sidebar_position: 3 title: “Nix & NixOS Setup” description: “Install and deploy Hermes Agent with Nix — from quick nix run to fully declarative NixOS module with container mode”

Nix & NixOS Setup

Hermes Agent ships a Nix flake with three levels of integration:

:::info What’s different from the standard install The curl | bash installer manages Python, Node, and dependencies itself. The Nix flake replaces all of that — every Python dependency is a Nix derivation built by uv2nix, and runtime tools (Node.js, git, ripgrep, ffmpeg) are wrapped into the binary’s PATH. There is no runtime pip, no venv activation, no npm install.

For non-NixOS users, this only changes the install step. Everything after (hermes setup, hermes gateway install, config editing) works identically to the standard install.

For NixOS module users, the entire lifecycle is different: configuration lives in configuration.nix, secrets go through sops-nix/agenix, the service is a systemd unit, and CLI config commands are blocked. You manage hermes the same way you manage any other NixOS service.

::

Prerequisites

• Nix with flakes enabled — Determinate Nix recommended (enables flakes by default)
• API keys for the services you want to use (at minimum: an OpenRouter or Anthropic key)

Quick Start (Any Nix User)

No clone needed. Nix fetches, builds, and runs everything:

# Run directly (builds on first use, cached after)
nix run github:NousResearch/hermes-agent -- setup
nix run github:NousResearch/hermes-agent -- chat

# Or install persistently
nix profile install github:NousResearch/hermes-agent
hermes setup
hermes chat

After nix profile install, hermes, hermes-agent, and hermes-acp are on your PATH. From here, the workflow is identical to the standard installation — hermes setup walks you through provider selection, hermes gateway install sets up a launchd (macOS) or systemd user service, and config lives in ~/.hermes/.

git clone https://github.com/NousResearch/hermes-agent.git
cd hermes-agent
nix build
./result/bin/hermes setup

NixOS Module

The flake exports nixosModules.default — a full NixOS service module that declaratively manages user creation, directories, config generation, secrets, documents, and service lifecycle.

::note This module requires NixOS. For non-NixOS systems (macOS, other Linux distros), use nix profile install and the standard CLI workflow above.

::

Add the Flake Input

# /etc/nixos/flake.nix (or your system flake)
{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    hermes-agent.url = "github:NousResearch/hermes-agent";
  };

  outputs = { nixpkgs, hermes-agent, ... }: {
    nixosConfigurations.your-host = nixpkgs.lib.nixosSystem {
      system = "x86_64-linux";
      modules = [
        hermes-agent.nixosModules.default
        ./configuration.nix
      ];
    };
  };
}

Minimal Configuration

# configuration.nix
{ config, ... }: {
  services.hermes-agent = {
    enable = true;
    settings.model.default = "anthropic/claude-sonnet-4";
    environmentFiles = [ config.sops.secrets."hermes-env".path ];
    addToSystemPackages = true;
  };
}

That’s it. nixos-rebuild switch creates the hermes user, generates config.yaml, wires up secrets, and starts the gateway — a long-running service that connects the agent to messaging platforms (Telegram, Discord, etc.) and listens for incoming messages.

::warning Secrets are required The environmentFiles line above assumes you have sops-nix or agenix configured. The file should contain at least one LLM provider key (e.g., OPENROUTER_API_KEY=sk-or-...). See Secrets Management for full setup. If you don’t have a secrets manager yet, you can use a plain file as a starting point — just ensure it’s not world-readable:

echo "OPENROUTER_API_KEY=sk-or-your-key" | sudo install -m 0600 -o hermes /dev/stdin /var/lib/hermes/env

services.hermes-agent.environmentFiles = [ "/var/lib/hermes/env" ];

:::

::tip addToSystemPackages Setting addToSystemPackages = true does two things: puts the hermes CLI on your system PATH and sets HERMES_HOME system-wide so the interactive CLI shares state (sessions, skills, cron) with the gateway service. Without it, running hermes in your shell creates a separate ~/.hermes/ directory.

::

::info Container-aware CLI When container.enable = true and addToSystemPackages = true, every hermes command on the host automatically routes into the managed container. This means your interactive CLI session runs inside the same environment as the gateway service — with access to all container-installed packages and tools.

