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[e2e] Host the abort-fetch slow endpoint inside the step - #3618

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[e2e] Host the abort-fetch slow endpoint inside the step#3618
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@alangenfeld

@alangenfeldalangenfeld commented Aug 18, 2026

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Summary & Motivation

The abort-fetch e2e tests raced a 2s sleep against a fetch to public slow endpoints (postman-echo, httpbin /delay/10), so upstream 5xxs and early returns from CI runners showed up as flakes. fetchWithSignal now stands up a loopback node:http server that holds each response open for ~30s, keeping the subject — cancelling a real in-flight fetch — with no external dependency. The 30s hold is longer than the tests' 60s budgets minus the race, so broken abort propagation still fails as a natural completion rather than a hang.

Test Plan

Existing abort-fetch e2e coverage runs in CI; workbench/example builds clean.

@alangenfeld
[e2e] Host the abort-fetch slow endpoint inside the step
d7b0736
The abort-fetch tests cancelled an in-flight fetch against external slow
endpoints (postman-echo, httpbin /delay/10, tried in order). Those
upstreams 5xx and return early from GH Actions runners often enough to
be a recurring flake class - the tests were measuring the public
internet instead of abort propagation - and heavier suite load (e.g.
re-enabling e2e concurrency, #2083) makes both upstreams flake at once.
fetchWithSignal now hosts its own slow endpoint: an in-process node:http
server on a loopback ephemeral port that holds each response open for
~30s. The subject is unchanged - a real in-flight HTTP fetch cancelled
mid-flight - with no external dependency. The 30s hold keeps regression
detection honest: broken abort propagation surfaces as natural
completion (ok: true) within the tests' 60s budgets.
A per-workbench /api/delay route was rejected earlier because it would
only exist on whichever workbench it was added to; the in-step server
travels with the workflow fixture to every app.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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⚠️ No Changeset found

Latest commit: d7b0736

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 (1 failed)

nextjs-turbopack-quickjs (1 failed):

⚠️ 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.

  • basic text response (nextjs-turbopack)

🛠 Infra Events (absorbed by the harness)

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

  • run-pickup-stall · addTenWorkflow (tanstack-start) · at 19:31:37Z · abandoned wrun_01M0B5PQWJHY8A8XDHNE27EWY3

E2E Test Summary

Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production347317384212
✅ 💻 Local Development381005584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
✅ 🌐 Cross-language Conformance90128137
✅ vercel-multi-region270027
Total152511254017792
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-quickjs15213
✅ nextjs-webpack-node15303
✅ nextjs-webpack-quickjs15303
✅ nitro-node128028
✅ nitro-quickjs128028
✅ nuxt-node128028
✅ nuxt-quickjs128028
✅ python-node80148
✅ sveltekit-node14709
✅ sveltekit-quickjs14709
✅ tanstack-start-node128028
✅ tanstack-start-quickjs128028
✅ vite-node128028
✅ vite-quickjs128028

✅ 💻 Local Development

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

✅ 📦 Local Production

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

✅ 🐘 Local Postgres

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

✅ 🪟 Windows

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

✅ 🌐 Cross-language Conformance

AppPassedFailedSkipped
✅ python90128

✅ vercel-multi-region

AppPassedFailedSkipped
✅ nextjs-turbopack2700

📋 View full workflow run

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📊 Workflow Benchmarks

commit d7b0736 · Tue, 18 Aug 2026 19:46:55 GMT · run logs

Backend: vercel · app: nextjs-turbopack

MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1376 (+464%) 🔻1504 🔴 (+32%) 🔻1540 🔴 (+26%) 🔻1585 🔴 (-8.8%)30
TTFSstream354 (+52%) 🔻1424 🔴 (+23%) 🔻1463 🔴 (+23%) 🔻1495 🔴 (+14%)30
TTFShook + stream1346 (+214%) 🔻1735 🔴 (+25%) 🔻1813 🔴 (+29%) 🔻1996 🔴 (+36%) 🔻30
Fan-out TTFSPromise.all(100 steps)1188 (-17%) 💚3255 (+29%) 🔻3428 (+30%) 🔻5328 (+61%) 🔻10
Fan-out TTLSPromise.all(100 steps)5371 (-25%) 💚7805 (-11%)10551 (+17%) 🔻10957 (+21%) 🔻10
STSO1020 steps (inline)122 (-25%) 💚167 (-44%) 💚204 (-42%) 💚412 (-25%) 💚1019
WO1020 steps170113 (-41%) 💚170113 (-41%) 💚170113 (-41%) 💚170113 (-41%) 💚1
CRTTfirst chunk (pooled)113 (+14%)166 (-1.8%)375 (+15%)3821 (+738%) 🔻28

Streams

Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (±0%)5 (±0%)5.1 (±0%)134 (-13%)172 (-21%)593 (+79%)3796 (+271%)157 (-51%)10
size sweep (100/s, 160B-12KB)100 (±0%)99.4 (-2%)334 (±0%)331 (-2%)123 (-2%)182 (-7%)234 (-76%)379 (-69%)159 (-23%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.4 (±0%)16.2 (±0%)16.3 (+1%)166 (+8%)142 (-27%)186 (-33%)402 (-50%)209 (-44%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)136 (-12%)140 (-11%)177 (-10%)326 (-21%)221 (-33%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)712 (±0%)134 (-35%)212 (-15%)308 (-7%)1219 (+6%)305 (-54%)3
📈 STSO distribution vs main (inline / queue-hop histograms)

1020 steps (inline)

Cumulative STSO time: main 287804ms → this run 168740ms (Δ -119064ms, -41%)

 100-150 ms ░░░░░░░░░░░░░░░░░░░░░░░┃ main 0 this 476 +476
150-200 ms █░░░░░░░░░░░░░░░░░░░░┃ main 27 this 432 +405
200-250 ms ██┃████████████ main 305 this 57 -248
250-300 ms ┃█████████████████████ main 431 this 25 -406
300-350 ms ┃██████ main 142 this 12 -130
350-400 ms ┃███ main 71 this 5 -66
400-450 ms ┃ main 11 this 4 -7
450-500 ms ┃ main 11 this 4 -7
500-550 ms ┃ main 10 this 0 -10
550-600 ms ┃ main 4 this 1 -3
600-650 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 2 this 1 -1
700-750 ms ┃ main 1 this 0 -1
800-850 ms ┃ main 1 this 0 -1
850-900 ms ┃ main 1 this 1 +0
1100-1150 ms ┃ main 1 this 0 -1
📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▂▁▁▁· 372.7 (+96%) 128 (-17%) 593 (+79%) 3796 (+271%) 3000
sweep ······▃█▂···· 139.9 (-29%) 128 (-10%) 234 (-76%) 379 (-69%) 3000
gw 1x ·····▁▅█▁···· 122 (-20%) 117 (-13%) 186 (-33%) 402 (-50%) 5295
eve 1x ·····▁▆█▁···· 118.1 (-10%) 104 (-11%) 177 (-10%) 326 (-21%) 5186
eve 2x ·····▁▂█▃▁▁·· 178.7 (-13%) 144 (-17%) 308 (-7%) 1219 (+6%) 7779

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

control █▇▆▅▄▄▂▄▃▁ 248–507ms
sweep █▇▃▅▅▅▃▂▄▁ 128–153ms
gw 1x █▃▁▄▃▂▃▂▃▃ 105–159ms
eve 1x ▃▂▄▃▁▂█▆▆▁ 105–141ms
eve 2x ▃█▂▂▁▂▄▅▂▁ 126–307ms

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

sweep ▂▁▄█▆▃▁ 139–142ms

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

control ▁▃▄▂▃▂▂█▁▂ 34–62ms
sweep ▁▇█▃▆▇▂▇▄▂ 46–61ms
gw 1x █▂▁▁▅▆▆▂▃▂ 31–42ms
eve 1x ▂▅▄▄▁▅▆▅▄█ 21–26ms
eve 2x ▅█▂▃▂▄▃▁▂▃ 20–37ms
ℹ️ Metric definitions & methodology

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

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

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

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

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

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

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

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

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

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

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Sim World

Simulated world deterministic testing for races. Traces

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

fence=per-spec

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

Full trace: world-sim.txt

@alangenfeld
alangenfeld marked this pull request as ready for review August 18, 2026 19:32
@alangenfeld
alangenfeld requested a review from a team as a code ownerAugust 18, 2026 19:32
VaguelySerious
VaguelySerious approved these changes Aug 18, 2026
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Smart

@alangenfeld
alangenfeld merged commit 8789f45 into mainAug 18, 2026
428 of 434 checks passed
@alangenfeld
alangenfeld deleted the alangenfeld/e2e-hermetic-abort-fetch branch August 18, 2026 21:59
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No backport to stable for 8789f45 (AI decision).

This is a test-only flake fix, which would normally qualify, but the behavior it covers does not exist on stable: git show origin/stable shows neither fetchWithSignal/SLOW_FETCH_URLS nor any AbortController/abort workflows in workbench/example/workflows/99_e2e.ts, and no abort-fetch cases in packages/core/e2e/e2e.test.ts (both files exist on stable, just without this coverage). With no abort-fetch tests on the maintenance line, there is no flake there to fix.

