Right, do you have the browser opened on the page that Fulcro is running? Also, if you want, enable "Experimental Features" on the Chlorine configuration, it makes Shadow-CLJS experience better IMHO

I am running fulcro with npx shadow-cljs server . It’s only a shadow-cljs app at the moment. I have a client.cljs file with

(ns app.client
  (:require
   [com.fulcrologic.fulcro.application :as app]
   [com.fulcrologic.fulcro.components :as comp :refer [defsc]]
   [com.fulcrologic.fulcro.dom :as dom]))

(defonce app (app/fulcro-app))

(defsc Root [this props]
  (dom/div "TODO"))

(defn ^:export init
  "Shadow-cljs sets this up to be our entry-point function. See shadow-cljs.edn `:init-fn` in the modules of the main build."
  []
  (app/mount! app Root "app")
  (js/console.log "Loaded"))

I’ll activate the “Experimental Features”