fix(mcp): stability fix pack — reload timeout, shutdown cleanup, event loop handler, OAuth non-blocking (#4757)
Four fixes for MCP server stability issues reported by community member (terminal lockup, zombie processes, escape sequence pollution, startup hang): 1. MCP reload timeout guard (cli.py): _check_config_mcp_changes now runs _reload_mcp in a separate daemon thread with a 30s hard timeout. Previously, a hung MCP server could block the process_loop thread indefinitely, freezing the entire TUI (user can type but nothing happens, only Ctrl+D/Ctrl+\ work). 2. MCP stdio subprocess PID tracking (mcp_tool.py): Tracks child PIDs spawned by stdio_client via before/after snapshots of /proc children. On shutdown, _stop_mcp_loop force-kills any tracked PIDs that survived the SDK's graceful SIGTERM→SIGKILL cleanup. Prevents zombie MCP server processes from accumulating across sessions. 3. MCP event loop exception handler (mcp_tool.py): Installs _mcp_loop_exception_handler on the MCP background event loop — same pattern as the existing _suppress_closed_loop_errors on prompt_toolkit's loop. Suppresses benign 'Event loop is closed' RuntimeError from httpx transport __del__ during MCP shutdown. Salvaged from PR #2538 (acsezen). 4. MCP OAuth non-blocking (mcp_oauth.py): Replaces blocking input() call in _wait_for_callback with OAuthNonInteractiveError raise. Adds _is_interactive() TTY detection. In non-interactive environments, build_oauth_auth() still returns a provider (cached tokens + refresh work), but the callback handler raises immediately instead of blocking the MCP event loop for 120s. Re-raises OAuth setup failures in _run_http so failed servers are reported cleanly without blocking others. Salvaged from PRs #4521 (voidborne-d) and #4465 (heathley). Closes #2537, closes #4462 Related: #4128, #3436
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Teknium
@@ -9,10 +9,13 @@ import pytest
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from tools.mcp_oauth import (
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HermesTokenStorage,
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OAuthNonInteractiveError,
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build_oauth_auth,
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remove_oauth_tokens,
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_find_free_port,
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_can_open_browser,
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_is_interactive,
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_wait_for_callback,
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)
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@@ -236,3 +239,99 @@ class TestRemoveOAuthTokens:
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def test_no_error_when_files_missing(self, tmp_path, monkeypatch):
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monkeypatch.setenv("HERMES_HOME", str(tmp_path))
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remove_oauth_tokens("nonexistent") # should not raise
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# ---------------------------------------------------------------------------
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# Non-interactive / startup-safety tests (issue #4462)
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# ---------------------------------------------------------------------------
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class TestIsInteractive:
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"""_is_interactive() detects headless/daemon/container environments."""
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def test_false_when_stdin_not_tty(self, monkeypatch):
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mock_stdin = MagicMock()
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mock_stdin.isatty.return_value = False
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monkeypatch.setattr("tools.mcp_oauth.sys.stdin", mock_stdin)
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assert _is_interactive() is False
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def test_true_when_stdin_is_tty(self, monkeypatch):
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mock_stdin = MagicMock()
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mock_stdin.isatty.return_value = True
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monkeypatch.setattr("tools.mcp_oauth.sys.stdin", mock_stdin)
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assert _is_interactive() is True
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def test_false_when_stdin_has_no_isatty(self, monkeypatch):
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"""Some environments replace stdin with an object without isatty()."""
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mock_stdin = object() # no isatty attribute
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monkeypatch.setattr("tools.mcp_oauth.sys.stdin", mock_stdin)
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assert _is_interactive() is False
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class TestWaitForCallbackNoBlocking:
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"""_wait_for_callback() must never call input() — it raises instead."""
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def test_raises_on_timeout_instead_of_input(self):
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"""When no auth code arrives, raises OAuthNonInteractiveError."""
