Fix :thread_count handling in TransferManager and Object transfer methods

gems/aws-sdk-s3/CHANGELOG.md

@@ -1,6 +1,10 @@
 Unreleased Changes
 ------------------
 
+* Issue - Remove `:thread_count` from transfer options even when a custom `:executor` is configured on `TransferManager`, fixing an `ArgumentError` raised on single-part `upload_file` calls.
+
+* Issue - Fix `:thread_count` being ignored by the deprecated `Object#download_file`, which always used the default thread count.
+
 1.232.2 (2026-09-25)
 ------------------
 

gems/aws-sdk-s3/lib/aws-sdk-s3/customizations/object.rb

@@ -567,7 +567,7 @@ def upload_file(source, options = {})
       # @see Client#head_object
       def download_file(destination, options = {})
         download_opts = options.merge(bucket: bucket_name, key: key)
-        executor = DefaultExecutor.new(max_threads: download_opts.delete([:thread_count]))
+        executor = DefaultExecutor.new(max_threads: download_opts.delete(:thread_count))
         begin
           downloader = FileDownloader.new(client: client, executor: executor)
           Aws::Plugins::UserAgent.metric('RESOURCE_MODEL') do

gems/aws-sdk-s3/lib/aws-sdk-s3/transfer_manager.rb

@@ -160,7 +160,8 @@ def initialize(options = {})
       #   * `:errors` - Array of errors for failed downloads (only present when failures occur)
       def download_directory(destination, bucket:, **options)
         Aws::Plugins::UserAgent.metric('S3_TRANSFER', 'S3_TRANSFER_DOWNLOAD_DIRECTORY') do
-          executor = @executor || DefaultExecutor.new(max_threads: options.delete(:thread_count))
+          thread_count = options.delete(:thread_count)
+          executor = @executor || DefaultExecutor.new(max_threads: thread_count)
           begin
             downloader = DirectoryDownloader.new(client: @client, executor: executor, logger: @logger)
             downloader.download(destination, bucket: bucket, **options)
@@ -247,7 +248,8 @@ def download_directory(destination, bucket:, **options)
       # @see Client#head_object
       def download_file(destination, bucket:, key:, **options)
         download_opts = options.merge(bucket: bucket, key: key)
-        executor = @executor || DefaultExecutor.new(max_threads: download_opts.delete(:thread_count))
+        thread_count = download_opts.delete(:thread_count)
+        executor = @executor || DefaultExecutor.new(max_threads: thread_count)
         begin
           downloader = FileDownloader.new(client: @client, executor: executor)
           downloader.download(destination, download_opts)
@@ -365,7 +367,8 @@ def download_file(destination, bucket:, key:, **options)
       #   * `:errors` - Array of error objects for failed uploads (only present when failures occur)
       def upload_directory(source, bucket:, **options)
         Aws::Plugins::UserAgent.metric('S3_TRANSFER', 'S3_TRANSFER_UPLOAD_DIRECTORY') do
-          executor = @executor || DefaultExecutor.new(max_threads: options.delete(:thread_count))
+          thread_count = options.delete(:thread_count)
+          executor = @executor || DefaultExecutor.new(max_threads: thread_count)
           begin
             uploader = DirectoryUploader.new(client: @client, executor: executor, logger: @logger)
             uploader.upload(source, bucket, **options.merge(http_chunk_size: resolve_http_chunk_size(options)))
@@ -450,8 +453,8 @@ def upload_directory(source, bucket:, **options)
       def upload_file(source, bucket:, key:, **options)
         upload_opts = options.merge(bucket: bucket, key: key)
         http_chunk_size = resolve_http_chunk_size(upload_opts)
-
-        executor = @executor || DefaultExecutor.new(max_threads: upload_opts.delete(:thread_count))
+        thread_count = upload_opts.delete(:thread_count)
+        executor = @executor || DefaultExecutor.new(max_threads: thread_count)
         begin
           uploader = FileUploader.new(
             multipart_threshold: upload_opts.delete(:multipart_threshold),
@@ -521,7 +524,8 @@ def upload_file(source, bucket:, key:, **options)
       # @see Client#upload_part
       def upload_stream(bucket:, key:, **options, &block)
         upload_opts = options.merge(bucket: bucket, key: key)
-        executor = @executor || DefaultExecutor.new(max_threads: upload_opts.delete(:thread_count))
+        thread_count = upload_opts.delete(:thread_count)
+        executor = @executor || DefaultExecutor.new(max_threads: thread_count)
         begin
           uploader = MultipartStreamUploader.new(
             client: @client,

gems/aws-sdk-s3/spec/object/download_file_spec.rb

@@ -28,6 +28,12 @@ module S3
           expect { subject.download_file(path) }.to raise_error(Aws::S3::Errors::NoSuchKey)
         end
 
+        it 'respects the thread_count option' do
+          custom_thread_count = 20
+          expect(DefaultExecutor).to receive(:new).with(max_threads: custom_thread_count).and_call_original
+          subject.download_file(path, thread_count: custom_thread_count)
+        end
+
         it 'shuts down the internally-created executor when download raises', thread_report_on_exception: false do
           client.stub_responses(:head_object, 'NoSuchKey')
           executor = nil