diff --git a/src/Gameboard.Api/Data/Entities/ChallengeSpec.cs b/src/Gameboard.Api/Data/Entities/ChallengeSpec.cs
index eb1614e3..ccae60a0 100644
--- a/src/Gameboard.Api/Data/Entities/ChallengeSpec.cs
+++ b/src/Gameboard.Api/Data/Entities/ChallengeSpec.cs
@@ -28,8 +28,8 @@ public class ChallengeSpec : IEntity
         // nav properties
         public string GameId { get; set; }
         public Game Game { get; set; }
-        public ICollection<Feedback> Feedback { get; set; } = new List<Feedback>();
+        public ICollection<Feedback> Feedback { get; set; } = [];
         public ICollection<FeedbackSubmissionChallengeSpec> FeedbackSubmissions { get; set; } = [];
-        public ICollection<ChallengeBonus> Bonuses { get; set; } = new List<ChallengeBonus>();
-        public ICollection<PublishedPracticeCertificate> PublishedPracticeCertificates { get; set; } = new List<PublishedPracticeCertificate>();
+        public ICollection<ChallengeBonus> Bonuses { get; set; } = [];
+        public ICollection<PublishedPracticeCertificate> PublishedPracticeCertificates { get; set; } = [];
 }
diff --git a/src/Gameboard.Api/Data/Entities/FeedbackSubmission.cs b/src/Gameboard.Api/Data/Entities/FeedbackSubmission.cs
index 73aabe07..e113f73d 100644
--- a/src/Gameboard.Api/Data/Entities/FeedbackSubmission.cs
+++ b/src/Gameboard.Api/Data/Entities/FeedbackSubmission.cs
@@ -10,10 +10,10 @@ public enum FeedbackSubmissionAttachedEntityType
     Game = 1
 }
 
-public abstract class FeedbackSubmission : IEntity
+public class FeedbackSubmission : IEntity
 {
     public string Id { get; set; }
-    public required FeedbackSubmissionAttachedEntityType AttachedEntityType { get; set; }
+    public FeedbackSubmissionAttachedEntityType AttachedEntityType { get; set; }
     public DateTimeOffset? WhenEdited { get; set; }
     public required DateTimeOffset WhenSubmitted { get; set; }
 
@@ -23,19 +23,19 @@ public abstract class FeedbackSubmission : IEntity
     // navs
     public required string TeamId { get; set; }
     public required string FeedbackTemplateId { get; set; }
-    public required FeedbackTemplate FeedbackTemplate { get; set; }
+    public FeedbackTemplate FeedbackTemplate { get; set; }
     public required string UserId { get; set; }
-    public required Data.User User { get; set; }
+    public Data.User User { get; set; }
 }
 
 public class FeedbackSubmissionChallengeSpec : FeedbackSubmission, IEntity
 {
     public required string ChallengeSpecId { get; set; }
-    public required Data.ChallengeSpec ChallengeSpec { get; set; }
+    public Data.ChallengeSpec ChallengeSpec { get; set; }
 }
 
 public class FeedbackSubmissionGame : FeedbackSubmission, IEntity
 {
     public required string GameId { get; set; }
-    public required Data.Game Game { get; set; }
+    public Data.Game Game { get; set; }
 }
diff --git a/src/Gameboard.Api/Features/Feedback/Feedback.cs b/src/Gameboard.Api/Features/Feedback/Feedback.cs
index 2feca039..25940900 100644
--- a/src/Gameboard.Api/Features/Feedback/Feedback.cs
+++ b/src/Gameboard.Api/Features/Feedback/Feedback.cs
@@ -7,7 +7,7 @@
 
 namespace Gameboard.Api.Features.Feedback;
 
