[e2e] Re-enable concurrent execution of the e2e suite - #3628

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[e2e] Re-enable concurrent execution of the e2e suite#3628
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@alangenfeld

@alangenfeldalangenfeld commented Aug 18, 2026

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Summary & Motivation

Serial e2e was the dominant wall-clock cost per matrix entry (~22 of 24 minutes on the Vercel lanes), and the blockers #2083 identified are now fixed. Making the suite concurrent required per-test attribution that survives interleaving: an auto fixture binds each test's name, tracked runs, and skip through AsyncLocalStorage, since vitest's getCurrentTest() is a module variable that goes stale after any await — so a failing test now dumps its own diagnostics rather than a sibling's. A test that genuinely cannot share a deployment can opt out with test.sequential.

Test Plan

  • Full suite passes 137/137 concurrently against a local nextjs-turbopack dev server in under 2 minutes, with a new unit test covering attribution across interleaved contexts.

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⚠️ No Changeset found

Latest commit: 0556953

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (4 failed)

python-node (4 failed):

  • hookMinRetentionWorkflow - terminal Hook cannot resume and its token stays unavailable
  • setAttributes setAttributesInsideStepWorkflow: step-body calls append attributed native events
  • setAttributes workflow throws after awaited setAttributes: attribute still persists on the failed run
  • setAttributes start: invalid initial attributes are rejected before a run is created

💻 Local Development (2 failed)

vite-stable-node (1 failed):

  • sleepWinsRaceWorkflow

vite-stable-quickjs (1 failed):

  • sleepWinsRaceWorkflow

🌐 Cross-language Conformance (4 failed)

python (4 failed):

  • hookGetConflictWorkflow - hook.getConflict() resolves with the conflicting run when token is already registered
  • hookSupersedeOwnerWorkflow - duplicate cancels the owner and claims the released token
  • setAttributes setAttributesInsideStepWorkflow: step-body calls append attributed native events
  • setAttributes start: invalid initial attributes are rejected before a run is created

⚠️ 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.

  • 'hookGetConflictWithPriorStepWorkflow' - hook.getConflict() does not block step execution (nextjs-webpack)
  • abortHookOrderingWorkflow [listener-first-abort-first]: addEventListener → hook.then → abort() → resumeHook (nextjs-turbopack)
  • sleepWinsRaceWorkflow (tanstack-start)
  • stepWinsRaceWorkflow (tanstack-start)
  • stepWinsRaceWorkflow (vite)

🛠 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 · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A23XH4SJQ0FNX8E7CB3
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A1G9EVVEC3JRD6BJJ42
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A283EJ651AYXCWK29D6
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A217P7RCCDYE20DQR33
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A26JACFPXDD69WJY0GW
  • run-pickup-stall · unknown (nuxt) · at 21:27:07Z · abandoned wrun_01M0BCA7Z3QP3SS95SFYPXNXBP

E2E Test Summary

Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production347247364212
❌ 💻 Local Development380825584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
❌ 🌐 Cross-language Conformance94124137
✅ vercel-multi-region270027
Total1524810253417792
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-node64146
✅ 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-node129126
❌ vite-stable-quickjs129126

✅ 📦 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
❌ python94124

✅ vercel-multi-region

AppPassedFailedSkipped
✅ nextjs-turbopack2700

📋 View full workflow run

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📊 Workflow Benchmarks

commit 68a9d5c · Tue, 18 Aug 2026 21:43:24 GMT · run logs

Backend: vercel · app: nextjs-turbopack

MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1341 (+36%) 🔻1430 🔴 (+25%) 🔻1513 🔴 (+29%) 🔻1607 🔴 (-4.3%)30
TTFSstream1370 (+215%) 🔻1447 🔴 (+24%) 🔻1495 🔴 (+26%) 🔻1535 🔴 (+27%) 🔻30
TTFShook + stream1663 (+256%) 🔻1740 🔴 (+5.8%)1792 🔴 (+5.7%)1884 🔴 (-0.9%)30
Fan-out TTFSPromise.all(100 steps)1388 (+9.5%)3068 (+26%) 🔻3113 (+20%) 🔻3290 (+9.6%)10
Fan-out TTLSPromise.all(100 steps)5966 (+12%)7650 (-4.4%)8579 (+3.0%)22196 (+82%) 🔻10
STSO1020 steps (inline)137 (+11%)195 (-32%) 💚281 (-21%) 💚411 (-50%) 💚1019
WO1020 steps199492 (-29%) 💚199492 (-29%) 💚199492 (-29%) 💚199492 (-29%) 💚1
CRTTfirst chunk (pooled)119 (+14%)196 (+22%) 🔻459 (+156%) 🔻4030 (+517%) 🔻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 (+2%)143 (-6%)166 (-33%)228 (-48%)468 (-25%)144 (-30%)10
size sweep (100/s, 160B-12KB)100 (±0%)101 (+1%)334 (±0%)337 (+1%)164 (+17%)160 (-13%)228 (-20%)414 (-17%)133 (-11%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)90.3 (+2%)16.2 (±0%)16.4 (+1%)459 (+250%)178 (+13%)273 (+31%)556 (+32%)355 (+23%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)2093 (+1467%)152 (-6%)207 (-6%)883 (+143%)530 (+76%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (+1%)710 (±0%)712 (+1%)147 (+26%)259 (-69%)561 (-54%)951 (-43%)463 (-40%)3
📈 STSO distribution vs main (inline / queue-hop histograms)

1020 steps (inline)

Cumulative STSO time: main 279211ms → this run 197976ms (Δ -81235ms, -29%)

 100-150 ms ┃ main 4 this 16 +12
150-200 ms ████░░░░░░░░░░░░░░░░░░░┃ main 120 this 769 +649
200-250 ms ██┃██████████ main 413 this 105 -308
250-300 ms ┃████████ main 282 this 48 -234
300-350 ms █┃█ main 91 this 54 -37
350-400 ms ┃ main 29 this 16 -13
400-450 ms ┃ main 26 this 7 -19
450-500 ms ┃ main 6 this 0 -6
500-550 ms ┃ main 13 this 2 -11
550-600 ms ┃ main 5 this 0 -5
600-650 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 5 this 0 -5
700-750 ms ┃ main 5 this 1 -4
750-800 ms ┃ main 4 this 0 -4
800-850 ms ┃ main 7 this 0 -7
850-900 ms ┃ main 4 this 0 -4
900-950 ms ┃ main 1 this 0 -1
1150-1200 ms ┃ main 1 this 0 -1
1250-1300 ms ┃ main 2 this 0 -2
📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▁···· 143.1 (-16%) 138 (-2%) 228 (-48%) 468 (-25%) 3000
sweep ······▂█▁···· 138.9 (-9%) 129 (-8%) 228 (-20%) 414 (-17%) 3000
gw 1x ······▂█▂▁··· 158.4 (+19%) 133 (+6%) 273 (+31%) 556 (+32%) 5295
eve 1x ·····▁▃█▁▁▁▁· 145.3 (+5%) 117 (-4%) 207 (-6%) 883 (+143%) 5186
eve 2x ······▁█▄▁▁·· 213.3 (-43%) 165 (-43%) 561 (-54%) 951 (-43%) 7779

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

control █▇▅▆▁▁▃▃▂▁ 130–165ms
sweep █▂▁▂▂▂▃▂▂▅ 126–174ms
gw 1x █▄▂▂▂▂▂▂▂▁ 120–298ms
eve 1x █▁▃▁▁▃▃▅▂▂ 107–246ms
eve 2x ▆█▅▁▁▂▂▃▃▁ 153–337ms

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

sweep ▆█▅▁▂▃▃ 138–141ms

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

control ▁▅█▆▅▅▆▆▃▄ 27–54ms
sweep ▁▆▆█▄▅▇▇▅▇ 34–67ms
gw 1x █▄▂▁▃▂▁▂▂▁ 35–75ms
eve 1x █▁▄▃▁▄▃▃▂▃ 21–36ms
eve 2x █▇▃▂▃▂▃▁▃▃ 22–47ms
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
[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
alangenfeldforce-pushed the alangenfeld/e2e-concurrent branch from 68a9d5c to 4e95ca7CompareAugust 18, 2026 22:12
@alangenfeld
[e2e] Bind per-test state via a task collector, not a fixture
0556953
CI on the first concurrent run caught the fixture design failing in the
one place skip-correctness is load-bearing: vitest resolves fixtures in
a separate async context, so an AsyncLocalStorage store bound around
use() never reaches the test body. Every ambient read silently fell to
the module fallback - conformance-gated tests on the Python lane ran
instead of skipping and hard-failed on fixtures missing from the
manifest ('declared in e2e-conformance.json but not in the deployed
manifest').
The suite's test is now built with createTaskCollector, mirroring
vitest's own argument normalization, and the wrapper binds the state
around the handler call itself - a direct call stack, so propagation is
guaranteed rather than assumed. Validated by a collector-pattern ALS
experiment (per-test store after awaits, mid-body skip targets self,
each/skip/todo chains), a conformance-file simulation reproducing the
Python failure shape (fixture-missing tests now skip with the right
note), and a 137/137 concurrent local run.
Also raises RACE_WINNER_MAX_DURATION_MS 5s -> 8s: the winner takes 1s,
the loser 10s, and the bound only has to sit clearly below the loser -
concurrent-suite queue latency pushed observed winner durations to
~6.5s on loaded local-dev lanes (vite, first concurrent CI run), so 5s
flaked without catching anything 8s misses.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
@alangenfeld
alangenfeldforce-pushed the alangenfeld/e2e-concurrent branch from 70a072a to 0556953CompareAugust 19, 2026 14:34
@vercel
vercelBottemporarily deployed to Preview – workflow-docs August 19, 2026 14:35 Inactive
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Superseded by the v2 branch of this PR — this branch's pull_request events stopped reaching GitHub Actions during the Aug 18 instability (pushes and close/reopen produced no check suites), so the same commits continue on a fresh branch.

