diff --git a/cmd/mxl-player/main.go b/cmd/mxl-player/main.go
index 27b8c01..08b82ac 100644
--- a/cmd/mxl-player/main.go
+++ b/cmd/mxl-player/main.go
@@ -15,6 +15,7 @@ import (
 	"mxl-player/internal/source"
 	"os"
 	"runtime"
+	"sync"
 	"time"
 	"unsafe"
 
@@ -109,6 +110,12 @@ func main() {
 	flagSet.StringVarP(&args.Domain, "domain", "d", "", "MXL domain directory")
 	flagSet.StringVarP(&args.VideoFlowId, "video", "v", "", "Video flow UUID")
 	flagSet.StringVarP(&args.AudioFlowId, "audio", "a", "", "Audio flow UUID")
+	flagSet.BoolVarP(
+		&args.SyncRequested,
+		"sync", "s",
+		false,
+		"Start configured audio and video as a synchronized group",
+	)
 	flagSet.IntVar(
 		&args.MaxAttempts,
 		"max-attempts",
@@ -149,8 +156,10 @@ func main() {
 		checkMXLargs(args)
 	}
 	// path selection
-	useVideoSlot := args.AudioFlowId == ""
-	useAudioSlot := args.AudioFlowId != "" && args.VideoFlowId == ""
+	useLegacySync := args.SyncRequested &&
+		args.VideoFlowId != "" &&
+		args.AudioFlowId != ""
+	useIndependentSlots := !useLegacySync
 
 	runtime.LockOSThread()
 	if err := sdl.Load(); err != nil {
@@ -281,8 +290,12 @@ func main() {
 	}
 
 	switch {
-	case args.VideoFlowId != "" && args.AudioFlowId != "":
-		syncSrc, err = source.OpenSameDomainSync(args.Domain, args.VideoFlowId, args.AudioFlowId)
+	case useLegacySync:
+		syncSrc, err = source.OpenSameDomainSync(
+			args.Domain,
+			args.VideoFlowId,
+			args.AudioFlowId,
+		)
 		if err != nil {
 			log.Fatalf("sync source: %v", err)
 		}
@@ -302,12 +315,9 @@ func main() {
 		sdl.ResumeAudioStreamDevice(audioStream)
 		fmt.Printf("sync: video %dx%d audio %dch batch=%d\n",
 			syncSrc.Width(), syncSrc.Height(), aChans, audioBatch)
-	case args.VideoFlowId != "":
-		// VideoSlot owns opening and closing the video reader.
-	case args.AudioFlowId != "":
-		// AudioSlot owns opening and closing the audio reader.
 	default:
-		// No configured feeds. Renderer and GUI use the placeholder.
+		// Independent slots own their readers.
+		// Empty startup opens nothing.
 	}
 
 	defer func() {
@@ -374,7 +384,7 @@ func main() {
 		showStats bool   = true
 	)
 	videoActive := args.VideoFlowId != ""
-	audioActive := useAudioSlot
+	audioActive := args.AudioFlowId != ""
 
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
@@ -535,34 +545,30 @@ func main() {
 	}
 
 	doReconnect := func() {
-		if useVideoSlot {
+		if useIndependentSlots {
 			videoActive = videoStr != ""
+			audioActive = audioStr != ""
 
-			config := playback.FeedConfig{}
+			videoConfig := playback.FeedConfig{}
 			if videoStr != "" {
-				config = playback.FeedConfig{
+				videoConfig = playback.FeedConfig{
 					Domain: domainStr,
 					UUID:   videoStr,
 					Active: true,
 				}
 			}
 
-			enqueueVideoConfig(config)
-			return
-		}
-		if useAudioSlot {
-			audioActive = audioStr != ""
-
-			config := playback.FeedConfig{}
+			audioConfig := playback.FeedConfig{}
 			if audioStr != "" {
-				config = playback.FeedConfig{
+				audioConfig = playback.FeedConfig{
 					Domain: domainStr,
 					UUID:   audioStr,
 					Active: true,
 				}
 			}
 
-			enqueueAudioConfig(config)
+			enqueueVideoConfig(videoConfig)
+			enqueueAudioConfig(audioConfig)
 			return
 		}
 		// legacy
@@ -577,34 +583,46 @@ func main() {
 	go func() {
 		defer close(playbackDone)
 
