fix(memory): consolidate history hidden by replay window

Co-authored-by: Cursor <cursoragent@cursor.com>

nanobot/agent/loop.py

@@ -969,6 +969,7 @@ class AgentLoop:
             await self.consolidator.maybe_consolidate_by_tokens(
                 session,
                 session_summary=pending,
+                replay_max_messages=self._max_messages,
             )
             # Persist subagent follow-ups into durable history BEFORE prompt
             # assembly. ContextBuilder merges adjacent same-role messages for
@@ -1013,7 +1014,12 @@ class AgentLoop:
             session.enforce_file_cap(on_archive=self.context.memory.raw_archive)
             self._clear_runtime_checkpoint(session)
             self.sessions.save(session)
-            self._schedule_background(self.consolidator.maybe_consolidate_by_tokens(session))
+            self._schedule_background(
+                self.consolidator.maybe_consolidate_by_tokens(
+                    session,
+                    replay_max_messages=self._max_messages,
+                )
+            )
             options = ask_user_options_from_messages(all_msgs) if stop_reason == "ask_user" else []
             content, buttons = ask_user_outbound(
                 final_content or "Background task completed.",
@@ -1066,6 +1072,7 @@ class AgentLoop:
         await self.consolidator.maybe_consolidate_by_tokens(
             session,
             session_summary=pending,
+            replay_max_messages=self._max_messages,
         )
 
         self._set_tool_context(
@@ -1179,7 +1186,12 @@ class AgentLoop:
         self._clear_pending_user_turn(session)
         self._clear_runtime_checkpoint(session)
         self.sessions.save(session)
-        self._schedule_background(self.consolidator.maybe_consolidate_by_tokens(session))
+        self._schedule_background(
+            self.consolidator.maybe_consolidate_by_tokens(
+                session,
+                replay_max_messages=self._max_messages,
+            )
+        )
 
         # When follow-up messages were injected mid-turn, a later natural
         # language reply may address those follow-ups and should not be

nanobot/agent/memory.py

@@ -17,6 +17,7 @@ from loguru import logger
 
 from nanobot.agent.runner import AgentRunner, AgentRunSpec
 from nanobot.agent.tools.registry import ToolRegistry
+from nanobot.session.manager import Session
 from nanobot.utils.gitstore import GitStore
 from nanobot.utils.helpers import (
     ensure_dir,
@@ -29,7 +30,7 @@ from nanobot.utils.prompt_templates import render_template
 
 if TYPE_CHECKING:
     from nanobot.providers.base import LLMProvider
-    from nanobot.session.manager import Session, SessionManager
+    from nanobot.session.manager import SessionManager
 
 
 # ---------------------------------------------------------------------------
@@ -508,14 +509,85 @@ class Consolidator:
 
         return last_boundary
 
+    @staticmethod
+    def _full_unconsolidated_history(
+        session: Session,
+        *,
+        include_timestamps: bool = False,
+    ) -> list[dict[str, Any]]:
+        """Return the whole unconsolidated tail for consolidation decisions."""
+        unconsolidated_count = len(session.messages) - session.last_consolidated
+        if unconsolidated_count <= 0:
+            return []
+        return session.get_history(
+            max_messages=unconsolidated_count,
+            include_timestamps=include_timestamps,
+        )
+
+    @staticmethod
+    def _replay_overflow_boundary(
+        session: Session,
+        replay_max_messages: int | None,
+    ) -> int | None:
+        if not replay_max_messages or replay_max_messages <= 0:
+            return None
+        tail = list(session.messages[session.last_consolidated:])
+        if len(tail) <= replay_max_messages:
+            return None
+
+        probe = Session(
+            key=session.key,
+            messages=[dict(message) for message in tail],
+            created_at=session.created_at,
+            updated_at=session.updated_at,
+            metadata={},
+            last_consolidated=0,
+        )
+        probe.retain_recent_legal_suffix(replay_max_messages)
+        cut = len(tail) - len(probe.messages)
+        if cut <= 0:
+            return None
+        return session.last_consolidated + cut
+
+    async def _consolidate_replay_overflow(
+        self,
+        session: Session,
+        replay_max_messages: int | None,
+    ) -> str | None:
+        """Archive messages that would be hidden by the replay message window."""
+        end_idx = self._replay_overflow_boundary(session, replay_max_messages)
+        if end_idx is None:
+            return None
+        chunk = session.messages[session.last_consolidated:end_idx]
+        if not chunk:
+            return None
+        logger.info(
+            "Replay-window consolidation for {}: chunk={} msgs, replay_max={}",
+            session.key,
+            len(chunk),
+            replay_max_messages,
+        )
+        summary = await self.archive(chunk)
+        session.last_consolidated = end_idx
+        self.sessions.save(session)
+        return summary
+
+    def _persist_last_summary(self, session: Session, summary: str | None) -> None:
+        if summary and summary != "(nothing)":
+            session.metadata["_last_summary"] = {
+                "text": summary,
+                "last_active": session.updated_at.isoformat(),
+            }
+            self.sessions.save(session)
+
     def estimate_session_prompt_tokens(
         self,
         session: Session,
         *,
         session_summary: str | None = None,
     ) -> tuple[int, str]:
-        """Estimate current prompt size for the normal session history view."""
-        history = session.get_history(max_messages=0, include_timestamps=True)
+        """Estimate prompt size from the full unconsolidated session tail."""
+        history = self._full_unconsolidated_history(session, include_timestamps=True)
         channel, chat_id = (session.key.split(":", 1) if ":" in session.key else (None, None))
         probe_messages = self._build_messages(
             history=history,
@@ -591,6 +663,7 @@ class Consolidator:
         session: Session,
         *,
         session_summary: str | None = None,
+        replay_max_messages: int | None = None,
     ) -> None:
         """Loop: archive old messages until prompt fits within safe budget.
 
