[ci] Track the /flow route bundle size against main by VaguelySerious · Pull Request #3739 · vercel/workflow

VaguelySerious · 2026-08-22T00:20:03Z

TLDR adds this comment to each PR that compares output sizes to main

Builds the nextjs-turbopack and hono workbench apps on every PR, measures the /.well-known/workflow/v1/flow route, and posts a sticky comment with the delta against main. Pushes to main produce the baseline artifacts PR runs download. Non-required: it lives in its own workflow file, so it cannot gate the E2E aggregate.

Two numbers per app

Neither app emits an isolable function bundle for that route. Next.js emits a ~1 KB turbopack chunk loader pointing at chunks shared with other routes; nitro inlines the handler into a single server entry.

Gated: what the workflow builders emit for the flow route, before the framework bundles it. Growth beyond max(2%, 50 KiB) raw fails the job. Override with the allow-bundle-size-growth label.
Informational: the framework's own build output. Unrelated changes move it, so it never gates.

Each is only ever compared against its own baseline, never against the other.

Verification

Reproducibility was checked before wiring the gate, since a noisy metric makes one useless: two clean builds of each app produce byte-identical reports.

	Flow bundle	Step registrations	Framework output
nextjs-turbopack	1.32 MiB	1.7 KiB	3.21 MiB
hono	1.28 MiB	261.0 KiB	7.70 MiB

Both loud-failure paths were exercised and exit non-zero: a Tier-1 bundle backdated one day against the build stamp, and a missing _workflows.ts from a skipped prebuild. A plausible wrong number (the 1 KB chunk loader, a stale artifact) is worse than a red job.

Pinned build env

WORKFLOW_SOURCEMAP, WORKFLOW_PUBLIC_MANIFEST and WORKFLOW_TARGET_WORLD are pinned and recorded in each report's fingerprint; the renderer refuses to diff reports whose fingerprints disagree.

WORKFLOW_SOURCEMAP=false is the one that moves the numbers: sourcemap mode defaults to inline outside a production build, which alone takes the Next flow bundle from 1.38 MB to 5.85 MB.

WORKFLOW_TARGET_WORLD was measured to have no effect. Building nextjs-turbopack with local and with vercel gives byte-identical reports on all three metrics, because every world the app depends on is bundled into the framework output either way and the choice is made at runtime. It is pinned anyway, as insurance: packages/next branches on it, so if it ever starts mattering the fingerprint turns that into a refused diff rather than a phantom code change.

Known limitation

The gate does not cover the world adapters. A change confined to @workflow/world-vercel will not move the gated numbers. Documented in the PR comment, the measurement script, and AGENTS.md. Gating world code would need a different metric.

Notes for review

The first PR run after this merges will show "No baseline on main yet" and gate nothing. Baselines exist only once this lands on main or the workflow is dispatched there.
Per-app bundle paths are read from scripts/create-test-matrix.mjs rather than restated, so there is one source of truth.
The app build uses the package script, not turbo run build: hono's turbo.json does not declare node_modules/.nitro/ as an output, so a cache hit would leave the gated file absent.

🤖 Generated with Claude Code

Builds the nextjs-turbopack and hono workbench apps on every PR, measures the /.well-known/workflow/v1/flow route, and posts a sticky comment with the delta against main. Pushes to main produce the baseline artifacts. Two numbers per app, because neither app emits an isolable function bundle for that route: Next.js emits a ~1 KB turbopack chunk loader pointing at chunks shared with other routes, and nitro inlines the handler into a single server entry. The gated number is what the workflow builders emit before the framework bundles it; the framework's own output is reported but never gates, since unrelated changes move it. Verified before wiring the gate: two clean builds of each app produce byte-identical reports, so a delta means a real change. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

