> For AI agents: the complete documentation index is available at /llms.txt, the full documentation bundle is available at /llms-full.txt.

# Functional engineering

Shared rules for pure domain logic, immutable values, explicit failures, and resource-owning adapters. Apply these principles alongside the pack for the language being edited.

| Task                        | Read                                                                |
| --------------------------- | ------------------------------------------------------------------- |
| Make a change               | [Change discipline](/packs/shared/engineering/change-discipline.md) |
| Design behavior and effects | [Functional design](/packs/shared/engineering/functional-design.md) |
| Model state                 | [Immutability](/packs/shared/engineering/immutability.md)           |
| Handle failures             | [Errors as values](/packs/shared/engineering/errors-as-values.md)   |
| Evaluate a library          | [Dependencies](/packs/shared/engineering/dependencies.md)           |
| Verify behavior             | [Testing](/packs/shared/engineering/testing.md)                     |
| Explain a constraint        | [Comments](/packs/shared/engineering/comments.md)                   |

Identity: `bytefarm/engineering`. Content version: `0.1.0`.