Hydrogen vs Carbon vs Argon: How to Choose, and How Orchestrator Pairs Them

The Gemini 4 family now has three tiers: Carbon, Argon, and Hydrogen. Google's official division of labor: Carbon is the strongest, Argon the balanced one, Hydrogen the fastest. But the AA index made things interesting: Hydrogen at 51 points, one point above Argon's 50. This article synthesizes orcarouter's and the-decoder's comparisons to explain how to actually choose between the three tiers, and how Antigravity's Orchestrator pairs Carbon with Hydrogen.

Three-tier comparison

All three have a 1M context window and a 65,536-token sync output cap; Hydrogen is adapted from Carbon.

51 vs 50: basically a tie — don't over-read it

Hydrogen's 51 against Argon's 50 is a 1-point gap — essentially a tie under the AA index's methodology. And the levels aren't symmetric: Hydrogen's 51 is its default high level, while Argon's default is medium — Hydrogen ships at a high level out of the box. On terminal work Hydrogen doesn't lead either: Artificial Analysis measured Terminal-Bench 4.0 at 54%, below Sol's 56% and Sonnet 5.5's 64%. The-decoder's judgment: xhigh's 54 is roughly on par with Sonnet 5.5 and GPT-6.1 Sol (55 each at max), but terminal work is weak.

Hydrogen's real advantages aren't the intelligence score — they're price, the free tier, and the hallucination rate: after December 1 its per-token price is 37.5% of Carbon/Argon's, it is the family's only model with a free tier, and its hallucination rate is just 8% (Sonnet 5.5: 43%, Sol: 52%).

The pricing ladder: December 1 is the dividing line

Today, Hydrogen is only 25% cheaper than Carbon/Argon's $2/$10 — but those are promo prices expiring November 30. After December 1, Carbon/Argon double to $4/$20, and Hydrogen's price is just 37.5% of theirs. Per-task cost (Artificial Analysis): Hydrogen high $1.87, Argon ~$1.99 at promo price and ~$3.98 at standard price — nearly equal during the promo, diverging after December 1. Carbon's high level costs $7.76 per task, more than 4× Hydrogen's high level.

Orchestrator: Carbon directs, Hydrogen works

Antigravity's Orchestrator (launched November 12, 2026 alongside Hydrogen) switches Carbon and Hydrogen dynamically within one session: Carbon first explores dependencies and plans in a read-only phase, Hydrogen writes the edits, updates packages, and runs tests, handing back to Carbon when stuck; in parallel, Carbon coordinates while Hydrogen powers worker and verifier agents in isolated workspaces. Google claims near-Carbon success rates with 24% less quota and 19% faster.

Two caveats, though. First, the benchmark version is self-contradictory — Google's main blog says Terminal-Bench 4.0, the Antigravity post says 4.1, and neither gives an actual success-rate number. Second, access is Ultra subscribers only ("additional models and plans supported in the future"); enterprises get it via Gemini for business. The Antigravity SDK lets developers assign roles directly (demo: Hydrogen for triage and code, Carbon for large refactors, new features, and security checks). The Antigravity post claims "tens of thousands of swarms" have been launched since Carbon arrived, with no exact count.

Decision table