[BUG] Extension install downloads but never completes/registers — silent failure on Windows

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?

When installing any extension (e.g. Filesystem) from the Connectors directory in the Claude Code desktop app on Windows, the extension package is downloaded successfully but the installation never completes. The UI shows no error, no confirmation, and no success — it simply closes and the extension does not appear as installed. Multiple install attempts each create a new dxt-install-* folder in AppData but none are registered.

What Should Happen?

After clicking Install, the extension should be installed, registered in the app, and appear as active/manageable in the Connectors UI with toggle on/off controls.

Error Messages/Logs

From C:\Users\HP\AppData\Roaming\Claude\logs\main.log:

[info] [download:2] Starting download from https://claude.ai/api/organizations/.../dxt/extensions/ant.dir.ant.anthropic.filesystem/download
[warn] Installing unsigned extension from C:\Users\HP\AppData\Local\Temp\dxt-download-1781354984207.mcpb

No further log entries — process ends silently with no success or error.

9 failed install attempts found in:
C:\Users\HP\AppData\Roaming\Claude\dxt-install-7oJE6U\package.mcpb
C:\Users\HP\AppData\Roaming\Claude\dxt-install-CFaEhe\package.mcpb
... (7 more)

Steps to Reproduce

1. Open Claude Code desktop app on Windows 11
2. Go to Connectors directory
3. Select any extension (e.g. Filesystem)
4. Click Install
5. Observe: no popup, no confirmation, no error — UI closes silently
6. Extension does not appear as installed or manageable
7. Check AppData\Roaming\Claude — a new dxt-install-* folder is created with package.mcpb inside but never registered

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

cant remember

Claude Code Version

1.12603.1

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

The extension works correctly when added manually to claude_desktop_config.json — confirming the underlying MCP server (@modelcontextprotocol/server-filesystem) is functional. The bug is isolated to the UI install/registration flow in the desktop app on Windows.