Another idea that doesn't work

sdk/core/Azure.Core/src/RequestFailedException.cs

@@ -150,7 +150,7 @@ public override void GetObjectData(SerializationInfo info, StreamingContext cont
 
         private static ErrorDetails CreateRequestFailedExceptionContent(Response response, RequestFailedDetailsParser? parser)
         {
-            response.Buffer();
+            BufferResponseIfNeeded(response);
 
             parser ??= response.RequestFailedDetailsParser;
 
@@ -224,24 +224,24 @@ private static ErrorDetails CreateRequestFailedExceptionContent(Response respons
             return new ErrorDetails(messageBuilder.ToString(), error?.Code, additionalInfo);
         }
 
-        //private static void BufferResponseIfNeeded(Response response)
-        //{
-        //    // Buffer into a memory stream if not already buffered
-        //    if (response.ContentStream is null or MemoryStream)
-        //    {
-        //        return;
-        //    }
+        private static void BufferResponseIfNeeded(Response response)
+        {
+            // Buffer into a memory stream if not already buffered
+            if (response.ContentStream is null or MemoryStream)
+            {
+                return;
+            }
 
-        //    var bufferedStream = new MemoryStream();
-        //    response.ContentStream.CopyTo(bufferedStream);
+            var bufferedStream = new MemoryStream();
+            response.ContentStream.CopyTo(bufferedStream);
 
-        //    // Dispose the unbuffered stream
-        //    response.ContentStream.Dispose();
+            // Dispose the unbuffered stream
+            response.ContentStream.Dispose();
 
-        //    // Reset the position of the buffered stream and set it on the response
-        //    bufferedStream.Position = 0;
-        //    response.ContentStream = bufferedStream;
-        //}
+            // Reset the position of the buffered stream and set it on the response
+            bufferedStream.Position = 0;
+            response.ContentStream = bufferedStream;
+        }
 
         // This class needs to be internal rather than private so that it can be used
         // by the System.Text.Json source generator.

sdk/core/Azure.Core/src/Response.cs

@@ -104,8 +104,6 @@ public override string ToString()
             return $"Status: {Status}, ReasonPhrase: {ReasonPhrase}";
         }
 
-        internal void Buffer() => BufferContent();
-
         internal static void DisposeStreamIfNotBuffered(ref Stream? stream)
         {
             // We want to keep the ContentStream readable

sdk/core/System.ClientModel/src/Message/PipelineResponse.cs

@@ -63,6 +63,11 @@ public virtual BinaryData Content
     {
         get
         {
+            if (_contentStream is not null)
+            {
+                return BinaryData.FromStream(_contentStream);
+            }
+
             if (_content is null)
             {
                 throw new InvalidOperationException($"The response is not fully buffered.");
@@ -96,8 +101,7 @@ public virtual BinaryData Content
     // Same value as Stream.CopyTo uses by default
     private const int DefaultCopyBufferSize = 81920;
 
-    // TODO: Prefer an approach that doesn't make this visible outside the dll
-    protected internal void BufferContent(TimeSpan? timeout = default, CancellationTokenSource? cts = default)
+    internal void BufferContent(TimeSpan? timeout = default, CancellationTokenSource? cts = default)
     {
         if (IsBuffered)
         {