[BUG] Cowork browser fallback crashes app, leaves it unable to launch ("This app can't open") — recurs even after reinstall

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

While Claude Desktop was fetching a URL I provided and hit the site's bot detection, it said (paraphrasing) "I got blocked, let me try on the actual browser instead" — triggering Cowork's sandboxed browser fallback — and the app crashed/closed on its own without any action from me. On relaunch, Windows showed:

This app can't open. There's a problem with Claude. Reinstall the application from its original install location or contact your administrator.

This happened 3 times in a row. Standard fixes (Advanced options > Repair, Advanced options > Reset, manually stopping/reconfiguring the CoworkVMService, killing lingering claude/Cowork/Anthropic* processes via PowerShell, re-registering the package via Add-AppxPackage -Register) did not resolve it. Only a full clean removal (Get-AppxPackage -Name "Claude" -AllUsers | Remove-AppxPackage -AllUsers) followed by a reboot followed by a fresh install from claude.ai/download resolved the immediate launch failure — but does not address the underlying trigger, which can recur with any site that forces the same browser fallback.

What Should Happen?

Claude Desktop should not crash outright when a web fetch is blocked and it falls back to the Cowork browser.
If a crash does occur, it should not leave the MSIX package in a state where the app can't relaunch — the "This app can't open, reinstall" screen is a disproportionate failure mode for what should be a recoverable in-app error.
Ideally: an in-app way to fully reset Cowork's state after a crash without requiring OS-level PowerShell intervention or reinstalling (related to the ask in #57371).

Error Messages/Logs

Steps to Reproduce

Open Claude Desktop, start a chat.
Ask Claude to check a URL from a site with bot/scraper detection (in my case, playmakerstats.com — any site returning a bot-block on direct fetch should reproduce this).
Claude's fetch gets blocked, and it attempts to fall back to loading the page in Cowork's sandboxed browser.
App crashes/closes unexpectedly during this fallback, with no user action taken.
On relaunch: Windows shows "This app can't open... Reinstall the application from its original install location."

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

1.32352.1.0

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

`Get-AppxPackage -Name "Claude" -AllUsers | Remove-AppxPackage -AllUsers

reboot

then reinstall from claude.ai/download`

This restored launch capability, but does not fix the underlying trigger — repeating the same URL-check that caused the original crash would likely reproduce the issue again, since the root cause (Cowork browser fallback interacting badly with CoworkVMService) is unresolved.