DefaultJsonTypeInfoResolver Can , but SourceGenerationContext Can't

[zms9110750]

if i no [JsonSerializable(typeof(ChatDelta))] then output 1.
else no output

string json = """
	{
		"index": 0,
		"delta": 1
	}
	""";

var c = JsonSerializer.Deserialize<ChatDelta>(json, PublicSourceGenerationContext.DebugOptions);
c.Message.Debug();

public record ChatDelta(
	 int Index,
	 int? Delta) : ChatChoice(Index, Delta)
{
	public int? Delta { get => Message; init => Message = value; }
}
public record ChatChoice(
	 int Index,
	 int? Message );

[JsonSourceGenerationOptions(
	PropertyNamingPolicy = JsonKnownNamingPolicy.SnakeCaseLower,  // 属性名转为蛇形命名（如：userName → user_name）
	UseStringEnumConverter = true,              // 枚举值转为字符串（但特性无法指定蛇形命名，需在实例覆盖）
	AllowOutOfOrderMetadataProperties = true,   // 允许元属性乱序（如JSON字段顺序和类定义不一致）
	DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull  // 自动忽略null值
)]

[JsonSerializable(typeof(ChatDelta))]
[JsonSerializable(typeof(int))]
internal partial class SourceGenerationContext : JsonSerializerContext
{
	// 调试配置（蛇形命名 + 格式化 + 动态源选择）
	[field: AllowNull]
	public static JsonSerializerOptions DebugOptions => field ??=
		new JsonSerializerOptions(Default.Options)
		{
			Converters = { new JsonStringEnumConverter(JsonNamingPolicy.SnakeCaseLower) },
			WriteIndented = true,                // 格式化输出（带缩进和换行）
			Encoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping, // 完全禁用转义 
			TypeInfoResolver = JsonTypeInfoResolver.Combine(
				Default.Options.TypeInfoResolver,  // 优先使用源生成
				new DefaultJsonTypeInfoResolver()) // 回退到反射 	
		};
}

public static class PublicSourceGenerationContext
{
	public static JsonSerializerOptions DebugOptions => SourceGenerationContext.DebugOptions; 

	public static T Debug<T>(this T obj, [CallerMemberName] string? paramName = null, [CallerLineNumber] int? lineNum = null, [CallerFilePath] string? filePath = null)
	{
#if DEBUG
		Console.WriteLine($"{Path.GetFileName(filePath)}  {lineNum}  {paramName}调用 ============ \n");
		Console.ForegroundColor = ConsoleColor.Red;
		Console.WriteLine(obj);
		Console.ForegroundColor = ConsoleColor.Black;
		Console.WriteLine($"\n{paramName}结束===============================\n");
#endif
		return obj;
	}
}