[KevinH]

Or just run it through a spellchecker to find previously hyphenated words with a space in between and fix them.

And to muddy the waters, make sure you are the author or copyright owner of the ebook before you submit its contents to a network based (non-private) AI like Google's Gemini as otherwise you are technically violating its copyright and you could be charged for it in some countries.

To make that clearer, many newly created epubs now explicitly include a statement that submitting a work in whole or part to any AI violates copyright, right in the text of the epub. Portions of that epub's text will be added to that AI's body of knowledge and with the right prompts, can be extracted. Effectively you have allowed a digital copy to be made that can be discovered by anyone.

If you feel you must use an AI, then look for a local AI engine that does not phone home with your (or the author's) valuable intellectual property.

And fyi, your prompt should have specified xhtml not html. They do differ. Hopefully you made a checkpoint before you submitted it and compared your result to that earlier checkpoint to make sure nothing was inadvertently added or removed.