Nit: The `setTimeout` fallback in `Promise.race` within `close()` is never cleared when `Promise.allSettled` resolves first. In Node.js, an active timer keeps the event loop alive, so the process cannot exit for up to 2 seconds after `close()` completes — this will cause test runners (Jest/Vitest) to report open handles. Fix by storing the timer ID and calling `clearTimeout` after the race, or by using `setTimeout(...).unref()`. Same issue exists in `streamableHttp.ts` line 462.