changeset-bot · 2026-08-22T00:20:10Z

🦋 Changeset detected

Latest commit: b9d0c1b

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

This PR includes changesets to release 0 packages

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

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

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

vercel · 2026-08-22T00:20:11Z

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 25, 2026 2:56pm
example-nextjs-workflow-webpack	Ready	Preview, v0	Aug 25, 2026 2:56pm
example-workflow	Ready	Preview, v0	Aug 25, 2026 2:56pm
workbench-astro-workflow	Ready	Preview, v0	Aug 25, 2026 2:56pm
workbench-express-workflow	Ready	Preview, v0	Aug 25, 2026 2:56pm
workbench-fastify-workflow	Ready	Preview, v0	Aug 25, 2026 2:56pm
workbench-hono-workflow	Ready	Preview, v0	Aug 25, 2026 2:56pm
workbench-nestjs-workflow	Ready	Preview, v0	Aug 25, 2026 2:56pm
workbench-nitro-workflow	Ready	Preview, v0	Aug 25, 2026 2:56pm
workbench-nuxt-workflow	Ready	Preview, v0	Aug 25, 2026 2:56pm
workbench-python-workflow	Ready	Preview, v0	Aug 25, 2026 2:56pm
workbench-sveltekit-workflow	Ready	Preview, v0	Aug 25, 2026 2:56pm
workbench-tanstack-start-workflow	Ready	Preview, v0	Aug 25, 2026 2:56pm
workbench-vite-workflow	Ready	Preview, v0	Aug 25, 2026 2:56pm
workflow-docs	Ready	Preview, v0	Aug 25, 2026 2:56pm
workflow-swc-playground	Ready	Preview, v0	Aug 25, 2026 2:56pm
workflow-tarballs	Ready	Preview, v0	Aug 25, 2026 2:56pm
workflow-web	Ready	Preview, v0	Aug 25, 2026 2:56pm

github-actions · 2026-08-22T00:20:21Z

🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

python-node (8 failed):

promiseAllWorkflow | wrun_41M0WQ2QFY0GQ8Y7FJ22Z5ZVVV | 🔍 observability
sleepingWorkflow | wrun_41M0WQ3CQY0GYZ9D47SVJ55P5R | 🔍 observability
parallelSleepWorkflow | wrun_41M0WQ3DHB0GPSEH8VBZBPHNDP | 🔍 observability
nullByteWorkflow | wrun_41M0WQ3MSW0GXPHDV3TCWBNXCS | 🔍 observability
cancelRun - cancelling a running workflow | wrun_41M0WQ8D1R0GXD2FPZRDVGQTTK | 🔍 observability
cancelRun via CLI - cancelling a running workflow | wrun_41M0WQ8GW00GHDGC3DBR3WNBTZ | 🔍 observability
sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0WQ8PM40GT0EMCGFF6XXF5A | 🔍 observability
resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0WQ98EH0GJWR20V1DHB3W96 | 🔍 observability

🌐 Cross-language Conformance (9 failed)

python (9 failed):

deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M0WQ5ZG1Y0QKQCRPWQS6Q7S8
promiseAllWorkflow | wrun_41M0WQ2QFY0GQ8Y7FJ22Z5ZVVV
sleepingWorkflow | wrun_41M0WQ3CQY0GYZ9D47SVJ55P5R
parallelSleepWorkflow | wrun_41M0WQ3DHB0GPSEH8VBZBPHNDP
nullByteWorkflow | wrun_41M0WQ3MSW0GXPHDV3TCWBNXCS
cancelRun - cancelling a running workflow | wrun_41M0WQ8D1R0GXD2FPZRDVGQTTK
cancelRun via CLI - cancelling a running workflow | wrun_41M0WQ8GW00GHDGC3DBR3WNBTZ
sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M0WQ8PM40GT0EMCGFF6XXF5A
resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M0WQ98EH0GJWR20V1DHB3W96

⚠️ Flaky E2E Tests (passed on retry)

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

addTenWorkflow (vite)
cancelRun via CLI - cancelling a running workflow (express)
cancelRun via CLI - cancelling a running workflow (nuxt)
fibonacciWorkflow - recursive workflow composition via start() (nextjs-webpack)
health check (CLI) - workflow health command reports healthy endpoints (nextjs-webpack)
sleepWinsRaceWorkflow (tanstack-start)
webhookWorkflow (fastify)

