Rust + axum — Claude Code rules

Cargo

• Rust 2024 edition. clippy::pedantic allowed with focused #[allow(...)] near the call site.
• One workspace crate per service. Shared types under crates/<name>-types.

axum

• Router::new() per module, composed at main. No global mutable state.
• Use axum::extract types (State, Path, Query, Json) over manual deserialisation.
• Handler return type is Result<impl IntoResponse, AppError> where AppError: IntoResponse.
• Plug tower_http::trace::TraceLayer + tower_http::cors::CorsLayer at the root.

Errors

• One application-level error enum via thiserror. Variants map to HTTP status codes through IntoResponse.
• anyhow is for bin/example crates only — never in library code that owns the error type.

Async

• tokio as the runtime. No blocking I/O in async fns; wrap with tokio::task::spawn_blocking when needed.
• Persistent connections live in AppState (cloneable Arc<…> interior).

Database

• sqlx with the postgres feature. Compile-time checked queries via sqlx::query!.
• Migrations under migrations/ managed by sqlx-cli.