Gemini 4 Carbon Arrives in Antigravity, but Only for Google AI Ultra

Update (Nov 10, 2026, evening): Antigravity CLI 1.5.5, released the same evening, adds Gemini 4 Carbon (Low, Medium and High) to /model and --model for people who sign in with Google Cloud Application Default Credentials, according to its changelog. On our Google AI Pro account nothing changed after the update: agy models still doesn't list Carbon. The 1.5.5 changelog also adds /swarm, but on our account it still answers "Unknown command" (details).

TL;DR: On November 10, 2026, Google made Gemini 4 Carbon available in Google Antigravity, together with a preview of the multi-agent /swarm mode. In Antigravity, Carbon is for Google AI Ultra subscribers (and Enterprise) only. On our Google AI Pro account it appeared in the model picker greyed out: "Unavailable · Gemini 4 Carbon is currently available to Ultra plan subscribers." Gemini 4 Argon stays available on paid Pro. Google AI Studio sets the same rule: Carbon needs Ultra or a paid Gemini API key. Developers can also use Carbon on the paid tier of the Gemini API, at an introductory price of $2 per million input tokens and $10 per million output tokens through November 30.

What Google announced

The Antigravity blog post from November 10 calls Carbon Google's strongest model for long-horizon software engineering, knowledge work, scientific discovery and cybersecurity. It says Ultra subscribers can use Carbon starting that day in the Antigravity app, the Antigravity CLI and the Antigravity IDE extensions. Enterprises get it through Gemini for business. Scientists and researchers can apply for a chance to get free access to Argon and Carbon on Antigravity's highest usage tier for six months.

Google positions the two Gemini 4 models side by side rather than replacing one with the other:

• Argon remains, in Google's words, "an ideal choice for most advanced engineering and knowledge work tasks". The AI Studio guide describes it as faster, with lower token spend per turn.
• Carbon spends more thinking tokens per turn to explore and verify its work, so it is slower and uses more tokens. Google suggests it for complex debugging, architecture, security auditing and, in a swarm, for the coordinator and verifier roles. The blog post says Carbon ranks first on CursorBench 4.0 and Perplexity's WANDR; that is Google's claim, and we did not check it.

Carbon itself was not brand new on November 10. According to VentureBeat, Google first announced it on October 28 for a limited group of cyber defenders, with wider access planned through its Fairwind program. November 10 is the general release: the AI Studio changelog marks Carbon as generally available that day.

Who gets Gemini 4 Carbon in Antigravity

The official models page lists reasoning models by plan. This is what it showed on November 10:

The same page gives Carbon the thinking levels Low, Medium and High, as for Argon.

What a Google AI Pro account sees

We record the model list that Antigravity receives from Google's servers on our Google AI Pro account. Carbon was not in it at 07:50 UTC on November 10. At 15:50 UTC it was there as a disabled entry with the tag "Unavailable" and the tooltip "Gemini 4 Carbon is currently available to Ultra plan subscribers." No update was needed: the list comes from the server, so CLI 1.5.4 and app 2.30.0 showed the new entry as they were.

In the Antigravity CLI the entry looks like this (/model in an interactive session):

The non-interactive agy models command, which lists the models you can use, did not include Carbon on the same account. Argon (Low, Medium, High) stayed available and selectable.

This is the same pattern as Argon's launch. On October 13, Argon also appeared on Pro as "Unavailable, currently available to Ultra plan subscribers", and Google opened it to Pro on October 15, two days later (our coverage). Whether Carbon will follow the same path, Google hasn't said. Its announcement names only Ultra, Enterprise and the research program.

Gemini 4 Carbon in Google AI Studio

Google AI Studio draws the same line. On our Google AI Pro account, AI Studio showed a "Gemini 4 Carbon is now available" banner, but choosing Carbon opened an upgrade dialog: "Gemini 4 Carbon needs a Google AI Ultra plan or a Gemini API key." The two options are a Google AI Ultra subscription or pay-as-you-go API billing.

The launch also changed how AI Studio describes Argon. Its model list used to call Argon "Our most capable model"; after the launch it says "A highly capable model", and Carbon is "Our most intelligent frontier model". AI Studio's app gallery got six new demo apps tagged Gemini 4 Carbon, mostly 3D browser games.

Gemini 4 Carbon in the Gemini API

Outside Antigravity, Carbon is generally available on the paid tier of the Gemini API and in Google AI Studio, according to the AI Studio changelog entry for November 10. The model ID is gemini-4-carbon. It appeared in the API's model list on our first check after the launch, at 16:01 UTC.

Source: AI Studio pricing, model page and What's new in Gemini 4 Carbon, read November 10, 2026.

Google says Carbon and Argon have the same per-token price. Because Carbon thinks longer per turn, the same task is likely to cost more with Carbon. Google's pricing note adds that every processed token is billed, including thinking tokens.

Carbon and /swarm

Google launched Carbon together with /swarm, a preview mode in which a coordinator agent runs parallel workers in separate git worktrees and verifier agents check their work on a shared message board. Agents in a swarm can be pinned to different models, and Google pitches Carbon for the coordinator and verifier roles while lighter models do the edits. The blog post also warns that parallel multi-agent systems use quota much faster than a normal chat. /swarm is rolling out in the app and the CLI; for the app, the changelog lists it in the 2.31.0 release notes of November 9. We covered the earlier signs in Antigravity is building a native swarm mode.

What this means for you

• On Google AI Ultra: Carbon should be in the model picker of the app, the CLI and the IDE extensions. Google suggests keeping Argon for everyday work and switching to Carbon for the hardest problems, since Carbon uses more tokens per turn.
• On Google AI Pro: nothing changes for now. Argon remains the strongest model you can pick in Antigravity. In AI Studio, Carbon needs Ultra or a paid API key as well. The greyed-out Carbon entry is a notice, not a bug. Availability is set by plan on Google's side, so updating the CLI or the app is not expected to enable it.
• On a free or Google AI Plus plan: Carbon is not available, and neither is Argon.
• If you use the Gemini API: Carbon is available on the paid tier now. The introductory price ends November 30, after which it doubles.
• If you're a researcher: the blog post mentions six months of free access to Argon and Carbon on Antigravity's highest usage tier for accepted applicants.

How to check it yourself

• In the Antigravity CLI, run agy and type /model: on Pro, Carbon shows as "Unavailable". agy models lists only the models you can select.
• In the Antigravity app, open the model selector under the prompt box.
• Check the plan table on Google's models page.

What we don't know

• Whether, or when, Carbon will reach Google AI Pro, as Argon did two days after it first appeared there as "Unavailable".
• How much of the Ultra quota a Carbon conversation uses compared with Argon. Google's documentation gives no figures.
• Which model the pro tier of custom subagents uses on Ultra now. On Pro it was a Gemini 3.8 Flash variant (our test); we can't test Ultra.

We will add an update if Google changes Carbon's availability.

Read next

• Antigravity Pro users lost Gemini 3.1 Pro and didn't get Argon at first
• Antigravity is building a native swarm mode
• Antigravity subagents on Google AI Pro: the "pro" tier isn't Gemini 4 Argon

Sources: the model list our Google AI Pro account received from Antigravity on November 10, 2026, the Antigravity CLI 1.5.4 model picker, Google AI Studio as our Pro account saw it, and our check of the Gemini API model list at 16:01 UTC; the Antigravity blog post, models page and changelog; Google AI Studio changelog, model page, pricing and What's new in Gemini 4 Carbon, all read November 10, 2026; VentureBeat on the October 28 announcement. In the CLI screenshot we covered the account email and local folder paths. How we work: editorial policy.