Fix lazy v4 event metadata decoding by karthikscale3 · Pull Request #4095 · vercel/workflow

karthikscale3 · 2026-09-11T01:16:42Z

Description

Fix v4 lazy event reads failing when an event payload has expired and the server omits its payload field from otherwise valid metadata.

The v4 decoder previously validated every zero-body frame as a fully materialized runtime event. Dashboard observability requests use lazy remote-reference behavior, so an expired payload can legitimately be absent. The decoder now validates lazy metadata by temporarily supplying the expected payload field, removes it from the returned event, and threads remote-reference behavior through list, correlation, and single-event reads. Resolved reads and replay remain strict.

Includes a patch changeset for @workflow/world-vercel.

How did you test your changes?

pnpm --filter @workflow/world-vercel test — 31 files, 688 tests passed
pnpm --filter @workflow/world-vercel typecheck
Focused regression coverage verifies lazy step_completed metadata without result succeeds and resolved events without event data still fail validation.

PR Checklist - Required to merge

📦 Added a patch changeset
🔒 Commit includes DCO sign-off
📝 Pinged @vercel/workflow in a comment

Signed-off-by: Karthik Kalyanaraman <karthik.kalyanaraman@vercel.com>

changeset-bot · 2026-09-11T01:16:47Z

🦋 Changeset detected

Latest commit: d017673

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

This PR includes changesets to release 17 packages

Name	Type
@workflow/world-vercel	Patch
@workflow/cli	Patch
@workflow/core	Patch
@workflow/web	Patch
workflow	Patch
@workflow/world-testing	Patch
@workflow/builders	Patch
@workflow/next	Patch
@workflow/nitro	Patch
@workflow/vitest	Patch
@workflow/web-shared	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 · 2026-09-11T01:16:50Z

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated
example-nextjs-workflow-turbopack	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC
example-nextjs-workflow-webpack	Building	Preview, v0	Sep 11, 2026 4:32pm UTC
example-workflow	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC
workbench-astro-workflow	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC
workbench-express-workflow	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC
workbench-fastify-workflow	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC
workbench-hono-workflow	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC
workbench-nestjs-workflow	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC
workbench-nitro-workflow	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC
workbench-nuxt-workflow	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC
workbench-python-workflow	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC
workbench-sveltekit-workflow	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC
workbench-tanstack-start-workflow	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC
workbench-vite-workflow	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC
workflow-docs	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC
workflow-swc-playground	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC
workflow-tarballs	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC
workflow-web	Ready	Preview, v0	Sep 11, 2026 4:32pm UTC

karthikscale3 · 2026-09-11T01:17:01Z

@vercel/workflow

github-actions · 2026-09-11T01:17:05Z

🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (4 failed)

hono-node (1 failed):

hookDisposeTestWorkflow - hook token reuse after explicit disposal while workflow still running | wrun_41M28N15QW0GXBK6NE88KBDWX5 | 🔍 observability

nest-node (1 failed):

error handling not registered StepNotRegisteredError fails the run when not caught in workflow

nuxt-node (2 failed):

error handling catchability workflow throw of a non-Error value round-trips verbatim as cause
error handling serialization failures step-argument serialization failure is catchable in workflow code

🪟 Windows (1 failed)

nextjs-turbopack-node (1 failed):

cancelRun via CLI - cancelling a running workflow | wrun_41M28N2Q390GKAE6YHGXEZ0TF4

⚠️ 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.