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, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
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}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

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[e2e] Re-enable concurrent execution of the e2e suite - #3628
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Summary & Motivation
Serial e2e was the dominant wall-clock cost per matrix entry (~22 of 24 minutes on the Vercel lanes), and the blockers #2083 identified are now fixed. Making the suite concurrent required per-test attribution that survives interleaving: an auto fixture binds each test's name, tracked runs, and skip through AsyncLocalStorage, since vitest's getCurrentTest() is a module variable that goes stale after any await — so a failing test now dumps its own diagnostics rather than a sibling's. A test that genuinely cannot share a deployment can opt out with test.sequential.
Test Plan
  •  Full suite passes 137/137 concurrently against a local nextjs-turbopack dev server in under 2 minutes, with a new unit test covering attribution across interleaved contexts.
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⚠️ No Changeset found
Latest commit: 0556953
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (4 failed)
python-node (4 failed):
  • hookMinRetentionWorkflow - terminal Hook cannot resume and its token stays unavailable
  • setAttributes setAttributesInsideStepWorkflow: step-body calls append attributed native events
  • setAttributes workflow throws after awaited setAttributes: attribute still persists on the failed run
  • setAttributes start: invalid initial attributes are rejected before a run is created
💻 Local Development (2 failed)
vite-stable-node (1 failed):
  • sleepWinsRaceWorkflow
vite-stable-quickjs (1 failed):
  • sleepWinsRaceWorkflow
🌐 Cross-language Conformance (4 failed)
python (4 failed):
  • hookGetConflictWorkflow - hook.getConflict() resolves with the conflicting run when token is already registered
  • hookSupersedeOwnerWorkflow - duplicate cancels the owner and claims the released token
  • setAttributes setAttributesInsideStepWorkflow: step-body calls append attributed native events
  • setAttributes start: invalid initial attributes are rejected before a run is created
⚠️ 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.
  • 'hookGetConflictWithPriorStepWorkflow' - hook.getConflict() does not block step execution (nextjs-webpack)
  • abortHookOrderingWorkflow [listener-first-abort-first]: addEventListener → hook.then → abort() → resumeHook (nextjs-turbopack)
  • sleepWinsRaceWorkflow (tanstack-start)
  • stepWinsRaceWorkflow (tanstack-start)
  • stepWinsRaceWorkflow (vite)
🛠 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 · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A23XH4SJQ0FNX8E7CB3
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A1G9EVVEC3JRD6BJJ42
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A283EJ651AYXCWK29D6
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A217P7RCCDYE20DQR33
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A26JACFPXDD69WJY0GW
  • run-pickup-stall · unknown (nuxt) · at 21:27:07Z · abandoned wrun_01M0BCA7Z3QP3SS95SFYPXNXBP
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production347247364212
❌ 💻 Local Development380825584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
❌ 🌐 Cross-language Conformance94124137
✅ vercel-multi-region270027
Total1524810253417792
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-node64146
✅ 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-node129126
❌ vite-stable-quickjs129126
✅ 📦 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
❌ python94124
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit 68a9d5c · Tue, 18 Aug 2026 21:43:24 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1341 (+36%) 🔻1430 🔴 (+25%) 🔻1513 🔴 (+29%) 🔻1607 🔴 (-4.3%)30
TTFSstream1370 (+215%) 🔻1447 🔴 (+24%) 🔻1495 🔴 (+26%) 🔻1535 🔴 (+27%) 🔻30
TTFShook + stream1663 (+256%) 🔻1740 🔴 (+5.8%)1792 🔴 (+5.7%)1884 🔴 (-0.9%)30
Fan-out TTFSPromise.all(100 steps)1388 (+9.5%)3068 (+26%) 🔻3113 (+20%) 🔻3290 (+9.6%)10
Fan-out TTLSPromise.all(100 steps)5966 (+12%)7650 (-4.4%)8579 (+3.0%)22196 (+82%) 🔻10
STSO1020 steps (inline)137 (+11%)195 (-32%) 💚281 (-21%) 💚411 (-50%) 💚1019
WO1020 steps199492 (-29%) 💚199492 (-29%) 💚199492 (-29%) 💚199492 (-29%) 💚1
CRTTfirst chunk (pooled)119 (+14%)196 (+22%) 🔻459 (+156%) 🔻4030 (+517%) 🔻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 (+2%)143 (-6%)166 (-33%)228 (-48%)468 (-25%)144 (-30%)10
size sweep (100/s, 160B-12KB)100 (±0%)101 (+1%)334 (±0%)337 (+1%)164 (+17%)160 (-13%)228 (-20%)414 (-17%)133 (-11%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)90.3 (+2%)16.2 (±0%)16.4 (+1%)459 (+250%)178 (+13%)273 (+31%)556 (+32%)355 (+23%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)2093 (+1467%)152 (-6%)207 (-6%)883 (+143%)530 (+76%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (+1%)710 (±0%)712 (+1%)147 (+26%)259 (-69%)561 (-54%)951 (-43%)463 (-40%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 279211ms → this run 197976ms (Δ -81235ms, -29%)
 100-150 ms ┃ main 4 this 16 +12
150-200 ms ████░░░░░░░░░░░░░░░░░░░┃ main 120 this 769 +649
200-250 ms ██┃██████████ main 413 this 105 -308
250-300 ms ┃████████ main 282 this 48 -234
300-350 ms █┃█ main 91 this 54 -37
350-400 ms ┃ main 29 this 16 -13
400-450 ms ┃ main 26 this 7 -19
450-500 ms ┃ main 6 this 0 -6
500-550 ms ┃ main 13 this 2 -11
550-600 ms ┃ main 5 this 0 -5
600-650 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 5 this 0 -5
700-750 ms ┃ main 5 this 1 -4
750-800 ms ┃ main 4 this 0 -4
800-850 ms ┃ main 7 this 0 -7
850-900 ms ┃ main 4 this 0 -4
900-950 ms ┃ main 1 this 0 -1
1150-1200 ms ┃ main 1 this 0 -1
1250-1300 ms ┃ main 2 this 0 -2

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▁···· 143.1 (-16%) 138 (-2%) 228 (-48%) 468 (-25%) 3000
sweep ······▂█▁···· 138.9 (-9%) 129 (-8%) 228 (-20%) 414 (-17%) 3000
gw 1x ······▂█▂▁··· 158.4 (+19%) 133 (+6%) 273 (+31%) 556 (+32%) 5295
eve 1x ·····▁▃█▁▁▁▁· 145.3 (+5%) 117 (-4%) 207 (-6%) 883 (+143%) 5186
eve 2x ······▁█▄▁▁·· 213.3 (-43%) 165 (-43%) 561 (-54%) 951 (-43%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control █▇▅▆▁▁▃▃▂▁ 130–165ms
sweep █▂▁▂▂▂▃▂▂▅ 126–174ms
gw 1x █▄▂▂▂▂▂▂▂▁ 120–298ms
eve 1x █▁▃▁▁▃▃▅▂▂ 107–246ms
eve 2x ▆█▅▁▁▂▂▃▃▁ 153–337ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▆█▅▁▂▃▃ 138–141ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▅█▆▅▅▆▆▃▄ 27–54ms
sweep ▁▆▆█▄▅▇▇▅▇ 34–67ms
gw 1x █▄▂▁▃▂▁▂▂▁ 35–75ms
eve 1x █▁▄▃▁▄▃▃▂▃ 21–36ms
eve 2x █▇▃▂▃▂▃▁▃▃ 22–47ms

