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[e2e] Assert only the positive direction of step source maps - #3620

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[e2e] Assert only the positive direction of step source maps#3620
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@alangenfeld

@alangenfeldalangenfeld commented Aug 18, 2026

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Summary & Motivation

Source maps apply nondeterministically on lanes where hasStepSourceMaps() reports them unsupported (nuxt, nextjs-webpack), so asserting their absence turned that nondeterminism into a flake — one of the classes blocking e2e concurrency re-enablement (#2083). hasStepSourceMaps() stays the record to update when a lane starts mapping reliably, checked by the positive assertions on the lanes it does promise.

Test Plan

  • Existing e2e coverage runs in CI

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⚠️ No Changeset found

Latest commit: bf2fcee

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🧪 E2E Test Results

✅ All tests passed

⚠️ Flaky E2E Tests (passed on retry)

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

  • plainModuleDoneHook resumed via plain API route (o2flow shape) (nextjs-webpack)

🛠 Infra Events (absorbed by the harness)

Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.

  • run-pickup-stall · addTenWorkflow (tanstack-start) · at 20:18:22Z · abandoned wrun_01M0B8CBX8C2DS0XB2RG0N0KYJ

E2E Test Summary

Summary
PassedFailedSkippedTotal
✅ ▲ Vercel Production347407384212
✅ 💻 Local Development381005584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
✅ 🌐 Cross-language Conformance90128137
✅ vercel-multi-region270027
Total152520254017792
Details by Category

✅ ▲ Vercel Production

AppPassedFailedSkipped
✅ astro-node128028
✅ astro-quickjs128028
✅ example-node128028
✅ example-quickjs128028
✅ express-node128028
✅ express-quickjs128028
✅ fastify-node128028
✅ fastify-quickjs128028
✅ hono-node128028
✅ hono-quickjs128028
✅ nest-node128028
✅ nest-quickjs128028
✅ nextjs-turbopack-node15303
✅ nextjs-turbopack-quickjs15303
✅ nextjs-webpack-node15303
✅ nextjs-webpack-quickjs15303
✅ nitro-node128028
✅ nitro-quickjs128028
✅ nuxt-node128028
✅ nuxt-quickjs128028
✅ python-node80148
✅ sveltekit-node14709
✅ sveltekit-quickjs14709
✅ tanstack-start-node128028
✅ tanstack-start-quickjs128028
✅ vite-node128028
✅ vite-quickjs128028

✅ 💻 Local Development

AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026

✅ 📦 Local Production

AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026

✅ 🐘 Local Postgres

AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026

✅ 🪟 Windows

AppPassedFailedSkipped
✅ nextjs-turbopack-node15600
✅ nextjs-turbopack-quickjs15600

✅ 🌐 Cross-language Conformance

AppPassedFailedSkipped
✅ python90128

✅ vercel-multi-region

AppPassedFailedSkipped
✅ nextjs-turbopack2700

📋 View full workflow run

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📊 Workflow Benchmarks

commit bf2fcee · Tue, 18 Aug 2026 20:32:13 GMT · run logs

Backend: vercel · app: nextjs-turbopack

MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1514 (+45%) 🔻1611 🔴 (+36%) 🔻1643 🔴 (+25%) 🔻1662 🔴 (+3.7%)30
TTFSstream1497 (+190%) 🔻1601 🔴 (+33%) 🔻1620 🔴 (+30%) 🔻1758 🔴 (+35%) 🔻30
TTFShook + stream1736 (+233%) 🔻1942 🔴 (+28%) 🔻2002 🔴 (+26%) 🔻2075 🔴 (+16%) 🔻30
Fan-out TTFSPromise.all(100 steps)1233 (+1.1%)2827 (+8.3%)2939 (+11%)3509 (+32%) 🔻10
Fan-out TTLSPromise.all(100 steps)5143 (-2.6%)6861 (-1.1%)10730 (+48%) 🔻11550 (+33%) 🔻10
STSO1020 steps (inline)114 (-17%) 💚158 (-42%) 💚182 (-41%) 💚341 (-15%) 💚1019
WO1020 steps159621 (-37%) 💚159621 (-37%) 💚159621 (-37%) 💚159621 (-37%) 💚1
CRTTfirst chunk (pooled)107 (-4.5%)181 (+1.7%)349 (+2.9%)625 (+64%) 🔻28

Streams

Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (+1%)5 (±0%)5.1 (+1%)146 (-18%)162 (-39%)275 (-51%)4328 (+494%)139 (-60%)10
size sweep (100/s, 160B-12KB)100 (±0%)100 (-1%)334 (±0%)334 (-1%)169 (+1%)153 (-38%)222 (-45%)445 (-38%)123 (-37%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.2 (±0%)16.2 (±0%)16.2 (±0%)119 (-27%)150 (-14%)233 (-23%)670 (-6%)282 (-43%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.6 (±0%)355 (±0%)354 (±0%)140 (-8%)200 (-5%)1158 (+154%)5107 (+642%)2304 (+310%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)712 (±0%)110 (-33%)224 (-55%)335 (-51%)967 (+6%)297 (-43%)3
📈 STSO distribution vs main (inline / queue-hop histograms)

1020 steps (inline)

Cumulative STSO time: main 253258ms → this run 159304ms (Δ -93954ms, -37%)

100-150 ms █░░░░░░░░░░░░░░░░░░░░░░┃ main 2 this 600 +598
150-200 ms █████░░░░░░░░┃ main 131 this 346 +215
200-250 ms █┃████████████████ main 457 this 40 -417
250-300 ms ┃███████████ main 294 this 16 -278
300-350 ms ┃███ main 98 this 7 -91
350-400 ms ┃ main 25 this 2 -23
400-450 ms ┃ main 6 this 4 -2
450-500 ms ┃ main 2 this 1 -1
500-550 ms ┃ main 2 this 1 -1
550-600 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 0 this 1 +1
700-750 ms ┃ main 1 this 0 -1
📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▃█▂··▁· 321.6 (+62%) 121 (-21%) 275 (-51%) 4328 (+494%) 3000
sweep ······▃█▁···· 132.9 (-26%) 124 (-16%) 222 (-45%) 445 (-38%) 3000
gw 1x ·····▁▄█▁▁··· 127.7 (-20%) 115 (-12%) 233 (-23%) 670 (-6%) 5295
eve 1x ·····▁▅█▂▁▁▁▁ 314.7 (+74%) 114 (-17%) 1158 (+154%) 5107 (+642%) 5186
eve 2x ·····▁▂█▃▁▁·· 171 (-42%) 143 (-44%) 335 (-51%) 967 (+6%) 7779

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

control ▂▁▁▁▂█▇▇▆▆ 121–562ms
sweep █▂▂▂▁▂▃▂▃▃ 118–176ms
gw 1x █▃▃▁▂▁▃▁▄▂ 112–177ms
eve 1x ▁▁█▄▁▁▁▁▁▁ 110–1378ms
eve 2x ▃▁▂▁▁▂▃▅█▂ 139–261ms

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

sweep ▄▄██▆▄▁ 130–135ms

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

control ▁▁▂▂█▃▂▂▂▂ 29–114ms
sweep ▁█▇▅▅▆█▆█▆ 31–58ms
gw 1x ▆▄▄▁▅▃█▃▄▅ 29–42ms
eve 1x ▂▂█▁▂▁▂▂▁▁ 22–67ms
eve 2x █▄▂▂▄▃▃▃▁▅ 20–31ms
📜 Previous results (1)

ca5a215

Tue, 18 Aug 2026 19:47:23 GMT · run logs

vercel / nextjs-turbopack

MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1397 (+473%) 🔻1507 🔴 (+32%) 🔻1535 🔴 (+25%) 🔻1595 🔴 (-8.2%)30
TTFSstream1368 (+487%) 🔻1476 🔴 (+27%) 🔻1496 🔴 (+26%) 🔻1582 🔴 (+21%) 🔻30
TTFShook + stream1674 (+290%) 🔻1789 🔴 (+29%) 🔻1858 🔴 (+32%) 🔻6774 🔴 (+362%) 🔻30
Fan-out TTFSPromise.all(100 steps)1492 (+4.5%)2991 (+19%) 🔻3052 (+16%) 🔻4634 (+40%) 🔻10
Fan-out TTLSPromise.all(100 steps)6100 (-14%)7525 (-14%)7551 (-16%) 💚13928 (+54%) 🔻10
STSO1020 steps (inline)146 (-10%)179 (-40%) 💚201 (-43%) 💚323 (-41%) 💚1019
WO1020 steps178365 (-38%) 💚178365 (-38%) 💚178365 (-38%) 💚178365 (-38%) 💚1
CRTTfirst chunk (pooled)119 (+20%) 🔻234 (+38%) 🔻402 (+23%) 🔻543 (+19%) 🔻28

Streams

Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (±0%)5 (±0%)5.1 (+1%)153 (-1%)212 (-3%)374 (+13%)565 (-45%)209 (-35%)10
size sweep (100/s, 160B-12KB)100 (±0%)101 (±0%)334 (±0%)337 (±0%)140 (+12%)165 (-16%)235 (-76%)708 (-42%)122 (-41%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.9 (+1%)16.2 (±0%)16.3 (+1%)380 (+148%)231 (+18%)349 (+26%)955 (+18%)495 (+33%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)168 (+9%)182 (+15%)243 (+23%)491 (+19%)370 (+11%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)711 (±0%)180 (-13%)311 (+25%)722 (+118%)1881 (+64%)778 (+16%)3
ℹ️ Metric definitions & methodology

Streams: writer/reader sustained rates (steady window, 10% trimmed each side), first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.

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

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

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

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

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

Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041

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

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

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

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Sim World

Simulated world deterministic testing for races. Traces

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

fence=per-spec

scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0

Full trace: world-sim.txt

@alangenfeld
alangenfeld marked this pull request as ready for review August 18, 2026 19:32
@alangenfeld
alangenfeld requested a review from a team as a code ownerAugust 18, 2026 19:32
@alangenfeld
[e2e] Assert only the positive direction of step source maps
bf2fcee
Where hasStepSourceMaps() reports maps unsupported, the tests asserted
their absence - but on some lanes (nuxt, nextjs-webpack) source maps
apply nondeterministically, so the negative assertion pinned that
nondeterminism as a flake (#2083 measured this as one of the three
flake classes blocking e2e concurrency re-enablement). A stack that
resolves to source where none was promised is an improvement, not a
failure; hasStepSourceMaps() remains the record to update when a lane
starts mapping reliably, verified by the positive assertions on the
lanes it does promise.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
@alangenfeld
alangenfeldforce-pushed the alangenfeld/e2e-sourcemap-negative branch from ca5a215 to bf2fceeCompareAugust 18, 2026 20:10
@alangenfeld
alangenfeld merged commit fb6f265 into mainAug 18, 2026
172 checks passed
@alangenfeld
alangenfeld deleted the alangenfeld/e2e-sourcemap-negative branch August 18, 2026 20:47
github-actionsBot added a commit that referenced this pull request Aug 18, 2026
@github-actions
[e2e] Assert only the positive direction of step source maps (#3620)
991fa93
Where hasStepSourceMaps() reports maps unsupported, the tests asserted
their absence - but on some lanes (nuxt, nextjs-webpack) source maps
apply nondeterministically, so the negative assertion pinned that
nondeterminism as a flake (#2083 measured this as one of the three
flake classes blocking e2e concurrency re-enablement). A stack that
resolves to source where none was promised is an improvement, not a
failure; hasStepSourceMaps() remains the record to update when a lane
starts mapping reliably, verified by the positive assertions on the
lanes it does promise.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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Backport PR opened against stable: #3624. Merge conflicts were resolved by AI — please review carefully. (backport job run)