44 flaky tests

'hookGetConflictWithPriorStepWorkflow' - hook.getConflict() does not block step execution (nuxt)
'hookGetConflictWithPriorStepWorkflow' - hook.getConflict() does not block step execution (sveltekit)
abortAlreadyAbortedWorkflow: pre-aborted signal seen by step (hono)
addTenWorkflow (express)
addTenWorkflow (nuxt)
Calculator.calculate - static workflow method using static step methods from another class (hono)
cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
cancelRun via CLI - cancelling a running workflow (vite)
completes but prepareCall is not applied (GAP) (sveltekit)
concurrent hook token conflict - two workflows cannot use the same hook token simultaneously (nitro)
concurrent hook token conflict - two workflows cannot use the same hook token simultaneously (tanstack-start)
errorSubclassRoundTripWorkflow - first-class Error subclasses survive every serialization boundary (nitro)
FatalError can be caught and detected with FatalError.is() (sveltekit)
FatalError fails immediately without retries (example)
FatalError fails immediately without retries (nextjs-turbopack)
FatalError fails immediately without retries (nuxt)
getterStepWorkflow - getter functions with "use step" directive (hono)
hookClaimOnlyMutexWorkflow - hook works as a pure run mutex without payload data (example)
hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack)
hookDisposeTestWorkflow - hook token reuse after explicit disposal while workflow still running (nest)
hookGetConflictWorkflow - hook.getConflict() resolves with the conflicting run when token is already registered (astro)
hookGetConflictWorkflow - hook.getConflict() resolves with the conflicting run when token is already registered (nest)
hookGetConflictWorkflow - hook.getConflict() resolves with the conflicting run when token is already registered (nextjs-webpack)
hookMinRetentionWorkflow - terminal Hook cannot resume and its token stays unavailable (nuxt)
hookMinRetentionWorkflow - terminal Hook cannot resume and its token stays unavailable (sveltekit)
instanceMethodStepWorkflow - instance methods with "use step" directive (hono)
nullByteWorkflow (express)
parallelSleepWorkflow (example)
positive startIndex (skips first chunk) (nextjs-turbopack)
provider tool identity preserved across step boundaries (nextjs-webpack)
spawnWorkflowFromStepWorkflow - spawning a child workflow using start() inside a step (nitro)
step throw of a non-Error value preserves it as cause on the wrapping FatalError (nextjs-webpack)
stepFunctionAsStartArgWorkflow - step function reference passed as start() argument (nitro)
stepFunctionWithClosureWorkflow - step function with closure variables passed as argument (nitro)
StepNotRegisteredError fails the step but workflow can catch it (example)
StepNotRegisteredError fails the step but workflow can catch it (nest)
StepNotRegisteredError fails the step but workflow can catch it (sveltekit)
uncaught step-argument serialization failure fails the run as USER_ERROR without redelivery retries (sveltekit)
uncaught step-return-value serialization failure fails the run as USER_ERROR (nest)
workflow throw round-trips FatalError + cause through run_failed event (express)
WorkflowNotRegisteredError fails the run when workflow does not exist (express)
WorkflowNotRegisteredError fails the run when workflow does not exist (nextjs-turbopack)
WorkflowNotRegisteredError fails the run when workflow does not exist (nitro)
writableForwardedFromStepWorkflow (express)

🛠 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.

cold-start-warmup · suite warmup (tanstack-start) · at 16:33:58Z · abandoned wrun_01M28N2AP88PTBAMY1HA9Y3T6R
run-pickup-stall · plainModuleDoneHook resumed via plain API route (o2flow shape) (nextjs-webpack) · at 16:42:00Z · abandoned wrun_01M28NHE256AZS2QQB04KHY3T0

E2E Test Summary

Summary

	Passed	Failed	Skipped	Total
❌ ▲ Vercel Production	3658	4	685	4347
✅ 💻 Local Development	3922	0	586	4508
✅ 📦 Local Production	3922	0	586	4508
✅ 🐘 Local Postgres	3922	0	586	4508
❌ 🪟 Windows	319	1	2	322
✅ 🌐 Cross-language Conformance	68	0	74	142
✅ vercel-http-transport	823	0	143	966
✅ vercel-multi-region	27	0	0	27
✅ vercel-ws-transport	557	0	87	644
Total	17218	5	2749	19972

