[core] Overlap workflow compilation with replay loading

[NathanColosimo]

Summary

• start the first-delivery run_started request before beginning speculative Node bundle compilation
• overlap compilation with the in-flight replay setup request
• replace a speculative compile when the authoritative returned workflow name differs
• skip Node compilation for QuickJS
• keep bundle evaluation inside each fresh VM after replay loading

workflow.bundle.compile and workflow.replay.load are sibling setup spans under workflow.execute. The workflow.run span begins afterward and contains fresh-VM context creation, bundle evaluation, input hydration, and replay execution.

Stack

Depends on #3797.

Validation

• focused runtime tracing and setup suites passed at the stack tip
• full @workflow/core suite passed at the stack tip — 2,295 tests
• pnpm --filter @workflow/core typecheck
• git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: c0fa289

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

[github-actions]

🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

python-node (8 failed):

• promiseAllWorkflow | wrun_41M1CKXZKY0GH5R9KPT1M83VGG | 🔍 observability
• sleepingWorkflow | wrun_41M1CKYKYB0GNDGFEC3SSB58PF | 🔍 observability
• parallelSleepWorkflow | wrun_41M1CKYMNP0GR7EV9XMDTRAZRC | 🔍 observability
• nullByteWorkflow | wrun_41M1CKYV5H0GMH1N1ZGNK8ER6T | 🔍 observability
• cancelRun - cancelling a running workflow | wrun_41M1CM37GQ0GWYY686EGK7SQ69 | 🔍 observability
• cancelRun via CLI - cancelling a running workflow | wrun_41M1CM37TZ0GJ2VHCDC0E56Y4S | 🔍 observability
• sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M1CM3M460GWNQ20F26999JWZ | 🔍 observability
• resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M1CM44M90GY9200M5TTVGK7D | 🔍 observability

🌐 Cross-language Conformance (9 failed)

python (9 failed):

• deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M1CM5RZF6Q2RH59M2R0Z7NJT
• promiseAllWorkflow | wrun_41M1CKXZKY0GH5R9KPT1M83VGG
• sleepingWorkflow | wrun_41M1CKYKYB0GNDGFEC3SSB58PF
• parallelSleepWorkflow | wrun_41M1CKYMNP0GR7EV9XMDTRAZRC
• nullByteWorkflow | wrun_41M1CKYV5H0GMH1N1ZGNK8ER6T
• cancelRun - cancelling a running workflow | wrun_41M1CM37GQ0GWYY686EGK7SQ69
• cancelRun via CLI - cancelling a running workflow | wrun_41M1CM37TZ0GJ2VHCDC0E56Y4S
• sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M1CM3M460GWNQ20F26999JWZ
• resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M1CM44M90GY9200M5TTVGK7D

⚠️ 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 (fastify)
• cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
• cancelRun via CLI - cancelling a running workflow (nuxt)
• deploymentId: 'latest' is a no-op in non-Vercel worlds (nuxt)
• hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nextjs-webpack)
• hookWorkflow (tanstack-start)
• hookWorkflow (vite)
• promiseAllWorkflow (hono)

🛠 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 19:16:50Z · abandoned wrun_41M1CKXTSM0GMZEHJE405037QS · (+7 more)
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZP0GVJ1FEYSBTFV8HT
• run-pickup-stall · promiseAllWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZG0GN6DPEK8Z6737RT
• run-pickup-stall · sleepingWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZP0GVJ1FEYSBTFV8HS
• run-pickup-stall · nullByteWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZS0GQ8SPJCE6GWTVHF
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1GDJ0GP3BATXWD6PBSFA
• cold-start-warmup · suite warmup (tanstack-start) · at 19:17:39Z · abandoned wrun_01M1CM247XTH7Y9XPP5HYBWRA2
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:17:40Z · abandoned wrun_41M1CM2GHC0GX4QVHEGCVZGP6Z
• cold-start-warmup · suite warmup (python) · at 19:17:56Z · abandoned wrun_01M1CKZTHFSH6N0E4WFKVNABDJ · (+7 more)
• run-pickup-stall · nullByteWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJN0GWTFQ2SYE88Q07Q
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJ40GJQN7XNBMWWKGAA
• run-pickup-stall · sleepingWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJT0GWA7SW2BRD7N0JX
• run-pickup-stall · promiseAllWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BPG0GJWC8333X3WVDEA
• run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPMEZFJDTC2AK4C1RCR
• run-pickup-stall · promiseAllWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPN2VHGXWQT08B8G223
• run-pickup-stall · sleepingWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPSJQDQER5K03H1AAGS
• run-pickup-stall · nullByteWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPY02SKKBQNEYV7EJQ2
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPVPQJZRRKG4B7BPBAQ
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:18:59Z · abandoned wrun_41M1CM3GE10GWKRJSMN3456GJQ
• run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 19:19:11Z · abandoned wrun_01M1CM5AA898Q04WQSMH7405SK
• run-pickup-stall · sleepingWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AADFJS3M3FZKKA684GY
• run-pickup-stall · promiseAllWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAB0RYMWWXNPDXRHAT4
• run-pickup-stall · nullByteWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAPDCNZAYST15FDVHCZ
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAFV21NWPEWFATNKRBY
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:20:11Z · abandoned wrun_01M1CM74XTJM7VX1F47PC1PCZ6
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:20:11Z · abandoned wrun_01M1CM74Y24WXKVB1RJCNAPJK6
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:11Z · abandoned wrun_01M1CM74Y0622STJ34M4QTPBB9
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:20:40Z · abandoned wrun_41M1CM63EP0GXCWTWBMK8SCC2X
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_01M1CM8295S7VXYPCDH5HBC3B4
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_01M1CM8297CYWNJC10D4TG4DA2
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_41M1CM5DE50GZZTTZTDHC84JD6
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:21:11Z · abandoned wrun_01M1CM8ZH61B6QTZ8GD84VEFAJ
• run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 19:22:47Z · abandoned wrun_01M1CMBX8PCCP9796WQM1XSM7T

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-ws-transport	553	0	87	640
Total	17026	17	2778	19821

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

✅ 📦 Local Production

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

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	134	0	26
✅ astro-stable-quickjs	134	0	26
✅ express-stable-node	134	0	26
✅ express-stable-quickjs	134	0	26
✅ fastify-stable-node	134	0	26
✅ fastify-stable-quickjs	134	0	26
✅ hono-stable-node	134	0	26
✅ hono-stable-quickjs	134	0	26
✅ nest-stable-node	134	0	26
✅ nest-stable-quickjs	134	0	26
✅ nextjs-turbopack-canary-node	141	0	19
✅ nextjs-turbopack-canary-quickjs	141	0	19
✅ nextjs-turbopack-stable-node	160	0	0
✅ nextjs-turbopack-stable-quickjs	160	0	0
✅ nextjs-webpack-canary-node	141	0	19
✅ nextjs-webpack-canary-quickjs	141	0	19
✅ nextjs-webpack-stable-node	160	0	0
✅ nextjs-webpack-stable-quickjs	160	0	0
✅ nitro-stable-node	134	0	26
✅ nitro-stable-quickjs	134	0	26
✅ nuxt-stable-node	134	0	26
✅ nuxt-stable-quickjs	134	0	26
✅ sveltekit-stable-node	153	0	7
✅ sveltekit-stable-quickjs	153	0	7
✅ tanstack-start-node	134	0	26
✅ tanstack-start-quickjs	134	0	26
✅ vite-stable-node	134	0	26
✅ vite-stable-quickjs	134	0	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	Failed	Skipped
✅ example	132	0	28
✅ express	132	0	28
✅ hono	132	0	28
✅ nextjs-turbopack	157	0	3
✅ nitro	132	0	28
✅ vite	132	0	28

✅ vercel-ws-transport

App	Passed	Failed	Skipped
✅ example	132	0	28
✅ express	132	0	28
✅ nextjs-turbopack	157	0	3
✅ vite	132	0	28

---

📋 View full workflow run

[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

[vercel]

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 31, 2026 7:10pm
example-nextjs-workflow-webpack	Ready	Preview, v0	Aug 31, 2026 7:10pm
example-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-astro-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-express-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-fastify-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-hono-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nestjs-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nitro-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nuxt-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-python-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-sveltekit-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-tanstack-start-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-vite-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-docs	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-swc-playground	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-tarballs	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-web	Ready	Preview, v0	Aug 31, 2026 7:10pm

[github-actions]

📊 Workflow Benchmarks

commit c0fa289 · Mon, 31 Aug 2026 19:30:51 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	256 (-70%) 💚	1310 🔴 (+5.8%)	1322 🔴 (+2.3%)	1577 🔴 (+1.2%)	30
TTFS	stream	258 (+1.6%)	1307 🔴 (+2.9%)	1368 🔴 (+2.3%)	1780 🔴 (+27%) 🔻	30
TTFS	hook + stream	388 (-31%) 💚	1570 🔴 (+10%)	1643 🔴 (+1.5%)	1725 🔴 (-18%) 💚	30
Fan-out TTFS	Promise.all(100 steps)	608 (+18%) 🔻	2097 (+16%) 🔻	2137 (+13%)	2142 (-3.9%)	10
Fan-out TTLS	Promise.all(100 steps)	2228 (+12%)	4561 (+7.7%)	4582 (-2.8%)	4974 (-38%) 💚	10
STSO	1020 steps (inline)	121 (+57%) 🔻	153 (+7.0%)	177 (+7.9%)	321 (+43%) 🔻	1019
WO	1020 steps	155301 (+8.4%)	155301 (+8.4%)	155301 (+8.4%)	155301 (+8.4%)	1
CRTT	first chunk (pooled)	96 (-13%)	184 (+9.5%)	291 (+44%) 🔻	766 (+150%) 🔻	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	154 (+2%)	242 (+34%)	336 (+19%)	878 (+51%)	333 (+126%)	10
size sweep (100/s, 160B-12KB)	152 (+9%)	159 (-19%)	331 (-27%)	917 (+2%)	144 (-19%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	145 (+1%)	138 (-33%)	195 (-94%)	532 (-89%)	346 (-27%)	3
replay eve-gpt-5.6-sol-2000t (1x)	109 (-57%)	144 (-20%)	201 (-15%)	399 (-46%)	388 (-38%)	2
replay eve-gpt-5.6-sol-2000t (2x)	111 (-34%)	198 (-15%)	269 (-24%)	468 (-23%)	284 (-14%)	3

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

1020 steps (inline)

Cumulative STSO time: main 143115ms → this run 154010ms (Δ +10895ms, +8%)

 50-100 ms ┃ main 1 this 0 -1
100-150 ms ███████████████████┃████ main 838 this 706 -132
150-200 ms █████░░┃ main 163 this 268 +105
200-250 ms ┃ main 8 this 28 +20
250-300 ms ┃ main 4 this 4 +0
300-350 ms ┃ main 3 this 5 +2
350-400 ms ┃ main 2 this 5 +3
400-450 ms ┃ main 0 this 1 +1
450-500 ms ┃ main 0 this 1 +1
800-850 ms ┃ main 0 this 1 +1

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

variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▃█▃▁··· 168.7 (+10%) 135 (-2%) 336 (+19%) 878 (+51%) 3000
sweep ······▃█▂▁··· 162.7 (-4%) 121 (-13%) 331 (-27%) 917 (+2%) 3000
gw 1x ·····▁▅█▁▁··· 121.9 (-65%) 108 (-27%) 195 (-94%) 532 (-89%) 5295
eve 1x ·····▁▆█▂▁··· 128.4 (-21%) 111 (-21%) 201 (-15%) 399 (-46%) 5186
eve 2x ·····▁▂█▃▁··· 157.5 (-18%) 140 (-16%) 269 (-24%) 468 (-23%) 7779

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

control ▆▄▅▄█▆▁▅▅▅ 134–199ms
sweep █▇▅▅▄▃▃▂▁▁ 122–218ms
gw 1x █▄▁▂▁▁▁▃▅▂ 106–169ms
eve 1x ▂▁▁▇▂▇▃█▄▂ 114–149ms
eve 2x ▅▁▂▂▁▄▆█▆▇ 121–201ms

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

sweep ▆██▄▁▁▄ 160–166ms

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

control ▁█▁▂▄▄▃▅▄▅ 35–56ms
sweep ▇▆▃▆▅▃█▂▁▃ 49–63ms
gw 1x █▅▄▁▃▃▄▆▄▆ 28–44ms
eve 1x ▄▅▁█▇█▃█▂▄ 24–28ms
eve 2x ▇▄▃▆▄▄▆▁▄█ 21–32ms

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-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]

Framework	Flow route	Step reg.	Framework output
hono	200.9 KiB (±0)	40.4 KiB (±0)	1.76 MiB (+896 B)
nextjs-turbopack	206.3 KiB (±0)	439 B (±0)	765.1 KiB (+732 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.

c0fa289 · run

[github-actions]

No backport to stable for ee6f917 (AI decision).