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[e2e] Assert only the positive direction of step source maps (#3620) (#…
234b904
…3624)
Co-authored-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit that referenced this pull request Aug 18, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
6713211
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit that referenced this pull request Aug 19, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
fc94f67
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Assert only the positive direction of step source maps by alangenfeld · Pull Request #3620 · vercel/workflow · GitHub
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[e2e] Assert only the positive direction of step source maps - #3620
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Summary & Motivation
Source maps apply nondeterministically on lanes where hasStepSourceMaps() reports them unsupported (nuxt, nextjs-webpack), so asserting their absence turned that nondeterminism into a flake — one of the classes blocking e2e concurrency re-enablement (#2083). hasStepSourceMaps() stays the record to update when a lane starts mapping reliably, checked by the positive assertions on the lanes it does promise.
Test Plan
  •  Existing e2e coverage runs in CI
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The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
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⚠️ No Changeset found
Latest commit: bf2fcee
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🧪 E2E Test Results
✅ All tests passed
⚠️ Flaky E2E Tests (passed on retry)
These tests failed at least once and passed on a retry. A recurring entry here is a real race worth investigating.
  • plainModuleDoneHook resumed via plain API route (o2flow shape) (nextjs-webpack)
🛠 Infra Events (absorbed by the harness)
Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.
  • run-pickup-stall · addTenWorkflow (tanstack-start) · at 20:18:22Z · abandoned wrun_01M0B8CBX8C2DS0XB2RG0N0KYJ
E2E Test Summary
Summary
PassedFailedSkippedTotal
✅ ▲ Vercel Production347407384212
✅ 💻 Local Development381005584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
✅ 🌐 Cross-language Conformance90128137
✅ vercel-multi-region270027
Total152520254017792
Details by Category
✅ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro-node128028
✅ astro-quickjs128028
✅ example-node128028
✅ example-quickjs128028
✅ express-node128028
✅ express-quickjs128028
✅ fastify-node128028
✅ fastify-quickjs128028
✅ hono-node128028
✅ hono-quickjs128028
✅ nest-node128028
✅ nest-quickjs128028
✅ nextjs-turbopack-node15303
✅ nextjs-turbopack-quickjs15303
✅ nextjs-webpack-node15303
✅ nextjs-webpack-quickjs15303
✅ nitro-node128028
✅ nitro-quickjs128028
✅ nuxt-node128028
✅ nuxt-quickjs128028
✅ python-node80148
✅ sveltekit-node14709
✅ sveltekit-quickjs14709
✅ tanstack-start-node128028
✅ tanstack-start-quickjs128028
✅ vite-node128028
✅ vite-quickjs128028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node15600
✅ nextjs-turbopack-quickjs15600
✅ 🌐 Cross-language Conformance
AppPassedFailedSkipped
✅ python90128
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit bf2fcee · Tue, 18 Aug 2026 20:32:13 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1514 (+45%) 🔻1611 🔴 (+36%) 🔻1643 🔴 (+25%) 🔻1662 🔴 (+3.7%)30
TTFSstream1497 (+190%) 🔻1601 🔴 (+33%) 🔻1620 🔴 (+30%) 🔻1758 🔴 (+35%) 🔻30
TTFShook + stream1736 (+233%) 🔻1942 🔴 (+28%) 🔻2002 🔴 (+26%) 🔻2075 🔴 (+16%) 🔻30
Fan-out TTFSPromise.all(100 steps)1233 (+1.1%)2827 (+8.3%)2939 (+11%)3509 (+32%) 🔻10
Fan-out TTLSPromise.all(100 steps)5143 (-2.6%)6861 (-1.1%)10730 (+48%) 🔻11550 (+33%) 🔻10
STSO1020 steps (inline)114 (-17%) 💚158 (-42%) 💚182 (-41%) 💚341 (-15%) 💚1019
WO1020 steps159621 (-37%) 💚159621 (-37%) 💚159621 (-37%) 💚159621 (-37%) 💚1
CRTTfirst chunk (pooled)107 (-4.5%)181 (+1.7%)349 (+2.9%)625 (+64%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (+1%)5 (±0%)5.1 (+1%)146 (-18%)162 (-39%)275 (-51%)4328 (+494%)139 (-60%)10
size sweep (100/s, 160B-12KB)100 (±0%)100 (-1%)334 (±0%)334 (-1%)169 (+1%)153 (-38%)222 (-45%)445 (-38%)123 (-37%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.2 (±0%)16.2 (±0%)16.2 (±0%)119 (-27%)150 (-14%)233 (-23%)670 (-6%)282 (-43%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.6 (±0%)355 (±0%)354 (±0%)140 (-8%)200 (-5%)1158 (+154%)5107 (+642%)2304 (+310%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)712 (±0%)110 (-33%)224 (-55%)335 (-51%)967 (+6%)297 (-43%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 253258ms → this run 159304ms (Δ -93954ms, -37%)
100-150 ms █░░░░░░░░░░░░░░░░░░░░░░┃ main 2 this 600 +598
150-200 ms █████░░░░░░░░┃ main 131 this 346 +215
200-250 ms █┃████████████████ main 457 this 40 -417
250-300 ms ┃███████████ main 294 this 16 -278
300-350 ms ┃███ main 98 this 7 -91
350-400 ms ┃ main 25 this 2 -23
400-450 ms ┃ main 6 this 4 -2
450-500 ms ┃ main 2 this 1 -1
500-550 ms ┃ main 2 this 1 -1
550-600 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 0 this 1 +1
700-750 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▃█▂··▁· 321.6 (+62%) 121 (-21%) 275 (-51%) 4328 (+494%) 3000
sweep ······▃█▁···· 132.9 (-26%) 124 (-16%) 222 (-45%) 445 (-38%) 3000
gw 1x ·····▁▄█▁▁··· 127.7 (-20%) 115 (-12%) 233 (-23%) 670 (-6%) 5295
eve 1x ·····▁▅█▂▁▁▁▁ 314.7 (+74%) 114 (-17%) 1158 (+154%) 5107 (+642%) 5186
eve 2x ·····▁▂█▃▁▁·· 171 (-42%) 143 (-44%) 335 (-51%) 967 (+6%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control ▂▁▁▁▂█▇▇▆▆ 121–562ms
sweep █▂▂▂▁▂▃▂▃▃ 118–176ms
gw 1x █▃▃▁▂▁▃▁▄▂ 112–177ms
eve 1x ▁▁█▄▁▁▁▁▁▁ 110–1378ms
eve 2x ▃▁▂▁▁▂▃▅█▂ 139–261ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▄▄██▆▄▁ 130–135ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▁▂▂█▃▂▂▂▂ 29–114ms
sweep ▁█▇▅▅▆█▆█▆ 31–58ms
gw 1x ▆▄▄▁▅▃█▃▄▅ 29–42ms
eve 1x ▂▂█▁▂▁▂▂▁▁ 22–67ms
eve 2x █▄▂▂▄▃▃▃▁▅ 20–31ms

