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Report replay divergence recovery episodes - #3208

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Report replay divergence recovery episodes#3208
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Summary & Motivation

Adds an optional replayDivergenceCount on event writes, making replay-divergence outcomes observable without GET-side effects or VQS changes.

  • Set once per invocation, on the first natural write after replay reaches a deterministic boundary — recovery and retry-exhaustion both land on a real event write, so no extra request is needed to surface either.
  • Reporting is managed by a stateful ReplayRecoveryReporter, which claims that write so an invocation reports its recovery exactly once even when several suspension writes race, and releases the claim if the write fails.
  • Request telemetry only: worlds may report it, but must not persist it into the event log.

Test Plan

Unit tests added for the reporter, the runtime and suspension paths, and the v4 wire field; typecheck and the core/world-vercel suites pass locally.

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🦋 Changeset detected

Latest commit: 39fd41c

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

This PR includes changesets to release 20 packages
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@workflow/corePatch
@workflow/worldPatch
@workflow/world-vercelPatch
@workflow/buildersPatch
@workflow/cliPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/vitestPatch
@workflow/web-sharedPatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/world-localPatch
@workflow/world-postgresPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch

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ProjectDeploymentActionsUpdated (UTC)
example-nextjs-workflow-turbopackReadyReadyPreviewJul 31, 2026 5:17pm
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🧪 E2E Test Results

✅ All tests passed

E2E Test Summary

Summary
PassedFailedSkippedTotal
✅ ▲ Vercel Production145502391694
✅ 💻 Local Development162102271848
✅ 📦 Local Production162102271848
✅ 🐘 Local Postgres162102271848
✅ 🪟 Windows15400154
✅ 📋 Other102002121232
✅ vercel-multi-region270027
Total7519011328651
Details by Category

✅ ▲ Vercel Production

AppPassedFailedSkipped
✅ astro126028
✅ example126028
✅ express126028
✅ fastify126028
✅ hono126028
✅ nextjs-turbopack15103
✅ nextjs-webpack15103
✅ nitro126028
✅ nuxt126028
✅ sveltekit14509
✅ vite126028

✅ 💻 Local Development

AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026

✅ 📦 Local Production

AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026

✅ 🐘 Local Postgres

AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026

✅ 🪟 Windows

AppPassedFailedSkipped
✅ nextjs-turbopack15400

✅ 📋 Other

AppPassedFailedSkipped
✅ e2e-local-dev-nest-stable128026
✅ e2e-local-dev-tanstack-start-128026
✅ e2e-local-postgres-nest-stable128026
✅ e2e-local-postgres-tanstack-start-128026
✅ e2e-local-prod-nest-stable128026
✅ e2e-local-prod-tanstack-start-128026
✅ e2e-vercel-prod-nest126028
✅ e2e-vercel-prod-tanstack-start126028

✅ vercel-multi-region

AppPassedFailedSkipped
✅ nextjs-turbopack2700

📋 View full workflow run

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📊 Workflow Benchmarks

commit 39fd41c · Fri, 31 Jul 2026 17:36:11 GMT · run logs

Backend: vercel · app: nextjs-turbopack

MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep258 (-51%) 💚1383 🔴 (+33%) 🔻1428 🔴 (+33%) 🔻1876 🔴 (+16%) 🔻30
TTFSstream242 (-74%) 💚1375 🔴 (+37%) 🔻1420 🔴 (+38%) 🔻1510 🔴 (+17%) 🔻30
TTFShook + stream395 (-6.2%)1602 🔴 (+21%) 🔻1636 🔴 (+21%) 🔻1786 🔴 (+0.9%)30
STSO1020 steps (inline)168 (+3.1%)486 (+2.5%)544 (+2.4%)747 (+11%)1016
STSO1020 steps (queue-hop)2441 (+17%) 🔻3262 (+2.0%)3262 (+2.0%)3262 (+2.0%)3
WO1020 steps425981 (+5.3%)425981 (+5.3%)425981 (+5.3%)425981 (+5.3%)1
SLstream latency102 (+24%) 🔻171 🔴 (+30%) 🔻183 🔴 (+24%) 🔻280 🔴 (+30%) 🔻30
SOstream overhead (text)131 (+30%) 🔻225 (+31%) 🔻241 (+13%)612 (+145%) 🔻30
SOstream overhead (structured)106 (-3.6%)194 (+15%)250 (+32%) 🔻377 (+65%) 🔻30
📈 STSO distribution vs main (inline / queue-hop histograms)

1020 steps (inline)

Cumulative STSO time: main 395612ms → this run 415909ms (Δ +20297ms, +5%)

 150-200 ms ┃████ main 36 this 10 -26
200-250 ms █████████┃███ main 92 this 74 -18
250-300 ms █████████████████┃██ main 145 this 130 -15
300-350 ms █████████████████┃█ main 139 this 133 -6
350-400 ms █████████████████┃█ main 138 this 130 -8
400-450 ms ██████████████████░░┃ main 134 this 150 +16
450-500 ms █████████████████████░░┃ main 150 this 174 +24
500-550 ms ███████████████░┃ main 107 this 121 +14
550-600 ms ██████┃ main 47 this 52 +5
600-650 ms █┃ main 16 this 17 +1
650-700 ms ┃ main 3 this 7 +4
700-750 ms ┃ main 3 this 9 +6
750-800 ms ┃ main 3 this 4 +1
800-850 ms ┃ main 1 this 1 +0
850-900 ms ┃ main 0 this 1 +1
950-1000 ms ┃ main 0 this 1 +1
1050-1100 ms ┃ main 1 this 0 -1
1200-1250 ms ┃ main 0 this 1 +1
1950-2000 ms ┃ main 1 this 0 -1
2350-2400 ms ┃ main 0 this 1 +1

1020 steps (queue-hop)

Cumulative STSO time: main 8138ms → this run 8741ms (Δ +603ms, +7%)

2000-2500 ms ███████████┃ main 1 this 1 +0
2500-3000 ms ┃███████████ main 1 this 0 -1
3000-3500 ms ████████████░░░░░░░░░░░┃ main 1 this 2 +1
📜 Previous results (3)

efc8f13

Thu, 30 Jul 2026 23:29:58 GMT · run logs

vercel / nextjs-turbopack

MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1259 (+24%) 🔻1326 🔴 (+17%) 🔻1390 🔴 (+20%) 🔻1623 🔴 (+28%) 🔻30
TTFSstream1264 (+517%) 🔻1315 🔴 (+19%) 🔻1349 🔴 (+19%) 🔻1490 🔴 (-8.1%)30
TTFShook + stream1488 (+12%)1581 🔴 (+10%)1615 🔴 (+11%)1929 🔴 (+18%) 🔻30
STSO1020 steps (inline)140 (-24%) 💚458 (-12%)513 (-11%)707 (-13%)1016
STSO1020 steps (queue-hop)2388 (+18%) 🔻3508 (-25%) 💚3508 (-25%) 💚3508 (-25%) 💚3
WO1020 steps393536 (-13%)393536 (-13%)393536 (-13%)393536 (-13%)1
SLstream latency79 (-29%) 💚139 🔴 (-16%) 💚158 🔴 (-24%) 💚274 🔴 (-30%) 💚30
SOstream overhead (text)92 (-30%) 💚173 (-40%) 💚200 (-60%) 💚268 (-90%) 💚30

a2ed26d

Thu, 30 Jul 2026 16:30:42 GMT · run logs

vercel / nextjs-turbopack

MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep243 (+10.0%)1323 🔴 (+24%) 🔻1370 🔴 (+25%) 🔻1440 🔴 (-6.2%)30
TTFSstream224 (-1.3%)1269 🔴 (+31%) 🔻1315 🔴 (+27%) 🔻1393 🔴 (+27%) 🔻30
TTFShook + stream438 (+4.0%)1506 🔴 (+25%) 🔻1551 🔴 (+24%) 🔻1925 🔴 (+35%) 🔻30
STSO1020 steps (1-20)196 (+11%)324 🔴 (+9.8%)388 🔴 (+14%)539 🔴 (+33%) 🔻19
STSO1020 steps (101-120)187 (-11%)279 🔴 (-19%) 💚298 🔴 (-29%) 💚310 🔴 (-72%) 💚19
STSO1020 steps (1001-1020)531 (+0.8%)572 🔴 (±0%)590 🔴 (-12%)611 🔴 (-14%)19
WO1020 steps416066 (-1.4%)416066 (-1.4%)416066 (-1.4%)416066 (-1.4%)1
SLstream latency86 (+1.2%)182 🔴 (+40%) 🔻208 🔴 (+25%) 🔻338 🔴 (-6.6%)30
SOstream overhead (text)108 (-10%)205 (-10%)243 (-7.3%)281 (-21%) 💚30
SOstream overhead (structured)133 (+6.4%)252 🔴 (+0.8%)305 (-4.4%)403 (-4.3%)30

91db81f

Thu, 30 Jul 2026 15:23:41 GMT · run logs

vercel / nextjs-turbopack

MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1245 (+27%) 🔻1312 🔴 (+28%) 🔻1369 🔴 (+29%) 🔻1406 🔴 (+17%) 🔻30
TTFSstream1245 (+27%) 🔻1291 🔴 (+27%) 🔻1310 🔴 (+25%) 🔻1354 🔴 (+25%) 🔻30
TTFShook + stream585 (-51%) 💚1568 🔴 (+20%) 🔻1638 🔴 (+20%) 🔻1723 🔴 (+16%) 🔻30
STSO1020 steps (1-20)167 (-1.2%)269 🔴 (-1.8%)294 🔴 (-14%)405 🔴 (-4.9%)19
STSO1020 steps (101-120)193 (-5.9%)261 🔴 (-14%)287 🔴 (-21%) 💚333 🔴 (-16%) 💚19
STSO1020 steps (1001-1020)480 (+0.6%)532 🔴 (-2.2%)616 🔴 (-3.9%)1074 🔴 (+38%) 🔻19
WO1020 steps390171 (-3.9%)390171 (-3.9%)390171 (-3.9%)390171 (-3.9%)1
SLstream latency90 (±0%)146 🔴 (-5.8%)160 🔴 (-18%) 💚204 🔴 (-11%)30
SOstream overhead (text)101 (-1.9%)159 (-25%) 💚187 (-21%) 💚253 (-5.9%)30
SOstream overhead (structured)95 (-1.0%)151 (-28%) 💚200 (-25%) 💚282 (-37%) 💚30
ℹ️ Metric definitions & methodology

The collapsed STSO distribution section above buckets every step gap of the sequential-steps run (not a sampled window), split by whether the step ending the gap ran inline — in the same warm process as the step before it, so the gap is pure framework overhead — or after a queue-hop — the first step of a fresh process, which pays queue dispatch, client reinit and event-log replay. Bars overlay the two runs: █ is main, ┃ marks where this run lands, ░ bridges the gap when this run has more samples in a bucket.

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, deployment clocks) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · SL: stream latency (in-deployment write → read propagation, readAt - writtenAt) · SO: stream overhead (end-to-end write+consume time beyond the modelled generation window)

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 · stream latency: parallel reader/writer steps on a dedicated stream; SL is the in-deployment write->read propagation (readAt - writtenAt) · stream overhead (text): writer streams 300 variable-length text token deltas paced at 100/s for 3s (a haiku-size LLM's token throughput) while a parallel reader drains the whole stream; SO is the end-to-end write+consume time beyond the 3s generation window (overhead/backpressure) · stream overhead (structured): same workload as stream overhead (text), but each delta is an AI-SDK-style structured object ({ type: 'text-delta', id, text }) instead of a raw string, so the SO gap vs the text scenario is the added serialization cost

🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600 · SL 50/60/125 · SO 250/500/1000

All metrics are measured from deployment-side timestamps only. Runs are triggered by an in-deployment route that stamps the anchor (clientStart) right before start(), so the CI runner’s request and its path through api.vercel.com sit outside every measured window. TTFS = in-deployment start() → first step body (turbo uses the in-process fast path, non-turbo the dispatch path), and includes the VQS dispatch hop plus any /flow cold start. STSO/WO are measured between step bodies on the deployment. SL is measured inside the workflow (parallel reader/writer steps), so it no longer includes the api.vercel.com read path.

Cold starts are kept in the numbers on purpose — they are part of real bursty-workload latency. The workbench deployment cold-starts the /flow invocation for a large fraction of runs, inflating P75+; the Best column shows the fastest (warm-start) sample for comparison.

@alangenfeld
alangenfeldforce-pushed the alangenfeld/replay-divergence-visibility branch from 91db81f to a2ed26dCompareJuly 30, 2026 16:06
@alangenfeld
alangenfeldforce-pushed the alangenfeld/replay-divergence-visibility branch from a2ed26d to 1cf8d4fCompareJuly 30, 2026 22:25
@alangenfeld
feat(core): report replay divergence recovery
39fd41c
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
@alangenfeld
alangenfeldforce-pushed the alangenfeld/replay-divergence-visibility branch from 83b140d to 39fd41cCompareJuly 31, 2026 17:12
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No backport to stable for 4017597 (AI decision).

