Every update failed at "Could not replace the existing files": the app relaunches the installer via ShellExecute without a working directory, so it inherited the app's CWD - which the Start Menu shortcut sets to <InstallDir>\app. A process's current directory is locked by Windows, so the installer blocked its own `app` -> `app.bak` rename. Retries and reboots could not help. - installer moves its CWD to %TEMP% at startup, and both relaunch sites in the UI pass an explicit WorkingDirectory - cache the release zip in %TEMP%\ClaudeDo-download-cache and reuse it on a retry while its SHA-256 still matches, so a failed attempt no longer costs another full download; drop it after a successful install, delete a mismatching one, prune zips of other versions - roll back a half-done stash: a leftover app.bak was deleted as a stale stash on the next attempt, and that copy was the only one left - name the blocked path in the error message