From 91c24b20f715a0d91095a9e87bd89b1832c4c0fe Mon Sep 17 00:00:00 2001
From: M1 <m1-pro@M1s-MacBook-Pro.local>
Date: Wed, 18 Mar 2026 23:18:49 +0400
Subject: [PATCH] fix: convert zpub to Ltub before LTC HD derivation

---
 apps/pay/package.json   |  9 +++++----
 apps/pay/src/address.ts | 12 +++++++++++-
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/apps/pay/package.json b/apps/pay/package.json
index c0e8a02..e4cde23 100644
--- a/apps/pay/package.json
+++ b/apps/pay/package.json
@@ -6,14 +6,15 @@
     "start": "bun run src/index.ts"
   },
   "dependencies": {
-    "@sinclair/typebox": "^0.34.0",
-    "elysia": "^1.4.27",
-    "postgres": "^3.4.8",
     "@dashevo/dashcore-lib": "^0.25.0",
+    "@sinclair/typebox": "^0.34.0",
     "bitcore-lib": "^10.10.7",
     "bitcore-lib-cash": "^10.10.5",
     "bitcore-lib-doge": "^10.9.0",
-    "bitcore-lib-ltc": "^10.10.5"
+    "bitcore-lib-ltc": "^10.10.5",
+    "bs58check": "^4.0.0",
+    "elysia": "^1.4.27",
+    "postgres": "^3.4.8"
   },
   "devDependencies": {
     "@types/bun": "^1.3.10",
diff --git a/apps/pay/src/address.ts b/apps/pay/src/address.ts
index 7e0af7c..7ba2bef 100644
--- a/apps/pay/src/address.ts
+++ b/apps/pay/src/address.ts
@@ -82,7 +82,17 @@ export function deriveAddressSafe(coin: string, index: number): string {
     return addr.replace(/^bitcoincash:/, "ecash:");
   }
   if (coin === "ltc") {
-    const hd = new bitcoreLtc.HDPublicKey(xpub);
+    // zpub uses BIP84 version bytes — convert to Ltub so bitcore-lib-ltc can parse it
+    let key = xpub;
+    if (xpub.startsWith("zpub") || xpub.startsWith("Zpub")) {
+      // Decode base58check, swap version bytes to Ltub (0x019da462), re-encode
+      const bs58check = await import("bs58check");
+      const decoded = bs58check.default.decode(xpub);
+      // Replace first 4 bytes with Ltub version: 0x019da462
+      decoded[0] = 0x01; decoded[1] = 0x9d; decoded[2] = 0xa4; decoded[3] = 0x62;
+      key = bs58check.default.encode(decoded);
+    }
+    const hd = new bitcoreLtc.HDPublicKey(key);
     return hd.deriveChild(0).deriveChild(index).publicKey.toAddress().toString();
   }
   if (coin === "doge") {