Skip to content

[world-vercel] Use stream control frame for transparent reconnection - #1790

Merged
VaguelySerious merged 1 commit into
stablefrom
peter/stream-reconnect-proper
Apr 17, 2026
Merged

[world-vercel] Use stream control frame for transparent reconnection#1790
VaguelySerious merged 1 commit into
stablefrom
peter/stream-reconnect-proper

Conversation

@VaguelySerious

@VaguelySeriousVaguelySerious commented Apr 17, 2026

Copy link
Copy Markdown
Member

Summary

Re-applies #1742's reconnect feature on `stable` — without the `arrayBuffer()` rewrite that shipped in 4.2.3 (#1766) and broke incremental streaming on Vercel (content only arrived on stream close). #1766 was reverted on `stable` (#1788, released as 4.2.4).

Root cause of the 4.2.3 regression: `await response.arrayBuffer()` inside `readFromStream` drained the upstream before returning the `ReadableStream`, so `run.getReadable()` blocked until the server closed the stream. The returned stream just replayed the already-complete buffer.

This PR restores the original hold-back buffer approach from #1742 (still in use on `main`), adapted to `stable`'s `readFromStream` signature.

What's in it

  • `readFromStream` returns the `ReadableStream` promptly. A hold-back buffer inside the pull loop keeps only the last 13 bytes (the control-frame size), forwarding surplus bytes as they arrive.
  • On upstream close, the tail is parsed:
    • `done=true` → close cleanly
    • `done=false` → reconnect from `nextIndex`
    • no frame → forward tail as data (older-server backward compat)
  • Network errors propagate via `controller.error()` rather than a silent close.
  • Reconnections capped at 50 (~100 min of streaming at 2-min server timeout).
  • New regression test (`emits upstream bytes to the consumer before the stream closes`) asserts data flows before upstream EOF — any buffer-then-replay implementation fails it. This specifically catches the class of bug that shipped as 4.2.3.

Test plan

  • `pnpm vitest run` — 67/67 world-vercel tests pass (28 streamer + 11 reconnect parser + 28 other)
  • Reconnect + backward-compat + control-frame-split tests from [backport] [world-vercel] Use stream control frame for transparent reconnection #1766 still pass
  • New regression test fails if `readFromStream` is rewritten to drain upstream first
  • CI + auto-created workflow-server preview e2e
  • Manual validation against flight-booking-app once a preview tarball is available

Notes

🤖 Generated with Claude Code

@changeset-bot

changeset-botBot commented Apr 17, 2026•
edited
Loading

Copy link
Copy Markdown

🦋 Changeset detected

Latest commit: ee258dc

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

This PR includes changesets to release 18 packages
NameType
@workflow/world-vercelPatch
@workflow/cliPatch
@workflow/corePatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/buildersPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/vitestPatch
@workflow/web-sharedPatch
@workflow/aiPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch

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

vercelBot commented Apr 17, 2026•
edited
Loading

Copy link
Copy Markdown
Contributor

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

ProjectDeploymentActionsUpdated (UTC)
example-nextjs-workflow-turbopackReadyReadyPreview, CommentApr 17, 2026 0:30am
example-nextjs-workflow-webpackReadyReadyPreview, CommentApr 17, 2026 0:30am
example-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-astro-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-express-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-fastify-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-hono-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-nitro-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-nuxt-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-sveltekit-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-vite-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workflow-docsReadyReadyPreview, Comment, Open in v0Apr 17, 2026 0:30am
workflow-swc-playgroundReadyReadyPreview, CommentApr 17, 2026 0:30am
workflow-webReadyReadyPreview, CommentApr 17, 2026 0:30am

@github-actions

github-actionsBot commented Apr 17, 2026•
edited
Loading

Copy link
Copy Markdown
Contributor

🧪 E2E Test Results

❌ Some tests failed

Summary

PassedFailedSkippedTotal
❌ ▲ Vercel Production900167968
✅ 💻 Local Development9700861056
✅ 📦 Local Production9700861056
✅ 🐘 Local Postgres9700861056
✅ 🪟 Windows880088
❌ 🌍 Community Worlds139830222
✅ 📋 Other246018264
Total4283843434710

❌ Failed Tests

▲ Vercel Production (1 failed)

sveltekit (1 failed):

  • error handling catchability FatalError can be caught and detected with FatalError.is()
🌍 Community Worlds (83 failed)

mongodb (11 failed):

  • readableStreamWorkflow | wrun_01KPCDEV0N8PQBX7HQXBRBVS64
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • webhookWorkflow | wrun_01KPCDFSP9DFEP41FPPJ2QYNP2
  • outputStreamWorkflow no startIndex (reads all chunks)
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions | wrun_01KPCDJRHYBET9BD520MHYJQG7
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97

redis (7 failed):

  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97

turso (65 failed):

  • addTenWorkflow | wrun_01KPCDEB45HR5F1E88RVZK3JAE
  • addTenWorkflow | wrun_01KPCDEB45HR5F1E88RVZK3JAE
  • wellKnownAgentWorkflow (.well-known/agent) | wrun_01KPCDF08KKPWAQ7PVD2SKCJ78
  • should work with react rendering in step
  • promiseAllWorkflow | wrun_01KPCDEHJWP5ETJS19AG89D448
  • promiseRaceWorkflow | wrun_01KPCDEQ1GD6AXHKS1E2FZMER9
  • promiseAnyWorkflow | wrun_01KPCDES15ZVBHEQ419230WC22
  • importedStepOnlyWorkflow | wrun_01KPCDFDB96AA2827YQ3CD8AJD
  • readableStreamWorkflow | wrun_01KPCDEV0N8PQBX7HQXBRBVS64
  • hookWorkflow | wrun_01KPCDF5S02DMW2T56KA1W34G2
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • webhookWorkflow | wrun_01KPCDFSP9DFEP41FPPJ2QYNP2
  • sleepingWorkflow | wrun_01KPCDFZ2DGN157PQ61KNDPAA3
  • parallelSleepWorkflow | wrun_01KPCDGB2FNK5G4XVQJ7GSZM8R
  • nullByteWorkflow | wrun_01KPCDGE8FE22NA1YJ1WFF6VBY
  • workflowAndStepMetadataWorkflow | wrun_01KPCDGGH4DQKZJZX552S74HRQ
  • outputStreamWorkflow no startIndex (reads all chunks)
  • outputStreamWorkflow positive startIndex (skips first chunk)
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions | wrun_01KPCDJRHYBET9BD520MHYJQG7
  • fetchWorkflow | wrun_01KPCDK5ENNGNJHHMJC1RKW1NT
  • promiseRaceStressTestWorkflow | wrun_01KPCDK8P00SQXPD3707XAM87T
  • error handling error propagation workflow errors nested function calls preserve message and stack trace
  • error handling error propagation workflow errors cross-file imports preserve message and stack trace
  • error handling error propagation step errors basic step error preserves message and stack trace
  • error handling error propagation step errors cross-file step error preserves message and function names in stack
  • error handling retry behavior regular Error retries until success
  • error handling retry behavior FatalError fails immediately without retries
  • error handling retry behavior RetryableError respects custom retryAfter delay
  • error handling retry behavior maxRetries=0 disables retries
  • error handling catchability FatalError can be caught and detected with FatalError.is()
  • error handling not registered WorkflowNotRegisteredError fails the run when workflow does not exist
  • error handling not registered StepNotRegisteredError fails the step but workflow can catch it
  • error handling not registered StepNotRegisteredError fails the run when not caught in workflow
  • hookCleanupTestWorkflow - hook token reuse after workflow completion | wrun_01KPCDPM3JVFJVVH4SBXR892QP
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • hookDisposeTestWorkflow - hook token reuse after explicit disposal while workflow still running | wrun_01KPCDQWKW6XF2NYGHMAD769N5
  • stepFunctionPassingWorkflow - step function references can be passed as arguments (without closure vars) | wrun_01KPCDRGBQGBX4PP2J61VG8MFW
  • stepFunctionWithClosureWorkflow - step function with closure variables passed as argument | wrun_01KPCDRRSK12SDD1NC9AF698RX
  • closureVariableWorkflow - nested step functions with closure variables | wrun_01KPCDRZ9C5MXV1S38E1EYN5BG
  • spawnWorkflowFromStepWorkflow - spawning a child workflow using start() inside a step | wrun_01KPCDS1EG8NXNNB1VYFR7246C
  • health check (queue-based) - workflow and step endpoints respond to health check messages
  • pathsAliasWorkflow - TypeScript path aliases resolve correctly | wrun_01KPCDSGJ3KQKHEHFAQ13QZCPF
  • Calculator.calculate - static workflow method using static step methods from another class | wrun_01KPCDSNXEVWHWXH3928ZG4X1T
  • AllInOneService.processNumber - static workflow method using sibling static step methods | wrun_01KPCDSW86T6BVEAKWY7EGFDV4
  • ChainableService.processWithThis - static step methods using this to reference the class | wrun_01KPCDT2MD8TR3WGMNYS0FKRCH
  • thisSerializationWorkflow - step function invoked with .call() and .apply() | wrun_01KPCDT8BW51BYHXX7QR5QZJ7G
  • customSerializationWorkflow - custom class serialization with WORKFLOW_SERIALIZE/WORKFLOW_DESERIALIZE | wrun_01KPCDTH53VT0AX0SWMD03EWA9
  • instanceMethodStepWorkflow - instance methods with "use step" directive | wrun_01KPCDTQK0WGZ0T10CH13Q2GZK
  • crossContextSerdeWorkflow - classes defined in step code are deserializable in workflow context | wrun_01KPCDV322NQVNK879EXAZ7AW4
  • stepFunctionAsStartArgWorkflow - step function reference passed as start() argument | wrun_01KPCDVAMGFBSHY0F50B9XRY6S
  • cancelRun - cancelling a running workflow | wrun_01KPCDVH3SYGSQWMH1V24W8DQ3
  • cancelRun via CLI - cancelling a running workflow | wrun_01KPCDVTNWAD8331GPPK683AWF
  • pages router addTenWorkflow via pages router
  • pages router promiseAllWorkflow via pages router
  • pages router sleepingWorkflow via pages router
  • hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep | wrun_01KPCDW6J1SYGVPA6PZ0HVTMYF
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_01KPCDWTJ0A2RBCBADY4TB6PZ7
  • sleepWithSequentialStepsWorkflow - sequential steps work with concurrent sleep (control) | wrun_01KPCDX4F3VP5DQDC942H624E4
  • importMetaUrlWorkflow - import.meta.url is available in step bundles | wrun_01KPCDXAT2MWN03RQDQCCVYB16
  • metadataFromHelperWorkflow - getWorkflowMetadata/getStepMetadata work from module-level helper (#1577) | wrun_01KPCDXCWM794ANQS89DT0VN2S
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97

Details by Category

❌ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro8107
✅ example8107
✅ express8107
✅ fastify8107
✅ hono8107
✅ nextjs-turbopack8602
✅ nextjs-webpack8602
✅ nitro8107
✅ nuxt8107
❌ sveltekit8017
✅ vite8107
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack8800
❌ 🌍 Community Worlds
AppPassedFailedSkipped
✅ mongodb-dev500
❌ mongodb58110
✅ redis-dev500
❌ redis6270
✅ turso-dev500
❌ turso4650
✅ 📋 Other
AppPassedFailedSkipped
✅ e2e-local-dev-nest-stable8206
✅ e2e-local-postgres-nest-stable8206
✅ e2e-local-prod-nest-stable8206

📋 View full workflow run

❌ Some E2E test jobs failed:

  • Vercel Prod: failure
  • Local Dev: success
  • Local Prod: success
  • Local Postgres: success
  • Windows: success

Check the workflow run for details.

@VaguelySerious@claude
[world-vercel] Use stream control frame for transparent reconnection,…
ee258dc
… with streaming hold-back buffer
Re-applies #1742's reconnect feature on stable, without the arrayBuffer()
rewrite that shipped in 4.2.3 (#1766) and defeated incremental streaming.
- readFromStream returns the ReadableStream promptly; a hold-back buffer
inside the pull loop holds only the last 13 bytes, forwarding surplus
bytes as they arrive. This preserves incremental delivery for AI UIs.
- On upstream close, the tail is parsed for a stream control frame
(done=true → close; done=false → reconnect from nextIndex; no frame →
forward tail as data for older servers).
- Network errors propagate via controller.error() rather than silent close.
- Caps reconnections at 50 (~100 min of streaming at 2-min server timeout).
Adds a regression test that asserts data reaches the consumer before
upstream close — any buffer-then-replay implementation fails it.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Signed-off-by: Peter Wielander <mittgfu@gmail.com>
@VaguelySerious
VaguelySeriousforce-pushed the peter/stream-reconnect-proper branch from d76d170 to ee258dcCompareApril 17, 2026 00:26
@VaguelySeriousVaguelySerious changed the title [world-vercel] Use stream control frame for transparent reconnection (proper streaming fix)[world-vercel] Use stream control frame for transparent reconnectionApr 17, 2026
@VaguelySerious
VaguelySerious marked this pull request as ready for review April 17, 2026 00:42
@VaguelySerious
VaguelySerious requested a review from a team as a code ownerApril 17, 2026 00:42
@VaguelySerious
VaguelySerious merged commit 5ef9ac2 into stableApr 17, 2026
87 of 89 checks passed
@VaguelySerious
VaguelySerious deleted the peter/stream-reconnect-proper branch April 17, 2026 00:48
@ghostghost mentioned this pull request Apr 17, 2026
Closed
This was referenced Apr 17, 2026
Closed
Merged
@TooTallNateTooTallNate mentioned this pull request Apr 25, 2026
Merged
@VaguelySeriousVaguelySerious mentioned this pull request May 2, 2026
Merged
Sign up for freeto join this conversation on GitHub. Already have an account? Sign in to comment

Reviewers

@TooTallNateTooTallNateTooTallNate approved these changes

Assignees

No one assigned

Labels

None yet

Projects

None yet

Milestone

No milestone

Development

Successfully merging this pull request may close these issues.

