Koray Kavukcuoglu, Google’s chief AI architect, introduced Gemini 4 Hydrogen on the company’s blog on 12 November. Google said it built the model for fast everyday coding and agentic work. The frontier models Gemini 4 Carbon and Argon are meant for long, demanding reasoning tasks, the company said. The model card states that Hydrogen is derived from Carbon.

Ars Technica reported that Hydrogen has replaced Gemini 3.8 Flash across Google’s products. The model has four reasoning effort levels: low, medium, high (the default) and the new xhigh.

The benchmark figures are Google’s own

Google said Hydrogen completes tasks 2.5 times faster than 3.8 Flash at the default level and makes more than five times fewer fabricated claims. On the Terminal-Bench 4.1 benchmark, Hydrogen scored 57 per cent and 3.8 Flash 18.2 per cent, Google said. On the Artificial Analysis Intelligence Index, Hydrogen scored 51 points at the default level and 54 at xhigh, against 50 for Argon, the company said.

Google also added Orchestrator to its Antigravity development environment. The feature switches between Carbon and Hydrogen within a single session. On Terminal-Bench 4.0, Orchestrator solved almost as large a share of tasks as Carbon while using on average 24 per cent less of the usage limit and finishing 19 per cent faster, Google said.

Price and a first test

In the API, Hydrogen costs $1.50 per million input tokens and $7.50 per million output tokens across its full 1 million-token context window. The model card says the model produces at most 64,000 tokens by default, but the limit rises to 1 million for long generations run in the background. Ars Technica reported that the price matches 3.8 Flash’s.

Programmer and blogger Simon Willison finds Gemini 4’s pricing confusing. Carbon and Argon now cost $2 and $10 per million input and output tokens, but on 1 December the prices rise to $4 and $20. For now, Hydrogen is only 25 per cent cheaper. From December it will cost 37.5 per cent of the Carbon and Argon price. Willison wrote that Hydrogen is still 15 times more expensive than Claude Haiku 5.5 and GPT-6 Luna.

Willison asked the models to draw a pelican riding a bicycle. According to an image he published, Hydrogen used 5,311 output tokens at the high level. Its drawing cost 3.99 cents and took 19 seconds. Carbon used 20,305 tokens; its drawing cost 20.31 cents and took more than four minutes. Willison said Hydrogen’s pelicans are clearly weaker. The comparison rests on a single informal prompt.

Safety and availability

The model card states that Hydrogen makes unjustified refusals 5.57 percentage points more often than 3.8 Flash, particularly when a prompt contains images or other media as well as text. Google assesses that the model does not reach the critical capability level for biological risks or cyberattacks, but that it reaches the alert threshold for both. The full safety report will be published later.

Google said Hydrogen is available to everyone in Google Search and also in the Gemini API, AI Studio and Gemini for business. 9to5Google reported that it is the default model for AI Mode in Search. In Antigravity, Hydrogen requires a paid AI Pro or Ultra subscription. Free users of the Gemini app get Hydrogen through automatic model selection when it suits the prompt, Google said. Ars Technica, however, reported that access is more limited in the Gemini app and AI Studio: free and AI Plus users still get the 3.5 Flash-Lite model.