[Bug] Windows update fails silently: bin\claude.exe not replaced during version upgrade

Bug Description
Windows native install: claude update reports success but never replaces bin\claude.exe.

Environment: Windows 11 Home 10.0.26200, installMethod "native", autoUpdates false,
HOME unset (empty), USERPROFILE C:\Users\<user>, %USERPROFILE%\.local is a plain
directory (no junction), bin\ and share\ on the same volume.

Symptom, observed today on 2.1.229 -> 2.1.231:
claude update printed "Successfully updated from 2.1.229 to version 2.1.231".
The new build was downloaded correctly to
%USERPROFILE%\.local\share\claude\versions\2.1.231, but %USERPROFILE%\.local\bin\claude.exe
stayed byte-identical to versions\2.1.229:

bin\claude.exe SHA256 5736C66B... FileVersion 2.1.229.0
versions\2.1.229 SHA256 5736C66B...
versions\2.1.231 SHA256 99DBF97E... (downloaded, never promoted)

Note both files are 307186848 bytes, so size alone does not reveal the failure.

This is not a one-off. The same failure occurred on 2.1.225 -> 2.1.226 and repeated for
several days, including when claude update was run from a clean terminal with no session
active, so an exclusive lock by the running process does not fully explain it.
Because versions\<new> already exists on disk, every subsequent run prints the same
success message again.

Two defects:

1. The promotion step from versions\<new> to bin\claude.exe fails silently.
2. Success is reported without verifying that the binary actually changed. A post-update

hash or FileVersion check would turn a silent failure into a visible error.

Working workaround (NTFS allows renaming a running .exe):
Move-Item $bin "$bin.old" -Force
Copy-Item ...\versions\<new> $bin -Force

Related: github.com/anthropics/claude-code/issues/69881 (closed as not planned).

Environment Info

• Platform: win32
• Terminal: windows-terminal
• Version: 2.1.229
• Feedback ID: 423b053d-a15d-434c-914f-2cd11b5d2833

Errors

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