# Gemini 4 Carbon vs Claude Opus 5.5: Which Top Model Wins?

URL: https://whatisagenticai.net/blog/gemini-4-carbon-vs-claude-opus-5-5/
Published: 2026-10-29
Publisher: Little Tough LLC, maker of AI Agent Assistant: Agentic AI (https://apps.apple.com/us/app/ai-agent-assistant-agentic-ai/id6761501260)

Gemini 4 Carbon vs Opus 5.5: Carbon leads the Intelligence Index 59 to 58 and costs less per task, but Opus wins computer use and coding, and is available now.

When the Artificial Analysis Intelligence Index v5 launched on October 27, 2026, Claude Opus 5.5 sat in first place. One day later, Google announced Gemini 4 Carbon, and it moved one point ahead. Now people are asking the obvious question: Gemini 4 Carbon vs Opus 5.5, which one is actually better?

The honest answer depends on two things: what kind of work you do, and whether you can get the model at all. Below we put the two side by side using only numbers that at least two sources agree on.

**TL;DR:** Gemini 4 Carbon beats Claude Opus 5.5 on the Artificial Analysis Intelligence Index v5 by one point (59 vs 58), costs about 23% less per test task, and wins most rows of Google’s launch chart, especially security work. Opus 5.5 still wins on using a computer (OSWorld-2.1: 87.2% vs 81.5%) and on coding agents (62 vs 59). The biggest difference is access: anyone can pay for Opus 5.5 today, while Carbon is limited to a small group of cyber defenders with no public date.

## Gemini 4 Carbon vs Claude Opus 5.5 at a glance

|  | Gemini 4 Carbon | Claude Opus 5.5 |
| --- | --- | --- |
| Made by | Google DeepMind | Anthropic |
| Announced | October 28, 2026 | September 22, 2026 |
| Who can use it | Selected cyber defenders in Google’s Fairwind Program | Paid Claude plans, Claude Code, API, AWS, Google Cloud, Azure, GitHub Copilot |
| List API price (per 1M tokens) | $4 in / $20 out (launch price $2 / $10) | $4 in / $20 out |
| Context window | 1 million tokens | 1 million tokens in, 128,000 out |
| Best known for | Security work, long many-step jobs | Coding, terminal work, using a computer |

The list prices are the same. Carbon looks cheaper on paper right now only because Google is running a half-price launch offer. Google’s post does not say when it ends.

## Gemini 4 Carbon vs Opus 5.5 benchmarks

These are the head-to-head scores we could confirm in at least two places. Most come from Artificial Analysis, an independent testing group, and Google’s own launch chart. For the Artificial Analysis tests, Carbon ran at "high" effort and Opus 5.5 at "max" effort.

| Test | What it checks | Carbon | Opus 5.5 | Winner |
| --- | --- | --- | --- | --- |
| AA Intelligence Index v5 | Overall smarts on many hard tests | 59 | 58 | Carbon |
| AA Coding Agent Index | Coding agents doing real tasks | 59 (Antigravity CLI) | 62 (Claude Code) | Opus 5.5 |
| OSWorld-2.1 subset | Using a computer like a person | 81.5% | 87.2% | Opus 5.5 |
| AA-Omniscience v1.1 | Knowing facts without making things up | 54 | 48 | Carbon |
| Vals Index | Work tasks in law, finance and more | 70.36% | 70.18% | Tie, in practice |

Two of these gaps are tiny. A 1-point lead on the Intelligence Index and a 0.18-point lead on the Vals Index are close to a tie. Anthropic itself says single scores can move by a few points from run to run. Our [guide to the Artificial Analysis Intelligence Index](https://whatisagenticai.net/blog/what-is-artificial-analysis-intelligence-index/) explains what that score does and does not tell you.

The bigger gaps are more useful. Carbon makes things up less often: on AA-Omniscience, Artificial Analysis measured an 11% hallucination rate for Carbon and 50% for Opus 5.5 at max effort. Opus 5.5 is clearly better at clicking through apps and websites on a computer, which matters for agents that do work for you.

Google’s full launch chart has 17 rows. Fello AI and OfficeChai both report that Carbon leads 15 of them. Opus 5.5 wins OSWorld-2.1, and GPT-6 Astra wins the FrontierSWE 2 coding test. Remember that Google picked the tests for its own chart.

## Which is cheaper: Gemini 4 Carbon or Opus 5.5?

Same list price, different bills. Carbon tends to write shorter answers, so it uses fewer tokens (small pieces of words) to finish the same job.

| Artificial Analysis test run | Carbon (high) | Opus 5.5 (max) |
| --- | --- | --- |
| Cost per Intelligence Index task | $7.76 | $10.04 |
| Output tokens per task | 123,000 | 173,000 |

That makes Carbon about 23% cheaper per task at full price, and it uses 29% fewer output tokens. With Google’s launch discount, the gap would be wider. But a lower price does not help if you cannot buy the model yet.