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

8789f4529b311205e41f38a7f6fb188677e6dcc7

alangenfeld added a commit that referenced this pull request Aug 18, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
6713211
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit that referenced this pull request Aug 19, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
fc94f67
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Host the abort-fetch slow endpoint inside the step by alangenfeld · Pull Request #3618 · vercel/workflow · GitHub
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[e2e] Host the abort-fetch slow endpoint inside the step - #3618
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[e2e] Host the abort-fetch slow endpoint inside the step#3618
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Summary & Motivation
The abort-fetch e2e tests raced a 2s sleep against a fetch to public slow endpoints (postman-echo, httpbin /delay/10), so upstream 5xxs and early returns from CI runners showed up as flakes. fetchWithSignal now stands up a loopback node:http server that holds each response open for ~30s, keeping the subject — cancelling a real in-flight fetch — with no external dependency. The 30s hold is longer than the tests' 60s budgets minus the race, so broken abort propagation still fails as a natural completion rather than a hang.
Test Plan
Existing abort-fetch e2e coverage runs in CI; workbench/example builds clean.
@alangenfeld
[e2e] Host the abort-fetch slow endpoint inside the step
d7b0736
The abort-fetch tests cancelled an in-flight fetch against external slow
endpoints (postman-echo, httpbin /delay/10, tried in order). Those
upstreams 5xx and return early from GH Actions runners often enough to
be a recurring flake class - the tests were measuring the public
internet instead of abort propagation - and heavier suite load (e.g.
re-enabling e2e concurrency, #2083) makes both upstreams flake at once.
fetchWithSignal now hosts its own slow endpoint: an in-process node:http
server on a loopback ephemeral port that holds each response open for
~30s. The subject is unchanged - a real in-flight HTTP fetch cancelled
mid-flight - with no external dependency. The 30s hold keeps regression
detection honest: broken abort propagation surfaces as natural
completion (ok: true) within the tests' 60s budgets.
A per-workbench /api/delay route was rejected earlier because it would
only exist on whichever workbench it was added to; the in-step server
travels with the workflow fixture to every app.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
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⚠️ No Changeset found
Latest commit: d7b0736
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (1 failed)
nextjs-turbopack-quickjs (1 failed):
⚠️ 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.
  • basic text response (nextjs-turbopack)
🛠 Infra Events (absorbed by the harness)
Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.
  • run-pickup-stall · addTenWorkflow (tanstack-start) · at 19:31:37Z · abandoned wrun_01M0B5PQWJHY8A8XDHNE27EWY3
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production347317384212
✅ 💻 Local Development381005584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
✅ 🌐 Cross-language Conformance90128137
✅ vercel-multi-region270027
Total152511254017792
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-quickjs15213
✅ nextjs-webpack-node15303
✅ nextjs-webpack-quickjs15303
✅ nitro-node128028
✅ nitro-quickjs128028
✅ nuxt-node128028
✅ nuxt-quickjs128028
✅ python-node80148
✅ sveltekit-node14709
✅ sveltekit-quickjs14709
✅ tanstack-start-node128028
✅ tanstack-start-quickjs128028
✅ vite-node128028
✅ vite-quickjs128028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node15600
✅ nextjs-turbopack-quickjs15600
✅ 🌐 Cross-language Conformance
AppPassedFailedSkipped
✅ python90128
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit d7b0736 · Tue, 18 Aug 2026 19:46:55 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1376 (+464%) 🔻1504 🔴 (+32%) 🔻1540 🔴 (+26%) 🔻1585 🔴 (-8.8%)30
TTFSstream354 (+52%) 🔻1424 🔴 (+23%) 🔻1463 🔴 (+23%) 🔻1495 🔴 (+14%)30
TTFShook + stream1346 (+214%) 🔻1735 🔴 (+25%) 🔻1813 🔴 (+29%) 🔻1996 🔴 (+36%) 🔻30
Fan-out TTFSPromise.all(100 steps)1188 (-17%) 💚3255 (+29%) 🔻3428 (+30%) 🔻5328 (+61%) 🔻10
Fan-out TTLSPromise.all(100 steps)5371 (-25%) 💚7805 (-11%)10551 (+17%) 🔻10957 (+21%) 🔻10
STSO1020 steps (inline)122 (-25%) 💚167 (-44%) 💚204 (-42%) 💚412 (-25%) 💚1019
WO1020 steps170113 (-41%) 💚170113 (-41%) 💚170113 (-41%) 💚170113 (-41%) 💚1
CRTTfirst chunk (pooled)113 (+14%)166 (-1.8%)375 (+15%)3821 (+738%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (±0%)5 (±0%)5.1 (±0%)134 (-13%)172 (-21%)593 (+79%)3796 (+271%)157 (-51%)10
size sweep (100/s, 160B-12KB)100 (±0%)99.4 (-2%)334 (±0%)331 (-2%)123 (-2%)182 (-7%)234 (-76%)379 (-69%)159 (-23%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.4 (±0%)16.2 (±0%)16.3 (+1%)166 (+8%)142 (-27%)186 (-33%)402 (-50%)209 (-44%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)136 (-12%)140 (-11%)177 (-10%)326 (-21%)221 (-33%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)712 (±0%)134 (-35%)212 (-15%)308 (-7%)1219 (+6%)305 (-54%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 287804ms → this run 168740ms (Δ -119064ms, -41%)
 100-150 ms ░░░░░░░░░░░░░░░░░░░░░░░┃ main 0 this 476 +476
150-200 ms █░░░░░░░░░░░░░░░░░░░░┃ main 27 this 432 +405
200-250 ms ██┃████████████ main 305 this 57 -248
250-300 ms ┃█████████████████████ main 431 this 25 -406
300-350 ms ┃██████ main 142 this 12 -130
350-400 ms ┃███ main 71 this 5 -66
400-450 ms ┃ main 11 this 4 -7
450-500 ms ┃ main 11 this 4 -7
500-550 ms ┃ main 10 this 0 -10
550-600 ms ┃ main 4 this 1 -3
600-650 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 2 this 1 -1
700-750 ms ┃ main 1 this 0 -1
800-850 ms ┃ main 1 this 0 -1
850-900 ms ┃ main 1 this 1 +0
1100-1150 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▂▁▁▁· 372.7 (+96%) 128 (-17%) 593 (+79%) 3796 (+271%) 3000
sweep ······▃█▂···· 139.9 (-29%) 128 (-10%) 234 (-76%) 379 (-69%) 3000
gw 1x ·····▁▅█▁···· 122 (-20%) 117 (-13%) 186 (-33%) 402 (-50%) 5295
eve 1x ·····▁▆█▁···· 118.1 (-10%) 104 (-11%) 177 (-10%) 326 (-21%) 5186
eve 2x ·····▁▂█▃▁▁·· 178.7 (-13%) 144 (-17%) 308 (-7%) 1219 (+6%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control █▇▆▅▄▄▂▄▃▁ 248–507ms
sweep █▇▃▅▅▅▃▂▄▁ 128–153ms
gw 1x █▃▁▄▃▂▃▂▃▃ 105–159ms
eve 1x ▃▂▄▃▁▂█▆▆▁ 105–141ms
eve 2x ▃█▂▂▁▂▄▅▂▁ 126–307ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▂▁▄█▆▃▁ 139–142ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▃▄▂▃▂▂█▁▂ 34–62ms
sweep ▁▇█▃▆▇▂▇▄▂ 46–61ms
gw 1x █▂▁▁▅▆▆▂▃▂ 31–42ms
eve 1x ▂▅▄▄▁▅▆▅▄█ 21–26ms
eve 2x ▅█▂▃▂▄▃▁▂▃ 20–37ms

ℹ️ Metric definitions & methodology
Streams: writer/reader sustained rates (steady window, 10% trimmed each side), first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.
The collapsed STSO distribution section above buckets every step gap, split inline (same warm process — pure framework overhead) vs queue-hop (fresh process — dispatch, reinit, replay). █ = main, ┃ = this run, ░ = fill.
The collapsed CRTT drill-down: per-variant RTT histograms (fixed log bins, · = empty) and mean RTT/positive-CDV profile lines over stream progress and chunk size. Histograms, avgs, and profiles merge exactly across runs; p50–p99 are percentile-of-percentiles. Per-index rows live in the artifacts.
Best/P75/P90/P99 deltas compare against the most recent benchmark run on main at the time of this run. 🔻 flags a delta worse than +15%, 💚 one better than −15%.
Metrics — TTFS: time to first step body (in-deployment start() → first step body) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)
Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles
Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600
All timestamps are deployment-side; runs are triggered in-deployment, so the CI runner and api.vercel.com sit outside every measured window. TTFS = start() → first step body (includes dispatch + any cold start); Fan-out TTFS/TTLS = first/last step completion of one Promise.all from the same anchor (the gap is the runtime’s fan-out spread); STSO/WO between step bodies; CRTT inside the workflow (excludes the api.vercel.com read path).
Cold starts stay in the numbers (real bursty-workload latency, inflates P75+); Best is the warm floor.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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No backport to stable for 8789f45 (AI decision).
This is a test-only flake fix, which would normally qualify, but the behavior it covers does not exist on stable: git show origin/stable shows neither fetchWithSignal/SLOW_FETCH_URLS nor any AbortController/abort workflows in workbench/example/workflows/99_e2e.ts, and no abort-fetch cases in packages/core/e2e/e2e.test.ts (both files exist on stable, just without this coverage). With no abort-fetch tests on the maintenance line, there is no flake there to fix.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
8789f4529b311205e41f38a7f6fb188677e6dcc7

