preview_screenshot MCP tool hangs session on Windows (works fine on macOS) #30122

Description

When using Claude Code (v2.1.63) on Windows 11 via Claude Desktop, calling preview_screenshot (and occasionally other preview MCP tools) causes the entire session to become non-responsive. The session never recovers — I have to kill and restart every time.

This never happens on macOS with the same Claude Code version and same projects. It's 100% reproducible on Windows.

Environment

• Claude Code version: 2.1.63
• OS: Windows 11 Pro 10.0.26200
• Client: Claude Desktop app
• Shell: Git Bash
• Affected tools: Primarily preview_screenshot, occasionally preview_snapshot

Steps to reproduce

1. Open any project in Claude Code on Windows via Claude Desktop
2. Start a dev server with preview_start
3. Make a code change and ask Claude to verify it visually
4. Claude calls preview_screenshot — session hangs indefinitely
5. Must kill and restart the session

Expected behavior

preview_screenshot should return the screenshot data (or timeout gracefully with an error) as it does on macOS.

Actual behavior

The session becomes completely non-responsive. No timeout, no error — just an indefinite hang. The only recovery is killing the session.

Workaround

Instructing Claude (via CLAUDE.md) to avoid preview_screenshot and use text-based alternatives (preview_snapshot, preview_inspect) instead. These text-based tools work reliably on Windows.

Analysis

This appears to be related to large binary data transfer over the MCP connection on Windows. preview_screenshot returns image data which is significantly larger than the text-based tools. Windows subprocess/IPC communication seems to handle this payload size poorly compared to macOS.

Possibly related issues:

• [FEATURE] Make MCP Tool Execution Timeout Configurable in Claude Desktop #22542 (MCP tool execution timeout not configurable in Desktop)
• [BUG] Claude becomes permanently unresponsive when processing invalid/malformed image data from screenshot tool #26126 (unresponsive processing invalid image data)
• [CRITICAL] MCP Server Causes 16+ Hour Hang - No Timeout or Stuck Detection #15945 (MCP server causes long hang)