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import tools.mcp_oauth as mod
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import asyncio
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mod._oauth_port = _find_free_port()
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async def instant_sleep(_seconds):
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pass
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with patch.object(mod.asyncio, "sleep", instant_sleep):
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with patch("builtins.input", side_effect=AssertionError("input() must not be called")):
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with pytest.raises(OAuthNonInteractiveError, match="callback timed out"):
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asyncio.run(_wait_for_callback())
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class TestBuildOAuthAuthNonInteractive:
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"""build_oauth_auth() in non-interactive mode."""
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def test_noninteractive_without_cached_tokens_warns(self, tmp_path, monkeypatch, caplog):
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"""Without cached tokens, non-interactive mode logs a clear warning."""
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try:
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from mcp.client.auth import OAuthClientProvider
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except ImportError:
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pytest.skip("MCP SDK auth not available")
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monkeypatch.setenv("HERMES_HOME", str(tmp_path))
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mock_stdin = MagicMock()
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mock_stdin.isatty.return_value = False
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monkeypatch.setattr("tools.mcp_oauth.sys.stdin", mock_stdin)
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import logging
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with caplog.at_level(logging.WARNING, logger="tools.mcp_oauth"):
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auth = build_oauth_auth("atlassian", "https://mcp.atlassian.com/v1/mcp")
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assert auth is not None
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assert "no cached tokens found" in caplog.text.lower()
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assert "non-interactive" in caplog.text.lower()
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def test_noninteractive_with_cached_tokens_no_warning(self, tmp_path, monkeypatch, caplog):
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"""With cached tokens, non-interactive mode logs no 'no cached tokens' warning."""
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try:
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from mcp.client.auth import OAuthClientProvider
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except ImportError:
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pytest.skip("MCP SDK auth not available")
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monkeypatch.setenv("HERMES_HOME", str(tmp_path))
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mock_stdin = MagicMock()
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mock_stdin.isatty.return_value = False
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monkeypatch.setattr("tools.mcp_oauth.sys.stdin", mock_stdin)
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# Pre-populate cached tokens
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d = tmp_path / "mcp-tokens"
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d.mkdir(parents=True)
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(d / "atlassian.json").write_text(json.dumps({
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"access_token": "cached",
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"token_type": "Bearer",
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}))
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import logging
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with caplog.at_level(logging.WARNING, logger="tools.mcp_oauth"):
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auth = build_oauth_auth("atlassian", "https://mcp.atlassian.com/v1/mcp")
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assert auth is not None
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assert "no cached tokens found" not in caplog.text.lower()
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143
tests/tools/test_mcp_stability.py
Normal file
143
tests/tools/test_mcp_stability.py
Normal file
@@ -0,0 +1,143 @@
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"""Tests for MCP stability fixes — event loop handler, PID tracking, shutdown robustness."""
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import asyncio
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import os
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import signal
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import threading
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from unittest.mock import patch, MagicMock
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import pytest
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# ---------------------------------------------------------------------------
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# Fix 1: MCP event loop exception handler
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# ---------------------------------------------------------------------------
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class TestMCPLoopExceptionHandler:
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"""_mcp_loop_exception_handler suppresses benign 'Event loop is closed'."""
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def test_suppresses_event_loop_closed(self):
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from tools.mcp_tool import _mcp_loop_exception_handler
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loop = MagicMock()
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context = {"exception": RuntimeError("Event loop is closed")}
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# Should NOT call default handler
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_mcp_loop_exception_handler(loop, context)
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loop.default_exception_handler.assert_not_called()
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def test_forwards_other_runtime_errors(self):
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from tools.mcp_tool import _mcp_loop_exception_handler
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loop = MagicMock()
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context = {"exception": RuntimeError("some other error")}
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_mcp_loop_exception_handler(loop, context)
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loop.default_exception_handler.assert_called_once_with(context)
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def test_forwards_non_runtime_errors(self):
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from tools.mcp_tool import _mcp_loop_exception_handler
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loop = MagicMock()
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context = {"exception": ValueError("bad value")}
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_mcp_loop_exception_handler(loop, context)
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loop.default_exception_handler.assert_called_once_with(context)
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def test_forwards_contexts_without_exception(self):
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from tools.mcp_tool import _mcp_loop_exception_handler
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loop = MagicMock()
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context = {"message": "just a message"}
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_mcp_loop_exception_handler(loop, context)
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loop.default_exception_handler.assert_called_once_with(context)
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def test_handler_installed_on_mcp_loop(self):
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"""_ensure_mcp_loop installs the exception handler on the new loop."""
