Overview
The AI SaaS Starter Kit is a complete, production-ready boilerplate for launching AI-powered SaaS products. It combines a polished user-facing chat interface with the backend infrastructure needed to run an AI business: user authentication, subscription billing with usage-based pricing, prompt management, conversation history, usage tracking, rate limiting, and cost monitoring. Instead of spending months wiring together auth, billing, and AI APIs, you get a working product on day one and can focus entirely on your AI differentiator.
Built with Next.js, TypeScript, PostgreSQL, Prisma, Stripe, OpenAI, and LangChain, the kit follows a modular architecture where each concern is cleanly separated. Swap OpenAI for Anthropic or a self-hosted model. Replace Stripe with another billing provider. The abstractions are designed for flexibility without over-engineering.
Architecture
The application is structured into six layers:
- Authentication & User Management -- Supabase Auth handles user registration, login (email/password, magic link, Google OAuth, GitHub OAuth), session management, and password reset. User profiles are stored in PostgreSQL with role-based access (User, Admin). The auth middleware protects all API routes and injects the authenticated user context.
- AI Conversation Engine -- The core AI layer uses LangChain to orchestrate interactions with language models. It supports streaming responses, conversation memory (short-term in Redis, long-term in PostgreSQL), system prompt configuration, and multi-model routing. The chat interface renders markdown, code blocks with syntax highlighting, and supports regenerating responses.
- Prompt Management -- An admin interface lets you define, version, and A/B test system prompts without redeploying. Prompts are stored in the database with version history. You can assign different prompts to different user segments or plan tiers, enabling experimentation and gradual rollout.
- Usage Tracking & Cost Control -- Every AI API call is logged with token counts (input and output), model used, latency, and estimated cost. Usage is aggregated per user and per billing period. Plan limits (e.g., 100 messages/month on the free tier, 1,000 on Pro) are enforced in real time. A cost dashboard shows your aggregate OpenAI spend.
- Subscription Billing -- Stripe integration handles plan management with three default tiers: Free, Pro, and Enterprise. The billing system supports flat-rate and usage-based pricing. When users exceed their plan limits, they see an upgrade prompt. Webhook handlers keep subscription state synchronized. The Stripe Customer Portal is integrated for self-service billing management.
- Rate Limiting & Abuse Prevention -- A Redis-backed rate limiter enforces per-user and per-IP request limits. Token-based limiting prevents a single request from consuming excessive resources. Configurable limits per plan tier ensure fair usage across your user base.
Key Features
- Streaming Chat Interface -- Real-time token-by-token streaming with a polished UI. Supports markdown rendering, code blocks, copy-to-clipboard, and conversation branching.
- Multi-Model Support -- Route requests to different models (GPT-4o, GPT-4o-mini, Claude) based on plan tier, request type, or user preference. LangChain abstraction makes adding new providers trivial.
- Conversation History -- Full conversation persistence with search, pagination, and the ability to continue previous conversations. Conversations are nameable and deletable.
- Prompt Versioning -- Version-controlled system prompts with rollback. A/B test different prompts and measure response quality and user satisfaction.
- Usage Analytics -- Per-user and aggregate dashboards showing message counts, token usage, estimated costs, and plan utilization. Export data for financial reporting.
- Plan-Based Feature Gating -- Middleware enforces plan limits on messages, tokens, and features. Higher tiers unlock longer context windows, faster models, and priority processing.
- Admin Dashboard -- Monitor active users, usage patterns, revenue, and AI costs. Manage users, view conversations (with appropriate privacy controls), and configure system settings.
- Responsive Design -- The chat interface works beautifully on desktop, tablet, and mobile. Built with Tailwind CSS with a clean, modern aesthetic.
What's Included
- Full Next.js application with App Router and Server Components
- Supabase Auth integration with email, magic link, and OAuth providers
- LangChain-based AI engine with streaming support
- Chat UI components (conversation list, message thread, input with file attachment support)
- Stripe billing integration with three plan tiers
- Usage tracking and rate limiting middleware
- Prompt management system with version control
- Admin dashboard with analytics
- PostgreSQL schema and migrations (Prisma)
- Redis configuration for caching, rate limiting, and session storage
- Comprehensive test suite (unit and integration)
- Tailwind CSS with a complete design system
- Deployment guides for Vercel, Railway, and Docker
- Environment variable reference and setup guide
Who Is This For?
This starter kit is for developers and founders who want to launch an AI-powered product without building the surrounding infrastructure from scratch. If you have a unique AI use case -- a specialized chatbot, a document analysis tool, a code assistant, a writing tool -- and you want to wrap it in a monetizable SaaS product with user accounts, billing, and usage tracking, this kit gets you there in days instead of months.
You should be comfortable with Next.js, TypeScript, and have an OpenAI API key. Everything else is configured and ready to deploy. The codebase is yours to extend, customize, and build upon.