fix(config): retire max messages setting

nanobot/agent/loop.py

@@ -57,7 +57,7 @@ from nanobot.session.goal_state import (
     sustained_goal_active,
 )
 from nanobot.session.keys import UNIFIED_SESSION_KEY, session_key_for_channel
-from nanobot.session.manager import Session, SessionManager
+from nanobot.session.manager import DEFAULT_REPLAY_MAX_MESSAGES, Session, SessionManager
 from nanobot.utils.document import extract_documents, reference_non_image_attachments
 from nanobot.utils.helpers import image_placeholder_text
 from nanobot.utils.helpers import truncate_text as truncate_text_fn
@@ -201,7 +201,7 @@ class AgentLoop:
         timezone: str | None = None,
         session_ttl_minutes: int = 0,
         consolidation_ratio: float = 0.5,
-        max_messages: int = 500,
+        max_messages: int = DEFAULT_REPLAY_MAX_MESSAGES,
         hooks: list[AgentHook] | None = None,
         unified_session: bool = False,
         disabled_skills: list[str] | None = None,
@@ -292,7 +292,9 @@ class AgentLoop:
             llm_wall_timeout_for_session=lambda sk: runner_wall_llm_timeout_s(self.sessions, sk),
         )
         self._unified_session = unified_session
-        self._max_messages = max_messages if max_messages > 0 else 500
+        self._max_messages = (
+            max_messages if max_messages > 0 else DEFAULT_REPLAY_MAX_MESSAGES
+        )
         self._running = False
         self._mcp_servers = mcp_servers or {}
         self._mcp_stacks: dict[str, AsyncExitStack] = {}
@@ -390,7 +392,6 @@ class AgentLoop:
             disabled_skills=defaults.disabled_skills,
             session_ttl_minutes=defaults.session_ttl_minutes,
             consolidation_ratio=defaults.consolidation_ratio,
-            max_messages=defaults.max_messages,
             tools_config=config.tools,
             model_presets=preset_helpers.configured_model_presets(config),
             model_preset=defaults.model_preset,

nanobot/config/loader.py

@@ -7,6 +7,7 @@ from pathlib import Path
 from typing import Any
 
 import pydantic
+from loguru import logger
 from pydantic import BaseModel
 
 from nanobot.config.schema import Config, _resolve_tool_config_refs
@@ -152,6 +153,23 @@ def _env_replace(match: re.Match[str]) -> str:
 
 def _migrate_config(data: dict) -> dict:
     """Migrate old config formats to current."""
+    agents = data.get("agents", {})
+    defaults = agents.get("defaults", {}) if isinstance(agents, dict) else {}
+    if isinstance(defaults, dict):
+        legacy_max_message_keys = [
+            key for key in ("maxMessages", "max_messages") if key in defaults
+        ]
+        if legacy_max_message_keys:
+            for key in legacy_max_message_keys:
+                defaults.pop(key, None)
+            # TODO(next version): Remove this legacy cleanup branch; the schema
+            # will silently ignore this field once the warning grace period ends.
+            logger.warning(
+                "agents.defaults.maxMessages/max_messages is legacy and ignored; "
+                "replay max messages is now an internal safety cap. Remove it from "
+                "config. This compatibility warning will be removed in the next version."
+            )
+
     # Move tools.exec.restrictToWorkspace → tools.restrictToWorkspace
     tools = data.get("tools", {})
     exec_cfg = tools.get("exec", {})

nanobot/config/schema.py

@@ -154,10 +154,6 @@ class AgentDefaults(Base):
         validation_alias=AliasChoices("idleCompactAfterMinutes", "sessionTtlMinutes"),
         serialization_alias="idleCompactAfterMinutes",
     )  # Auto-compact idle threshold in minutes (0 = disabled)
-    max_messages: int = Field(
-        default=500,
-        ge=0,
-    )  # Last-resort max messages to replay from session history (0 = use default 500)
     consolidation_ratio: float = Field(
         default=0.5,
         ge=0.1,

nanobot/session/manager.py

@@ -27,6 +27,7 @@ from nanobot.utils.helpers import (
 from nanobot.utils.subagent_channel_display import scrub_subagent_announce_body
 
 FILE_MAX_MESSAGES = 2000
+DEFAULT_REPLAY_MAX_MESSAGES = 500
 _MESSAGE_TIME_PREFIX_RE = re.compile(r"^\[Message Time: [^\]]+\]\n?")
 _LOCAL_IMAGE_BREADCRUMB_RE = re.compile(r"^\[image: (?:/|~)[^\]]+\]\s*$")
 _TOOL_CALL_ECHO_RE = re.compile(r'^\s*(?:generate_image|message)\([^)]*\)\s*$')
@@ -132,7 +133,7 @@ class Session:
 
     def get_history(
         self,
-        max_messages: int = 500,
+        max_messages: int = DEFAULT_REPLAY_MAX_MESSAGES,
         *,
         max_tokens: int = 0,
         extend_to_user: bool = False,
@@ -143,7 +144,7 @@ class Session:
         token budget from the tail (``max_tokens``) when provided.
         """
         unconsolidated = self.messages[self.last_consolidated:]
-        max_messages = max_messages if max_messages > 0 else 500
+        max_messages = max_messages if max_messages > 0 else DEFAULT_REPLAY_MAX_MESSAGES
         start_idx = recent_message_start_index(
             unconsolidated,
             max_messages,

tests/agent/test_max_messages_config.py

@@ -1,4 +1,4 @@
-"""Tests for max_messages config wiring into session history replay."""
+"""Tests for the internal max_messages replay cap."""
 
