diff --git a/packages/react-dom/src/__tests__/ReactDOMServerPartialHydration-test.internal.js b/packages/react-dom/src/__tests__/ReactDOMServerPartialHydration-test.internal.js
index 2572d7043ca..78f5e032b3d 100644
--- a/packages/react-dom/src/__tests__/ReactDOMServerPartialHydration-test.internal.js
+++ b/packages/react-dom/src/__tests__/ReactDOMServerPartialHydration-test.internal.js
@@ -4300,4 +4300,136 @@ describe('ReactDOMServerPartialHydration', () => {
     root.unmount();
     expect(container.innerHTML).toEqual('<!--&--><!--/&-->');
   });
+
+  it('recovers when an update changes a dehydrated boundary inside a suspended parent boundary', async () => {
+    let suspend = false;
+    let resolve;
+    const promise = new Promise(resolvePromise => (resolve = resolvePromise));
+
+    function Sibling() {
+      if (suspend) {
+        throw promise;
+      }
+      return <span id="sibling">Sibling</span>;
+    }
+
+    function App({showSiblingOnMount}) {
+      const [showSibling, setShowSibling] = React.useState(false);
+      React.useEffect(() => {
+        if (showSiblingOnMount) {
+          // Not a transition: this update reaches the dehydrated inner
+          // boundary at default priority, before it has hydrated.
+          setShowSibling(true);
+        }
+      }, [showSiblingOnMount]);
+      return (
+        <div>
+          <Suspense fallback={null}>
+            {showSibling ? <Sibling /> : null}
+            <Suspense fallback={null}>
+              <span id="content">{showSibling ? 'b' : 'a'}</span>
+            </Suspense>
+          </Suspense>
+        </div>
+      );
+    }
+
+    // Don't suspend on the server.
+    suspend = false;
+    const finalHTML = ReactDOMServer.renderToString(
+      <App showSiblingOnMount={false} />,
+    );
+    const container = document.createElement('div');
+    container.innerHTML = finalHTML;
+    expect(container.textContent).toBe('a');
+
+    // Hydrate. The first effect mounts a suspending sibling in the outer
+    // boundary (so the outer boundary shows its fallback and its primary
+    // content is hidden), and at the same time changes the input of the
+    // inner boundary, which is still dehydrated.
+    suspend = true;
+    await act(() => {
+      ReactDOMClient.hydrateRoot(container, <App showSiblingOnMount={true} />);
+    });
+
+    // The sibling's data arrives.
+    suspend = false;
+    await act(async () => {
+      resolve();
+      await promise;
+    });
+
+    // The outer boundary should reveal both the sibling and the updated
+    // inner content.
+    const sibling = container.querySelector('#sibling');
+    const content = container.querySelector('#content');
+    expect(sibling).not.toBe(null);
+    expect(sibling.style.display).not.toBe('none');
+    expect(content).not.toBe(null);
+    expect(content.style.display).not.toBe('none');
+    expect(content.textContent).toBe('b');
+  });
+
+  it('recovers when a transition changes a dehydrated boundary inside a suspended parent boundary', async () => {
+    // Same as the previous test, except the update is wrapped
+    // in startTransition.
