Fix steps bundle failing on Vite virtual modules by pranaygp · Pull Request #3873 · vercel/workflow

pranaygp · 2026-08-27T22:58:39Z

Closes #3859.

A step that transitively imports virtual:env/server from @vite-env/core currently prevents vite dev from starting.

Root cause

Nitro invokes build:before from Vite's config hook, before a dev-server plugin container exists and before host plugins run buildStart. In development, Workflow's standalone esbuild pass inlines local step dependencies, so it encounters the Vite-only module id and fails.

Fix

Defer only the initial Vite development workflow build.
Run it from Vite's awaited, post-ordered client buildStart hook after host plugins initialize.
Resolve and load otherwise-unresolved bare module ids through Nitro's server-environment plugin container as a last resort.
Propagate initial-build and host-plugin errors so Vite startup fails deterministically instead of racing the server-ready state.
Keep production and non-Vite build paths unchanged.

The resolver is step-only and runs only after normal filesystem and esbuild resolution decline, so it cannot shadow an existing file.

Intentionally out of scope

This is the smallest fix for the reported development failure. It does not add NodeNext ./x.js → ./x.ts fallback, transformed or TypeScript host modules, nested host-module graphs, or host-module HMR dependency tracking. Those are independent pre-existing limitations.

Verification

@workflow/builders: 251 tests passed.
@workflow/nitro: 32 tests passed, including startup error propagation and per-environment buildStart coverage.
Real workbench/vite development server compiled workflows before reporting ready; POST /api/virtual-module completed the workflow and returned postgres://virtual.
workbench/vite production build passed with one workflow compilation.
Builders and Nitro TypeScript builds passed.

A step that (transitively) imports a module id only the host bundler can resolve — e.g. `virtual:env/server` from `@vite-env/core` — failed the workflow build outright. Two independent defects: 1. Under Vite in dev, Nitro fires `build:before` from inside Vite's `config` hook, long before any plugin container exists. The dev path inlines project-local step dependencies, so a virtual id anywhere in that graph was unresolvable and `vite dev` never started. `workflow/vite` now defers the initial dev build to `configureServer`, where it can hand the builder a last-resort `hostResolver` backed by Vite's SSR plugin container. The module's source is inlined into the steps bundle instead. Awaited before the server listens, so no request can beat the generated bundles. Non-Vite Nitro apps are unchanged. 2. Neither the SWC plugin's enhanced-resolve pass nor `fastDiscoverEntries` mapped a TypeScript NodeNext `./db.js` specifier onto `./db.ts`. The former let the file fall through to esbuild and get inlined even on the production path (which is supposed to externalize it), failing `vite build` too; the latter silently dropped the import edge, so the file was never scanned for directives. Closes #3859 Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

changeset-bot · 2026-08-27T22:58:44Z

🦋 Changeset detected

Latest commit: 9390bc4

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

This PR includes changesets to release 16 packages

Name	Type
@workflow/builders	Patch
@workflow/nitro	Patch
@workflow/astro	Patch
@workflow/cli	Patch
@workflow/nest	Patch
@workflow/next	Patch
@workflow/rollup	Patch
@workflow/sveltekit	Patch
@workflow/vite	Patch
@workflow/vitest	Patch
@workflow/nuxt	Patch
workflow	Patch
@workflow/world-testing	Patch
@workflow/core	Patch
@workflow/web-shared	Patch
@workflow/web	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 · 2026-08-27T22:58:56Z

🧪 E2E Test Results

❌ Some tests failed

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

python-node (8 failed):

promiseAllWorkflow | wrun_41M158VEPG0GR8CTJGEAVSN31Z | 🔍 observability
sleepingWorkflow | wrun_41M158W61F0GPN7JERKVY108TX | 🔍 observability
parallelSleepWorkflow | wrun_41M158W66J0GNKJR13TPPWZMVD | 🔍 observability
nullByteWorkflow | wrun_41M158WD2F0GQEMMVSPEG99N2N | 🔍 observability
cancelRun - cancelling a running workflow | wrun_41M1590A9P0GP4VS8V6WGZCNYK | 🔍 observability
cancelRun via CLI - cancelling a running workflow | wrun_41M1590B2A0GNC4N98Q500X74C | 🔍 observability
sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M1590HN20GX6CA1XVPPHGMRA | 🔍 observability
resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M15913ET0GK1QH1EYST360TT | 🔍 observability

