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Gemini 4 Carbon vs Opus 5.5 vs GPT-6.1 Terra: Price & Access
Three new AI models landed within five weeks, and the first scoreboard puts Google on top. But Gemini 4 Carbon vs Claude Opus 5.5 vs GPT-6.1 Terra is not a simple race, because only two of the three are actually open to you today. Carbon, announced October 28, 2026, is limited to a small group of cyber defenders and has no public release date. Opus 5.5 has been available since September 22, and Terra launched on October 26 at a price four times lower than Opus. This guide shows who can use which model, what each costs in US dollars, how they score, and what a real monthly bill looks like, with three charts you can read in seconds.
Quick Answer: Gemini 4 Carbon vs Opus 5.5 vs GPT-6.1 Terra
• Highest independent score: Gemini 4 Carbon, 59 on the Artificial Analysis Intelligence Index v5. Claude Opus 5.5 is one point behind at 58.
• Who can use it today: Opus 5.5 and Terra, yes. Carbon, not yet, unless Google selects you for its Fairwind program.
• Cheapest: GPT-6.1 Terra at $1 per million input tokens and $5 per million output tokens.
• Best pick for most people right now: Opus 5.5 for coding agents and Terra for high-volume work. Wait on Carbon.
• Who can use it today: Opus 5.5 and Terra, yes. Carbon, not yet, unless Google selects you for its Fairwind program.
• Cheapest: GPT-6.1 Terra at $1 per million input tokens and $5 per million output tokens.
• Best pick for most people right now: Opus 5.5 for coding agents and Terra for high-volume work. Wait on Carbon.
Who Can Actually Use Each Model Today?
Release status is the biggest difference between these three, so check it before you look at any benchmark.
| Model | Released | Can you use it? | Where |
|---|---|---|---|
| Gemini 4 Carbon | Announced Oct 28, 2026 | No, not publicly | Limited to selected cyber defenders through Google's Fairwind Program. No date for developers, businesses or consumers. |
| Claude Opus 5.5 | Sept 22, 2026 | Yes | Claude Platform, plus AWS, Google Cloud and Azure. |
| GPT-6.1 Terra | Oct 26, 2026 | Yes, but not in regular ChatGPT Chat | The API (gpt-6.1-terra), plus ChatGPT Work and Codex for Plus, Pro, Enterprise and Edu. |
If you want a Gemini 4 model you can use right now, Gemini 4 Argon is the one. Google made it generally available on October 13, and it is the model Carbon builds on. Reports say Argon's $2 and $10 introductory price rises to $4 and $20 on December 1, so check Google's pricing page before you budget.
What Are These Three Models?
- Gemini 4 Carbon (Google): Google's strongest model so far, built for cybersecurity defense and long-running engineering tasks. It arrived two weeks after Argon.
- Claude Opus 5.5 (Anthropic): Anthropic's flagship for agentic coding and knowledge work. It has a 1 million token context window, up to 128,000 output tokens and a June 2026 knowledge cutoff. Anthropic says it costs about 40% less to run than Opus 5 on typical workloads. I covered it earlier in Claude Opus 5.5: what's new for developers.
- GPT-6.1 Terra (OpenAI): A fast, cheaper middle-tier GPT-6 model aimed at computer use, visual tasks and everyday work. It has a 1.05 million token context window, a 128,000 token output limit and a June 1, 2026 knowledge cutoff. Terra is not OpenAI's top model. GPT-6 Astra sits above it, and Panstag's GPT-6 Astra benchmarks guide explains that flagship.
Benchmarks: Who Scores Highest?
The only score that puts these models on one scale comes from the independent Artificial Analysis Intelligence Index, version 5. Terra is missing from the chart because independent testers were still catching up two days after its launch, and the reports I found disagreed.
Artificial Analysis Intelligence Index v5
Independent index, reported via secondary coverage. GPT-6.1 Terra not yet verified. Scale 0 to 100.
Gemini 4 Carbon
59
Claude Opus 5.5
58
GPT-6 Astra
57
Read the chart for what it shows: a near tie. A one-point lead on an aggregate score can flip with different prompts or reasoning settings, so it is a reason to test Carbon, not a reason to switch.
