ4X5
cold-start-warmup · suite warmup (python) · at 04:25:08Z · abandoned wrun_01M139PX6R4T2MD1NQ6BRFSAFF · (+7 more)
run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 04:25:23Z · abandoned wrun_01M139TJBRVT1BVE0E828J106H
run-pickup-stall · nullByteWorkflow (python) · at 04:25:23Z · abandoned wrun_01M139TJC25WWB6RWFEN6Y183D
run-pickup-stall · sleepingWorkflow (python) · at 04:25:23Z · abandoned wrun_01M139TJBXPQYFK50D1ZEMQVEV
run-pickup-stall · promiseAllWorkflow (python) · at 04:25:23Z · abandoned wrun_01M139TJBSWVB3F2M6PAACX264
run-pickup-stall · parallelSleepWorkflow (python) · at 04:25:23Z · abandoned wrun_01M139TJC0DKMMD4KGFBT100FR
run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 04:25:49Z · abandoned wrun_41M139SJPH0GTJ7R81B4YVA0TD
run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 04:25:49Z · abandoned wrun_41M139RRR90GRH24NK1HS3T3Q5
run-pickup-stall · parallelSleepWorkflow (python) · at 04:26:23Z · abandoned wrun_01M139WCZJFC0A3HP1QR3D631V
run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 04:26:23Z · abandoned wrun_01M139WCZG8VFXAZMW4JPC909Z
run-pickup-stall · sleepingWorkflow (python) · at 04:26:23Z · abandoned wrun_01M139WCZN0ZC9G9RQ5N5R51BS
run-pickup-stall · promiseAllWorkflow (python) · at 04:26:23Z · abandoned wrun_01M139WCZM66CD2EHM008FHTGP
run-pickup-stall · nullByteWorkflow (python) · at 04:26:23Z · abandoned wrun_01M139WCZS0GG6XFDEA8TH1GS1
run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 04:27:23Z · abandoned wrun_01M139Y7K08D76ZQAJQ8472PEF
run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 04:27:23Z · abandoned wrun_01M139Y7KDJF13G5YMSYH6F1KA
run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 04:27:23Z · abandoned wrun_01M139Y7K649MSREJBJCXD1BXT
run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 04:27:53Z · abandoned wrun_01M139Z4YM5R3FGGXRKTA60F88
run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 04:27:53Z · abandoned wrun_01M139Z4YP25WBCX9PVZHQRNZA
run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 04:28:23Z · abandoned wrun_01M13A026H8Z3JHDF7QYSS0VX8
run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 04:30:35Z · abandoned wrun_01M13A43FXXBVWTJTR1869H1BG
run-pickup-stall · concurrent hook token conflict - two workflows cannot use the same hook token simultaneously (nextjs-webpack) · at 04:30:35Z · abandoned wrun_01M13A43HN5ZJVTXDXVDXBMZ6B

E2E Test Summary

Summary

	Passed	Failed	Skipped	Total
❌ ▲ Vercel Production	3570	8	742	4320
✅ 💻 Local Development	3922	0	558	4480
✅ 📦 Local Production	3922	0	558	4480
✅ 🐘 Local Postgres	3922	0	558	4480
✅ 🪟 Windows	320	0	0	320
❌ 🌐 Cross-language Conformance	0	9	132	141
✅ vercel-http-transport	817	0	143	960
✅ vercel-multi-region	27	0	0	27
✅ vercel-ws-transport	553	0	87	640
Total	17053	17	2778	19848

Details by Category

❌ ▲ Vercel Production

App	Passed	Failed	Skipped
✅ astro-node	132	0	28
✅ astro-quickjs	132	0	28
✅ example-node	132	0	28
✅ example-quickjs	132	0	28
✅ express-node	132	0	28
✅ express-quickjs	132	0	28
✅ fastify-node	132	0	28
✅ fastify-quickjs	132	0	28
✅ hono-node	132	0	28
✅ hono-quickjs	132	0	28
✅ nest-node	132	0	28
✅ nest-quickjs	132	0	28
✅ nextjs-turbopack-node	157	0	3
✅ nextjs-turbopack-quickjs	157	0	3
✅ nextjs-webpack-node	157	0	3
✅ nextjs-webpack-quickjs	157	0	3
✅ nitro-node	132	0	28
✅ nitro-quickjs	132	0	28
✅ nuxt-node	132	0	28
✅ nuxt-quickjs	132	0	28
❌ python-node	0	8	152
✅ sveltekit-node	151	0	9
✅ sveltekit-quickjs	151	0	9
✅ tanstack-start-node	132	0	28
✅ tanstack-start-quickjs	132	0	28
✅ vite-node	132	0	28
✅ vite-quickjs	132	0	28

