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/packages/harness/deerflow/agents/lead_agent/agent.py

@@ -1,14 +1,16 @@
 import logging
 
 from langchain.agents import create_agent
-from langchain.agents.middleware import AgentMiddleware, SummarizationMiddleware
+from langchain.agents.middleware import AgentMiddleware
 from langchain_core.runnables import RunnableConfig
 
 from deerflow.agents.lead_agent.prompt import apply_prompt_template
+from deerflow.agents.memory.summarization_hook import memory_flush_hook
 from deerflow.agents.middlewares.clarification_middleware import ClarificationMiddleware
 from deerflow.agents.middlewares.loop_detection_middleware import LoopDetectionMiddleware
 from deerflow.agents.middlewares.memory_middleware import MemoryMiddleware
 from deerflow.agents.middlewares.subagent_limit_middleware import SubagentLimitMiddleware
+from deerflow.agents.middlewares.summarization_middleware import BeforeSummarizationHook, DeerFlowSummarizationMiddleware
 from deerflow.agents.middlewares.title_middleware import TitleMiddleware
 from deerflow.agents.middlewares.todo_middleware import TodoMiddleware
 from deerflow.agents.middlewares.token_usage_middleware import TokenUsageMiddleware
@@ -17,6 +19,7 @@ from deerflow.agents.middlewares.view_image_middleware import ViewImageMiddlewar
 from deerflow.agents.thread_state import ThreadState
 from deerflow.config.agents_config import load_agent_config
 from deerflow.config.app_config import get_app_config
+from deerflow.config.memory_config import get_memory_config
 from deerflow.config.summarization_config import get_summarization_config
 from deerflow.models import create_chat_model
 
@@ -38,7 +41,7 @@ def _resolve_model_name(requested_model_name: str | None = None) -> str:
     return default_model_name
 
 
-def _create_summarization_middleware() -> SummarizationMiddleware | None:
+def _create_summarization_middleware() -> DeerFlowSummarizationMiddleware | None:
     """Create and configure the summarization middleware from config."""
     config = get_summarization_config()
 
@@ -77,7 +80,11 @@ def _create_summarization_middleware() -> SummarizationMiddleware | None:
     if config.summary_prompt is not None:
         kwargs["summary_prompt"] = config.summary_prompt
 
-    return SummarizationMiddleware(**kwargs)
+    hooks: list[BeforeSummarizationHook] = []
+    if get_memory_config().enabled:
+        hooks.append(memory_flush_hook)
+
+    return DeerFlowSummarizationMiddleware(**kwargs, before_summarization=hooks)
 
 
 def _create_todo_list_middleware(is_plan_mode: bool) -> TodoMiddleware | None:

