feat(memory): support ephemeral gateway recall context

app-instance/backend/beaver/engine/context/builder.py

@@ -112,6 +112,7 @@ class ContextBuildInput:
     current_user_input: str | list[dict[str, Any]] | None = None
     memory_snapshot: MemorySnapshot | None = None
     activated_skills: list[SkillContext] = field(default_factory=list)
+    reference_messages: list[dict[str, Any]] = field(default_factory=list)
     session_context: SessionContext | None = None
     runtime_context: RuntimeContext | None = None
     execution_context: str | None = None
@@ -221,6 +222,11 @@ class ContextBuilder:
 
         messages.extend(self.build_skill_activation_messages(build_input.activated_skills))
 
+        for message in build_input.reference_messages:
+            if message.get("role") == "system":
+                continue
+            messages.append(self._provider_history_message(message))
+
         for message in build_input.history:
             # 当前 builder 自己负责生成唯一的 system prompt。
             # 如果上游 history 已经混入 system 消息，这里要主动跳过，避免双 system。

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"},
+    ]