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[core] Prepare replay payloads as event frames arrive - #3548

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codex/replay-stream-preparation
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[core] Prepare replay payloads as event frames arrive#3548
NathanColosimo wants to merge 8 commits into
codex/replay-compile-overlapfrom
codex/replay-stream-preparation

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@NathanColosimo

@NathanColosimo NathanColosimo commented Aug 14, 2026 •
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Summary

  • prepare validated Node replay payloads as streamed events arrive
  • lazily resolve the invocation encryption key and create the payload cache only after the run is known to use Node
  • skip host-side compile, key lookup, replay cache, and payload preparation for QuickJS
  • start run_started before speculative compile/cache work so setup I/O overlaps Node startup
  • correct speculative workflow names from persisted run_created
  • classify invalid VM configuration as run_failed in turbo, ordinary, and streamed setup paths
  • count materialized replay events without per-event spans
  • share one replay-run reconstruction path between run_started and atomic-hook preload
  • leave primitive payload caching uncapped

Prewarm deliberately scans the event array on each replay and relies on the existing event-ID map to skip prepared payloads. This avoids positional scan state, reset hooks, and event-log replacement wrappers; only the cheap array walk repeats. Prepared plaintext and memoized primitive results remain invocation-scoped.

Stack

Depends on #3798.

Validation

  • focused regression suites — 131 tests passed
  • final runtime regression suites — 60 tests passed
  • full @workflow/core suite — 2,295 tests passed
  • full @workflow/world-vercel suite — 572 tests passed
  • full @workflow/world suite — 165 tests passed
  • pnpm --filter @workflow/core typecheck
  • pnpm --filter @workflow/world-vercel typecheck
  • Biome check on changed files
  • git diff --check

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changeset-bot Bot commented Aug 14, 2026 •
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🦋 Changeset detected

Latest commit: 5654c82

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

This PR includes changesets to release 20 packages
Name Type
@workflow/core Patch
@workflow/world Patch
@workflow/world-vercel 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/world-local Patch
@workflow/world-postgres 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

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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 28, 2026 9:29pm
example-nextjs-workflow-webpack Ready Ready Preview, v0 Aug 28, 2026 9:29pm
example-workflow Ready Ready Preview, v0 Aug 28, 2026 9:29pm
workbench-astro-workflow Ready Ready Preview, v0 Aug 28, 2026 9:29pm
workbench-express-workflow Ready Ready Preview, v0 Aug 28, 2026 9:29pm
workbench-fastify-workflow Ready Ready Preview, v0 Aug 28, 2026 9:29pm
workbench-hono-workflow Ready Ready Preview, v0 Aug 28, 2026 9:29pm
workbench-nestjs-workflow Ready Ready Preview, v0 Aug 28, 2026 9:29pm
workbench-nitro-workflow Ready Ready Preview, v0 Aug 28, 2026 9:29pm
workbench-nuxt-workflow Ready Ready Preview, v0 Aug 28, 2026 9:29pm
workbench-python-workflow Ready Ready Preview, v0 Aug 28, 2026 9:29pm
workbench-sveltekit-workflow Ready Ready Preview, v0 Aug 28, 2026 9:29pm
workbench-tanstack-start-workflow Ready Ready Preview, v0 Aug 28, 2026 9:29pm
workbench-vite-workflow Ready Ready Preview, v0 Aug 28, 2026 9:29pm
workflow-docs Ready Ready Preview, v0 Aug 28, 2026 9:29pm
workflow-swc-playground Ready Ready Preview, v0 Aug 28, 2026 9:29pm
workflow-tarballs Ready Ready Preview, v0 Aug 28, 2026 9:29pm
workflow-web Ready Ready Preview, v0 Aug 28, 2026 9:29pm

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🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

python-node (8 failed):

  • promiseAllWorkflow | wrun_41M155HM2X0GVKQ69B2ZSPF12F | 🔍 observability
  • sleepingWorkflow | wrun_41M155J7QK0GXX0ZDVQN22JW05 | 🔍 observability
  • parallelSleepWorkflow | wrun_41M155J85M0GXYFYVJDGBKMWVR | 🔍 observability
  • nullByteWorkflow | wrun_41M155JEB80GJV97KQHEET23NT | 🔍 observability
  • cancelRun - cancelling a running workflow | wrun_41M155P2150GTEB21N4GNM8180 | 🔍 observability
  • cancelRun via CLI - cancelling a running workflow | wrun_41M155P4V60GVFNC2EA8Z2WNVY | 🔍 observability
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M155PBBG0GVWSQB8A01NZ1G9 | 🔍 observability
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M155PS8T0GS9C0494S5R9E8V | 🔍 observability