This is a latency optimization: it starts Node bundle compilation concurrently with the run_started / replay-load request, adds a new exported compileWorkflowBundle API and compiledWorkflowScripts session option, and skips Node compilation for QuickJS runs. No user-visible defect, crash, hang, or data-loss issue is being fixed — the existing sequential compile path works correctly on stable, it is merely slower, so this does not meet the bar for a maintenance branch.

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

ee6f917cdbfcf50a5fd697c7a9cb70dd1294f931

[NathanColosimo]

Summary

• start the first-delivery run_started request before beginning speculative Node bundle compilation
• overlap compilation with the in-flight replay setup request
• replace a speculative compile when the authoritative returned workflow name differs
• skip Node compilation for QuickJS
• keep bundle evaluation inside each fresh VM after replay loading

workflow.bundle.compile and workflow.replay.load are sibling setup spans under workflow.execute. The workflow.run span begins afterward and contains fresh-VM context creation, bundle evaluation, input hydration, and replay execution.

Stack

Depends on #3797.

Validation

• focused runtime tracing and setup suites passed at the stack tip
• full @workflow/core suite passed at the stack tip — 2,295 tests
• pnpm --filter @workflow/core typecheck
• git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: c0fa289

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

[github-actions]

🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

python-node (8 failed):

• promiseAllWorkflow | wrun_41M1CKXZKY0GH5R9KPT1M83VGG | 🔍 observability
• sleepingWorkflow | wrun_41M1CKYKYB0GNDGFEC3SSB58PF | 🔍 observability
• parallelSleepWorkflow | wrun_41M1CKYMNP0GR7EV9XMDTRAZRC | 🔍 observability
• nullByteWorkflow | wrun_41M1CKYV5H0GMH1N1ZGNK8ER6T | 🔍 observability
• cancelRun - cancelling a running workflow | wrun_41M1CM37GQ0GWYY686EGK7SQ69 | 🔍 observability
• cancelRun via CLI - cancelling a running workflow | wrun_41M1CM37TZ0GJ2VHCDC0E56Y4S | 🔍 observability
• sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M1CM3M460GWNQ20F26999JWZ | 🔍 observability
• resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M1CM44M90GY9200M5TTVGK7D | 🔍 observability

🌐 Cross-language Conformance (9 failed)

python (9 failed):

• deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M1CM5RZF6Q2RH59M2R0Z7NJT
• promiseAllWorkflow | wrun_41M1CKXZKY0GH5R9KPT1M83VGG
• sleepingWorkflow | wrun_41M1CKYKYB0GNDGFEC3SSB58PF
• parallelSleepWorkflow | wrun_41M1CKYMNP0GR7EV9XMDTRAZRC
• nullByteWorkflow | wrun_41M1CKYV5H0GMH1N1ZGNK8ER6T
• cancelRun - cancelling a running workflow | wrun_41M1CM37GQ0GWYY686EGK7SQ69
• cancelRun via CLI - cancelling a running workflow | wrun_41M1CM37TZ0GJ2VHCDC0E56Y4S
• sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M1CM3M460GWNQ20F26999JWZ
• resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M1CM44M90GY9200M5TTVGK7D

⚠️ 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 (fastify)
• cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
• cancelRun via CLI - cancelling a running workflow (nuxt)
• deploymentId: 'latest' is a no-op in non-Vercel worlds (nuxt)
• hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nextjs-webpack)
• hookWorkflow (tanstack-start)
• hookWorkflow (vite)
• promiseAllWorkflow (hono)

🛠 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 19:16:50Z · abandoned wrun_41M1CKXTSM0GMZEHJE405037QS · (+7 more)
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZP0GVJ1FEYSBTFV8HT
• run-pickup-stall · promiseAllWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZG0GN6DPEK8Z6737RT
• run-pickup-stall · sleepingWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZP0GVJ1FEYSBTFV8HS
• run-pickup-stall · nullByteWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZS0GQ8SPJCE6GWTVHF
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1GDJ0GP3BATXWD6PBSFA
• cold-start-warmup · suite warmup (tanstack-start) · at 19:17:39Z · abandoned wrun_01M1CM247XTH7Y9XPP5HYBWRA2
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:17:40Z · abandoned wrun_41M1CM2GHC0GX4QVHEGCVZGP6Z
• cold-start-warmup · suite warmup (python) · at 19:17:56Z · abandoned wrun_01M1CKZTHFSH6N0E4WFKVNABDJ · (+7 more)
• run-pickup-stall · nullByteWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJN0GWTFQ2SYE88Q07Q
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJ40GJQN7XNBMWWKGAA
• run-pickup-stall · sleepingWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJT0GWA7SW2BRD7N0JX
• run-pickup-stall · promiseAllWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BPG0GJWC8333X3WVDEA
• run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPMEZFJDTC2AK4C1RCR
• run-pickup-stall · promiseAllWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPN2VHGXWQT08B8G223
• run-pickup-stall · sleepingWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPSJQDQER5K03H1AAGS
• run-pickup-stall · nullByteWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPY02SKKBQNEYV7EJQ2
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPVPQJZRRKG4B7BPBAQ
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:18:59Z · abandoned wrun_41M1CM3GE10GWKRJSMN3456GJQ
• run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 19:19:11Z · abandoned wrun_01M1CM5AA898Q04WQSMH7405SK
• run-pickup-stall · sleepingWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AADFJS3M3FZKKA684GY
• run-pickup-stall · promiseAllWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAB0RYMWWXNPDXRHAT4
• run-pickup-stall · nullByteWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAPDCNZAYST15FDVHCZ
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAFV21NWPEWFATNKRBY
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:20:11Z · abandoned wrun_01M1CM74XTJM7VX1F47PC1PCZ6
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:20:11Z · abandoned wrun_01M1CM74Y24WXKVB1RJCNAPJK6
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:11Z · abandoned wrun_01M1CM74Y0622STJ34M4QTPBB9
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:20:40Z · abandoned wrun_41M1CM63EP0GXCWTWBMK8SCC2X
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_01M1CM8295S7VXYPCDH5HBC3B4
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_01M1CM8297CYWNJC10D4TG4DA2
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_41M1CM5DE50GZZTTZTDHC84JD6
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:21:11Z · abandoned wrun_01M1CM8ZH61B6QTZ8GD84VEFAJ
• run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 19:22:47Z · abandoned wrun_01M1CMBX8PCCP9796WQM1XSM7T

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-ws-transport	553	0	87	640
Total	17026	17	2778	19821

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

✅ 📦 Local Production

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

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	134	0	26
✅ astro-stable-quickjs	134	0	26
✅ express-stable-node	134	0	26
✅ express-stable-quickjs	134	0	26
✅ fastify-stable-node	134	0	26
✅ fastify-stable-quickjs	134	0	26
✅ hono-stable-node	134	0	26
✅ hono-stable-quickjs	134	0	26
✅ nest-stable-node	134	0	26
✅ nest-stable-quickjs	134	0	26
✅ nextjs-turbopack-canary-node	141	0	19
✅ nextjs-turbopack-canary-quickjs	141	0	19
✅ nextjs-turbopack-stable-node	160	0	0
✅ nextjs-turbopack-stable-quickjs	160	0	0
✅ nextjs-webpack-canary-node	141	0	19
✅ nextjs-webpack-canary-quickjs	141	0	19
✅ nextjs-webpack-stable-node	160	0	0
✅ nextjs-webpack-stable-quickjs	160	0	0
✅ nitro-stable-node	134	0	26
✅ nitro-stable-quickjs	134	0	26
✅ nuxt-stable-node	134	0	26
✅ nuxt-stable-quickjs	134	0	26
✅ sveltekit-stable-node	153	0	7
✅ sveltekit-stable-quickjs	153	0	7
✅ tanstack-start-node	134	0	26
✅ tanstack-start-quickjs	134	0	26
✅ vite-stable-node	134	0	26
✅ vite-stable-quickjs	134	0	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	Failed	Skipped
✅ example	132	0	28
✅ express	132	0	28
✅ hono	132	0	28
✅ nextjs-turbopack	157	0	3
✅ nitro	132	0	28
✅ vite	132	0	28

✅ vercel-ws-transport

App	Passed	Failed	Skipped
✅ example	132	0	28
✅ express	132	0	28
✅ nextjs-turbopack	157	0	3
✅ vite	132	0	28

---

📋 View full workflow run

[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

[vercel]

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 31, 2026 7:10pm
example-nextjs-workflow-webpack	Ready	Preview, v0	Aug 31, 2026 7:10pm
example-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-astro-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-express-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-fastify-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-hono-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nestjs-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nitro-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nuxt-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-python-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-sveltekit-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-tanstack-start-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-vite-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-docs	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-swc-playground	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-tarballs	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-web	Ready	Preview, v0	Aug 31, 2026 7:10pm

[github-actions]

📊 Workflow Benchmarks

commit c0fa289 · Mon, 31 Aug 2026 19:30:51 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	256 (-70%) 💚	1310 🔴 (+5.8%)	1322 🔴 (+2.3%)	1577 🔴 (+1.2%)	30
TTFS	stream	258 (+1.6%)	1307 🔴 (+2.9%)	1368 🔴 (+2.3%)	1780 🔴 (+27%) 🔻	30
TTFS	hook + stream	388 (-31%) 💚	1570 🔴 (+10%)	1643 🔴 (+1.5%)	1725 🔴 (-18%) 💚	30
Fan-out TTFS	Promise.all(100 steps)	608 (+18%) 🔻	2097 (+16%) 🔻	2137 (+13%)	2142 (-3.9%)	10
Fan-out TTLS	Promise.all(100 steps)	2228 (+12%)	4561 (+7.7%)	4582 (-2.8%)	4974 (-38%) 💚	10
STSO	1020 steps (inline)	121 (+57%) 🔻	153 (+7.0%)	177 (+7.9%)	321 (+43%) 🔻	1019
WO	1020 steps	155301 (+8.4%)	155301 (+8.4%)	155301 (+8.4%)	155301 (+8.4%)	1
CRTT	first chunk (pooled)	96 (-13%)	184 (+9.5%)	291 (+44%) 🔻	766 (+150%) 🔻	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	154 (+2%)	242 (+34%)	336 (+19%)	878 (+51%)	333 (+126%)	10
size sweep (100/s, 160B-12KB)	152 (+9%)	159 (-19%)	331 (-27%)	917 (+2%)	144 (-19%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	145 (+1%)	138 (-33%)	195 (-94%)	532 (-89%)	346 (-27%)	3
replay eve-gpt-5.6-sol-2000t (1x)	109 (-57%)	144 (-20%)	201 (-15%)	399 (-46%)	388 (-38%)	2
replay eve-gpt-5.6-sol-2000t (2x)	111 (-34%)	198 (-15%)	269 (-24%)	468 (-23%)	284 (-14%)	3

