sveltejs/kit · warning

The `message` property of `handleError` is deprecated. Use `

Error message

The `message` property of `handleError` is deprecated. Use `error.message` for expected and framework errors, or 'Internal Error' for unexpected errors.

What it means

Like the `status` twin, `message` on the `handleError` error argument is a deprecated getter that warns when read. For unexpected errors the real message is hidden for security, so the getter returns the fallback ('Internal Error'), and developers are told to use `error.message` for expected/framework errors or the literal string otherwise.

Source

Thrown at packages/kit/src/utils/error.js:65

 * properties of the `handleError` hook input.
 * @template {object} T
 * @param {T} input
 * @param {{ status: number; message: string }} fallback
 * @returns {T}
 */
export function add_deprecated_handle_error_properties(input, fallback) {
	Object.defineProperties(input, {
		status: {
			get() {
				console.warn(
					'The `status` property of `handleError` is deprecated. Use `error.status` for expected and framework errors, or `500` for unexpected errors.'
				);
				return fallback.status;
			}
		},
		message: {
			get() {
				console.warn(
					"The `message` property of `handleError` is deprecated. Use `error.message` for expected and framework errors, or 'Internal Error' for unexpected errors."
				);
				return fallback.message;
			}
		}
	});

	return input;
}

View on GitHub (pinned to 03f1687fe6)

Solutions

1. Read `error.message` from the original error and provide your own 'Internal Error' fallback for unexpected errors
2. Update the hook return to compute message explicitly based on error type
3. Silence noise by removing all reads of the deprecated properties

Example fix

// before
return { message: error.message };
// after
return { message: error instanceof Error && 'status' in error ? error.message : 'Internal Error' };

function resolveMessage(error) {
  return error instanceof Error && 'status' in error && error.status != null
    ? error.message
    : 'Internal Error';
}

function isFrameworkError(error) {
  return error instanceof Error && typeof error.message === 'string' && 'status' in error;
}

When it happens

Trigger: Accessing `.message` on the error argument inside `handleError` in hooks.server.js, triggering the getter defined by `add_deprecated_handle_error_properties`.

Common situations: Legacy hook code returning `{ message: error.message }`; third-party error trackers serializing the hook argument; templates copied from pre-deprecation docs.

Related errors

• The `status` property of `handleError` is deprecated. Use `e
• To use an async `handleError` hook to handle errors that occ
• Failed to get response header "set-cookie" — it must be incl
• Use `event.cookies.set(name, value, options)` instead of `ev
• Reading `config.kit` inside adapters is deprecated — it shou

AI-assisted analysis of sveltejs/kit@03f1687fe6 (2026-09-02). Data as JSON: /api/errors/9ac99cb22d0eb33f. Report an issue: GitHub.