[BUG] MCPB extraction fails with "undefined is not an object (evaluating 'H.length')" for valid zip files (tooluniverse@life-sciences)

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?

Claude Code's internal zip library fails to extract valid MCPB plugin bundles. The tooluniverse@life-sciences plugin downloads successfully but extraction crashes with a JavaScript error in the minified unzip code. The plugin MCP server never starts.

The MCPB file is valid - manual extraction works fine and the MCP server runs correctly when launched directly.

What Should Happen?

Claude Code should successfully extract the MCPB archive and start the plugin's MCP server.

Error Messages/Logs

2026-01-14T16:30:34.357Z [ERROR] Failed to load MCPB https://github.com/mims-harvard/ToolUniverse/releases/download/mcpb/tooluniverse.mcpb: Failed to read or unzip file: Failed to unzip file: undefined is not an object (evaluating 'H.length')

  2026-01-14T16:30:34.442Z [ERROR] Error: Error: Plugin MCP server error - mcpb-extract-failed: Failed to extract MCPB https://github.com/mims-harvard/ToolUniverse/releases/download/mcpb/tooluniverse.mcpb: Failed to read or unzip file: Failed to unzip file: undefined is not an object (evaluating 'H.length')

Steps to Reproduce

1. Install the tooluniverse plugin from the life-sciences marketplace
2. Enable it in settings.json: "tooluniverse@life-sciences": true
3. Start Claude Code
4. Run claude mcp list - tooluniverse is not connected
5. Check debug logs in ~/.claude/debug/ - extraction error appears

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.7

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_