Tubeless plug tool and a method to re-inflate.
To me it also depends on how far away I am /how easy it is to get back. Short local rides, I carry only the plug tool (and a pump and multitool). Longer ones, often carry one tube too, and for touring or places far away from the next train station, I’d take two tubes and patches too. Two tubes, because there are two wheels, and if it’s bad enough to need a tube, you are stuffed if you need one for the other wheel too. Patches if those tubes then need fixing!