feat: flush memory before summarization (#2176)

* feat: flush memory before summarization

* fix: keep agent-scoped memory on summarization flush

* fix: harden summarization hook plumbing

* fix: address summarization review feedback

* style: format memory middleware

backend/tests/test_lead_agent_model_resolution.py

@@ -8,6 +8,7 @@ import pytest
 
 from deerflow.agents.lead_agent import agent as lead_agent_module
 from deerflow.config.app_config import AppConfig
+from deerflow.config.memory_config import MemoryConfig
 from deerflow.config.model_config import ModelConfig
 from deerflow.config.sandbox_config import SandboxConfig
 from deerflow.config.summarization_config import SummarizationConfig
@@ -145,6 +146,7 @@ def test_create_summarization_middleware_uses_configured_model_alias(monkeypatch
         "get_summarization_config",
         lambda: SummarizationConfig(enabled=True, model_name="model-masswork"),
     )
+    monkeypatch.setattr(lead_agent_module, "get_memory_config", lambda: MemoryConfig(enabled=False))
 
     captured: dict[str, object] = {}
     fake_model = object()
@@ -156,10 +158,32 @@ def test_create_summarization_middleware_uses_configured_model_alias(monkeypatch
         return fake_model
 
     monkeypatch.setattr(lead_agent_module, "create_chat_model", _fake_create_chat_model)
-    monkeypatch.setattr(lead_agent_module, "SummarizationMiddleware", lambda **kwargs: kwargs)
+    monkeypatch.setattr(lead_agent_module, "DeerFlowSummarizationMiddleware", lambda **kwargs: kwargs)
 
     middleware = lead_agent_module._create_summarization_middleware()
 
     assert captured["name"] == "model-masswork"
     assert captured["thinking_enabled"] is False
     assert middleware["model"] is fake_model
+
+
+def test_create_summarization_middleware_registers_memory_flush_hook_when_memory_enabled(monkeypatch):
+    monkeypatch.setattr(
+        lead_agent_module,
+        "get_summarization_config",
+        lambda: SummarizationConfig(enabled=True),
+    )
+    monkeypatch.setattr(lead_agent_module, "get_memory_config", lambda: MemoryConfig(enabled=True))
+    monkeypatch.setattr(lead_agent_module, "create_chat_model", lambda **kwargs: object())
+
+    captured: dict[str, object] = {}
+
+    def _fake_middleware(**kwargs):
+        captured.update(kwargs)
+        return kwargs
+
+    monkeypatch.setattr(lead_agent_module, "DeerFlowSummarizationMiddleware", _fake_middleware)
+
+    lead_agent_module._create_summarization_middleware()
+
+    assert captured["before_summarization"] == [lead_agent_module.memory_flush_hook]