• The routing is transparent: hermes chat, hermes sessions list, hermes version, etc. all exec into the container under the hood
• All CLI flags are forwarded as-is
• If the container isn’t running, the CLI retries briefly (5s with a spinner for interactive use, 10s silently for scripts) then fails with a clear error — no silent fallback
• For developers working on the hermes codebase, set HERMES_DEV=1 to bypass container routing and run the local checkout directly

Set container.hostUsers to create a ~/.hermes symlink to the service state directory, so the host CLI and the container share sessions, config, and memories:

services.hermes-agent = {
  container.enable = true;
  container.hostUsers = [ "your-username" ];
  addToSystemPackages = true;
};

Users listed in hostUsers are automatically added to the hermes group for file permission access.

Podman users: The NixOS service runs the container as root. Docker users get access via the docker group socket, but Podman’s rootful containers require sudo. Grant passwordless sudo for your container runtime:

security.sudo.extraRules = [{
  users = [ "your-username" ];
  commands = [{
    command = "/run/current-system/sw/bin/podman";
    options = [ "NOPASSWD" ];
  }];
}];

The CLI auto-detects when sudo is needed and uses it transparently. Without this, you’ll need to run sudo hermes chat manually.

::

Verify It Works

After nixos-rebuild switch, check that the service is running:

# Check service status
systemctl status hermes-agent

# Watch logs (Ctrl+C to stop)
journalctl -u hermes-agent -f

# If addToSystemPackages is true, test the CLI
hermes version
hermes config       # shows the generated config

Choosing a Deployment Mode

The module supports two modes, controlled by container.enable:

To enable container mode, add one line:

{
  services.hermes-agent = {
    enable = true;
    container.enable = true;
    # ... rest of config is identical
  };
}

:::info Container mode auto-enables virtualisation.docker.enable via mkDefault. If you use Podman instead, set container.backend = "podman" and virtualisation.docker.enable = false.

::

Configuration

Declarative Settings

The settings option accepts an arbitrary attrset that is rendered as config.yaml. It supports deep merging across multiple module definitions (via lib.recursiveUpdate), so you can split config across files:

# base.nix
services.hermes-agent.settings = {
  model.default = "anthropic/claude-sonnet-4";
  toolsets = [ "all" ];
  terminal = { backend = "local"; timeout = 180; };
};

# personality.nix
services.hermes-agent.settings = {
  display = { compact = false; personality = "kawaii"; };
  memory = { memory_enabled = true; user_profile_enabled = true; };
};

Both are deep-merged at evaluation time. Nix-declared keys always win over keys in an existing config.yaml on disk, but user-added keys that Nix doesn’t touch are preserved. This means if the agent or a manual edit adds keys like skills.disabled or streaming.enabled, they survive nixos-rebuild switch.

::note Model naming settings.model.default uses the model identifier your provider expects. With OpenRouter (the default), these look like "anthropic/claude-sonnet-4" or "google/gemini-3-flash". If you’re using a provider directly (Anthropic, OpenAI), set settings.model.base_url to point at their API and use their native model IDs (e.g., "claude-sonnet-4-20250514"). When no base_url is set, Hermes defaults to OpenRouter.

::

::tip Discovering available config keys Run nix build .#configKeys && cat result to see every leaf config key extracted from Python’s DEFAULT_CONFIG. You can paste your existing config.yaml into the settings attrset — the structure maps 1:1.

::

{ config, ... }: {
  services.hermes-agent = {
    enable = true;
    container.enable = true;

    # ── Model ──────────────────────────────────────────────────────────
    settings = {
      model = {
        base_url = "https://openrouter.ai/api/v1";
        default = "anthropic/claude-opus-4.6";
      };
      toolsets = [ "all" ];
      max_turns = 100;
      terminal = { backend = "local"; cwd = "."; timeout = 180; };
      compression = {
        enabled = true;
        threshold = 0.85;
        summary_model = "google/gemini-3-flash-preview";
      };
      memory = { memory_enabled = true; user_profile_enabled = true; };
      display = { compact = false; personality = "kawaii"; };
      agent = { max_turns = 60; verbose = false; };
    };

    # ── Secrets ────────────────────────────────────────────────────────
    environmentFiles = [ config.sops.secrets."hermes-env".path ];

    # ── Documents ──────────────────────────────────────────────────────
    documents = {
      "SOUL.md" = builtins.readFile /home/user/.hermes/SOUL.md;
      "USER.md" = ./documents/USER.md;
    };