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
[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>
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@alangenfeld
[e2e] Bind per-test state via a task collector, not a fixture
0556953
CI on the first concurrent run caught the fixture design failing in the
one place skip-correctness is load-bearing: vitest resolves fixtures in
a separate async context, so an AsyncLocalStorage store bound around
use() never reaches the test body. Every ambient read silently fell to
the module fallback - conformance-gated tests on the Python lane ran
instead of skipping and hard-failed on fixtures missing from the
manifest ('declared in e2e-conformance.json but not in the deployed
manifest').
The suite's test is now built with createTaskCollector, mirroring
vitest's own argument normalization, and the wrapper binds the state
around the handler call itself - a direct call stack, so propagation is
guaranteed rather than assumed. Validated by a collector-pattern ALS
experiment (per-test store after awaits, mid-body skip targets self,
each/skip/todo chains), a conformance-file simulation reproducing the
Python failure shape (fixture-missing tests now skip with the right
note), and a 137/137 concurrent local run.
Also raises RACE_WINNER_MAX_DURATION_MS 5s -> 8s: the winner takes 1s,
the loser 10s, and the bound only has to sit clearly below the loser -
concurrent-suite queue latency pushed observed winner durations to
~6.5s on loaded local-dev lanes (vite, first concurrent CI run), so 5s
flaked without catching anything 8s misses.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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Superseded by the v2 branch of this PR — this branch's pull_request events stopped reaching GitHub Actions during the Aug 18 instability (pushes and close/reopen produced no check suites), so the same commits continue on a fresh branch.
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[e2e] Re-enable concurrent execution of the e2e suite - #3628
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Summary & Motivation
Serial e2e was the dominant wall-clock cost per matrix entry (~22 of 24 minutes on the Vercel lanes), and the blockers #2083 identified are now fixed. Making the suite concurrent required per-test attribution that survives interleaving: an auto fixture binds each test's name, tracked runs, and skip through AsyncLocalStorage, since vitest's getCurrentTest() is a module variable that goes stale after any await — so a failing test now dumps its own diagnostics rather than a sibling's. A test that genuinely cannot share a deployment can opt out with test.sequential.
Test Plan
  •  Full suite passes 137/137 concurrently against a local nextjs-turbopack dev server in under 2 minutes, with a new unit test covering attribution across interleaved contexts.
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The latest updates on your projects. Learn more about Vercel for GitHub.
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⚠️ No Changeset found
Latest commit: 0556953
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (4 failed)
python-node (4 failed):
  • hookMinRetentionWorkflow - terminal Hook cannot resume and its token stays unavailable
  • setAttributes setAttributesInsideStepWorkflow: step-body calls append attributed native events
  • setAttributes workflow throws after awaited setAttributes: attribute still persists on the failed run
  • setAttributes start: invalid initial attributes are rejected before a run is created
💻 Local Development (2 failed)
vite-stable-node (1 failed):
  • sleepWinsRaceWorkflow
vite-stable-quickjs (1 failed):
  • sleepWinsRaceWorkflow
🌐 Cross-language Conformance (4 failed)
python (4 failed):
  • hookGetConflictWorkflow - hook.getConflict() resolves with the conflicting run when token is already registered
  • hookSupersedeOwnerWorkflow - duplicate cancels the owner and claims the released token
  • setAttributes setAttributesInsideStepWorkflow: step-body calls append attributed native events
  • setAttributes start: invalid initial attributes are rejected before a run is created
⚠️ 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.
  • 'hookGetConflictWithPriorStepWorkflow' - hook.getConflict() does not block step execution (nextjs-webpack)
  • abortHookOrderingWorkflow [listener-first-abort-first]: addEventListener → hook.then → abort() → resumeHook (nextjs-turbopack)
  • sleepWinsRaceWorkflow (tanstack-start)
  • stepWinsRaceWorkflow (tanstack-start)
  • stepWinsRaceWorkflow (vite)
🛠 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 · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A23XH4SJQ0FNX8E7CB3
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A1G9EVVEC3JRD6BJJ42
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A283EJ651AYXCWK29D6
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A217P7RCCDYE20DQR33
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A26JACFPXDD69WJY0GW
  • run-pickup-stall · unknown (nuxt) · at 21:27:07Z · abandoned wrun_01M0BCA7Z3QP3SS95SFYPXNXBP
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production347247364212
❌ 💻 Local Development380825584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
❌ 🌐 Cross-language Conformance94124137
✅ vercel-multi-region270027
Total1524810253417792
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-node64146
✅ 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-node129126
❌ vite-stable-quickjs129126
✅ 📦 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
❌ python94124
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit 68a9d5c · Tue, 18 Aug 2026 21:43:24 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1341 (+36%) 🔻1430 🔴 (+25%) 🔻1513 🔴 (+29%) 🔻1607 🔴 (-4.3%)30
TTFSstream1370 (+215%) 🔻1447 🔴 (+24%) 🔻1495 🔴 (+26%) 🔻1535 🔴 (+27%) 🔻30
TTFShook + stream1663 (+256%) 🔻1740 🔴 (+5.8%)1792 🔴 (+5.7%)1884 🔴 (-0.9%)30
Fan-out TTFSPromise.all(100 steps)1388 (+9.5%)3068 (+26%) 🔻3113 (+20%) 🔻3290 (+9.6%)10
Fan-out TTLSPromise.all(100 steps)5966 (+12%)7650 (-4.4%)8579 (+3.0%)22196 (+82%) 🔻10
STSO1020 steps (inline)137 (+11%)195 (-32%) 💚281 (-21%) 💚411 (-50%) 💚1019
WO1020 steps199492 (-29%) 💚199492 (-29%) 💚199492 (-29%) 💚199492 (-29%) 💚1
CRTTfirst chunk (pooled)119 (+14%)196 (+22%) 🔻459 (+156%) 🔻4030 (+517%) 🔻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 (+2%)143 (-6%)166 (-33%)228 (-48%)468 (-25%)144 (-30%)10
size sweep (100/s, 160B-12KB)100 (±0%)101 (+1%)334 (±0%)337 (+1%)164 (+17%)160 (-13%)228 (-20%)414 (-17%)133 (-11%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)90.3 (+2%)16.2 (±0%)16.4 (+1%)459 (+250%)178 (+13%)273 (+31%)556 (+32%)355 (+23%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)2093 (+1467%)152 (-6%)207 (-6%)883 (+143%)530 (+76%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (+1%)710 (±0%)712 (+1%)147 (+26%)259 (-69%)561 (-54%)951 (-43%)463 (-40%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 279211ms → this run 197976ms (Δ -81235ms, -29%)
 100-150 ms ┃ main 4 this 16 +12
150-200 ms ████░░░░░░░░░░░░░░░░░░░┃ main 120 this 769 +649
200-250 ms ██┃██████████ main 413 this 105 -308
250-300 ms ┃████████ main 282 this 48 -234
300-350 ms █┃█ main 91 this 54 -37
350-400 ms ┃ main 29 this 16 -13
400-450 ms ┃ main 26 this 7 -19
450-500 ms ┃ main 6 this 0 -6
500-550 ms ┃ main 13 this 2 -11
550-600 ms ┃ main 5 this 0 -5
600-650 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 5 this 0 -5
700-750 ms ┃ main 5 this 1 -4
750-800 ms ┃ main 4 this 0 -4
800-850 ms ┃ main 7 this 0 -7
850-900 ms ┃ main 4 this 0 -4
900-950 ms ┃ main 1 this 0 -1
1150-1200 ms ┃ main 1 this 0 -1
1250-1300 ms ┃ main 2 this 0 -2

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▁···· 143.1 (-16%) 138 (-2%) 228 (-48%) 468 (-25%) 3000
sweep ······▂█▁···· 138.9 (-9%) 129 (-8%) 228 (-20%) 414 (-17%) 3000
gw 1x ······▂█▂▁··· 158.4 (+19%) 133 (+6%) 273 (+31%) 556 (+32%) 5295
eve 1x ·····▁▃█▁▁▁▁· 145.3 (+5%) 117 (-4%) 207 (-6%) 883 (+143%) 5186
eve 2x ······▁█▄▁▁·· 213.3 (-43%) 165 (-43%) 561 (-54%) 951 (-43%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control █▇▅▆▁▁▃▃▂▁ 130–165ms
sweep █▂▁▂▂▂▃▂▂▅ 126–174ms
gw 1x █▄▂▂▂▂▂▂▂▁ 120–298ms
eve 1x █▁▃▁▁▃▃▅▂▂ 107–246ms
eve 2x ▆█▅▁▁▂▂▃▃▁ 153–337ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▆█▅▁▂▃▃ 138–141ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▅█▆▅▅▆▆▃▄ 27–54ms
sweep ▁▆▆█▄▅▇▇▅▇ 34–67ms
gw 1x █▄▂▁▃▂▁▂▂▁ 35–75ms
eve 1x █▁▄▃▁▄▃▃▂▃ 21–36ms
eve 2x █▇▃▂▃▂▃▁▃▃ 22–47ms