This is additive observability feature work, not a fix: it introduces a new replayDivergenceCount field on the CreateEventParams API surface, a new ReplayRecoveryReporter class, and wires the new telemetry through the runtime, suspension handler, step executor, and the world-vercel v4 wire format. No existing defect on stable is corrected — replay divergence recovery already works; this only makes it observable. Feature enhancements stay on main regardless of how cleanly they would cherry-pick.

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

4017597a5f6a54da7ea3bf467c8c63b3bf3bc845

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Report replay divergence recovery episodes by alangenfeld · Pull Request #3208 · vercel/workflow · GitHub
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Report replay divergence recovery episodes - #3208
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alangenfeld merged 1 commit into
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alangenfeld/replay-divergence-visibility
Jul 31, 2026
Merged
Report replay divergence recovery episodes#3208
alangenfeld merged 1 commit into
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alangenfeld/replay-divergence-visibility
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@alangenfeld
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Summary & Motivation
Adds an optional replayDivergenceCount on event writes, making replay-divergence outcomes observable without GET-side effects or VQS changes.
  • Set once per invocation, on the first natural write after replay reaches a deterministic boundary — recovery and retry-exhaustion both land on a real event write, so no extra request is needed to surface either.
  • Reporting is managed by a stateful ReplayRecoveryReporter, which claims that write so an invocation reports its recovery exactly once even when several suspension writes race, and releases the claim if the write fails.
  • Request telemetry only: worlds may report it, but must not persist it into the event log.
Test Plan
Unit tests added for the reporter, the runtime and suspension paths, and the v4 wire field; typecheck and the core/world-vercel suites pass locally.
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🦋 Changeset detected
Latest commit: 39fd41c
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 20 packages
NameType
@workflow/corePatch
@workflow/worldPatch
@workflow/world-vercelPatch
@workflow/buildersPatch
@workflow/cliPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/vitestPatch
@workflow/web-sharedPatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/world-localPatch
@workflow/world-postgresPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
Not sure what this means? Click here to learn what changesets are.
Click here if you're a maintainer who wants to add another changeset to this PR
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The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
example-nextjs-workflow-turbopackReadyReadyPreviewJul 31, 2026 5:17pm
example-nextjs-workflow-webpackReadyReadyPreviewJul 31, 2026 5:17pm
example-workflowReadyReadyPreviewJul 31, 2026 5:17pm
workbench-astro-workflowReadyReadyPreviewJul 31, 2026 5:17pm
workbench-express-workflowReadyReadyPreviewJul 31, 2026 5:17pm
workbench-fastify-workflowReadyReadyPreviewJul 31, 2026 5:17pm
workbench-hono-workflowReadyReadyPreviewJul 31, 2026 5:17pm
workbench-nestjs-workflowReadyReadyPreviewJul 31, 2026 5:17pm
workbench-nitro-workflowReadyReadyPreviewJul 31, 2026 5:17pm
workbench-nuxt-workflowReadyReadyPreviewJul 31, 2026 5:17pm
workbench-sveltekit-workflowReadyReadyPreviewJul 31, 2026 5:17pm
workbench-tanstack-start-workflowReadyReadyPreviewJul 31, 2026 5:17pm
workbench-vite-workflowReadyReadyPreviewJul 31, 2026 5:17pm
workflow-docsReadyReadyPreview, v0Jul 31, 2026 5:17pm
workflow-swc-playgroundReadyReadyPreviewJul 31, 2026 5:17pm
workflow-tarballsReadyReadyPreviewJul 31, 2026 5:17pm
workflow-webReadyReadyPreviewJul 31, 2026 5:17pm
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🧪 E2E Test Results
✅ All tests passed
E2E Test Summary
Summary
PassedFailedSkippedTotal
✅ ▲ Vercel Production145502391694
✅ 💻 Local Development162102271848
✅ 📦 Local Production162102271848
✅ 🐘 Local Postgres162102271848
✅ 🪟 Windows15400154
✅ 📋 Other102002121232
✅ vercel-multi-region270027
Total7519011328651
Details by Category
✅ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro126028
✅ example126028
✅ express126028
✅ fastify126028
✅ hono126028
✅ nextjs-turbopack15103
✅ nextjs-webpack15103
✅ nitro126028
✅ nuxt126028
✅ sveltekit14509
✅ vite126028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack15400
✅ 📋 Other
AppPassedFailedSkipped
✅ e2e-local-dev-nest-stable128026
✅ e2e-local-dev-tanstack-start-128026
✅ e2e-local-postgres-nest-stable128026
✅ e2e-local-postgres-tanstack-start-128026
✅ e2e-local-prod-nest-stable128026
✅ e2e-local-prod-tanstack-start-128026
✅ e2e-vercel-prod-nest126028
✅ e2e-vercel-prod-tanstack-start126028
✅ vercel-multi-region
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✅ nextjs-turbopack2700
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📊 Workflow Benchmarks
commit 39fd41c · Fri, 31 Jul 2026 17:36:11 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep258 (-51%) 💚1383 🔴 (+33%) 🔻1428 🔴 (+33%) 🔻1876 🔴 (+16%) 🔻30
TTFSstream242 (-74%) 💚1375 🔴 (+37%) 🔻1420 🔴 (+38%) 🔻1510 🔴 (+17%) 🔻30
TTFShook + stream395 (-6.2%)1602 🔴 (+21%) 🔻1636 🔴 (+21%) 🔻1786 🔴 (+0.9%)30
STSO1020 steps (inline)168 (+3.1%)486 (+2.5%)544 (+2.4%)747 (+11%)1016
STSO1020 steps (queue-hop)2441 (+17%) 🔻3262 (+2.0%)3262 (+2.0%)3262 (+2.0%)3
WO1020 steps425981 (+5.3%)425981 (+5.3%)425981 (+5.3%)425981 (+5.3%)1
SLstream latency102 (+24%) 🔻171 🔴 (+30%) 🔻183 🔴 (+24%) 🔻280 🔴 (+30%) 🔻30
SOstream overhead (text)131 (+30%) 🔻225 (+31%) 🔻241 (+13%)612 (+145%) 🔻30
SOstream overhead (structured)106 (-3.6%)194 (+15%)250 (+32%) 🔻377 (+65%) 🔻30
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 395612ms → this run 415909ms (Δ +20297ms, +5%)
 150-200 ms ┃████ main 36 this 10 -26
200-250 ms █████████┃███ main 92 this 74 -18
250-300 ms █████████████████┃██ main 145 this 130 -15
300-350 ms █████████████████┃█ main 139 this 133 -6
350-400 ms █████████████████┃█ main 138 this 130 -8
400-450 ms ██████████████████░░┃ main 134 this 150 +16
450-500 ms █████████████████████░░┃ main 150 this 174 +24
500-550 ms ███████████████░┃ main 107 this 121 +14
550-600 ms ██████┃ main 47 this 52 +5
600-650 ms █┃ main 16 this 17 +1
650-700 ms ┃ main 3 this 7 +4
700-750 ms ┃ main 3 this 9 +6
750-800 ms ┃ main 3 this 4 +1
800-850 ms ┃ main 1 this 1 +0
850-900 ms ┃ main 0 this 1 +1
950-1000 ms ┃ main 0 this 1 +1
1050-1100 ms ┃ main 1 this 0 -1
1200-1250 ms ┃ main 0 this 1 +1
1950-2000 ms ┃ main 1 this 0 -1
2350-2400 ms ┃ main 0 this 1 +1

1020 steps (queue-hop)
Cumulative STSO time: main 8138ms → this run 8741ms (Δ +603ms, +7%)
2000-2500 ms ███████████┃ main 1 this 1 +0
2500-3000 ms ┃███████████ main 1 this 0 -1
3000-3500 ms ████████████░░░░░░░░░░░┃ main 1 this 2 +1

📜 Previous results (3)
efc8f13
Thu, 30 Jul 2026 23:29:58 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1259 (+24%) 🔻1326 🔴 (+17%) 🔻1390 🔴 (+20%) 🔻1623 🔴 (+28%) 🔻30
TTFSstream1264 (+517%) 🔻1315 🔴 (+19%) 🔻1349 🔴 (+19%) 🔻1490 🔴 (-8.1%)30
TTFShook + stream1488 (+12%)1581 🔴 (+10%)1615 🔴 (+11%)1929 🔴 (+18%) 🔻30
STSO1020 steps (inline)140 (-24%) 💚458 (-12%)513 (-11%)707 (-13%)1016
STSO1020 steps (queue-hop)2388 (+18%) 🔻3508 (-25%) 💚3508 (-25%) 💚3508 (-25%) 💚3
WO1020 steps393536 (-13%)393536 (-13%)393536 (-13%)393536 (-13%)1
SLstream latency79 (-29%) 💚139 🔴 (-16%) 💚158 🔴 (-24%) 💚274 🔴 (-30%) 💚30
SOstream overhead (text)92 (-30%) 💚173 (-40%) 💚200 (-60%) 💚268 (-90%) 💚30
a2ed26d
Thu, 30 Jul 2026 16:30:42 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep243 (+10.0%)1323 🔴 (+24%) 🔻1370 🔴 (+25%) 🔻1440 🔴 (-6.2%)30
TTFSstream224 (-1.3%)1269 🔴 (+31%) 🔻1315 🔴 (+27%) 🔻1393 🔴 (+27%) 🔻30
TTFShook + stream438 (+4.0%)1506 🔴 (+25%) 🔻1551 🔴 (+24%) 🔻1925 🔴 (+35%) 🔻30
STSO1020 steps (1-20)196 (+11%)324 🔴 (+9.8%)388 🔴 (+14%)539 🔴 (+33%) 🔻19
STSO1020 steps (101-120)187 (-11%)279 🔴 (-19%) 💚298 🔴 (-29%) 💚310 🔴 (-72%) 💚19
STSO1020 steps (1001-1020)531 (+0.8%)572 🔴 (±0%)590 🔴 (-12%)611 🔴 (-14%)19
WO1020 steps416066 (-1.4%)416066 (-1.4%)416066 (-1.4%)416066 (-1.4%)1
SLstream latency86 (+1.2%)182 🔴 (+40%) 🔻208 🔴 (+25%) 🔻338 🔴 (-6.6%)30
SOstream overhead (text)108 (-10%)205 (-10%)243 (-7.3%)281 (-21%) 💚30
SOstream overhead (structured)133 (+6.4%)252 🔴 (+0.8%)305 (-4.4%)403 (-4.3%)30
91db81f
Thu, 30 Jul 2026 15:23:41 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1245 (+27%) 🔻1312 🔴 (+28%) 🔻1369 🔴 (+29%) 🔻1406 🔴 (+17%) 🔻30
TTFSstream1245 (+27%) 🔻1291 🔴 (+27%) 🔻1310 🔴 (+25%) 🔻1354 🔴 (+25%) 🔻30
TTFShook + stream585 (-51%) 💚1568 🔴 (+20%) 🔻1638 🔴 (+20%) 🔻1723 🔴 (+16%) 🔻30
STSO1020 steps (1-20)167 (-1.2%)269 🔴 (-1.8%)294 🔴 (-14%)405 🔴 (-4.9%)19
STSO1020 steps (101-120)193 (-5.9%)261 🔴 (-14%)287 🔴 (-21%) 💚333 🔴 (-16%) 💚19
STSO1020 steps (1001-1020)480 (+0.6%)532 🔴 (-2.2%)616 🔴 (-3.9%)1074 🔴 (+38%) 🔻19
WO1020 steps390171 (-3.9%)390171 (-3.9%)390171 (-3.9%)390171 (-3.9%)1
SLstream latency90 (±0%)146 🔴 (-5.8%)160 🔴 (-18%) 💚204 🔴 (-11%)30
SOstream overhead (text)101 (-1.9%)159 (-25%) 💚187 (-21%) 💚253 (-5.9%)30
SOstream overhead (structured)95 (-1.0%)151 (-28%) 💚200 (-25%) 💚282 (-37%) 💚30
ℹ️ Metric definitions & methodology
The collapsed STSO distribution section above buckets every step gap of the sequential-steps run (not a sampled window), split by whether the step ending the gap ran inline — in the same warm process as the step before it, so the gap is pure framework overhead — or after a queue-hop — the first step of a fresh process, which pays queue dispatch, client reinit and event-log replay. Bars overlay the two runs: █ is main, ┃ marks where this run lands, ░ bridges the gap when this run has more samples in a bucket.
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, deployment clocks) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · SL: stream latency (in-deployment write → read propagation, readAt - writtenAt) · SO: stream overhead (end-to-end write+consume time beyond the modelled generation window)
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 · stream latency: parallel reader/writer steps on a dedicated stream; SL is the in-deployment write->read propagation (readAt - writtenAt) · stream overhead (text): writer streams 300 variable-length text token deltas paced at 100/s for 3s (a haiku-size LLM's token throughput) while a parallel reader drains the whole stream; SO is the end-to-end write+consume time beyond the 3s generation window (overhead/backpressure) · stream overhead (structured): same workload as stream overhead (text), but each delta is an AI-SDK-style structured object ({ type: 'text-delta', id, text }) instead of a raw string, so the SO gap vs the text scenario is the added serialization cost
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600 · SL 50/60/125 · SO 250/500/1000
All metrics are measured from deployment-side timestamps only. Runs are triggered by an in-deployment route that stamps the anchor (clientStart) right before start(), so the CI runner’s request and its path through api.vercel.com sit outside every measured window. TTFS = in-deployment start() → first step body (turbo uses the in-process fast path, non-turbo the dispatch path), and includes the VQS dispatch hop plus any /flow cold start. STSO/WO are measured between step bodies on the deployment. SL is measured inside the workflow (parallel reader/writer steps), so it no longer includes the api.vercel.com read path.
Cold starts are kept in the numbers on purpose — they are part of real bursty-workload latency. The workbench deployment cold-starts the /flow invocation for a large fraction of runs, inflating P75+; the Best column shows the fastest (warm-start) sample for comparison.
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feat(core): report replay divergence recovery
39fd41c
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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No backport to stable for 4017597 (AI decision).
This is additive observability feature work, not a fix: it introduces a new replayDivergenceCount field on the CreateEventParams API surface, a new ReplayRecoveryReporter class, and wires the new telemetry through the runtime, suspension handler, step executor, and the world-vercel v4 wire format. No existing defect on stable is corrected — replay divergence recovery already works; this only makes it observable. Feature enhancements stay on main regardless of how cleanly they would cherry-pick.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
4017597a5f6a54da7ea3bf467c8c63b3bf3bc845


