diff --git a/imgui.ini b/imgui.ini
index b8903b8..6a67a49 100644
--- a/imgui.ini
+++ b/imgui.ini
@@ -14,7 +14,7 @@ Size=200,200
 Collapsed=0
 
 [Window][Connection]
-Pos=475,529
-Size=640,352
+Pos=628,539
+Size=613,164
 Collapsed=0
 
diff --git a/internal/playback/session_plan.go b/internal/playback/session_plan.go
new file mode 100644
index 0000000..4a80de7
--- /dev/null
+++ b/internal/playback/session_plan.go
@@ -0,0 +1,76 @@
+package playback
+
+import "fmt"
+
+type SessionTopology uint8
+
+const (
+	TopologyIdle SessionTopology = iota
+	TopologyIndependent
+	TopologySynchronized
+)
+
+type SyncPredicate func(video, audio FeedConfig) bool
+
+type SessionPlan struct {
+	Topology SessionTopology
+
+	// Desired states for independent slots.
+	Video FeedConfig
+	Audio FeedConfig
+
+	// Desired state for the synchronized slot.
+	Sync SyncPairConfig
+}
+
+func BuildSessionPlan(
+	desired SessionConfig,
+	canSync SyncPredicate,
+) (SessionPlan, error) {
+	if err := desired.Validate(); err != nil {
+		return SessionPlan{}, fmt.Errorf("validate desired session: %w", err)
+	}
+
+	if desired.SyncRequested &&
+		desired.Video.Active &&
+		desired.Audio.Active &&
+		canSync != nil &&
+		canSync(desired.Video, desired.Audio) {
+		return SessionPlan{
+			Topology: TopologySynchronized,
+			Video:    stoppedFeed(desired.Video),
+			Audio:    stoppedFeed(desired.Audio),
+			Sync: SyncPairConfig{
+				Video: desired.Video,
+				Audio: desired.Audio,
+			},
+		}, nil
+	}
+
+	if desired.Video.Active || desired.Audio.Active {
+		return SessionPlan{
+			Topology: TopologyIndependent,
+			Video:    desired.Video,
+			Audio:    desired.Audio,
+			Sync: SyncPairConfig{
+				Video: stoppedFeed(desired.Video),
+				Audio: stoppedFeed(desired.Audio),
+			},
+		}, nil
+	}
+
+	return SessionPlan{
+		Topology: TopologyIdle,
+		Video:    stoppedFeed(desired.Video),
+		Audio:    stoppedFeed(desired.Audio),
+		Sync: SyncPairConfig{
+			Video: stoppedFeed(desired.Video),
+			Audio: stoppedFeed(desired.Audio),
+		},
+	}, nil
+}
+
+func stoppedFeed(config FeedConfig) FeedConfig {
+	config.Active = false
+	return config
+}
diff --git a/internal/playback/session_plan_test.go b/internal/playback/session_plan_test.go
new file mode 100644
index 0000000..b548e0f
--- /dev/null
+++ b/internal/playback/session_plan_test.go
@@ -0,0 +1,130 @@
+package playback
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestBuildSessionPlan(t *testing.T) {
+	base := validCommandSession()
+	stoppedVideo := stoppedFeed(base.Video)
+	stoppedAudio := stoppedFeed(base.Audio)
+	independent := func(video, audio FeedConfig) SessionPlan {
+		return SessionPlan{
+			Topology: TopologyIndependent,
+			Video:    video,
+			Audio:    audio,
+			Sync:     SyncPairConfig{Video: stoppedFeed(video), Audio: stoppedFeed(audio)},
+		}
+	}
+	idle := func(video, audio FeedConfig) SessionPlan {
+		return SessionPlan{
+			Topology: TopologyIdle,
+			Video:    stoppedFeed(video),
+			Audio:    stoppedFeed(audio),
+			Sync:     SyncPairConfig{Video: stoppedFeed(video), Audio: stoppedFeed(audio)},
+		}
+	}
+
+	tests := []struct {
+		name    string
+		desired SessionConfig
+		canSync SyncPredicate
+		want    SessionPlan
+	}{
+		{
+			name:    "both active with sync disabled stay independent",
+			desired: func() SessionConfig { c := base; c.SyncRequested = false; return c }(),
+			canSync: func(FeedConfig, FeedConfig) bool { return true },
+			want:    independent(base.Video, base.Audio),
+		},
+		{
+			name:    "eligible requested pair is synchronized",
+			desired: base,
+			canSync: func(FeedConfig, FeedConfig) bool { return true },
+			want: SessionPlan{
+				Topology: TopologySynchronized,
+				Video:    stoppedVideo,
+				Audio:    stoppedAudio,
+				Sync:     SyncPairConfig{Video: base.Video, Audio: base.Audio},
+			},
+		},
+		{
+			name:    "ineligible requested pair remains independent",
+			desired: base,
+			canSync: func(FeedConfig, FeedConfig) bool { return false },
+			want:    independent(base.Video, base.Audio),
+		},
+		{
+			name:    "nil capability remains independent",
+			desired: base,
+			want:    independent(base.Video, base.Audio),
+		},
+		{
+			name:    "video only",
+			desired: func() SessionConfig { c := base; c.Audio.Active = false; return c }(),
+			canSync: func(FeedConfig, FeedConfig) bool { return true },
+			want:    independent(base.Video, stoppedAudio),
+		},
+		{
+			name:    "audio only",
+			desired: func() SessionConfig { c := base; c.Video.Active = false; return c }(),
+			canSync: func(FeedConfig, FeedConfig) bool { return true },
+			want:    independent(stoppedVideo, base.Audio),
+		},
+		{
+			name:    "stopped feeds are idle and retain configuration",
+			desired: func() SessionConfig { c := base; c.Video.Active = false; c.Audio.Active = false; return c }(),
+			canSync: func(FeedConfig, FeedConfig) bool { return true },
+			want:    idle(stoppedVideo, stoppedAudio),
+		},
+		{
+			name:    "empty session is idle",
+			desired: func() SessionConfig { c := base; c.Video = FeedConfig{}; c.Audio = FeedConfig{}; return c }(),
+			canSync: func(FeedConfig, FeedConfig) bool { return true },
+			want:    idle(FeedConfig{}, FeedConfig{}),
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := BuildSessionPlan(tt.desired, tt.canSync)
+			if err != nil {
+				t.Fatalf("BuildSessionPlan() error = %v", err)
+			}
+			if got != tt.want {
+				t.Fatalf("BuildSessionPlan() = %#v, want %#v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestBuildSessionPlanRejectsInvalidSession(t *testing.T) {
+	desired := validCommandSession()
+	desired.Video = FeedConfig{UUID: "video", Active: true}
+	got, err := BuildSessionPlan(desired, nil)
+	if !errors.Is(err, ErrFeedDomainRequired) {
+		t.Fatalf("BuildSessionPlan() error = %v, want %v", err, ErrFeedDomainRequired)
+	}
+	if got != (SessionPlan{}) {
+		t.Fatalf("BuildSessionPlan() = %#v, want zero plan", got)
+	}
+}
+
+func TestBuildSessionPlanPassesCompleteFeedsToPredicate(t *testing.T) {
+	desired := validCommandSession()
+	called := false
+	_, err := BuildSessionPlan(desired, func(video, audio FeedConfig) bool {
+		called = true
+		if video != desired.Video || audio != desired.Audio {
+			t.Fatalf("predicate feeds = %#v %#v", video, audio)
+		}
+		return true
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !called {
+		t.Fatal("sync predicate was not called")
+	}
+}