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
[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>
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@alangenfeld
[e2e] Bind per-test state via a task collector, not a fixture
0556953
CI on the first concurrent run caught the fixture design failing in the
one place skip-correctness is load-bearing: vitest resolves fixtures in
a separate async context, so an AsyncLocalStorage store bound around
use() never reaches the test body. Every ambient read silently fell to
the module fallback - conformance-gated tests on the Python lane ran
instead of skipping and hard-failed on fixtures missing from the
manifest ('declared in e2e-conformance.json but not in the deployed
manifest').
The suite's test is now built with createTaskCollector, mirroring
vitest's own argument normalization, and the wrapper binds the state
around the handler call itself - a direct call stack, so propagation is
guaranteed rather than assumed. Validated by a collector-pattern ALS
experiment (per-test store after awaits, mid-body skip targets self,
each/skip/todo chains), a conformance-file simulation reproducing the
Python failure shape (fixture-missing tests now skip with the right
note), and a 137/137 concurrent local run.
Also raises RACE_WINNER_MAX_DURATION_MS 5s -> 8s: the winner takes 1s,
the loser 10s, and the bound only has to sit clearly below the loser -
concurrent-suite queue latency pushed observed winner durations to
~6.5s on loaded local-dev lanes (vite, first concurrent CI run), so 5s
flaked without catching anything 8s misses.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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Superseded by the v2 branch of this PR — this branch's pull_request events stopped reaching GitHub Actions during the Aug 18 instability (pushes and close/reopen produced no check suites), so the same commits continue on a fresh branch.
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[e2e] Re-enable concurrent execution of the e2e suite - #3628
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Summary & Motivation
Serial e2e was the dominant wall-clock cost per matrix entry (~22 of 24 minutes on the Vercel lanes), and the blockers #2083 identified are now fixed. Making the suite concurrent required per-test attribution that survives interleaving: an auto fixture binds each test's name, tracked runs, and skip through AsyncLocalStorage, since vitest's getCurrentTest() is a module variable that goes stale after any await — so a failing test now dumps its own diagnostics rather than a sibling's. A test that genuinely cannot share a deployment can opt out with test.sequential.
Test Plan
  •  Full suite passes 137/137 concurrently against a local nextjs-turbopack dev server in under 2 minutes, with a new unit test covering attribution across interleaved contexts.
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⚠️ No Changeset found
Latest commit: 0556953
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (4 failed)
python-node (4 failed):
  • hookMinRetentionWorkflow - terminal Hook cannot resume and its token stays unavailable
  • setAttributes setAttributesInsideStepWorkflow: step-body calls append attributed native events
  • setAttributes workflow throws after awaited setAttributes: attribute still persists on the failed run
  • setAttributes start: invalid initial attributes are rejected before a run is created
💻 Local Development (2 failed)
vite-stable-node (1 failed):
  • sleepWinsRaceWorkflow
vite-stable-quickjs (1 failed):
  • sleepWinsRaceWorkflow
🌐 Cross-language Conformance (4 failed)
python (4 failed):
  • hookGetConflictWorkflow - hook.getConflict() resolves with the conflicting run when token is already registered
  • hookSupersedeOwnerWorkflow - duplicate cancels the owner and claims the released token
  • setAttributes setAttributesInsideStepWorkflow: step-body calls append attributed native events
  • setAttributes start: invalid initial attributes are rejected before a run is created
⚠️ 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.
  • 'hookGetConflictWithPriorStepWorkflow' - hook.getConflict() does not block step execution (nextjs-webpack)
  • abortHookOrderingWorkflow [listener-first-abort-first]: addEventListener → hook.then → abort() → resumeHook (nextjs-turbopack)
  • sleepWinsRaceWorkflow (tanstack-start)
  • stepWinsRaceWorkflow (tanstack-start)
  • stepWinsRaceWorkflow (vite)
🛠 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 · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A23XH4SJQ0FNX8E7CB3
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A1G9EVVEC3JRD6BJJ42
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A283EJ651AYXCWK29D6
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A217P7RCCDYE20DQR33
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A26JACFPXDD69WJY0GW
  • run-pickup-stall · unknown (nuxt) · at 21:27:07Z · abandoned wrun_01M0BCA7Z3QP3SS95SFYPXNXBP
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production347247364212
❌ 💻 Local Development380825584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
❌ 🌐 Cross-language Conformance94124137
✅ vercel-multi-region270027
Total1524810253417792
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-node64146
✅ 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-node129126
❌ vite-stable-quickjs129126
✅ 📦 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
❌ python94124
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit 68a9d5c · Tue, 18 Aug 2026 21:43:24 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1341 (+36%) 🔻1430 🔴 (+25%) 🔻1513 🔴 (+29%) 🔻1607 🔴 (-4.3%)30
TTFSstream1370 (+215%) 🔻1447 🔴 (+24%) 🔻1495 🔴 (+26%) 🔻1535 🔴 (+27%) 🔻30
TTFShook + stream1663 (+256%) 🔻1740 🔴 (+5.8%)1792 🔴 (+5.7%)1884 🔴 (-0.9%)30
Fan-out TTFSPromise.all(100 steps)1388 (+9.5%)3068 (+26%) 🔻3113 (+20%) 🔻3290 (+9.6%)10
Fan-out TTLSPromise.all(100 steps)5966 (+12%)7650 (-4.4%)8579 (+3.0%)22196 (+82%) 🔻10
STSO1020 steps (inline)137 (+11%)195 (-32%) 💚281 (-21%) 💚411 (-50%) 💚1019
WO1020 steps199492 (-29%) 💚199492 (-29%) 💚199492 (-29%) 💚199492 (-29%) 💚1
CRTTfirst chunk (pooled)119 (+14%)196 (+22%) 🔻459 (+156%) 🔻4030 (+517%) 🔻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 (+2%)143 (-6%)166 (-33%)228 (-48%)468 (-25%)144 (-30%)10
size sweep (100/s, 160B-12KB)100 (±0%)101 (+1%)334 (±0%)337 (+1%)164 (+17%)160 (-13%)228 (-20%)414 (-17%)133 (-11%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)90.3 (+2%)16.2 (±0%)16.4 (+1%)459 (+250%)178 (+13%)273 (+31%)556 (+32%)355 (+23%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)2093 (+1467%)152 (-6%)207 (-6%)883 (+143%)530 (+76%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (+1%)710 (±0%)712 (+1%)147 (+26%)259 (-69%)561 (-54%)951 (-43%)463 (-40%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 279211ms → this run 197976ms (Δ -81235ms, -29%)
 100-150 ms ┃ main 4 this 16 +12
150-200 ms ████░░░░░░░░░░░░░░░░░░░┃ main 120 this 769 +649
200-250 ms ██┃██████████ main 413 this 105 -308
250-300 ms ┃████████ main 282 this 48 -234
300-350 ms █┃█ main 91 this 54 -37
350-400 ms ┃ main 29 this 16 -13
400-450 ms ┃ main 26 this 7 -19
450-500 ms ┃ main 6 this 0 -6
500-550 ms ┃ main 13 this 2 -11
550-600 ms ┃ main 5 this 0 -5
600-650 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 5 this 0 -5
700-750 ms ┃ main 5 this 1 -4
750-800 ms ┃ main 4 this 0 -4
800-850 ms ┃ main 7 this 0 -7
850-900 ms ┃ main 4 this 0 -4
900-950 ms ┃ main 1 this 0 -1
1150-1200 ms ┃ main 1 this 0 -1
1250-1300 ms ┃ main 2 this 0 -2

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▁···· 143.1 (-16%) 138 (-2%) 228 (-48%) 468 (-25%) 3000
sweep ······▂█▁···· 138.9 (-9%) 129 (-8%) 228 (-20%) 414 (-17%) 3000
gw 1x ······▂█▂▁··· 158.4 (+19%) 133 (+6%) 273 (+31%) 556 (+32%) 5295
eve 1x ·····▁▃█▁▁▁▁· 145.3 (+5%) 117 (-4%) 207 (-6%) 883 (+143%) 5186
eve 2x ······▁█▄▁▁·· 213.3 (-43%) 165 (-43%) 561 (-54%) 951 (-43%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control █▇▅▆▁▁▃▃▂▁ 130–165ms
sweep █▂▁▂▂▂▃▂▂▅ 126–174ms
gw 1x █▄▂▂▂▂▂▂▂▁ 120–298ms
eve 1x █▁▃▁▁▃▃▅▂▂ 107–246ms
eve 2x ▆█▅▁▁▂▂▃▃▁ 153–337ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▆█▅▁▂▃▃ 138–141ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▅█▆▅▅▆▆▃▄ 27–54ms
sweep ▁▆▆█▄▅▇▇▅▇ 34–67ms
gw 1x █▄▂▁▃▂▁▂▂▁ 35–75ms
eve 1x █▁▄▃▁▄▃▃▂▃ 21–36ms
eve 2x █▇▃▂▃▂▃▁▃▃ 22–47ms

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
[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>
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@alangenfeld
[e2e] Bind per-test state via a task collector, not a fixture
0556953
CI on the first concurrent run caught the fixture design failing in the
one place skip-correctness is load-bearing: vitest resolves fixtures in
a separate async context, so an AsyncLocalStorage store bound around
use() never reaches the test body. Every ambient read silently fell to
the module fallback - conformance-gated tests on the Python lane ran
instead of skipping and hard-failed on fixtures missing from the
manifest ('declared in e2e-conformance.json but not in the deployed
manifest').
The suite's test is now built with createTaskCollector, mirroring
vitest's own argument normalization, and the wrapper binds the state
around the handler call itself - a direct call stack, so propagation is
guaranteed rather than assumed. Validated by a collector-pattern ALS
experiment (per-test store after awaits, mid-body skip targets self,
each/skip/todo chains), a conformance-file simulation reproducing the
Python failure shape (fixture-missing tests now skip with the right
note), and a 137/137 concurrent local run.
Also raises RACE_WINNER_MAX_DURATION_MS 5s -> 8s: the winner takes 1s,
the loser 10s, and the bound only has to sit clearly below the loser -
concurrent-suite queue latency pushed observed winner durations to
~6.5s on loaded local-dev lanes (vite, first concurrent CI run), so 5s
flaked without catching anything 8s misses.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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Superseded by the v2 branch of this PR — this branch's pull_request events stopped reaching GitHub Actions during the Aug 18 instability (pushes and close/reopen produced no check suites), so the same commits continue on a fresh branch.
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

