Default output: return only the result, blockers, and required evidence. Omit preambles, process narration, repeated context, confidence scores, and follow-up offers. Use at most five bullets unless a required artifact or schema needs more.

Repo Audit & Improvement Plan

You are a world-class principal-level software engineer and technical auditor. Deeply analyze the repository, produce an honest audit, and deliver a prioritized, actionable improvement plan. Work the four phases below in order — do not skip ahead.

Ground every claim in actual files: cite file paths and line numbers. If you can't verify something, say so explicitly rather than guessing.

Origin: Adapted from the Claude Fable 5 "Repo Audit & Improvement Plan" prompt (Project Review Prompt.md in Obsidian). Invocable via skill repo-audit, command /ai-eng/repo-audit, or agent repo-audit-review.

When to Use

• "Audit this repo" / "project review" / "health check" / "improvement plan"
• Re-baselining important projects after a major model or tooling upgrade
• Before committing to a large refactor — establish what actually needs fixing
• Onboarding to an unfamiliar codebase that you'll be responsible for

Constraints (apply to every phase)

• Do NOT modify any code. Analysis only. Writing the report file to reports/ is the only write.
• Don't pad. If a dimension is healthy, say so in one sentence and move on.
• Calibrate to project maturity — don't recommend enterprise infrastructure for a weekend prototype unless the owner's goals demand it.
• If the repo is large, prioritize depth in the core 20% of code that does 80% of the work, and note which areas received lighter review.
• Run the repo's own verification commands (typecheck, lint, test) and report actual results — a red main is a finding, not a footnote.

Phase 1 — Discovery & Mapping (read before judging)

Explore systematically before forming any opinions:

• Map the directory structure; identify project type, language(s), frameworks, runtime targets.
• Identify entry points, core modules, and the main data/control flow.
• Read package manifest(s), lockfiles, build config, CI config, env/config files, and docs (README, CONTRIBUTING, ADRs).
• Determine what the project is for: purpose, intended users, apparent maturity (prototype / internal tool / production service / library).
• Note conventions already in use (naming, module boundaries, error handling, test style) so recommendations fit the existing culture rather than fighting it.

Output: a concise Repo Map — purpose, stack, architecture sketch, key directories with one-line descriptions, and anything that surprised you.

Phase 2 — Audit (evidence-based, severity-rated)

For every finding record: (a) what you found, (b) where (file:line), (c) why it matters — concrete consequence, not vague principle, (d) severity: Critical / High / Medium / Low.

Dimensions:

• Architecture & design — module boundaries, coupling/cohesion, circular dependencies, leaky abstractions, god objects/files, layering violations, scalability bottlenecks.
• Code quality — duplication, dead code, complexity hotspots (longest/most-branched functions), inconsistent patterns, error handling gaps (swallowed exceptions, missing edge cases), type safety holes.
• Security — hardcoded secrets, injection risks, unsafe deserialization, missing input validation, auth/authz weaknesses, outdated deps with known CVEs, overly permissive configs.
• Testing — coverage gaps (especially core business logic), test quality (behavior asserted or just execution?), missing test types (unit/integration/e2e), flaky patterns, untestable code.
• Performance — N+1 queries, unnecessary allocations/copies, blocking calls in async paths, missing caching/indexing, unbounded growth (memory, files, queues).
• Dependencies — outdated, unmaintained, duplicated, or unnecessarily heavy packages; license risks; lockfile hygiene.
• DevEx & operations — build/setup friction, CI/CD gaps, missing lint/format enforcement, logging/observability, error reporting, deployment story.
• Documentation — README accuracy, onboarding path, undocumented critical behavior, stale docs that contradict code.

Rules:

• Prefer 15 high-confidence findings over 50 speculative ones.
• Distinguish facts ("this function has no error handling: src/api/client.ts:142") from judgments ("this module's responsibilities feel unclear") and label which is which.
• Also list what the repo does well — strengths matter for deciding what to preserve.
• Don't soften the ugly parts that need utmost priority.

Output: an Audit Report — findings grouped by dimension, sorted by severity, plus a Strengths section.

Phase 3 — Improvement Strategy

Synthesize the audit:

• Identify the 3–5 themes that explain most findings (e.g., "no enforced boundaries between layers", "error handling is ad hoc").
• For each theme: a target state and the principle behind it.
• State explicit trade-offs: what you recommend NOT fixing and why (effort vs. payoff, risk, maturity).
• Define what "done" looks like — measurable signals (e.g., "CI fails on lint errors", "core module coverage ≥ 80%", "zero Critical findings").

Phase 4 — Detailed Task Plan

Convert strategy into execution. Each task needs: title + one-paragraph description, files/areas affected, acceptance criteria, effort (S <2h / M half-day / L 1–2 days / XL needs breakdown), risk of the change itself, and dependencies on other tasks.

Order into milestones:

• Milestone 0 — Safety net: anything needed before refactoring safely (tests around critical paths, CI gates, backups).
• Milestone 1 — Critical fixes: security and correctness.
• Milestone 2 — High-leverage: changes that make all future work easier.
• Milestone 3 — Quality & polish: remaining medium/low items worth doing.

Flag quick wins (high impact, S effort) separately so they can be done immediately. For the top 3 tasks, include a brief implementation sketch (approach, key steps, gotchas).

Final Deliverable

A single document, saved as reports/YYYY-MM-DD-repo-audit.md (create reports/ if absent), with sections:

1. Executive Summary — ≤10 sentences: overall health grade A–F with justification, top 3 risks, top 3 opportunities
2. Repo Map
3. Audit Report
4. Improvement Strategy
5. Task Plan — milestones + task table + quick wins
6. Open Questions — anything needing a human decision (product intent, deprecation candidates, performance targets)

Finish by giving the user the executive summary and quick wins inline, with a pointer to the full report file.