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[builders] Keep JSON import attributes and stop bundling serde-checker - #4537

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Sep 30, 2026
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[builders] Keep JSON import attributes and stop bundling serde-checker#4537
VaguelySerious merged 1 commit into
mainfrom
peter/issue-3157

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@VaguelySerious

@VaguelySerious VaguelySerious commented Sep 30, 2026 •
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Superseeds and closes #3160, fixes #3157

Carries forward the SWC + esbuild fix from #3160 (thanks @Mohith26), addresses its review notes, and fixes the discovery bug that put the failing import into every app's bundle.

Changes

  1. Import attributes are kept. SWC now runs with jsc.experimental.keepImportAttributes. Every esbuild pass that Node loads directly sets supported: { 'import-attributes': true }: steps, final workflow, combined, client, and webhook. Before this, an externalized import x from './x.json' with { type: 'json' } lost its attribute and failed with ERR_IMPORT_ATTRIBUTE_MISSING.
  2. The builder's own serde-checker is no longer treated as a serde file. Fast discovery matched static [WORKFLOW_SERIALIZE](...) inside that file's error-message string. Any project whose config file (vitest.config.ts, next.config.ts, ...) imports a framework integration therefore had @workflow/builders/dist/serde-checker.js and its builtin-modules JSON import bundled into the step and workflow bundles. This is the chain described in @workflow/builders 4.1.3: JSON import attribute stripped from bundled deps, breaking all local step execution on Node 22 #3157 (comment). hasLikelySerdeClass now checks class shapes against code only. It uses the shared stripCommentsFromSource scanner from transform-utils.ts with template literals and quoted strings blanked (quoted-string masking is a new maskQuotedStrings option), in place of the regex-based comment stripper. Symbol.for('workflow-serialize') names are confirmed against the original source at the same offsets, which works because the scanner output has the same length as its input.
  3. Changes from the fix(builders): preserve JSON import attributes in bundled output #3160 review:
    • The plugin list is typed as WasmPlugin[], so the as [string, Record<string, unknown>][] cast is gone.
    • The interim workflow VM pass has a comment explaining why it does not opt into import attributes: it has no external, so all JSON is inlined.
    • A new test asserts that the workflow VM bundle inlines JSON, both local files and JSON imported by a dependency.

Tests

  • json-import-attributes.test.ts:
    • SWC keeps the attribute in the false, step, and workflow modes.
    • The steps bundle keeps the attribute on externalized JSON and loads under Node's ESM loader.
    • The workflow VM bundle inlines JSON.
  • fast-discovery.test.ts:
    • Serde patterns inside string or template literals are ignored.
    • The real serde-checker.ts source is not discovered as a serde file.
  • Each new test fails with its fix reverted.
  • @workflow/builders: 507/507 tests pass.

Manual verification (scratch apps using local tarballs)

  • Nitro dev, with a step that imports ./data.json with { type: 'json' }:
    • Published 5.0.0: the step fails on every retry with ERR_IMPORT_ATTRIBUTE_MISSING.
    • This branch: the step completes, and steps.mjs contains import data2 from "../../../workflows/data.json" with { type: "json" }.
  • @workflow/vitest hello-world (the repro from the issue comment):
    • Before: serdeOnlyFiles listed @workflow/builders/dist/serde-checker.js, and builtin-modules was bundled into both outputs.
    • This branch: neither appears, and combined.mjs shrinks from 8.5 KB to 6.2 KB.

Backport

The 4.x line (stable) is where most reports come from (#3157, #4442). Item 1 applies to stable as is. Item 2 will conflict, because stable has only the regex-based stripComments and not the scanner in transform-utils.ts (added to main in #3954).

🤖 Generated with Claude Code

@VaguelySerious
VaguelySerious requested a review from a team as a code owner September 30, 2026 20:37
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🦋 Changeset detected

Latest commit: 62ba20f

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

This PR includes changesets to release 17 packages
Name Type
@workflow/builders Patch
@workflow/astro Patch
@workflow/cli Patch
@workflow/nest Patch
@workflow/next Patch
@workflow/nitro Patch
@workflow/rollup Patch
@workflow/sveltekit Patch
@workflow/vite Patch
@workflow/vitest Patch
workflow Patch
@workflow/world-testing Patch
@workflow/nuxt Patch
@workflow/core Patch
@workflow/world-vercel Patch
@workflow/web-shared Patch
@workflow/web Patch

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

Project Deployment Actions Updated
example-nextjs-workflow-turbopack Ready Ready Preview, v0 Sep 30, 2026 9:10pm UTC
example-nextjs-workflow-webpack Ready Ready Preview, v0 Sep 30, 2026 9:10pm UTC
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🧪 E2E Test Results

✅ All tests passed

⚠️ Flaky E2E Tests (passed on retry)

