X is buzzing with a new Horizon Alpha model that is beating all previous models on various vibe tests (read: unicorns on bicycles and so on) singlehandedly. This model has 256k context window, which is a solid, albeit not the most impressive, number.

Most probably it is a new OpenAI model (GPT-5?), as they already did the same trick before. You can try it on openrouter.ai completely for free, but remember not to provide it with any private data, as it is collected and used for model improvement.