I chose an OpenRouter (or Grok) model for my book, but some chapters were written by Gemini. Why, and how do I stop it?

Update to BookyAI 1.9.14 or later. Many models on OpenRouter and Grok think before they answer, and their thinking uses the same output budget as the chapter. In earlier versions such a model could use the whole budget thinking, return no text, and BookyAI treated that as a failed call and let the Gemini rotation write the chapter. Since 1.9.14 these models get extra room to think on top of the chapter budget, an answer that was all thinking is retried on the same model first, and slow models get more time (20 minutes for an answer; a streamed answer runs as long as the model keeps sending data). To make sure no other engine ever writes your book, go to Settings, "If my engine fails", and choose "Stay on my engine". Then use Regenerate on the chapters that show another model's name.