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

1020 steps (inline)

Cumulative STSO time: main 143115ms → this run 154010ms (Δ +10895ms, +8%)

 50-100 ms ┃ main 1 this 0 -1
100-150 ms ███████████████████┃████ main 838 this 706 -132
150-200 ms █████░░┃ main 163 this 268 +105
200-250 ms ┃ main 8 this 28 +20
250-300 ms ┃ main 4 this 4 +0
300-350 ms ┃ main 3 this 5 +2
350-400 ms ┃ main 2 this 5 +3
400-450 ms ┃ main 0 this 1 +1
450-500 ms ┃ main 0 this 1 +1
800-850 ms ┃ main 0 this 1 +1

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

variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▃█▃▁··· 168.7 (+10%) 135 (-2%) 336 (+19%) 878 (+51%) 3000
sweep ······▃█▂▁··· 162.7 (-4%) 121 (-13%) 331 (-27%) 917 (+2%) 3000
gw 1x ·····▁▅█▁▁··· 121.9 (-65%) 108 (-27%) 195 (-94%) 532 (-89%) 5295
eve 1x ·····▁▆█▂▁··· 128.4 (-21%) 111 (-21%) 201 (-15%) 399 (-46%) 5186
eve 2x ·····▁▂█▃▁··· 157.5 (-18%) 140 (-16%) 269 (-24%) 468 (-23%) 7779

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

control ▆▄▅▄█▆▁▅▅▅ 134–199ms
sweep █▇▅▅▄▃▃▂▁▁ 122–218ms
gw 1x █▄▁▂▁▁▁▃▅▂ 106–169ms
eve 1x ▂▁▁▇▂▇▃█▄▂ 114–149ms
eve 2x ▅▁▂▂▁▄▆█▆▇ 121–201ms

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

sweep ▆██▄▁▁▄ 160–166ms

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

control ▁█▁▂▄▄▃▅▄▅ 35–56ms
sweep ▇▆▃▆▅▃█▂▁▃ 49–63ms
gw 1x █▅▄▁▃▃▄▆▄▆ 28–44ms
eve 1x ▄▅▁█▇█▃█▂▄ 24–28ms
eve 2x ▇▄▃▆▄▄▆▁▄█ 21–32ms

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-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]

Framework	Flow route	Step reg.	Framework output
hono	200.9 KiB (±0)	40.4 KiB (±0)	1.76 MiB (+896 B)
nextjs-turbopack	206.3 KiB (±0)	439 B (±0)	765.1 KiB (+732 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.

c0fa289 · run

[github-actions]

No backport to stable for ee6f917 (AI decision).

This is a latency optimization: it starts Node bundle compilation concurrently with the run_started / replay-load request, adds a new exported compileWorkflowBundle API and compiledWorkflowScripts session option, and skips Node compilation for QuickJS runs. No user-visible defect, crash, hang, or data-loss issue is being fixed — the existing sequential compile path works correctly on stable, it is merely slower, so this does not meet the bar for a maintenance branch.

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

ee6f917cdbfcf50a5fd697c7a9cb70dd1294f931

[NathanColosimo]

Summary

• start the first-delivery run_started request before beginning speculative Node bundle compilation
• overlap compilation with the in-flight replay setup request
• replace a speculative compile when the authoritative returned workflow name differs
• skip Node compilation for QuickJS
• keep bundle evaluation inside each fresh VM after replay loading

workflow.bundle.compile and workflow.replay.load are sibling setup spans under workflow.execute. The workflow.run span begins afterward and contains fresh-VM context creation, bundle evaluation, input hydration, and replay execution.

Stack

Depends on #3797.

Validation

• focused runtime tracing and setup suites passed at the stack tip
• full @workflow/core suite passed at the stack tip — 2,295 tests
• pnpm --filter @workflow/core typecheck
• git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: c0fa289

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

[github-actions]

🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

python-node (8 failed):

• promiseAllWorkflow | wrun_41M1CKXZKY0GH5R9KPT1M83VGG | 🔍 observability
• sleepingWorkflow | wrun_41M1CKYKYB0GNDGFEC3SSB58PF | 🔍 observability
• parallelSleepWorkflow | wrun_41M1CKYMNP0GR7EV9XMDTRAZRC | 🔍 observability
• nullByteWorkflow | wrun_41M1CKYV5H0GMH1N1ZGNK8ER6T | 🔍 observability
• cancelRun - cancelling a running workflow | wrun_41M1CM37GQ0GWYY686EGK7SQ69 | 🔍 observability
• cancelRun via CLI - cancelling a running workflow | wrun_41M1CM37TZ0GJ2VHCDC0E56Y4S | 🔍 observability
• sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M1CM3M460GWNQ20F26999JWZ | 🔍 observability
• resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M1CM44M90GY9200M5TTVGK7D | 🔍 observability

🌐 Cross-language Conformance (9 failed)

python (9 failed):

• deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M1CM5RZF6Q2RH59M2R0Z7NJT
• promiseAllWorkflow | wrun_41M1CKXZKY0GH5R9KPT1M83VGG
• sleepingWorkflow | wrun_41M1CKYKYB0GNDGFEC3SSB58PF
• parallelSleepWorkflow | wrun_41M1CKYMNP0GR7EV9XMDTRAZRC
• nullByteWorkflow | wrun_41M1CKYV5H0GMH1N1ZGNK8ER6T
• cancelRun - cancelling a running workflow | wrun_41M1CM37GQ0GWYY686EGK7SQ69
• cancelRun via CLI - cancelling a running workflow | wrun_41M1CM37TZ0GJ2VHCDC0E56Y4S
• sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M1CM3M460GWNQ20F26999JWZ
• resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M1CM44M90GY9200M5TTVGK7D

⚠️ 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 (fastify)
• cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
• cancelRun via CLI - cancelling a running workflow (nuxt)
• deploymentId: 'latest' is a no-op in non-Vercel worlds (nuxt)
• hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nextjs-webpack)
• hookWorkflow (tanstack-start)
• hookWorkflow (vite)
• promiseAllWorkflow (hono)

🛠 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 19:16:50Z · abandoned wrun_41M1CKXTSM0GMZEHJE405037QS · (+7 more)
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZP0GVJ1FEYSBTFV8HT
• run-pickup-stall · promiseAllWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZG0GN6DPEK8Z6737RT
• run-pickup-stall · sleepingWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZP0GVJ1FEYSBTFV8HS
• run-pickup-stall · nullByteWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZS0GQ8SPJCE6GWTVHF
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1GDJ0GP3BATXWD6PBSFA
• cold-start-warmup · suite warmup (tanstack-start) · at 19:17:39Z · abandoned wrun_01M1CM247XTH7Y9XPP5HYBWRA2
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:17:40Z · abandoned wrun_41M1CM2GHC0GX4QVHEGCVZGP6Z
• cold-start-warmup · suite warmup (python) · at 19:17:56Z · abandoned wrun_01M1CKZTHFSH6N0E4WFKVNABDJ · (+7 more)
• run-pickup-stall · nullByteWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJN0GWTFQ2SYE88Q07Q
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJ40GJQN7XNBMWWKGAA
• run-pickup-stall · sleepingWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJT0GWA7SW2BRD7N0JX
• run-pickup-stall · promiseAllWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BPG0GJWC8333X3WVDEA
• run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPMEZFJDTC2AK4C1RCR
• run-pickup-stall · promiseAllWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPN2VHGXWQT08B8G223
• run-pickup-stall · sleepingWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPSJQDQER5K03H1AAGS
• run-pickup-stall · nullByteWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPY02SKKBQNEYV7EJQ2
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPVPQJZRRKG4B7BPBAQ
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:18:59Z · abandoned wrun_41M1CM3GE10GWKRJSMN3456GJQ
• run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 19:19:11Z · abandoned wrun_01M1CM5AA898Q04WQSMH7405SK
• run-pickup-stall · sleepingWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AADFJS3M3FZKKA684GY
• run-pickup-stall · promiseAllWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAB0RYMWWXNPDXRHAT4
• run-pickup-stall · nullByteWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAPDCNZAYST15FDVHCZ
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAFV21NWPEWFATNKRBY
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:20:11Z · abandoned wrun_01M1CM74XTJM7VX1F47PC1PCZ6
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:20:11Z · abandoned wrun_01M1CM74Y24WXKVB1RJCNAPJK6
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:11Z · abandoned wrun_01M1CM74Y0622STJ34M4QTPBB9
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:20:40Z · abandoned wrun_41M1CM63EP0GXCWTWBMK8SCC2X
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_01M1CM8295S7VXYPCDH5HBC3B4
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_01M1CM8297CYWNJC10D4TG4DA2
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_41M1CM5DE50GZZTTZTDHC84JD6
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:21:11Z · abandoned wrun_01M1CM8ZH61B6QTZ8GD84VEFAJ
• run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 19:22:47Z · abandoned wrun_01M1CMBX8PCCP9796WQM1XSM7T

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-ws-transport	553	0	87	640
Total	17026	17	2778	19821

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

✅ 📦 Local Production

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

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	134	0	26
✅ astro-stable-quickjs	134	0	26
✅ express-stable-node	134	0	26
✅ express-stable-quickjs	134	0	26
✅ fastify-stable-node	134	0	26
✅ fastify-stable-quickjs	134	0	26
✅ hono-stable-node	134	0	26
✅ hono-stable-quickjs	134	0	26
✅ nest-stable-node	134	0	26
✅ nest-stable-quickjs	134	0	26
✅ nextjs-turbopack-canary-node	141	0	19
✅ nextjs-turbopack-canary-quickjs	141	0	19
✅ nextjs-turbopack-stable-node	160	0	0
✅ nextjs-turbopack-stable-quickjs	160	0	0
✅ nextjs-webpack-canary-node	141	0	19
✅ nextjs-webpack-canary-quickjs	141	0	19
✅ nextjs-webpack-stable-node	160	0	0
✅ nextjs-webpack-stable-quickjs	160	0	0
✅ nitro-stable-node	134	0	26
✅ nitro-stable-quickjs	134	0	26
✅ nuxt-stable-node	134	0	26
✅ nuxt-stable-quickjs	134	0	26
✅ sveltekit-stable-node	153	0	7
✅ sveltekit-stable-quickjs	153	0	7
✅ tanstack-start-node	134	0	26
✅ tanstack-start-quickjs	134	0	26
✅ vite-stable-node	134	0	26
✅ vite-stable-quickjs	134	0	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	Failed	Skipped
✅ example	132	0	28
✅ express	132	0	28
✅ hono	132	0	28
✅ nextjs-turbopack	157	0	3
✅ nitro	132	0	28
✅ vite	132	0	28

✅ vercel-ws-transport

App	Passed	Failed	Skipped
✅ example	132	0	28
✅ express	132	0	28
✅ nextjs-turbopack	157	0	3
✅ vite	132	0	28

---

📋 View full workflow run

[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

[vercel]

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 31, 2026 7:10pm
example-nextjs-workflow-webpack	Ready	Preview, v0	Aug 31, 2026 7:10pm
example-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-astro-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-express-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-fastify-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-hono-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nestjs-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nitro-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nuxt-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-python-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-sveltekit-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-tanstack-start-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-vite-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-docs	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-swc-playground	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-tarballs	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-web	Ready	Preview, v0	Aug 31, 2026 7:10pm

[github-actions]

