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.

1. Classify the task before editing: compile failure, implementation, review,

refactor, dependency, public API, release, performance, or security.

1. Fix the root cause. Avoid silencing Rust with reflexive .clone(),

Arc<Mutex<_>>, broad trait bounds, unwrap, or unsafe.

1. Use repo-native gates first. When command surface is unclear, run

scripts/discover-rust-gates.mjs <repo-root>.

1. 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:

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:

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.