Google Antigravity rolls out Gemini 4 Hydrogen and Orchestrator

Google's Antigravity team is adding Gemini 4 Hydrogen to Google Antigravity, together with a new model selector option called Orchestrator that pairs Hydrogen with the recently released Gemini 4 Carbon. Rather than routing a whole task to one model up front, Orchestrator hands work back and forth between the two as a session evolves, for example letting Carbon plan and Hydrogen write edits and run tests. The team reports that on Terminal-Bench 4.1 it matched near-Carbon success while using 24% less quota and finishing 19% faster. Hydrogen also runs standalone with four reasoning levels, including a new xhigh tier, and an SDK for building explicit multi-model pipelines. Hydrogen is rolling out to paid Google AI Pro and Ultra subscribers; Orchestrator is limited to Ultra subscribers.