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Products with intelligence built in.

Fourlyn is a product studio. We build our own apps and developer tools, and we take on full-stack and AI work for teams who want the same care.

Start a project See our products

We design and build our own products: a voice-first memory app, a services marketplace, an SDK for Apple’s on-device models, a platform for recovery agencies and a marketplace for AI trends. The team that builds them can build yours.

Products

Five products. One team.

Coming soon · Mobile app

EverWhy

Remember why. Decide better.

A voice-first memory for the reasoning behind your life decisions. Stored on your phone.

Learn more
Version 1.0 built · Mobile app

Aura

Book experts by the slot.

A services marketplace app. Customers book and pay without signing in, and sellers run their store from the same app.

Learn more
In design · Consumer app

VibeShift

Every viral AI trend, one tap away.

A marketplace for AI photo and video trends, where the creators who start them get paid.

Learn more
Private platform · Operations platform

RecoveryOS

Run recovery from one system.

Case lifecycle, workforce and reconciliation for credit recovery agencies that work for several banks.

Learn more
Live on npm · Developer SDK

Apple Foundation Models SDK

Apple Intelligence, from React Native.

A TypeScript and Expo SDK for Apple’s on-device language models. No API keys, no server.

Learn more
assistant.ts
import { createSession } from '@fourlyn/apple-foundation-models';

const session = await createSession({
  instructions: 'You are a travel assistant.',
});

// Runs on the device. No API key, no server.
for await (const chunk of session.stream('Plan a day in Jaipur')) {
  console.log(chunk.text);
}

Services

Build with us.

The people who make these products also build for other companies. Bring an idea, a half-finished product or a process that still runs on spreadsheets.

Full-stack development

Web apps, back ends and the data model under them, from the first screen to production.

  • React and TypeScript front ends
  • APIs, databases and cloud functions
  • Design systems and marketing sites

AI-powered development

AI features inside real products: search, summaries, structured extraction and assistants.

  • Large language models in the cloud
  • On-device models where privacy matters
  • Prompts, schemas and evaluation

AI agent development

Agents that use your tools and data to finish a task, with a person approving what matters.

  • Tool calling over your own systems
  • Permissions that follow the user’s role
  • Logged actions and human approval

Mobile apps

iOS and Android apps from one codebase, with native modules where the platform needs them.

  • React Native and Expo
  • Swift modules for native APIs
  • Offline-first storage and sync

Approach

How we work.

The same four habits on our own products and on yours.

  1. 01

    Write it down first

    We agree what the software has to do, who uses it and which rules can never break, before choosing any technology.

  2. 02

    Design before code

    Screens and a design system come first, so you see the product and change it while change is cheap.

  3. 03

    Automation before AI

    Plain rules handle what plain rules can. AI goes where it earns its place, and a person signs off on sensitive decisions.

  4. 04

    Ship in phases

    The core workflow goes live first. Every later phase builds on software that people are already using.

Have something to build?

Tell us what it has to do. We’ll reply with how we’d build it.

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