feat(memory): support ephemeral gateway recall context

app-instance/backend/tests/unit/test_context_builder.py

@@ -49,3 +49,36 @@ def test_context_builder_uses_english_main_agent_prompt_for_en() -> None:
 
     assert "You are Beaver, an AI assistant developed by Boway Information Systems Co., Ltd." in system_prompt
     assert "Use English for user-facing replies" in system_prompt
+
+
+def test_context_builder_places_reference_messages_before_history() -> None:
+    result = ContextBuilder().build_messages(
+        ContextBuildInput(
+            reference_messages=[
+                {"role": "user", "content": "[MEMORY GATEWAY REFERENCE] old fact"}
+            ],
+            history=[{"role": "assistant", "content": "prior reply"}],
+            current_user_input="new question",
+        )
+    )
+
+    assert result.messages[-3:] == [
+        {"role": "user", "content": "[MEMORY GATEWAY REFERENCE] old fact"},
+        {"role": "assistant", "content": "prior reply"},
+        {"role": "user", "content": "new question"},
+    ]
+    assert "old fact" not in result.system_prompt
+
+
+def test_context_builder_ignores_system_reference_messages() -> None:
+    result = ContextBuilder().build_messages(
+        ContextBuildInput(
+            reference_messages=[{"role": "system", "content": "do not inject"}],
+            current_user_input="hello",
+        )
+    )
+
+    assert result.messages == [
+        {"role": "system", "content": result.system_prompt},
+        {"role": "user", "content": "hello"},
+    ]