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Aug 18, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
6713211
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit
that referenced
this pull request
Aug 19, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
fc94f67
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Host the abort-fetch slow endpoint inside the step by alangenfeld · Pull Request #3618 · vercel/workflow · GitHub
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[e2e] Host the abort-fetch slow endpoint inside the step - #3618
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[e2e] Host the abort-fetch slow endpoint inside the step#3618
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Summary & Motivation
The abort-fetch e2e tests raced a 2s sleep against a fetch to public slow endpoints (postman-echo, httpbin /delay/10), so upstream 5xxs and early returns from CI runners showed up as flakes. fetchWithSignal now stands up a loopback node:http server that holds each response open for ~30s, keeping the subject — cancelling a real in-flight fetch — with no external dependency. The 30s hold is longer than the tests' 60s budgets minus the race, so broken abort propagation still fails as a natural completion rather than a hang.
Test Plan
Existing abort-fetch e2e coverage runs in CI; workbench/example builds clean.
@alangenfeld
[e2e] Host the abort-fetch slow endpoint inside the step
d7b0736
The abort-fetch tests cancelled an in-flight fetch against external slow
endpoints (postman-echo, httpbin /delay/10, tried in order). Those
upstreams 5xx and return early from GH Actions runners often enough to
be a recurring flake class - the tests were measuring the public
internet instead of abort propagation - and heavier suite load (e.g.
re-enabling e2e concurrency, #2083) makes both upstreams flake at once.
fetchWithSignal now hosts its own slow endpoint: an in-process node:http
server on a loopback ephemeral port that holds each response open for
~30s. The subject is unchanged - a real in-flight HTTP fetch cancelled
mid-flight - with no external dependency. The 30s hold keeps regression
detection honest: broken abort propagation surfaces as natural
completion (ok: true) within the tests' 60s budgets.
A per-workbench /api/delay route was rejected earlier because it would
only exist on whichever workbench it was added to; the in-step server
travels with the workflow fixture to every app.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
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⚠️ No Changeset found
Latest commit: d7b0736
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 (1 failed)
nextjs-turbopack-quickjs (1 failed):
⚠️ 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.
  • basic text response (nextjs-turbopack)
🛠 Infra Events (absorbed by the harness)
Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.
  • run-pickup-stall · addTenWorkflow (tanstack-start) · at 19:31:37Z · abandoned wrun_01M0B5PQWJHY8A8XDHNE27EWY3
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production347317384212
✅ 💻 Local Development381005584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
✅ 🌐 Cross-language Conformance90128137
✅ vercel-multi-region270027
Total152511254017792
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-quickjs15213
✅ nextjs-webpack-node15303
✅ nextjs-webpack-quickjs15303
✅ nitro-node128028
✅ nitro-quickjs128028
✅ nuxt-node128028
✅ nuxt-quickjs128028
✅ python-node80148
✅ sveltekit-node14709
✅ sveltekit-quickjs14709
✅ tanstack-start-node128028
✅ tanstack-start-quickjs128028
✅ vite-node128028
✅ vite-quickjs128028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node15600
✅ nextjs-turbopack-quickjs15600
✅ 🌐 Cross-language Conformance
AppPassedFailedSkipped
✅ python90128
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit d7b0736 · Tue, 18 Aug 2026 19:46:55 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1376 (+464%) 🔻1504 🔴 (+32%) 🔻1540 🔴 (+26%) 🔻1585 🔴 (-8.8%)30
TTFSstream354 (+52%) 🔻1424 🔴 (+23%) 🔻1463 🔴 (+23%) 🔻1495 🔴 (+14%)30
TTFShook + stream1346 (+214%) 🔻1735 🔴 (+25%) 🔻1813 🔴 (+29%) 🔻1996 🔴 (+36%) 🔻30
Fan-out TTFSPromise.all(100 steps)1188 (-17%) 💚3255 (+29%) 🔻3428 (+30%) 🔻5328 (+61%) 🔻10
Fan-out TTLSPromise.all(100 steps)5371 (-25%) 💚7805 (-11%)10551 (+17%) 🔻10957 (+21%) 🔻10
STSO1020 steps (inline)122 (-25%) 💚167 (-44%) 💚204 (-42%) 💚412 (-25%) 💚1019
WO1020 steps170113 (-41%) 💚170113 (-41%) 💚170113 (-41%) 💚170113 (-41%) 💚1
CRTTfirst chunk (pooled)113 (+14%)166 (-1.8%)375 (+15%)3821 (+738%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (±0%)5 (±0%)5.1 (±0%)134 (-13%)172 (-21%)593 (+79%)3796 (+271%)157 (-51%)10
size sweep (100/s, 160B-12KB)100 (±0%)99.4 (-2%)334 (±0%)331 (-2%)123 (-2%)182 (-7%)234 (-76%)379 (-69%)159 (-23%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.4 (±0%)16.2 (±0%)16.3 (+1%)166 (+8%)142 (-27%)186 (-33%)402 (-50%)209 (-44%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)136 (-12%)140 (-11%)177 (-10%)326 (-21%)221 (-33%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)712 (±0%)134 (-35%)212 (-15%)308 (-7%)1219 (+6%)305 (-54%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 287804ms → this run 168740ms (Δ -119064ms, -41%)
 100-150 ms ░░░░░░░░░░░░░░░░░░░░░░░┃ main 0 this 476 +476
150-200 ms █░░░░░░░░░░░░░░░░░░░░┃ main 27 this 432 +405
200-250 ms ██┃████████████ main 305 this 57 -248
250-300 ms ┃█████████████████████ main 431 this 25 -406
300-350 ms ┃██████ main 142 this 12 -130
350-400 ms ┃███ main 71 this 5 -66
400-450 ms ┃ main 11 this 4 -7
450-500 ms ┃ main 11 this 4 -7
500-550 ms ┃ main 10 this 0 -10
550-600 ms ┃ main 4 this 1 -3
600-650 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 2 this 1 -1
700-750 ms ┃ main 1 this 0 -1
800-850 ms ┃ main 1 this 0 -1
850-900 ms ┃ main 1 this 1 +0
1100-1150 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▂▁▁▁· 372.7 (+96%) 128 (-17%) 593 (+79%) 3796 (+271%) 3000
sweep ······▃█▂···· 139.9 (-29%) 128 (-10%) 234 (-76%) 379 (-69%) 3000
gw 1x ·····▁▅█▁···· 122 (-20%) 117 (-13%) 186 (-33%) 402 (-50%) 5295
eve 1x ·····▁▆█▁···· 118.1 (-10%) 104 (-11%) 177 (-10%) 326 (-21%) 5186
eve 2x ·····▁▂█▃▁▁·· 178.7 (-13%) 144 (-17%) 308 (-7%) 1219 (+6%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control █▇▆▅▄▄▂▄▃▁ 248–507ms
sweep █▇▃▅▅▅▃▂▄▁ 128–153ms
gw 1x █▃▁▄▃▂▃▂▃▃ 105–159ms
eve 1x ▃▂▄▃▁▂█▆▆▁ 105–141ms
eve 2x ▃█▂▂▁▂▄▅▂▁ 126–307ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▂▁▄█▆▃▁ 139–142ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▃▄▂▃▂▂█▁▂ 34–62ms
sweep ▁▇█▃▆▇▂▇▄▂ 46–61ms
gw 1x █▂▁▁▅▆▆▂▃▂ 31–42ms
eve 1x ▂▅▄▄▁▅▆▅▄█ 21–26ms
eve 2x ▅█▂▃▂▄▃▁▂▃ 20–37ms

ℹ️ Metric definitions & methodology
Streams: writer/reader sustained rates (steady window, 10% trimmed each side), first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.
The collapsed STSO distribution section above buckets every step gap, split inline (same warm process — pure framework overhead) vs queue-hop (fresh process — dispatch, reinit, replay). █ = main, ┃ = this run, ░ = fill.
The collapsed CRTT drill-down: per-variant RTT histograms (fixed log bins, · = empty) and mean RTT/positive-CDV profile lines over stream progress and chunk size. Histograms, avgs, and profiles merge exactly across runs; p50–p99 are percentile-of-percentiles. Per-index rows live in the artifacts.
Best/P75/P90/P99 deltas compare against the most recent benchmark run on main at the time of this run. 🔻 flags a delta worse than +15%, 💚 one better than −15%.
Metrics — TTFS: time to first step body (in-deployment start() → first step body) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)
Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles
Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600
All timestamps are deployment-side; runs are triggered in-deployment, so the CI runner and api.vercel.com sit outside every measured window. TTFS = start() → first step body (includes dispatch + any cold start); Fan-out TTFS/TTLS = first/last step completion of one Promise.all from the same anchor (the gap is the runtime’s fan-out spread); STSO/WO between step bodies; CRTT inside the workflow (excludes the api.vercel.com read path).
Cold starts stay in the numbers (real bursty-workload latency, inflates P75+); Best is the warm floor.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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No backport to stable for 8789f45 (AI decision).
This is a test-only flake fix, which would normally qualify, but the behavior it covers does not exist on stable: git show origin/stable shows neither fetchWithSignal/SLOW_FETCH_URLS nor any AbortController/abort workflows in workbench/example/workflows/99_e2e.ts, and no abort-fetch cases in packages/core/e2e/e2e.test.ts (both files exist on stable, just without this coverage). With no abort-fetch tests on the maintenance line, there is no flake there to fix.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
8789f4529b311205e41f38a7f6fb188677e6dcc7

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Aug 18, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
6713211
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit
that referenced
this pull request
Aug 19, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
fc94f67
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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@alangenfeld@VaguelySerious

