diff --git a/apps/agent-runtime/src/domain/errors.py b/apps/agent-runtime/src/domain/errors.py
index fb2cc69..db6a88f 100644
--- a/apps/agent-runtime/src/domain/errors.py
+++ b/apps/agent-runtime/src/domain/errors.py
@@ -3,7 +3,7 @@
 from __future__ import annotations
 
 
-class DomainError(Exception):
+class DomainError(exception):
     """Base class for all domain errors."""