fix(core): reset request timeout on progress without an onprogress handler

[minglong51]

What

resetTimeoutOnProgress: true is documented to keep a long-running request alive as progress notifications arrive. In practice it only worked when an onprogress callback was also passed on the same request() call.

Without onprogress, the request did not advertise _meta.progressToken, and _onprogress treated any manually delivered progress as an unknown token before the timeout-reset code could run. (#2076)

Fix

• Advertise _meta.progressToken when either onprogress or resetTimeoutOnProgress is enabled.
• Treat a progress token as known when it belongs to either a registered progress handler or an in-flight request.
• Reset the timeout for the in-flight request even when no progress callback is registered.
• Invoke the progress callback only when one exists.

This preserves the existing task-progress path, where a progress handler may remain after the response handler is gone, and still reports genuinely unknown tokens.

Test plan

• Added a public Protocol.request() regression covering resetTimeoutOnProgress: true without onprogress.
• The regression asserts that the outbound request advertises a progress token, progress extends the timer beyond its original deadline, the request resolves successfully, and no spurious unknown-token error is emitted.
• pnpm exec vitest run test/shared/protocol.test.ts: 40 passed.
• pnpm --filter @modelcontextprotocol/core-internal test: 1,434 passed.
• pnpm --filter @modelcontextprotocol/core-internal check: passed.
• Pre-push repository hooks: build, typecheck, and lint passed across the workspace.

Scope

This PR targets main (SDK v2). The stable v1.x branch requires a separate backport PR if maintainers want the same fix there.

Fixes #2076

[changeset-bot]

🦋 Changeset detected

Latest commit: aa47d06

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

This PR includes changesets to release 6 packages

Name	Type
@modelcontextprotocol/client	Patch
@modelcontextprotocol/server	Patch
@modelcontextprotocol/core	Patch
@modelcontextprotocol/server-legacy	Patch
@modelcontextprotocol/codemod	Patch
@modelcontextprotocol/core-internal	Patch

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commit: aa47d06

[minglong51]

Gentle ping on this when you have review bandwidth. CI is green, the regression test covers #2076, and the change is scoped to preserving resetTimeoutOnProgress behavior even when no onprogress callback is supplied.

Happy to adjust if you prefer the timeout-reset ordering handled differently.

[minglong51]

Revived and rebased onto current main (aa47d066). The refresh also closes the outbound half of #2076: resetTimeoutOnProgress now advertises _meta.progressToken even without onprogress, so a peer can actually address progress to the request. The public Protocol.request() regression covers token advertisement, timeout extension, successful completion, and absence of the spurious unknown-token error. Workspace build, typecheck, and lint passed in the pre-push hook; the core-internal suite passed 1,434 tests. Ready for re-review.