sveltejs/kit · error · Error

Cannot call '${__.name}(...).updates(...)' on the server

Error message

Cannot call '${__.name}(...).updates(...)' on the server

What it means

Runtime guard on the promise returned by a remote command: the .updates() method is a client-only API for applying optimistic updates after a command resolves. On the server there is no reactive UI to update, so calling it there is unconditionally rejected by this stub.

Source

Thrown at packages/kit/src/runtime/app/server/remote/command.js:91

			const violation =
				state.is_in_remote_query || state.is_in_remote_prerender
					? `inside a query or prerender function`
					: `from a ${event.request.method} handler`;

			throw new Error(`Cannot call a command (${__.name}) ${violation}`);
		}

		if (state.is_in_render) {
			throw new Error(`Cannot call a command (${__.name}) during server-side rendering`);
		}

		const promise = Promise.resolve(
			run_remote_function(event, state, true, () => validate(arg), fn)
		);

		// @ts-expect-error
		promise.updates = () => {
			throw new Error(`Cannot call '${__.name}(...).updates(...)' on the server`);
		};

		return /** @type {ReturnType<RemoteCommand<Input, Output>>} */ (promise);
	};

	Object.defineProperty(wrapper, '__', { value: __ });

	// On the server, pending is always 0
	Object.defineProperty(wrapper, 'pending', {
		get: () => 0
	});

	return wrapper;
}

View on GitHub (pinned to 03f1687fe6)

Solutions

1. Only call .updates() in browser code, e.g. inside a form action callback that runs client-side
2. Gate the call with a $browser/ON_BROWSER check if the code is shared

When it happens

Trigger: Thrown at packages/kit/src/runtime/app/server/remote/command.js:91 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of sveltejs/kit@03f1687fe6 (2026-09-02). Data as JSON: /api/errors/a23bddace724ab4f. Report an issue: GitHub.