🛠 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 (python) · at 15:01:41Z · abandoned wrun_41M0WPYAE00GM6K1CDJ8DPERHV · (+7 more)
run-pickup-stall · promiseAllWorkflow (python) · at 15:01:57Z · abandoned wrun_41M0WQ1Z3D0GSBNMRD14YJH4YH
cold-start-warmup · suite warmup (tanstack-start) · at 15:01:57Z · abandoned wrun_01M0WQ1M5P1MRH6VYV0E38KMQK
run-pickup-stall · sleepingWorkflow (python) · at 15:01:57Z · abandoned wrun_41M0WQ1Z3G0GRQ9PE5NNA8G2DW
run-pickup-stall · nullByteWorkflow (python) · at 15:01:57Z · abandoned wrun_41M0WQ1Z3J0GTXBJ93TZKZGE7Y
run-pickup-stall · parallelSleepWorkflow (python) · at 15:01:57Z · abandoned wrun_41M0WQ1Z3G0GRQ9PE5NNA8G2DX
run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 15:01:57Z · abandoned wrun_41M0WQ1ZE60GJW11XKZMV7XA52
run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 15:02:29Z · abandoned wrun_41M0WQ2YX30GMX4WMFK2RBFVCB
cold-start-warmup · suite warmup (python) · at 15:02:37Z · abandoned wrun_01M0WQ0129FFFEBEER793NP4MT · (+7 more)
run-pickup-stall · promiseAllWorkflow (python) · at 15:02:52Z · abandoned wrun_01M0WQ3P6TZWQ5CYZ54HYTX8WK
run-pickup-stall · sleepingWorkflow (python) · at 15:02:52Z · abandoned wrun_01M0WQ3P6ZM2XPN5BN7FHCD7A7
run-pickup-stall · parallelSleepWorkflow (python) · at 15:02:52Z · abandoned wrun_01M0WQ3P71C20SWGPRXGX6BWQF
run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 15:02:52Z · abandoned wrun_01M0WQ3P6S56GZPJK2YZB4J1PD
run-pickup-stall · nullByteWorkflow (python) · at 15:02:52Z · abandoned wrun_01M0WQ3P73WDSRBS47HQWE6T2Z
run-pickup-stall · parallelSleepWorkflow (python) · at 15:02:58Z · abandoned wrun_41M0WQ3TEQ0GR0C3ESC9A4H591
run-pickup-stall · promiseAllWorkflow (python) · at 15:02:58Z · abandoned wrun_41M0WQ3TH90GM476R7C0VG0GA4
run-pickup-stall · sleepingWorkflow (python) · at 15:02:58Z · abandoned wrun_41M0WQ3TJC0GSMEN8BZEY4VXCV
run-pickup-stall · nullByteWorkflow (python) · at 15:02:59Z · abandoned wrun_41M0WQ3THE0GRV55VD6YQP50Q7
run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 15:03:48Z · abandoned wrun_41M0WQ3Y630GY12BXAV8KC4S1X
run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 15:03:52Z · abandoned wrun_01M0WQ5GTSM98T01GVJMRN9DKK
run-pickup-stall · parallelSleepWorkflow (python) · at 15:03:52Z · abandoned wrun_01M0WQ5GTYG1NP262A69DJNPX6
run-pickup-stall · promiseAllWorkflow (python) · at 15:03:52Z · abandoned wrun_01M0WQ5GTVV4B884BHZQKXMEZW
run-pickup-stall · sleepingWorkflow (python) · at 15:03:52Z · abandoned wrun_01M0WQ5GTXCS5X4N6GYS3F2K6D
run-pickup-stall · nullByteWorkflow (python) · at 15:03:52Z · abandoned wrun_01M0WQ5GV0P06TKS4MDSQGC65F
run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 15:04:52Z · abandoned wrun_01M0WQ7BECN6WHD7BPCXZK3VPV
run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 15:04:52Z · abandoned wrun_01M0WQ7BEPJQCFE3WZY252AJC1
run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 15:04:52Z · abandoned wrun_01M0WQ7BES58J7ME9WGFJZV8PM
run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 15:05:22Z · abandoned wrun_01M0WQ88T3V2QA7XNJJ4QK397W
run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 15:05:22Z · abandoned wrun_01M0WQ88T55S08JCJGF7T642ND
run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 15:05:29Z · abandoned wrun_41M0WQ5XEJ0GXKC1E0PA52B0NW
run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 15:05:30Z · abandoned wrun_41M0WQ5WWT0GQTMT46W0BBZ3A0
run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 15:05:52Z · abandoned wrun_01M0WQ961YBTQSJ78TRA3G9VB2
run-pickup-stall · StepNotRegisteredError fails the step but workflow can catch it (nextjs-webpack) · at 15:06:30Z · abandoned wrun_01M0WQABCRB90A05JYXWEK292Q
run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 15:06:48Z · abandoned wrun_01M0WQAWGKMNZ0W8C74Z5CFNXY

