fix(node,fastify): handle synchronous throws on the response-send path

[dinwwwh]

A synchronous throw while sending a response (an invalid header value in the node adapter, FST_ERR_BAD_STATUS_CODE in fastify) used to reject the promise while leaving the connection neither ended nor destroyed and the already-built body stream leaked. In the node adapter the client would hang until it gave up, since Node has no default response-send timeout.

Fixes

• Both adapters wrap the status/header/send sequence in try/catch: on failure the body stream is destroyed (a caller-supplied ReadableStream gets its cancel() called instead of staying locked), and the promise rejects with the original error.
• The node adapter also destroys the response socket, so the connection is no longer left half-open with partially applied headers.
• The fastify adapter deliberately leaves reply.raw intact — its error handler still delivers the 500.
• canWriteToNodeResponse now treats headersSent as non-writable, so a response whose headers were flushed upstream takes the graceful not-writable path instead of throwing ERR_HTTP_HEADERS_SENT with headers half-applied.

Testing

• New regression tests: invalid header value rejects and destroys both response and body; already-flushed headers resolve cleanly; fastify status outside [100, 599] rejects, cancels the body stream, and still returns fastify's 500.
• Full workspace suite passes (912 tests, 59 files) and all packages typecheck.

[pkg-pr-new]

• @standardserver/hono-node-playground
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commit: 658f629

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[codspeed-hq]

Merging this PR will not alter performance

✅ 26 untouched benchmarks
⏩ 108 skipped benchmarks¹

---

_{Comparing claude/response-send-throw-leak-56af52 (658f629) with main (d32b063)}

Footnotes

1. 108 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. ↩