Add support for readable streams in workflows local dev

[Caio-Nogueira]

We recently added workflows support for ReadableStream<Uint8Array>. We want to mirror behavior on local dev as well

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• Tests
  • Tests included/updated
  • Automated tests not possible - manual testing has been completed as follows:
  • Additional testing not necessary because:
• Public documentation
  • Cloudflare docs PR(s): Add docs for steps that return readable streams cloudflare-docs#29393
  • Documentation not necessary because:

A picture of a cute animal (not mandatory, but encouraged)

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[changeset-bot]

🦋 Changeset detected

Latest commit: 1dd568d

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

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[workers-devprod]

Codeowners approval required for this PR:

• ✅ @cloudflare/workflows
• ✅ @cloudflare/wrangler

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[ask-bonk]

I'm Bonk, and I've done a quick review of your PR.

This PR adds ReadableStream<Uint8Array> support to the local dev workflows engine by chunking streams into SQL storage, replaying them on cache hit, and handling various error/timeout/rollback scenarios.

Issues

1. streamOutputRolledBack on WorkflowTimeoutError is never set (low severity) — The StreamWriteTimeoutError type defines streamOutputRolledBack?: boolean and context.ts:536-541 reads it from the thrown error, but no code path ever sets this property to true on any error object. The read always evaluates to undefined (falsy), so the guard at line 704 is effectively dead. This is harmless since rollbackStreamOutput is idempotent, but the plumbing is misleading. If this is forward-looking (for production parity), a comment would help. Otherwise it can be removed.

2. Missing changeset (low severity) — The changeset bot flagged this. Since this changes user-visible behavior (stream outputs in local dev), a changeset for workflows-shared is likely needed unless the no-changeset-required label applies.

[ask-bonk]

Review posted on PR #13145. The PR is well-structured overall -- the stream chunking/replay infrastructure in streams.ts is solid, error handling is thorough with proper rollback on failures, and the test coverage is good (including edge cases for locked streams, unsupported chunks, oversized chunks, restart cleanup, TypedArray normalization, and timeout+rollback).

I flagged two low-severity items:

1. The streamOutputRolledBack property on WorkflowTimeoutError is typed and read but never actually set to true anywhere, making the check dead code. Harmless but misleading.
2. A missing changeset (already flagged by the bot).

github run

[pkg-pr-new]

create-cloudflare

npm i https://pkg.pr.new/create-cloudflare@13145

@cloudflare/kv-asset-handler

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miniflare

npm i https://pkg.pr.new/miniflare@13145

@cloudflare/pages-shared

npm i https://pkg.pr.new/@cloudflare/pages-shared@13145

@cloudflare/unenv-preset

npm i https://pkg.pr.new/@cloudflare/unenv-preset@13145

@cloudflare/vite-plugin

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@cloudflare/vitest-pool-workers

npm i https://pkg.pr.new/@cloudflare/vitest-pool-workers@13145

@cloudflare/workers-editor-shared

npm i https://pkg.pr.new/@cloudflare/workers-editor-shared@13145

wrangler

npm i https://pkg.pr.new/wrangler@13145

commit: 1dd568d

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 6 additional findings.

[github-actions]

Changeset Review

File: .changeset/all-fans-march.md

Package: @cloudflare/workflows-shared
Version Type: minor

Review

1. Version Type: ✅ minor is appropriate for a new feature (ReadableStream support)

2. Changelog Quality: ✅ Clear description explaining what the feature does and its benefit (overcoming 1MB limit per step output)

3. Markdown Headers: ✅ No h1/h2/h3 headers found

4. Analytics: ✅ Not applicable - no analytics collection mentioned

5. Dependabot: ✅ Not a dependency update changeset

6. Experimental features: ✅ Not applicable - this is adding new functionality to an internal package

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✅ All changesets look good

[penalosa]

Approving from a Wrangler perspective. I haven't closely reviewed the workflows-shared code

[workers-devprod]

Codeowners approval required for this PR:

• ✅ @cloudflare/workflows
• ✅ @cloudflare/wrangler

Show detailed file reviewers

[workers-devprod]

Codeowners reviews satisfied