# CLAUDE.md: Minecraft Fabric mod

## Commands
- `./gradlew build` (jar in `build/libs/`) · `./gradlew runClient` / `./gradlew runServer` (dev environments) · `./gradlew runDatagen` if data generation is set up.
- Minecraft, Fabric Loader, Fabric API, Loom and mappings versions live in `gradle.properties`. Never bump them as a side effect; a version change is its own task.

## Structure
- Common entrypoint (`ModInitializer`) registers blocks, items, entities, sounds and networking payloads. Client-only code (renderers, screens, keybinds, HUD) goes in the `ClientModInitializer` and the client source set.
- Never reference client classes (`MinecraftClient`, rendering, screens) from common code; it crashes dedicated servers. Run `runServer` after touching shared code.
- Register through `Registry.register(Registries.X, Identifier.of(MOD_ID, "name"), obj)` (or the helper the repo already uses) in one place per content type. IDs are lowercase snake_case.
- Assets and data follow vanilla layout: `assets/<modid>/` (models, textures, lang) and `data/<modid>/` (recipes, loot tables, tags). Prefer data generators over handwritten JSON when the repo has datagen.
- All user-visible text goes through translation keys in `en_us.json`.

## Mixins
- Use Fabric API events and hooks first. A mixin is a last resort: target the narrowest method, prefer `@Inject` at a specific point over `@Overwrite` or `@Redirect`, and give each mixin class a comment explaining why no API covers it.
- Accessor/invoker mixins for private fields instead of reflection. Keep mixins in the `mixins.json` matching their side (client vs common).

## Networking and logic
- Server is authoritative: validate every client-to-server payload (player can reach the block, has the item, values in range).
- Don't do heavy work on the main thread every tick; cache, throttle, or move IO off-thread and hand results back via the server task queue.

## Done when
`./gradlew build` succeeds and you state whether `runClient`/`runServer` were launched (they need a display or may not run here).