fix(config): retire max messages setting

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