Filament sorts a table column configured with counts(), avg(), sum(), min(), max() or exists() by ordering on the withCount-style alias. Our aggregates from PHPLARA-225 are hydrated after the documents are read, so orderBy('animals_count') throws by design. Filament offers this hook instead (filamentphp/filament#20442):

public function orderByRelationAggregate(string $relation, string|Expression $column, string $function, string $direction = 'asc', ?Closure $callback = null): static

$function is one of avg, count, exists, max, min, sum; $column is * for count/exists; $callback constrains the related query first. Implement with one $lookup (PHPLARA-281) plus $addFields ($size, $gt [$size, 0], $sum/$avg/$min/$max over the looked-up array) and a computed-field sort on the pipeline from the Query\Builder ticket. Must be a real public method; macros are not detected.

Filament feature this enables: sortable relationship aggregate columns (TextColumn::make('animals_count')>counts('animals')>sortable() and the other five functions, including the 'relation as alias' => Closure form).