diff --git a/src/db.py b/src/db.py
index f4afe12..550a4c7 100644
--- a/src/db.py
+++ b/src/db.py
@@ -1696,6 +1696,18 @@ _V22_TO_V23_MIGRATIONS = [
 # migration time, log a warning per affected row and leave them — the
 # operator must configure data_source.bigquery.project, restart, and
 # the migration will fire on next start (idempotent).
+def _replace_for_v24(project_id: str):
+    """Build a re.sub replacement function (not a string) so backslash
+    sequences in `project_id` aren't interpreted as group references.
+    GCP project IDs can't actually contain backslashes, but using a
+    function-form replacement is the defensive idiom — it makes the
+    intent explicit and removes the dependency on re.sub's replacement-
+    string escaping rules."""
+    def _repl(m):
+        return f"`{project_id}.{m.group(1)}.{m.group(2)}`"
+    return _repl
+
+
 def _v23_to_v24_finalize(conn: duckdb.DuckDBPyConnection) -> None:
     import re as _re
 
@@ -1714,26 +1726,35 @@ def _v23_to_v24_finalize(conn: duckdb.DuckDBPyConnection) -> None:
         "AND source_type = 'bigquery'"
     ).fetchall()
 
-    for row_id, sq in rows:
-        if sq is None:
-            continue
-        if not project_id:
-            logger.warning(
-                "v24 migration: skipping rewrite of source_query for row %r — "
-                "data_source.bigquery.project is not configured. Set it via "
-                "/admin/server-config and restart the app to retry the "
-                "migration.", row_id,
-            )
-            continue
-        new_sq = pattern.sub(rf'`{project_id}.\1.\2`', sq)
-        if new_sq != sq:
-            conn.execute(
-                "UPDATE table_registry SET source_query = ? WHERE id = ?",
-                [new_sq, row_id],
-            )
-            logger.info(
-                "v24 migration: rewrote source_query for row %r", row_id,
-            )
+    if not rows:
+        return  # Nothing to migrate; skip the transaction.
+
+    conn.execute("BEGIN TRANSACTION")
+    try:
+        for row_id, sq in rows:
+            if sq is None:
+                continue
+            if not project_id:
+                logger.warning(
+                    "v24 migration: skipping rewrite of source_query for row %r — "
+                    "data_source.bigquery.project is not configured. Set it via "
+                    "/admin/server-config and restart the app to retry the "
+                    "migration.", row_id,
+                )
+                continue
+            new_sq = pattern.sub(_replace_for_v24(project_id), sq)
+            if new_sq != sq:
+                conn.execute(
+                    "UPDATE table_registry SET source_query = ? WHERE id = ?",
+                    [new_sq, row_id],
+                )
+                logger.info(
+                    "v24 migration: rewrote source_query for row %r", row_id,
+                )
+        conn.execute("COMMIT")
+    except Exception:
+        conn.execute("ROLLBACK")
+        raise
 
 
 def _ensure_schema(conn: duckdb.DuckDBPyConnection) -> None:
diff --git a/tests/test_schema_v24_source_query_rewrite.py b/tests/test_schema_v24_source_query_rewrite.py
index 9a56130..2f0f947 100644
--- a/tests/test_schema_v24_source_query_rewrite.py
+++ b/tests/test_schema_v24_source_query_rewrite.py
@@ -124,3 +124,36 @@ def test_v24_logs_warning_when_project_not_configured(monkeypatch, caplog):
             )
         finally:
             conn.close()
+
+
+def test_v24_keboola_materialized_row_not_rewritten(monkeypatch):
+    """Materialized rows with source_type != 'bigquery' must not be touched
+    by v24. Keboola materialized has no notion of bq."ds"."tbl" syntax;
+    the SELECT's source_type filter pins this contract.
+    """
+    with tempfile.TemporaryDirectory() as tmp:
+        monkeypatch.setenv("DATA_DIR", tmp)
+        monkeypatch.setattr(
+            "app.instance_config.get_value",
+            lambda *args, **kw: "prj-data" if args == ("data_source", "bigquery", "project") else kw.get("default"),
+        )
+        Path(tmp, "state").mkdir(parents=True, exist_ok=True)
+        db_path = Path(tmp, "state", "system.duckdb")
+        conn = duckdb.connect(str(db_path))
+        try:
+            _seed_v23(conn)
+            # Keboola row that happens to contain `bq."..."` in its SQL
+            # (admin error or copy-paste from a BQ row). Migration must
+            # leave it alone — this is not the v24 contract.
+            conn.execute(
+                'INSERT INTO table_registry VALUES (?, ?, ?, ?, ?, ?, ?)',
+                ["kb1", "kb1", "keboola", "materialized", "ds", "tbl",
+                 'SELECT * FROM bq."ds"."tbl"'],
+            )
+            _ensure_schema(conn)
+            row = conn.execute(
+                "SELECT source_query FROM table_registry WHERE id='kb1'"
+            ).fetchone()
+            assert row[0] == 'SELECT * FROM bq."ds"."tbl"'
+        finally:
+            conn.close()