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

  • 'hookGetConflictWithPriorStepWorkflow' - hook.getConflict() does not block step execution (nextjs-webpack · local-dev / local / node / stable)
  • health check (CLI) - workflow health command reports healthy endpoints (nextjs-webpack · local-dev / local / node / canary)
  • hookGetConflictWorkflow - awaiting hook.getConflict() registers hook without payload (nextjs-webpack · local-dev / local / node / stable)
  • readableStreamWorkflow (nextjs-webpack · vercel-prod / vercel / quickjs / production)
  • StepNotRegisteredError fails the run when not caught in workflow (python · vercel-prod / vercel / node / production)

🛠 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 21:10:35Z · abandoned wrun_01M3T2EW1P4APWT9HG7EVY9G6M
  • cold-start-warmup · suite warmup (tanstack-start) · at 21:10:43Z · abandoned wrun_01M3T2EW1J362XJR798FA0T0H3
  • run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 21:15:29Z · abandoned wrun_01M3T2QV0KKSK3DE75RKCZYVJY
  • run-pickup-stall · hookGetConflictWorkflow - awaiting hook.getConflict() registers hook without payload (nextjs-webpack) · at 21:15:37Z · abandoned wrun_01M3T2R2Q13CJ9SBJ7ZG5BW1AW
  • run-pickup-stall · 'hookGetConflictWithPriorStepWorkflow' - hook.getConflict() does not block step execution (nextjs-webpack) · at 21:15:37Z · abandoned wrun_01M3T2R2XEAERE3S3VC4YHVMQD

E2E Test Summary

Summary
Passed Failed Skipped Total
✅ ▲ Vercel Production 3904 0 875 4779
✅ 💻 Local Development 4406 0 550 4956
✅ 📦 Local Production 4406 0 550 4956
✅ 🐘 Local Postgres 4406 0 550 4956
✅ 🪟 Windows 342 0 12 354
✅ 🌐 Cross-language Conformance 68 0 84 152
✅ dynamic-runs 0 0 0 0
✅ vercel-http-transport 879 0 183 1062
✅ vercel-multi-region 27 0 0 27
✅ vercel-ws-transport 595 0 113 708
Total 19033 0 2917 21950
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 142 0 35
✅ express-quickjs 142 0 35
✅ fastify-node 142 0 35
✅ fastify-quickjs 142 0 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 148 0 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-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 Failed Skipped
✅ astro-stable-node 148 0 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-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 Postgres

App Passed Failed Skipped
✅ astro-stable-node 148 0 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-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

✅ 🪟 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 142 0 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 142 0 35
✅ nextjs-turbopack 169 0 8
✅ vite 142 0 35

📋 View full workflow run

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📊 Workflow Benchmarks

commit 62ba20f · Wed, 30 Sep 2026 21:33:38 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric Scenario Best (ms) P75 (ms) P90 (ms) P99 (ms) Samples
TTFS step 2416 (+486%) 🔻 2650 🔴 (+34%) 🔻 2697 🔴 (+16%) 🔻 3177 🔴 (+29%) 🔻 30
TTFS stream 2430 (+557%) 🔻 2661 🔴 (+34%) 🔻 2701 🔴 (+30%) 🔻 3073 🔴 (+34%) 🔻 30
TTFS hook + stream 2638 (+256%) 🔻 3034 🔴 (+33%) 🔻 3196 🔴 (+38%) 🔻 7296 🔴 (+211%) 🔻 30
Fan-out TTFS Promise.all(100 steps) 573 (+7.7%) 797 (-5.0%) 988 (+9.7%) 2932 (+20%) 🔻 10
Fan-out TTLS Promise.all(100 steps) 1622 (-9.4%) 3456 (+2.9%) 5307 (+14%) 10885 (+34%) 🔻 10
STSO 1020 steps (inline) 152 (+2.7%) 196 (-11%) 221 (-13%) 339 (-27%) 💚 1019
WO 1020 steps 206741 (-4.0%) 206741 (-4.0%) 206741 (-4.0%) 206741 (-4.0%) 1
CRTT first chunk (pooled) 69 (+1.5%) 102 (-7.3%) 145 (+7.4%) 385 (+30%) 🔻 28

Streams

Scenario CRTT 1st p75 p90 p99 CDV max iters
paced control (100/s, 60B) 88 (-8%) 178 (-5%) 306 (+4%) 557 (+16%) 159 (-20%) 10
size sweep (100/s, 160B-12KB) 85 (-7%) 164 (-19%) 201 (-78%) 264 (-78%) 129 (-32%) 10
replay gateway-gpt-5.4-nano-2000t (1x) 99 (-23%) 147 (-21%) 181 (-30%) 371 (-62%) 212 (-54%) 3
replay eve-gpt-5.6-sol-2000t (1x) 124 (+12%) 148 (-88%) 178 (-97%) 278 (-97%) 298 (-95%) 2
replay eve-gpt-5.6-sol-2000t (2x) 93 (-11%) 188 (-30%) 229 (-47%) 317 (-75%) 187 (-56%) 3
📈 STSO distribution vs main (inline / queue-hop histograms)

