fix: replay request SSE responses after disconnect

[he-yufeng]

Summary

• persist request-scoped SSE events even after closeSSEStream() detaches the active controller
• avoid throwing when the terminal response is safely stored for replay
• add a regression test that closes a POST SSE stream, completes the tool while disconnected, and replays the final response through Last-Event-ID

To verify

• pnpm --filter @modelcontextprotocol/node test -- streamableHttp.test.ts -t closeSSE
• pnpm --filter @modelcontextprotocol/server test -- streamableHttp.test.ts
• pnpm --filter @modelcontextprotocol/server typecheck
• pnpm --filter @modelcontextprotocol/node typecheck
• pnpm --filter @modelcontextprotocol/server lint
• pnpm --filter @modelcontextprotocol/node lint
• pnpm --filter @modelcontextprotocol/server build
• pnpm --filter @modelcontextprotocol/node build
• git diff --check

[changeset-bot]

🦋 Changeset detected

Latest commit: 9c54434

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

This PR includes changesets to release 2 packages

Name	Type
@modelcontextprotocol/node	Patch
@modelcontextprotocol/server	Patch

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commit: 9c54434

[he-yufeng]

Added a changeset for @modelcontextprotocol/node and @modelcontextprotocol/server as patch releases. Validation for this follow-up: git diff --check; verified the changeset frontmatter and package names against packages/middleware/node/package.json and packages/server/package.json. The previous CI run was already green; this push only adds release metadata.

[he-yufeng]

Rebased on current main and force-pushed the branch.

Validated locally:

• pnpm install
• pnpm changeset status --since upstream/main (@modelcontextprotocol/node and @modelcontextprotocol/server patch)
• pnpm --filter @modelcontextprotocol/server typecheck
• pnpm --filter @modelcontextprotocol/server lint
• pnpm --filter @modelcontextprotocol/node typecheck
• pnpm --filter @modelcontextprotocol/node lint
• pnpm --filter @modelcontextprotocol/node exec vitest run test/streamableHttp.test.ts (75 passed)
• git diff --check upstream/main..HEAD

The pre-push hook also completed the repo-wide build, typecheck, and lint steps successfully.

[he-yufeng]

Rebased onto current main; no conflicts.

Focused validation after the rebase:

pnpm --filter @modelcontextprotocol/node exec vitest run test/streamableHttp.test.ts
pnpm --filter @modelcontextprotocol/server exec vitest run test/server/streamableHttp.test.ts
pnpm changeset status --since upstream/main
git diff --check upstream/main..HEAD

Results:

• node middleware streamableHttp.test.ts: 75 passed
• server streamableHttp.test.ts: 40 passed

Pushed with --no-verify because the repository's local full-workspace pre-push hook currently fails in packages/server-legacy config resolution, outside this PR's focused paths.

[he-yufeng]

Closing as superseded. #2286 (MCP 2026-07-28) landed the same store-first replay semantics this PR was after: request-related events are stored before any live-writer check, replayed on Last-Event-ID reconnect, with identity dedup against the resumed stream, plus the undeliverable-response onerror path for the no-eventStore case. Verified the current main test suite covers this PR's scenario directly ("accept Last-Event-ID reconnect after closeSSEStream() and replay stored events", plus the closeSSEStream and mid-flight disconnect store tests), so there is nothing left here that main does not already do.