app.mbt

Guide for writing, refactoring, and testing MoonBit projects. Use when working in MoonBit modules or packages, organizing MoonBit files, using moon tooling (build/check/run/test/doc/ide etc.), or following MoonBit-specific layout, documentation, and testing conventions.

Create formal spec-driven MoonBit APIs and test suites. Use when asked to set up a spec.mbt, spec-driven tests, or a formal contract-first workflow (e.g., "set up a formal spec & test suite for Yaml in MoonBit"), including moon.mod.json/moon.pkg.json scaffolding and guidance to implement in separate files.

Guide for writing MoonBit bindings to C libraries using native FFI. Use when adding extern "c" declarations, writing C stubs with moonbit.h, configuring native-stub and link.native in moon.pkg, choosing

Use this skill when the user needs help solving MoonBit language, code, compiler diagnostic, package, toolchain, backend, FFI, test, or "does MoonBit have X?" questions. Use it even when MoonBit is only implied by .mbt files, moon.mod.json, moon.pkg.json, moon commands, wasm/js/native targets, or mooncakes packages. This skill helps choose the right MoonBit source of truth, discover APIs with moon ide, avoid stale assumptions, and validate fixes.

Use when writing or refactoring proof-carrying code in MoonBit, especially for Why3-backed specifications, abstraction functions, representation invariants, proof assertions, recursive verified data structures, or reducing trusted proof bridges.

Refactor MoonBit code to be idiomatic: shrink public APIs, convert functions to methods, use pattern matching with views, add loop invariants, and ensure test coverage without regressions. Use when updating MoonBit packages or refactoring MoonBit APIs, modules, or tests.