E2E Test Summary

Summary

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

Details by Category

❌ ▲ Vercel Production

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

✅ 💻 Local Development

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

✅ 📦 Local Production

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

✅ 🐘 Local Postgres

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

✅ 🪟 Windows

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

❌ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
❌ python	0	9	132

✅ vercel-http-transport

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

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

✅ vercel-ws-transport

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

📋 View full workflow run

github-actions · 2026-08-22T00:20:25Z

📊 Workflow Benchmarks

commit b9d0c1b · Tue, 25 Aug 2026 15:18:15 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	1336 (+62%) 🔻	1461 🔴 (+30%) 🔻	1510 🔴 (+29%) 🔻	1704 🔴 (+15%)	30
TTFS	stream	999 (+350%) 🔻	1394 🔴 (+24%) 🔻	1416 🔴 (+25%) 🔻	1450 🔴 (-1.7%)	30
TTFS	hook + stream	550 (-56%) 💚	1788 🔴 (+30%) 🔻	1873 🔴 (+22%) 🔻	2008 🔴 (+20%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	660 (+6.5%)	2149 (+28%) 🔻	2300 (+32%) 🔻	2440 (-54%) 💚	10
Fan-out TTLS	Promise.all(100 steps)	2112 (+10%)	4222 (+14%)	4584 (+12%)	10550 (-4.6%)	10
STSO	1020 steps (inline)	136 (+62%) 🔻	185 (+43%) 🔻	219 (+44%) 🔻	315 (+25%) 🔻	1019
WO	1020 steps	183322 (+40%) 🔻	183322 (+40%) 🔻	183322 (+40%) 🔻	183322 (+40%) 🔻	1
CRTT	first chunk (pooled)	104 (+14%)	163 (+12%)	244 (+11%)	324 (-46%) 💚	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	142 (+23%)	154 (+2%)	235 (-35%)	502 (-27%)	153 (-25%)	10
size sweep (100/s, 160B-12KB)	131 (+12%)	168 (-22%)	264 (-30%)	400 (-46%)	119 (-49%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	198 (+100%)	129 (+9%)	171 (+13%)	322 (-17%)	162 (-50%)	3
replay eve-gpt-5.6-sol-2000t (1x)	165 (+37%)	175 (+28%)	231 (+5%)	1174 (+40%)	571 (-1%)	2
replay eve-gpt-5.6-sol-2000t (2x)	151 (-7%)	222 (-6%)	368 (-14%)	1031 (+44%)	283 (+20%)	3

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

1020 steps (inline)

Cumulative STSO time: main 130759ms → this run 183012ms (Δ +52253ms, +40%)

