diff --git a/eslint.config.js b/eslint.config.js
index c15c17e7dc..d8875d37f9 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -5,10 +5,18 @@ import lube from 'eslint-plugin-lube';
 export default [
 	...svelte_config,
 	{
+		languageOptions: {
+			parserOptions: {
+				project: true
+			}
+		},
 		plugins: {
 			lube
 		},
 		rules: {
+			'@typescript-eslint/await-thenable': 'error',
+			'@typescript-eslint/prefer-promise-reject-errors': 'error',
+			'@typescript-eslint/require-await': 'error',
 			'no-console': 'error',
 			'lube/svelte-naming-convention': ['error', { fixSameNames: true }],
 			// eslint isn't that well-versed with JSDoc to know that `foo: /** @type{..} */ (foo)` isn't a violation of this rule, so turn it off
@@ -43,7 +51,6 @@ export default [
 			'documentation',
 			// contains a fork of the REPL which doesn't adhere to eslint rules
 			'sites/svelte-5-preview/**',
-			'playgrounds/demo/src/**',
 			'tmp/**',
 			// wasn't checked previously, reenable at some point
 			'sites/svelte.dev/**'
diff --git a/playgrounds/demo/.prettierignore b/playgrounds/demo/.prettierignore
deleted file mode 100644
index 85de9cf933..0000000000
--- a/playgrounds/demo/.prettierignore
+++ /dev/null
@@ -1 +0,0 @@
-src
diff --git a/playgrounds/demo/package.json b/playgrounds/demo/package.json
index cc2739cb68..e96e8011ba 100644
--- a/playgrounds/demo/package.json
+++ b/playgrounds/demo/package.json
@@ -9,9 +9,7 @@
     "ssr": "node ./server.js",
     "build": "vite build --outDir dist/client && vite build --outDir dist/server --ssr src/entry-server.ts",
     "prod": "npm run build && node dist",
-    "preview": "vite preview",
-    "format": "prettier --check --write .",
-    "lint": "prettier --check . && eslint"
+    "preview": "vite preview"
   },
   "devDependencies": {
     "@sveltejs/vite-plugin-svelte": "^3.1.0",
diff --git a/playgrounds/sandbox/run.js b/playgrounds/sandbox/run.js
index 86ec3fc882..dffcc0af58 100644
--- a/playgrounds/sandbox/run.js
+++ b/playgrounds/sandbox/run.js
@@ -29,7 +29,7 @@ function mkdirp(dir) {
 const svelte_modules = glob('**/*.svelte', { cwd: `${cwd}/input` });
 const js_modules = glob('**/*.js', { cwd: `${cwd}/input` });
 
-for (const generate of ['client', 'server']) {
+for (const generate of /** @type {const} */ (['client', 'server'])) {
 	console.error(`\n--- generating ${generate} ---\n`);
 	for (const file of svelte_modules) {
 		const input = `${cwd}/input/${file}`;
diff --git a/playgrounds/sandbox/tsconfig.json b/playgrounds/sandbox/tsconfig.json
index 44ef7add23..8aa4b6f1e9 100644
--- a/playgrounds/sandbox/tsconfig.json
+++ b/playgrounds/sandbox/tsconfig.json
@@ -13,5 +13,5 @@
 		"allowJs": true,
 		"checkJs": true
 	},
-	"include": ["./input"]
+	"include": ["./run.js", "./input"]
 }