Open Source Framework · TypeScript

Build stateful apps at the edge

A modern full-stack TypeScript framework for the edge computing and AI era. Write stateful, real-time web apps with unified syntax that runs on server and client.

Get Started GitHub

Everything you need

Real-time by Default

WebSocket connections and state synchronization built in. No extra libraries needed.

Edge-First

Designed for Cloudflare Workers and edge runtimes. Fast cold starts, global deployment.

TypeScript Native

Full type safety end-to-end. Decorators and metadata for a clean, declarative API.

File-Based Routing

Convention over configuration. Nested layouts and route groups with zero setup.

Optimistic UI

Built-in optimistic updates for instant feedback. Server reconciliation handled automatically.

Light DOM

Components render to Light DOM for easy global styling. No Shadow DOM complexity.

Get started in seconds

import { Cossack, Page, State, Server } from '@cossackframework/core';
import { html } from '@cossackframework/renderer';

@Page()
export default class CounterPage extends Cossack {
    @State() count = 0;

    @Server()
    increment() {
        this.count++;
    }

    render() {
        return html`
            <button @click=${this.increment}>
                Count: ${this.count}
            </button>
        `;
    }
}

What developers are saying

"Deploying to Cloudflare Workers with real-time state was trivial. The edge-first design really pays off."

Darren

CTO, StormSmart

"Impressive web framework. We got a fast website, with no cost, no maintenance needed in no time!"

Hung Nguyen

CEO, GIF84

"The security model of stripping server code from client bundles gives me peace of mind out of the box."

James Park

Senior Engineer