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+---
+'astro': minor
+---
+
+Changes the default behavior for Astro Action form requests to a standard POST submission.
+
+In Astro 4.x, actions called from an HTML form would trigger a redirect with the result forwarded using cookies. This caused issues for large form errors and return values that exceeded the 4 KB limit of cookie-based storage.
+
+Astro 5.0 now renders the result of an action as a POST result without any forwarding. This will introduce a "confirm form resubmission?" dialog when a user attempts to refresh the page, though it no longer imposes a 4 KB limit on action return value.
+
+## Customize form submission behavior
+
+If you prefer to address the "confirm form resubmission?" dialog on refresh, or to preserve action results across sessions, you can now [customize action result handling from middleware](https://5-0-0-beta.docs.astro.build/en/guides/actions/#advanced-persist-action-results-with-a-session).
+
+We recommend using a session storage provider [as described in our Netlify Blob example](https://5-0-0-beta.docs.astro.build/en/guides/actions/#advanced-persist-action-results-with-a-session). However, if you prefer the cookie forwarding behavior from 4.X and accept the 4 KB size limit, you can implement the pattern as shown in this sample snippet:
+
+```ts 
+// src/middleware.ts
+import { defineMiddleware } from 'astro:middleware';
+import { getActionContext } from 'astro:actions';
+
+export const onRequest = defineMiddleware(async (context, next) => {
+  // Skip requests for prerendered pages
+  if (context.isPrerendered) return next();
+
+	const { action, setActionResult, serializeActionResult } = getActionContext(context);
+
+	// If an action result was forwarded as a cookie, set the result
+	// to be accessible from `Astro.getActionResult()`
+	const payload = context.cookies.get('ACTION_PAYLOAD');
+	if (payload) {
+		const { actionName, actionResult } = payload.json();
+		setActionResult(actionName, actionResult);
+		context.cookies.delete('ACTION_PAYLOAD');
+		return next();
+	}
+
+	// If an action was called from an HTML form action,
+	// call the action handler and redirect with the result as a cookie.
+	if (action?.calledFrom === 'form') {
+		const actionResult = await action.handler();
+
+		context.cookies.set('ACTION_PAYLOAD', {
+			actionName: action.name,
+			actionResult: serializeActionResult(actionResult),
+		});
+
+		if (actionResult.error) {
+		// Redirect back to the previous page on error
+			const referer = context.request.headers.get('Referer');
+			if (!referer) {
+				throw new Error('Internal: Referer unexpectedly missing from Action POST request.');
+			}
+			return context.redirect(referer);
+		}
+		// Redirect to the destination page on success
+		return context.redirect(context.originPathname);
+	}
+
+	return next();
+})
+```