Chatbot — full example

Python Backend Script

import asyncio, json, os
from fastapi import FastAPI, Request
from fastapi.responses import StreamingResponse
from openai import AsyncOpenAI

app = FastAPI()
client = AsyncOpenAI(api_key=os.getenv("OPENAI_API_KEY"))

SYSTEM_PROMPT = (
    "You are Nimbus Assistant, a helpful AI for the Nimbus "
    "desktop application. Answer concisely and accurately."
)
MAX_HISTORY = 20

@app.post("/api/chat")
async def chat(req: Request):
    body = await req.json()
    raw_messages = body.get("messages", [])

    history = raw_messages[-MAX_HISTORY:]
    messages = [{"role": "system", "content": SYSTEM_PROMPT}] + history

    async def event_stream():
        try:
            stream = await client.chat.completions.create(
                model="gpt-4o-mini",
                messages=messages,
                stream=True,
                temperature=0.7,
                max_tokens=1024,
            )
            async for chunk in stream:
                delta = chunk.choices[0].delta
                if delta.content:
                    yield f"data: {delta.content}\n\n"
            yield "data: [DONE]\n\n"
        except Exception as e:
            yield f"data: [ERROR] {str(e)}\n\n"

    return StreamingResponse(
        event_stream(),
        media_type="text/event-stream",
        headers={
            "Cache-Control": "no-cache",
            "Connection": "keep-alive",
            "X-Accel-Buffering": "no",
        },
    )

if __name__ == "__main__":
    import uvicorn
    uvicorn.run(app, host="0.0.0.0", port=8000)