-public class FeedbackSubmission
+public class FeedbackSubmissionLegacy
 {
     // UserId and PlayerId are set automatically when saved
     public string ChallengeId { get; set; }
diff --git a/src/Gameboard.Api/Features/Feedback/FeedbackController.cs b/src/Gameboard.Api/Features/Feedback/FeedbackController.cs
index 86285358..e0aec4d0 100644
--- a/src/Gameboard.Api/Features/Feedback/FeedbackController.cs
+++ b/src/Gameboard.Api/Features/Feedback/FeedbackController.cs
@@ -62,7 +62,7 @@ public async Task<Feedback> Retrieve([FromQuery] FeedbackSearchParams model)
     /// <param name="model"></param>
     /// <returns></returns>
     [HttpPut("submit")]
-    public async Task<Feedback> Submit([FromBody] FeedbackSubmission model)
+    public async Task<Feedback> Submit([FromBody] FeedbackSubmissionLegacy model)
     {
         await Authorize(FeedbackService.UserIsEnrolled(model.GameId, Actor.Id));
         await Validate(model);
@@ -109,4 +109,17 @@ public Task<FeedbackTemplateView> GetTemplateForGameOrChallengeSpec([FromRoute]
     [HttpGet("template")]
     public Task<ListFeedbackTemplatesResponse> ListTemplates()
         => _mediator.Send(new ListFeedbackTemplatesQuery());
+
+    /// <summary>
+    /// Create a new feedback response.
+    /// </summary>
+    /// <param name="request"></param>
+    /// <returns></returns>
+    [HttpPost()]
+    public Task<UpsertFeedbackSubmissionResponse> ResponseCreate([FromBody] UpsertFeedbackSubmissionRequest request)
+    {
+        var modelState = ModelState;
+        var things = modelState.ErrorCount;
+        return _mediator.Send(new UpsertFeedbackSubmissionCommand(request));
+    }
 }
diff --git a/src/Gameboard.Api/Features/Feedback/FeedbackMapper.cs b/src/Gameboard.Api/Features/Feedback/FeedbackMapper.cs
index c094a308..a34aa27c 100644
--- a/src/Gameboard.Api/Features/Feedback/FeedbackMapper.cs
+++ b/src/Gameboard.Api/Features/Feedback/FeedbackMapper.cs
@@ -22,7 +22,7 @@ public FeedbackMapper()
 
             CreateMap<Feedback, Data.Feedback>();
 
-            CreateMap<FeedbackSubmission, Data.Feedback>()
+            CreateMap<FeedbackSubmissionLegacy, Data.Feedback>()
                 .ForMember(d => d.Submitted, opt => opt.MapFrom(s => s.Submit))
                 .ForMember(d => d.Answers, opt => opt.MapFrom(s =>
                     JsonSerializer.Serialize(s.Questions, JsonOptions))
diff --git a/src/Gameboard.Api/Features/Feedback/FeedbackService.cs b/src/Gameboard.Api/Features/Feedback/FeedbackService.cs
index 0decc3a6..626ab91d 100644
--- a/src/Gameboard.Api/Features/Feedback/FeedbackService.cs
+++ b/src/Gameboard.Api/Features/Feedback/FeedbackService.cs
@@ -10,6 +10,7 @@
 using Gameboard.Api.Data;
 using Gameboard.Api.Features.Feedback;
 using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Internal;
 using Microsoft.Extensions.Caching.Memory;
 using Microsoft.Extensions.Logging;
 
@@ -92,6 +93,31 @@ public IEnumerable<QuestionStats> GetFeedbackQuestionStats(QuestionTemplate[] qu
             return questionStats;
         }
 
+        public async Task<FeedbackTemplate> ResolveTemplate(FeedbackSubmissionAttachedEntityType type, string id, CancellationToken cancellationToken)
+        {
+            var gameId = id;
+            if (type == FeedbackSubmissionAttachedEntityType.ChallengeSpec)
+            {
+                gameId = await _store
+                    .WithNoTracking<Data.ChallengeSpec>()
+                    .Where(s => s.Id == id)
+                    .Select(s => s.GameId)
+                    .SingleAsync(cancellationToken);
+            }
+
+            var gameTemplates = await _store
+                .WithNoTracking<Data.Game>()
+                .Where(g => g.Id == gameId)
+                .Select(g => new
+                {
+                    Game = g.FeedbackTemplate,
+                    Challenges = g.ChallengesFeedbackTemplate
+                })
+                .SingleAsync(cancellationToken);
+
+            return type == FeedbackSubmissionAttachedEntityType.Game ? gameTemplates.Game : gameTemplates.Challenges;
+        }
+
         public async Task<Features.Feedback.Feedback> Retrieve(FeedbackSearchParams model, string actorId)
         {
             // for normal challenge and game feedback, we can just do simple lookups on the provided IDs.
@@ -132,8 +158,12 @@ public IEnumerable<QuestionStats> GetFeedbackQuestionStats(QuestionTemplate[] qu
             return Mapper.Map<Features.Feedback.Feedback>(entity);
         }
 
+        public async Task<FeedbackSubmission> ResolveExistingSubmission(string userId, string teamId, FeedbackSubmissionAttachedEntityType entityType, string entityId)
+        {
+
+        }
 
