How I Built a Client-Side Shield for AI Chatbots (Open Source)

I was burning through API tokens on off-topic chatbot queries.

Every "Who are you?" = brand leak + wasted money.

So I built Shield by Vouch — a zero-cost, client-side filter that blocks prompt injections and off-topic queries before they hit your LLM.

You build an AI chatbot for your business. Users ask:

Every off-topic query = $0.002 gone. 1000 queries = $2 burned.

const shield = new VouchShield({
  businessType: 'restaurant',
  businessDesc: 'Italian food in Mumbai'
});

const result = shield.check("Who are you?");
// { blocked: true, response: "I can only help with our restaurant services..." }

Results

80% off-topic queries blocked client-side

Zero identity leaks

$2 saved per 1000 blocked queries

Try It

🚀 Live Demo

⭐ GitHub

MIT License. No signup. Single file drop-in.