diff --git a/src/Tgstation.Server.Api/Models/ErrorCode.cs b/src/Tgstation.Server.Api/Models/ErrorCode.cs
index b3b6167889..ecb96a8c53 100644
--- a/src/Tgstation.Server.Api/Models/ErrorCode.cs
+++ b/src/Tgstation.Server.Api/Models/ErrorCode.cs
@@ -234,7 +234,7 @@ namespace Tgstation.Server.Api.Models
 		/// <summary>
 		/// <see cref="Repository.NewTestMerges"/> contained duplicate <see cref="TestMergeParameters.Number"/>s.
 		/// </summary>
-		[Description("The same pull request was present more than once in the test merge requests!")]
+		[Description("The same pull request was present more than once in the test merge requests or is already merged!")]
 		RepoDuplicateTestMerge,
 
 		/// <summary>
@@ -303,5 +303,161 @@ namespace Tgstation.Server.Api.Models
 		/// </summary>
 		[Description("Set amount of chatChannels exceeds the configured channelLimit!")]
 		ChatBotMaxChannels,
+
+		/// <summary>
+		/// Failed to install DirectX with BYOND.
+		/// </summary>
+		[Description("Unable to start DirectX installer process! Is the server running with admin privileges?")]
+		ByondDirectXInstallFail,
+
+		/// <summary>
+		/// Failed to download a given BYOND version.
+		/// </summary>
+		[Description("Error downloading specified BYOND version!")]
+		ByondDownloadFail,
+
+		/// <summary>
+		/// Failed to lock BYOND executables.
+		/// </summary>
+		[Description("Could not acquire lock on BYOND installation as none exist!")]
+		ByondNoVersionsInstalled,
+
+		/// <summary>
+		/// The DMAPI never validated itself
+		/// </summary>
+		[Description("DreamDaemon exited without validating the DMAPI@")]
+		DreamMakerNeverValidated,
+
+		/// <summary>
+		/// The DMAPI sent an invalid validation request.
+		/// </summary>
+		[Description("The DMAPI sent an invalid validation request!")]
+		DreamMakerInvalidValidation,
+
+		/// <summary>
+		/// DMAPI validation timeout.
+		/// </summary>
+		[Description("The DreamDaemon startup timeout was hit before the DMAPI validated!")]
+		DreamMakerValidationTimeout,
+
+		/// <summary>
+		/// No .dme could be found for deployment.
+		/// </summary>
+		[Description("No .dme configured and could not automatically detect one!")]
+		DreamMakerNoDme,
+
+		/// <summary>
+		/// The configured .dme could not be found.
+		/// </summary>
+		[Description("Could not load configured .dme!")]
+		DreamMakerMissingDme,
+
+		/// <summary>
+		/// DreamMaker failed to compile.
+		/// </summary>
+		[Description("DreamMaker exited with a non-zero exit code!")]
+		DreamMakerExitCode,
+
+		/// <summary>
+		/// Deployment already in progress
+		/// </summary>
+		[Description("There is already a deployment operation in progress!")]
+		DreamMakerCompileJobInProgress,
+
+		/// <summary>
+		/// Missing <see cref="DreamDaemon"/> settings in database.
+		/// </summary>
+		[Description("Could not retrieve DreamDaemon settings from the database!")]
+		InstanceMissingDreamDaemonSettings,
+
+		/// <summary>
+		/// Missing <see cref="DreamMaker"/> settings in database.
+		/// </summary>
+		[Description("Could not retrieve DreamMaker settings from the database!")]
+		InstanceMissingDreamMakerSettings,
+
+		/// <summary>
+		/// Missing <see cref="Repository"/> settings in database.
+		/// </summary>
+		[Description("Could not retrieve Repository settings from the database!")]
+		InstanceMissingRepositorySettings,
+
+		/// <summary>
+		/// Performing an automatic update with the <see cref="Internal.RepositorySettings.AutoUpdatesKeepTestMerges"/> flag resulted in merge conflicts.
+		/// </summary>
+		[Description("Performing this automatic update as a merge would result in conficts. Aborting!")]
+		InstanceUpdateTestMergeConflict,
+
+		/// <summary>
+		/// <see cref="Internal.RepositorySettings.AccessUser"/> and <see cref="Internal.RepositorySettings.AccessToken"/> are required for this operation.
+		/// </summary>
+		[Description("Git credentials are required for this operation!")]
+		RepoCredentialsRequired,
+
+		/// <summary>
+		/// The remote returned an invalid authentication request.
+		/// </summary>
+		[Description("The remote is requesting authentication, but is not allowing credentials to be received!")]
+		RepoCannotAuthenticate,
+
+		/// <summary>
+		/// Cannot perform operation while not on a <see cref="Repository.Reference"/>.
+		/// </summary>
+		[Description("This git operation requires the repository HEAD to currently be on a tracked reference!")]
+		RepoReferenceRequired,
+
+		/// <summary>
+		/// Attempted to start the watchdog when it was already running.
+		/// </summary>
+		[Description("The watchdog is already running!")]
+		WatchdogRunning,
+
+		/// <summary>
+		/// Attempted to start the watchdog with a corrupted <see cref="CompileJob"/>.
+		/// </summary>
+		[Description("Cannot launch with active compile job as it is corrupted!")]
+		WatchdogCompileJobCorrupted,
+
+		/// <summary>
+		/// DreamDaemon exited before it finished starting.
+		/// </summary>
+		[Description("DreamDaemon failed to start!")]
+		WatchdogStartupFailed,
+
+		/// <summary>
+		/// DreamDaemon timed-out before it finished starting.
+		/// </summary>
+		[Description("DreamDaemon failed to start within the configured timeout!")]
+		WatchdogStartupTimeout,
+
+		/// <summary>
+		/// Attempted to test merge with an unsupported remote.
+		/// </summary>
+		[Description("Test merging with the current remote is not supported!")]
+		RepoUnsupportedTestMergeRemote,
+
+		/// <summary>
+		/// Either <see cref="Repository.CheckoutSha"/> or <see cref="Repository.Reference"/> was in one when it should have been the other.
+		/// </summary>
+		[Description("The value set for checkoutSha or reference should be in the other field!")]
+		RepoSwappedShaOrReference,
+
+		/// <summary>
+		/// A merge conflict occurred during a git operation.
+		/// </summary>
+		[Description("A merge conflict occurred while performing the operation!")]
+		RepoMergeConflict,
+
+		/// <summary>
+		/// The current <see cref="Repository.Reference"/> does not track a remote reference.
+		/// </summary>
+		[Description("The repository's current reference is unsuitable for this operation as it does not track a remote reference!")]
+		RepoReferenceNotTracking,
+
+		/// <summary>
+		/// Encounted merge conflicts while test merging.
+		/// </summary>
+		[Description("Encountered merge conflicts while test merging one or more pull requests!")]
+		RepoTestMergeConflict,
 	}
 }
\ No newline at end of file
diff --git a/src/Tgstation.Server.Api/Models/Internal/Job.cs b/src/Tgstation.Server.Api/Models/Internal/Job.cs
index 945d0d6aaa..3e5656e56e 100644
--- a/src/Tgstation.Server.Api/Models/Internal/Job.cs
+++ b/src/Tgstation.Server.Api/Models/Internal/Job.cs
@@ -15,6 +15,11 @@ namespace Tgstation.Server.Api.Models.Internal
 		[Required]
 		public string Description { get; set; }
 
