Inside Secure Playground — building an interactive prompt-injection simulator

This technical post walks through the design and implementation of Secure Playground: a local web app that simulates prompt-injection attacks against large language models and demonstrates simple defenses. Goals Provide a minimal, reproducible environment to test payloads and defensive strategies. Make it easy to add new providers and run mutation-based red-team experiments. Offer a leaderboard and scoring model so defenders can iterate on mitigations. High-level architecture Key components secu