withastro/astro · error · AggregateError

${cssTransformErrors[0].message}

Error message

${cssTransformErrors[0].message}

What it means

After the compiler runs, Astro processes `<style>` blocks and may produce CSS transform errors. If exactly one error exists it is re-thrown directly; if multiple exist they are wrapped in an `AggregateError` carrying all errors. This error has no static `code` — it surfaces the first CSS error's message. It represents a failure in transforming the CSS layer of an `.astro` component.

Source

Thrown at packages/astro/src/core/compile/compile.ts:119

			name: 'CompilerError',
			message: compilerError.text,
			location: {
				line: compilerError.labels[0].line,
				column: compilerError.labels[0].column,
				file: filename,
			},
			hint: compilerError.hint,
		});
	}

	switch (cssTransformErrors.length) {
		case 0:
			break;
		case 1: {
			throw cssTransformErrors[0];
		}
		default: {
			throw new AggregateError({
				...cssTransformErrors[0],
				errors: cssTransformErrors,
			});
		}
	}
}

function normalizeFilename(filename: string, root: URL) {
	const normalizedFilename = normalizePath(filename);
	const normalizedRoot = normalizePath(fileURLToPath(root));
	if (normalizedFilename.startsWith(normalizedRoot)) {
		return normalizedFilename.slice(normalizedRoot.length - 1);
	} else {
		return normalizedFilename;
	}
}

View on GitHub (pinned to d081033d5f)

Solutions

1. Inspect the surfaced CSS error message and fix the offending `<style>` block.
2. If an `AggregateError`, iterate `.errors` to see every failing rule.
3. Validate the CSS in isolation (e.g., paste into a linter) to catch syntax issues faster.
4. Check for a recent CSS tooling upgrade that changed validation strictness.

function isCssAggregate(e) { return e instanceof AggregateError && Array.isArray(e.errors); }

try {
  await build();
} catch (e) {
  const errs = e instanceof AggregateError ? e.errors : [e];
  for (const err of errs) { /* report CSS error */ }
}

When it happens

Trigger: An `.astro` component's `<style>` block contains CSS that fails the transform pipeline (e.g., invalid syntax caught by the CSS processor, or a preprocessing error). Multiple style errors in one component produce the `AggregateError` branch at `compile.ts:119`.

Common situations: Invalid CSS property values, unterminated declarations, unsupported `@import`, or a PostCSS/Lightning CSS transform rejecting the stylesheet; upgrading a CSS tool that newly rejects previously-tolerated input.

Related errors

• UnknownCompilerError
• CompilerError
• [RSS] You can only glob entries within 'src/pages/' when pas
• [astro:actions] `defineAction()` unexpectedly used on the cl
• [astro:actions] `getActionContext()` unexpectedly used on th

AI-assisted analysis of withastro/astro@d081033d5f (2026-08-12). Data as JSON: /api/errors/d2bba9013037c4d0. Report an issue: GitHub.