t3stack-fullstack-dev

name: t3stack-fullstack-dev description: Develop, debug, and ship T3 Stack applications using Next.js + TypeScript with better-auth, Prisma, tRPC, and Tailwind CSS. Use when implementing new fullstack features, auth/session flows, API procedures, database schema changes, high-quality frontend UI work with Tailwind, bug fixes, refactors, performance work, or GitHub-ready release preparation for this stack.

T3 Fullstack Dev

Quick Start

1. Detect package manager from lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock).
2. Run baseline checks before and after edits:
   • npm run lint
   • npm run typecheck
   • npm run check
3. Use scripts/t3_stack_audit.sh for fast stack validation when onboarding a repo.

Implementation Workflow

1. Confirm requirement boundaries: route, API contract, data model, auth constraint, UI state.
2. Start from schema/contracts, then build server logic, then client wiring, then styling.
3. Keep types single-source-of-truth from Prisma schema + tRPC router outputs.
4. Validate affected paths with targeted checks first, then run full npm run check.
5. Apply the OWASP Top 10:2025 security gate before finalizing any change.

OWASP Top 10:2025 Security Gate

• A01 Broken Access Control: Enforce authorization in server procedures and DB filters; never rely on client-side checks.
• A02 Security Misconfiguration: Keep secure defaults, disable debug exposure, and load all secrets from environment variables.
• A03 Software Supply Chain Failures: Pin dependency versions, review lockfile changes, and run dependency audit in CI.
• A04 Cryptographic Failures: Use modern algorithms and managed libraries; never create custom crypto implementations.
• A05 Injection: Validate all untrusted inputs with Zod and use Prisma parameterized queries/ORM patterns only.
• A06 Insecure Design: Add threat-aware acceptance criteria for new features and define misuse cases before implementation.
• A07 Authentication Failures: Use better-auth best practices, strict session validation, secure cookie settings, and short-lived tokens where needed.
• A08 Software or Data Integrity Failures: Verify build/deploy integrity, protect CI/CD secrets, and require trusted artifact sources.
• A09 Security Logging and Alerting Failures: Log security-relevant events with request/user context and create actionable alerts.
• A10 Mishandling of Exceptional Conditions: Fail securely on exceptions, return safe error messages, and avoid leaking internal details.

For detailed controls and review checklist, read references/owasp-2025-security-checklist.md.

better-auth Rules

• Keep auth config in a single server-only module.
• Resolve session on the server for protected data paths.
• Enforce authorization at tRPC procedure boundaries; do not trust client guards alone.
• Expose minimal user/session fields to clients.

Prisma Rules

• Change prisma/schema.prisma first for data model updates.
• Prefer explicit relations, indexes, and unique constraints for query paths.
• Use db:push for local iteration and migrations for durable environments.
• Keep query selection narrow (select/include) to avoid overfetching.

tRPC Rules

• Keep routers split by domain and merge in a central app router.
• Validate every input with Zod.
• Use protected/public procedures consistently.
• Return typed domain payloads; avoid any and ad-hoc casting.

Tailwind + UI Rules

• Build UI with frontend-developer quality, not only functional layouts.
• Keep utility classes readable; extract repeated patterns to components.
• Prefer design tokens via CSS variables for theme consistency.
• Preserve mobile-first behavior and verify responsive breakpoints.
• Keep loading/error/empty states explicit for async views.
• Use clear visual hierarchy: typography scale, spacing rhythm, and consistent component density.
• Add meaningful interaction polish: hover/focus/active/disabled states and subtle transitions.
• Keep accessibility first: visible focus, sufficient contrast, semantic HTML, keyboard usability.
• Avoid generic boilerplate visuals; keep each screen intentional and cohesive.

For detailed UI standards, read references/tailwind-ui-quality-guide.md.

TypeScript Rules

• Keep strict-safe code and avoid non-null assertions unless justified.
• Narrow unknown/error values before use.
• Prefer inferred types from source libraries (Prisma, tRPC, zod) over duplicate interfaces.

GitHub Publishing Workflow

1. Run npm run check and npm run build.
2. Ensure .env.example includes required variables without secrets.
3. Verify migrations and seed strategy are documented in project docs.
4. Confirm CI command parity (lint, typecheck, build).
5. Confirm OWASP Top 10:2025 security gate items are addressed for changed files.
6. Prepare a clear PR description with schema/API/auth impact.

For detailed release checklist, read references/github-publish-checklist.md. For architecture guardrails and patterns, read references/t3-implementation-playbook.md.