diff --git a/core/models.py b/core/models.py
index b21b1af..8cc5018 100644
--- a/core/models.py
+++ b/core/models.py
@@ -11,10 +11,10 @@ from datetime import datetime
 from typing import Any
 
 
-VALID_TASK_STATUSES = [
+VALID_TASK_STATUSES = frozenset({
     "pending", "in_progress", "review", "done",
     "blocked", "decomposed", "cancelled", "revising",
-]
+})
 
 VALID_COMPLETION_MODES = {"auto_complete", "review"}