Not a dev-rig issue, but rather something to do with the extensions-hello-world backend.js part. I replaced the Hapi, CORS-enabled (apparently) server with an express, CORS-enabled server, and it worked. I could have configured my nginx location block to do the same but that would have been a hack, a workaround, since the original (Hapi) solution doesn’t work as presented (CORS-enabled).