@@ -604,6 +677,10 @@ class Consolidator:
         async with lock:
             budget = self._input_token_budget
             target = int(budget * self.consolidation_ratio)
+            last_summary = await self._consolidate_replay_overflow(
+                session,
+                replay_max_messages,
+            )
             try:
                 estimated, source = self.estimate_session_prompt_tokens(
                     session,
@@ -613,6 +690,7 @@ class Consolidator:
                 logger.exception("Token estimation failed for {}", session.key)
                 estimated, source = 0, "error"
             if estimated <= 0:
+                self._persist_last_summary(session, last_summary)
                 return
             if estimated < budget:
                 unconsolidated_count = len(session.messages) - session.last_consolidated
@@ -624,9 +702,9 @@ class Consolidator:
                     source,
                     unconsolidated_count,
                 )
+                self._persist_last_summary(session, last_summary)
                 return
 
-            last_summary = None
             for round_num in range(self._MAX_CONSOLIDATION_ROUNDS):
                 if estimated <= target:
                     break
@@ -683,12 +761,7 @@ class Consolidator:
             # Persist the last summary to session metadata so it can be injected
             # into the runtime context on the next prepare_session() call, aligning
             # the summary injection strategy with AutoCompact._archive().
-            if last_summary and last_summary != "(nothing)":
-                session.metadata["_last_summary"] = {
-                    "text": last_summary,
-                    "last_active": session.updated_at.isoformat(),
-                }
-                self.sessions.save(session)
+            self._persist_last_summary(session, last_summary)
 
 
 # ---------------------------------------------------------------------------

tests/agent/test_consolidator.py

@@ -1,15 +1,15 @@
 """Tests for the lightweight Consolidator — append-only to HISTORY.md."""
 
+from unittest.mock import AsyncMock, MagicMock
+
 import pytest
-import asyncio
-from unittest.mock import AsyncMock, MagicMock, patch
 
 from nanobot.agent.memory import (
+    _ARCHIVE_SUMMARY_MAX_CHARS,
     Consolidator,
     MemoryStore,
-    _ARCHIVE_SUMMARY_MAX_CHARS,
-    _RAW_ARCHIVE_MAX_CHARS,
 )
+from nanobot.session.manager import Session
 
 
 @pytest.fixture
@@ -122,6 +122,51 @@ class TestConsolidatorTokenBudget:
         await consolidator.maybe_consolidate_by_tokens(session)
         consolidator.archive.assert_not_called()
 
+    async def test_estimate_uses_full_unconsolidated_tail(self, consolidator):
+        """Consolidation pressure must see messages hidden by the replay window."""
+        session = Session(key="test:full-tail")
+        for i in range(160):
+            session.add_message("user", f"msg-{i}")
+
+        captured: dict[str, list[dict]] = {}
+
+        def build_messages(**kwargs):
+            captured["history"] = kwargs["history"]
+            return kwargs["history"]
+
+        consolidator._build_messages = build_messages
+
+        consolidator.estimate_session_prompt_tokens(session)
+
+        assert len(captured["history"]) == 160
+        assert captured["history"][0]["content"].endswith("msg-0")
+
+    async def test_replay_window_overflow_is_archived_even_under_token_budget(
+        self,
+        consolidator,
+    ):
+        """Old messages that cannot be replayed should be materialized first."""
+        consolidator._SAFETY_BUFFER = 0
+        session = Session(key="test:replay-overflow")
+        for i in range(10):
+            session.add_message("user", f"u{i}")
+            session.add_message("assistant", f"a{i}")
+
+        consolidator.estimate_session_prompt_tokens = MagicMock(return_value=(100, "tiktoken"))
+        consolidator.archive = AsyncMock(return_value="old conversation summary")
+
+        await consolidator.maybe_consolidate_by_tokens(
+            session,
+            replay_max_messages=6,
+        )
+
+        archived_chunk = consolidator.archive.await_args.args[0]
+        assert archived_chunk[0]["content"] == "u0"
+        assert archived_chunk[-1]["content"] == "a6"
+        assert session.last_consolidated == 14
+        assert session.metadata["_last_summary"]["text"] == "old conversation summary"
+        consolidator.sessions.save.assert_called()
+
     async def test_large_chunk_archived_without_cap(self, consolidator):
         """Without chunk cap, the full range from pick_consolidation_boundary is archived."""
         consolidator._SAFETY_BUFFER = 0