Give an external consumer (NAS) a trustworthy, always-reachable busy/idle
readout it can poll before a disruptive lifecycle action (restart,
migrate, stop, auto-update). The dashboard /api/status is the only HTTP
surface guaranteed up on a hosted agent regardless of which gateway
platforms are enabled, and it already reads gateway_state.json.
Add to /api/status (additive, non-breaking):
- active_agents — in-flight gateway-turn count (now refreshed
per-turn by the companion gateway-side commit)
- gateway_busy — running AND active_agents > 0
- gateway_drainable — running and live (a valid begin-drain target)
- restart_drain_timeout — resolved seconds, so the consumer can size its
poll deadline without out-of-band knowledge
(env HERMES_RESTART_DRAIN_TIMEOUT → config
agent.restart_drain_timeout → default)
The busy/drainable contract is defined once in gateway.status
(derive_gateway_busy / derive_gateway_drainable) and consumed by both
/api/status and /health/detailed so the two surfaces can never disagree.
Liveness keys off gateway_running (a live PID/health probe), NEVER
gateway_updated_at — a healthy idle gateway never advances that timestamp.
All derived fields degrade to safe falsy values when the gateway is down
or the status file is absent/corrupt (never a spurious "busy" that would
wedge the consumer). active_sessions (the 5-min DB recency heuristic the
SPA reads) is left exactly as-is — new signal, new fields.
Tests (behaviour contracts, not snapshots): the pure derivation contract
across every running/state/count/liveness combination; /api/status
integration for busy, idle-drainable, draining, down, stale-busy-file,
corrupt-count, and timeout surfacing; and /health/detailed parity.
0ee75469d7