feat(streams): add WebSocket capability gate by alangenfeld · Pull Request #3764 · vercel/workflow

alangenfeld · 2026-08-24T21:00:38Z

Summary & Motivation

WORKFLOW_STREAMS_TRANSPORT=ws advertises client support for workflow-stream-ws/v1 on stream writes; anything else keeps HTTP. It's a capability signal only — the server decides each upgrade, so there's no version or tenant-policy heuristic on the client side.

Test Plan

Unit tests for the gate's accepted values; typecheck, build, and lint pass locally.

changeset-bot · 2026-08-24T21:00:44Z

🦋 Changeset detected

Latest commit: e8af2eb

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

vercel · 2026-08-24T21:00:56Z

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

Project	Deployment	Actions	Updated
example-nextjs-workflow-turbopack	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC
example-nextjs-workflow-webpack	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC
example-workflow	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC
workbench-astro-workflow	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC
workbench-express-workflow	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC
workbench-fastify-workflow	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC
workbench-hono-workflow	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC
workbench-nestjs-workflow	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC
workbench-nitro-workflow	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC
workbench-nuxt-workflow	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC
workbench-python-workflow	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC
workbench-sveltekit-workflow	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC
workbench-tanstack-start-workflow	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC
workbench-vite-workflow	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC
workflow-docs	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC
workflow-swc-playground	Building	Preview, v0	Sep 9, 2026 3:43pm UTC
workflow-tarballs	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC
workflow-web	Ready	Preview, v0	Sep 9, 2026 3:43pm UTC

github-actions · 2026-08-24T21:01:00Z

🧪 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.

35 flaky tests

cancelRun via CLI - cancelling a running workflow (astro) — flaked in 2 jobs
abortAfterCompletionWorkflow: abort after step completes is a no-op (astro)
abortFetchUncaughtWorkflow: uncaught fetch AbortError is FatalError, no retries (nextjs-webpack)
abortHookOrderingWorkflow [listener-first-abort-first]: addEventListener → hook.then → abort() → resumeHook (nest)
abortThrowIfAbortedWorkflow: throwIfAborted causes FatalError, no retries (hono)
abortVoidSleepTimeoutWorkflow: documented void sleep().then(abort) pattern works (nitro)
basic step error preserves message and stack trace (hono)
basic step error preserves message and stack trace (vite)
Calculator.calculate - static workflow method using static step methods from another class (hono)
Calculator.calculate - static workflow method using static step methods from another class (nitro)
cancelRun via CLI - cancelling a running workflow (python)
cancelRun via CLI - cancelling a running workflow (tanstack-start)
cancelRun via CLI - cancelling a running workflow (vite)
cross-file imports preserve message and stack trace (hono)
cross-file step error preserves message and function names in stack (nest)
crossContextSerdeWorkflow - classes defined in step code are deserializable in workflow context (nitro)
customSerializationWorkflow - custom class serialization with WORKFLOW_SERIALIZE/WORKFLOW_DESERIALIZE (nextjs-webpack)
fetchWorkflow (nest)
getChunks returns same content as reading the stream (example)
getterStepWorkflow - getter functions with "use step" directive (nuxt)
hookClaimOnlyMutexWorkflow - hook works as a pure run mutex without payload data (example)
hookCleanupTestWorkflow - hook token reuse after workflow completion (sveltekit)
hookDisposeTestWorkflow - hook token reuse after explicit disposal while workflow still running (tanstack-start)
hookGetConflictWorkflow - hook.getConflict() resolves with the conflicting run when token is already registered (hono)
hookGetConflictWorkflow - hook.getConflict() resolves with the conflicting run when token is already registered (nest)
hookGetConflictWorkflow - hook.getConflict() resolves with the conflicting run when token is already registered (nitro)
importMetaUrlWorkflow - import.meta.url is available in step bundles (tanstack-start)
pathsAliasWorkflow - TypeScript path aliases resolve correctly (nitro)
promiseAllWorkflow (hono)
runClassSerializationWorkflow - Run instances serialize across workflow/step boundaries (express)
start: initial attributes are seeded on run creation (nest)
stepFunctionPassingWorkflow - step function references can be passed as arguments (without closure vars) (example)
stepFunctionPassingWorkflow - step function references can be passed as arguments (without closure vars) (sveltekit)
StepNotRegisteredError fails the step but workflow can catch it (nest)
uncaught step-argument serialization failure fails the run as USER_ERROR without redelivery retries (nitro)