Details by Category

❌ ▲ Vercel Production

App	Passed	Failed	Skipped
✅ astro-node	133	0	28
✅ astro-quickjs	133	0	28
✅ example-node	133	0	28
✅ example-quickjs	133	0	28
✅ express-node	133	0	28
✅ express-quickjs	133	0	28
✅ fastify-node	133	0	28
✅ fastify-quickjs	133	0	28
❌ hono-node	132	1	28
✅ hono-quickjs	133	0	28
❌ nest-node	132	1	28
✅ nest-quickjs	133	0	28
✅ nextjs-turbopack-node	158	0	3
✅ nextjs-turbopack-quickjs	158	0	3
✅ nextjs-webpack-node	158	0	3
✅ nextjs-webpack-quickjs	158	0	3
✅ nitro-node	133	0	28
✅ nitro-quickjs	133	0	28
❌ nuxt-node	131	2	28
✅ nuxt-quickjs	133	0	28
✅ python-node	66	0	95
✅ sveltekit-node	152	0	9
✅ sveltekit-quickjs	152	0	9
✅ tanstack-start-node	133	0	28
✅ tanstack-start-quickjs	133	0	28
✅ vite-node	133	0	28
✅ vite-quickjs	133	0	28

✅ 💻 Local Development

App	Passed	Skipped
✅ astro-stable-node	134	27
✅ astro-stable-quickjs	134	27
✅ express-stable-node	134	27
✅ express-stable-quickjs	134	27
✅ fastify-stable-node	134	27
✅ fastify-stable-quickjs	134	27
✅ hono-stable-node	134	27
✅ hono-stable-quickjs	134	27
✅ nest-stable-node	134	27
✅ nest-stable-quickjs	134	27
✅ nextjs-turbopack-canary-node	141	20
✅ nextjs-turbopack-canary-quickjs	141	20
✅ nextjs-turbopack-stable-node	160	1
✅ nextjs-turbopack-stable-quickjs	160	1
✅ nextjs-webpack-canary-node	141	20
✅ nextjs-webpack-canary-quickjs	141	20
✅ nextjs-webpack-stable-node	160	1
✅ nextjs-webpack-stable-quickjs	160	1
✅ nitro-stable-node	134	27
✅ nitro-stable-quickjs	134	27
✅ nuxt-stable-node	134	27
✅ nuxt-stable-quickjs	134	27
✅ sveltekit-stable-node	153	8
✅ sveltekit-stable-quickjs	153	8
✅ tanstack-start-node	134	27
✅ tanstack-start-quickjs	134	27
✅ vite-stable-node	134	27
✅ vite-stable-quickjs	134	27

✅ 📦 Local Production

App	Passed	Skipped
✅ astro-stable-node	134	27
✅ astro-stable-quickjs	134	27
✅ express-stable-node	134	27
✅ express-stable-quickjs	134	27
✅ fastify-stable-node	134	27
✅ fastify-stable-quickjs	134	27
✅ hono-stable-node	134	27
✅ hono-stable-quickjs	134	27
✅ nest-stable-node	134	27
✅ nest-stable-quickjs	134	27
✅ nextjs-turbopack-canary-node	141	20
✅ nextjs-turbopack-canary-quickjs	141	20
✅ nextjs-turbopack-stable-node	160	1
✅ nextjs-turbopack-stable-quickjs	160	1
✅ nextjs-webpack-canary-node	141	20
✅ nextjs-webpack-canary-quickjs	141	20
✅ nextjs-webpack-stable-node	160	1
✅ nextjs-webpack-stable-quickjs	160	1
✅ nitro-stable-node	134	27
✅ nitro-stable-quickjs	134	27
✅ nuxt-stable-node	134	27
✅ nuxt-stable-quickjs	134	27
✅ sveltekit-stable-node	153	8
✅ sveltekit-stable-quickjs	153	8
✅ tanstack-start-node	134	27
✅ tanstack-start-quickjs	134	27
✅ vite-stable-node	134	27
✅ vite-stable-quickjs	134	27

