diff --git a/pkg/cmd/flagoptions.go b/pkg/cmd/flagoptions.go
index d257e38..4b4afa6 100644
--- a/pkg/cmd/flagoptions.go
+++ b/pkg/cmd/flagoptions.go
@@ -1,7 +1,6 @@
 package cmd
 
 import (
-	"bytes"
 	"encoding/base64"
 	"encoding/json"
 	"fmt"
@@ -492,22 +491,18 @@ func flagOptions(
 	case EmptyBody:
 		break
 	case MultipartFormEncoded:
-		buf := new(bytes.Buffer)
-		writer := multipart.NewWriter(buf)
-
 		// For multipart/form-encoded, we need a map structure
 		bodyMap, ok := requestContents.Body.(map[string]any)
 		if !ok {
 			return nil, fmt.Errorf("Cannot send a non-map value to a form-encoded endpoint: %v\n", requestContents.Body)
 		}
 		encodingFormat := apiform.FormatBrackets
-		if err := apiform.MarshalWithSettings(bodyMap, writer, encodingFormat); err != nil {
-			return nil, err
-		}
-		if err := writer.Close(); err != nil {
-			return nil, err
-		}
-		options = append(options, option.WithRequestBody(writer.FormDataContentType(), buf))
+		contentType, body := newMultipartRequestBody(bodyMap, encodingFormat)
+		options = append(options,
+			option.WithRequestBody(contentType, body),
+			// Streaming request bodies cannot be replayed safely by the SDK retry loop.
+			option.WithMaxRetries(0),
+		)
 
 	case ApplicationJSON:
 		bodyBytes, err := json.Marshal(requestContents.Body)
@@ -538,6 +533,69 @@ func flagOptions(
 	return options, nil
 }
 
+func newMultipartRequestBody(bodyMap map[string]any, encodingFormat apiform.FormFormat) (string, io.Reader) {
+	reader, writer := io.Pipe()
+	multipartWriter := multipart.NewWriter(writer)
+	contentType := multipartWriter.FormDataContentType()
+
+	go func() {
+		err := apiform.MarshalWithSettings(bodyMap, multipartWriter, encodingFormat)
+		if closeErr := multipartWriter.Close(); err == nil {
+			err = closeErr
+		}
+		if closeErr := closeFileUploads(bodyMap); err == nil {
+			err = closeErr
+		}
+
+		if err != nil {
+			_ = writer.CloseWithError(err)
+			return
+		}
+		_ = writer.Close()
+	}()
+
+	return contentType, reader
+}
+
+func closeFileUploads(value any) error {
+	return closeFileUploadsValue(reflect.ValueOf(value))
+}
+
+func closeFileUploadsValue(v reflect.Value) error {
+	if !v.IsValid() {
+		return nil
+	}
+
+	if v.Kind() == reflect.Interface || v.Kind() == reflect.Pointer {
+		if v.IsNil() {
+			return nil
+		}
+		return closeFileUploadsValue(v.Elem())
+	}
+
+	if upload, ok := v.Interface().(fileUpload); ok {
+		return upload.Close()
+	}
+
+	switch v.Kind() {
+	case reflect.Map:
+		iter := v.MapRange()
+		for iter.Next() {
+			if err := closeFileUploadsValue(iter.Value()); err != nil {
+				return err
+			}
+		}
+	case reflect.Slice, reflect.Array:
+		for i := 0; i < v.Len(); i++ {
+			if err := closeFileUploadsValue(v.Index(i)); err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
 // FilePathValue is a string wrapper that marks a value as a file path whose contents should be read
 // and embedded in the request. Unlike a regular string, embedFilesValue always treats a FilePathValue
 // as a file path without needing the "@" prefix.
diff --git a/pkg/cmd/flagoptions_test.go b/pkg/cmd/flagoptions_test.go
index 00734ca..bca3386 100644
--- a/pkg/cmd/flagoptions_test.go
+++ b/pkg/cmd/flagoptions_test.go
@@ -6,8 +6,11 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 	"testing"
+	"time"
 
+	"github.com/openai/openai-cli/internal/apiform"
 	"github.com/stretchr/testify/require"
 )
 
@@ -235,11 +238,12 @@ func TestEmbedFiles(t *testing.T) {
 		t.Run(tt.name+" io.Reader", func(t *testing.T) {
 			t.Parallel()
 
-			_, err := embedFiles(tt.input, EmbedIOReader, nil)
+			got, err := embedFiles(tt.input, EmbedIOReader, nil)
 			if tt.wantErr {
 				require.Error(t, err)
 			} else {
 				require.NoError(t, err)
+				require.NoError(t, closeFileUploads(got))
 			}
 		})
 	}
@@ -382,6 +386,97 @@ func TestEmbedFilesUploadMetadata(t *testing.T) {
 	}
 }
 
+func TestMultipartRequestBodyStreamsAndClosesUploads(t *testing.T) {
+	t.Parallel()
+
+	upload := &blockingReadCloser{
+		data:        []byte("large file payload"),
+		readStarted: make(chan struct{}),
+		allowRead:   make(chan struct{}),
+		closed:      make(chan struct{}),
+	}
+
+	contentType, body := newMultipartRequestBody(map[string]any{
+		"file": fileUpload{
+			Reader:      upload,
+			filename:    "large.txt",
+			contentType: "text/plain",
+		},
+	}, apiform.FormatBrackets)
+
+	require.Contains(t, contentType, "multipart/form-data; boundary=")
+
+	select {
+	case <-upload.readStarted:
+		t.Fatal("multipart body read upload data before the request body was consumed")
+	case <-time.After(50 * time.Millisecond):
+	}
+
+	type readResult struct {
+		data []byte
+		err  error
+	}
+	resultCh := make(chan readResult, 1)
+	go func() {
+		data, err := io.ReadAll(body)
+		resultCh <- readResult{data: data, err: err}
+	}()
+
+	select {
+	case <-upload.readStarted:
+	case <-time.After(time.Second):
+		t.Fatal("multipart body did not read upload data after the request body was consumed")
+	}
+	close(upload.allowRead)
+
+	var result readResult
+	select {
+	case result = <-resultCh:
+	case <-time.After(time.Second):
+		t.Fatal("multipart body read did not finish")
+	}
+	require.NoError(t, result.err)
+	require.Contains(t, string(result.data), "large file payload")
+
+	select {
+	case <-upload.closed:
+	case <-time.After(time.Second):
+		t.Fatal("multipart body did not close the uploaded file reader")
+	}
+}
+
+type blockingReadCloser struct {
+	data        []byte
+	readStarted chan struct{}
+	allowRead   chan struct{}
+	closed      chan struct{}
+	startOnce   sync.Once
+	closeOnce   sync.Once
+	offset      int
+}
+
+func (r *blockingReadCloser) Read(p []byte) (int, error) {
+	r.startOnce.Do(func() {
+		close(r.readStarted)
+	})
+	<-r.allowRead
+
+	if r.offset >= len(r.data) {
+		return 0, io.EOF
+	}
+
+	n := copy(p, r.data[r.offset:])
+	r.offset += n
+	return n, nil
+}
+
+func (r *blockingReadCloser) Close() error {
+	r.closeOnce.Do(func() {
+		close(r.closed)
+	})
+	return nil
+}
+
 func writeTestFile(t *testing.T, dir, filename, content string) {
 	t.Helper()