Gemini 4 Argon vs Claude Opus 5.5: Price, Benchmarks, and the Real Coding Verdict

Gemini 4 Argon launched globally on October 13, 2026, priced at $2 per million input tokens and $10 per million output tokens through November 30 (jumping to $4/$20 after that), and it edges out Claude Opus 5.5 on broad software-engineering benchmarks while losing the terminal and IDE-agent tests that actually matter for day-to-day coding work. If you're deciding which one to point Claude Code or Antigravity at this week, the short version is: Argon is cheaper and has the bigger context window, Opus 5.5 is the one that finishes the job.

I've spent the last two days running both models through the same prompts — a Next.js refactor, a flaky test suite fix, and a multi-file API migration — and the gap between what the benchmarks say and what actually happens in a terminal is wider than Google's launch post wants you to notice.

What is Gemini 4 Argon?

Argon is Google's new flagship reasoning model, announced September 30 and rolled out to everyone on October 13. It's built for long-horizon agentic work: software engineering, enterprise knowledge tasks like legal and finance review, and cybersecurity defense. The headline spec is a unified 1,048,576-token window shared across input, thinking, and output — which means the output cap jumped 16x from the old 64K ceiling to a full 1M tokens in a single response.

That's a genuinely big deal for anyone generating large files or long migration diffs in one shot. Google also claims the lowest hallucination rate of any frontier model at 15%, and says Argon matches GPT-6 Astra's score on the Artificial Analysis Intelligence Index at roughly 60% of the cost.

How much does Gemini 4 Argon cost?

Here's the pricing, plain and simple:

• Input: $2 per million tokens (through Nov 30, 2026), then $4
• Output: $10 per million tokens (through Nov 30, 2026), then $20
• Cached input: 95% off standard rate

Compare that to Claude Opus 5.5, which launched September 22 at $4 per million input and $20 per million output — exactly double Argon's introductory rate, and matching Argon's post-November price. Cache reads on Opus 5.5 run $0.20 per million, a 60% cut from Opus 5.

So for the next six weeks, Argon is the budget option at the same performance tier. After December 1, the two land at identical sticker prices, and the decision comes down entirely to what each model is actually good at.

Gemini 4 Argon benchmarks: how good is it at coding?

This is where it gets messy, because Argon wins some coding benchmarks and loses others, and the ones it loses are the ones that look most like real work.

Notice the pattern: Argon's strongest score is on a benchmark Google ran with its own harness, and its weakest scores are on the terminal-driven, agent-loop tests that mirror what Claude Code, Cursor, and Copilot agents actually do all day. FrontierSWE v2 specifically targets harder, more realistic repo tasks, and Argon drops over 10 points behind GPT-6 Astra there too.

On cost-per-task, Argon actually looks great for short jobs — $15.68 per test on the Vals Index versus $21.34 to $32.14 for the Claude models above it. But that flips hard on longer agentic runs: $193.78 per test on CUA-bench, $57.82 on code migration, $44.90 on Terminal-Bench Science. Long thinking loops eat the price advantage fast.

Gemini 4 Argon vs Claude Opus 5.5: which wins for real coding tasks?

In my own side-by-side testing, Opus 5.5 finished the Next.js refactor in one pass and caught a stale import I'd left in a hook. Argon got most of the way there, then stalled on an API compatibility mismatch between two package versions and handed back a partial diff with a note asking me to confirm an assumption. That tracks with a 21-run independent coding study that found Opus 5.5 produced the most complete implementations overall, while Argon more often delivered partial work and ran into delivery or API issues mid-task.

Honestly, this isn't shocking. Google optimized Argon for long-context reasoning and cyber defense workflows, not for the tight observe-act-verify loop that coding agents live in. Anthropic, meanwhile, has spent five major Opus versions tuning exactly that loop.

If you're running agent-driven coding work inside Claude Code, Copilot, or anything terminal-first, Opus 5.5's benchmark profile fits better and my testing backs that up. If you're doing broad software-engineering reasoning, big-context document analysis, or you just want Google's 1M-token output for generating a huge file in one go, Argon is worth the current discount.

Is Gemini 4 Argon worth switching to right now?

Depends on your workload, and I wouldn't do a blanket swap. Three honest takeaways after testing both for a couple of days:

• Cost-sensitive, short tasks: Argon wins on price until December 1, and Vibe Code Bench says quality is close enough not to matter for simple generation tasks.
• Agent-driven coding (Claude Code, Cursor, Copilot-style loops): Stick with Opus 5.5. The Terminal-Bench and FrontierSWE gaps are too consistent to ignore, and I hit that exact failure mode myself.
• Huge single-file output or massive context ingestion: Argon's 1M shared window is the only model in this comparison built for that, full stop.

I haven't tested Argon against production-scale repos yet, just focused refactors, so treat the terminal-agent verdict as directionally solid rather than final. Google's pricing cliff on December 1 is also worth watching: once the discount disappears, Argon's main edge narrows to the context window and the DeepSWE number, and that's a much thinner case.

If you want more on how Opus 5.5 stacks up against Anthropic's other 2026 releases, I covered the launch pricing in Claude Opus 5.5 review and pricing and did a head-to-head in Claude Opus 5 vs Fable 5.1. For the training story behind Google's 4-series, see Google Gemini 4 training. And if you're trying to pick a model stack for 2026 generally, the top AI tools of 2026 has the wider field.

Watch: Official announcements

Sources: Google's official Gemini 4 Argon announcement and Anthropic's Claude Opus 5.5 announcement.