Gemini 4 Argon vs Claude Opus 5.5: Which to Use for What (2026)

Neither model wins everywhere. As of October 2026, Claude Opus 5.5 (Anthropic) is ahead on most coding, agent and reasoning scores, while Gemini 4 Argon (Google) is half the price on the API until the end of November and is the one to try for direct, less padded writing and very long outputs. The fastest way to know which is better for you is to run the same prompt through both. You can do that in one chat on Zemith Professional, which has both models for $29.99 a month, instead of paying Anthropic and Google separately.

TL;DR

• Gemini 4 Argon reached the Gemini app for Google AI Pro and Ultra subscribers on October 13, 2026, after a September 30 launch to security partners.
• Claude Opus 5.5 launched on September 22, 2026 and is on Claude Pro, Max, Team and Enterprise.
• On the API, Argon is $2 per million input tokens and $10 per million output tokens through November 30, 2026, then $4 and $20. Opus 5.5 is $4 and $20.
• A third-party tracker that compares the two (LLM Stats, October 20, 2026) has Opus ahead on four of the six benchmarks they share and Argon ahead on two. Most of Argon's numbers are Google's own.
• In Zemith, both models are on the Professional plan only. Plus doesn't include them.

What is different about the two models?

Anthropic pitches Opus 5.5 at agentic coding, long-running agents and financial analysis. Google's Argon page describes a model for complex software engineering, deep math and science, and multi-step agents, and its launch post for the Gemini app says it gives more direct answers, hedges less and avoids cliché phrasing. That last point is the one you will notice in everyday writing.

Prices and availability as of October 20, 2026, from Anthropic, Google's API pricing and 9to5Google for the US AI Pro price.

Is Gemini 4 Argon better than Claude Opus 5.5?

For coding and agents, not yet on the published numbers. LLM Stats lists Opus 5.5 ahead on FrontierSWE V2, OSWorld 2.0, Terminal-Bench 4.0 and Terminal-Bench-Science 0.1, and Argon ahead on AutomationBench and DeepSWE 1.1. Treat all of this as early. The Argon figures are mostly vendor-reported, independent runs are still coming in, and a benchmark gap rarely maps to your own files.

For writing and everyday questions it is closer to taste. Google says Argon is built to skip the hedging, and Anthropic positions Opus for careful, long-running work. If you can't tell from a list of scores, a ten minute test beats a week of reading.

How do I test them on my own work?

Pick three jobs you do every week, and give both models exactly the same input. Here is a test that takes about ten minutes:

1. A writing job. Paste a rough draft or notes you need to turn into something you'd send. Prompt: "Rewrite this for [audience] in under 200 words. Keep every number. Cut anything that sounds like filler."
2. A reasoning or code job. Use a real bug, a spreadsheet formula, or a decision with trade-offs. Prompt: "Here is the problem and what I've tried. Find the cause, fix it, and tell me how you would check the fix."
3. A long input job. Paste a long document or thread. Prompt: "List every decision, owner and deadline mentioned. If something is unclear, say so instead of guessing."

Score each answer from 1 to 5 on three questions: Is it correct? Could I use it without editing? Did it invent anything? Add the totals. Run each job twice, once per model, in separate chats so one answer can't influence the other.

How can I try both without paying Google and Anthropic?

Use an app that carries both. On Zemith, both are in the model picker on the Professional plan:

1. Open a chat at zemith.com/app and tap Select model.
2. Choose Claude 5.5 Opus and send your first test prompt.
3. Switch to Gemini 4 Argon in the same chat and send the same prompt. You can change model at any time in a conversation, so the two answers sit one above the other.
4. Score them, then keep whichever won for that kind of job.

Cost in Zemith is in credits, and the two models are close. A prompt of about 2,000 tokens with an 800-token answer costs about 4,800 credits on Opus 5.5 and about 4,900 on Argon, before any thinking tokens. Professional includes 3 million credits a month, which is roughly 600 exchanges of that size on either model. Long documents and long reasoning use more. The multi-model chat page lists the other models you can switch to for cheaper jobs.

What does it cost to use both?

If you want both models on their own plans, you pay two companies. Claude Pro is $20 a month and Google AI Pro is $19.99, which is $39.99 monthly, or $439.88 a year if you take Claude's $200 yearly price. Zemith Professional is $29.99 a month or $299.88 a year, about $140 less over a year, and it adds the tools Zemith includes (research, files, image and video).

The trade is real. Google AI Pro also gives you storage and Google app features, which we covered in Google AI Plus vs Pro. Claude Pro includes Claude Code. Zemith credits are shared across all models, so a heavy day on one model uses the same pool. If you only ever use one of the two, that model's own plan can be the better value.

Is Gemini 4 Argon free?

No. Google's pricing page says Argon isn't available on the free API tier, and in the Gemini app it is for Google AI Pro and Ultra subscribers. Its introductory API price of $2 and $10 ends on November 30, 2026, after which it matches Opus 5.5 at $4 and $20. That means the price gap that makes Argon attractive for developers is temporary, and it may be worth locking in your testing before December.

What we don't know yet

Independent test results are thin because both models are weeks old. We haven't seen a reliable long-run comparison of how often either one invents details, and Google's launch post gives no usage limits for Argon in the Gemini app. Zemith's credit prices for both models can change, so check the model picker before you plan a month around them. For a wider look at the two companies' plans, see Claude vs Gemini, which was written before Argon reached the app.

Bottom line

Use Opus 5.5 when the job is code, a long agent run or careful analysis, and try Argon when you want shorter, more direct answers or a cheaper API bill until the end of November. If you're a developer weighing coding models, the Zemith page for developers shows how the comparison works in one tool. Run the ten minute test above on your own work, and let the scores decide.

How we compared: we read Anthropic's and Google's own pages, their pricing pages and the LLM Stats comparison on October 20, 2026, and checked the Zemith plan, model and credit details in the product's code.