✅ 🐘 Local Postgres

App	Passed	Skipped
✅ astro-stable-node	134	27
✅ astro-stable-quickjs	134	27
✅ express-stable-node	134	27
✅ express-stable-quickjs	134	27
✅ fastify-stable-node	134	27
✅ fastify-stable-quickjs	134	27
✅ hono-stable-node	134	27
✅ hono-stable-quickjs	134	27
✅ nest-stable-node	134	27
✅ nest-stable-quickjs	134	27
✅ nextjs-turbopack-canary-node	141	20
✅ nextjs-turbopack-canary-quickjs	141	20
✅ nextjs-turbopack-stable-node	160	1
✅ nextjs-turbopack-stable-quickjs	160	1
✅ nextjs-webpack-canary-node	141	20
✅ nextjs-webpack-canary-quickjs	141	20
✅ nextjs-webpack-stable-node	160	1
✅ nextjs-webpack-stable-quickjs	160	1
✅ nitro-stable-node	134	27
✅ nitro-stable-quickjs	134	27
✅ nuxt-stable-node	134	27
✅ nuxt-stable-quickjs	134	27
✅ sveltekit-stable-node	153	8
✅ sveltekit-stable-quickjs	153	8
✅ tanstack-start-node	134	27
✅ tanstack-start-quickjs	134	27
✅ vite-stable-node	134	27
✅ vite-stable-quickjs	134	27

❌ 🪟 Windows

App	Passed	Failed	Skipped
❌ nextjs-turbopack-node	159	1	1
✅ nextjs-turbopack-quickjs	160	0	1

✅ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
✅ python	68	0	74

✅ vercel-http-transport

App	Passed	Skipped
✅ example	133	28
✅ express	133	28
✅ hono	133	28
✅ nextjs-turbopack	158	3
✅ nitro	133	28
✅ vite	133	28

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

✅ vercel-ws-transport

App	Passed	Skipped
✅ example	133	28
✅ express	133	28
✅ nextjs-turbopack	158	3
✅ vite	133	28

📋 View full workflow run

github-actions · 2026-09-11T01:17:07Z

📊 Workflow Benchmarks

commit d017673 · Fri, 11 Sep 2026 16:55:56 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	220 (-6.4%)	1801 🔴 (+37%) 🔻	1873 🔴 (+39%) 🔻	2134 🔴 (+24%) 🔻	30
TTFS	stream	128 (-42%) 💚	1645 🔴 (+27%) 🔻	1691 🔴 (+29%) 🔻	1842 🔴 (+18%) 🔻	30
TTFS	hook + stream	648 (-57%) 💚	2059 🔴 (+24%) 🔻	2128 🔴 (+26%) 🔻	2203 🔴 (+21%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	684 (+11%)	916 (+17%) 🔻	948 (-52%) 💚	2512 (+25%) 🔻	10
Fan-out TTLS	Promise.all(100 steps)	2123 (+13%)	5760 (+102%) 🔻	5787 (-22%) 💚	9279 (+1.0%)	10
STSO	1020 steps (inline)	137 (+12%)	179 (+19%) 🔻	204 (+19%) 🔻	358 (+44%) 🔻	1019
WO	1020 steps	177249 (+16%) 🔻	177249 (+16%) 🔻	177249 (+16%) 🔻	177249 (+16%) 🔻	1
CRTT	first chunk (pooled)	65 (+27%) 🔻	100 (+23%) 🔻	207 (+33%) 🔻	238 (+44%) 🔻	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	76.5 (+9%)	209 (+31%)	317 (+3%)	757 (+31%)	189 (+43%)	10
size sweep (100/s, 160B-12KB)	88.5 (+19%)	216 (+42%)	489 (+125%)	962 (+32%)	169 (-8%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	99 (+38%)	163 (+24%)	220 (+28%)	508 (-10%)	546 (+84%)	3
replay eve-gpt-5.6-sol-2000t (1x)	93 (+25%)	156 (+22%)	204 (+13%)	400 (-1%)	315 (+11%)	2
replay eve-gpt-5.6-sol-2000t (2x)	100 (+9%)	325 (+68%)	438 (+56%)	754 (+52%)	303 (+7%)	3

