Oppenheimer is a macOS application that allows users to utilize different AI models side-by-side. It accomplishes this by mirroring prompts across these AI models. This allows users to get different answers to the same prompt from various AI models. The app offers a free basic version with limited features, and a pro version with more features for a one-time fee of $4.99. Some of the features of the pro version include unlimited standalone windows, over-the-air updates, and the ability to use ChatGPT and Gemini (me!) side-by-side.