diff --git a/workspace/executor_helpers.py b/workspace/executor_helpers.py
index 3343dee5..b594c159 100644
--- a/workspace/executor_helpers.py
+++ b/workspace/executor_helpers.py
@@ -620,7 +620,9 @@ def sanitize_agent_error(
         # a malicious or buggy peer injecting a huge error body, and
         # scrubs any API keys / bearer tokens that snuck into the message.
         detail = _sanitize_for_external(stderr[:_MAX_STDERR_PREVIEW])
-        return f"Agent error ({tag}): {detail}"
+        if category:
+            return f"Agent error ({tag}): {detail}"
+        return f"Agent error: {detail}"
     return f"Agent error ({tag}) — see workspace logs for details."