Sync wallet state across devices via encrypted Nostr events

Persist wallet state (addresses, utxos, history, indices, fees) as a NIP-44
encrypted, parameterized-replaceable event (kind 30078) addressed to self on
relay.coinos.io. The Nostr identity is derived from the same seed (NIP-06), so
no extra secret. On load we pull the latest state from Nostr — a device with
no local cache gets full state without re-scanning, and another device's
updates propagate — using savedAt to keep the newest copy. localStorage stays
as the instant/offline cache; state is published (debounced) on every change.

(Relay note: added kind 30078 to the strfry write-policy allowlist on prod.)

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

1 files changed, 6 insertions, 3 deletions

diff --git a/src/app.js b/src/app.js
index c64c650..e59b1bd 100644
--- a/src/app.js
+++ b/src/app.js
@@ -391,9 +391,12 @@ async function enterWallet(mnemonic, passphrase) {
     return;
   }
   try {
-    // With a cache, only check the live frontier (cheap) instead of a full
-    // re-scan; a full scan still runs for a brand-new wallet and periodically.
-    if (hadCache) await wallet.refreshLive();
+    // Cross-device state: pull the latest from Nostr (may supply state on a
+    // device with no local cache, or a newer copy from another device).
+    const hadNostr = await wallet.syncFromNostr();
+    // With existing state (local or remote), only check the live frontier;
+    // a brand-new wallet does one full scan.
+    if (hadCache || hadNostr) await wallet.refreshLive();
     else await wallet.scan();
     wallet.startRealtime();
   } catch {