fix(core): stop reconnecting cancelled streams by ctgowrie · Pull Request #3882 · vercel/workflow

ctgowrie · 2026-08-28T14:08:25Z

Description

Cancelling a reconnecting framed stream could be mistaken for a clean, incomplete EOF. The pending pull then reopened the World stream after cancellation, leaving the new reader unowned; local World consumers retained emitter listeners and polling intervals, eventually producing MaxListenersExceededWarning after repeated reads of the same durable stream.

The reader now latches cancellation across pending reads, completion checks, and reconnect acquisition. Reconnect work stops after cancellation, and a World stream that finishes opening after cancellation is immediately cancelled instead of being installed as the active reader.

How did you test your changes?

Added focused regressions for cancellation while completion metadata is pending and while a reconnect acquisition is pending. The complete @workflow/core suite passes: 107 test files passed, 1 skipped; 2,285 tests passed, 3 expected failures, and 1 skipped. @workflow/core also typechecks. Before applying the fix, a 20-turn local eve session deterministically retained one World reader per turn and warned on listener 11; with this change, the same run peaked at one reader and ended with zero.

PR Checklist - Required to merge

📦 pnpm changeset was run to create a changelog for this PR
- Use the correct semver bump type: patch for bug fixes, minor for new features, major for breaking changes.
- Use pnpm changeset --empty if you are changing documentation or workbench apps
🔒 DCO sign-off passes (run git commit --signoff on your commits)
📝 Ping @vercel/workflow in a comment once the PR is ready, and the above checklist is complete

vercel · 2026-08-28T14:08:29Z

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 2:17pm
example-nextjs-workflow-webpack	Ready	Preview, v0	Aug 28, 2026 2:17pm
example-workflow	Ready	Preview, v0	Aug 28, 2026 2:17pm
workbench-astro-workflow	Ready	Preview, v0	Aug 28, 2026 2:17pm
workbench-express-workflow	Ready	Preview, v0	Aug 28, 2026 2:17pm
workbench-fastify-workflow	Ready	Preview, v0	Aug 28, 2026 2:17pm
workbench-hono-workflow	Ready	Preview, v0	Aug 28, 2026 2:17pm
workbench-nestjs-workflow	Ready	Preview, v0	Aug 28, 2026 2:17pm
workbench-nitro-workflow	Ready	Preview, v0	Aug 28, 2026 2:17pm
workbench-nuxt-workflow	Ready	Preview, v0	Aug 28, 2026 2:17pm
workbench-python-workflow	Ready	Preview, v0	Aug 28, 2026 2:17pm
workbench-sveltekit-workflow	Ready	Preview, v0	Aug 28, 2026 2:17pm
workbench-tanstack-start-workflow	Ready	Preview, v0	Aug 28, 2026 2:17pm
workbench-vite-workflow	Ready	Preview, v0	Aug 28, 2026 2:17pm
workflow-docs	Ready	Preview, v0	Aug 28, 2026 2:17pm
workflow-swc-playground	Ready	Preview, v0	Aug 28, 2026 2:17pm
workflow-tarballs	Ready	Preview, v0	Aug 28, 2026 2:17pm
workflow-web	Ready	Preview, v0	Aug 28, 2026 2:17pm

changeset-bot · 2026-08-28T14:08:30Z

🦋 Changeset detected

Latest commit: c4f9c6d

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

ctgowrie · 2026-08-28T14:08:35Z

@vercel/workflow ready for review.

github-actions · 2026-08-28T14:08:45Z

🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

python-node (8 failed):

promiseAllWorkflow | wrun_41M14BRN6Z0GVR8W79STW2V7AV | 🔍 observability
sleepingWorkflow | wrun_41M14BSA4T0GKE1CTHASGMXYWK | 🔍 observability
parallelSleepWorkflow | wrun_41M14BSB650GMCXCMXFB1CQWC6 | 🔍 observability
nullByteWorkflow | wrun_41M14BSHPE0GJ9R01FFJ9D67AS | 🔍 observability
cancelRun - cancelling a running workflow | wrun_41M14BXYJX0GSJJJJA6A3J83J5 | 🔍 observability
cancelRun via CLI - cancelling a running workflow | wrun_41M14BY1560GS4G5RJ5BS3Z27A | 🔍 observability
sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M14BY9RE0GH4FDHZC0664Z2K | 🔍 observability
resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M14BYTSV0GHTAH6AG973HCC6 | 🔍 observability

