Desktop app crash (STATUS_BREAKPOINT) when opening embedded Claude Browser preview (Cowork VM Sandbox)

Environment

• Claude desktop client build: 1.26832.0.0
• OS: Windows 11 Pro (10.0.26200)
• Hyper-V: enabled and functioning (vmcompute.dll loads successfully, confirmed via cowork-service.log)

Summary
The desktop app crashes deterministically (Claude.exe, ExceptionCode=0x80000003 / STATUS_BREAKPOINT, offset 0x6dd36f9 in the main image) within ~2 seconds of calling the embedded browser 2Claude Browser" MCP tool / preview_start, which runs inside the Cowork Full VM Sandbox) - even though the tool call itself reports success (navOk: true, "Browser pane opened").

Steps to reproduce

1. On Windows 11 with Hyper-V enabled and working, open a task in Claude de.
2. Call the embedded "Claude Browser" preview tool on any URL (preview_start).
3. The tool call succeeds and returns navOk: true with a browser pane opened.
4. ~2 seconds later the app process crashes. cowork-service.log shows Persistent RPC: connection ended: failed to read length: EOF at the same timestamp as the crash dump.

What we ruled out

• Missing Hyper-V (vmcompute.dll not found): enabled Hyper-V, confirmed vmcompute.dll loaded successfully in cowork-service.log and a working vEthernet (Default Switch) adapter. Crash still occurs, same exception code and offset.

-tration: fully uninstalled and reinstalled the app. Crash still occurs, same exception code and offset.

• Both crashes (days apart, before/after the Hyper-V fix and the reinstall) landed at the exact same code location, and both times the immediately preceding action in the session log was a call to the embe

Crash details

• ExceptionCode: 0x80000003 (STATUS_BREAKPOINT - looks like a deliberate CHECK()/assert failure, not memory corruption)
• Faulting module: Claude.exe
• Offs Reproduced identically across two separate crash dumps.

Happy to share the .dmp files or additional logs if useful.