From 65bf651c2f99abae9f88affb207e84d76a55ba7a Mon Sep 17 00:00:00 2001
From: Sreeraj S <sreerajs@bitgo.com>
Date: Tue, 8 Sep 2026 18:44:00 +0000
Subject: [PATCH] fix(abstract-utxo): pass Zcash recovery block height

Add blockHeight to public recovery parameters and thread it into the Zcash PSBT builder.

Cover the NU6.2 branch ID at the activation height so non-BitGo ZEC recovery callers can
supply an independent current height instead of using the stale NU6.1 branch ID.

Ticket: SC-7552
Session-Id: f94964a3-36f2-408a-8e36-9d4dc606220b
Task-Id: 726038f1-9cab-4db1-9198-faec874137e8
---
 .../src/recovery/backupKeyRecovery.ts         |  6 ++++++
 .../test/unit/recovery/backupKeyRecovery.ts   | 20 +++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/modules/abstract-utxo/src/recovery/backupKeyRecovery.ts b/modules/abstract-utxo/src/recovery/backupKeyRecovery.ts
index 0e0e2dde7a..e3592b1176 100644
--- a/modules/abstract-utxo/src/recovery/backupKeyRecovery.ts
+++ b/modules/abstract-utxo/src/recovery/backupKeyRecovery.ts
@@ -100,6 +100,8 @@ export interface RecoverParams {
   recoveryProvider?: RecoveryProvider;
   /** Satoshi per byte */
   feeRate?: number;
+  /** Block height used to select the Zcash consensus branch ID. */
+  blockHeight?: number;
   /**
    * Transaction lock time (nLockTime). Set before signing — it is part of the sighash.
    * Used for ECX replay-protection sweeps (e.g. 499_999_999) and other custom lock-time needs.
@@ -270,6 +272,8 @@ export interface RecoverWithUnspentsParams {
   krsFee?: bigint;
   /** KRS fee address (required if krsFee > 0) */
   krsFeeAddress?: string;
+  /** Block height used to select the Zcash consensus branch ID. */
+  blockHeight?: number;
   /** Transaction lock time (nLockTime), set on the PSBT before signing */
   lockTime?: number;
   /** Input sequence number applied to every input */
@@ -313,6 +317,7 @@ export function backupKeyRecoveryWithWalletUnspents(
     recoveryDestination: recoveryDestination,
     keyRecoveryServiceFee: krsFee ?? BigInt(0),
     keyRecoveryServiceFeeAddress: krsFeeAddress,
+    blockHeight: params.blockHeight,
     lockTime: params.lockTime,
     sequence: params.sequence,
   });
@@ -565,6 +570,7 @@ export async function backupKeyRecovery(
       feeRateSatVB,
       krsFee,
       krsFeeAddress,
+      blockHeight: params.blockHeight,
       lockTime: params.lockTime,
       sequence: params.sequence,
     },
diff --git a/modules/abstract-utxo/test/unit/recovery/backupKeyRecovery.ts b/modules/abstract-utxo/test/unit/recovery/backupKeyRecovery.ts
index e1806bbcb7..c572bd3d46 100644
--- a/modules/abstract-utxo/test/unit/recovery/backupKeyRecovery.ts
+++ b/modules/abstract-utxo/test/unit/recovery/backupKeyRecovery.ts
@@ -176,6 +176,26 @@ function runWithScriptTypes(scriptTypes: ScriptType2Of3[]) {
 }
 
 describe('Backup Key Recovery PSBT', function () {
+  it('uses the supplied post-NU6.2 block height for Zcash', function () {
+    const { walletKeys: externalWallet } = createWasmWalletKeys('external');
+    const recoveryDestination = getWalletAddress('zec', externalWallet);
+    const unspent = toUnspent({ scriptType: 'p2sh', value: BigInt(1e8) }, 0, 'zec', wasmWalletKeys);
+
+    const psbt = backupKeyRecoveryWithWalletUnspents(
+      'zec',
+      {
+        walletKeys: wasmWalletKeys,
+        keys: [userPrivkey, backupPrivkey, wasmWalletKeys.bitgoKey()],
+        recoveryDestination,
+        feeRateSatVB: 1,
+        blockHeight: 3_364_600,
+      },
+      [unspent]
+    );
+
+    assert.strictEqual((psbt as fixedScriptWallet.ZcashBitGoPsbt).consensusBranchId, 0x5437f330);
+  });
+
   // compatible with all coins
   runWithScriptTypes(['p2sh']);