Feature-Sliced Design (FSD) v2.1

Source: fsd.how | Strictness can be adjusted based on project scale and team context.

How to use this skill. For placement decisions, start with the decision tree in Section 2 and use the placement table in Section 3 as a quick reference. To check a structure for violations, use the rules in Section 4. To resolve same-layer cross-imports, use Section 7. For task-specific guidance, load only the relevant reference files from Section 10; do not preload the rest.

1. Core philosophy & layer overview

FSD v2.1 core principle: "Start simple, extract when needed."

The extraction rule