dotnet/yarp · critical · InvalidOperationException

Routing Endpoint wasn't set for the current request.

Error message

Routing Endpoint wasn't set for the current request.

What it means

The `ProxyPipelineInitializerMiddleware` expects ASP.NET Core endpoint routing to have resolved an endpoint for the current request. It retrieves the endpoint via `context.GetEndpoint()`. If null, it means routing middleware (`UseRouting`) has not run, or this YARP middleware is placed in the pipeline before endpoint resolution. The proxy cannot proceed without knowing which route matched.

Source

Thrown at src/ReverseProxy/Model/ProxyPipelineInitializerMiddleware.cs:39

    private readonly ILogger _logger;
    private readonly RequestDelegate _next;
    private readonly IOptionsMonitor<RequestTimeoutOptions> _timeoutOptions;

    public ProxyPipelineInitializerMiddleware(RequestDelegate next, ILogger<ProxyPipelineInitializerMiddleware> logger, IOptionsMonitor<RequestTimeoutOptions> timeoutOptions)
    {
        ArgumentNullException.ThrowIfNull(logger);
        ArgumentNullException.ThrowIfNull(next);
        ArgumentNullException.ThrowIfNull(timeoutOptions);

        _logger = logger;
        _next = next;
        _timeoutOptions = timeoutOptions;
    }

    public Task Invoke(HttpContext context)
    {
        var endpoint = context.GetEndpoint()
           ?? throw new InvalidOperationException($"Routing Endpoint wasn't set for the current request.");

        var route = endpoint.Metadata.GetMetadata<RouteModel>()
            ?? throw new InvalidOperationException($"Routing Endpoint is missing {typeof(RouteModel).FullName} metadata.");

        var cluster = route.Cluster;
        // TODO: Validate on load https://github.com/dotnet/yarp/issues/797
        if (cluster is null)
        {
            Log.NoClusterFound(_logger, route.Config.RouteId);
            context.Response.StatusCode = StatusCodes.Status503ServiceUnavailable;
            return Task.CompletedTask;
        }

        EnsureRequestTimeoutPolicyIsAppliedCorrectly(context, endpoint, route);

        var destinationsState = cluster.DestinationsState;
        context.Features.Set<IReverseProxyFeature>(new ReverseProxyFeature
        {

View on GitHub (pinned to bd11867bee)

Solutions

Ensure `app.UseRouting()` is called before `app.MapReverseProxy()` in the middleware pipeline.
Verify `MapReverseProxy()` is called inside `app.UseEndpoints(...)` (or uses the modern minimal `app.MapReverseProxy()` which handles this internally).
Check that no middleware between `UseRouting` and the endpoint short-circuits the request before endpoint selection.
If using a custom middleware pipeline inside `MapReverseProxy`, ensure the proxy initializer middleware is not duplicated or misplaced.

Example fix

// before — UseRouting missing or after proxy
var app = builder.Build();
app.MapReverseProxy(); // no UseRouting — throws
app.Run();
// after — correct ordering
var app = builder.Build();
app.UseRouting();
app.UseEndpoints(endpoints =>
{
    endpoints.MapReverseProxy();
});
app.Run();

Defensive patterns

Strategy: validation

Validate before calling

// Verify middleware ordering at startup
// Ensure UseRouting is registered before the proxy endpoints
// This is a code-structure check, not a runtime validation
/*
Required order:
  app.UseRouting();
  app.UseEndpoints(endpoints => { endpoints.MapReverseProxy(); });
*/

Type guard

// No type guard — this is a pipeline-configuration issue.

Try / catch

// Not applicable — this is a startup configuration error.
// Fix by adding UseRouting() before the proxy endpoints.

Prevention

Always call app.UseRouting() before app.MapReverseProxy().
Use the standard Program.cs template from YARP documentation.
Review middleware ordering after refactoring Program.cs.

When it happens

Trigger: `ProxyPipelineInitializerMiddleware.Invoke` is called but `context.GetEndpoint()` returns null. This happens when `UseRouting()` was not called before the proxy middleware, or the middleware was accidentally added outside the endpoint-mapped pipeline (e.g., as a bare `app.UseMiddleware<ProxyPipelineInitializerMiddleware>()`).

Common situations: A developer removes `app.UseRouting()` while refactoring, not realizing YARP depends on endpoint routing. The YARP middleware is registered before `UseRouting` in the pipeline ordering. A misconfigured custom pipeline adds the proxy middleware at the wrong position.

Related errors

AI-assisted analysis of dotnet/yarp@bd11867bee (2026-08-13). Data as JSON: /api/errors/210382a39b94825d. Report an issue: GitHub.