fix(core): close lifecycle hook review follow-ups by TooTallNate · Pull Request #4439 · vercel/workflow

TooTallNate · 2026-09-25T22:14:07Z

Summary

Fast follow-up to #4216, addressing the actionable docs, diagnostics, and regression-test items from Pranay's review and Copilot's completion-dispatch observation.

Document per-framework registration support: Next.js ≥ 16.3.0 on Vercel, synchronous Nitro plugins, and the standalone Vercel builds that do not load app startup code. Include the next dev restart requirement and cross-evaluation unregister guidance.
Explain runtime module-copy identity in both lifecycle pages and JSDoc; show .is() guards, error codes, and structural properties. Correct the plain Error subclass claim in What's New.
Document reader-lock cleanup with a try/finally cancellation example, the limits of the cause-stream drain, and writable forwarding after terminal events.
Reject registration inside step context and give the workflow-side stub a startup-specific message instead of recommending registration in a step.
Preserve readable error fields when another field or toString throws; distinguish hook-property access from handler failures and log hydration fallback reasons.
Correlate lifecycle spans with workflow.run.id and workflow.name, and record isolated handler/hydration/stream failures as span events, independently of the log sink. Document that span duration includes the drain and that successful dispatch can have reporting-error events.
Move QuickJS's post-completion diagnostic outside the write catch and isolate it so a throwing logger cannot suppress a completion hook or fail the delivery after persistence.
Replace the registry-shape test with an actual second module instance; add hostile-error, step-context, cancellation, telemetry, and fixed-seed nested-drain regressions (60 trials, depth up to 3).

Scope decisions

The review explicitly identifies builder-owned registration, { key } registration/deduplication, and terminal Run pre-seeding as separate feature follow-ups. This PR documents the current topology and registration contract while closing the fast-follow correctness and documentation items. Cross-copy Symbol.hasInstance branding, an empty-registry diagnostic, and a configurable drain deadline remain optional design work; no new configuration or registration API is introduced here.

Validation

pnpm --filter @workflow/core test — 2,790 passed, 2 expected failures, 1 skipped.
pnpm --filter workflow test — 11 passed.
pnpm build --filter=@workflow/core --filter=workflow --output-logs=errors-only — 28 tasks passed (the root script builds all packages).
pnpm typecheck --filter=@workflow/core --filter=workflow --output-logs=errors-only — 23 tasks passed.
pnpm test:docs -t 'lifecycle-hooks|register-lifecycle-hooks|observability/tracing|whats-new' — 7 samples passed.
Biome on changed TypeScript files, node scripts/check-changesets.mjs, and git diff --check.

Rebased onto the latest origin/main before opening.

Docs Preview

Links use the workflow-docs Preview URL from this PR's Vercel bot comment and the current /v5/docs/ route prefix. They require Vercel team access.

Page	Preview
Lifecycle Hooks guide	Framework support, stream lifetime
registerLifecycleHooks API	API reference
Tracing	Spans
What's New	Richer serialization

Co-Authored-By: Nathan Rajlich <71256+TooTallNate@users.noreply.github.com>

changeset-bot · 2026-09-25T22:14:13Z

🦋 Changeset detected

Latest commit: fef849a

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

This PR includes changesets to release 16 packages

Name	Type
@workflow/core	Patch
workflow	Patch
@workflow/builders	Patch
@workflow/cli	Patch
@workflow/next	Patch
@workflow/nitro	Patch
@workflow/vitest	Patch
@workflow/web-shared	Patch
@workflow/web	Patch
@workflow/world-testing	Patch
@workflow/astro	Patch
@workflow/nest	Patch
@workflow/rollup	Patch
@workflow/sveltekit	Patch
@workflow/vite	Patch
@workflow/nuxt	Patch

