[world-vercel] Route requests through undici on Bun for transport parity by VaguelySerious · Pull Request #4576 · vercel/workflow

VaguelySerious · 2026-10-01T20:16:34Z

Follow-up to #4557 (#4555).

Problem

Under Bun, world-vercel's transport configuration does nothing. A bare undici import resolves to Bun's built-in module even when the package is installed, and its dispatcher classes are stubs. Bun's global fetch also ignores the dispatcher option. As a result, none of the following apply on Bun:

retries: 5xx and network errors on reads, and 5xx on stream close, which the close barrier relies on
per-phase timeouts
HTTP/2 multiplexing
pool limits

A silent origin is bounded only by Bun's 300s fetch default.

Change

On Bun 1.4.0 and later, world-vercel loads the installed undici package through its undici/index.js subpath. Bun only redirects the bare specifier, and undici publishes no exports map, so the subpath resolves. The package builds its dispatchers from that module and sends its requests through that module's fetch/request. Everything else in http-client.ts is untouched. The existing policies now apply as written.

Node: the code paths are unchanged, still on the global fetch.
Bundled builds under Bun: they already ship the real undici, so it is used directly and nothing extra is loaded.
Fallbacks: if the package can't be loaded, or the version is below 1.4.0, behavior is the same as today.
Caller-supplied dispatchers that can't dispatch() (an Agent built from a bare import under Bun) keep being ignored, as before, rather than failing.

Why 1.4.0: on Bun 1.3.x, undici.fetch never finishes reading a response body of 64 KiB or more (tested 1.3.4 through 1.3.11; 1.4.0 and 1.4.2 are fine). Event-log pages exceed that, so routing there would hang requests.

Not covered: queue requests

@vercel/queue's QueueClient calls the global fetch itself and accepts no fetch override. On every Bun version, acknowledgements and lease renewals therefore still get no connection limit and no 30s deadline. Closing that needs a fetch option in @vercel/queue, so it's a separate change.

Testing

Measured against the built dist, with local servers:

	Node 24	Bun 1.4.2 (before)	Bun 1.4.2 (this PR)	Bun 1.3.x (gated)
GET with 503, 503, 200	200 after 3 hits	503	200 after 3 hits	503
Stream close PUT with 503, 503, 200	200 after 3 hits	503	200 after 3 hits	503
Events `headersTimeout` against a silent origin	fails at 2.5s	waits 300s	fails at 2.5s	waits 300s

The "Bun 1.4.2 (before)" column is inferred, not measured on that version. Before this PR, Bun 1.4.2 used the same global-fetch path that the gated 1.3.4 run exercises, and I confirmed separately that Bun 1.4.2's global fetch ignores the dispatcher.

HTTP/2: on Bun 1.4.2, six concurrent requests multiplexed over one connection, with compose interceptors, against live hosts.
Issue layout: reproduced the setup from world-vercel: createQueueDispatcher crashes under Bun (Agent.compose is not a function), breaking SvelteKit builds since 4.7.4 #4555, a flat node_modules with bare undici resolving to Bun's built-in. Bun 1.4.2 routes and retries.
Unit tests: undici-runtime.test.ts covers the selection logic, plus a guard that undici/index.js keeps resolving to the same package as undici.
CI: new job world-vercel on Bun runs scripts/bun-parity.mjs on 1.4.2 (routing expected) and 1.3.11 (gate expected). vitest runs on Node, so nothing else exercises the Bun path. The job is not part of the required check.

🤖 Generated with Claude Code

Under Bun, a bare `undici` import resolves to Bun's built-in stub module and the global fetch ignores `dispatcher`, so every agent, retry policy, deadline and pool limit in http-client.ts was inert. On Bun >= 1.4.0, load the installed undici package via its `undici/index.js` subpath and dispatch world-vercel's requests through its fetch/request. Bun 1.3.x stays on the global fetch: its undici.fetch stalls reading any body of 64 KiB or more. The queue client still calls the global fetch on every Bun; closing that needs a `fetch` option in @vercel/queue. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