 50-100 ms  ┃                         main   1  this   0    -1
100-150 ms  ┃███████████████████████  main 900  this  46  -854
150-200 ms  ██░░░░░░░░░░░░░░░░░░░┃    main  91  this 814  +723
200-250 ms  █░┃                       main  16  this 104   +88
250-300 ms  ┃                         main   8  this  41   +33
300-350 ms  ┃                         main   2  this  10    +8
350-400 ms  ┃                         main   1  this   3    +2
650-700 ms  ┃                         main   0  this   1    +1

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

variant  RTT 1ms→5s+             avg         p50         p90          p99     n
control  ······▃█▁▁···   133.7 (+2%)  123 (+23%)  235 (-35%)   502 (-27%)  3000
sweep    ······▃█▁····   136.6 (-6%)   124 (+8%)  264 (-30%)   400 (-46%)  3000
gw 1x    ·····▁▇█▁····   110.8 (+6%)   103 (+6%)  171 (+13%)   322 (-17%)  5295
eve 1x   ·····▁▂█▂▁▁··  167.4 (+35%)  136 (+42%)   231 (+5%)  1174 (+40%)  5186
eve 2x   ·····▁▂█▃▁▁··   179.1 (+5%)   143 (+1%)  368 (-14%)  1031 (+44%)  7779

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

control  ▃▃▂▇▃▄▂▁▂█  116–162ms
sweep    ▆▁▃▆▃▄▆▄▅█  124–149ms
gw 1x    ▄█▃▄▇▃▁▂▄▄  101–123ms
eve 1x   █▁▁▂▂▂▁▂▁▁  131–354ms
eve 2x   █▂▂▂▁▃▃▄▄▂  128–297ms

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

sweep  ▆██▅▃▃▁  135–138ms

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

control  ▁▃▆█▄▇▃▃▄▄  29–47ms
sweep    ▁▅▆█▅▆▆▇▅▅  40–59ms
gw 1x    ▁█▅▂▅▃▄▅▃▃  27–35ms
eve 1x   █▁▁▂▄▅▄▃▂▂  22–36ms
eve 2x   █▅▄▂▄▂▃▂▁▃  18–32ms

📜 Previous results (2)

`de8da08`

Mon, 24 Aug 2026 19:22:14 GMT · run logs

vercel / nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	288 (-71%) 💚	1285 🔴 (+16%) 🔻	1304 🔴 (+13%)	1403 🔴 (+12%)	30
TTFS	stream	1245 (+76%) 🔻	1306 🔴 (+19%) 🔻	1335 🔴 (+20%) 🔻	1797 🔴 (+40%) 🔻	30
TTFS	hook + stream	1522 (+11%)	1622 🔴 (+10%)	1666 🔴 (+11%)	1824 🔴 (+14%)	30
Fan-out TTFS	Promise.all(100 steps)	667 (+2.6%)	934 (-45%) 💚	949 (-47%) 💚	1693 (-13%)	10
Fan-out TTLS	Promise.all(100 steps)	1854 (-4.0%)	2508 (-21%) 💚	2620 (-20%) 💚	4776 (-44%) 💚	10
STSO	1020 steps (inline)	122 (+16%) 🔻	163 (+10%)	183 (+8.9%)	280 (+28%) 🔻	1019
WO	1020 steps	163721 (+11%)	163721 (+11%)	163721 (+11%)	163721 (+11%)	1
CRTT	first chunk (pooled)	88 (±0%)	156 (+26%) 🔻	189 (-2.1%)	271 (-56%) 💚	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	113 (±0%)	128 (-2%)	195 (-8%)	373 (-51%)	122 (-15%)	10
size sweep (100/s, 160B-12KB)	108 (-4%)	134 (-6%)	174 (-7%)	431 (-62%)	118 (-14%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	120 (-2%)	120 (-82%)	154 (-95%)	266 (-94%)	174 (-20%)	3
replay eve-gpt-5.6-sol-2000t (1x)	128 (+8%)	116 (-13%)	145 (-14%)	321 (-7%)	272 (+4%)	2
replay eve-gpt-5.6-sol-2000t (2x)	156 (+27%)	157 (-14%)	222 (-16%)	727 (+32%)	388 (+70%)	3

