Hosts that accumulate 3 TLS handshake failures within 10 minutes are automatically switched to passthrough (no MITM) for 1 hour. After the TTL expires, a single failure re-trips immediately to avoid repeated breakage for the user. A successful MITM handshake clears all state. Portal host and IPs are excluded from the circuit breaker. Events are logged at warn level and visible in the activity feed. Works in both explicit and transparent proxy modes. In-memory only; resets on restart.