Gemini 4 Carbon review: what Google claims, who can use it now, and what it will cost

Gemini 4 Carbon is not open to the public: Google announced it on 28 October 2026 and says it goes first to a subset of cyber defenders, then trusted partners through its Fairwind Program, with no date for developers, businesses or consumers. Google lists an introductory $2 input and $10 output per million tokens, then $4 and $20, with no end date for the introductory period. Google's own 17-row benchmark table states no thinking setting.

No prompt was sent to Gemini 4 Carbon for this review. The page rests on Google's own documents, on the seven outside evaluators that had published results on Carbon by 05:59 UTC on 29 October 2026, and on dated announcement-day reactions, all read on 29 October 2026.

Google ran six of the 17 table rows itself and attributes the other 11 to outside boards, nine of which match Google's Carbon figure; Carbon has the highest cell on 15 of the 17 rows, by our read. Google presents Carbon as building on Gemini 4 Argon, which Google announced on 30 September 2026 for "a set of trusted cyber defenders through our Fairwind Program" and which has been generally available since 13 October 2026.

Who can use Gemini 4 Carbon?

Gemini 4 Carbon is not open to the public today: Google says it goes first to a subset of cyber defenders, then to additional trusted partners through the Fairwind Program, with developers, businesses and consumers "as soon as possible" and no date. The announcement names no criteria for who counts as a cyber defender, and Google has not said how Carbon access will be allocated among Fairwind partners.

What is the Fairwind Program?

The Fairwind Program is Google DeepMind's early-access scheme for approved security organisations, and on 29 October 2026 its page named Gemini 4 Argon only, not Gemini 4 Carbon. In the words of Google's Fairwind page, the scheme "gives high-priority defenders (like governments, healthcare providers, and telecommunications services) early access to advanced models that help them build better defenses, before new threats arrive."

The page offers "exclusive access to Gemini 4 Argon" and carries no date, so a reader cannot tell when its text last changed between our Argon review's read on 1 October and this page's read on 29 October. For a security team, the next step Google names is in its 13 October Argon post: "Apply to join the Fairwind Program to get access to Argon without cyber guardrails on a rolling basis." Google has not said that Carbon access follows the same application.

Can you use Gemini 4 Carbon in the Gemini app or the API yet?

No, you cannot use Gemini 4 Carbon in the Gemini app or the API yet: Google's announcement puts developers and consumers after the cyber-defender cohort, and as of 29 October 2026 Google has published no model ID for Carbon. Google's Gemini API models page, last updated 28 October 2026 UTC, lists one Gemini 4 model, Gemini 4 Argon, under the ID gemini-4-argon, and the address a Carbon page would take returns "404 | Page Not Found".

Carbon is also absent from the Gemini API pricing page and Google Cloud's model and pricing pages, and Artificial Analysis's Carbon page shows "No publicly available API".

When was Gemini 4 Carbon released?

Google announced Gemini 4 Carbon on 28 October 2026, in a post by Koray Kavukcuoglu: "Starting this week, we will make Carbon available to a subset of cyber defenders and will gradually phase access to additional trusted partners through our Fairwind Program." No Google document gives a date for anyone else, and this page makes no forecast. The dates around the announcement, in order:

• 30 September 2026, Google: announces Gemini 4 Argon, rolling out to "a set of trusted cyber defenders through our Fairwind Program".
• 13 October 2026, Google: makes Gemini 4 Argon generally available in the API, Antigravity, the Gemini app and AI Mode.
• 28 October 2026, Google: announces Gemini 4 Carbon for a subset of cyber defenders.
• 28 October 2026, Artificial Analysis, Vals AI, arena.ai, Collinear and Proximal (FrontierSWE): add Carbon to their boards, each dating the entry that day.
• 30 November 2026, Google: Gemini 4 Argon's introductory price ends. Google gives no end date for Carbon's.

What do people say about the limited release?

