Google's new Gemini 4 Hydrogen model powers what it calls its "biggest model improvement to Search yet," improving intent understanding, link and visual responses, and multilingual answers in AI Mode. Hydrogen runs 2.5x faster than Gemini 3.8 Flash and beats Gemini 4 Argon on the Artificial Analysis Intelligence Index at high thinking. Its stronger reasoning also improves query fan-out, which splits a prompt into subqueries, so it directly affects how brands get cited in AI search.