🌐 Cross-language Conformance (9 failed)

python (9 failed):

deploymentId: 'latest' is a no-op in non-Vercel worlds | wrun_01M15950JKXHA7ZGEGNC0H7RJV
promiseAllWorkflow | wrun_41M158VEPG0GR8CTJGEAVSN31Z
sleepingWorkflow | wrun_41M158W61F0GPN7JERKVY108TX
parallelSleepWorkflow | wrun_41M158W66J0GNKJR13TPPWZMVD
nullByteWorkflow | wrun_41M158WD2F0GQEMMVSPEG99N2N
cancelRun - cancelling a running workflow | wrun_41M1590A9P0GP4VS8V6WGZCNYK
cancelRun via CLI - cancelling a running workflow | wrun_41M1590B2A0GNC4N98Q500X74C
sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_41M1590HN20GX6CA1XVPPHGMRA
resilient start: addTenWorkflow completes when run_created returns 500 | wrun_41M15913ET0GK1QH1EYST360TT

⚠️ 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.

addTenWorkflow (sveltekit) — flaked in 2 jobs
addTenWorkflow (nest)
cancelRun via CLI - cancelling a running workflow (nextjs-turbopack)
deploymentId: 'latest' is a no-op in non-Vercel worlds (sveltekit)
hookWithSleepFinalStepWorkflow - step only on final payload (nextjs-turbopack)
hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nextjs-webpack)
hookWorkflow (tanstack-start)
hookWorkflow (vite)
promiseRaceWorkflow (sveltekit)

🛠 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.