🛠 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.

cold-start-warmup · suite warmup (tanstack-start) · at 15:46:37Z · abandoned wrun_01M23DJ5Z0BXYQA1RMHM2TTCY3
run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 15:51:23Z · abandoned wrun_01M23DVA490TJ21C26XJCA9TFA

E2E Test Summary

Summary

	Passed	Skipped	Total
✅ ▲ Vercel Production	3662	685	4347
✅ 💻 Local Development	3922	586	4508
✅ 📦 Local Production	3922	586	4508
✅ 🐘 Local Postgres	3922	586	4508
✅ 🪟 Windows	320	2	322
✅ 🌐 Cross-language Conformance	68	74	142
✅ vercel-http-transport	823	143	966
✅ vercel-multi-region	27	0	27
✅ vercel-ws-transport	557	87	644
Total	17223	2749	19972

Details by Category

✅ ▲ Vercel Production

App	Passed	Skipped
✅ astro-node	133	28
✅ astro-quickjs	133	28
✅ example-node	133	28
✅ example-quickjs	133	28
✅ express-node	133	28
✅ express-quickjs	133	28
✅ fastify-node	133	28
✅ fastify-quickjs	133	28
✅ hono-node	133	28
✅ hono-quickjs	133	28
✅ nest-node	133	28
✅ nest-quickjs	133	28
✅ nextjs-turbopack-node	158	3
✅ nextjs-turbopack-quickjs	158	3
✅ nextjs-webpack-node	158	3
✅ nextjs-webpack-quickjs	158	3
✅ nitro-node	133	28
✅ nitro-quickjs	133	28
✅ nuxt-node	133	28
✅ nuxt-quickjs	133	28
✅ python-node	66	95
✅ sveltekit-node	152	9
✅ sveltekit-quickjs	152	9
✅ tanstack-start-node	133	28
✅ tanstack-start-quickjs	133	28
✅ vite-node	133	28
✅ vite-quickjs	133	28

✅ 💻 Local Development

App	Passed	Skipped
✅ astro-stable-node	134	27
✅ astro-stable-quickjs	134	27
✅ express-stable-node	134	27
✅ express-stable-quickjs	134	27
✅ fastify-stable-node	134	27
✅ fastify-stable-quickjs	134	27
✅ hono-stable-node	134	27
✅ hono-stable-quickjs	134	27
✅ nest-stable-node	134	27
✅ nest-stable-quickjs	134	27
✅ nextjs-turbopack-canary-node	141	20
✅ nextjs-turbopack-canary-quickjs	141	20
✅ nextjs-turbopack-stable-node	160	1
✅ nextjs-turbopack-stable-quickjs	160	1
✅ nextjs-webpack-canary-node	141	20
✅ nextjs-webpack-canary-quickjs	141	20
✅ nextjs-webpack-stable-node	160	1
✅ nextjs-webpack-stable-quickjs	160	1
✅ nitro-stable-node	134	27
✅ nitro-stable-quickjs	134	27
✅ nuxt-stable-node	134	27
✅ nuxt-stable-quickjs	134	27
✅ sveltekit-stable-node	153	8
✅ sveltekit-stable-quickjs	153	8
✅ tanstack-start-node	134	27
✅ tanstack-start-quickjs	134	27
✅ vite-stable-node	134	27
✅ vite-stable-quickjs	134	27

