Failed file writes now try to put the original file back

Claude Code normally saves a file by writing a temporary copy and swapping it in. On some file systems that swap fails, and it writes over the file directly instead. It now remembers the original contents first. If the direct write fails partway, it tries to put the original back.

The error message says what state the file was left in and that the new content was kept at the temporary path. A failure to flush the file to disk is now logged and does not stop the write.