diff --git a/apps/web/src/components/PreviewModal.tsx b/apps/web/src/components/PreviewModal.tsx
index 161190739..14dcafd37 100644
--- a/apps/web/src/components/PreviewModal.tsx
+++ b/apps/web/src/components/PreviewModal.tsx
@@ -72,6 +72,22 @@ export function PreviewModal({
     return () => document.removeEventListener('keydown', onKey);
   }, [onClose, fullscreen]);
 
+  // Mirror native fullscreen state into React. Without this, a user in
+  // browser fullscreen has to press Esc twice: the first Esc exits the
+  // native fullscreen element (consumed by the browser; in some browsers no
+  // keydown is delivered) while our `fullscreen` state stays true and the
+  // overlay keeps its `ds-modal-fullscreen` class. Listening to
+  // fullscreenchange lets one Esc dismiss both layers in lock-step.
+  useEffect(() => {
+    const onFsChange = () => {
+      if (!document.fullscreenElement) {
+        setFullscreen(false);
+      }
+    };
+    document.addEventListener('fullscreenchange', onFsChange);
+    return () => document.removeEventListener('fullscreenchange', onFsChange);
+  }, []);
+
   // Close share popover on outside click / Escape.
   useEffect(() => {
     if (!shareOpen) return;
diff --git a/e2e/tests/preview-modal-fullscreen.test.tsx b/e2e/tests/preview-modal-fullscreen.test.tsx
new file mode 100644
index 000000000..54927109a
--- /dev/null
+++ b/e2e/tests/preview-modal-fullscreen.test.tsx
@@ -0,0 +1,109 @@
+import { act, cleanup, fireEvent, render } from '@testing-library/react';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { PreviewModal } from '../../apps/web/src/components/PreviewModal';
+
+// Regression coverage for nexu-io/open-design#141: pressing Esc in fullscreen
+// used to require two presses because the browser exits its native fullscreen
+// element on the first press without delivering a keydown to JS, leaving the
+// React `fullscreen` state stuck on. The fix listens to fullscreenchange and
+// mirrors the native state into React.
+
+const baseProps = {
+  title: 'Sample',
+  views: [{ id: 'main', label: 'Main', html: '<p>hi</p>' }],
+  exportTitleFor: (id: string) => id,
+};
+
+function dispatchFullscreenChange() {
+  act(() => {
+    document.dispatchEvent(new Event('fullscreenchange'));
+  });
+}
+
+function setNativeFullscreenElement(el: Element | null) {
+  Object.defineProperty(document, 'fullscreenElement', {
+    configurable: true,
+    get: () => el,
+  });
+}
+
+describe('PreviewModal fullscreen exit', () => {
+  afterEach(() => {
+    cleanup();
+    setNativeFullscreenElement(null);
+  });
+
+  it('drops the fullscreen overlay when the browser exits native fullscreen', () => {
+    const onClose = vi.fn();
+    const { container } = render(
+      <PreviewModal {...baseProps} onClose={onClose} />,
+    );
+
+    // Click the Fullscreen button. jsdom does not implement requestFullscreen
+    // on plain elements, so PreviewModal's fallback path runs and just sets
+    // the React state — exactly matching what happens after a successful
+    // browser fullscreen request.
+    const fsButton = container.querySelector(
+      'button[title="Fullscreen"]',
+    ) as HTMLButtonElement;
+    expect(fsButton).toBeTruthy();
+    fireEvent.click(fsButton);
+    const stage = container.querySelector('.ds-modal') as HTMLElement;
+    expect(stage.classList.contains('ds-modal-fullscreen')).toBe(true);
+
+    // Simulate the user pressing Esc in browser fullscreen: the browser
+    // exits its native fullscreen element and fires fullscreenchange, but
+    // (in browsers like Firefox) does not deliver the keydown to JS.
+    setNativeFullscreenElement(null);
+    dispatchFullscreenChange();
+
+    expect(stage.classList.contains('ds-modal-fullscreen')).toBe(false);
+    expect(onClose).not.toHaveBeenCalled();
+  });
+
+  it('keeps the modal mounted on Esc while fullscreen, and closes only on a second Esc', () => {
+    const onClose = vi.fn();
+    const { container } = render(
+      <PreviewModal {...baseProps} onClose={onClose} />,
+    );
+    const fsButton = container.querySelector(
+      'button[title="Fullscreen"]',
+    ) as HTMLButtonElement;
+    fireEvent.click(fsButton);
+    const stage = container.querySelector('.ds-modal') as HTMLElement;
+    expect(stage.classList.contains('ds-modal-fullscreen')).toBe(true);
+
+    // First Esc — drops fullscreen, must not close the modal.
+    fireEvent.keyDown(document, { key: 'Escape' });
+    expect(stage.classList.contains('ds-modal-fullscreen')).toBe(false);
+    expect(onClose).not.toHaveBeenCalled();
+
+    // Second Esc — closes the modal.
+    fireEvent.keyDown(document, { key: 'Escape' });
+    expect(onClose).toHaveBeenCalledTimes(1);
+  });
+
+  it('ignores fullscreenchange when another element is still fullscreen', () => {
+    const onClose = vi.fn();
+    const { container } = render(
+      <PreviewModal {...baseProps} onClose={onClose} />,
+    );
+    const fsButton = container.querySelector(
+      'button[title="Fullscreen"]',
+    ) as HTMLButtonElement;
+    fireEvent.click(fsButton);
+    const stage = container.querySelector('.ds-modal') as HTMLElement;
+    expect(stage.classList.contains('ds-modal-fullscreen')).toBe(true);
+
+    // Some other element is the active fullscreen target — our overlay must
+    // not collapse to non-fullscreen on transitions that leave a different
+    // element fullscreen.
+    const other = document.createElement('div');
+    document.body.appendChild(other);
+    setNativeFullscreenElement(other);
+    dispatchFullscreenChange();
+
+    expect(stage.classList.contains('ds-modal-fullscreen')).toBe(true);
+    document.body.removeChild(other);
+  });
+});