Gemini 4 Carbon

Canonical version: Gemini 4 Carbon.

Gemini 4 Carbon is Google DeepMind's second Gemini 4 model, announced on 28 October 2026, two weeks after Gemini 4 Argon became generally available. Google calls it "our strongest model with state-of-the-art cybersecurity and long horizon capabilities". It's built for long-running engineering and coding tasks, and for finding, exploiting and patching vulnerabilities.

The headline came from Artificial Analysis: Carbon scores 59 on its Intelligence Index v5, one point above Claude Opus 5.5 (58), which makes it the new number one. The catch is the same as with Argon at launch: almost nobody can use it yet.

Key facts

• Access: a subset of cyber defenders in Google's Fairwind Program first. Not in the Gemini app or the public API at announcement, and no date for a wider release. Argon took about two weeks to go from announcement to the API
• Pricing (per Artificial Analysis): $4 per million input tokens and $20 per million output tokens, the same as Argon's standard price. Cached input is 95% off ($0.20 per million). Google offers 50% off at launch ($2 / $10), with no confirmed end date
• Context window: 1M tokens
• Modalities: text, image, video and speech in; text out
• Google's claims: state-of-the-art on cybersecurity tasks, and secure code generated at "more than twice the success rate of Gemini 4 Argon on internal benchmarks". Secondary coverage cites 88.2% on SEC-bench Pro from Google's chart; I couldn't check it against the public leaderboard

Artificial Analysis results

Artificial Analysis tested Carbon at "high" reasoning (28 October 2026):

It leads four of the nine Index evaluations: HLE-Diamond, Terminal-Bench-Science, AA-Omniscience and AutomationBench-AA.

The number I find most interesting is hallucination again. On AA-Omniscience v1.1, Carbon answers 58% correctly (10 points more than Argon) and hallucinates 11% of the time. That's worse than Argon (4% on v1.1) but far better than Opus 5.5 and GPT-6 Astra, both at 50%. Google's Gemini 4 models still say "I don't know" much more often than the competition. Careful though: Hacker News commenters report plenty of hallucinations with Argon in the Gemini app, so the benchmark and the product experience don't fully match.

Read the #1 with care

• The index changed the day before. Artificial Analysis launched Intelligence Index v5 on 27 October 2026, one day before Carbon's announcement. v5 has four equal categories (knowledge work, coding, science, general), adds FrontierCode 2.0 and Terminal-Bench-Science (15% of the whole index), and drops GDPval-AA, SciCode and AA-LCR. 60% of it now relies on private test sets. Carbon leads Terminal-Bench-Science, so the new weighting helps it. On Hacker News, rbehrends pointed out that this one science benchmark moved a lot, for a skill most users don't need
• One point is not a lead. 59 vs 58 is a tie in practice. On the coding agent index, Claude Code with Opus 5.5 is still ahead
• Conflict of interest. Artificial Analysis also sells benchmarking services to labs, and most of the index is now private. That's good against contamination, but it also means you can't reproduce the numbers
• You can't test it. A leaderboard entry for a model only a few cyber defenders can access doesn't help you pick a model today. Several HN commenters asked Artificial Analysis to leave unreleased models out

My take

Google is clearly back at the frontier, and the hallucination numbers are the real differentiator: if a model knows when it doesn't know, I can trust it with research and knowledge work. But "number one" here means "one point ahead on a benchmark that changed the day before, for a model you can't use". The pattern repeats from Argon (and HN noticed the timing, right after Alphabet's earnings): announce, top a leaderboard, ship weeks later.

I'll wait for API access and independent long-horizon evals before I try it with my own agents. Until then, Opus 5.5 stays my default for coding, and Argon is the Gemini you can actually use.

References

• Artificial Analysis, "Gemini 4 Carbon is the new #1 in the Artificial Analysis Intelligence Index" (2026-10-28): https://artificialanalysis.ai/articles/gemini-4-carbon-new-number-1
• Artificial Analysis, Intelligence Index v5 (2026-10-27): https://artificialanalysis.ai/articles/artificial-analysis-intelligence-index-v5
• Google, "Introducing Gemini 4 Carbon" (2026-10-28): https://blog.google/innovation-and-ai/models-and-research/gemini-models/introducing-gemini-4-carbon/
• Hacker News discussion of the launch: https://news.ycombinator.com/item?id=50276792
• Hacker News discussion of the Artificial Analysis result: https://news.ycombinator.com/item?id=50288019
• Khaleej Times (Reuters), "Google launches Gemini 4 Carbon AI model with cybersecurity focus" (2026-10-28): https://www.khaleejtimes.com/business/google-launches-gemini-4-carbon-ai-model-with-cybersecurity-focus-2
• Vals AI model page: https://www.vals.ai/models/google_gemini-4-carbon

Related

• Gemini 4 Argon
• Gemini
• Google DeepMind
• Google
• Artificial Analysis
• Claude Opus 5.5
• GPT-6 Astra
• GPT-6.1 Sol
• Antigravity CLI
• Claude Code
• AI Hallucination
• AI Safety
• Goodhart's Law
• AI Frontier Model
• Large Language Models (LLMs)

About Sébastien

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