# Domain Layer
## Overview
Pure business logic and domain entities, decoupled from UI and infrastructure.
## Key Files
- `agent.rs` defines provider kinds, models, and model metadata.
- `session.rs` defines persisted session entities, statuses, and sizing logic.
- `project.rs`, `setting.rs`, `permission.rs`, and `input.rs` define shared application concepts.
## Docs
Changes to agent kinds, models, or session status/sizes require updating:
- `docs/site/content/docs/agents/backends.md` — agent backends and models.
- `docs/site/content/docs/usage/workflow.md` — session lifecycle and sizes.