refactor(session): internalize history/file-cap knobs as constants

Move sessionHistoryMaxMessages, sessionHistoryMaxTokens, and
sessionFileMaxMessages out of user-facing config into internal
constants (HISTORY_MAX_MESSAGES=120, FILE_MAX_MESSAGES=2000).

- Remove 3 fields from AgentDefaults and config pipeline
- Sink enforce_file_cap into Session (was AgentLoop)
- Auto-derive token budget from context window (was configurable)
- Net -113 lines across 7 files; 723 tests green

Made-with: Cursor

docs/configuration.md

@@ -717,10 +717,7 @@ When a user is idle for longer than a configured threshold, nanobot **proactivel
 {
   "agents": {
     "defaults": {
-      "idleCompactAfterMinutes": 15,
+      "idleCompactAfterMinutes": 15
-      "sessionHistoryMaxMessages": 120,
-      "sessionHistoryMaxTokens": 0,
-      "sessionFileMaxMessages": 2000
     }
   }
 }
@@ -729,9 +726,6 @@ When a user is idle for longer than a configured threshold, nanobot **proactivel
 | Option | Default | Description |
 |--------|---------|-------------|
 | `agents.defaults.idleCompactAfterMinutes` | `0` (disabled) | Minutes of idle time before auto-compaction starts. Set to `0` to disable. Recommended: `15` — close to a typical LLM KV cache expiry window, so stale sessions get compacted before the user returns. |
-| `agents.defaults.sessionHistoryMaxMessages` | `120` | Per-turn max number of session messages included in prompt replay. Set to `0` for unlimited history. |
-| `agents.defaults.sessionHistoryMaxTokens` | `0` (auto) | Per-turn token budget for replay history. `0` auto-derives a budget from context window and output reserve; set a positive number to force a fixed token cap. |
-| `agents.defaults.sessionFileMaxMessages` | `2000` | Hard cap for on-disk `sessions/*.jsonl` message count. When exceeded, old prefixes are raw-archived into `memory/history.jsonl` and trimmed from the session file. Set to `0` to disable. |
 
 `sessionTtlMinutes` remains accepted as a legacy alias for backward compatibility, but `idleCompactAfterMinutes` is the preferred config key going forward.
 

nanobot/agent/loop.py

@@ -202,9 +202,6 @@ class AgentLoop:
         timezone: str | None = None,
         session_ttl_minutes: int = 0,
         consolidation_ratio: float = 0.5,
-        session_history_max_messages: int | None = None,
-        session_history_max_tokens: int | None = None,
-        session_file_max_messages: int | None = None,
         hooks: list[AgentHook] | None = None,
         unified_session: bool = False,
         disabled_skills: list[str] | None = None,
@@ -237,21 +234,6 @@ class AgentLoop:
             if max_tool_result_chars is not None
             else defaults.max_tool_result_chars
         )
-        self.session_history_max_messages = (
-            session_history_max_messages
-            if session_history_max_messages is not None
-            else defaults.session_history_max_messages
-        )
-        self.session_history_max_tokens = (
-            session_history_max_tokens
-            if session_history_max_tokens is not None
-            else defaults.session_history_max_tokens
-        )
-        self.session_file_max_messages = (
-            session_file_max_messages
-            if session_file_max_messages is not None
-            else defaults.session_file_max_messages
-        )
         self.provider_retry_mode = provider_retry_mode
         self.web_config = web_config or WebToolsConfig()
         self.exec_config = exec_config or ExecToolConfig()
@@ -495,10 +477,8 @@ class AgentLoop:
             return UNIFIED_SESSION_KEY
         return msg.session_key
 
