Help writing GRD files for gradient

I’ve been vibe coding to create a Python app with Gemini and Claude that creates gradients that can be saved as .grd files for use in Photoshop.

But when I try to import the gradients into Photoshop I get an error message that they’re not compatible with the current version of Photoshop. Neither AI has been able to resolve it, Gemini even had me opening GRD files in a HEX editor to try to figure out the problem. But no luck. Is there any guidance somewhere on how to create GRD files that Photoshop can use?