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[e2e] Re-enable concurrent execution of the e2e suite - #3628
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[e2e] Re-enable concurrent execution of the e2e suite#3628
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@alangenfeld
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Summary & Motivation
Serial e2e was the dominant wall-clock cost per matrix entry (~22 of 24 minutes on the Vercel lanes), and the blockers #2083 identified are now fixed. Making the suite concurrent required per-test attribution that survives interleaving: an auto fixture binds each test's name, tracked runs, and skip through AsyncLocalStorage, since vitest's getCurrentTest() is a module variable that goes stale after any await — so a failing test now dumps its own diagnostics rather than a sibling's. A test that genuinely cannot share a deployment can opt out with test.sequential.
Test Plan
  •  Full suite passes 137/137 concurrently against a local nextjs-turbopack dev server in under 2 minutes, with a new unit test covering attribution across interleaved contexts.
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⚠️ No Changeset found
Latest commit: 0556953
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (4 failed)
python-node (4 failed):
  • hookMinRetentionWorkflow - terminal Hook cannot resume and its token stays unavailable
  • setAttributes setAttributesInsideStepWorkflow: step-body calls append attributed native events
  • setAttributes workflow throws after awaited setAttributes: attribute still persists on the failed run
  • setAttributes start: invalid initial attributes are rejected before a run is created
💻 Local Development (2 failed)
vite-stable-node (1 failed):
  • sleepWinsRaceWorkflow
vite-stable-quickjs (1 failed):
  • sleepWinsRaceWorkflow
🌐 Cross-language Conformance (4 failed)
python (4 failed):
  • hookGetConflictWorkflow - hook.getConflict() resolves with the conflicting run when token is already registered
  • hookSupersedeOwnerWorkflow - duplicate cancels the owner and claims the released token
  • setAttributes setAttributesInsideStepWorkflow: step-body calls append attributed native events
  • setAttributes start: invalid initial attributes are rejected before a run is created
⚠️ 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.
  • 'hookGetConflictWithPriorStepWorkflow' - hook.getConflict() does not block step execution (nextjs-webpack)
  • abortHookOrderingWorkflow [listener-first-abort-first]: addEventListener → hook.then → abort() → resumeHook (nextjs-turbopack)
  • sleepWinsRaceWorkflow (tanstack-start)
  • stepWinsRaceWorkflow (tanstack-start)
  • stepWinsRaceWorkflow (vite)
🛠 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 · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A23XH4SJQ0FNX8E7CB3
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A1G9EVVEC3JRD6BJJ42
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A283EJ651AYXCWK29D6
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A217P7RCCDYE20DQR33
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A26JACFPXDD69WJY0GW
  • run-pickup-stall · unknown (nuxt) · at 21:27:07Z · abandoned wrun_01M0BCA7Z3QP3SS95SFYPXNXBP
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production347247364212
❌ 💻 Local Development380825584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
❌ 🌐 Cross-language Conformance94124137
✅ vercel-multi-region270027
Total1524810253417792
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-node64146
✅ sveltekit-node14709
✅ sveltekit-quickjs14709
✅ tanstack-start-node128028
✅ tanstack-start-quickjs128028
✅ vite-node128028
✅ vite-quickjs128028
❌ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
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✅ nextjs-turbopack-canary-node137019
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✅ 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
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✅ nuxt-stable-node130026
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✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
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❌ vite-stable-node129126
❌ vite-stable-quickjs129126
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✅ hono-stable-node130026
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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
✅ 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
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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
✅ 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
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✅ 🪟 Windows
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✅ nextjs-turbopack-quickjs15600
❌ 🌐 Cross-language Conformance
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📋 View full workflow run
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📊 Workflow Benchmarks
commit 68a9d5c · Tue, 18 Aug 2026 21:43:24 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1341 (+36%) 🔻1430 🔴 (+25%) 🔻1513 🔴 (+29%) 🔻1607 🔴 (-4.3%)30
TTFSstream1370 (+215%) 🔻1447 🔴 (+24%) 🔻1495 🔴 (+26%) 🔻1535 🔴 (+27%) 🔻30
TTFShook + stream1663 (+256%) 🔻1740 🔴 (+5.8%)1792 🔴 (+5.7%)1884 🔴 (-0.9%)30
Fan-out TTFSPromise.all(100 steps)1388 (+9.5%)3068 (+26%) 🔻3113 (+20%) 🔻3290 (+9.6%)10
Fan-out TTLSPromise.all(100 steps)5966 (+12%)7650 (-4.4%)8579 (+3.0%)22196 (+82%) 🔻10
STSO1020 steps (inline)137 (+11%)195 (-32%) 💚281 (-21%) 💚411 (-50%) 💚1019
WO1020 steps199492 (-29%) 💚199492 (-29%) 💚199492 (-29%) 💚199492 (-29%) 💚1
CRTTfirst chunk (pooled)119 (+14%)196 (+22%) 🔻459 (+156%) 🔻4030 (+517%) 🔻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 (+2%)143 (-6%)166 (-33%)228 (-48%)468 (-25%)144 (-30%)10
size sweep (100/s, 160B-12KB)100 (±0%)101 (+1%)334 (±0%)337 (+1%)164 (+17%)160 (-13%)228 (-20%)414 (-17%)133 (-11%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)90.3 (+2%)16.2 (±0%)16.4 (+1%)459 (+250%)178 (+13%)273 (+31%)556 (+32%)355 (+23%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)2093 (+1467%)152 (-6%)207 (-6%)883 (+143%)530 (+76%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (+1%)710 (±0%)712 (+1%)147 (+26%)259 (-69%)561 (-54%)951 (-43%)463 (-40%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 279211ms → this run 197976ms (Δ -81235ms, -29%)
 100-150 ms ┃ main 4 this 16 +12
150-200 ms ████░░░░░░░░░░░░░░░░░░░┃ main 120 this 769 +649
200-250 ms ██┃██████████ main 413 this 105 -308
250-300 ms ┃████████ main 282 this 48 -234
300-350 ms █┃█ main 91 this 54 -37
350-400 ms ┃ main 29 this 16 -13
400-450 ms ┃ main 26 this 7 -19
450-500 ms ┃ main 6 this 0 -6
500-550 ms ┃ main 13 this 2 -11
550-600 ms ┃ main 5 this 0 -5
600-650 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 5 this 0 -5
700-750 ms ┃ main 5 this 1 -4
750-800 ms ┃ main 4 this 0 -4
800-850 ms ┃ main 7 this 0 -7
850-900 ms ┃ main 4 this 0 -4
900-950 ms ┃ main 1 this 0 -1
1150-1200 ms ┃ main 1 this 0 -1
1250-1300 ms ┃ main 2 this 0 -2

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▁···· 143.1 (-16%) 138 (-2%) 228 (-48%) 468 (-25%) 3000
sweep ······▂█▁···· 138.9 (-9%) 129 (-8%) 228 (-20%) 414 (-17%) 3000
gw 1x ······▂█▂▁··· 158.4 (+19%) 133 (+6%) 273 (+31%) 556 (+32%) 5295
eve 1x ·····▁▃█▁▁▁▁· 145.3 (+5%) 117 (-4%) 207 (-6%) 883 (+143%) 5186
eve 2x ······▁█▄▁▁·· 213.3 (-43%) 165 (-43%) 561 (-54%) 951 (-43%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control █▇▅▆▁▁▃▃▂▁ 130–165ms
sweep █▂▁▂▂▂▃▂▂▅ 126–174ms
gw 1x █▄▂▂▂▂▂▂▂▁ 120–298ms
eve 1x █▁▃▁▁▃▃▅▂▂ 107–246ms
eve 2x ▆█▅▁▁▂▂▃▃▁ 153–337ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▆█▅▁▂▃▃ 138–141ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▅█▆▅▅▆▆▃▄ 27–54ms
sweep ▁▆▆█▄▅▇▇▅▇ 34–67ms
gw 1x █▄▂▁▃▂▁▂▂▁ 35–75ms
eve 1x █▁▄▃▁▄▃▃▂▃ 21–36ms
eve 2x █▇▃▂▃▂▃▁▃▃ 22–47ms