🌐 Cross-language Conformance (9 failed)

python (9 failed):

deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M14D144BFRN6EYT44B7EBW0W
promiseAllWorkflow | wrun_41M14BRN6Z0GVR8W79STW2V7AV
sleepingWorkflow | wrun_41M14BSA4T0GKE1CTHASGMXYWK
parallelSleepWorkflow | wrun_41M14BSB650GMCXCMXFB1CQWC6
nullByteWorkflow | wrun_41M14BSHPE0GJ9R01FFJ9D67AS
cancelRun - cancelling a running workflow | wrun_41M14BXYJX0GSJJJJA6A3J83J5
cancelRun via CLI - cancelling a running workflow | wrun_41M14BY1560GS4G5RJ5BS3Z27A
sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M14BY9RE0GH4FDHZC0664Z2K
resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M14BYTSV0GHTAH6AG973HCC6

⚠️ 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 (tanstack-start)
cancelRun via CLI - cancelling a running workflow (express)
cancelRun via CLI - cancelling a running workflow (fastify)
cancelRun via CLI - cancelling a running workflow (hono)
hookWorkflow (vite)

🛠 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

run-pickup-stall · hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nextjs-webpack) · at 14:24:59Z · abandoned wrun_01M14C4F9PS1DJQBBQEVT5B8CY
cold-start-warmup · suite warmup (tanstack-start) · at 14:38:11Z · abandoned wrun_01M14CWD5T71ZF0W47EJKD5140
cold-start-warmup · suite warmup (python) · at 14:39:08Z · abandoned wrun_01M14CV5PNJPCAN7HDNWBCDQSP · (+7 more)
cold-start-warmup · suite warmup (python) · at 14:39:10Z · abandoned wrun_41M14CV8FN0GSSVP09BNKKJKEC · (+7 more)
run-pickup-stall · promiseAllWorkflow (python) · at 14:39:23Z · abandoned wrun_01M14CYTVE4GS60KTCX3TTDAY0
run-pickup-stall · sleepingWorkflow (python) · at 14:39:23Z · abandoned wrun_01M14CYTVMW912J74CT4DDW2FB
run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 14:39:23Z · abandoned wrun_01M14CYTVDFQF90A3C5E6QKBSN
run-pickup-stall · parallelSleepWorkflow (python) · at 14:39:23Z · abandoned wrun_01M14CYTVNST3HN9MRXESPZ5G9
run-pickup-stall · nullByteWorkflow (python) · at 14:39:23Z · abandoned wrun_01M14CYTVQ9HKM7MGHYM6BXFQ3
run-pickup-stall · parallelSleepWorkflow (python) · at 14:39:26Z · abandoned wrun_41M14CYXCH0GT5GZHBXQGXW977
run-pickup-stall · promiseAllWorkflow (python) · at 14:39:26Z · abandoned wrun_41M14CYXCB0GHV52WST03YBPGJ
run-pickup-stall · nullByteWorkflow (python) · at 14:39:27Z · abandoned wrun_41M14CYXCN0GMAT63512V2NY27
run-pickup-stall · sleepingWorkflow (python) · at 14:39:27Z · abandoned wrun_41M14CYXCH0GT5GZHBXQGXW976
run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 14:39:27Z · abandoned wrun_41M14CYXT20GRQWHPGVP39EFJW
run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 14:40:00Z · abandoned wrun_41M14CZXQD0GRX8VGF3BJYT61K
run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 14:40:23Z · abandoned wrun_01M14D0NF043ABJTAGAZP7JD1H
run-pickup-stall · promiseAllWorkflow (python) · at 14:40:23Z · abandoned wrun_01M14D0NF2E3NWFM0PQWN7GFWY
run-pickup-stall · sleepingWorkflow (python) · at 14:40:23Z · abandoned wrun_01M14D0NFAS7F015RX5K2VNH58
run-pickup-stall · parallelSleepWorkflow (python) · at 14:40:23Z · abandoned wrun_01M14D0NF9S5NDA68883EWRBF6
run-pickup-stall · nullByteWorkflow (python) · at 14:40:23Z · abandoned wrun_01M14D0NFDHW71X5XTPT7930MZ
run-pickup-stall · promiseAllWorkflow (python) · at 14:40:27Z · abandoned wrun_41M14D0RWB0GMDK75EDC1K4815
run-pickup-stall · nullByteWorkflow (python) · at 14:40:27Z · abandoned wrun_41M14D0RX40GRQ5HVS3022B922
run-pickup-stall · parallelSleepWorkflow (python) · at 14:40:27Z · abandoned wrun_41M14D0RXX0GJA7DSGND2GYDSY
run-pickup-stall · sleepingWorkflow (python) · at 14:40:28Z · abandoned wrun_41M14D0RVD0GS0RQ8QFSAWGYSX
run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 14:41:18Z · abandoned wrun_41M14D0XFN0GKMVQ8QV4J1GBWB
run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 14:41:23Z · abandoned wrun_01M14D2G2T861YPXD7CPM1HJBN
run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 14:41:23Z · abandoned wrun_01M14D2G2YZ5YR3DMBXXWYZQB5
run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 14:41:23Z · abandoned wrun_01M14D2G37XG0JYDAEPH59Y2WJ
run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 14:41:53Z · abandoned wrun_01M14D3DE1HH6RE1BHZV9435HT
run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 14:41:53Z · abandoned wrun_01M14D3DE3PHGC8SD7WCXWD6JJ
run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 14:42:23Z · abandoned wrun_01M14D4APA6V04N38FQYZRC05H
run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 14:43:39Z · abandoned wrun_41M14D3GR00GY35DPDM8XK9ZH5
run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 14:43:39Z · abandoned wrun_41M14D3NC70GJGXPMQ733MXA5G