backend/packages/harness/deerflow/agents/memory/message_processing.py

@@ -0,0 +1,109 @@
+"""Shared helpers for turning conversations into memory update inputs."""
+
+from __future__ import annotations
+
+import re
+from copy import copy
+from typing import Any
+
+_UPLOAD_BLOCK_RE = re.compile(r"<uploaded_files>[\s\S]*?</uploaded_files>\n*", re.IGNORECASE)
+_CORRECTION_PATTERNS = (
+    re.compile(r"\bthat(?:'s| is) (?:wrong|incorrect)\b", re.IGNORECASE),
+    re.compile(r"\byou misunderstood\b", re.IGNORECASE),
+    re.compile(r"\btry again\b", re.IGNORECASE),
+    re.compile(r"\bredo\b", re.IGNORECASE),
+    re.compile(r"不对"),
+    re.compile(r"你理解错了"),
+    re.compile(r"你理解有误"),
+    re.compile(r"重试"),
+    re.compile(r"重新来"),
+    re.compile(r"换一种"),
+    re.compile(r"改用"),
+)
+_REINFORCEMENT_PATTERNS = (
+    re.compile(r"\byes[,.]?\s+(?:exactly|perfect|that(?:'s| is) (?:right|correct|it))\b", re.IGNORECASE),
+    re.compile(r"\bperfect(?:[.!?]|$)", re.IGNORECASE),
+    re.compile(r"\bexactly\s+(?:right|correct)\b", re.IGNORECASE),
+    re.compile(r"\bthat(?:'s| is)\s+(?:exactly\s+)?(?:right|correct|what i (?:wanted|needed|meant))\b", re.IGNORECASE),
+    re.compile(r"\bkeep\s+(?:doing\s+)?that\b", re.IGNORECASE),
+    re.compile(r"\bjust\s+(?:like\s+)?(?:that|this)\b", re.IGNORECASE),
+    re.compile(r"\bthis is (?:great|helpful)\b(?:[.!?]|$)", re.IGNORECASE),
+    re.compile(r"\bthis is what i wanted\b(?:[.!?]|$)", re.IGNORECASE),
+    re.compile(r"对[，,]?\s*就是这样(?:[。！？!?.]|$)"),
+    re.compile(r"完全正确(?:[。！？!?.]|$)"),
+    re.compile(r"(?:对[，,]?\s*)?就是这个意思(?:[。！？!?.]|$)"),
+    re.compile(r"正是我想要的(?:[。！？!?.]|$)"),
+    re.compile(r"继续保持(?:[。！？!?.]|$)"),
+)
+
+
+def extract_message_text(message: Any) -> str:
+    """Extract plain text from message content for filtering and signal detection."""
+    content = getattr(message, "content", "")
+    if isinstance(content, list):
+        text_parts: list[str] = []
+        for part in content:
+            if isinstance(part, str):
+                text_parts.append(part)
+            elif isinstance(part, dict):
+                text_val = part.get("text")
+                if isinstance(text_val, str):
+                    text_parts.append(text_val)
+        return " ".join(text_parts)
+    return str(content)
+
+
+def filter_messages_for_memory(messages: list[Any]) -> list[Any]:
+    """Keep only user inputs and final assistant responses for memory updates."""
+    filtered = []
+    skip_next_ai = False
+    for msg in messages:
+        msg_type = getattr(msg, "type", None)
+
+        if msg_type == "human":
+            content_str = extract_message_text(msg)
+            if "<uploaded_files>" in content_str:
+                stripped = _UPLOAD_BLOCK_RE.sub("", content_str).strip()
+                if not stripped:
+                    skip_next_ai = True
+                    continue
+                clean_msg = copy(msg)
+                clean_msg.content = stripped
+                filtered.append(clean_msg)
+                skip_next_ai = False
+            else:
+                filtered.append(msg)
+                skip_next_ai = False
+        elif msg_type == "ai":
+            tool_calls = getattr(msg, "tool_calls", None)
+            if not tool_calls:
+                if skip_next_ai:
+                    skip_next_ai = False
+                    continue
+                filtered.append(msg)
+
+    return filtered
+
+
+def detect_correction(messages: list[Any]) -> bool:
+    """Detect explicit user corrections in recent conversation turns."""
+    recent_user_msgs = [msg for msg in messages[-6:] if getattr(msg, "type", None) == "human"]
+
+    for msg in recent_user_msgs:
+        content = extract_message_text(msg).strip()
+        if content and any(pattern.search(content) for pattern in _CORRECTION_PATTERNS):
+            return True
+
+    return False
+
+
+def detect_reinforcement(messages: list[Any]) -> bool:
+    """Detect explicit positive reinforcement signals in recent conversation turns."""
+    recent_user_msgs = [msg for msg in messages[-6:] if getattr(msg, "type", None) == "human"]
+
+    for msg in recent_user_msgs:
+        content = extract_message_text(msg).strip()
+        if content and any(pattern.search(content) for pattern in _REINFORCEMENT_PATTERNS):
+            return True
+
+    return False

backend/packages/harness/deerflow/agents/memory/queue.py

@@ -61,48 +61,88 @@ class MemoryUpdateQueue:
             return
 
         with self._lock:
-            existing_context = next(
+            self._enqueue_locked(
-                (context for context in self._queue if context.thread_id == thread_id),
-                None,
-            )
-            merged_correction_detected = correction_detected or (existing_context.correction_detected if existing_context is not None else False)
-            merged_reinforcement_detected = reinforcement_detected or (existing_context.reinforcement_detected if existing_context is not None else False)
-            context = ConversationContext(
                 thread_id=thread_id,
                 messages=messages,
                 agent_name=agent_name,
-                correction_detected=merged_correction_detected,
+                correction_detected=correction_detected,
-                reinforcement_detected=merged_reinforcement_detected,
+                reinforcement_detected=reinforcement_detected,
             )
-
-            # Check if this thread already has a pending update
-            # If so, replace it with the newer one
-            self._queue = [c for c in self._queue if c.thread_id != thread_id]
-            self._queue.append(context)
-
-            # Reset or start the debounce timer
             self._reset_timer()
 
         logger.info("Memory update queued for thread %s, queue size: %d", thread_id, len(self._queue))
 
+    def add_nowait(
+        self,
+        thread_id: str,
+        messages: list[Any],
+        agent_name: str | None = None,
+        correction_detected: bool = False,
+        reinforcement_detected: bool = False,
+    ) -> None:
+        """Add a conversation and start processing immediately in the background."""
+        config = get_memory_config()
+        if not config.enabled:
+            return
+
+        with self._lock:
+            self._enqueue_locked(
+                thread_id=thread_id,
+                messages=messages,
+                agent_name=agent_name,
+                correction_detected=correction_detected,
+                reinforcement_detected=reinforcement_detected,
+            )
+            self._schedule_timer(0)
+
+        logger.info("Memory update queued for immediate processing on thread %s, queue size: %d", thread_id, len(self._queue))
+
+    def _enqueue_locked(
+        self,
+        *,
+        thread_id: str,
+        messages: list[Any],
+        agent_name: str | None,
+        correction_detected: bool,
+        reinforcement_detected: bool,
+    ) -> None:
+        existing_context = next(
+            (context for context in self._queue if context.thread_id == thread_id),
+            None,
+        )
+        merged_correction_detected = correction_detected or (existing_context.correction_detected if existing_context is not None else False)
+        merged_reinforcement_detected = reinforcement_detected or (existing_context.reinforcement_detected if existing_context is not None else False)
+        context = ConversationContext(
+            thread_id=thread_id,
+            messages=messages,
+            agent_name=agent_name,
+            correction_detected=merged_correction_detected,
+            reinforcement_detected=merged_reinforcement_detected,
+        )
+
+        self._queue = [c for c in self._queue if c.thread_id != thread_id]
+        self._queue.append(context)
+
     def _reset_timer(self) -> None:
         """Reset the debounce timer."""
         config = get_memory_config()
+        self._schedule_timer(config.debounce_seconds)
 
