1 files changed, 21 insertions, 1 deletions
diff --git a/src/features/ark.js b/src/features/ark.js
index 0a529c5..b8e83a7 100644
--- a/src/features/ark.js
+++ b/src/features/ark.js
@@ -995,6 +995,26 @@ export function arkFeature(ctx) {
   // connections/offer belong to the nwc feature; when it isn't the caller
   // (an auto-withdraw setting changed, say) carry forward what's mirrored
   // rather than blanking someone's wallet connections.
+  // The mirror carries hundreds of pre-derived keys (BG_KEY_LOOKAHEAD) and
+  // is rewritten after every state change: derive each index once per
+  // account, not once per write.
+  const bgKeyMemo = new WeakMap(); // account node -> Map('chain:i' -> hex)
+  function bgKeyFor(account) {
+    let m = bgKeyMemo.get(account);
+    if (!m) { m = new Map(); bgKeyMemo.set(account, m); }
+    const chains = new Map();
+    return (chain, i) => {
+      const k = chain + ':' + i;
+      let v = m.get(k);
+      if (!v) {
+        let node = chains.get(chain);
+        if (!node) { node = account.deriveChild(chain); chains.set(chain, node); }
+        v = hex.encode(node.deriveChild(i).privateKey);
+        m.set(k, v);
+      }
+      return v;
+    };
+  }
   async function writeBgMirror(connections, offer, prefs) {
     const cfg = getArkConfig();
     if (!cfg || !ark || !ark.info || !ark.state) return;
@@ -1006,7 +1026,7 @@ export function arkFeature(ctx) {
       ark: { arkUrl: cfg.ark, esploraUrl: cfg.esplora, network: getNetwork(), serverPubkey: ark.info.serverPubkey, honorsExpired: !!cfg.honorsExpired },
       mgrState: ark.state,
       custody: getCustody(),
-      keyFor: (chain, i) => hex.encode(ark.account.deriveChild(chain).deriveChild(i).privateKey),
+      keyFor: bgKeyFor(ark.account),
       connections,
       offer,
       autowithdraw: await awMirror(prev),