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 · 2026-08-28T14:08:51Z

📊 Workflow Benchmarks

commit c4f9c6d · Fri, 28 Aug 2026 14:40:29 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	315 (+65%) 🔻	1420 🔴 (+37%) 🔻	1498 🔴 (+38%) 🔻	2058 🔴 (+31%) 🔻	30
TTFS	stream	265 (+36%) 🔻	1426 🔴 (+37%) 🔻	1529 🔴 (+44%) 🔻	1881 🔴 (+71%) 🔻	30
TTFS	hook + stream	479 (-58%) 💚	1674 🔴 (+33%) 🔻	1719 🔴 (+21%) 🔻	1773 🔴 (+14%)	30
Fan-out TTFS	Promise.all(100 steps)	548 (-6.3%)	2167 (+31%) 🔻	2214 (+32%) 🔻	6596 (+285%) 🔻	10
Fan-out TTLS	Promise.all(100 steps)	2064 (+37%) 🔻	4134 (+48%) 🔻	5593 (+40%) 🔻	13889 (+229%) 🔻	10
STSO	1020 steps (inline)	104 (+44%) 🔻	141 (+2.9%)	167 (+9.2%)	276 (+9.5%)	1019
WO	1020 steps	144127 (+5.0%)	144127 (+5.0%)	144127 (+5.0%)	144127 (+5.0%)	1
CRTT	first chunk (pooled)	101 (+6.3%)	145 (-12%)	191 (-14%)	414 (+54%) 🔻	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	122 (-6%)	169 (+4%)	233 (-35%)	3012 (+382%)	128 (-36%)	10
size sweep (100/s, 160B-12KB)	139 (-11%)	158 (-13%)	237 (-17%)	330 (-44%)	118 (-19%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	143 (-3%)	149 (-3%)	199 (-1%)	364 (-17%)	239 (-10%)	3
replay eve-gpt-5.6-sol-2000t (1x)	136 (-39%)	132 (-16%)	169 (-25%)	314 (-65%)	256 (-66%)	2
replay eve-gpt-5.6-sol-2000t (2x)	148 (+3%)	174 (-45%)	241 (-42%)	436 (-36%)	224 (-43%)	3