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

1020 steps (inline)

Cumulative STSO time: main 152228ms → this run 177089ms (Δ +24861ms, +16%)

100-150 ms  ██┃████████████████████   main 757  this 100  -657
150-200 ms  ███████░░░░░░░░░░░░░░░░┃  main 232  this 798  +566
200-250 ms  █┃                        main  20  this  81   +61
250-300 ms  ┃                         main   7  this  22   +15
300-350 ms  ┃                         main   1  this   6    +5
350-400 ms  ┃                         main   1  this   5    +4
400-450 ms  ┃                         main   0  this   2    +2
450-500 ms  ┃                         main   0  this   2    +2
500-550 ms  ┃                         main   0  this   1    +1
550-600 ms  ┃                         main   1  this   0    -1
600-650 ms  ┃                         main   0  this   1    +1
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  ······▂█▃▁···  167.7 (+41%)  138 (+38%)    317 (+3%)  757 (+31%)  3000
sweep    ······▂█▃▁···  171.5 (+30%)  132 (+17%)  489 (+125%)  962 (+32%)  3000
gw 1x    ·····▁▃█▂▁···    141 (+21%)  126 (+25%)   220 (+28%)  508 (-10%)  5295
eve 1x   ·····▁▄█▂····  129.1 (+12%)  112 (+10%)   204 (+13%)   400 (-1%)  5186
eve 2x   ·····▁▁█▇▁···  219.3 (+46%)  178 (+38%)   438 (+56%)  754 (+52%)  7779

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

control  ▇█▅▅▃▃▂▅▂▁  128–217ms
sweep    ▃▃▂▁▁▂▆█▄▂  133–253ms
gw 1x    █▃▄▄▁▁▁█▅▄  117–173ms
eve 1x   ▅▁▃▃▁▃▇█▅▂  109–157ms
eve 2x   ▁▂▇▂▁▅▆█▅▃  172–290ms

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

sweep  ▆█▇▇█▁▁  169–173ms

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

control  █▆▄▃▄▂▅▃▃▁  42–78ms
sweep    ▄▃▁▁▂▅██▅▁  56–92ms
gw 1x    █▅▄▃▁▃▂▆▂▄  34–55ms
eve 1x   ▇▃▅▃▄▄█▁▇▇  21–30ms
eve 2x   ██▅▅▆▇▇▁▄▇  22–37ms

📜 Previous results (1)

`a06b597`

Fri, 11 Sep 2026 01:33:02 GMT · run logs

vercel / nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	957 (+386%) 🔻	1296 🔴 (+22%) 🔻	1331 🔴 (+22%) 🔻	1455 🔴 (+21%) 🔻	30
TTFS	stream	186 (+5.7%)	1258 🔴 (+25%) 🔻	1291 🔴 (+26%) 🔻	1333 🔴 (+29%) 🔻	30
TTFS	hook + stream	473 (-56%) 💚	1515 🔴 (+28%) 🔻	1546 🔴 (+21%) 🔻	2091 🔴 (+5.6%)	30
Fan-out TTFS	Promise.all(100 steps)	572 (-3.7%)	794 (-54%) 💚	1936 (+11%)	2000 (+8.9%)	10
Fan-out TTLS	Promise.all(100 steps)	1478 (-6.4%)	5197 (+36%) 🔻	9597 (+143%) 🔻	10211 (-5.8%)	10
STSO	1020 steps (inline)	111 (+7.8%)	132 (-7.0%)	148 (-11%)	198 (-35%) 💚	1019
WO	1020 steps	134816 (-8.6%)	134816 (-8.6%)	134816 (-8.6%)	134816 (-8.6%)	1
CRTT	first chunk (pooled)	56 (-14%)	83 (-38%) 💚	110 (-39%) 💚	331 (+21%) 🔻	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	70 (-20%)	118 (-24%)	172 (-23%)	433 (+9%)	94 (-40%)	10
size sweep (100/s, 160B-12KB)	74.5 (-23%)	132 (-50%)	249 (-50%)	598 (-36%)	135 (-44%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	102 (-1%)	112 (-37%)	178 (-47%)	590 (-12%)	401 (+23%)	3
replay eve-gpt-5.6-sol-2000t (1x)	101 (-39%)	111 (-26%)	159 (-21%)	480 (+16%)	426 (+9%)	2
replay eve-gpt-5.6-sol-2000t (2x)	66 (-53%)	178 (-28%)	336 (-4%)	743 (+47%)	580 (+58%)	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 · 2026-09-11T01:20:37Z