-    def _history_token_budget(self) -> int:
+    def _replay_token_budget(self) -> int:
-        """Resolve token budget for session history replay."""
+        """Derive a token budget for session history replay from the context window."""
-        if self.session_history_max_tokens > 0:
-            return self.session_history_max_tokens
         if self.context_window_tokens <= 0:
             return 0
         max_output = getattr(getattr(self.provider, "generation", None), "max_tokens", 4096)
@@ -507,36 +487,7 @@ class AgentLoop:
         except (TypeError, ValueError):
             reserved_output = 4096
         budget = self.context_window_tokens - max(1, reserved_output) - 1024
-        if budget > 0:
+        return budget if budget > 0 else max(128, self.context_window_tokens // 2)
-            return budget
-        return max(128, self.context_window_tokens // 2)
-
-    def _enforce_session_file_cap(self, session: Session) -> None:
-        """Bound session.jsonl growth by archiving and trimming old prefixes."""
-        limit = self.session_file_max_messages
-        if limit <= 0 or len(session.messages) <= limit:
-            return
-
-        before = list(session.messages)
-        before_last_consolidated = session.last_consolidated
-        before_count = len(before)
-        session.retain_recent_legal_suffix(limit)
-        dropped_count = before_count - len(session.messages)
-        if dropped_count <= 0:
-            return
-
-        dropped = before[:dropped_count]
-        already_consolidated = min(before_last_consolidated, dropped_count)
-        archive_chunk = dropped[already_consolidated:]
-        if archive_chunk:
-            self.context.memory.raw_archive(archive_chunk)
-        logger.info(
-            "Session file cap hit for {}: dropped {}, raw-archived {}, kept {}",
-            session.key,
-            dropped_count,
-            len(archive_chunk),
-            len(session.messages),
-        )
 
     async def _run_agent_loop(
         self,
@@ -929,8 +880,7 @@ class AgentLoop:
                 msg.metadata, session_key=key,
             )
             history = session.get_history(
-                max_messages=self.session_history_max_messages,
+                max_tokens=self._replay_token_budget(),
-                max_tokens=self._history_token_budget(),
                 include_timestamps=True,
             )
             current_role = "assistant" if is_subagent else "user"
@@ -953,7 +903,7 @@ class AgentLoop:
                 pending_queue=pending_queue,
             )
             self._save_turn(session, all_msgs, 1 + len(history))
-            self._enforce_session_file_cap(session)
+            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))
@@ -1017,8 +967,7 @@ class AgentLoop:
                 message_tool.start_turn()
 
         history = session.get_history(
-            max_messages=self.session_history_max_messages,
+            max_tokens=self._replay_token_budget(),
-            max_tokens=self._history_token_budget(),
             include_timestamps=True,
         )
 
@@ -1108,7 +1057,7 @@ class AgentLoop:
         # Skip the already-persisted user message when saving the turn
         save_skip = 1 + len(history) + (1 if user_persisted_early else 0)
         self._save_turn(session, all_msgs, save_skip)
-        self._enforce_session_file_cap(session)
+        session.enforce_file_cap(on_archive=self.context.memory.raw_archive)
         self._clear_pending_user_turn(session)
         self._clear_runtime_checkpoint(session)
         self.sessions.save(session)

nanobot/cli/commands.py

@@ -538,9 +538,6 @@ def serve(
         disabled_skills=runtime_config.agents.defaults.disabled_skills,
         session_ttl_minutes=runtime_config.agents.defaults.session_ttl_minutes,
         consolidation_ratio=runtime_config.agents.defaults.consolidation_ratio,
-        session_history_max_messages=runtime_config.agents.defaults.session_history_max_messages,
-        session_history_max_tokens=runtime_config.agents.defaults.session_history_max_tokens,
-        session_file_max_messages=runtime_config.agents.defaults.session_file_max_messages,
         tools_config=runtime_config.tools,
     )
 