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

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

vercel · 2026-09-25T22:14:21Z

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

Project	Deployment	Actions	Updated
example-nextjs-workflow-turbopack	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC
example-nextjs-workflow-webpack	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC
example-workflow	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC
workbench-astro-workflow	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC
workbench-express-workflow	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC
workbench-fastify-workflow	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC
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workbench-nestjs-workflow	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC
workbench-nitro-workflow	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC
workbench-nuxt-workflow	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC
workbench-python-workflow	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC
workbench-sveltekit-workflow	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC
workbench-tanstack-start-workflow	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC
workbench-vite-workflow	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC
workflow-docs	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC
workflow-swc-playground	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC
workflow-tarballs	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC
workflow-web	Ready	Preview, v0	Sep 29, 2026 7:48pm UTC

github-actions · 2026-09-25T22:14:24Z

🧪 E2E Test Results

✅ All tests passed

⚠️ 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.

a run can take over its own earlier hook (nextjs-turbopack · windows / local / quickjs)
abortDeterministicBranchFromStepWorkflow: branches stay consistent when abort comes from a step (nextjs-turbopack · vercel-ws-transport / vercel / node / ws)

🛠 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.

run-pickup-stall · runs app-generated source against a registered step (tanstack-start) · at 19:51:47Z · abandoned wrun_01M3QBHVK2VX0SV98GR4F9MKHF
cold-start-warmup · suite warmup (tanstack-start) · at 19:51:50Z · abandoned wrun_01M3QBHVJPVJTBJF38SV2S2EEF
run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 20:00:14Z · abandoned wrun_01M3QC1B3JX2TEHHTMBB81R9RX

E2E Test Summary

Summary

	Passed	Skipped	Total
✅ ▲ Vercel Production	3904	875	4779
✅ 💻 Local Development	4230	549	4779
✅ 📦 Local Production	4406	550	4956
✅ 🐘 Local Postgres	4406	550	4956
✅ 🪟 Windows	342	12	354
✅ 🌐 Cross-language Conformance	68	84	152
✅ dynamic-runs	0	0	0
✅ vercel-http-transport	879	183	1062
✅ vercel-multi-region	27	0	27
✅ vercel-ws-transport	595	113	708
Total	18857	2916	21773

Details by Category

✅ ▲ Vercel Production

App	Passed	Skipped
✅ astro-node	142	35
✅ astro-quickjs	142	35
✅ example-node	142	35
✅ example-quickjs	142	35
✅ express-node	142	35
✅ express-quickjs	142	35
✅ fastify-node	142	35
✅ fastify-quickjs	142	35
✅ hono-node	142	35
✅ hono-quickjs	142	35
✅ nest-node	142	35
✅ nest-quickjs	142	35
✅ nextjs-turbopack-node	169	8
✅ nextjs-turbopack-quickjs	169	8
✅ nextjs-webpack-node	169	8
✅ nextjs-webpack-quickjs	169	8
✅ nitro-node	142	35
✅ nitro-quickjs	142	35
✅ nuxt-node	142	35
✅ nuxt-quickjs	142	35
✅ python-node	66	111
✅ sveltekit-node	161	16
✅ sveltekit-quickjs	161	16
✅ tanstack-start-node	142	35
✅ tanstack-start-quickjs	142	35
✅ vite-node	142	35
✅ vite-quickjs	142	35

✅ 💻 Local Development

App	Passed	Skipped
✅ astro-stable-node	148	29
✅ astro-stable-quickjs	148	29
✅ express-stable-node	148	29
✅ express-stable-quickjs	148	29
✅ fastify-stable-node	148	29
✅ fastify-stable-quickjs	148	29
✅ hono-stable-node	148	29
✅ hono-stable-quickjs	148	29
✅ nest-stable-node	148	29
✅ nest-stable-quickjs	148	29
✅ nextjs-turbopack-canary-node	176	1
✅ nextjs-turbopack-canary-quickjs	176	1
✅ nextjs-turbopack-stable-node	176	1
✅ nextjs-turbopack-stable-quickjs	176	1
✅ nextjs-webpack-canary-node	176	1
✅ nextjs-webpack-canary-quickjs	176	1
✅ nextjs-webpack-stable-quickjs	176	1
✅ nitro-stable-node	148	29
✅ nitro-stable-quickjs	148	29
✅ nuxt-stable-node	148	29
✅ nuxt-stable-quickjs	148	29
✅ sveltekit-stable-node	167	10
✅ sveltekit-stable-quickjs	167	10
✅ tanstack-start-node	148	29
✅ tanstack-start-quickjs	148	29
✅ vite-stable-node	148	29
✅ vite-stable-quickjs	148	29

