SillyTavern is a full-stack web application (Node.js/Express backend, jQuery/Webpack frontend) that serves as a highly customizable frontend for interacting with large language models (LLMs) for roleplaying and chat. It supports dozens of AI backends (OpenAI, Anthropic, Kobold, Ollama, vLLM, etc.) via streaming text and chat completions, and provides an extensive plugin/extension system for TTS, translation, image generation, vector search, and more. The application features a sophisticated macro engine (Chevrotain-based CST parser) for dynamic prompt templating, a slash command framework with typed arguments and autocomplete, and a rich UI with themes, backgrounds, character management, and branching chat history. It is designed for power users who want fine-grained control over prompts, model parameters, and UI behavior, and includes multi-user support with authentication, secrets management, and per-user data isolation.