diff --git a/loop/agent.go b/loop/agent.go
index 910b4cc..f5b12f7 100644
--- a/loop/agent.go
+++ b/loop/agent.go
@@ -985,7 +985,7 @@
 		}
 	}()
 
-	// Main response loop - continue as long as the model is using tools
+	// Main response loop - continue as long as the model is using tools or a tool use fails.
 	resp := initialResp
 	for {
 		// Check if we are over budget
@@ -1009,6 +1009,10 @@
 			return nil
 		}
 
+		if toolResp == nil {
+			return fmt.Errorf("cannot continue conversation with a nil tool response")
+		}
+
 		// Set the response for the next iteration
 		resp = toolResp
 	}