hermes-homeassistant

Official Hermes Agent plugin for Home Assistant. It provides two things:

Gateway platform homeassistant: subscribes to Home Assistant's WebSocket event bus and forwards state_changed events to the agent, with domain/entity filters and per-entity cooldowns. The agent's replies show up as Home Assistant persistent notifications titled "Hermes Agent". Cron jobs can deliver to deliver=homeassistant[:target] through the notify.notify service, without a running gateway.
Toolset homeassistant: four tools the model can call to query and control devices over the REST API: ha_list_entities, ha_get_state, ha_list_services, ha_call_service.

This used to be built into Hermes core. It now ships as a standalone plugin with the same platform name, toolset, tool names and schemas, env vars and config keys. If you already used Home Assistant with Hermes, you don't need to change anything: hermes update (or the first start after updating) installs and enables this plugin for you.

Install

From the Hermes plugin catalog:

hermes plugins install homeassistant

The plugin's only Python dependency is aiohttp (>=3.9,<4, resolved under Hermes's own pins). It needs a Hermes Agent release of 0.21.5 or newer.

Configuration

1. Create a Long-Lived Access Token

Open your Home Assistant instance.
Go to your Profile (click your name in the sidebar).
Scroll to Long-Lived Access Tokens.
Click Create Token, name it something like "Hermes Agent", and copy it.

2. Environment variables

# ~/.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 cron deliver=homeassistant
# (a notify service target, e.g. mobile_app_my_phone)
HASS_HOME_CHANNEL=mobile_app_my_phone

Variable	Required	Purpose
`HASS_TOKEN`	yes	Long-Lived Access Token. Enables both the tools and the gateway platform.
`HASS_URL`	no	Base URL of your instance. Default `http://homeassistant.local:8123`. Seeds `platforms.homeassistant.extra.url` when the platform is enabled from env.
`HASS_HOME_CHANNEL`	no	Default target for cron `deliver=homeassistant`. `HASS_HOME_CHANNEL_NAME` sets a display name.

3. Tools

The four tools only appear when HASS_TOKEN is set. Turn the homeassistant toolset on or off per platform with hermes tools.

4. Gateway platform

hermes gateway

By default, no events are forwarded. Configure at least one of watch_domains, watch_entities or watch_all, otherwise a warning is logged at startup and every state change is dropped. Settings go under the platform's extra section in ~/.hermes/config.yaml:

platforms:
  homeassistant:
    enabled: true
    extra:
      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`	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`	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

Events come from the instance the adapter authenticated to with HASS_TOKEN, so they are not subject to a user allowlist. The adapter reconnects automatically with 5s → 10s → 30s → 60s backoff.

Security

ha_call_service refuses service domains that allow arbitrary code execution on the Home Assistant host or requests to your local network. Home Assistant has no service-level access control, so this blocklist is the only guard:

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

Domain and service names must match ^[a-z][a-z0-9_]*$ and entity IDs ^[a-z_][a-z0-9_]*\.[a-z0-9_]+$, which rules out path traversal into other REST endpoints (e.g. shell_command/../light).

What the plugin does on your network: it talks only to the Home Assistant URL you configure (REST and WebSocket) using your HASS_TOKEN. It stores no state and sends no telemetry.

Development

Tests need a hermes-agent checkout on PYTHONPATH plus pytest and pytest-asyncio:

PYTHONPATH=/path/to/hermes-agent python -m pytest tests -q

homeassistant

What it adds

Tools 4

Environment variables it needs 1

README