Use when the user asks how to expose a Rust struct as an R class, which R class system to use (R6 vs S3 vs S4 vs S7 vs Env vs Vctrs), how method dispatch works, how constructors are generated, how trait methods map to R, or when working in miniextendr-macros/src/miniextendr_impl/*.rs or miniextendr-macros/src/r_class_formatter.rs.
Use when the user asks about converting between R and Rust types, how TryFromSexp or IntoR work, what NA handling looks like, how strict mode differs from normal coercion, why Vec<i32> from an empty R vector panics, or how bool, Option<T>, or large integer types behave across the R-Rust boundary.
Use when the user asks about ExternalPtr, how Rust structs are stored as R objects, TypedExternal, Box<Box<dyn Any>> storage, pointer provenance for cached_ptr, the release_any finalizer, sidecar field accessors, the TYPE_NAME_CSTR vs TYPE_ID_CSTR distinction, or how to pass an ExternalPtr across crate or package boundaries.
Use when a new user asks how to start a miniextendr-backed R package from zero, how to scaffold via minirextendr::use_miniextendr(), what their first Rust function should look like, what the dev loop is, or "can I add Rust to an existing R package". Also use when someone is confused about which package is which (miniextendr vs minirextendr).
Use when the user asks how
Use when debugging configure.ac failures, Makevars issues, Cargo.lock mismatches, vendor tarball problems, build mode confusion, or the cdylib-to-staticlib double-link pipeline. Also use when changing a Makevars value, diagnosing a latch-leak, understanding the bash-vs-sh configure requirement, or working with m4 quoting in configure.ac.
Use when working in an R package with a miniextendr Rust backend and you need orientation — how the build pipeline works (configure → Makevars → cargo → wrapper generation), which files are generated vs hand-written, what the dev loop is, how to add a function or a Cargo feature, or which of the other miniextendr skills to load for a specific task.
Use when building, checking, or releasing a miniextendr-backed R package — producing the CRAN tarball, vendoring Rust dependencies (inst/vendor.tar.xz), offline installs, R CMD check --as-cran, a leftover vendor tarball breaking dev builds, Cargo.lock complaints, release CI for binaries, or version bumps.