Vendor-Reported Benchmarks (Not Directly Comparable)
| Benchmark | Reported by | Result |
|---|---|---|
| SEC-bench Pro (finding vulnerabilities) | Carbon: 88.2% | |
| ExploitGym (exploitation) | Carbon: 54.8% | |
| CWE-bench (patching) | Carbon: 71.0% | |
| FrontierCode (agentic coding, default effort) | Anthropic | Opus 5.5: 54.6% vs GPT-6 Astra: 53.3% |
Each company chose the tests it expected to win, and no neutral lab has repeated these results yet. They show where each model is strong: Carbon on security, Opus 5.5 on agent-style coding. Terra has no published numbers on these specific tests, because it is positioned as a cheaper high-volume model, not a coding flagship. If you are weighing the security side of these models, Panstag's explainer on GPT-6 Astra's Critical cyber risk rating shows why labs now limit access to their strongest models.
Price: What Each Model Costs in US Dollars
Prices below are per million tokens on each vendor's standard API. A million tokens is roughly 750,000 words.
API Price per 1 Million Tokens (USD)
Standard list prices as of October 31, 2026. Carbon's price is introductory. Scale 0 to $20.
Input tokens
GPT-6.1 Terra
$1
Gemini 4 Carbon
$2
Claude Opus 5.5
$4
Output tokens
GPT-6.1 Terra
$5
Gemini 4 Carbon
$10
Claude Opus 5.5
$20
| Price detail | GPT-6.1 Terra | Gemini 4 Carbon | Claude Opus 5.5 |
|---|---|---|---|
| Input (per 1M tokens) | $1 | $2 (introductory) | $4 |
| Output (per 1M tokens) | $5 | $10 (introductory) | $20 |
| Cached input | $0.05 | Reported 95% off input | $0.20 |
| Cheaper batch option | Half price (Batch and Flex) | Not confirmed | $2 and $10 (Batch API) |
| Faster option | Fast mode at double price | Not confirmed | Fast mode $8 and $40 |
Two warnings. Google calls Carbon's $2 and $10 an introductory price, so plan for it to rise. Some coverage says $4 and $20 afterward, but I could not confirm that for Carbon, only for Argon. And Terra's rates apply to requests up to about 272,000 input tokens. Longer prompts cost more.
What a Real Monthly Bill Looks Like
Take a medium workload, such as a support or coding assistant that uses 50 million input tokens and 5 million output tokens a month. These are my own calculations from the list prices above, before caching.
Estimated Monthly Cost: 50M Input + 5M Output Tokens (USD)
My calculation from list prices. No caching or negotiated discounts. Scale 0 to $300.
GPT-6.1 Terra
$75
Carbon (intro price)
$150
Opus 5.5 (batch)
$150
Opus 5.5 (standard)
$300
Terra costs half of Carbon's introductory bill and a quarter of Opus 5.5's standard bill. Opus 5.5's batch discount closes part of that gap, but only for jobs that can wait.
Which Model Should You Choose?
| Your situation | Pick | Why |
|---|---|---|
| Coding agents and software teams | Claude Opus 5.5 | Strongest published agentic-coding evidence, available now. The caveat is that most of that evidence is Anthropic's own. |
| High-volume automation, form filling, support triage | GPT-6.1 Terra | Lowest price, built for computer use. It is new, so independent scores are thin. |
| Security research and defense | Gemini 4 Carbon | Best published security numbers, but you need Google's approval. |
| A Gemini model you can use today | Gemini 4 Argon | Generally available since October 13. |
| Solo bloggers and small teams on a budget | Terra, or a cheaper tier | The difference between $75 and $300 a month matters more than a one-point benchmark gap. |
Many teams will end up using two models: a strong one to plan and review, and a cheap one to do the bulk work. If you plan to let an AI agent touch your accounts or email, read Panstag's guide to AI agent permission management before you connect anything. And for an earlier look at how a rival launch was hyped against its independent results, see Grok 4.6 vs GPT-5.6.
Final Verdict
Google's Carbon wins the first scoreboard by a single point and the security tests Google chose, but you probably cannot use it yet. Claude Opus 5.5 is the safer pick for coding agents, and GPT-6.1 Terra is the cheapest way to run work at scale. Test the two you can access on your own tasks, and revisit Carbon once Google confirms who gets in and what it costs after the introductory period.
Sources: Google's Gemini 4 Carbon announcement and coverage (Oct 28, 2026), OpenAI's GPT-6.1 Terra launch and pricing pages (Oct 26, 2026), Anthropic's Claude Opus 5.5 pricing documentation and launch post, Artificial Analysis Intelligence Index v5 as reported by i-SCOOP and others, and Tech Insider's Oct 30, 2026 comparison. Vendor-reported benchmarks are not independently reproduced. Prices and availability change quickly, so verify on each vendor's page. Monthly cost figures are my own estimates.
