Ln 22 Codebase Auditor Skill for Claude

Codebase Auditor

Goal: Perform a broad, read-only production-code health audit. Find concrete cross-cutting failure, security, delivery, and maintenance risks without turning detector matches or personal style preferences into findings. Do not substitute for documentation trust, test-portfolio, whole-architecture, or persistence-specific review.

Execution contract: Treat the ordered checkbox workflow below as this skill's Definition of Done. Work through every item in order, and mark it complete only when its action and required evidence are complete. N/A, skipped, unavailable, or delegated items remain incomplete.

Before returning, apply this skill's verdict, decision, and approval rules to every incomplete item and prepend Checklist: X/Y complete<br>Incomplete: None | section/item — reason; outcome impact; exact next action; list every incomplete item.

Tool Routing

| Need | Preferred tool | Use it when | Fallback |

|---|---|---|---|

| Repository map and stack detection | Native file listing, manifests, build files, and repository instructions | Establishing scope, generated areas, entrypoints, supported runtimes, and commands | Targeted tree inspection and known entrypoints |

| Symbols, callers, ownership, and data flow | Language server or host-native code intelligence | A finding depends on symbol identity, references, overrides, route wiring, or cross-file behavior | Narrow text search plus direct inspection of every relevant match |

| Current changes and historical context | Git status, diff, log, and blame | Separating current work, regressions, intentional constraints, and dead compatibility paths | Current implementation and explicit decision records |

| Delivery health | Repository-defined build, lint, type, test, and smoke commands | Establishing whether the project can ship in its documented environment | Inspect CI and scripts; mark execution unavailable |

| Dependency and security state | Native package-manager audit, manifests, lockfiles, and official advisories | Checking known vulnerabilities, unsupported versions, and dependency health | Official registry and vendor sources; never guess severity |

| Runtime evidence | Existing logs, metrics, traces, profiles, and diagnostics | Static analysis cannot establish frequency, reachability, or operational impact | Call-path analysis with an explicit static-only limitation |

| Current external behavior | Official specifications, vendor documentation, and release notes | A finding depends on current API, runtime, or standard behavior | Primary-source web research; otherwise mark UNVERIFIED |

Start with summary-level discovery and narrow before reading deeply. Run only repository-defined or clearly safe diagnostic commands; never publish, deploy, migrate production data, rotate secrets, or rewrite files during the audit.

Evidence Rules

• A pattern match is a candidate, not a finding. Confirm reachability, context, and consequence.
• Runtime failure or deterministic command output outweighs static suspicion; static evidence remains valid when execution is unavailable and the limitation is explicit.
• Generated, vendored, fixture, migration-history, and intentionally compatible code require context-specific treatment.
• External best practice is actionable only when it addresses a concrete repository defect or risk.
• Score or count only findings with distinct root causes; deduplicate symptoms that share one correction.

Checklist

1. Establish Scope and Baseline

• [ ] Detect languages, frameworks, package managers, entrypoints, deployment model, generated areas, and the repository's supported verification commands.
• [ ] Classify each runtime surface as long-running service, CLI, library, job, serverless function, or platform-managed component before requiring probes, telemetry, signal handling, or shutdown behavior.
• [ ] Read applicable instructions and identify security boundaries, critical business paths, public interfaces, and irreversible operations.
• [ ] Inspect Git state so the audit does not overwrite, misattribute, or ignore unrelated user changes.
• [ ] Establish build, lint, type, test, and smoke baseline where feasible; record commands, environment, exit status, and relevant output.
• [ ] Define exclusions and depth based on risk rather than scanning every file with equal effort.
• [ ] Keep the audit read-only. Allow only permitted caches and build artifacts and disclose them when created.

2. Audit Security and Delivery Boundaries

• [ ] Search for committed secrets, unsafe credential patterns, sensitive defaults, debug bypasses, and accidental exposure through logs or errors.
• [ ] For credential findings, never expose the raw value: distinguish live material from placeholders, fixtures, examples, and allowlisted fingerprints; report only the type, location, and redacted evidence, and recommend revocation, rotation, or history remediation only for confirmed exposure without performing it during the audit.
• [ ] Trace untrusted input into SQL, shell, templates, HTML, file paths, URLs, deserialization, redirects, and other injection-sensitive sinks.
• [ ] Check authentication, authorization, tenant or ownership isolation, privilege transitions, insecure direct object access, and default-deny behavior.
• [ ] Check validation at trust boundaries, canonicalization, size and rate limits, unsafe file operations, and destructive-action confirmation or guards.
• [ ] Verify security findings against actual call paths, framework behavior, configuration, and current official guidance before assigning severity.
• [ ] Inspect compiler, linter, type checker, tests, packaging, and CI configuration for skipped gates, ignored failures, environment drift, and non-reproducible delivery.
• [ ] Verify that successful packaging produces the intended entrypoints, assets, metadata, target platform, and deployable artifact; exit code zero alone does not prove a shippable build.
• [ ] Find stale skip, quarantine, allow-failure, continue-on-error, and warning-suppression paths that make required signals appear green.
• [ ] Check configuration completeness, required environment validation, unsafe fallbacks, missing examples, and differences between local, CI, and deployment settings.