+        logger.debug("Memory update timer set for %ss", config.debounce_seconds)
+
+    def _schedule_timer(self, delay_seconds: float) -> None:
+        """Schedule queue processing after the provided delay."""
         # Cancel existing timer if any
         if self._timer is not None:
             self._timer.cancel()
 
-        # Start new timer
         self._timer = threading.Timer(
-            config.debounce_seconds,
+            delay_seconds,
             self._process_queue,
         )
         self._timer.daemon = True
         self._timer.start()
 
-        logger.debug("Memory update timer set for %ss", config.debounce_seconds)
-
     def _process_queue(self) -> None:
         """Process all queued conversation contexts."""
         # Import here to avoid circular dependency
@@ -110,8 +150,8 @@ class MemoryUpdateQueue:
 
         with self._lock:
             if self._processing:
-                # Already processing, reschedule
+                # Preserve immediate flush semantics even if another worker is active.
-                self._reset_timer()
+                self._schedule_timer(0)
                 return
 
             if not self._queue:
@@ -164,6 +204,13 @@ class MemoryUpdateQueue:
 
         self._process_queue()
 
+    def flush_nowait(self) -> None:
+        """Start queue processing immediately in a background thread."""
+        with self._lock:
+            # Daemon thread: queued messages may be lost if the process exits
+            # before _process_queue completes. Acceptable for best-effort memory updates.
+            self._schedule_timer(0)
+
     def clear(self) -> None:
         """Clear the queue without processing.
 

backend/packages/harness/deerflow/agents/memory/summarization_hook.py

@@ -0,0 +1,31 @@
+"""Hooks fired before summarization removes messages from state."""
+
+from __future__ import annotations
+
+from deerflow.agents.memory.message_processing import detect_correction, detect_reinforcement, filter_messages_for_memory
+from deerflow.agents.memory.queue import get_memory_queue
+from deerflow.agents.middlewares.summarization_middleware import SummarizationEvent
+from deerflow.config.memory_config import get_memory_config
+
+
+def memory_flush_hook(event: SummarizationEvent) -> None:
+    """Flush messages about to be summarized into the memory queue."""
+    if not get_memory_config().enabled or not event.thread_id:
+        return
+
+    filtered_messages = filter_messages_for_memory(list(event.messages_to_summarize))
+    user_messages = [message for message in filtered_messages if getattr(message, "type", None) == "human"]
+    assistant_messages = [message for message in filtered_messages if getattr(message, "type", None) == "ai"]
+    if not user_messages or not assistant_messages:
+        return
+
+    correction_detected = detect_correction(filtered_messages)
+    reinforcement_detected = not correction_detected and detect_reinforcement(filtered_messages)
+    queue = get_memory_queue()
+    queue.add_nowait(
+        thread_id=event.thread_id,
+        messages=filtered_messages,
+        agent_name=event.agent_name,
+        correction_detected=correction_detected,
+        reinforcement_detected=reinforcement_detected,
+    )

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

@@ -1,50 +1,19 @@
 """Middleware for memory mechanism."""
 
 import logging
-import re
+from typing import override
-from typing import Any, override
 
 from langchain.agents import AgentState
 from langchain.agents.middleware import AgentMiddleware
 from langgraph.config import get_config
 from langgraph.runtime import Runtime
 
+from deerflow.agents.memory.message_processing import detect_correction, detect_reinforcement, filter_messages_for_memory
 from deerflow.agents.memory.queue import get_memory_queue
 from deerflow.config.memory_config import get_memory_config
 
 logger = logging.getLogger(__name__)
 
-_UPLOAD_BLOCK_RE = re.compile(r"<uploaded_files>[\s\S]*?</uploaded_files>\n*", re.IGNORECASE)
-_CORRECTION_PATTERNS = (
-    re.compile(r"\bthat(?:'s| is) (?:wrong|incorrect)\b", re.IGNORECASE),
-    re.compile(r"\byou misunderstood\b", re.IGNORECASE),
-    re.compile(r"\btry again\b", re.IGNORECASE),
-    re.compile(r"\bredo\b", re.IGNORECASE),
-    re.compile(r"不对"),
-    re.compile(r"你理解错了"),
-    re.compile(r"你理解有误"),
-    re.compile(r"重试"),
-    re.compile(r"重新来"),
-    re.compile(r"换一种"),
-    re.compile(r"改用"),
-)
-
-_REINFORCEMENT_PATTERNS = (
-    re.compile(r"\byes[,.]?\s+(?:exactly|perfect|that(?:'s| is) (?:right|correct|it))\b", re.IGNORECASE),
-    re.compile(r"\bperfect(?:[.!?]|$)", re.IGNORECASE),
-    re.compile(r"\bexactly\s+(?:right|correct)\b", re.IGNORECASE),
-    re.compile(r"\bthat(?:'s| is)\s+(?:exactly\s+)?(?:right|correct|what i (?:wanted|needed|meant))\b", re.IGNORECASE),
-    re.compile(r"\bkeep\s+(?:doing\s+)?that\b", re.IGNORECASE),
-    re.compile(r"\bjust\s+(?:like\s+)?(?:that|this)\b", re.IGNORECASE),
-    re.compile(r"\bthis is (?:great|helpful)\b(?:[.!?]|$)", re.IGNORECASE),
-    re.compile(r"\bthis is what i wanted\b(?:[.!?]|$)", re.IGNORECASE),
-    re.compile(r"对[，,]?\s*就是这样(?:[。！？!?.]|$)"),
-    re.compile(r"完全正确(?:[。！？!?.]|$)"),
-    re.compile(r"(?:对[，,]?\s*)?就是这个意思(?:[。！？!?.]|$)"),
-    re.compile(r"正是我想要的(?:[。！？!?.]|$)"),
-    re.compile(r"继续保持(?:[。！？!?.]|$)"),
-)
-
 
