diff --git a/src/SIL.Machine.AspNetCore/Models/Corpus.cs b/src/SIL.Machine.AspNetCore/Models/Corpus.cs
index 84dda461f..c33bc52ce 100644
--- a/src/SIL.Machine.AspNetCore/Models/Corpus.cs
+++ b/src/SIL.Machine.AspNetCore/Models/Corpus.cs
@@ -5,7 +5,9 @@ public class Corpus
     public string Id { get; set; } = default!;
     public string SourceLanguage { get; set; } = default!;
     public string TargetLanguage { get; set; } = default!;
+    public bool TrainOnAll { get; set; }
     public bool PretranslateAll { get; set; }
+    public HashSet<string> TrainOnTextIds { get; set; } = default!;
     public HashSet<string> PretranslateTextIds { get; set; } = default!;
     public List<CorpusFile> SourceFiles { get; set; } = default!;
     public List<CorpusFile> TargetFiles { get; set; } = default!;
diff --git a/src/SIL.Machine.AspNetCore/Services/NmtPreprocessBuildJob.cs b/src/SIL.Machine.AspNetCore/Services/NmtPreprocessBuildJob.cs
index e1202dec8..3fbc41ee0 100644
--- a/src/SIL.Machine.AspNetCore/Services/NmtPreprocessBuildJob.cs
+++ b/src/SIL.Machine.AspNetCore/Services/NmtPreprocessBuildJob.cs
@@ -76,8 +76,11 @@ async IAsyncEnumerable<Pretranslation> ProcessRowsAsync()
 
                 foreach (ParallelTextRow row in parallelCorpus)
                 {
-                    await sourceTrainWriter.WriteAsync($"{row.SourceText}\n");
-                    await targetTrainWriter.WriteAsync($"{row.TargetText}\n");
+                    if (corpus.TrainOnAll || corpus.TrainOnTextIds.Contains(row.TextId))
+                    {
+                        await sourceTrainWriter.WriteAsync($"{row.SourceText}\n");
+                        await targetTrainWriter.WriteAsync($"{row.TargetText}\n");
+                    }
                     if (
                         (corpus.PretranslateAll || corpus.PretranslateTextIds.Contains(row.TextId))
                         && row.SourceSegment.Count > 0
diff --git a/src/SIL.Machine.AspNetCore/Services/S3WriteStream.cs b/src/SIL.Machine.AspNetCore/Services/S3WriteStream.cs
index fc2173053..35329ffc0 100644
--- a/src/SIL.Machine.AspNetCore/Services/S3WriteStream.cs
+++ b/src/SIL.Machine.AspNetCore/Services/S3WriteStream.cs
@@ -55,37 +55,40 @@ public override void Flush() { }
 
     public override async Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
     {
-        try
+        if (count > 0)
         {
-            using MemoryStream ms = new(buffer, offset, count);
-            int partNumber = _uploadResponses.Count + 1;
-            UploadPartRequest request =
-                new()
-                {
-                    BucketName = _bucketName,
-                    Key = _key,
-                    UploadId = _uploadId,
-                    PartNumber = partNumber,
-                    InputStream = ms,
-                    PartSize = MaxPartSize
-                };
-            request.StreamTransferProgress += new EventHandler<StreamTransferProgressArgs>(
-                (_, e) =>
-                {
-                    _logger.LogDebug($"Transferred {e.TransferredBytes}/{e.TotalBytes}");
-                }
-            );
-            UploadPartResponse response = await _client.UploadPartAsync(request);
-            if (response.HttpStatusCode != HttpStatusCode.OK)
-                throw new HttpRequestException(
-                    $"Tried to upload part {partNumber} of upload {_uploadId} to {_bucketName}/{_key} but received response code {response.HttpStatusCode}"
+            try
+            {
+                using MemoryStream ms = new(buffer, offset, count);
+                int partNumber = _uploadResponses.Count + 1;
+                UploadPartRequest request =
+                    new()
+                    {
+                        BucketName = _bucketName,
+                        Key = _key,
+                        UploadId = _uploadId,
+                        PartNumber = partNumber,
+                        InputStream = ms,
+                        PartSize = MaxPartSize
+                    };
+                request.StreamTransferProgress += new EventHandler<StreamTransferProgressArgs>(
+                    (_, e) =>
+                    {
+                        _logger.LogDebug($"Transferred {e.TransferredBytes}/{e.TotalBytes}");
+                    }
                 );
-            _uploadResponses.Add(response);
-        }
-        catch (Exception e)
-        {
-            await AbortAsync(e);
-            throw;
+                UploadPartResponse response = await _client.UploadPartAsync(request);
+                if (response.HttpStatusCode != HttpStatusCode.OK)
+                    throw new HttpRequestException(
+                        $"Tried to upload part {partNumber} of upload {_uploadId} to {_bucketName}/{_key} but received response code {response.HttpStatusCode}"
+                    );
+                _uploadResponses.Add(response);
+            }
+            catch (Exception e)
+            {
+                await AbortAsync(e);
+                throw;
+            }
         }
     }
 