35 infra events

cold-start-warmup · suite warmup (python) · at 22:47:13Z · abandoned wrun_41M158RWXP0GWQZ8BRNDVJPWD5 · (+7 more)
run-pickup-stall · sleepingWorkflow (python) · at 22:47:30Z · abandoned wrun_41M158WJ0P0GKT8YKH0CM87C76
run-pickup-stall · parallelSleepWorkflow (python) · at 22:47:30Z · abandoned wrun_41M158WJ0P0GKT8YKH0CM87C77
run-pickup-stall · promiseAllWorkflow (python) · at 22:47:30Z · abandoned wrun_41M158WJ0G0GJ9QZVB3YWB0VAR
run-pickup-stall · nullByteWorkflow (python) · at 22:47:30Z · abandoned wrun_41M158WJ0T0GW2JGEMF12GH9TM
run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 22:47:30Z · abandoned wrun_41M158WJE80GP4M1Y94TXXV27B
run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 22:48:03Z · abandoned wrun_41M158XJAQ0GR0T38HHMC57TWQ
run-pickup-stall · promiseAllWorkflow (python) · at 22:48:31Z · abandoned wrun_41M158YDP50GMDXXTQMH2XZJJZ
run-pickup-stall · sleepingWorkflow (python) · at 22:48:31Z · abandoned wrun_41M158YDHW0GTKKGG4W1S0C99N
run-pickup-stall · nullByteWorkflow (python) · at 22:48:31Z · abandoned wrun_41M158YDPA0GJN809Y0ST1X7RB
run-pickup-stall · parallelSleepWorkflow (python) · at 22:48:35Z · abandoned wrun_41M158YDMH0GNACQTQ30XY32N3
run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 22:49:22Z · abandoned wrun_41M158YKNT0GMVKEV5X0THDMR1
cold-start-warmup · suite warmup (tanstack-start) · at 22:49:25Z · abandoned wrun_01M158ZR4E7RF9K3F0Z3DXWW51
cold-start-warmup · suite warmup (python) · at 22:50:35Z · abandoned wrun_01M158Z24CG82PM3SKXN077RHD · (+7 more)
run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 22:50:50Z · abandoned wrun_01M1592Q8SGXSD1QFEAZ4F9ASS
run-pickup-stall · promiseAllWorkflow (python) · at 22:50:50Z · abandoned wrun_01M1592Q8VM035JR1DCTG6EF2P
run-pickup-stall · sleepingWorkflow (python) · at 22:50:50Z · abandoned wrun_01M1592Q90YMAAMFWR85K32NNH
run-pickup-stall · parallelSleepWorkflow (python) · at 22:50:50Z · abandoned wrun_01M1592Q929NY09MXY6X7YB0Z2
run-pickup-stall · nullByteWorkflow (python) · at 22:50:50Z · abandoned wrun_01M1592Q95503E4NV3KQ7XCCPX
run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 22:50:54Z · abandoned wrun_41M1590FY20GZHD40KRKRXT60T
run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 22:50:56Z · abandoned wrun_41M1590K5W0GX56SG990FR8R78
run-pickup-stall · promiseAllWorkflow (python) · at 22:51:50Z · abandoned wrun_01M1594HX4ZHG4BVT66EQ15W76
run-pickup-stall · sleepingWorkflow (python) · at 22:51:50Z · abandoned wrun_01M1594HX6K8SR6WBBK6SC2ZXS
run-pickup-stall · deploymentId: 'latest' is a no-op in non-Vercel worlds (python) · at 22:51:50Z · abandoned wrun_01M1594HX0C007QS8CGY3CKHDM
run-pickup-stall · parallelSleepWorkflow (python) · at 22:51:50Z · abandoned wrun_01M1594HX9YMVPEEKTAP0DR920
run-pickup-stall · nullByteWorkflow (python) · at 22:51:50Z · abandoned wrun_01M1594HXGZS4CM65E1X77JWXY
run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 22:51:54Z · abandoned wrun_41M15938WC0GJFXTJ44MATNEX0
run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 22:52:50Z · abandoned wrun_01M1596CGK7RC6SGXNS0JR2JXJ
run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 22:52:50Z · abandoned wrun_01M1596CGV2CP8HZ8CN6S59WCT
run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 22:52:50Z · abandoned wrun_01M1596CGYN7KG8XBR9K7AKBAD
run-pickup-stall · cancelRun - cancelling a running workflow (python) · at 22:53:20Z · abandoned wrun_01M15979W0W035WH9D53K8X66K
run-pickup-stall · cancelRun via CLI - cancelling a running workflow (python) · at 22:53:20Z · abandoned wrun_01M15979W7WKDY8AVXN9J1VTKQ
run-pickup-stall · sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration (python) · at 22:53:50Z · abandoned wrun_01M159874028ZJTXNK9R0KGGDJ
run-pickup-stall · plainModuleDoneHook resumed via plain API route (o2flow shape) (nextjs-webpack) · at 22:57:13Z · abandoned wrun_01M159ECXA749E8B02ZGVJ9P3W
run-pickup-stall · hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep (nextjs-webpack) · at 22:57:17Z · abandoned wrun_01M159EH5YFTTKHDXZQJHH0R9D

E2E Test Summary

Summary

	Passed	Failed	Skipped	Total
❌ ▲ Vercel Production	3570	8	742	4320
✅ 💻 Local Development	3922	0	558	4480
✅ 📦 Local Production	3922	0	558	4480
✅ 🐘 Local Postgres	3922	0	558	4480
✅ 🪟 Windows	320	0	0	320
❌ 🌐 Cross-language Conformance	0	9	132	141
✅ vercel-http-transport	817	0	143	960
✅ vercel-multi-region	27	0	0	27
✅ vercel-ws-transport	553	0	87	640
Total	17053	17	2778	19848