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@VaguelySeriousVaguelySeriousVaguelySerious approved these changes
@karthikscale3karthikscale3karthikscale3 approved these changes
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Report replay divergence recovery episodes by alangenfeld · Pull Request #3208 · vercel/workflow · GitHub
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Report replay divergence recovery episodes - #3208
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Report replay divergence recovery episodes#3208
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Summary & Motivation
Adds an optional replayDivergenceCount on event writes, making replay-divergence outcomes observable without GET-side effects or VQS changes.
  • Set once per invocation, on the first natural write after replay reaches a deterministic boundary — recovery and retry-exhaustion both land on a real event write, so no extra request is needed to surface either.
  • Reporting is managed by a stateful ReplayRecoveryReporter, which claims that write so an invocation reports its recovery exactly once even when several suspension writes race, and releases the claim if the write fails.
  • Request telemetry only: worlds may report it, but must not persist it into the event log.
Test Plan
Unit tests added for the reporter, the runtime and suspension paths, and the v4 wire field; typecheck and the core/world-vercel suites pass locally.
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🦋 Changeset detected
Latest commit: 39fd41c
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 20 packages
NameType
@workflow/corePatch
@workflow/worldPatch
@workflow/world-vercelPatch
@workflow/buildersPatch
@workflow/cliPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/vitestPatch
@workflow/web-sharedPatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/world-localPatch
@workflow/world-postgresPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
Not sure what this means? Click here to learn what changesets are.
Click here if you're a maintainer who wants to add another changeset to this PR
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The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
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🧪 E2E Test Results
✅ All tests passed
E2E Test Summary
Summary
PassedFailedSkippedTotal
✅ ▲ Vercel Production145502391694
✅ 💻 Local Development162102271848
✅ 📦 Local Production162102271848
✅ 🐘 Local Postgres162102271848
✅ 🪟 Windows15400154
✅ 📋 Other102002121232
✅ vercel-multi-region270027
Total7519011328651
Details by Category
✅ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro126028
✅ example126028
✅ express126028
✅ fastify126028
✅ hono126028
✅ nextjs-turbopack15103
✅ nextjs-webpack15103
✅ nitro126028
✅ nuxt126028
✅ sveltekit14509
✅ vite126028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack15400
✅ 📋 Other
AppPassedFailedSkipped
✅ e2e-local-dev-nest-stable128026
✅ e2e-local-dev-tanstack-start-128026
✅ e2e-local-postgres-nest-stable128026
✅ e2e-local-postgres-tanstack-start-128026
✅ e2e-local-prod-nest-stable128026
✅ e2e-local-prod-tanstack-start-128026
✅ e2e-vercel-prod-nest126028
✅ e2e-vercel-prod-tanstack-start126028
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit 39fd41c · Fri, 31 Jul 2026 17:36:11 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep258 (-51%) 💚1383 🔴 (+33%) 🔻1428 🔴 (+33%) 🔻1876 🔴 (+16%) 🔻30
TTFSstream242 (-74%) 💚1375 🔴 (+37%) 🔻1420 🔴 (+38%) 🔻1510 🔴 (+17%) 🔻30
TTFShook + stream395 (-6.2%)1602 🔴 (+21%) 🔻1636 🔴 (+21%) 🔻1786 🔴 (+0.9%)30
STSO1020 steps (inline)168 (+3.1%)486 (+2.5%)544 (+2.4%)747 (+11%)1016
STSO1020 steps (queue-hop)2441 (+17%) 🔻3262 (+2.0%)3262 (+2.0%)3262 (+2.0%)3
WO1020 steps425981 (+5.3%)425981 (+5.3%)425981 (+5.3%)425981 (+5.3%)1
SLstream latency102 (+24%) 🔻171 🔴 (+30%) 🔻183 🔴 (+24%) 🔻280 🔴 (+30%) 🔻30
SOstream overhead (text)131 (+30%) 🔻225 (+31%) 🔻241 (+13%)612 (+145%) 🔻30
SOstream overhead (structured)106 (-3.6%)194 (+15%)250 (+32%) 🔻377 (+65%) 🔻30
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 395612ms → this run 415909ms (Δ +20297ms, +5%)
 150-200 ms ┃████ main 36 this 10 -26
200-250 ms █████████┃███ main 92 this 74 -18
250-300 ms █████████████████┃██ main 145 this 130 -15
300-350 ms █████████████████┃█ main 139 this 133 -6
350-400 ms █████████████████┃█ main 138 this 130 -8
400-450 ms ██████████████████░░┃ main 134 this 150 +16
450-500 ms █████████████████████░░┃ main 150 this 174 +24
500-550 ms ███████████████░┃ main 107 this 121 +14
550-600 ms ██████┃ main 47 this 52 +5
600-650 ms █┃ main 16 this 17 +1
650-700 ms ┃ main 3 this 7 +4
700-750 ms ┃ main 3 this 9 +6
750-800 ms ┃ main 3 this 4 +1
800-850 ms ┃ main 1 this 1 +0
850-900 ms ┃ main 0 this 1 +1
950-1000 ms ┃ main 0 this 1 +1
1050-1100 ms ┃ main 1 this 0 -1
1200-1250 ms ┃ main 0 this 1 +1
1950-2000 ms ┃ main 1 this 0 -1
2350-2400 ms ┃ main 0 this 1 +1

1020 steps (queue-hop)
Cumulative STSO time: main 8138ms → this run 8741ms (Δ +603ms, +7%)
2000-2500 ms ███████████┃ main 1 this 1 +0
2500-3000 ms ┃███████████ main 1 this 0 -1
3000-3500 ms ████████████░░░░░░░░░░░┃ main 1 this 2 +1

📜 Previous results (3)
efc8f13
Thu, 30 Jul 2026 23:29:58 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1259 (+24%) 🔻1326 🔴 (+17%) 🔻1390 🔴 (+20%) 🔻1623 🔴 (+28%) 🔻30
TTFSstream1264 (+517%) 🔻1315 🔴 (+19%) 🔻1349 🔴 (+19%) 🔻1490 🔴 (-8.1%)30
TTFShook + stream1488 (+12%)1581 🔴 (+10%)1615 🔴 (+11%)1929 🔴 (+18%) 🔻30
STSO1020 steps (inline)140 (-24%) 💚458 (-12%)513 (-11%)707 (-13%)1016
STSO1020 steps (queue-hop)2388 (+18%) 🔻3508 (-25%) 💚3508 (-25%) 💚3508 (-25%) 💚3
WO1020 steps393536 (-13%)393536 (-13%)393536 (-13%)393536 (-13%)1
SLstream latency79 (-29%) 💚139 🔴 (-16%) 💚158 🔴 (-24%) 💚274 🔴 (-30%) 💚30
SOstream overhead (text)92 (-30%) 💚173 (-40%) 💚200 (-60%) 💚268 (-90%) 💚30
a2ed26d
Thu, 30 Jul 2026 16:30:42 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep243 (+10.0%)1323 🔴 (+24%) 🔻1370 🔴 (+25%) 🔻1440 🔴 (-6.2%)30
TTFSstream224 (-1.3%)1269 🔴 (+31%) 🔻1315 🔴 (+27%) 🔻1393 🔴 (+27%) 🔻30
TTFShook + stream438 (+4.0%)1506 🔴 (+25%) 🔻1551 🔴 (+24%) 🔻1925 🔴 (+35%) 🔻30
STSO1020 steps (1-20)196 (+11%)324 🔴 (+9.8%)388 🔴 (+14%)539 🔴 (+33%) 🔻19
STSO1020 steps (101-120)187 (-11%)279 🔴 (-19%) 💚298 🔴 (-29%) 💚310 🔴 (-72%) 💚19
STSO1020 steps (1001-1020)531 (+0.8%)572 🔴 (±0%)590 🔴 (-12%)611 🔴 (-14%)19
WO1020 steps416066 (-1.4%)416066 (-1.4%)416066 (-1.4%)416066 (-1.4%)1
SLstream latency86 (+1.2%)182 🔴 (+40%) 🔻208 🔴 (+25%) 🔻338 🔴 (-6.6%)30
SOstream overhead (text)108 (-10%)205 (-10%)243 (-7.3%)281 (-21%) 💚30
SOstream overhead (structured)133 (+6.4%)252 🔴 (+0.8%)305 (-4.4%)403 (-4.3%)30
91db81f
Thu, 30 Jul 2026 15:23:41 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1245 (+27%) 🔻1312 🔴 (+28%) 🔻1369 🔴 (+29%) 🔻1406 🔴 (+17%) 🔻30
TTFSstream1245 (+27%) 🔻1291 🔴 (+27%) 🔻1310 🔴 (+25%) 🔻1354 🔴 (+25%) 🔻30
TTFShook + stream585 (-51%) 💚1568 🔴 (+20%) 🔻1638 🔴 (+20%) 🔻1723 🔴 (+16%) 🔻30
STSO1020 steps (1-20)167 (-1.2%)269 🔴 (-1.8%)294 🔴 (-14%)405 🔴 (-4.9%)19
STSO1020 steps (101-120)193 (-5.9%)261 🔴 (-14%)287 🔴 (-21%) 💚333 🔴 (-16%) 💚19
STSO1020 steps (1001-1020)480 (+0.6%)532 🔴 (-2.2%)616 🔴 (-3.9%)1074 🔴 (+38%) 🔻19
WO1020 steps390171 (-3.9%)390171 (-3.9%)390171 (-3.9%)390171 (-3.9%)1
SLstream latency90 (±0%)146 🔴 (-5.8%)160 🔴 (-18%) 💚204 🔴 (-11%)30
SOstream overhead (text)101 (-1.9%)159 (-25%) 💚187 (-21%) 💚253 (-5.9%)30
SOstream overhead (structured)95 (-1.0%)151 (-28%) 💚200 (-25%) 💚282 (-37%) 💚30
ℹ️ Metric definitions & methodology
The collapsed STSO distribution section above buckets every step gap of the sequential-steps run (not a sampled window), split by whether the step ending the gap ran inline — in the same warm process as the step before it, so the gap is pure framework overhead — or after a queue-hop — the first step of a fresh process, which pays queue dispatch, client reinit and event-log replay. Bars overlay the two runs: █ is main, ┃ marks where this run lands, ░ bridges the gap when this run has more samples in a bucket.
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, deployment clocks) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · SL: stream latency (in-deployment write → read propagation, readAt - writtenAt) · SO: stream overhead (end-to-end write+consume time beyond the modelled generation window)
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 · stream latency: parallel reader/writer steps on a dedicated stream; SL is the in-deployment write->read propagation (readAt - writtenAt) · stream overhead (text): writer streams 300 variable-length text token deltas paced at 100/s for 3s (a haiku-size LLM's token throughput) while a parallel reader drains the whole stream; SO is the end-to-end write+consume time beyond the 3s generation window (overhead/backpressure) · stream overhead (structured): same workload as stream overhead (text), but each delta is an AI-SDK-style structured object ({ type: 'text-delta', id, text }) instead of a raw string, so the SO gap vs the text scenario is the added serialization cost
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600 · SL 50/60/125 · SO 250/500/1000
All metrics are measured from deployment-side timestamps only. Runs are triggered by an in-deployment route that stamps the anchor (clientStart) right before start(), so the CI runner’s request and its path through api.vercel.com sit outside every measured window. TTFS = in-deployment start() → first step body (turbo uses the in-process fast path, non-turbo the dispatch path), and includes the VQS dispatch hop plus any /flow cold start. STSO/WO are measured between step bodies on the deployment. SL is measured inside the workflow (parallel reader/writer steps), so it no longer includes the api.vercel.com read path.
Cold starts are kept in the numbers on purpose — they are part of real bursty-workload latency. The workbench deployment cold-starts the /flow invocation for a large fraction of runs, inflating P75+; the Best column shows the fastest (warm-start) sample for comparison.
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@alangenfeld
feat(core): report replay divergence recovery
39fd41c
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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No backport to stable for 4017597 (AI decision).
This is additive observability feature work, not a fix: it introduces a new replayDivergenceCount field on the CreateEventParams API surface, a new ReplayRecoveryReporter class, and wires the new telemetry through the runtime, suspension handler, step executor, and the world-vercel v4 wire format. No existing defect on stable is corrected — replay divergence recovery already works; this only makes it observable. Feature enhancements stay on main regardless of how cleanly they would cherry-pick.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
4017597a5f6a54da7ea3bf467c8c63b3bf3bc845


