[lijiashu1]

Summary

• Return a clear 400 response for malformed JSON without exposing parser details.
• Log unexpected server-side request errors and return a generic 500 response instead of misclassifying every failure as a client error.
• Destroy the response if headers have already been sent, avoiding a second writeHead attempt.
• Add regression tests for malformed input, unexpected errors, and already-started responses.

Validation

• Added unit tests for the error-response helper.
• Automated test suite has not been run in this workflow.

[wjc2821296948]

had conflicts.