📜 Previous results (1)
ca5a215
Tue, 18 Aug 2026 19:47:23 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1397 (+473%) 🔻1507 🔴 (+32%) 🔻1535 🔴 (+25%) 🔻1595 🔴 (-8.2%)30
TTFSstream1368 (+487%) 🔻1476 🔴 (+27%) 🔻1496 🔴 (+26%) 🔻1582 🔴 (+21%) 🔻30
TTFShook + stream1674 (+290%) 🔻1789 🔴 (+29%) 🔻1858 🔴 (+32%) 🔻6774 🔴 (+362%) 🔻30
Fan-out TTFSPromise.all(100 steps)1492 (+4.5%)2991 (+19%) 🔻3052 (+16%) 🔻4634 (+40%) 🔻10
Fan-out TTLSPromise.all(100 steps)6100 (-14%)7525 (-14%)7551 (-16%) 💚13928 (+54%) 🔻10
STSO1020 steps (inline)146 (-10%)179 (-40%) 💚201 (-43%) 💚323 (-41%) 💚1019
WO1020 steps178365 (-38%) 💚178365 (-38%) 💚178365 (-38%) 💚178365 (-38%) 💚1
CRTTfirst chunk (pooled)119 (+20%) 🔻234 (+38%) 🔻402 (+23%) 🔻543 (+19%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (±0%)5 (±0%)5.1 (+1%)153 (-1%)212 (-3%)374 (+13%)565 (-45%)209 (-35%)10
size sweep (100/s, 160B-12KB)100 (±0%)101 (±0%)334 (±0%)337 (±0%)140 (+12%)165 (-16%)235 (-76%)708 (-42%)122 (-41%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.9 (+1%)16.2 (±0%)16.3 (+1%)380 (+148%)231 (+18%)349 (+26%)955 (+18%)495 (+33%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)168 (+9%)182 (+15%)243 (+23%)491 (+19%)370 (+11%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)711 (±0%)180 (-13%)311 (+25%)722 (+118%)1881 (+64%)778 (+16%)3
ℹ️ Metric definitions & methodology
Streams: writer/reader sustained rates (steady window, 10% trimmed each side), first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.
The collapsed STSO distribution section above buckets every step gap, split inline (same warm process — pure framework overhead) vs queue-hop (fresh process — dispatch, reinit, replay). █ = main, ┃ = this run, ░ = fill.
The collapsed CRTT drill-down: per-variant RTT histograms (fixed log bins, · = empty) and mean RTT/positive-CDV profile lines over stream progress and chunk size. Histograms, avgs, and profiles merge exactly across runs; p50–p99 are percentile-of-percentiles. Per-index rows live in the artifacts.
Best/P75/P90/P99 deltas compare against the most recent benchmark run on main at the time of this run. 🔻 flags a delta worse than +15%, 💚 one better than −15%.
Metrics — TTFS: time to first step body (in-deployment start() → first step body) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)
Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles
Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600
All timestamps are deployment-side; runs are triggered in-deployment, so the CI runner and api.vercel.com sit outside every measured window. TTFS = start() → first step body (includes dispatch + any cold start); Fan-out TTFS/TTLS = first/last step completion of one Promise.all from the same anchor (the gap is the runtime’s fan-out spread); STSO/WO between step bodies; CRTT inside the workflow (excludes the api.vercel.com read path).
Cold starts stay in the numbers (real bursty-workload latency, inflates P75+); Best is the warm floor.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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[e2e] Assert only the positive direction of step source maps
bf2fcee
Where hasStepSourceMaps() reports maps unsupported, the tests asserted
their absence - but on some lanes (nuxt, nextjs-webpack) source maps
apply nondeterministically, so the negative assertion pinned that
nondeterminism as a flake (#2083 measured this as one of the three
flake classes blocking e2e concurrency re-enablement). A stack that
resolves to source where none was promised is an improvement, not a
failure; hasStepSourceMaps() remains the record to update when a lane
starts mapping reliably, verified by the positive assertions on the
lanes it does promise.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Assert only the positive direction of step source maps (#3620)
991fa93
Where hasStepSourceMaps() reports maps unsupported, the tests asserted
their absence - but on some lanes (nuxt, nextjs-webpack) source maps
apply nondeterministically, so the negative assertion pinned that
nondeterminism as a flake (#2083 measured this as one of the three
flake classes blocking e2e concurrency re-enablement). A stack that
resolves to source where none was promised is an improvement, not a
failure; hasStepSourceMaps() remains the record to update when a lane
starts mapping reliably, verified by the positive assertions on the
lanes it does promise.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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Backport PR opened against stable: #3624. Merge conflicts were resolved by AI — please review carefully. (backport job run)
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[e2e] Assert only the positive direction of step source maps (#3620) (#…
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…3624)
Co-authored-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Re-enable concurrent execution of the e2e suite
6713211
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit
that referenced
this pull request
Aug 19, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
fc94f67
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Assert only the positive direction of step source maps by alangenfeld · Pull Request #3620 · vercel/workflow · GitHub
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[e2e] Assert only the positive direction of step source maps - #3620
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Summary & Motivation
Source maps apply nondeterministically on lanes where hasStepSourceMaps() reports them unsupported (nuxt, nextjs-webpack), so asserting their absence turned that nondeterminism into a flake — one of the classes blocking e2e concurrency re-enablement (#2083). hasStepSourceMaps() stays the record to update when a lane starts mapping reliably, checked by the positive assertions on the lanes it does promise.
Test Plan
  •  Existing e2e coverage runs in CI
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The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
example-nextjs-workflow-turbopackReadyReadyPreviewAug 18, 2026 8:15pm
example-nextjs-workflow-webpackReadyReadyPreviewAug 18, 2026 8:15pm
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Latest commit: bf2fcee
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🧪 E2E Test Results
✅ All tests passed
⚠️ Flaky E2E Tests (passed on retry)
These tests failed at least once and passed on a retry. A recurring entry here is a real race worth investigating.
  • plainModuleDoneHook resumed via plain API route (o2flow shape) (nextjs-webpack)
🛠 Infra Events (absorbed by the harness)
Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.
  • run-pickup-stall · addTenWorkflow (tanstack-start) · at 20:18:22Z · abandoned wrun_01M0B8CBX8C2DS0XB2RG0N0KYJ
E2E Test Summary
Summary
PassedFailedSkippedTotal
✅ ▲ Vercel Production347407384212
✅ 💻 Local Development381005584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
✅ 🌐 Cross-language Conformance90128137
✅ vercel-multi-region270027
Total152520254017792
Details by Category
✅ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro-node128028
✅ astro-quickjs128028
✅ example-node128028
✅ example-quickjs128028
✅ express-node128028
✅ express-quickjs128028
✅ fastify-node128028
✅ fastify-quickjs128028
✅ hono-node128028
✅ hono-quickjs128028
✅ nest-node128028
✅ nest-quickjs128028
✅ nextjs-turbopack-node15303
✅ nextjs-turbopack-quickjs15303
✅ nextjs-webpack-node15303
✅ nextjs-webpack-quickjs15303
✅ nitro-node128028
✅ nitro-quickjs128028
✅ nuxt-node128028
✅ nuxt-quickjs128028
✅ python-node80148
✅ sveltekit-node14709
✅ sveltekit-quickjs14709
✅ tanstack-start-node128028
✅ tanstack-start-quickjs128028
✅ vite-node128028
✅ vite-quickjs128028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node15600
✅ nextjs-turbopack-quickjs15600
✅ 🌐 Cross-language Conformance
AppPassedFailedSkipped
✅ python90128
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit bf2fcee · Tue, 18 Aug 2026 20:32:13 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1514 (+45%) 🔻1611 🔴 (+36%) 🔻1643 🔴 (+25%) 🔻1662 🔴 (+3.7%)30
TTFSstream1497 (+190%) 🔻1601 🔴 (+33%) 🔻1620 🔴 (+30%) 🔻1758 🔴 (+35%) 🔻30
TTFShook + stream1736 (+233%) 🔻1942 🔴 (+28%) 🔻2002 🔴 (+26%) 🔻2075 🔴 (+16%) 🔻30
Fan-out TTFSPromise.all(100 steps)1233 (+1.1%)2827 (+8.3%)2939 (+11%)3509 (+32%) 🔻10
Fan-out TTLSPromise.all(100 steps)5143 (-2.6%)6861 (-1.1%)10730 (+48%) 🔻11550 (+33%) 🔻10
STSO1020 steps (inline)114 (-17%) 💚158 (-42%) 💚182 (-41%) 💚341 (-15%) 💚1019
WO1020 steps159621 (-37%) 💚159621 (-37%) 💚159621 (-37%) 💚159621 (-37%) 💚1
CRTTfirst chunk (pooled)107 (-4.5%)181 (+1.7%)349 (+2.9%)625 (+64%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (+1%)5 (±0%)5.1 (+1%)146 (-18%)162 (-39%)275 (-51%)4328 (+494%)139 (-60%)10
size sweep (100/s, 160B-12KB)100 (±0%)100 (-1%)334 (±0%)334 (-1%)169 (+1%)153 (-38%)222 (-45%)445 (-38%)123 (-37%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.2 (±0%)16.2 (±0%)16.2 (±0%)119 (-27%)150 (-14%)233 (-23%)670 (-6%)282 (-43%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.6 (±0%)355 (±0%)354 (±0%)140 (-8%)200 (-5%)1158 (+154%)5107 (+642%)2304 (+310%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)712 (±0%)110 (-33%)224 (-55%)335 (-51%)967 (+6%)297 (-43%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 253258ms → this run 159304ms (Δ -93954ms, -37%)
100-150 ms █░░░░░░░░░░░░░░░░░░░░░░┃ main 2 this 600 +598
150-200 ms █████░░░░░░░░┃ main 131 this 346 +215
200-250 ms █┃████████████████ main 457 this 40 -417
250-300 ms ┃███████████ main 294 this 16 -278
300-350 ms ┃███ main 98 this 7 -91
350-400 ms ┃ main 25 this 2 -23
400-450 ms ┃ main 6 this 4 -2
450-500 ms ┃ main 2 this 1 -1
500-550 ms ┃ main 2 this 1 -1
550-600 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 0 this 1 +1
700-750 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▃█▂··▁· 321.6 (+62%) 121 (-21%) 275 (-51%) 4328 (+494%) 3000
sweep ······▃█▁···· 132.9 (-26%) 124 (-16%) 222 (-45%) 445 (-38%) 3000
gw 1x ·····▁▄█▁▁··· 127.7 (-20%) 115 (-12%) 233 (-23%) 670 (-6%) 5295
eve 1x ·····▁▅█▂▁▁▁▁ 314.7 (+74%) 114 (-17%) 1158 (+154%) 5107 (+642%) 5186
eve 2x ·····▁▂█▃▁▁·· 171 (-42%) 143 (-44%) 335 (-51%) 967 (+6%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control ▂▁▁▁▂█▇▇▆▆ 121–562ms
sweep █▂▂▂▁▂▃▂▃▃ 118–176ms
gw 1x █▃▃▁▂▁▃▁▄▂ 112–177ms
eve 1x ▁▁█▄▁▁▁▁▁▁ 110–1378ms
eve 2x ▃▁▂▁▁▂▃▅█▂ 139–261ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▄▄██▆▄▁ 130–135ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▁▂▂█▃▂▂▂▂ 29–114ms
sweep ▁█▇▅▅▆█▆█▆ 31–58ms
gw 1x ▆▄▄▁▅▃█▃▄▅ 29–42ms
eve 1x ▂▂█▁▂▁▂▂▁▁ 22–67ms
eve 2x █▄▂▂▄▃▃▃▁▅ 20–31ms