2 participants

@VaguelySerious@TooTallNate
, 'i'); if (__m === '*' || __re.test(location.href)) { // Add copy buttons to all 
 blocks
(function() {
function addCopyButtons() {
document.querySelectorAll('pre code').forEach(function(codeBlock) {
if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;
codeBlock.parentElement.setAttribute('data-copy-added', 'true');
var btn = document.createElement('button');
btn.textContent = 'Copy';
btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';
btn.onmouseover = function() { this.style.opacity = '1'; };
btn.onmouseout = function() { this.style.opacity = '0.7'; };
btn.onclick = function() {
navigator.clipboard.writeText(codeBlock.textContent).then(function() {
btn.textContent = 'Copied!';
setTimeout(function() { btn.textContent = 'Copy'; }, 1500);
});
};
codeBlock.parentElement.style.position = 'relative';
codeBlock.parentElement.appendChild(btn);
});
}
addCopyButtons();
// Re-run on dynamic content
var observer = new MutationObserver(addCopyButtons);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
[world-vercel] Use stream control frame for transparent reconnection by VaguelySerious · Pull Request #1790 · vercel/workflow · GitHub
Skip to content
[world-vercel] Use stream control frame for transparent reconnection - #1790
Merged
VaguelySerious merged 1 commit into
stablefrom 
peter/stream-reconnect-proper
Apr 17, 2026
Merged
[world-vercel] Use stream control frame for transparent reconnection#1790
VaguelySerious merged 1 commit into
stablefrom 
peter/stream-reconnect-proper
Conversation
@VaguelySerious
@VaguelySeriousVaguelySerious
commented
Apr 17, 2026

Copy link


Copy Markdown

Member
Summary
Re-applies #1742's reconnect feature on `stable` — without the `arrayBuffer()` rewrite that shipped in 4.2.3 (#1766) and broke incremental streaming on Vercel (content only arrived on stream close). #1766 was reverted on `stable` (#1788, released as 4.2.4).
Root cause of the 4.2.3 regression: `await response.arrayBuffer()` inside `readFromStream` drained the upstream before returning the `ReadableStream`, so `run.getReadable()` blocked until the server closed the stream. The returned stream just replayed the already-complete buffer.
This PR restores the original hold-back buffer approach from #1742 (still in use on `main`), adapted to `stable`'s `readFromStream` signature.
What's in it
  • `readFromStream` returns the `ReadableStream` promptly. A hold-back buffer inside the pull loop keeps only the last 13 bytes (the control-frame size), forwarding surplus bytes as they arrive.
  • On upstream close, the tail is parsed:

    • `done=true` → close cleanly
    • `done=false` → reconnect from `nextIndex`
    • no frame → forward tail as data (older-server backward compat)
  • Network errors propagate via `controller.error()` rather than a silent close.
  • Reconnections capped at 50 (~100 min of streaming at 2-min server timeout).
  • New regression test (`emits upstream bytes to the consumer before the stream closes`) asserts data flows before upstream EOF — any buffer-then-replay implementation fails it. This specifically catches the class of bug that shipped as 4.2.3.
Test plan
  •  `pnpm vitest run` — 67/67 world-vercel tests pass (28 streamer + 11 reconnect parser + 28 other)
  •  Reconnect + backward-compat + control-frame-split tests from [backport] [world-vercel] Use stream control frame for transparent reconnection #1766 still pass
  •  New regression test fails if `readFromStream` is rewritten to drain upstream first
  •  CI + auto-created workflow-server preview e2e
  •  Manual validation against flight-booking-app once a preview tarball is available
Notes
🤖 Generated with Claude Code
@changeset-bot
changeset-botBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

🦋 Changeset detected
Latest commit: ee258dc
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 18 packages
NameType
@workflow/world-vercelPatch
@workflow/cliPatch
@workflow/corePatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/buildersPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/vitestPatch
@workflow/web-sharedPatch
@workflow/aiPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
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
vercelBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

Contributor
The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
example-nextjs-workflow-turbopackReadyReadyPreview, CommentApr 17, 2026 0:30am
example-nextjs-workflow-webpackReadyReadyPreview, CommentApr 17, 2026 0:30am
example-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-astro-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-express-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-fastify-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-hono-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-nitro-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-nuxt-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-sveltekit-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-vite-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workflow-docsReadyReadyPreview, Comment, Open in v0Apr 17, 2026 0:30am
workflow-swc-playgroundReadyReadyPreview, CommentApr 17, 2026 0:30am
workflow-webReadyReadyPreview, CommentApr 17, 2026 0:30am
@github-actions
github-actionsBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

Contributor
🧪 E2E Test Results
❌ Some tests failed
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production900167968
✅ 💻 Local Development9700861056
✅ 📦 Local Production9700861056
✅ 🐘 Local Postgres9700861056
✅ 🪟 Windows880088
❌ 🌍 Community Worlds139830222
✅ 📋 Other246018264
Total4283843434710
❌ Failed Tests
▲ Vercel Production (1 failed)
sveltekit (1 failed):
  • error handling catchability FatalError can be caught and detected with FatalError.is()
🌍 Community Worlds (83 failed)
mongodb (11 failed):
  • readableStreamWorkflow | wrun_01KPCDEV0N8PQBX7HQXBRBVS64
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • webhookWorkflow | wrun_01KPCDFSP9DFEP41FPPJ2QYNP2
  • outputStreamWorkflow no startIndex (reads all chunks)
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions | wrun_01KPCDJRHYBET9BD520MHYJQG7
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
redis (7 failed):
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
turso (65 failed):
  • addTenWorkflow | wrun_01KPCDEB45HR5F1E88RVZK3JAE
  • addTenWorkflow | wrun_01KPCDEB45HR5F1E88RVZK3JAE
  • wellKnownAgentWorkflow (.well-known/agent) | wrun_01KPCDF08KKPWAQ7PVD2SKCJ78
  • should work with react rendering in step
  • promiseAllWorkflow | wrun_01KPCDEHJWP5ETJS19AG89D448
  • promiseRaceWorkflow | wrun_01KPCDEQ1GD6AXHKS1E2FZMER9
  • promiseAnyWorkflow | wrun_01KPCDES15ZVBHEQ419230WC22
  • importedStepOnlyWorkflow | wrun_01KPCDFDB96AA2827YQ3CD8AJD
  • readableStreamWorkflow | wrun_01KPCDEV0N8PQBX7HQXBRBVS64
  • hookWorkflow | wrun_01KPCDF5S02DMW2T56KA1W34G2
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • webhookWorkflow | wrun_01KPCDFSP9DFEP41FPPJ2QYNP2
  • sleepingWorkflow | wrun_01KPCDFZ2DGN157PQ61KNDPAA3
  • parallelSleepWorkflow | wrun_01KPCDGB2FNK5G4XVQJ7GSZM8R
  • nullByteWorkflow | wrun_01KPCDGE8FE22NA1YJ1WFF6VBY
  • workflowAndStepMetadataWorkflow | wrun_01KPCDGGH4DQKZJZX552S74HRQ
  • outputStreamWorkflow no startIndex (reads all chunks)
  • outputStreamWorkflow positive startIndex (skips first chunk)
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions | wrun_01KPCDJRHYBET9BD520MHYJQG7
  • fetchWorkflow | wrun_01KPCDK5ENNGNJHHMJC1RKW1NT
  • promiseRaceStressTestWorkflow | wrun_01KPCDK8P00SQXPD3707XAM87T
  • error handling error propagation workflow errors nested function calls preserve message and stack trace
  • error handling error propagation workflow errors cross-file imports preserve message and stack trace
  • error handling error propagation step errors basic step error preserves message and stack trace
  • error handling error propagation step errors cross-file step error preserves message and function names in stack
  • error handling retry behavior regular Error retries until success
  • error handling retry behavior FatalError fails immediately without retries
  • error handling retry behavior RetryableError respects custom retryAfter delay
  • error handling retry behavior maxRetries=0 disables retries
  • error handling catchability FatalError can be caught and detected with FatalError.is()
  • error handling not registered WorkflowNotRegisteredError fails the run when workflow does not exist
  • error handling not registered StepNotRegisteredError fails the step but workflow can catch it
  • error handling not registered StepNotRegisteredError fails the run when not caught in workflow
  • hookCleanupTestWorkflow - hook token reuse after workflow completion | wrun_01KPCDPM3JVFJVVH4SBXR892QP
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • hookDisposeTestWorkflow - hook token reuse after explicit disposal while workflow still running | wrun_01KPCDQWKW6XF2NYGHMAD769N5
  • stepFunctionPassingWorkflow - step function references can be passed as arguments (without closure vars) | wrun_01KPCDRGBQGBX4PP2J61VG8MFW
  • stepFunctionWithClosureWorkflow - step function with closure variables passed as argument | wrun_01KPCDRRSK12SDD1NC9AF698RX
  • closureVariableWorkflow - nested step functions with closure variables | wrun_01KPCDRZ9C5MXV1S38E1EYN5BG
  • spawnWorkflowFromStepWorkflow - spawning a child workflow using start() inside a step | wrun_01KPCDS1EG8NXNNB1VYFR7246C
  • health check (queue-based) - workflow and step endpoints respond to health check messages
  • pathsAliasWorkflow - TypeScript path aliases resolve correctly | wrun_01KPCDSGJ3KQKHEHFAQ13QZCPF
  • Calculator.calculate - static workflow method using static step methods from another class | wrun_01KPCDSNXEVWHWXH3928ZG4X1T
  • AllInOneService.processNumber - static workflow method using sibling static step methods | wrun_01KPCDSW86T6BVEAKWY7EGFDV4
  • ChainableService.processWithThis - static step methods using this to reference the class | wrun_01KPCDT2MD8TR3WGMNYS0FKRCH
  • thisSerializationWorkflow - step function invoked with .call() and .apply() | wrun_01KPCDT8BW51BYHXX7QR5QZJ7G
  • customSerializationWorkflow - custom class serialization with WORKFLOW_SERIALIZE/WORKFLOW_DESERIALIZE | wrun_01KPCDTH53VT0AX0SWMD03EWA9
  • instanceMethodStepWorkflow - instance methods with "use step" directive | wrun_01KPCDTQK0WGZ0T10CH13Q2GZK
  • crossContextSerdeWorkflow - classes defined in step code are deserializable in workflow context | wrun_01KPCDV322NQVNK879EXAZ7AW4
  • stepFunctionAsStartArgWorkflow - step function reference passed as start() argument | wrun_01KPCDVAMGFBSHY0F50B9XRY6S
  • cancelRun - cancelling a running workflow | wrun_01KPCDVH3SYGSQWMH1V24W8DQ3
  • cancelRun via CLI - cancelling a running workflow | wrun_01KPCDVTNWAD8331GPPK683AWF
  • pages router addTenWorkflow via pages router
  • pages router promiseAllWorkflow via pages router
  • pages router sleepingWorkflow via pages router
  • hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep | wrun_01KPCDW6J1SYGVPA6PZ0HVTMYF
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_01KPCDWTJ0A2RBCBADY4TB6PZ7
  • sleepWithSequentialStepsWorkflow - sequential steps work with concurrent sleep (control) | wrun_01KPCDX4F3VP5DQDC942H624E4
  • importMetaUrlWorkflow - import.meta.url is available in step bundles | wrun_01KPCDXAT2MWN03RQDQCCVYB16
  • metadataFromHelperWorkflow - getWorkflowMetadata/getStepMetadata work from module-level helper (#1577) | wrun_01KPCDXCWM794ANQS89DT0VN2S
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
Details by Category
❌ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro8107
✅ example8107
✅ express8107
✅ fastify8107
✅ hono8107
✅ nextjs-turbopack8602
✅ nextjs-webpack8602
✅ nitro8107
✅ nuxt8107
❌ sveltekit8017
✅ vite8107
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack8800
❌ 🌍 Community Worlds
AppPassedFailedSkipped
✅ mongodb-dev500
❌ mongodb58110
✅ redis-dev500
❌ redis6270
✅ turso-dev500
❌ turso4650
✅ 📋 Other
AppPassedFailedSkipped
✅ e2e-local-dev-nest-stable8206
✅ e2e-local-postgres-nest-stable8206
✅ e2e-local-prod-nest-stable8206
📋 View full workflow run
❌ Some E2E test jobs failed:
  • Vercel Prod: failure
  • Local Dev: success
  • Local Prod: success
  • Local Postgres: success
  • Windows: success
Check the workflow run for details.
@VaguelySerious@claude
[world-vercel] Use stream control frame for transparent reconnection,…
ee258dc
… with streaming hold-back buffer
Re-applies #1742's reconnect feature on stable, without the arrayBuffer()
rewrite that shipped in 4.2.3 (#1766) and defeated incremental streaming.
- readFromStream returns the ReadableStream promptly; a hold-back buffer
inside the pull loop holds only the last 13 bytes, forwarding surplus
bytes as they arrive. This preserves incremental delivery for AI UIs.
- On upstream close, the tail is parsed for a stream control frame
(done=true → close; done=false → reconnect from nextIndex; no frame →
forward tail as data for older servers).
- Network errors propagate via controller.error() rather than silent close.
- Caps reconnections at 50 (~100 min of streaming at 2-min server timeout).
Adds a regression test that asserts data reaches the consumer before
upstream close — any buffer-then-replay implementation fails it.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Signed-off-by: Peter Wielander <mittgfu@gmail.com>
@VaguelySerious
VaguelySeriousforce-pushed
the
peter/stream-reconnect-proper
branch
from
d76d170 to
ee258dcCompareApril 17, 2026 00:26
@VaguelySeriousVaguelySerious
changed the title
[world-vercel] Use stream control frame for transparent reconnection (proper streaming fix)[world-vercel] Use stream control frame for transparent reconnectionApr 17, 2026
@VaguelySerious
VaguelySerious
marked this pull request as ready for review
April 17, 2026 00:42
@VaguelySerious
VaguelySerious
requested a review
from a team
as a code ownerApril 17, 2026 00:42
@VaguelySerious
VaguelySerious
merged commit 5ef9ac2
into
stableApr 17, 2026

87 of 89 checks passed

@VaguelySerious
VaguelySerious
deleted the

peter/stream-reconnect-proper

branch
April 17, 2026 00:48
@ghostghost
mentioned this pull request
Apr 17, 2026
 Closed


This was referenced Apr 17, 2026
 Closed

 Merged

@TooTallNateTooTallNate
mentioned this pull request
Apr 25, 2026
 Merged

@VaguelySeriousVaguelySerious
mentioned this pull request
May 2, 2026
 Merged

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@TooTallNateTooTallNateTooTallNate approved these changes

Assignees


No one assigned


Labels


None yet


Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

2 participants

@VaguelySerious@TooTallNate

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Force GitHub README to respect dark mode
(function() {
var style = document.createElement('style');
style.textContent = '
.markdown-body {
color-scheme: dark light;
}
.markdown-body pre { background: #161b22 !important; }
.markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }
.markdown-body table th, .markdown-body table td { border-color: #30363d !important; }
.markdown-body img { background: #0d1117; }
.markdown-body blockquote { border-left-color: #8b949e; }
.markdown-body hr { border-color: #30363d; }
';
document.head.appendChild(style);
})();
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
[world-vercel] Use stream control frame for transparent reconnection by VaguelySerious · Pull Request #1790 · vercel/workflow · GitHub
Skip to content
[world-vercel] Use stream control frame for transparent reconnection - #1790
Merged
VaguelySerious merged 1 commit into
stablefrom 
peter/stream-reconnect-proper
Apr 17, 2026
Merged
[world-vercel] Use stream control frame for transparent reconnection#1790
VaguelySerious merged 1 commit into
stablefrom 
peter/stream-reconnect-proper
Conversation
@VaguelySerious
@VaguelySeriousVaguelySerious
commented
Apr 17, 2026