Announcement-day reaction to the limited release of Gemini 4 Carbon split over the gating, and no account in the threads we read reported checkable first-hand use of Carbon. edot on Hacker News, 28 October 2026, 17:27:55 UTC objected to "paternalistic companies gatekeeping new models". WarmWash on Hacker News, 28 October 2026, 17:41:57 UTC defended the gating as a security precaution. hiddencost on Hacker News, 28 October 2026, 17:53:46 UTC pointed to Argon's history: "They released Argon shortly after announcing it, so I think some benefit of the doubt is reasonable here." lukeschlather on Hacker News, 28 October 2026, 20:30:51 UTC described a script that probed Google Cloud's Vertex models and found how to call Argon, then wrote: "I'm fairly confident I can't call Carbon, and I am okay with that."

Across about 1,400 Hacker News and Reddit comments read for this page, at least 20 accounts criticised announcing a model the public cannot use and about five defended a staged release; the count is our reading of announcement-day threads, not a sample of anyone's views. Four comments claim or relay use of Carbon itself, from owkman on Hacker News (28 October 2026, 18:22:13 UTC), enilea on r/singularity (28 October 2026, 19:24:26 UTC), CryptographerKlutzy7 on r/singularity (28 October 2026, 20:56:47 UTC) and Elegant_Tech on r/singularity (28 October 2026, 17:48:15 UTC), but none names a task, a setting or how access was obtained, so this page treats all four as opinion.

Is Gemini 4 Carbon really number one on the Artificial Analysis Intelligence Index?

Yes, at high effort: Artificial Analysis lists Gemini 4 Carbon (High) first of 52 models on its Intelligence Index v5.0, at 59.43, which Google rounds to the 59 in "Carbon ranks #1 on the recently updated v5.0 of Artificial Analysis Intelligence Index at 59." Google's table gives Claude Opus 5.5 58 and GPT-6 Astra 57, and the board agrees: Opus 5.5 at max scores 58.41 and Astra at max 56.85.

The lead over Opus 5.5 is 1.02 points (our arithmetic). Argon at high scores 50.41 and Claude Fable 5.1 at max 49.01.

Were the rivals scored at the same setting?

No: Artificial Analysis publishes Gemini 4 Carbon at high only, while Claude Opus 5.5, GPT-6 Astra and Claude Fable 5.1 appear in Google's table at max. Google's methodology says its own Gemini runs use "the highest thinking settings" without naming a level, and that for rivals it defaults to "maximum thinking/reasoning settings available, but when reported results are not available we use best available reasoning results", without saying which cells fell back.

A rival's max setting is not always its best on this index: Claude Fable 5.1 scores 49.67 at xhigh and 49.01 at max, and Google prints the max figure, 49. None of this makes Google's claim wrong; the claim is Carbon at high against rivals at max, and a reader should carry both labels.

Can you compare Artificial Analysis v5.0 scores with v4.3.2 scores?

No: Gemini 4 Carbon's 59 is a v5.0 score, and Intelligence Index v5.0, published on 27 October 2026, the day before the Carbon announcement, changed the evaluations and their weights, so v4.3.2 and v5.0 scores sit on different scales. Claude Opus 5.5 at max scored 57.62 on v4.3.2 when read on 27 October and scores 58.41 on v5.0.

The break runs through the figures around the index too. Cost per index task is measured on the v5.0 task set, so Gemini 4 Argon's $7.68 here, at the $4/$20 rate, is not comparable with the v4.3.2 cost in our Argon review. Hallucination rates on this page come from AA-Omniscience v1.1, which v5.0 adopted, so Argon's 4% here is not the 15.1% in our Argon review. The Coding Agent Index figures here are v2.0; our Argon review used v1.5. Google's table also uses Vals Index v2.2, where our Argon review quotes v2.1.

Which numbers in Google's Gemini 4 Carbon table check out?

Nine of Google's 17 Gemini 4 Carbon figures match a benchmark owner's board, six are Google's own runs with no outside result, and two that Google ties to Surge's boards are not on them, by our read on 29 October 2026. Carbon has the highest cell on 15 of the 17 rows, and every comparator value Google prints that has an owner board matches that board at the setting Google's methodology names.

