The PostgreSQL Health Diagnostics Agent performs comprehensive database health checks by querying PostgreSQL system catalogs and statistics views. It connects via libpq protocol and inspects pg_stat_activity to identify long-running queries, blocked sessions, and connection pool saturation. The agent analyzes query performance through pg_stat_statements, ranking queries by total_exec_time, calls, and mean_exec_time to surface optimization candidates. It checks index health via pg_stat_user_indexes to find unused indexes consuming disk space and missing indexes indicated by sequential scan ratios in pg_stat_user_tables. Table bloat is estimated by comparing pg_class.relpages against actual row counts, while vacuum health is monitored through last_autovacuum and n_dead_tup columns in pg_stat_all_tables. Lock contention analysis uses pg_locks joined with pg_stat_activity to identify blocking chains. The diagnostics agent also checks replication lag via pg_stat_replication, validates WAL archiving status, and monitors tablespace usage for capacity planning.