I’m working on integrating Identity into my .NET Core 8.0 application and implementing JWT Bearer authentication. However, I’m encountering the error
System.InvalidOperationException: Scheme already exists: Bearer
when running the application.

My Program.cs code is :

using Solv.Identity.Api.Common;
using Solv.Identity.Api.Configurations;
using Solv.Identity.Api.Endpoints;
using Solv.Identity.Infrastructure;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.IdentityModel.Tokens;
using Solv.Identity.Application.Auth;
using Solv.Identity.Application.Features.Configuration;
using System.Text;
using Solv.Identity.Application.Features.Users;
using System;
using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
using Microsoft.AspNetCore.Identity;

var builder = WebApplication.CreateBuilder(args);

// Register AuthService
builder.Services.AddTransient<AuthService>();

// Add authentication and authorization

builder.Services.AddAuthentication(x =>
{
    x.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
    x.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
}).AddJwtBearer(x =>
{
    x.TokenValidationParameters = new TokenValidationParameters
    {
        IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(Configuration.PrivateKey)),
        ValidateIssuer = false,
        ValidateAudience = false
    };
});

builder.Services.AddAuthorization(x =>
{
    x.AddPolicy("tech", p => p.RequireRole("developer"));
});

// Controllers
builder.AddValidationSetup();
// Swagger
builder.Services.AddSwaggerSetup();
// Persistence
builder.Services.AddPersistenceSetup(builder.Configuration);
// Application layer setup
builder.Services.AddApplicationSetup();
// Request response compression
builder.Services.AddCompressionSetup();
//// HttpContextAcessor
builder.Services.AddHttpContextAccessor();
//// Mediator
builder.Services.AddMediatRSetup();
//// Exception handler
builder.Services.AddExceptionHandler<ExceptionHandler>();

builder.Logging.ClearProviders();

// Add serilog
if (builder.Environment.EnvironmentName != "Testing")
{
    //builder.Host.UseLoggingSetup(builder.Configuration);

    // Add opentelemetry
    builder.AddOpenTemeletrySetup();
}

builder.Services.AddHttpClient();

#region Keycloak
builder.Services.AddKeycloakServices();
builder.AddKeycloakSettings();
builder.AddKeycloakAuthorization();
#endregion

var app = builder.Build();

// Configure the HTTP request pipeline.
app.UseResponseCompression();

if (app.Environment.IsDevelopment())
{
    app.UseDeveloperExceptionPage();
}

app.UseRouting();

app.UseSwaggerSetup();
app.UseHsts();

app.UseResponseCompression();
app.UseHttpsRedirection();

// Configure middleware
app.UseAuthentication();
app.UseAuthorization();


// Define endpoints
app.MapGet("/login", (AuthService service) =>
{
    var user = new User(
        1,
        "M.Sohail",
        "M.Sohail",
        "[email protected]",
        "abcd123",
        new[] { "developer" });

    return service.Create(user);
});

app.MapGet("/test", () => "OK!")
    .RequireAuthorization();

app.MapGet("/test/tech", () => "tech OK!")
    .RequireAuthorization("tech");


app.UseMiddleware<LoggingMiddleware>();
await app.Migrate();
await app.RunAsync();

I have tried rearranging the order of middleware and authentication setup in Program.cs, but the error persists.
I have checked for duplicate calls to AddAuthentication and AddJwtBearer methods.

If needed, I can provide a simplified version of my code focusing on the authentication setup that causes the error.

Environment:

.NET Core 8.0,
Identity framework version 8.0.0,
Visual Studio 2022,
Windows 10