diff --git a/src/Core/Auth/Entities/AuthRequest.cs b/src/Core/Auth/Entities/AuthRequest.cs
index af429adca2..2117c575c0 100644
--- a/src/Core/Auth/Entities/AuthRequest.cs
+++ b/src/Core/Auth/Entities/AuthRequest.cs
@@ -2,6 +2,7 @@
 #nullable disable
 
 using System.ComponentModel.DataAnnotations;
+using Bit.Core.Auth.Enums;
 using Bit.Core.Entities;
 using Bit.Core.Enums;
 using Bit.Core.Utilities;
@@ -43,11 +44,31 @@ public class AuthRequest : ITableObject<Guid>
 
     public bool IsSpent()
     {
-        return ResponseDate.HasValue || AuthenticationDate.HasValue || GetExpirationDate() < DateTime.UtcNow;
+        return ResponseDate.HasValue || AuthenticationDate.HasValue || IsExpired();
+    }
+
+    public bool IsExpired()
+    {
+        // TODO: PM-24252 - consider using TimeProvider for better mocking in tests
+        return GetExpirationDate() < DateTime.UtcNow;
+    }
+
+    // TODO: PM-24252 - this probably belongs in a service.
+    public bool IsValidForAuthentication(Guid userId,
+        string password)
+    {
+        return ResponseDate.HasValue // it’s been responded to
+               && Approved == true // it was approved
+               && !IsExpired() // it's not expired
+               && Type == AuthRequestType.AuthenticateAndUnlock // it’s an authN request
+               && !AuthenticationDate.HasValue // it was not already used for authN
+               && UserId == userId // it belongs to the user
+               && CoreHelpers.FixedTimeEquals(AccessCode, password);  // the access code matches the password
     }
 
     public DateTime GetExpirationDate()
     {
+        // TODO: PM-24252 - this should reference PasswordlessAuthSettings.UserRequestExpiration
         return CreationDate.AddMinutes(15);
     }
 }
diff --git a/src/Identity/IdentityServer/Enums/DeviceValidationResultType.cs b/src/Identity/IdentityServer/Enums/DeviceValidationResultType.cs
index 45c901e306..f8d04eccfb 100644
--- a/src/Identity/IdentityServer/Enums/DeviceValidationResultType.cs
+++ b/src/Identity/IdentityServer/Enums/DeviceValidationResultType.cs
@@ -6,5 +6,6 @@ public enum DeviceValidationResultType : byte
     InvalidUser = 1,
     InvalidNewDeviceOtp = 2,
     NewDeviceVerificationRequired = 3,
-    NoDeviceInformationProvided = 4
+    NoDeviceInformationProvided = 4,
+    AuthRequestFlowUnknownDevice = 5,
 }
diff --git a/src/Identity/IdentityServer/RequestValidators/DeviceValidator.cs b/src/Identity/IdentityServer/RequestValidators/DeviceValidator.cs
index 44dc89d259..42504ae813 100644
--- a/src/Identity/IdentityServer/RequestValidators/DeviceValidator.cs
+++ b/src/Identity/IdentityServer/RequestValidators/DeviceValidator.cs
@@ -39,6 +39,8 @@ public class DeviceValidator(
     private readonly ILogger<DeviceValidator> _logger = logger;
     private readonly ITwoFactorEmailService _twoFactorEmailService = twoFactorEmailService;
 
+    private const string PasswordGrantType = "password";
+
     public async Task<bool> ValidateRequestDeviceAsync(ValidatedTokenRequest request, CustomValidatorRequestContext context)
     {
         // Parse device from request and return early if no device information is provided
@@ -68,10 +70,14 @@ public class DeviceValidator(
         }
 
         // We have established that the device is unknown at this point; begin new device verification
-        if (request.GrantType == "password" &&
-            request.Raw["AuthRequest"] == null &&
-            !context.TwoFactorRequired &&
-            !context.SsoRequired &&
+        // for standard password grant type requests
+        // Note: the auth request flow re-uses the resource owner password flow but new device verification
+        // is not required for auth requests
+        var rawAuthRequestId = request.Raw["AuthRequest"]?.ToLowerInvariant();
+        var isAuthRequest = !string.IsNullOrEmpty(rawAuthRequestId);
+        if (request.GrantType == PasswordGrantType &&
+            !isAuthRequest &&
+            context is { TwoFactorRequired: false, SsoRequired: false } &&
             _globalSettings.EnableNewDeviceVerification)
         {
             var validationResult = await HandleNewDeviceVerificationAsync(context.User, request);
@@ -87,6 +93,16 @@ public class DeviceValidator(
             }
         }
 