    # ── MCP Servers ────────────────────────────────────────────────────
    mcpServers.filesystem = {
      command = "npx";
      args = [ "-y" "@modelcontextprotocol/server-filesystem" "/data/workspace" ];
    };

    # ── Container options ──────────────────────────────────────────────
    container = {
      image = "ubuntu:24.04";
      backend = "docker";
      hostUsers = [ "your-username" ];
      extraVolumes = [ "/home/user/projects:/projects:rw" ];
      extraOptions = [ "--gpus" "all" ];
    };

    # ── Service tuning ─────────────────────────────────────────────────
    addToSystemPackages = true;
    extraArgs = [ "--verbose" ];
    restart = "always";
    restartSec = 5;
  };
}

Escape Hatch: Bring Your Own Config

If you’d rather manage config.yaml entirely outside Nix, use configFile:

services.hermes-agent.configFile = /etc/hermes/config.yaml;

This bypasses settings entirely — no merge, no generation. The file is copied as-is to $HERMES_HOME/config.yaml on each activation.

Customization Cheatsheet

Quick reference for the most common things Nix users want to customize:

Secrets Management

:::danger Never put API keys in settings or environment Values in Nix expressions end up in /nix/store, which is world-readable. Always use environmentFiles with a secrets manager.

::

Both environment (non-secret vars) and environmentFiles (secret files) are merged into $HERMES_HOME/.env at activation time (nixos-rebuild switch). Hermes reads this file on every startup, so changes take effect with a systemctl restart hermes-agent — no container recreation needed.

sops-nix

{
  sops = {
    defaultSopsFile = ./secrets/hermes.yaml;
    age.keyFile = "/home/user/.config/sops/age/keys.txt";
    secrets."hermes-env" = { format = "yaml"; };
  };

  services.hermes-agent.environmentFiles = [
    config.sops.secrets."hermes-env".path
  ];
}

The secrets file contains key-value pairs:

# secrets/hermes.yaml (encrypted with sops)
hermes-env: |
    OPENROUTER_API_KEY=sk-or-...
    TELEGRAM_BOT_TOKEN=123456:ABC...
    ANTHROPIC_API_KEY=sk-ant-...

agenix

{
  age.secrets.hermes-env.file = ./secrets/hermes-env.age;

  services.hermes-agent.environmentFiles = [
    config.age.secrets.hermes-env.path
  ];
}

OAuth / Auth Seeding

For platforms requiring OAuth (e.g., Discord), use authFile to seed credentials on first deploy:

{
  services.hermes-agent = {
    authFile = config.sops.secrets."hermes/auth.json".path;
    # authFileForceOverwrite = true;  # overwrite on every activation
  };
}

The file is only copied if auth.json doesn’t already exist (unless authFileForceOverwrite = true). Runtime OAuth token refreshes are written to the state directory and preserved across rebuilds.

Documents

The documents option installs files into the agent’s working directory (the workingDirectory, which the agent reads as its workspace). Hermes looks for specific filenames by convention:

• SOUL.md — the agent’s system prompt / personality. Hermes reads this on startup and uses it as persistent instructions that shape its behavior across all conversations.
• USER.md — context about the user the agent is interacting with.
• Any other files you place here are visible to the agent as workspace files.

{
  services.hermes-agent.documents = {
    "SOUL.md" = ''
      You are a helpful research assistant specializing in NixOS packaging.
      Always cite sources and prefer reproducible solutions.
    '';
    "USER.md" = ./documents/USER.md;  # path reference, copied from Nix store
  };
}

Values can be inline strings or path references. Files are installed on every nixos-rebuild switch.

MCP Servers

The mcpServers option declaratively configures MCP (Model Context Protocol) servers. Each server uses either stdio (local command) or HTTP (remote URL) transport.

Stdio Transport (Local Servers)

{
  services.hermes-agent.mcpServers = {
    filesystem = {
      command = "npx";
      args = [ "-y" "@modelcontextprotocol/server-filesystem" "/data/workspace" ];
    };
    github = {
      command = "npx";
      args = [ "-y" "@modelcontextprotocol/server-github" ];
      env.GITHUB_PERSONAL_ACCESS_TOKEN = "\${GITHUB_TOKEN}"; # resolved from .env
    };
  };
}

:::tip Environment variables in env values are resolved from $HERMES_HOME/.env at runtime. Use environmentFiles to inject secrets — never put tokens directly in Nix config.

