fix(harness): preserve dynamic context across summarization (#2823)

backend/packages/harness/deerflow/agents/middlewares/dynamic_context_middleware.py

@@ -45,6 +45,7 @@ logger = logging.getLogger(__name__)
 
 _DATE_RE = re.compile(r"<current_date>([^<]+)</current_date>")
 _DYNAMIC_CONTEXT_REMINDER_KEY = "dynamic_context_reminder"
+_SUMMARY_MESSAGE_NAME = "summary"
 
 
 def _extract_date(content: str) -> str | None:
@@ -72,6 +73,16 @@ def _last_injected_date(messages: list) -> str | None:
     return None
 
 
+def is_dynamic_context_reminder(message: object) -> bool:
+    """Return whether *message* is a hidden dynamic-context reminder."""
+    return isinstance(message, HumanMessage) and bool(message.additional_kwargs.get(_DYNAMIC_CONTEXT_REMINDER_KEY))
+
+
+def _is_user_injection_target(message: object) -> bool:
+    """Return whether *message* can receive a dynamic-context reminder."""
+    return isinstance(message, HumanMessage) and not is_dynamic_context_reminder(message) and message.name != _SUMMARY_MESSAGE_NAME
+
+
 class DynamicContextMiddleware(AgentMiddleware):
     """Inject memory and current date into HumanMessages as a <system-reminder>.
 
@@ -163,7 +174,7 @@ class DynamicContextMiddleware(AgentMiddleware):
 
         if last_date is None:
             # ── First turn: inject full reminder as a separate HumanMessage ─────
-            first_idx = next((i for i, m in enumerate(messages) if isinstance(m, HumanMessage)), None)
+            first_idx = next((i for i, m in enumerate(messages) if _is_user_injection_target(m)), None)
             if first_idx is None:
                 return None
             full_reminder = self._build_full_reminder()
@@ -181,7 +192,7 @@ class DynamicContextMiddleware(AgentMiddleware):
             return None
 
         # ── Midnight crossed: inject date-update reminder as a separate HumanMessage ──
-        last_human_idx = next((i for i in reversed(range(len(messages))) if isinstance(messages[i], HumanMessage)), None)
+        last_human_idx = next((i for i in reversed(range(len(messages))) if _is_user_injection_target(messages[i])), None)
         if last_human_idx is None:
             return None
 

backend/packages/harness/deerflow/agents/middlewares/summarization_middleware.py

@@ -14,6 +14,7 @@ from langgraph.config import get_config
 from langgraph.graph.message import REMOVE_ALL_MESSAGES
 from langgraph.runtime import Runtime
 
+from deerflow.agents.middlewares.dynamic_context_middleware import is_dynamic_context_reminder
 from deerflow.agents.middlewares.tool_call_metadata import clone_ai_message_with_tool_calls
 
 logger = logging.getLogger(__name__)
@@ -135,6 +136,7 @@ class DeerFlowSummarizationMiddleware(SummarizationMiddleware):
             return None
 
         messages_to_summarize, preserved_messages = self._partition_with_skill_rescue(messages, cutoff_index)
+        messages_to_summarize, preserved_messages = self._preserve_dynamic_context_reminders(messages_to_summarize, preserved_messages)
         self._fire_hooks(messages_to_summarize, preserved_messages, runtime)
         summary = self._create_summary(messages_to_summarize)
         new_messages = self._build_new_messages(summary)
@@ -160,6 +162,7 @@ class DeerFlowSummarizationMiddleware(SummarizationMiddleware):
             return None
 
         messages_to_summarize, preserved_messages = self._partition_with_skill_rescue(messages, cutoff_index)
+        messages_to_summarize, preserved_messages = self._preserve_dynamic_context_reminders(messages_to_summarize, preserved_messages)
         self._fire_hooks(messages_to_summarize, preserved_messages, runtime)
         summary = await self._acreate_summary(messages_to_summarize)
         new_messages = self._build_new_messages(summary)
@@ -179,6 +182,24 @@ class DeerFlowSummarizationMiddleware(SummarizationMiddleware):
         """
         return [HumanMessage(content=f"Here is a summary of the conversation to date:\n\n{summary}", name="summary")]
 
+    def _preserve_dynamic_context_reminders(
+        self,
+        messages_to_summarize: list[AnyMessage],
+        preserved_messages: list[AnyMessage],
+    ) -> tuple[list[AnyMessage], list[AnyMessage]]:
+        """Keep hidden dynamic-context reminders out of summary compression.
+
+        These reminders carry the current date and optional memory. If summarization
+        removes them, DynamicContextMiddleware can mistake the summary HumanMessage
+        for the first user message and inject the reminder in the wrong place.
+        """
+        reminders = [msg for msg in messages_to_summarize if is_dynamic_context_reminder(msg)]
+        if not reminders:
+            return messages_to_summarize, preserved_messages
+
+        remaining = [msg for msg in messages_to_summarize if not is_dynamic_context_reminder(msg)]
+        return remaining, reminders + preserved_messages
+
     def _partition_with_skill_rescue(
         self,
         messages: list[AnyMessage],

backend/tests/test_dynamic_context_middleware.py

@@ -139,6 +139,30 @@ def test_injects_only_into_first_human_message_not_later_ones():
     assert all(m.id != "msg-2" for m in msgs)
 
