@User the above is in your backend code. On the frontend, the config should be:

supertokens.init({
  appInfo: {
    appName: "WorkoutApp",
    apiDomain: "https://blah.amazonaws.com",
    apiBasePath: "/dev/auth",
    websiteDomain: "http://localhost:3000",
    websiteBasePath: "/dev/auth"
  },
  recipeList: [EmailPassword.init(), Session.init()],
})

notice here that the

apiBasePath

is

/dev/auth

.