Add parent-controlled visibility hooks to step-sequence animations

2026/mcp-connect/animations/shared/diagram-helpers.js

@@ -143,14 +143,16 @@ function runStepSequence(steps, { initialDelay = 100, stepPause, startOnLoad = t
     }, initialDelay);
   }
 
-  const start = () => {
+  const stop = () => {
     runId++;
-
     if (animationTimer) {
       clearTimeout(animationTimer);
       animationTimer = null;
     }
+  };
 
+  const start = () => {
+    stop();
     currentStep = 0;
     runStep(runId);
   };
@@ -171,4 +173,18 @@ function runStepSequence(steps, { initialDelay = 100, stepPause, startOnLoad = t
   } else {
     start();
   }
+
+  // Parent-controlled visibility for embedded slide iframes.
+  window.addEventListener('message', (event) => {
+    const data = event.data;
+    if (!data || data.type !== 'marp-slide-visibility') {
+      return;
+    }
+
+    if (data.active) {
+      start();
+    } else {
+      stop();
+    }
+  });
 }