ScriptsMar 31, 2026·2 min read

Chainlit — Build Conversational AI Apps Fast

Python framework for building production conversational AI interfaces in minutes. Chat UI, streaming, file upload, feedback, auth, and LangChain/LlamaIndex integration. 12K+ stars.

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Quick Use

Use it first, then decide how deep to go

This block should tell both the user and the agent what to copy, install, and apply first.

pip install chainlit
# app.py
import chainlit as cl

@cl.on_message
async def main(message: cl.Message):
    response = f"You said: {message.content}"
    await cl.Message(content=response).send()
chainlit run app.py

Open http://localhost:8000 — you have a chat UI.

Intro

Chainlit is a Python framework for building production conversational AI interfaces in minutes. It provides a polished chat UI with streaming, file upload, feedback collection, authentication, and data persistence — out of the box. Integrates natively with LangChain, LlamaIndex, Haystack, and any Python LLM library. 12,000+ GitHub stars, Apache 2.0.

Best for: Python developers who need a chat interface for their AI app without building frontend Works with: OpenAI, Anthropic, LangChain, LlamaIndex, Haystack, any Python LLM library

Key Features

Instant Chat UI

Beautiful, responsive chat interface with zero frontend code. Streaming, markdown, code highlighting, and LaTeX.

File Upload & Display

Users can upload files. Agents can send images, PDFs, and data visualizations.

Feedback & Human Evaluation

Built-in thumbs up/down feedback on AI responses. Export for fine-tuning.

Multi-Step Display

Show intermediate "thinking" steps, tool calls, and chain-of-thought reasoning.

Authentication

Built-in auth with OAuth (Google, GitHub) or custom login.

Data Persistence

Conversation history saved automatically. Resume sessions across visits.

Framework Integration

# LangChain integration
@cl.on_message
async def main(message):
    result = await chain.ainvoke({"input": message.content},
        callbacks=[cl.LangchainCallbackHandler()])
    await cl.Message(content=result).send()

FAQ

Q: What is Chainlit? A: A Python framework for building conversational AI interfaces in minutes — chat UI, streaming, file upload, feedback, and auth included. 12K+ stars.

Q: How is Chainlit different from Streamlit? A: Chainlit is purpose-built for chat/conversational AI with streaming, multi-step display, and LLM framework integrations. Streamlit is a general data app framework.

🙏

Source & Thanks

Created by Chainlit. Licensed under Apache 2.0. Chainlit/chainlit — 12,000+ GitHub stars

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