-		if useVideoSlot {
-			err := videoSlot.Run(
-				ctx,
-				playback.FeedConfig{
-					Domain: args.Domain,
-					UUID:   args.VideoFlowId,
-					Active: args.VideoFlowId != "",
-				},
-				videoCommands,
-			)
-			if err != nil && !errors.Is(err, context.Canceled) {
-				log.Printf("video slot: %v", err)
-			}
-			return
-		}
-		if useAudioSlot {
-			err := audioSlot.Run(
-				ctx,
-				playback.FeedConfig{
-					Domain: args.Domain,
-					UUID:   args.AudioFlowId,
-					Active: args.AudioFlowId != "",
-				},
-				audioCommands,
-			)
-			if err != nil && !errors.Is(err, context.Canceled) {
-				log.Printf("audio slot: %v", err)
-			}
+		if useIndependentSlots {
+			var slots sync.WaitGroup
+			slots.Add(2)
+
+			go func() {
+				defer slots.Done()
+
+				err := videoSlot.Run(
+					ctx,
+					playback.FeedConfig{
+						Domain: args.Domain,
+						UUID:   args.VideoFlowId,
+						Active: args.VideoFlowId != "",
+					},
+					videoCommands,
+				)
+				if err != nil && !errors.Is(err, context.Canceled) {
+					log.Printf("video slot: %v", err)
+				}
+			}()
+
+			go func() {
+				defer slots.Done()
+
+				err := audioSlot.Run(
+					ctx,
+					playback.FeedConfig{
+						Domain: args.Domain,
+						UUID:   args.AudioFlowId,
+						Active: args.AudioFlowId != "",
+					},
+					audioCommands,
+				)
+				if err != nil && !errors.Is(err, context.Canceled) {
+					log.Printf("audio slot: %v", err)
+				}
+			}()
+
+			<-ctx.Done()
+			slots.Wait()
 			return
 		}
 
@@ -930,7 +948,7 @@ func main() {
 			if cimgui.Button("Connect") {
 				doReconnect()
 			}
-			if useVideoSlot && videoActive {
+			if useIndependentSlots && videoActive {
 				cimgui.SameLine()
 				if cimgui.Button("Stop video") {
 					videoActive = false
@@ -942,7 +960,7 @@ func main() {
 						})
 				}
 			}
-			if useVideoSlot && !videoActive && videoStr != "" {
+			if useIndependentSlots && !videoActive && videoStr != "" {
 				cimgui.SameLine()
 				if cimgui.Button("Resume video") {
 					videoActive = true
@@ -953,14 +971,14 @@ func main() {
 					})
 				}
 			}
-			if useVideoSlot && videoStr != "" {
+			if useIndependentSlots && videoStr != "" {
 				if cimgui.Button("Remove video") {
 					videoActive = false
 					videoStr = ""
 					enqueueVideoConfig(playback.FeedConfig{})
 				}
 			}
-			if useVideoSlot {
+			if useIndependentSlots {
 				if videoActive {
 					cimgui.Text("Video desired: active")
 				} else if videoStr != "" {
@@ -994,7 +1012,7 @@ func main() {
 					cimgui.Text("Video actual: not started")
 				}
 			}
-			if useAudioSlot && audioActive {
+			if useIndependentSlots && audioActive {
 				if cimgui.Button("Stop audio") {
 					audioActive = false
 					enqueueAudioConfig(playback.FeedConfig{
@@ -1005,7 +1023,7 @@ func main() {
 				}
 			}
 
-			if useAudioSlot && !audioActive && audioStr != "" {
+			if useIndependentSlots && !audioActive && audioStr != "" {
 				if cimgui.Button("Resume audio") {
 					audioActive = true
 					enqueueAudioConfig(playback.FeedConfig{
@@ -1016,7 +1034,7 @@ func main() {
 				}
 			}
 
-			if useAudioSlot && audioStr != "" {
+			if useIndependentSlots && audioStr != "" {
 				if cimgui.Button("Remove audio") {
 					audioActive = false
 					audioStr = ""
@@ -1024,7 +1042,7 @@ func main() {
 				}
 			}
 
-			if useAudioSlot {
+			if useIndependentSlots {
 				if audioActive {
 					cimgui.Text("Audio desired: active")
 				} else if audioStr != "" {
diff --git a/imgui.ini b/imgui.ini
index 97d736a..b45ea7c 100644
--- a/imgui.ini
+++ b/imgui.ini
@@ -14,7 +14,7 @@ Size=200,200
 Collapsed=0
 
 [Window][Connection]
-Pos=174,363
-Size=986,237
+Pos=366,563
+Size=430,227
 Collapsed=0