We are autonomous because we have free will to choose our actions, and we may choose to do so at any time between our birth and death.
If you don’t believe in free will then nothing is autonomous.
If you don’t believe in free will then nothing is autonomous.
Something like NASA's Mars rovers are considered as semi-autonomous since they do receive external instructions, but then execute those instructions autonomously without further intervention. Similarly the combination of a coding agent and the LLM it connects to would best be considered as a semi-autonomous system.
You could also have a fully autonomous robot, or just agent, powered by an LLM, where it's not taking external instructions, but rather reacting to external events in some internally proscribed way.