Copy link


Copy Markdown

Member
Summary
Re-applies #1742's reconnect feature on `stable` — without the `arrayBuffer()` rewrite that shipped in 4.2.3 (#1766) and broke incremental streaming on Vercel (content only arrived on stream close). #1766 was reverted on `stable` (#1788, released as 4.2.4).
Root cause of the 4.2.3 regression: `await response.arrayBuffer()` inside `readFromStream` drained the upstream before returning the `ReadableStream`, so `run.getReadable()` blocked until the server closed the stream. The returned stream just replayed the already-complete buffer.
This PR restores the original hold-back buffer approach from #1742 (still in use on `main`), adapted to `stable`'s `readFromStream` signature.
What's in it
  • `readFromStream` returns the `ReadableStream` promptly. A hold-back buffer inside the pull loop keeps only the last 13 bytes (the control-frame size), forwarding surplus bytes as they arrive.
  • On upstream close, the tail is parsed:

    • `done=true` → close cleanly
    • `done=false` → reconnect from `nextIndex`
    • no frame → forward tail as data (older-server backward compat)
  • Network errors propagate via `controller.error()` rather than a silent close.
  • Reconnections capped at 50 (~100 min of streaming at 2-min server timeout).
  • New regression test (`emits upstream bytes to the consumer before the stream closes`) asserts data flows before upstream EOF — any buffer-then-replay implementation fails it. This specifically catches the class of bug that shipped as 4.2.3.
Test plan
  •  `pnpm vitest run` — 67/67 world-vercel tests pass (28 streamer + 11 reconnect parser + 28 other)
  •  Reconnect + backward-compat + control-frame-split tests from [backport] [world-vercel] Use stream control frame for transparent reconnection #1766 still pass
  •  New regression test fails if `readFromStream` is rewritten to drain upstream first
  •  CI + auto-created workflow-server preview e2e
  •  Manual validation against flight-booking-app once a preview tarball is available
Notes
🤖 Generated with Claude Code
@changeset-bot
changeset-botBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

🦋 Changeset detected
Latest commit: ee258dc
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 18 packages
NameType
@workflow/world-vercelPatch
@workflow/cliPatch
@workflow/corePatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/buildersPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/vitestPatch
@workflow/web-sharedPatch
@workflow/aiPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
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
vercelBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

Contributor
The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
example-nextjs-workflow-turbopackReadyReadyPreview, CommentApr 17, 2026 0:30am
example-nextjs-workflow-webpackReadyReadyPreview, CommentApr 17, 2026 0:30am
example-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-astro-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-express-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-fastify-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-hono-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-nitro-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-nuxt-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-sveltekit-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-vite-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workflow-docsReadyReadyPreview, Comment, Open in v0Apr 17, 2026 0:30am
workflow-swc-playgroundReadyReadyPreview, CommentApr 17, 2026 0:30am
workflow-webReadyReadyPreview, CommentApr 17, 2026 0:30am
@github-actions
github-actionsBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

Contributor
🧪 E2E Test Results
❌ Some tests failed
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production900167968
✅ 💻 Local Development9700861056
✅ 📦 Local Production9700861056
✅ 🐘 Local Postgres9700861056
✅ 🪟 Windows880088
❌ 🌍 Community Worlds139830222
✅ 📋 Other246018264
Total4283843434710
❌ Failed Tests
▲ Vercel Production (1 failed)
sveltekit (1 failed):
  • error handling catchability FatalError can be caught and detected with FatalError.is()
🌍 Community Worlds (83 failed)
mongodb (11 failed):
  • readableStreamWorkflow | wrun_01KPCDEV0N8PQBX7HQXBRBVS64
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • webhookWorkflow | wrun_01KPCDFSP9DFEP41FPPJ2QYNP2
  • outputStreamWorkflow no startIndex (reads all chunks)
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions | wrun_01KPCDJRHYBET9BD520MHYJQG7
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
redis (7 failed):
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
turso (65 failed):
  • addTenWorkflow | wrun_01KPCDEB45HR5F1E88RVZK3JAE
  • addTenWorkflow | wrun_01KPCDEB45HR5F1E88RVZK3JAE
  • wellKnownAgentWorkflow (.well-known/agent) | wrun_01KPCDF08KKPWAQ7PVD2SKCJ78
  • should work with react rendering in step
  • promiseAllWorkflow | wrun_01KPCDEHJWP5ETJS19AG89D448
  • promiseRaceWorkflow | wrun_01KPCDEQ1GD6AXHKS1E2FZMER9
  • promiseAnyWorkflow | wrun_01KPCDES15ZVBHEQ419230WC22
  • importedStepOnlyWorkflow | wrun_01KPCDFDB96AA2827YQ3CD8AJD
  • readableStreamWorkflow | wrun_01KPCDEV0N8PQBX7HQXBRBVS64
  • hookWorkflow | wrun_01KPCDF5S02DMW2T56KA1W34G2
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • webhookWorkflow | wrun_01KPCDFSP9DFEP41FPPJ2QYNP2
  • sleepingWorkflow | wrun_01KPCDFZ2DGN157PQ61KNDPAA3
  • parallelSleepWorkflow | wrun_01KPCDGB2FNK5G4XVQJ7GSZM8R
  • nullByteWorkflow | wrun_01KPCDGE8FE22NA1YJ1WFF6VBY
  • workflowAndStepMetadataWorkflow | wrun_01KPCDGGH4DQKZJZX552S74HRQ
  • outputStreamWorkflow no startIndex (reads all chunks)
  • outputStreamWorkflow positive startIndex (skips first chunk)
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions | wrun_01KPCDJRHYBET9BD520MHYJQG7
  • fetchWorkflow | wrun_01KPCDK5ENNGNJHHMJC1RKW1NT
  • promiseRaceStressTestWorkflow | wrun_01KPCDK8P00SQXPD3707XAM87T
  • error handling error propagation workflow errors nested function calls preserve message and stack trace
  • error handling error propagation workflow errors cross-file imports preserve message and stack trace
  • error handling error propagation step errors basic step error preserves message and stack trace
  • error handling error propagation step errors cross-file step error preserves message and function names in stack
  • error handling retry behavior regular Error retries until success
  • error handling retry behavior FatalError fails immediately without retries
  • error handling retry behavior RetryableError respects custom retryAfter delay
  • error handling retry behavior maxRetries=0 disables retries
  • error handling catchability FatalError can be caught and detected with FatalError.is()
  • error handling not registered WorkflowNotRegisteredError fails the run when workflow does not exist
  • error handling not registered StepNotRegisteredError fails the step but workflow can catch it
  • error handling not registered StepNotRegisteredError fails the run when not caught in workflow
  • hookCleanupTestWorkflow - hook token reuse after workflow completion | wrun_01KPCDPM3JVFJVVH4SBXR892QP
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • hookDisposeTestWorkflow - hook token reuse after explicit disposal while workflow still running | wrun_01KPCDQWKW6XF2NYGHMAD769N5
  • stepFunctionPassingWorkflow - step function references can be passed as arguments (without closure vars) | wrun_01KPCDRGBQGBX4PP2J61VG8MFW
  • stepFunctionWithClosureWorkflow - step function with closure variables passed as argument | wrun_01KPCDRRSK12SDD1NC9AF698RX
  • closureVariableWorkflow - nested step functions with closure variables | wrun_01KPCDRZ9C5MXV1S38E1EYN5BG
  • spawnWorkflowFromStepWorkflow - spawning a child workflow using start() inside a step | wrun_01KPCDS1EG8NXNNB1VYFR7246C
  • health check (queue-based) - workflow and step endpoints respond to health check messages
  • pathsAliasWorkflow - TypeScript path aliases resolve correctly | wrun_01KPCDSGJ3KQKHEHFAQ13QZCPF
  • Calculator.calculate - static workflow method using static step methods from another class | wrun_01KPCDSNXEVWHWXH3928ZG4X1T
  • AllInOneService.processNumber - static workflow method using sibling static step methods | wrun_01KPCDSW86T6BVEAKWY7EGFDV4
  • ChainableService.processWithThis - static step methods using this to reference the class | wrun_01KPCDT2MD8TR3WGMNYS0FKRCH
  • thisSerializationWorkflow - step function invoked with .call() and .apply() | wrun_01KPCDT8BW51BYHXX7QR5QZJ7G
  • customSerializationWorkflow - custom class serialization with WORKFLOW_SERIALIZE/WORKFLOW_DESERIALIZE | wrun_01KPCDTH53VT0AX0SWMD03EWA9
  • instanceMethodStepWorkflow - instance methods with "use step" directive | wrun_01KPCDTQK0WGZ0T10CH13Q2GZK
  • crossContextSerdeWorkflow - classes defined in step code are deserializable in workflow context | wrun_01KPCDV322NQVNK879EXAZ7AW4
  • stepFunctionAsStartArgWorkflow - step function reference passed as start() argument | wrun_01KPCDVAMGFBSHY0F50B9XRY6S
  • cancelRun - cancelling a running workflow | wrun_01KPCDVH3SYGSQWMH1V24W8DQ3
  • cancelRun via CLI - cancelling a running workflow | wrun_01KPCDVTNWAD8331GPPK683AWF
  • pages router addTenWorkflow via pages router
  • pages router promiseAllWorkflow via pages router
  • pages router sleepingWorkflow via pages router
  • hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep | wrun_01KPCDW6J1SYGVPA6PZ0HVTMYF
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_01KPCDWTJ0A2RBCBADY4TB6PZ7
  • sleepWithSequentialStepsWorkflow - sequential steps work with concurrent sleep (control) | wrun_01KPCDX4F3VP5DQDC942H624E4
  • importMetaUrlWorkflow - import.meta.url is available in step bundles | wrun_01KPCDXAT2MWN03RQDQCCVYB16
  • metadataFromHelperWorkflow - getWorkflowMetadata/getStepMetadata work from module-level helper (#1577) | wrun_01KPCDXCWM794ANQS89DT0VN2S
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
Details by Category
❌ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro8107
✅ example8107
✅ express8107
✅ fastify8107
✅ hono8107
✅ nextjs-turbopack8602
✅ nextjs-webpack8602
✅ nitro8107
✅ nuxt8107
❌ sveltekit8017
✅ vite8107
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack8800
❌ 🌍 Community Worlds
AppPassedFailedSkipped
✅ mongodb-dev500
❌ mongodb58110
✅ redis-dev500
❌ redis6270
✅ turso-dev500
❌ turso4650
✅ 📋 Other
AppPassedFailedSkipped
✅ e2e-local-dev-nest-stable8206
✅ e2e-local-postgres-nest-stable8206
✅ e2e-local-prod-nest-stable8206
📋 View full workflow run
❌ Some E2E test jobs failed:
  • Vercel Prod: failure
  • Local Dev: success
  • Local Prod: success
  • Local Postgres: success
  • Windows: success
Check the workflow run for details.
@VaguelySerious@claude
[world-vercel] Use stream control frame for transparent reconnection,…
ee258dc
… with streaming hold-back buffer
Re-applies #1742's reconnect feature on stable, without the arrayBuffer()
rewrite that shipped in 4.2.3 (#1766) and defeated incremental streaming.
- readFromStream returns the ReadableStream promptly; a hold-back buffer
inside the pull loop holds only the last 13 bytes, forwarding surplus
bytes as they arrive. This preserves incremental delivery for AI UIs.
- On upstream close, the tail is parsed for a stream control frame
(done=true → close; done=false → reconnect from nextIndex; no frame →
forward tail as data for older servers).
- Network errors propagate via controller.error() rather than silent close.
- Caps reconnections at 50 (~100 min of streaming at 2-min server timeout).
Adds a regression test that asserts data reaches the consumer before
upstream close — any buffer-then-replay implementation fails it.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Signed-off-by: Peter Wielander <mittgfu@gmail.com>
@VaguelySerious
VaguelySeriousforce-pushed
the
peter/stream-reconnect-proper
branch
from
d76d170 to
ee258dcCompareApril 17, 2026 00:26
@VaguelySeriousVaguelySerious
changed the title
[world-vercel] Use stream control frame for transparent reconnection (proper streaming fix)[world-vercel] Use stream control frame for transparent reconnectionApr 17, 2026
@VaguelySerious
VaguelySerious
marked this pull request as ready for review
April 17, 2026 00:42
@VaguelySerious
VaguelySerious
requested a review
from a team
as a code ownerApril 17, 2026 00:42
@VaguelySerious
VaguelySerious
merged commit 5ef9ac2
into
stableApr 17, 2026

87 of 89 checks passed

@VaguelySerious
VaguelySerious
deleted the

peter/stream-reconnect-proper

branch
April 17, 2026 00:48
@ghostghost
mentioned this pull request
Apr 17, 2026
 Closed


This was referenced Apr 17, 2026
 Closed

 Merged

@TooTallNateTooTallNate
mentioned this pull request
Apr 25, 2026
 Merged

@VaguelySeriousVaguelySerious
mentioned this pull request
May 2, 2026
 Merged

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@TooTallNateTooTallNateTooTallNate approved these changes

Assignees


No one assigned


Labels


None yet


Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

2 participants

@VaguelySerious@TooTallNate

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Highlight search terms from Google/DuckDuckGo/Bing referrer
(function() {
var ref = document.referrer;
var terms = [];
if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {
var url = new URL(ref);
var q = url.searchParams.get('q') || url.searchParams.get('p');
if (q) {
terms = q.split(/\s+/).filter(function(t) { return t.length > 2; });
}
}
if (terms.length === 0) return;
var style = document.createElement('style');
style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';
document.head.appendChild(style);
function highlight(node) {
if (node.nodeType === 3) { // text node
var text = node.textContent;
var found = false;
terms.forEach(function(term) {
var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\]\\]/g, '\\') + ')', 'gi');
if (regex.test(text)) {
found = true;
var frag = document.createDocumentFragment();
var parts = text.split(regex);
parts.forEach(function(part, i) {
if (i % 2 === 0) {
frag.appendChild(document.createTextNode(part));
} else {
var span = document.createElement('span');
span.className = 'userscript-highlight';
span.textContent = part;
frag.appendChild(span);
}
});
node.parentNode.replaceChild(frag, node);
}
});
} else if (node.nodeType === 1 && node.childNodes) { // element
var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];
if (!skipTags.includes(node.tagName)) {
Array.from(node.childNodes).forEach(highlight);
}
}
}
highlight(document.body);
// Re-highlight on dynamic content
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1 || node.nodeType === 3) highlight(node);
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
[world-vercel] Use stream control frame for transparent reconnection by VaguelySerious · Pull Request #1790 · vercel/workflow · GitHub
Skip to content
[world-vercel] Use stream control frame for transparent reconnection - #1790
Merged
VaguelySerious merged 1 commit into
stablefrom 
peter/stream-reconnect-proper
Apr 17, 2026
Merged
[world-vercel] Use stream control frame for transparent reconnection#1790
VaguelySerious merged 1 commit into
stablefrom 
peter/stream-reconnect-proper
Conversation
@VaguelySerious
@VaguelySeriousVaguelySerious
commented
Apr 17, 2026