vercel · 2026-10-01T20:16:42Z

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

Project	Deployment	Actions	Updated
example-nextjs-workflow-turbopack	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
example-nextjs-workflow-webpack	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
example-workflow	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
workbench-astro-workflow	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
workbench-express-workflow	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
workbench-fastify-workflow	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
workbench-hono-workflow	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
workbench-nestjs-workflow	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
workbench-nitro-workflow	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
workbench-nuxt-workflow	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
workbench-python-workflow	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
workbench-sveltekit-workflow	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
workbench-tanstack-start-workflow	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
workbench-vite-workflow	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
workflow-docs	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
workflow-swc-playground	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
workflow-tarballs	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC
workflow-web	Ready	Preview, v0	Oct 1, 2026 8:21pm UTC

changeset-bot · 2026-10-01T20:16:44Z

🦋 Changeset detected

Latest commit: af8e8a3

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

This PR includes changesets to release 17 packages

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

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

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

github-actions · 2026-10-01T20:16:56Z

📊 Workflow Benchmarks

commit af8e8a3 · Thu, 01 Oct 2026 20:43:11 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	2128 (+192%) 🔻	2763 🔴 (+153%) 🔻	2824 🔴 (+154%) 🔻	3204 🔴 (+166%) 🔻	30
TTFS	stream	2104 (+856%) 🔻	2642 🔴 (+151%) 🔻	2662 🔴 (+143%) 🔻	2738 🔴 (+92%) 🔻	30
TTFS	hook + stream	2497 (+185%) 🔻	2623 🔴 (+98%) 🔻	2817 🔴 (+101%) 🔻	4855 🔴 (+211%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	475 (-45%) 💚	971 (-43%) 💚	1066 (-40%) 💚	3235 (+73%) 🔻	10
Fan-out TTLS	Promise.all(100 steps)	2046 (-11%)	3212 (-12%)	3565 (-5.6%)	10520 (+46%) 🔻	10
STSO	1020 steps (inline)	175 (+75%) 🔻	215 (+65%) 🔻	235 (+53%) 🔻	348 (+71%) 🔻	1019
WO	1020 steps	212786 (+62%) 🔻	212786 (+62%) 🔻	212786 (+62%) 🔻	212786 (+62%) 🔻	1
CRTT	first chunk (pooled)	73 (+1.4%)	105 (-26%) 💚	142 (-33%) 💚	376 (+5.9%)	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	102 (+4%)	178 (-7%)	284 (-6%)	466 (-5%)	147 (-35%)	10
size sweep (100/s, 160B-12KB)	93 (-10%)	176 (-22%)	281 (-20%)	577 (-9%)	151 (-29%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	85 (-38%)	166 (-13%)	200 (-38%)	317 (-45%)	159 (-64%)	3
replay eve-gpt-5.6-sol-2000t (1x)	115 (+10%)	165 (-16%)	196 (-36%)	319 (-42%)	295 (-35%)	2
replay eve-gpt-5.6-sol-2000t (2x)	111 (-22%)	264 (-19%)	3677 (+655%)	4481 (+377%)	192 (-59%)	3

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

1020 steps (inline)

Cumulative STSO time: main 131526ms → this run 212365ms (Δ +80839ms, +61%)

100-150 ms  ┃███████████████████████  main 899  this   0  -899
150-200 ms  ███░░░░░░░░░┃             main 108  this 493  +385
200-250 ms  █░░░░░░░░░░┃              main   8  this 464  +456
250-300 ms  ┃                         main   2  this  42   +40
300-350 ms  ┃                         main   0  this  10   +10
350-400 ms  ┃                         main   1  this   5    +4
400-450 ms  ┃                         main   1  this   3    +2
450-500 ms  ┃                         main   0  this   1    +1
600-650 ms  ┃                         main   0  this   1    +1

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

variant  RTT 1ms→5s+             avg         p50           p90           p99     n
control  ······▂█▂····     149 (-6%)   139 (+1%)     284 (-6%)     466 (-5%)  3000
sweep    ······▁█▂▁···  152.7 (-13%)  140 (-10%)    281 (-20%)     577 (-9%)  3000
gw 1x    ······▂█▁····  141.5 (-11%)   137 (+1%)    200 (-38%)    317 (-45%)  5295
eve 1x   ······▂█▁▁···  142.3 (-13%)   132 (-2%)    196 (-36%)    319 (-42%)  5186
eve 2x   ······▁█▃▁▁▁·  393.3 (+70%)  173 (-20%)  3677 (+655%)  4481 (+377%)  7779

