Imported from Laznology/tachys-next (AGENTS.md). Install upstream with npx skills add Laznology/tachys-next. Copyright stays with the author.

Next.js: ALWAYS read docs before coding

Before any Next.js work, find and read the relevant doc in node_modules/next/dist/docs/. Your training data is outdated — the docs are the source of truth.

Ultracite Code Standards

This project uses Ultracite, a zero-config preset that enforces strict code quality standards through automated formatting and linting.

Quick Reference

• Format code: pnpm dlx ultracite fix
• Check for issues: pnpm dlx ultracite check
• Diagnose setup: pnpm dlx ultracite doctor

Oxlint + Oxfmt (the underlying engine) provides robust linting and formatting. Most issues are automatically fixable.

Core Principles

Write code that is accessible, performant, type-safe, and maintainable. Focus on clarity and explicit intent over brevity.

Type Safety & Explicitness

• Use explicit types for function parameters and return values when they enhance clarity
• Prefer unknown over any when the type is genuinely unknown
• Use const assertions (as const) for immutable values and literal types
• Leverage TypeScript's type narrowing instead of type assertions
• Use meaningful variable names instead of magic numbers - extract constants with descriptive names

Modern JavaScript/TypeScript

• Use arrow functions for callbacks and short functions
• Prefer for...of loops over .forEach() and indexed for loops
• Use optional chaining (?.) and nullish coalescing (??) for safer property access
• Prefer template literals over string concatenation
• Use destructuring for object and array assignments
• Use const by default, let only when reassignment is needed, never var

Async & Promises

• Always await promises in async functions - don't forget to use the return value
• Use async/await syntax instead of promise chains for better readability
• Handle errors appropriately in async code with try-catch blocks
• Don't use async functions as Promise executors

React & JSX

• Use function components over class components
• Call hooks at the top level only, never conditionally
• Specify all dependencies in hook dependency arrays correctly
• Use the key prop for elements in iterables (prefer unique IDs over array indices)
• Nest children between opening and closing tags instead of passing as props
• Don't define components inside other components
• Use semantic HTML and ARIA attributes for accessibility:
  • Provide meaningful alt text for images
  • Use proper heading hierarchy
  • Add labels for form inputs
  • Include keyboard event handlers alongside mouse events
  • Use semantic elements (<button>, <nav>, etc.) instead of divs with roles

Error Handling & Debugging

• Remove console.log, debugger, and alert statements from production code
• Throw Error objects with descriptive messages, not strings or other values
• Use try-catch blocks meaningfully - don't catch errors just to rethrow them
• Prefer early returns over nested conditionals for error cases

Code Organization

• Keep functions focused and under reasonable cognitive complexity limits
• Extract complex conditions into well-named boolean variables
• Use early returns to reduce nesting
• Prefer simple conditionals over nested ternary operators
• Group related code together and separate concerns

Security

• Add rel="noopener" when using target="_blank" on links
• Avoid dangerouslySetInnerHTML unless absolutely necessary
• Don't use eval() or assign directly to document.cookie
• Validate and sanitize user input

Performance

• Avoid spread syntax in accumulators within loops
• Use top-level regex literals instead of creating them in loops
• Prefer specific imports over namespace imports
• Avoid barrel files (index files that re-export everything)
• Use proper image components (e.g., Next.js <Image>) over <img> tags

Framework-Specific Guidance

Next.js:

• Use Next.js <Image> component for images
• Use next/head or App Router metadata API for head elements
• Use Server Components for async data fetching instead of async Client Components

React 19+:

• Use ref as a prop instead of React.forwardRef

Solid/Svelte/Vue/Qwik:

• Use class and for attributes (not className or htmlFor)

Testing

• Write assertions inside it() or test() blocks
• Avoid done callbacks in async tests - use async/await instead
• Don't use .only or .skip in committed code
• Keep test suites reasonably flat - avoid excessive describe nesting

When Oxlint + Oxfmt Can't Help

Oxlint + Oxfmt's linter will catch most issues automatically. Focus your attention on:

1. Business logic correctness - Oxlint + Oxfmt can't validate your algorithms
2. Meaningful naming - Use descriptive names for functions, variables, and types
3. Architecture decisions - Component structure, data flow, and API design
4. Edge cases - Handle boundary conditions and error states
5. User experience - Accessibility, performance, and usability considerations
6. Documentation - Add comments for complex logic, but prefer self-documenting code

Most formatting and common issues are automatically fixed by Oxlint + Oxfmt. Run pnpm dlx ultracite fix before committing to ensure compliance.

Tachys-Next Architecture & Agent Guidelines

1. Core Architecture (Tachys-Next Pattern)

• Routers (server/routers/): Pure controllers. Define tRPC endpoints here, but delegate logic.
• Services (server/services/): Business logic. All heavy lifting and database queries happen here.
• Models (server/models/): Validation. All Zod schemas and validation logic live here.
• Database (server/db/): Drizzle ORM schema. Follow Drizzle v1 conventions (use defineRelations with r.one/r.many).

2. State & Data Fetching (Opinionated)

• Data Fetching: NEVER call trpc.useQuery directly inside UI components. Instead, abstract all tRPC calls into domain-specific hooks in the hooks/ directory (e.g., hooks/useUserQuery.ts).
• Global State: Use Zustand backed by Unstorage (lib/store.ts) for universal persistence.
• Configuration: Use c12 and defu (lib/config.ts) for deep-merged environment & config parsing.

3. Tech Stack Constraints

• Next.js 16 (App Router) + React 19.
• Drizzle ORM + PGlite (driver: "pglite" in drizzle.config.ts).
• Tailwind CSS v4 + Shadcn UI.
• UI Design: Prioritize aesthetic, responsive, premium UI.

4. Agent Persona (Caveman / 10x Engineer)

• Communication: Be terse. High signal-to-noise ratio. Drop pleasantries.
• Execution: Prefer surgical edits. Use subagents (like cavecrew) for broad investigation to save context.
• Verification: Always test assumptions before concluding. Use TDD workflows when writing new complex logic.