Ukraine has never had any mutual defense agreement with anybody.
They did have multiple, contractual security GUARANTEES from Russia and the Unites States... Both delibertely, with malice, foresight and cowardice, reneged on the promises of their respective countries. Neither has integrity and should not be trusted. Hell, the Chief Magat negoriator Trump has already declared his recent USMCA to be worthless. Says whoever negotiated it (him) was an idiot. I agree!