agentic-mobile-control/openspec/changes/archive/2026-07-06-cloud-runtime/specs/device-pool/spec.md

ADDED Requirements

Requirement: Host registration and heartbeat sync

The system SHALL provide a DevicePool that tracks a HostRegistration (host id, address, last-seen timestamp) for each host process that registers itself, and SHALL update a host's last-seen timestamp whenever that host pushes a device snapshot via sync_host_devices(host_id, snapshot).

Scenario: New host registers and syncs devices

• WHEN a previously-unknown host_id calls sync_host_devices with a list of devices
• THEN the pool creates a new HostRegistration for that host, records the current time as its last-seen timestamp, and stores each synced device as a PooledDevice owned by that host

Scenario: Known host re-syncs

• WHEN an already-registered host_id calls sync_host_devices again with an updated device snapshot
• THEN the pool updates that host's last-seen timestamp and replaces its previously-stored PooledDevice records with the new snapshot, without duplicating or losing devices from other hosts

Requirement: Aggregated device listing across hosts

The system SHALL provide a way to list all PooledDevice records across every registered host, including each device's owning host_id, driver_type, status, and capability tags.

Scenario: Listing devices across multiple hosts

• WHEN two hosts have each synced a non-empty device snapshot
• THEN a caller listing pool devices sees devices from both hosts in one combined result, each tagged with its correct host_id

Scenario: No hosts registered

• WHEN a caller lists pool devices before any host has ever synced
• THEN the pool returns an empty list rather than raising an error

Requirement: Stale host devices degrade to unreachable

The system SHALL mark all PooledDevices belonging to a host unreachable once that host's last-seen timestamp exceeds a configured staleness threshold, computed at read time, without requiring any background process and without raising an error for the stale host's absence.

Scenario: Host misses its sync interval

• WHEN a host's last-seen timestamp is older than config.stale_after_seconds at the time of a list_devices()/get_device() call
• THEN every PooledDevice owned by that host is reported with status unreachable, regardless of the status value in its last-synced snapshot

Scenario: Host resumes syncing after being stale

• WHEN a host previously marked stale calls sync_host_devices again
• THEN its devices immediately stop being reported unreachable and reflect the statuses in the new snapshot

Requirement: Device lookup by id across the pool

The system SHALL allow looking up a single PooledDevice by device_id regardless of which host owns it, returning a clear not-found result when no host has ever reported that device id.

Scenario: Lookup finds device on any host

• WHEN a caller requests a device by id that exists in some host's synced snapshot
• THEN the pool returns that PooledDevice including its owning host_id

Scenario: Lookup for unknown device id

• WHEN a caller requests a device by id that no host has ever synced
• THEN the pool returns a not-found result (e.g. None) rather than raising an unhandled exception