withastro · astrobot-houston · Jul 3, 2026 · Jul 3, 2026
diff --git a/packages/astro/src/vite-plugin-config-alias/index.ts b/packages/astro/src/vite-plugin-config-alias/index.ts
@@ -142,6 +142,8 @@ export default function configAliasVitePlugin({
 
 					const replaceAliases = (match: string, importId: string) => {
 						if (!importId) return match;
+						// Skip data URIs — they are inline content, not file paths.
+						if (importId.startsWith('data:')) return match;
 
 						const resolved = resolveWithAlias(importId, configAlias);
 						if (resolved) {

diff --git a/packages/astro/test/alias-css-url-data-uri.test.ts b/packages/astro/test/alias-css-url-data-uri.test.ts
@@ -0,0 +1,28 @@
+import assert from 'node:assert/strict';
+import { before, describe, it } from 'node:test';
+import * as cheerio from 'cheerio';
+import { type Fixture, loadFixture } from './test-utils.ts';
+
+// Regression test for https://github.com/withastro/astro/issues/17293
+// CSS url() with data URIs should not crash when tsconfig baseUrl is set.
+describe('CSS url() with data URIs and tsconfig baseUrl', () => {
+	let fixture: Fixture;
+
+	before(async () => {
+		fixture = await loadFixture({
+			root: './fixtures/alias-css-url-data-uri/',
+		});
+		await fixture.build();
+	});
+
+	it('preserves data URIs in url() without ENAMETOOLONG crash', async () => {
+		const html = await fixture.readFile('/index.html');
+		const $ = cheerio.load(html);
+
+		const styleTag = $('style').html() || '';
+		assert.ok(
+			styleTag.includes('data:image/svg+xml;base64,'),
+			'CSS should preserve the data URI',
+		);
+	});
+});
diff --git a/packages/astro/test/fixtures/alias-css-url-data-uri/astro.config.mjs b/packages/astro/test/fixtures/alias-css-url-data-uri/astro.config.mjs
@@ -0,0 +1,2 @@
+import { defineConfig } from 'astro/config';
+export default defineConfig({});
diff --git a/packages/astro/test/fixtures/alias-css-url-data-uri/package.json b/packages/astro/test/fixtures/alias-css-url-data-uri/package.json
@@ -0,0 +1,3 @@
+{
+	"name": "@test/alias-css-url-data-uri"
+}
diff --git a/packages/astro/test/fixtures/alias-css-url-data-uri/src/pages/index.astro b/packages/astro/test/fixtures/alias-css-url-data-uri/src/pages/index.astro
@@ -0,0 +1,11 @@
+---
+
+---
+
+<html><body><h1>Hello</h1></body></html>
+
+<style>
+  .icon {
+    background-image: url('data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHZpZXdCb3g9IjAgMCAyNCAyNCIgZmlsbD0ibm9uZSIgc3Ryb2tlPSJjdXJyZW50Q29sb3IiIHN0cm9rZS13aWR0aD0iMiI+PHBhdGggZD0iTTEyIDJMMiA3bDEwIDUgMTAtNS0xMC01eiIvPjwvc3ZnPg==');
+  }
+</style>
diff --git a/packages/astro/test/fixtures/alias-css-url-data-uri/tsconfig.json b/packages/astro/test/fixtures/alias-css-url-data-uri/tsconfig.json
@@ -0,0 +1,5 @@
+{
+	"compilerOptions": {
+		"baseUrl": "."
+	}
+}
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		import { defineConfig } from 'astro/config';
		export default defineConfig({});