Skip empty memory summaries in context window

src/memory.py

@@ -366,12 +366,16 @@ def get_context_window(
             ):
                 self._save_summary_state()
 
-        summary_message = {
-            "role": "system",
-            "content": f"Previous Summary: {self.summary or '[none]'}",
-        }
-
-        return [system_message, summary_message, *recent_history]
+        summary_message = None
+        if self.summary:
+            summary_message = {
+                "role": "system",
+                "content": f"Previous Summary: {self.summary}"
+            }
+
+        if summary_message:
+            return [system_message, summary_message, *recent_history]
+        return [system_message, *recent_history]
 
     def clear_memory(self) -> None:
         """Clear history and summary state."""

tests/test_memory.py

@@ -45,10 +45,29 @@ def summarizer(old_msgs, prev_summary):
     assert window[-1]["content"] == "msg 3"
 
 
-def test_non_markdown_memory_file_results_in_empty_history(tmp_path):
-    memory_file = tmp_path / "memory.md"
-    summary_file = tmp_path / "summary.md"
-    memory_file.write_text('{"role":"user","content":"legacy"}', encoding="utf-8")
+def test_context_window_skips_empty_summary_message(tmp_path):
+    memory_file = tmp_path / "memory.json"
+    manager = MemoryManager(memory_file=str(memory_file))
+
+    for i in range(3):
+        manager.add_entry("user", f"msg {i}")
+
+    def summarizer(_old_msgs, _prev_summary):
+        return ""
+
+    window = manager.get_context_window("SYS", max_messages=1, summarizer=summarizer)
+
+    assert window[0]["role"] == "system"
+    assert window[0]["content"] == "SYS"
+    assert len(window) == 2  # system prompt + 1 recent message
+    assert manager.summary == ""
+
+
+def test_loads_legacy_memory_format(tmp_path):
+    legacy_file = tmp_path / "legacy.json"
+    legacy_payload = [{"role": "user", "content": "legacy hi", "metadata": {}}]
+    with open(legacy_file, "w", encoding="utf-8") as f:
+        json.dump(legacy_payload, f)
 
     manager = MemoryManager(
         memory_file=str(memory_file),