✅ 📦 Local Production

App	Passed	Skipped
✅ astro-stable-node	134	27
✅ astro-stable-quickjs	134	27
✅ express-stable-node	134	27
✅ express-stable-quickjs	134	27
✅ fastify-stable-node	134	27
✅ fastify-stable-quickjs	134	27
✅ hono-stable-node	134	27
✅ hono-stable-quickjs	134	27
✅ nest-stable-node	134	27
✅ nest-stable-quickjs	134	27
✅ nextjs-turbopack-canary-node	141	20
✅ nextjs-turbopack-canary-quickjs	141	20
✅ nextjs-turbopack-stable-node	160	1
✅ nextjs-turbopack-stable-quickjs	160	1
✅ nextjs-webpack-canary-node	141	20
✅ nextjs-webpack-canary-quickjs	141	20
✅ nextjs-webpack-stable-node	160	1
✅ nextjs-webpack-stable-quickjs	160	1
✅ nitro-stable-node	134	27
✅ nitro-stable-quickjs	134	27
✅ nuxt-stable-node	134	27
✅ nuxt-stable-quickjs	134	27
✅ sveltekit-stable-node	153	8
✅ sveltekit-stable-quickjs	153	8
✅ tanstack-start-node	134	27
✅ tanstack-start-quickjs	134	27
✅ vite-stable-node	134	27
✅ vite-stable-quickjs	134	27

✅ 🐘 Local Postgres

App	Passed	Skipped
✅ astro-stable-node	134	27
✅ astro-stable-quickjs	134	27
✅ express-stable-node	134	27
✅ express-stable-quickjs	134	27
✅ fastify-stable-node	134	27
✅ fastify-stable-quickjs	134	27
✅ hono-stable-node	134	27
✅ hono-stable-quickjs	134	27
✅ nest-stable-node	134	27
✅ nest-stable-quickjs	134	27
✅ nextjs-turbopack-canary-node	141	20
✅ nextjs-turbopack-canary-quickjs	141	20
✅ nextjs-turbopack-stable-node	160	1
✅ nextjs-turbopack-stable-quickjs	160	1
✅ nextjs-webpack-canary-node	141	20
✅ nextjs-webpack-canary-quickjs	141	20
✅ nextjs-webpack-stable-node	160	1
✅ nextjs-webpack-stable-quickjs	160	1
✅ nitro-stable-node	134	27
✅ nitro-stable-quickjs	134	27
✅ nuxt-stable-node	134	27
✅ nuxt-stable-quickjs	134	27
✅ sveltekit-stable-node	153	8
✅ sveltekit-stable-quickjs	153	8
✅ tanstack-start-node	134	27
✅ tanstack-start-quickjs	134	27
✅ vite-stable-node	134	27
✅ vite-stable-quickjs	134	27

✅ 🪟 Windows

App	Passed	Failed	Skipped
✅ nextjs-turbopack-node	160	0	1
✅ nextjs-turbopack-quickjs	160	0	1

✅ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
✅ python	68	0	74

✅ vercel-http-transport

App	Passed	Skipped
✅ example	133	28
✅ express	133	28
✅ hono	133	28
✅ nextjs-turbopack	158	3
✅ nitro	133	28
✅ vite	133	28

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

✅ vercel-ws-transport

App	Passed	Skipped
✅ example	133	28
✅ express	133	28
✅ nextjs-turbopack	158	3
✅ vite	133	28