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Report replay divergence recovery episodes by alangenfeld · Pull Request #3208 · vercel/workflow · GitHub
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Report replay divergence recovery episodes - #3208
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Report replay divergence recovery episodes#3208
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Summary & Motivation
Adds an optional replayDivergenceCount on event writes, making replay-divergence outcomes observable without GET-side effects or VQS changes.
  • Set once per invocation, on the first natural write after replay reaches a deterministic boundary — recovery and retry-exhaustion both land on a real event write, so no extra request is needed to surface either.
  • Reporting is managed by a stateful ReplayRecoveryReporter, which claims that write so an invocation reports its recovery exactly once even when several suspension writes race, and releases the claim if the write fails.
  • Request telemetry only: worlds may report it, but must not persist it into the event log.
Test Plan
Unit tests added for the reporter, the runtime and suspension paths, and the v4 wire field; typecheck and the core/world-vercel suites pass locally.
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🦋 Changeset detected
Latest commit: 39fd41c
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 20 packages
NameType
@workflow/corePatch
@workflow/worldPatch
@workflow/world-vercelPatch
@workflow/buildersPatch
@workflow/cliPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/vitestPatch
@workflow/web-sharedPatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/world-localPatch
@workflow/world-postgresPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
Not sure what this means? Click here to learn what changesets are.
Click here if you're a maintainer who wants to add another changeset to this PR
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The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
example-nextjs-workflow-turbopackReadyReadyPreviewJul 31, 2026 5:17pm
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🧪 E2E Test Results
✅ All tests passed
E2E Test Summary
Summary
PassedFailedSkippedTotal
✅ ▲ Vercel Production145502391694
✅ 💻 Local Development162102271848
✅ 📦 Local Production162102271848
✅ 🐘 Local Postgres162102271848
✅ 🪟 Windows15400154
✅ 📋 Other102002121232
✅ vercel-multi-region270027
Total7519011328651
Details by Category
✅ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro126028
✅ example126028
✅ express126028
✅ fastify126028
✅ hono126028
✅ nextjs-turbopack15103
✅ nextjs-webpack15103
✅ nitro126028
✅ nuxt126028
✅ sveltekit14509
✅ vite126028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack15400
✅ 📋 Other
AppPassedFailedSkipped
✅ e2e-local-dev-nest-stable128026
✅ e2e-local-dev-tanstack-start-128026
✅ e2e-local-postgres-nest-stable128026
✅ e2e-local-postgres-tanstack-start-128026
✅ e2e-local-prod-nest-stable128026
✅ e2e-local-prod-tanstack-start-128026
✅ e2e-vercel-prod-nest126028
✅ e2e-vercel-prod-tanstack-start126028
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit 39fd41c · Fri, 31 Jul 2026 17:36:11 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep258 (-51%) 💚1383 🔴 (+33%) 🔻1428 🔴 (+33%) 🔻1876 🔴 (+16%) 🔻30
TTFSstream242 (-74%) 💚1375 🔴 (+37%) 🔻1420 🔴 (+38%) 🔻1510 🔴 (+17%) 🔻30
TTFShook + stream395 (-6.2%)1602 🔴 (+21%) 🔻1636 🔴 (+21%) 🔻1786 🔴 (+0.9%)30
STSO1020 steps (inline)168 (+3.1%)486 (+2.5%)544 (+2.4%)747 (+11%)1016
STSO1020 steps (queue-hop)2441 (+17%) 🔻3262 (+2.0%)3262 (+2.0%)3262 (+2.0%)3
WO1020 steps425981 (+5.3%)425981 (+5.3%)425981 (+5.3%)425981 (+5.3%)1
SLstream latency102 (+24%) 🔻171 🔴 (+30%) 🔻183 🔴 (+24%) 🔻280 🔴 (+30%) 🔻30
SOstream overhead (text)131 (+30%) 🔻225 (+31%) 🔻241 (+13%)612 (+145%) 🔻30
SOstream overhead (structured)106 (-3.6%)194 (+15%)250 (+32%) 🔻377 (+65%) 🔻30
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 395612ms → this run 415909ms (Δ +20297ms, +5%)
 150-200 ms ┃████ main 36 this 10 -26
200-250 ms █████████┃███ main 92 this 74 -18
250-300 ms █████████████████┃██ main 145 this 130 -15
300-350 ms █████████████████┃█ main 139 this 133 -6
350-400 ms █████████████████┃█ main 138 this 130 -8
400-450 ms ██████████████████░░┃ main 134 this 150 +16
450-500 ms █████████████████████░░┃ main 150 this 174 +24
500-550 ms ███████████████░┃ main 107 this 121 +14
550-600 ms ██████┃ main 47 this 52 +5
600-650 ms █┃ main 16 this 17 +1
650-700 ms ┃ main 3 this 7 +4
700-750 ms ┃ main 3 this 9 +6
750-800 ms ┃ main 3 this 4 +1
800-850 ms ┃ main 1 this 1 +0
850-900 ms ┃ main 0 this 1 +1
950-1000 ms ┃ main 0 this 1 +1
1050-1100 ms ┃ main 1 this 0 -1
1200-1250 ms ┃ main 0 this 1 +1
1950-2000 ms ┃ main 1 this 0 -1
2350-2400 ms ┃ main 0 this 1 +1

1020 steps (queue-hop)
Cumulative STSO time: main 8138ms → this run 8741ms (Δ +603ms, +7%)
2000-2500 ms ███████████┃ main 1 this 1 +0
2500-3000 ms ┃███████████ main 1 this 0 -1
3000-3500 ms ████████████░░░░░░░░░░░┃ main 1 this 2 +1

📜 Previous results (3)
efc8f13
Thu, 30 Jul 2026 23:29:58 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1259 (+24%) 🔻1326 🔴 (+17%) 🔻1390 🔴 (+20%) 🔻1623 🔴 (+28%) 🔻30
TTFSstream1264 (+517%) 🔻1315 🔴 (+19%) 🔻1349 🔴 (+19%) 🔻1490 🔴 (-8.1%)30
TTFShook + stream1488 (+12%)1581 🔴 (+10%)1615 🔴 (+11%)1929 🔴 (+18%) 🔻30
STSO1020 steps (inline)140 (-24%) 💚458 (-12%)513 (-11%)707 (-13%)1016
STSO1020 steps (queue-hop)2388 (+18%) 🔻3508 (-25%) 💚3508 (-25%) 💚3508 (-25%) 💚3
WO1020 steps393536 (-13%)393536 (-13%)393536 (-13%)393536 (-13%)1
SLstream latency79 (-29%) 💚139 🔴 (-16%) 💚158 🔴 (-24%) 💚274 🔴 (-30%) 💚30
SOstream overhead (text)92 (-30%) 💚173 (-40%) 💚200 (-60%) 💚268 (-90%) 💚30
a2ed26d
Thu, 30 Jul 2026 16:30:42 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep243 (+10.0%)1323 🔴 (+24%) 🔻1370 🔴 (+25%) 🔻1440 🔴 (-6.2%)30
TTFSstream224 (-1.3%)1269 🔴 (+31%) 🔻1315 🔴 (+27%) 🔻1393 🔴 (+27%) 🔻30
TTFShook + stream438 (+4.0%)1506 🔴 (+25%) 🔻1551 🔴 (+24%) 🔻1925 🔴 (+35%) 🔻30
STSO1020 steps (1-20)196 (+11%)324 🔴 (+9.8%)388 🔴 (+14%)539 🔴 (+33%) 🔻19
STSO1020 steps (101-120)187 (-11%)279 🔴 (-19%) 💚298 🔴 (-29%) 💚310 🔴 (-72%) 💚19
STSO1020 steps (1001-1020)531 (+0.8%)572 🔴 (±0%)590 🔴 (-12%)611 🔴 (-14%)19
WO1020 steps416066 (-1.4%)416066 (-1.4%)416066 (-1.4%)416066 (-1.4%)1
SLstream latency86 (+1.2%)182 🔴 (+40%) 🔻208 🔴 (+25%) 🔻338 🔴 (-6.6%)30
SOstream overhead (text)108 (-10%)205 (-10%)243 (-7.3%)281 (-21%) 💚30
SOstream overhead (structured)133 (+6.4%)252 🔴 (+0.8%)305 (-4.4%)403 (-4.3%)30
91db81f
Thu, 30 Jul 2026 15:23:41 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1245 (+27%) 🔻1312 🔴 (+28%) 🔻1369 🔴 (+29%) 🔻1406 🔴 (+17%) 🔻30
TTFSstream1245 (+27%) 🔻1291 🔴 (+27%) 🔻1310 🔴 (+25%) 🔻1354 🔴 (+25%) 🔻30
TTFShook + stream585 (-51%) 💚1568 🔴 (+20%) 🔻1638 🔴 (+20%) 🔻1723 🔴 (+16%) 🔻30
STSO1020 steps (1-20)167 (-1.2%)269 🔴 (-1.8%)294 🔴 (-14%)405 🔴 (-4.9%)19
STSO1020 steps (101-120)193 (-5.9%)261 🔴 (-14%)287 🔴 (-21%) 💚333 🔴 (-16%) 💚19
STSO1020 steps (1001-1020)480 (+0.6%)532 🔴 (-2.2%)616 🔴 (-3.9%)1074 🔴 (+38%) 🔻19
WO1020 steps390171 (-3.9%)390171 (-3.9%)390171 (-3.9%)390171 (-3.9%)1
SLstream latency90 (±0%)146 🔴 (-5.8%)160 🔴 (-18%) 💚204 🔴 (-11%)30
SOstream overhead (text)101 (-1.9%)159 (-25%) 💚187 (-21%) 💚253 (-5.9%)30
SOstream overhead (structured)95 (-1.0%)151 (-28%) 💚200 (-25%) 💚282 (-37%) 💚30
ℹ️ Metric definitions & methodology
The collapsed STSO distribution section above buckets every step gap of the sequential-steps run (not a sampled window), split by whether the step ending the gap ran inline — in the same warm process as the step before it, so the gap is pure framework overhead — or after a queue-hop — the first step of a fresh process, which pays queue dispatch, client reinit and event-log replay. Bars overlay the two runs: █ is main, ┃ marks where this run lands, ░ bridges the gap when this run has more samples in a bucket.
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, deployment clocks) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · SL: stream latency (in-deployment write → read propagation, readAt - writtenAt) · SO: stream overhead (end-to-end write+consume time beyond the modelled generation window)
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 · stream latency: parallel reader/writer steps on a dedicated stream; SL is the in-deployment write->read propagation (readAt - writtenAt) · stream overhead (text): writer streams 300 variable-length text token deltas paced at 100/s for 3s (a haiku-size LLM's token throughput) while a parallel reader drains the whole stream; SO is the end-to-end write+consume time beyond the 3s generation window (overhead/backpressure) · stream overhead (structured): same workload as stream overhead (text), but each delta is an AI-SDK-style structured object ({ type: 'text-delta', id, text }) instead of a raw string, so the SO gap vs the text scenario is the added serialization cost
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600 · SL 50/60/125 · SO 250/500/1000
All metrics are measured from deployment-side timestamps only. Runs are triggered by an in-deployment route that stamps the anchor (clientStart) right before start(), so the CI runner’s request and its path through api.vercel.com sit outside every measured window. TTFS = in-deployment start() → first step body (turbo uses the in-process fast path, non-turbo the dispatch path), and includes the VQS dispatch hop plus any /flow cold start. STSO/WO are measured between step bodies on the deployment. SL is measured inside the workflow (parallel reader/writer steps), so it no longer includes the api.vercel.com read path.
Cold starts are kept in the numbers on purpose — they are part of real bursty-workload latency. The workbench deployment cold-starts the /flow invocation for a large fraction of runs, inflating P75+; the Best column shows the fastest (warm-start) sample for comparison.
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feat(core): report replay divergence recovery
39fd41c
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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No backport to stable for 4017597 (AI decision).
This is additive observability feature work, not a fix: it introduces a new replayDivergenceCount field on the CreateEventParams API surface, a new ReplayRecoveryReporter class, and wires the new telemetry through the runtime, suspension handler, step executor, and the world-vercel v4 wire format. No existing defect on stable is corrected — replay divergence recovery already works; this only makes it observable. Feature enhancements stay on main regardless of how cleanly they would cherry-pick.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
4017597a5f6a54da7ea3bf467c8c63b3bf3bc845


