Based on Noah Smith's writing at https://noahpinion.substack.com/p/why-i-think-an-invasion-of-taiwan?utm_source=post-email-title&publication_id=35345&post_id=80290500&isFreemail=false&utm_medium=email.
Closes YES if China invades Taiwan and does not preemptively attack U.S. bases, and the U.S. intervenes. Closes NO if that happens and the U.S does not intervene. Closes N/A if China invades Taiwan and preemptively attacks U.S. bases, or if China does not invade Taiwan before the market closes.
"Intervene militarily" is pretty subjective. A formal declaration of war counts, providing substantial material support like in Ukraine does not. I'll tentatively say that the dividing line is "at least 100 Chinese soldiers being killed by U.S. soldiers," but ultimately this will resolve based on my judgement. As such, I will not be betting in this market.