Skill Claude CodeCodex
Create or audit maintainable diagrams when relationships, sequence, state, hierarchy, or quantitative comparisons are materially clearer visually than in prose. Selects a format the destination actually renders, preserves source authority, validates output, and includes an accessible text explanation.
Skill Claude CodeCodex
Domain-Driven Design patterns for TypeScript. Use when implementing ubiquitous language, value objects, entities, aggregates, domain events, domain services, or bounded contexts. Only applies to projects that explicitly use DDD. Do NOT use for simple CRUD or projects without domain modeling.
Skill Claude CodeCodex
Get a rigorous read-only second opinion on finished work through the host's available reviewer capabilities, preferably from a different model provider. Falls back to a fresh same-provider agent only when necessary and labels the reduced independence. Every review includes a mandatory scope-fidelity check against the…
Skill Claude CodeCodex
Research and compare established libraries, open-source tools and applications, managed services, and standard, framework, or platform primitives against an explicit bespoke baseline before committing to a material generic mechanism. Use for library/tool recommendations, build-versus-adopt questions, custom-mechanism…
Skill Claude CodeCodex
Event sourcing patterns for functional TypeScript — persist state as an append-only log of past events and rebuild it by folding them. Use when implementing a Decider write model, an event store, projections and read models, event versioning, or snapshots. Builds on the Decider from domain-driven-design and the…
Skill Claude CodeCodex
Capture learnings, gotchas, and decisions in their durable owner while context is fresh. Use when documenting a discovery, recording a decision, deciding whether guidance is reusable or project-local, or routing knowledge to code, tests, a glossary, an ADR, active plans, or repository guidance.
Skill Claude CodeCodex
Adversarially review an existing written artifact — stories, plans, acceptance criteria, specs, or design mocks — to surface missing states, unhandled edge cases, unstated assumptions, unverifiable criteria, and slices still too broad or horizontal. Works interactively, one question at a time, writing each answer back…
Skill Claude CodeCodex
Discover and, with authorization, install agent skills from the open skills ecosystem. Use when the user explicitly asks to find or install a skill from the external skills ecosystem, asks whether an installable agent skill exists for a task, or wants to extend agent capabilities through skills.sh or a skill…
Skill Claude CodeCodex
Use when existing code has untestable dependencies that prevent writing tests -- direct construction of collaborators, static or global function calls, tight coupling to external systems, or singleton access patterns. Specifically for identifying substitution points (seams) that make legacy or tightly-coupled code…
Skill Claude CodeCodex
Deprecated compatibility alias for structure-codebase. Activate only for the exact legacy name folder-structure or an explicit $folder-structure invocation. Contains no independent architecture guidance and must delegate to the canonical sibling skill.
Skill Claude CodeCodex
Behavior-driven UI testing patterns across Vitest Browser Mode, Playwright E2E evidence boundaries, and DOM Testing Library. Use when testing any front-end application, writing UI or end-to-end tests, querying DOM elements, simulating user interactions, or choosing the lightest harness that proves a browser-observable…
Skill Claude CodeCodex
Functional programming patterns with immutable data. Use when writing logic, data transformations, or encountering mutation bugs. Covers immutability violations catalog, pure functions, composition, early returns, and options objects. Do NOT over-apply heavy FP abstractions (monads, fp-ts) unless the project requires…
Skill Claude CodeCodex
Compose installed agent skills into one orchestrated multi-agent run: an agent graph where each node is a sub-agent that loads exactly one skill, edges carry structured data, and stages fan work out, adversarially verify it, and synthesize one deliverable. Claude Code calls the executable form a dynamic workflow; the…
Skill Claude CodeCodex
Use only when the user or project explicitly adopts hexagonal (ports and adapters) architecture. Implements TypeScript ports, driving/driven adapters, dependency inversion, and domain isolation. Do NOT infer hexagonal architecture from a generic adapter, interface, test seam, or isolation request.
Skill Claude CodeCodex
Audit an existing repository or multi-module subsystem for evidence-backed architecture improvements, rank bounded candidates, and present them in a visual HTML report with before-and-after diagrams and a top recommendation. Use when the user asks where architecture investment would pay off across a codebase, wants…
Skill Claude CodeCodex
Set up and run mutation testing with Stryker, including full-project and focused diff runs against the current review base, then use surviving mutants to strengthen weak or missing tests. Use as the end-of-phase PR-readiness gate after implementation and refactoring are complete, not inside each RED-GREEN increment.…
Skill Claude CodeCodex
Observability as an engineering discipline — wide events / canonical log lines, OpenTelemetry instrumentation (traces, metrics, context propagation, sampling, Collector), SLIs/SLOs/error budgets, symptom-based alerting with burn rates, telemetry hygiene, and testing instrumentation as behavior. Use when instrumenting…
Skill Claude CodeCodex
Composable multi-agent code review of any change boundary — the working tree mid-development, a branch diff, a stacked layer, or a pull request: one orchestrator fans out sub-agents, each loading exactly one installed skill as a review lens (hexagonal-architecture, domain-driven-design, structure-codebase…
Skill Claude CodeCodex
Planning work as vertical slices or an explicitly selected mechanism-reduction program in small, known-good increments, with independent pull requests or an optional stacked-PR topology across one or more ordered slices. Use when starting significant work, turning already-split stories into implementation plans…
Skill Claude CodeCodex
Create an application-specific production parity skill by inspecting an app's docs, source, tests, CI, deployment, infrastructure, config, auth, and environment setup, then asking targeted harness questions only for source-unanswerable decisions. Use when local, CI, PR, preview, staging, or other non-production…
Skill Claude CodeCodex
Make React and Next.js performance changes that are measured, evidence-backed, and behaviorally safe. Routes to the right rule catalogue — vercel-react-best-practices for the 72 prioritized React/Next rules, vercel-composition-patterns for component API shape, next-best-practices for App Router semantics…
Skill Claude CodeCodex
React component testing patterns including components, hooks, context, and forms. Covers Vitest Browser Mode with vitest-browser-react and @testing-library/react. Use when testing React applications. For general UI testing patterns, see the front-end-testing skill.
Skill Claude CodeCodex
Reduce total mechanism in a selected existing system or behavior path while conserving its agreed observable behavior and non-functional guarantees. Use when the user explicitly wants fewer branches, states, dependencies, layers, flags, retries, jobs, adapters, or operational moving parts and needs evidence that…
Skill Claude CodeCodex
Refactoring assessment and behavior-preserving patterns for code with a passing baseline and proportionate preservation evidence. Use when the user asks to clean up, simplify, or restructure a selected area, or after GREEN establishes the passing baseline for a TDD increment. Mutation testing verifies the accumulated…