3. Audit Maintainability and Dependencies

• [ ] Find evidence-backed duplication across functions, handlers, modules, configuration, and integration code; distinguish shared domain concepts from coincidental similarity.
• [ ] Identify over-abstraction, unused extension points, excessive factories or wrappers, parallel mechanisms, and custom utilities that duplicate declared platform capabilities.
• [ ] Before merging duplication or removing an abstraction, check lifecycle and ownership boundaries, intentional decoupling, dependency injection or test seams, framework requirements, public extension contracts, and expected independent evolution.
• [ ] Inspect complexity hotspots, long methods, god modules, deep nesting, excessive parameters, boolean-mode APIs, misleading names, and mixed responsibilities.
• [ ] Check algorithms for early-exit mistakes, duplicate-key loss, boundary errors, unbounded work, repeated scans, mutation during iteration, and hidden shared state.
• [ ] Check hardcoded operational values, URLs, timeouts, limits, identifiers, and environment-specific behavior that should be explicit configuration or named policy.
• [ ] Trace one concept across external contracts, DTOs, services, persistence, and storage; flag synonym or casing drift only when no explicit serializer, code-generation, or ORM boundary mapping explains it.
• [ ] Audit dependency vulnerabilities, support status, license or runtime constraints, duplicate packages, unused packages, and credible replacement or removal opportunities.
• [ ] Verify vulnerability findings against the installed version and whether the vulnerable API or feature is reachable; distinguish affected code from a package merely present in the lockfile.
• [ ] Recommend native, existing-dependency, or external replacements only after checking required feature parity, migration surface, maintenance, license, security history, and domain-specific behavior.
• [ ] Find unreachable code, unused imports and exports, commented-out implementations, obsolete flags, dead compatibility shims, and replacement code left beside its successor.
• [ ] Confirm dead-code findings against reflection, registration, framework discovery, configuration, serialization, templates, and external entrypoints before reporting deletion as safe.

4. Audit Diagnosability, Concurrency, and Lifecycle

• [ ] Check whether logs are structured, correctly leveled, actionable, correlated across a request or job, and free of secrets and excessive payload data.
• [ ] Verify that correlation context crosses outbound calls, queues, retries, scheduled work, and detached async boundaries instead of existing only in the first request log.
• [ ] Check metrics, traces, health signals, and error context for critical paths; require observability only where operators need it to detect or diagnose failure.
• [ ] Trace shared mutable state, lock ordering, atomicity, async task ownership, cancellation, retries, and race windows on reachable concurrent paths.
• [ ] Inspect read-modify-write across await or yield points and build a resource/accessor timeline for shared files, subprocesses, terminal or OS resources, and repeated user triggers; include accessors outside the current process.
• [ ] Check blocking I/O or synchronous waits in async paths, unbounded concurrency, orphan tasks, deadlocks, TOCTOU hazards, and thread-unsafe resources.
• [ ] Inspect startup ordering, dependency readiness, configuration validation, fail-fast behavior, signal handling, graceful shutdown, and in-flight work draining.
• [ ] Inventory resources acquired during startup and runtime, then match each to idempotent cleanup in safe reverse dependency order on success, failure, timeout, cancellation, and repeated shutdown signals.
• [ ] Keep probe semantics distinct: liveness proves the process can recover without checking fragile dependencies, while readiness withholds traffic until required dependencies and initialization are usable; neither probe should create material load or side effects.

5. Validate Findings and Report

• [ ] Research external APIs, standards, vulnerabilities, and runtime behavior only when they can change a finding, using official sources matching the relevant version.
• [ ] Filter framework conventions, generated code, bounded administrative paths, tests, examples, and documented tradeoffs before confirming a candidate.
• [ ] Reproduce high-severity issues with a safe command, test, minimal call trace, or complete static failure path whenever possible.
• [ ] Classify findings as P0-P3 based on exploitability, data or availability impact, delivery blockage, recurrence, and remediation urgency.
• [ ] Include location, evidence, trigger or failure path, impact, confidence, effort, and smallest credible remediation for every finding.
• [ ] Order remediation by risk reduction and dependency, not by file order or detector category.
• [ ] Use BLOCKED when a required safety environment, high-risk behavior, or authoritative contract cannot be verified without a credible fallback; use FAIL for an evidenced unresolved P0/P1, required failing delivery gate, or demonstrated unsafe behavior; use CONCERNS only for verified non-blocking risks, and PASS only when required checks complete with no material finding.
• [ ] Return the verdict with executed checks, excluded scope, verified findings, unverified candidates, and residual codebase risk.

Output Contract

# Codebase Audit

**Verdict:** PASS | CONCERNS | FAIL | BLOCKED

## Scope and baseline
- Stack, entrypoints, and exclusions
- Commands and environments checked
- Static and runtime evidence available

## Health summary
| Area | Status | Evidence |
|---|---|---|
| Security | PASS / CONCERNS / FAIL | ... |
| Delivery | PASS / CONCERNS / FAIL | ... |
| Maintainability | PASS / CONCERNS / FAIL | ... |
| Dependencies and dead code | PASS / CONCERNS / FAIL | ... |
| Diagnosability, concurrency, lifecycle | PASS / CONCERNS / FAIL | ... |

## Findings
### [P0 | P1 | P2 | P3] Finding title
- Location and path to failure
- Evidence and confidence
- Impact and affected surface
- Required change and effort

## Remediation order and residual risks
Dependency-aware next actions, blind spots, and unverified candidates.