 class MemoryMiddlewareState(AgentState):
     """Compatible with the `ThreadState` schema."""
@@ -52,125 +21,6 @@ class MemoryMiddlewareState(AgentState):
     pass
 
 
-def _extract_message_text(message: Any) -> str:
-    """Extract plain text from message content for filtering and signal detection."""
-    content = getattr(message, "content", "")
-    if isinstance(content, list):
-        text_parts: list[str] = []
-        for part in content:
-            if isinstance(part, str):
-                text_parts.append(part)
-            elif isinstance(part, dict):
-                text_val = part.get("text")
-                if isinstance(text_val, str):
-                    text_parts.append(text_val)
-        return " ".join(text_parts)
-    return str(content)
-
-
-def _filter_messages_for_memory(messages: list[Any]) -> list[Any]:
-    """Filter messages to keep only user inputs and final assistant responses.
-
-    This filters out:
-    - Tool messages (intermediate tool call results)
-    - AI messages with tool_calls (intermediate steps, not final responses)
-    - The <uploaded_files> block injected by UploadsMiddleware into human messages
-      (file paths are session-scoped and must not persist in long-term memory).
-      The user's actual question is preserved; only turns whose content is entirely
-      the upload block (nothing remains after stripping) are dropped along with
-      their paired assistant response.
-
-    Only keeps:
-    - Human messages (with the ephemeral upload block removed)
-    - AI messages without tool_calls (final assistant responses), unless the
-      paired human turn was upload-only and had no real user text.
-
-    Args:
-        messages: List of all conversation messages.
-
-    Returns:
-        Filtered list containing only user inputs and final assistant responses.
-    """
-    filtered = []
-    skip_next_ai = False
-    for msg in messages:
-        msg_type = getattr(msg, "type", None)
-
-        if msg_type == "human":
-            content_str = _extract_message_text(msg)
-            if "<uploaded_files>" in content_str:
-                # Strip the ephemeral upload block; keep the user's real question.
-                stripped = _UPLOAD_BLOCK_RE.sub("", content_str).strip()
-                if not stripped:
-                    # Nothing left — the entire turn was upload bookkeeping;
-                    # skip it and the paired assistant response.
-                    skip_next_ai = True
-                    continue
-                # Rebuild the message with cleaned content so the user's question
-                # is still available for memory summarisation.
-                from copy import copy
-
-                clean_msg = copy(msg)
-                clean_msg.content = stripped
-                filtered.append(clean_msg)
-                skip_next_ai = False
-            else:
-                filtered.append(msg)
-                skip_next_ai = False
-        elif msg_type == "ai":
-            tool_calls = getattr(msg, "tool_calls", None)
-            if not tool_calls:
-                if skip_next_ai:
-                    skip_next_ai = False
-                    continue
-                filtered.append(msg)
-        # Skip tool messages and AI messages with tool_calls
-
-    return filtered
-
-
-def detect_correction(messages: list[Any]) -> bool:
-    """Detect explicit user corrections in recent conversation turns.
-
-    The queue keeps only one pending context per thread, so callers pass the
-    latest filtered message list. Checking only recent user turns keeps signal
-    detection conservative while avoiding stale corrections from long histories.
-    """
-    recent_user_msgs = [msg for msg in messages[-6:] if getattr(msg, "type", None) == "human"]
-
-    for msg in recent_user_msgs:
-        content = _extract_message_text(msg).strip()
-        if not content:
-            continue
-        if any(pattern.search(content) for pattern in _CORRECTION_PATTERNS):
-            return True
-
-    return False
-
-
-def detect_reinforcement(messages: list[Any]) -> bool:
-    """Detect explicit positive reinforcement signals in recent conversation turns.
-
-    Complements detect_correction() by identifying when the user confirms the
-    agent's approach was correct. This allows the memory system to record what
-    worked well, not just what went wrong.
-
-    The queue keeps only one pending context per thread, so callers pass the
-    latest filtered message list. Checking only recent user turns keeps signal
-    detection conservative while avoiding stale signals from long histories.
-    """
-    recent_user_msgs = [msg for msg in messages[-6:] if getattr(msg, "type", None) == "human"]
-
-    for msg in recent_user_msgs:
-        content = _extract_message_text(msg).strip()
-        if not content:
-            continue
-        if any(pattern.search(content) for pattern in _REINFORCEMENT_PATTERNS):
-            return True
-
-    return False
-
-
 class MemoryMiddleware(AgentMiddleware[MemoryMiddlewareState]):
     """Middleware that queues conversation for memory update after agent execution.
 