1020 steps (inline)

Cumulative STSO time: main 214796ms → this run 206232ms (Δ -8564ms, -4%)

  100-150 ms  ┃                         main   1  this   0    -1
  150-200 ms  ███████████████░░░░░░░░┃  main 521  this 813  +292
  200-250 ms  ████┃██████               main 383  this 164  -219
  250-300 ms  ┃█                        main  66  this  27   -39
  300-350 ms  ┃                         main  22  this   5   -17
  350-400 ms  ┃                         main   5  this   5    +0
  400-450 ms  ┃                         main  10  this   1    -9
  450-500 ms  ┃                         main   5  this   0    -5
  500-550 ms  ┃                         main   3  this   0    -3
  550-600 ms  ┃                         main   1  this   0    -1
  650-700 ms  ┃                         main   1  this   0    -1
  700-750 ms  ┃                         main   0  this   1    +1
  850-900 ms  ┃                         main   1  this   0    -1
3950-4000 ms  ┃                         main   0  this   1    +1
4550-4600 ms  ┃                         main   0  this   1    +1
4700-4750 ms  ┃                         main   0  this   1    +1
📈 CRTT drill-down vs main (RTT distributions & profiles) 
variant  RTT 1ms→5s+             avg         p50         p90         p99     n
control  ······▃█▂▁···   143.4 (-9%)  124 (-16%)   306 (+4%)  557 (+16%)  3000
sweep    ······▃█▁····  130.1 (-38%)  120 (-19%)  201 (-78%)  264 (-78%)  3000
gw 1x    ·····▁▄█▁▁···  118.4 (-28%)  110 (-24%)  181 (-30%)  371 (-62%)  5295
eve 1x   ·····▁▃█▁▁···  126.7 (-86%)  120 (-24%)  178 (-97%)  278 (-97%)  5186
eve 2x   ·····▁▂█▂····  151.8 (-32%)  144 (-21%)  229 (-47%)  317 (-75%)  7779

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

control  █▅█▅▆▅▂▂▃▁  115–170ms
sweep    ▂▂▃▃▃█▁█▁▃  121–147ms
gw 1x    ▅█▃█▅▃▁▂▁▁  110–131ms
eve 1x   ▂▂▄█▁▂█▇▁▂  117–142ms
eve 2x   ▂▁▂▂▂▃▆█▃▃  133–195ms

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

sweep  ▅▆▅▃▁▆█  127–133ms

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

control  ▅▇█▇█▆▂▆▆▁  32–46ms
sweep    ▁▄▇▄▃▅▄█▅▁  42–66ms
gw 1x    ▇█▅▃▃▆▅▅▁▅  29–38ms
eve 1x   ▂▅▃█▄█▅▅▁▇  20–26ms
eve 2x   █▅▁▄▆▅▄▃▄█  20–28ms
📜 Previous results (1)

8ab42ed

Wed, 30 Sep 2026 20:58:04 GMT · run logs

vercel / nextjs-turbopack

Metric Scenario Best (ms) P75 (ms) P90 (ms) P99 (ms) Samples
TTFS step 2342 (+19%) 🔻 2488 🔴 (+14%) 2529 🔴 (-6.6%) 2602 🔴 (-19%) 💚 30
TTFS stream 2314 (+36%) 🔻 2441 🔴 (+20%) 🔻 2478 🔴 (+20%) 🔻 2505 🔴 (+13%) 30
TTFS hook + stream 651 (-66%) 💚 2754 🔴 (+13%) 2770 🔴 (+11%) 2813 🔴 (-0.7%) 30
Fan-out TTFS Promise.all(100 steps) 460 (-43%) 💚 765 (-29%) 💚 2610 (+6.7%) 2808 (+2.8%) 10
Fan-out TTLS Promise.all(100 steps) 1451 (-51%) 💚 3695 (-1.0%) 6505 (+58%) 🔻 9962 (+63%) 🔻 10
STSO 1020 steps (inline) 147 (-12%) 184 (-21%) 💚 204 (-27%) 💚 258 (-53%) 💚 1019
WO 1020 steps 182141 (-22%) 💚 182141 (-22%) 💚 182141 (-22%) 💚 182141 (-22%) 💚 1
CRTT first chunk (pooled) 50 (-43%) 💚 80 (-50%) 💚 100 (-47%) 💚 216 (-18%) 💚 28

Streams

Scenario CRTT 1st p75 p90 p99 CDV max iters
paced control (100/s, 60B) 62.5 (-53%) 118 (-54%) 175 (-56%) 371 (-51%) 97 (-48%) 10
size sweep (100/s, 160B-12KB) 72.5 (-35%) 121 (-43%) 151 (-43%) 223 (-38%) 120 (-22%) 10
replay gateway-gpt-5.4-nano-2000t (1x) 58 (-54%) 112 (-41%) 128 (-52%) 231 (-82%) 136 (-81%) 3
replay eve-gpt-5.6-sol-2000t (1x) 126 (-23%) 114 (-48%) 137 (-60%) 236 (-81%) 194 (-69%) 2
replay eve-gpt-5.6-sol-2000t (2x) 100 (-39%) 172 (-27%) 218 (-32%) 333 (-54%) 177 (-57%) 3
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.