📜 Previous results (1)
ca5a215
Tue, 18 Aug 2026 19:47:23 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1397 (+473%) 🔻1507 🔴 (+32%) 🔻1535 🔴 (+25%) 🔻1595 🔴 (-8.2%)30
TTFSstream1368 (+487%) 🔻1476 🔴 (+27%) 🔻1496 🔴 (+26%) 🔻1582 🔴 (+21%) 🔻30
TTFShook + stream1674 (+290%) 🔻1789 🔴 (+29%) 🔻1858 🔴 (+32%) 🔻6774 🔴 (+362%) 🔻30
Fan-out TTFSPromise.all(100 steps)1492 (+4.5%)2991 (+19%) 🔻3052 (+16%) 🔻4634 (+40%) 🔻10
Fan-out TTLSPromise.all(100 steps)6100 (-14%)7525 (-14%)7551 (-16%) 💚13928 (+54%) 🔻10
STSO1020 steps (inline)146 (-10%)179 (-40%) 💚201 (-43%) 💚323 (-41%) 💚1019
WO1020 steps178365 (-38%) 💚178365 (-38%) 💚178365 (-38%) 💚178365 (-38%) 💚1
CRTTfirst chunk (pooled)119 (+20%) 🔻234 (+38%) 🔻402 (+23%) 🔻543 (+19%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (±0%)5 (±0%)5.1 (+1%)153 (-1%)212 (-3%)374 (+13%)565 (-45%)209 (-35%)10
size sweep (100/s, 160B-12KB)100 (±0%)101 (±0%)334 (±0%)337 (±0%)140 (+12%)165 (-16%)235 (-76%)708 (-42%)122 (-41%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.9 (+1%)16.2 (±0%)16.3 (+1%)380 (+148%)231 (+18%)349 (+26%)955 (+18%)495 (+33%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)168 (+9%)182 (+15%)243 (+23%)491 (+19%)370 (+11%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)711 (±0%)180 (-13%)311 (+25%)722 (+118%)1881 (+64%)778 (+16%)3
ℹ️ Metric definitions & methodology
Streams: writer/reader sustained rates (steady window, 10% trimmed each side), first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.
The collapsed STSO distribution section above buckets every step gap, split inline (same warm process — pure framework overhead) vs queue-hop (fresh process — dispatch, reinit, replay). █ = main, ┃ = this run, ░ = fill.
The collapsed CRTT drill-down: per-variant RTT histograms (fixed log bins, · = empty) and mean RTT/positive-CDV profile lines over stream progress and chunk size. Histograms, avgs, and profiles merge exactly across runs; p50–p99 are percentile-of-percentiles. Per-index rows live in the artifacts.
Best/P75/P90/P99 deltas compare against the most recent benchmark run on main at the time of this run. 🔻 flags a delta worse than +15%, 💚 one better than −15%.
Metrics — TTFS: time to first step body (in-deployment start() → first step body) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)
Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles
Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600
All timestamps are deployment-side; runs are triggered in-deployment, so the CI runner and api.vercel.com sit outside every measured window. TTFS = start() → first step body (includes dispatch + any cold start); Fan-out TTFS/TTLS = first/last step completion of one Promise.all from the same anchor (the gap is the runtime’s fan-out spread); STSO/WO between step bodies; CRTT inside the workflow (excludes the api.vercel.com read path).
Cold starts stay in the numbers (real bursty-workload latency, inflates P75+); Best is the warm floor.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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[e2e] Assert only the positive direction of step source maps
bf2fcee
Where hasStepSourceMaps() reports maps unsupported, the tests asserted
their absence - but on some lanes (nuxt, nextjs-webpack) source maps
apply nondeterministically, so the negative assertion pinned that
nondeterminism as a flake (#2083 measured this as one of the three
flake classes blocking e2e concurrency re-enablement). A stack that
resolves to source where none was promised is an improvement, not a
failure; hasStepSourceMaps() remains the record to update when a lane
starts mapping reliably, verified by the positive assertions on the
lanes it does promise.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Assert only the positive direction of step source maps (#3620)
991fa93
Where hasStepSourceMaps() reports maps unsupported, the tests asserted
their absence - but on some lanes (nuxt, nextjs-webpack) source maps
apply nondeterministically, so the negative assertion pinned that
nondeterminism as a flake (#2083 measured this as one of the three
flake classes blocking e2e concurrency re-enablement). A stack that
resolves to source where none was promised is an improvement, not a
failure; hasStepSourceMaps() remains the record to update when a lane
starts mapping reliably, verified by the positive assertions on the
lanes it does promise.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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Backport PR opened against stable: #3624. Merge conflicts were resolved by AI — please review carefully. (backport job run)
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[e2e] Assert only the positive direction of step source maps (#3620) (#…
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…3624)
Co-authored-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Re-enable concurrent execution of the e2e suite
6713211
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit
that referenced
this pull request
Aug 19, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
fc94f67
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Assert only the positive direction of step source maps by alangenfeld · Pull Request #3620 · vercel/workflow · GitHub
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Summary & Motivation
Source maps apply nondeterministically on lanes where hasStepSourceMaps() reports them unsupported (nuxt, nextjs-webpack), so asserting their absence turned that nondeterminism into a flake — one of the classes blocking e2e concurrency re-enablement (#2083). hasStepSourceMaps() stays the record to update when a lane starts mapping reliably, checked by the positive assertions on the lanes it does promise.
Test Plan
  •  Existing e2e coverage runs in CI
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The latest updates on your projects. Learn more about Vercel for GitHub.
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🧪 E2E Test Results
✅ All tests passed
⚠️ Flaky E2E Tests (passed on retry)
These tests failed at least once and passed on a retry. A recurring entry here is a real race worth investigating.
  • plainModuleDoneHook resumed via plain API route (o2flow shape) (nextjs-webpack)
🛠 Infra Events (absorbed by the harness)
Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.
  • run-pickup-stall · addTenWorkflow (tanstack-start) · at 20:18:22Z · abandoned wrun_01M0B8CBX8C2DS0XB2RG0N0KYJ
E2E Test Summary
Summary
PassedFailedSkippedTotal
✅ ▲ Vercel Production347407384212
✅ 💻 Local Development381005584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
✅ 🌐 Cross-language Conformance90128137
✅ vercel-multi-region270027
Total152520254017792
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✅ nest-stable-node130026
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✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
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✅ nitro-stable-node130026
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✅ 📦 Local Production
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✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
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✅ nitro-stable-node130026
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📊 Workflow Benchmarks
commit bf2fcee · Tue, 18 Aug 2026 20:32:13 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1514 (+45%) 🔻1611 🔴 (+36%) 🔻1643 🔴 (+25%) 🔻1662 🔴 (+3.7%)30
TTFSstream1497 (+190%) 🔻1601 🔴 (+33%) 🔻1620 🔴 (+30%) 🔻1758 🔴 (+35%) 🔻30
TTFShook + stream1736 (+233%) 🔻1942 🔴 (+28%) 🔻2002 🔴 (+26%) 🔻2075 🔴 (+16%) 🔻30
Fan-out TTFSPromise.all(100 steps)1233 (+1.1%)2827 (+8.3%)2939 (+11%)3509 (+32%) 🔻10
Fan-out TTLSPromise.all(100 steps)5143 (-2.6%)6861 (-1.1%)10730 (+48%) 🔻11550 (+33%) 🔻10
STSO1020 steps (inline)114 (-17%) 💚158 (-42%) 💚182 (-41%) 💚341 (-15%) 💚1019
WO1020 steps159621 (-37%) 💚159621 (-37%) 💚159621 (-37%) 💚159621 (-37%) 💚1
CRTTfirst chunk (pooled)107 (-4.5%)181 (+1.7%)349 (+2.9%)625 (+64%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (+1%)5 (±0%)5.1 (+1%)146 (-18%)162 (-39%)275 (-51%)4328 (+494%)139 (-60%)10
size sweep (100/s, 160B-12KB)100 (±0%)100 (-1%)334 (±0%)334 (-1%)169 (+1%)153 (-38%)222 (-45%)445 (-38%)123 (-37%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.2 (±0%)16.2 (±0%)16.2 (±0%)119 (-27%)150 (-14%)233 (-23%)670 (-6%)282 (-43%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.6 (±0%)355 (±0%)354 (±0%)140 (-8%)200 (-5%)1158 (+154%)5107 (+642%)2304 (+310%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)712 (±0%)110 (-33%)224 (-55%)335 (-51%)967 (+6%)297 (-43%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 253258ms → this run 159304ms (Δ -93954ms, -37%)
100-150 ms █░░░░░░░░░░░░░░░░░░░░░░┃ main 2 this 600 +598
150-200 ms █████░░░░░░░░┃ main 131 this 346 +215
200-250 ms █┃████████████████ main 457 this 40 -417
250-300 ms ┃███████████ main 294 this 16 -278
300-350 ms ┃███ main 98 this 7 -91
350-400 ms ┃ main 25 this 2 -23
400-450 ms ┃ main 6 this 4 -2
450-500 ms ┃ main 2 this 1 -1
500-550 ms ┃ main 2 this 1 -1
550-600 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 0 this 1 +1
700-750 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▃█▂··▁· 321.6 (+62%) 121 (-21%) 275 (-51%) 4328 (+494%) 3000
sweep ······▃█▁···· 132.9 (-26%) 124 (-16%) 222 (-45%) 445 (-38%) 3000
gw 1x ·····▁▄█▁▁··· 127.7 (-20%) 115 (-12%) 233 (-23%) 670 (-6%) 5295
eve 1x ·····▁▅█▂▁▁▁▁ 314.7 (+74%) 114 (-17%) 1158 (+154%) 5107 (+642%) 5186
eve 2x ·····▁▂█▃▁▁·· 171 (-42%) 143 (-44%) 335 (-51%) 967 (+6%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control ▂▁▁▁▂█▇▇▆▆ 121–562ms
sweep █▂▂▂▁▂▃▂▃▃ 118–176ms
gw 1x █▃▃▁▂▁▃▁▄▂ 112–177ms
eve 1x ▁▁█▄▁▁▁▁▁▁ 110–1378ms
eve 2x ▃▁▂▁▁▂▃▅█▂ 139–261ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▄▄██▆▄▁ 130–135ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▁▂▂█▃▂▂▂▂ 29–114ms
sweep ▁█▇▅▅▆█▆█▆ 31–58ms
gw 1x ▆▄▄▁▅▃█▃▄▅ 29–42ms
eve 1x ▂▂█▁▂▁▂▂▁▁ 22–67ms
eve 2x █▄▂▂▄▃▃▃▁▅ 20–31ms

📜 Previous results (1)
ca5a215
Tue, 18 Aug 2026 19:47:23 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1397 (+473%) 🔻1507 🔴 (+32%) 🔻1535 🔴 (+25%) 🔻1595 🔴 (-8.2%)30
TTFSstream1368 (+487%) 🔻1476 🔴 (+27%) 🔻1496 🔴 (+26%) 🔻1582 🔴 (+21%) 🔻30
TTFShook + stream1674 (+290%) 🔻1789 🔴 (+29%) 🔻1858 🔴 (+32%) 🔻6774 🔴 (+362%) 🔻30
Fan-out TTFSPromise.all(100 steps)1492 (+4.5%)2991 (+19%) 🔻3052 (+16%) 🔻4634 (+40%) 🔻10
Fan-out TTLSPromise.all(100 steps)6100 (-14%)7525 (-14%)7551 (-16%) 💚13928 (+54%) 🔻10
STSO1020 steps (inline)146 (-10%)179 (-40%) 💚201 (-43%) 💚323 (-41%) 💚1019
WO1020 steps178365 (-38%) 💚178365 (-38%) 💚178365 (-38%) 💚178365 (-38%) 💚1
CRTTfirst chunk (pooled)119 (+20%) 🔻234 (+38%) 🔻402 (+23%) 🔻543 (+19%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (±0%)5 (±0%)5.1 (+1%)153 (-1%)212 (-3%)374 (+13%)565 (-45%)209 (-35%)10
size sweep (100/s, 160B-12KB)100 (±0%)101 (±0%)334 (±0%)337 (±0%)140 (+12%)165 (-16%)235 (-76%)708 (-42%)122 (-41%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.9 (+1%)16.2 (±0%)16.3 (+1%)380 (+148%)231 (+18%)349 (+26%)955 (+18%)495 (+33%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)168 (+9%)182 (+15%)243 (+23%)491 (+19%)370 (+11%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)711 (±0%)180 (-13%)311 (+25%)722 (+118%)1881 (+64%)778 (+16%)3
ℹ️ Metric definitions & methodology
Streams: writer/reader sustained rates (steady window, 10% trimmed each side), first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.
The collapsed STSO distribution section above buckets every step gap, split inline (same warm process — pure framework overhead) vs queue-hop (fresh process — dispatch, reinit, replay). █ = main, ┃ = this run, ░ = fill.
The collapsed CRTT drill-down: per-variant RTT histograms (fixed log bins, · = empty) and mean RTT/positive-CDV profile lines over stream progress and chunk size. Histograms, avgs, and profiles merge exactly across runs; p50–p99 are percentile-of-percentiles. Per-index rows live in the artifacts.
Best/P75/P90/P99 deltas compare against the most recent benchmark run on main at the time of this run. 🔻 flags a delta worse than +15%, 💚 one better than −15%.
Metrics — TTFS: time to first step body (in-deployment start() → first step body) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)
Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles
Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600
All timestamps are deployment-side; runs are triggered in-deployment, so the CI runner and api.vercel.com sit outside every measured window. TTFS = start() → first step body (includes dispatch + any cold start); Fan-out TTFS/TTLS = first/last step completion of one Promise.all from the same anchor (the gap is the runtime’s fan-out spread); STSO/WO between step bodies; CRTT inside the workflow (excludes the api.vercel.com read path).
Cold starts stay in the numbers (real bursty-workload latency, inflates P75+); Best is the warm floor.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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[e2e] Assert only the positive direction of step source maps
bf2fcee
Where hasStepSourceMaps() reports maps unsupported, the tests asserted
their absence - but on some lanes (nuxt, nextjs-webpack) source maps
apply nondeterministically, so the negative assertion pinned that
nondeterminism as a flake (#2083 measured this as one of the three
flake classes blocking e2e concurrency re-enablement). A stack that
resolves to source where none was promised is an improvement, not a
failure; hasStepSourceMaps() remains the record to update when a lane
starts mapping reliably, verified by the positive assertions on the
lanes it does promise.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Assert only the positive direction of step source maps (#3620)
991fa93
Where hasStepSourceMaps() reports maps unsupported, the tests asserted
their absence - but on some lanes (nuxt, nextjs-webpack) source maps
apply nondeterministically, so the negative assertion pinned that
nondeterminism as a flake (#2083 measured this as one of the three
flake classes blocking e2e concurrency re-enablement). A stack that
resolves to source where none was promised is an improvement, not a
failure; hasStepSourceMaps() remains the record to update when a lane
starts mapping reliably, verified by the positive assertions on the
lanes it does promise.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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Backport PR opened against stable: #3624. Merge conflicts were resolved by AI — please review carefully. (backport job run)
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[e2e] Assert only the positive direction of step source maps (#3620) (#…
234b904
…3624)
Co-authored-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
6713211
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit
that referenced
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Aug 19, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
fc94f67
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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@alangenfeld@VaguelySerious