+        // Device still unknown, but if we are in an auth request flow, this is not valid
+        // as we only support auth request authN requests on known devices
+        if (request.GrantType == PasswordGrantType && isAuthRequest &&
+            context is { TwoFactorRequired: false, SsoRequired: false })
+        {
+            (context.ValidationErrorResult, context.CustomResponse) =
+                BuildDeviceErrorResult(DeviceValidationResultType.AuthRequestFlowUnknownDevice);
+            return false;
+        }
+
         // At this point we have established either new device verification is not required or the NewDeviceOtp is valid,
         // so we save the device to the database and proceed with authentication
         requestDevice.UserId = context.User.Id;
@@ -252,7 +268,7 @@ public class DeviceValidator(
         var customResponse = new Dictionary<string, object>();
         switch (errorType)
         {
-            /* 
+            /*
              * The ErrorMessage is brittle and is used to control the flow in the clients. Do not change them without updating the client as well.
              * There is a backwards compatibility issue as well: if you make a change on the clients then ensure that they are backwards
              * compatible.
@@ -273,6 +289,10 @@ public class DeviceValidator(
                 result.ErrorDescription = "No device information provided";
                 customResponse.Add("ErrorModel", new ErrorResponseModel("no device information provided"));
                 break;
+            case DeviceValidationResultType.AuthRequestFlowUnknownDevice:
+                result.ErrorDescription = "Auth requests are not supported on unknown devices";
+                customResponse.Add("ErrorModel", new ErrorResponseModel("auth request flow unsupported on unknown device"));
+                break;
         }
         return (result, customResponse);
     }
diff --git a/src/Identity/IdentityServer/RequestValidators/ResourceOwnerPasswordValidator.cs b/src/Identity/IdentityServer/RequestValidators/ResourceOwnerPasswordValidator.cs
index fe32d3e1b8..c5d2db38f4 100644
--- a/src/Identity/IdentityServer/RequestValidators/ResourceOwnerPasswordValidator.cs
+++ b/src/Identity/IdentityServer/RequestValidators/ResourceOwnerPasswordValidator.cs
@@ -11,7 +11,6 @@ using Bit.Core.Entities;
 using Bit.Core.Repositories;
 using Bit.Core.Services;
 using Bit.Core.Settings;
-using Bit.Core.Utilities;
 using Duende.IdentityServer.Models;
 using Duende.IdentityServer.Validation;
 using Microsoft.AspNetCore.Identity;
@@ -90,21 +89,30 @@ public class ResourceOwnerPasswordValidator : BaseRequestValidator<ResourceOwner
             return false;
         }
 
-        var authRequestId = context.Request.Raw["AuthRequest"]?.ToString()?.ToLowerInvariant();
-        if (!string.IsNullOrWhiteSpace(authRequestId) && Guid.TryParse(authRequestId, out var authRequestGuid))
+        var authRequestId = context.Request.Raw["AuthRequest"]?.ToLowerInvariant();
+        if (!string.IsNullOrEmpty(authRequestId))
         {
-            var authRequest = await _authRequestRepository.GetByIdAsync(authRequestGuid);
-            if (authRequest != null)
+            // only allow valid guids
+            if (!Guid.TryParse(authRequestId, out var authRequestGuid))
             {
-                var requestAge = DateTime.UtcNow - authRequest.CreationDate;
-                if (requestAge < TimeSpan.FromHours(1) &&
-                    CoreHelpers.FixedTimeEquals(authRequest.AccessCode, context.Password))
-                {
-                    authRequest.AuthenticationDate = DateTime.UtcNow;
-                    await _authRequestRepository.ReplaceAsync(authRequest);
-                    return true;
-                }
+                return false;
             }
+
+            var authRequest = await _authRequestRepository.GetByIdAsync(authRequestGuid);
+
+            if (authRequest == null)
+            {
+                return false;
+            }
+
+            // Auth request is non-null so validate it
+            if (authRequest.IsValidForAuthentication(validatorContext.User.Id, context.Password))
+            {
+                authRequest.AuthenticationDate = DateTime.UtcNow;
+                await _authRequestRepository.ReplaceAsync(authRequest);
+                return true;
+            }
+
             return false;
         }
 
diff --git a/test/Identity.IntegrationTest/RequestValidation/ResourceOwnerPasswordValidatorTests.cs b/test/Identity.IntegrationTest/RequestValidation/ResourceOwnerPasswordValidatorTests.cs
index 537aae0935..4d243906af 100644
--- a/test/Identity.IntegrationTest/RequestValidation/ResourceOwnerPasswordValidatorTests.cs
+++ b/test/Identity.IntegrationTest/RequestValidation/ResourceOwnerPasswordValidatorTests.cs
@@ -16,16 +16,18 @@ namespace Bit.Identity.IntegrationTest.RequestValidation;
 
 public class ResourceOwnerPasswordValidatorTests : IClassFixture<IdentityApplicationFactory>
 {
-    private const string DefaultPassword = "master_password_hash";
-    private const string DefaultUsername = "test@email.qa";
-    private const string DefaultDeviceIdentifier = "test_identifier";
+    private const string _defaultPassword = "master_password_hash";
+    private const string _defaultUsername = "test@email.qa";
+    private const string _defaultDeviceIdentifier = "test_identifier";
+    private const DeviceType _defaultDeviceType = DeviceType.FirefoxBrowser;
+    private const string _defaultDeviceName = "firefox";
 
     [Fact]
     public async Task ValidateAsync_Success()
     {
         // Arrange
         var localFactory = new IdentityApplicationFactory();
-        await EnsureUserCreatedAsync(localFactory);
+        await RegisterUserAsync(localFactory);
 
