diff --git a/cylc/uiserver/resolvers.py b/cylc/uiserver/resolvers.py
index 0633e83e..3e8251da 100644
--- a/cylc/uiserver/resolvers.py
+++ b/cylc/uiserver/resolvers.py
@@ -339,8 +339,6 @@ async def play(cls, workflows, args, workflows_mgr, log):
                     )
                     raise Exception(
                         msg
-                        # include possible traceback in debug mode
-                        + (f' - {err}' if DEBUG else '')
                     )
 
             except Exception as exc: