We are currently implementing a Redundant Setup using both the Facebook App SDKs (Android & iOS) and the Conversions API (CAPI). We need a definitive answer regarding the correct parameter name for deduplication on the mobile SDK side.

The Context: We want to ensure that events logged via the mobile SDK (e.g., Purchase) are correctly deduplicated against the same events sent via CAPI using the event_id field.

Our Questions:

For Android SDK: When passing a unique ID in the Bundle, should the key be "event_id" or "eventID"?

For iOS SDK: When logging events via AppEvents.shared.logEvent, what is the correct key string to use in the parameters dictionary? Is it "event_id" or "eventID"?

Documentation Inconsistency:

The Pixel/Web documentation consistently uses eventID.

The CAPI and App Event API references use event_id.

Neither the Android AppEventsConstants nor the iOS AppEvents.ParameterName provides a predefined constant for deduplication IDs.

We need to know which string key will be recognized by Meta's backend as the top-level deduplication key for mobile app events, rather than just a custom parameter.

Thank you for your assistance.