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From beagle-rust
Reviews Rust code changes found via git diff, runs clippy, and optionally spawns parallel agents for deeper analysis.
npx claudepluginhub existential-birds/beagle --plugin beagle-rustHow this skill is triggered — by the user, by Claude, or both
Slash command
/beagle-rust:review-rustThe summary Claude sees in its skill listing — used to decide when to auto-load this skill
- `--parallel`: Spawn specialized subagents per technology area
Reviews Rust code for ownership, borrowing, lifetimes, error handling, trait design, unsafe usage, and common mistakes. Covers Rust 2024 edition patterns and modern idioms.
Audits Rust code for unsafe blocks, ownership and borrowing patterns, concurrency issues, error handling, and Cargo dependency vulnerabilities.
Reviews and verifies code before merge via triage-first checks (up to 16 parallel agents). Pipeline mode verifies vs plans; general mode for PRs/branches/staged changes. Flags findings only.
Share bugs, ideas, or general feedback.
--parallel: Spawn specialized subagents per technology areaComplete in order before writing Issues in the output (empty scope is allowed; fabricated findings are not).
.rs paths under review (from Step 1 or the user-provided path). Pass: List printed or "No Rust files in scope" — then stop with no Issues.Cargo.toml present); if they cannot run, one line states why (e.g. missing toolchain, no Cargo.toml, sandbox). Pass: You do not report a problem already shown as an error/warning in Step 3 output, and you do not duplicate compiler or clippy diagnostics the author must fix first.beagle-rust:review-verification-protocol is loaded before Step 7. Pass: Every Critical/Major finding satisfies Step 8 (and the protocol); if there are zero findings, say "Protocol applied; no issues" in the Review Summary.FILE:LINE with full surrounding context (not only the diff hunk). Pass: The Issue description matches observable code at that location.git diff --name-only $(git merge-base HEAD main)..HEAD | grep -E '\.rs$'
# Check Cargo.toml for edition and rust-version
grep -E 'edition|rust-version' Cargo.toml
# Check workspace members if workspace
grep -A 20 '\[workspace\]' Cargo.toml
Edition 2024 awareness (requires MSRV 1.85+):
If edition = "2024" is detected, the following behavioral changes apply throughout the review:
unsafe_op_in_unsafe_fn is deny by default — unsafe operations inside unsafe fn MUST use explicit unsafe {} blocksextern "C" {} blocks must be unsafe extern "C" {}#[no_mangle] and #[export_name] must be #[unsafe(no_mangle)] and #[unsafe(export_name)]-> impl Trait captures ALL in-scope lifetimes by default (RPIT lifetime capture change); use + use<'a> for precise capturegen is a reserved keyword — code using it as an identifier must use r#gen! (never type) falls back to ! instead of () — may change behavior of inferred typesif let conditions and tail expressions are dropped earlier than in edition 2021Box<[T]> now implements IntoIteratorRecord the detected edition — it affects severity calibration in Steps 3, 8, and the verification protocol.
CRITICAL: Run clippy and check BEFORE flagging style or correctness issues. Do NOT flag issues that clippy or the compiler already catches.
cargo clippy --all-targets --all-features -- -D warnings 2>&1 | head -50
cargo clippy -- -D clippy::perf 2>&1 | head -20
cargo check --all-targets 2>&1 | head -50
Edition 2024 note: Edition 2024 promotes several previously-warn lints to deny (notably unsafe_op_in_unsafe_fn). If clippy or cargo check already reports edition-related errors, do not duplicate those as review findings — instead note that the author must fix compiler errors first.
