diff --git a/src/generate-mobile-index.mjs b/src/generate-mobile-index.mjs
new file mode 100644
index 0000000..e9269a3
--- /dev/null
+++ b/src/generate-mobile-index.mjs
@@ -0,0 +1,52 @@
+// Bundle a starter BNS index for the Ariadne mobile app.
+//
+// The mobile Bns.java stores its disk cache as a JSON array of {name, category,
+// records, txid, height, updatedTxid} — the shape saveDisk() writes and
+// loadDisk() reads. When the on-device cache is empty (fresh install), the app
+// falls back to a bundled copy in APK assets so the first .bch page opens
+// without waiting on a full electrum walk.
+//
+// This script builds that bundle from the raw name-beacon snapshot on disk
+// (produced by src/snapshot-name-to-file.mjs). Runs the SAME reduction
+// (buildIndexFromSnapshot) so the bundled index is byte-for-byte what a live
+// buildIndex would produce from the same chain state.
+//
+//   node src/generate-mobile-index.mjs [outfile]
+//
+// Default outfile: AriadneResolver/mobile/app/assets/bns-index.json — the
+// path build.ps1 packages via aapt2's `-A` flag.
+
+import { readFileSync, writeFileSync, mkdirSync } from "node:fs";
+import { fileURLToPath } from "node:url";
+import path from "node:path";
+
+import { buildIndexFromSnapshot } from "./lib/resolver-web.js";
+
+const IN = fileURLToPath(new URL("../../TheseusNavigator/snapshots/bns-name-snapshot.json", import.meta.url));
+const OUT = process.argv[2] || fileURLToPath(
+  new URL("../../AriadneResolver/mobile/app/assets/bns-index.json", import.meta.url),
+);
+
+const snap = JSON.parse(readFileSync(IN, "utf8"));
+console.log(`snapshot: ${snap.history.length} beacon txs, root=${snap.root}`);
+
+const idx = buildIndexFromSnapshot({ snapshot: snap });
+// Serialise in mobile Bns.saveDisk() shape. `records` stays as a JSON object
+// (Bns.Entry stores it as JSONObject and re-serialises identically on save).
+// `updatedTxid` is null-safe: mobile writes JSONObject.NULL for null; JSON.stringify
+// emits `null` which is the same thing over the wire.
+const out = [];
+for (const entry of idx.values()) {
+  out.push({
+    name: entry.name,
+    category: entry.category,
+    records: entry.records ?? {},
+    txid: entry.txid,
+    height: entry.height,
+    updatedTxid: entry.updatedTxid ?? null,
+  });
+}
+
+mkdirSync(path.dirname(OUT), { recursive: true });
+writeFileSync(OUT, JSON.stringify(out));
+console.log(`wrote ${idx.size} names to ${OUT}`);