“The CIA has shared info with friendly foreign intelligence agencies since their birth - and visa versa.”
Secretly, and in violation of US law that clearly prohibits them from domestic spying. The early CIA came up with this evasion of the law. It was never a treaty or legal agreement. It is no more legal than if the CIA hired Blackwater to spy on Americans so they could claim their hands were clean.
It’s un-American for a US intel agency to hire a foreign government to spy on US citizens. To paraphrase Andy Jackson, “the CIA is a damned nest of vipers”.
“...prohibits them from domestic spying.....”
Yes, and when domestic spying is involved, the CIA will tell you that is only as an extension of foreign espionage, that they are linked. I have heard it before, in my younger years.