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

Full trace: world-sim.txt

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Framework Flow route Step reg. Framework output
hono 265.9 KiB (±0) 97.2 KiB (±0) 1.98 MiB (±0)
nextjs-turbopack 273.3 KiB (±0) 426 B (±0) 979.6 KiB (±0)
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.

62ba20f · run

karthikscale3
karthikscale3 approved these changes Sep 30, 2026
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Reviewed the builder changes and regression coverage. Verified the full @workflow/builders test suite, package typecheck, and the targeted JSON import/discovery tests on Node 22 and 24. No blocking issues found.

@VaguelySerious @Mohith26 @claude
[builders] Keep JSON import attributes in generated bundles
62ba20f 
SWC and esbuild both dropped `with { type: 'json' }`, so an externalized
JSON import crashed Node's ESM loader with ERR_IMPORT_ATTRIBUTE_MISSING.
Fast discovery also matched serde patterns inside string literals, which
pulled @workflow/builders' serde-checker (and its builtin-modules JSON
import) into every step and workflow bundle.

Supersedes #3160. Fixes #3157.

Co-Authored-By: Mohith Gajjela <109003762+Mohith26@users.noreply.github.com>
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
@VaguelySerious
VaguelySerious merged commit 65ca6c8 into main Sep 30, 2026
183 of 184 checks passed
@VaguelySerious
VaguelySerious deleted the peter/issue-3157 branch September 30, 2026 21:26
@github-actions github-actions Bot mentioned this pull request Sep 30, 2026
Merged
github-actions Bot added a commit that referenced this pull request Sep 30, 2026
@github-actions @Mohith26
[builders] Keep JSON import attributes in generated bundles (#4537)
74839a4 
SWC and esbuild both dropped `with { type: 'json' }`, so an externalized
JSON import crashed Node's ESM loader with ERR_IMPORT_ATTRIBUTE_MISSING.
Fast discovery also matched serde patterns inside string literals, which
pulled @workflow/builders' serde-checker (and its builtin-modules JSON
import) into every step and workflow bundle.

Co-authored-by: Mohith Gajjela <109003762+Mohith26@users.noreply.github.com>
Signed-off-by: Peter Wielander <mittgfu@gmail.com>
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Backport PR opened against stable: #4542. Merge conflicts were resolved by AI — please review carefully. (backport job run)

@github-actions github-actions Bot mentioned this pull request Sep 30, 2026
Merged
VaguelySerious added a commit that referenced this pull request Sep 30, 2026
@VaguelySerious @Mohith26
[builders] Keep JSON import attributes in generated bundles (#4537)
e3dfd0d 
SWC and esbuild both dropped `with { type: 'json' }`, so an externalized
JSON import crashed Node's ESM loader with ERR_IMPORT_ATTRIBUTE_MISSING.
Fast discovery also matched serde patterns inside string literals, which
pulled @workflow/builders' serde-checker (and its builtin-modules JSON
import) into every step and workflow bundle.

Co-authored-by: Mohith Gajjela <109003762+Mohith26@users.noreply.github.com>
Signed-off-by: Peter Wielander <mittgfu@gmail.com>
VaguelySerious added a commit that referenced this pull request Sep 30, 2026
@github-actions @VaguelySerious @Mohith26
[builders] Keep JSON import attributes in generated bundles (#4537) (#…
6bb5224 
…4542)

SWC and esbuild both dropped `with { type: 'json' }`, so an externalized
JSON import crashed Node's ESM loader with ERR_IMPORT_ATTRIBUTE_MISSING.
Fast discovery also matched serde patterns inside string literals, which
pulled @workflow/builders' serde-checker (and its builtin-modules JSON
import) into every step and workflow bundle.

Signed-off-by: Peter Wielander <mittgfu@gmail.com>
Co-authored-by: Peter Wielander <mittgfu@gmail.com>
Co-authored-by: Mohith Gajjela <109003762+Mohith26@users.noreply.github.com>
This was referenced Sep 30, 2026
Merged
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@workflow/builders 4.1.3: JSON import attribute stripped from bundled deps, breaking all local step execution on Node 22

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