rust-expert git:20260508.73f7c45A

Immutable. This exact content is served forever at /api/v1/blob/30602a73dda83556.

---
name: rust-expert
description: "Core implicit Rust engineering skill. Use for Rust implementation, debugging, code review, refactors, compiler errors, ownership/lifetimes, traits/generics, async/concurrency internals, typed errors, API design, Cargo/toolchain/MSRV, crate selection, tests, performance, unsafe, and security. Excludes focused framework or product-surface work when a narrower Rust specialist skill applies."
---

# Rust Expert

Use this as the default Rust engineering router. Inspect the repo first, load
only the references needed for the task, then use compiler/test feedback as
design evidence.

## Operating Model

1. Read the local guidance and manifests first: `AGENTS.md`, `Cargo.toml`,
   `Cargo.lock`, `rust-toolchain.toml`, `.cargo/config.toml`, CI, `justfile`,
   `mise.toml`, and nearby tests.
2. Classify the task before editing: compile failure, implementation, review,
   refactor, dependency, public API, release, performance, or security.
3. Fix the root cause. Avoid silencing Rust with reflexive `.clone()`,
   `Arc<Mutex<_>>`, broad trait bounds, `unwrap`, or `unsafe`.
4. Use repo-native gates first. When command surface is unclear, run
   `scripts/discover-rust-gates.mjs <repo-root>`.
5. Research current docs/source when facts can drift: dependency additions or
   upgrades, version-sensitive APIs, Tauri/plugin support, public API/release
   decisions, security, unsafe/FFI, or novel crates.

## Domain Routing

Use these implicit specialist skills when the task clearly belongs there:

| Signal | Prefer |
| --- | --- |
| Command-line app, subcommands, flags, config precedence, JSON/stdout contracts | `rust-cli-clap` |
| Terminal UI, interactive dashboards, Ratatui widgets/layout/events | `rust-tui-ratatui` |
| Tauri v2, `src-tauri`, commands, capabilities, IPC, updater, mobile layout | `rust-tauri-apps` |
| HTTP APIs/services, Axum, Tower, Tokio server runtime, DB pools | `rust-web-services` |
| Broad architecture review or multi-domain Rust planning explicitly requested | `rust-mega-eng` |

If no specialist owns the task, stay in `rust-expert`.

## Reference Map

Load the smallest needed set:

- `references/toolchain-cargo.md`: editions, MSRV, resolver, lockfiles, features,
  workspace policy, verification commands.
- `references/ownership-async-errors.md`: borrow checker, ownership,
  lifetimes, async `Send`, task ownership, typed errors.
- `references/crate-selection.md`: preferred crates, dependency decision rules,
  feature hygiene, source-refresh triggers.
- `references/testing-quality.md`: unit/integration/doctest/property/snapshot/
  benchmark checks and reviewable test design.
- `references/performance-security.md`: measurement, allocations, unsafe/FFI,
  supply chain, cargo-deny/audit, secrets and subprocesses.

## Toolchain Policy

Existing repos: preserve detected contracts first. Do not change edition,
resolver, `rust-version`, lockfile policy, or exact toolchain pins unless the
task is explicitly a migration or the repo is missing required metadata.

Greenfield defaults:

- `edition = "2024"`.
- Set `[workspace] resolver = "3"` explicitly for virtual workspaces.
- Add an explicit `rust-version` and document the policy.
- Commit `Cargo.lock` by default; for public libraries, also test latest
  dependency resolution because consumers use `Cargo.toml`.
- Avoid exact `rust-toolchain.toml` version pins unless reproducibility,
  nightly, embedded/custom targets, or release policy requires them.

## Verification Ladder

Start narrow, then broaden:

```bash
cargo check -p <crate>
cargo test -p <crate> <test_name>
cargo fmt --all -- --check
cargo clippy --workspace --all-targets --all-features --locked -- -D warnings
cargo test --workspace --all-targets --all-features --locked
cargo test --doc --workspace --locked
```

Use `cargo nextest run` when configured. Add `cargo hack`, `cargo deny`,
`cargo audit`, `cargo semver-checks`, or release tooling only when the repo or
change surface warrants it.

## Helper Scripts

- `scripts/discover-rust-gates.mjs [repo-root]`: print likely Rust gates.
- `scripts/check-reference-links.mjs <skill-dir...>`: validate local skill links.
- `scripts/check-trigger-evals.mjs <skill-dir...>`: validate trigger eval JSON.