+		/// <summary>
+		/// The <see cref="Models.ErrorCode"/> associated with the <see cref="Job"/> if any.
+		/// </summary>
+		public ErrorCode? ErrorCode { get; set; }
+
 		/// <summary>
 		/// Details of any exceptions caught during the <see cref="Job"/>
 		/// </summary>
diff --git a/src/Tgstation.Server.Host/Components/Byond/ByondManager.cs b/src/Tgstation.Server.Host/Components/Byond/ByondManager.cs
index 38c57a09d0..1af10cf0e2 100644
--- a/src/Tgstation.Server.Host/Components/Byond/ByondManager.cs
+++ b/src/Tgstation.Server.Host/Components/Byond/ByondManager.cs
@@ -1,13 +1,13 @@
 using Microsoft.Extensions.Logging;
 using System;
 using System.Collections.Generic;
-using System.Globalization;
 using System.Linq;
 using System.Net;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 using Tgstation.Server.Api;
+using Tgstation.Server.Api.Models;
 using Tgstation.Server.Host.Core;
 using Tgstation.Server.Host.IO;
 using Tgstation.Server.Host.Jobs;
@@ -162,7 +162,7 @@ namespace Tgstation.Server.Host.Components.Byond
 				catch (WebException e)
 				{
 					// since the user can easily provide non-exitent version numbers, we'll turn this into a JobException
-					throw new JobException(String.Format(CultureInfo.InvariantCulture, "Error downloading BYOND version: {0}", e.Message));
+					throw new JobException(ErrorCode.ByondDownloadFail, e);
 				}
 				catch (OperationCanceledException)
 				{
@@ -207,7 +207,7 @@ namespace Tgstation.Server.Host.Components.Byond
 		{
 			var versionToUse = requiredVersion ?? ActiveVersion;
 			if (versionToUse == null)
-				throw new JobException("No BYOND versions installed!");
+				throw new JobException(ErrorCode.ByondNoVersionsInstalled);
 			await InstallVersion(versionToUse, cancellationToken).ConfigureAwait(false);
 
 			var versionKey = VersionKey(versionToUse);
diff --git a/src/Tgstation.Server.Host/Components/Byond/WindowsByondInstaller.cs b/src/Tgstation.Server.Host/Components/Byond/WindowsByondInstaller.cs
index 7f26bfac61..a2ea8589dc 100644
--- a/src/Tgstation.Server.Host/Components/Byond/WindowsByondInstaller.cs
+++ b/src/Tgstation.Server.Host/Components/Byond/WindowsByondInstaller.cs
@@ -1,9 +1,9 @@
 using Microsoft.Extensions.Logging;
 using System;
-using System.Globalization;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
+using Tgstation.Server.Api.Models;
 using Tgstation.Server.Host.Core;
 using Tgstation.Server.Host.IO;
 using Tgstation.Server.Host.Jobs;
@@ -114,7 +114,7 @@ namespace Tgstation.Server.Host.Components.Byond
 						}
 						catch (Exception e)
 						{
-							throw new JobException("Unable to start DirectX installer process! Is the server running with admin privileges?", e);
+							throw new JobException(ErrorCode.ByondDirectXInstallFail, e);
 						}
 
 						using (directXInstaller)
@@ -125,7 +125,7 @@ namespace Tgstation.Server.Host.Components.Byond
 							cancellationToken.ThrowIfCancellationRequested();
 
