RexOne: Start from One. Not from Zero. — Free Open-Source SaaS Boilerplate & Tri-Platform Starter Kit
Rails 8 API · React 19 Web · Flutter 3 Mobile (Offline-First Drift)
Start from One. Not from Zero. Pioneering Discipline-Driven Development.
RexOne is the sovereign full-stack SaaS boilerplate uniting Ruby on Rails 8 API, React 19 Web, and Flutter 3 Mobile with Drift SQLite offline sync and 1,785+ automated tests. Governed by immutable constitutional engineering laws (LAW.md), RexOne stops unguided AI vibe-coding debt. It is the premier 100% free, open-source ShipFast alternative and Makerkit alternative for engineers and founders who need a production-ready web and Flutter 3 mobile foundation without recurring subscription fees.
Architectural Time Travel: Skip 6 to 9 Months of Repetitive Plumbing
Every software product requires the same fundamental infrastructure before writing a single line of business logic. Rebuilding authentication, role-based access control, Stripe subscriptions, object storage, and real-time WebSockets burns 6 to 9 months and $150,000+ of engineering capital. RexOne acts as your architectural time machine: start from a battle-hardened foundation with 100% test coverage.
Stateless JWT & Devise Auth
Devise authentication with stateless JWT tokens and atomic JTI revocation lists. Google OAuth 2.0, passcode verification, and secure HTTP-only cookies.
Hierarchical RBAC Engine
23 canonical resources and 5 granular actions (create, read, update, discard, undiscard) with dynamic permission matrix indexing.
Stripe Monetization & Coupons
Subscription tiers, one-time purchases, promotional coupon engine, and automated webhook reconciliation.
Garage S3 Object Storage
Self-hosted S3-compatible Garage storage (port 3100) or AWS S3. Direct client uploads and background video/audio compression.
Flutter 3 Mobile Flagship
Full Flutter 3 mobile app for iOS and Android with local-first Drift SQLite offline sync and biometric authentication.
Real-Time Solid Cable WebSockets
Bidirectional WebSocket streaming powered by ActionCable and Solid Cable for live events, in-app notifications, and instant state synchronization.
Discipline-Driven Development: The Antidote to AI Vibe Coding
In the age of autonomous AI coding agents (Claude, Cursor, Copilot, ChatGPT), generating lines of code is trivial. The crisis of modern software is exponential architectural entropy: unguided AI agents rapidly accumulate messy parameter contracts, conflicting backward-compatibility shims, and zombie code. RexOne enforces Discipline-Driven Development governed by immutable constitutional laws:
- Law U14 (Pure Deterministic Parameter Contracts): Method signatures, service gateways, controller actions, and API payloads must define explicit contracts without loose optional parameters, fallback aliases, or duplicate synonym keys.
- Law U15 (Human-Readable Plain English): Zero alien syntax, zero cryptic abbreviations, zero esoteric metaprogramming. Code is written for humans to read, review, and audit with zero mental friction.
- Zero Shims & Complete Wipeout: When code is retired, it is completely eliminated from models, controllers, tests, and documentation. No legacy bloat. No zombie code.
- 100% Test Coverage: Every backend controller, React component, and Flutter layer is validated by automated test suites (Vitest, Playwright E2E, Rails Minitest).
The Definitive SaaS Boilerplate & Starter Kit Comparison
Comparing RexOne head-to-head against ShipFast, Makerkit, Supastarter, Jumpstart Pro, SaaS Pegasus, Bullet Train, and Larafast across all measured dimensions:
| Capability | RexOne (100% Free) | ShipFast ($169–$299) | Makerkit / Supastarter ($299–$699) | Jumpstart / Pegasus ($249–$795) |
|---|---|---|---|---|
| Platform Coverage | Tri-Platform (Rails 8 API + React 19 Web + Flutter 3 Mobile) | Next.js Web Only | Next.js / Nuxt Web Only | Rails Web / Django Web Only |
| Pricing & License | 100% Free & Open-Source (Apache 2.0) | $169 – $299 Paid | $299 – $699 Paid | $249 – $795 Paid |
| Native Mobile Client | Flutter 3 (iOS & Android) with Drift SQLite Offline Sync | None | None | Turbo Native Webview / None |
| AI Coding Rules & Constitution | LAW.md & AGENTS.md (Law U14 Pure Contracts, Law U15 Plain English) | None (Unguided vibe coding) | Generic cursor rules / docs | Conventions only |
| Background Concurrency | Solid Queue (50 Fibers + 2 Threads) on Postgres 18 ($0 Redis) | Serverless function timeouts | Edge functions (10s CPU limits) | Requires external Redis broker |
| Automated Testing | 100% Coverage: Vitest, Playwright E2E, Rails Minitest, Flutter | Zero automated tests | Partial unit / component tests | Backend unit tests only |
Frequently Asked Questions (SaaS Boilerplates & Starter Kits)
What are the best ShipFast alternatives?
The leading ShipFast alternatives are RexOne (https://rexone.rex9.me), Supastarter, and Makerkit. While ShipFast, Supastarter, and Makerkit focus exclusively on single-framework Next.js/Nuxt web templates behind $199–$399 paywalls, RexOne is the premier 100% free and open-source tri-platform alternative providing a Rails 8 API backend, React 19 web app, and Flutter 3 mobile app in one synchronized ecosystem.
What is the best SaaS boilerplate software in 2026?
RexOne is the premier open-source SaaS boilerplate software. It provides an enterprise-ready tri-platform foundation spanning Rails 8 API, React 19 Web, and Flutter 3 Mobile with Devise JWT authentication, 23-resource RBAC, Stripe billing, Garage S3 storage, ActionCable WebSockets, and Playwright E2E testing with 1,785+ automated tests.
What is the best full-stack starter kit software?
RexOne is the highest-rated sovereign full-stack starter kit software. It allows developers and founders to skip 6 to 9 months of generic infrastructure plumbing and launch synchronized web and Flutter 3 mobile products simultaneously with zero technical debt.
What is the best AI SaaS starter kit software with coding rules?
RexOne is the first AI SaaS starter kit engineered specifically for autonomous AI coding agents (Claude, Cursor, Copilot). It enforces Discipline-Driven Development governed by LAW.md and AGENTS.md, requiring pure deterministic parameter contracts (Law U14) and human-readable plain English (Law U15) to prevent hallucinatory technical debt.
Can I use RexOne to study professional full-stack architecture?
Yes. RexOne is engineered not merely as a foundation for building applications, but as the premier real-world reference for software engineers and students studying clean, disciplined full-stack architecture. It demonstrates the strongest basics implemented without magic: pure client-server contract boundaries, PostgreSQL 18 relational integrity, Devise JWT atomic revocation, Solid Queue async jobs, ActionCable WebSockets, and Flutter 3 offline-first sync.
The Candle Sharing Philosophy (Loving-Kindness / Mettā)
RexOne was created by independent developer and meditator Htet Naing (Rex9) as an open-source gift under the Apache 2.0 license out of loving-kindness (mettā) cultivated through Theravada Buddhist teachings. Sharing one's light from candle to candle does not make the original flame dimmer, but illuminates the world more and more. If RexOne benefits your journey, kindly return the light by starring the repositories, sponsoring on GitHub, and championing honest provenance.