Copy link


Copy Markdown

Member
Summary
Re-applies #1742's reconnect feature on `stable` — without the `arrayBuffer()` rewrite that shipped in 4.2.3 (#1766) and broke incremental streaming on Vercel (content only arrived on stream close). #1766 was reverted on `stable` (#1788, released as 4.2.4).
Root cause of the 4.2.3 regression: `await response.arrayBuffer()` inside `readFromStream` drained the upstream before returning the `ReadableStream`, so `run.getReadable()` blocked until the server closed the stream. The returned stream just replayed the already-complete buffer.
This PR restores the original hold-back buffer approach from #1742 (still in use on `main`), adapted to `stable`'s `readFromStream` signature.
What's in it
  • `readFromStream` returns the `ReadableStream` promptly. A hold-back buffer inside the pull loop keeps only the last 13 bytes (the control-frame size), forwarding surplus bytes as they arrive.
  • On upstream close, the tail is parsed:

    • `done=true` → close cleanly
    • `done=false` → reconnect from `nextIndex`
    • no frame → forward tail as data (older-server backward compat)
  • Network errors propagate via `controller.error()` rather than a silent close.
  • Reconnections capped at 50 (~100 min of streaming at 2-min server timeout).
  • New regression test (`emits upstream bytes to the consumer before the stream closes`) asserts data flows before upstream EOF — any buffer-then-replay implementation fails it. This specifically catches the class of bug that shipped as 4.2.3.
Test plan
  •  `pnpm vitest run` — 67/67 world-vercel tests pass (28 streamer + 11 reconnect parser + 28 other)
  •  Reconnect + backward-compat + control-frame-split tests from [backport] [world-vercel] Use stream control frame for transparent reconnection #1766 still pass
  •  New regression test fails if `readFromStream` is rewritten to drain upstream first
  •  CI + auto-created workflow-server preview e2e
  •  Manual validation against flight-booking-app once a preview tarball is available
Notes
🤖 Generated with Claude Code
@changeset-bot
changeset-botBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

🦋 Changeset detected
Latest commit: ee258dc
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 18 packages
NameType
@workflow/world-vercelPatch
@workflow/cliPatch
@workflow/corePatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/buildersPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/vitestPatch
@workflow/web-sharedPatch
@workflow/aiPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
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
vercelBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

Contributor
The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
example-nextjs-workflow-turbopackReadyReadyPreview, CommentApr 17, 2026 0:30am
example-nextjs-workflow-webpackReadyReadyPreview, CommentApr 17, 2026 0:30am
example-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-astro-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-express-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-fastify-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-hono-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-nitro-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-nuxt-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-sveltekit-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-vite-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workflow-docsReadyReadyPreview, Comment, Open in v0Apr 17, 2026 0:30am
workflow-swc-playgroundReadyReadyPreview, CommentApr 17, 2026 0:30am
workflow-webReadyReadyPreview, CommentApr 17, 2026 0:30am
@github-actions
github-actionsBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

Contributor
🧪 E2E Test Results
❌ Some tests failed
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production900167968
✅ 💻 Local Development9700861056
✅ 📦 Local Production9700861056
✅ 🐘 Local Postgres9700861056
✅ 🪟 Windows880088
❌ 🌍 Community Worlds139830222
✅ 📋 Other246018264
Total4283843434710
❌ Failed Tests
▲ Vercel Production (1 failed)
sveltekit (1 failed):
  • error handling catchability FatalError can be caught and detected with FatalError.is()
🌍 Community Worlds (83 failed)
mongodb (11 failed):
  • readableStreamWorkflow | wrun_01KPCDEV0N8PQBX7HQXBRBVS64
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • webhookWorkflow | wrun_01KPCDFSP9DFEP41FPPJ2QYNP2
  • outputStreamWorkflow no startIndex (reads all chunks)
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions | wrun_01KPCDJRHYBET9BD520MHYJQG7
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
redis (7 failed):
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
turso (65 failed):
  • addTenWorkflow | wrun_01KPCDEB45HR5F1E88RVZK3JAE
  • addTenWorkflow | wrun_01KPCDEB45HR5F1E88RVZK3JAE
  • wellKnownAgentWorkflow (.well-known/agent) | wrun_01KPCDF08KKPWAQ7PVD2SKCJ78
  • should work with react rendering in step
  • promiseAllWorkflow | wrun_01KPCDEHJWP5ETJS19AG89D448
  • promiseRaceWorkflow | wrun_01KPCDEQ1GD6AXHKS1E2FZMER9
  • promiseAnyWorkflow | wrun_01KPCDES15ZVBHEQ419230WC22
  • importedStepOnlyWorkflow | wrun_01KPCDFDB96AA2827YQ3CD8AJD
  • readableStreamWorkflow | wrun_01KPCDEV0N8PQBX7HQXBRBVS64
  • hookWorkflow | wrun_01KPCDF5S02DMW2T56KA1W34G2
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • webhookWorkflow | wrun_01KPCDFSP9DFEP41FPPJ2QYNP2
  • sleepingWorkflow | wrun_01KPCDFZ2DGN157PQ61KNDPAA3
  • parallelSleepWorkflow | wrun_01KPCDGB2FNK5G4XVQJ7GSZM8R
  • nullByteWorkflow | wrun_01KPCDGE8FE22NA1YJ1WFF6VBY
  • workflowAndStepMetadataWorkflow | wrun_01KPCDGGH4DQKZJZX552S74HRQ
  • outputStreamWorkflow no startIndex (reads all chunks)
  • outputStreamWorkflow positive startIndex (skips first chunk)
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions | wrun_01KPCDJRHYBET9BD520MHYJQG7
  • fetchWorkflow | wrun_01KPCDK5ENNGNJHHMJC1RKW1NT
  • promiseRaceStressTestWorkflow | wrun_01KPCDK8P00SQXPD3707XAM87T
  • error handling error propagation workflow errors nested function calls preserve message and stack trace
  • error handling error propagation workflow errors cross-file imports preserve message and stack trace
  • error handling error propagation step errors basic step error preserves message and stack trace
  • error handling error propagation step errors cross-file step error preserves message and function names in stack
  • error handling retry behavior regular Error retries until success
  • error handling retry behavior FatalError fails immediately without retries
  • error handling retry behavior RetryableError respects custom retryAfter delay
  • error handling retry behavior maxRetries=0 disables retries
  • error handling catchability FatalError can be caught and detected with FatalError.is()
  • error handling not registered WorkflowNotRegisteredError fails the run when workflow does not exist
  • error handling not registered StepNotRegisteredError fails the step but workflow can catch it
  • error handling not registered StepNotRegisteredError fails the run when not caught in workflow
  • hookCleanupTestWorkflow - hook token reuse after workflow completion | wrun_01KPCDPM3JVFJVVH4SBXR892QP
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • hookDisposeTestWorkflow - hook token reuse after explicit disposal while workflow still running | wrun_01KPCDQWKW6XF2NYGHMAD769N5
  • stepFunctionPassingWorkflow - step function references can be passed as arguments (without closure vars) | wrun_01KPCDRGBQGBX4PP2J61VG8MFW
  • stepFunctionWithClosureWorkflow - step function with closure variables passed as argument | wrun_01KPCDRRSK12SDD1NC9AF698RX
  • closureVariableWorkflow - nested step functions with closure variables | wrun_01KPCDRZ9C5MXV1S38E1EYN5BG
  • spawnWorkflowFromStepWorkflow - spawning a child workflow using start() inside a step | wrun_01KPCDS1EG8NXNNB1VYFR7246C
  • health check (queue-based) - workflow and step endpoints respond to health check messages
  • pathsAliasWorkflow - TypeScript path aliases resolve correctly | wrun_01KPCDSGJ3KQKHEHFAQ13QZCPF
  • Calculator.calculate - static workflow method using static step methods from another class | wrun_01KPCDSNXEVWHWXH3928ZG4X1T
  • AllInOneService.processNumber - static workflow method using sibling static step methods | wrun_01KPCDSW86T6BVEAKWY7EGFDV4
  • ChainableService.processWithThis - static step methods using this to reference the class | wrun_01KPCDT2MD8TR3WGMNYS0FKRCH
  • thisSerializationWorkflow - step function invoked with .call() and .apply() | wrun_01KPCDT8BW51BYHXX7QR5QZJ7G
  • customSerializationWorkflow - custom class serialization with WORKFLOW_SERIALIZE/WORKFLOW_DESERIALIZE | wrun_01KPCDTH53VT0AX0SWMD03EWA9
  • instanceMethodStepWorkflow - instance methods with "use step" directive | wrun_01KPCDTQK0WGZ0T10CH13Q2GZK
  • crossContextSerdeWorkflow - classes defined in step code are deserializable in workflow context | wrun_01KPCDV322NQVNK879EXAZ7AW4
  • stepFunctionAsStartArgWorkflow - step function reference passed as start() argument | wrun_01KPCDVAMGFBSHY0F50B9XRY6S
  • cancelRun - cancelling a running workflow | wrun_01KPCDVH3SYGSQWMH1V24W8DQ3
  • cancelRun via CLI - cancelling a running workflow | wrun_01KPCDVTNWAD8331GPPK683AWF
  • pages router addTenWorkflow via pages router
  • pages router promiseAllWorkflow via pages router
  • pages router sleepingWorkflow via pages router
  • hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep | wrun_01KPCDW6J1SYGVPA6PZ0HVTMYF
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_01KPCDWTJ0A2RBCBADY4TB6PZ7
  • sleepWithSequentialStepsWorkflow - sequential steps work with concurrent sleep (control) | wrun_01KPCDX4F3VP5DQDC942H624E4
  • importMetaUrlWorkflow - import.meta.url is available in step bundles | wrun_01KPCDXAT2MWN03RQDQCCVYB16
  • metadataFromHelperWorkflow - getWorkflowMetadata/getStepMetadata work from module-level helper (#1577) | wrun_01KPCDXCWM794ANQS89DT0VN2S
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
Details by Category
❌ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro8107
✅ example8107
✅ express8107
✅ fastify8107
✅ hono8107
✅ nextjs-turbopack8602
✅ nextjs-webpack8602
✅ nitro8107
✅ nuxt8107
❌ sveltekit8017
✅ vite8107
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack8800
❌ 🌍 Community Worlds
AppPassedFailedSkipped
✅ mongodb-dev500
❌ mongodb58110
✅ redis-dev500
❌ redis6270
✅ turso-dev500
❌ turso4650
✅ 📋 Other
AppPassedFailedSkipped
✅ e2e-local-dev-nest-stable8206
✅ e2e-local-postgres-nest-stable8206
✅ e2e-local-prod-nest-stable8206
📋 View full workflow run
❌ Some E2E test jobs failed:
  • Vercel Prod: failure
  • Local Dev: success
  • Local Prod: success
  • Local Postgres: success
  • Windows: success
Check the workflow run for details.
@VaguelySerious@claude
[world-vercel] Use stream control frame for transparent reconnection,…
ee258dc
… with streaming hold-back buffer
Re-applies #1742's reconnect feature on stable, without the arrayBuffer()
rewrite that shipped in 4.2.3 (#1766) and defeated incremental streaming.
- readFromStream returns the ReadableStream promptly; a hold-back buffer
inside the pull loop holds only the last 13 bytes, forwarding surplus
bytes as they arrive. This preserves incremental delivery for AI UIs.
- On upstream close, the tail is parsed for a stream control frame
(done=true → close; done=false → reconnect from nextIndex; no frame →
forward tail as data for older servers).
- Network errors propagate via controller.error() rather than silent close.
- Caps reconnections at 50 (~100 min of streaming at 2-min server timeout).
Adds a regression test that asserts data reaches the consumer before
upstream close — any buffer-then-replay implementation fails it.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Signed-off-by: Peter Wielander <mittgfu@gmail.com>
@VaguelySerious
VaguelySeriousforce-pushed
the
peter/stream-reconnect-proper
branch
from
d76d170 to
ee258dcCompareApril 17, 2026 00:26
@VaguelySeriousVaguelySerious
changed the title
[world-vercel] Use stream control frame for transparent reconnection (proper streaming fix)[world-vercel] Use stream control frame for transparent reconnectionApr 17, 2026
@VaguelySerious
VaguelySerious
marked this pull request as ready for review
April 17, 2026 00:42
@VaguelySerious
VaguelySerious
requested a review
from a team
as a code ownerApril 17, 2026 00:42
@VaguelySerious
VaguelySerious
merged commit 5ef9ac2
into
stableApr 17, 2026

87 of 89 checks passed

@VaguelySerious
VaguelySerious
deleted the

peter/stream-reconnect-proper

branch
April 17, 2026 00:48
@ghostghost
mentioned this pull request
Apr 17, 2026
 Closed


This was referenced Apr 17, 2026
 Closed

 Merged

@TooTallNateTooTallNate
mentioned this pull request
Apr 25, 2026
 Merged

@VaguelySeriousVaguelySerious
mentioned this pull request
May 2, 2026
 Merged

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@TooTallNateTooTallNateTooTallNate approved these changes

Assignees


No one assigned


Labels


None yet


Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

2 participants

@VaguelySerious@TooTallNate

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
(function() {
var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',
'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
'ref', 'ref_src', 'source', 'medium', 'campaign'];
function cleanUrl(url) {
try {
var u = new URL(url, window.location.origin);
var changed = false;
trackingParams.forEach(function(p) {
if (u.searchParams.has(p)) {
u.searchParams.delete(p);
changed = true;
}
});
return changed ? u.toString() : url;
} catch (e) {
return url;
}
}
function cleanLinks() {
document.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
cleanLinks();
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1) {
if (node.tagName === 'A') cleanLinks();
node.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
[world-vercel] Use stream control frame for transparent reconnection by VaguelySerious · Pull Request #1790 · vercel/workflow · GitHub
Skip to content
[world-vercel] Use stream control frame for transparent reconnection - #1790
Merged
VaguelySerious merged 1 commit into
stablefrom 
peter/stream-reconnect-proper
Apr 17, 2026
Merged
[world-vercel] Use stream control frame for transparent reconnection#1790
VaguelySerious merged 1 commit into
stablefrom 
peter/stream-reconnect-proper
Conversation
@VaguelySerious
@VaguelySeriousVaguelySerious
commented
Apr 17, 2026