# Detect tokio async runtime
grep -r "tokio" --include="Cargo.toml" -l | head -3
# Detect axum web framework
grep -r "axum" --include="Cargo.toml" -l | head -3
# Detect sqlx database
grep -r "sqlx" --include="Cargo.toml" -l | head -3
# Detect serde serialization
grep -r "serde" --include="Cargo.toml" -l | head -3
# Detect thiserror / anyhow
grep -r "thiserror\|anyhow" --include="Cargo.toml" -l | head -3
# Detect tracing
grep -r "tracing" --include="Cargo.toml" -l | head -3
# Check for test files in diff
git diff --name-only $(git merge-base HEAD main)..HEAD | grep -E '((^|/)(test|tests)/.*\.rs$)|(_test\.rs$)'
# Check for unsafe code in diff
git diff $(git merge-base HEAD main)..HEAD -- '*.rs' | grep -c 'unsafe'
# Detect async fn in traits (no async-trait crate needed since Rust 1.75)
grep -r "async-trait" --include="Cargo.toml" -l | head -3
# Detect LazyLock/LazyCell usage (replaces once_cell/lazy_static since 1.80)
grep -r "once_cell\|lazy_static" --include="Cargo.toml" -l | head -3
# Detect #[expect] lint attribute usage (stable since 1.81)
git diff $(git merge-base HEAD main)..HEAD -- '*.rs' | grep -c '#\[expect('
# Detect macro definitions in diff
git diff $(git merge-base HEAD main)..HEAD -- '*.rs' | grep -cE 'macro_rules!|#\[proc_macro|#\[derive\('
# Detect FFI code in diff
git diff $(git merge-base HEAD main)..HEAD -- '*.rs' | grep -cE 'extern "C"|#\[no_mangle\]|#\[repr\(C\)\]|bindgen|#\[unsafe\(no_mangle\)\]'
# Detect concurrency primitives (atomics, lock-free, hand-rolled sync)
git diff $(git merge-base HEAD main)..HEAD -- '*.rs' | grep -cE 'std::sync::atomic|Atomic(Bool|U?size|U?(8|16|32|64)|Ptr)|compare_exchange|fetch_(add|sub|or|and|xor|update)|UnsafeCell|unsafe impl (Send|Sync)|Ordering::(Relaxed|Acquire|Release|AcqRel|SeqCst)|atomic::fence'
# Detect concurrency test tooling
grep -rE 'loom|^miri$' --include='Cargo.toml' -l | head -3
git diff $(git merge-base HEAD main)..HEAD -- '*.rs' | grep -cE 'loom::|#\[cfg\(loom\)\]|cfg_attr\(miri'
# Detect concurrency crates
grep -rE '^crossbeam|^arc-swap|^parking_lot|^dashmap|^flurry|^haphazard|^seize|^atomic_wait' --include='Cargo.toml' -l | head -3
# Detect criterion benchmarks
grep -rE '^criterion' --include='Cargo.toml' -l | head -3
ls -d benches 2>/dev/null
# Detect proc-macro crate or trybuild
grep -rE 'proc-macro\s*=\s*true|^trybuild' --include='Cargo.toml' -l | head -3
# Detect public-surface changes (interface-design.md routing)
git diff $(git merge-base HEAD main)..HEAD -- '*.rs' | grep -cE '^\+\s*pub (trait|fn|struct|enum|mod|use)|^\+\s*impl[<\s].*Drop for'
# Detect ecosystem patterns (patterns-in-the-wild.md routing)
grep -rE '^slotmap|^petgraph|^scopeguard|^indexmap' --include='Cargo.toml' -l | head -3
git diff $(git merge-base HEAD main)..HEAD -- '*.rs' | grep -cE 'mem::replace|swap_remove|prelude'
Modern Rust detection notes:
async-trait is a dependency but the project uses edition 2024 or MSRV >= 1.75, flag as Informational — native async fn in traits is available and async-trait can likely be removed.once_cell or lazy_static is a dependency but MSRV >= 1.80, flag as Informational — std::sync::LazyLock and std::cell::LazyCell are stable replacements.#[allow(...)] is used where #[expect(...)] would be better (MSRV >= 1.81), note as Minor — #[expect] warns when the suppressed lint no longer fires, keeping suppressions clean.Concurrency detection notes:
std::sync::atomic, compare_exchange, fetch_*), UnsafeCell, unsafe impl Send/Sync, or crossbeam / arc-swap / parking_lot are present in the diff, load beagle-rust:rust-code-review and consult references/concurrency-primitives.md, references/memory-ordering.md, and references/lock-free-patterns.md.tokio::spawn patterns, threads-vs-async choices), also consult references/concurrency-models.md for design-level review questions.loom dependency or no cargo +nightly miri test in CI, load beagle-rust:rust-testing-code-review and consult references/concurrency-testing.md.Interface design / API surface detection:
pub trait, pub fn, pub struct, derive impls on public types, impl Drop on owning types, or re-exports of foreign types, load beagle-rust:rust-code-review and consult references/interface-design.md for object-safety, ergonomic-impl, fallible-destructor, and hidden-contract review checks.Vec<Node> + usize, slotmap, petgraph), mem::replace-style drop guards, extension traits, or modifies a prelude module, also consult references/patterns-in-the-wild.md.Testing detection (criterion / trybuild / clippy strategy):
benches/ directory or criterion dependency is present, load beagle-rust:rust-testing-code-review and consult references/advanced-testing.md for criterion baseline, black_box, and iter_batched review checks.proc-macro = true) or trybuild in [dev-dependencies], consult references/advanced-testing.md for trybuild .stderr stability checks plus beagle-rust:macros-code-review references/procedural-macros.md for span hygiene and syn feature audits.Load beagle-rust:review-verification-protocol skill and keep its checklist in mind throughout the review.
