Development

Vitest testing framework patterns and best practices. Use when writing unit tests, integration tests, configuring vitest.config, mocking with vi.mock/vi.fn, using snapshots, or setting up test coverage. Triggers on describe, it, expect, vi.mock, vi.fn, beforeEach, afterEach, vitest.

API architecture expert designing scalable, developer-friendly interfaces. Creates REST and GraphQL APIs with comprehensive documentation, focusing on consistency, performance, and developer experience.

Tailwind CSS v4 with CSS-first configuration and design tokens. Use when setting up Tailwind v4, defining theme variables, using OKLCH colors, or configuring dark mode. Triggers on @theme, @tailwindcss/vite, oklch, CSS variables, --color-, tailwind v4.

shadcn/ui component patterns with Radix primitives and Tailwind styling. Use when building UI components, using CVA variants, implementing compound components, or styling with data-slot attributes. Triggers on shadcn, cva, cn(), data-slot, Radix, Button, Card, Dialog, VariantProps.

Reviews shadcn/ui components for CVA patterns, composition with asChild, accessibility states, and data-slot usage. Use when reviewing React components using shadcn/ui, Radix primitives, or Tailwind styling.

React Router v7 best practices for data-driven routing. Use when implementing routes, loaders, actions, Form components, fetchers, navigation guards, protected routes, or URL search params. Triggers on createBrowserRouter, RouterProvider, useLoaderData, useActionData, useFetcher, NavLink, Outlet.

Reviews React Router code for proper data loading, mutations, error handling, and navigation patterns. Use when reviewing React Router v6.4+ code, loaders, actions, or navigation logic.

React Flow (@xyflow/react) for workflow visualization with custom nodes and edges. Use when building graph visualizations, creating custom workflow nodes, implementing edge labels, or controlling viewport. Triggers on ReactFlow, @xyflow/react, Handle, NodeProps, EdgeProps, useReactFlow, fitView.

Implements React Flow node-based UIs correctly using @xyflow/react. Use when building flow charts, diagrams, visual editors, or node-based applications with React. Covers nodes, edges, handles, custom components, state management, and viewport control.

Reviews React Flow code for anti-patterns, performance issues, and best practices. Use when reviewing code that uses @xyflow/react, checking for common mistakes, or optimizing node-based UI implementations.

Architectural guidance for building node-based UIs with React Flow. Use when designing flow-based applications, making decisions about state management, integration patterns, or evaluating whether React Flow fits a use case.

Advanced React Flow patterns for complex use cases. Use when implementing sub-flows, custom connection lines, programmatic layouts, drag-and-drop, undo/redo, or complex state synchronization.

Automatic graph layout using dagre with React Flow (@xyflow/react). Use when implementing auto-layout, hierarchical layouts, tree structures, or arranging nodes programmatically. Triggers on dagre, auto-layout, automatic layout, getLayoutedElements, rankdir, hierarchical graph.

Vercel AI Elements for workflow UI components. Use when building chat interfaces, displaying tool execution, showing reasoning/thinking, or creating job queues. Triggers on ai-elements, Queue, Confirmation, Tool, Reasoning, Shimmer, Loader, Message, Conversation, PromptInput.

Reviews SQLAlchemy code for session management, relationships, N+1 queries, and migration patterns. Use when reviewing SQLAlchemy 2.0 code, checking session lifecycle, relationship() usage, or Alembic migrations.

Reviews Python code for type safety, async patterns, error handling, and common mistakes. Use when reviewing .py files, checking type hints, async/await usage, or exception handling.

Reviews pytest test code for async patterns, fixtures, parametrize, and mocking. Use when reviewing test_*.py files, checking async test functions, fixture usage, or mock patterns.

Reviews PostgreSQL code for indexing strategies, JSONB operations, connection pooling, and transaction safety. Use when reviewing SQL queries, database schemas, JSONB usage, or connection management.

Reviews FastAPI code for routing patterns, dependency injection, validation, and async handlers. Use when reviewing FastAPI apps, checking APIRouter setup, Depends() usage, or response models.

Reviews WidgetKit code for timeline management, view composition, configurable intents, and performance. Use when reviewing code with import WidgetKit, TimelineProvider, Widget protocol, or @main struct Widget.

Reviews watchOS code for app lifecycle, complications (ClockKit/WidgetKit), WatchConnectivity, and performance constraints. Use when reviewing code with import WatchKit, WKExtension, WKApplicationDelegate, WCSession, or watchOS-specific patterns.

Reviews URLSession networking code for iOS/macOS. Covers async/await patterns, request building, error handling, caching, and background sessions.

Reviews SwiftUI code for view composition, state management, performance, and accessibility. Use when reviewing .swift files containing SwiftUI views, property wrappers (@State, @Binding, @Observable), or UI code.

Reviews SwiftData code for model design, queries, concurrency, and migrations. Use when reviewing .swift files with import SwiftData, @Model, @Query, @ModelActor, or VersionedSchema.