# Staleness & Drift Prep — PREP-AIRGAP-CTL-58-001-BLOCKED-ON-57-002

Status: Draft (2025-11-20)
Owners: AirGap Controller Guild · AirGap Time Guild
Scope: Capture the staleness/drift requirements for controller status once seal/unseal telemetry (57-002) is available.

## Inputs
- Time anchor ingestion from Time service (Roughtime/RFC3161) via `time_anchor_id`, `drift_seconds`, `staleness_budget_seconds`.
- Bundle metadata from importer (bundle_id, manifest hash, generated_at).

## Proposed status enrichments
- Add fields to `GET /system/airgap/status`:
  - `staleness_seconds_remaining`
  - `bundle_id`
  - `time_anchor_id`
  - `drift_seconds`
- Compute `staleness_seconds_remaining = staleness_budget_seconds - drift_seconds` (floor at 0).
- Determinism: calculations purely from stored numbers; no wall-clock calls beyond persisted anchor timestamps.

## Observability
- Metrics: `airgap_staleness_seconds{tenant}` (gauge), `airgap_drift_seconds{tenant}`.
- Timeline events emitted when budgets breached: `airgap.staleness.threshold`.

## Handoff
Use this prep note to satisfy PREP-AIRGAP-CTL-58-001. After integrating sealed-startup telemetry and time anchor verification, implement the above fields and metrics, then mark the implementation task DOING.