gh-jezweb-claude-skills-skills-thesys-generative-ui/templates/python-backend

Python Backend Templates for TheSys Generative UI

This directory contains production-ready Python backend templates for integrating TheSys C1 Generative UI API.

Available Templates

1. FastAPI Backend (fastapi-chat.py)

Modern async web framework with automatic API documentation.

Features:

• Async streaming support
• Built-in request validation with Pydantic
• Automatic OpenAPI docs
• CORS middleware configured
• Type hints throughout

Run:

# Install dependencies
pip install -r requirements.txt

# Set environment variable
export THESYS_API_KEY=sk-th-your-key-here

# Run server
python fastapi-chat.py

# Or with uvicorn directly
uvicorn fastapi-chat:app --reload --port 8000

API Docs: Visit http://localhost:8000/docs for interactive API documentation

---

2. Flask Backend (flask-chat.py)

Lightweight and flexible web framework.

Features:

• Simple and familiar Flask API
• CORS support with flask-cors
• Streaming response handling
• Easy to customize and extend

Run:

# Install dependencies
pip install -r requirements.txt

# Set environment variable
export THESYS_API_KEY=sk-th-your-key-here

# Run server
python flask-chat.py

# Or with flask CLI
export FLASK_APP=flask-chat.py
flask run --port 5000

---

Setup

1. Install Dependencies

# Create virtual environment
python -m venv venv
source venv/bin/activate  # On Windows: venv\Scripts\activate

# Install all dependencies
pip install -r requirements.txt

# OR install only what you need
pip install thesys-genui-sdk openai python-dotenv

# For FastAPI
pip install fastapi uvicorn

# For Flask
pip install flask flask-cors

2. Environment Variables

Create a .env file:

THESYS_API_KEY=sk-th-your-api-key-here

Get your API key from: https://console.thesys.dev/keys

3. Choose Your Model

Both templates use different models by default to show variety:

FastAPI: Uses Claude Sonnet 4

model="c1/anthropic/claude-sonnet-4/v-20250930"

Flask: Uses GPT 5

model="c1/openai/gpt-5/v-20250930"

Change to any supported model:

• c1/anthropic/claude-sonnet-4/v-20250930 - Claude Sonnet 4 (stable)
• c1/openai/gpt-5/v-20250930 - GPT 5 (stable)
• c1-exp/openai/gpt-4.1/v-20250617 - GPT 4.1 (experimental)
• c1-exp/anthropic/claude-3.5-haiku/v-20250709 - Claude 3.5 Haiku (experimental)

---

Frontend Integration

React + Vite Example

const makeApiCall = async (prompt: string) => {
  const response = await fetch("http://localhost:8000/api/chat", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ prompt })
  });

  const reader = response.body?.getReader();
  const decoder = new TextDecoder();

  while (true) {
    const { done, value } = await reader.read();
    if (done) break;

    const chunk = decoder.decode(value);
    setC1Response(prev => prev + chunk);
  }
};

Next.js API Route (Proxy)

// app/api/chat/route.ts
export async function POST(req: Request) {
  const { prompt } = await req.json();

  const response = await fetch("http://localhost:8000/api/chat", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ prompt })
  });

  return new Response(response.body, {
    headers: {
      "Content-Type": "text/event-stream",
      "Cache-Control": "no-cache"
    }
  });
}

---

Production Deployment

Environment Variables

# Production
THESYS_API_KEY=sk-th-production-key
HOST=0.0.0.0
PORT=8000
ENVIRONMENT=production
ALLOWED_ORIGINS=https://your-frontend.com

FastAPI (Recommended for Production)

# Install production server
pip install gunicorn

# Run with Gunicorn
gunicorn fastapi-chat:app \
  --workers 4 \
  --worker-class uvicorn.workers.UvicornWorker \
  --bind 0.0.0.0:8000 \
  --timeout 120

Flask Production

# Install production server
pip install gunicorn

# Run with Gunicorn
gunicorn flask-chat:app \
  --workers 4 \
  --bind 0.0.0.0:5000 \
  --timeout 120

Docker Example

FROM python:3.12-slim

WORKDIR /app

COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

COPY fastapi-chat.py .

ENV THESYS_API_KEY=""
ENV PORT=8000

CMD ["uvicorn", "fastapi-chat:app", "--host", "0.0.0.0", "--port", "8000"]

---

Troubleshooting

Common Issues

1. Import Error: thesys_genui_sdk not found

pip install thesys-genui-sdk

2. CORS Errors Update CORS configuration in the template to match your frontend URL:

allow_origins=["http://localhost:5173"]  # Vite default

3. Streaming Not Working Ensure:

• stream=True in the API call
• Using @with_c1_response decorator
• Proper response headers set

4. Authentication Failed (401) Check that THESYS_API_KEY is set correctly:

import os
print(os.getenv("THESYS_API_KEY"))  # Should not be None

---

Next Steps

1. Copy the template you want to use
2. Install dependencies from requirements.txt
3. Set your THESYS_API_KEY in .env
4. Run the server
5. Connect your React frontend
6. Customize the system prompt and model as needed

For more examples, see the main SKILL.md documentation.