@@ -223,7 +73,7 @@ class MemoryMiddleware(AgentMiddleware[MemoryMiddlewareState]):
             return None
 
         # Filter to only keep user inputs and final assistant responses
-        filtered_messages = _filter_messages_for_memory(messages)
+        filtered_messages = filter_messages_for_memory(messages)
 
         # Only queue if there's meaningful conversation
         # At minimum need one user message and one assistant response

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

@@ -0,0 +1,151 @@
+"""Summarization middleware extensions for DeerFlow."""
+
+from __future__ import annotations
+
+import logging
+from dataclasses import dataclass
+from typing import Protocol, runtime_checkable
+
+from langchain.agents import AgentState
+from langchain.agents.middleware import SummarizationMiddleware
+from langchain_core.messages import AnyMessage, RemoveMessage
+from langgraph.config import get_config
+from langgraph.graph.message import REMOVE_ALL_MESSAGES
+from langgraph.runtime import Runtime
+
+logger = logging.getLogger(__name__)
+
+
+@dataclass(frozen=True)
+class SummarizationEvent:
+    """Context emitted before conversation history is summarized away."""
+
+    messages_to_summarize: tuple[AnyMessage, ...]
+    preserved_messages: tuple[AnyMessage, ...]
+    thread_id: str | None
+    agent_name: str | None
+    runtime: Runtime
+
+
+@runtime_checkable
+class BeforeSummarizationHook(Protocol):
+    """Hook invoked before summarization removes messages from state."""
+
+    def __call__(self, event: SummarizationEvent) -> None: ...
+
+
+def _resolve_thread_id(runtime: Runtime) -> str | None:
+    """Resolve the current thread ID from runtime context or LangGraph config."""
+    thread_id = runtime.context.get("thread_id") if runtime.context else None
+    if thread_id is None:
+        try:
+            config_data = get_config()
+        except RuntimeError:
+            return None
+        thread_id = config_data.get("configurable", {}).get("thread_id")
+    return thread_id
+
+
+def _resolve_agent_name(runtime: Runtime) -> str | None:
+    """Resolve the current agent name from runtime context or LangGraph config."""
+    agent_name = runtime.context.get("agent_name") if runtime.context else None
+    if agent_name is None:
+        try:
+            config_data = get_config()
+        except RuntimeError:
+            return None
+        agent_name = config_data.get("configurable", {}).get("agent_name")
+    return agent_name
+
+
+class DeerFlowSummarizationMiddleware(SummarizationMiddleware):
+    """Summarization middleware with pre-compression hook dispatch."""
+
+    def __init__(
+        self,
+        *args,
+        before_summarization: list[BeforeSummarizationHook] | None = None,
+        **kwargs,
+    ) -> None:
+        super().__init__(*args, **kwargs)
+        self._before_summarization_hooks = before_summarization or []
+
+    def before_model(self, state: AgentState, runtime: Runtime) -> dict | None:
+        return self._maybe_summarize(state, runtime)
+
+    async def abefore_model(self, state: AgentState, runtime: Runtime) -> dict | None:
+        return await self._amaybe_summarize(state, runtime)
+
+    def _maybe_summarize(self, state: AgentState, runtime: Runtime) -> dict | None:
+        messages = state["messages"]
+        self._ensure_message_ids(messages)
+
+        total_tokens = self.token_counter(messages)
+        if not self._should_summarize(messages, total_tokens):
+            return None
+
+        cutoff_index = self._determine_cutoff_index(messages)
+        if cutoff_index <= 0:
+            return None
+
+        messages_to_summarize, preserved_messages = self._partition_messages(messages, cutoff_index)
+        self._fire_hooks(messages_to_summarize, preserved_messages, runtime)
+        summary = self._create_summary(messages_to_summarize)
+        new_messages = self._build_new_messages(summary)
+
+        return {
+            "messages": [
+                RemoveMessage(id=REMOVE_ALL_MESSAGES),
+                *new_messages,
+                *preserved_messages,
+            ]
+        }
+
+    async def _amaybe_summarize(self, state: AgentState, runtime: Runtime) -> dict | None:
+        messages = state["messages"]
+        self._ensure_message_ids(messages)
+
+        total_tokens = self.token_counter(messages)
+        if not self._should_summarize(messages, total_tokens):
+            return None
+
+        cutoff_index = self._determine_cutoff_index(messages)
+        if cutoff_index <= 0:
+            return None
+
+        messages_to_summarize, preserved_messages = self._partition_messages(messages, cutoff_index)
+        self._fire_hooks(messages_to_summarize, preserved_messages, runtime)
+        summary = await self._acreate_summary(messages_to_summarize)
+        new_messages = self._build_new_messages(summary)
+
+        return {
+            "messages": [
+                RemoveMessage(id=REMOVE_ALL_MESSAGES),
+                *new_messages,
+                *preserved_messages,
+            ]
+        }
+
+    def _fire_hooks(
+        self,
+        messages_to_summarize: list[AnyMessage],
+        preserved_messages: list[AnyMessage],
+        runtime: Runtime,
+    ) -> None:
+        if not self._before_summarization_hooks:
+            return
+
+        event = SummarizationEvent(
+            messages_to_summarize=tuple(messages_to_summarize),
+            preserved_messages=tuple(preserved_messages),
+            thread_id=_resolve_thread_id(runtime),
+            agent_name=_resolve_agent_name(runtime),
+            runtime=runtime,
+        )
+
+        for hook in self._before_summarization_hooks:
+            try:
+                hook(event)
+            except Exception:
+                hook_name = getattr(hook, "__name__", None) or type(hook).__name__
+                logger.exception("before_summarization hook %s failed", hook_name)

