I just spent some time going through your book. It’s good and I thank you for writing it, but I had to mention a quibble I had with this post’s title.

The term run-on sentence refers specifically to sentences in which two independent clauses are joined together without an appropriate conjunction or punctuation mark (there’s usually a comma splice). It’s not a synonym for “long sentence”. The example you give is not a run-on sentence, as it has a one independent and one dependent clause:

Independent clause

“On December 6th, 2023, Google announced Gemini, a new Large Multimodal Model (LMM)”

Dependent clause

“that is able to interact with and answer questions about data presented in text, images, video, and audio.”

An example of a run-on sentence would be if we joined the next sentence in the original post with the sentence that follows using a comma.

On December 6th, 2023, Google announced Gemini, a new Large Multimodal Model (LMM) that is able to interact with and answer questions about data presented in text, images, video, and audio, Gemini’s text capabilities were introduced into Bard on the same day.

This is a terminology nitpick, but I’d also like to take an opportunity to defend long sentences! Writing a long sentence that is easy to follow requires a bit of care – and I’m certainly guilty of constructing some careless ones – but it can be done! Not every long sentence is a run-on per se, nor will it necessarily confuse the reader. I highly recommend the thorough investigation of this subject in Chapter 4 of Steven Pinker’s The Sense of Style.