Details by Category

❌ ▲ Vercel Production

App	Passed	Failed	Skipped
✅ astro-node	132	0	28
✅ astro-quickjs	132	0	28
✅ example-node	132	0	28
✅ example-quickjs	132	0	28
✅ express-node	132	0	28
✅ express-quickjs	132	0	28
✅ fastify-node	132	0	28
✅ fastify-quickjs	132	0	28
✅ hono-node	132	0	28
✅ hono-quickjs	132	0	28
✅ nest-node	132	0	28
✅ nest-quickjs	132	0	28
✅ nextjs-turbopack-node	157	0	3
✅ nextjs-turbopack-quickjs	157	0	3
✅ nextjs-webpack-node	157	0	3
✅ nextjs-webpack-quickjs	157	0	3
✅ nitro-node	132	0	28
✅ nitro-quickjs	132	0	28
✅ nuxt-node	132	0	28
✅ nuxt-quickjs	132	0	28
❌ python-node	0	8	152
✅ sveltekit-node	151	0	9
✅ sveltekit-quickjs	151	0	9
✅ tanstack-start-node	132	0	28
✅ tanstack-start-quickjs	132	0	28
✅ vite-node	132	0	28
✅ vite-quickjs	132	0	28

✅ 💻 Local Development

App	Passed	Skipped
✅ astro-stable-node	134	26
✅ astro-stable-quickjs	134	26
✅ express-stable-node	134	26
✅ express-stable-quickjs	134	26
✅ fastify-stable-node	134	26
✅ fastify-stable-quickjs	134	26
✅ hono-stable-node	134	26
✅ hono-stable-quickjs	134	26
✅ nest-stable-node	134	26
✅ nest-stable-quickjs	134	26
✅ nextjs-turbopack-canary-node	141	19
✅ nextjs-turbopack-canary-quickjs	141	19
✅ nextjs-turbopack-stable-node	160	0
✅ nextjs-turbopack-stable-quickjs	160	0
✅ nextjs-webpack-canary-node	141	19
✅ nextjs-webpack-canary-quickjs	141	19
✅ nextjs-webpack-stable-node	160	0
✅ nextjs-webpack-stable-quickjs	160	0
✅ nitro-stable-node	134	26
✅ nitro-stable-quickjs	134	26
✅ nuxt-stable-node	134	26
✅ nuxt-stable-quickjs	134	26
✅ sveltekit-stable-node	153	7
✅ sveltekit-stable-quickjs	153	7
✅ tanstack-start-node	134	26
✅ tanstack-start-quickjs	134	26
✅ vite-stable-node	134	26
✅ vite-stable-quickjs	134	26

✅ 📦 Local Production

App	Passed	Skipped
✅ astro-stable-node	134	26
✅ astro-stable-quickjs	134	26
✅ express-stable-node	134	26
✅ express-stable-quickjs	134	26
✅ fastify-stable-node	134	26
✅ fastify-stable-quickjs	134	26
✅ hono-stable-node	134	26
✅ hono-stable-quickjs	134	26
✅ nest-stable-node	134	26
✅ nest-stable-quickjs	134	26
✅ nextjs-turbopack-canary-node	141	19
✅ nextjs-turbopack-canary-quickjs	141	19
✅ nextjs-turbopack-stable-node	160	0
✅ nextjs-turbopack-stable-quickjs	160	0
✅ nextjs-webpack-canary-node	141	19
✅ nextjs-webpack-canary-quickjs	141	19
✅ nextjs-webpack-stable-node	160	0
✅ nextjs-webpack-stable-quickjs	160	0
✅ nitro-stable-node	134	26
✅ nitro-stable-quickjs	134	26
✅ nuxt-stable-node	134	26
✅ nuxt-stable-quickjs	134	26
✅ sveltekit-stable-node	153	7
✅ sveltekit-stable-quickjs	153	7
✅ tanstack-start-node	134	26
✅ tanstack-start-quickjs	134	26
✅ vite-stable-node	134	26
✅ vite-stable-quickjs	134	26

