Gandalf: Agent Breaker is a hacking simulator game developed by Lakera that challenges players to exploit real-world vulnerabilities in agentic AI applications, highlighting the security risks associated with GenAI systems. This interactive game allows users to engage with realistic scenarios, such as prompt attacks, memory tampering, and tool abuse, to understand how these systems can be broken and why traditional security measures may be inadequate. By navigating through multiple levels of increasing difficulty, players gain hands-on experience in identifying and mitigating these vulnerabilities, learning to think like a hacker and develop effective defenses. Gandalf: Agent Breaker is designed for a diverse audience, including security professionals, AI engineers, and gamers, and offers a global leaderboard for users to showcase their skills and strategies in securing GenAI applications.