Have they announced that it definitely won't be? If not, it might be just a roll-out hiccup, because Argon is available to me as an agent in Xcode and I only have a Gemini Pro subscription. (Whether or not I'll ever use Argon in Xcode is a different question. I've been so impressed by Claude that I rarely even use my Codex sub. I'll be very interested to hear from others how well Argon does with Swift and SwiftUI.)

Their official documentation says it's available to Pro subscribers in the Gemini app only, and available to Ultra subscribers in Antigravity.