fix(core): reload manifest on watcher changes

.changeset/itchy-ghosts-flow.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes an issue where adding new pages weren't correctly shown when using the development server.

packages/astro/src/manifest/serialized.ts

@@ -1,4 +1,4 @@
-import type { Plugin } from 'vite';
+import type { Plugin, ViteDevServer } from 'vite';
 import { ACTIONS_ENTRYPOINT_VIRTUAL_MODULE_ID } from '../actions/consts.js';
 import { toFallbackType } from '../core/app/common.js';
 import { toRoutingStrategy } from '../core/app/index.js';
@@ -23,6 +23,7 @@ import { VIRTUAL_PAGES_MODULE_ID } from '../vite-plugin-pages/index.js';
 import { ASTRO_RENDERERS_MODULE_ID } from '../vite-plugin-renderers/index.js';
 import { ASTRO_ROUTES_MODULE_ID } from '../vite-plugin-routes/index.js';
 import { sessionConfigToManifest } from '../core/session/utils.js';
+import { ASTRO_VITE_ENVIRONMENT_NAMES } from '../core/constants.js';
 
 // This is used by Cloudflare optimizeDeps config
 export const SERIALIZED_MANIFEST_ID = 'virtual:astro:manifest';
@@ -37,9 +38,24 @@ export function serializedManifestPlugin({
 	command: 'dev' | 'build';
 	sync: boolean;
 }): Plugin {
+	function reloadManifest(path: string | null, server: ViteDevServer) {
+		if (path != null && path.startsWith(settings.config.srcDir.pathname)) {
+			const environment = server.environments[ASTRO_VITE_ENVIRONMENT_NAMES.ssr];
+			const virtualMod = environment.moduleGraph.getModuleById(SERIALIZED_MANIFEST_ID);
+			if (!virtualMod) return;
+
+			environment.moduleGraph.invalidateModule(virtualMod);
+		}
+	}
+
 	return {
 		name: SERIALIZED_MANIFEST_ID,
 		enforce: 'pre',
+		configureServer(server) {
+			server.watcher.on('add', (path) => reloadManifest(path, server));
+			server.watcher.on('unlink', (path) => reloadManifest(path, server));
+			server.watcher.on('change', (path) => reloadManifest(path, server));
+		},
 
 		resolveId: {
 			filter: {