Lexicon is a rich text editor that combines grammar checking with AI-powered writing tools such as rewriting, tone adjustment, and summarization. All features run entirely on your local machine, ensuring complete privacy without requiring accounts, API calls, or data uploads. Grammar, spelling, and punctuation checking are powered locally by LanguageTool, while the AI features use a lightweight quantized model bundled with the application through llama.cpp, or can connect to your existing Ollama server. Available for Windows and macOS, Lexicon is an installable desktop application with built-in automatic updates.