feat(hd): HD message signing support in SDK

packages/komodo_defi_rpc_methods/lib/src/rpc_methods/utility/message_signing.dart

@@ -9,6 +9,10 @@ class SignMessageRequest
     required String rpcPass,
     required this.coin,
     required this.message,
+    this.derivationPath,
+    this.accountId,
+    this.chain,
+    this.addressId,
   }) : super(method: 'sign_message', rpcPass: rpcPass, mmrpc: RpcVersion.v2_0);
 
   /// The coin to sign a message with
@@ -17,11 +21,42 @@ class SignMessageRequest
   /// The message you want to sign
   final String message;
 
+  /// Optional HD address selector: full derivation path
+  /// Example: m/84'/2'/0'/0/1
+  final String? derivationPath;
+
+  /// Optional HD address selector components
+  /// When provided together with [chain], [addressId] they form the BIP44 path
+  /// m/44'/COIN_ID'/accountId'/chain/addressId
+  final int? accountId;
+
+  /// Optional HD address selector chain. Must be "Internal" or "External" if provided.
+  final String? chain;
+
+  /// Optional HD address selector: address index within the chain
+  final int? addressId;
+
   @override
   Map<String, dynamic> toJson() {
-    return super.toJson().deepMerge({
-      'params': {'coin': coin, 'message': message},
-    });
+    final params = <String, dynamic>{
+      'coin': coin,
+      'message': message,
+    };
+
+    // HD address selection (preferred nested under 'address')
+    final address = <String, dynamic>{};
+    if (derivationPath != null && derivationPath!.isNotEmpty) {
+      address['derivation_path'] = derivationPath;
+    } else if (accountId != null && chain != null && addressId != null) {
+      address['account_id'] = accountId;
+      address['chain'] = chain;
+      address['address_id'] = addressId;
+    }
+    if (address.isNotEmpty) {
+      params['address'] = address;
+    }
+
+    return super.toJson().deepMerge({'params': params});
   }
 
   @override

packages/komodo_defi_rpc_methods/lib/src/rpc_methods/utility/message_signing_rpc_namespace.dart

@@ -9,9 +9,21 @@ class MessageSigningMethodsNamespace extends BaseRpcMethodNamespace {
   Future<SignMessageResponse> signMessage({
     required String coin,
     required String message,
+    String? derivationPath,
+    int? accountId,
+    String? chain,
+    int? addressId,
   }) {
     return execute(
-      SignMessageRequest(rpcPass: rpcPass ?? '', coin: coin, message: message),
+      SignMessageRequest(
+        rpcPass: rpcPass ?? '',
+        coin: coin,
+        message: message,
+        derivationPath: derivationPath,
+        accountId: accountId,
+        chain: chain,
+        addressId: addressId,
+      ),
     );
   }
 

packages/komodo_defi_rpc_methods/lib/src/rpc_methods_library.dart

@@ -172,9 +172,21 @@ class UtilityMethods extends BaseRpcMethodNamespace {
   Future<SignMessageResponse> signMessage({
     required String coin,
     required String message,
+    String? derivationPath,
+    int? accountId,
+    String? chain,
+    int? addressId,
     String? rpcPass,
   }) => execute(
-    SignMessageRequest(coin: coin, message: message, rpcPass: rpcPass ?? ''),
+    SignMessageRequest(
+      coin: coin,
+      message: message,
+      rpcPass: rpcPass ?? '',
+      derivationPath: derivationPath,
+      accountId: accountId,
+      chain: chain,
+      addressId: addressId,
+    ),
   );
 
   /// Verifies a message signature

packages/komodo_defi_sdk/example/lib/widgets/asset/asset_header_widget.dart

@@ -185,6 +185,7 @@ class _AssetHeaderWidgetState extends State<AssetHeaderWidget> {
             coin: widget.asset.id.id,
             message: message,
             address: widget.pubkeys!.keys.first.address,
+            derivationPath: widget.pubkeys!.keys.first.derivationPath,
           );
       setState(() => _signedMessage = signature);
     } catch (e) {

packages/komodo_defi_sdk/lib/src/message_signing/message_signing_manager.dart

@@ -17,9 +17,9 @@ class MessageSigningManager {
   /// This method creates a cryptographic signature that can be used to prove
   /// ownership of an address.
   ///
-  /// The `address` parameter is not used in the signing process and will be
-  /// ignored. This is in preparation for the near future when KDF will add HD
-  /// wallet support.
+  /// For HD wallets, you can optionally pass a specific derivation to sign
+  /// from using either a full `derivationPath` (preferred) or the
+  /// `accountId`/`chain`/`addressId` components.
   ///
   /// Parameters:
   /// - [coin]: The ticker of the coin to use for signing (e.g., "BTC").
@@ -39,10 +39,18 @@ class MessageSigningManager {
     required String coin,
     required String message,
     required String address,
+    String? derivationPath,
+    int? accountId,
+    String? chain,
+    int? addressId,
   }) async {
     final response = await _client.rpc.utility.signMessage(
       coin: coin,
       message: message,
+      derivationPath: derivationPath,
+      accountId: accountId,
+      chain: chain,
+      addressId: addressId,
     );
     return response.signature;
   }