How Health data is merged

If you wear an Oura Ring and don’t write Oura into Apple Health, a Health-only app thinks you have no HRV. Hammr merges both APIs per metric so Recovery and Readiness still compute.

Merge steps

1. Fetch Apple Health summary for the date.
2. Fetch Oura summary for the date.
3. For each metric (HRV, RHR, sleep, steps, and so on), pick a value:
   • apple_oura — Apple first, Oura fills gaps
   • oura_apple — Oura first, Apple fills gaps
   • apple_only
   • oura_only
4. Attach which source supplied each field.
5. Recovery, Readiness, and Mental Stress consume the merged snapshot.

Configure this in Settings → Connected Devices → Primary wearable / merge priority.

What you should notice

• Oura-only users get full recovery/readiness.
• Dual-device users get best-of-both without counting the same night twice.
• Advanced audit surfaces can show the source per metric.

Widgets and Watch update after sync (including silent push after Oura). You should not need to open the app for rings to move.

Nutrition from other apps is a separate system: Apple Health nutrition sync.