Copy link


Copy Markdown

Member
Summary
Re-applies #1742's reconnect feature on `stable` — without the `arrayBuffer()` rewrite that shipped in 4.2.3 (#1766) and broke incremental streaming on Vercel (content only arrived on stream close). #1766 was reverted on `stable` (#1788, released as 4.2.4).
Root cause of the 4.2.3 regression: `await response.arrayBuffer()` inside `readFromStream` drained the upstream before returning the `ReadableStream`, so `run.getReadable()` blocked until the server closed the stream. The returned stream just replayed the already-complete buffer.
This PR restores the original hold-back buffer approach from #1742 (still in use on `main`), adapted to `stable`'s `readFromStream` signature.
What's in it
  • `readFromStream` returns the `ReadableStream` promptly. A hold-back buffer inside the pull loop keeps only the last 13 bytes (the control-frame size), forwarding surplus bytes as they arrive.
  • On upstream close, the tail is parsed:

    • `done=true` → close cleanly
    • `done=false` → reconnect from `nextIndex`
    • no frame → forward tail as data (older-server backward compat)
  • Network errors propagate via `controller.error()` rather than a silent close.
  • Reconnections capped at 50 (~100 min of streaming at 2-min server timeout).
  • New regression test (`emits upstream bytes to the consumer before the stream closes`) asserts data flows before upstream EOF — any buffer-then-replay implementation fails it. This specifically catches the class of bug that shipped as 4.2.3.
Test plan
  •  `pnpm vitest run` — 67/67 world-vercel tests pass (28 streamer + 11 reconnect parser + 28 other)
  •  Reconnect + backward-compat + control-frame-split tests from [backport] [world-vercel] Use stream control frame for transparent reconnection #1766 still pass
  •  New regression test fails if `readFromStream` is rewritten to drain upstream first
  •  CI + auto-created workflow-server preview e2e
  •  Manual validation against flight-booking-app once a preview tarball is available
Notes
🤖 Generated with Claude Code
@changeset-bot
changeset-botBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

🦋 Changeset detected
Latest commit: ee258dc
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 18 packages
NameType
@workflow/world-vercelPatch
@workflow/cliPatch
@workflow/corePatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/buildersPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/vitestPatch
@workflow/web-sharedPatch
@workflow/aiPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
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
vercelBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

Contributor
The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
example-nextjs-workflow-turbopackReadyReadyPreview, CommentApr 17, 2026 0:30am
example-nextjs-workflow-webpackReadyReadyPreview, CommentApr 17, 2026 0:30am
example-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-astro-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-express-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-fastify-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-hono-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-nitro-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-nuxt-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-sveltekit-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-vite-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workflow-docsReadyReadyPreview, Comment, Open in v0Apr 17, 2026 0:30am
workflow-swc-playgroundReadyReadyPreview, CommentApr 17, 2026 0:30am
workflow-webReadyReadyPreview, CommentApr 17, 2026 0:30am
@github-actions
github-actionsBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

Contributor
🧪 E2E Test Results
❌ Some tests failed
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production900167968
✅ 💻 Local Development9700861056
✅ 📦 Local Production9700861056
✅ 🐘 Local Postgres9700861056
✅ 🪟 Windows880088
❌ 🌍 Community Worlds139830222
✅ 📋 Other246018264
Total4283843434710
❌ Failed Tests
▲ Vercel Production (1 failed)
sveltekit (1 failed):
  • error handling catchability FatalError can be caught and detected with FatalError.is()
🌍 Community Worlds (83 failed)
mongodb (11 failed):
  • readableStreamWorkflow | wrun_01KPCDEV0N8PQBX7HQXBRBVS64
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • webhookWorkflow | wrun_01KPCDFSP9DFEP41FPPJ2QYNP2
  • outputStreamWorkflow no startIndex (reads all chunks)
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions | wrun_01KPCDJRHYBET9BD520MHYJQG7
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
redis (7 failed):
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
turso (65 failed):
  • addTenWorkflow | wrun_01KPCDEB45HR5F1E88RVZK3JAE
  • addTenWorkflow | wrun_01KPCDEB45HR5F1E88RVZK3JAE
  • wellKnownAgentWorkflow (.well-known/agent) | wrun_01KPCDF08KKPWAQ7PVD2SKCJ78
  • should work with react rendering in step
  • promiseAllWorkflow | wrun_01KPCDEHJWP5ETJS19AG89D448
  • promiseRaceWorkflow | wrun_01KPCDEQ1GD6AXHKS1E2FZMER9
  • promiseAnyWorkflow | wrun_01KPCDES15ZVBHEQ419230WC22
  • importedStepOnlyWorkflow | wrun_01KPCDFDB96AA2827YQ3CD8AJD
  • readableStreamWorkflow | wrun_01KPCDEV0N8PQBX7HQXBRBVS64
  • hookWorkflow | wrun_01KPCDF5S02DMW2T56KA1W34G2
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • webhookWorkflow | wrun_01KPCDFSP9DFEP41FPPJ2QYNP2
  • sleepingWorkflow | wrun_01KPCDFZ2DGN157PQ61KNDPAA3
  • parallelSleepWorkflow | wrun_01KPCDGB2FNK5G4XVQJ7GSZM8R
  • nullByteWorkflow | wrun_01KPCDGE8FE22NA1YJ1WFF6VBY
  • workflowAndStepMetadataWorkflow | wrun_01KPCDGGH4DQKZJZX552S74HRQ
  • outputStreamWorkflow no startIndex (reads all chunks)
  • outputStreamWorkflow positive startIndex (skips first chunk)
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions | wrun_01KPCDJRHYBET9BD520MHYJQG7
  • fetchWorkflow | wrun_01KPCDK5ENNGNJHHMJC1RKW1NT
  • promiseRaceStressTestWorkflow | wrun_01KPCDK8P00SQXPD3707XAM87T
  • error handling error propagation workflow errors nested function calls preserve message and stack trace
  • error handling error propagation workflow errors cross-file imports preserve message and stack trace
  • error handling error propagation step errors basic step error preserves message and stack trace
  • error handling error propagation step errors cross-file step error preserves message and function names in stack
  • error handling retry behavior regular Error retries until success
  • error handling retry behavior FatalError fails immediately without retries
  • error handling retry behavior RetryableError respects custom retryAfter delay
  • error handling retry behavior maxRetries=0 disables retries
  • error handling catchability FatalError can be caught and detected with FatalError.is()
  • error handling not registered WorkflowNotRegisteredError fails the run when workflow does not exist
  • error handling not registered StepNotRegisteredError fails the step but workflow can catch it
  • error handling not registered StepNotRegisteredError fails the run when not caught in workflow
  • hookCleanupTestWorkflow - hook token reuse after workflow completion | wrun_01KPCDPM3JVFJVVH4SBXR892QP
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • hookDisposeTestWorkflow - hook token reuse after explicit disposal while workflow still running | wrun_01KPCDQWKW6XF2NYGHMAD769N5
  • stepFunctionPassingWorkflow - step function references can be passed as arguments (without closure vars) | wrun_01KPCDRGBQGBX4PP2J61VG8MFW
  • stepFunctionWithClosureWorkflow - step function with closure variables passed as argument | wrun_01KPCDRRSK12SDD1NC9AF698RX
  • closureVariableWorkflow - nested step functions with closure variables | wrun_01KPCDRZ9C5MXV1S38E1EYN5BG
  • spawnWorkflowFromStepWorkflow - spawning a child workflow using start() inside a step | wrun_01KPCDS1EG8NXNNB1VYFR7246C
  • health check (queue-based) - workflow and step endpoints respond to health check messages
  • pathsAliasWorkflow - TypeScript path aliases resolve correctly | wrun_01KPCDSGJ3KQKHEHFAQ13QZCPF
  • Calculator.calculate - static workflow method using static step methods from another class | wrun_01KPCDSNXEVWHWXH3928ZG4X1T
  • AllInOneService.processNumber - static workflow method using sibling static step methods | wrun_01KPCDSW86T6BVEAKWY7EGFDV4
  • ChainableService.processWithThis - static step methods using this to reference the class | wrun_01KPCDT2MD8TR3WGMNYS0FKRCH
  • thisSerializationWorkflow - step function invoked with .call() and .apply() | wrun_01KPCDT8BW51BYHXX7QR5QZJ7G
  • customSerializationWorkflow - custom class serialization with WORKFLOW_SERIALIZE/WORKFLOW_DESERIALIZE | wrun_01KPCDTH53VT0AX0SWMD03EWA9
  • instanceMethodStepWorkflow - instance methods with "use step" directive | wrun_01KPCDTQK0WGZ0T10CH13Q2GZK
  • crossContextSerdeWorkflow - classes defined in step code are deserializable in workflow context | wrun_01KPCDV322NQVNK879EXAZ7AW4
  • stepFunctionAsStartArgWorkflow - step function reference passed as start() argument | wrun_01KPCDVAMGFBSHY0F50B9XRY6S
  • cancelRun - cancelling a running workflow | wrun_01KPCDVH3SYGSQWMH1V24W8DQ3
  • cancelRun via CLI - cancelling a running workflow | wrun_01KPCDVTNWAD8331GPPK683AWF
  • pages router addTenWorkflow via pages router
  • pages router promiseAllWorkflow via pages router
  • pages router sleepingWorkflow via pages router
  • hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep | wrun_01KPCDW6J1SYGVPA6PZ0HVTMYF
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_01KPCDWTJ0A2RBCBADY4TB6PZ7
  • sleepWithSequentialStepsWorkflow - sequential steps work with concurrent sleep (control) | wrun_01KPCDX4F3VP5DQDC942H624E4
  • importMetaUrlWorkflow - import.meta.url is available in step bundles | wrun_01KPCDXAT2MWN03RQDQCCVYB16
  • metadataFromHelperWorkflow - getWorkflowMetadata/getStepMetadata work from module-level helper (#1577) | wrun_01KPCDXCWM794ANQS89DT0VN2S
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
Details by Category
❌ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro8107
✅ example8107
✅ express8107
✅ fastify8107
✅ hono8107
✅ nextjs-turbopack8602
✅ nextjs-webpack8602
✅ nitro8107
✅ nuxt8107
❌ sveltekit8017
✅ vite8107
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack8800
❌ 🌍 Community Worlds
AppPassedFailedSkipped
✅ mongodb-dev500
❌ mongodb58110
✅ redis-dev500
❌ redis6270
✅ turso-dev500
❌ turso4650
✅ 📋 Other
AppPassedFailedSkipped
✅ e2e-local-dev-nest-stable8206
✅ e2e-local-postgres-nest-stable8206
✅ e2e-local-prod-nest-stable8206
📋 View full workflow run
❌ Some E2E test jobs failed:
  • Vercel Prod: failure
  • Local Dev: success
  • Local Prod: success
  • Local Postgres: success
  • Windows: success
Check the workflow run for details.
@VaguelySerious@claude
[world-vercel] Use stream control frame for transparent reconnection,…
ee258dc
… with streaming hold-back buffer
Re-applies #1742's reconnect feature on stable, without the arrayBuffer()
rewrite that shipped in 4.2.3 (#1766) and defeated incremental streaming.
- readFromStream returns the ReadableStream promptly; a hold-back buffer
inside the pull loop holds only the last 13 bytes, forwarding surplus
bytes as they arrive. This preserves incremental delivery for AI UIs.
- On upstream close, the tail is parsed for a stream control frame
(done=true → close; done=false → reconnect from nextIndex; no frame →
forward tail as data for older servers).
- Network errors propagate via controller.error() rather than silent close.
- Caps reconnections at 50 (~100 min of streaming at 2-min server timeout).
Adds a regression test that asserts data reaches the consumer before
upstream close — any buffer-then-replay implementation fails it.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Signed-off-by: Peter Wielander <mittgfu@gmail.com>
@VaguelySerious
VaguelySeriousforce-pushed
the
peter/stream-reconnect-proper
branch
from
d76d170 to
ee258dcCompareApril 17, 2026 00:26
@VaguelySeriousVaguelySerious
changed the title
[world-vercel] Use stream control frame for transparent reconnection (proper streaming fix)[world-vercel] Use stream control frame for transparent reconnectionApr 17, 2026
@VaguelySerious
VaguelySerious
marked this pull request as ready for review
April 17, 2026 00:42
@VaguelySerious
VaguelySerious
requested a review
from a team
as a code ownerApril 17, 2026 00:42
@VaguelySerious
VaguelySerious
merged commit 5ef9ac2
into
stableApr 17, 2026

87 of 89 checks passed

@VaguelySerious
VaguelySerious
deleted the

peter/stream-reconnect-proper

branch
April 17, 2026 00:48
@ghostghost
mentioned this pull request
Apr 17, 2026
 Closed


This was referenced Apr 17, 2026
 Closed

 Merged

@TooTallNateTooTallNate
mentioned this pull request
Apr 25, 2026
 Merged

@VaguelySeriousVaguelySerious
mentioned this pull request
May 2, 2026
 Merged

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@TooTallNateTooTallNateTooTallNate approved these changes

Assignees


No one assigned


Labels


None yet


Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

2 participants

@VaguelySerious@TooTallNate

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
(function() {
function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
if (btn && !btn.classList.contains('activated')) {
btn.click();
}
}
// Try immediately
tryTheater();
// Try after navigation (SPA)
var lastUrl = location.href;
setInterval(function() {
if (location.href !== lastUrl) {
lastUrl = location.href;
setTimeout(tryTheater, 500);
}
}, 1000);
// Also try on player load
var observer = new MutationObserver(tryTheater);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
[world-vercel] Use stream control frame for transparent reconnection by VaguelySerious · Pull Request #1790 · vercel/workflow · GitHub
Skip to content
[world-vercel] Use stream control frame for transparent reconnection - #1790
Merged
VaguelySerious merged 1 commit into
stablefrom 
peter/stream-reconnect-proper
Apr 17, 2026
Merged
[world-vercel] Use stream control frame for transparent reconnection#1790
VaguelySerious merged 1 commit into
stablefrom 
peter/stream-reconnect-proper
Conversation
@VaguelySerious
@VaguelySeriousVaguelySerious
commented
Apr 17, 2026

Copy link


Copy Markdown

Member
Summary
Re-applies #1742's reconnect feature on `stable` — without the `arrayBuffer()` rewrite that shipped in 4.2.3 (#1766) and broke incremental streaming on Vercel (content only arrived on stream close). #1766 was reverted on `stable` (#1788, released as 4.2.4).
Root cause of the 4.2.3 regression: `await response.arrayBuffer()` inside `readFromStream` drained the upstream before returning the `ReadableStream`, so `run.getReadable()` blocked until the server closed the stream. The returned stream just replayed the already-complete buffer.
This PR restores the original hold-back buffer approach from #1742 (still in use on `main`), adapted to `stable`'s `readFromStream` signature.
What's in it
  • `readFromStream` returns the `ReadableStream` promptly. A hold-back buffer inside the pull loop keeps only the last 13 bytes (the control-frame size), forwarding surplus bytes as they arrive.
  • On upstream close, the tail is parsed:

