MatrAIx is an evaluation platform that uses 8.3 billion AI-powered persona agents to test how AI systems and digital products perform with diverse user types. The system includes a dataset of 1 million personas (half human-grounded, half synthetic), four interactive environments (survey, chatbot, web, app), and over 1,000 tasks across 25 domains. Testing showed the personas accurately express behavioral attributes 91.5% of the time, capturing real variation in user preferences like price sensitivity and failure tolerance.