agentic-mobile-control/openspec/changes/task-cancellation/specs/host-agent-protocol/spec.md

MODIFIED Requirements

Requirement: Active execution renews its lease

The Host Agent SHALL renew the active assignment lease before expiry while execution continues, and SHALL treat loss or rejection of the lease, or an observed cancellation request, as a stop condition for further planned actions where interruption is possible.

Scenario: Lease renewal succeeds

• WHEN the owning Host Agent renews an unexpired active lease
• THEN the control plane extends its expiry without changing the task attempt or device assignment

Scenario: Lease is stale or foreign

• WHEN a Host Agent attempts to renew an expired, replaced, or differently owned lease
• THEN the control plane returns a conflict and does not revive or alter the current attempt

Scenario: Renewal response signals a pending cancellation

• WHEN the control plane's renewal response for an active lease indicates a pending cancellation request
• THEN the Host Agent stops further planned actions at the next available step boundary, the same way it stops on lease loss

Requirement: Terminal result reporting is idempotent

The Host Agent SHALL report a terminal result using the task, attempt, and lease identifiers, and repeating the same report SHALL return the already recorded outcome without duplicating state transitions. The terminal result SHALL be done, failed, or cancelled.

Scenario: Report a successful result

• WHEN the active lease owner reports successful completion
• THEN the control plane marks the scheduled task done, releases the device reservation, and records the result metadata

Scenario: Report a cancelled result

• WHEN the active lease owner reports that its execution stopped because of an observed cancellation request
• THEN the control plane marks the scheduled task cancelled, releases the device reservation, and records the result metadata

Scenario: Retry a result after response loss

• WHEN the Host Agent repeats the identical terminal report for an already completed active lease
• THEN the control plane returns the recorded terminal result without creating a new attempt or error

Scenario: Stale attempt reports after requeue

• WHEN an expired earlier attempt reports after a newer attempt has been created
• THEN the control plane rejects the stale report and preserves the newer attempt's state

ADDED Requirements

Requirement: Host distinguishes cancellation stop from lease-loss stop when reporting outcome

The Host Agent SHALL track whether its active execution stopped because of an observed cancellation request or for another stop reason (lost or rejected lease), and SHALL report cancelled only in the cancellation case, reporting failed for other stop reasons.

Scenario: Stop triggered by cancellation

• WHEN the Host Agent's collaborative-stop mechanism is triggered by a renewal response signaling a pending cancellation
• THEN the terminal result it reports for that attempt is cancelled

Scenario: Stop triggered by lease loss

• WHEN the Host Agent's collaborative-stop mechanism is triggered by a rejected or lost lease unrelated to any cancellation signal
• THEN the terminal result it reports for that attempt is failed, not cancelled