Index is a state-of-the-art browser agent framework that autonomously performs complex tasks on the web by leveraging reasoning LLMs with vision capabilities. It supports multiple backends including Gemini 2.5 Pro, Claude 3.7 Sonnet, and OpenAI o4-mini. The framework provides a Python SDK for integration, a CLI for interactive use, and can be deployed as a serverless API. It includes structured output support via Pydantic schemas and observability tooling powered by Laminar.