ChatPlayground AI, a platform that lets users run multiple AI models side by side and compare their responses to the same prompt in one window, is on sale for a lifetime subscription. According to PCMag, the tool supports more than 25 models, including ChatGPT, Gemini, Claude, DeepSeek, Llama, and Perplexity, and sends any prompt to several models at once, lining up the responses so users can see how they differ. It also offers prompt engineering tools to refine and reuse prompts, allows uploading images and PDFs for questioning, and keeps saved chat history. The Unlimited Plan is a lifetime subscription with unlimited messages each month, aimed at prompt engineers, startups, and teams that test or use AI heavily. It works on any desktop running a recent version of Chrome, Edge, or Firefox, with no set limit on how many devices users sign in from. Until September 20, the ChatPlayground AI lifetime subscription is on sale for $54.97, reduced from an MSRP of $619, a savings of $564.03, at StackSocial.