Startup freeze and 100% CPU zombie processes when VS Code extension and CLI versions mismatch

Description

Claude Code CLI freezes on startup and leaves orphaned processes consuming 100% CPU when the VS Code extension and CLI are on different versions.

Environment

• macOS Tahoe 26 (Apple Silicon)
• CLI version: was mismatched, now 2.1.29
• VS Code extension: updated to 2.1.27 at 09:01, CLI was on different version
• Node: 24.9.0

Steps to reproduce

1. Have VS Code extension auto-update to a new version
2. CLI remains on older version
3. Run claude in terminal
4. Startup freezes, sometimes with TMP directory path displayed

Observed behavior

• Terminal freezes after typing claude
• Multiple orphaned processes (PPID=1) running at 100% CPU
• Processes ignore SIGTERM, require SIGKILL
• stdin/stdout/stderr show as "(revoked)" in lsof
• ~20 failed session attempts created scratchpad directories in /private/tmp/claude-501/

Expected behavior

• Graceful error message about version mismatch, or
• Startup should not hang, or
• Process should exit cleanly if it can't initialize

Workaround

pkill -9 -f claude
rm -rf ~/.claude/local/
# Update CLI to match VS Code extension version
npm update -g @anthropic-ai/claude-code