How to ignore parent Trace and instead of nested Span, create a Trace Link to it?

[CezaryKlus]

Hi I want to treat separately traces from clients that call my backend ASP.NET Core API and link the corresponding traces instead of propagate Client Trace into backend.

I tried with this:

    /// <summary>
    /// A <see cref="TextMapPropagator"/> that intercepts the incoming W3C TraceContext and stores it
    /// in an <see cref="AsyncLocal{T}"/> so it can be attached as an <see cref="ActivityLink"/> instead
    /// of becoming the parent of the current service's root span.
    /// </summary>
    private sealed class LinkingTextMapPropagator() : TextMapPropagator
    {
        readonly TextMapPropagator inner = new TraceContextPropagator();

        /// <summary>Key used to store the remote <see cref="ActivityContext"/> in <see cref="HttpContext.Items"/>.</summary>
        public static readonly object RemoteContextItemKey = new();

        public override ISet<string> Fields => inner.Fields!;

        public override PropagationContext Extract<T>(PropagationContext context, T carrier, Func<T, string, IEnumerable<string>?> getter)
        {
            var extracted = inner.Extract(context, carrier, getter);

            // Only intercept HTTP carriers: OTel AspNetCore instrumentation passes HttpRequest.
            // Non-HTTP propagation (MassTransit, Hangfire, gRPC…) must preserve the parent context unchanged.
            if (carrier is HttpRequest httpRequest && extracted.ActivityContext.IsValid())
            {
                // Store the remote context on the request itself so it is explicitly scoped to this HTTP
                // request and can be read by EnrichWithHttpRequest without relying on async-local state.
                httpRequest.HttpContext.Items[RemoteContextItemKey] = extracted.ActivityContext;

                // Return an empty ActivityContext so the incoming trace does NOT become the parent span.
                return new PropagationContext(default, extracted.Baggage);
            }

            return extracted;
        }

        public override void Inject<T>(PropagationContext context, T carrier, Action<T, string, string> setter)
            => inner.Inject(context, carrier, setter);
    }

and

        services.AddOpenTelemetry()
            .WithTracing(tracerProviderBuilder =>
                tracerProviderBuilder
                    .AddAspNetCoreInstrumentation(o =>
                    {
                        o.EnrichWithHttpRequest = (activity, request) =>
                        {
                            // If an incoming remote trace context was captured by the LinkingTextMapPropagator,
                            // add it as an ActivityLink so the relationship is preserved without making the
                            // remote trace the parent of this service's root span.
                            if (request.HttpContext.Items.TryGetValue(LinkingTextMapPropagator.RemoteContextItemKey, out var item)
                                && item is ActivityContext remoteContext && remoteContext.IsValid())
                            {
                                activity.AddLink(new ActivityLink(remoteContext));
                            }
                        };

But current Activity still has the Client originating ParentId