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Update caveats for Activity rendering behavior #8067

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Oct 13, 2025
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Update caveats for Activity rendering behavior #8067

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Update caveats for Activity rendering behavior
TkDodo Oct 9, 2025
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Apply suggestion from @eps1lon
eps1lon Oct 13, 2025
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3 changes: 2 additions & 1 deletion src/content/reference/react/Activity.md
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Expand Up @@ -48,6 +48,7 @@ In this way, Activity can be thought of as a mechanism for rendering "background
#### Caveats {/*caveats*/}

- If an Activity is rendered inside of a [ViewTransition](/reference/react/ViewTransition), and it becomes visible as a result of an update caused by [startTransition](/reference/react/startTransition), it will activate the ViewTransition's `enter` animation. If it becomes hidden, it will activate its `exit` animation.
- An Activity that just renders text will not render anything rather than rendering hidden text, because there’s no corresponding DOM element to apply visibility changes to. For example, `<Activity mode="hidden"><ComponentThatJustReturnsText /></Activity>` will not produce any output in the DOM for `const ComponentThatJustReturnsText = () => "Hello, World!"`.

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Expand Down Expand Up @@ -1248,4 +1249,4 @@ When an `<Activity>` is "hidden", all its children's Effects are cleaned up. Con

If you're relying on an Effect mounting to clean up a component's side effects, refactor the Effect to do the work in the returned cleanup function instead.

To eagerly find problematic Effects, we recommend adding [`<StrictMode>`](/reference/react/StrictMode) which will eagerly perform Activity unmounts and mounts to catch any unexpected side-effects.
To eagerly find problematic Effects, we recommend adding [`<StrictMode>`](/reference/react/StrictMode) which will eagerly perform Activity unmounts and mounts to catch any unexpected side-effects.