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ModelFusion

Free

A TypeScript library for building apps with LLMs and other ML models (speech-to-text, text-to-speech, image generation).

FreeFree tier
Inputs: text, image, audioOutputs: text, image, audio
Type
Open Source
Company
Vercel
Visit Website GitHub (38 stars)

About ModelFusion

ModelFusion is an abstraction layer for integrating AI models into JavaScript and TypeScript applications, unifying the API for common operations such as text streaming, structured object generation, and tool usage. It provides production-ready features including observability hooks, logging, automatic retries, throttling, and error handling. Multi-modal support spans text generation, image generation, vision, text-to-speech, speech-to-text, and embedding models. ModelFusion is vendor-neutral, enforces TypeScript type inference and validation, and is designed for serverless and tree-shakeable deployments. Note: ModelFusion has joined Vercel and is being integrated into the Vercel AI SDK; the repository is now archived.

Key Features

Vendor-neutral abstraction layer for AI models
Multi-modal support: text generation, image generation, vision, text-to-speech, speech-to-text, embeddings
Unified API for text streaming, structured object generation, and tool usage
TypeScript type inference and response validation
Observability hooks and logging for production monitoring
Resilience features: automatic retries, throttling, and error handling
Production-ready: tree-shakeable, serverless-friendly, minimal dependencies

Pros & Cons

Pros
  • Vendor-neutral: works with multiple model providers without lock-in
  • Multi-modal: supports text, image, audio, and embeddings in one library
  • TypeScript native: full type inference and validation for model outputs
  • Production observability: built-in logging and observer hooks
  • Robust: automatic retries and throttling for reliability
  • Lightweight: tree-shakeable and minimal dependencies for serverless
Cons
  • Repository archived: no longer actively maintained as standalone; being merged into Vercel AI SDK
  • Limited to TypeScript/JavaScript ecosystems
  • Requires external API keys or local setup for most models (no built-in model hosting)

Best For

Building conversational AI chatbots and agentsGenerating structured data from LLMs (object generation)Multi-modal applications combining text, images, and audioTool-calling and function execution with language modelsText streaming for real-time response generationServerless AI applications with observability

FAQ

What happened to ModelFusion?
ModelFusion has joined Vercel and is being integrated into the Vercel AI SDK. The best parts are being brought over, starting with text generation, structured object generation, and tool calls. The original repository is now archived.
Is ModelFusion free to use?
Yes, ModelFusion is an open-source library (MIT license) and free to use. You only pay for the underlying model APIs (e.g., OpenAI, Anthropic) or run local models yourself.
What programming languages does ModelFusion support?
ModelFusion is a TypeScript library for JavaScript and TypeScript applications. It can be used in Node.js, browser, and serverless environments.
What types of models does ModelFusion support?
ModelFusion supports text generation, image generation, vision (image analysis), text-to-speech, speech-to-text, and embedding models from multiple providers.