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
[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>
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@alangenfeld
[e2e] Bind per-test state via a task collector, not a fixture
0556953
CI on the first concurrent run caught the fixture design failing in the
one place skip-correctness is load-bearing: vitest resolves fixtures in
a separate async context, so an AsyncLocalStorage store bound around
use() never reaches the test body. Every ambient read silently fell to
the module fallback - conformance-gated tests on the Python lane ran
instead of skipping and hard-failed on fixtures missing from the
manifest ('declared in e2e-conformance.json but not in the deployed
manifest').
The suite's test is now built with createTaskCollector, mirroring
vitest's own argument normalization, and the wrapper binds the state
around the handler call itself - a direct call stack, so propagation is
guaranteed rather than assumed. Validated by a collector-pattern ALS
experiment (per-test store after awaits, mid-body skip targets self,
each/skip/todo chains), a conformance-file simulation reproducing the
Python failure shape (fixture-missing tests now skip with the right
note), and a 137/137 concurrent local run.
Also raises RACE_WINNER_MAX_DURATION_MS 5s -> 8s: the winner takes 1s,
the loser 10s, and the bound only has to sit clearly below the loser -
concurrent-suite queue latency pushed observed winner durations to
~6.5s on loaded local-dev lanes (vite, first concurrent CI run), so 5s
flaked without catching anything 8s misses.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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Superseded by the v2 branch of this PR — this branch's pull_request events stopped reaching GitHub Actions during the Aug 18 instability (pushes and close/reopen produced no check suites), so the same commits continue on a fresh branch.
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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[e2e] Re-enable concurrent execution of the e2e suite - #3628
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Summary & Motivation
Serial e2e was the dominant wall-clock cost per matrix entry (~22 of 24 minutes on the Vercel lanes), and the blockers #2083 identified are now fixed. Making the suite concurrent required per-test attribution that survives interleaving: an auto fixture binds each test's name, tracked runs, and skip through AsyncLocalStorage, since vitest's getCurrentTest() is a module variable that goes stale after any await — so a failing test now dumps its own diagnostics rather than a sibling's. A test that genuinely cannot share a deployment can opt out with test.sequential.
Test Plan
  •  Full suite passes 137/137 concurrently against a local nextjs-turbopack dev server in under 2 minutes, with a new unit test covering attribution across interleaved contexts.
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⚠️ No Changeset found
Latest commit: 0556953
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (4 failed)
python-node (4 failed):
  • hookMinRetentionWorkflow - terminal Hook cannot resume and its token stays unavailable
  • setAttributes setAttributesInsideStepWorkflow: step-body calls append attributed native events
  • setAttributes workflow throws after awaited setAttributes: attribute still persists on the failed run
  • setAttributes start: invalid initial attributes are rejected before a run is created
💻 Local Development (2 failed)
vite-stable-node (1 failed):
  • sleepWinsRaceWorkflow
vite-stable-quickjs (1 failed):
  • sleepWinsRaceWorkflow
🌐 Cross-language Conformance (4 failed)
python (4 failed):
  • hookGetConflictWorkflow - hook.getConflict() resolves with the conflicting run when token is already registered
  • hookSupersedeOwnerWorkflow - duplicate cancels the owner and claims the released token
  • setAttributes setAttributesInsideStepWorkflow: step-body calls append attributed native events
  • setAttributes start: invalid initial attributes are rejected before a run is created
⚠️ 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.
  • 'hookGetConflictWithPriorStepWorkflow' - hook.getConflict() does not block step execution (nextjs-webpack)
  • abortHookOrderingWorkflow [listener-first-abort-first]: addEventListener → hook.then → abort() → resumeHook (nextjs-turbopack)
  • sleepWinsRaceWorkflow (tanstack-start)
  • stepWinsRaceWorkflow (tanstack-start)
  • stepWinsRaceWorkflow (vite)
🛠 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 · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A23XH4SJQ0FNX8E7CB3
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A1G9EVVEC3JRD6BJJ42
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A283EJ651AYXCWK29D6
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A217P7RCCDYE20DQR33
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A26JACFPXDD69WJY0GW
  • run-pickup-stall · unknown (nuxt) · at 21:27:07Z · abandoned wrun_01M0BCA7Z3QP3SS95SFYPXNXBP
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production347247364212
❌ 💻 Local Development380825584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
❌ 🌐 Cross-language Conformance94124137
✅ vercel-multi-region270027
Total1524810253417792
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-node64146
✅ 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-node129126
❌ vite-stable-quickjs129126
✅ 📦 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
❌ python94124
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit 68a9d5c · Tue, 18 Aug 2026 21:43:24 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1341 (+36%) 🔻1430 🔴 (+25%) 🔻1513 🔴 (+29%) 🔻1607 🔴 (-4.3%)30
TTFSstream1370 (+215%) 🔻1447 🔴 (+24%) 🔻1495 🔴 (+26%) 🔻1535 🔴 (+27%) 🔻30
TTFShook + stream1663 (+256%) 🔻1740 🔴 (+5.8%)1792 🔴 (+5.7%)1884 🔴 (-0.9%)30
Fan-out TTFSPromise.all(100 steps)1388 (+9.5%)3068 (+26%) 🔻3113 (+20%) 🔻3290 (+9.6%)10
Fan-out TTLSPromise.all(100 steps)5966 (+12%)7650 (-4.4%)8579 (+3.0%)22196 (+82%) 🔻10
STSO1020 steps (inline)137 (+11%)195 (-32%) 💚281 (-21%) 💚411 (-50%) 💚1019
WO1020 steps199492 (-29%) 💚199492 (-29%) 💚199492 (-29%) 💚199492 (-29%) 💚1
CRTTfirst chunk (pooled)119 (+14%)196 (+22%) 🔻459 (+156%) 🔻4030 (+517%) 🔻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 (+2%)143 (-6%)166 (-33%)228 (-48%)468 (-25%)144 (-30%)10
size sweep (100/s, 160B-12KB)100 (±0%)101 (+1%)334 (±0%)337 (+1%)164 (+17%)160 (-13%)228 (-20%)414 (-17%)133 (-11%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)90.3 (+2%)16.2 (±0%)16.4 (+1%)459 (+250%)178 (+13%)273 (+31%)556 (+32%)355 (+23%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)2093 (+1467%)152 (-6%)207 (-6%)883 (+143%)530 (+76%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (+1%)710 (±0%)712 (+1%)147 (+26%)259 (-69%)561 (-54%)951 (-43%)463 (-40%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 279211ms → this run 197976ms (Δ -81235ms, -29%)
 100-150 ms ┃ main 4 this 16 +12
150-200 ms ████░░░░░░░░░░░░░░░░░░░┃ main 120 this 769 +649
200-250 ms ██┃██████████ main 413 this 105 -308
250-300 ms ┃████████ main 282 this 48 -234
300-350 ms █┃█ main 91 this 54 -37
350-400 ms ┃ main 29 this 16 -13
400-450 ms ┃ main 26 this 7 -19
450-500 ms ┃ main 6 this 0 -6
500-550 ms ┃ main 13 this 2 -11
550-600 ms ┃ main 5 this 0 -5
600-650 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 5 this 0 -5
700-750 ms ┃ main 5 this 1 -4
750-800 ms ┃ main 4 this 0 -4
800-850 ms ┃ main 7 this 0 -7
850-900 ms ┃ main 4 this 0 -4
900-950 ms ┃ main 1 this 0 -1
1150-1200 ms ┃ main 1 this 0 -1
1250-1300 ms ┃ main 2 this 0 -2

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▁···· 143.1 (-16%) 138 (-2%) 228 (-48%) 468 (-25%) 3000
sweep ······▂█▁···· 138.9 (-9%) 129 (-8%) 228 (-20%) 414 (-17%) 3000
gw 1x ······▂█▂▁··· 158.4 (+19%) 133 (+6%) 273 (+31%) 556 (+32%) 5295
eve 1x ·····▁▃█▁▁▁▁· 145.3 (+5%) 117 (-4%) 207 (-6%) 883 (+143%) 5186
eve 2x ······▁█▄▁▁·· 213.3 (-43%) 165 (-43%) 561 (-54%) 951 (-43%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control █▇▅▆▁▁▃▃▂▁ 130–165ms
sweep █▂▁▂▂▂▃▂▂▅ 126–174ms
gw 1x █▄▂▂▂▂▂▂▂▁ 120–298ms
eve 1x █▁▃▁▁▃▃▅▂▂ 107–246ms
eve 2x ▆█▅▁▁▂▂▃▃▁ 153–337ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▆█▅▁▂▃▃ 138–141ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▅█▆▅▅▆▆▃▄ 27–54ms
sweep ▁▆▆█▄▅▇▇▅▇ 34–67ms
gw 1x █▄▂▁▃▂▁▂▂▁ 35–75ms
eve 1x █▁▄▃▁▄▃▃▂▃ 21–36ms
eve 2x █▇▃▂▃▂▃▁▃▃ 22–47ms