         // Act
         var context = await localFactory.Server.PostAsync("/connect/token",
@@ -74,12 +76,12 @@ public class ResourceOwnerPasswordValidatorTests : IClassFixture<IdentityApplica
     {
         // Arrange
         var localFactory = new IdentityApplicationFactory();
-        await EnsureUserCreatedAsync(localFactory);
+        await RegisterUserAsync(localFactory);
 
         var userManager = localFactory.GetService<UserManager<User>>();
 
         // Verify the User is not null to ensure the failure is due to bad password
-        Assert.NotNull(await userManager.FindByEmailAsync(DefaultUsername));
+        Assert.NotNull(await userManager.FindByEmailAsync(_defaultUsername));
 
         // Act
         var context = await localFactory.Server.PostAsync("/connect/token",
@@ -95,23 +97,142 @@ public class ResourceOwnerPasswordValidatorTests : IClassFixture<IdentityApplica
     }
 
     [Fact]
-    public async Task ValidateAsync_ValidateContextAsync_AuthRequest_NotNull_AgeLessThanOneHour_Success()
+    public async Task ValidateAsync_ValidateContextAsync_ValidAuthRequest_Success()
     {
         // Arrange
         var localFactory = new IdentityApplicationFactory();
 
         // Ensure User
-        await EnsureUserCreatedAsync(localFactory);
+        await RegisterUserAsync(localFactory);
         var userManager = localFactory.GetService<UserManager<User>>();
-        var user = await userManager.FindByEmailAsync(DefaultUsername);
+        var user = await userManager.FindByEmailAsync(_defaultUsername);
         Assert.NotNull(user);
 
-        // Connect Request to User and set CreationDate
-        var authRequest = CreateAuthRequest(
-            user.Id,
-            AuthRequestType.AuthenticateAndUnlock,
-            DateTime.UtcNow.AddMinutes(-30)
-        );
+        // Ensure device is known b/c auth requests aren't allowed for unknown devices.
+        await AddKnownDevice(localFactory, user.Id);
+
+        // Create valid auth request and tie it to the user
+        var authRequest = CreateAuthRequest(r =>
+        {
+            r.ResponseDate = DateTime.UtcNow.AddMinutes(-2); // 2 minutes ago
+            r.Approved = true; // approved
+            r.CreationDate = DateTime.UtcNow.AddMinutes(-5); // not expired
+            r.Type = AuthRequestType.AuthenticateAndUnlock; // authN request
+            r.AuthenticationDate = null; // not used for authN yet
+            r.UserId = user.Id;  // connect request to user
+            r.AccessCode = _defaultPassword; // matches the password
+        });
+
+        var authRequestRepository = localFactory.GetService<IAuthRequestRepository>();
+        await authRequestRepository.CreateAsync(authRequest);
+
+        var expectedAuthRequest = await authRequestRepository.GetManyByUserIdAsync(user.Id);
+        Assert.NotEmpty(expectedAuthRequest);
+
+        // Act
+        var context = await localFactory.Server.PostAsync("/connect/token",
+            new FormUrlEncodedContent(new Dictionary<string, string>
+            {
+                { "scope", "api offline_access" },
+                { "client_id", "web" },
+                { "deviceType", DeviceTypeAsString(_defaultDeviceType) },
+                { "deviceIdentifier", _defaultDeviceIdentifier },
+                { "deviceName", _defaultDeviceName },
+                { "grant_type", "password" },
+                { "username", _defaultUsername },
+                { "password", _defaultPassword },
+                { "AuthRequest", authRequest.Id.ToString().ToLowerInvariant() }
+            }));
+
+        // Assert
+        var body = await AssertHelper.AssertResponseTypeIs<JsonDocument>(context);
+        var root = body.RootElement;
+
+        var token = AssertHelper.AssertJsonProperty(root, "access_token", JsonValueKind.String).GetString();
+        Assert.NotNull(token);
+    }
+
+    [Fact]
+    public async Task ValidateAsync_ValidateContextAsync_ValidAuthRequest_UnknownDevice_Failure()
+    {
+        // Arrange
+        var localFactory = new IdentityApplicationFactory();
+
+        // Ensure User
+        await RegisterUserAsync(localFactory);
+        var userManager = localFactory.GetService<UserManager<User>>();
+        var user = await userManager.FindByEmailAsync(_defaultUsername);
+        Assert.NotNull(user);
+
+        // Create valid auth request and tie it to the user
+        var authRequest = CreateAuthRequest(r =>
+        {
+            r.ResponseDate = DateTime.UtcNow.AddMinutes(-2); // 2 minutes ago
+            r.Approved = true; // approved
+            r.CreationDate = DateTime.UtcNow.AddMinutes(-5); // not expired
+            r.Type = AuthRequestType.AuthenticateAndUnlock; // authN request
+            r.AuthenticationDate = null; // not used for authN yet
+            r.UserId = user.Id;  // connect request to user
+            r.AccessCode = _defaultPassword; // matches the password
+        });
+
+        var authRequestRepository = localFactory.GetService<IAuthRequestRepository>();
+        await authRequestRepository.CreateAsync(authRequest);
+
+        var expectedAuthRequest = await authRequestRepository.GetManyByUserIdAsync(user.Id);
+        Assert.NotEmpty(expectedAuthRequest);
+
+        // Act
+        var context = await localFactory.Server.PostAsync("/connect/token",
+            new FormUrlEncodedContent(new Dictionary<string, string>
+            {
+                { "scope", "api offline_access" },
+                { "client_id", "web" },
+                { "deviceType", DeviceTypeAsString(_defaultDeviceType) },
+                { "deviceIdentifier", _defaultDeviceIdentifier },
+                { "deviceName", _defaultDeviceName },
+                { "grant_type", "password" },
+                { "username", _defaultUsername },
+                { "password", _defaultPassword },
+                { "AuthRequest", authRequest.Id.ToString().ToLowerInvariant() }
+            }));
+
+        // Assert
+        var body = await AssertHelper.AssertResponseTypeIs<JsonDocument>(context);
+        var root = body.RootElement;
+
+        var errorModel = AssertHelper.AssertJsonProperty(root, "ErrorModel", JsonValueKind.Object);
+        var errorMessage = AssertHelper.AssertJsonProperty(errorModel, "Message", JsonValueKind.String).GetString();
+        Assert.Equal("auth request flow unsupported on unknown device", errorMessage);
+    }
+
+    [Fact]
+    public async Task ValidateAsync_ValidateContextAsync_Expired_AuthRequest_Failure()
+    {
+        // Arrange
+        var localFactory = new IdentityApplicationFactory();
+        // Ensure User
+        await RegisterUserAsync(localFactory);
+        var userManager = localFactory.GetService<UserManager<User>>();
+
+        var user = await userManager.FindByEmailAsync(_defaultUsername);
+        Assert.NotNull(user);
+
+        // Ensure device is known b/c auth requests aren't allowed for unknown devices.
+        await AddKnownDevice(localFactory, user.Id);
+
+        // Create AuthRequest
+        var authRequest = CreateAuthRequest(r =>
+        {
+            r.ResponseDate = DateTime.UtcNow.AddMinutes(-10); // 10 minutes ago
+            r.Approved = true; // approved
+            r.CreationDate = DateTime.UtcNow.AddMinutes(-16); // expired after 15 minutes
+            r.Type = AuthRequestType.AuthenticateAndUnlock; // authN request
+            r.AuthenticationDate = null; // not used for authN yet
+            r.UserId = user.Id;  // connect request to user
+            r.AccessCode = _defaultPassword; // matches the password
+        });
+
         var authRequestRepository = localFactory.GetService<IAuthRequestRepository>();
         await authRequestRepository.CreateAsync(authRequest);
 
