ha-integration-dev

# 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] ``` The first three rules cause 90% of integration bugs. The fourth rule (`runtime_data`) is the modern pattern since HA 2024.4 - it provides type safety and cleaner lifecycle management. ## The Process ``` User request │ ▼ Clarify: API type, auth, entities │ ▼ Ask: HACS preparation? │ ▼ Select template │ ▼ Read relevant references │ ▼ Generate integration code │ ▼ Run pre-completion checklist │ ├──if HACS=yes──▶ Generate HACS files ──▶ Deliver integration │ └──if HACS=no───▶ Deliver integration ``` ## Common Pitfalls Watch out for these Iron Law violations: | Thought | Reality | |---------|---------| | "datetime.now() is fine" | WRON...