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5089c84dbf
A stdio MCP server (e.g. `npx -y mcp-remote <url>`) is spawned as a direct
child of the Hermes process. Existing teardown (MCPServerTask.shutdown() /
_kill_orphaned_mcp_children()) reaps it correctly on a clean exit, but a
kill -9 / crash / force-quit of the Hermes process skips that path entirely
-- the child (and its own descendants, e.g. mcp-remote's spawned node
process) is orphaned and keeps running. Repeated ungraceful restarts pile up
N orphaned processes racing to hold the same upstream SSE session, producing
errors like 'Invalid request parameters' on legitimate reconnects.
macOS/Linux have no portable equivalent of prctl(PR_SET_PDEATHSIG) at the
Python subprocess level, so this adds a thin supervisor
(tools/mcp_stdio_watchdog.py) that:
- execs the real command as its own child in its own process group
- passes stdin/stdout/stderr through untouched (MCP stdio protocol
talks directly over those streams)
- polls the original spawning PID with the same orphan-detection
algorithm already proven in tui_gateway/slash_worker.py (ppid
comparison + psutil creation-time guard against PID reuse)
- SIGTERM-then-SIGKILL's the child's process group the moment the
original parent is gone
Wired into _run_stdio via a new _wrap_command_with_watchdog() helper,
POSIX-only (matches the existing killpg-based cleanup's platform scope),
fails open (any error resolving pid/create-time falls back to the
unwrapped command) so this can never be the reason a working MCP server
stops starting.
Verified: reproduced the exact orphan scenario standalone (fake parent
process spawns watchdog + fake long-running MCP child, kill -9 the fake
parent, confirm the watchdog reaps the child within its poll window with
zero leaked processes). Updated test_mcp_tool_issue_948.py's resolved-path
assertion to check the watchdog-wrapped command instead of the raw
resolved binary. Full test_mcp_tool.py + test_mcp_stability.py +
test_mcp_tool_issue_948.py suite: 232 passed. Full -k mcp sweep across the
whole test tree: 1003 passed, 2 skipped, 0 failed.
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| .. | ||
| acp | ||
| acp_adapter | ||
| agent | ||
| ci | ||
| cli | ||
| computer_use | ||
| cron | ||
| dashboard | ||
| docker | ||
| e2e | ||
| fakes | ||
| fixtures/plugins/example-dashboard/dashboard | ||
| gateway | ||
| hermes_cli | ||
| hermes_state | ||
| honcho_plugin | ||
| integration | ||
| manual | ||
| openviking_plugin | ||
| plugins | ||
| providers | ||
| run_agent | ||
| scripts | ||
| secret_sources | ||
| skills | ||
| stress | ||
| tools | ||
| tui_gateway | ||
| website | ||
| __init__.py | ||
| conftest.py | ||
| run_interrupt_test.py | ||
| test_account_usage.py | ||
| test_assistant_ui_tap_compat.py | ||
| test_atomic_replace_symlinks.py | ||
| test_background_review_list_shapes.py | ||
| test_background_review_session_isolation.py | ||
| test_base_url_hostname.py | ||
| test_batch_runner_checkpoint.py | ||
| test_bitwarden_secrets.py | ||
| test_cli_file_drop.py | ||
| test_cli_manual_compress.py | ||
| test_cli_skin_integration.py | ||
| test_code_skew.py | ||
| test_copilot_initiator.py | ||
| test_ctx_halving_fix.py | ||
| test_dashboard_sidecar_close_on_disconnect.py | ||
| test_delegate_cascade_49148.py | ||
| test_desktop_electron_pin.py | ||
| test_desktop_mac_entitlements.py | ||
| test_dispatch_session_id.py | ||
| test_empty_model_fallback.py | ||