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

1020 steps (inline)

Cumulative STSO time: main 136205ms → this run 142863ms (Δ +6658ms, +5%)

   50-100 ms  ┃                         main   1  this   0    -1
  100-150 ms  ██████████████████████┃█  main 889  this 836   -53
  150-200 ms  ███┃                      main 104  this 154   +50
  200-250 ms  ┃                         main  14  this  18    +4
  250-300 ms  ┃                         main   5  this   2    -3
  300-350 ms  ┃                         main   2  this   4    +2
  350-400 ms  ┃                         main   3  this   2    -1
  400-450 ms  ┃                         main   0  this   1    +1
  500-550 ms  ┃                         main   0  this   1    +1
  850-900 ms  ┃                         main   1  this   0    -1
1000-1050 ms  ┃                         main   0  this   1    +1

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

variant  RTT 1ms→5s+             avg         p50         p90           p99     n
control  ······▂█▁··▁·  217.8 (+47%)   134 (+9%)  233 (-35%)  3012 (+382%)  3000
sweep    ······▃█▁····  132.4 (-11%)   123 (-6%)  237 (-17%)    330 (-44%)  3000
gw 1x    ·····▁▄█▁····   126.3 (-8%)   122 (-2%)   199 (-1%)    364 (-17%)  5295
eve 1x   ·····▁▇█▁····  113.1 (-21%)  102 (-17%)  169 (-25%)    314 (-65%)  5186
eve 2x   ·····▁▃█▂▁···  142.2 (-30%)  131 (-21%)  241 (-42%)    436 (-36%)  7779

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

control  ▂▁▁▁▁▁▁██▇  129–418ms
sweep    ▆█▄▄▁▃▄▂▅▃  120–152ms
gw 1x    ▂▁▅█▄▆▄▂▃▆  114–141ms
eve 1x   ▁▁▂▃▁▃▃█▄▃  104–139ms
eve 2x   ▄▄▄▄▁▅▆█▃▃  110–181ms

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

sweep  ▁▄█▅▆▇▂  131–134ms

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

control  ▁▁▂▂▂▁▂█▃▁  34–90ms
sweep    ▁▄▆█▇▅▅▆█▆  39–56ms
gw 1x    ▁▃▃▄█▅▄█▃▇  33–39ms
eve 1x   ▁▃▅▅▅▃█▅▃█  19–26ms
eve 2x   ▆▆▁▅▅██▃▆█  17–24ms

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 · 2026-08-28T14:11:40Z

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 · 2026-08-28T14:12:21Z

Framework	Flow route	Step reg.	Framework output
hono	200.9 KiB (±0)	40.4 KiB (±0)	1.76 MiB (+133 B)
nextjs-turbopack	206.3 KiB (±0)	439 B (±0)	763.8 KiB (+69 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.

c4f9c6d · run

Signed-off-by: Casey Gowrie <ctgowrie@gmail.com>

ctgowrie requested a review from a team as a code owner August 28, 2026 14:08

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fix(core): stop reconnecting cancelled streams

c4f9c6d

Signed-off-by: Casey Gowrie <ctgowrie@gmail.com>

ctgowrie force-pushed the fix/reconnecting-stream-cancellation branch from b99dc7d to c4f9c6d Compare August 28, 2026 14:13

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fix(core): stop reconnecting cancelled streams - #3882

fix(core): stop reconnecting cancelled streams#3882
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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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Sim World

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