📋 View full workflow run

github-actions · 2026-08-24T21:01:02Z

📊 Workflow Benchmarks

commit 6fe4fa9 · Wed, 09 Sep 2026 16:07:45 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	185 (-6.1%)	1163 🔴 (+11%)	1396 🔴 (+26%) 🔻	1414 🔴 (+23%) 🔻	30
TTFS	stream	205 (-1.4%)	1373 🔴 (+33%) 🔻	1395 🔴 (+32%) 🔻	1477 🔴 (+18%) 🔻	30
TTFS	hook + stream	1557 (+67%) 🔻	1690 🔴 (+31%) 🔻	1747 🔴 (+33%) 🔻	1789 🔴 (+31%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	583 (-5.0%)	2055 (+12%)	2177 (+18%) 🔻	2227 (+19%) 🔻	10
Fan-out TTLS	Promise.all(100 steps)	1995 (+37%) 🔻	4486 (+13%)	5220 (+27%) 🔻	8505 (+71%) 🔻	10
STSO	1020 steps (inline)	82 (-18%) 💚	134 (-2.2%)	161 (+3.9%)	1028 (+295%) 🔻	1019
WO	1020 steps	154135 (+14%)	154135 (+14%)	154135 (+14%)	154135 (+14%)	1
CRTT	first chunk (pooled)	62 (-1.6%)	145 (+12%)	220 (+36%) 🔻	635 (+211%) 🔻	28

Streams

Scenario	CRTT 1st	p75	p90	p99	CDV max	iters
paced control (100/s, 60B)	109 (+25%)	146 (-18%)	192 (-41%)	595 (-40%)	116 (-34%)	10
size sweep (100/s, 160B-12KB)	109 (+3%)	166 (-21%)	221 (-40%)	322 (-48%)	144 (-20%)	10
replay gateway-gpt-5.4-nano-2000t (1x)	86 (-29%)	462 (+148%)	1592 (+273%)	3179 (+117%)	373 (-43%)	3
replay eve-gpt-5.6-sol-2000t (1x)	356 (+170%)	173 (-6%)	247 (-30%)	431 (-79%)	473 (-51%)	2
replay eve-gpt-5.6-sol-2000t (2x)	111 (-17%)	201 (-29%)	315 (-26%)	1496 (+135%)	325 (-24%)	3

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

1020 steps (inline)

Cumulative STSO time: main 135480ms → this run 152696ms (Δ +17216ms, +13%)

   50-100 ms  ┃                         main   0  this   4    +4
  100-150 ms  ███████████████████████┃  main 886  this 870   -16
  150-200 ms  █┃█                       main 103  this  91   -12
  200-250 ms  ┃                         main  18  this  17    -1
  250-300 ms  ┃                         main   6  this   7    +1
  300-350 ms  ┃                         main   4  this   3    -1
  350-400 ms  ┃                         main   1  this   0    -1
  450-500 ms  ┃                         main   0  this   2    +2
  550-600 ms  ┃                         main   1  this   1    +0
  600-650 ms  ┃                         main   0  this   6    +6
  650-700 ms  ┃                         main   0  this   1    +1
  700-750 ms  ┃                         main   0  this   1    +1
  750-800 ms  ┃                         main   0  this   2    +2
  800-850 ms  ┃                         main   0  this   1    +1
  900-950 ms  ┃                         main   0  this   1    +1
1000-1050 ms  ┃                         main   0  this   2    +2
1050-1100 ms  ┃                         main   0  this   2    +2
1100-1150 ms  ┃                         main   0  this   1    +1
1150-1200 ms  ┃                         main   0  this   1    +1
1200-1250 ms  ┃                         main   0  this   2    +2
1350-1400 ms  ┃                         main   0  this   1    +1
1400-1450 ms  ┃                         main   0  this   1    +1
1700-1750 ms  ┃                         main   0  this   2    +2

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

variant  RTT 1ms→5s+             avg         p50           p90           p99     n
control  ······▄█▁▁···  126.3 (-23%)  114 (-17%)    192 (-41%)    595 (-40%)  3000
sweep    ······▄█▂····  130.2 (-18%)  116 (-13%)    221 (-40%)    322 (-48%)  3000
gw 1x    ·····▁▅█▁▁▁▁·  235.9 (+37%)  115 (-13%)  1592 (+273%)  3179 (+117%)  5295
eve 1x   ·····▁▄█▂▁···  143.1 (-30%)   119 (-5%)    247 (-30%)    431 (-79%)  5186
eve 2x   ·····▁▂█▃▁▁··  184.3 (-17%)  137 (-29%)    315 (-26%)  1496 (+135%)  7779