📊 Workflow Benchmarks

commit c0fa289 · Mon, 31 Aug 2026 19:30:51 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	256 (-70%) 💚	1310 🔴 (+5.8%)	1322 🔴 (+2.3%)	1577 🔴 (+1.2%)	30
TTFS	stream	258 (+1.6%)	1307 🔴 (+2.9%)	1368 🔴 (+2.3%)	1780 🔴 (+27%) 🔻	30
TTFS	hook + stream	388 (-31%) 💚	1570 🔴 (+10%)	1643 🔴 (+1.5%)	1725 🔴 (-18%) 💚	30
Fan-out TTFS	Promise.all(100 steps)	608 (+18%) 🔻	2097 (+16%) 🔻	2137 (+13%)	2142 (-3.9%)	10
Fan-out TTLS	Promise.all(100 steps)	2228 (+12%)	4561 (+7.7%)	4582 (-2.8%)	4974 (-38%) 💚	10
STSO	1020 steps (inline)	121 (+57%) 🔻	153 (+7.0%)	177 (+7.9%)	321 (+43%) 🔻	1019
WO	1020 steps	155301 (+8.4%)	155301 (+8.4%)	155301 (+8.4%)	155301 (+8.4%)	1
CRTT	first chunk (pooled)	96 (-13%)	184 (+9.5%)	291 (+44%) 🔻	766 (+150%) 🔻	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	154 (+2%)	242 (+34%)	336 (+19%)	878 (+51%)	333 (+126%)	10
size sweep (100/s, 160B-12KB)	152 (+9%)	159 (-19%)	331 (-27%)	917 (+2%)	144 (-19%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	145 (+1%)	138 (-33%)	195 (-94%)	532 (-89%)	346 (-27%)	3
replay eve-gpt-5.6-sol-2000t (1x)	109 (-57%)	144 (-20%)	201 (-15%)	399 (-46%)	388 (-38%)	2
replay eve-gpt-5.6-sol-2000t (2x)	111 (-34%)	198 (-15%)	269 (-24%)	468 (-23%)	284 (-14%)	3

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

1020 steps (inline)

Cumulative STSO time: main 143115ms → this run 154010ms (Δ +10895ms, +8%)

 50-100 ms ┃ main 1 this 0 -1
100-150 ms ███████████████████┃████ main 838 this 706 -132
150-200 ms █████░░┃ main 163 this 268 +105
200-250 ms ┃ main 8 this 28 +20
250-300 ms ┃ main 4 this 4 +0
300-350 ms ┃ main 3 this 5 +2
350-400 ms ┃ main 2 this 5 +3
400-450 ms ┃ main 0 this 1 +1
450-500 ms ┃ main 0 this 1 +1
800-850 ms ┃ main 0 this 1 +1

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

variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▃█▃▁··· 168.7 (+10%) 135 (-2%) 336 (+19%) 878 (+51%) 3000
sweep ······▃█▂▁··· 162.7 (-4%) 121 (-13%) 331 (-27%) 917 (+2%) 3000
gw 1x ·····▁▅█▁▁··· 121.9 (-65%) 108 (-27%) 195 (-94%) 532 (-89%) 5295
eve 1x ·····▁▆█▂▁··· 128.4 (-21%) 111 (-21%) 201 (-15%) 399 (-46%) 5186
eve 2x ·····▁▂█▃▁··· 157.5 (-18%) 140 (-16%) 269 (-24%) 468 (-23%) 7779

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

control ▆▄▅▄█▆▁▅▅▅ 134–199ms
sweep █▇▅▅▄▃▃▂▁▁ 122–218ms
gw 1x █▄▁▂▁▁▁▃▅▂ 106–169ms
eve 1x ▂▁▁▇▂▇▃█▄▂ 114–149ms
eve 2x ▅▁▂▂▁▄▆█▆▇ 121–201ms

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

sweep ▆██▄▁▁▄ 160–166ms

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

control ▁█▁▂▄▄▃▅▄▅ 35–56ms
sweep ▇▆▃▆▅▃█▂▁▃ 49–63ms
gw 1x █▅▄▁▃▃▄▆▄▆ 28–44ms
eve 1x ▄▅▁█▇█▃█▂▄ 24–28ms
eve 2x ▇▄▃▆▄▄▆▁▄█ 21–32ms

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-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]

Framework	Flow route	Step reg.	Framework output
hono	200.9 KiB (±0)	40.4 KiB (±0)	1.76 MiB (+896 B)
nextjs-turbopack	206.3 KiB (±0)	439 B (±0)	765.1 KiB (+732 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.

c0fa289 · run

[github-actions]

No backport to stable for ee6f917 (AI decision).

This is a latency optimization: it starts Node bundle compilation concurrently with the run_started / replay-load request, adds a new exported compileWorkflowBundle API and compiledWorkflowScripts session option, and skips Node compilation for QuickJS runs. No user-visible defect, crash, hang, or data-loss issue is being fixed — the existing sequential compile path works correctly on stable, it is merely slower, so this does not meet the bar for a maintenance branch.

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

ee6f917cdbfcf50a5fd697c7a9cb70dd1294f931

[NathanColosimo]

Summary

• start the first-delivery run_started request before beginning speculative Node bundle compilation
• overlap compilation with the in-flight replay setup request
• replace a speculative compile when the authoritative returned workflow name differs
• skip Node compilation for QuickJS
• keep bundle evaluation inside each fresh VM after replay loading

workflow.bundle.compile and workflow.replay.load are sibling setup spans under workflow.execute. The workflow.run span begins afterward and contains fresh-VM context creation, bundle evaluation, input hydration, and replay execution.

Stack

Depends on #3797.

Validation

• focused runtime tracing and setup suites passed at the stack tip
• full @workflow/core suite passed at the stack tip — 2,295 tests
• pnpm --filter @workflow/core typecheck
• git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: c0fa289

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

[github-actions]

🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

python-node (8 failed):

• promiseAllWorkflow | wrun_41M1CKXZKY0GH5R9KPT1M83VGG | 🔍 observability
• sleepingWorkflow | wrun_41M1CKYKYB0GNDGFEC3SSB58PF | 🔍 observability
• parallelSleepWorkflow | wrun_41M1CKYMNP0GR7EV9XMDTRAZRC | 🔍 observability
• nullByteWorkflow | wrun_41M1CKYV5H0GMH1N1ZGNK8ER6T | 🔍 observability
• cancelRun - cancelling a running workflow | wrun_41M1CM37GQ0GWYY686EGK7SQ69 | 🔍 observability
• cancelRun via CLI - cancelling a running workflow | wrun_41M1CM37TZ0GJ2VHCDC0E56Y4S | 🔍 observability
• sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M1CM3M460GWNQ20F26999JWZ | 🔍 observability
• resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M1CM44M90GY9200M5TTVGK7D | 🔍 observability

🌐 Cross-language Conformance (9 failed)

python (9 failed):

• deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M1CM5RZF6Q2RH59M2R0Z7NJT
• promiseAllWorkflow | wrun_41M1CKXZKY0GH5R9KPT1M83VGG
• sleepingWorkflow | wrun_41M1CKYKYB0GNDGFEC3SSB58PF
• parallelSleepWorkflow | wrun_41M1CKYMNP0GR7EV9XMDTRAZRC
• nullByteWorkflow | wrun_41M1CKYV5H0GMH1N1ZGNK8ER6T
• cancelRun - cancelling a running workflow | wrun_41M1CM37GQ0GWYY686EGK7SQ69
• cancelRun via CLI - cancelling a running workflow | wrun_41M1CM37TZ0GJ2VHCDC0E56Y4S
• sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M1CM3M460GWNQ20F26999JWZ
• resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M1CM44M90GY9200M5TTVGK7D

⚠️ 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 (fastify)
• cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
• cancelRun via CLI - cancelling a running workflow (nuxt)
• deploymentId: 'latest' is a no-op in non-Vercel worlds (nuxt)
• hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nextjs-webpack)
• hookWorkflow (tanstack-start)
• hookWorkflow (vite)
• promiseAllWorkflow (hono)

🛠 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 19:16:50Z · abandoned wrun_41M1CKXTSM0GMZEHJE405037QS · (+7 more)
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZP0GVJ1FEYSBTFV8HT
• run-pickup-stall · promiseAllWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZG0GN6DPEK8Z6737RT
• run-pickup-stall · sleepingWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZP0GVJ1FEYSBTFV8HS
• run-pickup-stall · nullByteWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZS0GQ8SPJCE6GWTVHF
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1GDJ0GP3BATXWD6PBSFA
• cold-start-warmup · suite warmup (tanstack-start) · at 19:17:39Z · abandoned wrun_01M1CM247XTH7Y9XPP5HYBWRA2
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:17:40Z · abandoned wrun_41M1CM2GHC0GX4QVHEGCVZGP6Z
• cold-start-warmup · suite warmup (python) · at 19:17:56Z · abandoned wrun_01M1CKZTHFSH6N0E4WFKVNABDJ · (+7 more)
• run-pickup-stall · nullByteWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJN0GWTFQ2SYE88Q07Q
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJ40GJQN7XNBMWWKGAA
• run-pickup-stall · sleepingWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJT0GWA7SW2BRD7N0JX
• run-pickup-stall · promiseAllWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BPG0GJWC8333X3WVDEA
• run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPMEZFJDTC2AK4C1RCR
• run-pickup-stall · promiseAllWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPN2VHGXWQT08B8G223
• run-pickup-stall · sleepingWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPSJQDQER5K03H1AAGS
• run-pickup-stall · nullByteWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPY02SKKBQNEYV7EJQ2
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPVPQJZRRKG4B7BPBAQ
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:18:59Z · abandoned wrun_41M1CM3GE10GWKRJSMN3456GJQ
• run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 19:19:11Z · abandoned wrun_01M1CM5AA898Q04WQSMH7405SK
• run-pickup-stall · sleepingWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AADFJS3M3FZKKA684GY
• run-pickup-stall · promiseAllWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAB0RYMWWXNPDXRHAT4
• run-pickup-stall · nullByteWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAPDCNZAYST15FDVHCZ
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAFV21NWPEWFATNKRBY
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:20:11Z · abandoned wrun_01M1CM74XTJM7VX1F47PC1PCZ6
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:20:11Z · abandoned wrun_01M1CM74Y24WXKVB1RJCNAPJK6
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:11Z · abandoned wrun_01M1CM74Y0622STJ34M4QTPBB9
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:20:40Z · abandoned wrun_41M1CM63EP0GXCWTWBMK8SCC2X
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_01M1CM8295S7VXYPCDH5HBC3B4
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_01M1CM8297CYWNJC10D4TG4DA2
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_41M1CM5DE50GZZTTZTDHC84JD6
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:21:11Z · abandoned wrun_01M1CM8ZH61B6QTZ8GD84VEFAJ
• run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 19:22:47Z · abandoned wrun_01M1CMBX8PCCP9796WQM1XSM7T

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-ws-transport	553	0	87	640
Total	17026	17	2778	19821

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

✅ 📦 Local Production

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

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	134	0	26
✅ astro-stable-quickjs	134	0	26
✅ express-stable-node	134	0	26
✅ express-stable-quickjs	134	0	26
✅ fastify-stable-node	134	0	26
✅ fastify-stable-quickjs	134	0	26
✅ hono-stable-node	134	0	26
✅ hono-stable-quickjs	134	0	26
✅ nest-stable-node	134	0	26
✅ nest-stable-quickjs	134	0	26
✅ nextjs-turbopack-canary-node	141	0	19
✅ nextjs-turbopack-canary-quickjs	141	0	19
✅ nextjs-turbopack-stable-node	160	0	0
✅ nextjs-turbopack-stable-quickjs	160	0	0
✅ nextjs-webpack-canary-node	141	0	19
✅ nextjs-webpack-canary-quickjs	141	0	19
✅ nextjs-webpack-stable-node	160	0	0
✅ nextjs-webpack-stable-quickjs	160	0	0
✅ nitro-stable-node	134	0	26
✅ nitro-stable-quickjs	134	0	26
✅ nuxt-stable-node	134	0	26
✅ nuxt-stable-quickjs	134	0	26
✅ sveltekit-stable-node	153	0	7
✅ sveltekit-stable-quickjs	153	0	7
✅ tanstack-start-node	134	0	26
✅ tanstack-start-quickjs	134	0	26
✅ vite-stable-node	134	0	26
✅ vite-stable-quickjs	134	0	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	Failed	Skipped
✅ example	132	0	28
✅ express	132	0	28
✅ hono	132	0	28
✅ nextjs-turbopack	157	0	3
✅ nitro	132	0	28
✅ vite	132	0	28

