Adds an opt-in dependency supervisor inside the Host Agent that probes,
spawns, and restarts the two local processes the macOS single-machine
real-device workflow depends on: the Appium server (gates Driver.connect())
and the local Runtime API (local inspection). Default-off; gated by
HOST_AGENT_DEPENDENCY_SUPERVISOR_ENABLED plus per-dependency *_SUPERVISED
flags.
Mitigates the live-incident failure mode where forgetting to start Appium
silently keeps devices offline and tasks queued forever with no error
surfaced in Host Agent logs.
Behavior (per openspec change):
- Adopt-don't-fight: probe (TCP + dependency-specific HTTP health check)
before spawn. Healthy listener → adopted (never killed/restarted).
Unhealthy listener → port-conflict error, skip. No listener → spawn.
- Only supervisor-spawned processes are restarted on crash, with capped
exponential backoff (1s/2s/4s/8s, capped at 30s) and a per-process-lifetime
attempt ceiling (HOST_AGENT_DEPENDENCY_RESTART_MAX_ATTEMPTS, default 5).
- Spawn failures (e.g. missing executable) logged distinctly from crashes.
- Graceful stop terminates only spawned children; adopted processes untouched.
- Supervisor starts before the heartbeat loop's first connect_devices() pass
and stops alongside existing heartbeat/console teardown.
Validation: ruff check + format clean, compileall clean, openspec validate
--strict valid. Non-integration suite 503 passed / 44 deselected / 2 failed
(both failures pre-existing from unrelated 03c7c30 LLM_PROVIDER_ENC_KEY;
verified by stashing this change). macOS real-device manual verification
(task 6.4) deferred to a macOS host.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