+    let suspend = false;
+    let resolve;
+    const promise = new Promise(resolvePromise => (resolve = resolvePromise));
+
+    function Sibling() {
+      if (suspend) {
+        throw promise;
+      }
+      return <span id="sibling">Sibling</span>;
+    }
+
+    function App({showSiblingOnMount}) {
+      const [showSibling, setShowSibling] = React.useState(false);
+      React.useEffect(() => {
+        if (showSiblingOnMount) {
+          React.startTransition(() => {
+            setShowSibling(true);
+          });
+        }
+      }, [showSiblingOnMount]);
+      return (
+        <div>
+          <Suspense fallback={null}>
+            {showSibling ? <Sibling /> : null}
+            <Suspense fallback={null}>
+              <span id="content">{showSibling ? 'b' : 'a'}</span>
+            </Suspense>
+          </Suspense>
+        </div>
+      );
+    }
+
+    suspend = false;
+    const finalHTML = ReactDOMServer.renderToString(
+      <App showSiblingOnMount={false} />,
+    );
+    const container = document.createElement('div');
+    container.innerHTML = finalHTML;
+    expect(container.textContent).toBe('a');
+
+    suspend = true;
+    await act(() => {
+      ReactDOMClient.hydrateRoot(container, <App showSiblingOnMount={true} />);
+    });
+
+    suspend = false;
+    await act(async () => {
+      resolve();
+      await promise;
+    });
+
+    const sibling = container.querySelector('#sibling');
+    const content = container.querySelector('#content');
+    expect(sibling).not.toBe(null);
+    expect(sibling.style.display).not.toBe('none');
+    expect(content).not.toBe(null);
+    expect(content.style.display).not.toBe('none');
+    expect(content.textContent).toBe('b');
+  });
 });
diff --git a/packages/react-dom/src/__tests__/ReactDOMServerPartialHydrationActivity-test.internal.js b/packages/react-dom/src/__tests__/ReactDOMServerPartialHydrationActivity-test.internal.js
index 0921920cb55..48d650c05e7 100644
--- a/packages/react-dom/src/__tests__/ReactDOMServerPartialHydrationActivity-test.internal.js
+++ b/packages/react-dom/src/__tests__/ReactDOMServerPartialHydrationActivity-test.internal.js
@@ -2976,4 +2976,129 @@ describe('ReactDOMServerPartialHydrationActivity', () => {
       '<div>1</div><span>client</span><div>2</div>',
     );
   });
+
+  it('commits new suspending content next to a dehydrated Activity that hides', async () => {
+    let suspend = false;
+    let resolve;
+    const promise = new Promise(resolvePromise => (resolve = resolvePromise));
+
+    function Second() {
+      if (suspend) {
+        throw promise;
+      }
+      return <span id="second">Second</span>;
+    }
+
+    function App({showSecondOnMount}) {
+      const [active, setActive] = React.useState('first');
+      React.useEffect(() => {
+        if (showSecondOnMount) {
+          // Not a transition: this update reaches the dehydrated Activity at
+          // default priority, before it has hydrated.
+          setActive('second');
+        }
+      }, [showSecondOnMount]);
+      return (
+        <div>
+          <Suspense fallback={null}>
+            {active === 'second' ? <Second /> : null}
+            <Activity mode={active === 'first' ? 'visible' : 'hidden'}>
+              <span id="first">First</span>
+            </Activity>
+          </Suspense>
+        </div>
+      );
+    }
+
+    // Don't suspend on the server.
+    suspend = false;
+    const finalHTML = ReactDOMServer.renderToString(
+      <App showSecondOnMount={false} />,
+    );
+    const container = document.createElement('div');
+    container.innerHTML = finalHTML;
+    expect(container.textContent).toBe('First');
+
+    // Hydrate. The first effect mounts new content (still loading) and hides
+    // the server-rendered Activity while its subtree is still dehydrated.
+    suspend = true;
+    await act(() => {
+      ReactDOMClient.hydrateRoot(container, <App showSecondOnMount={true} />);
+    });
+
+    // The data for the new row arrives.
+    suspend = false;
+    await act(async () => {
+      resolve();
+      await promise;
+    });
+
+    // The new row should be visible and the old row hidden.
+    const second = container.querySelector('#second');
+    const first = container.querySelector('#first');
+    expect(second).not.toBe(null);
+    expect(second.style.display).not.toBe('none');
+    expect(first === null || first.style.display === 'none').toBe(true);
+  });
+
+  it('commits new suspending content next to a dehydrated Activity that hides (transition)', async () => {
+    // Same as the previous test, except the update is wrapped
+    // in startTransition.