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import tools.mcp_tool as mcp_mod
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try:
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mcp_mod._ensure_mcp_loop()
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with mcp_mod._lock:
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loop = mcp_mod._mcp_loop
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assert loop is not None
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assert loop.get_exception_handler() is mcp_mod._mcp_loop_exception_handler
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finally:
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mcp_mod._stop_mcp_loop()
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# ---------------------------------------------------------------------------
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# Fix 2: stdio PID tracking
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# ---------------------------------------------------------------------------
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class TestStdioPidTracking:
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"""_snapshot_child_pids and _stdio_pids track subprocess PIDs."""
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def test_snapshot_returns_set(self):
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from tools.mcp_tool import _snapshot_child_pids
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result = _snapshot_child_pids()
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assert isinstance(result, set)
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# All elements should be ints
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for pid in result:
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assert isinstance(pid, int)
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def test_stdio_pids_starts_empty(self):
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from tools.mcp_tool import _stdio_pids, _lock
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with _lock:
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# Might have residual state from other tests, just check type
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assert isinstance(_stdio_pids, set)
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def test_kill_orphaned_noop_when_empty(self):
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"""_kill_orphaned_mcp_children does nothing when no PIDs tracked."""
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from tools.mcp_tool import _kill_orphaned_mcp_children, _stdio_pids, _lock
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with _lock:
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_stdio_pids.clear()
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# Should not raise
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_kill_orphaned_mcp_children()
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def test_kill_orphaned_handles_dead_pids(self):
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"""_kill_orphaned_mcp_children gracefully handles already-dead PIDs."""
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from tools.mcp_tool import _kill_orphaned_mcp_children, _stdio_pids, _lock
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# Use a PID that definitely doesn't exist
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fake_pid = 999999999
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with _lock:
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_stdio_pids.add(fake_pid)
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# Should not raise (ProcessLookupError is caught)
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_kill_orphaned_mcp_children()
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with _lock:
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assert fake_pid not in _stdio_pids
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# ---------------------------------------------------------------------------
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# Fix 3: MCP reload timeout (cli.py)
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# ---------------------------------------------------------------------------
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class TestMCPReloadTimeout:
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"""_check_config_mcp_changes uses a timeout on _reload_mcp."""
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def test_reload_timeout_does_not_block_forever(self, tmp_path, monkeypatch):
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"""If _reload_mcp hangs, the config watcher times out and returns."""
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import time
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# Create a mock HermesCLI-like object with the needed attributes
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class FakeCLI:
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_config_mtime = 0.0
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_config_mcp_servers = {}
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_last_config_check = 0.0
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_command_running = False
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config = {}
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agent = None
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def _reload_mcp(self):
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# Simulate a hang — sleep longer than the timeout
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time.sleep(60)
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def _slow_command_status(self, cmd):
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return cmd
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# This test verifies the timeout mechanism exists in the code
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# by checking that _check_config_mcp_changes doesn't call
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# _reload_mcp directly (it uses a thread now)
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import inspect
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from cli import HermesCLI
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source = inspect.getsource(HermesCLI._check_config_mcp_changes)
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# The fix adds threading.Thread for _reload_mcp
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assert "Thread" in source or "thread" in source.lower(), \
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"_check_config_mcp_changes should use a thread for _reload_mcp"
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