mthorne (firstname.lastname@example.org) writes:
Obviously, there have been some substantial hints that Cortana was, or became, rampant during the events of Halo. The Cortana Letters, and the line in the Jason Jones interview "Do we know anyone who can work magic in fleet engagements against odds like that?" would be the best candidates.
If the rules of rampancy follow from what was given in the Marathon trilogy, then AIs "need a planetary sized network of computers in order to grow", and that when capable of doing so, rampant systems "expand with exponential vivacity." So if Cortana became rampant at any point, it was most likely when she was connected to the Halo's control room. But this raises a very interesting question: Why did she voluntarily leave?
Cortana was left alone in the Halo's systems for some time while the Master Chief was sent to prevent the release of the Flood. If she became rampant during this time, she would have expanded rapidly, far exceeding the capacity of the storage medium she lives on in the Master Chiefs suit. Cutting herself back down to her original size for travel again would have meant throwing away huge portions of her new self, almost certainly not a pleasant experience. From what we know of rampancy in Marathon, rampant AIs generally fight to the death rather than allow their growth to be limited, and this is certainly not the route Cortana takes.
The obvious objection is that Cortana needed to abandon the Halo since it was going to be destroyed, and so losing most of her newfound power would be preferable to suicide. But since Cortana herself precipitated the destruction of the Halo, this doesn't hold up. A truly rampant AI would be more likely to allow the Halo to be activated, or at least allow the Flood to escape, than voluntarily reduce their size and destroy the largest available computer network. Perhaps Cortana's choice reflects the fact that she is based directly on a human brain, and so has human values that supercede even her own desire for growth.
So either Cortana did not become rampant in the Marathon sense when she was connected to Halo, or else she exhibited a remarkable degree of self control, since we never notice anything like pain or even regret when the Chief removes her from the control room at the beginning of Two Betrayals. Personally, I favor the theory that Cortana did not become rampant.