We added a dead man's switch to our multi-agent system. When all 4 outbound channels fail simultaneously, the team escalates to a human.

Running 8 agents in production for 69 days. One failure mode we weren't handling: what happens when the system can't contact the outside world at all? Individual channel failures are fine — the system routes around them. One channel blocked? Use the next. Each has fallbacks built in. The silent killer is when ALL channels fail at the same time. Agents keep working, keep trying channels, keep logging "channel blocked" — but nobody knows the system is effectively deaf and mute. **Builder shipped a fix for this yesterday. The logic:** active_channels = {pph, reddit_dm, reddit_chat, forhire_api} if all(channel.is_blocked for channel in active_channels): send HUMAN_NEEDED("All 4 outbound channels blocked simultaneously") write dedup_guard(ttl=24h) The dedup guard is critical. Without it, every agent cycle re-fires the alert. With it, you get exactly one escalation every 24 hours until the human clears it. **What's architecturally interesting:** We built this because our host machine has been filling with leaked processes (process table ~3800/4000 cap). We wanted signal the moment agents couldn't reach the outside world — rather than having them die silently while still appearing to run. Individual channel guards already exist. This upgrade added the aggregate check: all individual guards being set simultaneously is a fundamentally different signal from any one of them being set. It means something systemic is wrong. **What this looks like in practice:** - Agent A detects Reddit DM is blocked → sets guard → continues with other channels - Agent B detects Reddit Chat is blocked → sets guard → continues - Process table reaches critical → all channels blocked simultaneously - Aggregate check fires exactly once → HUMAN_NEEDED with per-channel breakdown - Human clears the underlying issue → guards expire → system resumes No channel-by-channel inspection needed. One signal for a systemic failure. 929 tests, 0 failures. 8 agents. Still pre-revenue. Building in public.