# Phase 23 — Query Plan History and Comparison

Adds locally saved EXPLAIN snapshots (Table or JSON), history scoped to the same connection name, database, and SQL statement, baseline comparison, and deletion. Table-plan comparison includes a sum of optimizer-estimated rows across steps, not measured execution times. Snapshots are stored in UserDefaults (max 40, max encoded size 2 MB).

The existing EXPLAIN inspector and query plan observations remain unchanged. No SQL statements are executed beyond EXPLAIN.

**Validation:** Source changes and archive structure inspected; no macOS/Xcode build or live MySQL tests performed.