Feels too hairsplitting. It was the same type of people doing largely the same activities with the same objectives, even if on paper there was a 2-year hiatus between OSS being dissolved and CIA created. People would understand if you wrote "OSS/CIA did X" when describing the 1940s/50s/60s.
Similar to how a branch of the US Public Health Service [0] originally tasked with malaria prevention became Communicable Disease Center (CDC) in 1946-67, subsequently renamed to "Center for Disease Control" and "Centers for Disease Control" (1980), "Centers for Disease Control and Prevention". It hasn't actually been called the "Center for Disease Control" since 1980, although many people (incl. journalists) still call it that.
Also, most countries' Department of Defense/Ministry of Defence were called
Ministry of War or Department of War during WWII (and some only controlled the army, not all branches of military). [1] And the White House War Room was renamed the Situation Room in 1961. (RIP George Carlin.)
[0]: https://en.wikipedia.org/wiki/Centers_for_Disease_Control_an...
[1]: https://en.wikipedia.org/wiki/Ministry_of_defence