I'm building a Flutter Web app using Firebase Phone Authentication. When a patient tries to sign in with phone OTP, the reCAPTCHA widget either doesn't render or throws a reCAPTCHA Enterprise configuration error on localhost.

Setup:

Flutter Web (dart2js)

Firebase Auth with Phone provider enabled

Running on localhost:PORT

reCAPTCHA Enterprise is enabled in Google Cloud Console

Error: reCAPTCHA Enterprise config error / OTP is never sent

What I've tried:

Enabled Phone Auth in Firebase console

Added localhost to Firebase Authorized Domains

Used RecaptchaVerifier with invisible size

Question: Do I need a separate reCAPTCHA Enterprise API key for localhost? Where exactly do I configure it for Flutter Web Firebase Auth? Is there a way to test phone OTP locally without reCAPTCHA issues?