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[e2e] Host the abort-fetch slow endpoint inside the step by alangenfeld · Pull Request #3618 · vercel/workflow · GitHub
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[e2e] Host the abort-fetch slow endpoint inside the step - #3618
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[e2e] Host the abort-fetch slow endpoint inside the step#3618
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Summary & Motivation
The abort-fetch e2e tests raced a 2s sleep against a fetch to public slow endpoints (postman-echo, httpbin /delay/10), so upstream 5xxs and early returns from CI runners showed up as flakes. fetchWithSignal now stands up a loopback node:http server that holds each response open for ~30s, keeping the subject — cancelling a real in-flight fetch — with no external dependency. The 30s hold is longer than the tests' 60s budgets minus the race, so broken abort propagation still fails as a natural completion rather than a hang.
Test Plan
Existing abort-fetch e2e coverage runs in CI; workbench/example builds clean.
@alangenfeld
[e2e] Host the abort-fetch slow endpoint inside the step
d7b0736
The abort-fetch tests cancelled an in-flight fetch against external slow
endpoints (postman-echo, httpbin /delay/10, tried in order). Those
upstreams 5xx and return early from GH Actions runners often enough to
be a recurring flake class - the tests were measuring the public
internet instead of abort propagation - and heavier suite load (e.g.
re-enabling e2e concurrency, #2083) makes both upstreams flake at once.
fetchWithSignal now hosts its own slow endpoint: an in-process node:http
server on a loopback ephemeral port that holds each response open for
~30s. The subject is unchanged - a real in-flight HTTP fetch cancelled
mid-flight - with no external dependency. The 30s hold keeps regression
detection honest: broken abort propagation surfaces as natural
completion (ok: true) within the tests' 60s budgets.
A per-workbench /api/delay route was rejected earlier because it would
only exist on whichever workbench it was added to; the in-step server
travels with the workflow fixture to every app.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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⚠️ No Changeset found
Latest commit: d7b0736
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (1 failed)
nextjs-turbopack-quickjs (1 failed):
⚠️ 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.
  • basic text response (nextjs-turbopack)
🛠 Infra Events (absorbed by the harness)
Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.
  • run-pickup-stall · addTenWorkflow (tanstack-start) · at 19:31:37Z · abandoned wrun_01M0B5PQWJHY8A8XDHNE27EWY3
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production347317384212
✅ 💻 Local Development381005584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
✅ 🌐 Cross-language Conformance90128137
✅ vercel-multi-region270027
Total152511254017792
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-quickjs15213
✅ nextjs-webpack-node15303
✅ nextjs-webpack-quickjs15303
✅ nitro-node128028
✅ nitro-quickjs128028
✅ nuxt-node128028
✅ nuxt-quickjs128028
✅ python-node80148
✅ sveltekit-node14709
✅ sveltekit-quickjs14709
✅ tanstack-start-node128028
✅ tanstack-start-quickjs128028
✅ vite-node128028
✅ vite-quickjs128028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node15600
✅ nextjs-turbopack-quickjs15600
✅ 🌐 Cross-language Conformance
AppPassedFailedSkipped
✅ python90128
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit d7b0736 · Tue, 18 Aug 2026 19:46:55 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1376 (+464%) 🔻1504 🔴 (+32%) 🔻1540 🔴 (+26%) 🔻1585 🔴 (-8.8%)30
TTFSstream354 (+52%) 🔻1424 🔴 (+23%) 🔻1463 🔴 (+23%) 🔻1495 🔴 (+14%)30
TTFShook + stream1346 (+214%) 🔻1735 🔴 (+25%) 🔻1813 🔴 (+29%) 🔻1996 🔴 (+36%) 🔻30
Fan-out TTFSPromise.all(100 steps)1188 (-17%) 💚3255 (+29%) 🔻3428 (+30%) 🔻5328 (+61%) 🔻10
Fan-out TTLSPromise.all(100 steps)5371 (-25%) 💚7805 (-11%)10551 (+17%) 🔻10957 (+21%) 🔻10
STSO1020 steps (inline)122 (-25%) 💚167 (-44%) 💚204 (-42%) 💚412 (-25%) 💚1019
WO1020 steps170113 (-41%) 💚170113 (-41%) 💚170113 (-41%) 💚170113 (-41%) 💚1
CRTTfirst chunk (pooled)113 (+14%)166 (-1.8%)375 (+15%)3821 (+738%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (±0%)5 (±0%)5.1 (±0%)134 (-13%)172 (-21%)593 (+79%)3796 (+271%)157 (-51%)10
size sweep (100/s, 160B-12KB)100 (±0%)99.4 (-2%)334 (±0%)331 (-2%)123 (-2%)182 (-7%)234 (-76%)379 (-69%)159 (-23%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.4 (±0%)16.2 (±0%)16.3 (+1%)166 (+8%)142 (-27%)186 (-33%)402 (-50%)209 (-44%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)136 (-12%)140 (-11%)177 (-10%)326 (-21%)221 (-33%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)712 (±0%)134 (-35%)212 (-15%)308 (-7%)1219 (+6%)305 (-54%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 287804ms → this run 168740ms (Δ -119064ms, -41%)
 100-150 ms ░░░░░░░░░░░░░░░░░░░░░░░┃ main 0 this 476 +476
150-200 ms █░░░░░░░░░░░░░░░░░░░░┃ main 27 this 432 +405
200-250 ms ██┃████████████ main 305 this 57 -248
250-300 ms ┃█████████████████████ main 431 this 25 -406
300-350 ms ┃██████ main 142 this 12 -130
350-400 ms ┃███ main 71 this 5 -66
400-450 ms ┃ main 11 this 4 -7
450-500 ms ┃ main 11 this 4 -7
500-550 ms ┃ main 10 this 0 -10
550-600 ms ┃ main 4 this 1 -3
600-650 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 2 this 1 -1
700-750 ms ┃ main 1 this 0 -1
800-850 ms ┃ main 1 this 0 -1
850-900 ms ┃ main 1 this 1 +0
1100-1150 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▂▁▁▁· 372.7 (+96%) 128 (-17%) 593 (+79%) 3796 (+271%) 3000
sweep ······▃█▂···· 139.9 (-29%) 128 (-10%) 234 (-76%) 379 (-69%) 3000
gw 1x ·····▁▅█▁···· 122 (-20%) 117 (-13%) 186 (-33%) 402 (-50%) 5295
eve 1x ·····▁▆█▁···· 118.1 (-10%) 104 (-11%) 177 (-10%) 326 (-21%) 5186
eve 2x ·····▁▂█▃▁▁·· 178.7 (-13%) 144 (-17%) 308 (-7%) 1219 (+6%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control █▇▆▅▄▄▂▄▃▁ 248–507ms
sweep █▇▃▅▅▅▃▂▄▁ 128–153ms
gw 1x █▃▁▄▃▂▃▂▃▃ 105–159ms
eve 1x ▃▂▄▃▁▂█▆▆▁ 105–141ms
eve 2x ▃█▂▂▁▂▄▅▂▁ 126–307ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▂▁▄█▆▃▁ 139–142ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▃▄▂▃▂▂█▁▂ 34–62ms
sweep ▁▇█▃▆▇▂▇▄▂ 46–61ms
gw 1x █▂▁▁▅▆▆▂▃▂ 31–42ms
eve 1x ▂▅▄▄▁▅▆▅▄█ 21–26ms
eve 2x ▅█▂▃▂▄▃▁▂▃ 20–37ms

ℹ️ Metric definitions & methodology
Streams: writer/reader sustained rates (steady window, 10% trimmed each side), first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.
The collapsed STSO distribution section above buckets every step gap, split inline (same warm process — pure framework overhead) vs queue-hop (fresh process — dispatch, reinit, replay). █ = main, ┃ = this run, ░ = fill.
The collapsed CRTT drill-down: per-variant RTT histograms (fixed log bins, · = empty) and mean RTT/positive-CDV profile lines over stream progress and chunk size. Histograms, avgs, and profiles merge exactly across runs; p50–p99 are percentile-of-percentiles. Per-index rows live in the artifacts.
Best/P75/P90/P99 deltas compare against the most recent benchmark run on main at the time of this run. 🔻 flags a delta worse than +15%, 💚 one better than −15%.
Metrics — TTFS: time to first step body (in-deployment start() → first step body) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)
Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles
Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600
All timestamps are deployment-side; runs are triggered in-deployment, so the CI runner and api.vercel.com sit outside every measured window. TTFS = start() → first step body (includes dispatch + any cold start); Fan-out TTFS/TTLS = first/last step completion of one Promise.all from the same anchor (the gap is the runtime’s fan-out spread); STSO/WO between step bodies; CRTT inside the workflow (excludes the api.vercel.com read path).
Cold starts stay in the numbers (real bursty-workload latency, inflates P75+); Best is the warm floor.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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No backport to stable for 8789f45 (AI decision).
This is a test-only flake fix, which would normally qualify, but the behavior it covers does not exist on stable: git show origin/stable shows neither fetchWithSignal/SLOW_FETCH_URLS nor any AbortController/abort workflows in workbench/example/workflows/99_e2e.ts, and no abort-fetch cases in packages/core/e2e/e2e.test.ts (both files exist on stable, just without this coverage). With no abort-fetch tests on the maintenance line, there is no flake there to fix.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
8789f4529b311205e41f38a7f6fb188677e6dcc7

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@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
6713211
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit
that referenced
this pull request
Aug 19, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
fc94f67
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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@alangenfeld@VaguelySerious

