Antigravity Subagents on Google AI Pro: the “pro” Tier Isn't Gemini 4 Argon

By Lesia Kapliuk · Published November 10, 2026 · Updated November 10, 2026

TL;DR: In Antigravity you pick a tier for a custom subagent, not a model: inherit, flash or pro. On a Google AI Pro account (CLI 1.5.4, November 10, 2026), a pro subagent ran gemini-3.8-flash-tiered, not Gemini 4 Argon, whether the main agent was Flash or Argon. Only an inherit subagent under an Argon main agent ran Argon. A Flash agent can still ask Argon separately by running the Antigravity CLI, which uses the same Argon quota.

Why we checked

A post titled "Subagents, lol" in r/google_antigravity described a plan many Pro subscribers will recognize. The author writes that Gemini 4 Argon's weekly quota runs out fast, so they let Gemini 3.8 Flash manage and execute and asked it to consult a fresh Argon subagent only when needed. After three days, they say, the Argon quota still showed 100%. When asked, the Flash agent said it spawned the subagent with "inherit" or "pro" and claimed that "pro" was Gemini 4. The author's conclusion: in app 2.29.0, 3.8 Flash can't spawn Argon.

The agent's explanation proves nothing: a model describing its own setup can be wrong. But the setup can be checked, because since CLI 1.5.3 the /agents panel shows which model each subagent runs on. The 1.5.3 changelog lists this as a new feature.

What the documentation says

The custom subagents documentation defines a model field in the subagent's Markdown file. It takes a "model tier", with three values: inherit (the default), flash and pro. The documentation lists only these three values and gives no way to name a specific model such as Gemini 4 Argon. It doesn't say which model each tier maps to on each plan.

Our test

We made two custom subagents in an empty test folder. Both had no tools and the same instruction: answer in one short sentence. The only difference was the tier, pro for one and inherit for the other. We asked the main agent to invoke both with the task "Say hello in one short sentence", then opened /agents to see the models. We ran it twice on our Google AI Pro account with Antigravity CLI 1.5.4. Between the runs we only reworded the subagents' descriptions; the model values stayed the same.

Main agent (thinking level)	Subagent with `pro`	Subagent with `inherit`
Gemini 3.8 Flash (Medium)	gemini-3.8-flash-tiered, 26 s	Gemini 3.8 Flash, 8 s
Gemini 4 Argon (Low)	gemini-3.8-flash-tiered, 13 s	Gemini 4 Argon, 12 s

With Flash as the main agent, the pro subagent did not get Argon:

Note the main agent's own summary above the panel: it reports the pro subagent's model only as "Pro tier", without a model name. The list below it is what the CLI itself displays for each subagent.

With Argon as the main agent, inherit gave Argon and pro still gave the Flash variant. The main model's name isn't in the screenshot; inherit takes the main agent's model, which is why it shows Gemini 4 Argon:

The detail view of the pro subagent from the first run shows the same model and how long it thought before saying hello:

What the "pro" tier seems to be

The pro subagent runs on a model with its own name, gemini-3.8-flash-tiered, which is not in the model menu. In the first run it thought for 25 seconds and about 2,800 tokens before a one-line greeting, while the inherit subagent on regular 3.8 Flash finished in 8 seconds. In the second run it took 13 seconds, about as long as the Argon subagent (12 seconds). Our guess is that the pro tier is Gemini 3.8 Flash with a larger thinking budget, but Google doesn't document it, and two short runs are not a benchmark.

We also checked our quota readings right after both runs. Neither the Gemini nor the Argon figure had changed. That could be a reporting delay or simply because two one-sentence replies use too little to show, so we don't treat it as evidence either way.

What this means for you

If you hoped to save Argon quota with a Flash manager: in our test, the only setup that gave a subagent Argon was making Argon the main model and leaving the subagent on inherit, the default. Such a subagent presumably draws on the Argon quota too, so the "cheap manager, expensive consultant" split from the Reddit post didn't work for us with custom subagents on a Pro plan.
If you want subagents to stay off Argon while the main agent runs Argon: pro did that in both our runs. flash probably maps to regular 3.8 Flash, but we didn't test it.
If you want to save Argon quota anyway: the most upvoted reply under the Reddit post suggests the reverse setup: Argon (Medium or Low) researches and plans as the main agent, and 3.8 Flash executes. That fits our result, since only the main agent's model reaches inherit subagents, and pro ones stay on the Flash variant.
If an agent tells you which model its subagent uses: check /agents instead. In our first run, the main agent itself couldn't name the model.

We didn't test the built-in self subagent, subagents defined during a session, or the Python SDK, whose changelog says it can set a model per subagent (as can the native swarm mode Google is preparing).

Can a Flash agent call Argon another way?

Yes, but not as a subagent. In app 2.30.0, with Gemini 3.8 Flash as the conversation model, we asked the agent to run a one-line Antigravity CLI prompt with Gemini 4 Argon selected, and the reply came back from Argon:

This is a separate CLI session. It doesn't see your conversation, it needs the Antigravity CLI installed, and it uses the same Argon quota as any other Argon request. It doesn't get around any limit; it only lets a cheaper model decide when an Argon answer is worth paying for, the same way other tools can call the CLI for a second opinion.

The app ran the command without asking only because our permission preset was Turbo, which runs all commands without restrictions and gives the agent full access to your files. Under Default, the app asks before running such a command. Turbo removes the safety prompts; we don't recommend it for this, and Default is the safer setting. In the CLI's non-interactive print mode we couldn't get it to run at all: the call was denied even with an allow rule for the command.

What we don't know

Whether the mapping differs on Ultra, where Argon quota is part of the larger Gemini quota, or on Enterprise. We tested only Pro.
Whether the desktop app behaves the same. The documentation describes one model field for both, and the Reddit author's observation in app 2.29.0 fits our result, but we tested only the CLI.
What the flash tier maps to.
Whether Google will document the tiers or change them. We will update this article if it does.