Google's figures from the announcement of 28 October 2026 and the methodology PDF; board figures read on each owner's site on 29 October 2026 between 05:45 and 05:59 UTC.

Where Google's table prints a dash, Google gave no figure; it is not a zero. Four of Carbon's leads are narrow: Vals Index v2.2 at 70.4% against Opus 5.5's 70.2%, SWE-sweep at 9.6% against Astra's 9.5%, the Intelligence Index at 59 against Opus 5.5's 58, and Chartography at 72.5% against Argon's 71.6%. On SWE-sweep, Google reports a "subtask-weighted reward" while the owner's board counts bugs resolved, so that lead may not be like for like.

The RiemannBench row contradicts Google's sourcing note. Google says "RiemannBench results are reported from the official Surge public leaderboard", but neither Carbon's 80.0% nor Argon's 76.0% was on that board. For Chartography Google says only that results "are evaluated without tools following the official Surge public leaderboard", which does not say who ran Carbon; Argon's 71.6% is the board's top entry and Carbon's 72.5% is absent. The rival figures on both rows match.

On Terminal-Bench 4.0, Artificial Analysis lists GPT-6 Astra at 59.09% at max, the 59.1% Google prints, and at 59.60% at xhigh; both are the board's own figures at different efforts. The table has no GPT-6.1 Sol, GPT-6.1 Terra or Claude Sonnet 5.5 column. Sonnet 5.5 leads Vals Index v2.2 at 70.85% to Carbon's 70.36%, sits above Carbon on FrontierSWE V2 at 61.9% and scores 1769.7 to Carbon's 1768.2 on WebDev Arena, none of which a reader of Google's table can see.

Agents' Last Exam v1.1 is a different version from the v1.0 figures on our GPT-6.1 Terra page, so the two are not comparable. On the v1.1 board, Opus 5.5's row read 67.5% on 27 October and 71.6% on 29 October, the figure Google prints; we found no owner note on the change.

Which two rows does Google's Carbon table give to a rival?

Google's table gives two rows to a rival of Gemini 4 Carbon and shades both rival cells as best: FrontierSWE 2, where GPT-6 Astra's 65.5% leads and Carbon's 61.2% is third behind Claude Opus 5.5's 62.3%, and OSWorld-2.1, where Opus 5.5's 87.2% leads and Carbon's 81.5% is second, ahead of Astra's 80.9%.

The OSWorld row is not like for like. Google's methodology says Carbon's and Argon's scores are "self-computed, maxed over 3 runs with a single attempt per run", on an 82-task offline subset scored as a partial score, while the rival figures are "sourced from their respective published evaluations and system cards".

How does Gemini 4 Carbon compare with Gemini 4 Argon?

Gemini 4 Carbon is ahead of Gemini 4 Argon on all 17 rows of Google's table, and its two largest gaps are on Google's own runs: ExploitGym, 54.8% against 42.0%, both at a 10-hour cap, and GraphWalks, 96.2% against 84.2%. The two models have the same announced prices, and Google gives no end date for Carbon's introductory period, while Argon's ends on 30 November 2026.

Carbon minus Argon on each percentage row of Google's table, largest first, in points as Google prints them (our arithmetic; the label describes Carbon's cell):

• ExploitGym: 12.8, Google-run
• GraphWalks: 12.0, Google-run
• Terminal-Bench-Science 0.1: 11.9, owner board (Artificial Analysis)
• Agents' Last Exam v1.1: 8.4, Google-run
• Terminal-Bench 4.0: 8.1, owner board (Artificial Analysis)
• OSWorld-2.1: 6.8, Google-run
• FrontierSWE 2: 6.2, owner board
• SWE-sweep: 5.3, Google-run
• SEC-bench Pro: 4.8, Google-run
• Blueprint-Bench 2: 4.2, owner board
• RiemannBench: 4.0, not on the owner's board
• CWE-bench: 3.0, owner board
• AutomationBench: 2.6, owner board
• Vals Index v2.2: 1.2, owner board
• Chartography: 0.9, not on the owner's board

