chore(msw): upgrade MSW to v3 while keeping v2 support

[dinwwwh]

Upgrades the msw dev dependency of @orpc/experimental-msw to v3 and keeps MSW v2 support tested. Supersedes #2200.

Changes

• Upgrade: msw devDependency ^2.15.0 → ^3.0.2. The package source needs no changes: http.all, passthrough, HttpHandler, ResponseResolverInfo, HttpRequestResolverExtras and PathParams are unchanged in v3. The existing msw: ">=2.0.0" peer range already covers v3.
• Tests: v3 renamed the listen() option onUnhandledRequest to onUnhandledFrame and silently ignores the old name, so the tests were no longer strict about unhandled requests. Switched to onUnhandledFrame: 'error'.
• v2 test run: added msw-v2 (npm:msw@^2.15.0) as a devDependency and an msw-v2 vitest project that reruns packages/msw/**/*.test.ts with msw / msw/* aliased to it. Both the package source and the tests then load v2. The v2 run is lenient about unhandled requests, since v2 ignores onUnhandledFrame.
• Node 20: MSW v3 requires Node.js 22.12+. Its interceptors call Promise.withResolvers, so the v3 run fails on the Node 20 CI job. On Node < 22, the default project excludes packages/msw, and the msw-v2 project still runs the full msw suite there.
• Docs: the MSW integration page notes that both MSW v2 and v3 are supported, and the passthrough section names onUnhandledFrame (onUnhandledRequest in v2).

Testing

• pnpm vitest run packages/msw: 56 tests pass on Node 22 (28 on v3, 28 on v2), and 28 pass on Node 20 (v2 only). A temporary probe test confirmed each project loads the intended msw version (3.0.2 / 2.15.0).
• Full pnpm vitest run, root tsc (which covers test files), eslint, sherif and pnpm docs:validate all pass.

Notes for users upgrading to MSW v3

v3 requires Node.js 22.12+ and TypeScript 5.9+. It also no longer manages cookies in Node.js, and request.headers.get('cookie') returns null, so a context option that reads cookies from the request headers should use the cookies resolver argument instead.

🤖 Generated with Claude Code

https://claude.ai/code/session_01NNXLdknBGr7KSffPGDLHB9

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	orpc	125071d	Commit Preview URL Branch Preview URL	Oct 10 2026, 06:57 AM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[pkg-pr-new]

More templates

• @orpc/bun-playground
• @orpc/cloudflare-playground
• @orpc/nest-playground
• @orpc/next-playground

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@orpc/node

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commit: 125071d

[codspeed]

Merging this PR will not alter performance

⚠️ 5 benchmarks spent significant time in system calls

System calls cannot be consistently instrumented, so they are not included in the measure, which understates the real cost. Please switch to the Walltime instrument to accurately measure system calls.

Measurement and system calls

• serve deeply nested encoded path
• not found fall through
• range request
• serve file
• not modified (304)

✅ 28 untouched benchmarks
⏩ 2 skipped benchmarks¹

---

_{Comparing claude/festive-cori-p3cz11 (125071d) with main (d1b6ad0)}

Footnotes

1. 2 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[pullfrog]

Important

Upgrading the msw devDependency to v3 will turn the test_matrix (20) CI job red. The root vitest project loads this v3 copy for the msw suite, and v3 (via @mswjs/interceptors@0.45.7) calls Promise.withResolvers, which does not exist in Node 20. This needs a CI-matrix change (or a Node gate on the msw tests) before merge.

Reviewed changes

• msw devDependency bump ^2.15.0 → ^3.0.2; the msw: ">=2.0.0" peer range is untouched (correctly covers v3), and package source is unchanged.
• msw-v2 alias + second vitest project (vitest.config.ts:42-56) aliases msw → msw-v2 so packages/msw/**/*.test.ts also runs against MSW v2. Verified the alias actually resolves v2 (msw/package.json → 2.15.0 in the msw-v2 project, 3.0.2 in the root project).
• listen() option rename to onUnhandledFrame: 'error' in the three msw test files — correct for v3 (v2 ignores the unknown key, so the v2 run stays lenient as described).
• Docs note v2/v3 support and document the renamed passthrough option.

  ^{｜ Fix all ➔ ｜ Fix 👍s ➔ ｜ View workflow run ｜ Using deepseek-v4.1-flash (free via Pullfrog for OSS) ｜ 𝕏}

[pullfrog]

✅ No new issues found.

Reviewed changes — delta since the prior pullfrog review (new commit a2a3c91f):

• Node-version gate on the msw v3 project (vitest.config.ts:36-43): the root project excludes ./packages/msw/** when Number.parseInt(process.versions.node) < 22, so on Node 20 only the msw-v2 project runs the suite and the v3-only Promise.withResolvers failure is avoided.

Verified locally: Node 20.20.2 runs 28 tests (all msw-v2, pass); Node 24 runs 56 tests (v3 + v2, pass). This addresses the Node 20 CI concern raised in the prior review.

  ^{｜ View workflow run ｜ Using deepseek-v4.1-flash (free via Pullfrog for OSS) ｜ 𝕏}

[dinwwwh]

Update: Workers Builds: orpc ran again on the current head, 125071d, and passed in about 3 minutes. The preview deployed. The earlier failure on 80d45a5 was a one-off build problem and needs no action.

Original note

Workers Builds: orpc (the Cloudflare docs deploy) failed on 80d45a5, an earlier commit of this PR. It ran for about 31 minutes and reported no error output to GitHub.

A local blume build compiled all the content and rendered /docs/integrations/msw and its OG image. pnpm docs:validate (blume validate --strict) also passes. Nothing pointed to this PR's docs change, which is an :::info block and a link on the MSW integration page.

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