Home Assistant Integration Development

Reference skill for developing Home Assistant custom integrations in Python.

Overview

Core principle: Home Assistant integrations run in the same Python process as Core with full filesystem access. Security, proper async patterns, and correct timestamp handling are non-negotiable.

Context: This skill requires understanding the integration type (polling vs push, cloud vs local) before generating code. The DataUpdateCoordinator pattern is mandatory for most integrations.

The Iron Law

TIMESTAMPS: dt_util.now() / dt_util.utcnow() - NEVER datetime.now()
ATTRIBUTES: JSON-SERIALIZABLE ONLY - NO DATACLASSES, NO DATETIME OBJECTS
ASYNC: aiohttp FOR HTTP - NEVER requests
STORAGE: entry.runtime_data - NEVER hass.data[DOMAIN]