`c9af771`

Sat, 22 Aug 2026 00:57:36 GMT · run logs

vercel / nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	268 (-74%) 💚	1331 🔴 (+16%) 🔻	1371 🔴 (+16%) 🔻	1545 🔴 (+18%) 🔻	30
TTFS	stream	240 (-77%) 💚	1373 🔴 (+21%) 🔻	1409 🔴 (+21%) 🔻	1515 🔴 (+26%) 🔻	30
TTFS	hook + stream	1534 (+26%) 🔻	1723 🔴 (+21%) 🔻	1753 🔴 (+17%) 🔻	1975 🔴 (+2.4%)	30
Fan-out TTFS	Promise.all(100 steps)	539 (-28%) 💚	2016 (+4.3%)	2044 (+5.1%)	2069 (+1.9%)	10
Fan-out TTLS	Promise.all(100 steps)	1709 (-66%) 💚	5864 (-21%) 💚	7006 (-11%)	7951 (-7.5%)	10
STSO	1020 steps (inline)	136 (+31%) 🔻	194 (+37%) 🔻	222 (+38%) 🔻	337 (+73%) 🔻	1019
WO	1020 steps	189480 (+33%) 🔻	189480 (+33%) 🔻	189480 (+33%) 🔻	189480 (+33%) 🔻	1
CRTT	first chunk (pooled)	95 (-22%) 💚	157 (-11%)	184 (-16%) 💚	281 (-49%) 💚	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	126 (-8%)	161 (-65%)	239 (-63%)	372 (-93%)	133 (-14%)	10
size sweep (100/s, 160B-12KB)	139 (-15%)	179 (-10%)	278 (-9%)	4827 (+963%)	170 (-9%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	152 (-15%)	138 (-47%)	187 (-68%)	612 (-58%)	296 (-64%)	3
replay eve-gpt-5.6-sol-2000t (1x)	145 (-4%)	125 (-34%)	168 (-51%)	293 (-78%)	239 (-70%)	2
replay eve-gpt-5.6-sol-2000t (2x)	147 (-16%)	192 (-29%)	344 (-9%)	1005 (+41%)	412 (+11%)	3

ℹ️ Metric definitions & methodology

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

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

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

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

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

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

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

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

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

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

github-actions · 2026-08-22T00:20:59Z

Sim World

Simulated world deterministic testing for races. Traces

🟠 world-sim scenario book — 1 fail of 41 total

fence=per-spec

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

Full trace: world-sim.txt

github-actions · 2026-08-22T00:23:52Z

Framework	Flow route	Step reg.	Framework output
hono	211.3 KiB	40.1 KiB	1.76 MiB
nextjs-turbopack	216.7 KiB	439 B	771.9 KiB

About these numbers

Sizes are gzip.
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.
No baseline on main yet for some rows.

b9d0c1b · run

The same hono build produces 55 files under .output/server on a Linux runner and 54 on macOS, so a report measured off-runner is not comparable to one measured on it. Node's major version was already recorded because zlib ships with Node and moves the gzip numbers; platform and arch cover the raw ones. Cheap to add now: no baseline exists on main yet, so nothing is invalidated. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

The table is the comment; the notes explaining what the numbers are, what gates the job, and which commit produced them sit behind a disclosure so the default view is four rows and nothing else.

alangenfeld

nice seems like good defense to have

github-actions · 2026-08-25T20:08:02Z

No backport to stable for c8bcde5 (AI decision).

This commit adds a brand-new CI capability (a bundle-size measurement workflow, measurement/rendering scripts, tests, and AGENTS.md documentation for it) rather than fixing anything broken on stable. It is not needed to keep the maintenance line buildable, testable, or releasable, and its triggers are scoped to main anyway, so it would gate nothing useful on stable.

