release guide

site/src/routes/guides/release-notes/+page.svx

@@ -206,6 +206,29 @@ need to pass a new config to your client:
 
 </DeepDive>
 
+### Mutation return value changed
+
+Because of the change in Houdini's default error handling, mutations were brought
+in line with query behavior and return the full query result with `data`, `errors`,
+etc.
+
+```diff:title=src/components/AddFriend.svelte
+<script>
+    const mutation = graphql(`
+        mutation AddFriend {
+            addFriend {
+                ...
+            }
+        }
+    `)
+
+    async function onClick() {
+-       const { addFriend } = await mutation.mutate()
++       const { data: { addFriend } } = await mutation.mutate()
+    }
+</script>
+```
+
 ### Grouped `apiUrl`, `schemaPollHeaders`, and `schemaPollInterval` together
 
 In order to clarify the difference between the `apiUrl` config value and the