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observer.observe(document.body, { childList: true, subtree: true });
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} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
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var __re = new RegExp('^' + "youtube\\.com" + '
[e2e] Host the abort-fetch slow endpoint inside the step by alangenfeld · Pull Request #3618 · vercel/workflow · GitHub
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[e2e] Host the abort-fetch slow endpoint inside the step - #3618
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[e2e] Host the abort-fetch slow endpoint inside the step#3618
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Summary & Motivation
The abort-fetch e2e tests raced a 2s sleep against a fetch to public slow endpoints (postman-echo, httpbin /delay/10), so upstream 5xxs and early returns from CI runners showed up as flakes. fetchWithSignal now stands up a loopback node:http server that holds each response open for ~30s, keeping the subject — cancelling a real in-flight fetch — with no external dependency. The 30s hold is longer than the tests' 60s budgets minus the race, so broken abort propagation still fails as a natural completion rather than a hang.
Test Plan
Existing abort-fetch e2e coverage runs in CI; workbench/example builds clean.
@alangenfeld
[e2e] Host the abort-fetch slow endpoint inside the step
d7b0736
The abort-fetch tests cancelled an in-flight fetch against external slow
endpoints (postman-echo, httpbin /delay/10, tried in order). Those
upstreams 5xx and return early from GH Actions runners often enough to
be a recurring flake class - the tests were measuring the public
internet instead of abort propagation - and heavier suite load (e.g.
re-enabling e2e concurrency, #2083) makes both upstreams flake at once.
fetchWithSignal now hosts its own slow endpoint: an in-process node:http
server on a loopback ephemeral port that holds each response open for
~30s. The subject is unchanged - a real in-flight HTTP fetch cancelled
mid-flight - with no external dependency. The 30s hold keeps regression
detection honest: broken abort propagation surfaces as natural
completion (ok: true) within the tests' 60s budgets.
A per-workbench /api/delay route was rejected earlier because it would
only exist on whichever workbench it was added to; the in-step server
travels with the workflow fixture to every app.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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ProjectDeploymentActionsUpdated (UTC)
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⚠️ No Changeset found
Latest commit: d7b0736
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (1 failed)
nextjs-turbopack-quickjs (1 failed):
⚠️ 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.
  • basic text response (nextjs-turbopack)
🛠 Infra Events (absorbed by the harness)
Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.
  • run-pickup-stall · addTenWorkflow (tanstack-start) · at 19:31:37Z · abandoned wrun_01M0B5PQWJHY8A8XDHNE27EWY3
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production347317384212
✅ 💻 Local Development381005584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
✅ 🌐 Cross-language Conformance90128137
✅ vercel-multi-region270027
Total152511254017792
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-quickjs15213
✅ nextjs-webpack-node15303
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✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
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📋 View full workflow run
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📊 Workflow Benchmarks
commit d7b0736 · Tue, 18 Aug 2026 19:46:55 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1376 (+464%) 🔻1504 🔴 (+32%) 🔻1540 🔴 (+26%) 🔻1585 🔴 (-8.8%)30
TTFSstream354 (+52%) 🔻1424 🔴 (+23%) 🔻1463 🔴 (+23%) 🔻1495 🔴 (+14%)30
TTFShook + stream1346 (+214%) 🔻1735 🔴 (+25%) 🔻1813 🔴 (+29%) 🔻1996 🔴 (+36%) 🔻30
Fan-out TTFSPromise.all(100 steps)1188 (-17%) 💚3255 (+29%) 🔻3428 (+30%) 🔻5328 (+61%) 🔻10
Fan-out TTLSPromise.all(100 steps)5371 (-25%) 💚7805 (-11%)10551 (+17%) 🔻10957 (+21%) 🔻10
STSO1020 steps (inline)122 (-25%) 💚167 (-44%) 💚204 (-42%) 💚412 (-25%) 💚1019
WO1020 steps170113 (-41%) 💚170113 (-41%) 💚170113 (-41%) 💚170113 (-41%) 💚1
CRTTfirst chunk (pooled)113 (+14%)166 (-1.8%)375 (+15%)3821 (+738%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (±0%)5 (±0%)5.1 (±0%)134 (-13%)172 (-21%)593 (+79%)3796 (+271%)157 (-51%)10
size sweep (100/s, 160B-12KB)100 (±0%)99.4 (-2%)334 (±0%)331 (-2%)123 (-2%)182 (-7%)234 (-76%)379 (-69%)159 (-23%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.4 (±0%)16.2 (±0%)16.3 (+1%)166 (+8%)142 (-27%)186 (-33%)402 (-50%)209 (-44%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)136 (-12%)140 (-11%)177 (-10%)326 (-21%)221 (-33%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)712 (±0%)134 (-35%)212 (-15%)308 (-7%)1219 (+6%)305 (-54%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 287804ms → this run 168740ms (Δ -119064ms, -41%)
 100-150 ms ░░░░░░░░░░░░░░░░░░░░░░░┃ main 0 this 476 +476
150-200 ms █░░░░░░░░░░░░░░░░░░░░┃ main 27 this 432 +405
200-250 ms ██┃████████████ main 305 this 57 -248
250-300 ms ┃█████████████████████ main 431 this 25 -406
300-350 ms ┃██████ main 142 this 12 -130
350-400 ms ┃███ main 71 this 5 -66
400-450 ms ┃ main 11 this 4 -7
450-500 ms ┃ main 11 this 4 -7
500-550 ms ┃ main 10 this 0 -10
550-600 ms ┃ main 4 this 1 -3
600-650 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 2 this 1 -1
700-750 ms ┃ main 1 this 0 -1
800-850 ms ┃ main 1 this 0 -1
850-900 ms ┃ main 1 this 1 +0
1100-1150 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▂▁▁▁· 372.7 (+96%) 128 (-17%) 593 (+79%) 3796 (+271%) 3000
sweep ······▃█▂···· 139.9 (-29%) 128 (-10%) 234 (-76%) 379 (-69%) 3000
gw 1x ·····▁▅█▁···· 122 (-20%) 117 (-13%) 186 (-33%) 402 (-50%) 5295
eve 1x ·····▁▆█▁···· 118.1 (-10%) 104 (-11%) 177 (-10%) 326 (-21%) 5186
eve 2x ·····▁▂█▃▁▁·· 178.7 (-13%) 144 (-17%) 308 (-7%) 1219 (+6%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control █▇▆▅▄▄▂▄▃▁ 248–507ms
sweep █▇▃▅▅▅▃▂▄▁ 128–153ms
gw 1x █▃▁▄▃▂▃▂▃▃ 105–159ms
eve 1x ▃▂▄▃▁▂█▆▆▁ 105–141ms
eve 2x ▃█▂▂▁▂▄▅▂▁ 126–307ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▂▁▄█▆▃▁ 139–142ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▃▄▂▃▂▂█▁▂ 34–62ms
sweep ▁▇█▃▆▇▂▇▄▂ 46–61ms
gw 1x █▂▁▁▅▆▆▂▃▂ 31–42ms
eve 1x ▂▅▄▄▁▅▆▅▄█ 21–26ms
eve 2x ▅█▂▃▂▄▃▁▂▃ 20–37ms

ℹ️ Metric definitions & methodology
Streams: writer/reader sustained rates (steady window, 10% trimmed each side), first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.
The collapsed STSO distribution section above buckets every step gap, split inline (same warm process — pure framework overhead) vs queue-hop (fresh process — dispatch, reinit, replay). █ = main, ┃ = this run, ░ = fill.
The collapsed CRTT drill-down: per-variant RTT histograms (fixed log bins, · = empty) and mean RTT/positive-CDV profile lines over stream progress and chunk size. Histograms, avgs, and profiles merge exactly across runs; p50–p99 are percentile-of-percentiles. Per-index rows live in the artifacts.
Best/P75/P90/P99 deltas compare against the most recent benchmark run on main at the time of this run. 🔻 flags a delta worse than +15%, 💚 one better than −15%.
Metrics — TTFS: time to first step body (in-deployment start() → first step body) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)
Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles
Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600
All timestamps are deployment-side; runs are triggered in-deployment, so the CI runner and api.vercel.com sit outside every measured window. TTFS = start() → first step body (includes dispatch + any cold start); Fan-out TTFS/TTLS = first/last step completion of one Promise.all from the same anchor (the gap is the runtime’s fan-out spread); STSO/WO between step bodies; CRTT inside the workflow (excludes the api.vercel.com read path).
Cold starts stay in the numbers (real bursty-workload latency, inflates P75+); Best is the warm floor.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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No backport to stable for 8789f45 (AI decision).
This is a test-only flake fix, which would normally qualify, but the behavior it covers does not exist on stable: git show origin/stable shows neither fetchWithSignal/SLOW_FETCH_URLS nor any AbortController/abort workflows in workbench/example/workflows/99_e2e.ts, and no abort-fetch cases in packages/core/e2e/e2e.test.ts (both files exist on stable, just without this coverage). With no abort-fetch tests on the maintenance line, there is no flake there to fix.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
8789f4529b311205e41f38a7f6fb188677e6dcc7

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Aug 18, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
6713211
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit
that referenced
this pull request
Aug 19, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
fc94f67
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Host the abort-fetch slow endpoint inside the step by alangenfeld · Pull Request #3618 · vercel/workflow · GitHub
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[e2e] Host the abort-fetch slow endpoint inside the step - #3618
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[e2e] Host the abort-fetch slow endpoint inside the step#3618
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Summary & Motivation
The abort-fetch e2e tests raced a 2s sleep against a fetch to public slow endpoints (postman-echo, httpbin /delay/10), so upstream 5xxs and early returns from CI runners showed up as flakes. fetchWithSignal now stands up a loopback node:http server that holds each response open for ~30s, keeping the subject — cancelling a real in-flight fetch — with no external dependency. The 30s hold is longer than the tests' 60s budgets minus the race, so broken abort propagation still fails as a natural completion rather than a hang.
Test Plan
Existing abort-fetch e2e coverage runs in CI; workbench/example builds clean.
@alangenfeld
[e2e] Host the abort-fetch slow endpoint inside the step
d7b0736
The abort-fetch tests cancelled an in-flight fetch against external slow
endpoints (postman-echo, httpbin /delay/10, tried in order). Those
upstreams 5xx and return early from GH Actions runners often enough to
be a recurring flake class - the tests were measuring the public
internet instead of abort propagation - and heavier suite load (e.g.
re-enabling e2e concurrency, #2083) makes both upstreams flake at once.
fetchWithSignal now hosts its own slow endpoint: an in-process node:http
server on a loopback ephemeral port that holds each response open for
~30s. The subject is unchanged - a real in-flight HTTP fetch cancelled
mid-flight - with no external dependency. The 30s hold keeps regression
detection honest: broken abort propagation surfaces as natural
completion (ok: true) within the tests' 60s budgets.
A per-workbench /api/delay route was rejected earlier because it would
only exist on whichever workbench it was added to; the in-step server
travels with the workflow fixture to every app.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (1 failed)
nextjs-turbopack-quickjs (1 failed):
⚠️ 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.
  • basic text response (nextjs-turbopack)
🛠 Infra Events (absorbed by the harness)
Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.
  • run-pickup-stall · addTenWorkflow (tanstack-start) · at 19:31:37Z · abandoned wrun_01M0B5PQWJHY8A8XDHNE27EWY3
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production347317384212
✅ 💻 Local Development381005584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
✅ 🌐 Cross-language Conformance90128137
✅ vercel-multi-region270027
Total152511254017792
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-quickjs15213
✅ nextjs-webpack-node15303
✅ nextjs-webpack-quickjs15303
✅ nitro-node128028
✅ nitro-quickjs128028
✅ nuxt-node128028
✅ nuxt-quickjs128028
✅ python-node80148
✅ sveltekit-node14709
✅ sveltekit-quickjs14709
✅ tanstack-start-node128028
✅ tanstack-start-quickjs128028
✅ vite-node128028
✅ vite-quickjs128028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node15600
✅ nextjs-turbopack-quickjs15600
✅ 🌐 Cross-language Conformance
AppPassedFailedSkipped
✅ python90128
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit d7b0736 · Tue, 18 Aug 2026 19:46:55 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1376 (+464%) 🔻1504 🔴 (+32%) 🔻1540 🔴 (+26%) 🔻1585 🔴 (-8.8%)30
TTFSstream354 (+52%) 🔻1424 🔴 (+23%) 🔻1463 🔴 (+23%) 🔻1495 🔴 (+14%)30
TTFShook + stream1346 (+214%) 🔻1735 🔴 (+25%) 🔻1813 🔴 (+29%) 🔻1996 🔴 (+36%) 🔻30
Fan-out TTFSPromise.all(100 steps)1188 (-17%) 💚3255 (+29%) 🔻3428 (+30%) 🔻5328 (+61%) 🔻10
Fan-out TTLSPromise.all(100 steps)5371 (-25%) 💚7805 (-11%)10551 (+17%) 🔻10957 (+21%) 🔻10
STSO1020 steps (inline)122 (-25%) 💚167 (-44%) 💚204 (-42%) 💚412 (-25%) 💚1019
WO1020 steps170113 (-41%) 💚170113 (-41%) 💚170113 (-41%) 💚170113 (-41%) 💚1
CRTTfirst chunk (pooled)113 (+14%)166 (-1.8%)375 (+15%)3821 (+738%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (±0%)5 (±0%)5.1 (±0%)134 (-13%)172 (-21%)593 (+79%)3796 (+271%)157 (-51%)10
size sweep (100/s, 160B-12KB)100 (±0%)99.4 (-2%)334 (±0%)331 (-2%)123 (-2%)182 (-7%)234 (-76%)379 (-69%)159 (-23%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.4 (±0%)16.2 (±0%)16.3 (+1%)166 (+8%)142 (-27%)186 (-33%)402 (-50%)209 (-44%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)136 (-12%)140 (-11%)177 (-10%)326 (-21%)221 (-33%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)712 (±0%)134 (-35%)212 (-15%)308 (-7%)1219 (+6%)305 (-54%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 287804ms → this run 168740ms (Δ -119064ms, -41%)
 100-150 ms ░░░░░░░░░░░░░░░░░░░░░░░┃ main 0 this 476 +476
150-200 ms █░░░░░░░░░░░░░░░░░░░░┃ main 27 this 432 +405
200-250 ms ██┃████████████ main 305 this 57 -248
250-300 ms ┃█████████████████████ main 431 this 25 -406
300-350 ms ┃██████ main 142 this 12 -130
350-400 ms ┃███ main 71 this 5 -66
400-450 ms ┃ main 11 this 4 -7
450-500 ms ┃ main 11 this 4 -7
500-550 ms ┃ main 10 this 0 -10
550-600 ms ┃ main 4 this 1 -3
600-650 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 2 this 1 -1
700-750 ms ┃ main 1 this 0 -1
800-850 ms ┃ main 1 this 0 -1
850-900 ms ┃ main 1 this 1 +0
1100-1150 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▂▁▁▁· 372.7 (+96%) 128 (-17%) 593 (+79%) 3796 (+271%) 3000
sweep ······▃█▂···· 139.9 (-29%) 128 (-10%) 234 (-76%) 379 (-69%) 3000
gw 1x ·····▁▅█▁···· 122 (-20%) 117 (-13%) 186 (-33%) 402 (-50%) 5295
eve 1x ·····▁▆█▁···· 118.1 (-10%) 104 (-11%) 177 (-10%) 326 (-21%) 5186
eve 2x ·····▁▂█▃▁▁·· 178.7 (-13%) 144 (-17%) 308 (-7%) 1219 (+6%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control █▇▆▅▄▄▂▄▃▁ 248–507ms
sweep █▇▃▅▅▅▃▂▄▁ 128–153ms
gw 1x █▃▁▄▃▂▃▂▃▃ 105–159ms
eve 1x ▃▂▄▃▁▂█▆▆▁ 105–141ms
eve 2x ▃█▂▂▁▂▄▅▂▁ 126–307ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▂▁▄█▆▃▁ 139–142ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▃▄▂▃▂▂█▁▂ 34–62ms
sweep ▁▇█▃▆▇▂▇▄▂ 46–61ms
gw 1x █▂▁▁▅▆▆▂▃▂ 31–42ms
eve 1x ▂▅▄▄▁▅▆▅▄█ 21–26ms
eve 2x ▅█▂▃▂▄▃▁▂▃ 20–37ms

