Files
hermes-agent/tests/test_cli_mcp_config_watch.py
Teknium 5e92a4ce5a fix: auto-reload MCP tools when mcp_servers config changes without restart (#1474)
Fixes #1036

After adding an MCP server to config.yaml, users had to restart Hermes
before the new tools became visible — even though /reload-mcp existed.

Add _check_config_mcp_changes() called from process_loop every 5s:
- stat() config.yaml for mtime changes (fast path, no YAML parse)
- On mtime change, parse and compare mcp_servers section
- If mcp_servers changed, auto-trigger _reload_mcp() and notify user
- Skip check while agent is running to avoid interrupting tool calls
- Throttled to CONFIG_WATCH_INTERVAL=5s to avoid busy-polling

/reload-mcp still works for manual force-reload.

Tests: 6 new tests in TestMCPConfigWatch, all passed

Co-authored-by: teyrebaz33 <hakanerten02@hotmail.com>
2026-03-15 19:03:34 -07:00

104 lines
4.0 KiB
Python

"""Tests for automatic MCP reload when config.yaml mcp_servers section changes."""
import time
from pathlib import Path
from unittest.mock import MagicMock, patch
def _make_cli(tmp_path, mcp_servers=None):
"""Create a minimal HermesCLI instance with mocked config."""
import cli as cli_mod
obj = object.__new__(cli_mod.HermesCLI)
obj.config = {"mcp_servers": mcp_servers or {}}
obj._agent_running = False
obj._last_config_check = 0.0
obj._config_mcp_servers = mcp_servers or {}
cfg_file = tmp_path / "config.yaml"
cfg_file.write_text("mcp_servers: {}\n")
obj._config_mtime = cfg_file.stat().st_mtime
obj._reload_mcp = MagicMock()
obj._busy_command = MagicMock()
obj._busy_command.return_value.__enter__ = MagicMock(return_value=None)
obj._busy_command.return_value.__exit__ = MagicMock(return_value=False)
obj._slow_command_status = MagicMock(return_value="reloading...")
return obj, cfg_file
class TestMCPConfigWatch:
def test_no_change_does_not_reload(self, tmp_path):
"""If mtime and mcp_servers unchanged, _reload_mcp is NOT called."""
obj, cfg_file = _make_cli(tmp_path)
with patch("hermes_cli.config.get_config_path", return_value=cfg_file):
obj._check_config_mcp_changes()
obj._reload_mcp.assert_not_called()
def test_mtime_change_with_same_mcp_servers_does_not_reload(self, tmp_path):
"""If file mtime changes but mcp_servers is identical, no reload."""
import yaml
obj, cfg_file = _make_cli(tmp_path, mcp_servers={"fs": {"command": "npx"}})
# Write same mcp_servers but touch the file
cfg_file.write_text(yaml.dump({"mcp_servers": {"fs": {"command": "npx"}}}))
# Force mtime to appear changed
obj._config_mtime = 0.0
with patch("hermes_cli.config.get_config_path", return_value=cfg_file):
obj._check_config_mcp_changes()
obj._reload_mcp.assert_not_called()
def test_new_mcp_server_triggers_reload(self, tmp_path):
"""Adding a new MCP server to config triggers auto-reload."""
import yaml
obj, cfg_file = _make_cli(tmp_path, mcp_servers={})
# Simulate user adding a new MCP server to config.yaml
cfg_file.write_text(yaml.dump({"mcp_servers": {"github": {"url": "https://mcp.github.com"}}}))
obj._config_mtime = 0.0 # force stale mtime
with patch("hermes_cli.config.get_config_path", return_value=cfg_file):
obj._check_config_mcp_changes()
obj._reload_mcp.assert_called_once()
def test_removed_mcp_server_triggers_reload(self, tmp_path):
"""Removing an MCP server from config triggers auto-reload."""
import yaml
obj, cfg_file = _make_cli(tmp_path, mcp_servers={"github": {"url": "https://mcp.github.com"}})
# Simulate user removing the server
cfg_file.write_text(yaml.dump({"mcp_servers": {}}))
obj._config_mtime = 0.0
with patch("hermes_cli.config.get_config_path", return_value=cfg_file):
obj._check_config_mcp_changes()
obj._reload_mcp.assert_called_once()
def test_interval_throttle_skips_check(self, tmp_path):
"""If called within CONFIG_WATCH_INTERVAL, stat() is skipped."""
obj, cfg_file = _make_cli(tmp_path)
obj._last_config_check = time.monotonic() # just checked
with patch("hermes_cli.config.get_config_path", return_value=cfg_file), \
patch.object(Path, "stat") as mock_stat:
obj._check_config_mcp_changes()
mock_stat.assert_not_called()
obj._reload_mcp.assert_not_called()
def test_missing_config_file_does_not_crash(self, tmp_path):
"""If config.yaml doesn't exist, _check_config_mcp_changes is a no-op."""
obj, cfg_file = _make_cli(tmp_path)
missing = tmp_path / "nonexistent.yaml"
with patch("hermes_cli.config.get_config_path", return_value=missing):
obj._check_config_mcp_changes() # should not raise
obj._reload_mcp.assert_not_called()