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if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
(function() {
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'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
'ref', 'ref_src', 'source', 'medium', 'campaign'];
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var u = new URL(url, window.location.origin);
var changed = false;
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if (u.searchParams.has(p)) {
u.searchParams.delete(p);
changed = true;
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});
return changed ? u.toString() : url;
} catch (e) {
return url;
}
}
function cleanLinks() {
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if (clean !== a.href) a.href = clean;
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}
cleanLinks();
var observer = new MutationObserver(function(mutations) {
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if (node.nodeType === 1) {
if (node.tagName === 'A') cleanLinks();
node.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
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});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
[e2e] Assert only the positive direction of step source maps by alangenfeld · Pull Request #3620 · vercel/workflow · GitHub
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[e2e] Assert only the positive direction of step source maps - #3620
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[e2e] Assert only the positive direction of step source maps#3620
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Summary & Motivation
Source maps apply nondeterministically on lanes where hasStepSourceMaps() reports them unsupported (nuxt, nextjs-webpack), so asserting their absence turned that nondeterminism into a flake — one of the classes blocking e2e concurrency re-enablement (#2083). hasStepSourceMaps() stays the record to update when a lane starts mapping reliably, checked by the positive assertions on the lanes it does promise.
Test Plan
  •  Existing e2e coverage runs in CI
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The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
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⚠️ No Changeset found
Latest commit: bf2fcee
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🧪 E2E Test Results
✅ All tests passed
⚠️ Flaky E2E Tests (passed on retry)
These tests failed at least once and passed on a retry. A recurring entry here is a real race worth investigating.
  • plainModuleDoneHook resumed via plain API route (o2flow shape) (nextjs-webpack)
🛠 Infra Events (absorbed by the harness)
Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.
  • run-pickup-stall · addTenWorkflow (tanstack-start) · at 20:18:22Z · abandoned wrun_01M0B8CBX8C2DS0XB2RG0N0KYJ
E2E Test Summary
Summary
PassedFailedSkippedTotal
✅ ▲ Vercel Production347407384212
✅ 💻 Local Development381005584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
✅ 🌐 Cross-language Conformance90128137
✅ vercel-multi-region270027
Total152520254017792
Details by Category
✅ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro-node128028
✅ astro-quickjs128028
✅ example-node128028
✅ example-quickjs128028
✅ express-node128028
✅ express-quickjs128028
✅ fastify-node128028
✅ fastify-quickjs128028
✅ hono-node128028
✅ hono-quickjs128028
✅ nest-node128028
✅ nest-quickjs128028
✅ nextjs-turbopack-node15303
✅ nextjs-turbopack-quickjs15303
✅ nextjs-webpack-node15303
✅ nextjs-webpack-quickjs15303
✅ nitro-node128028
✅ nitro-quickjs128028
✅ nuxt-node128028
✅ nuxt-quickjs128028
✅ python-node80148
✅ sveltekit-node14709
✅ sveltekit-quickjs14709
✅ tanstack-start-node128028
✅ tanstack-start-quickjs128028
✅ vite-node128028
✅ vite-quickjs128028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node15600
✅ nextjs-turbopack-quickjs15600
✅ 🌐 Cross-language Conformance
AppPassedFailedSkipped
✅ python90128
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit bf2fcee · Tue, 18 Aug 2026 20:32:13 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1514 (+45%) 🔻1611 🔴 (+36%) 🔻1643 🔴 (+25%) 🔻1662 🔴 (+3.7%)30
TTFSstream1497 (+190%) 🔻1601 🔴 (+33%) 🔻1620 🔴 (+30%) 🔻1758 🔴 (+35%) 🔻30
TTFShook + stream1736 (+233%) 🔻1942 🔴 (+28%) 🔻2002 🔴 (+26%) 🔻2075 🔴 (+16%) 🔻30
Fan-out TTFSPromise.all(100 steps)1233 (+1.1%)2827 (+8.3%)2939 (+11%)3509 (+32%) 🔻10
Fan-out TTLSPromise.all(100 steps)5143 (-2.6%)6861 (-1.1%)10730 (+48%) 🔻11550 (+33%) 🔻10
STSO1020 steps (inline)114 (-17%) 💚158 (-42%) 💚182 (-41%) 💚341 (-15%) 💚1019
WO1020 steps159621 (-37%) 💚159621 (-37%) 💚159621 (-37%) 💚159621 (-37%) 💚1
CRTTfirst chunk (pooled)107 (-4.5%)181 (+1.7%)349 (+2.9%)625 (+64%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (+1%)5 (±0%)5.1 (+1%)146 (-18%)162 (-39%)275 (-51%)4328 (+494%)139 (-60%)10
size sweep (100/s, 160B-12KB)100 (±0%)100 (-1%)334 (±0%)334 (-1%)169 (+1%)153 (-38%)222 (-45%)445 (-38%)123 (-37%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.2 (±0%)16.2 (±0%)16.2 (±0%)119 (-27%)150 (-14%)233 (-23%)670 (-6%)282 (-43%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.6 (±0%)355 (±0%)354 (±0%)140 (-8%)200 (-5%)1158 (+154%)5107 (+642%)2304 (+310%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)712 (±0%)110 (-33%)224 (-55%)335 (-51%)967 (+6%)297 (-43%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 253258ms → this run 159304ms (Δ -93954ms, -37%)
100-150 ms █░░░░░░░░░░░░░░░░░░░░░░┃ main 2 this 600 +598
150-200 ms █████░░░░░░░░┃ main 131 this 346 +215
200-250 ms █┃████████████████ main 457 this 40 -417
250-300 ms ┃███████████ main 294 this 16 -278
300-350 ms ┃███ main 98 this 7 -91
350-400 ms ┃ main 25 this 2 -23
400-450 ms ┃ main 6 this 4 -2
450-500 ms ┃ main 2 this 1 -1
500-550 ms ┃ main 2 this 1 -1
550-600 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 0 this 1 +1
700-750 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▃█▂··▁· 321.6 (+62%) 121 (-21%) 275 (-51%) 4328 (+494%) 3000
sweep ······▃█▁···· 132.9 (-26%) 124 (-16%) 222 (-45%) 445 (-38%) 3000
gw 1x ·····▁▄█▁▁··· 127.7 (-20%) 115 (-12%) 233 (-23%) 670 (-6%) 5295
eve 1x ·····▁▅█▂▁▁▁▁ 314.7 (+74%) 114 (-17%) 1158 (+154%) 5107 (+642%) 5186
eve 2x ·····▁▂█▃▁▁·· 171 (-42%) 143 (-44%) 335 (-51%) 967 (+6%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control ▂▁▁▁▂█▇▇▆▆ 121–562ms
sweep █▂▂▂▁▂▃▂▃▃ 118–176ms
gw 1x █▃▃▁▂▁▃▁▄▂ 112–177ms
eve 1x ▁▁█▄▁▁▁▁▁▁ 110–1378ms
eve 2x ▃▁▂▁▁▂▃▅█▂ 139–261ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▄▄██▆▄▁ 130–135ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▁▂▂█▃▂▂▂▂ 29–114ms
sweep ▁█▇▅▅▆█▆█▆ 31–58ms
gw 1x ▆▄▄▁▅▃█▃▄▅ 29–42ms
eve 1x ▂▂█▁▂▁▂▂▁▁ 22–67ms
eve 2x █▄▂▂▄▃▃▃▁▅ 20–31ms

📜 Previous results (1)
ca5a215
Tue, 18 Aug 2026 19:47:23 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1397 (+473%) 🔻1507 🔴 (+32%) 🔻1535 🔴 (+25%) 🔻1595 🔴 (-8.2%)30
TTFSstream1368 (+487%) 🔻1476 🔴 (+27%) 🔻1496 🔴 (+26%) 🔻1582 🔴 (+21%) 🔻30
TTFShook + stream1674 (+290%) 🔻1789 🔴 (+29%) 🔻1858 🔴 (+32%) 🔻6774 🔴 (+362%) 🔻30
Fan-out TTFSPromise.all(100 steps)1492 (+4.5%)2991 (+19%) 🔻3052 (+16%) 🔻4634 (+40%) 🔻10
Fan-out TTLSPromise.all(100 steps)6100 (-14%)7525 (-14%)7551 (-16%) 💚13928 (+54%) 🔻10
STSO1020 steps (inline)146 (-10%)179 (-40%) 💚201 (-43%) 💚323 (-41%) 💚1019
WO1020 steps178365 (-38%) 💚178365 (-38%) 💚178365 (-38%) 💚178365 (-38%) 💚1
CRTTfirst chunk (pooled)119 (+20%) 🔻234 (+38%) 🔻402 (+23%) 🔻543 (+19%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (±0%)5 (±0%)5.1 (+1%)153 (-1%)212 (-3%)374 (+13%)565 (-45%)209 (-35%)10
size sweep (100/s, 160B-12KB)100 (±0%)101 (±0%)334 (±0%)337 (±0%)140 (+12%)165 (-16%)235 (-76%)708 (-42%)122 (-41%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.9 (+1%)16.2 (±0%)16.3 (+1%)380 (+148%)231 (+18%)349 (+26%)955 (+18%)495 (+33%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)168 (+9%)182 (+15%)243 (+23%)491 (+19%)370 (+11%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)711 (±0%)180 (-13%)311 (+25%)722 (+118%)1881 (+64%)778 (+16%)3
ℹ️ Metric definitions & methodology
Streams: writer/reader sustained rates (steady window, 10% trimmed each side), first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.
The collapsed STSO distribution section above buckets every step gap, split inline (same warm process — pure framework overhead) vs queue-hop (fresh process — dispatch, reinit, replay). █ = main, ┃ = this run, ░ = fill.
The collapsed CRTT drill-down: per-variant RTT histograms (fixed log bins, · = empty) and mean RTT/positive-CDV profile lines over stream progress and chunk size. Histograms, avgs, and profiles merge exactly across runs; p50–p99 are percentile-of-percentiles. Per-index rows live in the artifacts.
Best/P75/P90/P99 deltas compare against the most recent benchmark run on main at the time of this run. 🔻 flags a delta worse than +15%, 💚 one better than −15%.
Metrics — TTFS: time to first step body (in-deployment start() → first step body) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)
Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles
Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600
All timestamps are deployment-side; runs are triggered in-deployment, so the CI runner and api.vercel.com sit outside every measured window. TTFS = start() → first step body (includes dispatch + any cold start); Fan-out TTFS/TTLS = first/last step completion of one Promise.all from the same anchor (the gap is the runtime’s fan-out spread); STSO/WO between step bodies; CRTT inside the workflow (excludes the api.vercel.com read path).
Cold starts stay in the numbers (real bursty-workload latency, inflates P75+); Best is the warm floor.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
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Full trace: world-sim.txt
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[e2e] Assert only the positive direction of step source maps
bf2fcee
Where hasStepSourceMaps() reports maps unsupported, the tests asserted
their absence - but on some lanes (nuxt, nextjs-webpack) source maps
apply nondeterministically, so the negative assertion pinned that
nondeterminism as a flake (#2083 measured this as one of the three
flake classes blocking e2e concurrency re-enablement). A stack that
resolves to source where none was promised is an improvement, not a
failure; hasStepSourceMaps() remains the record to update when a lane
starts mapping reliably, verified by the positive assertions on the
lanes it does promise.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Assert only the positive direction of step source maps (#3620)
991fa93
Where hasStepSourceMaps() reports maps unsupported, the tests asserted
their absence - but on some lanes (nuxt, nextjs-webpack) source maps
apply nondeterministically, so the negative assertion pinned that
nondeterminism as a flake (#2083 measured this as one of the three
flake classes blocking e2e concurrency re-enablement). A stack that
resolves to source where none was promised is an improvement, not a
failure; hasStepSourceMaps() remains the record to update when a lane
starts mapping reliably, verified by the positive assertions on the
lanes it does promise.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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Backport PR opened against stable: #3624. Merge conflicts were resolved by AI — please review carefully. (backport job run)
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[e2e] Assert only the positive direction of step source maps (#3620) (#…
234b904
…3624)
Co-authored-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
6713211
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit
that referenced
this pull request
Aug 19, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
fc94f67
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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@alangenfeld@VaguelySerious

