OpenRouter just announced a new stealth model, called Horizon Alpha: https://openrouter.ai/openrouter/horizon-alpha

In the past, Quasar Alpha & Optimus Alpha were eventually officially revealed to be versions of GPT-4.1. (Within <2 weeks of initially being available)

Resolves YES if an official OpenRouter or OpenAI account confirms that Horizon Alpha is in fact GPT-5. This would resolve YES for any versions of GPT-5, eg: 5.0, 5.1, 5-nano, 5-experimental. This would resolve NO for any non-5 OpenAI models, eg: o4, GPT-4.7, etc.

Resolves NO if Horizon Alpha is confirmed to not be GPT-5.

Resolves NO if the model is not confirmed either way within 2 months (at the end of September).