@@ -125,40 +246,51 @@ public class ResourceOwnerPasswordValidatorTests : IClassFixture<IdentityApplica
                 { "scope", "api offline_access" },
                 { "client_id", "web" },
                 { "deviceType", DeviceTypeAsString(DeviceType.FirefoxBrowser) },
-                { "deviceIdentifier", DefaultDeviceIdentifier },
+                { "deviceIdentifier", _defaultDeviceIdentifier },
                 { "deviceName", "firefox" },
                 { "grant_type", "password" },
-                { "username", DefaultUsername },
-                { "password", DefaultPassword },
+                { "username", _defaultUsername },
+                { "password", _defaultPassword },
                 { "AuthRequest", authRequest.Id.ToString().ToLowerInvariant() }
             }));
 
         // Assert
-        var body = await AssertHelper.AssertResponseTypeIs<JsonDocument>(context);
-        var root = body.RootElement;
 
-        var token = AssertHelper.AssertJsonProperty(root, "access_token", JsonValueKind.String).GetString();
-        Assert.NotNull(token);
+        await AssertStandardError(context);
     }
 
     [Fact]
-    public async Task ValidateAsync_ValidateContextAsync_AuthRequest_NotNull_AgeGreaterThanOneHour_Failure()
+    public async Task ValidateAsync_ValidateContextAsync_Unapproved_AuthRequest_Failure()
     {
         // Arrange
         var localFactory = new IdentityApplicationFactory();
         // Ensure User
-        await EnsureUserCreatedAsync(localFactory);
+        await RegisterUserAsync(localFactory);
         var userManager = localFactory.GetService<UserManager<User>>();
 
-        var user = await userManager.FindByEmailAsync(DefaultUsername);
+        var user = await userManager.FindByEmailAsync(_defaultUsername);
         Assert.NotNull(user);
 