    • `done=true` → close cleanly
    • `done=false` → reconnect from `nextIndex`
    • no frame → forward tail as data (older-server backward compat)
  • Network errors propagate via `controller.error()` rather than a silent close.
  • Reconnections capped at 50 (~100 min of streaming at 2-min server timeout).
  • New regression test (`emits upstream bytes to the consumer before the stream closes`) asserts data flows before upstream EOF — any buffer-then-replay implementation fails it. This specifically catches the class of bug that shipped as 4.2.3.
Test plan
  •  `pnpm vitest run` — 67/67 world-vercel tests pass (28 streamer + 11 reconnect parser + 28 other)
  •  Reconnect + backward-compat + control-frame-split tests from [backport] [world-vercel] Use stream control frame for transparent reconnection #1766 still pass
  •  New regression test fails if `readFromStream` is rewritten to drain upstream first
  •  CI + auto-created workflow-server preview e2e
  •  Manual validation against flight-booking-app once a preview tarball is available
Notes
🤖 Generated with Claude Code
@changeset-bot
changeset-botBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

🦋 Changeset detected
Latest commit: ee258dc
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 18 packages
NameType
@workflow/world-vercelPatch
@workflow/cliPatch
@workflow/corePatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/buildersPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/vitestPatch
@workflow/web-sharedPatch
@workflow/aiPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
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
vercelBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

Contributor
The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
example-nextjs-workflow-turbopackReadyReadyPreview, CommentApr 17, 2026 0:30am
example-nextjs-workflow-webpackReadyReadyPreview, CommentApr 17, 2026 0:30am
example-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-astro-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-express-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-fastify-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-hono-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-nitro-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-nuxt-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-sveltekit-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-vite-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workflow-docsReadyReadyPreview, Comment, Open in v0Apr 17, 2026 0:30am
workflow-swc-playgroundReadyReadyPreview, CommentApr 17, 2026 0:30am
workflow-webReadyReadyPreview, CommentApr 17, 2026 0:30am
@github-actions
github-actionsBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

Contributor
🧪 E2E Test Results
❌ Some tests failed
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production900167968
✅ 💻 Local Development9700861056
✅ 📦 Local Production9700861056
✅ 🐘 Local Postgres9700861056
✅ 🪟 Windows880088
❌ 🌍 Community Worlds139830222
✅ 📋 Other246018264
Total4283843434710
❌ Failed Tests
▲ Vercel Production (1 failed)
sveltekit (1 failed):
  • error handling catchability FatalError can be caught and detected with FatalError.is()
🌍 Community Worlds (83 failed)
mongodb (11 failed):
  • readableStreamWorkflow | wrun_01KPCDEV0N8PQBX7HQXBRBVS64
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • webhookWorkflow | wrun_01KPCDFSP9DFEP41FPPJ2QYNP2
  • outputStreamWorkflow no startIndex (reads all chunks)
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions | wrun_01KPCDJRHYBET9BD520MHYJQG7
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
redis (7 failed):
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
turso (65 failed):
  • addTenWorkflow | wrun_01KPCDEB45HR5F1E88RVZK3JAE
  • addTenWorkflow | wrun_01KPCDEB45HR5F1E88RVZK3JAE
  • wellKnownAgentWorkflow (.well-known/agent) | wrun_01KPCDF08KKPWAQ7PVD2SKCJ78
  • should work with react rendering in step
  • promiseAllWorkflow | wrun_01KPCDEHJWP5ETJS19AG89D448
  • promiseRaceWorkflow | wrun_01KPCDEQ1GD6AXHKS1E2FZMER9
  • promiseAnyWorkflow | wrun_01KPCDES15ZVBHEQ419230WC22
  • importedStepOnlyWorkflow | wrun_01KPCDFDB96AA2827YQ3CD8AJD
  • readableStreamWorkflow | wrun_01KPCDEV0N8PQBX7HQXBRBVS64
  • hookWorkflow | wrun_01KPCDF5S02DMW2T56KA1W34G2
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • webhookWorkflow | wrun_01KPCDFSP9DFEP41FPPJ2QYNP2
  • sleepingWorkflow | wrun_01KPCDFZ2DGN157PQ61KNDPAA3
  • parallelSleepWorkflow | wrun_01KPCDGB2FNK5G4XVQJ7GSZM8R
  • nullByteWorkflow | wrun_01KPCDGE8FE22NA1YJ1WFF6VBY
  • workflowAndStepMetadataWorkflow | wrun_01KPCDGGH4DQKZJZX552S74HRQ
  • outputStreamWorkflow no startIndex (reads all chunks)
  • outputStreamWorkflow positive startIndex (skips first chunk)
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions | wrun_01KPCDJRHYBET9BD520MHYJQG7
  • fetchWorkflow | wrun_01KPCDK5ENNGNJHHMJC1RKW1NT
  • promiseRaceStressTestWorkflow | wrun_01KPCDK8P00SQXPD3707XAM87T
  • error handling error propagation workflow errors nested function calls preserve message and stack trace
  • error handling error propagation workflow errors cross-file imports preserve message and stack trace
  • error handling error propagation step errors basic step error preserves message and stack trace
  • error handling error propagation step errors cross-file step error preserves message and function names in stack
  • error handling retry behavior regular Error retries until success
  • error handling retry behavior FatalError fails immediately without retries
  • error handling retry behavior RetryableError respects custom retryAfter delay
  • error handling retry behavior maxRetries=0 disables retries
  • error handling catchability FatalError can be caught and detected with FatalError.is()
  • error handling not registered WorkflowNotRegisteredError fails the run when workflow does not exist
  • error handling not registered StepNotRegisteredError fails the step but workflow can catch it
  • error handling not registered StepNotRegisteredError fails the run when not caught in workflow
  • hookCleanupTestWorkflow - hook token reuse after workflow completion | wrun_01KPCDPM3JVFJVVH4SBXR892QP
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • hookDisposeTestWorkflow - hook token reuse after explicit disposal while workflow still running | wrun_01KPCDQWKW6XF2NYGHMAD769N5
  • stepFunctionPassingWorkflow - step function references can be passed as arguments (without closure vars) | wrun_01KPCDRGBQGBX4PP2J61VG8MFW
  • stepFunctionWithClosureWorkflow - step function with closure variables passed as argument | wrun_01KPCDRRSK12SDD1NC9AF698RX
  • closureVariableWorkflow - nested step functions with closure variables | wrun_01KPCDRZ9C5MXV1S38E1EYN5BG
  • spawnWorkflowFromStepWorkflow - spawning a child workflow using start() inside a step | wrun_01KPCDS1EG8NXNNB1VYFR7246C
  • health check (queue-based) - workflow and step endpoints respond to health check messages
  • pathsAliasWorkflow - TypeScript path aliases resolve correctly | wrun_01KPCDSGJ3KQKHEHFAQ13QZCPF
  • Calculator.calculate - static workflow method using static step methods from another class | wrun_01KPCDSNXEVWHWXH3928ZG4X1T
  • AllInOneService.processNumber - static workflow method using sibling static step methods | wrun_01KPCDSW86T6BVEAKWY7EGFDV4
  • ChainableService.processWithThis - static step methods using this to reference the class | wrun_01KPCDT2MD8TR3WGMNYS0FKRCH
  • thisSerializationWorkflow - step function invoked with .call() and .apply() | wrun_01KPCDT8BW51BYHXX7QR5QZJ7G
  • customSerializationWorkflow - custom class serialization with WORKFLOW_SERIALIZE/WORKFLOW_DESERIALIZE | wrun_01KPCDTH53VT0AX0SWMD03EWA9
  • instanceMethodStepWorkflow - instance methods with "use step" directive | wrun_01KPCDTQK0WGZ0T10CH13Q2GZK
  • crossContextSerdeWorkflow - classes defined in step code are deserializable in workflow context | wrun_01KPCDV322NQVNK879EXAZ7AW4
  • stepFunctionAsStartArgWorkflow - step function reference passed as start() argument | wrun_01KPCDVAMGFBSHY0F50B9XRY6S
  • cancelRun - cancelling a running workflow | wrun_01KPCDVH3SYGSQWMH1V24W8DQ3
  • cancelRun via CLI - cancelling a running workflow | wrun_01KPCDVTNWAD8331GPPK683AWF
  • pages router addTenWorkflow via pages router
  • pages router promiseAllWorkflow via pages router
  • pages router sleepingWorkflow via pages router
  • hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep | wrun_01KPCDW6J1SYGVPA6PZ0HVTMYF
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_01KPCDWTJ0A2RBCBADY4TB6PZ7
  • sleepWithSequentialStepsWorkflow - sequential steps work with concurrent sleep (control) | wrun_01KPCDX4F3VP5DQDC942H624E4
  • importMetaUrlWorkflow - import.meta.url is available in step bundles | wrun_01KPCDXAT2MWN03RQDQCCVYB16
  • metadataFromHelperWorkflow - getWorkflowMetadata/getStepMetadata work from module-level helper (#1577) | wrun_01KPCDXCWM794ANQS89DT0VN2S
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
Details by Category
❌ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro8107
✅ example8107
✅ express8107
✅ fastify8107
✅ hono8107
✅ nextjs-turbopack8602
✅ nextjs-webpack8602
✅ nitro8107
✅ nuxt8107
❌ sveltekit8017
✅ vite8107
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack8800
❌ 🌍 Community Worlds
AppPassedFailedSkipped
✅ mongodb-dev500
❌ mongodb58110
✅ redis-dev500
❌ redis6270
✅ turso-dev500
❌ turso4650
✅ 📋 Other
AppPassedFailedSkipped
✅ e2e-local-dev-nest-stable8206
✅ e2e-local-postgres-nest-stable8206
✅ e2e-local-prod-nest-stable8206
📋 View full workflow run
❌ Some E2E test jobs failed:
  • Vercel Prod: failure
  • Local Dev: success
  • Local Prod: success
  • Local Postgres: success
  • Windows: success
Check the workflow run for details.
@VaguelySerious@claude
[world-vercel] Use stream control frame for transparent reconnection,…
ee258dc
… with streaming hold-back buffer
Re-applies #1742's reconnect feature on stable, without the arrayBuffer()
rewrite that shipped in 4.2.3 (#1766) and defeated incremental streaming.
- readFromStream returns the ReadableStream promptly; a hold-back buffer
inside the pull loop holds only the last 13 bytes, forwarding surplus
bytes as they arrive. This preserves incremental delivery for AI UIs.
- On upstream close, the tail is parsed for a stream control frame
(done=true → close; done=false → reconnect from nextIndex; no frame →
forward tail as data for older servers).
- Network errors propagate via controller.error() rather than silent close.
- Caps reconnections at 50 (~100 min of streaming at 2-min server timeout).
Adds a regression test that asserts data reaches the consumer before
upstream close — any buffer-then-replay implementation fails it.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Signed-off-by: Peter Wielander <mittgfu@gmail.com>
@VaguelySerious
VaguelySeriousforce-pushed
the
peter/stream-reconnect-proper
branch
from
d76d170 to
ee258dcCompareApril 17, 2026 00:26
@VaguelySeriousVaguelySerious
changed the title
[world-vercel] Use stream control frame for transparent reconnection (proper streaming fix)[world-vercel] Use stream control frame for transparent reconnectionApr 17, 2026
@VaguelySerious
VaguelySerious
marked this pull request as ready for review
April 17, 2026 00:42
@VaguelySerious
VaguelySerious
requested a review
from a team
as a code ownerApril 17, 2026 00:42
@VaguelySerious
VaguelySerious
merged commit 5ef9ac2
into
stableApr 17, 2026

87 of 89 checks passed

@VaguelySerious
VaguelySerious
deleted the

peter/stream-reconnect-proper

branch
April 17, 2026 00:48
@ghostghost
mentioned this pull request
Apr 17, 2026
 Closed


This was referenced Apr 17, 2026
 Closed

 Merged

@TooTallNateTooTallNate
mentioned this pull request
Apr 25, 2026
 Merged

@VaguelySeriousVaguelySerious
mentioned this pull request
May 2, 2026
 Merged

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@TooTallNateTooTallNateTooTallNate approved these changes

Assignees


No one assigned


Labels


None yet


Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

2 participants

@VaguelySerious@TooTallNate

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Remove or un-stick sticky/fixed headers that block content
(function() {
function unstick() {
document.querySelectorAll('header, nav, [role="banner"], .header, .navbar, .sticky, .fixed-top, [style*="position: fixed"], [style*="position:sticky"]').forEach(function(el) {
if (el.style.position === 'fixed' || el.style.position === 'sticky' || getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {
el.style.position = 'static';
el.style.top = 'auto';
el.style.zIndex = 'auto';
}
});
}
unstick();
var observer = new MutationObserver(unstick);
observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });
})();
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
[world-vercel] Use stream control frame for transparent reconnection by VaguelySerious · Pull Request #1790 · vercel/workflow · GitHub
Skip to content
[world-vercel] Use stream control frame for transparent reconnection - #1790
Merged
VaguelySerious merged 1 commit into
stablefrom 
peter/stream-reconnect-proper
Apr 17, 2026
Merged
[world-vercel] Use stream control frame for transparent reconnection#1790
VaguelySerious merged 1 commit into
stablefrom 
peter/stream-reconnect-proper
Conversation
@VaguelySerious
@VaguelySeriousVaguelySerious
commented
Apr 17, 2026

Copy link


Copy Markdown

Member
Summary
Re-applies #1742's reconnect feature on `stable` — without the `arrayBuffer()` rewrite that shipped in 4.2.3 (#1766) and broke incremental streaming on Vercel (content only arrived on stream close). #1766 was reverted on `stable` (#1788, released as 4.2.4).
Root cause of the 4.2.3 regression: `await response.arrayBuffer()` inside `readFromStream` drained the upstream before returning the `ReadableStream`, so `run.getReadable()` blocked until the server closed the stream. The returned stream just replayed the already-complete buffer.
This PR restores the original hold-back buffer approach from #1742 (still in use on `main`), adapted to `stable`'s `readFromStream` signature.
What's in it
  • `readFromStream` returns the `ReadableStream` promptly. A hold-back buffer inside the pull loop keeps only the last 13 bytes (the control-frame size), forwarding surplus bytes as they arrive.
  • On upstream close, the tail is parsed:

    • `done=true` → close cleanly
    • `done=false` → reconnect from `nextIndex`
    • no frame → forward tail as data (older-server backward compat)
  • Network errors propagate via `controller.error()` rather than a silent close.
  • Reconnections capped at 50 (~100 min of streaming at 2-min server timeout).
  • New regression test (`emits upstream bytes to the consumer before the stream closes`) asserts data flows before upstream EOF — any buffer-then-replay implementation fails it. This specifically catches the class of bug that shipped as 4.2.3.
Test plan
  •  `pnpm vitest run` — 67/67 world-vercel tests pass (28 streamer + 11 reconnect parser + 28 other)
  •  Reconnect + backward-compat + control-frame-split tests from [backport] [world-vercel] Use stream control frame for transparent reconnection #1766 still pass
  •  New regression test fails if `readFromStream` is rewritten to drain upstream first
  •  CI + auto-created workflow-server preview e2e
  •  Manual validation against flight-booking-app once a preview tarball is available
Notes
🤖 Generated with Claude Code
@changeset-bot
changeset-botBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