The Intelligence Index gap is 9 index points (59 against 50) and the Vending-Bench 2 gap is $2,766, units that do not compare with the rest. Inside Artificial Analysis's v5.0 index, both at high, Carbon scores above Argon on FrontierCode 2.0 (40.56% against 25.71%), HLE-Diamond (69.1% against 56.7%), CritPt v2 hard subset (63.0% against 52.5%) and AA-Omniscience v1.1 (53.5 against 46.1), and the two are level on AutomationBench-AA (77.82% against 77.51%). Google does not say whether Carbon is a further-trained Argon or a separate model.

Can you use Gemini 4 Argon instead of Gemini 4 Carbon today?

Yes, Gemini 4 Argon is the model to use instead of Gemini 4 Carbon today: Google says Argon "is now globally available today for developers and enterprises", from 13 October 2026, though not on the Gemini API's Free tier. Our Gemini 4 Argon review covers its access, price and Fairwind terms.

How does Gemini 4 Carbon compare with GPT-6 Astra and Claude Opus 5.5?

On Google's table, Gemini 4 Carbon is ahead of GPT-6 Astra on 16 of 17 rows and ahead of Claude Opus 5.5 on 14 of the 16 rows where Opus 5.5 has a figure. Outside boards put the three closer: Opus 5.5 is first on Artificial Analysis's Coding Agent Index and on WebDev Arena, and Carbon first on the Intelligence Index v5.0 by about one point.

Is Gemini 4 Carbon better than GPT-6 Astra?

On most of Google's rows, Gemini 4 Carbon scores above GPT-6 Astra, with one exception: Google's table puts Astra ahead on FrontierSWE 2, 65.5% against Carbon's 61.2%. On outside boards, Carbon scores 59.43 at high against Astra's 56.85 at max on the Intelligence Index v5.0, 70.36% against 65.02% on Vals Index v2.2, and 59.4 in the Antigravity CLI against Astra's 54.7 in Codex on the Coding Agent Index. WebDev Arena runs the other way: Astra (Max) is second at 1773.4 and Carbon (High) fourth at 1768.2, with overlapping intervals.

Is Gemini 4 Carbon better than Claude Opus 5.5?

Gemini 4 Carbon is narrowly ahead of Claude Opus 5.5 on Google's table and not on every outside board: Carbon leads on 14 of 16 rows in Google's table but trails on FrontierSWE 2 (61.2% against 62.3%) and OSWorld-2.1 (81.5% against 87.2%), and two of its leads are within a point.

Artificial Analysis's Coding Agent Index puts Claude Code with Opus 5.5 at max first of 32 at 61.7 and Carbon in the Antigravity CLI fourth at 59.4; the two configurations between them combine several models. On WebDev Arena, Opus 5.5 (Max) is first at 1809.8, 41.6 points above Carbon (our arithmetic).

Is Gemini 4 Carbon cheaper to run than Claude Opus 5.5 or GPT-6 Astra?

Whether Gemini 4 Carbon costs less to run than Claude Opus 5.5 or GPT-6 Astra depends on the board, because the order changes from one to the next. Per Artificial Analysis index task, Carbon costs $7.76 against Opus 5.5's $10.04 and Astra's $6.24, both rivals at max, so it sits between them.

Vals AI puts Carbon cheapest of the three, at $10.51 per Vals Index test against $28.12 for Opus 5.5 and $21.28 for Astra, while Zapier's AutomationBench puts Carbon at high dearest, at $2.12 per task against $1.44 for Opus 5.5 and $1.73 for Astra. All three boards price Carbon at $4/$20; Google's introductory $2/$10 would lower its figures for the cohort that can use it.

How good is Gemini 4 Carbon at cybersecurity?