 							if (exitCode != 0)
-								throw new JobException(String.Format(CultureInfo.InvariantCulture, "Failed to install included DirectX! Exit code: {0}", exitCode));
+								throw new JobException(ErrorCode.ByondDirectXInstallFail, new JobException($"Invalid exit code: {exitCode}"));
 							installedDirectX = true;
 						}
 					}
diff --git a/src/Tgstation.Server.Host/Components/Deployment/DreamMaker.cs b/src/Tgstation.Server.Host/Components/Deployment/DreamMaker.cs
index ae05724d6b..0a7a26153a 100644
--- a/src/Tgstation.Server.Host/Components/Deployment/DreamMaker.cs
+++ b/src/Tgstation.Server.Host/Components/Deployment/DreamMaker.cs
@@ -193,34 +193,31 @@ namespace Tgstation.Server.Host.Components.Deployment
 				{
 					var validationStatus = controller.ApiValidationStatus;
 					logger.LogTrace("API validation status: {0}", validationStatus);
+
+					job.DMApiVersion = controller.DMApiVersion;
 					switch (validationStatus)
 					{
 						case ApiValidationStatus.RequiresUltrasafe:
 							job.MinimumSecurityLevel = DreamDaemonSecurity.Ultrasafe;
 							return;
 						case ApiValidationStatus.RequiresSafe:
-							if (securityLevel == DreamDaemonSecurity.Ultrasafe)
-								throw new JobException("This game must be run with at least the 'Safe' DreamDaemon security level!");
 							job.MinimumSecurityLevel = DreamDaemonSecurity.Safe;
 							return;
 						case ApiValidationStatus.RequiresTrusted:
-							if (securityLevel != DreamDaemonSecurity.Trusted)
-								throw new JobException("This game must be run with at least the 'Trusted' DreamDaemon security level!");
 							job.MinimumSecurityLevel = DreamDaemonSecurity.Trusted;
 							return;
 						case ApiValidationStatus.NeverValidated:
-							break;
+							throw new JobException(ErrorCode.DreamMakerNeverValidated);
 						case ApiValidationStatus.BadValidationRequest:
-							throw new JobException("Recieved an unrecognized API validation request from DreamDaemon!");
+							throw new JobException(ErrorCode.DreamMakerInvalidValidation);
 						case ApiValidationStatus.UnaskedValidationRequest:
 						default:
-							throw new InvalidOperationException(String.Format(CultureInfo.InvariantCulture, "Session controller returned unexpected ApiValidationStatus: {0}", validationStatus));
+							throw new InvalidOperationException(
+								$"Session controller returned unexpected ApiValidationStatus: {validationStatus}");
 					}
-
-					job.DMApiVersion = controller.DMApiVersion;
 				}
 
-				throw new JobException("DMAPI validation timed out! Is the security level too high?");
+				throw new JobException(ErrorCode.DreamMakerValidationTimeout);
 			}
 		}
 
@@ -395,7 +392,7 @@ namespace Tgstation.Server.Host.Components.Deployment
 					var foundPaths = await ioManager.GetFilesWithExtension(dirA, DmeExtension, cancellationToken).ConfigureAwait(false);
 					var foundPath = foundPaths.FirstOrDefault();
 					if (foundPath == default)
-						throw new JobException("Unable to find any .dme!");
+						throw new JobException(ErrorCode.DreamMakerNoDme);
 					var dmeWithExtension = ioManager.GetFileName(foundPath);
 					job.DmeName = dmeWithExtension.Substring(0, dmeWithExtension.Length - DmeExtension.Length - 1);
 				}
@@ -404,7 +401,7 @@ namespace Tgstation.Server.Host.Components.Deployment
 					var targetDme = ioManager.ConcatPath(dirA, String.Join('.', job.DmeName, DmeExtension));
 					var targetDmeExists = await ioManager.FileExists(targetDme, cancellationToken).ConfigureAwait(false);
 					if (!targetDmeExists)
-						throw new JobException("Unable to locate specified .dme!");
+						throw new JobException(ErrorCode.DreamMakerMissingDme);
 				}
 
 				logger.LogDebug("Selected {0}.dme for compilation!", job.DmeName);
@@ -418,7 +415,9 @@ namespace Tgstation.Server.Host.Components.Deployment
 				try
 				{
 					if (exitCode != 0)
-						throw new JobException(String.Format(CultureInfo.InvariantCulture, "DM exited with a non-zero code: {0}{1}{2}", exitCode, Environment.NewLine, job.Output));
+						throw new JobException(
+							ErrorCode.DreamMakerExitCode,
+							new JobException($"Exit code: {exitCode}{Environment.NewLine}{Environment.NewLine}{job.Output}"));
 
 					await VerifyApi(apiValidateTimeout, dreamMakerSettings.ApiValidationSecurityLevel.Value, job, byondLock, dreamMakerSettings.ApiValidationPort.Value, cancellationToken).ConfigureAwait(false);
 				}
@@ -476,7 +475,7 @@ namespace Tgstation.Server.Host.Components.Deployment
 			lock (this)
 			{
 				if (compiling)
-					throw new JobException("There is already a compile job in progress!");
+					throw new JobException(ErrorCode.DreamMakerCompileJobInProgress);
 				compiling = true;
 			}
 
