Admin UI not working as expected for extended / merged list schema

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I have two lists, Product and ProductRange. There is a many-to-one relationship between these lists, so each Product is linked to a single ProductRange. This means that I have a field called productRangeId in the Prisma model for Product.

I want to use this field to sort any queries for multiple products, so products from the same range are grouped together. I'm attempting to do this by extending my schema as shown in the docs. My code is below.

export function extendGraphqlSchema(baseSchema: GraphQLSchema) {
  return mergeSchemas({
    schemas: [baseSchema],
    typeDefs: `
    type Query {
      products(where: ProductWhereInput): [Product]!
    }`,
    resolvers: {
      Query: {
        products: (root, { where, orderBy, skip, take }, context: Context, info: GraphQLResolveInfo) => {
          return context.prisma.product.findMany({ orderBy: { 'productRangeId': 'asc' }, skip, take, where });
        },
      }
    },
  })
}

This works as expected in the API explorer, but no products are listed in the admin UI - see screengrabs.

However if I remove the where param from the findMany query (see below) it seems to fix the issue in admin.

...
    products: (root, { where, orderBy, skip, take }, context: Context, info: GraphQLResolveInfo) => {
      return context.prisma.product.findMany({ orderBy: { 'productRangeId': 'asc' }, skip, take });
    },
...

For requests from admin the where query is { OR: [] }. Obviously this isn't really doing anything and could be tested for and removed, but wanted to ask whether there an issue with my approach, or is this a bug?

Node is v24.7.0
@keystone-6/core is 6.5.1
Browser is Safari

Thanks for you efforts building Keystone - it's great!!