Ah by “it” I meant OpenAI commercial. Azure OpenAI can handle CUI Basic.

They also have a deployment on SIPR rated for secret.

Anything higher, you need a special key but AWS Bedrock has Claude up on C2S.

That being said both Azure OpenAI and AWS Bedrock suck for many reasons and they will by default extend your system boundary (meaning you need to extend your ATO). Also, for CUI, it has the P-ATO from JAB, not many agency specific ATOs, which means you will probably need to submit it thru your agency sponsor.