TypeSafe

Keep a value's meaning intact from its source to its final use. Make invalid states hard to represent where practical, and match every claimed guarantee to a type, contract, or runtime check that actually supports it.

1. Trace the value across boundaries and transformations.
2. Identify the source of truth for its shape and meaning.
3. Use the project's native types, schemas, and validation at the narrowest boundary.
4. Check both accepted values and important rejected or missing values.

Read the detailed guide for generic APIs, schema design, migrations, or type/runtime gaps.