diff --git a/.changeset/lucky-dragons-speak.md b/.changeset/lucky-dragons-speak.md
new file mode 100644
index 000000000..5aa4f937d
--- /dev/null
+++ b/.changeset/lucky-dragons-speak.md
@@ -0,0 +1,5 @@
+---
+'sv': patch
+---
+
+chore: simplify `runes` option
diff --git a/packages/sv/src/cli/tests/snapshots/create-only/svelte.config.js b/packages/sv/src/cli/tests/snapshots/create-only/svelte.config.js
index 58d330bd3..0c3412e9f 100644
--- a/packages/sv/src/cli/tests/snapshots/create-only/svelte.config.js
+++ b/packages/sv/src/cli/tests/snapshots/create-only/svelte.config.js
@@ -1,17 +1,10 @@
 import adapter from '@sveltejs/adapter-auto';
-import { relative, sep } from 'node:path';
 
 /** @type {import('@sveltejs/kit').Config} */
 const config = {
 	compilerOptions: {
-		// defaults to rune mode for the project, except for `node_modules`. Can be removed in svelte 6.
-		runes: ({ filename }) => {
-			const relativePath = relative(import.meta.dirname, filename);
-			const pathSegments = relativePath.toLowerCase().split(sep);
-			const isExternalLibrary = pathSegments.includes('node_modules');
-
-			return isExternalLibrary ? undefined : true;
-		}
+		// Force runes mode for the project, except for libraries. Can be removed in svelte 6.
+		runes: ({ filename }) => (filename.split(/[/\\]/).includes('node_modules') ? undefined : true)
 	},
 	kit: {
 		// adapter-auto only supports some environments, see https://svelte.dev/docs/kit/adapter-auto for a list.
diff --git a/packages/sv/src/cli/tests/snapshots/create-with-all-addons/svelte.config.js b/packages/sv/src/cli/tests/snapshots/create-with-all-addons/svelte.config.js
index 2aeeecd4e..6479320f8 100644
--- a/packages/sv/src/cli/tests/snapshots/create-with-all-addons/svelte.config.js
+++ b/packages/sv/src/cli/tests/snapshots/create-with-all-addons/svelte.config.js
@@ -1,18 +1,11 @@
 import { mdsvex } from 'mdsvex';
 import adapter from '@sveltejs/adapter-node';
-import { relative, sep } from 'node:path';
 
 /** @type {import('@sveltejs/kit').Config} */
 const config = {
 	compilerOptions: {
-		// defaults to rune mode for the project, except for `node_modules`. Can be removed in svelte 6.
-		runes: ({ filename }) => {
-			const relativePath = relative(import.meta.dirname, filename);
-			const pathSegments = relativePath.toLowerCase().split(sep);
-			const isExternalLibrary = pathSegments.includes('node_modules');
-
-			return isExternalLibrary ? undefined : true;
-		}
+		// Force runes mode for the project, except for libraries. Can be removed in svelte 6.
+		runes: ({ filename }) => filename.split(/[/\\]/).includes('node_modules') ? undefined : true
 	},
 	kit: { adapter: adapter() },
 	preprocess: [mdsvex({ extensions: ['.svx', '.md'] })],
diff --git a/packages/sv/src/create/shared/+typescript/svelte.config.js b/packages/sv/src/create/shared/+typescript/svelte.config.js
index 58d330bd3..0c3412e9f 100644
--- a/packages/sv/src/create/shared/+typescript/svelte.config.js
+++ b/packages/sv/src/create/shared/+typescript/svelte.config.js
@@ -1,17 +1,10 @@
 import adapter from '@sveltejs/adapter-auto';
-import { relative, sep } from 'node:path';
 
 /** @type {import('@sveltejs/kit').Config} */
 const config = {
 	compilerOptions: {
-		// defaults to rune mode for the project, except for `node_modules`. Can be removed in svelte 6.
-		runes: ({ filename }) => {
-			const relativePath = relative(import.meta.dirname, filename);
-			const pathSegments = relativePath.toLowerCase().split(sep);
-			const isExternalLibrary = pathSegments.includes('node_modules');
-
-			return isExternalLibrary ? undefined : true;
-		}
+		// Force runes mode for the project, except for libraries. Can be removed in svelte 6.
+		runes: ({ filename }) => (filename.split(/[/\\]/).includes('node_modules') ? undefined : true)
 	},
 	kit: {
 		// adapter-auto only supports some environments, see https://svelte.dev/docs/kit/adapter-auto for a list.
diff --git a/packages/sv/src/create/shared/-typescript/svelte.config.js b/packages/sv/src/create/shared/-typescript/svelte.config.js
index 58d330bd3..0c3412e9f 100644
--- a/packages/sv/src/create/shared/-typescript/svelte.config.js
+++ b/packages/sv/src/create/shared/-typescript/svelte.config.js
@@ -1,17 +1,10 @@
 import adapter from '@sveltejs/adapter-auto';
-import { relative, sep } from 'node:path';
 
 /** @type {import('@sveltejs/kit').Config} */
 const config = {
 	compilerOptions: {
-		// defaults to rune mode for the project, except for `node_modules`. Can be removed in svelte 6.
-		runes: ({ filename }) => {
-			const relativePath = relative(import.meta.dirname, filename);
-			const pathSegments = relativePath.toLowerCase().split(sep);
-			const isExternalLibrary = pathSegments.includes('node_modules');
-
-			return isExternalLibrary ? undefined : true;
-		}
+		// Force runes mode for the project, except for libraries. Can be removed in svelte 6.
+		runes: ({ filename }) => (filename.split(/[/\\]/).includes('node_modules') ? undefined : true)
 	},
 	kit: {
 		// adapter-auto only supports some environments, see https://svelte.dev/docs/kit/adapter-auto for a list.