🦋 Changeset detected
Latest commit: ee258dc
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 18 packages
NameType
@workflow/world-vercelPatch
@workflow/cliPatch
@workflow/corePatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/buildersPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/vitestPatch
@workflow/web-sharedPatch
@workflow/aiPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
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
vercelBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

Contributor
The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
example-nextjs-workflow-turbopackReadyReadyPreview, CommentApr 17, 2026 0:30am
example-nextjs-workflow-webpackReadyReadyPreview, CommentApr 17, 2026 0:30am
example-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-astro-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-express-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-fastify-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-hono-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-nitro-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-nuxt-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-sveltekit-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-vite-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workflow-docsReadyReadyPreview, Comment, Open in v0Apr 17, 2026 0:30am
workflow-swc-playgroundReadyReadyPreview, CommentApr 17, 2026 0:30am
workflow-webReadyReadyPreview, CommentApr 17, 2026 0:30am
@github-actions
github-actionsBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

Contributor
🧪 E2E Test Results
❌ Some tests failed
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production900167968
✅ 💻 Local Development9700861056
✅ 📦 Local Production9700861056
✅ 🐘 Local Postgres9700861056
✅ 🪟 Windows880088
❌ 🌍 Community Worlds139830222
✅ 📋 Other246018264
Total4283843434710
❌ Failed Tests
▲ Vercel Production (1 failed)
sveltekit (1 failed):
  • error handling catchability FatalError can be caught and detected with FatalError.is()
🌍 Community Worlds (83 failed)
mongodb (11 failed):
  • readableStreamWorkflow | wrun_01KPCDEV0N8PQBX7HQXBRBVS64
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • webhookWorkflow | wrun_01KPCDFSP9DFEP41FPPJ2QYNP2
  • outputStreamWorkflow no startIndex (reads all chunks)
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions | wrun_01KPCDJRHYBET9BD520MHYJQG7
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
redis (7 failed):
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
turso (65 failed):
  • addTenWorkflow | wrun_01KPCDEB45HR5F1E88RVZK3JAE
  • addTenWorkflow | wrun_01KPCDEB45HR5F1E88RVZK3JAE
  • wellKnownAgentWorkflow (.well-known/agent) | wrun_01KPCDF08KKPWAQ7PVD2SKCJ78
  • should work with react rendering in step
  • promiseAllWorkflow | wrun_01KPCDEHJWP5ETJS19AG89D448
  • promiseRaceWorkflow | wrun_01KPCDEQ1GD6AXHKS1E2FZMER9
  • promiseAnyWorkflow | wrun_01KPCDES15ZVBHEQ419230WC22
  • importedStepOnlyWorkflow | wrun_01KPCDFDB96AA2827YQ3CD8AJD
  • readableStreamWorkflow | wrun_01KPCDEV0N8PQBX7HQXBRBVS64
  • hookWorkflow | wrun_01KPCDF5S02DMW2T56KA1W34G2
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • webhookWorkflow | wrun_01KPCDFSP9DFEP41FPPJ2QYNP2
  • sleepingWorkflow | wrun_01KPCDFZ2DGN157PQ61KNDPAA3
  • parallelSleepWorkflow | wrun_01KPCDGB2FNK5G4XVQJ7GSZM8R
  • nullByteWorkflow | wrun_01KPCDGE8FE22NA1YJ1WFF6VBY
  • workflowAndStepMetadataWorkflow | wrun_01KPCDGGH4DQKZJZX552S74HRQ
  • outputStreamWorkflow no startIndex (reads all chunks)
  • outputStreamWorkflow positive startIndex (skips first chunk)
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions | wrun_01KPCDJRHYBET9BD520MHYJQG7
  • fetchWorkflow | wrun_01KPCDK5ENNGNJHHMJC1RKW1NT
  • promiseRaceStressTestWorkflow | wrun_01KPCDK8P00SQXPD3707XAM87T
  • error handling error propagation workflow errors nested function calls preserve message and stack trace
  • error handling error propagation workflow errors cross-file imports preserve message and stack trace
  • error handling error propagation step errors basic step error preserves message and stack trace
  • error handling error propagation step errors cross-file step error preserves message and function names in stack
  • error handling retry behavior regular Error retries until success
  • error handling retry behavior FatalError fails immediately without retries
  • error handling retry behavior RetryableError respects custom retryAfter delay
  • error handling retry behavior maxRetries=0 disables retries
  • error handling catchability FatalError can be caught and detected with FatalError.is()
  • error handling not registered WorkflowNotRegisteredError fails the run when workflow does not exist
  • error handling not registered StepNotRegisteredError fails the step but workflow can catch it
  • error handling not registered StepNotRegisteredError fails the run when not caught in workflow
  • hookCleanupTestWorkflow - hook token reuse after workflow completion | wrun_01KPCDPM3JVFJVVH4SBXR892QP
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • hookDisposeTestWorkflow - hook token reuse after explicit disposal while workflow still running | wrun_01KPCDQWKW6XF2NYGHMAD769N5
  • stepFunctionPassingWorkflow - step function references can be passed as arguments (without closure vars) | wrun_01KPCDRGBQGBX4PP2J61VG8MFW
  • stepFunctionWithClosureWorkflow - step function with closure variables passed as argument | wrun_01KPCDRRSK12SDD1NC9AF698RX
  • closureVariableWorkflow - nested step functions with closure variables | wrun_01KPCDRZ9C5MXV1S38E1EYN5BG
  • spawnWorkflowFromStepWorkflow - spawning a child workflow using start() inside a step | wrun_01KPCDS1EG8NXNNB1VYFR7246C
  • health check (queue-based) - workflow and step endpoints respond to health check messages
  • pathsAliasWorkflow - TypeScript path aliases resolve correctly | wrun_01KPCDSGJ3KQKHEHFAQ13QZCPF
  • Calculator.calculate - static workflow method using static step methods from another class | wrun_01KPCDSNXEVWHWXH3928ZG4X1T
  • AllInOneService.processNumber - static workflow method using sibling static step methods | wrun_01KPCDSW86T6BVEAKWY7EGFDV4
  • ChainableService.processWithThis - static step methods using this to reference the class | wrun_01KPCDT2MD8TR3WGMNYS0FKRCH
  • thisSerializationWorkflow - step function invoked with .call() and .apply() | wrun_01KPCDT8BW51BYHXX7QR5QZJ7G
  • customSerializationWorkflow - custom class serialization with WORKFLOW_SERIALIZE/WORKFLOW_DESERIALIZE | wrun_01KPCDTH53VT0AX0SWMD03EWA9
  • instanceMethodStepWorkflow - instance methods with "use step" directive | wrun_01KPCDTQK0WGZ0T10CH13Q2GZK
  • crossContextSerdeWorkflow - classes defined in step code are deserializable in workflow context | wrun_01KPCDV322NQVNK879EXAZ7AW4
  • stepFunctionAsStartArgWorkflow - step function reference passed as start() argument | wrun_01KPCDVAMGFBSHY0F50B9XRY6S
  • cancelRun - cancelling a running workflow | wrun_01KPCDVH3SYGSQWMH1V24W8DQ3
  • cancelRun via CLI - cancelling a running workflow | wrun_01KPCDVTNWAD8331GPPK683AWF
  • pages router addTenWorkflow via pages router
  • pages router promiseAllWorkflow via pages router
  • pages router sleepingWorkflow via pages router
  • hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep | wrun_01KPCDW6J1SYGVPA6PZ0HVTMYF
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_01KPCDWTJ0A2RBCBADY4TB6PZ7
  • sleepWithSequentialStepsWorkflow - sequential steps work with concurrent sleep (control) | wrun_01KPCDX4F3VP5DQDC942H624E4
  • importMetaUrlWorkflow - import.meta.url is available in step bundles | wrun_01KPCDXAT2MWN03RQDQCCVYB16
  • metadataFromHelperWorkflow - getWorkflowMetadata/getStepMetadata work from module-level helper (#1577) | wrun_01KPCDXCWM794ANQS89DT0VN2S
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
Details by Category
❌ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro8107
✅ example8107
✅ express8107
✅ fastify8107
✅ hono8107
✅ nextjs-turbopack8602
✅ nextjs-webpack8602
✅ nitro8107
✅ nuxt8107
❌ sveltekit8017
✅ vite8107
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack8800
❌ 🌍 Community Worlds
AppPassedFailedSkipped
✅ mongodb-dev500
❌ mongodb58110
✅ redis-dev500
❌ redis6270
✅ turso-dev500
❌ turso4650
✅ 📋 Other
AppPassedFailedSkipped
✅ e2e-local-dev-nest-stable8206
✅ e2e-local-postgres-nest-stable8206
✅ e2e-local-prod-nest-stable8206
📋 View full workflow run
❌ Some E2E test jobs failed:
  • Vercel Prod: failure
  • Local Dev: success
  • Local Prod: success
  • Local Postgres: success
  • Windows: success
Check the workflow run for details.
@VaguelySerious@claude
[world-vercel] Use stream control frame for transparent reconnection,…
ee258dc
… with streaming hold-back buffer
Re-applies #1742's reconnect feature on stable, without the arrayBuffer()
rewrite that shipped in 4.2.3 (#1766) and defeated incremental streaming.
- readFromStream returns the ReadableStream promptly; a hold-back buffer
inside the pull loop holds only the last 13 bytes, forwarding surplus
bytes as they arrive. This preserves incremental delivery for AI UIs.
- On upstream close, the tail is parsed for a stream control frame
(done=true → close; done=false → reconnect from nextIndex; no frame →
forward tail as data for older servers).
- Network errors propagate via controller.error() rather than silent close.
- Caps reconnections at 50 (~100 min of streaming at 2-min server timeout).
Adds a regression test that asserts data reaches the consumer before
upstream close — any buffer-then-replay implementation fails it.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Signed-off-by: Peter Wielander <mittgfu@gmail.com>
@VaguelySerious
VaguelySeriousforce-pushed
the
peter/stream-reconnect-proper
branch
from
d76d170 to
ee258dcCompareApril 17, 2026 00:26
@VaguelySeriousVaguelySerious
changed the title
[world-vercel] Use stream control frame for transparent reconnection (proper streaming fix)[world-vercel] Use stream control frame for transparent reconnectionApr 17, 2026
@VaguelySerious
VaguelySerious
marked this pull request as ready for review
April 17, 2026 00:42
@VaguelySerious
VaguelySerious
requested a review
from a team
as a code ownerApril 17, 2026 00:42
@VaguelySerious
VaguelySerious
merged commit 5ef9ac2
into
stableApr 17, 2026

87 of 89 checks passed

@VaguelySerious
VaguelySerious
deleted the

peter/stream-reconnect-proper

branch
April 17, 2026 00:48
@ghostghost
mentioned this pull request
Apr 17, 2026
 Closed


This was referenced Apr 17, 2026
 Closed

 Merged

@TooTallNateTooTallNate
mentioned this pull request
Apr 25, 2026
 Merged

@VaguelySeriousVaguelySerious
mentioned this pull request
May 2, 2026
 Merged

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@TooTallNateTooTallNateTooTallNate approved these changes

Assignees


No one assigned


Labels


None yet


Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

2 participants

@VaguelySerious@TooTallNate

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Universal Dark Mode - works on any site
(function() {
var enabled = true;
function applyDarkMode() {
if (!enabled) return;
// Create style element if it doesn't exist
var style = document.getElementById('universal-dark-mode-style');
if (!style) {
style = document.createElement('style');
style.id = 'universal-dark-mode-style';
document.head.appendChild(style);
}
// Dark mode CSS - inverts colors but preserves images/video
style.textContent = '
/* Invert everything except media */
html {
filter: invert(1) hue-rotate(180deg) !important;
background: #1a1a2e !important;
}
/* Restore images, videos, iframes, canvas */
img, video, iframe, canvas, svg, picture, [style*="background-image"] {
filter: invert(1) hue-rotate(180deg) !important;
}
/* Preserve specific elements that should not be inverted */
.no-dark-mode, .no-dark-mode *,
[data-theme="light"], [data-theme="light"],
.ace_editor, .ace_editor *,
.CodeMirror, .CodeMirror *,
.monaco-editor, .monaco-editor *,
.markdown-body pre, .markdown-body pre *,
.highlight, .highlight *,
pre code, pre code * {
filter: none !important;
}
/* Fix common UI elements */
.modal, .popup, .dropdown-menu, .tooltip, .popover {
filter: invert(1) hue-rotate(180deg) !important;
background: #2d2d44 !important;
border-color: #444 !important;
}
/* Scrollbars */
::-webkit-scrollbar { background: #1a1a2e !important; }
::-webkit-scrollbar-thumb { background: #444 !important; }
::-webkit-scrollbar-thumb:hover { background: #555 !important; }
/* Selection */
::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
';
}
function removeDarkMode() {
var style = document.getElementById('universal-dark-mode-style');
if (style) style.remove();
}
// Toggle with Alt+Shift+D
document.addEventListener('keydown', function(e) {
if (e.altKey && e.shiftKey && e.key === 'D') {
e.preventDefault();
enabled = !enabled;
if (enabled) {
applyDarkMode();
console.log('[Universal Dark Mode] Enabled');
} else {
removeDarkMode();
console.log('[Universal Dark Mode] Disabled');
}
}
});
// Apply on load
applyDarkMode();
// Re-apply on dynamic content
var observer = new MutationObserver(function(mutations) {
if (enabled && !document.getElementById('universal-dark-mode-style')) {
applyDarkMode();
}
});
observer.observe(document.head, { childList: true });
console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');
})();
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();
[world-vercel] Use stream control frame for transparent reconnection by VaguelySerious · Pull Request #1790 · vercel/workflow · GitHub
Skip to content
[world-vercel] Use stream control frame for transparent reconnection - #1790
Merged
VaguelySerious merged 1 commit into
stablefrom 
peter/stream-reconnect-proper
Apr 17, 2026
Merged
[world-vercel] Use stream control frame for transparent reconnection#1790
VaguelySerious merged 1 commit into
stablefrom 
peter/stream-reconnect-proper
Conversation
@VaguelySerious
@VaguelySeriousVaguelySerious
commented
Apr 17, 2026

Copy link


Copy Markdown

Member
Summary
Re-applies #1742's reconnect feature on `stable` — without the `arrayBuffer()` rewrite that shipped in 4.2.3 (#1766) and broke incremental streaming on Vercel (content only arrived on stream close). #1766 was reverted on `stable` (#1788, released as 4.2.4).
Root cause of the 4.2.3 regression: `await response.arrayBuffer()` inside `readFromStream` drained the upstream before returning the `ReadableStream`, so `run.getReadable()` blocked until the server closed the stream. The returned stream just replayed the already-complete buffer.
This PR restores the original hold-back buffer approach from #1742 (still in use on `main`), adapted to `stable`'s `readFromStream` signature.
What's in it
  • `readFromStream` returns the `ReadableStream` promptly. A hold-back buffer inside the pull loop keeps only the last 13 bytes (the control-frame size), forwarding surplus bytes as they arrive.
  • On upstream close, the tail is parsed:

