diff --git a/apps/app/src/components/generative-ui/open-generative-ui/__tests__/open-generative-ui-renderer.test.tsx b/apps/app/src/components/generative-ui/open-generative-ui/__tests__/open-generative-ui-renderer.test.tsx
index 65cdb2a..4b3cd60 100644
--- a/apps/app/src/components/generative-ui/open-generative-ui/__tests__/open-generative-ui-renderer.test.tsx
+++ b/apps/app/src/components/generative-ui/open-generative-ui/__tests__/open-generative-ui-renderer.test.tsx
@@ -647,4 +647,11 @@ describe("OpenGenUIActivityRenderer", () => {
     });
     expect(parsed.success).toBe(true);
   });
+
+  it.each([[-100, "50px"], [0, "50px"], [50000, "4000px"], [300.2, "301px"], [NaN, "200px"], [Infinity, "200px"]])("bounds invalid initial activity height %s", async (initialHeight, expected) => {
+    const { container } = renderRenderer({ initialHeight, generating: true });
+    await flushImport();
+    expect(container.querySelector<HTMLElement>("div[style]")!.style.height).toBe(expected);
+  });
+
 });
diff --git a/apps/app/src/components/generative-ui/open-generative-ui/renderer.tsx b/apps/app/src/components/generative-ui/open-generative-ui/renderer.tsx
index 4fb3a40..7ac28fd 100644
--- a/apps/app/src/components/generative-ui/open-generative-ui/renderer.tsx
+++ b/apps/app/src/components/generative-ui/open-generative-ui/renderer.tsx
@@ -145,7 +145,7 @@ function styleIframe(iframe: HTMLIFrameElement) {
 
 const OpenGenUIActivityRendererInner = React.memo(
   function OpenGenUIActivityRendererInner({ content }: InnerProps) {
-    const initialHeight = content.initialHeight ?? 200;
+    const initialHeight = clampReportedHeight(content.initialHeight) ?? 200;
     const [autoHeight, setAutoHeight] = useState<number | null>(null);
     const sandboxFunctions = useSandboxFunctions();