✅ 📦 Local Production

App	Passed	Skipped
✅ astro-stable-node	148	29
✅ astro-stable-quickjs	148	29
✅ express-stable-node	148	29
✅ express-stable-quickjs	148	29
✅ fastify-stable-node	148	29
✅ fastify-stable-quickjs	148	29
✅ hono-stable-node	148	29
✅ hono-stable-quickjs	148	29
✅ nest-stable-node	148	29
✅ nest-stable-quickjs	148	29
✅ nextjs-turbopack-canary-node	176	1
✅ nextjs-turbopack-canary-quickjs	176	1
✅ nextjs-turbopack-stable-node	176	1
✅ nextjs-turbopack-stable-quickjs	176	1
✅ nextjs-webpack-canary-node	176	1
✅ nextjs-webpack-canary-quickjs	176	1
✅ nextjs-webpack-stable-node	176	1
✅ nextjs-webpack-stable-quickjs	176	1
✅ nitro-stable-node	148	29
✅ nitro-stable-quickjs	148	29
✅ nuxt-stable-node	148	29
✅ nuxt-stable-quickjs	148	29
✅ sveltekit-stable-node	167	10
✅ sveltekit-stable-quickjs	167	10
✅ tanstack-start-node	148	29
✅ tanstack-start-quickjs	148	29
✅ vite-stable-node	148	29
✅ vite-stable-quickjs	148	29

✅ 🐘 Local Postgres

App	Passed	Skipped
✅ astro-stable-node	148	29
✅ astro-stable-quickjs	148	29
✅ express-stable-node	148	29
✅ express-stable-quickjs	148	29
✅ fastify-stable-node	148	29
✅ fastify-stable-quickjs	148	29
✅ hono-stable-node	148	29
✅ hono-stable-quickjs	148	29
✅ nest-stable-node	148	29
✅ nest-stable-quickjs	148	29
✅ nextjs-turbopack-canary-node	176	1
✅ nextjs-turbopack-canary-quickjs	176	1
✅ nextjs-turbopack-stable-node	176	1
✅ nextjs-turbopack-stable-quickjs	176	1
✅ nextjs-webpack-canary-node	176	1
✅ nextjs-webpack-canary-quickjs	176	1
✅ nextjs-webpack-stable-node	176	1
✅ nextjs-webpack-stable-quickjs	176	1
✅ nitro-stable-node	148	29
✅ nitro-stable-quickjs	148	29
✅ nuxt-stable-node	148	29
✅ nuxt-stable-quickjs	148	29
✅ sveltekit-stable-node	167	10
✅ sveltekit-stable-quickjs	167	10
✅ tanstack-start-node	148	29
✅ tanstack-start-quickjs	148	29
✅ vite-stable-node	148	29
✅ vite-stable-quickjs	148	29

✅ 🪟 Windows

App	Passed	Failed	Skipped
✅ nextjs-turbopack-node	171	0	6
✅ nextjs-turbopack-quickjs	171	0	6