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
[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>
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@alangenfeld
[e2e] Bind per-test state via a task collector, not a fixture
0556953
CI on the first concurrent run caught the fixture design failing in the
one place skip-correctness is load-bearing: vitest resolves fixtures in
a separate async context, so an AsyncLocalStorage store bound around
use() never reaches the test body. Every ambient read silently fell to
the module fallback - conformance-gated tests on the Python lane ran
instead of skipping and hard-failed on fixtures missing from the
manifest ('declared in e2e-conformance.json but not in the deployed
manifest').
The suite's test is now built with createTaskCollector, mirroring
vitest's own argument normalization, and the wrapper binds the state
around the handler call itself - a direct call stack, so propagation is
guaranteed rather than assumed. Validated by a collector-pattern ALS
experiment (per-test store after awaits, mid-body skip targets self,
each/skip/todo chains), a conformance-file simulation reproducing the
Python failure shape (fixture-missing tests now skip with the right
note), and a 137/137 concurrent local run.
Also raises RACE_WINNER_MAX_DURATION_MS 5s -> 8s: the winner takes 1s,
the loser 10s, and the bound only has to sit clearly below the loser -
concurrent-suite queue latency pushed observed winner durations to
~6.5s on loaded local-dev lanes (vite, first concurrent CI run), so 5s
flaked without catching anything 8s misses.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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Superseded by the v2 branch of this PR — this branch's pull_request events stopped reaching GitHub Actions during the Aug 18 instability (pushes and close/reopen produced no check suites), so the same commits continue on a fresh branch.
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try {
var __m = "*";
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[e2e] Re-enable concurrent execution of the e2e suite - #3628
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[e2e] Re-enable concurrent execution of the e2e suite#3628
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Summary & Motivation
Serial e2e was the dominant wall-clock cost per matrix entry (~22 of 24 minutes on the Vercel lanes), and the blockers #2083 identified are now fixed. Making the suite concurrent required per-test attribution that survives interleaving: an auto fixture binds each test's name, tracked runs, and skip through AsyncLocalStorage, since vitest's getCurrentTest() is a module variable that goes stale after any await — so a failing test now dumps its own diagnostics rather than a sibling's. A test that genuinely cannot share a deployment can opt out with test.sequential.
Test Plan
  •  Full suite passes 137/137 concurrently against a local nextjs-turbopack dev server in under 2 minutes, with a new unit test covering attribution across interleaved contexts.
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⚠️ No Changeset found
Latest commit: 0556953
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (4 failed)
python-node (4 failed):
  • hookMinRetentionWorkflow - terminal Hook cannot resume and its token stays unavailable
  • setAttributes setAttributesInsideStepWorkflow: step-body calls append attributed native events
  • setAttributes workflow throws after awaited setAttributes: attribute still persists on the failed run
  • setAttributes start: invalid initial attributes are rejected before a run is created
💻 Local Development (2 failed)
vite-stable-node (1 failed):
  • sleepWinsRaceWorkflow
vite-stable-quickjs (1 failed):
  • sleepWinsRaceWorkflow
🌐 Cross-language Conformance (4 failed)
python (4 failed):
  • hookGetConflictWorkflow - hook.getConflict() resolves with the conflicting run when token is already registered
  • hookSupersedeOwnerWorkflow - duplicate cancels the owner and claims the released token
  • setAttributes setAttributesInsideStepWorkflow: step-body calls append attributed native events
  • setAttributes start: invalid initial attributes are rejected before a run is created
⚠️ 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.
  • 'hookGetConflictWithPriorStepWorkflow' - hook.getConflict() does not block step execution (nextjs-webpack)
  • abortHookOrderingWorkflow [listener-first-abort-first]: addEventListener → hook.then → abort() → resumeHook (nextjs-turbopack)
  • sleepWinsRaceWorkflow (tanstack-start)
  • stepWinsRaceWorkflow (tanstack-start)
  • stepWinsRaceWorkflow (vite)
🛠 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 · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A23XH4SJQ0FNX8E7CB3
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A1G9EVVEC3JRD6BJJ42
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A283EJ651AYXCWK29D6
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A217P7RCCDYE20DQR33
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A26JACFPXDD69WJY0GW
  • run-pickup-stall · unknown (nuxt) · at 21:27:07Z · abandoned wrun_01M0BCA7Z3QP3SS95SFYPXNXBP
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production347247364212
❌ 💻 Local Development380825584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
❌ 🌐 Cross-language Conformance94124137
✅ vercel-multi-region270027
Total1524810253417792
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-node64146
✅ 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-node129126
❌ vite-stable-quickjs129126
✅ 📦 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
❌ python94124
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit 68a9d5c · Tue, 18 Aug 2026 21:43:24 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1341 (+36%) 🔻1430 🔴 (+25%) 🔻1513 🔴 (+29%) 🔻1607 🔴 (-4.3%)30
TTFSstream1370 (+215%) 🔻1447 🔴 (+24%) 🔻1495 🔴 (+26%) 🔻1535 🔴 (+27%) 🔻30
TTFShook + stream1663 (+256%) 🔻1740 🔴 (+5.8%)1792 🔴 (+5.7%)1884 🔴 (-0.9%)30
Fan-out TTFSPromise.all(100 steps)1388 (+9.5%)3068 (+26%) 🔻3113 (+20%) 🔻3290 (+9.6%)10
Fan-out TTLSPromise.all(100 steps)5966 (+12%)7650 (-4.4%)8579 (+3.0%)22196 (+82%) 🔻10
STSO1020 steps (inline)137 (+11%)195 (-32%) 💚281 (-21%) 💚411 (-50%) 💚1019
WO1020 steps199492 (-29%) 💚199492 (-29%) 💚199492 (-29%) 💚199492 (-29%) 💚1
CRTTfirst chunk (pooled)119 (+14%)196 (+22%) 🔻459 (+156%) 🔻4030 (+517%) 🔻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 (+2%)143 (-6%)166 (-33%)228 (-48%)468 (-25%)144 (-30%)10
size sweep (100/s, 160B-12KB)100 (±0%)101 (+1%)334 (±0%)337 (+1%)164 (+17%)160 (-13%)228 (-20%)414 (-17%)133 (-11%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)90.3 (+2%)16.2 (±0%)16.4 (+1%)459 (+250%)178 (+13%)273 (+31%)556 (+32%)355 (+23%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)2093 (+1467%)152 (-6%)207 (-6%)883 (+143%)530 (+76%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (+1%)710 (±0%)712 (+1%)147 (+26%)259 (-69%)561 (-54%)951 (-43%)463 (-40%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 279211ms → this run 197976ms (Δ -81235ms, -29%)
 100-150 ms ┃ main 4 this 16 +12
150-200 ms ████░░░░░░░░░░░░░░░░░░░┃ main 120 this 769 +649
200-250 ms ██┃██████████ main 413 this 105 -308
250-300 ms ┃████████ main 282 this 48 -234
300-350 ms █┃█ main 91 this 54 -37
350-400 ms ┃ main 29 this 16 -13
400-450 ms ┃ main 26 this 7 -19
450-500 ms ┃ main 6 this 0 -6
500-550 ms ┃ main 13 this 2 -11
550-600 ms ┃ main 5 this 0 -5
600-650 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 5 this 0 -5
700-750 ms ┃ main 5 this 1 -4
750-800 ms ┃ main 4 this 0 -4
800-850 ms ┃ main 7 this 0 -7
850-900 ms ┃ main 4 this 0 -4
900-950 ms ┃ main 1 this 0 -1
1150-1200 ms ┃ main 1 this 0 -1
1250-1300 ms ┃ main 2 this 0 -2

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▁···· 143.1 (-16%) 138 (-2%) 228 (-48%) 468 (-25%) 3000
sweep ······▂█▁···· 138.9 (-9%) 129 (-8%) 228 (-20%) 414 (-17%) 3000
gw 1x ······▂█▂▁··· 158.4 (+19%) 133 (+6%) 273 (+31%) 556 (+32%) 5295
eve 1x ·····▁▃█▁▁▁▁· 145.3 (+5%) 117 (-4%) 207 (-6%) 883 (+143%) 5186
eve 2x ······▁█▄▁▁·· 213.3 (-43%) 165 (-43%) 561 (-54%) 951 (-43%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control █▇▅▆▁▁▃▃▂▁ 130–165ms
sweep █▂▁▂▂▂▃▂▂▅ 126–174ms
gw 1x █▄▂▂▂▂▂▂▂▁ 120–298ms
eve 1x █▁▃▁▁▃▃▅▂▂ 107–246ms
eve 2x ▆█▅▁▁▂▂▃▃▁ 153–337ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▆█▅▁▂▃▃ 138–141ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▅█▆▅▅▆▆▃▄ 27–54ms
sweep ▁▆▆█▄▅▇▇▅▇ 34–67ms
gw 1x █▄▂▁▃▂▁▂▂▁ 35–75ms
eve 1x █▁▄▃▁▄▃▃▂▃ 21–36ms
eve 2x █▇▃▂▃▂▃▁▃▃ 22–47ms