✅ 🐘 Local Postgres

App	Passed	Skipped
✅ astro-stable-node	134	26
✅ astro-stable-quickjs	134	26
✅ express-stable-node	134	26
✅ express-stable-quickjs	134	26
✅ fastify-stable-node	134	26
✅ fastify-stable-quickjs	134	26
✅ hono-stable-node	134	26
✅ hono-stable-quickjs	134	26
✅ nest-stable-node	134	26
✅ nest-stable-quickjs	134	26
✅ nextjs-turbopack-canary-node	141	19
✅ nextjs-turbopack-canary-quickjs	141	19
✅ nextjs-turbopack-stable-node	160	0
✅ nextjs-turbopack-stable-quickjs	160	0
✅ nextjs-webpack-canary-node	141	19
✅ nextjs-webpack-canary-quickjs	141	19
✅ nextjs-webpack-stable-node	160	0
✅ nextjs-webpack-stable-quickjs	160	0
✅ nitro-stable-node	134	26
✅ nitro-stable-quickjs	134	26
✅ nuxt-stable-node	134	26
✅ nuxt-stable-quickjs	134	26
✅ sveltekit-stable-node	153	7
✅ sveltekit-stable-quickjs	153	7
✅ tanstack-start-node	134	26
✅ tanstack-start-quickjs	134	26
✅ vite-stable-node	134	26
✅ vite-stable-quickjs	134	26

✅ 🪟 Windows

App	Passed	Failed	Skipped
✅ nextjs-turbopack-node	160	0	0
✅ nextjs-turbopack-quickjs	160	0	0

❌ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
❌ python	0	9	132

✅ vercel-http-transport

App	Passed	Skipped
✅ example	132	28
✅ express	132	28
✅ hono	132	28
✅ nextjs-turbopack	157	3
✅ nitro	132	28
✅ vite	132	28

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

✅ vercel-ws-transport

App	Passed	Skipped
✅ example	132	28
✅ express	132	28
✅ nextjs-turbopack	157	3
✅ vite	132	28

📋 View full workflow run

github-actions · 2026-08-27T22:59:05Z

📊 Workflow Benchmarks

commit 9390bc4 · Fri, 28 Aug 2026 23:11:25 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	1283 (+89%) 🔻	1383 🔴 (+22%) 🔻	1444 🔴 (+27%) 🔻	1656 🔴 (+44%) 🔻	30
TTFS	stream	960 (+319%) 🔻	1335 🔴 (+24%) 🔻	1357 🔴 (+23%) 🔻	1367 🔴 (+17%) 🔻	30
TTFS	hook + stream	481 (-1.8%)	1570 🔴 (+17%) 🔻	1614 🔴 (+17%) 🔻	1849 🔴 (+27%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	659 (+17%) 🔻	2037 (+19%) 🔻	2048 (+13%)	2095 (+6.6%)	10
Fan-out TTLS	Promise.all(100 steps)	2022 (-8.0%)	3809 (+2.7%)	3860 (+2.6%)	4460 (-43%) 💚	10
STSO	1020 steps (inline)	107 (-5.3%)	135 (-3.6%)	152 (-5.6%)	215 (+9.1%)	1019
WO	1020 steps	134936 (-4.2%)	134936 (-4.2%)	134936 (-4.2%)	134936 (-4.2%)	1
CRTT	first chunk (pooled)	95 (-17%) 💚	142 (-39%) 💚	219 (-57%) 💚	295 (-56%) 💚	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	116 (-20%)	166 (-67%)	284 (-60%)	556 (-43%)	141 (-69%)	10
size sweep (100/s, 160B-12KB)	112 (-37%)	149 (-36%)	225 (-60%)	4352 (+383%)	136 (-42%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	187 (-5%)	149 (-36%)	180 (-59%)	319 (-67%)	285 (-61%)	3
replay eve-gpt-5.6-sol-2000t (1x)	178 (-54%)	169 (-70%)	331 (-81%)	558 (-86%)	306 (-86%)	2
replay eve-gpt-5.6-sol-2000t (2x)	132 (-16%)	178 (-76%)	244 (-77%)	798 (-40%)	333 (-41%)	3

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

1020 steps (inline)