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

control  ▄▃▆█▂▃▃▁▂▁  135–176ms
sweep    ▂▁▁▂█▂▂▅▁▄  144–177ms
gw 1x    ▁▁▁▄▆█▆▃▁▂  135–154ms
eve 1x   ▄▂▃▂▂▁█▆▆▆  130–159ms
eve 2x   ▁▁▁▁▁▁▁▄█▅  143–1350ms

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

sweep  ▁█▇▆▇▄▃  150–154ms

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

control  ▂▅▃█▁▇▂▃▅▅  42–52ms
sweep    ▁▁▄▆▂▁▆▂▃█  62–84ms
gw 1x    ▃▄▃▁▅▇█▃▃▃  41–52ms
eve 1x   ▅▄▁▃▂▄▆▅█▇  24–34ms
eve 2x   ▃▃▂▁▂▂▂█▃▂  26–58ms

ℹ️ Metric definitions & methodology

_{Streams: first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.}

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

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

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

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

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

_{Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000t eaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t 6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041}

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

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

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

github-actions · 2026-10-01T20:17:22Z

🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

express-node (2 failed):

webhookWorkflow | wrun_41M3WHX6YQ0GTX7ZRYC95JWDST | 🔍 observability
parallelStepsThenWebhookWorkflow - no hook_conflict from same-tick replay race | wrun_41M3WHX7SS0GWDMZB976AN1XCA | 🔍 observability

express-quickjs (2 failed):

webhookWorkflow | wrun_41M3WHX6YQ0GTX7ZRYC95JWDST | 🔍 observability
parallelStepsThenWebhookWorkflow - no hook_conflict from same-tick replay race | wrun_41M3WHX7SS0GWDMZB976AN1XCA | 🔍 observability

fastify-node (2 failed):

webhookWorkflow | wrun_41M3WHX6YQ0GTX7ZRYC95JWDST | 🔍 observability
parallelStepsThenWebhookWorkflow - no hook_conflict from same-tick replay race | wrun_41M3WHX7SS0GWDMZB976AN1XCA | 🔍 observability

fastify-quickjs (2 failed):

webhookWorkflow | wrun_41M3WHX6YQ0GTX7ZRYC95JWDST | 🔍 observability
parallelStepsThenWebhookWorkflow - no hook_conflict from same-tick replay race | wrun_41M3WHX7SS0GWDMZB976AN1XCA | 🔍 observability

💻 Local Development (1 failed)

astro-stable-node (1 failed):

createHook({ experimental_force: true }) a run can take over its own earlier hook

vercel-http-transport (2 failed)

express (2 failed):

webhookWorkflow | wrun_41M3WHX6YQ0GTX7ZRYC95JWDST
parallelStepsThenWebhookWorkflow - no hook_conflict from same-tick replay race | wrun_41M3WHX7SS0GWDMZB976AN1XCA

vercel-ws-transport (2 failed)

express (2 failed):

webhookWorkflow | wrun_41M3WHX6YQ0GTX7ZRYC95JWDST
parallelStepsThenWebhookWorkflow - no hook_conflict from same-tick replay race | wrun_41M3WHX7SS0GWDMZB976AN1XCA

⚠️ 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.

hookGetConflictWorkflow - awaiting hook.getConflict() registers hook without payload (nextjs-webpack · local-dev / local / node / stable)

🛠 Infra Events (absorbed by the harness)

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

run-pickup-stall · runs app-generated source against a registered step (tanstack-start) · at 20:22:04Z · abandoned wrun_01M3WJ2R10CXZMR9H82V0S78MQ
cold-start-warmup · suite warmup (tanstack-start) · at 20:22:07Z · abandoned wrun_01M3WJ2R0HGAKVP49HW66Z5T78
run-pickup-stall · abortTimeoutWorkflow: timeout cancels long-running step (nuxt) · at 20:25:11Z · abandoned wrun_01M3WJ8ENSHVJ7YY9EC4BAESB9
run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 20:28:17Z · abandoned wrun_01M3WJE49DFXYH6ETQPB3WZ7C3
run-pickup-stall · hookGetConflictWorkflow - awaiting hook.getConflict() registers hook without payload (nextjs-webpack) · at 20:28:24Z · abandoned wrun_01M3WJEBQB3EC78BR4FDK3FGYM

