<PackageReference Include="System.ClientModel" Version="1.11.0" />

System.ClientModel.Internal.UnsafeBufferSequence

This class is a helper to write to a IBufferWriter<T> in a thread safe manner. It uses the shared pool to allocate buffers and returns them to the pool when disposed. Since there is no way to ensure someone didn't keep a reference to one of the buffers it must be disposed of in the same context it was created and its referenced should not be stored or shared.
namespace System.ClientModel.Internal { internal sealed class UnsafeBufferSequence : IBufferWriter<byte>, IDisposable { public UnsafeBufferSequence(int segmentSize = 16384); public void Advance(int bytesWritten); public Memory<byte> GetMemory(int sizeHint = 0); public Span<byte> GetSpan(int sizeHint = 0); public void Dispose(); public Reader ExtractReader(); } }