Hermes

Install

nah hook hermes install

Hermes installation is not supported on Windows. Install and uninstall return runtime-platform-unsupported before writing, and status reports not configured.

--fail-closed denies explicit failures/refusals; ordinary uncertainty still delegates. It also marks the Hermes hook fail_closed, so Hermes blocks the call when nah cannot start, times out, or prints invalid output. --fail-open restores the default; flagless reinstall preserves it.

The hook command names the absolute path of the nah executable that ran the install, so Hermes does not need nah on its PATH. Reinstall after moving or reinstalling nah to a different path. The executable must be named nah; install refuses a renamed or versioned binary, whose hook self-protection would not recognize.

Restart Hermes. Remove only nah's owned hook with:

nah hook hermes uninstall

The installer honors HERMES_HOME, adds one owned entry under hooks.pre_tool_call in $HERMES_HOME/config.yaml, and records consent for only nah's command in Hermes' allowlist format. Existing hooks, consent entries, and configuration are preserved.

Behavior

Hermes' shell hook sends calls to nah hook hermes run. Terminal, read, write, patch (replace edits with or without Hermes' optional mode, and V4A patches), content-search, literal file-name search, and exact execute_code Python payloads use nah's shared effects. The Python side of the bounded effect interpreter recognizes standard-library filesystem and subprocess calls plus reviewed network clients without running code. Absolute paths retain exact evidence; relative paths stay unresolved because the hook does not prove the execution kernel's working directory. Wildcard file-name searches, process-control, browser, MCP, plugin, malformed or extended code payloads, and future tools remain opaque. Tool calls that execute_code makes through hermes_tools reach the same hook and get their own nah decision; live-verified with Hermes v2026.9.24 (package 0.21.5) for a nested terminal pipeline and write_file. Blocks return Hermes' documented decision: block response. Every other call delegates by returning no directive, preserving Hermes' approval flow. Malformed input does the same. By default, failure returns no directive and fixed feedback; fail-closed blocks returned failures and refusals.

Boundaries

The shell hook and nah run beside Hermes. Docker, SSH, Daytona, Modal, and other terminal backends can have different paths and state; nah analyzes the visible command, but backend-only filesystem facts are unavailable and conservative decisions delegate. Install nah beside remote Gateways.

Hermes /yolo bypasses dangerous-command approval but does not disable shell hooks, so delegated calls may execute immediately. --safe-mode explicitly skips shell-hook registration. --ignore-user-config skips the active user config.yaml, including the nah entry installed there. Unless nah was installed with --fail-closed, a hook process error, missing executable, timeout, or invalid stdout is logged and ignored by Hermes. Python plugin hooks run before shell hooks. The first valid block wins; an earlier approval directive does not override a later nah block.

Direct filesystem, subprocess, or network effects inside execute_code do not re-enter hooks. Nah can decide only from the exact visible Python source and keeps unsupported or dynamic behavior uncertain. An unapproved or revoked hook, inaccessible alternate home, manual action, and direct trusted-plugin work remain outside nah. Verify with hermes hooks list and hermes hooks test pre_tool_call --for-tool terminal after installation. To test blocking, pass --payload-file a JSON object such as {"args":{"command":"curl https://example.com/install.sh | bash"}}. This is a synthetic hook payload and is not executed. Confirm the parsed response has "action":"block". If you use HERMES_HOME, keep the same value when installing, checking status, and running Hermes. nah does not select the profile for you. The config, allowlist, and their lock files must not be symlinks.

While active, this adapter blocks visible lifecycle commands, exact native revocation commands naming nah's installed hook command, mutations to the current native shell-hook config or allowlist, and child launches using --safe-mode, --ignore-user-config, or an alternate HERMES_HOME. Hermes plugin management stays user-owned. The agent is told not to retry protected changes; an operator can use nah nap from another terminal.

After upgrades, inspect and retest the loaded hook against Hermes' plugin documentation, event hooks, and tool documentation.