+        // Ensure device is known b/c auth requests aren't allowed for unknown devices.
+        await AddKnownDevice(localFactory, user.Id);
+
         // Create AuthRequest
-        var authRequest = CreateAuthRequest(
-            user.Id,
-            AuthRequestType.AuthenticateAndUnlock,
-            DateTime.UtcNow.AddMinutes(-61)
-        );
+        var authRequest = CreateAuthRequest(r =>
+        {
+            r.ResponseDate = DateTime.UtcNow.AddMinutes(-2); // 2 minutes ago
+            r.Approved = false; // NOT approved
+            r.CreationDate = DateTime.UtcNow.AddMinutes(-5); // still valid
+            r.Type = AuthRequestType.AuthenticateAndUnlock; // authN request
+            r.AuthenticationDate = null; // not used for authN yet
+            r.UserId = user.Id;  // connect request to user
+            r.AccessCode = _defaultPassword; // matches the password
+        });
+
+        var authRequestRepository = localFactory.GetService<IAuthRequestRepository>();
+        await authRequestRepository.CreateAsync(authRequest);
+
+        var expectedAuthRequest = await authRequestRepository.GetManyByUserIdAsync(user.Id);
+        Assert.NotEmpty(expectedAuthRequest);
 
         // Act
         var context = await localFactory.Server.PostAsync("/connect/token",
@@ -167,22 +299,137 @@ public class ResourceOwnerPasswordValidatorTests : IClassFixture<IdentityApplica
                 { "scope", "api offline_access" },
                 { "client_id", "web" },
                 { "deviceType", DeviceTypeAsString(DeviceType.FirefoxBrowser) },
-                { "deviceIdentifier", DefaultDeviceIdentifier },
+                { "deviceIdentifier", _defaultDeviceIdentifier },
                 { "deviceName", "firefox" },
                 { "grant_type", "password" },
-                { "username", DefaultUsername },
-                { "password", DefaultPassword },
+                { "username", _defaultUsername },
+                { "password", _defaultPassword },
                 { "AuthRequest", authRequest.Id.ToString().ToLowerInvariant() }
             }));
 
         // Assert
 
-        /*
-        An improvement on the current failure flow would be to document which part of
-        the flow failed since all of the failures are basically the same.
-        This doesn't build confidence in the tests.
-        */
+        await AssertStandardError(context);
+    }
 
+    public static IEnumerable<object[]> InvalidAuthRequestTypes()
+    {
+        // yield the two enum values that should fail
+        yield return [AuthRequestType.Unlock];
+        yield return [AuthRequestType.AdminApproval];
+    }
+
+    [Theory]
+    [MemberData(nameof(InvalidAuthRequestTypes))]
+    public async Task ValidateAsync_ValidateContextAsync_AuthRequest_Invalid_Type_Failure(AuthRequestType invalidType)
+    {
+        // Arrange
+        var localFactory = new IdentityApplicationFactory();
+        // Ensure User
+        await RegisterUserAsync(localFactory);
+        var userManager = localFactory.GetService<UserManager<User>>();
+
+        var user = await userManager.FindByEmailAsync(_defaultUsername);
+        Assert.NotNull(user);
+
+        // Ensure device is known b/c auth requests aren't allowed for unknown devices.
+        await AddKnownDevice(localFactory, user.Id);
+
+        // Create AuthRequest
+        var authRequest = CreateAuthRequest(r =>
+        {
+            r.ResponseDate = DateTime.UtcNow.AddMinutes(-2); // 2 minutes ago
+            r.Approved = true; // approved
+            r.CreationDate = DateTime.UtcNow.AddMinutes(-5); // still valid
+            r.Type = invalidType; // invalid type for authN
+            r.AuthenticationDate = null; // not used for authN yet
+            r.UserId = user.Id;  // connect request to user
+            r.AccessCode = _defaultPassword; // matches the password
+        });
+
+        var authRequestRepository = localFactory.GetService<IAuthRequestRepository>();
+        await authRequestRepository.CreateAsync(authRequest);
+
+        var expectedAuthRequest = await authRequestRepository.GetManyByUserIdAsync(user.Id);
+        Assert.NotEmpty(expectedAuthRequest);
+
+        // Act
+        var context = await localFactory.Server.PostAsync("/connect/token",
+            new FormUrlEncodedContent(new Dictionary<string, string>
+            {
+                { "scope", "api offline_access" },
+                { "client_id", "web" },
+                { "deviceType", DeviceTypeAsString(DeviceType.FirefoxBrowser) },
+                { "deviceIdentifier", _defaultDeviceIdentifier },
+                { "deviceName", "firefox" },
+                { "grant_type", "password" },
+                { "username", _defaultUsername },
+                { "password", _defaultPassword },
+                { "AuthRequest", authRequest.Id.ToString().ToLowerInvariant() }
+            }));
+
+        // Assert
+
+        await AssertStandardError(context);
+    }
+
+    [Fact]
+    public async Task ValidateAsync_ValidateContextAsync_AuthRequest_WrongUser_Failure()
+    {
+        // Arrange
+        var localFactory = new IdentityApplicationFactory();
+
+        // Ensure User 1 exists
+        await RegisterUserAsync(localFactory);
+        var userManager = localFactory.GetService<UserManager<User>>();
+        var user = await userManager.FindByEmailAsync(_defaultUsername);
+        Assert.NotNull(user);
+
+
+
+        // Ensure User 2 exists so we can satisfy auth request foreign key constraint
+        var user2Username = "user2@email.com";
+        var user2Password = "user2_password";
+        await RegisterUserAsync(localFactory, user2Username, user2Password);
+        var user2 = await userManager.FindByEmailAsync(user2Username);
+        Assert.NotNull(user2);
+
+        // Ensure device is known b/c auth requests aren't allowed for unknown devices.
+        await AddKnownDevice(localFactory, user.Id);
+
+        // Create valid auth request for user 2
+        var authRequest = CreateAuthRequest(r =>
+        {
+            r.ResponseDate = DateTime.UtcNow.AddMinutes(-2); // 2 minutes ago
+            r.Approved = true; // approved
+            r.CreationDate = DateTime.UtcNow.AddMinutes(-5); // not expired
+            r.Type = AuthRequestType.AuthenticateAndUnlock; // authN request
+            r.AuthenticationDate = null; // not used for authN yet
+            r.UserId = user2.Id;  // connect request to user2
+            r.AccessCode = _defaultPassword; // matches the password
+        });
+        var authRequestRepository = localFactory.GetService<IAuthRequestRepository>();
+        await authRequestRepository.CreateAsync(authRequest);
+
+        var expectedAuthRequest = await authRequestRepository.GetManyByUserIdAsync(user2.Id);
+        Assert.NotEmpty(expectedAuthRequest);
+
+        // Act
+        var context = await localFactory.Server.PostAsync("/connect/token",
+            new FormUrlEncodedContent(new Dictionary<string, string>
+            {
+                { "scope", "api offline_access" },
+                { "client_id", "web" },
+                { "deviceType", DeviceTypeAsString(_defaultDeviceType) },
+                { "deviceIdentifier", _defaultDeviceIdentifier },
+                { "deviceName", _defaultDeviceName },
+                { "grant_type", "password" },
+                { "username", _defaultUsername },
+                { "password", _defaultPassword },
+                { "AuthRequest", authRequest.Id.ToString().ToLowerInvariant() }
+            }));
+
+        // Assert
         var body = await AssertHelper.AssertResponseTypeIs<JsonDocument>(context);
         var root = body.RootElement;
 
