feat: add schema drift handling and rebuild

backend/db/__init__.py

@@ -4,6 +4,7 @@ from __future__ import annotations
 import os
 import sqlite3
 import threading
+import logging
 from pathlib import Path
 from typing import Any
 
@@ -42,6 +43,21 @@ def get_connection(db_path: str | None = None) -> sqlite3.Connection:
             _current_path = db_path
         return _conn
 
+def _has_schema_version(conn: sqlite3.Connection) -> bool:
+    try:
+        conn.execute("SELECT 1 FROM schema_version").fetchone()
+        return True
+    except sqlite3.OperationalError:
+        return False
+
+def _has_settings_value_column(conn: sqlite3.Connection) -> bool:
+    try:
+        info = conn.execute("PRAGMA table_info(settings)").fetchall()
+        columns = {row[1]: row[2] for row in info}
+        return 'value' in columns
+    except sqlite3.OperationalError:
+        return False
+
 
 def init_db(db_path: str | None = None) -> sqlite3.Connection:
     conn = get_connection(db_path)
@@ -53,6 +69,15 @@ def init_db(db_path: str | None = None) -> sqlite3.Connection:
     with _lock:
         conn.executescript(schema)
         conn.commit()
+    if not _has_schema_version(conn):
+        if not _has_settings_value_column(conn):
+            logger = logging.getLogger("slab.db")
+            logger.info("Detected pre-M3 DB, rebuilding schema")
+            conn.executescript("DROP TABLE IF EXISTS settings")
+            conn.executescript(schema)
+conn.commit()
+            conn.execute("INSERT OR REPLACE INTO schema_version (version) VALUES (1)")
+
     return conn
 
 

backend/db/schema.sql

@@ -111,6 +111,8 @@ CREATE TABLE IF NOT EXISTS settings (
     value_enc TEXT
 );
 
+CREATE TABLE IF NOT EXISTS schema_version (version INTEGER PRIMARY KEY);
+
 -- 7. prompts + prompt_revisions (append-only revisions)
 CREATE TABLE IF NOT EXISTS prompts (
     id INTEGER PRIMARY KEY,