Agent Skills: Code Change Verification

Code Change Verification

Use this skill to review code changes consistently before merge, before release, and during incident follow-up.

Quick Start

1. Read the scope: commit, PR, patch, or file list.
2. Map each changed area by risk and user impact.
3. Inspect each risky change in context.
4. Report findings first, ordered by severity.
5. Close with residual risks and verification recommendations.

Core Workflow

1) Scope and assumptions

• Confirm change source (diff, commit, PR, files), target branch, language/runtime, and version.
• If context is missing, state assumptions before deeper analysis.
• Focus only on requested scope; avoid reviewing unrelated files.

2) Risk map

• Prioritize in this order:
  • Data correctness and user-visible behavior
  • API/contract compatibility
  • Security and authz/authn boundaries
  • Concurrency and lifecycle correctness
  • Performance and resource usage
• Give higher priority to stateful paths, migration logic, defaults, and error handling.

3) Evidence-based inspection

• Read each modified hunk with neighboring context.
• Trace call paths and call-site expectations.
• Check for:
  • invariant breaks and missing guards
  • unchecked assumptions and null/empty/error-path handling
  • stale tests, fixtures, and configs
  • hidden coupling to shared helpers/constants/features
• If a point is uncertain, mark it as an open question instead of guessing.

Rust-specific checks (apply to all Rust changes)

• unwrap/expect in production: Search changed files for .unwrap() and .expect( outside test modules. Every unwrap() in production code must have a justification comment or be replaced with ?.
• Silent type truncation: Search for as u8/u16/u32/u64/usize/i8/i16/i32/i64/isize casts. Every as cast must be justified; negative-to-unsigned and large-to-small are bugs by default. Use try_into() or explicit clamping.
• Unnecessary cloning: Check .clone() calls in loops, per-request paths, and on structs with >5 heap-allocated fields. Consider Arc, references, or Cow<str>.
• Lock ordering: If the change acquires multiple locks, verify the order matches all other call sites. Document the order in a comment.
• Locks across .await: Flag any tokio::sync::RwLock/Mutex guard held across an .await point without bounded hold time.
• Recursion depth: If the change adds or modifies a recursive function, verify it has a depth limit or uses iterative traversal with an explicit stack.
• Error types: Flag Result<_, String>, Box<dyn Error>, and missing Error::source() implementations in public APIs.
• Test assertions: Every test function must have at least one assert!. Flag tests that only call code without verifying results.
• println/eprintln: Search changed files for println!/eprintln! outside test modules. Production code must use tracing macros.
• Serde safety: Structs deserialized from untrusted input (S3 API, user config) should have #[serde(deny_unknown_fields)].

4) Findings-first output

• Order findings by severity:
  • P0: critical failure, security breach, or data loss risk
  • P1: high-impact regression
  • P2: medium risk correctness gap
  • P3: low risk/quality debt
• For each finding include:
  • Severity
  • path:line reference
  • concise issue statement
  • impact and likely failure mode
  • specific fix or mitigation
  • validation step to confirm
• If no issues exist, explicitly state No findings and why.

5) Close

• Report assumptions and unknowns.
• Suggest targeted checks (tests, canary checks, logs/metrics, migration validation).

Output Template

1. Findings
2. No findings (if applicable)
3. Assumptions / Unknowns
4. Recommended verification steps

Finding Template

• [P1] Missing timeout for downstream call
  • Location: path/to/file.rs:123
  • Issue: ...
  • Impact: ...
  • Fix suggestion: ...
  • Validation: ...