Chainlit

Chainlit gives Python developers a fast path from an LLM script to a shareable chat application. The open source framework pairs a Python backend with a prebuilt web frontend, so a few decorators on ordinary functions produce a conversational UI with streamed messages, step-based execution tracking for agent and tool calls, and async task handling. It integrates with LangChain, LlamaIndex, and the OpenAI and Anthropic SDKs, and works with vector stores such as ChromaDB and Pinecone, which makes it a common choice for prototyping RAG assistants and agent demos before investing in a custom frontend. Chainlit is released under the Apache 2.0 license; since May 2025 the project has been community maintained after the original team stepped back, with community maintainers handling code review and releases. Typical users are ML engineers and Python developers who want an interactive chat interface over their models without writing JavaScript.