fix: handle cancellation for request id zero

[he-yufeng]

Summary

• preserve requestId: 0 when handling notifications/cancelled
• add a regression test that cancels an inbound request whose JSON-RPC id is 0

Fixes #2115.

Validation

• pnpm --filter @modelcontextprotocol/core exec vitest run test/shared/protocol.test.ts -t "notifications/cancelled behavior"
• pnpm --filter @modelcontextprotocol/core exec vitest run test/shared/protocol.test.ts
• pnpm --filter @modelcontextprotocol/core run typecheck
• pnpm --filter @modelcontextprotocol/core run lint
• pre-push hook: pnpm -r typecheck, pnpm -r build, pnpm sync:snippets --check, pnpm -r lint
• git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: 553b6b6

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

This PR includes changesets to release 1 package

Name	Type
@modelcontextprotocol/core	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[pkg-pr-new]

Open in StackBlitz

@modelcontextprotocol/client

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@2138

@modelcontextprotocol/codemod

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/codemod@2138

@modelcontextprotocol/server

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@2138

@modelcontextprotocol/express

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/express@2138

@modelcontextprotocol/fastify

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/fastify@2138

@modelcontextprotocol/hono

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/hono@2138

@modelcontextprotocol/node

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/node@2138

commit: 553b6b6

[he-yufeng]

Rebased this on the latest main and re-ran the focused/core checks locally:

• pnpm --filter @modelcontextprotocol/core exec vitest run test/shared/protocol.test.ts -t "requestId 0"
• pnpm --filter @modelcontextprotocol/core exec vitest run test/shared/protocol.test.ts
• pnpm --filter @modelcontextprotocol/core run typecheck
• pnpm --filter @modelcontextprotocol/core run lint
• git diff --check upstream/main..HEAD
• pre-push hook: pnpm -r typecheck, pnpm -r build, pnpm sync:snippets --check, pnpm -r lint

[he-yufeng]

Added the @modelcontextprotocol/core patch changeset and force-pushed 553b6b6. Local validation: changeset status shows @modelcontextprotocol/core patch; focused requestId 0 test passed; full core protocol.test.ts passed with 151 tests; core typecheck and lint passed; git diff --check passed. Pre-push typecheck, build, and lint also passed.