::

HTTP Transport (Remote Servers)

{
  services.hermes-agent.mcpServers.remote-api = {
    url = "https://mcp.example.com/v1/mcp";
    headers.Authorization = "Bearer \${MCP_REMOTE_API_KEY}";
    timeout = 180;
  };
}

HTTP Transport with OAuth

Set auth = "oauth" for servers using OAuth 2.1. Hermes implements the full PKCE flow — metadata discovery, dynamic client registration, token exchange, and automatic refresh.

{
  services.hermes-agent.mcpServers.my-oauth-server = {
    url = "https://mcp.example.com/mcp";
    auth = "oauth";
  };
}

Tokens are stored in $HERMES_HOME/mcp-tokens/<server-name>.json and persist across restarts and rebuilds.

# Container mode
docker exec -it hermes-agent \
  hermes mcp add my-oauth-server --url https://mcp.example.com/mcp --auth oauth

# Native mode
sudo -u hermes HERMES_HOME=/var/lib/hermes/.hermes \
  hermes mcp add my-oauth-server --url https://mcp.example.com/mcp --auth oauth

hermes mcp add my-oauth-server --url https://mcp.example.com/mcp --auth oauth
scp ~/.hermes/mcp-tokens/my-oauth-server{,.client}.json \
    server:/var/lib/hermes/.hermes/mcp-tokens/
# Ensure: chown hermes:hermes, chmod 0600

Sampling (Server-Initiated LLM Requests)

Some MCP servers can request LLM completions from the agent:

{
  services.hermes-agent.mcpServers.analysis = {
    command = "npx";
    args = [ "-y" "analysis-server" ];
    sampling = {
      enabled = true;
      model = "google/gemini-3-flash";
      max_tokens_cap = 4096;
      timeout = 30;
      max_rpm = 10;
    };
  };
}

Managed Mode

When hermes runs via the NixOS module, the following CLI commands are blocked with a descriptive error pointing you to configuration.nix:

This prevents drift between what Nix declares and what’s on disk. Detection uses two signals:

1. HERMES_MANAGED=true environment variable — set by the systemd service, visible to the gateway process
2. .managed marker file in HERMES_HOME — set by the activation script, visible to interactive shells (e.g., docker exec -it hermes-agent hermes config set ... is also blocked)

To change configuration, edit your Nix config and run sudo nixos-rebuild switch.

Container Architecture

:::info This section is only relevant if you’re using container.enable = true. Skip it for native mode deployments.

::

When container mode is enabled, hermes runs inside a persistent Ubuntu container with the Nix-built binary bind-mounted read-only from the host:

Host                                    Container
────                                    ─────────
/nix/store/...-hermes-agent-0.1.0  ──►  /nix/store/... (ro)
~/.hermes -> /var/lib/hermes/.hermes       (symlink bridge, per hostUsers)
/var/lib/hermes/                    ──►  /data/          (rw)
  ├── current-package -> /nix/store/...    (symlink, updated each rebuild)
  ├── .gc-root -> /nix/store/...           (prevents nix-collect-garbage)
  ├── .container-identity                  (sha256 hash, triggers recreation)
  ├── .hermes/                             (HERMES_HOME)
  │   ├── .env                             (merged from environment + environmentFiles)
  │   ├── config.yaml                      (Nix-generated, deep-merged by activation)
  │   ├── .managed                         (marker file)
  │   ├── .container-mode                  (routing metadata: backend, exec_user, etc.)
  │   ├── state.db, sessions/, memories/   (runtime state)
  │   └── mcp-tokens/                      (OAuth tokens for MCP servers)
  ├── home/                                ──►  /home/hermes    (rw)
  └── workspace/                           (MESSAGING_CWD)
      ├── SOUL.md                          (from documents option)
      └── (agent-created files)

Container writable layer (apt/pip/npm):   /usr, /usr/local, /tmp

The Nix-built binary works inside the Ubuntu container because /nix/store is bind-mounted — it brings its own interpreter and all dependencies, so there’s no reliance on the container’s system libraries. The container entrypoint resolves through a current-package symlink: /data/current-package/bin/hermes gateway run --replace. On nixos-rebuild switch, only the symlink is updated — the container keeps running.

What Persists Across What

The container is only recreated when its identity hash changes. The hash covers: schema version, image, extraVolumes, extraOptions, and the entrypoint script. Changes to environment variables, settings, documents, or the hermes package itself do not trigger recreation.