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[e2e] Assert only the positive direction of step source maps by alangenfeld · Pull Request #3620 · vercel/workflow · GitHub
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[e2e] Assert only the positive direction of step source maps - #3620
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[e2e] Assert only the positive direction of step source maps#3620
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Summary & Motivation
Source maps apply nondeterministically on lanes where hasStepSourceMaps() reports them unsupported (nuxt, nextjs-webpack), so asserting their absence turned that nondeterminism into a flake — one of the classes blocking e2e concurrency re-enablement (#2083). hasStepSourceMaps() stays the record to update when a lane starts mapping reliably, checked by the positive assertions on the lanes it does promise.
Test Plan
  •  Existing e2e coverage runs in CI
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The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
example-nextjs-workflow-turbopackReadyReadyPreviewAug 18, 2026 8:15pm
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⚠️ No Changeset found
Latest commit: bf2fcee
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🧪 E2E Test Results
✅ All tests passed
⚠️ Flaky E2E Tests (passed on retry)
These tests failed at least once and passed on a retry. A recurring entry here is a real race worth investigating.
  • plainModuleDoneHook resumed via plain API route (o2flow shape) (nextjs-webpack)
🛠 Infra Events (absorbed by the harness)
Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.
  • run-pickup-stall · addTenWorkflow (tanstack-start) · at 20:18:22Z · abandoned wrun_01M0B8CBX8C2DS0XB2RG0N0KYJ
E2E Test Summary
Summary
PassedFailedSkippedTotal
✅ ▲ Vercel Production347407384212
✅ 💻 Local Development381005584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
✅ 🌐 Cross-language Conformance90128137
✅ vercel-multi-region270027
Total152520254017792
Details by Category
✅ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro-node128028
✅ astro-quickjs128028
✅ example-node128028
✅ example-quickjs128028
✅ express-node128028
✅ express-quickjs128028
✅ fastify-node128028
✅ fastify-quickjs128028
✅ hono-node128028
✅ hono-quickjs128028
✅ nest-node128028
✅ nest-quickjs128028
✅ nextjs-turbopack-node15303
✅ nextjs-turbopack-quickjs15303
✅ nextjs-webpack-node15303
✅ nextjs-webpack-quickjs15303
✅ nitro-node128028
✅ nitro-quickjs128028
✅ nuxt-node128028
✅ nuxt-quickjs128028
✅ python-node80148
✅ sveltekit-node14709
✅ sveltekit-quickjs14709
✅ tanstack-start-node128028
✅ tanstack-start-quickjs128028
✅ vite-node128028
✅ vite-quickjs128028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node15600
✅ nextjs-turbopack-quickjs15600
✅ 🌐 Cross-language Conformance
AppPassedFailedSkipped
✅ python90128
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit bf2fcee · Tue, 18 Aug 2026 20:32:13 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1514 (+45%) 🔻1611 🔴 (+36%) 🔻1643 🔴 (+25%) 🔻1662 🔴 (+3.7%)30
TTFSstream1497 (+190%) 🔻1601 🔴 (+33%) 🔻1620 🔴 (+30%) 🔻1758 🔴 (+35%) 🔻30
TTFShook + stream1736 (+233%) 🔻1942 🔴 (+28%) 🔻2002 🔴 (+26%) 🔻2075 🔴 (+16%) 🔻30
Fan-out TTFSPromise.all(100 steps)1233 (+1.1%)2827 (+8.3%)2939 (+11%)3509 (+32%) 🔻10
Fan-out TTLSPromise.all(100 steps)5143 (-2.6%)6861 (-1.1%)10730 (+48%) 🔻11550 (+33%) 🔻10
STSO1020 steps (inline)114 (-17%) 💚158 (-42%) 💚182 (-41%) 💚341 (-15%) 💚1019
WO1020 steps159621 (-37%) 💚159621 (-37%) 💚159621 (-37%) 💚159621 (-37%) 💚1
CRTTfirst chunk (pooled)107 (-4.5%)181 (+1.7%)349 (+2.9%)625 (+64%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (+1%)5 (±0%)5.1 (+1%)146 (-18%)162 (-39%)275 (-51%)4328 (+494%)139 (-60%)10
size sweep (100/s, 160B-12KB)100 (±0%)100 (-1%)334 (±0%)334 (-1%)169 (+1%)153 (-38%)222 (-45%)445 (-38%)123 (-37%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.2 (±0%)16.2 (±0%)16.2 (±0%)119 (-27%)150 (-14%)233 (-23%)670 (-6%)282 (-43%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.6 (±0%)355 (±0%)354 (±0%)140 (-8%)200 (-5%)1158 (+154%)5107 (+642%)2304 (+310%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)712 (±0%)110 (-33%)224 (-55%)335 (-51%)967 (+6%)297 (-43%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 253258ms → this run 159304ms (Δ -93954ms, -37%)
100-150 ms █░░░░░░░░░░░░░░░░░░░░░░┃ main 2 this 600 +598
150-200 ms █████░░░░░░░░┃ main 131 this 346 +215
200-250 ms █┃████████████████ main 457 this 40 -417
250-300 ms ┃███████████ main 294 this 16 -278
300-350 ms ┃███ main 98 this 7 -91
350-400 ms ┃ main 25 this 2 -23
400-450 ms ┃ main 6 this 4 -2
450-500 ms ┃ main 2 this 1 -1
500-550 ms ┃ main 2 this 1 -1
550-600 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 0 this 1 +1
700-750 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▃█▂··▁· 321.6 (+62%) 121 (-21%) 275 (-51%) 4328 (+494%) 3000
sweep ······▃█▁···· 132.9 (-26%) 124 (-16%) 222 (-45%) 445 (-38%) 3000
gw 1x ·····▁▄█▁▁··· 127.7 (-20%) 115 (-12%) 233 (-23%) 670 (-6%) 5295
eve 1x ·····▁▅█▂▁▁▁▁ 314.7 (+74%) 114 (-17%) 1158 (+154%) 5107 (+642%) 5186
eve 2x ·····▁▂█▃▁▁·· 171 (-42%) 143 (-44%) 335 (-51%) 967 (+6%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control ▂▁▁▁▂█▇▇▆▆ 121–562ms
sweep █▂▂▂▁▂▃▂▃▃ 118–176ms
gw 1x █▃▃▁▂▁▃▁▄▂ 112–177ms
eve 1x ▁▁█▄▁▁▁▁▁▁ 110–1378ms
eve 2x ▃▁▂▁▁▂▃▅█▂ 139–261ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▄▄██▆▄▁ 130–135ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▁▂▂█▃▂▂▂▂ 29–114ms
sweep ▁█▇▅▅▆█▆█▆ 31–58ms
gw 1x ▆▄▄▁▅▃█▃▄▅ 29–42ms
eve 1x ▂▂█▁▂▁▂▂▁▁ 22–67ms
eve 2x █▄▂▂▄▃▃▃▁▅ 20–31ms