✅ vercel-ws-transport

App	Passed	Failed	Skipped
✅ example	132	0	28
✅ express	132	0	28
✅ nextjs-turbopack	157	0	3
✅ vite	132	0	28

---

📋 View full workflow run

[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

[vercel]

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 31, 2026 7:10pm
example-nextjs-workflow-webpack	Ready	Preview, v0	Aug 31, 2026 7:10pm
example-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-astro-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-express-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-fastify-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-hono-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nestjs-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nitro-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nuxt-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-python-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-sveltekit-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-tanstack-start-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-vite-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-docs	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-swc-playground	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-tarballs	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-web	Ready	Preview, v0	Aug 31, 2026 7:10pm

[github-actions]

📊 Workflow Benchmarks

commit c0fa289 · Mon, 31 Aug 2026 19:30:51 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	256 (-70%) 💚	1310 🔴 (+5.8%)	1322 🔴 (+2.3%)	1577 🔴 (+1.2%)	30
TTFS	stream	258 (+1.6%)	1307 🔴 (+2.9%)	1368 🔴 (+2.3%)	1780 🔴 (+27%) 🔻	30
TTFS	hook + stream	388 (-31%) 💚	1570 🔴 (+10%)	1643 🔴 (+1.5%)	1725 🔴 (-18%) 💚	30
Fan-out TTFS	Promise.all(100 steps)	608 (+18%) 🔻	2097 (+16%) 🔻	2137 (+13%)	2142 (-3.9%)	10
Fan-out TTLS	Promise.all(100 steps)	2228 (+12%)	4561 (+7.7%)	4582 (-2.8%)	4974 (-38%) 💚	10
STSO	1020 steps (inline)	121 (+57%) 🔻	153 (+7.0%)	177 (+7.9%)	321 (+43%) 🔻	1019
WO	1020 steps	155301 (+8.4%)	155301 (+8.4%)	155301 (+8.4%)	155301 (+8.4%)	1
CRTT	first chunk (pooled)	96 (-13%)	184 (+9.5%)	291 (+44%) 🔻	766 (+150%) 🔻	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	154 (+2%)	242 (+34%)	336 (+19%)	878 (+51%)	333 (+126%)	10
size sweep (100/s, 160B-12KB)	152 (+9%)	159 (-19%)	331 (-27%)	917 (+2%)	144 (-19%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	145 (+1%)	138 (-33%)	195 (-94%)	532 (-89%)	346 (-27%)	3
replay eve-gpt-5.6-sol-2000t (1x)	109 (-57%)	144 (-20%)	201 (-15%)	399 (-46%)	388 (-38%)	2
replay eve-gpt-5.6-sol-2000t (2x)	111 (-34%)	198 (-15%)	269 (-24%)	468 (-23%)	284 (-14%)	3

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

1020 steps (inline)

Cumulative STSO time: main 143115ms → this run 154010ms (Δ +10895ms, +8%)

 50-100 ms ┃ main 1 this 0 -1
100-150 ms ███████████████████┃████ main 838 this 706 -132
150-200 ms █████░░┃ main 163 this 268 +105
200-250 ms ┃ main 8 this 28 +20
250-300 ms ┃ main 4 this 4 +0
300-350 ms ┃ main 3 this 5 +2
350-400 ms ┃ main 2 this 5 +3
400-450 ms ┃ main 0 this 1 +1
450-500 ms ┃ main 0 this 1 +1
800-850 ms ┃ main 0 this 1 +1

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

variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▃█▃▁··· 168.7 (+10%) 135 (-2%) 336 (+19%) 878 (+51%) 3000
sweep ······▃█▂▁··· 162.7 (-4%) 121 (-13%) 331 (-27%) 917 (+2%) 3000
gw 1x ·····▁▅█▁▁··· 121.9 (-65%) 108 (-27%) 195 (-94%) 532 (-89%) 5295
eve 1x ·····▁▆█▂▁··· 128.4 (-21%) 111 (-21%) 201 (-15%) 399 (-46%) 5186
eve 2x ·····▁▂█▃▁··· 157.5 (-18%) 140 (-16%) 269 (-24%) 468 (-23%) 7779

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

control ▆▄▅▄█▆▁▅▅▅ 134–199ms
sweep █▇▅▅▄▃▃▂▁▁ 122–218ms
gw 1x █▄▁▂▁▁▁▃▅▂ 106–169ms
eve 1x ▂▁▁▇▂▇▃█▄▂ 114–149ms
eve 2x ▅▁▂▂▁▄▆█▆▇ 121–201ms

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

sweep ▆██▄▁▁▄ 160–166ms

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

control ▁█▁▂▄▄▃▅▄▅ 35–56ms
sweep ▇▆▃▆▅▃█▂▁▃ 49–63ms
gw 1x █▅▄▁▃▃▄▆▄▆ 28–44ms
eve 1x ▄▅▁█▇█▃█▂▄ 24–28ms
eve 2x ▇▄▃▆▄▄▆▁▄█ 21–32ms

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-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]

Framework	Flow route	Step reg.	Framework output
hono	200.9 KiB (±0)	40.4 KiB (±0)	1.76 MiB (+896 B)
nextjs-turbopack	206.3 KiB (±0)	439 B (±0)	765.1 KiB (+732 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.

c0fa289 · run

[github-actions]

No backport to stable for ee6f917 (AI decision).

This is a latency optimization: it starts Node bundle compilation concurrently with the run_started / replay-load request, adds a new exported compileWorkflowBundle API and compiledWorkflowScripts session option, and skips Node compilation for QuickJS runs. No user-visible defect, crash, hang, or data-loss issue is being fixed — the existing sequential compile path works correctly on stable, it is merely slower, so this does not meet the bar for a maintenance branch.

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

ee6f917cdbfcf50a5fd697c7a9cb70dd1294f931

[NathanColosimo]

Summary

• start the first-delivery run_started request before beginning speculative Node bundle compilation
• overlap compilation with the in-flight replay setup request
• replace a speculative compile when the authoritative returned workflow name differs
• skip Node compilation for QuickJS
• keep bundle evaluation inside each fresh VM after replay loading

workflow.bundle.compile and workflow.replay.load are sibling setup spans under workflow.execute. The workflow.run span begins afterward and contains fresh-VM context creation, bundle evaluation, input hydration, and replay execution.

Stack

Depends on #3797.

Validation

• focused runtime tracing and setup suites passed at the stack tip
• full @workflow/core suite passed at the stack tip — 2,295 tests
• pnpm --filter @workflow/core typecheck
• git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: c0fa289

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

[github-actions]

🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

python-node (8 failed):

• promiseAllWorkflow | wrun_41M1CKXZKY0GH5R9KPT1M83VGG | 🔍 observability
• sleepingWorkflow | wrun_41M1CKYKYB0GNDGFEC3SSB58PF | 🔍 observability
• parallelSleepWorkflow | wrun_41M1CKYMNP0GR7EV9XMDTRAZRC | 🔍 observability
• nullByteWorkflow | wrun_41M1CKYV5H0GMH1N1ZGNK8ER6T | 🔍 observability
• cancelRun - cancelling a running workflow | wrun_41M1CM37GQ0GWYY686EGK7SQ69 | 🔍 observability
• cancelRun via CLI - cancelling a running workflow | wrun_41M1CM37TZ0GJ2VHCDC0E56Y4S | 🔍 observability
• sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M1CM3M460GWNQ20F26999JWZ | 🔍 observability
• resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M1CM44M90GY9200M5TTVGK7D | 🔍 observability

🌐 Cross-language Conformance (9 failed)

python (9 failed):

• deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M1CM5RZF6Q2RH59M2R0Z7NJT
• promiseAllWorkflow | wrun_41M1CKXZKY0GH5R9KPT1M83VGG
• sleepingWorkflow | wrun_41M1CKYKYB0GNDGFEC3SSB58PF
• parallelSleepWorkflow | wrun_41M1CKYMNP0GR7EV9XMDTRAZRC
• nullByteWorkflow | wrun_41M1CKYV5H0GMH1N1ZGNK8ER6T
• cancelRun - cancelling a running workflow | wrun_41M1CM37GQ0GWYY686EGK7SQ69
• cancelRun via CLI - cancelling a running workflow | wrun_41M1CM37TZ0GJ2VHCDC0E56Y4S
• sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M1CM3M460GWNQ20F26999JWZ
• resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M1CM44M90GY9200M5TTVGK7D

⚠️ 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 (fastify)
• cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
• cancelRun via CLI - cancelling a running workflow (nuxt)
• deploymentId: 'latest' is a no-op in non-Vercel worlds (nuxt)
• hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nextjs-webpack)
• hookWorkflow (tanstack-start)
• hookWorkflow (vite)
• promiseAllWorkflow (hono)

🛠 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 19:16:50Z · abandoned wrun_41M1CKXTSM0GMZEHJE405037QS · (+7 more)
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZP0GVJ1FEYSBTFV8HT
• run-pickup-stall · promiseAllWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZG0GN6DPEK8Z6737RT
• run-pickup-stall · sleepingWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZP0GVJ1FEYSBTFV8HS
• run-pickup-stall · nullByteWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZS0GQ8SPJCE6GWTVHF
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1GDJ0GP3BATXWD6PBSFA
• cold-start-warmup · suite warmup (tanstack-start) · at 19:17:39Z · abandoned wrun_01M1CM247XTH7Y9XPP5HYBWRA2
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:17:40Z · abandoned wrun_41M1CM2GHC0GX4QVHEGCVZGP6Z
• cold-start-warmup · suite warmup (python) · at 19:17:56Z · abandoned wrun_01M1CKZTHFSH6N0E4WFKVNABDJ · (+7 more)
• run-pickup-stall · nullByteWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJN0GWTFQ2SYE88Q07Q
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJ40GJQN7XNBMWWKGAA
• run-pickup-stall · sleepingWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJT0GWA7SW2BRD7N0JX
• run-pickup-stall · promiseAllWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BPG0GJWC8333X3WVDEA
• run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPMEZFJDTC2AK4C1RCR
• run-pickup-stall · promiseAllWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPN2VHGXWQT08B8G223
• run-pickup-stall · sleepingWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPSJQDQER5K03H1AAGS
• run-pickup-stall · nullByteWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPY02SKKBQNEYV7EJQ2
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPVPQJZRRKG4B7BPBAQ
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:18:59Z · abandoned wrun_41M1CM3GE10GWKRJSMN3456GJQ
• run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 19:19:11Z · abandoned wrun_01M1CM5AA898Q04WQSMH7405SK
• run-pickup-stall · sleepingWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AADFJS3M3FZKKA684GY
• run-pickup-stall · promiseAllWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAB0RYMWWXNPDXRHAT4
• run-pickup-stall · nullByteWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAPDCNZAYST15FDVHCZ
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAFV21NWPEWFATNKRBY
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:20:11Z · abandoned wrun_01M1CM74XTJM7VX1F47PC1PCZ6
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:20:11Z · abandoned wrun_01M1CM74Y24WXKVB1RJCNAPJK6
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:11Z · abandoned wrun_01M1CM74Y0622STJ34M4QTPBB9
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:20:40Z · abandoned wrun_41M1CM63EP0GXCWTWBMK8SCC2X
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_01M1CM8295S7VXYPCDH5HBC3B4
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_01M1CM8297CYWNJC10D4TG4DA2
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_41M1CM5DE50GZZTTZTDHC84JD6
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:21:11Z · abandoned wrun_01M1CM8ZH61B6QTZ8GD84VEFAJ
• run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 19:22:47Z · abandoned wrun_01M1CMBX8PCCP9796WQM1XSM7T