    • `done=true` → close cleanly
    • `done=false` → reconnect from `nextIndex`
    • no frame → forward tail as data (older-server backward compat)
  • Network errors propagate via `controller.error()` rather than a silent close.
  • Reconnections capped at 50 (~100 min of streaming at 2-min server timeout).
  • New regression test (`emits upstream bytes to the consumer before the stream closes`) asserts data flows before upstream EOF — any buffer-then-replay implementation fails it. This specifically catches the class of bug that shipped as 4.2.3.
Test plan
  •  `pnpm vitest run` — 67/67 world-vercel tests pass (28 streamer + 11 reconnect parser + 28 other)
  •  Reconnect + backward-compat + control-frame-split tests from [backport] [world-vercel] Use stream control frame for transparent reconnection #1766 still pass
  •  New regression test fails if `readFromStream` is rewritten to drain upstream first
  •  CI + auto-created workflow-server preview e2e
  •  Manual validation against flight-booking-app once a preview tarball is available
Notes
🤖 Generated with Claude Code
@changeset-bot
changeset-botBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

🦋 Changeset detected
Latest commit: ee258dc
The changes in this PR will be included in the next version bump.
This PR includes changesets to release 18 packages
NameType
@workflow/world-vercelPatch
@workflow/cliPatch
@workflow/corePatch
@workflow/webPatch
workflowPatch
@workflow/world-testingPatch
@workflow/buildersPatch
@workflow/nextPatch
@workflow/nitroPatch
@workflow/vitestPatch
@workflow/web-sharedPatch
@workflow/aiPatch
@workflow/astroPatch
@workflow/nestPatch
@workflow/rollupPatch
@workflow/sveltekitPatch
@workflow/vitePatch
@workflow/nuxtPatch
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
vercelBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

Contributor
The latest updates on your projects. Learn more about Vercel for GitHub.
ProjectDeploymentActionsUpdated (UTC)
example-nextjs-workflow-turbopackReadyReadyPreview, CommentApr 17, 2026 0:30am
example-nextjs-workflow-webpackReadyReadyPreview, CommentApr 17, 2026 0:30am
example-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-astro-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-express-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-fastify-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-hono-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-nitro-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-nuxt-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-sveltekit-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workbench-vite-workflowReadyReadyPreview, CommentApr 17, 2026 0:30am
workflow-docsReadyReadyPreview, Comment, Open in v0Apr 17, 2026 0:30am
workflow-swc-playgroundReadyReadyPreview, CommentApr 17, 2026 0:30am
workflow-webReadyReadyPreview, CommentApr 17, 2026 0:30am
@github-actions
github-actionsBot
commented
Apr 17, 2026•

edited

Loading

Copy link


Copy Markdown

Contributor
🧪 E2E Test Results
❌ Some tests failed
Summary
PassedFailedSkippedTotal
❌ ▲ Vercel Production900167968
✅ 💻 Local Development9700861056
✅ 📦 Local Production9700861056
✅ 🐘 Local Postgres9700861056
✅ 🪟 Windows880088
❌ 🌍 Community Worlds139830222
✅ 📋 Other246018264
Total4283843434710
❌ Failed Tests
▲ Vercel Production (1 failed)
sveltekit (1 failed):
  • error handling catchability FatalError can be caught and detected with FatalError.is()
🌍 Community Worlds (83 failed)
mongodb (11 failed):
  • readableStreamWorkflow | wrun_01KPCDEV0N8PQBX7HQXBRBVS64
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • webhookWorkflow | wrun_01KPCDFSP9DFEP41FPPJ2QYNP2
  • outputStreamWorkflow no startIndex (reads all chunks)
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions | wrun_01KPCDJRHYBET9BD520MHYJQG7
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
redis (7 failed):
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
turso (65 failed):
  • addTenWorkflow | wrun_01KPCDEB45HR5F1E88RVZK3JAE
  • addTenWorkflow | wrun_01KPCDEB45HR5F1E88RVZK3JAE
  • wellKnownAgentWorkflow (.well-known/agent) | wrun_01KPCDF08KKPWAQ7PVD2SKCJ78
  • should work with react rendering in step
  • promiseAllWorkflow | wrun_01KPCDEHJWP5ETJS19AG89D448
  • promiseRaceWorkflow | wrun_01KPCDEQ1GD6AXHKS1E2FZMER9
  • promiseAnyWorkflow | wrun_01KPCDES15ZVBHEQ419230WC22
  • importedStepOnlyWorkflow | wrun_01KPCDFDB96AA2827YQ3CD8AJD
  • readableStreamWorkflow | wrun_01KPCDEV0N8PQBX7HQXBRBVS64
  • hookWorkflow | wrun_01KPCDF5S02DMW2T56KA1W34G2
  • hookWorkflow is not resumable via public webhook endpoint | wrun_01KPCDFH1YQSFSVV015W1WK17T
  • webhookWorkflow | wrun_01KPCDFSP9DFEP41FPPJ2QYNP2
  • sleepingWorkflow | wrun_01KPCDFZ2DGN157PQ61KNDPAA3
  • parallelSleepWorkflow | wrun_01KPCDGB2FNK5G4XVQJ7GSZM8R
  • nullByteWorkflow | wrun_01KPCDGE8FE22NA1YJ1WFF6VBY
  • workflowAndStepMetadataWorkflow | wrun_01KPCDGGH4DQKZJZX552S74HRQ
  • outputStreamWorkflow no startIndex (reads all chunks)
  • outputStreamWorkflow positive startIndex (skips first chunk)
  • outputStreamWorkflow negative startIndex (reads from end)
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns correct index after stream completes
  • outputStreamWorkflow - getTailIndex and getStreamChunks getTailIndex returns -1 before any chunks are written
  • outputStreamWorkflow - getTailIndex and getStreamChunks getStreamChunks returns same content as reading the stream
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions | wrun_01KPCDJRHYBET9BD520MHYJQG7
  • fetchWorkflow | wrun_01KPCDK5ENNGNJHHMJC1RKW1NT
  • promiseRaceStressTestWorkflow | wrun_01KPCDK8P00SQXPD3707XAM87T
  • error handling error propagation workflow errors nested function calls preserve message and stack trace
  • error handling error propagation workflow errors cross-file imports preserve message and stack trace
  • error handling error propagation step errors basic step error preserves message and stack trace
  • error handling error propagation step errors cross-file step error preserves message and function names in stack
  • error handling retry behavior regular Error retries until success
  • error handling retry behavior FatalError fails immediately without retries
  • error handling retry behavior RetryableError respects custom retryAfter delay
  • error handling retry behavior maxRetries=0 disables retries
  • error handling catchability FatalError can be caught and detected with FatalError.is()
  • error handling not registered WorkflowNotRegisteredError fails the run when workflow does not exist
  • error handling not registered StepNotRegisteredError fails the step but workflow can catch it
  • error handling not registered StepNotRegisteredError fails the run when not caught in workflow
  • hookCleanupTestWorkflow - hook token reuse after workflow completion | wrun_01KPCDPM3JVFJVVH4SBXR892QP
  • concurrent hook token conflict - two workflows cannot use the same hook token simultaneously | wrun_01KPCDQ7X1M91F15KWCSG7H033
  • hookDisposeTestWorkflow - hook token reuse after explicit disposal while workflow still running | wrun_01KPCDQWKW6XF2NYGHMAD769N5
  • stepFunctionPassingWorkflow - step function references can be passed as arguments (without closure vars) | wrun_01KPCDRGBQGBX4PP2J61VG8MFW
  • stepFunctionWithClosureWorkflow - step function with closure variables passed as argument | wrun_01KPCDRRSK12SDD1NC9AF698RX
  • closureVariableWorkflow - nested step functions with closure variables | wrun_01KPCDRZ9C5MXV1S38E1EYN5BG
  • spawnWorkflowFromStepWorkflow - spawning a child workflow using start() inside a step | wrun_01KPCDS1EG8NXNNB1VYFR7246C
  • health check (queue-based) - workflow and step endpoints respond to health check messages
  • pathsAliasWorkflow - TypeScript path aliases resolve correctly | wrun_01KPCDSGJ3KQKHEHFAQ13QZCPF
  • Calculator.calculate - static workflow method using static step methods from another class | wrun_01KPCDSNXEVWHWXH3928ZG4X1T
  • AllInOneService.processNumber - static workflow method using sibling static step methods | wrun_01KPCDSW86T6BVEAKWY7EGFDV4
  • ChainableService.processWithThis - static step methods using this to reference the class | wrun_01KPCDT2MD8TR3WGMNYS0FKRCH
  • thisSerializationWorkflow - step function invoked with .call() and .apply() | wrun_01KPCDT8BW51BYHXX7QR5QZJ7G
  • customSerializationWorkflow - custom class serialization with WORKFLOW_SERIALIZE/WORKFLOW_DESERIALIZE | wrun_01KPCDTH53VT0AX0SWMD03EWA9
  • instanceMethodStepWorkflow - instance methods with "use step" directive | wrun_01KPCDTQK0WGZ0T10CH13Q2GZK
  • crossContextSerdeWorkflow - classes defined in step code are deserializable in workflow context | wrun_01KPCDV322NQVNK879EXAZ7AW4
  • stepFunctionAsStartArgWorkflow - step function reference passed as start() argument | wrun_01KPCDVAMGFBSHY0F50B9XRY6S
  • cancelRun - cancelling a running workflow | wrun_01KPCDVH3SYGSQWMH1V24W8DQ3
  • cancelRun via CLI - cancelling a running workflow | wrun_01KPCDVTNWAD8331GPPK683AWF
  • pages router addTenWorkflow via pages router
  • pages router promiseAllWorkflow via pages router
  • pages router sleepingWorkflow via pages router
  • hookWithSleepWorkflow - hook payloads delivered correctly with concurrent sleep | wrun_01KPCDW6J1SYGVPA6PZ0HVTMYF
  • sleepInLoopWorkflow - sleep inside loop with steps actually delays each iteration | wrun_01KPCDWTJ0A2RBCBADY4TB6PZ7
  • sleepWithSequentialStepsWorkflow - sequential steps work with concurrent sleep (control) | wrun_01KPCDX4F3VP5DQDC942H624E4
  • importMetaUrlWorkflow - import.meta.url is available in step bundles | wrun_01KPCDXAT2MWN03RQDQCCVYB16
  • metadataFromHelperWorkflow - getWorkflowMetadata/getStepMetadata work from module-level helper (#1577) | wrun_01KPCDXCWM794ANQS89DT0VN2S
  • resilient start: addTenWorkflow completes when run_created returns 500 | wrun_01KPCDXEXGCXH0VHDT49AAHF97
Details by Category
❌ ▲ Vercel Production
AppPassedFailedSkipped
✅ astro8107
✅ example8107
✅ express8107
✅ fastify8107
✅ hono8107
✅ nextjs-turbopack8602
✅ nextjs-webpack8602
✅ nitro8107
✅ nuxt8107
❌ sveltekit8017
✅ vite8107
✅ 💻 Local Development
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 📦 Local Production
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 🐘 Local Postgres
AppPassedFailedSkipped
✅ astro-stable8206
✅ express-stable8206
✅ fastify-stable8206
✅ hono-stable8206
✅ nextjs-turbopack-canary69019
✅ nextjs-turbopack-stable8800
✅ nextjs-webpack-canary69019
✅ nextjs-webpack-stable8800
✅ nitro-stable8206
✅ nuxt-stable8206
✅ sveltekit-stable8206
✅ vite-stable8206
✅ 🪟 Windows
AppPassedFailedSkipped
✅ nextjs-turbopack8800
❌ 🌍 Community Worlds
AppPassedFailedSkipped
✅ mongodb-dev500
❌ mongodb58110
✅ redis-dev500
❌ redis6270
✅ turso-dev500
❌ turso4650
✅ 📋 Other
AppPassedFailedSkipped
✅ e2e-local-dev-nest-stable8206
✅ e2e-local-postgres-nest-stable8206
✅ e2e-local-prod-nest-stable8206
📋 View full workflow run
❌ Some E2E test jobs failed:
  • Vercel Prod: failure
  • Local Dev: success
  • Local Prod: success
  • Local Postgres: success
  • Windows: success
Check the workflow run for details.
@VaguelySerious@claude
[world-vercel] Use stream control frame for transparent reconnection,…
ee258dc
… with streaming hold-back buffer
Re-applies #1742's reconnect feature on stable, without the arrayBuffer()
rewrite that shipped in 4.2.3 (#1766) and defeated incremental streaming.
- readFromStream returns the ReadableStream promptly; a hold-back buffer
inside the pull loop holds only the last 13 bytes, forwarding surplus
bytes as they arrive. This preserves incremental delivery for AI UIs.
- On upstream close, the tail is parsed for a stream control frame
(done=true → close; done=false → reconnect from nextIndex; no frame →
forward tail as data for older servers).
- Network errors propagate via controller.error() rather than silent close.
- Caps reconnections at 50 (~100 min of streaming at 2-min server timeout).
Adds a regression test that asserts data reaches the consumer before
upstream close — any buffer-then-replay implementation fails it.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Signed-off-by: Peter Wielander <mittgfu@gmail.com>
@VaguelySerious
VaguelySeriousforce-pushed
the
peter/stream-reconnect-proper
branch
from
d76d170 to
ee258dcCompareApril 17, 2026 00:26
@VaguelySeriousVaguelySerious
changed the title
[world-vercel] Use stream control frame for transparent reconnection (proper streaming fix)[world-vercel] Use stream control frame for transparent reconnectionApr 17, 2026
@VaguelySerious
VaguelySerious
marked this pull request as ready for review
April 17, 2026 00:42
@VaguelySerious
VaguelySerious
requested a review
from a team
as a code ownerApril 17, 2026 00:42
@VaguelySerious
VaguelySerious
merged commit 5ef9ac2
into
stableApr 17, 2026

87 of 89 checks passed

@VaguelySerious
VaguelySerious
deleted the

peter/stream-reconnect-proper

branch
April 17, 2026 00:48
@ghostghost
mentioned this pull request
Apr 17, 2026
 Closed


This was referenced Apr 17, 2026
 Closed

 Merged

@TooTallNateTooTallNate
mentioned this pull request
Apr 25, 2026
 Merged

@VaguelySeriousVaguelySerious
mentioned this pull request
May 2, 2026
 Merged

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@TooTallNateTooTallNateTooTallNate approved these changes

Assignees


No one assigned


Labels


None yet


Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

2 participants

@VaguelySerious@TooTallNate