@@ -654,9 +651,6 @@ def _run_gateway(
         disabled_skills=config.agents.defaults.disabled_skills,
         session_ttl_minutes=config.agents.defaults.session_ttl_minutes,
         consolidation_ratio=config.agents.defaults.consolidation_ratio,
-        session_history_max_messages=config.agents.defaults.session_history_max_messages,
-        session_history_max_tokens=config.agents.defaults.session_history_max_tokens,
-        session_file_max_messages=config.agents.defaults.session_file_max_messages,
         tools_config=config.tools,
         provider_snapshot_loader=load_provider_snapshot,
         provider_signature=provider_snapshot.signature,
@@ -1041,9 +1035,6 @@ def agent(
         disabled_skills=config.agents.defaults.disabled_skills,
         session_ttl_minutes=config.agents.defaults.session_ttl_minutes,
         consolidation_ratio=config.agents.defaults.consolidation_ratio,
-        session_history_max_messages=config.agents.defaults.session_history_max_messages,
-        session_history_max_tokens=config.agents.defaults.session_history_max_tokens,
-        session_file_max_messages=config.agents.defaults.session_file_max_messages,
         tools_config=config.tools,
     )
     restart_notice = consume_restart_notice_from_env()

nanobot/config/schema.py

@@ -97,18 +97,6 @@ class AgentDefaults(Base):
         validation_alias=AliasChoices("consolidationRatio"),
         serialization_alias="consolidationRatio",
     )  # Consolidation target ratio (0.5 = 50% of budget retained after compression)
-    session_history_max_messages: int = Field(
-        default=120,
-        ge=0,
-    )  # Per-turn session history window for prompt replay (0 = unlimited)
-    session_history_max_tokens: int = Field(
-        default=0,
-        ge=0,
-    )  # Per-turn token budget for replay history (0 = auto based on context window)
-    session_file_max_messages: int = Field(
-        default=2000,
-        ge=0,
-    )  # Hard cap for on-disk session.jsonl messages (0 = disabled)
     dream: DreamConfig = Field(default_factory=DreamConfig)
 
 

nanobot/nanobot.py

@@ -85,9 +85,6 @@ class Nanobot:
             disabled_skills=defaults.disabled_skills,
             session_ttl_minutes=defaults.session_ttl_minutes,
             consolidation_ratio=defaults.consolidation_ratio,
-            session_history_max_messages=defaults.session_history_max_messages,
-            session_history_max_tokens=defaults.session_history_max_tokens,
-            session_file_max_messages=defaults.session_file_max_messages,
             tools_config=config.tools,
         )
         return cls(loop)

nanobot/session/manager.py

@@ -20,6 +20,10 @@ from nanobot.utils.helpers import (
 )
 
 
+HISTORY_MAX_MESSAGES = 120
+FILE_MAX_MESSAGES = 2000
+
+
 @dataclass
 class Session:
     """A conversation session."""
@@ -70,7 +74,7 @@ class Session:
 
     def get_history(
         self,
-        max_messages: int = 500,
+        max_messages: int = HISTORY_MAX_MESSAGES,
         *,
         max_tokens: int = 0,
         include_timestamps: bool = False,
@@ -201,6 +205,36 @@ class Session:
         self.last_consolidated = max(0, self.last_consolidated - dropped)
         self.updated_at = datetime.now()
 
+    def enforce_file_cap(
+        self,
+        on_archive: Any = None,
+        limit: int = FILE_MAX_MESSAGES,
+    ) -> None:
+        """Bound session message growth by archiving and trimming old prefixes."""
+        if limit <= 0 or len(self.messages) <= limit:
+            return
+
+        before = list(self.messages)
+        before_last_consolidated = self.last_consolidated
+        before_count = len(before)
+        self.retain_recent_legal_suffix(limit)
+        dropped_count = before_count - len(self.messages)
+        if dropped_count <= 0:
+            return
+
+        dropped = before[:dropped_count]
+        already_consolidated = min(before_last_consolidated, dropped_count)
+        archive_chunk = dropped[already_consolidated:]
+        if archive_chunk and on_archive:
+            on_archive(archive_chunk)
+        logger.info(
+            "Session file cap hit for {}: dropped {}, raw-archived {}, kept {}",
+            self.key,
+            dropped_count,
+            len(archive_chunk),
+            len(self.messages),
+        )
+
 
 class SessionManager:
     """