-        public async Task<Features.Feedback.Feedback> Submit(Features.Feedback.FeedbackSubmission model, string actorId)
+        public async Task<Features.Feedback.Feedback> Submit(FeedbackSubmissionLegacy model, string actorId)
         {
             var lookup = MakeFeedbackLookup(model.GameId, model.ChallengeId, model.ChallengeSpecId, actorId);
             var entity = await LoadFeedback(lookup);
diff --git a/src/Gameboard.Api/Features/Feedback/FeedbackValidator.cs b/src/Gameboard.Api/Features/Feedback/FeedbackValidator.cs
index 7b8a22cf..3cb5b468 100644
--- a/src/Gameboard.Api/Features/Feedback/FeedbackValidator.cs
+++ b/src/Gameboard.Api/Features/Feedback/FeedbackValidator.cs
@@ -14,13 +14,13 @@ public class FeedbackValidator(IStore store) : IModelValidator
 
         public Task Validate(object model)
         {
-            if (model is Features.Feedback.FeedbackSubmission)
-                return _validate(model as Features.Feedback.FeedbackSubmission);
+            if (model is Features.Feedback.FeedbackSubmissionLegacy)
+                return _validate(model as Features.Feedback.FeedbackSubmissionLegacy);
 
             throw new System.NotImplementedException();
         }
 
-        private async Task _validate(Features.Feedback.FeedbackSubmission model)
+        private async Task _validate(Features.Feedback.FeedbackSubmissionLegacy model)
         {
             if (!await _store.AnyAsync<Data.Game>(g => g.Id == model.GameId, CancellationToken.None))
                 throw new ResourceNotFound<Data.Game>(model.GameId);
diff --git a/src/Gameboard.Api/Features/Feedback/Requests/UpsertFeedbackSubmission/UpsertFeedbackSubmission.cs b/src/Gameboard.Api/Features/Feedback/Requests/UpsertFeedbackSubmission/UpsertFeedbackSubmission.cs
new file mode 100644
index 00000000..b1c87e86
--- /dev/null
+++ b/src/Gameboard.Api/Features/Feedback/Requests/UpsertFeedbackSubmission/UpsertFeedbackSubmission.cs
@@ -0,0 +1,153 @@
+using System;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Gameboard.Api.Common.Services;
+using Gameboard.Api.Data;
+using Gameboard.Api.Features.Teams;
+using Gameboard.Api.Services;
+using Gameboard.Api.Structure.MediatR;
+using MediatR;
+using Microsoft.EntityFrameworkCore;
+
+namespace Gameboard.Api.Features.Feedback;
+
+public record UpsertFeedbackSubmissionCommand(UpsertFeedbackSubmissionRequest Request) : IRequest<UpsertFeedbackSubmissionResponse>;
+
+// TODO: refactor this into separate commands for game/challenge that share an injected validator
+internal sealed class UpsertFeedbackSubmissionHandler
+(
+    IActingUserService actingUserService,
+    FeedbackService feedbackService,
+    INowService now,
+    IStore store,
+    ITeamService teamService,
+    IValidatorService validatorService
+) : IRequestHandler<UpsertFeedbackSubmissionCommand, UpsertFeedbackSubmissionResponse>
+{
+    private readonly IActingUserService _actingUserService = actingUserService;
+    private readonly FeedbackService _feedbackService = feedbackService;
+    private readonly INowService _nowService = now;
+    private readonly IStore _store = store;
+    private readonly ITeamService _teamService = teamService;
+    private readonly IValidatorService _validator = validatorService;
+
+    public async Task<UpsertFeedbackSubmissionResponse> Handle(UpsertFeedbackSubmissionCommand request, CancellationToken cancellationToken)
+    {
+        var actingUserId = _actingUserService.Get()?.Id;
+
+        _validator
+            .Auth(c => c.RequireAuthentication())
+            .AddValidator(ctx =>
+            {
+                if (request.Request.AttachedEntity.EntityType != FeedbackSubmissionAttachedEntityType.ChallengeSpec && request.Request.AttachedEntity.EntityType != FeedbackSubmissionAttachedEntityType.Game)
+                {
+                    ctx.AddValidationException(new InvalidParameterValue<FeedbackSubmissionAttachedEntityType>(nameof(request.Request.AttachedEntity.EntityType), "Must be either game or challengespec", request.Request.AttachedEntity.EntityType));
+                }
+            })
+            .AddValidator(async ctx =>
+            {
+                if (!await _teamService.IsOnTeam(request.Request.AttachedEntity.TeamId, _actingUserService.Get().Id))
+                {
+                    ctx.AddValidationException(new UserIsntOnTeam(actingUserId, request.Request.AttachedEntity.TeamId, $"User isn't on the expected team."));
+                }
+            })
+            .AddValidator(async ctx =>
+            {
+                var template = await _feedbackService.ResolveTemplate(request.Request.AttachedEntity.EntityType, request.Request.AttachedEntity.Id, cancellationToken);
+
+                if (template is null || template.Id != request.Request.FeedbackTemplateId)
+                {
+                    ctx.AddValidationException(new InvalidFeedbackTemplateId(request.Request.FeedbackTemplateId, request.Request.AttachedEntity.EntityType, request.Request.AttachedEntity.Id));
+                }
+
+            })
+            .AddEntityExistsValidator<FeedbackTemplate>(request.Request.FeedbackTemplateId);
+
+        if (request.Request.AttachedEntity.EntityType == FeedbackSubmissionAttachedEntityType.ChallengeSpec)
+        {
+            _validator.AddEntityExistsValidator<Data.ChallengeSpec>(request.Request.AttachedEntity.Id);
+
+            if (request.Request.Id.IsNotEmpty())
+            {
+                _validator.AddEntityExistsValidator<FeedbackSubmissionChallengeSpec>(request.Request.Id);
+            }
+        }
+        else
+        {
+            _validator.AddEntityExistsValidator<Data.Game>(request.Request.AttachedEntity.Id);