 from __future__ import annotations
 
@@ -11,9 +11,9 @@ from nanobot.agent.loop import AgentLoop
 from nanobot.bus.events import InboundMessage
 from nanobot.bus.queue import MessageBus
 from nanobot.providers.base import LLMResponse
-from nanobot.session.manager import Session
+from nanobot.session.manager import DEFAULT_REPLAY_MAX_MESSAGES, Session
 
-DEFAULT_MAX_MESSAGES = 500
+DEFAULT_MAX_MESSAGES = DEFAULT_REPLAY_MAX_MESSAGES
 
 
 def _make_loop(tmp_path: Path, max_messages: int = DEFAULT_MAX_MESSAGES) -> AgentLoop:
@@ -103,10 +103,10 @@ class TestGetHistoryWithMaxMessages:
 
 
 class TestMaxMessagesIntegration:
-    """Verify the config flows from AgentLoop into get_history calls."""
+    """Verify AgentLoop passes the replay cap into get_history calls."""
 
     @pytest.mark.asyncio
-    async def test_process_message_passes_config_to_history_call(self, tmp_path: Path) -> None:
+    async def test_process_message_passes_limit_to_history_call(self, tmp_path: Path) -> None:
         """The real message path should pass max_messages into session history replay."""
         loop = _make_loop(tmp_path, max_messages=25)
         loop.provider.chat_with_retry = AsyncMock(
@@ -127,7 +127,7 @@ class TestMaxMessagesIntegration:
         assert mock_hist.call_args.kwargs["extend_to_user"] is False
 
     @pytest.mark.asyncio
-    async def test_zero_config_passes_builtin_limit_to_history_call(self, tmp_path: Path) -> None:
+    async def test_zero_limit_passes_builtin_limit_to_history_call(self, tmp_path: Path) -> None:
         loop = _make_loop(tmp_path, max_messages=0)
         loop.provider.chat_with_retry = AsyncMock(
             return_value=LLMResponse(content="ok", tool_calls=[], usage={})
@@ -182,31 +182,3 @@ class TestMaxMessagesIntegration:
         sent_text = "\n".join(str(message.get("content")) for message in sent_messages)
         assert "new question" in sent_text
         assert "long older turn" not in sent_text
-
-
-class TestSchemaConfig:
-    """Verify the config schema accepts max_messages."""
-
-    def test_schema_default(self) -> None:
-        from nanobot.config.schema import AgentDefaults
-
-        defaults = AgentDefaults()
-        assert defaults.max_messages == DEFAULT_MAX_MESSAGES
-
-    def test_schema_accepts_zero_as_builtin_limit(self) -> None:
-        from nanobot.config.schema import AgentDefaults
-
-        defaults = AgentDefaults(max_messages=0)
-        assert defaults.max_messages == 0
-
-    def test_schema_accepts_positive(self) -> None:
-        from nanobot.config.schema import AgentDefaults
-
-        defaults = AgentDefaults(max_messages=25)
-        assert defaults.max_messages == 25
-
-    def test_schema_rejects_negative(self) -> None:
-        from nanobot.config.schema import AgentDefaults
-
-        with pytest.raises(Exception):  # Pydantic validation error
-            AgentDefaults(max_messages=-1)

tests/config/test_config_migration.py

@@ -2,6 +2,8 @@ import json
 import socket
 from unittest.mock import patch
 
+import pytest
+
 from nanobot.config.loader import load_config, save_config
 from nanobot.security.network import validate_url_target
 
@@ -93,6 +95,41 @@ def test_onboard_does_not_crash_with_legacy_memory_window(tmp_path, monkeypatch)
     assert result.exit_code == 0
 
 
+@pytest.mark.parametrize("field_name", ["maxMessages", "max_messages"])
+def test_load_config_warns_and_ignores_legacy_max_messages(tmp_path, field_name) -> None:
+    config_path = tmp_path / "config.json"
+    config_path.write_text(
+        json.dumps({"agents": {"defaults": {field_name: 25, "maxTokens": 1234}}}),
+        encoding="utf-8",
+    )
+
+    with patch("nanobot.config.loader.logger.warning") as warning:
+        config = load_config(config_path)
+
+    assert config.agents.defaults.max_tokens == 1234
+    assert not hasattr(config.agents.defaults, "max_messages")
+    warning.assert_called_once()
+    message = warning.call_args.args[0]
+    assert "legacy and ignored" in message
+    assert "next version" in message
+
+
+def test_save_config_drops_legacy_max_messages(tmp_path) -> None:
+    config_path = tmp_path / "config.json"
+    config_path.write_text(
+        json.dumps({"agents": {"defaults": {"maxMessages": 25}}}),
+        encoding="utf-8",
+    )
+
+    with patch("nanobot.config.loader.logger.warning"):
+        config = load_config(config_path)
+    save_config(config, config_path)
+    saved = json.loads(config_path.read_text(encoding="utf-8"))
+
+    assert "maxMessages" not in saved["agents"]["defaults"]
+    assert "max_messages" not in saved["agents"]["defaults"]
+
+
 def test_onboard_refresh_backfills_missing_channel_fields(tmp_path, monkeypatch) -> None:
     from types import SimpleNamespace