📜 Previous results (1)
ca5a215
Tue, 18 Aug 2026 19:47:23 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1397 (+473%) 🔻1507 🔴 (+32%) 🔻1535 🔴 (+25%) 🔻1595 🔴 (-8.2%)30
TTFSstream1368 (+487%) 🔻1476 🔴 (+27%) 🔻1496 🔴 (+26%) 🔻1582 🔴 (+21%) 🔻30
TTFShook + stream1674 (+290%) 🔻1789 🔴 (+29%) 🔻1858 🔴 (+32%) 🔻6774 🔴 (+362%) 🔻30
Fan-out TTFSPromise.all(100 steps)1492 (+4.5%)2991 (+19%) 🔻3052 (+16%) 🔻4634 (+40%) 🔻10
Fan-out TTLSPromise.all(100 steps)6100 (-14%)7525 (-14%)7551 (-16%) 💚13928 (+54%) 🔻10
STSO1020 steps (inline)146 (-10%)179 (-40%) 💚201 (-43%) 💚323 (-41%) 💚1019
WO1020 steps178365 (-38%) 💚178365 (-38%) 💚178365 (-38%) 💚178365 (-38%) 💚1
CRTTfirst chunk (pooled)119 (+20%) 🔻234 (+38%) 🔻402 (+23%) 🔻543 (+19%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (±0%)5 (±0%)5.1 (+1%)153 (-1%)212 (-3%)374 (+13%)565 (-45%)209 (-35%)10
size sweep (100/s, 160B-12KB)100 (±0%)101 (±0%)334 (±0%)337 (±0%)140 (+12%)165 (-16%)235 (-76%)708 (-42%)122 (-41%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.9 (+1%)16.2 (±0%)16.3 (+1%)380 (+148%)231 (+18%)349 (+26%)955 (+18%)495 (+33%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)168 (+9%)182 (+15%)243 (+23%)491 (+19%)370 (+11%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)711 (±0%)180 (-13%)311 (+25%)722 (+118%)1881 (+64%)778 (+16%)3
ℹ️ Metric definitions & methodology
Streams: writer/reader sustained rates (steady window, 10% trimmed each side), first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.
The collapsed STSO distribution section above buckets every step gap, split inline (same warm process — pure framework overhead) vs queue-hop (fresh process — dispatch, reinit, replay). █ = main, ┃ = this run, ░ = fill.
The collapsed CRTT drill-down: per-variant RTT histograms (fixed log bins, · = empty) and mean RTT/positive-CDV profile lines over stream progress and chunk size. Histograms, avgs, and profiles merge exactly across runs; p50–p99 are percentile-of-percentiles. Per-index rows live in the artifacts.
Best/P75/P90/P99 deltas compare against the most recent benchmark run on main at the time of this run. 🔻 flags a delta worse than +15%, 💚 one better than −15%.
Metrics — TTFS: time to first step body (in-deployment start() → first step body) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)
Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles
Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600
All timestamps are deployment-side; runs are triggered in-deployment, so the CI runner and api.vercel.com sit outside every measured window. TTFS = start() → first step body (includes dispatch + any cold start); Fan-out TTFS/TTLS = first/last step completion of one Promise.all from the same anchor (the gap is the runtime’s fan-out spread); STSO/WO between step bodies; CRTT inside the workflow (excludes the api.vercel.com read path).
Cold starts stay in the numbers (real bursty-workload latency, inflates P75+); Best is the warm floor.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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[e2e] Assert only the positive direction of step source maps
bf2fcee
Where hasStepSourceMaps() reports maps unsupported, the tests asserted
their absence - but on some lanes (nuxt, nextjs-webpack) source maps
apply nondeterministically, so the negative assertion pinned that
nondeterminism as a flake (#2083 measured this as one of the three
flake classes blocking e2e concurrency re-enablement). A stack that
resolves to source where none was promised is an improvement, not a
failure; hasStepSourceMaps() remains the record to update when a lane
starts mapping reliably, verified by the positive assertions on the
lanes it does promise.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Assert only the positive direction of step source maps (#3620)
991fa93
Where hasStepSourceMaps() reports maps unsupported, the tests asserted
their absence - but on some lanes (nuxt, nextjs-webpack) source maps
apply nondeterministically, so the negative assertion pinned that
nondeterminism as a flake (#2083 measured this as one of the three
flake classes blocking e2e concurrency re-enablement). A stack that
resolves to source where none was promised is an improvement, not a
failure; hasStepSourceMaps() remains the record to update when a lane
starts mapping reliably, verified by the positive assertions on the
lanes it does promise.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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Backport PR opened against stable: #3624. Merge conflicts were resolved by AI — please review carefully. (backport job run)
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[e2e] Assert only the positive direction of step source maps (#3620) (#…
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…3624)
Co-authored-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Re-enable concurrent execution of the e2e suite
6713211
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit
that referenced
this pull request
Aug 19, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
fc94f67
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Assert only the positive direction of step source maps by alangenfeld · Pull Request #3620 · vercel/workflow · GitHub
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[e2e] Assert only the positive direction of step source maps - #3620
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Summary & Motivation
Source maps apply nondeterministically on lanes where hasStepSourceMaps() reports them unsupported (nuxt, nextjs-webpack), so asserting their absence turned that nondeterminism into a flake — one of the classes blocking e2e concurrency re-enablement (#2083). hasStepSourceMaps() stays the record to update when a lane starts mapping reliably, checked by the positive assertions on the lanes it does promise.
Test Plan
  •  Existing e2e coverage runs in CI
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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
⚠️ Flaky E2E Tests (passed on retry)
These tests failed at least once and passed on a retry. A recurring entry here is a real race worth investigating.
  • plainModuleDoneHook resumed via plain API route (o2flow shape) (nextjs-webpack)
🛠 Infra Events (absorbed by the harness)
Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.
  • run-pickup-stall · addTenWorkflow (tanstack-start) · at 20:18:22Z · abandoned wrun_01M0B8CBX8C2DS0XB2RG0N0KYJ
E2E Test Summary
Summary
PassedFailedSkippedTotal
✅ ▲ Vercel Production347407384212
✅ 💻 Local Development381005584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
✅ 🌐 Cross-language Conformance90128137
✅ vercel-multi-region270027
Total152520254017792
Details by Category
✅ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro-node128028
✅ astro-quickjs128028
✅ example-node128028
✅ example-quickjs128028
✅ express-node128028
✅ express-quickjs128028
✅ fastify-node128028
✅ fastify-quickjs128028
✅ hono-node128028
✅ hono-quickjs128028
✅ nest-node128028
✅ nest-quickjs128028
✅ nextjs-turbopack-node15303
✅ nextjs-turbopack-quickjs15303
✅ nextjs-webpack-node15303
✅ nextjs-webpack-quickjs15303
✅ nitro-node128028
✅ nitro-quickjs128028
✅ nuxt-node128028
✅ nuxt-quickjs128028
✅ python-node80148
✅ sveltekit-node14709
✅ sveltekit-quickjs14709
✅ tanstack-start-node128028
✅ tanstack-start-quickjs128028
✅ vite-node128028
✅ vite-quickjs128028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node15600
✅ nextjs-turbopack-quickjs15600
✅ 🌐 Cross-language Conformance
AppPassedFailedSkipped
✅ python90128
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit bf2fcee · Tue, 18 Aug 2026 20:32:13 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1514 (+45%) 🔻1611 🔴 (+36%) 🔻1643 🔴 (+25%) 🔻1662 🔴 (+3.7%)30
TTFSstream1497 (+190%) 🔻1601 🔴 (+33%) 🔻1620 🔴 (+30%) 🔻1758 🔴 (+35%) 🔻30
TTFShook + stream1736 (+233%) 🔻1942 🔴 (+28%) 🔻2002 🔴 (+26%) 🔻2075 🔴 (+16%) 🔻30
Fan-out TTFSPromise.all(100 steps)1233 (+1.1%)2827 (+8.3%)2939 (+11%)3509 (+32%) 🔻10
Fan-out TTLSPromise.all(100 steps)5143 (-2.6%)6861 (-1.1%)10730 (+48%) 🔻11550 (+33%) 🔻10
STSO1020 steps (inline)114 (-17%) 💚158 (-42%) 💚182 (-41%) 💚341 (-15%) 💚1019
WO1020 steps159621 (-37%) 💚159621 (-37%) 💚159621 (-37%) 💚159621 (-37%) 💚1
CRTTfirst chunk (pooled)107 (-4.5%)181 (+1.7%)349 (+2.9%)625 (+64%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (+1%)5 (±0%)5.1 (+1%)146 (-18%)162 (-39%)275 (-51%)4328 (+494%)139 (-60%)10
size sweep (100/s, 160B-12KB)100 (±0%)100 (-1%)334 (±0%)334 (-1%)169 (+1%)153 (-38%)222 (-45%)445 (-38%)123 (-37%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.2 (±0%)16.2 (±0%)16.2 (±0%)119 (-27%)150 (-14%)233 (-23%)670 (-6%)282 (-43%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.6 (±0%)355 (±0%)354 (±0%)140 (-8%)200 (-5%)1158 (+154%)5107 (+642%)2304 (+310%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)712 (±0%)110 (-33%)224 (-55%)335 (-51%)967 (+6%)297 (-43%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 253258ms → this run 159304ms (Δ -93954ms, -37%)
100-150 ms █░░░░░░░░░░░░░░░░░░░░░░┃ main 2 this 600 +598
150-200 ms █████░░░░░░░░┃ main 131 this 346 +215
200-250 ms █┃████████████████ main 457 this 40 -417
250-300 ms ┃███████████ main 294 this 16 -278
300-350 ms ┃███ main 98 this 7 -91
350-400 ms ┃ main 25 this 2 -23
400-450 ms ┃ main 6 this 4 -2
450-500 ms ┃ main 2 this 1 -1
500-550 ms ┃ main 2 this 1 -1
550-600 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 0 this 1 +1
700-750 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▃█▂··▁· 321.6 (+62%) 121 (-21%) 275 (-51%) 4328 (+494%) 3000
sweep ······▃█▁···· 132.9 (-26%) 124 (-16%) 222 (-45%) 445 (-38%) 3000
gw 1x ·····▁▄█▁▁··· 127.7 (-20%) 115 (-12%) 233 (-23%) 670 (-6%) 5295
eve 1x ·····▁▅█▂▁▁▁▁ 314.7 (+74%) 114 (-17%) 1158 (+154%) 5107 (+642%) 5186
eve 2x ·····▁▂█▃▁▁·· 171 (-42%) 143 (-44%) 335 (-51%) 967 (+6%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control ▂▁▁▁▂█▇▇▆▆ 121–562ms
sweep █▂▂▂▁▂▃▂▃▃ 118–176ms
gw 1x █▃▃▁▂▁▃▁▄▂ 112–177ms
eve 1x ▁▁█▄▁▁▁▁▁▁ 110–1378ms
eve 2x ▃▁▂▁▁▂▃▅█▂ 139–261ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▄▄██▆▄▁ 130–135ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▁▂▂█▃▂▂▂▂ 29–114ms
sweep ▁█▇▅▅▆█▆█▆ 31–58ms
gw 1x ▆▄▄▁▅▃█▃▄▅ 29–42ms
eve 1x ▂▂█▁▂▁▂▂▁▁ 22–67ms
eve 2x █▄▂▂▄▃▃▃▁▅ 20–31ms