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
[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>
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@alangenfeld
[e2e] Bind per-test state via a task collector, not a fixture
0556953
CI on the first concurrent run caught the fixture design failing in the
one place skip-correctness is load-bearing: vitest resolves fixtures in
a separate async context, so an AsyncLocalStorage store bound around
use() never reaches the test body. Every ambient read silently fell to
the module fallback - conformance-gated tests on the Python lane ran
instead of skipping and hard-failed on fixtures missing from the
manifest ('declared in e2e-conformance.json but not in the deployed
manifest').
The suite's test is now built with createTaskCollector, mirroring
vitest's own argument normalization, and the wrapper binds the state
around the handler call itself - a direct call stack, so propagation is
guaranteed rather than assumed. Validated by a collector-pattern ALS
experiment (per-test store after awaits, mid-body skip targets self,
each/skip/todo chains), a conformance-file simulation reproducing the
Python failure shape (fixture-missing tests now skip with the right
note), and a 137/137 concurrent local run.
Also raises RACE_WINNER_MAX_DURATION_MS 5s -> 8s: the winner takes 1s,
the loser 10s, and the bound only has to sit clearly below the loser -
concurrent-suite queue latency pushed observed winner durations to
~6.5s on loaded local-dev lanes (vite, first concurrent CI run), so 5s
flaked without catching anything 8s misses.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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Superseded by the v2 branch of this PR — this branch's pull_request events stopped reaching GitHub Actions during the Aug 18 instability (pushes and close/reopen produced no check suites), so the same commits continue on a fresh branch.
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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[e2e] Re-enable concurrent execution of the e2e suite - #3628
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Summary & Motivation
Serial e2e was the dominant wall-clock cost per matrix entry (~22 of 24 minutes on the Vercel lanes), and the blockers #2083 identified are now fixed. Making the suite concurrent required per-test attribution that survives interleaving: an auto fixture binds each test's name, tracked runs, and skip through AsyncLocalStorage, since vitest's getCurrentTest() is a module variable that goes stale after any await — so a failing test now dumps its own diagnostics rather than a sibling's. A test that genuinely cannot share a deployment can opt out with test.sequential.
Test Plan
  •  Full suite passes 137/137 concurrently against a local nextjs-turbopack dev server in under 2 minutes, with a new unit test covering attribution across interleaved contexts.
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The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
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1 Skipped Deployment
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⚠️ No Changeset found
Latest commit: 0556953
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (4 failed)
python-node (4 failed):
  • hookMinRetentionWorkflow - terminal Hook cannot resume and its token stays unavailable
  • setAttributes setAttributesInsideStepWorkflow: step-body calls append attributed native events
  • setAttributes workflow throws after awaited setAttributes: attribute still persists on the failed run
  • setAttributes start: invalid initial attributes are rejected before a run is created
💻 Local Development (2 failed)
vite-stable-node (1 failed):
  • sleepWinsRaceWorkflow
vite-stable-quickjs (1 failed):
  • sleepWinsRaceWorkflow
🌐 Cross-language Conformance (4 failed)
python (4 failed):
  • hookGetConflictWorkflow - hook.getConflict() resolves with the conflicting run when token is already registered
  • hookSupersedeOwnerWorkflow - duplicate cancels the owner and claims the released token
  • setAttributes setAttributesInsideStepWorkflow: step-body calls append attributed native events
  • setAttributes start: invalid initial attributes are rejected before a run is created
⚠️ 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.
  • 'hookGetConflictWithPriorStepWorkflow' - hook.getConflict() does not block step execution (nextjs-webpack)
  • abortHookOrderingWorkflow [listener-first-abort-first]: addEventListener → hook.then → abort() → resumeHook (nextjs-turbopack)
  • sleepWinsRaceWorkflow (tanstack-start)
  • stepWinsRaceWorkflow (tanstack-start)
  • stepWinsRaceWorkflow (vite)
🛠 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 · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A23XH4SJQ0FNX8E7CB3
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A1G9EVVEC3JRD6BJJ42
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A283EJ651AYXCWK29D6
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A217P7RCCDYE20DQR33
  • run-pickup-stall · unknown (tanstack-start) · at 21:26:04Z · abandoned wrun_01M0BC8A26JACFPXDD69WJY0GW
  • run-pickup-stall · unknown (nuxt) · at 21:27:07Z · abandoned wrun_01M0BCA7Z3QP3SS95SFYPXNXBP
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production347247364212
❌ 💻 Local Development380825584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
❌ 🌐 Cross-language Conformance94124137
✅ vercel-multi-region270027
Total1524810253417792
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-node64146
✅ 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-node129126
❌ vite-stable-quickjs129126
✅ 📦 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
❌ python94124
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit 68a9d5c · Tue, 18 Aug 2026 21:43:24 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1341 (+36%) 🔻1430 🔴 (+25%) 🔻1513 🔴 (+29%) 🔻1607 🔴 (-4.3%)30
TTFSstream1370 (+215%) 🔻1447 🔴 (+24%) 🔻1495 🔴 (+26%) 🔻1535 🔴 (+27%) 🔻30
TTFShook + stream1663 (+256%) 🔻1740 🔴 (+5.8%)1792 🔴 (+5.7%)1884 🔴 (-0.9%)30
Fan-out TTFSPromise.all(100 steps)1388 (+9.5%)3068 (+26%) 🔻3113 (+20%) 🔻3290 (+9.6%)10
Fan-out TTLSPromise.all(100 steps)5966 (+12%)7650 (-4.4%)8579 (+3.0%)22196 (+82%) 🔻10
STSO1020 steps (inline)137 (+11%)195 (-32%) 💚281 (-21%) 💚411 (-50%) 💚1019
WO1020 steps199492 (-29%) 💚199492 (-29%) 💚199492 (-29%) 💚199492 (-29%) 💚1
CRTTfirst chunk (pooled)119 (+14%)196 (+22%) 🔻459 (+156%) 🔻4030 (+517%) 🔻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 (+2%)143 (-6%)166 (-33%)228 (-48%)468 (-25%)144 (-30%)10
size sweep (100/s, 160B-12KB)100 (±0%)101 (+1%)334 (±0%)337 (+1%)164 (+17%)160 (-13%)228 (-20%)414 (-17%)133 (-11%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)90.3 (+2%)16.2 (±0%)16.4 (+1%)459 (+250%)178 (+13%)273 (+31%)556 (+32%)355 (+23%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)2093 (+1467%)152 (-6%)207 (-6%)883 (+143%)530 (+76%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (+1%)710 (±0%)712 (+1%)147 (+26%)259 (-69%)561 (-54%)951 (-43%)463 (-40%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 279211ms → this run 197976ms (Δ -81235ms, -29%)
 100-150 ms ┃ main 4 this 16 +12
150-200 ms ████░░░░░░░░░░░░░░░░░░░┃ main 120 this 769 +649
200-250 ms ██┃██████████ main 413 this 105 -308
250-300 ms ┃████████ main 282 this 48 -234
300-350 ms █┃█ main 91 this 54 -37
350-400 ms ┃ main 29 this 16 -13
400-450 ms ┃ main 26 this 7 -19
450-500 ms ┃ main 6 this 0 -6
500-550 ms ┃ main 13 this 2 -11
550-600 ms ┃ main 5 this 0 -5
600-650 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 5 this 0 -5
700-750 ms ┃ main 5 this 1 -4
750-800 ms ┃ main 4 this 0 -4
800-850 ms ┃ main 7 this 0 -7
850-900 ms ┃ main 4 this 0 -4
900-950 ms ┃ main 1 this 0 -1
1150-1200 ms ┃ main 1 this 0 -1
1250-1300 ms ┃ main 2 this 0 -2

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▁···· 143.1 (-16%) 138 (-2%) 228 (-48%) 468 (-25%) 3000
sweep ······▂█▁···· 138.9 (-9%) 129 (-8%) 228 (-20%) 414 (-17%) 3000
gw 1x ······▂█▂▁··· 158.4 (+19%) 133 (+6%) 273 (+31%) 556 (+32%) 5295
eve 1x ·····▁▃█▁▁▁▁· 145.3 (+5%) 117 (-4%) 207 (-6%) 883 (+143%) 5186
eve 2x ······▁█▄▁▁·· 213.3 (-43%) 165 (-43%) 561 (-54%) 951 (-43%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control █▇▅▆▁▁▃▃▂▁ 130–165ms
sweep █▂▁▂▂▂▃▂▂▅ 126–174ms
gw 1x █▄▂▂▂▂▂▂▂▁ 120–298ms
eve 1x █▁▃▁▁▃▃▅▂▂ 107–246ms
eve 2x ▆█▅▁▁▂▂▃▃▁ 153–337ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▆█▅▁▂▃▃ 138–141ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▅█▆▅▅▆▆▃▄ 27–54ms
sweep ▁▆▆█▄▅▇▇▅▇ 34–67ms
gw 1x █▄▂▁▃▂▁▂▂▁ 35–75ms
eve 1x █▁▄▃▁▄▃▃▂▃ 21–36ms
eve 2x █▇▃▂▃▂▃▁▃▃ 22–47ms

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
[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>
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@alangenfeld
[e2e] Bind per-test state via a task collector, not a fixture
0556953
CI on the first concurrent run caught the fixture design failing in the
one place skip-correctness is load-bearing: vitest resolves fixtures in
a separate async context, so an AsyncLocalStorage store bound around
use() never reaches the test body. Every ambient read silently fell to
the module fallback - conformance-gated tests on the Python lane ran
instead of skipping and hard-failed on fixtures missing from the
manifest ('declared in e2e-conformance.json but not in the deployed
manifest').
The suite's test is now built with createTaskCollector, mirroring
vitest's own argument normalization, and the wrapper binds the state
around the handler call itself - a direct call stack, so propagation is
guaranteed rather than assumed. Validated by a collector-pattern ALS
experiment (per-test store after awaits, mid-body skip targets self,
each/skip/todo chains), a conformance-file simulation reproducing the
Python failure shape (fixture-missing tests now skip with the right
note), and a 137/137 concurrent local run.
Also raises RACE_WINNER_MAX_DURATION_MS 5s -> 8s: the winner takes 1s,
the loser 10s, and the bound only has to sit clearly below the loser -
concurrent-suite queue latency pushed observed winner durations to
~6.5s on loaded local-dev lanes (vite, first concurrent CI run), so 5s
flaked without catching anything 8s misses.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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Aug 19, 2026

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Superseded by the v2 branch of this PR — this branch's pull_request events stopped reaching GitHub Actions during the Aug 18 instability (pushes and close/reopen produced no check suites), so the same commits continue on a fresh branch.
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