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]

backend/tests/test_memory_queue.py

@@ -1,3 +1,5 @@
+import threading
+import time
 from unittest.mock import MagicMock, patch
 
 from deerflow.agents.memory.queue import ConversationContext, MemoryUpdateQueue
@@ -89,3 +91,74 @@ def test_process_queue_forwards_reinforcement_flag_to_updater() -> None:
         correction_detected=False,
         reinforcement_detected=True,
     )
+
+
+def test_flush_nowait_cancels_existing_timer_and_starts_immediate_timer() -> None:
+    queue = MemoryUpdateQueue()
+    existing_timer = MagicMock()
+    queue._timer = existing_timer
+    created_timer = MagicMock()
+
+    with patch("deerflow.agents.memory.queue.threading.Timer", return_value=created_timer) as timer_cls:
+        queue.flush_nowait()
+
+    existing_timer.cancel.assert_called_once_with()
+    timer_cls.assert_called_once_with(0, queue._process_queue)
+    assert created_timer.daemon is True
+    created_timer.start.assert_called_once_with()
+    assert queue._timer is created_timer
+
+
+def test_add_nowait_cancels_existing_timer_and_starts_immediate_timer() -> None:
+    queue = MemoryUpdateQueue()
+    existing_timer = MagicMock()
+    queue._timer = existing_timer
+    created_timer = MagicMock()
+
+    with (
+        patch("deerflow.agents.memory.queue.get_memory_config", return_value=_memory_config(enabled=True)),
+        patch("deerflow.agents.memory.queue.threading.Timer", return_value=created_timer) as timer_cls,
+    ):
+        queue.add_nowait(thread_id="thread-1", messages=["conversation"], agent_name="lead-agent")
+
+    existing_timer.cancel.assert_called_once_with()
+    timer_cls.assert_called_once_with(0, queue._process_queue)
+    assert queue.pending_count == 1
+    assert queue._queue[0].agent_name == "lead-agent"
+    assert created_timer.daemon is True
+    created_timer.start.assert_called_once_with()
+
+
+def test_process_queue_reschedules_immediately_when_already_processing() -> None:
+    queue = MemoryUpdateQueue()
+    queue._processing = True
+    created_timer = MagicMock()
+
+    with patch("deerflow.agents.memory.queue.threading.Timer", return_value=created_timer) as timer_cls:
+        queue._process_queue()
+
+    timer_cls.assert_called_once_with(0, queue._process_queue)
+    assert created_timer.daemon is True
+    created_timer.start.assert_called_once_with()
+
+
+def test_flush_nowait_is_non_blocking() -> None:
+    queue = MemoryUpdateQueue()
+    started = threading.Event()
+    finished = threading.Event()
+
+    def _slow_process_queue() -> None:
+        started.set()
+        time.sleep(0.2)
+        finished.set()
+
+    queue._process_queue = _slow_process_queue
+
+    start = time.perf_counter()
+    queue.flush_nowait()
+    elapsed = time.perf_counter() - start
+
+    assert started.wait(0.1) is True
+    assert elapsed < 0.1
+    assert finished.is_set() is False
+    assert finished.wait(1.0) is True

backend/tests/test_memory_upload_filtering.py

@@ -3,14 +3,14 @@
 Covers two functions introduced to prevent ephemeral file-upload context from
 persisting in long-term memory:
 
-  - _filter_messages_for_memory  (memory_middleware)
+  - filter_messages_for_memory  (message_processing)
   - _strip_upload_mentions_from_memory  (updater)
 """
 
 from langchain_core.messages import AIMessage, HumanMessage, ToolMessage
 
+from deerflow.agents.memory.message_processing import detect_correction, detect_reinforcement, filter_messages_for_memory
 from deerflow.agents.memory.updater import _strip_upload_mentions_from_memory
-from deerflow.agents.middlewares.memory_middleware import _filter_messages_for_memory, detect_correction, detect_reinforcement
 
 # ---------------------------------------------------------------------------
 # Helpers
@@ -31,7 +31,7 @@ def _ai(text: str, tool_calls=None) -> AIMessage:
 
 
 # ===========================================================================
-# _filter_messages_for_memory
+# filter_messages_for_memory
 # ===========================================================================
 