diff --git a/src/Tgstation.Server.Host/Components/Instance.cs b/src/Tgstation.Server.Host/Components/Instance.cs
index 6dba85ae04..34d582a381 100644
--- a/src/Tgstation.Server.Host/Components/Instance.cs
+++ b/src/Tgstation.Server.Host/Components/Instance.cs
@@ -169,13 +169,13 @@ namespace Tgstation.Server.Host.Components
 				throw new ArgumentNullException(nameof(progressReporter));
 
 			var ddSettings = await databaseContext.DreamDaemonSettings.Where(x => x.InstanceId == metadata.Id).Select(x => new DreamDaemonSettings
-				{
-					StartupTimeout = x.StartupTimeout,
-				})
+			{
+				StartupTimeout = x.StartupTimeout,
+			})
 				.FirstOrDefaultAsync(cancellationToken)
 				.ConfigureAwait(false);
 			if (ddSettings == default)
-				throw new JobException("Missing DreamDaemonSettings in DB!");
+				throw new JobException(Api.Models.ErrorCode.InstanceMissingDreamDaemonSettings);
 
 			var previousCompileJobs = await databaseContext.CompileJobs
 				.Where(x => x.Job.Instance.Id == metadata.Id)
@@ -191,18 +191,17 @@ namespace Tgstation.Server.Host.Components
 
 			var dreamMakerSettings = await databaseContext.DreamMakerSettings.Where(x => x.InstanceId == metadata.Id).FirstAsync(cancellationToken).ConfigureAwait(false);
 			if (dreamMakerSettings == default)
-				throw new JobException("Missing DreamMakerSettings in DB!");
+				throw new JobException(Api.Models.ErrorCode.InstanceMissingDreamMakerSettings);
 
 			RepositorySettings repositorySettings = null;
 			string repoOwner = null;
 			string repoName = null;
 			CompileJob compileJob;
 			RevisionInformation revInfo;
-			bool loadedRepositorySettings;
 			using (var repo = await RepositoryManager.LoadRepository(cancellationToken).ConfigureAwait(false))
 			{
 				if (repo == null)
-					throw new JobException("Missing Repository!");
+					throw new JobException(Api.Models.ErrorCode.RepoMissing);
 
 				if (repo.IsGitHubRepository)
 				{
@@ -219,10 +218,9 @@ namespace Tgstation.Server.Host.Components
 						})
 						.FirstOrDefaultAsync(cancellationToken)
 						.ConfigureAwait(false);
-					loadedRepositorySettings = true;
+					if (repositorySettings == default)
+						throw new JobException(Api.Models.ErrorCode.InstanceMissingRepositorySettings);
 				}
-				else
-					loadedRepositorySettings = false;
 
 				var repoSha = repo.Head;
 				revInfo = await databaseContext.RevisionInformations.Where(x => x.CommitSha == repoSha && x.Instance.Id == metadata.Id).Include(x => x.ActiveTestMerges).ThenInclude(x => x.TestMerge).ThenInclude(x => x.MergedBy).FirstOrDefaultAsync().ConfigureAwait(false);
@@ -243,7 +241,7 @@ namespace Tgstation.Server.Host.Components
 				}
 
 				TimeSpan? averageSpan = null;
-				if(previousCompileJobs.Count != 0)
+				if (previousCompileJobs.Count != 0)
 				{
 					var totalSpan = TimeSpan.Zero;
 					foreach (var I in previousCompileJobs)
@@ -260,80 +258,74 @@ namespace Tgstation.Server.Host.Components
 
 			job.PostComplete = ct => compileJobConsumer.LoadCompileJob(compileJob, ct);
 
-			if (loadedRepositorySettings)
+			if (repositorySettings?.AccessToken != null)
 			{
-				if (repositorySettings == default)
-					throw new JobException("Missing repository settings!");
+				// potential for commenting on a test merge change
+				var outgoingCompileJob = LatestCompileJob();
 
-				if (repositorySettings.AccessToken != null)
+				if (outgoingCompileJob != null && outgoingCompileJob.RevisionInformation.CommitSha != compileJob.RevisionInformation.CommitSha && repositorySettings.PostTestMergeComment.Value)
 				{
-					// potential for commenting on a test merge change
-					var outgoingCompileJob = LatestCompileJob();
+					var gitHubClient = gitHubClientFactory.CreateClient(repositorySettings.AccessToken);
 
