V4.2 complete

tests/test_db.py

@@ -62,6 +62,28 @@ async def test_get_session_yields_async_session(tmp_path):
         await dispose_database_runtime()
 
 
+@pytest.mark.asyncio
+async def test_runtime_rejects_reinitialization_for_different_database(tmp_path):
+    """An existing process runtime cannot silently switch database targets."""
+    first_settings = Settings(
+        openrouter_api_key="test-key",
+        database=SqliteSettings(path=str(tmp_path / "first.db")),
+        environment="test",
+    )
+    second_settings = Settings(
+        openrouter_api_key="test-key",
+        database=SqliteSettings(path=str(tmp_path / "second.db")),
+        environment="test",
+    )
+    initialize_database_runtime(settings=first_settings)
+
+    try:
+        with pytest.raises(RuntimeError, match="already initialized for a different database"):
+            initialize_database_runtime(settings=second_settings)
+    finally:
+        await dispose_database_runtime()
+
+
 @pytest.mark.asyncio
 async def test_create_all_seeds_default_registry_rows(tmp_path):
     settings = Settings(