What is claude-mythos-ai-anthropic-app?

Claude Mythos AI App is an unofficial, third-party desktop program that gives you a custom interface for chatting with Anthropic's Claude AI models. You bring your own Anthropic API key, and the application connects to Claude directly from your computer. The project is not affiliated with Anthropic and is not an official product from that company. The app is styled with what the developers call a Mythos aesthetic, which is a dark, modern visual design. It supports conversations for creative writing, roleplay, coding assistance, and long-form reasoning tasks. It also includes multimodal support, meaning you can include images and documents along with text messages. A few features the README highlights: streaming responses so text appears as it arrives rather than all at once, the ability to write custom system prompts to shape how Claude responds, and local storage of your chat history on your own device. The app states that chat data is stored and encrypted locally rather than passing through a third-party server beyond the API call itself. Setup is described as simple: download the release archive, extract it, run the executable, paste your Anthropic API key, and start chatting. The README lists Windows, macOS, and Linux as supported platforms. Because this application calls the Anthropic API directly, any per-message costs are billed to the API key you provide. The repository includes a disclaimer that users are responsible for their own API usage and any resulting charges. It is an open-source project and the authors invite contributions to the design and feature set.