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

control  █▇█▄▅▂▁▂▂▁  110–150ms
sweep    █▆▃▃▃▂▁▂▃▃  112–170ms
gw 1x    ▁▁▁▁▁▁▆█▃▂  106–693ms
eve 1x   █▆▅▃▃▁▆█▅▂  127–159ms
eve 2x   ▂▁▂▁▁▁▂▅█▂  123–409ms

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

sweep  ▅█▆▄▂▁▄  128–133ms

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

control  ▁█▃██▄▂▇▄▃  34–42ms
sweep    ▁▄▇▇█▇▄▇▅▅  40–58ms
gw 1x    ▂▁▂▂▂▂█▂▄▃  29–74ms
eve 1x   ▆█▂▁▅▂▂▂▄▄  25–35ms
eve 2x   ▆▅▁▁▂▂▃█▂▇  23–33ms

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 · 2026-08-24T21:03:42Z

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 · 2026-08-26T17:13:53Z

Framework	Flow route	Step reg.	Framework output
hono	201.6 KiB (±0)	41.7 KiB (±0)	1.78 MiB (-11 B)
nextjs-turbopack	207.8 KiB (±0)	439 B (±0)	771.6 KiB (-4 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.

6fe4fa9 · run

VaguelySerious

LGTM, with some specific issues the agent found, noted below

VaguelySerious · 2026-09-08T23:39:43Z

+- Factory option: none
+- CLI flag: none
+- Default: `http`
+- Experimental stream-write transport capability. Set to exactly `ws` to advertise support for [`workflow-stream-ws/v1`](#workflow_streams_transport) when it becomes available. The server authoritatively accepts or declines an upgrade; a decline uses HTTP directly. Stream reads remain HTTP and demand-driven.


AI Review: Nit

[workflow-stream-ws/v1](#workflow_streams_transport) links to the section it is written inside, so it takes the reader nowhere. Either drop the link and leave the protocol name as code, or point it at wherever the v1 wire format is actually described.

VaguelySerious · 2026-09-08T23:39:43Z

+ * server. v1 is `/websockets/v1`, independently versioned from REST v2/v4 and
+ * persisted workflow spec versions.
+ */
+export function isWsStreamsTransportEnabled(): boolean {


AI Review: Nit

Worth a sentence here on why this gate is exact-match while isWsEventsTransportEnabled above it trims and lowercases. The reasoning differs in a way that is defensible but not self-evident: the events gate defaults on, so a mistyped opt-out is the dangerous case and case-insensitivity protects the person reaching for the escape hatch; this gate defaults off, so a mistyped opt-in fails toward the compatibility path and costs nothing. The accompanying test pins 'WS' and 'ws ' to false deliberately, and the docs say "exactly ws", so the behaviour is intentional and covered. It is only the contrast with the neighbouring function, which spends 20 lines arguing the opposite way, that will read as an oversight to the next person editing this file.

Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

github-actions · 2026-09-09T16:48:57Z

No backport to stable for fdeb642 (AI decision).

This commit adds a new opt-in capability: a WORKFLOW_STREAMS_TRANSPORT environment variable and a new exported isWsStreamsTransportEnabled() function in @workflow/world-vercel, plus docs for the new setting. It is additive feature work (new config flag and API surface) for an experimental WebSocket stream-write protocol, not a fix to existing behavior, so it does not belong on the maintenance line even though it carries a patch changeset and would cherry-pick cleanly.

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

fdeb6422705afe70da5749057905dfc2027bd049

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VaguelySerious approved these changes Sep 8, 2026

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alangenfeld added 2 commits September 9, 2026 10:32

feat(streams): add WebSocket capability gate

91b3824

Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

docs(streams): clarify WebSocket opt-in gate

6fe4fa9

Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

github-actions Bot mentioned this pull request Sep 9, 2026

Version Packages (beta) #4011

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VaguelySerious mentioned this pull request Oct 2, 2026

[world-vercel] Document the state of WebSocket stream transports #4592

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feat(streams): add WebSocket capability gate - #3764

feat(streams): add WebSocket capability gate#3764
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