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[core] Retain workflow VMs across attributes - #3609

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NathanColosimo merged 6 commits into
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codex/retain-vm-with-attributes
Aug 25, 2026
Merged

[core] Retain workflow VMs across attributes#3609
NathanColosimo merged 6 commits into
mainfrom
codex/retain-vm-with-attributes

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@NathanColosimo

@NathanColosimo NathanColosimo commented Aug 18, 2026

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Summary

  • retain the workflow VM across workflow attribute writes
  • generation-guard attribute suspension signals
  • keep waits on the cold-replay path

Verification

  • pnpm --filter @workflow/core... build
  • pnpm --filter @workflow/core test
  • pnpm --filter @workflow/core typecheck
  • focused Biome check (existing complexity warnings only)

@changeset-bot

changeset-bot Bot commented Aug 18, 2026 •
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🦋 Changeset detected

Latest commit: f980c84

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

This PR includes changesets to release 16 packages
Name Type
@workflow/core Patch
@workflow/builders Patch
@workflow/cli Patch
@workflow/next Patch
@workflow/nitro Patch
@workflow/vitest Patch
@workflow/web-shared Patch
@workflow/web Patch
workflow Patch
@workflow/world-testing Patch
@workflow/astro Patch
@workflow/nest Patch
@workflow/rollup Patch
@workflow/sveltekit Patch
@workflow/vite Patch
@workflow/nuxt Patch

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

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

@vercel

vercel Bot commented Aug 18, 2026 •
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The latest updates on your projects. Learn more about Vercel for GitHub.

Project Deployment Actions Updated (UTC)
example-nextjs-workflow-turbopack Ready Ready Preview, v0 Aug 25, 2026 10:13pm
example-nextjs-workflow-webpack Ready Ready Preview, v0 Aug 25, 2026 10:13pm
example-workflow Ready Ready Preview, v0 Aug 25, 2026 10:13pm
workbench-astro-workflow Ready Ready Preview, v0 Aug 25, 2026 10:13pm
workbench-express-workflow Ready Ready Preview, v0 Aug 25, 2026 10:13pm
workbench-fastify-workflow Ready Ready Preview, v0 Aug 25, 2026 10:13pm
workbench-hono-workflow Ready Ready Preview, v0 Aug 25, 2026 10:13pm
workbench-nestjs-workflow Ready Ready Preview, v0 Aug 25, 2026 10:13pm
workbench-nitro-workflow Ready Ready Preview, v0 Aug 25, 2026 10:13pm
workbench-nuxt-workflow Ready Ready Preview, v0 Aug 25, 2026 10:13pm
workbench-python-workflow Ready Ready Preview, v0 Aug 25, 2026 10:13pm
workbench-sveltekit-workflow Ready Ready Preview, v0 Aug 25, 2026 10:13pm
workbench-tanstack-start-workflow Ready Ready Preview, v0 Aug 25, 2026 10:13pm
workbench-vite-workflow Ready Ready Preview, v0 Aug 25, 2026 10:13pm
workflow-swc-playground Ready Ready Preview, v0 Aug 25, 2026 10:13pm
workflow-tarballs Ready Ready Preview, v0 Aug 25, 2026 10:13pm
workflow-web Ready Ready Preview, v0 Aug 25, 2026 10:13pm
1 Skipped Deployment
Project Deployment Actions Updated (UTC)
workflow-docs Skipped Skipped v0 Aug 25, 2026 10:13pm

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🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

python-node (8 failed):

  • promiseAllWorkflow | wrun_41M0XFN5PF0GYJ6G6SXYSGCKBP | 🔍 observability
  • sleepingWorkflow | wrun_41M0XFNYK50GSETQ4D3R6F3RCG | 🔍 observability
  • parallelSleepWorkflow | wrun_41M0XFNYPN0GMQNDY61H9M4HH8 | 🔍 observability
  • nullByteWorkflow | wrun_41M0XFP8SP0GHHJ2GNMTZAEWXR | 🔍 observability
  • cancelRun - cancelling a running workflow | wrun_41M0XFTXA20GW06GCGP3KGMCT8 | 🔍 observability
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XFTY680GNF9TXAPN79ZSGZ | 🔍 observability
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XFV8NQ0GZWRBKSMP7KM18R | 🔍 observability
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XFVV990GS26KPE0P4HAF1W | 🔍 observability

🌐 Cross-language Conformance (9 failed)

python (9 failed):

  • deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M0XFVJ4Q5N1HH8PZ8PNMZJGM
  • promiseAllWorkflow | wrun_41M0XFN5PF0GYJ6G6SXYSGCKBP
  • sleepingWorkflow | wrun_41M0XFNYK50GSETQ4D3R6F3RCG
  • parallelSleepWorkflow | wrun_41M0XFNYPN0GMQNDY61H9M4HH8
  • nullByteWorkflow | wrun_41M0XFP8SP0GHHJ2GNMTZAEWXR
  • cancelRun - cancelling a running workflow | wrun_41M0XFTXA20GW06GCGP3KGMCT8
  • cancelRun via CLI - cancelling a running workflow | wrun_41M0XFTY680GNF9TXAPN79ZSGZ
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0XFV8NQ0GZWRBKSMP7KM18R
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0XFVV990GS26KPE0P4HAF1W

⚠️ 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 (nitro)
  • deploymentId: 'latest' is a no-op in non-Vercel worlds (nest)
  • promiseAllWorkflow (tanstack-start)

🛠 Infra Events (absorbed by the harness)

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

36 infra events
  • cold-start-warmup · suite warmup (tanstack-start) · at 22:12:44Z · abandoned wrun_01M0XFPDAXWJQ7SD4FCKWQZYRA
  • run-pickup-stall · readableStreamWorkflow (nuxt) · at 22:13:10Z · abandoned wrun_01M0XFQJSYN1EQ26EFWPB3FX7R
  • cold-start-warmup · suite warmup (python) · at 22:13:14Z · abandoned wrun_41M0XFMGBW0GW4N24MJB4H7RZ2 · (+7 more)
  • run-pickup-stall · promiseAllWorkflow (python) · at 22:13:30Z · abandoned wrun_41M0XFR5680GKBWE9XG0BBRZ9M
  • run-pickup-stall · nullByteWorkflow (python) · at 22:13:30Z · abandoned wrun_41M0XFR56G0GGHTT01RVT5ZPQR
  • run-pickup-stall · parallelSleepWorkflow (python) · at 22:13:30Z · abandoned wrun_41M0XFR56D0GGXH8CCPSM3Z9K0
  • run-pickup-stall · sleepingWorkflow (python) · at 22:13:30Z · abandoned wrun_41M0XFR56C0GNDC6T0ZY9S0GWJ
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 22:13:30Z · abandoned wrun_41M0XFR5FK0GT4GR0302EQNF4C
  • cold-start-warmup · suite warmup (python) · at 22:13:50Z · abandoned wrun_01M0XFNKQ582S72PXQHAGBHJWF · (+7 more)
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 22:14:03Z · abandoned wrun_41M0XFS5AQ0GQYVWX4P4E6BHBP
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 22:14:05Z · abandoned wrun_01M0XFS8VG6MYP4JCRF0YND76P
  • run-pickup-stall · promiseAllWorkflow (python) · at 22:14:05Z · abandoned wrun_01M0XFS8VHYJRWT478MJQ5ATEM
  • run-pickup-stall · sleepingWorkflow (python) · at 22:14:05Z · abandoned wrun_01M0XFS8VPDWD6VRV31BCMBYKY
  • run-pickup-stall · parallelSleepWorkflow (python) · at 22:14:05Z · abandoned wrun_01M0XFS8VR3R0PYV37K2YVRRRT
  • run-pickup-stall · nullByteWorkflow (python) · at 22:14:05Z · abandoned wrun_01M0XFS8VS4X2AZC5TRBB4JGXA
  • run-pickup-stall · sleepingWorkflow (python) · at 22:14:30Z · abandoned wrun_41M0XFT0FH0GMQFFRGHVXJJ4Z8
  • run-pickup-stall · nullByteWorkflow (python) · at 22:14:30Z · abandoned wrun_41M0XFT0HP0GSMD2Y4Y5A9Z9YN
  • run-pickup-stall · promiseAllWorkflow (python) · at 22:14:31Z · abandoned wrun_41M0XFT0KQ0GSSSERV48EGPZSX
  • run-pickup-stall · parallelSleepWorkflow (python) · at 22:14:31Z · abandoned wrun_41M0XFT0KW0GG34XF8JV5G9XBZ
  • run-pickup-stall · spawnWorkflowFromStepWorkflow - spawning a child workflow using start() inside a step (nuxt) · at 22:14:36Z · abandoned wrun_01M0XFT6K1JSH0VSC613AMTMGZ
  • run-pickup-stall · parallelSleepWorkflow (python) · at 22:15:05Z · abandoned wrun_01M0XFV3FJRBBQF23Q3566PCDC
  • run-pickup-stall · nullByteWorkflow (python) · at 22:15:05Z · abandoned wrun_01M0XFV3FKN4FY46S8NDW7FZC3
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 22:15:05Z · abandoned wrun_01M0XFV3FD12ZSSQN6DBYV3TYQ
  • run-pickup-stall · sleepingWorkflow (python) · at 22:15:05Z · abandoned wrun_01M0XFV3FHR4YF1YXKYJEBBFF8
  • run-pickup-stall · promiseAllWorkflow (python) · at 22:15:05Z · abandoned wrun_01M0XFV3FFR71T5MAHWFM1Q4XZ
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 22:15:21Z · abandoned wrun_41M0XFT4Y30GMP0Z8BB64YMFJV
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 22:16:05Z · abandoned wrun_01M0XFWY33ZDAP24JG416SA097
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 22:16:05Z · abandoned wrun_01M0XFWY3AQJN5VYNF0Q0J4EWH
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 22:16:05Z · abandoned wrun_01M0XFWY3EYEP30QARW9VV86X7
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 22:16:35Z · abandoned wrun_01M0XFXVEHZ4Q2CVSNNP7Z9KYH
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 22:16:35Z · abandoned wrun_01M0XFXVEJ4WZR29NMCBTBKBQ3
  • run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 22:16:56Z · abandoned wrun_01M0XFYFBN0RT2K0DG7ZMKDBMN
  • run-pickup-stall · concurrent hook token conflict - two workflows cannot use the same hook token simultaneously (nextjs-webpack) · at 22:17:00Z · abandoned wrun_01M0XFYK9380895PK345J1CJ1D
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 22:17:02Z · abandoned wrun_41M0XFWWTM0GJJ8E84Y8DP0DJN
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 22:17:03Z · abandoned wrun_41M0XFWRC40GSMR0C35G2N42CZ
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 22:17:05Z · abandoned wrun_01M0XFYRPJNQB6GCV3QJYQ45M9