ℹ️ Metric definitions & methodology
Streams: writer/reader sustained rates (steady window, 10% trimmed each side), first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.
The collapsed STSO distribution section above buckets every step gap, split inline (same warm process — pure framework overhead) vs queue-hop (fresh process — dispatch, reinit, replay). █ = main, ┃ = this run, ░ = fill.
The collapsed CRTT drill-down: per-variant RTT histograms (fixed log bins, · = empty) and mean RTT/positive-CDV profile lines over stream progress and chunk size. Histograms, avgs, and profiles merge exactly across runs; p50–p99 are percentile-of-percentiles. Per-index rows live in the artifacts.
Best/P75/P90/P99 deltas compare against the most recent benchmark run on main at the time of this run. 🔻 flags a delta worse than +15%, 💚 one better than −15%.
Metrics — TTFS: time to first step body (in-deployment start() → first step body) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)
Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles
Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600
All timestamps are deployment-side; runs are triggered in-deployment, so the CI runner and api.vercel.com sit outside every measured window. TTFS = start() → first step body (includes dispatch + any cold start); Fan-out TTFS/TTLS = first/last step completion of one Promise.all from the same anchor (the gap is the runtime’s fan-out spread); STSO/WO between step bodies; CRTT inside the workflow (excludes the api.vercel.com read path).
Cold starts stay in the numbers (real bursty-workload latency, inflates P75+); Best is the warm floor.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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No backport to stable for 8789f45 (AI decision).
This is a test-only flake fix, which would normally qualify, but the behavior it covers does not exist on stable: git show origin/stable shows neither fetchWithSignal/SLOW_FETCH_URLS nor any AbortController/abort workflows in workbench/example/workflows/99_e2e.ts, and no abort-fetch cases in packages/core/e2e/e2e.test.ts (both files exist on stable, just without this coverage). With no abort-fetch tests on the maintenance line, there is no flake there to fix.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
8789f4529b311205e41f38a7f6fb188677e6dcc7

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@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
6713211
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit
that referenced
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Aug 19, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
fc94f67
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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@alangenfeld@VaguelySerious

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[e2e] Host the abort-fetch slow endpoint inside the step by alangenfeld · Pull Request #3618 · vercel/workflow · GitHub
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[e2e] Host the abort-fetch slow endpoint inside the step - #3618
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[e2e] Host the abort-fetch slow endpoint inside the step#3618
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Summary & Motivation
The abort-fetch e2e tests raced a 2s sleep against a fetch to public slow endpoints (postman-echo, httpbin /delay/10), so upstream 5xxs and early returns from CI runners showed up as flakes. fetchWithSignal now stands up a loopback node:http server that holds each response open for ~30s, keeping the subject — cancelling a real in-flight fetch — with no external dependency. The 30s hold is longer than the tests' 60s budgets minus the race, so broken abort propagation still fails as a natural completion rather than a hang.
Test Plan
Existing abort-fetch e2e coverage runs in CI; workbench/example builds clean.
@alangenfeld
[e2e] Host the abort-fetch slow endpoint inside the step
d7b0736
The abort-fetch tests cancelled an in-flight fetch against external slow
endpoints (postman-echo, httpbin /delay/10, tried in order). Those
upstreams 5xx and return early from GH Actions runners often enough to
be a recurring flake class - the tests were measuring the public
internet instead of abort propagation - and heavier suite load (e.g.
re-enabling e2e concurrency, #2083) makes both upstreams flake at once.
fetchWithSignal now hosts its own slow endpoint: an in-process node:http
server on a loopback ephemeral port that holds each response open for
~30s. The subject is unchanged - a real in-flight HTTP fetch cancelled
mid-flight - with no external dependency. The 30s hold keeps regression
detection honest: broken abort propagation surfaces as natural
completion (ok: true) within the tests' 60s budgets.
A per-workbench /api/delay route was rejected earlier because it would
only exist on whichever workbench it was added to; the in-step server
travels with the workflow fixture to every app.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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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: d7b0736
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🧪 E2E Test Results
❌ Some tests failed
❌ Failed E2E Tests
▲ Vercel Production (1 failed)
nextjs-turbopack-quickjs (1 failed):
⚠️ 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.
  • basic text response (nextjs-turbopack)
🛠 Infra Events (absorbed by the harness)
Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.
  • run-pickup-stall · addTenWorkflow (tanstack-start) · at 19:31:37Z · abandoned wrun_01M0B5PQWJHY8A8XDHNE27EWY3
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production347317384212
✅ 💻 Local Development381005584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
✅ 🌐 Cross-language Conformance90128137
✅ vercel-multi-region270027
Total152511254017792
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-quickjs15213
✅ nextjs-webpack-node15303
✅ nextjs-webpack-quickjs15303
✅ nitro-node128028
✅ nitro-quickjs128028
✅ nuxt-node128028
✅ nuxt-quickjs128028
✅ python-node80148
✅ sveltekit-node14709
✅ sveltekit-quickjs14709
✅ tanstack-start-node128028
✅ tanstack-start-quickjs128028
✅ vite-node128028
✅ vite-quickjs128028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node15600
✅ nextjs-turbopack-quickjs15600
✅ 🌐 Cross-language Conformance
AppPassedFailedSkipped
✅ python90128
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit d7b0736 · Tue, 18 Aug 2026 19:46:55 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1376 (+464%) 🔻1504 🔴 (+32%) 🔻1540 🔴 (+26%) 🔻1585 🔴 (-8.8%)30
TTFSstream354 (+52%) 🔻1424 🔴 (+23%) 🔻1463 🔴 (+23%) 🔻1495 🔴 (+14%)30
TTFShook + stream1346 (+214%) 🔻1735 🔴 (+25%) 🔻1813 🔴 (+29%) 🔻1996 🔴 (+36%) 🔻30
Fan-out TTFSPromise.all(100 steps)1188 (-17%) 💚3255 (+29%) 🔻3428 (+30%) 🔻5328 (+61%) 🔻10
Fan-out TTLSPromise.all(100 steps)5371 (-25%) 💚7805 (-11%)10551 (+17%) 🔻10957 (+21%) 🔻10
STSO1020 steps (inline)122 (-25%) 💚167 (-44%) 💚204 (-42%) 💚412 (-25%) 💚1019
WO1020 steps170113 (-41%) 💚170113 (-41%) 💚170113 (-41%) 💚170113 (-41%) 💚1
CRTTfirst chunk (pooled)113 (+14%)166 (-1.8%)375 (+15%)3821 (+738%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (±0%)5 (±0%)5.1 (±0%)134 (-13%)172 (-21%)593 (+79%)3796 (+271%)157 (-51%)10
size sweep (100/s, 160B-12KB)100 (±0%)99.4 (-2%)334 (±0%)331 (-2%)123 (-2%)182 (-7%)234 (-76%)379 (-69%)159 (-23%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.4 (±0%)16.2 (±0%)16.3 (+1%)166 (+8%)142 (-27%)186 (-33%)402 (-50%)209 (-44%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)136 (-12%)140 (-11%)177 (-10%)326 (-21%)221 (-33%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)712 (±0%)134 (-35%)212 (-15%)308 (-7%)1219 (+6%)305 (-54%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 287804ms → this run 168740ms (Δ -119064ms, -41%)
 100-150 ms ░░░░░░░░░░░░░░░░░░░░░░░┃ main 0 this 476 +476
150-200 ms █░░░░░░░░░░░░░░░░░░░░┃ main 27 this 432 +405
200-250 ms ██┃████████████ main 305 this 57 -248
250-300 ms ┃█████████████████████ main 431 this 25 -406
300-350 ms ┃██████ main 142 this 12 -130
350-400 ms ┃███ main 71 this 5 -66
400-450 ms ┃ main 11 this 4 -7
450-500 ms ┃ main 11 this 4 -7
500-550 ms ┃ main 10 this 0 -10
550-600 ms ┃ main 4 this 1 -3
600-650 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 2 this 1 -1
700-750 ms ┃ main 1 this 0 -1
800-850 ms ┃ main 1 this 0 -1
850-900 ms ┃ main 1 this 1 +0
1100-1150 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▂▁▁▁· 372.7 (+96%) 128 (-17%) 593 (+79%) 3796 (+271%) 3000
sweep ······▃█▂···· 139.9 (-29%) 128 (-10%) 234 (-76%) 379 (-69%) 3000
gw 1x ·····▁▅█▁···· 122 (-20%) 117 (-13%) 186 (-33%) 402 (-50%) 5295
eve 1x ·····▁▆█▁···· 118.1 (-10%) 104 (-11%) 177 (-10%) 326 (-21%) 5186
eve 2x ·····▁▂█▃▁▁·· 178.7 (-13%) 144 (-17%) 308 (-7%) 1219 (+6%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control █▇▆▅▄▄▂▄▃▁ 248–507ms
sweep █▇▃▅▅▅▃▂▄▁ 128–153ms
gw 1x █▃▁▄▃▂▃▂▃▃ 105–159ms
eve 1x ▃▂▄▃▁▂█▆▆▁ 105–141ms
eve 2x ▃█▂▂▁▂▄▅▂▁ 126–307ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▂▁▄█▆▃▁ 139–142ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▃▄▂▃▂▂█▁▂ 34–62ms
sweep ▁▇█▃▆▇▂▇▄▂ 46–61ms
gw 1x █▂▁▁▅▆▆▂▃▂ 31–42ms
eve 1x ▂▅▄▄▁▅▆▅▄█ 21–26ms
eve 2x ▅█▂▃▂▄▃▁▂▃ 20–37ms

