diff --git a/src/content/docs/en/guides/upgrade-to/v6.mdx b/src/content/docs/en/guides/upgrade-to/v6.mdx
index 19f0edd3b4235..a96344079bc9d 100644
--- a/src/content/docs/en/guides/upgrade-to/v6.mdx
+++ b/src/content/docs/en/guides/upgrade-to/v6.mdx
@@ -453,6 +453,20 @@ app.render(request, { routeData, locals })
 
 <ReadMore>Learn more about the [Adapter API](/en/reference/adapter-reference/).</ReadMore>
 
+### Removed: `app.setManifestData()` (Adapter API)
+
+<SourcePR number="14758" title="chore(astro)!: remove app.setManifestData()"/>
+
+In Astro 5.0, the `app.setManifestData()` method was available on `App` and `NodeApp`, but is no longer used nor needed.
+
+Astro 6.0 removes this method entirely.
+
+#### What should I do?
+
+Remove any call to `app.setManifestData()`. If you need to update the manifest, create a new `App` instance.
+
+<ReadMore>Learn more about the [Adapter API](/en/reference/adapter-reference/).</ReadMore>
+
 ### Removed: `handleForms` prop for the `<ClientRouter />` component
 
 <SourcePR number="14462" title="feat: clean deprecated APIs"/>