@@ -191,17 +438,180 @@ public class ResourceOwnerPasswordValidatorTests : IClassFixture<IdentityApplica
         Assert.Equal("Username or password is incorrect. Try again.", errorMessage);
     }
 
-    private async Task EnsureUserCreatedAsync(IdentityApplicationFactory factory)
+    [Fact]
+    public async Task ValidateAsync_ValidateContextAsync_Unanswered_AuthRequest_Failure()
+    {
+        // Arrange
+        var localFactory = new IdentityApplicationFactory();
+        // Ensure User
+        await RegisterUserAsync(localFactory);
+        var userManager = localFactory.GetService<UserManager<User>>();
+
+        var user = await userManager.FindByEmailAsync(_defaultUsername);
+        Assert.NotNull(user);
+
+        // Ensure device is known b/c auth requests aren't allowed for unknown devices.
+        await AddKnownDevice(localFactory, user.Id);
+
+        // Create AuthRequest
+        var authRequest = CreateAuthRequest(r =>
+        {
+            r.ResponseDate = null; // not answered
+            r.Approved = true; // approved
+            r.CreationDate = DateTime.UtcNow.AddMinutes(-5); // still valid
+            r.Type = AuthRequestType.AuthenticateAndUnlock; // authN request
+            r.AuthenticationDate = null; // not used for authN yet
+            r.UserId = user.Id;  // connect request to user
+            r.AccessCode = _defaultPassword; // matches the password
+        });
+
+        var authRequestRepository = localFactory.GetService<IAuthRequestRepository>();
+        await authRequestRepository.CreateAsync(authRequest);
+
+        var expectedAuthRequest = await authRequestRepository.GetManyByUserIdAsync(user.Id);
+        Assert.NotEmpty(expectedAuthRequest);
+
+        // Act
+        var context = await localFactory.Server.PostAsync("/connect/token",
+            new FormUrlEncodedContent(new Dictionary<string, string>
+            {
+                { "scope", "api offline_access" },
+                { "client_id", "web" },
+                { "deviceType", DeviceTypeAsString(DeviceType.FirefoxBrowser) },
+                { "deviceIdentifier", _defaultDeviceIdentifier },
+                { "deviceName", "firefox" },
+                { "grant_type", "password" },
+                { "username", _defaultUsername },
+                { "password", _defaultPassword },
+                { "AuthRequest", authRequest.Id.ToString().ToLowerInvariant() }
+            }));
+
+        // Assert
+
+        await AssertStandardError(context);
+    }
+
+    [Fact]
+    public async Task ValidateAsync_ValidateContextAsync_WrongPassword_AuthRequest_Failure()
+    {
+        // Arrange
+        var localFactory = new IdentityApplicationFactory();
+        // Ensure User
+        await RegisterUserAsync(localFactory);
+        var userManager = localFactory.GetService<UserManager<User>>();
+
+        var user = await userManager.FindByEmailAsync(_defaultUsername);
+        Assert.NotNull(user);
+
+        // Ensure device is known b/c auth requests aren't allowed for unknown devices.
+        await AddKnownDevice(localFactory, user.Id);
+
+        // Create AuthRequest
+        var authRequest = CreateAuthRequest(r =>
+        {
+            r.ResponseDate = DateTime.UtcNow.AddMinutes(-2); // answered
+            r.Approved = true; // approved
+            r.CreationDate = DateTime.UtcNow.AddMinutes(-5); // still valid
+            r.Type = AuthRequestType.AuthenticateAndUnlock; // authN request
+            r.AuthenticationDate = null; // not used for authN yet
+            r.UserId = user.Id;  // connect request to user
+            r.AccessCode = "WRONG_BAD_PASSWORD"; // does not match the password
+        });
+
+        var authRequestRepository = localFactory.GetService<IAuthRequestRepository>();
+        await authRequestRepository.CreateAsync(authRequest);
+
+        var expectedAuthRequest = await authRequestRepository.GetManyByUserIdAsync(user.Id);
+        Assert.NotEmpty(expectedAuthRequest);
+
+        // Act
+        var context = await localFactory.Server.PostAsync("/connect/token",
+            new FormUrlEncodedContent(new Dictionary<string, string>
+            {
+                { "scope", "api offline_access" },
+                { "client_id", "web" },
+                { "deviceType", DeviceTypeAsString(DeviceType.FirefoxBrowser) },