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-ws-transport	553	0	87	640
Total	17026	17	2778	19821

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

✅ 📦 Local Production

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

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	134	0	26
✅ astro-stable-quickjs	134	0	26
✅ express-stable-node	134	0	26
✅ express-stable-quickjs	134	0	26
✅ fastify-stable-node	134	0	26
✅ fastify-stable-quickjs	134	0	26
✅ hono-stable-node	134	0	26
✅ hono-stable-quickjs	134	0	26
✅ nest-stable-node	134	0	26
✅ nest-stable-quickjs	134	0	26
✅ nextjs-turbopack-canary-node	141	0	19
✅ nextjs-turbopack-canary-quickjs	141	0	19
✅ nextjs-turbopack-stable-node	160	0	0
✅ nextjs-turbopack-stable-quickjs	160	0	0
✅ nextjs-webpack-canary-node	141	0	19
✅ nextjs-webpack-canary-quickjs	141	0	19
✅ nextjs-webpack-stable-node	160	0	0
✅ nextjs-webpack-stable-quickjs	160	0	0
✅ nitro-stable-node	134	0	26
✅ nitro-stable-quickjs	134	0	26
✅ nuxt-stable-node	134	0	26
✅ nuxt-stable-quickjs	134	0	26
✅ sveltekit-stable-node	153	0	7
✅ sveltekit-stable-quickjs	153	0	7
✅ tanstack-start-node	134	0	26
✅ tanstack-start-quickjs	134	0	26
✅ vite-stable-node	134	0	26
✅ vite-stable-quickjs	134	0	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	Failed	Skipped
✅ example	132	0	28
✅ express	132	0	28
✅ hono	132	0	28
✅ nextjs-turbopack	157	0	3
✅ nitro	132	0	28
✅ vite	132	0	28

✅ vercel-ws-transport

App	Passed	Failed	Skipped
✅ example	132	0	28
✅ express	132	0	28
✅ nextjs-turbopack	157	0	3
✅ vite	132	0	28

---

📋 View full workflow run

[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

[vercel]

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 31, 2026 7:10pm
example-nextjs-workflow-webpack	Ready	Preview, v0	Aug 31, 2026 7:10pm
example-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-astro-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-express-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-fastify-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-hono-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nestjs-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nitro-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nuxt-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-python-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-sveltekit-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-tanstack-start-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-vite-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-docs	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-swc-playground	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-tarballs	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-web	Ready	Preview, v0	Aug 31, 2026 7:10pm

[github-actions]

📊 Workflow Benchmarks

commit c0fa289 · Mon, 31 Aug 2026 19:30:51 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	256 (-70%) 💚	1310 🔴 (+5.8%)	1322 🔴 (+2.3%)	1577 🔴 (+1.2%)	30
TTFS	stream	258 (+1.6%)	1307 🔴 (+2.9%)	1368 🔴 (+2.3%)	1780 🔴 (+27%) 🔻	30
TTFS	hook + stream	388 (-31%) 💚	1570 🔴 (+10%)	1643 🔴 (+1.5%)	1725 🔴 (-18%) 💚	30
Fan-out TTFS	Promise.all(100 steps)	608 (+18%) 🔻	2097 (+16%) 🔻	2137 (+13%)	2142 (-3.9%)	10
Fan-out TTLS	Promise.all(100 steps)	2228 (+12%)	4561 (+7.7%)	4582 (-2.8%)	4974 (-38%) 💚	10
STSO	1020 steps (inline)	121 (+57%) 🔻	153 (+7.0%)	177 (+7.9%)	321 (+43%) 🔻	1019
WO	1020 steps	155301 (+8.4%)	155301 (+8.4%)	155301 (+8.4%)	155301 (+8.4%)	1
CRTT	first chunk (pooled)	96 (-13%)	184 (+9.5%)	291 (+44%) 🔻	766 (+150%) 🔻	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	154 (+2%)	242 (+34%)	336 (+19%)	878 (+51%)	333 (+126%)	10
size sweep (100/s, 160B-12KB)	152 (+9%)	159 (-19%)	331 (-27%)	917 (+2%)	144 (-19%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	145 (+1%)	138 (-33%)	195 (-94%)	532 (-89%)	346 (-27%)	3
replay eve-gpt-5.6-sol-2000t (1x)	109 (-57%)	144 (-20%)	201 (-15%)	399 (-46%)	388 (-38%)	2
replay eve-gpt-5.6-sol-2000t (2x)	111 (-34%)	198 (-15%)	269 (-24%)	468 (-23%)	284 (-14%)	3

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

1020 steps (inline)

Cumulative STSO time: main 143115ms → this run 154010ms (Δ +10895ms, +8%)

 50-100 ms ┃ main 1 this 0 -1
100-150 ms ███████████████████┃████ main 838 this 706 -132
150-200 ms █████░░┃ main 163 this 268 +105
200-250 ms ┃ main 8 this 28 +20
250-300 ms ┃ main 4 this 4 +0
300-350 ms ┃ main 3 this 5 +2
350-400 ms ┃ main 2 this 5 +3
400-450 ms ┃ main 0 this 1 +1
450-500 ms ┃ main 0 this 1 +1
800-850 ms ┃ main 0 this 1 +1

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

variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▃█▃▁··· 168.7 (+10%) 135 (-2%) 336 (+19%) 878 (+51%) 3000
sweep ······▃█▂▁··· 162.7 (-4%) 121 (-13%) 331 (-27%) 917 (+2%) 3000
gw 1x ·····▁▅█▁▁··· 121.9 (-65%) 108 (-27%) 195 (-94%) 532 (-89%) 5295
eve 1x ·····▁▆█▂▁··· 128.4 (-21%) 111 (-21%) 201 (-15%) 399 (-46%) 5186
eve 2x ·····▁▂█▃▁··· 157.5 (-18%) 140 (-16%) 269 (-24%) 468 (-23%) 7779

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

control ▆▄▅▄█▆▁▅▅▅ 134–199ms
sweep █▇▅▅▄▃▃▂▁▁ 122–218ms
gw 1x █▄▁▂▁▁▁▃▅▂ 106–169ms
eve 1x ▂▁▁▇▂▇▃█▄▂ 114–149ms
eve 2x ▅▁▂▂▁▄▆█▆▇ 121–201ms

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

sweep ▆██▄▁▁▄ 160–166ms

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

control ▁█▁▂▄▄▃▅▄▅ 35–56ms
sweep ▇▆▃▆▅▃█▂▁▃ 49–63ms
gw 1x █▅▄▁▃▃▄▆▄▆ 28–44ms
eve 1x ▄▅▁█▇█▃█▂▄ 24–28ms
eve 2x ▇▄▃▆▄▄▆▁▄█ 21–32ms

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-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]

Framework	Flow route	Step reg.	Framework output
hono	200.9 KiB (±0)	40.4 KiB (±0)	1.76 MiB (+896 B)
nextjs-turbopack	206.3 KiB (±0)	439 B (±0)	765.1 KiB (+732 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.

c0fa289 · run

[github-actions]

No backport to stable for ee6f917 (AI decision).

This is a latency optimization: it starts Node bundle compilation concurrently with the run_started / replay-load request, adds a new exported compileWorkflowBundle API and compiledWorkflowScripts session option, and skips Node compilation for QuickJS runs. No user-visible defect, crash, hang, or data-loss issue is being fixed — the existing sequential compile path works correctly on stable, it is merely slower, so this does not meet the bar for a maintenance branch.

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

ee6f917cdbfcf50a5fd697c7a9cb70dd1294f931

[NathanColosimo]

Summary

• start the first-delivery run_started request before beginning speculative Node bundle compilation
• overlap compilation with the in-flight replay setup request
• replace a speculative compile when the authoritative returned workflow name differs
• skip Node compilation for QuickJS
• keep bundle evaluation inside each fresh VM after replay loading

workflow.bundle.compile and workflow.replay.load are sibling setup spans under workflow.execute. The workflow.run span begins afterward and contains fresh-VM context creation, bundle evaluation, input hydration, and replay execution.

Stack

Depends on #3797.

Validation

• focused runtime tracing and setup suites passed at the stack tip
• full @workflow/core suite passed at the stack tip — 2,295 tests
• pnpm --filter @workflow/core typecheck
• git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: c0fa289

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

[github-actions]

🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

python-node (8 failed):

• promiseAllWorkflow | wrun_41M1CKXZKY0GH5R9KPT1M83VGG | 🔍 observability
• sleepingWorkflow | wrun_41M1CKYKYB0GNDGFEC3SSB58PF | 🔍 observability
• parallelSleepWorkflow | wrun_41M1CKYMNP0GR7EV9XMDTRAZRC | 🔍 observability
• nullByteWorkflow | wrun_41M1CKYV5H0GMH1N1ZGNK8ER6T | 🔍 observability
• cancelRun - cancelling a running workflow | wrun_41M1CM37GQ0GWYY686EGK7SQ69 | 🔍 observability
• cancelRun via CLI - cancelling a running workflow | wrun_41M1CM37TZ0GJ2VHCDC0E56Y4S | 🔍 observability
• sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M1CM3M460GWNQ20F26999JWZ | 🔍 observability
• resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M1CM44M90GY9200M5TTVGK7D | 🔍 observability

🌐 Cross-language Conformance (9 failed)

python (9 failed):

• deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M1CM5RZF6Q2RH59M2R0Z7NJT
• promiseAllWorkflow | wrun_41M1CKXZKY0GH5R9KPT1M83VGG
• sleepingWorkflow | wrun_41M1CKYKYB0GNDGFEC3SSB58PF
• parallelSleepWorkflow | wrun_41M1CKYMNP0GR7EV9XMDTRAZRC
• nullByteWorkflow | wrun_41M1CKYV5H0GMH1N1ZGNK8ER6T
• cancelRun - cancelling a running workflow | wrun_41M1CM37GQ0GWYY686EGK7SQ69
• cancelRun via CLI - cancelling a running workflow | wrun_41M1CM37TZ0GJ2VHCDC0E56Y4S
• sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M1CM3M460GWNQ20F26999JWZ
• resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M1CM44M90GY9200M5TTVGK7D

⚠️ 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 (fastify)
• cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
• cancelRun via CLI - cancelling a running workflow (nuxt)
• deploymentId: 'latest' is a no-op in non-Vercel worlds (nuxt)
• hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nextjs-webpack)
• hookWorkflow (tanstack-start)
• hookWorkflow (vite)
• promiseAllWorkflow (hono)

