diff --git a/docs/index.md b/docs/index.md
index 6a2736b..1a6fe31 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -26,6 +26,13 @@ Welcome to BincioActivity — a federated, self-hosted activity stats platform.
 
 **[CLI Reference](reference/cli.md)** — All bincio commands and options.
 
+## Mobile App
+
+The mobile app (Expo/React Native) source code is now in the separate `bincio_autarchive` repository. See:
+
+- **[Mobile App Design](mobile-app.md)** — Architecture, Pyodide extraction, Karoo integration, sync protocol (reference documentation)
+- **`bincio_autarchive/DEVELOPMENT.md`** — Build & development instructions
+
 ## Quick Links
 
 - [GitHub repo](https://github.com/brutsalvadi/bincio-activity)
diff --git a/docs/mobile-app.md b/docs/mobile-app.md
index c42d27f..941f5ce 100644
--- a/docs/mobile-app.md
+++ b/docs/mobile-app.md
@@ -1,5 +1,7 @@
 # Bincio Mobile App — Design Document
 
+> **Note:** The mobile app source code is now in the separate `bincio_autarchive` repository. This document remains here as the authoritative design reference. For build & development instructions, see the `bincio_autarchive/DEVELOPMENT.md` file.
+
 ## Vision
 
 The long-term goal is full independence from Garmin Connect, Strava, Hammerhead,