diff --git a/lib/src/algorithm/ssh_kex_type.dart b/lib/src/algorithm/ssh_kex_type.dart
index 2866319..420a749 100644
--- a/lib/src/algorithm/ssh_kex_type.dart
+++ b/lib/src/algorithm/ssh_kex_type.dart
@@ -7,6 +7,15 @@ class SSHKexType extends SSHAlgorithm {
     digestFactory: digestSha256,
   );
 
+  /// RFC 8731 name for the same algorithm as [x25519]. Servers hardened to a
+  /// single kex commonly offer only this spelling, and OpenSSH matches names
+  /// literally — without it the handshake dies with "no matching key exchange
+  /// method found".
+  static const x25519Rfc = SSHKexType._(
+    name: 'curve25519-sha256',
+    digestFactory: digestSha256,
+  );
+
   static const nistp256 = SSHKexType._(
     name: 'ecdh-sha2-nistp256',
     digestFactory: digestSha256,
diff --git a/lib/src/ssh_algorithm.dart b/lib/src/ssh_algorithm.dart
index fc57995..1107647 100644
--- a/lib/src/ssh_algorithm.dart
+++ b/lib/src/ssh_algorithm.dart
@@ -46,6 +46,7 @@ class SSHAlgorithms {
   const SSHAlgorithms({
     this.kex = const [
       SSHKexType.x25519,
+      SSHKexType.x25519Rfc,
       SSHKexType.nistp521,
       SSHKexType.nistp384,
       SSHKexType.nistp256,
diff --git a/lib/src/ssh_transport.dart b/lib/src/ssh_transport.dart
index ff46a42..c61ce10 100644
--- a/lib/src/ssh_transport.dart
+++ b/lib/src/ssh_transport.dart
@@ -1196,6 +1196,7 @@ class SSHTransport {
 
     switch (_kexType) {
       case SSHKexType.x25519:
+      case SSHKexType.x25519Rfc:
         _kex = await SSHKexX25519.createAsync();
         break;
       case SSHKexType.nistp256:
diff --git a/test/src/algorithm/ssh_cipher_type_test.dart b/test/src/algorithm/ssh_cipher_type_test.dart
index 132b226..a13b575 100644
--- a/test/src/algorithm/ssh_cipher_type_test.dart
+++ b/test/src/algorithm/ssh_cipher_type_test.dart
@@ -106,6 +106,7 @@ void main() {
         algorithms.kex,
         equals([
           SSHKexType.x25519,
+          SSHKexType.x25519Rfc,
           SSHKexType.nistp521,
           SSHKexType.nistp384,
           SSHKexType.nistp256,