diff --git a/.prettierignore b/.prettierignore
index d5c124353c..72cd10aca8 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -7,6 +7,7 @@ packages/**/config/*.js
 
 # packages/svelte
 packages/svelte/messages/**/*.md
+packages/svelte/scripts/_bundle.js
 packages/svelte/src/compiler/errors.js
 packages/svelte/src/compiler/warnings.js
 packages/svelte/src/internal/client/errors.js
@@ -25,8 +26,7 @@ packages/svelte/tests/hydration/samples/*/_expected.html
 packages/svelte/tests/hydration/samples/*/_override.html
 packages/svelte/types
 packages/svelte/compiler/index.js
-playgrounds/sandbox/input/**.svelte
-playgrounds/sandbox/output
+playgrounds/sandbox/src/*
 
 # sites/svelte.dev
 sites/svelte.dev/static/svelte-app.json
diff --git a/eslint.config.js b/eslint.config.js
index d6c977a36a..d7044fc9f1 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -87,6 +87,7 @@ export default [
 			'**/*.d.ts',
 			'**/tests',
 			'packages/svelte/scripts/process-messages/templates/*.js',
+			'packages/svelte/scripts/_bundle.js',
 			'packages/svelte/src/compiler/errors.js',
 			'packages/svelte/src/internal/client/errors.js',
 			'packages/svelte/src/internal/client/warnings.js',
diff --git a/packages/svelte/scripts/check-treeshakeability.js b/packages/svelte/scripts/check-treeshakeability.js
index 1501ee6954..e883496fe2 100644
--- a/packages/svelte/scripts/check-treeshakeability.js
+++ b/packages/svelte/scripts/check-treeshakeability.js
@@ -118,36 +118,40 @@ const bundle = await bundle_code(
 	).js.code
 );
 
-if (!bundle.includes('hydrate_node') && !bundle.includes('hydrate_next')) {
-	// eslint-disable-next-line no-console
-	console.error(`✅ Hydration code treeshakeable`);
-} else {
-	failed = true;
-	// eslint-disable-next-line no-console
-	console.error(`❌ Hydration code not treeshakeable`);
-}
+/**
+ * @param {string} case_name
+ * @param {string[]} strings
+ */
+function check_bundle(case_name, ...strings) {
+	for (const string of strings) {
+		const index = bundle.indexOf(string);
+		if (index >= 0) {
+			// eslint-disable-next-line no-console
+			console.error(`❌ ${case_name} not treeshakeable`);
+			failed = true;
 
-if (!bundle.includes('component_context.l')) {
-	// eslint-disable-next-line no-console
-	console.error(`✅ Legacy code treeshakeable`);
-} else {
-	failed = true;
+			let lines = bundle.slice(index - 500, index + 500).split('\n');
+			const target_line = lines.findIndex((line) => line.includes(string));
+			// mark the failed line
+			lines = lines
+				.map((line, i) => (i === target_line ? `> ${line}` : `| ${line}`))
+				.slice(target_line - 5, target_line + 6);
+			// eslint-disable-next-line no-console
+			console.error('The first failed line:\n' + lines.join('\n'));
+			return;
+		}
+	}
 	// eslint-disable-next-line no-console
-	console.error(`❌ Legacy code not treeshakeable`);
+	console.error(`✅ ${case_name} treeshakeable`);
 }
 
-if (!bundle.includes(`'CreatedAt'`)) {
-	// eslint-disable-next-line no-console
-	console.error(`✅ $inspect.trace code treeshakeable`);
-} else {
-	failed = true;
-	// eslint-disable-next-line no-console
-	console.error(`❌ $inspect.trace code not treeshakeable`);
-}
+check_bundle('Hydration code', 'hydrate_node', 'hydrate_next');
+check_bundle('Legacy code', 'component_context.l');
+check_bundle('$inspect.trace', `'CreatedAt'`);
 
 if (failed) {
 	// eslint-disable-next-line no-console
-	console.error(bundle);
+	console.error('Full bundle at', path.resolve('scripts/_bundle.js'));
 	fs.writeFileSync('scripts/_bundle.js', bundle);
 }