E2E Test Summary

Summary

	Passed	Failed	Skipped	Total
❌ ▲ Vercel Production	3896	8	875	4779
❌ 💻 Local Development	4581	1	551	5133
✅ 📦 Local Production	4582	0	551	5133
✅ 🐘 Local Postgres	4582	0	551	5133
✅ 🪟 Windows	342	0	12	354
✅ 🌐 Cross-language Conformance	68	0	84	152
✅ dynamic-runs	0	0	0	0
❌ vercel-http-transport	877	2	183	1062
✅ vercel-multi-region	27	0	0	27
❌ vercel-ws-transport	593	2	113	708
Total	19548	13	2920	22481

Details by Category

❌ ▲ Vercel Production

App	Passed	Failed	Skipped
✅ astro-node	142	0	35
✅ astro-quickjs	142	0	35
✅ example-node	142	0	35
✅ example-quickjs	142	0	35
❌ express-node	140	2	35
❌ express-quickjs	140	2	35
❌ fastify-node	140	2	35
❌ fastify-quickjs	140	2	35
✅ hono-node	142	0	35
✅ hono-quickjs	142	0	35
✅ nest-node	142	0	35
✅ nest-quickjs	142	0	35
✅ nextjs-turbopack-node	169	0	8
✅ nextjs-turbopack-quickjs	169	0	8
✅ nextjs-webpack-node	169	0	8
✅ nextjs-webpack-quickjs	169	0	8
✅ nitro-node	142	0	35
✅ nitro-quickjs	142	0	35
✅ nuxt-node	142	0	35
✅ nuxt-quickjs	142	0	35
✅ python-node	66	0	111
✅ sveltekit-node	161	0	16
✅ sveltekit-quickjs	161	0	16
✅ tanstack-start-node	142	0	35
✅ tanstack-start-quickjs	142	0	35
✅ vite-node	142	0	35
✅ vite-quickjs	142	0	35

❌ 💻 Local Development

App	Passed	Failed	Skipped
❌ astro-stable-node	147	1	29
✅ astro-stable-quickjs	148	0	29
✅ express-stable-node	148	0	29
✅ express-stable-quickjs	148	0	29
✅ fastify-stable-node	148	0	29
✅ fastify-stable-quickjs	148	0	29
✅ hono-stable-node	148	0	29
✅ hono-stable-quickjs	148	0	29
✅ nest-stable-node	148	0	29
✅ nest-stable-quickjs	148	0	29
✅ nextjs-turbopack-canary-node	176	0	1
✅ nextjs-turbopack-canary-quickjs	176	0	1
✅ nextjs-turbopack-quickjs-snapshot	176	0	1
✅ nextjs-turbopack-stable-node	176	0	1
✅ nextjs-turbopack-stable-quickjs	176	0	1
✅ nextjs-webpack-canary-node	176	0	1
✅ nextjs-webpack-canary-quickjs	176	0	1
✅ nextjs-webpack-stable-node	176	0	1
✅ nextjs-webpack-stable-quickjs	176	0	1
✅ nitro-stable-node	148	0	29
✅ nitro-stable-quickjs	148	0	29
✅ nuxt-stable-node	148	0	29
✅ nuxt-stable-quickjs	148	0	29
✅ sveltekit-stable-node	167	0	10
✅ sveltekit-stable-quickjs	167	0	10
✅ tanstack-start-node	148	0	29
✅ tanstack-start-quickjs	148	0	29
✅ vite-stable-node	148	0	29
✅ vite-stable-quickjs	148	0	29

✅ 📦 Local Production

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

✅ 🐘 Local Postgres

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

✅ 🪟 Windows

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

✅ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
✅ python	68	0	84

✅ dynamic-runs

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

❌ vercel-http-transport

App	Passed	Failed	Skipped
✅ example	142	0	35
❌ express	140	2	35
✅ hono	142	0	35
✅ nextjs-turbopack	169	0	8
✅ nitro	142	0	35
✅ vite	142	0	35

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

❌ vercel-ws-transport

App	Passed	Failed	Skipped
✅ example	142	0	35
❌ express	140	2	35
✅ nextjs-turbopack	169	0	8
✅ vite	142	0	35