ℹ️ Metric definitions & methodology
Streams: writer/reader sustained rates (steady window, 10% trimmed each side), first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.
The collapsed STSO distribution section above buckets every step gap, split inline (same warm process — pure framework overhead) vs queue-hop (fresh process — dispatch, reinit, replay). █ = main, ┃ = this run, ░ = fill.
The collapsed CRTT drill-down: per-variant RTT histograms (fixed log bins, · = empty) and mean RTT/positive-CDV profile lines over stream progress and chunk size. Histograms, avgs, and profiles merge exactly across runs; p50–p99 are percentile-of-percentiles. Per-index rows live in the artifacts.
Best/P75/P90/P99 deltas compare against the most recent benchmark run on main at the time of this run. 🔻 flags a delta worse than +15%, 💚 one better than −15%.
Metrics — TTFS: time to first step body (in-deployment start() → first step body) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)
Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles
Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600
All timestamps are deployment-side; runs are triggered in-deployment, so the CI runner and api.vercel.com sit outside every measured window. TTFS = start() → first step body (includes dispatch + any cold start); Fan-out TTFS/TTLS = first/last step completion of one Promise.all from the same anchor (the gap is the runtime’s fan-out spread); STSO/WO between step bodies; CRTT inside the workflow (excludes the api.vercel.com read path).
Cold starts stay in the numbers (real bursty-workload latency, inflates P75+); Best is the warm floor.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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No backport to stable for 8789f45 (AI decision).
This is a test-only flake fix, which would normally qualify, but the behavior it covers does not exist on stable: git show origin/stable shows neither fetchWithSignal/SLOW_FETCH_URLS nor any AbortController/abort workflows in workbench/example/workflows/99_e2e.ts, and no abort-fetch cases in packages/core/e2e/e2e.test.ts (both files exist on stable, just without this coverage). With no abort-fetch tests on the maintenance line, there is no flake there to fix.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
8789f4529b311205e41f38a7f6fb188677e6dcc7

alangenfeld added a commit
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Aug 18, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
6713211
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit
that referenced
this pull request
Aug 19, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
fc94f67
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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[e2e] Host the abort-fetch slow endpoint inside the step by alangenfeld · Pull Request #3618 · vercel/workflow · GitHub
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[e2e] Host the abort-fetch slow endpoint inside the step - #3618
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[e2e] Host the abort-fetch slow endpoint inside the step#3618
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Summary & Motivation
The abort-fetch e2e tests raced a 2s sleep against a fetch to public slow endpoints (postman-echo, httpbin /delay/10), so upstream 5xxs and early returns from CI runners showed up as flakes. fetchWithSignal now stands up a loopback node:http server that holds each response open for ~30s, keeping the subject — cancelling a real in-flight fetch — with no external dependency. The 30s hold is longer than the tests' 60s budgets minus the race, so broken abort propagation still fails as a natural completion rather than a hang.
Test Plan
Existing abort-fetch e2e coverage runs in CI; workbench/example builds clean.
@alangenfeld
[e2e] Host the abort-fetch slow endpoint inside the step
d7b0736
The abort-fetch tests cancelled an in-flight fetch against external slow
endpoints (postman-echo, httpbin /delay/10, tried in order). Those
upstreams 5xx and return early from GH Actions runners often enough to
be a recurring flake class - the tests were measuring the public
internet instead of abort propagation - and heavier suite load (e.g.
re-enabling e2e concurrency, #2083) makes both upstreams flake at once.
fetchWithSignal now hosts its own slow endpoint: an in-process node:http
server on a loopback ephemeral port that holds each response open for
~30s. The subject is unchanged - a real in-flight HTTP fetch cancelled
mid-flight - with no external dependency. The 30s hold keeps regression
detection honest: broken abort propagation surfaces as natural
completion (ok: true) within the tests' 60s budgets.
A per-workbench /api/delay route was rejected earlier because it would
only exist on whichever workbench it was added to; the in-step server
travels with the workflow fixture to every app.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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ProjectDeploymentActionsUpdated (UTC)
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⚠️ No Changeset found
Latest commit: d7b0736
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 (1 failed)
nextjs-turbopack-quickjs (1 failed):
⚠️ 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.
  • basic text response (nextjs-turbopack)
🛠 Infra Events (absorbed by the harness)
Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.
  • run-pickup-stall · addTenWorkflow (tanstack-start) · at 19:31:37Z · abandoned wrun_01M0B5PQWJHY8A8XDHNE27EWY3
E2E Test Summary
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production347317384212
✅ 💻 Local Development381005584368
✅ 📦 Local Production381005584368
✅ 🐘 Local Postgres381005584368
✅ 🪟 Windows31200312
✅ 🌐 Cross-language Conformance90128137
✅ vercel-multi-region270027
Total152511254017792
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-quickjs15213
✅ nextjs-webpack-node15303
✅ nextjs-webpack-quickjs15303
✅ nitro-node128028
✅ nitro-quickjs128028
✅ nuxt-node128028
✅ nuxt-quickjs128028
✅ python-node80148
✅ sveltekit-node14709
✅ sveltekit-quickjs14709
✅ tanstack-start-node128028
✅ tanstack-start-quickjs128028
✅ vite-node128028
✅ vite-quickjs128028
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable-node130026
✅ astro-stable-quickjs130026
✅ express-stable-node130026
✅ express-stable-quickjs130026
✅ fastify-stable-node130026
✅ fastify-stable-quickjs130026
✅ hono-stable-node130026
✅ hono-stable-quickjs130026
✅ nest-stable-node130026
✅ nest-stable-quickjs130026
✅ nextjs-turbopack-canary-node137019
✅ nextjs-turbopack-canary-quickjs137019
✅ nextjs-turbopack-stable-node15600
✅ nextjs-turbopack-stable-quickjs15600
✅ nextjs-webpack-canary-node137019
✅ nextjs-webpack-canary-quickjs137019
✅ nextjs-webpack-stable-node15600
✅ nextjs-webpack-stable-quickjs15600
✅ nitro-stable-node130026
✅ nitro-stable-quickjs130026
✅ nuxt-stable-node130026
✅ nuxt-stable-quickjs130026
✅ sveltekit-stable-node14907
✅ sveltekit-stable-quickjs14907
✅ tanstack-start-node130026
✅ tanstack-start-quickjs130026
✅ vite-stable-node130026
✅ vite-stable-quickjs130026
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack-node15600
✅ nextjs-turbopack-quickjs15600
✅ 🌐 Cross-language Conformance
AppPassedFailedSkipped
✅ python90128
✅ vercel-multi-region
AppPassedFailedSkipped
✅ nextjs-turbopack2700
📋 View full workflow run
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📊 Workflow Benchmarks
commit d7b0736 · Tue, 18 Aug 2026 19:46:55 GMT · run logs
Backend: vercel · app: nextjs-turbopack
MetricScenarioBest (ms)P75 (ms)P90 (ms)P99 (ms)Samples
TTFSstep1376 (+464%) 🔻1504 🔴 (+32%) 🔻1540 🔴 (+26%) 🔻1585 🔴 (-8.8%)30
TTFSstream354 (+52%) 🔻1424 🔴 (+23%) 🔻1463 🔴 (+23%) 🔻1495 🔴 (+14%)30
TTFShook + stream1346 (+214%) 🔻1735 🔴 (+25%) 🔻1813 🔴 (+29%) 🔻1996 🔴 (+36%) 🔻30
Fan-out TTFSPromise.all(100 steps)1188 (-17%) 💚3255 (+29%) 🔻3428 (+30%) 🔻5328 (+61%) 🔻10
Fan-out TTLSPromise.all(100 steps)5371 (-25%) 💚7805 (-11%)10551 (+17%) 🔻10957 (+21%) 🔻10
STSO1020 steps (inline)122 (-25%) 💚167 (-44%) 💚204 (-42%) 💚412 (-25%) 💚1019
WO1020 steps170113 (-41%) 💚170113 (-41%) 💚170113 (-41%) 💚170113 (-41%) 💚1
CRTTfirst chunk (pooled)113 (+14%)166 (-1.8%)375 (+15%)3821 (+738%) 🔻28
Streams
Scenariowr c/srd c/swr KiB/srd KiB/sCRTT 1stp75p90p99CDV maxiters
paced control (100/s, 60B)100 (±0%)101 (±0%)5 (±0%)5.1 (±0%)134 (-13%)172 (-21%)593 (+79%)3796 (+271%)157 (-51%)10
size sweep (100/s, 160B-12KB)100 (±0%)99.4 (-2%)334 (±0%)331 (-2%)123 (-2%)182 (-7%)234 (-76%)379 (-69%)159 (-23%)10
replay gateway-gpt-5.4-nano-2000t (1x)89.2 (±0%)89.4 (±0%)16.2 (±0%)16.3 (+1%)166 (+8%)142 (-27%)186 (-33%)402 (-50%)209 (-44%)3
replay eve-gpt-5.6-sol-2000t (1x)54.7 (±0%)54.7 (±0%)355 (±0%)355 (±0%)136 (-12%)140 (-11%)177 (-10%)326 (-21%)221 (-33%)2
replay eve-gpt-5.6-sol-2000t (2x)109 (±0%)110 (±0%)710 (±0%)712 (±0%)134 (-35%)212 (-15%)308 (-7%)1219 (+6%)305 (-54%)3
📈 STSO distribution vs main (inline / queue-hop histograms)
1020 steps (inline)
Cumulative STSO time: main 287804ms → this run 168740ms (Δ -119064ms, -41%)
 100-150 ms ░░░░░░░░░░░░░░░░░░░░░░░┃ main 0 this 476 +476
150-200 ms █░░░░░░░░░░░░░░░░░░░░┃ main 27 this 432 +405
200-250 ms ██┃████████████ main 305 this 57 -248
250-300 ms ┃█████████████████████ main 431 this 25 -406
300-350 ms ┃██████ main 142 this 12 -130
350-400 ms ┃███ main 71 this 5 -66
400-450 ms ┃ main 11 this 4 -7
450-500 ms ┃ main 11 this 4 -7
500-550 ms ┃ main 10 this 0 -10
550-600 ms ┃ main 4 this 1 -3
600-650 ms ┃ main 1 this 1 +0
650-700 ms ┃ main 2 this 1 -1
700-750 ms ┃ main 1 this 0 -1
800-850 ms ┃ main 1 this 0 -1
850-900 ms ┃ main 1 this 1 +0
1100-1150 ms ┃ main 1 this 0 -1

