Unknown error on login after verifying account in Firebase Auth Emulator

[abazena]

Description: After deploying Marble and the Firebase Auth Emulator, creating a new user, and verifying the account via the verification link, attempting to log in via the frontend shows an “unknown error” message. All backend API requests return status 200 Success, but the frontend cannot complete login.

Steps to Reproduce:

Deploy Marble with Docker Compose using the Firebase Auth Emulator.

Create a new account via the frontend (or directly via emulator accounts.json).

Verify the account using the verification link provided by the emulator logs.

Attempt to log in via the frontend.

Expected Behavior: The login should succeed and return a valid session/token.

Actual Behavior: Frontend shows an “unknown error” message. Backend API calls all return 200.

Environment:

Docker image: europe-west1-docker.pkg.dev/marble-infra/marble/firebase-emulator:latest

Backend environment variables:

FIREBASE_AUTH_EMULATOR_HOST: firebase-auth:9099 GOOGLE_CLOUD_PROJECT: dummy-project FIREBASE_API_KEY: dummy-key

Notes / Logs:

Emulator logs show email verification link successfully generated:

To verify the email address [email protected], follow this link: ...

Frontend network tab shows 200 responses for all auth requests.

Frontend shows "unknown error".

No UI is being used (FIREBASE_EMULATOR_UI_ENABLED: false).