-					if(outgoingCompileJob != null && outgoingCompileJob.RevisionInformation.CommitSha != compileJob.RevisionInformation.CommitSha && repositorySettings.PostTestMergeComment.Value)
+					async Task CommentOnPR(int prNumber, string comment)
 					{
-						var gitHubClient = gitHubClientFactory.CreateClient(repositorySettings.AccessToken);
-
-						async Task CommentOnPR(int prNumber, string comment)
+						try
 						{
-							try
-							{
-								await gitHubClient.Issue.Comment.Create(repoOwner, repoName, prNumber, comment).ConfigureAwait(false);
-							}
-							catch (ApiException e)
-							{
-								logger.LogWarning("Error posting GitHub comment! Exception: {0}", e);
-							}
+							await gitHubClient.Issue.Comment.Create(repoOwner, repoName, prNumber, comment).ConfigureAwait(false);
+						}
+						catch (ApiException e)
+						{
+							logger.LogWarning("Error posting GitHub comment! Exception: {0}", e);
 						}
-
-						var tasks = new List<Task>();
-
-						string FormatTestMerge(TestMerge testMerge, bool updated) => String.Format(CultureInfo.InvariantCulture, "#### Test Merge {4}{0}{0}##### Server Instance{0}{5}{1}{0}{0}##### Revision{0}Origin: {6}{0}Pull Request: {2}{0}Server: {7}{3}",
-							Environment.NewLine,
-							repositorySettings.ShowTestMergeCommitters.Value ? String.Format(CultureInfo.InvariantCulture, "{0}{0}##### Merged By{0}{1}", Environment.NewLine, testMerge.MergedBy.Name) : String.Empty,
-							testMerge.PullRequestRevision,
-							testMerge.Comment != null ? String.Format(CultureInfo.InvariantCulture, "{0}{0}##### Comment{0}{1}", Environment.NewLine, testMerge.Comment) : String.Empty,
-							updated ? "Updated" : "Deployed",
-							metadata.Name,
-							compileJob.RevisionInformation.OriginCommitSha,
-							compileJob.RevisionInformation.CommitSha);
-
-						// added prs
-						foreach (var I in compileJob
-							.RevisionInformation
-							.ActiveTestMerges
-							.Select(x => x.TestMerge)
-							.Where(x => !outgoingCompileJob
-								.RevisionInformation
-								.ActiveTestMerges
-								.Any(y => y.TestMerge.Number == x.Number)))
-							tasks.Add(CommentOnPR(I.Number, FormatTestMerge(I, false)));
-
-						// removed prs
-						foreach (var I in outgoingCompileJob
-							.RevisionInformation
-							.ActiveTestMerges
-							.Select(x => x.TestMerge)
-								.Where(x => !compileJob
-								.RevisionInformation
-								.ActiveTestMerges
-								.Any(y => y.TestMerge.Number == x.Number)))
-							tasks.Add(CommentOnPR(I.Number, "#### Test Merge Removed"));
-
-						// updated prs
-						foreach(var I in compileJob
-							.RevisionInformation
-							.ActiveTestMerges
-							.Select(x => x.TestMerge)
-							.Where(x => outgoingCompileJob
-								.RevisionInformation
-								.ActiveTestMerges
-								.Any(y => y.TestMerge.Number == x.Number)))
-							tasks.Add(CommentOnPR(I.Number, FormatTestMerge(I, true)));
-
-						if (tasks.Any())
-							await Task.WhenAll(tasks).ConfigureAwait(false);
 					}
+
+					var tasks = new List<Task>();
+
+					string FormatTestMerge(TestMerge testMerge, bool updated) => String.Format(CultureInfo.InvariantCulture, "#### Test Merge {4}{0}{0}##### Server Instance{0}{5}{1}{0}{0}##### Revision{0}Origin: {6}{0}Pull Request: {2}{0}Server: {7}{3}",
+						Environment.NewLine,
+						repositorySettings.ShowTestMergeCommitters.Value ? String.Format(CultureInfo.InvariantCulture, "{0}{0}##### Merged By{0}{1}", Environment.NewLine, testMerge.MergedBy.Name) : String.Empty,
+						testMerge.PullRequestRevision,
+						testMerge.Comment != null ? String.Format(CultureInfo.InvariantCulture, "{0}{0}##### Comment{0}{1}", Environment.NewLine, testMerge.Comment) : String.Empty,
+						updated ? "Updated" : "Deployed",
+						metadata.Name,
+						compileJob.RevisionInformation.OriginCommitSha,
+						compileJob.RevisionInformation.CommitSha);
+
+					// added prs
+					foreach (var I in compileJob
+						.RevisionInformation
+						.ActiveTestMerges
+						.Select(x => x.TestMerge)
+						.Where(x => !outgoingCompileJob
+							.RevisionInformation
+							.ActiveTestMerges
+							.Any(y => y.TestMerge.Number == x.Number)))
+						tasks.Add(CommentOnPR(I.Number, FormatTestMerge(I, false)));
+
+					// removed prs
+					foreach (var I in outgoingCompileJob
+						.RevisionInformation
+						.ActiveTestMerges
+						.Select(x => x.TestMerge)
+							.Where(x => !compileJob
+							.RevisionInformation
+							.ActiveTestMerges
+							.Any(y => y.TestMerge.Number == x.Number)))
+						tasks.Add(CommentOnPR(I.Number, "#### Test Merge Removed"));
+
+					// updated prs
+					foreach (var I in compileJob
+						.RevisionInformation
+						.ActiveTestMerges
+						.Select(x => x.TestMerge)
+						.Where(x => outgoingCompileJob
+							.RevisionInformation
+							.ActiveTestMerges
+							.Any(y => y.TestMerge.Number == x.Number)))
+						tasks.Add(CommentOnPR(I.Number, FormatTestMerge(I, true)));
+
+					if (tasks.Any())
+						await Task.WhenAll(tasks).ConfigureAwait(false);
 				}
 			}
 		}
@@ -464,7 +456,7 @@ namespace Tgstation.Server.Host.Components
 									var result = await repo.MergeOrigin(repositorySettings.CommitterName, repositorySettings.CommitterEmail, NextProgressReporter(), jobCancellationToken).ConfigureAwait(false);
 
 									if (!result.HasValue)
-										throw new JobException("Merge conflict while preserving test merges!");
+										throw new JobException(Api.Models.ErrorCode.InstanceUpdateTestMergeConflict);
 
 									currentRevInfo = await currentRevInfoTask.ConfigureAwait(false);
 
