Create expert-level Ruby on Rails generators for models, services, controllers, and full-stack features, plus application templates for whole-app setup. Use when building custom generators, scaffolds, code generation tools, or Rails application templates (rails new -m, app:template, starter-app automation, multi-tenant setup), or when the user mentions Rails generators, Thor DSL, or automated code generation.
A refactoring advisor grounded in Martin Fowler's "Refactoring: Improving the Design of Existing Code" (2nd edition). Diagnoses code smells, guides or applies refactorings using Fowler's step-by-step mechanics (small behavior-preserving steps with tests between them), and teaches when and why to use each of the 64 catalog refactorings — language-agnostic. Use this skill whenever the user invokes the `/fowler` command, OR whenever they ask to refactor, clean up, restructure, simplify, or untangle existing code, complain that code is hard to read, hard to change, too long, duplicated, or messy, ask about code smells, technical debt, or legacy code improvement, or mention Martin Fowler, the Refactoring book, or any catalog refactoring by name (Extract Function, Extract Class, Replace Conditional with Polymorphism, Introduce Parameter Object, Replace Temp with Query, and the rest). Trigger this even when the user doesn't say "refactor" or "fowler" explicitly but is wrestling with how to safely improve the structu
A specialized object-oriented design advisor channeling Sandi Metz's approach (from "Practical Object-Oriented Design in Ruby" and "99 Bottles of OOP"). Acts as a planner, code reviewer, refactoring guide, and OOP teacher — language-agnostic. Use this skill whenever the user invokes the `/sandi` command, OR whenever they ask about object-oriented design, software architecture, how to structure or plan a feature, how to refactor code, code review of classes/objects, dependency management, code smells, SOLID principles, design patterns, duck typing, or mention Sandi Metz, POODR, "99 Bottles", "shameless green", "flocking rules", "squint test", "Law of Demeter", or "tell don't ask". Trigger this even when the user doesn't say "Sandi" explicitly but is wrestling with how to design, structure, or improve OO code, plan a feature's architecture, or evaluate a PR's design.
Diagnose and fix slow RSpec test suites using TestProf and proven optimization techniques. Use this skill whenever the user mentions slow tests, test suite performance, RSpec speed, profiling specs, TestProf, TagProf, let_it_be, TPS profiler, or complains that their test suite takes too long. Also use it when the user sees high GC time in tests, wants to parallelize with test-queue, or asks which profiler to run against an RSpec suite. Prefer this skill over generic performance advice whenever RSpec is in the picture.
Comprehensive ESLint agent for JavaScript/TypeScript code quality. Use when setting up ESLint, configuring linting rules, analyzing code for issues, fixing violations, or integrating ESLint into development workflows. Triggers on requests involving code quality, linting, static analysis, or ESLint configuration for JavaScript, TypeScript, React, or Node.js projects.
Writing high-quality unit tests for JavaScript and TypeScript using Jest. Covers test structure (AAA pattern, USE naming), breaking dependencies (stubs, mocks, dependency injection), testing async code (promises, callbacks, timers), avoiding flaky tests, and test-driven development. Use when writing tests, debugging test failures, refactoring tests for maintainability, or questions about Jest, TDD, mocks, stubs, or test best practices.
Comprehensive Vitest testing framework guide with strong emphasis on Jest-to-Vitest migration. Covers automated migration using codemods, configuration setup, API differences, best practices, and troubleshooting. Use when migrating from Jest, setting up Vitest, writing tests, configuring test environments, or resolving migration issues. Primary focus is seamless Jest migration with minimal code changes.
Comprehensive guide for creating software diagrams using Mermaid syntax. Use when users need to create, visualize, or document software through diagrams including class diagrams (domain modeling, object-oriented design), sequence diagrams (application flows, API interactions, code execution), flowcharts (processes, algorithms, user journeys), entity relationship diagrams (database schemas), C4 architecture diagrams (system context, containers, components), state diagrams, git graphs, pie charts, gantt charts, or any other diagram type. Triggers include requests to "diagram", "visualize", "model", "map out", "show the flow", or when explaining system architecture, database design, code structure, or user/application flows.