::warning Writable layer loss When the identity hash changes (image upgrade, new volumes, new container options), the container is destroyed and recreated from a fresh pull of container.image. Any apt install, pip install, or npm install packages in the writable layer are lost. State in /data and /home/hermes is preserved (these are bind mounts).

If the agent relies on specific packages, consider baking them into a custom image (container.image = "my-registry/hermes-base:latest") or scripting their installation in the agent’s SOUL.md.

::

GC Root Protection

The preStart script creates a GC root at ${stateDir}/.gc-root pointing to the current hermes package. This prevents nix-collect-garbage from removing the running binary. If the GC root somehow breaks, restarting the service recreates it.

Development

Dev Shell

The flake provides a development shell with Python 3.11, uv, Node.js, and all runtime tools:

cd hermes-agent
nix develop

# Shell provides:
#   - Python 3.11 + uv (deps installed into .venv on first entry)
#   - Node.js 20, ripgrep, git, openssh, ffmpeg on PATH
#   - Stamp-file optimization: re-entry is near-instant if deps haven't changed

hermes setup
hermes chat

direnv (Recommended)

The included .envrc activates the dev shell automatically:

cd hermes-agent
direnv allow    # one-time
# Subsequent entries are near-instant (stamp file skips dep install)

Flake Checks

The flake includes build-time verification that runs in CI and locally:

# Run all checks
nix flake check

# Individual checks
nix build .#checks.x86_64-linux.package-contents   # binaries exist + version
nix build .#checks.x86_64-linux.entry-points-sync  # pyproject.toml ↔ Nix package sync
nix build .#checks.x86_64-linux.cli-commands        # gateway/config subcommands
nix build .#checks.x86_64-linux.managed-guard       # HERMES_MANAGED blocks mutation
nix build .#checks.x86_64-linux.bundled-skills      # skills present in package
nix build .#checks.x86_64-linux.config-roundtrip    # merge script preserves user keys

Options Reference

Core

Configuration

Secrets & Environment

Documents

MCP Servers

Service Behavior

Container

Directory Layout

Native Mode

/var/lib/hermes/                     # stateDir (owned by hermes:hermes, 0750)
├── .hermes/                         # HERMES_HOME
│   ├── config.yaml                  # Nix-generated (deep-merged each rebuild)
│   ├── .managed                     # Marker: CLI config mutation blocked
│   ├── .env                         # Merged from environment + environmentFiles
│   ├── auth.json                    # OAuth credentials (seeded, then self-managed)
│   ├── gateway.pid
│   ├── state.db
│   ├── mcp-tokens/                  # OAuth tokens for MCP servers
│   ├── sessions/
│   ├── memories/
│   ├── skills/
│   ├── cron/
│   └── logs/
├── home/                            # Agent HOME
└── workspace/                       # MESSAGING_CWD
    ├── SOUL.md                      # From documents option
    └── (agent-created files)

Container Mode

Same layout, mounted into the container:

Updating

# Update the flake input
nix flake update hermes-agent --flake /etc/nixos

# Rebuild
sudo nixos-rebuild switch

In container mode, the current-package symlink is updated and the agent picks up the new binary on restart. No container recreation, no loss of installed packages.

Troubleshooting

:::tip Podman users All docker commands below work the same with podman. Substitute accordingly if you set container.backend = "podman".

::

Service Logs

# Both modes use the same systemd unit
journalctl -u hermes-agent -f

# Container mode: also available directly
docker logs -f hermes-agent

Container Inspection

systemctl status hermes-agent
docker ps -a --filter name=hermes-agent
docker inspect hermes-agent --format='{{.State.Status}}'
docker exec -it hermes-agent bash
docker exec hermes-agent readlink /data/current-package
docker exec hermes-agent cat /data/.container-identity

Force Container Recreation

If you need to reset the writable layer (fresh Ubuntu):

sudo systemctl stop hermes-agent
docker rm -f hermes-agent
sudo rm /var/lib/hermes/.container-identity
sudo systemctl start hermes-agent

Verify Secrets Are Loaded

If the agent starts but can’t authenticate with the LLM provider, check that the .env file was merged correctly:

# Native mode
sudo -u hermes cat /var/lib/hermes/.hermes/.env

# Container mode
docker exec hermes-agent cat /data/.hermes/.env

GC Root Verification

nix-store --query --roots $(docker exec hermes-agent readlink /data/current-package)

Common Issues