Добавьте файлы проекта.

YandexMusic.API/Models/Ynison/Messages/YYnisonErrorMessage.cs

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+namespace YandexMusic.API.Models.Ynison.Messages
+{
+    public class YYnisonErrorMessage : Exception
+    {
+        public YYnisonError Error { get; set; }
+    }
+}

YandexMusic.API/Models/Ynison/Messages/YYnisonMessage.cs

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+namespace YandexMusic.API.Models.Ynison.Messages
+{
+    public class YYnisonMessage
+    {
+        public string Rid { get; set; } = Guid.NewGuid().ToString();
+    }
+}

YandexMusic.API/Models/Ynison/Messages/YYnisonMessageType.cs

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+namespace YandexMusic.API.Models.Ynison.Messages
+{
+    /// <summary>
+    /// Типы сообщений Ynison
+    /// </summary>
+    public enum YYnisonMessageType
+    {
+        Redirect,
+        State,
+        Error
+    }
+}

YandexMusic.API/Models/Ynison/Messages/YYnisonUpdateFullStateMessage.cs

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+namespace YandexMusic.API.Models.Ynison.Messages
+{
+    public class YYnisonUpdateFullStateMessage : YYnisonUpdateMessage
+    {
+        public YYnisonFullState UpdateFullState { get; set; }
+    }
+}

YandexMusic.API/Models/Ynison/Messages/YYnisonUpdateMessage.cs

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+namespace YandexMusic.API.Models.Ynison.Messages
+{
+    public class YYnisonUpdateMessage : YYnisonMessage
+    {
+#warning нужен enum
+        public string ActivityInterceptionType { get; set; } = "DO_NOT_INTERCEPT_BY_DEFAULT";
+
+        public decimal PlayerActionTimestampMs { get; set; } = DateTimeOffset.Now.ToUnixTimeMilliseconds();
+    }
+}

YandexMusic.API/Models/Ynison/Messages/YYnisonUpdatePlayerStateMessage.cs

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+namespace YandexMusic.API.Models.Ynison.Messages
+{
+    public class YYnisonUpdatePlayerStateMessage : YYnisonUpdateMessage
+    {
+        public YYnisonPlayerState UpdatePlayerState { get; set; }
+    }
+}