Alternatives to Fabric

Marvin is an open-source Python framework that turns ordinary functions into AI-powered tools using decorators like @ai_fn and @ai_classifier.

Open-source React framework for adding agent chat, generative UI, and shared state to any AG-UI backend.

Eino is an open-source Go framework from ByteDance for building LLM apps, agents, and graphs in your existing Go backend.

OpenUI is an open-source framework that lets AI agents stream interactive UI from your own React, Vue, Svelte or React Native components instead of raw JSON.

Google's open-source framework for building AI-powered and agentic apps in TypeScript, Go, Python, and Dart.

Open-source (MIT) MCP testing and full-stack MCP App framework for building ChatGPT Apps and Claude Connectors from one React codebase.

Mirascope is an open-source Python library that turns LLM calls, tools, and prompt versioning into plain decorated functions.

Open-source TypeScript toolkit for building AI apps and agents across 100+ models with streaming, tools, and fallbacks

Open-source Python library that constrains LLM decoding with finite-state machines so Pydantic, JSON Schema, regex, and grammar outputs come out valid every

Open-source Python library for constraining LLM output with regex, context-free grammars, and inline control flow — archived since October 2023.

Open-source LLM from UC Berkeley that turns natural language into API calls and tool-using agent actions.

Open-source Rust library for building streaming, parallel LLM pipelines — data indexing, retrieval-augmented generation, and autonomous agents.

Open-source Go SDK giving one unified API across 25+ LLM providers with streaming, typed structured output, and MCP support.

Open Harness is an MIT-licensed TypeScript SDK for building Claude Code-style agents with stateless primitives and composable middleware.

Open-source Python library that turns messy text into typed, queryable Semantic DataFrames built on Polars

Open source Python and TypeScript SDKs for building production AI agent harnesses you control end to end.

Open-source Java library that puts a unified LLM and vector store API inside your JVM app

MIT-licensed open-source Swift package for calling the OpenAI API with async/await and Combine from Apple platforms.

Open-source React toolkit for generative UI — let an agent render your own components from natural language

Open-source Django library for adding LLM assistants, chat, RAG, and Tool Calling to your existing app

LMQL is a programming language for LLMs that uses types, templates and constraints to make prompts modular and outputs reliable.

tokf is an open-source Rust CLI that filters noisy terminal command output before your AI coding assistant reads it.

OpenAI Cookbook is a free, MIT-licensed GitHub repository of example code and guides for working with the OpenAI API.

Free browser markdown editor with Battle Mode for comparing OpenAI, Claude, and Gemini prompt outputs, client-side only.

MIT-licensed Ruby gem that plugs MCP servers into RubyLLM chat workflows with idiomatic Ruby APIs

xsAI is an extra-small OpenAI-compatible AI SDK for JavaScript that cuts install size roughly 40x versus the Vercel AI SDK.

Prompt engineering IDE to build, test, and optimize prompts against 150+ LLMs from 15 providers.

flompt is a free visual prompt builder that compiles prompts into Claude-optimized XML blocks

BAML is a type-safe programming language for building AI agents and structured LLM output that compiles instead of guessing.

Pydantic AI is a typed Python agent SDK: define a model string and an output type, get validated structured results every run.