🛠 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 19:16:50Z · abandoned wrun_41M1CKXTSM0GMZEHJE405037QS · (+7 more)
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZP0GVJ1FEYSBTFV8HT
• run-pickup-stall · promiseAllWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZG0GN6DPEK8Z6737RT
• run-pickup-stall · sleepingWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZP0GVJ1FEYSBTFV8HS
• run-pickup-stall · nullByteWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZS0GQ8SPJCE6GWTVHF
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1GDJ0GP3BATXWD6PBSFA
• cold-start-warmup · suite warmup (tanstack-start) · at 19:17:39Z · abandoned wrun_01M1CM247XTH7Y9XPP5HYBWRA2
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:17:40Z · abandoned wrun_41M1CM2GHC0GX4QVHEGCVZGP6Z
• cold-start-warmup · suite warmup (python) · at 19:17:56Z · abandoned wrun_01M1CKZTHFSH6N0E4WFKVNABDJ · (+7 more)
• run-pickup-stall · nullByteWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJN0GWTFQ2SYE88Q07Q
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJ40GJQN7XNBMWWKGAA
• run-pickup-stall · sleepingWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJT0GWA7SW2BRD7N0JX
• run-pickup-stall · promiseAllWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BPG0GJWC8333X3WVDEA
• run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPMEZFJDTC2AK4C1RCR
• run-pickup-stall · promiseAllWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPN2VHGXWQT08B8G223
• run-pickup-stall · sleepingWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPSJQDQER5K03H1AAGS
• run-pickup-stall · nullByteWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPY02SKKBQNEYV7EJQ2
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPVPQJZRRKG4B7BPBAQ
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:18:59Z · abandoned wrun_41M1CM3GE10GWKRJSMN3456GJQ
• run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 19:19:11Z · abandoned wrun_01M1CM5AA898Q04WQSMH7405SK
• run-pickup-stall · sleepingWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AADFJS3M3FZKKA684GY
• run-pickup-stall · promiseAllWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAB0RYMWWXNPDXRHAT4
• run-pickup-stall · nullByteWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAPDCNZAYST15FDVHCZ
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAFV21NWPEWFATNKRBY
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:20:11Z · abandoned wrun_01M1CM74XTJM7VX1F47PC1PCZ6
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:20:11Z · abandoned wrun_01M1CM74Y24WXKVB1RJCNAPJK6
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:11Z · abandoned wrun_01M1CM74Y0622STJ34M4QTPBB9
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:20:40Z · abandoned wrun_41M1CM63EP0GXCWTWBMK8SCC2X
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_01M1CM8295S7VXYPCDH5HBC3B4
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_01M1CM8297CYWNJC10D4TG4DA2
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_41M1CM5DE50GZZTTZTDHC84JD6
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:21:11Z · abandoned wrun_01M1CM8ZH61B6QTZ8GD84VEFAJ
• run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 19:22:47Z · abandoned wrun_01M1CMBX8PCCP9796WQM1XSM7T

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-ws-transport	553	0	87	640
Total	17026	17	2778	19821

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

✅ 📦 Local Production

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

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	134	0	26
✅ astro-stable-quickjs	134	0	26
✅ express-stable-node	134	0	26
✅ express-stable-quickjs	134	0	26
✅ fastify-stable-node	134	0	26
✅ fastify-stable-quickjs	134	0	26
✅ hono-stable-node	134	0	26
✅ hono-stable-quickjs	134	0	26
✅ nest-stable-node	134	0	26
✅ nest-stable-quickjs	134	0	26
✅ nextjs-turbopack-canary-node	141	0	19
✅ nextjs-turbopack-canary-quickjs	141	0	19
✅ nextjs-turbopack-stable-node	160	0	0
✅ nextjs-turbopack-stable-quickjs	160	0	0
✅ nextjs-webpack-canary-node	141	0	19
✅ nextjs-webpack-canary-quickjs	141	0	19
✅ nextjs-webpack-stable-node	160	0	0
✅ nextjs-webpack-stable-quickjs	160	0	0
✅ nitro-stable-node	134	0	26
✅ nitro-stable-quickjs	134	0	26
✅ nuxt-stable-node	134	0	26
✅ nuxt-stable-quickjs	134	0	26
✅ sveltekit-stable-node	153	0	7
✅ sveltekit-stable-quickjs	153	0	7
✅ tanstack-start-node	134	0	26
✅ tanstack-start-quickjs	134	0	26
✅ vite-stable-node	134	0	26
✅ vite-stable-quickjs	134	0	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	Failed	Skipped
✅ example	132	0	28
✅ express	132	0	28
✅ hono	132	0	28
✅ nextjs-turbopack	157	0	3
✅ nitro	132	0	28
✅ vite	132	0	28

✅ vercel-ws-transport

App	Passed	Failed	Skipped
✅ example	132	0	28
✅ express	132	0	28
✅ nextjs-turbopack	157	0	3
✅ vite	132	0	28

---

📋 View full workflow run

[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

[vercel]

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 31, 2026 7:10pm
example-nextjs-workflow-webpack	Ready	Preview, v0	Aug 31, 2026 7:10pm
example-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-astro-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-express-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-fastify-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-hono-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nestjs-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nitro-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nuxt-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-python-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-sveltekit-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-tanstack-start-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-vite-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-docs	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-swc-playground	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-tarballs	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-web	Ready	Preview, v0	Aug 31, 2026 7:10pm

[github-actions]

📊 Workflow Benchmarks

commit c0fa289 · Mon, 31 Aug 2026 19:30:51 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	256 (-70%) 💚	1310 🔴 (+5.8%)	1322 🔴 (+2.3%)	1577 🔴 (+1.2%)	30
TTFS	stream	258 (+1.6%)	1307 🔴 (+2.9%)	1368 🔴 (+2.3%)	1780 🔴 (+27%) 🔻	30
TTFS	hook + stream	388 (-31%) 💚	1570 🔴 (+10%)	1643 🔴 (+1.5%)	1725 🔴 (-18%) 💚	30
Fan-out TTFS	Promise.all(100 steps)	608 (+18%) 🔻	2097 (+16%) 🔻	2137 (+13%)	2142 (-3.9%)	10
Fan-out TTLS	Promise.all(100 steps)	2228 (+12%)	4561 (+7.7%)	4582 (-2.8%)	4974 (-38%) 💚	10
STSO	1020 steps (inline)	121 (+57%) 🔻	153 (+7.0%)	177 (+7.9%)	321 (+43%) 🔻	1019
WO	1020 steps	155301 (+8.4%)	155301 (+8.4%)	155301 (+8.4%)	155301 (+8.4%)	1
CRTT	first chunk (pooled)	96 (-13%)	184 (+9.5%)	291 (+44%) 🔻	766 (+150%) 🔻	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	154 (+2%)	242 (+34%)	336 (+19%)	878 (+51%)	333 (+126%)	10
size sweep (100/s, 160B-12KB)	152 (+9%)	159 (-19%)	331 (-27%)	917 (+2%)	144 (-19%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	145 (+1%)	138 (-33%)	195 (-94%)	532 (-89%)	346 (-27%)	3
replay eve-gpt-5.6-sol-2000t (1x)	109 (-57%)	144 (-20%)	201 (-15%)	399 (-46%)	388 (-38%)	2
replay eve-gpt-5.6-sol-2000t (2x)	111 (-34%)	198 (-15%)	269 (-24%)	468 (-23%)	284 (-14%)	3

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

1020 steps (inline)

Cumulative STSO time: main 143115ms → this run 154010ms (Δ +10895ms, +8%)

 50-100 ms ┃ main 1 this 0 -1
100-150 ms ███████████████████┃████ main 838 this 706 -132
150-200 ms █████░░┃ main 163 this 268 +105
200-250 ms ┃ main 8 this 28 +20
250-300 ms ┃ main 4 this 4 +0
300-350 ms ┃ main 3 this 5 +2
350-400 ms ┃ main 2 this 5 +3
400-450 ms ┃ main 0 this 1 +1
450-500 ms ┃ main 0 this 1 +1
800-850 ms ┃ main 0 this 1 +1

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

variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▃█▃▁··· 168.7 (+10%) 135 (-2%) 336 (+19%) 878 (+51%) 3000
sweep ······▃█▂▁··· 162.7 (-4%) 121 (-13%) 331 (-27%) 917 (+2%) 3000
gw 1x ·····▁▅█▁▁··· 121.9 (-65%) 108 (-27%) 195 (-94%) 532 (-89%) 5295
eve 1x ·····▁▆█▂▁··· 128.4 (-21%) 111 (-21%) 201 (-15%) 399 (-46%) 5186
eve 2x ·····▁▂█▃▁··· 157.5 (-18%) 140 (-16%) 269 (-24%) 468 (-23%) 7779

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

control ▆▄▅▄█▆▁▅▅▅ 134–199ms
sweep █▇▅▅▄▃▃▂▁▁ 122–218ms
gw 1x █▄▁▂▁▁▁▃▅▂ 106–169ms
eve 1x ▂▁▁▇▂▇▃█▄▂ 114–149ms
eve 2x ▅▁▂▂▁▄▆█▆▇ 121–201ms

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

sweep ▆██▄▁▁▄ 160–166ms

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

control ▁█▁▂▄▄▃▅▄▅ 35–56ms
sweep ▇▆▃▆▅▃█▂▁▃ 49–63ms
gw 1x █▅▄▁▃▃▄▆▄▆ 28–44ms
eve 1x ▄▅▁█▇█▃█▂▄ 24–28ms
eve 2x ▇▄▃▆▄▄▆▁▄█ 21–32ms

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-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]

Framework	Flow route	Step reg.	Framework output
hono	200.9 KiB (±0)	40.4 KiB (±0)	1.76 MiB (+896 B)
nextjs-turbopack	206.3 KiB (±0)	439 B (±0)	765.1 KiB (+732 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.

c0fa289 · run

[github-actions]

No backport to stable for ee6f917 (AI decision).

This is a latency optimization: it starts Node bundle compilation concurrently with the run_started / replay-load request, adds a new exported compileWorkflowBundle API and compiledWorkflowScripts session option, and skips Node compilation for QuickJS runs. No user-visible defect, crash, hang, or data-loss issue is being fixed — the existing sequential compile path works correctly on stable, it is merely slower, so this does not meet the bar for a maintenance branch.

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

ee6f917cdbfcf50a5fd697c7a9cb70dd1294f931

[NathanColosimo]

Summary

• start the first-delivery run_started request before beginning speculative Node bundle compilation
• overlap compilation with the in-flight replay setup request
• replace a speculative compile when the authoritative returned workflow name differs
• skip Node compilation for QuickJS
• keep bundle evaluation inside each fresh VM after replay loading

workflow.bundle.compile and workflow.replay.load are sibling setup spans under workflow.execute. The workflow.run span begins afterward and contains fresh-VM context creation, bundle evaluation, input hydration, and replay execution.

Stack

Depends on #3797.