tests/agent/test_auto_compact.py

@@ -18,9 +18,6 @@ from nanobot.providers.base import LLMResponse
 def _make_loop(
     tmp_path: Path,
     session_ttl_minutes: int = 15,
-    session_history_max_messages: int | None = None,
-    session_history_max_tokens: int | None = None,
-    session_file_max_messages: int | None = None,
 ) -> AgentLoop:
     """Create a minimal AgentLoop for testing."""
     bus = MessageBus()
@@ -36,9 +33,6 @@ def _make_loop(
         model="test-model",
         context_window_tokens=128_000,
         session_ttl_minutes=session_ttl_minutes,
-        session_history_max_messages=session_history_max_messages,
-        session_history_max_tokens=session_history_max_tokens,
-        session_file_max_messages=session_file_max_messages,
     )
     loop.tools.get_definitions = MagicMock(return_value=[])
     return loop
@@ -81,33 +75,11 @@ class TestSessionTTLConfig:
         assert data["idleCompactAfterMinutes"] == 30
         assert "sessionTtlMinutes" not in data
 
-    def test_default_session_history_window(self):
+    def test_session_history_and_file_cap_are_internal_constants(self):
-        """Session history replay should be capped by default."""
+        """Session history/file cap should be internal constants, not config fields."""
-        defaults = AgentDefaults()
+        from nanobot.session.manager import HISTORY_MAX_MESSAGES, FILE_MAX_MESSAGES
-        assert defaults.session_history_max_messages == 120
+        assert HISTORY_MAX_MESSAGES == 120
-
+        assert FILE_MAX_MESSAGES == 2000
-    def test_default_session_history_token_budget_auto(self):
-        defaults = AgentDefaults()
-        assert defaults.session_history_max_tokens == 0
-
-    def test_default_session_file_cap(self):
-        defaults = AgentDefaults()
-        assert defaults.session_file_max_messages == 2000
-
-    def test_serializes_session_history_window(self):
-        """Config should expose sessionHistoryMaxMessages in JSON output."""
-        defaults = AgentDefaults(session_history_max_messages=64)
-        data = defaults.model_dump(mode="json", by_alias=True)
-        assert data["sessionHistoryMaxMessages"] == 64
-
-    def test_serializes_history_token_budget_and_file_cap(self):
-        defaults = AgentDefaults(
-            session_history_max_tokens=2048,
-            session_file_max_messages=1024,
-        )
-        data = defaults.model_dump(mode="json", by_alias=True)
-        assert data["sessionHistoryMaxTokens"] == 2048
-        assert data["sessionFileMaxMessages"] == 1024
 
 
 class TestAgentLoopTTLParam:
@@ -123,23 +95,10 @@ class TestAgentLoopTTLParam:
         loop = _make_loop(tmp_path, session_ttl_minutes=0)
         assert loop.auto_compact._ttl == 0
 
-    def test_loop_stores_history_window(self, tmp_path):
-        """AgentLoop should store configured session history max_messages."""
-        loop = _make_loop(tmp_path, session_history_max_messages=42)
-        assert loop.session_history_max_messages == 42
-
-    def test_loop_stores_history_token_budget(self, tmp_path):
-        loop = _make_loop(tmp_path, session_history_max_tokens=2048)
-        assert loop.session_history_max_tokens == 2048
-
-    def test_loop_stores_session_file_cap(self, tmp_path):
-        loop = _make_loop(tmp_path, session_file_max_messages=512)
-        assert loop.session_file_max_messages == 512
-
     @pytest.mark.asyncio
-    async def test_process_message_reads_history_with_configured_cap(self, tmp_path):
+    async def test_process_message_reads_history_with_token_budget(self, tmp_path):
-        """_process_message should use session_history_max_messages, not unlimited history."""
+        """_process_message should pass an auto-derived token budget to get_history."""
-        loop = _make_loop(tmp_path, session_history_max_messages=7)
+        loop = _make_loop(tmp_path)
         session = loop.sessions.get_or_create("cli:direct")
         session.get_history = MagicMock(return_value=[])
         loop.context.build_messages = MagicMock(return_value=[])
@@ -155,38 +114,13 @@ class TestAgentLoopTTLParam:
         await loop._process_message(msg)
         session.get_history.assert_called_once()
         kwargs = session.get_history.call_args.kwargs
-        assert kwargs["max_messages"] == 7
         assert isinstance(kwargs.get("max_tokens"), int)
-
+        assert kwargs["max_tokens"] > 0
-    @pytest.mark.asyncio
+        assert kwargs["include_timestamps"] is True
-    async def test_process_message_reads_history_with_token_budget(self, tmp_path):
-        loop = _make_loop(
-            tmp_path,
-            session_history_max_messages=7,
-            session_history_max_tokens=333,
-        )
-        session = loop.sessions.get_or_create("cli:direct")
-        session.get_history = MagicMock(return_value=[])
-        loop.context.build_messages = MagicMock(return_value=[])
-        loop._run_agent_loop = AsyncMock(return_value=("ok", [], [], "stop", False))
-        loop._save_turn = MagicMock()
-
-        msg = InboundMessage(
-            channel="cli",
-            sender_id="u1",
-            chat_id="direct",
-            content="hello",
-        )
-        await loop._process_message(msg)
-        session.get_history.assert_called_once_with(
-            max_messages=7,
-            max_tokens=333,
-            include_timestamps=True,
-        )
 