+                { "deviceIdentifier", _defaultDeviceIdentifier },
+                { "deviceName", "firefox" },
+                { "grant_type", "password" },
+                { "username", _defaultUsername },
+                { "password", _defaultPassword },
+                { "AuthRequest", authRequest.Id.ToString().ToLowerInvariant() }
+            }));
+
+        // Assert
+
+        await AssertStandardError(context);
+    }
+
+    [Fact]
+    public async Task ValidateAsync_ValidateContextAsync_Spent_AuthRequest_Failure()
+    {
+        // Arrange
+        var localFactory = new IdentityApplicationFactory();
+        // Ensure User
+        await RegisterUserAsync(localFactory);
+        var userManager = localFactory.GetService<UserManager<User>>();
+
+        var user = await userManager.FindByEmailAsync(_defaultUsername);
+        Assert.NotNull(user);
+
+        // Ensure device is known b/c auth requests aren't allowed for unknown devices.
+        await AddKnownDevice(localFactory, user.Id);
+
+        // Create AuthRequest
+        var authRequest = CreateAuthRequest(r =>
+        {
+            r.ResponseDate = DateTime.UtcNow.AddMinutes(-2); // answered
+            r.Approved = true; // approved
+            r.CreationDate = DateTime.UtcNow.AddMinutes(-5); // still valid
+            r.Type = AuthRequestType.AuthenticateAndUnlock; // authN request
+            r.AuthenticationDate = DateTime.UtcNow.AddMinutes(-2); // spent request - already has been used for authN
+            r.UserId = user.Id;  // connect request to user
+            r.AccessCode = _defaultPassword; // does not match the password
+        });
+
+        var authRequestRepository = localFactory.GetService<IAuthRequestRepository>();
+        await authRequestRepository.CreateAsync(authRequest);
+
+        var expectedAuthRequest = await authRequestRepository.GetManyByUserIdAsync(user.Id);
+        Assert.NotEmpty(expectedAuthRequest);
+
+        // Act
+        var context = await localFactory.Server.PostAsync("/connect/token",
+            new FormUrlEncodedContent(new Dictionary<string, string>
+            {
+                { "scope", "api offline_access" },
+                { "client_id", "web" },
+                { "deviceType", DeviceTypeAsString(DeviceType.FirefoxBrowser) },
+                { "deviceIdentifier", _defaultDeviceIdentifier },
+                { "deviceName", "firefox" },
+                { "grant_type", "password" },
+                { "username", _defaultUsername },
+                { "password", _defaultPassword },
+                { "AuthRequest", authRequest.Id.ToString().ToLowerInvariant() }
+            }));
+
+        // Assert
+        await AssertStandardError(context);
+    }
+
+
+
+    private async Task RegisterUserAsync(
+        IdentityApplicationFactory factory,
+        string username = _defaultUsername,
+        string password = _defaultPassword
+)
     {
-        // Register user
         await factory.RegisterNewIdentityFactoryUserAsync(
             new RegisterFinishRequestModel
             {
-                Email = DefaultUsername,
-                MasterPasswordHash = DefaultPassword,
+                Email = username,
+                MasterPasswordHash = password,
                 Kdf = KdfType.PBKDF2_SHA256,
                 KdfIterations = AuthConstants.PBKDF2_ITERATIONS.Default,
-                UserAsymmetricKeys = new KeysRequestModel()
+                UserAsymmetricKeys = new KeysRequestModel
                 {
                     PublicKey = "public_key",
                     EncryptedPrivateKey = "private_key"
@@ -218,11 +628,11 @@ public class ResourceOwnerPasswordValidatorTests : IClassFixture<IdentityApplica
             { "scope", "api offline_access" },
             { "client_id", "web" },
             { "deviceType", DeviceTypeAsString(DeviceType.FirefoxBrowser) },
-            { "deviceIdentifier", deviceId ?? DefaultDeviceIdentifier },
+            { "deviceIdentifier", deviceId ?? _defaultDeviceIdentifier },
             { "deviceName", "firefox" },
             { "grant_type", "password" },
-            { "username", username ?? DefaultUsername },
-            { "password", password ?? DefaultPassword },
+            { "username", username ?? _defaultUsername },
+            { "password", password ?? _defaultPassword },
         });
     }
 
