diff --git a/pkg/mcp/mcp.go b/pkg/mcp/mcp.go
index b5ae8a9..d6bee82 100644
--- a/pkg/mcp/mcp.go
+++ b/pkg/mcp/mcp.go
@@ -123,11 +123,8 @@ func New(opts Options) (*Service, error) {
 		if sn, ok := sub.(SubsystemWithNotifier); ok {
 			sn.SetNotifier(s)
 		}
-		// Wire channel callback for subsystems that use func-based notification
-		type channelWirer interface {
-			OnChannel(func(ctx context.Context, channel string, data any))
-		}
-		if cw, ok := sub.(channelWirer); ok {
+		// Wire channel callback for subsystems that use func-based notification.
+		if cw, ok := sub.(SubsystemWithChannelCallback); ok {
 			svc := s // capture for closure
 			cw.OnChannel(func(ctx context.Context, channel string, data any) {
 				svc.ChannelSend(ctx, channel, data)
diff --git a/pkg/mcp/subsystem.go b/pkg/mcp/subsystem.go
index d643603..3a26ac6 100644
--- a/pkg/mcp/subsystem.go
+++ b/pkg/mcp/subsystem.go
@@ -63,3 +63,14 @@ type SubsystemWithNotifier interface {
 	Subsystem
 	SetNotifier(n Notifier)
 }
+
+// SubsystemWithChannelCallback extends Subsystem for implementations that
+// expose an OnChannel callback instead of a Notifier interface.
+//
+//	brain.OnChannel(func(ctx context.Context, channel string, data any) {
+//	    mcpService.ChannelSend(ctx, channel, data)
+//	})
+type SubsystemWithChannelCallback interface {
+	Subsystem
+	OnChannel(func(ctx context.Context, channel string, data any))
+}