Home Assistant Integration

Hermes Agent integrates with Home Assistant through the official homeassistant plugin from the plugin catalog. The plugin is maintained by Nous Research in NousResearch/hermes-official-plugins and is not part of Hermes core. It provides two things:

1. Gateway platform — subscribes to real-time state changes via WebSocket and responds to events
2. Smart home tools — four LLM-callable tools (the homeassistant toolset) for querying and controlling devices via the REST API

Install

hermes plugins install homeassistant

Plugins are installed per profile. To use Home Assistant in another profile, install it there too:

hermes -p <profile> plugins install homeassistant

The plugin declares its own Python dependency (aiohttp), so there is no pip extra to install. The old hermes-agent[homeassistant] extra has been removed.

Upgrading from a release that bundled Home Assistant

Nothing to do. Every profile that was already using Home Assistant — HASS_TOKEN in its .env, platforms.homeassistant enabled (or given a token) in config.yaml, or the homeassistant toolset listed in platform_toolsets — gets the plugin installed automatically from the catalog by hermes update (for all profiles sharing the install). If that step could not run, Hermes installs it the first time the profile starts (agent or gateway start; this honours security.allow_lazy_installs). After a failed attempt (offline, catalog unreachable) starts retry at most once an hour; hermes update always retries. The outcome is reported in the terminal, the Desktop app and chat. This happens once per profile: if you later remove the plugin (hermes plugins remove homeassistant), it stays removed.

Your configuration carries over unchanged: the same HASS_TOKEN / HASS_URL variables, the same homeassistant platform name and platforms.homeassistant keys, the same homeassistant toolset and tool names, and the same cron deliver: homeassistant:<notify target> syntax. One difference: like every plugin tool, the ha_* tools sit behind Tool Search (tool_search / tool_call) when it is on, instead of being listed directly.

Setup

1. Create a Long-Lived Access Token

1. Open your Home Assistant instance
2. Go to your Profile (click your name in the sidebar)
3. Scroll to Long-Lived Access Tokens
4. Click Create Token, give it a name like "Hermes Agent"
5. Copy the token

2. Configure Environment Variables

# Add to ~/.hermes/.env

# Required: your Long-Lived Access Token
HASS_TOKEN=your-long-lived-access-token

# Optional: HA URL (default: http://homeassistant.local:8123)
HASS_URL=http://192.168.1.100:8123

# Optional: default notify target for a bare `deliver: homeassistant`
HASS_HOME_CHANNEL=mobile_app_my_phone

info

With the plugin installed, the homeassistant toolset is enabled automatically when HASS_TOKEN is set. Both the gateway platform and the device control tools activate from this single token.

3. Start the Gateway

hermes gateway

Home Assistant will appear as a connected platform alongside any other messaging platforms (Telegram, Discord, etc.).

Available Tools

The plugin registers four tools for smart home control in the homeassistant toolset:

ha_list_entities

List Home Assistant entities, optionally filtered by domain or area.

Parameters:

• domain (optional) — Filter by entity domain: light, switch, climate, sensor, binary_sensor, cover, fan, media_player, etc.
• area (optional) — Filter by area/room name (matches against friendly names): living room, kitchen, bedroom, etc.

Example:

List all lights in the living room

Returns entity IDs, states, and friendly names.

ha_get_state

Get detailed state of a single entity, including all attributes (brightness, color, temperature setpoint, sensor readings, etc.).

Parameters:

• entity_id (required) — The entity to query, e.g., light.living_room, climate.thermostat, sensor.temperature

Example:

What's the current state of climate.thermostat?

Returns: state, all attributes, last changed/updated timestamps.

ha_list_services

List available services (actions) for device control. Shows what actions can be performed on each device type and what parameters they accept.

Parameters:

• domain (optional) — Filter by domain, e.g., light, climate, switch

Example:

What services are available for climate devices?

ha_call_service

Call a Home Assistant service to control a device.

Parameters:

• domain (required) — Service domain: light, switch, climate, cover, media_player, fan, scene, script
• service (required) — Service name: turn_on, turn_off, toggle, set_temperature, set_hvac_mode, open_cover, close_cover, set_volume_level
• entity_id (optional) — Target entity, e.g., light.living_room
• data (optional) — Additional parameters as a JSON object

Examples:

Turn on the living room lights
→ ha_call_service(domain="light", service="turn_on", entity_id="light.living_room")

Set the thermostat to 22 degrees in heat mode
→ ha_call_service(domain="climate", service="set_temperature",
    entity_id="climate.thermostat", data={"temperature": 22, "hvac_mode": "heat"})

Set living room lights to blue at 50% brightness
→ ha_call_service(domain="light", service="turn_on",
    entity_id="light.living_room", data={"brightness": 128, "color_name": "blue"})

Gateway Platform: Real-Time Events

The Home Assistant gateway adapter connects via WebSocket and subscribes to state_changed events. When a device state changes and matches your filters, it's forwarded to the agent as a message.

Event Filtering

Required Configuration

By default, no events are forwarded. You must configure at least one of watch_domains, watch_entities, or watch_all to receive events. Without filters, a warning is logged at startup and all state changes are silently dropped.