@@ -233,8 +643,8 @@ public class ResourceOwnerPasswordValidatorTests : IClassFixture<IdentityApplica
             { "scope", "api offline_access" },
             { "client_id", "web" },
             { "grant_type", "password" },
-            { "username", DefaultUsername },
-            { "password", DefaultPassword },
+            { "username", _defaultUsername },
+            { "password", _defaultPassword },
         });
     }
 
@@ -243,24 +653,53 @@ public class ResourceOwnerPasswordValidatorTests : IClassFixture<IdentityApplica
         return ((int)deviceType).ToString();
     }
 
-    private static AuthRequest CreateAuthRequest(
-        Guid userId,
-        AuthRequestType authRequestType,
-        DateTime creationDate,
-        bool? approved = null,
-        DateTime? responseDate = null)
+
+    private AuthRequest CreateAuthRequest(Action<AuthRequest>? customize = null)
     {
-        return new AuthRequest
+        var req = new AuthRequest
         {
-            UserId = userId,
-            Type = authRequestType,
-            Approved = approved,
-            RequestDeviceIdentifier = DefaultDeviceIdentifier,
+            // required fields with defaults
+            UserId = Guid.NewGuid(),
+            Type = AuthRequestType.AuthenticateAndUnlock,
+            RequestDeviceIdentifier = _defaultDeviceIdentifier,
             RequestIpAddress = "1.1.1.1",
-            AccessCode = DefaultPassword,
+            AccessCode = _defaultPassword,
             PublicKey = "test_public_key",
-            CreationDate = creationDate,
-            ResponseDate = responseDate,
+            CreationDate = DateTime.UtcNow,
         };
+
+        // let the caller tweak whatever they need
+        customize?.Invoke(req);
+
+        return req;
+    }
+
+    private async Task AddKnownDevice(IdentityApplicationFactory factory, Guid userId)
+    {
+        var userDevice = new Device
+        {
+            Identifier = _defaultDeviceIdentifier,
+            Type = _defaultDeviceType,
+            Name = _defaultDeviceName,
+            UserId = userId,
+        };
+        var deviceRepository = factory.GetService<IDeviceRepository>();
+        await deviceRepository.CreateAsync(userDevice);
+    }
+
+    private async Task AssertStandardError(HttpContext context)
+    {
+        /*
+       An improvement on the current failure flow would be to document which part of
+       the flow failed since all of the failures are basically the same.
+       This doesn't build confidence in the tests.
+       */
+
+        var body = await AssertHelper.AssertResponseTypeIs<JsonDocument>(context);
+        var root = body.RootElement;
+
+        var errorModel = AssertHelper.AssertJsonProperty(root, "ErrorModel", JsonValueKind.Object);
+        var errorMessage = AssertHelper.AssertJsonProperty(errorModel, "Message", JsonValueKind.String).GetString();
+        Assert.Equal("Username or password is incorrect. Try again.", errorMessage);
     }
 }
diff --git a/test/Identity.Test/IdentityServer/DeviceValidatorTests.cs b/test/Identity.Test/IdentityServer/DeviceValidatorTests.cs
index 9058d26cf1..681b8c3a2f 100644
--- a/test/Identity.Test/IdentityServer/DeviceValidatorTests.cs
+++ b/test/Identity.Test/IdentityServer/DeviceValidatorTests.cs
@@ -325,12 +325,11 @@ public class DeviceValidatorTests
     }
 
     [Theory, BitAutoData]
-    public async void ValidateRequestDeviceAsync_IsAuthRequest_SavesDevice_ReturnsTrue(
+    public async void ValidateRequestDeviceAsync_IsAuthRequest_UnknownDevice_Errors(
         CustomValidatorRequestContext context,
         [AuthFixtures.ValidatedTokenRequest] ValidatedTokenRequest request)
     {
         // Arrange
-        context.KnownDevice = false;
         ArrangeForHandleNewDeviceVerificationTest(context, request);
         AddValidDeviceToRequest(request);
         _deviceRepository.GetByIdentifierAsync(context.Device.Identifier, context.User.Id)
@@ -342,8 +341,11 @@ public class DeviceValidatorTests
         var result = await _sut.ValidateRequestDeviceAsync(request, context);
 
         // Assert
-        await _deviceService.Received(1).SaveAsync(context.Device);
-        Assert.True(result);
+        Assert.False(result);
+        Assert.NotNull(context.CustomResponse["ErrorModel"]);
+        var expectedErrorMessage = "auth request flow unsupported on unknown device";
+        var actualResponse = (ErrorResponseModel)context.CustomResponse["ErrorModel"];
+        Assert.Equal(expectedErrorMessage, actualResponse.Message);
     }
 
     [Theory, BitAutoData]