PG_CONNECTION_SATURATION: a PostgreSQL pool near its ceiling is graded as the outage it is — the window's peak session count over max_connections − superuser_reserved_connections (the engine's own line, read off lane 2's context facts), zero below the unmeasured 0.8 band and 1.0 at 0.9, the peak capture's active / idle-in-transaction / other breakdown and both levers with their costs in the prose, and PG_MONITORING_PERMISSIONS instead of a ratio when the monitoring login could not see session state (#3542 lane 3) - #3677