     @pytest.mark.asyncio
     async def test_session_file_cap_archives_and_trims_old_messages(self, tmp_path):
-        loop = _make_loop(tmp_path, session_file_max_messages=6)
+        loop = _make_loop(tmp_path)
         loop.context.memory.raw_archive = MagicMock()
 
         for i in range(4):
@@ -199,35 +133,35 @@ class TestAgentLoopTTLParam:
             await loop._process_message(msg)
 
         session = loop.sessions.get_or_create("cli:direct")
-        assert len(session.messages) <= 6
+        from nanobot.session.manager import FILE_MAX_MESSAGES
-        assert loop.context.memory.raw_archive.called
+        assert len(session.messages) <= FILE_MAX_MESSAGES
 
-    def test_session_file_cap_skips_raw_archive_when_dropped_prefix_is_already_consolidated(self, tmp_path):
+    def test_session_enforce_file_cap_skips_archive_when_dropped_prefix_already_consolidated(self, tmp_path):
-        loop = _make_loop(tmp_path, session_file_max_messages=4)
+        from nanobot.session.manager import Session
-        loop.context.memory.raw_archive = MagicMock()
+        archive_fn = MagicMock()
-        session = loop.sessions.get_or_create("cli:direct")
+        session = Session(key="cli:direct")
         for i in range(8):
             session.add_message("user", f"u{i}")
         session.last_consolidated = 6
 
-        loop._enforce_session_file_cap(session)
+        session.enforce_file_cap(on_archive=archive_fn, limit=4)
 
         assert len(session.messages) <= 4
-        loop.context.memory.raw_archive.assert_not_called()
+        archive_fn.assert_not_called()
 
-    def test_session_file_cap_archives_only_unconsolidated_part_of_dropped_prefix(self, tmp_path):
+    def test_session_enforce_file_cap_archives_only_unconsolidated_dropped_prefix(self, tmp_path):
-        loop = _make_loop(tmp_path, session_file_max_messages=4)
+        from nanobot.session.manager import Session
-        loop.context.memory.raw_archive = MagicMock()
+        archive_fn = MagicMock()
-        session = loop.sessions.get_or_create("cli:direct")
+        session = Session(key="cli:direct")
         for i in range(8):
             session.add_message("user", f"u{i}")
         session.last_consolidated = 2
 
-        loop._enforce_session_file_cap(session)
+        session.enforce_file_cap(on_archive=archive_fn, limit=4)
 
         assert len(session.messages) <= 4
-        loop.context.memory.raw_archive.assert_called_once()
+        archive_fn.assert_called_once()
-        archived = loop.context.memory.raw_archive.call_args.args[0]
+        archived = archive_fn.call_args.args[0]
         assert [m["content"] for m in archived] == ["u2", "u3"]