diff --git a/agent/core/engine.py b/agent/core/engine.py
index 46b2288..8150321 100644
--- a/agent/core/engine.py
+++ b/agent/core/engine.py
@@ -177,6 +177,13 @@ def _execute_and_record_tool(self, name: str, args: dict, call_id: str):
         finally:
             stop_spinner()
 
+        # Validate result is not None before recording
+        if result is None:
+            err_msg = f"Tool {name} returned None (crash or unhandled exception)"
+            print(error(f"  {err_msg}"))
+            self.conversation.add_tool_result(call_id, name, err_msg)
+            return
+
         # Display result
         print(f"  {format_tool_result(name, result)}")