✅ 💻 Local Development

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

✅ 📦 Local Production

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

✅ 🐘 Local Postgres

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

✅ 🪟 Windows

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

❌ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
❌ python	0	9	132

✅ vercel-http-transport

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

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

✅ vercel-ws-transport

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

📋 View full workflow run

github-actions · 2026-08-28T03:22:05Z

📊 Workflow Benchmarks

commit dd087fa · Fri, 28 Aug 2026 04:43:57 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	1234 (+26%) 🔻	1316 🔴 (+22%) 🔻	1354 🔴 (+24%) 🔻	1396 🔴 (-3.2%)	30
TTFS	stream	350 (+70%) 🔻	1307 🔴 (+24%) 🔻	1325 🔴 (+23%) 🔻	1369 🔴 (+19%) 🔻	30
TTFS	hook + stream	451 (+6.1%)	1586 🔴 (+19%) 🔻	1690 🔴 (+20%) 🔻	1899 🔴 (+31%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	656 (+9.9%)	1987 (+99%) 🔻	2062 (+28%) 🔻	2203 (+24%) 🔻	10
Fan-out TTLS	Promise.all(100 steps)	2153 (+6.2%)	4106 (+38%) 🔻	6228 (+87%) 🔻	9070 (+33%) 🔻	10
STSO	1020 steps (inline)	108 (-6.1%)	134 (-2.2%)	156 (-1.9%)	222 (+4.7%)	1019
WO	1020 steps	135208 (-2.0%)	135208 (-2.0%)	135208 (-2.0%)	135208 (-2.0%)	1
CRTT	first chunk (pooled)	94 (-10%)	195 (+15%) 🔻	374 (-20%) 💚	485 (-28%) 💚	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	128 (-21%)	147 (-34%)	396 (+1%)	4555 (+598%)	101 (-57%)	10
size sweep (100/s, 160B-12KB)	129 (-11%)	155 (-37%)	284 (-38%)	825 (+34%)	167 (-21%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	106 (-23%)	128 (-70%)	167 (-69%)	278 (-65%)	168 (-63%)	3
replay eve-gpt-5.6-sol-2000t (1x)	119 (-64%)	125 (-65%)	154 (-70%)	392 (-51%)	263 (-49%)	2
replay eve-gpt-5.6-sol-2000t (2x)	214 (+55%)	185 (-28%)	244 (-56%)	474 (-51%)	241 (-42%)	3

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

1020 steps (inline)

Cumulative STSO time: main 137827ms → this run 135034ms (Δ -2793ms, -2%)

100-150 ms  ███████████████████████┃  main 869  this 880   +11
150-200 ms  ██┃█                      main 133  this 121   -12
200-250 ms  ┃                         main  10  this  10    +0
250-300 ms  ┃                         main   5  this   4    -1
300-350 ms  ┃                         main   2  this   4    +2

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

variant  RTT 1ms→5s+             avg         p50         p90           p99     n
control  ······▄█▁▁·▁·  323.3 (+83%)  117 (-18%)   396 (+1%)  4555 (+598%)  3000
sweep    ······▆█▂▁···  135.2 (-26%)  106 (-26%)  284 (-38%)    825 (+34%)  3000
gw 1x    ·····▁▆█▁····  111.4 (-47%)  107 (-23%)  167 (-69%)    278 (-65%)  5295
eve 1x   ·····▁██▁▁···  106.1 (-49%)   94 (-28%)  154 (-70%)    392 (-51%)  5186
eve 2x   ·····▁▂█▂▁···  152.7 (-32%)  139 (-22%)  244 (-56%)    474 (-51%)  7779