🌐 Cross-language Conformance (9 failed)

python (9 failed):

  • deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M155S6456B92ZH0CZCXVWSM3
  • promiseAllWorkflow | wrun_41M155HM2X0GVKQ69B2ZSPF12F
  • sleepingWorkflow | wrun_41M155J7QK0GXX0ZDVQN22JW05
  • parallelSleepWorkflow | wrun_41M155J85M0GXYFYVJDGBKMWVR
  • nullByteWorkflow | wrun_41M155JEB80GJV97KQHEET23NT
  • cancelRun - cancelling a running workflow | wrun_41M155P2150GTEB21N4GNM8180
  • cancelRun via CLI - cancelling a running workflow | wrun_41M155P4V60GVFNC2EA8Z2WNVY
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M155PBBG0GVWSQB8A01NZ1G9
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M155PS8T0GS9C0494S5R9E8V

⚠️ Flaky E2E Tests (passed on retry)

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

  • addTenWorkflow (vite)
  • deploymentId: 'latest' is a no-op in non-Vercel worlds (hono)
  • hookWithSleepFinalStepWorkflow - step only on final payload (nextjs-turbopack)
  • hookWorkflow (tanstack-start)
  • promiseRaceWorkflow (nitro)

🛠 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.

34 infra events
  • cold-start-warmup · suite warmup (tanstack-start) · at 21:50:29Z · abandoned wrun_01M155KT90YH6ECFHMV4EJM6WC
  • cold-start-warmup · suite warmup (python) · at 21:50:41Z · abandoned wrun_41M155HC2P0GVB7EFY4GX90TEY · (+7 more)
  • run-pickup-stall · parallelSleepWorkflow (python) · at 21:50:57Z · abandoned wrun_41M155N12Z0GQPA77P2Y8T11ZV
  • run-pickup-stall · promiseAllWorkflow (python) · at 21:50:57Z · abandoned wrun_41M155N12S0GGDYGWJ7VWK5ZRP
  • run-pickup-stall · nullByteWorkflow (python) · at 21:50:57Z · abandoned wrun_41M155N1320GK6ET8DJE07ZEJN
  • run-pickup-stall · sleepingWorkflow (python) · at 21:50:57Z · abandoned wrun_41M155N12Z0GQPA77P2Y8T11ZT
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 21:50:58Z · abandoned wrun_41M155N1FN0GXZ567W6NPTX3WY
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 21:51:31Z · abandoned wrun_41M155P1PT0GYEGGNRHQJ6C7NJ
  • cold-start-warmup · suite warmup (python) · at 21:51:42Z · abandoned wrun_01M155K7PFA9469W3DF4XA41KN · (+7 more)
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 21:51:57Z · abandoned wrun_01M155PWV353X5FJVXJMBNZQ98
  • run-pickup-stall · promiseAllWorkflow (python) · at 21:51:57Z · abandoned wrun_01M155PWV353X5FJVXJMBNZQ99
  • run-pickup-stall · nullByteWorkflow (python) · at 21:51:57Z · abandoned wrun_01M155PWVDD2P4JQEJTBK0CXXQ
  • run-pickup-stall · sleepingWorkflow (python) · at 21:51:57Z · abandoned wrun_01M155PWV9JX0CW8PXT29PD6N9
  • run-pickup-stall · parallelSleepWorkflow (python) · at 21:51:57Z · abandoned wrun_01M155PWVBPEJ1B9SGNMAZBDFF
  • run-pickup-stall · nullByteWorkflow (python) · at 21:51:58Z · abandoned wrun_41M155PWKY0GPGB5K9E7Y4SCB8
  • run-pickup-stall · promiseAllWorkflow (python) · at 21:51:58Z · abandoned wrun_41M155PWM30GGJARWXFXJERDCD
  • run-pickup-stall · sleepingWorkflow (python) · at 21:51:58Z · abandoned wrun_41M155PWVA0GYQQ5C3R98AKZ7P
  • run-pickup-stall · parallelSleepWorkflow (python) · at 21:51:58Z · abandoned wrun_41M155PWTB0GYB308PY1PJXWQR
  • run-pickup-stall · promiseAllWorkflow (python) · at 21:52:57Z · abandoned wrun_01M155RQEVSXFJ69CKP2MVFCCG
  • run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 21:52:57Z · abandoned wrun_01M155RQEW3ENYRAR7K4CTG117
  • run-pickup-stall · nullByteWorkflow (python) · at 21:52:57Z · abandoned wrun_01M155RQF4N3ZZ63JY6FDQ9JF9
  • run-pickup-stall · parallelSleepWorkflow (python) · at 21:52:57Z · abandoned wrun_01M155RQF2DZ8YDSJRND7YXHV9
  • run-pickup-stall · sleepingWorkflow (python) · at 21:52:57Z · abandoned wrun_01M155RQF107SHW6Z13H70N00E
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 21:53:28Z · abandoned wrun_41M155Q14Q0GGRPQ46FWSPEEMS
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 21:53:57Z · abandoned wrun_01M155TJ2G5NQK9A42FK80A9RC
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 21:53:57Z · abandoned wrun_01M155TJ2KHNGA3BY66W0Z6PH0
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 21:53:57Z · abandoned wrun_01M155TJ2W93XB4RJKPTD4YCQ0
  • run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 21:54:27Z · abandoned wrun_01M155VFDDA8HY1Z0Y48JVPQA4
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 21:54:27Z · abandoned wrun_01M155VFDVNVVREQ2SSR9KG0CJ
  • run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 21:54:34Z · abandoned wrun_01M155VP9DF0GQY8NYK1K68NEC
  • run-pickup-stall · concurrent hook token conflict - two workflows cannot use the same hook token simultaneously (nextjs-webpack) · at 21:54:36Z · abandoned wrun_01M155VRGZ4ABPYR0JHFEWD3ZP
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 21:54:57Z · abandoned wrun_01M155WCNYPW5AJZT2XY8QJGSP
  • run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 21:55:10Z · abandoned wrun_41M155SMGH0GH4HEB19D3MHR2C
  • run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 21:55:10Z · abandoned wrun_41M155RYCR0GV6FG623R4C2MJV