Cumulative STSO time: main 139837ms → this run 134785ms (Δ -5052ms, -4%)

100-150 ms  ███████████████████████┃  main 857  this 905   +48
150-200 ms  ██┃█                      main 152  this  98   -54
200-250 ms  ┃                         main   8  this  11    +3
250-300 ms  ┃                         main   0  this   3    +3
300-350 ms  ┃                         main   2  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  ······▃█▂▁···  137.5 (-51%)  122 (-36%)  284 (-60%)    556 (-43%)  3000
sweep    ······▄█▁··▁·  292.2 (+40%)  111 (-35%)  225 (-60%)  4352 (+383%)  3000
gw 1x    ·····▁▄█▁····  124.3 (-39%)  114 (-30%)  180 (-59%)    319 (-67%)  5295
eve 1x   ·····▁▇█▂▁···  137.1 (-68%)  107 (-41%)  331 (-81%)    558 (-86%)  5186
eve 2x   ·····▁▃█▂▁···  153.4 (-60%)  131 (-47%)  244 (-77%)    798 (-40%)  7779

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

control  ▄▂██▆▁▅▄▅▅  111–163ms
sweep    ▁▁▁▁▁▆█▇▇▆  110–522ms
gw 1x    ▅██▃▁▅▅▅▃▅  110–135ms
eve 1x   ▃▁▁▆▁▃▆█▅▃  100–192ms
eve 2x   ▃▁▇▃▁▃▄█▂▂  113–229ms

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

sweep  ▁▂▂▂█▇▅  288–298ms

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

control  ▁▁▆█▂▃▆▄▆▇  32–53ms
sweep    ▁▁▁▂▁█▂▂▁▂  41–152ms
gw 1x    ▃█▄▁▂▆▅▅▄▃  31–46ms
eve 1x   ▅▁▁█▂▄▆▇▄▆  19–32ms
eve 2x   ▆▃▁▂▂▃▄▂▄█  21–27ms

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 · 2026-08-27T23:01:54Z

Sim World

Simulated world deterministic testing for races. Traces

🟠 world-sim scenario book — 1 fail of 41 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
✅ `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 · 2026-08-27T23:02:34Z

Framework	Flow route	Step reg.	Framework output
hono	200.9 KiB (±0)	40.3 KiB (-99 B)	1.76 MiB (-2.1 KiB)
nextjs-turbopack	206.3 KiB (±0)	439 B (±0)	763.5 KiB (-407 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.

9390bc4 · run

vercel · 2026-08-28T01:41:33Z

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

Project	Deployment	Actions	Updated (UTC)
example-nextjs-workflow-turbopack	Ready	Preview, v0	Aug 28, 2026 10:47pm
example-nextjs-workflow-webpack	Ready	Preview, v0	Aug 28, 2026 10:47pm
example-workflow	Ready	Preview, v0	Aug 28, 2026 10:47pm
workbench-astro-workflow	Ready	Preview, v0	Aug 28, 2026 10:47pm
workbench-express-workflow	Ready	Preview, v0	Aug 28, 2026 10:47pm
workbench-fastify-workflow	Ready	Preview, v0	Aug 28, 2026 10:47pm
workbench-hono-workflow	Ready	Preview, v0	Aug 28, 2026 10:47pm
workbench-nestjs-workflow	Ready	Preview, v0	Aug 28, 2026 10:47pm
workbench-nitro-workflow	Ready	Preview, v0	Aug 28, 2026 10:47pm
workbench-nuxt-workflow	Ready	Preview, v0	Aug 28, 2026 10:47pm
workbench-python-workflow	Ready	Preview, v0	Aug 28, 2026 10:47pm
workbench-sveltekit-workflow	Ready	Preview, v0	Aug 28, 2026 10:47pm
workbench-tanstack-start-workflow	Ready	Preview, v0	Aug 28, 2026 10:47pm
workbench-vite-workflow	Ready	Preview, v0	Aug 28, 2026 10:47pm
workflow-docs	Ready	Preview, v0	Aug 28, 2026 10:47pm
workflow-swc-playground	Ready	Preview, v0	Aug 28, 2026 10:47pm
workflow-tarballs	Ready	Preview, v0	Aug 28, 2026 10:47pm
workflow-web	Ready	Preview, v0	Aug 28, 2026 10:47pm