 
+def test_summary_human_message_is_not_used_as_injection_target():
+    """After summarization, the synthetic summary HumanMessage is not a user turn."""
+    mw = _make_middleware()
+    state = {
+        "messages": [
+            HumanMessage(content="Here is a summary of the conversation to date:\n\n...", id="summary-1", name="summary"),
+            AIMessage(content="Earlier reply"),
+            HumanMessage(content="Follow-up", id="msg-2"),
+        ]
+    }
+
+    with mock.patch("deerflow.agents.lead_agent.prompt._get_memory_context", return_value=""), mock.patch("deerflow.agents.middlewares.dynamic_context_middleware.datetime") as mock_dt:
+        mock_dt.now.return_value.strftime.return_value = "2026-05-08, Friday"
+        result = mw.before_agent(state, _fake_runtime())
+
+    assert result is not None
+    msgs = result["messages"]
+    assert len(msgs) == 2
+    assert msgs[0].id == "msg-2"
+    assert msgs[0].additional_kwargs.get(_DYNAMIC_CONTEXT_REMINDER_KEY) is True
+    assert msgs[1].id == "msg-2__user"
+    assert msgs[1].content == "Follow-up"
+
+
 # ---------------------------------------------------------------------------
 # Edge cases
 # ---------------------------------------------------------------------------

backend/tests/test_summarization_middleware.py

@@ -1,12 +1,14 @@
 from __future__ import annotations
 
 from types import SimpleNamespace
+from unittest import mock
 from unittest.mock import MagicMock
 
 import pytest
 from langchain_core.messages import AIMessage, HumanMessage, RemoveMessage, ToolMessage
 
 from deerflow.agents.memory.summarization_hook import memory_flush_hook
+from deerflow.agents.middlewares.dynamic_context_middleware import _DYNAMIC_CONTEXT_REMINDER_KEY, DynamicContextMiddleware
 from deerflow.agents.middlewares.summarization_middleware import DeerFlowSummarizationMiddleware, SummarizationEvent
 from deerflow.config.memory_config import MemoryConfig
 
@@ -20,6 +22,14 @@ def _messages() -> list:
     ]
 
 
+def _dynamic_context_reminder(msg_id: str = "reminder-1") -> HumanMessage:
+    return HumanMessage(
+        content="<system-reminder>\n<current_date>2026-05-08, Friday</current_date>\n</system-reminder>",
+        id=msg_id,
+        additional_kwargs={"hide_from_ui": True, _DYNAMIC_CONTEXT_REMINDER_KEY: True},
+    )
+
+
 def _runtime(thread_id: str | None = "thread-1", agent_name: str | None = None) -> SimpleNamespace:
     context = {}
     if thread_id is not None:
@@ -98,6 +108,38 @@ def test_before_summarization_hook_receives_messages_before_compression() -> Non
     assert result["messages"][1].content.startswith("Here is a summary")
 
 
+def test_dynamic_context_reminder_is_preserved_across_summarization() -> None:
+    captured: list[SummarizationEvent] = []
+    middleware = _middleware(before_summarization=[captured.append])
+    reminder = _dynamic_context_reminder()
+
+    result = middleware.before_model(
+        {
+            "messages": [
+                reminder,
+                HumanMessage(content="user-1"),
+                AIMessage(content="assistant-1"),
+                HumanMessage(content="user-2"),
+            ]
+        },
+        _runtime(),
+    )
+
+    assert len(captured) == 1
+    assert [message.content for message in captured[0].messages_to_summarize] == ["user-1"]
+    assert captured[0].preserved_messages[0] is reminder
+
+    emitted = result["messages"]
+    assert isinstance(emitted[0], RemoveMessage)
+    assert emitted[1].name == "summary"
+    assert emitted[2] is reminder
+
+    followup_state = {"messages": [*emitted[1:], HumanMessage(content="Follow-up", id="msg-2")]}
+    with mock.patch("deerflow.agents.middlewares.dynamic_context_middleware.datetime") as mock_dt:
+        mock_dt.now.return_value.strftime.return_value = "2026-05-08, Friday"
+        assert DynamicContextMiddleware().before_agent(followup_state, _runtime()) is None
+
+
 def test_before_summarization_hook_not_called_when_threshold_not_met() -> None:
     captured: list[SummarizationEvent] = []
     middleware = _middleware(before_summarization=[captured.append], trigger=("messages", 10))