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Report replay divergence recovery episodes by alangenfeld · Pull Request #3208 · vercel/workflow · GitHub
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Report replay divergence recovery episodes - #3208
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Report replay divergence recovery episodes#3208
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Summary & Motivation
Adds an optional replayDivergenceCount on event writes, making replay-divergence outcomes observable without GET-side effects or VQS changes.
  • Set once per invocation, on the first natural write after replay reaches a deterministic boundary — recovery and retry-exhaustion both land on a real event write, so no extra request is needed to surface either.
  • Reporting is managed by a stateful ReplayRecoveryReporter, which claims that write so an invocation reports its recovery exactly once even when several suspension writes race, and releases the claim if the write fails.
  • Request telemetry only: worlds may report it, but must not persist it into the event log.
Test Plan
Unit tests added for the reporter, the runtime and suspension paths, and the v4 wire field; typecheck and the core/world-vercel suites pass locally.
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🦋 Changeset detected
Latest commit: 39fd41c
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 20 packages
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@workflow/corePatch
@workflow/worldPatch
@workflow/world-vercelPatch
@workflow/buildersPatch
@workflow/cliPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/vitestPatch
@workflow/web-sharedPatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/world-localPatch
@workflow/world-postgresPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
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Click here if you're a maintainer who wants to add another changeset to this PR
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The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
example-nextjs-workflow-turbopackReadyReadyPreviewJul 31, 2026 5:17pm
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🧪 E2E Test Results
✅ All tests passed
E2E Test Summary
Summary
PassedFailedSkippedTotal
✅ ▲ Vercel Production145502391694
✅ 💻 Local Development162102271848
✅ 📦 Local Production162102271848
✅ 🐘 Local Postgres162102271848
✅ 🪟 Windows15400154
✅ 📋 Other102002121232
✅ vercel-multi-region270027
Total7519011328651
Details by Category
✅ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro126028
✅ example126028
✅ express126028
✅ fastify126028
✅ hono126028
✅ nextjs-turbopack15103
✅ nextjs-webpack15103
✅ nitro126028
✅ nuxt126028
✅ sveltekit14509
✅ vite126028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack15400
✅ 📋 Other
AppPassedFailedSkipped
✅ e2e-local-dev-nest-stable128026
✅ e2e-local-dev-tanstack-start-128026
✅ e2e-local-postgres-nest-stable128026
✅ e2e-local-postgres-tanstack-start-128026
✅ e2e-local-prod-nest-stable128026
✅ e2e-local-prod-tanstack-start-128026
✅ e2e-vercel-prod-nest126028
✅ e2e-vercel-prod-tanstack-start126028
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
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📊 Workflow Benchmarks
commit 39fd41c · Fri, 31 Jul 2026 17:36:11 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep258 (-51%) 💚1383 🔴 (+33%) 🔻1428 🔴 (+33%) 🔻1876 🔴 (+16%) 🔻30
TTFSstream242 (-74%) 💚1375 🔴 (+37%) 🔻1420 🔴 (+38%) 🔻1510 🔴 (+17%) 🔻30
TTFShook + stream395 (-6.2%)1602 🔴 (+21%) 🔻1636 🔴 (+21%) 🔻1786 🔴 (+0.9%)30
STSO1020 steps (inline)168 (+3.1%)486 (+2.5%)544 (+2.4%)747 (+11%)1016
STSO1020 steps (queue-hop)2441 (+17%) 🔻3262 (+2.0%)3262 (+2.0%)3262 (+2.0%)3
WO1020 steps425981 (+5.3%)425981 (+5.3%)425981 (+5.3%)425981 (+5.3%)1
SLstream latency102 (+24%) 🔻171 🔴 (+30%) 🔻183 🔴 (+24%) 🔻280 🔴 (+30%) 🔻30
SOstream overhead (text)131 (+30%) 🔻225 (+31%) 🔻241 (+13%)612 (+145%) 🔻30
SOstream overhead (structured)106 (-3.6%)194 (+15%)250 (+32%) 🔻377 (+65%) 🔻30
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 395612ms → this run 415909ms (Δ +20297ms, +5%)
 150-200 ms ┃████ main 36 this 10 -26
200-250 ms █████████┃███ main 92 this 74 -18
250-300 ms █████████████████┃██ main 145 this 130 -15
300-350 ms █████████████████┃█ main 139 this 133 -6
350-400 ms █████████████████┃█ main 138 this 130 -8
400-450 ms ██████████████████░░┃ main 134 this 150 +16
450-500 ms █████████████████████░░┃ main 150 this 174 +24
500-550 ms ███████████████░┃ main 107 this 121 +14
550-600 ms ██████┃ main 47 this 52 +5
600-650 ms █┃ main 16 this 17 +1
650-700 ms ┃ main 3 this 7 +4
700-750 ms ┃ main 3 this 9 +6
750-800 ms ┃ main 3 this 4 +1
800-850 ms ┃ main 1 this 1 +0
850-900 ms ┃ main 0 this 1 +1
950-1000 ms ┃ main 0 this 1 +1
1050-1100 ms ┃ main 1 this 0 -1
1200-1250 ms ┃ main 0 this 1 +1
1950-2000 ms ┃ main 1 this 0 -1
2350-2400 ms ┃ main 0 this 1 +1

1020 steps (queue-hop)
Cumulative STSO time: main 8138ms → this run 8741ms (Δ +603ms, +7%)
2000-2500 ms ███████████┃ main 1 this 1 +0
2500-3000 ms ┃███████████ main 1 this 0 -1
3000-3500 ms ████████████░░░░░░░░░░░┃ main 1 this 2 +1

📜 Previous results (3)
efc8f13
Thu, 30 Jul 2026 23:29:58 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1259 (+24%) 🔻1326 🔴 (+17%) 🔻1390 🔴 (+20%) 🔻1623 🔴 (+28%) 🔻30
TTFSstream1264 (+517%) 🔻1315 🔴 (+19%) 🔻1349 🔴 (+19%) 🔻1490 🔴 (-8.1%)30
TTFShook + stream1488 (+12%)1581 🔴 (+10%)1615 🔴 (+11%)1929 🔴 (+18%) 🔻30
STSO1020 steps (inline)140 (-24%) 💚458 (-12%)513 (-11%)707 (-13%)1016
STSO1020 steps (queue-hop)2388 (+18%) 🔻3508 (-25%) 💚3508 (-25%) 💚3508 (-25%) 💚3
WO1020 steps393536 (-13%)393536 (-13%)393536 (-13%)393536 (-13%)1
SLstream latency79 (-29%) 💚139 🔴 (-16%) 💚158 🔴 (-24%) 💚274 🔴 (-30%) 💚30
SOstream overhead (text)92 (-30%) 💚173 (-40%) 💚200 (-60%) 💚268 (-90%) 💚30
a2ed26d
Thu, 30 Jul 2026 16:30:42 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep243 (+10.0%)1323 🔴 (+24%) 🔻1370 🔴 (+25%) 🔻1440 🔴 (-6.2%)30
TTFSstream224 (-1.3%)1269 🔴 (+31%) 🔻1315 🔴 (+27%) 🔻1393 🔴 (+27%) 🔻30
TTFShook + stream438 (+4.0%)1506 🔴 (+25%) 🔻1551 🔴 (+24%) 🔻1925 🔴 (+35%) 🔻30
STSO1020 steps (1-20)196 (+11%)324 🔴 (+9.8%)388 🔴 (+14%)539 🔴 (+33%) 🔻19
STSO1020 steps (101-120)187 (-11%)279 🔴 (-19%) 💚298 🔴 (-29%) 💚310 🔴 (-72%) 💚19
STSO1020 steps (1001-1020)531 (+0.8%)572 🔴 (±0%)590 🔴 (-12%)611 🔴 (-14%)19
WO1020 steps416066 (-1.4%)416066 (-1.4%)416066 (-1.4%)416066 (-1.4%)1
SLstream latency86 (+1.2%)182 🔴 (+40%) 🔻208 🔴 (+25%) 🔻338 🔴 (-6.6%)30
SOstream overhead (text)108 (-10%)205 (-10%)243 (-7.3%)281 (-21%) 💚30
SOstream overhead (structured)133 (+6.4%)252 🔴 (+0.8%)305 (-4.4%)403 (-4.3%)30
91db81f
Thu, 30 Jul 2026 15:23:41 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1245 (+27%) 🔻1312 🔴 (+28%) 🔻1369 🔴 (+29%) 🔻1406 🔴 (+17%) 🔻30
TTFSstream1245 (+27%) 🔻1291 🔴 (+27%) 🔻1310 🔴 (+25%) 🔻1354 🔴 (+25%) 🔻30
TTFShook + stream585 (-51%) 💚1568 🔴 (+20%) 🔻1638 🔴 (+20%) 🔻1723 🔴 (+16%) 🔻30
STSO1020 steps (1-20)167 (-1.2%)269 🔴 (-1.8%)294 🔴 (-14%)405 🔴 (-4.9%)19
STSO1020 steps (101-120)193 (-5.9%)261 🔴 (-14%)287 🔴 (-21%) 💚333 🔴 (-16%) 💚19
STSO1020 steps (1001-1020)480 (+0.6%)532 🔴 (-2.2%)616 🔴 (-3.9%)1074 🔴 (+38%) 🔻19
WO1020 steps390171 (-3.9%)390171 (-3.9%)390171 (-3.9%)390171 (-3.9%)1
SLstream latency90 (±0%)146 🔴 (-5.8%)160 🔴 (-18%) 💚204 🔴 (-11%)30
SOstream overhead (text)101 (-1.9%)159 (-25%) 💚187 (-21%) 💚253 (-5.9%)30
SOstream overhead (structured)95 (-1.0%)151 (-28%) 💚200 (-25%) 💚282 (-37%) 💚30
ℹ️ Metric definitions & methodology
The collapsed STSO distribution section above buckets every step gap of the sequential-steps run (not a sampled window), split by whether the step ending the gap ran inline — in the same warm process as the step before it, so the gap is pure framework overhead — or after a queue-hop — the first step of a fresh process, which pays queue dispatch, client reinit and event-log replay. Bars overlay the two runs: █ is main, ┃ marks where this run lands, ░ bridges the gap when this run has more samples in a bucket.
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, deployment clocks) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · SL: stream latency (in-deployment write → read propagation, readAt - writtenAt) · SO: stream overhead (end-to-end write+consume time beyond the modelled generation window)
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 · stream latency: parallel reader/writer steps on a dedicated stream; SL is the in-deployment write->read propagation (readAt - writtenAt) · stream overhead (text): writer streams 300 variable-length text token deltas paced at 100/s for 3s (a haiku-size LLM's token throughput) while a parallel reader drains the whole stream; SO is the end-to-end write+consume time beyond the 3s generation window (overhead/backpressure) · stream overhead (structured): same workload as stream overhead (text), but each delta is an AI-SDK-style structured object ({ type: 'text-delta', id, text }) instead of a raw string, so the SO gap vs the text scenario is the added serialization cost
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600 · SL 50/60/125 · SO 250/500/1000
All metrics are measured from deployment-side timestamps only. Runs are triggered by an in-deployment route that stamps the anchor (clientStart) right before start(), so the CI runner’s request and its path through api.vercel.com sit outside every measured window. TTFS = in-deployment start() → first step body (turbo uses the in-process fast path, non-turbo the dispatch path), and includes the VQS dispatch hop plus any /flow cold start. STSO/WO are measured between step bodies on the deployment. SL is measured inside the workflow (parallel reader/writer steps), so it no longer includes the api.vercel.com read path.
Cold starts are kept in the numbers on purpose — they are part of real bursty-workload latency. The workbench deployment cold-starts the /flow invocation for a large fraction of runs, inflating P75+; the Best column shows the fastest (warm-start) sample for comparison.
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feat(core): report replay divergence recovery
39fd41c
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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No backport to stable for 4017597 (AI decision).
This is additive observability feature work, not a fix: it introduces a new replayDivergenceCount field on the CreateEventParams API surface, a new ReplayRecoveryReporter class, and wires the new telemetry through the runtime, suspension handler, step executor, and the world-vercel v4 wire format. No existing defect on stable is corrected — replay divergence recovery already works; this only makes it observable. Feature enhancements stay on main regardless of how cleanly they would cherry-pick.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
4017597a5f6a54da7ea3bf467c8c63b3bf3bc845


