only check address validation once for old addresses

cw_bitcoin/lib/bitcoin_address_record.dart

@@ -67,6 +67,7 @@ class BitcoinAddressRecord extends BaseBitcoinAddressRecord {
     required super.index,
     super.accountIndex = 0,
     super.isHidden = false,
+    this.isHiddenChecked = false,
     super.isLegacyDerivation = false,
     super.txCount = 0,
     super.balance = 0,
@@ -110,6 +111,7 @@ class BitcoinAddressRecord extends BaseBitcoinAddressRecord {
       index: decoded['index'] as int,
       accountIndex: decoded['accountIndex'] as int? ?? 0,
       isHidden: decoded['isHidden'] as bool? ?? false,
+      isHiddenChecked: decoded['isHiddenChecked'] as bool? ?? false,
       isLegacyDerivation: parsedIsLegacy,
       isUsed: decoded['isUsed'] as bool? ?? false,
       txCount: decoded['txCount'] as int? ?? 0,
@@ -121,6 +123,10 @@ class BitcoinAddressRecord extends BaseBitcoinAddressRecord {
     );
   }
 
+  /// Whether [isHidden] has been checked against the wallet's keys. Records created from the
+  /// wallet's own keys are correct by construction; older ones are checked once on wallet open.
+  bool isHiddenChecked;
+
   String? scriptHash;
 
   static int _purposeForType(BitcoinAddressType type) {
@@ -179,6 +185,7 @@ class BitcoinAddressRecord extends BaseBitcoinAddressRecord {
         'index': index,
         'accountIndex': accountIndex,
         'isHidden': isHidden,
+        'isHiddenChecked': isHiddenChecked,
         'isLegacyDerivation': isLegacyDerivation,
         'isUsed': isUsed,
         'txCount': txCount,

cw_bitcoin/lib/electrum_wallet_addresses.dart

@@ -571,6 +571,7 @@ abstract class ElectrumWalletAddressesBase extends WalletAddresses with Store {
       index: newAddressIndex,
       accountIndex: accountIndex,
       isHidden: false,
+      isHiddenChecked: true,
       isLegacyDerivation: false,
       name: label,
       type: addressPageType,
@@ -957,6 +958,7 @@ abstract class ElectrumWalletAddressesBase extends WalletAddresses with Store {
           await getAddressAsync(index: i, hd: hd, addressType: addrType),
           index: i,
           isHidden: isHidden,
+          isHiddenChecked: true,
           isLegacyDerivation: isLegacyDerivation,
           type: addrType,
           network: network,
@@ -1023,37 +1025,31 @@ abstract class ElectrumWalletAddressesBase extends WalletAddresses with Store {
   }
 
   Future<void> _validateAddress(BitcoinAddressRecord element) async {
+    if (element.isHiddenChecked) return;
+
     if (element.type == SegwitAddresType.mweb) {
       // this would add a ton of startup lag for mweb addresses since we have 1000 of them
       return;
     }
 
-      try {
-        final mainHd = _hdForAddressGeneration(
-            isHidden: false,
-            type: element.type,
-            isLegacyDerivation: element.isLegacyDerivation,
-            accountIndex: element.accountIndex);
-        final sideHd = _hdForAddressGeneration(
-            isHidden: true,
-            type: element.type,
-            isLegacyDerivation: element.isLegacyDerivation,
-            accountIndex: element.accountIndex);
-        if (!element.isHidden &&
-            element.address !=
-                await getAddressAsync(
-                    index: element.index, hd: mainHd, addressType: element.type)) {
-          element.isHidden = true;
-        } else if (element.isHidden &&
-            element.address !=
-                await getAddressAsync(
-                    index: element.index, hd: sideHd, addressType: element.type)) {
-          element.isHidden = false;
-        }
-      } on UnsupportedAddressTypeForAccountException catch (e) {
-        printV("_validateAddresses: skipping ${element.address}: $e");
+    try {
+      // Relabel only when the address re-derives from the other chain. A record from a path these
+      // keys don't produce matches neither chain, so it keeps its label instead of flipping.
+      final otherChainHd = _hdForAddressGeneration(
+        isHidden: !element.isHidden,
+        type: element.type,
+        isLegacyDerivation: element.isLegacyDerivation,
+        accountIndex: element.accountIndex,
+      );
+      final otherChainAddress =
+          await getAddressAsync(index: element.index, hd: otherChainHd, addressType: element.type);
+      if (element.address == otherChainAddress) {
+        element.isHidden = !element.isHidden;
       }
-    });
+      element.isHiddenChecked = true;
+    } on UnsupportedAddressTypeForAccountException catch (e) {
+      printV("_validateAddresses: skipping ${element.address}: $e");
+    }
   }
 
   @override

cw_bitcoin_cash/lib/src/bitcoin_cash_wallet.dart

@@ -150,6 +150,7 @@ abstract class BitcoinCashWalletBase extends ElectrumWallet with Store {
             addr.address,
             index: addr.index,
             isHidden: addr.isHidden,
+            isHiddenChecked: addr.isHiddenChecked,
             name: addr.name,
             type: P2pkhAddressType.p2pkh,
             network: BitcoinCashNetwork.mainnet,
@@ -159,6 +160,7 @@ abstract class BitcoinCashWalletBase extends ElectrumWallet with Store {
             AddressUtils.getCashAddrFormat(addr.address),
             index: addr.index,
             isHidden: addr.isHidden,
+            isHiddenChecked: addr.isHiddenChecked,
             name: addr.name,
             type: P2pkhAddressType.p2pkh,
             network: BitcoinCashNetwork.mainnet,