📜 Previous results (1)
ca5a215
Tue, 18 Aug 2026 19:47:23 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1397 (+473%) 🔻1507 🔴 (+32%) 🔻1535 🔴 (+25%) 🔻1595 🔴 (-8.2%)30
TTFSstream1368 (+487%) 🔻1476 🔴 (+27%) 🔻1496 🔴 (+26%) 🔻1582 🔴 (+21%) 🔻30
TTFShook + stream1674 (+290%) 🔻1789 🔴 (+29%) 🔻1858 🔴 (+32%) 🔻6774 🔴 (+362%) 🔻30
Fan-out TTFSPromise.all(100 steps)1492 (+4.5%)2991 (+19%) 🔻3052 (+16%) 🔻4634 (+40%) 🔻10
Fan-out TTLSPromise.all(100 steps)6100 (-14%)7525 (-14%)7551 (-16%) 💚13928 (+54%) 🔻10
STSO1020 steps (inline)146 (-10%)179 (-40%) 💚201 (-43%) 💚323 (-41%) 💚1019
WO1020 steps178365 (-38%) 💚178365 (-38%) 💚178365 (-38%) 💚178365 (-38%) 💚1
CRTTfirst chunk (pooled)119 (+20%) 🔻234 (+38%) 🔻402 (+23%) 🔻543 (+19%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (±0%)5 (±0%)5.1 (+1%)153 (-1%)212 (-3%)374 (+13%)565 (-45%)209 (-35%)10
size sweep (100/s, 160B-12KB)100 (±0%)101 (±0%)334 (±0%)337 (±0%)140 (+12%)165 (-16%)235 (-76%)708 (-42%)122 (-41%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.9 (+1%)16.2 (±0%)16.3 (+1%)380 (+148%)231 (+18%)349 (+26%)955 (+18%)495 (+33%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)168 (+9%)182 (+15%)243 (+23%)491 (+19%)370 (+11%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)711 (±0%)180 (-13%)311 (+25%)722 (+118%)1881 (+64%)778 (+16%)3
ℹ️ Metric definitions & methodology
Streams: writer/reader sustained rates (steady window, 10% trimmed each side), first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.
The collapsed STSO distribution section above buckets every step gap, split inline (same warm process — pure framework overhead) vs queue-hop (fresh process — dispatch, reinit, replay). █ = main, ┃ = this run, ░ = fill.
The collapsed CRTT drill-down: per-variant RTT histograms (fixed log bins, · = empty) and mean RTT/positive-CDV profile lines over stream progress and chunk size. Histograms, avgs, and profiles merge exactly across runs; p50–p99 are percentile-of-percentiles. Per-index rows live in the artifacts.
Best/P75/P90/P99 deltas compare against the most recent benchmark run on main at the time of this run. 🔻 flags a delta worse than +15%, 💚 one better than −15%.
Metrics — TTFS: time to first step body (in-deployment start() → first step body) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)
Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles
Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600
All timestamps are deployment-side; runs are triggered in-deployment, so the CI runner and api.vercel.com sit outside every measured window. TTFS = start() → first step body (includes dispatch + any cold start); Fan-out TTFS/TTLS = first/last step completion of one Promise.all from the same anchor (the gap is the runtime’s fan-out spread); STSO/WO between step bodies; CRTT inside the workflow (excludes the api.vercel.com read path).
Cold starts stay in the numbers (real bursty-workload latency, inflates P75+); Best is the warm floor.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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[e2e] Assert only the positive direction of step source maps
bf2fcee
Where hasStepSourceMaps() reports maps unsupported, the tests asserted
their absence - but on some lanes (nuxt, nextjs-webpack) source maps
apply nondeterministically, so the negative assertion pinned that
nondeterminism as a flake (#2083 measured this as one of the three
flake classes blocking e2e concurrency re-enablement). A stack that
resolves to source where none was promised is an improvement, not a
failure; hasStepSourceMaps() remains the record to update when a lane
starts mapping reliably, verified by the positive assertions on the
lanes it does promise.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Assert only the positive direction of step source maps (#3620)
991fa93
Where hasStepSourceMaps() reports maps unsupported, the tests asserted
their absence - but on some lanes (nuxt, nextjs-webpack) source maps
apply nondeterministically, so the negative assertion pinned that
nondeterminism as a flake (#2083 measured this as one of the three
flake classes blocking e2e concurrency re-enablement). A stack that
resolves to source where none was promised is an improvement, not a
failure; hasStepSourceMaps() remains the record to update when a lane
starts mapping reliably, verified by the positive assertions on the
lanes it does promise.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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Backport PR opened against stable: #3624. Merge conflicts were resolved by AI — please review carefully. (backport job run)
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[e2e] Assert only the positive direction of step source maps (#3620) (#…
234b904
…3624)
Co-authored-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
6713211
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit
that referenced
this pull request
Aug 19, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
fc94f67
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Assert only the positive direction of step source maps by alangenfeld · Pull Request #3620 · vercel/workflow · GitHub
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[e2e] Assert only the positive direction of step source maps - #3620
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[e2e] Assert only the positive direction of step source maps#3620
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Summary & Motivation
Source maps apply nondeterministically on lanes where hasStepSourceMaps() reports them unsupported (nuxt, nextjs-webpack), so asserting their absence turned that nondeterminism into a flake — one of the classes blocking e2e concurrency re-enablement (#2083). hasStepSourceMaps() stays the record to update when a lane starts mapping reliably, checked by the positive assertions on the lanes it does promise.
Test Plan
  •  Existing e2e coverage runs in CI
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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
⚠️ Flaky E2E Tests (passed on retry)
These tests failed at least once and passed on a retry. A recurring entry here is a real race worth investigating.
  • plainModuleDoneHook resumed via plain API route (o2flow shape) (nextjs-webpack)
🛠 Infra Events (absorbed by the harness)
Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.
  • run-pickup-stall · addTenWorkflow (tanstack-start) · at 20:18:22Z · abandoned wrun_01M0B8CBX8C2DS0XB2RG0N0KYJ
E2E Test Summary
Summary
PassedFailedSkippedTotal
✅ ▲ Vercel Production347407384212
✅ 💻 Local Development381005584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
✅ 🌐 Cross-language Conformance90128137
✅ vercel-multi-region270027
Total152520254017792
Details by Category
✅ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro-node128028
✅ astro-quickjs128028
✅ example-node128028
✅ example-quickjs128028
✅ express-node128028
✅ express-quickjs128028
✅ fastify-node128028
✅ fastify-quickjs128028
✅ hono-node128028
✅ hono-quickjs128028
✅ nest-node128028
✅ nest-quickjs128028
✅ nextjs-turbopack-node15303
✅ nextjs-turbopack-quickjs15303
✅ nextjs-webpack-node15303
✅ nextjs-webpack-quickjs15303
✅ nitro-node128028
✅ nitro-quickjs128028
✅ nuxt-node128028
✅ nuxt-quickjs128028
✅ python-node80148
✅ sveltekit-node14709
✅ sveltekit-quickjs14709
✅ tanstack-start-node128028
✅ tanstack-start-quickjs128028
✅ vite-node128028
✅ vite-quickjs128028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node15600
✅ nextjs-turbopack-quickjs15600
✅ 🌐 Cross-language Conformance
AppPassedFailedSkipped
✅ python90128
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit bf2fcee · Tue, 18 Aug 2026 20:32:13 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1514 (+45%) 🔻1611 🔴 (+36%) 🔻1643 🔴 (+25%) 🔻1662 🔴 (+3.7%)30
TTFSstream1497 (+190%) 🔻1601 🔴 (+33%) 🔻1620 🔴 (+30%) 🔻1758 🔴 (+35%) 🔻30
TTFShook + stream1736 (+233%) 🔻1942 🔴 (+28%) 🔻2002 🔴 (+26%) 🔻2075 🔴 (+16%) 🔻30
Fan-out TTFSPromise.all(100 steps)1233 (+1.1%)2827 (+8.3%)2939 (+11%)3509 (+32%) 🔻10
Fan-out TTLSPromise.all(100 steps)5143 (-2.6%)6861 (-1.1%)10730 (+48%) 🔻11550 (+33%) 🔻10
STSO1020 steps (inline)114 (-17%) 💚158 (-42%) 💚182 (-41%) 💚341 (-15%) 💚1019
WO1020 steps159621 (-37%) 💚159621 (-37%) 💚159621 (-37%) 💚159621 (-37%) 💚1
CRTTfirst chunk (pooled)107 (-4.5%)181 (+1.7%)349 (+2.9%)625 (+64%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (+1%)5 (±0%)5.1 (+1%)146 (-18%)162 (-39%)275 (-51%)4328 (+494%)139 (-60%)10
size sweep (100/s, 160B-12KB)100 (±0%)100 (-1%)334 (±0%)334 (-1%)169 (+1%)153 (-38%)222 (-45%)445 (-38%)123 (-37%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.2 (±0%)16.2 (±0%)16.2 (±0%)119 (-27%)150 (-14%)233 (-23%)670 (-6%)282 (-43%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.6 (±0%)355 (±0%)354 (±0%)140 (-8%)200 (-5%)1158 (+154%)5107 (+642%)2304 (+310%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)712 (±0%)110 (-33%)224 (-55%)335 (-51%)967 (+6%)297 (-43%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 253258ms → this run 159304ms (Δ -93954ms, -37%)
100-150 ms █░░░░░░░░░░░░░░░░░░░░░░┃ main 2 this 600 +598
150-200 ms █████░░░░░░░░┃ main 131 this 346 +215
200-250 ms █┃████████████████ main 457 this 40 -417
250-300 ms ┃███████████ main 294 this 16 -278
300-350 ms ┃███ main 98 this 7 -91
350-400 ms ┃ main 25 this 2 -23
400-450 ms ┃ main 6 this 4 -2
450-500 ms ┃ main 2 this 1 -1
500-550 ms ┃ main 2 this 1 -1
550-600 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 0 this 1 +1
700-750 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▃█▂··▁· 321.6 (+62%) 121 (-21%) 275 (-51%) 4328 (+494%) 3000
sweep ······▃█▁···· 132.9 (-26%) 124 (-16%) 222 (-45%) 445 (-38%) 3000
gw 1x ·····▁▄█▁▁··· 127.7 (-20%) 115 (-12%) 233 (-23%) 670 (-6%) 5295
eve 1x ·····▁▅█▂▁▁▁▁ 314.7 (+74%) 114 (-17%) 1158 (+154%) 5107 (+642%) 5186
eve 2x ·····▁▂█▃▁▁·· 171 (-42%) 143 (-44%) 335 (-51%) 967 (+6%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control ▂▁▁▁▂█▇▇▆▆ 121–562ms
sweep █▂▂▂▁▂▃▂▃▃ 118–176ms
gw 1x █▃▃▁▂▁▃▁▄▂ 112–177ms
eve 1x ▁▁█▄▁▁▁▁▁▁ 110–1378ms
eve 2x ▃▁▂▁▁▂▃▅█▂ 139–261ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▄▄██▆▄▁ 130–135ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▁▂▂█▃▂▂▂▂ 29–114ms
sweep ▁█▇▅▅▆█▆█▆ 31–58ms
gw 1x ▆▄▄▁▅▃█▃▄▅ 29–42ms
eve 1x ▂▂█▁▂▁▂▂▁▁ 22–67ms
eve 2x █▄▂▂▄▃▃▃▁▅ 20–31ms

📜 Previous results (1)
ca5a215
Tue, 18 Aug 2026 19:47:23 GMT · run logs
vercel / nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1397 (+473%) 🔻1507 🔴 (+32%) 🔻1535 🔴 (+25%) 🔻1595 🔴 (-8.2%)30
TTFSstream1368 (+487%) 🔻1476 🔴 (+27%) 🔻1496 🔴 (+26%) 🔻1582 🔴 (+21%) 🔻30
TTFShook + stream1674 (+290%) 🔻1789 🔴 (+29%) 🔻1858 🔴 (+32%) 🔻6774 🔴 (+362%) 🔻30
Fan-out TTFSPromise.all(100 steps)1492 (+4.5%)2991 (+19%) 🔻3052 (+16%) 🔻4634 (+40%) 🔻10
Fan-out TTLSPromise.all(100 steps)6100 (-14%)7525 (-14%)7551 (-16%) 💚13928 (+54%) 🔻10
STSO1020 steps (inline)146 (-10%)179 (-40%) 💚201 (-43%) 💚323 (-41%) 💚1019
WO1020 steps178365 (-38%) 💚178365 (-38%) 💚178365 (-38%) 💚178365 (-38%) 💚1
CRTTfirst chunk (pooled)119 (+20%) 🔻234 (+38%) 🔻402 (+23%) 🔻543 (+19%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (±0%)5 (±0%)5.1 (+1%)153 (-1%)212 (-3%)374 (+13%)565 (-45%)209 (-35%)10
size sweep (100/s, 160B-12KB)100 (±0%)101 (±0%)334 (±0%)337 (±0%)140 (+12%)165 (-16%)235 (-76%)708 (-42%)122 (-41%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.9 (+1%)16.2 (±0%)16.3 (+1%)380 (+148%)231 (+18%)349 (+26%)955 (+18%)495 (+33%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)168 (+9%)182 (+15%)243 (+23%)491 (+19%)370 (+11%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)711 (±0%)180 (-13%)311 (+25%)722 (+118%)1881 (+64%)778 (+16%)3
ℹ️ Metric definitions & methodology
Streams: writer/reader sustained rates (steady window, 10% trimmed each side), first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.
The collapsed STSO distribution section above buckets every step gap, split inline (same warm process — pure framework overhead) vs queue-hop (fresh process — dispatch, reinit, replay). █ = main, ┃ = this run, ░ = fill.
The collapsed CRTT drill-down: per-variant RTT histograms (fixed log bins, · = empty) and mean RTT/positive-CDV profile lines over stream progress and chunk size. Histograms, avgs, and profiles merge exactly across runs; p50–p99 are percentile-of-percentiles. Per-index rows live in the artifacts.
Best/P75/P90/P99 deltas compare against the most recent benchmark run on main at the time of this run. 🔻 flags a delta worse than +15%, 💚 one better than −15%.
Metrics — TTFS: time to first step body (in-deployment start() → first step body) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)
Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles
Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600
All timestamps are deployment-side; runs are triggered in-deployment, so the CI runner and api.vercel.com sit outside every measured window. TTFS = start() → first step body (includes dispatch + any cold start); Fan-out TTFS/TTLS = first/last step completion of one Promise.all from the same anchor (the gap is the runtime’s fan-out spread); STSO/WO between step bodies; CRTT inside the workflow (excludes the api.vercel.com read path).
Cold starts stay in the numbers (real bursty-workload latency, inflates P75+); Best is the warm floor.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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[e2e] Assert only the positive direction of step source maps
bf2fcee
Where hasStepSourceMaps() reports maps unsupported, the tests asserted
their absence - but on some lanes (nuxt, nextjs-webpack) source maps
apply nondeterministically, so the negative assertion pinned that
nondeterminism as a flake (#2083 measured this as one of the three
flake classes blocking e2e concurrency re-enablement). A stack that
resolves to source where none was promised is an improvement, not a
failure; hasStepSourceMaps() remains the record to update when a lane
starts mapping reliably, verified by the positive assertions on the
lanes it does promise.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Assert only the positive direction of step source maps (#3620)
991fa93
Where hasStepSourceMaps() reports maps unsupported, the tests asserted
their absence - but on some lanes (nuxt, nextjs-webpack) source maps
apply nondeterministically, so the negative assertion pinned that
nondeterminism as a flake (#2083 measured this as one of the three
flake classes blocking e2e concurrency re-enablement). A stack that
resolves to source where none was promised is an improvement, not a
failure; hasStepSourceMaps() remains the record to update when a lane
starts mapping reliably, verified by the positive assertions on the
lanes it does promise.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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Backport PR opened against stable: #3624. Merge conflicts were resolved by AI — please review carefully. (backport job run)
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[e2e] Assert only the positive direction of step source maps (#3620) (#…
234b904
…3624)
Co-authored-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit
that referenced
this pull request
Aug 18, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
6713211
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit
that referenced
this pull request
Aug 19, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
fc94f67
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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