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Report replay divergence recovery episodes by alangenfeld · Pull Request #3208 · vercel/workflow · GitHub
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Report replay divergence recovery episodes - #3208
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Report replay divergence recovery episodes#3208
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Summary & Motivation
Adds an optional replayDivergenceCount on event writes, making replay-divergence outcomes observable without GET-side effects or VQS changes.
  • Set once per invocation, on the first natural write after replay reaches a deterministic boundary — recovery and retry-exhaustion both land on a real event write, so no extra request is needed to surface either.
  • Reporting is managed by a stateful ReplayRecoveryReporter, which claims that write so an invocation reports its recovery exactly once even when several suspension writes race, and releases the claim if the write fails.
  • Request telemetry only: worlds may report it, but must not persist it into the event log.
Test Plan
Unit tests added for the reporter, the runtime and suspension paths, and the v4 wire field; typecheck and the core/world-vercel suites pass locally.
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🦋 Changeset detected
Latest commit: 39fd41c
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 20 packages
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@workflow/corePatch
@workflow/worldPatch
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@workflow/nextPatch
@workflow/nitroPatch
@workflow/vitestPatch
@workflow/web-sharedPatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/world-localPatch
@workflow/world-postgresPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
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🧪 E2E Test Results
✅ All tests passed
E2E Test Summary
Summary
PassedFailedSkippedTotal
✅ ▲ Vercel Production145502391694
✅ 💻 Local Development162102271848
✅ 📦 Local Production162102271848
✅ 🐘 Local Postgres162102271848
✅ 🪟 Windows15400154
✅ 📋 Other102002121232
✅ vercel-multi-region270027
Total7519011328651
Details by Category
✅ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro126028
✅ example126028
✅ express126028
✅ fastify126028
✅ hono126028
✅ nextjs-turbopack15103
✅ nextjs-webpack15103
✅ nitro126028
✅ nuxt126028
✅ sveltekit14509
✅ vite126028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack15400
✅ 📋 Other
AppPassedFailedSkipped
✅ e2e-local-dev-nest-stable128026
✅ e2e-local-dev-tanstack-start-128026
✅ e2e-local-postgres-nest-stable128026
✅ e2e-local-postgres-tanstack-start-128026
✅ e2e-local-prod-nest-stable128026
✅ e2e-local-prod-tanstack-start-128026
✅ e2e-vercel-prod-nest126028
✅ e2e-vercel-prod-tanstack-start126028
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
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📊 Workflow Benchmarks
commit 39fd41c · Fri, 31 Jul 2026 17:36:11 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep258 (-51%) 💚1383 🔴 (+33%) 🔻1428 🔴 (+33%) 🔻1876 🔴 (+16%) 🔻30
TTFSstream242 (-74%) 💚1375 🔴 (+37%) 🔻1420 🔴 (+38%) 🔻1510 🔴 (+17%) 🔻30
TTFShook + stream395 (-6.2%)1602 🔴 (+21%) 🔻1636 🔴 (+21%) 🔻1786 🔴 (+0.9%)30
STSO1020 steps (inline)168 (+3.1%)486 (+2.5%)544 (+2.4%)747 (+11%)1016
STSO1020 steps (queue-hop)2441 (+17%) 🔻3262 (+2.0%)3262 (+2.0%)3262 (+2.0%)3
WO1020 steps425981 (+5.3%)425981 (+5.3%)425981 (+5.3%)425981 (+5.3%)1
SLstream latency102 (+24%) 🔻171 🔴 (+30%) 🔻183 🔴 (+24%) 🔻280 🔴 (+30%) 🔻30
SOstream overhead (text)131 (+30%) 🔻225 (+31%) 🔻241 (+13%)612 (+145%) 🔻30
SOstream overhead (structured)106 (-3.6%)194 (+15%)250 (+32%) 🔻377 (+65%) 🔻30
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 395612ms → this run 415909ms (Δ +20297ms, +5%)
 150-200 ms ┃████ main 36 this 10 -26
200-250 ms █████████┃███ main 92 this 74 -18
250-300 ms █████████████████┃██ main 145 this 130 -15
300-350 ms █████████████████┃█ main 139 this 133 -6
350-400 ms █████████████████┃█ main 138 this 130 -8
400-450 ms ██████████████████░░┃ main 134 this 150 +16
450-500 ms █████████████████████░░┃ main 150 this 174 +24
500-550 ms ███████████████░┃ main 107 this 121 +14
550-600 ms ██████┃ main 47 this 52 +5
600-650 ms █┃ main 16 this 17 +1
650-700 ms ┃ main 3 this 7 +4
700-750 ms ┃ main 3 this 9 +6
750-800 ms ┃ main 3 this 4 +1
800-850 ms ┃ main 1 this 1 +0
850-900 ms ┃ main 0 this 1 +1
950-1000 ms ┃ main 0 this 1 +1
1050-1100 ms ┃ main 1 this 0 -1
1200-1250 ms ┃ main 0 this 1 +1
1950-2000 ms ┃ main 1 this 0 -1
2350-2400 ms ┃ main 0 this 1 +1

1020 steps (queue-hop)
Cumulative STSO time: main 8138ms → this run 8741ms (Δ +603ms, +7%)
2000-2500 ms ███████████┃ main 1 this 1 +0
2500-3000 ms ┃███████████ main 1 this 0 -1
3000-3500 ms ████████████░░░░░░░░░░░┃ main 1 this 2 +1

📜 Previous results (3)
efc8f13
Thu, 30 Jul 2026 23:29:58 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1259 (+24%) 🔻1326 🔴 (+17%) 🔻1390 🔴 (+20%) 🔻1623 🔴 (+28%) 🔻30
TTFSstream1264 (+517%) 🔻1315 🔴 (+19%) 🔻1349 🔴 (+19%) 🔻1490 🔴 (-8.1%)30
TTFShook + stream1488 (+12%)1581 🔴 (+10%)1615 🔴 (+11%)1929 🔴 (+18%) 🔻30
STSO1020 steps (inline)140 (-24%) 💚458 (-12%)513 (-11%)707 (-13%)1016
STSO1020 steps (queue-hop)2388 (+18%) 🔻3508 (-25%) 💚3508 (-25%) 💚3508 (-25%) 💚3
WO1020 steps393536 (-13%)393536 (-13%)393536 (-13%)393536 (-13%)1
SLstream latency79 (-29%) 💚139 🔴 (-16%) 💚158 🔴 (-24%) 💚274 🔴 (-30%) 💚30
SOstream overhead (text)92 (-30%) 💚173 (-40%) 💚200 (-60%) 💚268 (-90%) 💚30
a2ed26d
Thu, 30 Jul 2026 16:30:42 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep243 (+10.0%)1323 🔴 (+24%) 🔻1370 🔴 (+25%) 🔻1440 🔴 (-6.2%)30
TTFSstream224 (-1.3%)1269 🔴 (+31%) 🔻1315 🔴 (+27%) 🔻1393 🔴 (+27%) 🔻30
TTFShook + stream438 (+4.0%)1506 🔴 (+25%) 🔻1551 🔴 (+24%) 🔻1925 🔴 (+35%) 🔻30
STSO1020 steps (1-20)196 (+11%)324 🔴 (+9.8%)388 🔴 (+14%)539 🔴 (+33%) 🔻19
STSO1020 steps (101-120)187 (-11%)279 🔴 (-19%) 💚298 🔴 (-29%) 💚310 🔴 (-72%) 💚19
STSO1020 steps (1001-1020)531 (+0.8%)572 🔴 (±0%)590 🔴 (-12%)611 🔴 (-14%)19
WO1020 steps416066 (-1.4%)416066 (-1.4%)416066 (-1.4%)416066 (-1.4%)1
SLstream latency86 (+1.2%)182 🔴 (+40%) 🔻208 🔴 (+25%) 🔻338 🔴 (-6.6%)30
SOstream overhead (text)108 (-10%)205 (-10%)243 (-7.3%)281 (-21%) 💚30
SOstream overhead (structured)133 (+6.4%)252 🔴 (+0.8%)305 (-4.4%)403 (-4.3%)30
91db81f
Thu, 30 Jul 2026 15:23:41 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1245 (+27%) 🔻1312 🔴 (+28%) 🔻1369 🔴 (+29%) 🔻1406 🔴 (+17%) 🔻30
TTFSstream1245 (+27%) 🔻1291 🔴 (+27%) 🔻1310 🔴 (+25%) 🔻1354 🔴 (+25%) 🔻30
TTFShook + stream585 (-51%) 💚1568 🔴 (+20%) 🔻1638 🔴 (+20%) 🔻1723 🔴 (+16%) 🔻30
STSO1020 steps (1-20)167 (-1.2%)269 🔴 (-1.8%)294 🔴 (-14%)405 🔴 (-4.9%)19
STSO1020 steps (101-120)193 (-5.9%)261 🔴 (-14%)287 🔴 (-21%) 💚333 🔴 (-16%) 💚19
STSO1020 steps (1001-1020)480 (+0.6%)532 🔴 (-2.2%)616 🔴 (-3.9%)1074 🔴 (+38%) 🔻19
WO1020 steps390171 (-3.9%)390171 (-3.9%)390171 (-3.9%)390171 (-3.9%)1
SLstream latency90 (±0%)146 🔴 (-5.8%)160 🔴 (-18%) 💚204 🔴 (-11%)30
SOstream overhead (text)101 (-1.9%)159 (-25%) 💚187 (-21%) 💚253 (-5.9%)30
SOstream overhead (structured)95 (-1.0%)151 (-28%) 💚200 (-25%) 💚282 (-37%) 💚30
ℹ️ Metric definitions & methodology
The collapsed STSO distribution section above buckets every step gap of the sequential-steps run (not a sampled window), split by whether the step ending the gap ran inline — in the same warm process as the step before it, so the gap is pure framework overhead — or after a queue-hop — the first step of a fresh process, which pays queue dispatch, client reinit and event-log replay. Bars overlay the two runs: █ is main, ┃ marks where this run lands, ░ bridges the gap when this run has more samples in a bucket.
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, deployment clocks) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · SL: stream latency (in-deployment write → read propagation, readAt - writtenAt) · SO: stream overhead (end-to-end write+consume time beyond the modelled generation window)
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 · stream latency: parallel reader/writer steps on a dedicated stream; SL is the in-deployment write->read propagation (readAt - writtenAt) · stream overhead (text): writer streams 300 variable-length text token deltas paced at 100/s for 3s (a haiku-size LLM's token throughput) while a parallel reader drains the whole stream; SO is the end-to-end write+consume time beyond the 3s generation window (overhead/backpressure) · stream overhead (structured): same workload as stream overhead (text), but each delta is an AI-SDK-style structured object ({ type: 'text-delta', id, text }) instead of a raw string, so the SO gap vs the text scenario is the added serialization cost
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600 · SL 50/60/125 · SO 250/500/1000
All metrics are measured from deployment-side timestamps only. Runs are triggered by an in-deployment route that stamps the anchor (clientStart) right before start(), so the CI runner’s request and its path through api.vercel.com sit outside every measured window. TTFS = in-deployment start() → first step body (turbo uses the in-process fast path, non-turbo the dispatch path), and includes the VQS dispatch hop plus any /flow cold start. STSO/WO are measured between step bodies on the deployment. SL is measured inside the workflow (parallel reader/writer steps), so it no longer includes the api.vercel.com read path.
Cold starts are kept in the numbers on purpose — they are part of real bursty-workload latency. The workbench deployment cold-starts the /flow invocation for a large fraction of runs, inflating P75+; the Best column shows the fastest (warm-start) sample for comparison.
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feat(core): report replay divergence recovery
39fd41c
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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No backport to stable for 4017597 (AI decision).
This is additive observability feature work, not a fix: it introduces a new replayDivergenceCount field on the CreateEventParams API surface, a new ReplayRecoveryReporter class, and wires the new telemetry through the runtime, suspension handler, step executor, and the world-vercel v4 wire format. No existing defect on stable is corrected — replay divergence recovery already works; this only makes it observable. Feature enhancements stay on main regardless of how cleanly they would cherry-pick.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
4017597a5f6a54da7ea3bf467c8c63b3bf3bc845


