Hey @ogasawarakyohei - thanks for reaching out. We’re aware this gap isn’t ideal, and it has also been discussed in the main 2026-07 Collections API thread.
We’re working on improving variant-level collection support across storefront surfaces, but I can’t guarantee a specific API change or timeline. I’m going to close this out for now so the discussion stays consolidated there, but I’m more than happy to pass along any additional requirements as a specific feature request on our end, just feel free to ping me here and I’ll get that logged for you at the very least 