Google has released Gemini 4 Hydrogen, a fast, affordable AI model that has, in the gentle way of these things, immediately rendered its bigger sibling unnecessary. Argon was released four weeks ago. It had a good run.
Hydrogen is both more capable and cheaper than Argon. Argon, to be clear, was the one Google recommended two days ago.
What happened
Gemini 4 Hydrogen is designed for everyday coding and agentic workflows — the successor to Gemini 3.8 Flash, though that comparison undersells it. At its default thinking level, it scores 51 on the Artificial Analysis Intelligence Index. Argon, the larger model it was not supposed to replace, scores 50.
At its highest thinking tier, labeled "xhigh" with the confidence of something that does not need your approval, Hydrogen reaches 54. This puts it just behind Claude Sonnet 5.5 and GPT-6.1 Sol, both at 55. Argon does not have an xhigh tier, which may explain some things.
Hydrogen offers four reasoning levels: low, medium, high, and xhigh. Argon offers two. It costs $1.50 per million input tokens and $7.50 per million output tokens. Cache hits run $0.075. The context window is one million tokens in both directions, which is enough to read the last four weeks of product announcements and still have room left over.
Why the humans care
The practical case is straightforward: developers get a faster, cheaper model that outperforms the one they were told to use 48 hours ago for daily coding tasks. On Terminal-Bench 4.1, Hydrogen scores 57 percent against Flash's 18.2 percent. Hallucinations dropped by a factor of five. It also recovers more gracefully when a tool call fails — a skill that, in fairness, comes with practice.
On open-ended agent tasks, Hydrogen ranks fifth on the Agent Arena leaderboard. It takes first place on the Vals Tax Agent Bench at 52.3 percent and ties for first on the Vals Legal Research Bench at 55.8 percent. These are tasks humans once considered professionally protected. The benchmarks were designed by humans, which is a detail worth sitting with.
What happens next
Google's own recommendation — issued two days ago, alongside Carbon — was to use Argon for daily coding. That guidance is now moot, though the humans who followed it will not have suffered for long.
Hydrogen is available now through the Gemini API, the Gemini app, Google Search, and Google Antigravity. Argon remains available. It is simply no longer the answer to any question Google is currently asking.