Claude Code hangs with high CPU after parallel Bash tool calls (unresponsive to SIGINT/SIGTERM)

Environment

• Claude Code version: 2.1.14
• OS: Linux 6.14.0-37-generic (Ubuntu)
• Session ID: 97042e0c-5555-40c1-8721-092f9edebfa4

Description

Claude Code became completely unresponsive after issuing parallel Bash tool calls. The process consumed 123% CPU continuously for 30+ minutes with no terminal output. The terminal became unusable (couldn't type), and the process ignored both SIGINT and SIGTERM signals - only SIGKILL terminated it.

This is the second time this hang has occurred.

Steps to Reproduce

1. Start Claude Code session with Playwright MCP server (npm exec @playwright/mcp@latest)
2. Work on a multi-step task involving file operations
3. Claude issues multiple parallel Bash commands (in this case: head and find)
4. Process hangs indefinitely

Last Successful Activity

• Timestamp: 2026-01-21T20:11:24Z
• Last tool calls issued (never received results):
• head -100 /tmp/claude/.../tholmes_ei4.sql
• find /home/scottstein -type d -name "3riversbca" 2>/dev/null
• Both commands complete in <1 second when run manually

Observed Behavior

• 16 tool_use calls in session log, only 14 tool_result entries
• CPU: 123%+ sustained
• State: Running (R) then Sleeping (S), but still high CPU
• Terminal: No output for 26+ minutes (last I/O at 14:11)
• Signals: SIGINT ignored, SIGTERM ignored, only SIGKILL worked
• 15 threads active, high context switch count

Expected Behavior

Tool calls should complete or timeout gracefully, and the process should respond to interrupt signals.

Additional Context

• Playwright MCP server was running as a child process
• The hang appears related to parallel tool execution
• No OOM or system-level errors in dmesg