 
@@ -45,7 +45,7 @@ class TestFilterMessagesForMemory:
             _human(_UPLOAD_BLOCK),
             _ai("I have read the file. It says: Hello."),
         ]
-        result = _filter_messages_for_memory(msgs)
+        result = filter_messages_for_memory(msgs)
         assert result == []
 
     def test_upload_with_real_question_preserves_question(self):
@@ -56,7 +56,7 @@ class TestFilterMessagesForMemory:
             _human(combined),
             _ai("The file contains: Hello DeerFlow."),
         ]
-        result = _filter_messages_for_memory(msgs)
+        result = filter_messages_for_memory(msgs)
 
         assert len(result) == 2
         human_result = result[0]
@@ -71,7 +71,7 @@ class TestFilterMessagesForMemory:
             _human("What is the capital of France?"),
             _ai("The capital of France is Paris."),
         ]
-        result = _filter_messages_for_memory(msgs)
+        result = filter_messages_for_memory(msgs)
         assert len(result) == 2
         assert result[0].content == "What is the capital of France?"
         assert result[1].content == "The capital of France is Paris."
@@ -84,7 +84,7 @@ class TestFilterMessagesForMemory:
             ToolMessage(content="Search results", tool_call_id="1"),
             _ai("Here are the results."),
         ]
-        result = _filter_messages_for_memory(msgs)
+        result = filter_messages_for_memory(msgs)
         human_msgs = [m for m in result if m.type == "human"]
         ai_msgs = [m for m in result if m.type == "ai"]
         assert len(human_msgs) == 1
@@ -101,7 +101,7 @@ class TestFilterMessagesForMemory:
             _human("What is 2 + 2?"),
             _ai("4"),
         ]
-        result = _filter_messages_for_memory(msgs)
+        result = filter_messages_for_memory(msgs)
         human_contents = [m.content for m in result if m.type == "human"]
         ai_contents = [m.content for m in result if m.type == "ai"]
 
@@ -121,14 +121,14 @@ class TestFilterMessagesForMemory:
             ]
         )
         msgs = [msg, _ai("Done.")]
-        result = _filter_messages_for_memory(msgs)
+        result = filter_messages_for_memory(msgs)
         assert result == []
 
     def test_file_path_not_in_filtered_content(self):
         """After filtering, no upload file path should appear in any message."""
         combined = _UPLOAD_BLOCK + "\n\nSummarise the file please."
         msgs = [_human(combined), _ai("It says hello.")]
-        result = _filter_messages_for_memory(msgs)
+        result = filter_messages_for_memory(msgs)
         all_content = " ".join(m.content for m in result if isinstance(m.content, str))
         assert "/mnt/user-data/uploads/" not in all_content
         assert "<uploaded_files>" not in all_content