📋 View full workflow run

github-actions · 2026-10-01T20:20:42Z

Sim World

Simulated world deterministic testing for races. Traces

🟠 world-sim scenario book — 1 fail of 42 total

fence=per-spec

scenario	outcome	events	virt	replay
✅ `smoke-no-steps`	completed	3	0ms	ok
✅ `smoke-one-step`	completed	6	0ms	ok
✅ `hook-at-step-started`	completed	12	0ms	ok
✅ `hook-at-step-completed`	completed	12	0ms	ok
✅ `hook-at-hook-created`	completed	12	0ms	ok
✅ `deadline-hook-wins`	completed	7	1.0h	ok
✅ `deadline-expires`	completed	7	1.0h	ok
✅ `step-vs-timer-early-settlement`	completed	8	1.0h	ok
✅ `long-sleep`	completed	11	30.0d	ok
✅ `hook-never-arrives`	stalled	3	0ms	skipped
✅ `step-retries-twice`	completed	10	2.0s	ok
✅ `parallel-steps`	completed	9	0ms	ok
✅ `hook-on-execution-state`	completed	12	0ms	ok
✅ `peek-hook-before-branch`	completed	12	0ms	ok
✅ `peek-hook-after-branch`	completed	12	0ms	ok
✅ `peek-hook-at-registration`	completed	12	0ms	ok
✅ `race-hook-before-probe`	completed	12	0ms	ok
✅ `race-hook-after-probe`	completed	12	0ms	ok
✅ `race-duplicate-delivery`	completed	13	0ms	ok
✅ `attr-hook-before-step`	completed	11	0ms	ok
✅ `attr-hook-after-step`	completed	11	0ms	ok
✅ `attr-from-step-body`	completed	13	0ms	ok
✅ `fork-hook-after-timeout`	completed	14	1.0m	ok
✅ `fork-hook-before-timeout`	completed	14	1.0m	ok
✅ `count-hook-after-timeout`	completed	17	1.0m	ok
✅ `count-hook-before-timeout`	completed	20	1.0m	ok
✅ `stale-read-step-count-fork`	completed	20	1.0m	ok
✅ `stale-read-equal-step-counts`	completed	14	1.0m	ok
✅ `step-vs-step-fork`	completed	12	0ms	ok
✅ `step-vs-step-fork-fenced`	completed	12	0ms	ok
✅ `fence-catches-benign-direction`	completed	12	5ms	ok
✅ `in-flight-before-decision`	completed	17	1.0m	ok
❌ `in-flight-before-decision-counted`	completed	17	1.0m	ok
✅ `in-flight-after-decision`	completed	19	2.0m	ok
✅ `stale-read-step-count-fork-fenced`	completed	20	1.0m	ok
✅ `fork-hook-wins`	completed	13	1.0m	ok
✅ `fork-timeout-wins`	completed	13	1.0m	ok
✅ `unclaimed-payload-under-fork`	completed	17	1.0m	ok
✅ `claimed-payload-under-fork`	completed	17	1.0m	ok
✅ `writers-independent-step-bodies`	completed	12	0ms	ok
✅ `writers-scripted-tempo`	completed	12	0ms	ok
✅ `cancel-mid-step`	cancelled	7	0ms	skipped

Full trace: world-sim.txt

github-actions · 2026-10-01T20:22:02Z

Framework	Flow route	Step reg.	Framework output
hono	267.2 KiB (±0)	97.3 KiB (±0)	2.00 MiB (+1.3 KiB)
nextjs-turbopack	274.6 KiB (±0)	426 B (±0)	986.0 KiB (+423 B)

About these numbers

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

af8e8a3 · run

vercel Bot deployed to Preview – workflow-docs October 1, 2026 20:18 View deployment

VaguelySerious mentioned this pull request Oct 1, 2026

world-vercel: createQueueDispatcher crashes under Bun (Agent.compose is not a function), breaking SvelteKit builds since 4.7.4 #4555

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[world-vercel] Route requests through undici on Bun for transport parity - #4576

[world-vercel] Route requests through undici on Bun for transport parity#4576
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peter/bun-network-parity

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VaguelySerious commented Oct 1, 2026

Problem

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Not covered: queue requests

Testing

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🦋 Changeset detected

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🧪 E2E Test Results

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

💻 Local Development (1 failed)

vercel-http-transport (2 failed)

vercel-ws-transport (2 failed)

⚠️ Flaky E2E Tests (passed on retry)

🛠 Infra Events (absorbed by the harness)

E2E Test Summary

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Sim World

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