@@ -93,30 +96,49 @@ protected override void Dispose(bool disposing)
     {
         if (disposing)
         {
-            try
+            if (_uploadResponses.Count == 0)
             {
-                CompleteMultipartUploadRequest request =
+                AbortAsync().WaitAndUnwrapException();
+                PutObjectRequest request =
                     new()
                     {
                         BucketName = _bucketName,
                         Key = _key,
-                        UploadId = _uploadId
+                        ContentBody = ""
                     };
-                request.AddPartETags(_uploadResponses);
-                CompleteMultipartUploadResponse response = _client
-                    .CompleteMultipartUploadAsync(request)
-                    .WaitAndUnwrapException();
-                Dispose(disposing: false);
-                GC.SuppressFinalize(this);
+                PutObjectResponse response = _client.PutObjectAsync(request).WaitAndUnwrapException();
                 if (response.HttpStatusCode != HttpStatusCode.OK)
                     throw new HttpRequestException(
-                        $"Tried to complete {_uploadId} to {_bucketName}/{_key} but received response code {response.HttpStatusCode}"
+                        $"Tried to upload empty file to {_bucketName}/{_key} but received response code {response.HttpStatusCode}"
                     );
             }
-            catch (Exception e)
+            else
             {
-                AbortAsync(e).WaitAndUnwrapException();
-                throw;
+                try
+                {
+                    CompleteMultipartUploadRequest request =
+                        new()
+                        {
+                            BucketName = _bucketName,
+                            Key = _key,
+                            UploadId = _uploadId
+                        };
+                    request.AddPartETags(_uploadResponses);
+                    CompleteMultipartUploadResponse response = _client
+                        .CompleteMultipartUploadAsync(request)
+                        .WaitAndUnwrapException();
+                    Dispose(disposing: false);
+                    GC.SuppressFinalize(this);
+                    if (response.HttpStatusCode != HttpStatusCode.OK)
+                        throw new HttpRequestException(
+                            $"Tried to complete {_uploadId} to {_bucketName}/{_key} but received response code {response.HttpStatusCode}"
+                        );
+                }
+                catch (Exception e)
+                {
+                    AbortAsync(e).WaitAndUnwrapException();
+                    throw;
+                }
             }
         }
         base.Dispose(disposing);
@@ -124,6 +146,23 @@ protected override void Dispose(bool disposing)
 
     public async override ValueTask DisposeAsync()
     {
+        if (_uploadResponses.Count == 0)
+        {
+            await AbortAsync();
+            PutObjectRequest request =
+                new()
+                {
+                    BucketName = _bucketName,
+                    Key = _key,
+                    ContentBody = ""
+                };
+            PutObjectResponse response = await _client.PutObjectAsync(request);
+            if (response.HttpStatusCode != HttpStatusCode.OK)
+                throw new HttpRequestException(
+                    $"Tried to upload empty file to {_bucketName}/{_key} but received response code {response.HttpStatusCode}"
+                );
+            return;
+        }
         try
         {
             CompleteMultipartUploadRequest request =
@@ -148,9 +187,10 @@ public async override ValueTask DisposeAsync()
         }
     }
 
-    private async Task AbortAsync(Exception e)
+    private async Task AbortAsync(Exception? e = null)
     {
-        _logger.LogError(e, $"Aborted upload {_uploadId} to {_bucketName}/{_key}");
+        if (e is not null)
+            _logger.LogError(e, $"Aborted upload {_uploadId} to {_bucketName}/{_key}");
         AbortMultipartUploadRequest abortMPURequest =
             new()
             {
diff --git a/src/SIL.Machine.AspNetCore/Services/ServalTranslationEngineServiceV1.cs b/src/SIL.Machine.AspNetCore/Services/ServalTranslationEngineServiceV1.cs
index f57038f01..a0b010c61 100644
--- a/src/SIL.Machine.AspNetCore/Services/ServalTranslationEngineServiceV1.cs
+++ b/src/SIL.Machine.AspNetCore/Services/ServalTranslationEngineServiceV1.cs
@@ -236,7 +236,9 @@ private static Models.Corpus Map(Serval.Translation.V1.Corpus source)
             Id = source.Id,
             SourceLanguage = source.SourceLanguage,
             TargetLanguage = source.TargetLanguage,
+            TrainOnAll = source.TrainOnAll,
             PretranslateAll = source.PretranslateAll,
+            TrainOnTextIds = source.TrainOnTextIds.ToHashSet(),
             PretranslateTextIds = source.PretranslateTextIds.ToHashSet(),
             SourceFiles = source.SourceFiles.Select(Map).ToList(),
             TargetFiles = source.TargetFiles.Select(Map).ToList()