E2E Test Summary

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

❌ ▲ Vercel Production

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

✅ 💻 Local Development

App Passed 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-multi-region

App Passed Failed Skipped
✅ nextjs-turbopack 27 0 0

✅ 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

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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

@NathanColosimo
NathanColosimo force-pushed the codex/retain-vm-with-attributes branch from 4e16715 to 17de0bb Compare August 18, 2026 18:18
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📊 Workflow Benchmarks

commit f980c84 · Tue, 25 Aug 2026 22:35:16 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric Scenario Best (ms) P75 (ms) P90 (ms) P99 (ms) Samples
TTFS step 1289 (+30%) 🔻 1390 🔴 (+27%) 🔻 1423 🔴 (+26%) 🔻 1502 🔴 (+14%) 30
TTFS stream 251 (-15%) 💚 1370 🔴 (+21%) 🔻 1390 🔴 (+21%) 🔻 1511 🔴 (+24%) 🔻 30
TTFS hook + stream 1587 (+20%) 🔻 1724 🔴 (+19%) 🔻 1776 🔴 (+18%) 🔻 5891 🔴 (+283%) 🔻 30
Fan-out TTFS Promise.all(100 steps) 652 (+5.8%) 2053 (+65%) 🔻 2209 (+18%) 🔻 2396 (+21%) 🔻 10
Fan-out TTLS Promise.all(100 steps) 2103 (-2.0%) 4041 (+3.2%) 4273 (-33%) 💚 11906 (+45%) 🔻 10
STSO 1020 steps (inline) 121 (+17%) 🔻 161 (-12%) 178 (-15%) 236 (-72%) 💚 1019
WO 1020 steps 159955 (-15%) 159955 (-15%) 159955 (-15%) 159955 (-15%) 1
CRTT first chunk (pooled) 119 (-2.5%) 183 (+11%) 212 (+9.8%) 329 (-18%) 💚 28

Streams

Scenario CRTT 1st p75 p90 p99 CDV max iters
paced control (100/s, 60B) 147 (+2%) 170 (-23%) 208 (-56%) 320 (-61%) 120 (-47%) 10
size sweep (100/s, 160B-12KB) 134 (-6%) 196 (-5%) 310 (+12%) 536 (+25%) 138 (-21%) 10
replay gateway-gpt-5.4-nano-2000t (1x) 149 (-6%) 157 (-20%) 188 (-28%) 409 (-13%) 263 (-13%) 3
replay eve-gpt-5.6-sol-2000t (1x) 167 (+4%) 144 (-19%) 180 (-19%) 360 (-5%) 214 (-28%) 2
replay eve-gpt-5.6-sol-2000t (2x) 139 (-5%) 191 (-64%) 250 (-75%) 404 (-75%) 241 (-76%) 3
📈 STSO distribution vs main (inline / queue-hop histograms)