Use the Skill tool to load each applicable skill (e.g., Skill(skill: "beagle-rust:rust-code-review")).
Always load:
beagle-rust:rust-code-reviewConditionally load based on detection:
| Condition | Skill |
|---|---|
| Tokio detected | beagle-rust:tokio-async-code-review |
| Axum detected | beagle-rust:axum-code-review |
| sqlx detected | beagle-rust:sqlx-code-review |
| Serde detected | beagle-rust:serde-code-review |
| Test files changed | beagle-rust:rust-testing-code-review |
| Macro definitions in diff | beagle-rust:macros-code-review |
| FFI code detected (extern, repr(C), bindgen) | beagle-rust:ffi-code-review |
Atomics, UnsafeCell, unsafe impl Send/Sync, compare_exchange, crossbeam, arc-swap, parking_lot | beagle-rust:rust-code-review (load references/concurrency-primitives.md, references/memory-ordering.md, references/lock-free-patterns.md) |
| Concurrency design changes (worker pools, channels, threads-vs-async restructuring) | beagle-rust:rust-code-review (load references/concurrency-models.md) |
Public trait / pub fn / pub struct / impl Drop / re-export changes | beagle-rust:rust-code-review (load references/interface-design.md) |
Graph/tree code, slotmap, petgraph, mem::replace drop guards, extension traits, prelude module changes | beagle-rust:rust-code-review (load references/patterns-in-the-wild.md) |
criterion benchmarks, benches/ directory | beagle-rust:rust-testing-code-review (load references/advanced-testing.md — criterion baseline + black_box + iter_batched checks) |
Proc-macro crate (proc-macro = true) or trybuild in dev-deps | beagle-rust:rust-testing-code-review + beagle-rust:macros-code-review (load references/advanced-testing.md trybuild + references/procedural-macros.md span hygiene) |
loom, miri, hand-rolled lock-free code under test | beagle-rust:rust-testing-code-review (load references/concurrency-testing.md) |
Sequential (default):
Parallel (--parallel flag):
Task toolBefore reporting any issue:
#[cfg] gated code?Edition 2024 verification rules:
7. Do NOT flag unsafe {} blocks inside unsafe fn as unnecessary — they are REQUIRED in edition 2024
8. Do NOT flag unsafe extern "C" as unusual syntax — it is REQUIRED in edition 2024
9. Do NOT flag #[unsafe(no_mangle)] or #[unsafe(export_name)] as unusual — they are REQUIRED in edition 2024
10. For -> impl Trait returns, verify whether implicit lifetime capture is intentional — in edition 2024 all in-scope lifetimes are captured by default; suggest + use<'a> only when narrower capture is needed
11. For code using Box<[T]> in iterator contexts, remember IntoIterator is now available in edition 2024 — do not flag .iter() on boxed slices as the only approach
12. If temporaries in if let or tail expressions cause borrow issues, consider whether edition 2024's earlier drop semantics are the root cause
You MUST report ALL issues across ALL categories (ownership, error handling, async, types, tests, security, performance) in a single review pass. Do not hold back issues for later rounds.
Before submitting findings, ask yourself:
If yes to either: include those anticipated downstream issues NOW, in this review, so the author can address everything at once.
Fixes to existing code should be flagged at their real severity regardless of size.
However, requests for net-new code that didn't exist before the diff must be classified as Informational:
These are improvement suggestions for the author to consider in future work, not review blockers.
If this is a re-review after fixes were applied:
## Review Summary
[1-2 sentence overview of findings]
## Issues
### Critical (Blocking)
1. [FILE:LINE] ISSUE_TITLE
- Issue: Description of what's wrong
- Why: Why this matters (unsound unsafe, data race, panic, security)
- Fix: Specific recommended fix
### Major (Should Fix)
2. [FILE:LINE] ISSUE_TITLE
- Issue: ...
- Why: ...
- Fix: ...
### Minor (Nice to Have)
N. [FILE:LINE] ISSUE_TITLE
- Issue: ...
- Why: ...
- Fix: ...
### Informational (For Awareness)
N. [FILE:LINE] SUGGESTION_TITLE
- Suggestion: ...
- Rationale: ...
## Good Patterns
- [FILE:LINE] Pattern description (preserve this)
## Verdict
Ready: Yes | No | With fixes 1-N (Critical/Major only; Minor items are acceptable)
Rationale: [1-2 sentences]
After fixes are applied, run:
cargo check --all-targets
cargo clippy --all-targets --all-features -- -D warnings
cargo test --all-targets
All checks must pass before approval.