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

@NathanColosimo NathanColosimo changed the title Prepare replay payloads during event streaming [core] Prepare replay payloads as event frames arrive Aug 14, 2026
This was referenced Aug 14, 2026
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@NathanColosimo
NathanColosimo force-pushed the codex/replay-stream-preparation branch from 388b6ea to 294d4b7 Compare August 14, 2026 03:56
@github-actions

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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

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📊 Workflow Benchmarks

commit 5654c82 · Fri, 28 Aug 2026 21:50:26 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric Scenario Best (ms) P75 (ms) P90 (ms) P99 (ms) Samples
TTFS step 208 (-69%) 💚 1279 🔴 (+13%) 1321 🔴 (+16%) 🔻 1476 🔴 (+28%) 🔻 30
TTFS stream 194 (-15%) 💚 1278 🔴 (+18%) 🔻 1301 🔴 (+18%) 🔻 1436 🔴 (+23%) 🔻 30
TTFS hook + stream 1142 (+133%) 🔻 1544 🔴 (+15%) 1591 🔴 (+15%) 🔻 1682 🔴 (+16%) 🔻 30
Fan-out TTFS Promise.all(100 steps) 559 (-0.7%) 1930 (+13%) 2041 (+12%) 2118 (+7.8%) 10
Fan-out TTLS Promise.all(100 steps) 1896 (-14%) 3545 (-4.4%) 4506 (+20%) 🔻 4509 (-43%) 💚 10
STSO 1020 steps (inline) 102 (-9.7%) 151 (+7.9%) 175 (+8.7%) 819 (+316%) 🔻 1019
WO 1020 steps 155606 (+10%) 155606 (+10%) 155606 (+10%) 155606 (+10%) 1
CRTT first chunk (pooled) 96 (-17%) 💚 144 (-38%) 💚 186 (-63%) 💚 3260 (+391%) 🔻 28