✅ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
✅ python	68	0	84

✅ dynamic-runs

App	Passed	Failed	Skipped
✅ astro-vercel	0	0	0
✅ example-vercel	0	0	0
✅ express-vercel	0	0	0
✅ fastify-vercel	0	0	0
✅ hono-vercel	0	0	0
✅ nest-vercel	0	0	0
✅ nextjs-turbopack-vercel	0	0	0
✅ nextjs-webpack-vercel	0	0	0
✅ nitro-vercel	0	0	0
✅ nuxt-vercel	0	0	0
✅ sveltekit-vercel	0	0	0
✅ tanstack-start-vercel	0	0	0
✅ vite-vercel	0	0	0

✅ vercel-http-transport

App	Passed	Skipped
✅ example	142	35
✅ express	142	35
✅ hono	142	35
✅ nextjs-turbopack	169	8
✅ nitro	142	35
✅ vite	142	35

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

✅ vercel-ws-transport

App	Passed	Skipped
✅ example	142	35
✅ express	142	35
✅ nextjs-turbopack	169	8
✅ vite	142	35

📋 View full workflow run

github-actions · 2026-09-25T22:14:26Z

📊 Workflow Benchmarks

commit fef849a · Tue, 29 Sep 2026 20:12:37 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	2589 (+627%) 🔻	2804 🔴 (+27%) 🔻	2874 🔴 (+23%) 🔻	3138 🔴 (+12%)	30
TTFS	stream	539 (+107%) 🔻	2619 🔴 (+23%) 🔻	2788 🔴 (+26%) 🔻	2995 🔴 (+28%) 🔻	30
TTFS	hook + stream	2495 (+262%) 🔻	3011 🔴 (+20%) 🔻	3117 🔴 (+21%) 🔻	3230 🔴 (+18%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	822 (+29%) 🔻	1043 (+30%) 🔻	1108 (+27%) 🔻	3203 (+24%) 🔻	10
Fan-out TTLS	Promise.all(100 steps)	2375 (-9.7%)	3640 (-33%) 💚	3877 (-33%) 💚	11541 (+16%) 🔻	10
STSO	1020 steps (inline)	170 (+30%) 🔻	201 (+28%) 🔻	220 (+27%) 🔻	316 (-66%) 💚	1019
WO	1020 steps	201799 (+17%) 🔻	201799 (+17%) 🔻	201799 (+17%) 🔻	201799 (+17%) 🔻	1
CRTT	first chunk (pooled)	77 (+22%) 🔻	133 (+25%) 🔻	237 (+44%) 🔻	4306 (+28%) 🔻	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	99.5 (+23%)	179 (+11%)	290 (+15%)	574 (+5%)	148 (-10%)	10
size sweep (100/s, 160B-12KB)	106 (+11%)	183 (+22%)	364 (+40%)	4289 (+29%)	160 (-13%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	116 (+29%)	192 (+54%)	231 (+30%)	606 (+66%)	445 (+132%)	3
replay eve-gpt-5.6-sol-2000t (1x)	120 (+2%)	190 (+36%)	224 (+16%)	423 (-30%)	344 (-35%)	2
replay eve-gpt-5.6-sol-2000t (2x)	161 (+50%)	243 (+59%)	351 (+89%)	840 (+140%)	384 (+55%)	3

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

1020 steps (inline)

Cumulative STSO time: main 171647ms → this run 201457ms (Δ +29810ms, +17%)

  100-150 ms  ┃███████████████████      main 630  this   0  -630
  150-200 ms  ███████████░░░░░░░░░░░░┃  main 347  this 748  +401
  200-250 ms  █░░░░░░┃                  main  16  this 235  +219
  250-300 ms  ┃                         main   4  this  21   +17
  300-350 ms  ┃                         main   0  this   7    +7
  350-400 ms  ┃                         main   0  this   2    +2
  400-450 ms  ┃                         main   1  this   3    +2
  450-500 ms  ┃                         main   0  this   2    +2
  650-700 ms  ┃                         main   1  this   1    +0
  700-750 ms  ┃                         main   1  this   0    -1
  750-800 ms  ┃                         main   2  this   0    -2
  800-850 ms  ┃                         main   2  this   0    -2
  850-900 ms  ┃                         main   3  this   0    -3
  900-950 ms  ┃                         main   4  this   0    -4
 950-1000 ms  ┃                         main   2  this   0    -2
1000-1050 ms  ┃                         main   1  this   0    -1
1050-1100 ms  ┃                         main   1  this   0    -1
1200-1250 ms  ┃                         main   1  this   0    -1
1250-1300 ms  ┃                         main   2  this   0    -2
1300-1350 ms  ┃                         main   1  this   0    -1