+    let suspend = false;
+    let resolve;
+    const promise = new Promise(resolvePromise => (resolve = resolvePromise));
+
+    function Second() {
+      if (suspend) {
+        throw promise;
+      }
+      return <span id="second">Second</span>;
+    }
+
+    function App({showSecondOnMount}) {
+      const [active, setActive] = React.useState('first');
+      React.useEffect(() => {
+        if (showSecondOnMount) {
+          React.startTransition(() => {
+            setActive('second');
+          });
+        }
+      }, [showSecondOnMount]);
+      return (
+        <div>
+          <Suspense fallback={null}>
+            {active === 'second' ? <Second /> : null}
+            <Activity mode={active === 'first' ? 'visible' : 'hidden'}>
+              <span id="first">First</span>
+            </Activity>
+          </Suspense>
+        </div>
+      );
+    }
+
+    suspend = false;
+    const finalHTML = ReactDOMServer.renderToString(
+      <App showSecondOnMount={false} />,
+    );
+    const container = document.createElement('div');
+    container.innerHTML = finalHTML;
+    expect(container.textContent).toBe('First');
+
+    suspend = true;
+    await act(() => {
+      ReactDOMClient.hydrateRoot(container, <App showSecondOnMount={true} />);
+    });
+
+    suspend = false;
+    await act(async () => {
+      resolve();
+      await promise;
+    });
+
+    const second = container.querySelector('#second');
+    const first = container.querySelector('#first');
+    expect(second).not.toBe(null);
+    expect(second.style.display).not.toBe('none');
+    expect(first === null || first.style.display === 'none').toBe(true);
+  });
 });
diff --git a/packages/react-reconciler/src/ReactFiberBeginWork.js b/packages/react-reconciler/src/ReactFiberBeginWork.js
index 815dc8b9961..29269e32924 100644
--- a/packages/react-reconciler/src/ReactFiberBeginWork.js
+++ b/packages/react-reconciler/src/ReactFiberBeginWork.js
@@ -204,6 +204,7 @@ import {
 import {
   pushHiddenContext,
   reuseHiddenContextOnStack,
+  isCurrentTreeHidden,
 } from './ReactFiberHiddenContext';
 import {findFirstSuspended} from './ReactFiberSuspenseComponent';
 import {
@@ -1019,6 +1020,19 @@ function updateDehydratedActivityComponent(
     if (didReceiveUpdate || hasContextChanged) {
       // This boundary has changed since the first render. This means that we are now unable to
       // hydrate it. We might still be able to hydrate it using a higher priority lane.
+      if (isCurrentTreeHidden()) {
+        // This boundary is inside a hidden subtree, where all work is
+        // deferred until the tree is revealed. Selective hydration works by
+        // rendering the boundary at a higher priority before the update
+        // applies, so it can't make progress here; delaying the commit to
+        // wait for it would deadlock. Replacing hidden content isn't
+        // visible, so give up and client render.
+        return retryActivityComponentWithoutHydrating(
+          current,
+          workInProgress,
+          renderLanes,
+        );
+      }
       const root = getWorkInProgressRoot();
       if (root !== null) {
         const attemptHydrationAtLane = getBumpedLaneForHydration(
@@ -3028,6 +3042,19 @@ function updateDehydratedSuspenseComponent(
     if (didReceiveUpdate || hasContextChanged) {
       // This boundary has changed since the first render. This means that we are now unable to
       // hydrate it. We might still be able to hydrate it using a higher priority lane.
+      if (isCurrentTreeHidden()) {
+        // This boundary is inside a hidden subtree, where all work is
+        // deferred until the tree is revealed. Selective hydration works by
+        // rendering the boundary at a higher priority before the update
+        // applies, so it can't make progress here; delaying the commit to
+        // wait for it would deadlock. Replacing hidden content isn't
+        // visible, so give up and client render.
+        return retrySuspenseComponentWithoutHydrating(
+          current,
+          workInProgress,
+          renderLanes,
+        );
+      }
       const root = getWorkInProgressRoot();
       if (root !== null) {
         const attemptHydrationAtLane = getBumpedLaneForHydration(