diff --git a/src/Tgstation.Server.Host/Components/Repository/LibGit2RepositoryFactory.cs b/src/Tgstation.Server.Host/Components/Repository/LibGit2RepositoryFactory.cs
index 3d4663dde3..69059f93cc 100644
--- a/src/Tgstation.Server.Host/Components/Repository/LibGit2RepositoryFactory.cs
+++ b/src/Tgstation.Server.Host/Components/Repository/LibGit2RepositoryFactory.cs
@@ -4,6 +4,7 @@ using Microsoft.Extensions.Logging;
 using System;
 using System.Threading;
 using System.Threading.Tasks;
+using Tgstation.Server.Api.Models;
 using Tgstation.Server.Host.Jobs;
 
 namespace Tgstation.Server.Host.Components.Repository
@@ -93,9 +94,9 @@ namespace Tgstation.Server.Host.Components.Repository
 				return new DefaultCredentials();
 
 			if (supportsUserPass)
-				throw new JobException("Remote does not support anonymous authentication!");
+				throw new JobException(ErrorCode.RepoCredentialsRequired);
 
-			throw new JobException("Server does not support anonymous or username/password authentication!");
+			throw new JobException(ErrorCode.RepoCannotAuthenticate);
 		};
 	}
 }
diff --git a/src/Tgstation.Server.Host/Components/Repository/Repository.cs b/src/Tgstation.Server.Host/Components/Repository/Repository.cs
index 6a1c0abf2d..947e82cb77 100644
--- a/src/Tgstation.Server.Host/Components/Repository/Repository.cs
+++ b/src/Tgstation.Server.Host/Components/Repository/Repository.cs
@@ -465,7 +465,7 @@ namespace Tgstation.Server.Host.Components.Repository
 			if (progressReporter == null)
 				throw new ArgumentNullException(nameof(progressReporter));
 			if (!Tracking)
-				throw new JobException("Cannot reset to origin while not on a tracked reference!");
+				throw new JobException(ErrorCode.RepoReferenceRequired);
 			logger.LogTrace("Reset to origin...");
 			var trackedBranch = libGitRepo.Head.TrackedBranch;
 			await eventConsumer.HandleEvent(EventType.RepoResetOrigin, new List<string> { trackedBranch.FriendlyName, trackedBranch.Tip.Sha }, cancellationToken).ConfigureAwait(false);
@@ -521,7 +521,7 @@ namespace Tgstation.Server.Host.Components.Repository
 			await Task.Factory.StartNew(() =>
 			{
 				if (!Tracking)
-					throw new JobException("Cannot reset to origin while not on a tracked reference!");
+					throw new JobException(ErrorCode.RepoReferenceRequired);
 
 				libGitRepo.RemoveUntrackedFiles();
 
diff --git a/src/Tgstation.Server.Host/Components/Watchdog/ExperimentalWatchdog.cs b/src/Tgstation.Server.Host/Components/Watchdog/ExperimentalWatchdog.cs
index d83712d943..333582ed73 100644
--- a/src/Tgstation.Server.Host/Components/Watchdog/ExperimentalWatchdog.cs
+++ b/src/Tgstation.Server.Host/Components/Watchdog/ExperimentalWatchdog.cs
@@ -185,7 +185,7 @@ namespace Tgstation.Server.Host.Components.Watchdog
 						var dmbBackup = await DmbFactory.FromCompileJob(monitorState.ActiveServer.Dmb.CompileJob, cancellationToken).ConfigureAwait(false);
 
 						if (dmbBackup == null) // NANI!?
-							throw new JobException("Creating backup DMB provider failed!"); // just give up, if THAT compile job is failing then the ActiveServer is gonna crash soon too or already has
+							throw new InvalidOperationException("Watchdog double crit-fail!"); // just give up, if THAT compile job is failing then the ActiveServer is gonna crash soon too or already has
 
 						monitorState.InactiveServer = await SessionControllerFactory.LaunchNew(
 							dmbBackup,
diff --git a/src/Tgstation.Server.Host/Components/Watchdog/WatchdogBase.cs b/src/Tgstation.Server.Host/Components/Watchdog/WatchdogBase.cs
index 2b61522029..b3877611ec 100644
--- a/src/Tgstation.Server.Host/Components/Watchdog/WatchdogBase.cs
+++ b/src/Tgstation.Server.Host/Components/Watchdog/WatchdogBase.cs
@@ -4,10 +4,10 @@ using Microsoft.Extensions.Logging;
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Globalization;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
+using Tgstation.Server.Api.Models;
 using Tgstation.Server.Api.Models.Internal;
 using Tgstation.Server.Api.Rights;
 using Tgstation.Server.Host.Components.Chat;
@@ -253,10 +253,10 @@ namespace Tgstation.Server.Host.Components.Watchdog
 			Logger.LogTrace("Begin LaunchNoLock");
 
 			if (Running)
-				throw new JobException("Watchdog already running!");
+				throw new JobException(ErrorCode.WatchdogRunning);
 
 			if (!DmbFactory.DmbAvailable)
-				throw new JobException("Corrupted compilation, please redeploy!");
+				throw new JobException(ErrorCode.WatchdogCompileJobCorrupted);
 
 			// this is necessary, the monitor could be in it's sleep loop trying to restart, if so cancel THAT monitor and start our own with blackjack and hookers
 			Task chatTask;
@@ -371,9 +371,13 @@ namespace Tgstation.Server.Host.Components.Watchdog
 
