Rest framework removes min_value and max_value kwargs for readonly fields:

But drf-spectacluar uses these values to detect when format: int64 should be added:

Here it sets minimum and maximum by these values:
https://github.com/tfranzel/drf-spectacular/blob/5734744545bd0c4801c4c010d13edc77328fd412/drf_spectacular/openapi.py#L932

And here adds format if minimum or maximum are outside integer range:
https://github.com/tfranzel/drf-spectacular/blob/5734744545bd0c4801c4c010d13edc77328fd412/drf_spectacular/openapi.py#L846

I'm not sure how this should work. Writing to rest-framework because it first erases information about integer range.