+
+            if (request.Request.Id.IsNotEmpty())
+            {
+                _validator.AddEntityExistsValidator<FeedbackSubmissionGame>(request.Request.Id);
+            }
+        }
+
+        await _validator.Validate(cancellationToken);
+
+        // if updating, update
+        if (request.Request.Id.IsNotEmpty())
+        {
+            if (request.Request.AttachedEntity.EntityType == FeedbackSubmissionAttachedEntityType.ChallengeSpec)
+            {
+                var existingSubmission = await _store
+                    .WithNoTracking<FeedbackSubmissionChallengeSpec>()
+                    .Where(s => s.Id == request.Request.Id)
+                    .SingleAsync(cancellationToken);
+
+                existingSubmission.WhenEdited = _nowService.Get();
+                existingSubmission.Responses = [.. request.Request.Responses];
+                await _store.SaveUpdate(existingSubmission, cancellationToken);
+                return new UpsertFeedbackSubmissionResponse { Submission = existingSubmission };
+            }
+            else if (request.Request.AttachedEntity.EntityType == FeedbackSubmissionAttachedEntityType.Game)
+            {
+                var existingSubmission = await _store
+                    .WithNoTracking<FeedbackSubmissionGame>()
+                    .Where(s => s.Id == request.Request.Id)
+                    .SingleAsync(cancellationToken);
+
+                existingSubmission.WhenEdited = _nowService.Get();
+                existingSubmission.Responses = [.. request.Request.Responses];
+                await _store.SaveUpdate(existingSubmission, cancellationToken);
+                return new UpsertFeedbackSubmissionResponse { Submission = existingSubmission };
+            }
+        }
+        else
+        {
+            // if creating, create
+            if (request.Request.AttachedEntity.EntityType == FeedbackSubmissionAttachedEntityType.ChallengeSpec)
+            {
+                var result = await _store
+                    .Create<FeedbackSubmissionChallengeSpec>(new()
+                    {
+                        ChallengeSpecId = request.Request.AttachedEntity.Id,
+                        FeedbackTemplateId = request.Request.FeedbackTemplateId,
+                        Responses = [.. request.Request.Responses],
+                        TeamId = request.Request.AttachedEntity.TeamId,
+                        UserId = actingUserId,
+                        WhenSubmitted = _nowService.Get(),
+                    }, cancellationToken);
+
+                return new UpsertFeedbackSubmissionResponse { Submission = result };
+            }
+            else
+            {
+                var result = await _store
+                    .Create<FeedbackSubmissionGame>(new()
+                    {
+                        GameId = request.Request.AttachedEntity.Id,
+                        FeedbackTemplateId = request.Request.FeedbackTemplateId,
+                        Responses = [.. request.Request.Responses],
+                        TeamId = request.Request.AttachedEntity.TeamId,
+                        UserId = actingUserId,
+                        WhenSubmitted = _nowService.Get(),
+                    }, cancellationToken);
+
+                return new UpsertFeedbackSubmissionResponse { Submission = result };
+            }
+        }
+
+        throw new NotImplementedException();
+    }
+}
diff --git a/src/Gameboard.Api/Features/Feedback/Requests/UpsertFeedbackSubmission/UpsertFeedbackSubmissionModels.cs b/src/Gameboard.Api/Features/Feedback/Requests/UpsertFeedbackSubmission/UpsertFeedbackSubmissionModels.cs
new file mode 100644
index 00000000..29969dc7
--- /dev/null
+++ b/src/Gameboard.Api/Features/Feedback/Requests/UpsertFeedbackSubmission/UpsertFeedbackSubmissionModels.cs
@@ -0,0 +1,34 @@
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Text.Json.Serialization;
+using Gameboard.Api.Data;
+using Gameboard.Api.Structure;
+
+namespace Gameboard.Api.Features.Feedback;
+
+public sealed class InvalidFeedbackTemplateId : GameboardValidationException
+{
+    public InvalidFeedbackTemplateId(string id, FeedbackSubmissionAttachedEntityType type, string entityId)
+        : base($"The template id {id} was not valid for {type} {entityId}") { }
+}
+
+public sealed class UpsertFeedbackSubmissionRequest
+{
+    public string Id { get; set; }
+    public required UpsertFeedbackSubmissionRequestAttachedEntity AttachedEntity { get; set; }
+    public required string FeedbackTemplateId { get; set; }
+    public IEnumerable<QuestionSubmission> Responses { get; set; }
+}
+
+public sealed class UpsertFeedbackSubmissionRequestAttachedEntity
+{
+    public required string Id { get; set; }
+    // [TypeConverter(typeof(JsonStringEnumConverter<FeedbackSubmissionAttachedEntityType>))]
+    public required FeedbackSubmissionAttachedEntityType EntityType { get; set; }
+    public required string TeamId { get; set; }
+}
+
+public sealed class UpsertFeedbackSubmissionResponse
+{
+    public required FeedbackSubmission Submission { get; set; }
+}
diff --git a/src/Gameboard.Api/Structure/MediatR/Validators/ValidatorService.cs b/src/Gameboard.Api/Structure/MediatR/Validators/ValidatorService.cs
index 15c55f10..c0ee83c8 100644
--- a/src/Gameboard.Api/Structure/MediatR/Validators/ValidatorService.cs
+++ b/src/Gameboard.Api/Structure/MediatR/Validators/ValidatorService.cs
@@ -4,12 +4,15 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Gameboard.Api.Common.Services;
+using Gameboard.Api.Data;
 using Gameboard.Api.Structure.MediatR.Validators;
+using Microsoft.EntityFrameworkCore;
 