 			// Dead sessions won't trigger this
 			if (launchResult.ExitCode.HasValue) // you killed us ray...
-				throw new JobException(String.Format(CultureInfo.InvariantCulture, "{0} failed to start: {1}", serverName, launchResult));
+				throw new JobException(
+					ErrorCode.WatchdogStartupFailed,
+					new JobException($"{serverName} failed to start: {launchResult}"));
 			if (!launchResult.StartupTime.HasValue)
-				throw new JobException(String.Format(CultureInfo.InvariantCulture, "{0} timed out on startup: {1}s", serverName, ActiveLaunchParameters.StartupTimeout.Value));
+				throw new JobException(
+					ErrorCode.WatchdogStartupTimeout,
+					new JobException($"{serverName} timed out on startup: {ActiveLaunchParameters.StartupTimeout.Value}s"));
 		}
 
 		/// <summary>
diff --git a/src/Tgstation.Server.Host/Controllers/RepositoryController.cs b/src/Tgstation.Server.Host/Controllers/RepositoryController.cs
index f2006ed345..3e9fa3fedc 100644
--- a/src/Tgstation.Server.Host/Controllers/RepositoryController.cs
+++ b/src/Tgstation.Server.Host/Controllers/RepositoryController.cs
@@ -198,7 +198,7 @@ namespace Tgstation.Server.Host.Controllers
 					using (var repos = await repoManager.CloneRepository(new Uri(origin), cloneBranch, currentModel.AccessUser, currentModel.AccessToken, progressReporter, ct).ConfigureAwait(false))
 					{
 						if (repos == null)
-							throw new JobException("Filesystem conflict while cloning repository!");
+							throw new JobException(ErrorCode.RepoExists);
 						var instance = new Models.Instance
 						{
 							Id = Instance.Id
@@ -447,7 +447,7 @@ namespace Tgstation.Server.Host.Controllers
 				using (var repo = await repoManager.LoadRepository(ct).ConfigureAwait(false))
 				{
 					if (repo == null)
-						throw new JobException("Repository could not be loaded!");
+						throw new JobException(ErrorCode.RepoMissing);
 
 					var modelHasShaOrReference = model.CheckoutSha != null || model.Reference != null;
 
@@ -456,7 +456,7 @@ namespace Tgstation.Server.Host.Controllers
 					string postUpdateSha = null;
 
 					if (newTestMerges && !repo.IsGitHubRepository)
-						throw new JobException("Cannot test merge on a non GitHub based repository!");
+						throw new JobException(ErrorCode.RepoUnsupportedTestMergeRemote);
 
 					var committerName = currentModel.ShowTestMergeCommitters.Value
 						? AuthenticationContext.User.Name
@@ -501,14 +501,14 @@ namespace Tgstation.Server.Host.Controllers
 						if (model.UpdateFromOrigin == true)
 						{
 							if (!repo.Tracking)
-								throw new JobException("Not on an updatable reference!");
+								throw new JobException(ErrorCode.RepoReferenceRequired);
 							await repo.FetchOrigin(currentModel.AccessUser, currentModel.AccessToken, NextProgressReporter(), ct).ConfigureAwait(false);
 							doneSteps = 1;
 							if (!modelHasShaOrReference)
 							{
 								var fastForward = await repo.MergeOrigin(committerName, currentModel.CommitterEmail, NextProgressReporter(), ct).ConfigureAwait(false);
 								if (!fastForward.HasValue)
-									throw new JobException("Merge conflict occurred during origin update!");
+									throw new JobException(ErrorCode.RepoMergeConflict);
 								await UpdateRevInfo().ConfigureAwait(false);
 								if (fastForward.Value)
 								{
@@ -531,7 +531,7 @@ namespace Tgstation.Server.Host.Controllers
 								var isSha = await repo.IsSha(committish, cancellationToken).ConfigureAwait(false);
 
 								if ((isSha && model.Reference != null) || (!isSha && model.CheckoutSha != null))
-									throw new JobException("Attempted to checkout a SHA or reference that was actually the opposite!");
+									throw new JobException(ErrorCode.RepoSwappedShaOrReference);
 
 								await repo.CheckoutObject(committish, NextProgressReporter(), ct).ConfigureAwait(false);
 								await LoadRevisionInformation(repo, databaseContext, attachedInstance, null, x => lastRevisionInfo = x, ct).ConfigureAwait(false); // we've either seen origin before or what we're checking out is on origin
@@ -542,7 +542,7 @@ namespace Tgstation.Server.Host.Controllers
 							if (hardResettingToOriginReference)
 							{
 								if (!repo.Tracking)
-									throw new JobException("Checked out reference does not track a remote object!");
+									throw new JobException(ErrorCode.RepoReferenceNotTracking);
 								await repo.ResetToOrigin(NextProgressReporter(), ct).ConfigureAwait(false);
 								await repo.Sychronize(currentModel.AccessUser, currentModel.AccessToken, currentModel.CommitterName, currentModel.CommitterEmail, NextProgressReporter(), true, ct).ConfigureAwait(false);
 								await LoadRevisionInformation(repo, databaseContext, attachedInstance, null, x => lastRevisionInfo = x, ct).ConfigureAwait(false);
@@ -692,29 +692,36 @@ namespace Tgstation.Server.Host.Controllers
 									string errorMessage = null;
 
 									if (lastRevisionInfo.ActiveTestMerges.Any(x => x.TestMerge.Number == I.Number))
-										throw new JobException("Cannot test merge the same PR twice in one HEAD!");
+										throw new JobException(ErrorCode.RepoDuplicateTestMerge);
 
