How to create optional value with Tanstack form and Zod?

How to create optional value with Tanstack form and Zod?

<script setup lang="ts">
    import { useI18n } from 'vue-i18n';
    import { z } from 'zod';
    import { revalidateLogic, useForm } from '@tanstack/vue-form';
    import { tWithJosa } from '@/utils/i18nJosa.ts';

    const { t } = useI18n({ useScope: 'global' });

    const schema = z.object({
        cover_letter: z
            .string()
            .trim()
            .nonempty({
                message: t('common.form.required_value', {
                    what: tWithJosa('recruit.cover_letter.label', '을/를'),
                }),
            })
            .max(1500, { message: t('common.form.max_notice', { count: 1500 }) }),
        attachments: z.array(z.file()).optional(),
        agreements: z.array(z.boolean()).refine((agreements) => agreements.length > 0, {
            message: t('common.form.agree_notice'),
        }),
    });

    const form = useForm({
        defaultValues: {
            cover_letter: '',
            attachments: [],
            agreements: [],
        },
        validationLogic: revalidateLogic(),
        validators: {
            onDynamic: schema,
        },
        onSubmit: ({ value }) => {
            console.log(value);
        },
    });
</script>

There is an error when registering validators(onDynamic).

I think it's a type mismatch problem, but I'm not sure.