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@VaguelySeriousVaguelySeriousVaguelySerious approved these changes
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Report replay divergence recovery episodes by alangenfeld · Pull Request #3208 · vercel/workflow · GitHub
Skip to content
Report replay divergence recovery episodes - #3208
Merged
alangenfeld merged 1 commit into
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alangenfeld/replay-divergence-visibility
Jul 31, 2026
Merged
Report replay divergence recovery episodes#3208
alangenfeld merged 1 commit into
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Summary & Motivation
Adds an optional replayDivergenceCount on event writes, making replay-divergence outcomes observable without GET-side effects or VQS changes.
  • Set once per invocation, on the first natural write after replay reaches a deterministic boundary — recovery and retry-exhaustion both land on a real event write, so no extra request is needed to surface either.
  • Reporting is managed by a stateful ReplayRecoveryReporter, which claims that write so an invocation reports its recovery exactly once even when several suspension writes race, and releases the claim if the write fails.
  • Request telemetry only: worlds may report it, but must not persist it into the event log.
Test Plan
Unit tests added for the reporter, the runtime and suspension paths, and the v4 wire field; typecheck and the core/world-vercel suites pass locally.
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🦋 Changeset detected
Latest commit: 39fd41c
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 20 packages
NameType
@workflow/corePatch
@workflow/worldPatch
@workflow/world-vercelPatch
@workflow/buildersPatch
@workflow/cliPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/vitestPatch
@workflow/web-sharedPatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/world-localPatch
@workflow/world-postgresPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
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ProjectDeploymentActionsUpdated (UTC)
example-nextjs-workflow-turbopackReadyReadyPreviewJul 31, 2026 5:17pm
example-nextjs-workflow-webpackReadyReadyPreviewJul 31, 2026 5:17pm
example-workflowReadyReadyPreviewJul 31, 2026 5:17pm
workbench-astro-workflowReadyReadyPreviewJul 31, 2026 5:17pm
workbench-express-workflowReadyReadyPreviewJul 31, 2026 5:17pm
workbench-fastify-workflowReadyReadyPreviewJul 31, 2026 5:17pm
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workbench-tanstack-start-workflowReadyReadyPreviewJul 31, 2026 5:17pm
workbench-vite-workflowReadyReadyPreviewJul 31, 2026 5:17pm
workflow-docsReadyReadyPreview, v0Jul 31, 2026 5:17pm
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🧪 E2E Test Results
✅ All tests passed
E2E Test Summary
Summary
PassedFailedSkippedTotal
✅ ▲ Vercel Production145502391694
✅ 💻 Local Development162102271848
✅ 📦 Local Production162102271848
✅ 🐘 Local Postgres162102271848
✅ 🪟 Windows15400154
✅ 📋 Other102002121232
✅ vercel-multi-region270027
Total7519011328651
Details by Category
✅ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro126028
✅ example126028
✅ express126028
✅ fastify126028
✅ hono126028
✅ nextjs-turbopack15103
✅ nextjs-webpack15103
✅ nitro126028
✅ nuxt126028
✅ sveltekit14509
✅ vite126028
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AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
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✅ express-stable128026
✅ fastify-stable128026
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✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
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✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 🪟 Windows
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✅ nextjs-turbopack15400
✅ 📋 Other
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✅ e2e-local-postgres-tanstack-start-128026
✅ e2e-local-prod-nest-stable128026
✅ e2e-local-prod-tanstack-start-128026
✅ e2e-vercel-prod-nest126028
✅ e2e-vercel-prod-tanstack-start126028
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📊 Workflow Benchmarks
commit 39fd41c · Fri, 31 Jul 2026 17:36:11 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep258 (-51%) 💚1383 🔴 (+33%) 🔻1428 🔴 (+33%) 🔻1876 🔴 (+16%) 🔻30
TTFSstream242 (-74%) 💚1375 🔴 (+37%) 🔻1420 🔴 (+38%) 🔻1510 🔴 (+17%) 🔻30
TTFShook + stream395 (-6.2%)1602 🔴 (+21%) 🔻1636 🔴 (+21%) 🔻1786 🔴 (+0.9%)30
STSO1020 steps (inline)168 (+3.1%)486 (+2.5%)544 (+2.4%)747 (+11%)1016
STSO1020 steps (queue-hop)2441 (+17%) 🔻3262 (+2.0%)3262 (+2.0%)3262 (+2.0%)3
WO1020 steps425981 (+5.3%)425981 (+5.3%)425981 (+5.3%)425981 (+5.3%)1
SLstream latency102 (+24%) 🔻171 🔴 (+30%) 🔻183 🔴 (+24%) 🔻280 🔴 (+30%) 🔻30
SOstream overhead (text)131 (+30%) 🔻225 (+31%) 🔻241 (+13%)612 (+145%) 🔻30
SOstream overhead (structured)106 (-3.6%)194 (+15%)250 (+32%) 🔻377 (+65%) 🔻30
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 395612ms → this run 415909ms (Δ +20297ms, +5%)
 150-200 ms ┃████ main 36 this 10 -26
200-250 ms █████████┃███ main 92 this 74 -18
250-300 ms █████████████████┃██ main 145 this 130 -15
300-350 ms █████████████████┃█ main 139 this 133 -6
350-400 ms █████████████████┃█ main 138 this 130 -8
400-450 ms ██████████████████░░┃ main 134 this 150 +16
450-500 ms █████████████████████░░┃ main 150 this 174 +24
500-550 ms ███████████████░┃ main 107 this 121 +14
550-600 ms ██████┃ main 47 this 52 +5
600-650 ms █┃ main 16 this 17 +1
650-700 ms ┃ main 3 this 7 +4
700-750 ms ┃ main 3 this 9 +6
750-800 ms ┃ main 3 this 4 +1
800-850 ms ┃ main 1 this 1 +0
850-900 ms ┃ main 0 this 1 +1
950-1000 ms ┃ main 0 this 1 +1
1050-1100 ms ┃ main 1 this 0 -1
1200-1250 ms ┃ main 0 this 1 +1
1950-2000 ms ┃ main 1 this 0 -1
2350-2400 ms ┃ main 0 this 1 +1

1020 steps (queue-hop)
Cumulative STSO time: main 8138ms → this run 8741ms (Δ +603ms, +7%)
2000-2500 ms ███████████┃ main 1 this 1 +0
2500-3000 ms ┃███████████ main 1 this 0 -1
3000-3500 ms ████████████░░░░░░░░░░░┃ main 1 this 2 +1

📜 Previous results (3)
efc8f13
Thu, 30 Jul 2026 23:29:58 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1259 (+24%) 🔻1326 🔴 (+17%) 🔻1390 🔴 (+20%) 🔻1623 🔴 (+28%) 🔻30
TTFSstream1264 (+517%) 🔻1315 🔴 (+19%) 🔻1349 🔴 (+19%) 🔻1490 🔴 (-8.1%)30
TTFShook + stream1488 (+12%)1581 🔴 (+10%)1615 🔴 (+11%)1929 🔴 (+18%) 🔻30
STSO1020 steps (inline)140 (-24%) 💚458 (-12%)513 (-11%)707 (-13%)1016
STSO1020 steps (queue-hop)2388 (+18%) 🔻3508 (-25%) 💚3508 (-25%) 💚3508 (-25%) 💚3
WO1020 steps393536 (-13%)393536 (-13%)393536 (-13%)393536 (-13%)1
SLstream latency79 (-29%) 💚139 🔴 (-16%) 💚158 🔴 (-24%) 💚274 🔴 (-30%) 💚30
SOstream overhead (text)92 (-30%) 💚173 (-40%) 💚200 (-60%) 💚268 (-90%) 💚30
a2ed26d
Thu, 30 Jul 2026 16:30:42 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep243 (+10.0%)1323 🔴 (+24%) 🔻1370 🔴 (+25%) 🔻1440 🔴 (-6.2%)30
TTFSstream224 (-1.3%)1269 🔴 (+31%) 🔻1315 🔴 (+27%) 🔻1393 🔴 (+27%) 🔻30
TTFShook + stream438 (+4.0%)1506 🔴 (+25%) 🔻1551 🔴 (+24%) 🔻1925 🔴 (+35%) 🔻30
STSO1020 steps (1-20)196 (+11%)324 🔴 (+9.8%)388 🔴 (+14%)539 🔴 (+33%) 🔻19
STSO1020 steps (101-120)187 (-11%)279 🔴 (-19%) 💚298 🔴 (-29%) 💚310 🔴 (-72%) 💚19
STSO1020 steps (1001-1020)531 (+0.8%)572 🔴 (±0%)590 🔴 (-12%)611 🔴 (-14%)19
WO1020 steps416066 (-1.4%)416066 (-1.4%)416066 (-1.4%)416066 (-1.4%)1
SLstream latency86 (+1.2%)182 🔴 (+40%) 🔻208 🔴 (+25%) 🔻338 🔴 (-6.6%)30
SOstream overhead (text)108 (-10%)205 (-10%)243 (-7.3%)281 (-21%) 💚30
SOstream overhead (structured)133 (+6.4%)252 🔴 (+0.8%)305 (-4.4%)403 (-4.3%)30
91db81f
Thu, 30 Jul 2026 15:23:41 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1245 (+27%) 🔻1312 🔴 (+28%) 🔻1369 🔴 (+29%) 🔻1406 🔴 (+17%) 🔻30
TTFSstream1245 (+27%) 🔻1291 🔴 (+27%) 🔻1310 🔴 (+25%) 🔻1354 🔴 (+25%) 🔻30
TTFShook + stream585 (-51%) 💚1568 🔴 (+20%) 🔻1638 🔴 (+20%) 🔻1723 🔴 (+16%) 🔻30
STSO1020 steps (1-20)167 (-1.2%)269 🔴 (-1.8%)294 🔴 (-14%)405 🔴 (-4.9%)19
STSO1020 steps (101-120)193 (-5.9%)261 🔴 (-14%)287 🔴 (-21%) 💚333 🔴 (-16%) 💚19
STSO1020 steps (1001-1020)480 (+0.6%)532 🔴 (-2.2%)616 🔴 (-3.9%)1074 🔴 (+38%) 🔻19
WO1020 steps390171 (-3.9%)390171 (-3.9%)390171 (-3.9%)390171 (-3.9%)1
SLstream latency90 (±0%)146 🔴 (-5.8%)160 🔴 (-18%) 💚204 🔴 (-11%)30
SOstream overhead (text)101 (-1.9%)159 (-25%) 💚187 (-21%) 💚253 (-5.9%)30
SOstream overhead (structured)95 (-1.0%)151 (-28%) 💚200 (-25%) 💚282 (-37%) 💚30
ℹ️ Metric definitions & methodology
The collapsed STSO distribution section above buckets every step gap of the sequential-steps run (not a sampled window), split by whether the step ending the gap ran inline — in the same warm process as the step before it, so the gap is pure framework overhead — or after a queue-hop — the first step of a fresh process, which pays queue dispatch, client reinit and event-log replay. Bars overlay the two runs: █ is main, ┃ marks where this run lands, ░ bridges the gap when this run has more samples in a bucket.
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, deployment clocks) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · SL: stream latency (in-deployment write → read propagation, readAt - writtenAt) · SO: stream overhead (end-to-end write+consume time beyond the modelled generation window)
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 · stream latency: parallel reader/writer steps on a dedicated stream; SL is the in-deployment write->read propagation (readAt - writtenAt) · stream overhead (text): writer streams 300 variable-length text token deltas paced at 100/s for 3s (a haiku-size LLM's token throughput) while a parallel reader drains the whole stream; SO is the end-to-end write+consume time beyond the 3s generation window (overhead/backpressure) · stream overhead (structured): same workload as stream overhead (text), but each delta is an AI-SDK-style structured object ({ type: 'text-delta', id, text }) instead of a raw string, so the SO gap vs the text scenario is the added serialization cost
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600 · SL 50/60/125 · SO 250/500/1000
All metrics are measured from deployment-side timestamps only. Runs are triggered by an in-deployment route that stamps the anchor (clientStart) right before start(), so the CI runner’s request and its path through api.vercel.com sit outside every measured window. TTFS = in-deployment start() → first step body (turbo uses the in-process fast path, non-turbo the dispatch path), and includes the VQS dispatch hop plus any /flow cold start. STSO/WO are measured between step bodies on the deployment. SL is measured inside the workflow (parallel reader/writer steps), so it no longer includes the api.vercel.com read path.
Cold starts are kept in the numbers on purpose — they are part of real bursty-workload latency. The workbench deployment cold-starts the /flow invocation for a large fraction of runs, inflating P75+; the Best column shows the fastest (warm-start) sample for comparison.
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feat(core): report replay divergence recovery
39fd41c
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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No backport to stable for 4017597 (AI decision).
This is additive observability feature work, not a fix: it introduces a new replayDivergenceCount field on the CreateEventParams API surface, a new ReplayRecoveryReporter class, and wires the new telemetry through the runtime, suspension handler, step executor, and the world-vercel v4 wire format. No existing defect on stable is corrected — replay divergence recovery already works; this only makes it observable. Feature enhancements stay on main regardless of how cleanly they would cherry-pick.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
4017597a5f6a54da7ea3bf467c8c63b3bf3bc845


