kosmojs.dev

What It Is

KosmoJS is a composable Vite-based meta-framework for full-stack TypeScript projects. It advocates using Multiple Source Folders to organize several separate areas of concern—such as a marketing site, customer app, and admin dashboard—within a single project, while sharing the same package.json, node_modules, types, and infrastructure. Compared with a traditional monorepo or microservices setup, it aims to reduce the maintenance burden around package boundaries, release versions, and build configuration.

Core Capabilities

Its routing uses a file-system convention: the structure of api/ and pages/ maps directly to API and page routes, with support for dynamic parameters, optional parameters, splats, mixed segments, and advanced path-to-regexp v8 patterns. Type safety is a major focus: developers define parameters, request bodies, and response bodies with TypeScript types, and KosmoJS uses AST plus AOT generation to produce JSON Schema, runtime validation logic, client-side validation, a typed Fetch Client, and OpenAPI 3.1. For middleware, it supports Slots overrides and cascading use.ts middleware, making it suitable for organizing authentication, logging, and similar logic by route tree. On the frontend, it also supports nested layouts and optional SSR.

Frameworks, Deployment, and Pricing

The crawled text explicitly mentions backend support for Koa and Hono, and frontend support for React, Vue, SolidJS, and MDX. Build outputs can include an API server, frontend static assets, and an SSR bundle, and can be deployed to Node.js, Deno, Bun, containers, serverless, or edge environments, with self-hosting support. The page does not provide pricing, license, or open-source/closed-source status information, so commercial risk and compliance still need further verification.

Pros and Cons

Its strengths are that type definitions, runtime validation, the Fetch Client, and OpenAPI all share a single source of truth, which can significantly reduce frontend-backend API drift. Source Folders are attractive for teams managing multiple applications but not wanting to introduce a heavyweight monorepo. The documentation sections are complete, examples are plentiful, and it also provides LLM-friendly Markdown. The downsides are that framework abstractions and code generation bring learning and debugging costs, while the current text does not demonstrate community size, version maturity, performance benchmarks, or production case studies. Non-TypeScript projects will see limited benefit.

Who It’s For and Access from China

KosmoJS is best suited to teams familiar with Vite/TypeScript that need to maintain multiple related web applications and care about API type safety and automated documentation. Access from China cannot be determined from the crawled text and should be marked as unknown; payment methods are also not disclosed. If ecosystem maturity is a concern, compare it with Next.js, Nuxt, Remix, Astro, SvelteKit, and TanStack Start, or consider alternative combinations such as tRPC, Hono, NestJS, and Nx/Turborepo.