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,