I changed the tone, the audience or the author voice of my book after some chapters were written. What happens to those chapters?

From version 1.9.19 every chapter remembers the settings it was written with. When you change the writing style, the tone, the target audience, the narration, the form of address, the intensity level, the author voice, the language, the title or the subtitle, a card appears on the book's page: "Changed since the chapters were written". It lists each change, which chapters still carry the old choice, and what else is touched (front and back matter written for the old settings, the description on the back cover, translated editions, narrated chapters). You then choose. "Restyle" rewrites those chapters in the new settings while their facts, structure, headings, length and your own edits stay, one AI call per chapter, with the old text kept in Versions. "Regenerate" writes them again from the outline. "Keep as written" leaves them as they are and applies the change only to what is written from now on. Chapters written before version 1.9.19 have no memory of their settings and are treated as current; the card starts working for a book after its next generation or restyle.