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

control  ▂▁▁▁▂██▇▇▆  133–546ms
sweep    ▆▅▄▃▂▁▂█▆▅  104–174ms
gw 1x    ▃▄▅▄▃▃█▄▁▅  101–124ms
eve 1x   ▇▄██▂▁▄▅▃▁  96–118ms
eve 2x   ▃▂█▃▁▄▆▆▄▂  126–190ms

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

sweep  █▇▇▄▄▁▁  134–137ms

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

control  ▁▁▁▂█▂▂▁▁▁  30–110ms
sweep    ▁▃▁▆▃▂▅█▂▃  40–63ms
gw 1x    ▃▆▆▃▅▅█▆▁▆  27–37ms
eve 1x   ▄▇▅█▁▂█▂▆▆  19–24ms
eve 2x   ██▅▆▅▇▇▁▄▅  18–26ms

📜 Previous results (1)

`0ce1d94`

Fri, 28 Aug 2026 03:46:33 GMT · run logs

vercel / nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	195 (+3.7%)	1313 🔴 (+18%) 🔻	1436 🔴 (+25%) 🔻	1843 🔴 (+27%) 🔻	30
TTFS	stream	189 (+17%) 🔻	1309 🔴 (+16%) 🔻	1351 🔴 (+17%) 🔻	1552 🔴 (+14%)	30
TTFS	hook + stream	1167 (-2.3%)	1643 🔴 (+18%) 🔻	1724 🔴 (+19%) 🔻	1882 🔴 (+23%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	570 (-12%)	2155 (+22%) 🔻	2209 (+15%)	2214 (+5.1%)	10
Fan-out TTLS	Promise.all(100 steps)	1843 (-1.2%)	3619 (-2.7%)	4289 (+13%)	4431 (-36%) 💚	10
STSO	1020 steps (inline)	111 (+1.8%)	155 (-2.5%)	184 (-0.5%)	406 (+42%) 🔻	1019
WO	1020 steps	155064 (+0.8%)	155064 (+0.8%)	155064 (+0.8%)	155064 (+0.8%)	1
CRTT	first chunk (pooled)	90 (-5.3%)	137 (-14%)	152 (-24%) 💚	405 (+22%) 🔻	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	119 (-13%)	144 (-21%)	195 (-21%)	378 (-31%)	123 (-33%)	10
size sweep (100/s, 160B-12KB)	128 (-2%)	214 (+1%)	416 (-29%)	3795 (+328%)	233 (+10%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	137 (+1%)	145 (-19%)	184 (-23%)	352 (-15%)	264 (-20%)	3
replay eve-gpt-5.6-sol-2000t (1x)	151 (+5%)	139 (-25%)	170 (-41%)	347 (-49%)	417 (-34%)	2
replay eve-gpt-5.6-sol-2000t (2x)	132 (-12%)	211 (-16%)	336 (-34%)	617 (-34%)	378 (-21%)	3

ℹ️ Metric definitions & methodology

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

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

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

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

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

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

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

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

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

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

github-actions · 2026-08-28T03:25:08Z

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

Full trace: world-sim.txt

github-actions · 2026-08-28T03:25:35Z

Framework	Flow route	Step reg.	Framework output
hono	200.9 KiB (±0)	40.3 KiB (-27 B)	1.76 MiB (-637 B)
nextjs-turbopack	206.3 KiB (±0)	439 B (±0)	763.6 KiB (-108 B)

About these numbers

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

dd087fa · run

fix(core): re-arm late-claimed hook deliveries

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NathanColosimo requested a review from a team as a code owner August 28, 2026 03:21

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refactor(core): clarify delivery barrier lifecycle

dd087fa

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

fix(core): re-arm late-claimed hook deliveries#3879
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Verification

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🧪 E2E Test Results

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

🌐 Cross-language Conformance (9 failed)

⚠️ Flaky E2E Tests (passed on retry)

🛠 Infra Events (absorbed by the harness)

E2E Test Summary

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📊 Workflow Benchmarks

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