Yikes. What did I do? I updated reagent in my deps.edn from 1.2.0 to 1.3.0 and am now getting 1800 or so warnings from shadow-cljs (more than my terminal can display, so I only see the last few hundred or so), and browser console says "reagent.core is undefined." I tried to go back to 1.2.0 and same thing.
I figured it out. Somehow I said yes to VS Code (or maybe it's clj-kondo) offering to create a 'reagent.core' namespace in my src directory. Didn't notice it.
i hate when that happens