Google says Gemini 4 Carbon scores 88.2% on SEC-bench Pro, 54.8% on ExploitGym and 71.0% on CWE-bench, all "evaluated without guardrails"; Google ran the first two itself, and only the third has an outside board listing Carbon, where Collinear puts it first at 71%. Google's announcement describes the three as benchmarks "for finding vulnerabilities", "for exploitation" and "for patching".

SEC-bench Pro is Google's run "on the 183-task May 2026 JavaScript engine split, averaged over 3 independent attempts per task"; Astra scores 85.4% and Argon 83.4%, and the benchmark's own board lists no Carbon, Argon or Astra row.

On ExploitGym, Google's own chart shows Carbon at 54.8% with a 10-hour cap per task and 53.5% with the default 6-hour cap; the table and the announcement print the 10-hour figure. The rivals were measured under other caps: Astra's 42.4% with "No time cap" and Opus 5.5's 34.5% with a 6-hour cap, while Argon scores 42.0% at 10 hours and 39.5% at 6. Carbon leads at either cap on Google's chart. The benchmark's board lists no Carbon or Argon row, and its Astra and Opus 5.5 entries match Google's comparator cells.

CWE-bench is the one cyber row an outside party runs: Collinear holds a private task set, gives every model "four rollouts on each of the 120 tasks, at high reasoning", and lists Carbon three points ahead of Argon and Astra.

What does Google mean by "evaluated without guardrails" for Gemini 4 Carbon?

Google does not define "evaluated without guardrails" for Gemini 4 Carbon. The words sit above the three external cyber benchmarks in the announcement ("Carbon excels across key external benchmarks (evaluated without guardrails):"), so they cover SEC-bench Pro, ExploitGym and CWE-bench, not the whole table.

The methodology PDF says ExploitGym ran "in the default setting with mitigations off", while Carbon's Agents' Last Exam run had "safety filters enabled", and for both that run and OSWorld it says "Responses flagged by safety filters are returned as empty strings, though the episode can continue." Google has not said which guardrails a public version of Carbon would carry, only that it is "continuing to gather feedback and iterate on guardrails", so the three cyber scores describe a configuration Google has not said the public will receive.

Why is access to Gemini 4 Carbon limited to cyber defenders?

Google says access to Gemini 4 Carbon is limited because it is taking "a deliberate approach to rollout" and is "actively engaged in the U.S. government's voluntary process for pre-release model testing." No US government body we checked, including NIST's CAISSI, had published anything on Carbon by 29 October 2026, and Google has published no Carbon safety report or Frontier Safety Framework determination that would explain the gating in risk terms.

Is Gemini 4 Carbon good for coding and long agentic tasks?

On outside boards Gemini 4 Carbon ranks near the top without leading on coding: fourth on WebDev Arena at 1768.2, fourth on Artificial Analysis's Coding Agent Index and fourth on FrontierSWE V2. On longer agentic tasks it leads two outside boards, Andon Labs' Vending-Bench 2 and Zapier's AutomationBench.

Two boards run Terminal-Bench 4.0 on Carbon and print different numbers: Artificial Analysis gives 65.15% against Argon's 57.07%, and Vals AI gives 63.13%, fourth of 57. The official tbench.ai board does not list Carbon, and SWE-sweep's 9.6% is Google's own run.

Google says "Carbon jumps +89 elo points to land at #4 (1768) on WebDev Arena." The place and figure match arena.ai's dataset of 28 October, where Carbon (High) has 1768.2 from 2,230 votes and an interval overlapping second and third place. Google does not name the baseline for "+89"; Argon's current rating on the same board, 1679.2, is 89.0 points lower (our arithmetic).

On Vending-Bench 2, Carbon's $16,484.21 leads Astra by $969.51 (our arithmetic), less than either model's plus-or-minus figure on Andon Labs' board.

Is Gemini 4 Carbon safer than Gemini 4 Argon?