Configure which events the agent sees in ~/.hermes/config.yaml under the Home Assistant platform's extra section:

platforms:
  homeassistant:
    enabled: true
    extra:
      url: http://192.168.1.100:8123   # optional; same as HASS_URL
      watch_domains:
        - climate
        - binary_sensor
        - alarm_control_panel
        - light
      watch_entities:
        - sensor.front_door_battery
      ignore_entities:
        - sensor.uptime
        - sensor.cpu_usage
        - sensor.memory_usage
      cooldown_seconds: 30

Setting	Default	Description
url	HASS_URL, else http://homeassistant.local:8123	Home Assistant base URL
watch_domains	(none)	Only watch these entity domains (e.g., climate, light, binary_sensor)
watch_entities	(none)	Only watch these specific entity IDs
watch_all	false	Set to true to receive all state changes (not recommended for most setups)
ignore_entities	(none)	Always ignore these entities (applied before domain/entity filters)
cooldown_seconds	30	Minimum seconds between events for the same entity

tip

Start with a focused set of domains — climate, binary_sensor, and alarm_control_panel cover the most useful automations. Add more as needed. Use ignore_entities to suppress noisy sensors like CPU temperature or uptime counters.

Event Formatting

State changes are formatted as human-readable messages based on domain:

Domain	Format
climate	"HVAC mode changed from 'off' to 'heat' (current: 21, target: 23)"
sensor	"changed from 21°C to 22°C"
binary_sensor	"triggered" / "cleared"
light, switch, fan	"turned on" / "turned off"
alarm_control_panel	"alarm state changed from 'armed_away' to 'triggered'"
(other)	"changed from 'old' to 'new'"

Agent Responses

Outbound messages from the agent are delivered as Home Assistant persistent notifications (via persistent_notification.create). These appear in the HA notification panel with the title "Hermes Agent".

The platform uses the minimal display defaults (no tool-progress or streaming chatter in notifications). Override them under display.platforms.homeassistant in config.yaml if you want more.

Cron and Webhook Delivery

Scheduled jobs and webhook routes can deliver to Home Assistant:

deliver: homeassistant:mobile_app_my_phone   # explicit notify target
deliver: homeassistant                       # uses HASS_HOME_CHANNEL

The bare homeassistant form needs HASS_HOME_CHANNEL set to a default notify target. See Scheduled Tasks and Webhooks.

Connection Management

• WebSocket with 30-second heartbeat for real-time events
• Automatic reconnection with backoff: 5s → 10s → 30s → 60s
• REST API for outbound notifications (separate session to avoid WebSocket conflicts)
• Authorization — HA events are always authorized (no user allowlist or pairing needed: HASS_TOKEN authenticates the connection and there is no human sender)

Security

The Home Assistant tools enforce security restrictions:

Blocked Domains

The following service domains are blocked to prevent arbitrary code execution on the HA host:

• shell_command — arbitrary shell commands
• command_line — sensors/switches that execute commands
• python_script — scripted Python execution
• pyscript — broader scripting integration
• hassio — addon control, host shutdown/reboot
• rest_command — HTTP requests from HA server (SSRF vector)

Attempting to call services in these domains returns an error.

Entity IDs are validated against the pattern ^[a-z_][a-z0-9_]*\.[a-z0-9_]+$ to prevent injection attacks.

Example Automations

Morning Routine

User: Start my morning routine

Agent:
1. ha_call_service(domain="light", service="turn_on",
     entity_id="light.bedroom", data={"brightness": 128})
2. ha_call_service(domain="climate", service="set_temperature",
     entity_id="climate.thermostat", data={"temperature": 22})
3. ha_call_service(domain="media_player", service="turn_on",
     entity_id="media_player.kitchen_speaker")

Security Check

User: Is the house secure?

Agent:
1. ha_list_entities(domain="binary_sensor")
     → checks door/window sensors
2. ha_get_state(entity_id="alarm_control_panel.home")
     → checks alarm status
3. ha_list_entities(domain="lock")
     → checks lock states
4. Reports: "All doors closed, alarm is armed_away, all locks engaged."

Reactive Automation (via Gateway Events)

When connected as a gateway platform, the agent can react to events:

[Home Assistant] Front Door: triggered (was cleared)

Agent automatically:
1. ha_get_state(entity_id="binary_sensor.front_door")
2. ha_call_service(domain="light", service="turn_on",
     entity_id="light.hallway")
3. Sends notification: "Front door opened. Hallway lights turned on."

Troubleshooting

Platform or tools missing. Check that the plugin is installed and enabled in the active profile with hermes plugins list. If it is missing, run hermes plugins install homeassistant (or hermes -p <profile> plugins install homeassistant) and restart the gateway. With security.allow_lazy_installs turned off, the automatic first-start install is skipped and you must install the plugin yourself.

Environment variables not picked up. The adapter reads credentials from ~/.hermes/.env (auto-merged at startup) or from config.yaml. Double-check the file lives under the active Hermes profile home and that there's no stray quoting around the URL/token. Restart the gateway after editing — env changes are only applied on process start.

REST auth failing (401 Unauthorized). The token must be a Long-Lived Access Token created from your HA user profile page (Profile → Security → Long-lived access tokens). Short-lived UI session tokens won't work. Also verify the base URL includes the scheme and port (e.g. http://homeassistant.local:8123) and is reachable from the host running Hermes — curl -H "Authorization: Bearer <token>" <url>/api/ should return {"message": "API running."}.