Alternatives to Langchain4j

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 Django library for adding LLM assistants, chat, and RAG inside your existing Django app

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

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

Open-source SuperAgent harness that researches, codes, and creates inside a persistent Docker sandbox — MIT licensed and self-hosted.

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

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

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 multi-agent framework that assigns PM, architect, engineer and QA roles to LLMs for structured software tasks

CopilotKit is the open-source React framework for adding agent chat, generative UI, and shared state to any AG-UI backend.

Imbue is an open AI lab publishing modular, open-source coding-agent tools you run and inspect yourself.

Microsoft's open-source framework for building conversational and event-driven AI agents in Python and .NET.

Open-source TypeScript framework for building durable AI agents and workflows, with a hosted platform for observability and cloud deployment.

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

Open-source agentic data assistant: your LLM connects to databases, writes SQL and code, and runs analysis in sandboxes

Microsoft's open-source SDK for building AI agents and copilots with plugins, memory, and multi-agent orchestration.

Microsoft's open-source, code-first Python framework for building stateful, data-intensive conversational AI agents.

Hermes Desktop is an open-source desktop GUI for the Hermes Agent, with a built-in learning loop that turns your tasks into reusable skills

Open-source, self-hosted AI agent whose SquillaRouter routes each step to cheap or flagship models to cut token cost.

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

Open-source, self-hosted AI agent that plans tasks, runs tools, and grows its own memory.

Open-source AI agent loop that iterates a task list in Docker Sandboxes and commits the results.

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

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.

Rig is a free, MIT-licensed Rust library for building LLM apps and agents behind one unified API across 20+ model providers.

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

Open Harness is an open-source TypeScript SDK for building Claude Code-style agent harnesses with stateless primitives and composable middleware.

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

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

Open-source JavaScript library that runs small LLMs like Llama 3.2 1B Instruct inside the browser via WebAssembly and WebGPU.