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

c8bcde53d01781454bdb2fbef05577d843f91aae

vercel Bot deployed to Preview – workbench-python-workflow August 22, 2026 00:20 View deployment

vercel Bot deployed to Preview – workflow-web August 22, 2026 00:20 View deployment

vercel Bot deployed to Preview – workflow-tarballs August 22, 2026 00:21 View deployment

vercel Bot deployed to Preview – workbench-nitro-workflow August 22, 2026 00:21 View deployment

vercel Bot deployed to Preview – workbench-hono-workflow August 22, 2026 00:21 View deployment

vercel Bot deployed to Preview – workbench-fastify-workflow August 22, 2026 00:21 View deployment

vercel Bot deployed to Preview – workbench-astro-workflow August 22, 2026 00:21 View deployment

vercel Bot deployed to Preview – workbench-nestjs-workflow August 22, 2026 00:21 View deployment

vercel Bot deployed to Preview – workbench-vite-workflow August 22, 2026 00:21 View deployment

vercel Bot deployed to Preview – workbench-sveltekit-workflow August 22, 2026 00:21 View deployment

vercel Bot deployed to Preview – workbench-tanstack-start-workflow August 22, 2026 00:21 View deployment

vercel Bot deployed to Preview – example-workflow August 22, 2026 00:21 View deployment

vercel Bot deployed to Preview – workbench-express-workflow August 22, 2026 00:21 View deployment

vercel Bot deployed to Preview – workbench-nuxt-workflow August 22, 2026 00:21 View deployment

vercel Bot deployed to Preview – example-nextjs-workflow-turbopack August 22, 2026 00:21 View deployment

vercel Bot deployed to Preview – example-nextjs-workflow-webpack August 22, 2026 00:22 View deployment

vercel Bot deployed to Preview – workflow-docs August 22, 2026 00:22 View deployment

vercel Bot deployed to Preview – workflow-swc-playground August 22, 2026 00:23 View deployment

vercel Bot deployed to Preview – workbench-python-workflow August 22, 2026 00:33 View deployment

vercel Bot deployed to Preview – workflow-web August 22, 2026 00:33 View deployment

vercel Bot deployed to Preview – example-nextjs-workflow-turbopack August 22, 2026 00:33 View deployment

vercel Bot deployed to Preview – workflow-tarballs August 22, 2026 00:33 View deployment

vercel Bot deployed to Preview – workbench-express-workflow August 24, 2026 19:03 View deployment

vercel Bot deployed to Preview – workflow-tarballs August 24, 2026 19:03 View deployment

vercel Bot deployed to Preview – workbench-sveltekit-workflow August 24, 2026 19:03 View deployment

vercel Bot deployed to Preview – workbench-astro-workflow August 24, 2026 19:03 View deployment

vercel Bot deployed to Preview – workbench-tanstack-start-workflow August 24, 2026 19:03 View deployment

vercel Bot deployed to Preview – workbench-vite-workflow August 24, 2026 19:03 View deployment

vercel Bot deployed to Preview – example-workflow August 24, 2026 19:03 View deployment

vercel Bot deployed to Preview – workbench-nuxt-workflow August 24, 2026 19:03 View deployment

vercel Bot deployed to Preview – example-nextjs-workflow-webpack August 24, 2026 19:03 View deployment

vercel Bot deployed to Preview – workflow-docs August 24, 2026 19:04 View deployment

vercel Bot deployed to Preview – workflow-swc-playground August 24, 2026 19:05 View deployment

[ci] Move the bundle-size footnotes into an accordion

b9d0c1b

The table is the comment; the notes explaining what the numbers are, what gates the job, and which commit produced them sit behind a disclosure so the default view is four rows and nothing else.

vercel Bot deployed to Preview – workbench-python-workflow August 25, 2026 14:52 View deployment