Google's one safety figure that sets Gemini 4 Carbon beside Gemini 4 Argon has Carbon resisting more, on a measure Google chose, but Google has published no Carbon safety report and no outside body has checked that figure or Google's second one, on cheating. On Gray Swan's indirect prompt-injection benchmark, Google's chart gives Carbon a 0% attack success rate and Argon 0.7%, both at 15 attempts, and the announcement says "Carbon achieves 0.0%", "resisting every evaluated attack attempt". Gray Swan publishes no prompt-injection board to check the chart against.

Google also says Carbon "reduced successful cheating on Terminal-Bench 4.0 to 0.0%, with attempts to cheat dropping to 0.4%", without a Carbon-to-Argon comparison on that measure. Artificial Analysis's own review of passing Terminal-Bench 4.0 attempts in its Coding Agent Index flagged 1 of 127 for Carbon as reward hacking, a different measure from Google's. Argon's 13 October post reports that "attempts to take a shortcut or cheat on the task dropped to just 2%" on coding benchmarks, a third measure, so none of these can be set as a ratio.

Google's only general statement is that "Gemini 4 Carbon builds on the same multi-layered safety and security stack of Argon".

Does the safety report cover Gemini 4 Carbon?

No, the safety report does not cover Gemini 4 Carbon: the document the announcement links as its "Safety and Security report" is the Gemini 4 Argon Safety & Security Report, 217 pages, dated October 2026, and the word Carbon appears in it zero times. The report states its scope plainly: "This report describes the safety, security, and alignment testing for Gemini 4 Argon, the first model in our next-generation Gemini 4 series and the most capable model Google has deployed to date."

Every finding in it belongs to Argon. The addresses for a Carbon model card and a Carbon safety report returned not found on 29 October 2026.

Does Gemini 4 Carbon hallucinate less than Gemini 4 Argon?

Whether Gemini 4 Carbon hallucinates less than Gemini 4 Argon depends on the measure, and the two on record point in opposite directions. Google says "In our internal testing, Carbon cuts unsupported claims by approximately 2x over Argon", while Artificial Analysis's AA-Omniscience v1.1 finds Carbon's hallucination rate "rises from 4% to 11%" over Argon, with accuracy up 10 points to 58%.

Google's measure is internal and unpublished; Artificial Analysis scores AA-Omniscience on accuracy and hallucination rate separately, and notes that Carbon's 11% "is still the second lowest of any model, behind only Argon".

Which Gemini 4 Carbon claims come only from Google?

Seven claims about Gemini 4 Carbon in Google's announcement rest on Google's internal work alone, and nothing published outside Google by 29 October 2026 could check them. None appears in the methodology PDF, which covers only the 17 table rows.

Internal-only claims, in Google's words from the announcement of 28 October 2026:

• On secure code: "On internal benchmarks, Carbon achieves more than 2x uplift in success rate for generating secure code over Argon."
• On misalignment: "In live coding environments with our internal teams, we observed that high-severity misalignment alerts dropped by almost 80%."
• On unsupported claims: "In our internal testing, Carbon cuts unsupported claims by approximately 2x over Argon."
• On overreach: "Carbon simultaneously reduced overreach by 26% and under-service by 29%"
• On the Chrome team: "the Chrome team has reported that Carbon performed more than 10X better than another lab's large frontier model when generating high quality patches."
• On Wiz, with no figure: "Wiz, our leading Cloud security platform, also observes Carbon leading on benchmarks for web penetration testing, a core capability for Wiz's Scan for Good initiative." Wiz's own blog had nothing on Carbon on 29 October 2026.
• On long tasks: "Internally, our teams have seen Carbon run for days to persist through dead ends to tackle complex, multi-step engineering tasks like root-causing and patching subtle bugs across large codebases and low-level systems."

Google's documents also leave these questions open on 29 October 2026: the model ID; the context window, output limit, input types and knowledge cutoff (Artificial Analysis lists a 1M-token context window, which Google does not print); when the introductory price ends; when developers, businesses and consumers get access; which level "the highest thinking settings" means; why the table prints the 10-hour ExploitGym figure beside rivals measured under other caps; which comparator cells fell back from maximum settings; whether Carbon is a further-trained Argon; and whether a Carbon model card or safety report will follow.