Exception "No method by the name 'initialize' is found."

When starting my languageserver from my extension I get an exception from "VS/IDE/TaskStatusCenter/RunningRegisteredTaskFailed":

            StreamJsonRpc.RemoteMethodNotFoundException: No method by the name 'initialize' is found.
            at StreamJsonRpc.JsonRpc.<InvokeCoreAsync>d__154`1.MoveNext()
            --- End of stack trace from previous location where exception was thrown ---
            at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
            at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
            at Microsoft.VisualStudio.LanguageServer.Client.JsonRpcExtensionMethods.<SendMethodRequestWithTelemetryAsync>d__0`2.MoveNext()
            --- End of stack trace from previous location where exception was thrown ---
            at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
            at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
            at Microsoft.VisualStudio.LanguageServer.Client.RemoteLanguageClientInstance.<SendInitializeRequestAsync>d__115.MoveNext()
            --- End of stack trace from previous location where exception was thrown ---
            at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
            at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
            at Microsoft.VisualStudio.LanguageServer.Client.RemoteLanguageClientInstance.<InitializeAsync>d__110.MoveNext()
            --- End of stack trace from previous location where exception was thrown ---
            at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
            at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
            at Microsoft.VisualStudio.Threading.TplExtensions.<WithTimeout>d__5.MoveNext()
            --- End of stack trace from previous location where exception was thrown ---
            at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
            at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
            at Microsoft.VisualStudio.LanguageServer.Client.RemoteLanguageClientInstance.<TrackTaskAsync>d__113.MoveNext()
            --- End of stack trace from previous location where exception was thrown ---
            at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
            at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
            at Microsoft.VisualStudio.LanguageServer.Client.RemoteLanguageClientInstance.<ActivateLanguageClientAsync>d__122.MoveNext()

What does this message mean? For which class is the "initialize" method missing?

I use

• omnisharp.extensions.languageserver 0.19.9
• Visual Studio Extensibility Sdk and Visual Studio Extensibility Framework 17.10.2084
• VS2022
• Nerdbank-Streams (as suggested)

Here is my language-server-provider:

using System.Diagnostics;
using System.IO.Pipelines;
using JetBrains.Annotations;
using Microsoft.VisualStudio.Extensibility;
using Microsoft.VisualStudio.Extensibility.LanguageServer;
using Microsoft.VisualStudio.RpcContracts.LanguageServerProvider;
using Nerdbank.Streams;
using ReniLSP;

namespace Reni.LSPVSIX;

#pragma warning disable VSEXTPREVIEW_LSP
[VisualStudioContribution]
[UsedImplicitly]
public sealed class ReniLanguageServerProvider : LanguageServerProvider
{
	[UsedImplicitly]
	Task? ServerPipeTask;

	public ReniLanguageServerProvider
		(ExtensionCore container, VisualStudioExtensibility extensibilityObject, TraceSource traceSource)
		: base(container, extensibilityObject) { }

	public override LanguageServerProviderConfiguration LanguageServerProviderConfiguration =>
		new("Reni Language Server",
			new[]
			{
				DocumentFilter.FromDocumentType(Constants.LanguageName),
			});

	// Activate the language server and return a duplex pipe that communicates with the server. 
	public override Task<IDuplexPipe?> CreateServerConnectionAsync(CancellationToken token)
	{
		var (pipeToServer, pipeToVS) = FullDuplexStream.CreatePair();

		ServerPipeTask = Task.Run(
			() => MainContainer.RunServer(pipeToVS.UsePipeReader(), pipeToServer.UsePipeWriter())
			, token
		);

		return Task.FromResult<IDuplexPipe?>(new DuplexPipe(pipeToServer.UsePipeReader(), pipeToVS.UsePipeWriter()));
	}

	protected override void Dispose(bool isDisposing)
	{
		if(isDisposing)
			ServerPipeTask?.Dispose();
		base.Dispose(isDisposing);
	}

	public override Task OnServerInitializationResultAsync
	(
		ServerInitializationResult startState, LanguageServerInitializationFailureInfo? initializationFailureInfo
		, CancellationToken cancellationToken
	) =>
		// Method called when server activation was completed successfully or failed, denoted by "startState".
		Task.CompletedTask;
}

Start with ReniLanguageServerProvider.CreateServerConnectionAsync and trace the MainContainer.RunServer call, using the reported OmniSharp and Visual Studio Extensibility versions as constraints. Compare the server connection with the initialization request that Visual Studio sends. Done means explaining which side lacks the initialize method and identifying the compatible configuration or integration change.