gcr.io as pull through cache "Failed to ping endpoint"

[Zappelphilipp]

I am sucessfully using harbor as pull through cache for docker.io. ghcr.io and quay.io but i am not able to add new registry endpoint for gcr.io. I always get the error "Failes to ping endpoint".

the logs of the harbor-core container show

2025-09-10T10:43:29Z [ERROR] [/pkg/reg/adapter/googlegcr/adapter.go:137]: failed to ping registry https://gcr.io: http status code: 400, body: {"errors":[{"code":"UNKNOWN","message":"Unable to parse json key."}]}

Harbor Version: v2.13.0-db1569ae