# Zoo Context

Open one leaf whose dominant need matches the task.

| Need | Open | Do not open |
|---|---|---|
| Look up the shipped state-model families | [States catalog](states-catalog.md) | Adding a model or changing register mechanics |
| Add or revise a state model | [Add a state model](add-state-model.md) | Catalog-only questions |
| Look up immediate circuit families | [Circuits catalog](circuits-catalog.md) | Adding a circuit or authoring a protocol |
| Add or revise an immediate circuit | [Add a circuit](add-circuit.md) | Catalog-only questions |
| Look up resumable protocol families and implementation gaps | [Protocols catalog](protocols-catalog.md) | Adding a protocol or changing transport internals |
| Add or revise a resumable protocol | [Add a protocol](add-protocol.md) | Catalog-only questions |
