Vellium is a free, open-source desktop AI workspace for character chat, multi-character roleplay, long-form writing, RAG, LoreBooks, MCP tools and plugins. Bring your own backend—OpenAI-compatible APIs, OpenRouter, LM Studio, Ollama or KoboldCpp—while chats, characters, projects and knowledge stay in a local SQLite database. Native builds are available for macOS, Windows and Linux.