Can we register for FID and token both in firebase cloud messaging?

[livefielddev]

FID becomes unregistered after requesting a registration token

Description

I'm migrating my Firebase Cloud Messaging implementation from a registration token based approach to the newer Firebase Installation ID (FID) based approach.

For device-specific messaging, sending notifications to the FID works as expected.

However, my application also uses FCM Topics. Currently, topic subscription APIs require a registration token, as there doesn't appear to be a way to subscribe an FID directly to a topic.

Steps

1. Create a Firebase Installation and obtain its FID.
2. Send device-specific messages using the FID (works correctly).
3. Call getToken() to obtain an FCM registration token so the device can subscribe to topics.
4. Attempt to send another device-specific message to the original FID.

Expected behavior

Requesting an FCM registration token for topic subscriptions should not invalidate or unregister the existing FID. The same installation should continue to receive device-specific messages while also being able to use topic subscriptions.

Actual behavior

After calling getToken(), sending a message to the previously working FID returns a NotRegistered error. Messages to the registration token continue to work.

Question

Is this expected behavior?

If so, what is the recommended approach for applications that need both:

• Device-specific messaging using FIDs.
• Topic subscriptions, which currently require registration tokens.

Is there a supported migration path for applications that want to adopt FID-based messaging while continuing to use FCM Topics?