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

variant  RTT 1ms→5s+             avg         p50         p90          p99     n
control  ······▂█▂▁···  153.6 (+12%)  140 (+26%)  290 (+15%)    574 (+5%)  3000
sweep    ······▁█▂·▁▁·  426.4 (+43%)  140 (+27%)  364 (+40%)  4289 (+29%)  3000
gw 1x    ······▁█▂▁···  170.6 (+52%)  160 (+52%)  231 (+30%)   606 (+66%)  5295
eve 1x   ······▁█▂▁···  166.7 (+30%)  159 (+50%)  224 (+16%)   423 (-30%)  5186
eve 2x   ······▁█▅▁···  201.2 (+58%)  186 (+58%)  351 (+89%)  840 (+140%)  7779

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

control  ▆▃▁▂▃▃█▄▂▄  141–175ms
sweep    █▇▇▆▅▄▃▃▁▁  288–564ms
gw 1x    ▃▄▂▂▁▇█▂▃▂  156–203ms
eve 1x   ▁▂▂▂▁█▄▅▃▂  156–192ms
eve 2x   ▂▂▂▁▂▂▅█▃▂  168–291ms

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

sweep  █▆▃▄▁▁▅  424–430ms

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

control  ▆▁▃▄▅▅▃█▃▆  41–60ms
sweep    ▁▄█▆▇▆▆▄▄▄  47–72ms
gw 1x    ▅▆▄▁▅▄█▄▅▃  43–66ms
eve 1x   ▃█▂▆▆▇▄▆▁█  27–37ms
eve 2x   █▇▂▂▇▃▂▁▁▆  27–39ms

📜 Previous results (1)

`02d642e`

Fri, 25 Sep 2026 22:40:35 GMT · run logs

vercel / nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	337 (-81%) 💚	2327 🔴 (+23%) 🔻	2396 🔴 (+25%) 🔻	2742 🔴 (+41%) 🔻	30
TTFS	stream	351 (-16%) 💚	2776 🔴 (+47%) 🔻	2861 🔴 (+50%) 🔻	3004 🔴 (+57%) 🔻	30
TTFS	hook + stream	595 (-33%) 💚	2699 🔴 (+24%) 🔻	2727 🔴 (+16%) 🔻	2831 🔴 (+17%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	652 (+6.9%)	908 (+4.8%)	913 (-61%) 💚	2918 (+23%) 🔻	10
Fan-out TTLS	Promise.all(100 steps)	3096 (+18%) 🔻	3885 (-19%) 💚	6089 (-26%) 💚	6728 (-23%) 💚	10
STSO	1020 steps (inline)	121 (+14%)	160 (+15%) 🔻	185 (+19%) 🔻	308 (+39%) 🔻	1019
WO	1020 steps	159244 (+15%)	159244 (+15%)	159244 (+15%)	159244 (+15%)	1
CRTT	first chunk (pooled)	90 (+48%) 🔻	137 (+21%) 🔻	174 (-12%)	220 (-18%) 💚	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	114 (-7%)	163 (-43%)	204 (-73%)	352 (-72%)	128 (-37%)	10
size sweep (100/s, 160B-12KB)	116 (+23%)	156 (-28%)	202 (-39%)	509 (+1%)	124 (-36%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	162 (+67%)	152 (-9%)	185 (-19%)	363 (-12%)	250 (-33%)	3
replay eve-gpt-5.6-sol-2000t (1x)	95.5 (+20%)	169 (-5%)	281 (+11%)	662 (+35%)	470 (+17%)	2
replay eve-gpt-5.6-sol-2000t (2x)	101 (+1%)	173 (-29%)	215 (-38%)	404 (-49%)	296 (-22%)	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 · 2026-09-25T22:18:02Z