 namespace Gameboard.Api.Structure.MediatR;
 
 public interface IValidatorService
 {
+    IValidatorService AddEntityExistsValidator<TEntity>(string id) where TEntity : class, IEntity;
     IValidatorService AddValidator(IGameboardValidator validator);
     IValidatorService AddValidator(Action<RequestValidationContext> validationAction);
     IValidatorService AddValidator(Func<RequestValidationContext, Task> validationTask);
@@ -19,12 +22,36 @@ public interface IValidatorService
     Task Validate(CancellationToken cancellationToken);
 }
 
-internal class ValidatorService(IActingUserService actingUserService, UserRolePermissionsValidator userRolePermissionsValidator) : IValidatorService
+internal class ValidatorService
+(
+    IActingUserService actingUserService,
+    IStore store,
+    UserRolePermissionsValidator userRolePermissionsValidator
+) : IValidatorService
 {
     private readonly IActingUserService _actingUserService = actingUserService;
     private readonly IList<Func<RequestValidationContext, Task>> _validationTasks = [];
+    private readonly IStore _store = store;
     private readonly UserRolePermissionsValidator _userRolePermissionsValidator = userRolePermissionsValidator;
 
+    public IValidatorService AddEntityExistsValidator<TEntity>(string id) where TEntity : class, IEntity
+    {
+        _validationTasks.Add(async ctx =>
+        {
+            var exists = await _store
+                .WithNoTracking<TEntity>()
+                .Where(e => e.Id == id)
+                .AnyAsync();
+
+            if (!exists)
+            {
+                ctx.AddValidationException(new ResourceNotFound<TEntity>(id));
+            }
+        });
+
+        return this;
+    }
+
     public IValidatorService AddValidator(IGameboardValidator validator)
     {
         _validationTasks.Add(validator.GetValidationTask(default));