| test_empty_session_hygiene.py | ||
| test_env_loader_op_bootstrap.py | ||
| test_env_loader_secret_sources.py | ||
| test_evidence_store.py | ||
| test_fast_safe_load.py | ||
| test_gateway_streaming_nested_config.py | ||
| test_get_tool_definitions_cache_isolation.py | ||
| test_hermes_bootstrap.py | ||
| test_hermes_constants.py | ||
| test_hermes_home_profile_warning.py | ||
| test_hermes_logging.py | ||
| test_hermes_state.py | ||
| test_hermes_state_compression_locks.py | ||
| test_hermes_state_wal_fallback.py | ||
| test_honcho_client_concurrency.py | ||
| test_honcho_client_config.py | ||
| test_honcho_session_context.py | ||
| test_honcho_startup_fail_open.py | ||
| test_install_diverged_update.py | ||
| test_install_lockfile_churn.py | ||
| test_install_no_initial_commit.py | ||
| test_install_ps1_native_stderr_eap.py | ||
| test_install_ps1_node_path_for_npm.py | ||
| test_install_ps1_python_fallback_venv.py | ||
| test_install_ps1_uv_powershell_host.py | ||
| test_install_ps1_web_server_syntax_probe.py | ||
| test_install_sh_browser_install.py | ||
| test_install_sh_install_method_stamp.py | ||
| test_install_sh_node_global_prefix.py | ||
| test_install_sh_pythonpath_sanitization.py | ||
| test_install_sh_root_fhs_uv_python_path.py | ||
| test_install_sh_setup_wizard_tty_probe.py | ||
| test_install_sh_symlink_stomp.py | ||
| test_install_sh_termux_network_prereqs.py | ||
| test_install_unmerged_index.py | ||
| test_ipv4_preference.py | ||
| test_lazy_session_regressions.py | ||
| test_lint_config.py | ||
| test_live_system_guard_self_test.py | ||
| test_mcp_serve.py | ||
| test_mini_swe_runner.py | ||
| test_minimax_model_validation.py | ||
| test_minimax_oauth.py | ||
| test_minisweagent_path.py | ||
| test_model_forces_max_completion_tokens.py | ||
| test_model_picker_scroll.py | ||
| test_model_tools.py | ||
| test_model_tools_async_bridge.py | ||
| test_ollama_num_ctx.py | ||
| test_onepassword_secrets.py | ||
| test_output_cap_parsing.py | ||
| test_package_json_lazy_deps.py | ||
| test_packaging_metadata.py | ||
| test_plugin_skills.py | ||
| test_plugin_utils.py | ||
| test_process_loop_event_loop_warning.py | ||
| test_profile_isolation_runtime.py | ||
| test_project_metadata.py | ||
| test_pty_keepalive_ws.py | ||
| test_pty_session.py | ||
| test_retry_utils.py | ||
| test_run_tests_parallel.py | ||
| test_sanitize_tool_error.py | ||
| test_setup_temporary_outputs.py | ||
| test_slash_worker_watchdog.py | ||
| test_sql_injection.py | ||
| test_stale_utils_module_import.py | ||
| test_state_db_malformed_repair.py | ||
| test_subprocess_home_isolation.py | ||
| test_termux_all_extra_compat.py | ||
| test_timezone.py | ||
| test_toolset_distributions.py | ||
| test_toolsets.py | ||
| test_trajectory_compressor.py | ||
| test_trajectory_compressor_async.py | ||
| test_transform_llm_output_hook.py | ||
| test_transform_tool_result_hook.py | ||
| test_tui_gateway_loop_noise.py | ||
| test_tui_gateway_queue_on_busy.py | ||
| test_tui_gateway_server.py | ||
| test_tui_gateway_ws.py | ||
| test_tui_mcp_late_refresh.py | ||
| test_utils_truthy_values.py | ||
| test_web_server.py | ||
| test_wheel_locales_e2e.py | ||
| test_windows_subprocess_no_window_flags.py | ||
| test_yaml_indent_consistency_31999.py | ||
| test_yuanbao_integration.py | ||
| test_yuanbao_markdown.py | ||
| test_yuanbao_pipeline.py | ||
| test_yuanbao_proto.py | ||
| test_yuanbao_reconnect_set_active.py | ||
| test_yuanbao_shutdown.py | ||