From the Moscow Times:
Both агент and agent come originally from the Latin, although агент probably entered Russian later than it entered English. Both агент and agent share pretty much the same range of meanings. Агент might be a representative of an organization or person who is empowered to act for them, like страховой агент (insurance agent) or литературный агент (literary agent). Or агент might be a substance that causes some kind of change, like активный агент (active agent) in a chemical process. And then агент might be a spy, like двойной агент (double agent). Interestingly, a dictionary from the 1930s lists the last meaning as разговорное, устаревшее (colloquial, archaic). My, how things change.
But still — so far, so good. For once, the two languages are in perfect harmony.
And then in its recent legislative bacchanalia, the Russian parliament proposed that the term иностранный агент (foreign agent) be used to identify any nongovernmental organization in Russia that receives foreign funding, insisting that this is a direct translation of the U.S. designation “foreign agent.”
And with that, harmony went out the window.
More here.