diff --git a/crates/g3-core/src/lib.rs b/crates/g3-core/src/lib.rs
index 6ff44f1..7e0a8a5 100644
--- a/crates/g3-core/src/lib.rs
+++ b/crates/g3-core/src/lib.rs
@@ -4550,20 +4550,20 @@ impl<W: UiWriter> Agent<W> {
                         }
                         
                         // Add any text response to context before prompting for continuation
-                        if has_response {
-                            let response_text = if !current_response.is_empty() {
-                                current_response.clone()
-                            } else {
-                                full_response.clone()
-                            };
-                            if !response_text.trim().is_empty() {
-                                let assistant_msg = Message::new(
-                                    MessageRole::Assistant,
-                                    response_text.trim().to_string(),
-                                );
-                                self.context_window.add_message(assistant_msg);
-                            }
-                        }
+                        // IMPORTANT: We must always add an assistant message to maintain User/Assistant alternation
+                        // Without this, consecutive User messages confuse the LLM and cause empty responses
+                        let response_text = if !current_response.is_empty() {
+                            current_response.clone()
+                        } else if !full_response.is_empty() {
+                            full_response.clone()
+                        } else {
+                            "[empty response]".to_string()
+                        };
+                        let assistant_msg = Message::new(
+                            MessageRole::Assistant,
+                            if response_text.trim().is_empty() { "[empty response]".to_string() } else { response_text.trim().to_string() },
+                        );
+                        self.context_window.add_message(assistant_msg);
                         
                         // Add a follow-up message asking for continuation
                         let continue_prompt = if has_incomplete_tool_call {