Antigravity is the harness like Codex / Claude Code. Argon is the model. You can actually also get Opus and Sonnet 5.5 in agy too.

OpenAI has too many options that may confuse users. I don't know if I should use ChatGPT app or Codex CLI or Astra for development.

Android Studio, and if that doesn't cover your use case the paid Jetbrains version.