## Can I use Gemini 4 Carbon or Opus 5.5 today?

This is where the two are furthest apart.

- **Claude Opus 5.5:** yes. Pick it in the Claude app or claude.ai on a paid plan, run it in Claude Code, call claude-opus-5-5 in the API, or choose it in GitHub Copilot on Pro+ and higher plans.

- **Gemini 4 Carbon:** not unless you are one of the security teams Google invited. Google says developers, businesses and consumers will get it "as soon as possible," with no date. It is also going through the US government’s voluntary testing before wide release.

If you want Google’s best model you can actually use now, that is still [Gemini 4 Argon](https://whatisagenticai.net/blog/what-is-gemini-4-argon/).

## Gemini 4 Carbon vs Opus 5.5 for security work

This is Carbon’s home turf. Google built it to find and fix security holes, and it scored 88.2% on SEC-bench Pro and 71.0% on CWE-bench, a patching test. Opus 5.5 goes the other way: Anthropic sends most cybersecurity requests to the older Opus 4.8 as a safety step, so some security jobs get a weaker model or a refusal. For security teams with Fairwind access, Carbon is the clear pick. For everyone else, it is not an option yet.

## Verdict: which one should you pick?

- **You need a model today:** Opus 5.5. Carbon is not on sale.

- **Coding agents and computer use:** Opus 5.5 leads on both confirmed tests.

- **Fewer made-up facts and lower cost per task:** Carbon, once it opens up.

- **Security research:** Carbon, if Google lets you in.

Want the full background on each? Read [What is Gemini 4 Carbon?](https://whatisagenticai.net/blog/what-is-gemini-4-carbon/) and [What is Claude Opus 5.5?](https://whatisagenticai.net/blog/what-is-claude-opus-5-5/)

## What this means for you

In the last five weeks we got Opus 5.5, Gemini 4 Argon, [GPT-6.1 Terra](https://whatisagenticai.net/blog/what-is-gpt-6-1-terra/) and now Carbon. The leader keeps changing by a point or two, and the newest one often has a waitlist on day one.

For normal tasks like planning a trip, drafting a report or comparing products, that one point will not change your result. What changes your result is having AI that plans the steps and finishes the job. That is the idea behind [agentic AI](https://whatisagenticai.net/what-is-agentic-ai/).

That is how our app works. **Agentic AI** gives you a team of ready-made expert agents on iPhone and iPad, running on frontier models. You can put up to 4 agents on one task, there is no account to create, and your first 3 tasks are free.

## Quick answers

**Is Gemini 4 Carbon better than Claude Opus 5.5?** On overall test scores, slightly: 59 vs 58 on the Artificial Analysis Intelligence Index v5. Opus 5.5 still wins on computer use and coding agents, and you can use it today.

**Gemini 4 Carbon vs Opus 5.5 for coding: which is better?** Opus 5.5 in Claude Code scores 62 on the Artificial Analysis Coding Agent Index, 3 points above Carbon in Google’s Antigravity CLI at 59.

**Is Gemini 4 Carbon cheaper than Opus 5.5?** Both list at $4 per million input tokens and $20 per million output tokens. Carbon costs about 23% less per task in Artificial Analysis tests because it uses fewer tokens, and it has a half-price launch offer.

**Can I use Gemini 4 Carbon now?** Only if you are a cyber defender in Google’s Fairwind Program. Google has not given a date for developers or the Gemini app.

**Gemini 4 Carbon vs Opus 5.5 vs GPT-6 Astra: who wins?** On the Intelligence Index v5, Carbon leads, Opus 5.5 is one point behind, and GPT-6 Astra is cheapest per task at $6.25 in Artificial Analysis tests.

New to words like tokens, benchmarks or context windows? Our [agentic AI glossary](https://whatisagenticai.net/agentic-ai-glossary/) explains them in plain English.

**Sources:** [Google: Gemini 4 Carbon](https://blog.google/innovation-and-ai/models-and-research/gemini-models/introducing-gemini-4-carbon/) · [Artificial Analysis](https://artificialanalysis.ai/articles/gemini-4-carbon-new-number-1) · [The Decoder](https://the-decoder.com/google-deepmind-releases-gemini-4-carbon-just-two-weeks-after-argon-with-gains-across-the-board/) · [OfficeChai](https://officechai.com/ai/gemini-4-carbon-benchmarks/) · [Fello AI](https://felloai.com/gemini-4-carbon/) · [Anthropic: Claude Opus 5.5](https://www.anthropic.com/news/claude-opus-5-5)