1020 steps (inline)

Cumulative STSO time: main 186880ms → this run 159772ms (Δ -27108ms, -15%)

100-150 ms  █░░░░░░░░░░┃              main  40  this 434  +394
150-200 ms  ███████████████┃████████  main 841  this 557  -284
200-250 ms  ┃██                       main 104  this  21   -83
250-300 ms  ┃                         main  17  this   3   -14
300-350 ms  ┃                         main   0  this   4    +4
350-400 ms  ┃                         main   2  this   0    -2
400-450 ms  ┃                         main   1  this   0    -1
500-550 ms  ┃                         main   1  this   0    -1
800-850 ms  ┃                         main   2  this   0    -2
850-900 ms  ┃                         main  10  this   0   -10
900-950 ms  ┃                         main   1  this   0    -1
📈 CRTT drill-down vs main (RTT distributions & profiles) 
variant  RTT 1ms→5s+             avg         p50         p90         p99     n
control  ······▂█▁····  142.1 (-17%)   136 (-5%)  208 (-56%)  320 (-61%)  3000
sweep    ······▂█▂▁···  149.8 (-10%)  133 (-14%)  310 (+12%)  536 (+25%)  3000
gw 1x    ·····▁▃█▁▁···  131.6 (-16%)  125 (-12%)  188 (-28%)  409 (-13%)  5295
eve 1x   ·····▁▃█▁····  126.6 (-17%)  117 (-15%)  180 (-19%)   360 (-5%)  5186
eve 2x   ·····▁▁█▃····  163.7 (-50%)  151 (-27%)  250 (-75%)  404 (-75%)  7779

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

control  █▅▄▄▃▃▄▃▁▄  126–162ms
sweep    █▃▅▆▂▃█▇▄▁  130–168ms
gw 1x    ▃▃▆▅▂▄█▅█▁  121–143ms
eve 1x   ▄▂▄▄▂▂▆█▃▁  115–151ms
eve 2x   ▅▂▄▃▁▅▇█▆▄  132–196ms

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

sweep  ▅█▆▄▁▁▁  148–153ms

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

control  ▁▅▄▇▇▄█▃▂▃  38–47ms
sweep    ▁▂▆▇▃▆█▅▆▃  43–67ms
gw 1x    ▂▃▃▁▃▄█▅▄▂  35–48ms
eve 1x   ▅▄▃▅▄▇██▄▁  21–25ms
eve 2x   █▆▅▄▄▇▄▁▄▅  21–29ms
ℹ️ Metric definitions & methodology

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

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

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

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

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

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

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

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

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

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

@NathanColosimo
NathanColosimo force-pushed the codex/retain-vm-with-attributes branch from 6a6f030 to b2e9b8c Compare August 18, 2026 22:41
This was referenced Aug 21, 2026
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VaguelySerious
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AI review: blocking issues found

Comment thread packages/core/src/runtime.ts
Comment thread packages/core/src/runtime.test.ts
VaguelySerious
VaguelySerious approved these changes Aug 24, 2026
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LGTM assuming e2e passes (except python)

TooTallNate
TooTallNate approved these changes Aug 24, 2026
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AI: Approved. I found no blocking issues in the attribute-retention changes relative to the stacked #3604 base.

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github-actions Bot commented Aug 25, 2026 •
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Framework Flow route Step reg. Framework output
hono 200.9 KiB (±0) 40.5 KiB (±0) 1.76 MiB (-106 B)
nextjs-turbopack 206.3 KiB (±0) 439 B (±0) 763.2 KiB (+353 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.

f980c84 · run

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github-actions Bot commented Aug 25, 2026

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No backport to stable for 82e2678 (AI decision).

This commit extends the retained-VM optimization to cover workflow attribute writes, making attribute suspensions retainable (new generation guard for attribute signals, no_step_driver becomes no_replay_driver). It is a performance enhancement to an existing optimization path, not a fix for a correctness, crash, or data-loss defect on stable, and it changes when a live VM is resumed versus cold-replayed — behavior risk a maintenance line should not take on. The patch changeset does not make it a stability fix.

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

82e267893917e06f5d3ce316baefc27cd024a912

@github-actions github-actions Bot mentioned this pull request Aug 26, 2026
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@pranaygp pranaygp mentioned this pull request Sep 3, 2026
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@TooTallNate TooTallNate TooTallNate approved these changes
@VaguelySerious VaguelySerious VaguelySerious approved these changes
@msullivan msullivan Awaiting requested review from msullivan
@fantix fantix Awaiting requested review from fantix

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@NathanColosimo @TooTallNate @VaguelySerious