Sim World

Simulated world deterministic testing for races. Traces

🟠 world-sim scenario book — 1 fail of 42 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
✅ `step-vs-timer-early-settlement`	completed	8	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

Copilot

Copilot review overview

🟡 Changes recommended

Resolve the hook-property access issue and the two documentation inconsistencies identified in review.

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Review effort: Lite
Findings: 1

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Capture hook callable during guarded property read · New

What changed in this PR

This PR hardens lifecycle-hook registration, diagnostics, telemetry, stream cleanup, and completion handling while expanding documentation and regression coverage.

Changes:

Reject workflow/step-context registration and clarify framework startup support.
Isolate reporting failures and add lifecycle tracing.
Add coverage for hostile errors, cancellation, module copies, telemetry, and nested drains.

File	Reviewed changes
`packages/workflow/src/api-workflow.ts`	Workflow-side registration error
`packages/workflow/src/api-workflow.test.ts`	Registration error regression test
`packages/workflow/README.md`	Startup registration guidance
`packages/core/src/runtime/quickjs-lifecycle.test.ts`	Completion diagnostic regression coverage
`packages/core/src/runtime/quickjs-entrypoint.ts`	Isolated completion diagnostics
`packages/core/src/runtime/lifecycle-hooks.ts`	Registration guards, diagnostics, draining, and tracing
`packages/core/src/runtime/lifecycle-hooks.test.ts`	Lifecycle regression coverage
`packages/core/README.md`	Lifecycle and stream documentation
`docs/content/docs/v5/whats-new.mdx`	Error serialization guidance
`docs/content/docs/v5/observability/tracing.mdx`	Lifecycle span documentation
`docs/content/docs/v5/observability/lifecycle-hooks.mdx`	Framework and stream guidance
`docs/content/docs/v5/api-reference/workflow-api/register-lifecycle-hooks.mdx`	API reference updates
`.changeset/lifecycle-review-follow-up.md`	Release metadata

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    const registered = getRegistry()
      .slice()
      .filter((hooks) => {
        try {
          return Boolean(hooks[event]);


github-actions · 2026-09-25T22:18:50Z

Framework	Flow route	Step reg.	Framework output
hono	265.9 KiB (±0)	97.2 KiB (+29 B)	1.98 MiB (+172 B)
nextjs-turbopack	273.3 KiB (±0)	426 B (±0)	979.2 KiB (+134 B)

About these numbers

Sizes are gzip; parentheses show the change against main.
Flow route and Step reg. gate this job, on raw bytes rather than the gzip shown, at max(2%, 50.0 KiB). Framework output is informational.

fef849a · run

fix(core): address lifecycle hook review follow-ups

02d642e

Co-Authored-By: Nathan Rajlich <71256+TooTallNate@users.noreply.github.com>

TooTallNate requested a review from a team as a code owner September 25, 2026 22:14

Copilot AI lite review requested due to automatic review settings September 25, 2026 22:14

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Comment thread packages/core/src/runtime/lifecycle-hooks.ts

Comment on lines 195 to 199

const registered = getRegistry()

.slice()

.filter((hooks) => {

try {

return Boolean(hooks[event]);

pranaygp mentioned this pull request Sep 28, 2026

test(e2e): expect a takeover when the World raises a force-claim victim to its executor's spec version #4462

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Merge branch 'main' into fast-follow-pr-for-4216-review-comments

fef849a

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fix(core): close lifecycle hook review follow-ups - #4439

fix(core): close lifecycle hook review follow-ups#4439
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🧪 E2E Test Results

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📊 Workflow Benchmarks

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