# Architecture decision

> A decision about how Home Assistant is built, discussed and recorded in the home-assistant/architecture repository.

Source: https://contributors.home-assistant.io/glossary/architecture-decision/

- In code: `home-assistant/architecture`
- Also: ADR, architecture decision record, architecture discussion

Big changes, like a new type of entity or a new rule for integrations, start as a discussion there. Once decided, the decision is written down as an architecture decision record (ADR) in the `adr` folder of the repository, so everyone can look up what was decided and why.

## Related terms

- [Backward-incompatible change](https://contributors.home-assistant.io/glossary/backward-incompatible-change/): A change that requires users or developers to change something on their side, like their configuration or their custom integration.
- [Opportunity](https://contributors.home-assistant.io/glossary/opportunity/): An issue in the roadmap repository that describes a problem worth solving, why it matters, and the solution foreseen for it.
- [Epic](https://contributors.home-assistant.io/glossary/epic/): A larger body of work in the home-assistant/epics repository, made up of tasks that can span several repositories.