New thread investigating 20-concurrent call teardowns at fixed 126s.
### Findings So Far:
- sip_guardian: NO 126s timer (only 5s/10min timers found)
- DialogManager: 10-min TTL, read-only tracking (doesn't close conns)
- caddy-l4 proxy: NO explicit SetDeadline/timeout in proxy or dial code
- No connection pools, goroutine limits, or concurrency-triggered teardowns
### Symptom Profile:
- Dead-consistent 126s (not jittery) = hard-coded timer
- Load-dependent (20-concurrent yes, 1-concurrent survives 150s+)
- Treatment-independent (Echo = Wait both die)
- Survives conntrack bump to 1800s on both hosts
- TCP transport from Twilio
### Next Investigation:
Need to check for:
1. Go net package TCP KeepAlive defaults
2. Asterisk PJSIP TCP transport settings
3. Whether this is an upstream (carrier or Twilio) timer
Recommending bypass test (direct proxy without sip_guardian) to isolate
whether it's caddy-l4 itself or something in our handler chain.
See: docs/agent-threads/proxy-association-timer-126s/001-*
Ryan Malloy
7fc037ec4a