Google rolls out Gemini 4 Hydrogen, finally replacing 3.8 Flash

Google is continuing its elemental AI naming scheme with the new Gemini 4 Hydrogen. These names are less descriptive than the Pro/Flash monikers of earlier releases, but Hydrogen’s purpose is clear: It replaces the faster, more economical Flash models most people in Google’s ecosystem use.

With Google’s recent Argon and Carbon releases, the rollout was staged and began with cybersecurity researchers. Even when general availability began, Google restricted access to users paying for its most expensive AI subscription. The limits for Hydrogen are much more relaxed, with access beginning immediately. This model has replaced Gemini 3.8 Flash across the company’s products.

Google claims that Hydrogen represents a major improvement versus the previous Flash model. It runs in one of four thinking levels (low, medium, high, and the new xhigh), and even in high mode, it’s 2.5 times faster than Flash 3.8. Plus, it reduces “fabricated claims” by more than 5x, according to Google’s analysis. Users will also see gains in code generation, with Hydrogen more than tripling 3.8 Flash’s score in Terminal-Bench. In some cases, Hydrogen even trades blows with Argon. It managed a score of 54 in the popular Artificial Analysis Intelligence Index with xhigh mode versus 50 for Argon.

Hydrogen compared to the mid-tier options from OpenAI and Anthropic.

Credit: Google

Google believes Hydrogen will be a key part of how developers work with agentic coding tools. While it still positions Argon and Carbon as the best for long-horizon tasks and security, Hydrogen’s speed makes it ideal for generating simpler code and running tests without blowing through token budgets.

Hydrogen is also being integrated with Google Search, which the company says is the biggest update to its AI-powered search tools ever. The new model should better handle long, multipart questions, and the responses in both AI Overviews and AI Mode will have more visual elements. The company also claims Hydrogen’s fan-out search has been tuned to link to more sources, but we’ve heard that from Google before.

Everyone will reportedly get access to Hydrogen in search, but it’s a bit more restricted in the Gemini app and AI Studio. The new model is live for AI Pro and Ultra subscribers, but AI Plus and free users are still stuck with the old 3.5 Flash-Lite model. Developers can plug into Hydrogen via the API at $1.50 per million input tokens and $7.50 per million output tokens, which is unchanged from 3.8 Flash. Carbon and Argon are currently $2/$10, but they will go up to $4/$20 starting next month.