Alternatives to Promptmetheus

Free, zero-knowledge browser markdown editor for prompt testing and multi-model comparison.

Python library for guaranteed valid structured outputs from LLMs using FSM constrained decoding

Type-safe Rust library for building AI agents across 20+ providers

Run LLMs in-browser with WebGPU — headless React hooks, just useLLM().

Open-source MCP testing & app framework for building ChatGPT Apps and Claude Connectors.

GoAI SDK: one unified Go API across 25+ LLM providers with streaming, structured output, MCP support.

Local-first AI workbench to build, evaluate, and optimize AI systems.

An open-source Python framework that turns ordinary functions into AI-powered tools via simple decorators.

Mirascope: Build LLM apps with decorators, observability, and full control.

LangSmith is an AI agent observability platform for tracing, monitoring, and evaluating LLM apps and long-running agents.

Arena AI is a free, community-voted LLM leaderboard ranking chat models, agents, and fullstack code on live head-to-head battles.

The frontend stack for agentic user experience — drop-in chat, generative UI, and shared state for React apps on any AG-UI backend

Agent evaluation and simulation platform that catches hallucinations before they reach production

Mastra is an open-source TypeScript agent framework for building durable AI agents and workflows that run for days.

Turn plain English into production-ready Honeycomb queries and debug faster with AI Copilot.

Vercel AI SDK is an open-source TypeScript toolkit for building AI apps with 100+ models, real-time streaming, fallbacks, and agents

Guidance is an open-source Python library for constrained LLM generation with regex, CFG, and native control flow.

Type-safe programming language for building AI agents with compile-time guarantees.

Pydantic AI is the Python AI SDK for typed agents, realtime voice, image generation, and embeddings — every model a string swap away.

Open-source LLM that turns natural language into API calls for tool-using agents

Free GitHub repo of OpenAI API code examples, guides, and Jupyter notebooks.

Go-native LLM framework by ByteDance for building production-grade AI applications.

Open-source benchmark for AI agents on multi-step, real-world software company tasks.

LangChain中文文档与社区，助你快速掌握LLM应用开发

Open-source streaming-first toolkit that turns AI agent output into interactive UI, not JSON.

Google's open-source framework for building agentic AI apps in JS, Go, Python & Dart.

Compress AI agent context by up to 90% with a local, open-source MCP server.

Free, MIT-licensed local dashboard that reads your AI coding agents' log files to show tokens, cost, and traces — no SDK or API key.

Document-aware AI editing SDK for rich-text editors

Interactive coding agent benchmark simulating 9 apps and 457 APIs to evaluate agent reliability.