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Report replay divergence recovery episodes by alangenfeld · Pull Request #3208 · vercel/workflow · GitHub
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Report replay divergence recovery episodes - #3208
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Report replay divergence recovery episodes#3208
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Summary & Motivation
Adds an optional replayDivergenceCount on event writes, making replay-divergence outcomes observable without GET-side effects or VQS changes.
  • Set once per invocation, on the first natural write after replay reaches a deterministic boundary — recovery and retry-exhaustion both land on a real event write, so no extra request is needed to surface either.
  • Reporting is managed by a stateful ReplayRecoveryReporter, which claims that write so an invocation reports its recovery exactly once even when several suspension writes race, and releases the claim if the write fails.
  • Request telemetry only: worlds may report it, but must not persist it into the event log.
Test Plan
Unit tests added for the reporter, the runtime and suspension paths, and the v4 wire field; typecheck and the core/world-vercel suites pass locally.
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🦋 Changeset detected
Latest commit: 39fd41c
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 20 packages
NameType
@workflow/corePatch
@workflow/worldPatch
@workflow/world-vercelPatch
@workflow/buildersPatch
@workflow/cliPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/vitestPatch
@workflow/web-sharedPatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/world-localPatch
@workflow/world-postgresPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
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Not sure what this means? Click here to learn what changesets are.
Click here if you're a maintainer who wants to add another changeset to this PR
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The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
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🧪 E2E Test Results
✅ All tests passed
E2E Test Summary
Summary
PassedFailedSkippedTotal
✅ ▲ Vercel Production145502391694
✅ 💻 Local Development162102271848
✅ 📦 Local Production162102271848
✅ 🐘 Local Postgres162102271848
✅ 🪟 Windows15400154
✅ 📋 Other102002121232
✅ vercel-multi-region270027
Total7519011328651
Details by Category
✅ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro126028
✅ example126028
✅ express126028
✅ fastify126028
✅ hono126028
✅ nextjs-turbopack15103
✅ nextjs-webpack15103
✅ nitro126028
✅ nuxt126028
✅ sveltekit14509
✅ vite126028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable128026
✅ express-stable128026
✅ fastify-stable128026
✅ hono-stable128026
✅ nextjs-turbopack-canary135019
✅ nextjs-turbopack-stable15400
✅ nextjs-webpack-canary135019
✅ nextjs-webpack-stable15400
✅ nitro-stable128026
✅ nuxt-stable128026
✅ sveltekit-stable14707
✅ vite-stable128026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack15400
✅ 📋 Other
AppPassedFailedSkipped
✅ e2e-local-dev-nest-stable128026
✅ e2e-local-dev-tanstack-start-128026
✅ e2e-local-postgres-nest-stable128026
✅ e2e-local-postgres-tanstack-start-128026
✅ e2e-local-prod-nest-stable128026
✅ e2e-local-prod-tanstack-start-128026
✅ e2e-vercel-prod-nest126028
✅ e2e-vercel-prod-tanstack-start126028
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit 39fd41c · Fri, 31 Jul 2026 17:36:11 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep258 (-51%) 💚1383 🔴 (+33%) 🔻1428 🔴 (+33%) 🔻1876 🔴 (+16%) 🔻30
TTFSstream242 (-74%) 💚1375 🔴 (+37%) 🔻1420 🔴 (+38%) 🔻1510 🔴 (+17%) 🔻30
TTFShook + stream395 (-6.2%)1602 🔴 (+21%) 🔻1636 🔴 (+21%) 🔻1786 🔴 (+0.9%)30
STSO1020 steps (inline)168 (+3.1%)486 (+2.5%)544 (+2.4%)747 (+11%)1016
STSO1020 steps (queue-hop)2441 (+17%) 🔻3262 (+2.0%)3262 (+2.0%)3262 (+2.0%)3
WO1020 steps425981 (+5.3%)425981 (+5.3%)425981 (+5.3%)425981 (+5.3%)1
SLstream latency102 (+24%) 🔻171 🔴 (+30%) 🔻183 🔴 (+24%) 🔻280 🔴 (+30%) 🔻30
SOstream overhead (text)131 (+30%) 🔻225 (+31%) 🔻241 (+13%)612 (+145%) 🔻30
SOstream overhead (structured)106 (-3.6%)194 (+15%)250 (+32%) 🔻377 (+65%) 🔻30
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 395612ms → this run 415909ms (Δ +20297ms, +5%)
 150-200 ms ┃████ main 36 this 10 -26
200-250 ms █████████┃███ main 92 this 74 -18
250-300 ms █████████████████┃██ main 145 this 130 -15
300-350 ms █████████████████┃█ main 139 this 133 -6
350-400 ms █████████████████┃█ main 138 this 130 -8
400-450 ms ██████████████████░░┃ main 134 this 150 +16
450-500 ms █████████████████████░░┃ main 150 this 174 +24
500-550 ms ███████████████░┃ main 107 this 121 +14
550-600 ms ██████┃ main 47 this 52 +5
600-650 ms █┃ main 16 this 17 +1
650-700 ms ┃ main 3 this 7 +4
700-750 ms ┃ main 3 this 9 +6
750-800 ms ┃ main 3 this 4 +1
800-850 ms ┃ main 1 this 1 +0
850-900 ms ┃ main 0 this 1 +1
950-1000 ms ┃ main 0 this 1 +1
1050-1100 ms ┃ main 1 this 0 -1
1200-1250 ms ┃ main 0 this 1 +1
1950-2000 ms ┃ main 1 this 0 -1
2350-2400 ms ┃ main 0 this 1 +1

1020 steps (queue-hop)
Cumulative STSO time: main 8138ms → this run 8741ms (Δ +603ms, +7%)
2000-2500 ms ███████████┃ main 1 this 1 +0
2500-3000 ms ┃███████████ main 1 this 0 -1
3000-3500 ms ████████████░░░░░░░░░░░┃ main 1 this 2 +1

📜 Previous results (3)
efc8f13
Thu, 30 Jul 2026 23:29:58 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1259 (+24%) 🔻1326 🔴 (+17%) 🔻1390 🔴 (+20%) 🔻1623 🔴 (+28%) 🔻30
TTFSstream1264 (+517%) 🔻1315 🔴 (+19%) 🔻1349 🔴 (+19%) 🔻1490 🔴 (-8.1%)30
TTFShook + stream1488 (+12%)1581 🔴 (+10%)1615 🔴 (+11%)1929 🔴 (+18%) 🔻30
STSO1020 steps (inline)140 (-24%) 💚458 (-12%)513 (-11%)707 (-13%)1016
STSO1020 steps (queue-hop)2388 (+18%) 🔻3508 (-25%) 💚3508 (-25%) 💚3508 (-25%) 💚3
WO1020 steps393536 (-13%)393536 (-13%)393536 (-13%)393536 (-13%)1
SLstream latency79 (-29%) 💚139 🔴 (-16%) 💚158 🔴 (-24%) 💚274 🔴 (-30%) 💚30
SOstream overhead (text)92 (-30%) 💚173 (-40%) 💚200 (-60%) 💚268 (-90%) 💚30
a2ed26d
Thu, 30 Jul 2026 16:30:42 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep243 (+10.0%)1323 🔴 (+24%) 🔻1370 🔴 (+25%) 🔻1440 🔴 (-6.2%)30
TTFSstream224 (-1.3%)1269 🔴 (+31%) 🔻1315 🔴 (+27%) 🔻1393 🔴 (+27%) 🔻30
TTFShook + stream438 (+4.0%)1506 🔴 (+25%) 🔻1551 🔴 (+24%) 🔻1925 🔴 (+35%) 🔻30
STSO1020 steps (1-20)196 (+11%)324 🔴 (+9.8%)388 🔴 (+14%)539 🔴 (+33%) 🔻19
STSO1020 steps (101-120)187 (-11%)279 🔴 (-19%) 💚298 🔴 (-29%) 💚310 🔴 (-72%) 💚19
STSO1020 steps (1001-1020)531 (+0.8%)572 🔴 (±0%)590 🔴 (-12%)611 🔴 (-14%)19
WO1020 steps416066 (-1.4%)416066 (-1.4%)416066 (-1.4%)416066 (-1.4%)1
SLstream latency86 (+1.2%)182 🔴 (+40%) 🔻208 🔴 (+25%) 🔻338 🔴 (-6.6%)30
SOstream overhead (text)108 (-10%)205 (-10%)243 (-7.3%)281 (-21%) 💚30
SOstream overhead (structured)133 (+6.4%)252 🔴 (+0.8%)305 (-4.4%)403 (-4.3%)30
91db81f
Thu, 30 Jul 2026 15:23:41 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1245 (+27%) 🔻1312 🔴 (+28%) 🔻1369 🔴 (+29%) 🔻1406 🔴 (+17%) 🔻30
TTFSstream1245 (+27%) 🔻1291 🔴 (+27%) 🔻1310 🔴 (+25%) 🔻1354 🔴 (+25%) 🔻30
TTFShook + stream585 (-51%) 💚1568 🔴 (+20%) 🔻1638 🔴 (+20%) 🔻1723 🔴 (+16%) 🔻30
STSO1020 steps (1-20)167 (-1.2%)269 🔴 (-1.8%)294 🔴 (-14%)405 🔴 (-4.9%)19
STSO1020 steps (101-120)193 (-5.9%)261 🔴 (-14%)287 🔴 (-21%) 💚333 🔴 (-16%) 💚19
STSO1020 steps (1001-1020)480 (+0.6%)532 🔴 (-2.2%)616 🔴 (-3.9%)1074 🔴 (+38%) 🔻19
WO1020 steps390171 (-3.9%)390171 (-3.9%)390171 (-3.9%)390171 (-3.9%)1
SLstream latency90 (±0%)146 🔴 (-5.8%)160 🔴 (-18%) 💚204 🔴 (-11%)30
SOstream overhead (text)101 (-1.9%)159 (-25%) 💚187 (-21%) 💚253 (-5.9%)30
SOstream overhead (structured)95 (-1.0%)151 (-28%) 💚200 (-25%) 💚282 (-37%) 💚30
ℹ️ Metric definitions & methodology
The collapsed STSO distribution section above buckets every step gap of the sequential-steps run (not a sampled window), split by whether the step ending the gap ran inline — in the same warm process as the step before it, so the gap is pure framework overhead — or after a queue-hop — the first step of a fresh process, which pays queue dispatch, client reinit and event-log replay. Bars overlay the two runs: █ is main, ┃ marks where this run lands, ░ bridges the gap when this run has more samples in a bucket.
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, deployment clocks) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · SL: stream latency (in-deployment write → read propagation, readAt - writtenAt) · SO: stream overhead (end-to-end write+consume time beyond the modelled generation window)
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 · stream latency: parallel reader/writer steps on a dedicated stream; SL is the in-deployment write->read propagation (readAt - writtenAt) · stream overhead (text): writer streams 300 variable-length text token deltas paced at 100/s for 3s (a haiku-size LLM's token throughput) while a parallel reader drains the whole stream; SO is the end-to-end write+consume time beyond the 3s generation window (overhead/backpressure) · stream overhead (structured): same workload as stream overhead (text), but each delta is an AI-SDK-style structured object ({ type: 'text-delta', id, text }) instead of a raw string, so the SO gap vs the text scenario is the added serialization cost
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600 · SL 50/60/125 · SO 250/500/1000
All metrics are measured from deployment-side timestamps only. Runs are triggered by an in-deployment route that stamps the anchor (clientStart) right before start(), so the CI runner’s request and its path through api.vercel.com sit outside every measured window. TTFS = in-deployment start() → first step body (turbo uses the in-process fast path, non-turbo the dispatch path), and includes the VQS dispatch hop plus any /flow cold start. STSO/WO are measured between step bodies on the deployment. SL is measured inside the workflow (parallel reader/writer steps), so it no longer includes the api.vercel.com read path.
Cold starts are kept in the numbers on purpose — they are part of real bursty-workload latency. The workbench deployment cold-starts the /flow invocation for a large fraction of runs, inflating P75+; the Best column shows the fastest (warm-start) sample for comparison.
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feat(core): report replay divergence recovery
39fd41c
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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Jul 31, 2026

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No backport to stable for 4017597 (AI decision).
This is additive observability feature work, not a fix: it introduces a new replayDivergenceCount field on the CreateEventParams API surface, a new ReplayRecoveryReporter class, and wires the new telemetry through the runtime, suspension handler, step executor, and the world-vercel v4 wire format. No existing defect on stable is corrected — replay divergence recovery already works; this only makes it observable. Feature enhancements stay on main regardless of how cleanly they would cherry-pick.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
4017597a5f6a54da7ea3bf467c8c63b3bf3bc845


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@VaguelySeriousVaguelySeriousVaguelySerious approved these changes
@karthikscale3karthikscale3karthikscale3 approved these changes
@ijjkijjkAwaiting requested review from ijjk

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@alangenfeld@VaguelySerious@karthikscale3