CLI freezes daily: silent TCP drop leaves process in kevent64 with zero API connections (macOS, university network)

Summary

Claude Code CLI often keeps spinning for an hour without any progress (no token exchanged etc)

Related: #26224, #33949, #37534, #32116

Environment

• macOS 26.3.1, ARM64 (Mac Studio)
• Claude Code v2.1.92
• University network with dynamic IP (DHCP/NAT): dyn-*.dyn.columbia.edu
• MCP servers: claude-in-chrome, google_workspace

Diagnosis

Captured diagnostics from a frozen session (PID 73304) while a working session (PID 83840) ran on the same machine.

The frozen process has zero TCP connections — the API connection silently dropped:

# Frozen process — no network connections
$ lsof -p 73304 -i TCP | grep "^2.1"
(empty)

Process sampling (10s, 1ms interval) shows 94% of time in kevent64 — idle-waiting for I/O that will never arrive on a dead connection.

The freeze occurred during a subagent API call ("Cerebrating… 55m 30s").

Likely mechanism

1. Session is mid-API-call
2. Network reassigns IP or NAT entry expires
3. TCP connection silently drops (no RST/FIN)
4. No request timeout or TCP keepalive detects the dead connection
5. Process waits forever

🤖 Generated with Claude Code