backend/tests/test_summarization_middleware.py

@@ -0,0 +1,186 @@
+from __future__ import annotations
+
+from types import SimpleNamespace
+from unittest.mock import MagicMock
+
+import pytest
+from langchain_core.messages import AIMessage, HumanMessage, RemoveMessage
+
+from deerflow.agents.memory.summarization_hook import memory_flush_hook
+from deerflow.agents.middlewares.summarization_middleware import DeerFlowSummarizationMiddleware, SummarizationEvent
+from deerflow.config.memory_config import MemoryConfig
+
+
+def _messages() -> list:
+    return [
+        HumanMessage(content="user-1"),
+        AIMessage(content="assistant-1"),
+        HumanMessage(content="user-2"),
+        AIMessage(content="assistant-2"),
+    ]
+
+
+def _runtime(thread_id: str | None = "thread-1", agent_name: str | None = None) -> SimpleNamespace:
+    context = {}
+    if thread_id is not None:
+        context["thread_id"] = thread_id
+    if agent_name is not None:
+        context["agent_name"] = agent_name
+    return SimpleNamespace(context=context)
+
+
+def _middleware(*, before_summarization=None, trigger=("messages", 4), keep=("messages", 2)) -> DeerFlowSummarizationMiddleware:
+    model = MagicMock()
+    model.invoke.return_value = SimpleNamespace(text="compressed summary")
+    return DeerFlowSummarizationMiddleware(
+        model=model,
+        trigger=trigger,
+        keep=keep,
+        token_counter=len,
+        before_summarization=before_summarization,
+    )
+
+
+def test_before_summarization_hook_receives_messages_before_compression() -> None:
+    captured: list[SummarizationEvent] = []
+    middleware = _middleware(before_summarization=[captured.append])
+
+    result = middleware.before_model({"messages": _messages()}, _runtime())
+
+    assert len(captured) == 1
+    assert [message.content for message in captured[0].messages_to_summarize] == ["user-1", "assistant-1"]
+    assert [message.content for message in captured[0].preserved_messages] == ["user-2", "assistant-2"]
+    assert captured[0].thread_id == "thread-1"
+    assert captured[0].agent_name is None
+    assert isinstance(result["messages"][0], RemoveMessage)
+    assert result["messages"][1].content.startswith("Here is a summary")
+
+
+def test_before_summarization_hook_not_called_when_threshold_not_met() -> None:
+    captured: list[SummarizationEvent] = []
+    middleware = _middleware(before_summarization=[captured.append], trigger=("messages", 10))
+
+    result = middleware.before_model({"messages": _messages()}, _runtime())
+
+    assert captured == []
+    assert result is None
+
+
+def test_before_summarization_hook_exception_does_not_block_compression(caplog: pytest.LogCaptureFixture) -> None:
+    def _broken_hook(_: SummarizationEvent) -> None:
+        raise RuntimeError("hook failure")
+
+    middleware = _middleware(before_summarization=[_broken_hook])
+
+    with caplog.at_level("ERROR"):
+        result = middleware.before_model({"messages": _messages()}, _runtime())
+
+    assert "before_summarization hook _broken_hook failed" in caplog.text
+    assert isinstance(result["messages"][0], RemoveMessage)
+
+
+def test_multiple_before_summarization_hooks_run_in_registration_order() -> None:
+    call_order: list[str] = []
+
+    def _hook(name: str):
+        return lambda _: call_order.append(name)
+
+    middleware = _middleware(before_summarization=[_hook("first"), _hook("second"), _hook("third")])
+
+    middleware.before_model({"messages": _messages()}, _runtime())
+
+    assert call_order == ["first", "second", "third"]
+
+
+@pytest.mark.anyio
+async def test_abefore_model_calls_hooks_same_as_sync() -> None:
+    captured: list[SummarizationEvent] = []
+    middleware = _middleware(before_summarization=[captured.append])
+
+    await middleware.abefore_model({"messages": _messages()}, _runtime())
+
+    assert len(captured) == 1
+    assert [message.content for message in captured[0].messages_to_summarize] == ["user-1", "assistant-1"]
+
+
+def test_memory_flush_hook_skips_when_memory_disabled(monkeypatch: pytest.MonkeyPatch) -> None:
+    queue = MagicMock()
+    monkeypatch.setattr("deerflow.agents.memory.summarization_hook.get_memory_config", lambda: MemoryConfig(enabled=False))
+    monkeypatch.setattr("deerflow.agents.memory.summarization_hook.get_memory_queue", lambda: queue)
+
+    memory_flush_hook(
+        SummarizationEvent(
+            messages_to_summarize=tuple(_messages()[:2]),
+            preserved_messages=(),
+            thread_id="thread-1",
+            agent_name=None,
+            runtime=_runtime(),
+        )
+    )
+
+    queue.add_nowait.assert_not_called()
+
+
+def test_memory_flush_hook_skips_when_thread_id_missing(monkeypatch: pytest.MonkeyPatch) -> None:
+    queue = MagicMock()
+    monkeypatch.setattr("deerflow.agents.memory.summarization_hook.get_memory_config", lambda: MemoryConfig(enabled=True))
+    monkeypatch.setattr("deerflow.agents.memory.summarization_hook.get_memory_queue", lambda: queue)
+
+    memory_flush_hook(
+        SummarizationEvent(
+            messages_to_summarize=tuple(_messages()[:2]),
+            preserved_messages=(),
+            thread_id=None,
+            agent_name=None,
+            runtime=_runtime(None),
+        )
+    )
+
+    queue.add_nowait.assert_not_called()
+
+
+def test_memory_flush_hook_enqueues_filtered_messages_and_flushes(monkeypatch: pytest.MonkeyPatch) -> None:
+    queue = MagicMock()
+    messages = [
+        HumanMessage(content="Question"),
+        AIMessage(content="Calling tool", tool_calls=[{"name": "search", "id": "tool-1", "args": {}}]),
+        AIMessage(content="Final answer"),
+    ]
+    monkeypatch.setattr("deerflow.agents.memory.summarization_hook.get_memory_config", lambda: MemoryConfig(enabled=True))
+    monkeypatch.setattr("deerflow.agents.memory.summarization_hook.get_memory_queue", lambda: queue)
+
+    memory_flush_hook(
+        SummarizationEvent(
+            messages_to_summarize=tuple(messages),
+            preserved_messages=(),
+            thread_id="thread-1",
+            agent_name=None,
+            runtime=_runtime(),
+        )
+    )
+
+    queue.add_nowait.assert_called_once()
+    add_kwargs = queue.add_nowait.call_args.kwargs
+    assert add_kwargs["thread_id"] == "thread-1"
+    assert [message.content for message in add_kwargs["messages"]] == ["Question", "Final answer"]
+    assert add_kwargs["correction_detected"] is False
+    assert add_kwargs["reinforcement_detected"] is False
+
+
+def test_memory_flush_hook_preserves_agent_scoped_memory(monkeypatch: pytest.MonkeyPatch) -> None:
+    queue = MagicMock()
+    monkeypatch.setattr("deerflow.agents.memory.summarization_hook.get_memory_config", lambda: MemoryConfig(enabled=True))
+    monkeypatch.setattr("deerflow.agents.memory.summarization_hook.get_memory_queue", lambda: queue)
+
+    memory_flush_hook(
+        SummarizationEvent(
+            messages_to_summarize=tuple(_messages()[:2]),
+            preserved_messages=(),
+            thread_id="thread-1",
+            agent_name="research-agent",
+            runtime=_runtime(agent_name="research-agent"),
+        )
+    )
+
+    queue.add_nowait.assert_called_once()
+    assert queue.add_nowait.call_args.kwargs["agent_name"] == "research-agent"