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DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

← All of v2.1.227 Home All releases ←olderv2.1.226 v2.1.228newer→
Claude Code v2.1.227

Headless write failures produce a result object, not silence

You'll notice
Useful4 Signal2
Headless Mode

Headless output write failures now produce a proper failed result object in stream-json.

What

If a message cannot be written to the headless output stream, Claude now writes an Error: line to stderr, marks the turn's summary as failed, and in stream-json mode emits a result object with an error_during_execution subtype built by a shared helper.

Details
  • The stderr line begins Could not write a message to the output stream.
  • Paired with a tengu_headless_fatal_error event carrying the site, message type, control subtype, drained message count, outstanding stdout bytes and whether stdout was destroyed.
  • None of this existed in v2.1.226.
Evidence

Could not write a message to the output stream

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

Related

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

See this entry in the whole of v2.1.227 →