Why does Apple Health backfill return empty arrays?

Apple Health data lives on the device, so historical data cannot be backfilled through the web/REST API.

Apple Health data lives on the device, so historical data cannot be backfilled through the web/REST API. The web API only returns data the mobile SDK has already retrieved and sent through.

To backfill:

1

Initialise the mobile SDK in your app.

2

Call its data functions on-device (getActivity, getDaily, getSleep) with toWebhook=true.

Long ranges (even years) can be requested in a single call because the data is chunked automatically (no paging needed). Unsolicited payloads on connection are the SDK's background delivery feature.

The Terra companion app does not support remote backfills via /sdk/backfills in its current version, but the end user can trigger a backfill of up to two weeks from within the app. There is no direct flag marking SDK-backfill payloads, but each backfill is split into 7-day chunks that share one common payload reference, which you can use as the backfill signal. See the mobile-only sources docs for SDK setup.