Cowork plugin install fails with HTTP 404: Failed to fetch browsable plugins

Description

Installing plugins from the Cowork UI consistently fails with the error "Failed to install plugin." The underlying error in the logs is:

Error: Failed to fetch browsable plugins (HTTP 404)

Steps to Reproduce

1. Open Claude Desktop app (v1.1.3541)
2. Go to the Cowork tab
3. Try to install any plugin (e.g., enterprise-search from knowledge-work-plugins)
4. Installation fails immediately with "Failed to install plugin."

Error Details

From ~/Library/Logs/Claude/claude.ai-web.log:

[REACT_QUERY_CLIENT] QueryClient error: Error: Error invoking remote method 
'$eipc_message$..._$_CustomPlugins_$_installPlugin': 
Error: Failed to fetch browsable plugins (HTTP 404)

This error occurs every time installPlugin is called. The HTTP 404 suggests the server-side API endpoint for browsable plugins is not found.

Environment

• macOS: Darwin 24.6.0 (Apple Silicon)
• Claude Desktop: v1.1.3541
• Claude Code CLI: v2.1.47
• VM kernel: Ubuntu 22.04 with kernel 6.8.0-94-generic on Apple Virtualization

Additional Context

• The VM itself boots and runs fine — plugin marketplace list, plugin list --available, and plugin marketplace update all succeed with exit code 0 inside the VM
• The error happens at the Electron/UI layer before reaching the VM
• The marketplace (knowledge-work-plugins from anthropics/knowledge-work-plugins) is properly configured and the plugin can be installed via CLI (claude plugin install enterprise-search@knowledge-work-plugins)
• The issue persists across fresh VM recreations and clean ~/.claude directories
• The error has been occurring consistently since at least 2026-02-19 12:51

Additional note: Kernel panics in VM (separate issue)

Prior to recreating the VM, the Cowork VM was also experiencing repeated kernel panics when spawning plugin processes. The crash occurred in xt_net_init (x_tables/iptables module) triggered by bwrap (bubblewrap sandbox) creating network namespaces, leading to cascading NULL pointer dereferences and full kernel panics (Attempted to kill init!). Recreating the VM (deleting claudevm.bundle) resolved the kernel panic issue, but the HTTP 404 error persists independently.