diff --git a/packages/core/src/runtime/bridge.test.ts b/packages/core/src/runtime/bridge.test.ts
index ae94404c7e..bdde120c57 100644
--- a/packages/core/src/runtime/bridge.test.ts
+++ b/packages/core/src/runtime/bridge.test.ts
@@ -27,11 +27,54 @@ function createMockDeps() {
 
 function makeControlMessage(action: string, extra?: Record<string, unknown>) {
   return new MessageEvent("message", {
+    source: window.parent,
     data: { source: "hf-parent", type: "control", action, ...extra },
   });
 }
 
 describe("installRuntimeControlBridge", () => {
+  it("rejects foreign and null senders before dispatching controls", () => {
+    const foreign = document.createElement("iframe");
+    document.body.append(foreign);
+    const deps = createMockDeps();
+    const handler = installRuntimeControlBridge(deps);
+    try {
+      for (const source of [foreign.contentWindow, null]) {
+        handler(
+          new MessageEvent("message", {
+            source,
+            data: { source: "hf-parent", type: "control", action: "play" },
+          }),
+        );
+      }
+      expect(deps.onPlay).not.toHaveBeenCalled();
+      handler(
+        new MessageEvent("message", {
+          source: window,
+          data: { source: "hf-parent", type: "control", action: "play" },
+        }),
+      );
+      expect(deps.onPlay).toHaveBeenCalledOnce();
+    } finally {
+      window.removeEventListener("message", handler);
+      foreign.remove();
+    }
+  });
+  it("accepts an embedding parent distinct from the runtime window", () => {
+    const frame = document.createElement("iframe");
+    document.body.append(frame);
+    vi.stubGlobal("parent", frame.contentWindow);
+    const deps = createMockDeps();
+    const handler = installRuntimeControlBridge(deps);
+    try {
+      handler(makeControlMessage("play"));
+      expect(deps.onPlay).toHaveBeenCalledOnce();
+    } finally {
+      window.removeEventListener("message", handler);
+      vi.unstubAllGlobals();
+      frame.remove();
+    }
+  });
   it("dispatches play command", () => {
     const deps = createMockDeps();
     const handler = installRuntimeControlBridge(deps);
diff --git a/packages/core/src/runtime/bridge.ts b/packages/core/src/runtime/bridge.ts
index 4de5ff306d..8ed2ac3191 100644
--- a/packages/core/src/runtime/bridge.ts
+++ b/packages/core/src/runtime/bridge.ts
@@ -123,6 +123,7 @@ function handleFlashElements(data: BridgeControlData): void {
 
 export function installRuntimeControlBridge(deps: BridgeDeps): (event: MessageEvent) => void {
   const handler = (event: MessageEvent) => {
+    if (event.source !== window.parent && event.source !== window) return;
     const data = event.data as BridgeControlData | null;
     if (!data || data.source !== "hf-parent" || data.type !== "control") return;
     if (rejectUnsupportedProtocol(data)) return;
diff --git a/packages/core/src/runtime/init.test.ts b/packages/core/src/runtime/init.test.ts
index e40335dac3..7a8991ac6f 100644
--- a/packages/core/src/runtime/init.test.ts
+++ b/packages/core/src/runtime/init.test.ts
@@ -169,6 +169,7 @@ describe("initSandboxRuntimeModular", () => {
 
     window.dispatchEvent(
       new MessageEvent("message", {
+        source: window.parent,
         data: { source: "hf-parent", type: "control", action: "set-volume", volume: 1 },
       }),
     );
@@ -239,6 +240,7 @@ describe("initSandboxRuntimeModular", () => {
     window.addEventListener("error", onError);
     window.dispatchEvent(
       new MessageEvent("message", {
+        source: window.parent,
         data: { source: "hf-parent", type: "control", action: "set-volume", volume: 1 },
       }),
     );
@@ -2846,6 +2848,7 @@ describe("initSandboxRuntimeModular", () => {
       if (payload.source !== "hf-preview" || payload.type !== "ready") return;
       window.dispatchEvent(
         new MessageEvent("message", {
+          source: window.parent,
           data: {
             source: "hf-parent",
             type: "control",
@@ -2856,6 +2859,7 @@ describe("initSandboxRuntimeModular", () => {
       );
       window.dispatchEvent(
         new MessageEvent("message", {
+          source: window.parent,
           data: {
             source: "hf-parent",
             type: "control",
@@ -3049,6 +3053,7 @@ describe("initSandboxRuntimeModular", () => {
 
     window.dispatchEvent(
       new MessageEvent("message", {
+        source: window.parent,
         data: { source: "hf-parent", type: "control", action: "set-muted", muted: false },
       }),
     );
@@ -3058,6 +3063,7 @@ describe("initSandboxRuntimeModular", () => {
 
     window.dispatchEvent(
       new MessageEvent("message", {
+        source: window.parent,
         data: { source: "hf-parent", type: "control", action: "set-muted", muted: true },
       }),
     );
@@ -3067,6 +3073,7 @@ describe("initSandboxRuntimeModular", () => {
 
     window.dispatchEvent(
       new MessageEvent("message", {
+        source: window.parent,
         data: { source: "hf-parent", type: "control", action: "set-muted", muted: false },
       }),
     );
@@ -3100,6 +3107,7 @@ describe("initSandboxRuntimeModular", () => {
 
     window.dispatchEvent(
       new MessageEvent("message", {
+        source: window.parent,
         data: {
           source: "hf-parent",
           type: "control",
@@ -3148,6 +3156,7 @@ describe("initSandboxRuntimeModular", () => {
 
     window.dispatchEvent(
       new MessageEvent("message", {
+        source: window.parent,
         data: {
           source: "hf-parent",
           type: "control",