Your blank-slate Rails + React starter.

What is Build New?

Build New is an opinionated, full-stack starter template — Rails 8 + React 19 + PostgreSQL, bridged by Inertia.js — pre-wired with the patterns I reach for on every project. It’s the starter I use to ship every new product I build, so I never spend a week on auth, layout, and CI again.

Every piece is chosen so the whole thing agrees with itself, and so your AI coding agent has a coherent system to build on top of.

Requirements

• Ruby 3.3.6
• Node.js 20.19+ (or 22.12+)
• PostgreSQL 10+ running locally

Installation

Clone the repo and run:

bin/setup      # installs gems, creates and migrates the database
npm install    # installs JavaScript dependencies

By default Rails connects to the Postgres on your machine using your OS username. If your local Postgres needs different credentials, set them in your environment as DATABASE_URL.

Running the app

bin/dev

This boots Rails and the frontend dev server together. Visit http://localhost:3000, click “Sign up”, and you’re in.

Learn to build

Want a step-by-step tutorial on how to build real apps on top of this template? That’s exactly what I teach in my Become the Builder course, included with Builder Methods Pro. You’ll learn how I plan, prompt, and ship full-stack apps using Build New as the starting point — alongside direct support from me and the rest of the community.

Tech stack

• Rails 8 — the backend
• Inertia.js — connects Rails to React with no separate API to maintain
• React 19 + TypeScript — the frontend
• Tailwind CSS v4 + shadcn/ui — the design system
• Vite 7 — fast dev server and build tool
• PostgreSQL — handles app data, jobs, cache, and real-time updates

This is the exact stack I use in every product I ship.

Why React?

Rails has great built-in view tools, so why pull in React? Two reasons, both about working with AI:

AI models know it cold. React + Tailwind is the most-trained-on UI stack in the world. Every coding agent — Claude, Cursor, Copilot — writes sharper, less buggy frontend code in React than in any other style. You spend less time correcting the model and more time shipping.

Components are the right shape for agents. A React component file holds the layout, behavior, and styles for one piece of UI in one place. That’s much easier for an agent to read and change than the same feature spread across a Ruby template, a JavaScript file, and a separate CSS file.

If you’re hand-coding everything yourself, classic Rails views are wonderful. If an AI agent is your main collaborator, React earns its place — that’s why I use it.

Auth & users

Sign up, log in, log out, and password reset are all wired up out of the box. Each new user automatically gets their browser timezone saved so dates and times display correctly.

There’s also an admin flag on every user account that controls access to the admin area.

Admin area

Everything under /admin is locked down to admin users. The starter includes a user list and the live design system reference.

Users with admin set to true get access.

Design system

Build New comes with my AI Design System pre-installed — the same primitives, tokens, and agent rules that power the standalone Design System Skill, baked in from day one.

You can browse your live reference at /admin/design-system: colors, typography, buttons, inputs, dialogs, badges, dropdowns, page layouts, and a working light/dark theme toggle.

Because the design system rules ship inside the template, your AI agent stays consistent build after build — it knows to reuse the existing pieces instead of inventing new ones every time. For full details, see the AI Design System docs.

CLAUDE.md

CLAUDE.md is a file at the root of the repo that AI coding agents like Claude Code read first when they open the project. Think of it as a brief for your agent — the rules, conventions, and gotchas of this codebase, written in plain English so it gets them right on the first try.

The one in Build New covers the architecture, where files live, the pattern for adding a new page, common Rails-with-React pitfalls, the page metadata rules, and how server-side rendering works.

As your app grows, keep adding to it — every convention you teach your agent in chat should end up in here, so the next session inherits it. I treat CLAUDE.md as one of the most important files in the repo. It’s where your agent’s institutional knowledge lives.

Background jobs, cache, and websockets

Three things every real app eventually needs:

• Background jobs — for sending emails, processing uploads, anything that shouldn’t block a page load
• Cache — for speeding up expensive queries and pages
• Websockets — for real-time features like chat or live updates

Most Rails apps add Redis or a message queue for these. Build New doesn’t — Rails 8 does all three on top of your existing Postgres database. One less service to run, one less thing to deploy.

That’s a big reason I picked this stack: less infrastructure means less to break.

Email

In development, outgoing emails open in your browser instead of actually sending. Visit /letter_opener to see them. When you deploy, plug in any mail provider you want — Resend, Postmark, SendGrid, etc.

SSR & SEO

Server-side rendering is on by default in production. That means when a search engine, social network, or AI crawler (GPTBot, ClaudeBot, PerplexityBot, etc.) visits one of your public pages, it sees fully rendered HTML — your headlines, your copy, your prices — instead of a blank shell.

The template also includes a sitemap, a robots.txt, an llms.txt (a sitemap for AI crawlers), and the required title, description, and social-preview tags on every page. Forking this template means your app shows up properly in Google, Slack previews, ChatGPT answers, and everywhere else from day one.

CI & code quality

Every time you push code or open a pull request, GitHub automatically runs your tests, type checks, linting, and a security scan. Nothing to set up — it’s already wired in.

That automated check matters even more when you’re building with AI. An agent will happily ship code that looks right but doesn’t hold up — CI is the safety net that catches regressions, broken types, and security issues before they reach production, so you can move fast without flying blind.

Should you use it?

When to use it

• You’re building with AI and want a stack and conventions your agent already understands
• You want a working full-stack app on day one without spending a week on auth, layout, and CI
• You’re comfortable with Rails or React and want to learn the other side without leaving the same repo
• You’re building a real product — you want a database, users, background jobs, and email from the start

When to skip it

• You only need a static landing page or marketing site
• You need a non-Rails backend (Node, Python, Go) — this template is Rails-first
• You already have a working app and just want to lift one piece (design system, SSR, etc.) — copy the relevant files instead of starting over

Next steps

• Get the code on GitHub
• Get help inside Builder Methods Pro
• Stay in the loop with the Builder Briefing