Code quality and diagnosis

A reproduction summary, diagnostic table, proposed patch and verification checklist.

A scenario matrix, test code, run instructions and coverage gaps.

Refactoring steps, before and after structure, compatibility risks and verification matrix.

Evidence-backed risks, defensive fixes, retest steps and residual risks.

A performance evidence table, prioritized changes and repeatable measurement budgets.

Bottleneck findings, candidate rewrites, index suggestions and a comparison plan.

Diagnoses intermittent concurrency bugs by mapping shared state and the interleavings that break it, adds targeted instrumentation and proposes a fix. Use for bugs seen only under load.

Finds a memory leak from heap snapshots, memory metrics and code, naming the retaining path and the minimal fix with a regression check. Use when memory grows until a process is killed or restarted.

Finds why a test passes and fails intermittently and fixes the cause instead of adding retries. Use when a test fails only sometimes, locally or in CI.

Reviews failure paths for swallowed errors, lost context, unsafe retries, missing timeouts and internal details leaking to users, with ranked fixes. Use on code that calls I/O or external services.