[BUG] Cowork "RPC pipe closed" on Windows when app is installed on non-C: drive - signature verification requires C:\Program Files\WindowsApps, workspace reinstall fails at ~80%

Environment

Claude Desktop 1.30096.1, Windows 11 x64. App package installed on D: drive (Windows "Where new content is saved" pointed to D:, a supported Windows setting).

What's wrong

After updating Claude Desktop on 14 Aug 2026, Cowork fails to start with "Failed to start Claude's workspace / RPC pipe closed". CoworkVMService stays Running throughout. "Reinstall the workspace" fails at ~78-80% on every attempt.

Logs show the root cause is a client signature verification that hard-codes the C: WindowsApps path:

[vm-client] Event resubscribe failed: Error: signature verification failed: client D:\WindowsApps\Claude_1.30096.1.0_x64__pzs8sxrjxfjjc\app\claude.exe was not started from the package directory C:\Program Files\WindowsApps\Claude_1.30096.1.0_x64__pzs8sxrjxfjjc
[VM:start] Startup failed: Error: RPC pipe closed (ERR_VM_PIPE_CLOSED)

The package is legitimately installed via Windows' supported "save new apps to D:" setting, so the check compares the real install path (D:\WindowsApps\...) against an expected path hard-coded to C:\Program Files\WindowsApps\... and always fails. Cowork worked on this same machine until this update.

Windows' native "Move" to C: also fails (0x80073cf6), so affected users must fully uninstall and reinstall to C:.

Expected behavior

Signature verification should resolve the actual package install root rather than assuming C:, or the error should clearly tell the user the install drive is the problem instead of a generic "RPC pipe closed".

Related

#86543 reports MCP/Cowork issues on the same build; this signature failure appears distinct from the schema validation problem.