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When the Hermes Docker image runs an stdio MCP server configured with an
explicit env.PATH that omits /usr/local/bin (a common pattern when users
hand-author PATH for sandboxing), the MCP env-filter passes that narrow
PATH straight through to the subprocess. _resolve_stdio_command's
fallback for bare 'npx' / 'npm' / 'node' commands only checked
$HERMES_HOME/node/bin/ and ~/.local/bin/, so execvp() failed with
'[Errno 2] No such file or directory: npx' on every Node-based stdio
MCP server (Railway, Anthropic, GitHub Copilot, etc.).
The naive workaround — symlink /usr/local/bin/npx into the user's PATH —
fails one layer deeper because npx's shebang re-execs /usr/bin/env node
and node also lives at /usr/local/bin/node.
Fix: add /usr/local/bin/<cmd> as a third candidate in the fallback list.
This is the canonical install location for Node on:
- Linux from-source builds
- the upstream node:bookworm-slim image, which the Hermes Docker
image copies node + npm + corepack from since #4977 (the Node 22 LTS
refactor that exposed this)
- macOS Homebrew on Intel
Because the resolver already calls _prepend_path(resolved_env, command_dir)
after locating the command, /usr/local/bin gets prepended to the env's
PATH automatically, which also fixes the second-layer shebang failure
(npx-cli.js can now find node).
Scope is intentionally narrow: the fix activates only when the bare
command isn't otherwise locatable through the user's PATH. Users who
explicitly narrowed PATH for a non-Node MCP server see no change in
behavior.
Tested:
- tests/tools/test_mcp_tool_issue_948.py: new test
test_resolve_stdio_command_falls_back_to_usr_local_bin (mirrors the
existing hermes-node-bin fallback test)
- Full MCP test suite: 254/254 pass across 7 test files
- E2E against a freshly-built Docker image: reproduced the original
failure mode (env.PATH=/opt/data/bin:/usr/bin:/bin), confirmed the
resolver returns /usr/local/bin/npx and prepends /usr/local/bin to
PATH; subprocess.run of the resolved command prints '10.9.8' and
exits 0 with empty stderr
- Negative E2E on the host (where Node is already on PATH via mise):
resolver still hits the mise install dir, /usr/local/bin candidate
is not consulted, PATH is unchanged
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| .. | ||
| acp | ||
| acp_adapter | ||
| agent | ||
| cli | ||
| cron | ||
| docker | ||
| e2e | ||
| fakes | ||
| gateway | ||
| hermes_cli | ||
| hermes_state | ||
| honcho_plugin | ||
| integration | ||
| openviking_plugin | ||
| plugins | ||
| providers | ||
| run_agent | ||
| scripts | ||
| skills | ||
| stress | ||
| tools | ||
| tui_gateway | ||
| website | ||
| __init__.py | ||
| conftest.py | ||
| run_interrupt_test.py | ||
| test_account_usage.py | ||
| test_atomic_replace_symlinks.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_ctx_halving_fix.py | ||
| test_docker_home_override_scripts.py | ||
| test_empty_model_fallback.py | ||
| test_env_loader_secret_sources.py | ||
| test_evidence_store.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_wal_fallback.py | ||
| test_honcho_client_config.py | ||
| test_honcho_session_context.py | ||
| test_install_sh_browser_install.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_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_picker_scroll.py | ||
| test_model_tools.py | ||
| test_model_tools_async_bridge.py | ||
| test_ollama_num_ctx.py | ||
| test_package_json_lazy_deps.py | ||
| test_packaging_metadata.py | ||
| test_plugin_skills.py | ||
| test_process_loop_event_loop_warning.py | ||
| test_project_metadata.py | ||
| test_retry_utils.py | ||
| test_run_tests_parallel.py | ||
| test_sanitize_tool_error.py | ||
| test_sql_injection.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_server.py | ||
| test_utils_truthy_values.py | ||
| test_yuanbao_integration.py | ||
| test_yuanbao_markdown.py | ||
| test_yuanbao_pipeline.py | ||
| test_yuanbao_proto.py | ||