Streams

Scenario CRTT 1st p75 p90 p99 CDV max iters
paced control (100/s, 60B) 112 (-22%) 148 (-70%) 220 (-69%) 558 (-43%) 137 (-70%) 10
size sweep (100/s, 160B-12KB) 126 (-29%) 147 (-37%) 215 (-62%) 3229 (+258%) 124 (-47%) 10
replay gateway-gpt-5.4-nano-2000t (1x) 136 (-31%) 140 (-40%) 194 (-56%) 536 (-45%) 263 (-64%) 3
replay eve-gpt-5.6-sol-2000t (1x) 147 (-62%) 140 (-75%) 197 (-89%) 505 (-88%) 738 (-66%) 2
replay eve-gpt-5.6-sol-2000t (2x) 148 (-6%) 182 (-75%) 231 (-78%) 358 (-73%) 240 (-58%) 3
📈 STSO distribution vs main (inline / queue-hop histograms)

1020 steps (inline)

Cumulative STSO time: main 139837ms → this run 155448ms (Δ +15611ms, +11%)

  100-150 ms  ████████████████████┃███  main 857  this 749  -108
  150-200 ms  ████░┃                    main 152  this 211   +59
  200-250 ms  ┃                         main   8  this  28   +20
  250-300 ms  ┃                         main   0  this   9    +9
  300-350 ms  ┃                         main   2  this   5    +3
  350-400 ms  ┃                         main   0  this   2    +2
  400-450 ms  ┃                         main   0  this   1    +1
  450-500 ms  ┃                         main   0  this   1    +1
  650-700 ms  ┃                         main   0  this   1    +1
  800-850 ms  ┃                         main   0  this   3    +3
  850-900 ms  ┃                         main   0  this   1    +1
  900-950 ms  ┃                         main   0  this   1    +1
 950-1000 ms  ┃                         main   0  this   1    +1
1050-1100 ms  ┃                         main   0  this   1    +1
1100-1150 ms  ┃                         main   0  this   1    +1
1150-1200 ms  ┃                         main   0  this   1    +1
1200-1250 ms  ┃                         main   0  this   2    +2
1450-1500 ms  ┃                         main   0  this   1    +1
📈 CRTT drill-down vs main (RTT distributions & profiles) 
variant  RTT 1ms→5s+             avg         p50         p90           p99     n
control  ······▄█▁▁···  125.4 (-55%)  112 (-42%)  220 (-69%)    558 (-43%)  3000
sweep    ······▅█▁▁▁▁·  290.3 (+39%)  111 (-35%)  215 (-62%)  3229 (+258%)  3000
gw 1x    ·····▁▅█▁▁···  123.7 (-40%)  110 (-33%)  194 (-56%)    536 (-45%)  5295
eve 1x   ·····▁▆█▁▁···  122.5 (-71%)  106 (-42%)  197 (-89%)    505 (-88%)  5186
eve 2x   ·····▁▂█▂····  147.4 (-62%)  137 (-44%)  231 (-78%)    358 (-73%)  7779

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

control  ▆▄▁▁▁▃▁█▅▂  115–147ms
sweep    █▇▆▆▅▄▄▃▂▁  145–436ms
gw 1x    ▂▂▂▃▃▃▁▁█▂  109–173ms
eve 1x   ▂▁▃▇▄▄█▆▂▂  98–158ms
eve 2x   ▂▁▃▁▂▃▅█▅▁  128–192ms

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

sweep  █▇▄▂▁▂▃  287–295ms

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

control  ▁▅▃▂▃▃▆▇▅█  31–44ms
sweep    ▁▄█▆▇▆▆▅▅▄  31–59ms
gw 1x    ▂▃▁▂▆▆▃▄█▂  32–42ms
eve 1x   ▂▁▂▇▅▅█▅▂▄  21–31ms
eve 2x   ▂▂▃▁█▄▁▂▅▃  23–30ms
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/replay-stream-preparation branch from 7471e77 to 184d506 Compare August 14, 2026 20:01
VaguelySerious
VaguelySerious reviewed Aug 21, 2026
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AI review: blocking issues found

Comment thread packages/core/src/replay-payload-cache.ts Outdated
Comment thread packages/world/src/events.ts Outdated
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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) 40.4 KiB (±0) 1.76 MiB (+1.5 KiB)
nextjs-turbopack 206.3 KiB (±0) 439 B (±0) 765.3 KiB (+1.3 KiB)
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.

5654c82 · run

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