pranaygp marked this pull request as ready for review August 27, 2026 22:59

pranaygp requested a review from a team as a code owner August 27, 2026 22:59

vercel Bot reviewed Aug 27, 2026

View reviewed changes

Comment thread packages/nitro/src/vite.ts Outdated

pranaygp mentioned this pull request Aug 28, 2026

fix(builders): shim __dirname/__filename in fully-bundled ESM output #3876

Merged

fix(vite): harden virtual module workflow builds

e9a4001

vercel Bot deployed to Preview – workbench-python-workflow August 28, 2026 01:41 View deployment

vercel Bot deployed to Preview – workflow-web August 28, 2026 01:42 View deployment

vercel Bot deployed to Preview – workflow-tarballs August 28, 2026 01:42 View deployment

vercel Bot deployed to Preview – workbench-nestjs-workflow August 28, 2026 01:42 View deployment

vercel Bot deployed to Preview – workbench-hono-workflow August 28, 2026 01:42 View deployment

vercel Bot deployed to Preview – workbench-express-workflow August 28, 2026 01:42 View deployment

vercel Bot deployed to Preview – workbench-fastify-workflow August 28, 2026 01:42 View deployment

vercel Bot deployed to Preview – workbench-nitro-workflow August 28, 2026 01:42 View deployment

vercel Bot deployed to Preview – workbench-vite-workflow August 28, 2026 01:42 View deployment

vercel Bot deployed to Preview – workbench-astro-workflow August 28, 2026 01:42 View deployment

vercel Bot deployed to Preview – workbench-tanstack-start-workflow August 28, 2026 01:42 View deployment

vercel Bot deployed to Preview – workbench-sveltekit-workflow August 28, 2026 01:42 View deployment

vercel Bot deployed to Preview – example-workflow August 28, 2026 01:43 View deployment

vercel Bot deployed to Preview – workbench-nuxt-workflow August 28, 2026 01:43 View deployment

vercel Bot deployed to Preview – example-nextjs-workflow-turbopack August 28, 2026 01:43 View deployment

vercel Bot deployed to Preview – example-nextjs-workflow-webpack August 28, 2026 01:43 View deployment

vercel Bot deployed to Preview – workflow-docs August 28, 2026 01:43 View deployment

vercel Bot deployed to Preview – workflow-swc-playground August 28, 2026 01:44 View deployment

vercel Bot deployed to Preview – workflow-tarballs August 28, 2026 21:34 View deployment

vercel Bot deployed to Preview – workbench-hono-workflow August 28, 2026 21:34 View deployment

vercel Bot deployed to Preview – workbench-vite-workflow August 28, 2026 21:34 View deployment

vercel Bot deployed to Preview – workbench-nitro-workflow August 28, 2026 21:34 View deployment

vercel Bot deployed to Preview – workbench-fastify-workflow August 28, 2026 21:34 View deployment

vercel Bot deployed to Preview – example-workflow August 28, 2026 21:34 View deployment

vercel Bot deployed to Preview – workbench-astro-workflow August 28, 2026 21:34 View deployment

vercel Bot deployed to Preview – workbench-tanstack-start-workflow August 28, 2026 21:34 View deployment

vercel Bot deployed to Preview – workbench-sveltekit-workflow August 28, 2026 21:34 View deployment

vercel Bot deployed to Preview – workbench-express-workflow August 28, 2026 21:34 View deployment

vercel Bot deployed to Preview – workbench-nuxt-workflow August 28, 2026 21:34 View deployment

vercel Bot deployed to Preview – example-nextjs-workflow-webpack August 28, 2026 21:34 View deployment

vercel Bot deployed to Preview – example-nextjs-workflow-turbopack August 28, 2026 21:35 View deployment

