I upgraded my .NET 8 solution to .NET 9 and replaced SwaggerGen with the new OpenAPI that .NET 9 provides. This is how everything related to this feature is setup in my program:
...
builder.Services.AddOpenApi("dev");
...
if (app.Environment.IsDevelopment())
{
app.MapOpenApi();
app.MapScalarApiReference();
app.UseHttpLogging();
}
...
app.Use(async (ctx, next) =>
{
ctx.Request.EnableBuffering();
await next(ctx); // -> exception