Validation

• focused runtime tracing and setup suites passed at the stack tip
• full @workflow/core suite passed at the stack tip — 2,295 tests
• pnpm --filter @workflow/core typecheck
• git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: c0fa289

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

[github-actions]

🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

python-node (8 failed):

• promiseAllWorkflow | wrun_41M1CKXZKY0GH5R9KPT1M83VGG | 🔍 observability
• sleepingWorkflow | wrun_41M1CKYKYB0GNDGFEC3SSB58PF | 🔍 observability
• parallelSleepWorkflow | wrun_41M1CKYMNP0GR7EV9XMDTRAZRC | 🔍 observability
• nullByteWorkflow | wrun_41M1CKYV5H0GMH1N1ZGNK8ER6T | 🔍 observability
• cancelRun - cancelling a running workflow | wrun_41M1CM37GQ0GWYY686EGK7SQ69 | 🔍 observability
• cancelRun via CLI - cancelling a running workflow | wrun_41M1CM37TZ0GJ2VHCDC0E56Y4S | 🔍 observability
• sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M1CM3M460GWNQ20F26999JWZ | 🔍 observability
• resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M1CM44M90GY9200M5TTVGK7D | 🔍 observability

🌐 Cross-language Conformance (9 failed)

python (9 failed):

• deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M1CM5RZF6Q2RH59M2R0Z7NJT
• promiseAllWorkflow | wrun_41M1CKXZKY0GH5R9KPT1M83VGG
• sleepingWorkflow | wrun_41M1CKYKYB0GNDGFEC3SSB58PF
• parallelSleepWorkflow | wrun_41M1CKYMNP0GR7EV9XMDTRAZRC
• nullByteWorkflow | wrun_41M1CKYV5H0GMH1N1ZGNK8ER6T
• cancelRun - cancelling a running workflow | wrun_41M1CM37GQ0GWYY686EGK7SQ69
• cancelRun via CLI - cancelling a running workflow | wrun_41M1CM37TZ0GJ2VHCDC0E56Y4S
• sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M1CM3M460GWNQ20F26999JWZ
• resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M1CM44M90GY9200M5TTVGK7D

⚠️ 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 (fastify)
• cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
• cancelRun via CLI - cancelling a running workflow (nuxt)
• deploymentId: 'latest' is a no-op in non-Vercel worlds (nuxt)
• hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nextjs-webpack)
• hookWorkflow (tanstack-start)
• hookWorkflow (vite)
• promiseAllWorkflow (hono)

🛠 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 19:16:50Z · abandoned wrun_41M1CKXTSM0GMZEHJE405037QS · (+7 more)
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZP0GVJ1FEYSBTFV8HT
• run-pickup-stall · promiseAllWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZG0GN6DPEK8Z6737RT
• run-pickup-stall · sleepingWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZP0GVJ1FEYSBTFV8HS
• run-pickup-stall · nullByteWorkflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1FZS0GQ8SPJCE6GWTVHF
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:17:07Z · abandoned wrun_41M1CM1GDJ0GP3BATXWD6PBSFA
• cold-start-warmup · suite warmup (tanstack-start) · at 19:17:39Z · abandoned wrun_01M1CM247XTH7Y9XPP5HYBWRA2
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:17:40Z · abandoned wrun_41M1CM2GHC0GX4QVHEGCVZGP6Z
• cold-start-warmup · suite warmup (python) · at 19:17:56Z · abandoned wrun_01M1CKZTHFSH6N0E4WFKVNABDJ · (+7 more)
• run-pickup-stall · nullByteWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJN0GWTFQ2SYE88Q07Q
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJ40GJQN7XNBMWWKGAA
• run-pickup-stall · sleepingWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BJT0GWA7SW2BRD7N0JX
• run-pickup-stall · promiseAllWorkflow (python) · at 19:18:08Z · abandoned wrun_41M1CM3BPG0GJWC8333X3WVDEA
• run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPMEZFJDTC2AK4C1RCR
• run-pickup-stall · promiseAllWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPN2VHGXWQT08B8G223
• run-pickup-stall · sleepingWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPSJQDQER5K03H1AAGS
• run-pickup-stall · nullByteWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPY02SKKBQNEYV7EJQ2
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:18:11Z · abandoned wrun_01M1CM3FPVPQJZRRKG4B7BPBAQ
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:18:59Z · abandoned wrun_41M1CM3GE10GWKRJSMN3456GJQ
• run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 19:19:11Z · abandoned wrun_01M1CM5AA898Q04WQSMH7405SK
• run-pickup-stall · sleepingWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AADFJS3M3FZKKA684GY
• run-pickup-stall · promiseAllWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAB0RYMWWXNPDXRHAT4
• run-pickup-stall · nullByteWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAPDCNZAYST15FDVHCZ
• run-pickup-stall · parallelSleepWorkflow (python) · at 19:19:11Z · abandoned wrun_01M1CM5AAFV21NWPEWFATNKRBY
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:20:11Z · abandoned wrun_01M1CM74XTJM7VX1F47PC1PCZ6
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:20:11Z · abandoned wrun_01M1CM74Y24WXKVB1RJCNAPJK6
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:11Z · abandoned wrun_01M1CM74Y0622STJ34M4QTPBB9
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:20:40Z · abandoned wrun_41M1CM63EP0GXCWTWBMK8SCC2X
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_01M1CM8295S7VXYPCDH5HBC3B4
• run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_01M1CM8297CYWNJC10D4TG4DA2
• run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 19:20:41Z · abandoned wrun_41M1CM5DE50GZZTTZTDHC84JD6
• run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 19:21:11Z · abandoned wrun_01M1CM8ZH61B6QTZ8GD84VEFAJ
• run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 19:22:47Z · abandoned wrun_01M1CMBX8PCCP9796WQM1XSM7T

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-ws-transport	553	0	87	640
Total	17026	17	2778	19821

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

✅ 📦 Local Production

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

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable-node	134	0	26
✅ astro-stable-quickjs	134	0	26
✅ express-stable-node	134	0	26
✅ express-stable-quickjs	134	0	26
✅ fastify-stable-node	134	0	26
✅ fastify-stable-quickjs	134	0	26
✅ hono-stable-node	134	0	26
✅ hono-stable-quickjs	134	0	26
✅ nest-stable-node	134	0	26
✅ nest-stable-quickjs	134	0	26
✅ nextjs-turbopack-canary-node	141	0	19
✅ nextjs-turbopack-canary-quickjs	141	0	19
✅ nextjs-turbopack-stable-node	160	0	0
✅ nextjs-turbopack-stable-quickjs	160	0	0
✅ nextjs-webpack-canary-node	141	0	19
✅ nextjs-webpack-canary-quickjs	141	0	19
✅ nextjs-webpack-stable-node	160	0	0
✅ nextjs-webpack-stable-quickjs	160	0	0
✅ nitro-stable-node	134	0	26
✅ nitro-stable-quickjs	134	0	26
✅ nuxt-stable-node	134	0	26
✅ nuxt-stable-quickjs	134	0	26
✅ sveltekit-stable-node	153	0	7
✅ sveltekit-stable-quickjs	153	0	7
✅ tanstack-start-node	134	0	26
✅ tanstack-start-quickjs	134	0	26
✅ vite-stable-node	134	0	26
✅ vite-stable-quickjs	134	0	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	Failed	Skipped
✅ example	132	0	28
✅ express	132	0	28
✅ hono	132	0	28
✅ nextjs-turbopack	157	0	3
✅ nitro	132	0	28
✅ vite	132	0	28

✅ vercel-ws-transport

App	Passed	Failed	Skipped
✅ example	132	0	28
✅ express	132	0	28
✅ nextjs-turbopack	157	0	3
✅ vite	132	0	28

---

📋 View full workflow run

[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

[vercel]

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 31, 2026 7:10pm
example-nextjs-workflow-webpack	Ready	Preview, v0	Aug 31, 2026 7:10pm
example-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-astro-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-express-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-fastify-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-hono-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nestjs-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nitro-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-nuxt-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-python-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-sveltekit-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-tanstack-start-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workbench-vite-workflow	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-docs	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-swc-playground	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-tarballs	Ready	Preview, v0	Aug 31, 2026 7:10pm
workflow-web	Ready	Preview, v0	Aug 31, 2026 7:10pm

[github-actions]

📊 Workflow Benchmarks

commit c0fa289 · Mon, 31 Aug 2026 19:30:51 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	256 (-70%) 💚	1310 🔴 (+5.8%)	1322 🔴 (+2.3%)	1577 🔴 (+1.2%)	30
TTFS	stream	258 (+1.6%)	1307 🔴 (+2.9%)	1368 🔴 (+2.3%)	1780 🔴 (+27%) 🔻	30
TTFS	hook + stream	388 (-31%) 💚	1570 🔴 (+10%)	1643 🔴 (+1.5%)	1725 🔴 (-18%) 💚	30
Fan-out TTFS	Promise.all(100 steps)	608 (+18%) 🔻	2097 (+16%) 🔻	2137 (+13%)	2142 (-3.9%)	10
Fan-out TTLS	Promise.all(100 steps)	2228 (+12%)	4561 (+7.7%)	4582 (-2.8%)	4974 (-38%) 💚	10
STSO	1020 steps (inline)	121 (+57%) 🔻	153 (+7.0%)	177 (+7.9%)	321 (+43%) 🔻	1019
WO	1020 steps	155301 (+8.4%)	155301 (+8.4%)	155301 (+8.4%)	155301 (+8.4%)	1
CRTT	first chunk (pooled)	96 (-13%)	184 (+9.5%)	291 (+44%) 🔻	766 (+150%) 🔻	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	154 (+2%)	242 (+34%)	336 (+19%)	878 (+51%)	333 (+126%)	10
size sweep (100/s, 160B-12KB)	152 (+9%)	159 (-19%)	331 (-27%)	917 (+2%)	144 (-19%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	145 (+1%)	138 (-33%)	195 (-94%)	532 (-89%)	346 (-27%)	3
replay eve-gpt-5.6-sol-2000t (1x)	109 (-57%)	144 (-20%)	201 (-15%)	399 (-46%)	388 (-38%)	2
replay eve-gpt-5.6-sol-2000t (2x)	111 (-34%)	198 (-15%)	269 (-24%)	468 (-23%)	284 (-14%)	3

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

1020 steps (inline)

Cumulative STSO time: main 143115ms → this run 154010ms (Δ +10895ms, +8%)

 50-100 ms ┃ main 1 this 0 -1
100-150 ms ███████████████████┃████ main 838 this 706 -132
150-200 ms █████░░┃ main 163 this 268 +105
200-250 ms ┃ main 8 this 28 +20
250-300 ms ┃ main 4 this 4 +0
300-350 ms ┃ main 3 this 5 +2
350-400 ms ┃ main 2 this 5 +3
400-450 ms ┃ main 0 this 1 +1
450-500 ms ┃ main 0 this 1 +1
800-850 ms ┃ main 0 this 1 +1

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

variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▃█▃▁··· 168.7 (+10%) 135 (-2%) 336 (+19%) 878 (+51%) 3000
sweep ······▃█▂▁··· 162.7 (-4%) 121 (-13%) 331 (-27%) 917 (+2%) 3000
gw 1x ·····▁▅█▁▁··· 121.9 (-65%) 108 (-27%) 195 (-94%) 532 (-89%) 5295
eve 1x ·····▁▆█▂▁··· 128.4 (-21%) 111 (-21%) 201 (-15%) 399 (-46%) 5186
eve 2x ·····▁▂█▃▁··· 157.5 (-18%) 140 (-16%) 269 (-24%) 468 (-23%) 7779

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

control ▆▄▅▄█▆▁▅▅▅ 134–199ms
sweep █▇▅▅▄▃▃▂▁▁ 122–218ms
gw 1x █▄▁▂▁▁▁▃▅▂ 106–169ms
eve 1x ▂▁▁▇▂▇▃█▄▂ 114–149ms
eve 2x ▅▁▂▂▁▄▆█▆▇ 121–201ms

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

sweep ▆██▄▁▁▄ 160–166ms

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

control ▁█▁▂▄▄▃▅▄▅ 35–56ms
sweep ▇▆▃▆▅▃█▂▁▃ 49–63ms
gw 1x █▅▄▁▃▃▄▆▄▆ 28–44ms
eve 1x ▄▅▁█▇█▃█▂▄ 24–28ms
eve 2x ▇▄▃▆▄▄▆▁▄█ 21–32ms

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-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]

Framework	Flow route	Step reg.	Framework output
hono	200.9 KiB (±0)	40.4 KiB (±0)	1.76 MiB (+896 B)
nextjs-turbopack	206.3 KiB (±0)	439 B (±0)	765.1 KiB (+732 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.

c0fa289 · run

[github-actions]

No backport to stable for ee6f917 (AI decision).

This is a latency optimization: it starts Node bundle compilation concurrently with the run_started / replay-load request, adds a new exported compileWorkflowBundle API and compiledWorkflowScripts session option, and skips Node compilation for QuickJS runs. No user-visible defect, crash, hang, or data-loss issue is being fixed — the existing sequential compile path works correctly on stable, it is merely slower, so this does not meet the bar for a maintenance branch.

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

ee6f917cdbfcf50a5fd697c7a9cb70dd1294f931