[BUG] Sequential MCP tool calls hang indefinitely on second call (regression in 2.1.78)

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?

Version: 2.1.78
Platform: Linux (Ubuntu 22.04)
Model: Opus 4.6 (1M context) · Claude Max

What's wrong:
Multiple sequential MCP tool calls hang indefinitely on the second call.
The first MCP call completes successfully, but the second one shows
"Running..." and never returns a response.

This is a regression — worked fine in previous versions (confirmed
working yesterday with the same workflow).

What Should Happen?

Both MCP calls complete and Claude returns a response

Error Messages/Logs

Steps to Reproduce

1. Send a prompt that requires 2+ sequential Graylog MCP calls
2. First call completes (returns results)
3. Second call shows "Running..." and hangs indefinitely with no output

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.78

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Other

Additional Information

_No response_