VaguelySerious force-pushed the peter/bundle-size-flow-route branch from 2bafe9c to b9d0c1b Compare August 25, 2026 14:52

vercel Bot deployed to Preview – workbench-python-workflow August 25, 2026 14:53 View deployment

vercel Bot deployed to Preview – example-nextjs-workflow-turbopack August 25, 2026 14:53 View deployment

vercel Bot deployed to Preview – workbench-hono-workflow August 25, 2026 14:53 View deployment

vercel Bot deployed to Preview – workbench-nitro-workflow August 25, 2026 14:53 View deployment

vercel Bot deployed to Preview – workflow-web August 25, 2026 14:53 View deployment

vercel Bot deployed to Preview – workbench-nestjs-workflow August 25, 2026 14:53 View deployment

vercel Bot deployed to Preview – workflow-tarballs August 25, 2026 14:54 View deployment

vercel Bot deployed to Preview – workbench-express-workflow August 25, 2026 14:54 View deployment

vercel Bot deployed to Preview – workbench-fastify-workflow August 25, 2026 14:54 View deployment

vercel Bot deployed to Preview – workbench-astro-workflow August 25, 2026 14:54 View deployment

vercel Bot deployed to Preview – workbench-tanstack-start-workflow August 25, 2026 14:54 View deployment

vercel Bot deployed to Preview – workbench-sveltekit-workflow August 25, 2026 14:54 View deployment

vercel Bot deployed to Preview – example-workflow August 25, 2026 14:54 View deployment

vercel Bot deployed to Preview – workbench-vite-workflow August 25, 2026 14:54 View deployment

alangenfeld approved these changes Aug 25, 2026

View reviewed changes

Navigation Menu

Uh oh!

[ci] Track the /flow route bundle size against main - #3739

[ci] Track the /flow route bundle size against main#3739
VaguelySerious merged 4 commits into
mainfrom
peter/bundle-size-flow-route

VaguelySerious commented Aug 22, 2026 •

edited

Loading

Uh oh!

changeset-bot Bot commented Aug 22, 2026 •

edited

Loading

Uh oh!

vercel Bot commented Aug 22, 2026 •

edited

Loading

Uh oh!

github-actions Bot commented Aug 22, 2026 •

edited

Loading

Uh oh!

github-actions Bot commented Aug 22, 2026 •

edited

Loading

`de8da08`

`c9af771`

Uh oh!

github-actions Bot commented Aug 22, 2026 •

edited

Loading

Uh oh!

github-actions Bot commented Aug 22, 2026 •

edited

Loading

Uh oh!

alangenfeld left a comment

Uh oh!

github-actions Bot commented Aug 25, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Uh oh!

Conversation

VaguelySerious commented Aug 22, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Two numbers per app

Verification

Pinned build env

Known limitation

Notes for review

Uh oh!

changeset-bot Bot commented Aug 22, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

🦋 Changeset detected

Uh oh!

vercel Bot commented Aug 22, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

github-actions Bot commented Aug 22, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

🧪 E2E Test Results

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

🌐 Cross-language Conformance (9 failed)

⚠️ Flaky E2E Tests (passed on retry)

🛠 Infra Events (absorbed by the harness)

E2E Test Summary

Uh oh!

github-actions Bot commented Aug 22, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

📊 Workflow Benchmarks

de8da08

c9af771

Uh oh!

github-actions Bot commented Aug 22, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Sim World

Uh oh!

github-actions Bot commented Aug 22, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

alangenfeld left a comment

Choose a reason for hiding this comment

Uh oh!

github-actions Bot commented Aug 25, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

VaguelySerious commented Aug 22, 2026 •

edited

Loading

changeset-bot Bot commented Aug 22, 2026 •

edited

Loading

vercel Bot commented Aug 22, 2026 •

edited

Loading

github-actions Bot commented Aug 22, 2026 •

edited

Loading

github-actions Bot commented Aug 22, 2026 •

edited

Loading

`de8da08`

`c9af771`

github-actions Bot commented Aug 22, 2026 •

edited

Loading

github-actions Bot commented Aug 22, 2026 •

edited

Loading