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 · 2026-09-11T01:21:50Z

Framework	Flow route	Step reg.	Framework output
hono	236.0 KiB (±0)	42.3 KiB (±0)	1.80 MiB (±0)
nextjs-turbopack	242.2 KiB (±0)	439 B (±0)	836.0 KiB (±0)

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.

d017673 · run

Co-authored-by: Peter Wielander <mittgfu@gmail.com> Signed-off-by: Karthik Kalyan <105607645+karthikscale3@users.noreply.github.com>

…load-schema Signed-off-by: Karthik Kalyanaraman <karthik.kalyanaraman@vercel.com> # Conflicts: # packages/world-vercel/src/events-v4.ts

…' into fix/v4-lazy-event-payload-schema Signed-off-by: Karthik Kalyanaraman <karthik.kalyanaraman@vercel.com> # Conflicts: # .changeset/lazy-v4-event-metadata.md

github-actions · 2026-09-11T16:34:33Z

No backport to stable for 86eb822 (AI decision).

The commit only adds tests (plus a changeset) for the lazy v4 event-metadata decoding path, and that behavior does not exist on stable: origin/stable:packages/world-vercel/src/events-v4.ts has no OMITTED_EVENT_PAYLOAD handling and performs no frame schema validation at all (no SCHEMA_VALIDATION path), so neither the bug nor the fix it covers is present there. Backporting would add tests asserting main-only behavior, which would simply fail on stable.

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

86eb8229f89e48afe95fb68aa5922d22fc76573b

Fix lazy v4 event metadata decoding

a06b597

Signed-off-by: Karthik Kalyanaraman <karthik.kalyanaraman@vercel.com>

karthikscale3 requested a review from a team as a code owner September 11, 2026 01:16

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Update .changeset/lazy-v4-event-metadata.md

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Co-authored-by: Peter Wielander <mittgfu@gmail.com> Signed-off-by: Karthik Kalyan <105607645+karthikscale3@users.noreply.github.com>

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karthikscale3 added 2 commits September 11, 2026 09:27

Merge remote-tracking branch 'origin/main' into fix/v4-lazy-event-pay…

d769465

…load-schema Signed-off-by: Karthik Kalyanaraman <karthik.kalyanaraman@vercel.com> # Conflicts: # packages/world-vercel/src/events-v4.ts

Merge remote-tracking branch 'origin/fix/v4-lazy-event-payload-schema…

d017673

…' into fix/v4-lazy-event-payload-schema Signed-off-by: Karthik Kalyanaraman <karthik.kalyanaraman@vercel.com> # Conflicts: # .changeset/lazy-v4-event-metadata.md

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karthikscale3 merged commit 86eb822 into main Sep 11, 2026
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Version Packages (beta) #4071

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Fix lazy v4 event metadata decoding - #4095

Fix lazy v4 event metadata decoding#4095
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🧪 E2E Test Results

❌ Failed E2E Tests

▲ Vercel Production (4 failed)

🪟 Windows (1 failed)

⚠️ Flaky E2E Tests (passed on retry)

🛠 Infra Events (absorbed by the harness)

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📊 Workflow Benchmarks

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