[BUG] Claude Desktop Windows: CustomPlugins listAvailablePlugins fails schema validation (v1.1.6679)

Bug Description

After a fresh install of Claude Desktop on Windows 11, the plugin marketplace fails to load. The listAvailablePlugins method in the CustomPlugins IPC interface consistently fails schema validation, preventing the integrations/plugins panel from rendering.

Error Message

[REACT_QUERY_CLIENT] QueryClient error: Error: Error invoking remote method '$eipc_message$_3db1afa4-a79f-4598-ad1e-dc19b92f6285_$_claude.web_$_CustomPlugins_$_listAvailablePlugins': Error: Result from method "listAvailablePlugins" in interface "CustomPlugins" failed to pass validation

Additional Errors in Logs

1. CSP blocking Anthropic API endpoint:

``
Connecting to 'https://a-api.anthropic.com/v1/m' violates the following Content Security Policy directive: "connect-src 'self' https://api.segment.io https://*.segment.io ..."
``

1. MCP registry returns 0 servers (even after successful login):

``
[MCP] Unified registry fetch succeeded but returned 0 servers
``

1. Google Drive connection failure:

``
[REACT_QUERY_CLIENT] QueryClient error: Error: Failed to connect to Google Drive
``

Environment

• OS: Windows 11 Education 10.0.26200
• Claude Desktop Version: 1.1.6679.0 (MSIX, installed from claude.ai website)
• Claude Code (CCD): 2.1.74
• Node Version: 24.13.0
• Architecture: x64
• Install method: Downloaded from https://claude.ai/download (not Microsoft Store)

Steps to Reproduce

1. Install Claude Desktop v1.1.6679 on Windows 11 from the claude.ai download page
2. Log in successfully
3. Open the Integrations/Plugins panel
4. Observe white/blank screen or error — plugin list fails to load

What Works

• Login and account authentication ✅
• Claude Code binary download and installation (v2.1.74) ✅
• Skills plugin sync (14 skills downloaded) ✅
• OAuth token caching ✅
• Marketplace plugin metadata generation in main process ✅

What Doesn't Work

• listAvailablePlugins IPC call fails validation in renderer ❌
• Plugin marketplace UI does not render ❌
• CSP blocks a-api.anthropic.com connections ❌

Relevant Log Excerpts

main.log (main process — plugins load fine here):

[CCDMarketplacePluginManagerCLI] Marketplace refreshed: claude-plugins-official
[SkillsPlugin] Sync complete: 14 downloaded, 0 removed, 0 orphans cleaned
[CCD] Status: ready (version: 2.1.74)

unknown-window.log (renderer — fails here):

[REACT_QUERY_CLIENT] QueryClient error: Error: Error invoking remote method '..._CustomPlugins_$_listAvailablePlugins': Error: Result from method "listAvailablePlugins" in interface "CustomPlugins" failed to pass validation

This suggests the main process successfully fetches plugin data, but the IPC response fails schema validation when passed to the renderer process.

Installation History

Initial install encountered HRESULT: 0x80073CF6 (package registration failure with sub-error 0x80073D05). Resolved after PC reboot and reinstall. The listAvailablePlugins issue persists on the clean reinstall.

Related Issues

• #24328 (similar validation error with getPlugins in LocalPlugins)
• #30717 (listAvailablePlugins checksum verification failure on macOS)
• #29428 (VM service / CustomPlugins errors on Windows)