vercel Bot deployed to Preview – workflow-docs August 28, 2026 21:35 View deployment

vercel Bot deployed to Preview – workflow-swc-playground August 28, 2026 21:36 View deployment

fix(vite): narrow host resolver bridge

9390bc4

vercel Bot deployed to Preview – workbench-python-workflow August 28, 2026 22:44 View deployment

vercel Bot deployed to Preview – workflow-web August 28, 2026 22:45 View deployment

vercel Bot deployed to Preview – workbench-nitro-workflow August 28, 2026 22:45 View deployment

vercel Bot deployed to Preview – workbench-hono-workflow August 28, 2026 22:45 View deployment

vercel Bot deployed to Preview – workflow-tarballs August 28, 2026 22:45 View deployment

vercel Bot deployed to Preview – workbench-fastify-workflow August 28, 2026 22:45 View deployment

vercel Bot deployed to Preview – workbench-nestjs-workflow August 28, 2026 22:45 View deployment

vercel Bot deployed to Preview – workbench-astro-workflow August 28, 2026 22:45 View deployment

vercel Bot deployed to Preview – workbench-express-workflow August 28, 2026 22:45 View deployment

vercel Bot deployed to Preview – example-workflow August 28, 2026 22:45 View deployment

vercel Bot deployed to Preview – workbench-sveltekit-workflow August 28, 2026 22:45 View deployment

vercel Bot deployed to Preview – workbench-vite-workflow August 28, 2026 22:45 View deployment

vercel Bot deployed to Preview – workbench-tanstack-start-workflow August 28, 2026 22:45 View deployment

vercel Bot deployed to Preview – example-nextjs-workflow-turbopack August 28, 2026 22:45 View deployment

Navigation Menu

Uh oh!

Fix steps bundle failing on Vite virtual modules - #3873

Fix steps bundle failing on Vite virtual modules#3873
pranaygp wants to merge 8 commits into
mainfrom
pgp/vite-virtual-module

pranaygp commented Aug 27, 2026 •

edited by NathanColosimo

Loading

Uh oh!

changeset-bot Bot commented Aug 27, 2026 •

edited

Loading

Uh oh!

github-actions Bot commented Aug 27, 2026 •

edited

Loading

Uh oh!

github-actions Bot commented Aug 27, 2026 •

edited

Loading

Uh oh!

github-actions Bot commented Aug 27, 2026 •

edited

Loading

Uh oh!

github-actions Bot commented Aug 27, 2026 •

edited

Loading

Uh oh!

Uh oh!

vercel Bot commented Aug 28, 2026 •

edited

Loading

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Uh oh!

Conversation

pranaygp commented Aug 27, 2026 • edited by NathanColosimo Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Root cause

Fix

Intentionally out of scope

Verification

Uh oh!

changeset-bot Bot commented Aug 27, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

🦋 Changeset detected

Uh oh!

github-actions Bot commented Aug 27, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

🧪 E2E Test Results

❌ Failed E2E Tests

▲ Vercel Production (8 failed)

🌐 Cross-language Conformance (9 failed)

⚠️ Flaky E2E Tests (passed on retry)

🛠 Infra Events (absorbed by the harness)

E2E Test Summary

Uh oh!

github-actions Bot commented Aug 27, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

📊 Workflow Benchmarks

Uh oh!

github-actions Bot commented Aug 27, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Sim World

Uh oh!

github-actions Bot commented Aug 27, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Uh oh!

vercel Bot commented Aug 28, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

pranaygp commented Aug 27, 2026 •

edited by NathanColosimo

Loading

changeset-bot Bot commented Aug 27, 2026 •

edited

Loading

github-actions Bot commented Aug 27, 2026 •

edited

Loading

github-actions Bot commented Aug 27, 2026 •

edited

Loading

github-actions Bot commented Aug 27, 2026 •

edited

Loading

github-actions Bot commented Aug 27, 2026 •

edited

Loading

vercel Bot commented Aug 28, 2026 •

edited

Loading