📈 CRTT drill-down vs main (RTT distributions & profiles)
variant RTT 1ms→5s+ avg p50 p90 p99 n
control ······▂█▂▁▁▁· 372.7 (+96%) 128 (-17%) 593 (+79%) 3796 (+271%) 3000
sweep ······▃█▂···· 139.9 (-29%) 128 (-10%) 234 (-76%) 379 (-69%) 3000
gw 1x ·····▁▅█▁···· 122 (-20%) 117 (-13%) 186 (-33%) 402 (-50%) 5295
eve 1x ·····▁▆█▁···· 118.1 (-10%) 104 (-11%) 177 (-10%) 326 (-21%) 5186
eve 2x ·····▁▂█▃▁▁·· 178.7 (-13%) 144 (-17%) 308 (-7%) 1219 (+6%) 7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):
control █▇▆▅▄▄▂▄▃▁ 248–507ms
sweep █▇▃▅▅▅▃▂▄▁ 128–153ms
gw 1x █▃▁▄▃▂▃▂▃▃ 105–159ms
eve 1x ▃▂▄▃▁▂█▆▆▁ 105–141ms
eve 2x ▃█▂▂▁▂▄▅▂▁ 126–307ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):
sweep ▂▁▄█▆▃▁ 139–142ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):
control ▁▃▄▂▃▂▂█▁▂ 34–62ms
sweep ▁▇█▃▆▇▂▇▄▂ 46–61ms
gw 1x █▂▁▁▅▆▆▂▃▂ 31–42ms
eve 1x ▂▅▄▄▁▅▆▅▄█ 21–26ms
eve 2x ▅█▂▃▂▄▃▁▂▃ 20–37ms

ℹ️ Metric definitions & methodology
Streams: writer/reader sustained rates (steady window, 10% trimmed each side), first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.
The collapsed STSO distribution section above buckets every step gap, split inline (same warm process — pure framework overhead) vs queue-hop (fresh process — dispatch, reinit, replay). █ = main, ┃ = this run, ░ = fill.
The collapsed CRTT drill-down: per-variant RTT histograms (fixed log bins, · = empty) and mean RTT/positive-CDV profile lines over stream progress and chunk size. Histograms, avgs, and profiles merge exactly across runs; p50–p99 are percentile-of-percentiles. Per-index rows live in the artifacts.
Best/P75/P90/P99 deltas compare against the most recent benchmark run on main at the time of this run. 🔻 flags a delta worse than +15%, 💚 one better than −15%.
Metrics — TTFS: time to first step body (in-deployment start() → first step body) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)
Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles
Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000teaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041
🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600
All timestamps are deployment-side; runs are triggered in-deployment, so the CI runner and api.vercel.com sit outside every measured window. TTFS = start() → first step body (includes dispatch + any cold start); Fan-out TTFS/TTLS = first/last step completion of one Promise.all from the same anchor (the gap is the runtime’s fan-out spread); STSO/WO between step bodies; CRTT inside the workflow (excludes the api.vercel.com read path).
Cold starts stay in the numbers (real bursty-workload latency, inflates P75+); Best is the warm floor.
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Sim World
Simulated world deterministic testing for races. Traces
🟠 world-sim scenario book — 1 fail of 41 total
fence=per-spec
scenariooutcomeeventsvirtreplayviolations
✅ smoke-no-stepscompleted30msok0
✅ smoke-one-stepcompleted60msok0
✅ hook-at-step-startedcompleted120msok0
✅ hook-at-step-completedcompleted120msok0
✅ hook-at-hook-createdcompleted120msok0
✅ deadline-hook-winscompleted71.0hok0
✅ deadline-expirescompleted71.0hok0
✅ long-sleepcompleted1130.0dok0
✅ hook-never-arrivesstalled30msskipped0
✅ step-retries-twicecompleted102.0sok0
✅ parallel-stepscompleted90msok0
✅ hook-on-execution-statecompleted120msok0
✅ peek-hook-before-branchcompleted120msok0
✅ peek-hook-after-branchcompleted120msok0
✅ peek-hook-at-registrationcompleted120msok0
✅ race-hook-before-probecompleted120msok0
✅ race-hook-after-probecompleted120msok0
✅ race-duplicate-deliverycompleted130msok0
✅ attr-hook-before-stepcompleted110msok0
✅ attr-hook-after-stepcompleted110msok0
✅ attr-from-step-bodycompleted130msok0
✅ fork-hook-after-timeoutcompleted141.0mok0
✅ fork-hook-before-timeoutcompleted141.0mok0
✅ count-hook-after-timeoutcompleted171.0mok0
✅ count-hook-before-timeoutcompleted201.0mok0
✅ stale-read-step-count-forkcompleted201.0mok0
✅ stale-read-equal-step-countscompleted141.0mok0
✅ step-vs-step-forkcompleted120msok0
✅ step-vs-step-fork-fencedcompleted120msok0
✅ fence-catches-benign-directioncompleted125msok0
✅ in-flight-before-decisioncompleted171.0mok0
❌ in-flight-before-decision-countedcompleted171.0mok0
✅ in-flight-after-decisioncompleted192.0mok0
✅ stale-read-step-count-fork-fencedcompleted201.0mok0
✅ fork-hook-winscompleted131.0mok0
✅ fork-timeout-winscompleted131.0mok0
✅ unclaimed-payload-under-forkcompleted171.0mok0
✅ claimed-payload-under-forkcompleted171.0mok0
✅ writers-independent-step-bodiescompleted120msok0
✅ writers-scripted-tempocompleted120msok0
✅ cancel-mid-stepcancelled70msskipped0
Full trace: world-sim.txt
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merged commit 8789f45
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August 18, 2026 21:59
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No backport to stable for 8789f45 (AI decision).
This is a test-only flake fix, which would normally qualify, but the behavior it covers does not exist on stable: git show origin/stable shows neither fetchWithSignal/SLOW_FETCH_URLS nor any AbortController/abort workflows in workbench/example/workflows/99_e2e.ts, and no abort-fetch cases in packages/core/e2e/e2e.test.ts (both files exist on stable, just without this coverage). With no abort-fetch tests on the maintenance line, there is no flake there to fix.
To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:
8789f4529b311205e41f38a7f6fb188677e6dcc7

alangenfeld added a commit
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Aug 18, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
6713211
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
alangenfeld added a commit
that referenced
this pull request
Aug 19, 2026
@alangenfeld
[e2e] Re-enable concurrent execution of the e2e suite
fc94f67
Serial execution has been the dominant wall-clock cost per matrix entry
since concurrency was disabled before conf (78048e0): ~128 tests at
~22 of 24 minutes on the Vercel lanes, and lately the slowest lane
cannot finish under its 30-minute job timeout on a slow runner day at
all. #2083 measured the concurrent suite at ~3x job wall-clock (4-5x on
the vitest phase) and identified what broke; its blockers are now fixed:
world-local writeExclusive is atomic (write-then-link), abort-fetch
tests are hermetic (#3618), the fibonacci tree fits the scheduler
(#3619), and source-map assertions are positive-only (#3620).
What this change adds is concurrency-safe per-test attribution. The
harness tracked runs and test names in module globals reset by a
beforeEach - under concurrency every test clobbered every other's
state, so a failing test dumped an unrelated sibling's diagnostics.
vitest's getCurrentTest() cannot substitute: it is a plain module
variable, wrong after any await. Instead an auto fixture - the one
place that receives the test's own context unambiguously - binds a
per-test state (name, tracked runs, the test's own skip) via
AsyncLocalStorage around each test body, and trackRun /
recordInfraEvent / requireFixture read it ambiently with no call-site
changes. The conformance gates skip through the bound state's skip, so
a mid-body requireFixture skips the right test. Sequential suites
(dev, agent, region) keep setupRunTracking's module-global fallback.
Full suite passes 137/137 concurrently against a local dev server in
under 2 minutes. A test that genuinely cannot share a deployment can
opt out with test.sequential.
Builds on VaguelySerious's investigation in #2083.
Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>
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