+									Exception exception = null;
 									try
 									{
 										// load from cache if possible
 										if (prMap == null || !prMap.TryGetValue(I.Number, out pr))
 											pr = await gitHubClient.PullRequest.Get(repoOwner, repoName, I.Number).ConfigureAwait(false);
 									}
-									catch (Octokit.RateLimitExceededException)
+									catch (Octokit.RateLimitExceededException ex)
 									{
 										// you look at your anonymous access and sigh
-										errorMessage = "P.R.E. RATE LIMITED";
+										errorMessage = "REMOTE API ERROR: RATE LIMITED";
+										exception = ex;
 									}
-									catch (Octokit.AuthorizationException)
+									catch (Octokit.AuthorizationException ex)
 									{
-										errorMessage = "P.R.E. BAD CREDENTIALS";
+										errorMessage = "REMOTE API ERROR: BAD CREDENTIALS";
+										exception = ex;
 									}
-									catch (Octokit.NotFoundException)
+									catch (Octokit.NotFoundException ex)
 									{
 										// you look at your shithub and sigh
-										errorMessage = "P.R.E. NOT FOUND";
+										errorMessage = "REMOTE API ERROR: PULL REQUEST NOT FOUND";
+										exception = ex;
 									}
 
+									if (exception != null)
+										Logger.LogWarning("Error retrieving pull request metadata: {0}", exception);
+
 									// we want to take the earliest truth possible to prevent RCEs, if this fails AddTestMerge will set it
 									if (I.PullRequestRevision == null && pr != null)
 										I.PullRequestRevision = pr.Head.Sha;
@@ -729,7 +736,10 @@ namespace Tgstation.Server.Host.Controllers
 										ct).ConfigureAwait(false);
 
 									if (!mergeResult.HasValue)
-										throw new JobException(String.Format(CultureInfo.InvariantCulture, "Merge of PR #{0} at {1} conflicted!", I.Number, I.PullRequestRevision.Substring(0, 7)));
+										throw new JobException(
+											ErrorCode.RepoTestMergeConflict,
+											new JobException(
+												$"Merge of PR #{I.Number} at {I.PullRequestRevision.Substring(0, 7)} conflicted!"));
 
 									++doneSteps;
 
diff --git a/src/Tgstation.Server.Host/Jobs/JobException.cs b/src/Tgstation.Server.Host/Jobs/JobException.cs
index 40469a0e59..55f2bb97d5 100644
--- a/src/Tgstation.Server.Host/Jobs/JobException.cs
+++ b/src/Tgstation.Server.Host/Jobs/JobException.cs
@@ -1,4 +1,5 @@
 using System;
+using Tgstation.Server.Api.Models;
 
 namespace Tgstation.Server.Host.Jobs
 {
@@ -7,6 +8,11 @@ namespace Tgstation.Server.Host.Jobs
 	/// </summary>
 	public sealed class JobException : Exception
 	{
+		/// <summary>
+		/// The <see cref="Api.Models.ErrorCode"/> associated with the <see cref="JobException"/>.
+		/// </summary>
+		public ErrorCode? ErrorCode { get; set; }
+
 		/// <summary>
 		/// Construct a <see cref="JobException"/>
 		/// </summary>
@@ -30,5 +36,22 @@ namespace Tgstation.Server.Host.Jobs
 		public JobException(string message, Exception innerException) : base(message, innerException)
 		{
 		}
+
+		/// <summary>
+		/// Construct a <see cref="JobException"/> with a <paramref name="errorCode"/>.
+		/// </summary>
+		/// <param name="errorCode">The associated <see cref="Api.Models.ErrorCode"/>.</param>
+		public JobException(ErrorCode errorCode) : base(errorCode.Describe())
+		{
+		}
+
+		/// <summary>
+		/// Construct a <see cref="JobException"/> with a <paramref name="errorCode"/> and <paramref name="innerException"/>.
+		/// </summary>
+		/// <param name="errorCode">The associated <see cref="Api.Models.ErrorCode"/>.</param>
+		/// <param name="innerException">The inner <see cref="Exception"/> for the nase <see cref="Exception"/></param>
+		public JobException(ErrorCode errorCode, Exception innerException) : base(errorCode.Describe(), innerException)
+		{
+		}
 	}
 }
diff --git a/src/Tgstation.Server.Host/Jobs/JobManager.cs b/src/Tgstation.Server.Host/Jobs/JobManager.cs
index 677cb36238..055748b4a0 100644
--- a/src/Tgstation.Server.Host/Jobs/JobManager.cs
+++ b/src/Tgstation.Server.Host/Jobs/JobManager.cs
@@ -89,10 +89,16 @@ namespace Tgstation.Server.Host.Jobs
 						}
 						catch (JobException e)
 						{
+							job.ErrorCode = e.ErrorCode;
 							job.ExceptionDetails = e.Message;
 							LogRegularException();
 							if (e.InnerException != null)
-								logger.LogDebug("Inner exception for job {0}: {1}", job.Id, e.InnerException);
+								logger.LogDebug(
+									"Inner exception for job {0}: {1}",
+									job.Id,
+									e.InnerException is JobException
+										? e.InnerException.Message
+										: e.InnerException.ToString());
 						}
 						catch (Exception e)
 						{