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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.

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Claude Code v2.1.223

Atomic file writes no longer copy through the temp file on the fallback path

You'll notice
Useful3 Signal0
File Writes

File writes are safer on the fallback path and refuse to follow a symlink at the destination.

What

When rename fails, the atomic-write fallback now writes content straight to the destination instead of copying the temp file over it.

Details
  • applies to both the sync and async fallbacks
  • the destination is opened with O_WRONLY|O_CREAT|O_TRUNC|O_NOFOLLOW, so a symlink at the path is refused rather than followed
  • permissions are applied by chmod on the open descriptor
  • on failure the descriptor is closed and the partial destination is unlinked
Evidence

U1.constants.O_NOFOLLOW

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 v2.1.223 →