They had that?! I saw that some people wrote skills and plugins to call claude cli and gemini cli to still be able to use the subscription.
I would also wish that this was supported out of the box, something similar to goose cli providers or acp providers (https://block.github.io/goose/docs/guides/acp-providers).
But I don't want to spend testing yet another agent harness or change the workflow when I somewhat got used to one way of working on things (the churn is real).
As others have mentioned Vault, Keycloak, Flink are language agnostic. Regarding the switch from Java to .NET, I would rather recommend switching to Kotlin instead of .NET for a developer experience similar to C#, while still keeping your existing expertise in Java and its ecosystem.
And this comes from someone in a .NET shop currently, but have worked with Java before.
IMHO both languages and surrounding ecosystems are good. Both have their pros and cons and quirks.