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Teaches when to use Server Components vs Client Components in React 19, including the 'use client' directive and boundary patterns. Use when architecting components, choosing component types, or working with Server Components.

Manage PrismaClient lifecycle with graceful shutdown, proper disconnect timing, and logging configuration. Use when setting up application shutdown handlers, configuring logging for development or production, or implementing proper connection cleanup in Node.js servers, serverless functions, or test suites.

Teaches when and how to use unknown instead of any type in TypeScript. Use when working with TypeScript code that has any types, needs type safety, handling external data, or when designing APIs. Critical for preventing type safety violations.

Configure transaction isolation levels to prevent race conditions and handle concurrent access. Use when dealing with concurrent updates, financial operations, inventory management, or when users mention race conditions, dirty reads, phantom reads, or concurrent modifications.

Teach async request APIs in Next.js 16 - params, searchParams, cookies(), headers(), draftMode() are now async. Use when migrating from Next.js 15, fixing type errors, or working with request data.

Teaches when type assertions are safe versus dangerous in TypeScript. Use when considering using 'as' keyword, type casting, or when working with external data that might use assertions instead of proper validation.

Teaches resource preloading APIs in React 19 including prefetchDNS, preconnect, preload, and preinit. Use when optimizing initial load or navigation performance.

Review state management patterns for React 19 best practices. Use when reviewing component state, Context usage, or state architecture.

Teaches Context API patterns in React 19 including use() hook for conditional context access. Use when implementing Context, avoiding prop drilling, or managing global state.

Teaches React Testing Library patterns for React 19 components. Use when writing component tests, testing interactions, or testing with Server Actions.

Teaches testing custom hooks in React 19 using renderHook from React Testing Library. Use when testing custom hooks or hook behavior.

Review React 19 test quality including coverage, patterns, and React 19 API testing. Use when reviewing tests or test coverage.

Teaches testing Server Actions in isolation in React 19. Use when testing Server Actions, form handling, or server-side logic.

Teaches what React Compiler handles automatically in React 19, reducing need for manual memoization. Use when optimizing performance or deciding when to use useMemo/useCallback.

Teaches code splitting with lazy() and Suspense in React 19 for reducing initial bundle size. Use when implementing lazy loading, route-based splitting, or optimizing performance.

Teaches useReducer for complex state logic in React 19. Use when state updates depend on previous state, multiple related state values, or complex update logic.

Review Server Actions for security, validation, and best practices in React 19. Use when reviewing forms, mutations, or server-side logic.

Teaches Server Actions in React 19 for form handling and data mutations. Use when implementing forms, mutations, or server-side logic. Server Actions are async functions marked with 'use server'.

Guide to Zod v4 new features including top-level string formats, string transformations, codecs, and stringbool

Avoid non-null assertion operator (!) and use type-safe alternatives instead

Automated tooling and detection patterns for JavaScript/TypeScript code quality review

Analyze TypeScript errors and provide detailed diagnostics with root cause analysis and specific fix recommendations

Review Vitest configuration for deprecated patterns and best practices. Use when reviewing test configuration or vitest setup.

Optimize Zod validation performance with safeParse, bulk array validation, schema reuse, and passthrough patterns

Teaches Web Components (Custom Elements) support in React 19, including property vs attribute handling and custom events. Use when integrating Web Components or working with custom HTML elements.

Fix React Rules of Hooks violations - conditional calls, hooks in loops/callbacks/classes

Migrate from Vitest 2.x/3.x to 4.x with pool options, coverage config, workspace to projects, and browser mode updates. Use when upgrading Vitest versions or encountering deprecated patterns.

Optimize queries by selecting only required fields and avoiding N+1 problems. Use when writing queries with relations or large result sets.

Integrate Zod v4 with React Hook Form, Next.js, Express, tRPC, and other frameworks for type-safe validation

Deploy migrations to production safely using migrate deploy in CI/CD. Use when setting up production deployment pipelines.

Test Zod schemas comprehensively with unit tests, integration tests, and type tests for validation logic

Write type-safe transformations with Zod including string methods, custom transforms, codecs, and pipelines

Review code for Next.js 16 compliance - security patterns, caching, breaking changes. Use when reviewing Next.js code, preparing for migration, or auditing for violations.

Validate code for Zod v4 compatibility by detecting deprecated APIs and ensuring adherence to v4 patterns

Teach parallel routes and slot patterns in Next.js 16. Use when implementing parallel routes, working with @slot syntax, or encountering missing default.tsx errors.

Set up Vitest browser mode with Playwright or WebDriverIO providers, use page and userEvent APIs, test components. Use when testing browser-specific code or UI components.

Teach Data Access Layer pattern to prevent CVE-2025-29927 middleware authentication bypass. Use when implementing authentication, authorization, protecting routes, or working with server actions that need auth.

Use Prisma's generated types, `Prisma.validator`, and `GetPayload` for type-safe queries.

Migrate from Tailwind CSS v3 to v4 including configuration migration (JS to CSS), utility renames, opacity changes, and color system updates. Use when upgrading existing projects to v4.

Write Vitest tests with describe/test blocks, expect assertions, vi mocking, async testing, and parameterized tests. Use when creating or modifying test files.

Create custom utilities with @utility directive supporting static utilities, functional utilities with values, theme-based utilities, and multi-value utilities. Use when extending Tailwind with custom CSS properties or patterns.

Code review skill that checks TypeScript type safety, exported for use by cross-cutting review plugin

Automated tooling and detection patterns for analyzing npm dependencies, unused packages, and dead code. Provides tool commands and what to look for—not how to structure output.

Use interactive transactions with $transaction callback for atomic operations and automatic rollback. Use when operations must succeed or fail together.

Review Tailwind CSS v4 patterns for configuration, theming, and utility usage. Use when reviewing CSS files, Vite configs, or components using Tailwind.

Teach image optimization configuration changes in Next.js 16. Use when configuring images, troubleshooting image loading, or migrating image settings.

Implement query result caching with Redis and proper invalidation strategies for Prisma 6. Use when optimizing frequently accessed data, improving read-heavy application performance, or reducing database load through caching.

Implement cursor-based or offset pagination for Prisma queries. Use for datasets 100k+, APIs with page navigation, or infinite scroll/pagination mentions.

Refactor inline types into reusable, well-organized type definitions using interfaces, type aliases, and generics

Analyze code complexity and maintainability including cyclomatic complexity, function length, nesting depth, and cognitive load. Use when reviewing code maintainability, refactoring candidates, or technical debt assessment.