I landed my first Point of Sale (POS) SaaS client project and built it inside Google Antigravity , trusting Gemini 3.1 Pro for all agentic coding. Bad move. Midway through, severe bugs hit—fixing sales inputs completely broke my dashboard analytics. Frustrated, I switched to the GPT stack (Codex, GPT-5.5, GPT-5.6 Sol). But that brought a new headache: token quotas drained in minutes and API bills went through the roof. The breakthrough? Community stats on Agent Arena showed Flash models...