Google announced the new Gemini 4 Hydrogen model on Thursday 12 November, along with a new model option in its coding tool Antigravity. Called Orchestrator, the option does not use one model from start to finish but switches between Gemini 4 Carbon or Argon and Hydrogen within the same session.

A typical model router guesses a task’s difficulty from the first prompt and hands the whole task to the cheapest model that can handle it, the Antigravity team wrote in its blog. In long agent tasks, however, difficulty changes as the work progresses. In Google’s example, Carbon first examines the dependencies without changing any files and drafts a plan. Hydrogen can then write the changes, update the packages and run the tests. If Hydrogen runs into problems, it hands the work back to Carbon, which reviews the situation, revises the plan and carries on.

/swarm, introduced the same week, runs parallel teams of agents on large tasks. Orchestrator, by contrast, is meant for everyday work in a single session.

Google said Orchestrator came close to Carbon’s success rate on the Terminal-Bench benchmark. It used on average 24 per cent less of the usage limit and finished 19 per cent faster. The figures are Google’s own, and the company does not give exact success rates. The benchmark version also differs between sources: Google’s main blog names Terminal-Bench 4.0, the Antigravity blog 4.1.

Google: Hydrogen surpasses Argon

Hydrogen is designed for fast everyday coding and agent work, and the model card says it is derived from Carbon. Google said Hydrogen scores 51 points on the Artificial Analysis Intelligence Index at its default reasoning effort, high, against 50 for Argon. At the highest level, xhigh, it scores 54. Google also said Hydrogen’s Terminal-Bench 4.1 score rose from 18.2 per cent for its predecessor, Gemini 3.8 Flash, to 57 per cent.

In Artificial Analysis’s own measurement, Hydrogen trailed its competitors in command-line work, The Decoder reported. It scored 54 per cent on Terminal-Bench 4.0, against 64 per cent for Claude Sonnet 5.5 (max). Artificial Analysis said xhigh uses almost twice as many output tokens as high, raising the cost per task from $1.87 to $3.16.

According to the model card, Hydrogen does not reach the critical capability levels for biological or cyber risks, but it does reach their alert thresholds. In automated evaluation, its rate of unjustified refusals was 5.57 percentage points higher than that of 3.8 Flash. The card lists hallucinations, occasional slowness and timeouts as known limitations.

Availability and price

Orchestrator is coming to Google AI Ultra subscribers in Carbon and Argon versions and to paid AI Pro subscribers in an Argon version. Businesses get it through Gemini for business. Hydrogen works in Antigravity for paid Pro and Ultra subscribers.

In the Gemini API, Hydrogen costs $1.50 per million input tokens and $7.50 per million output tokens across its full 1 million-token context window. Google advertises 1 million tokens of output. The model card says, however, that a standard call outputs at most 64,000 tokens by default; only long generation running in the background reaches 1 million.