Gemini 4 vs Claude Opus 5.5: What the Gap Actually Is

Choosing between Gemini 4 and Claude Opus 5.5 is not a choice between two models of the same kind, and that is the first thing worth knowing. Gemini 4 Argon, the model G​oogle announced on 2026-09-30 and put into general availability on its paid tier on 2026-10-13, is the only callable member of the Gemini 4 line — there is no bare gemini-4 model ID, no Pro tier and no Ultra tier beside it. Claude Opus 5.5 is a generally available flagship that Anthropic shipped on 2026-09-22 and that sits in a four-model line where every rung is priced and documented. So one side of this comparison is a line with one member and the other is a line with four, and the numbers below come from Gemini 4 Argon because there is nothing else on the Gemini 4 side to measure.

This page is written for the reader who already has both names and wants to know which to build on. It is not an introduction to either, and it is not a news piece. The announcement above is used to date the model, not to report an event.

What each side of the comparison actually is

G​oogle's Gemini 4 documentation lists exactly one entry: gemini-4-argon, marked Stable, described as the flagship reasoning model, with a unified 1M-token context window and long decodes up to 1M tokens. Read the same page a second time looking for a second Gemini 4 model and you find none — everything else on it is Gemini 3.x. G​oogle's pricing page agrees: Argon is the only Gemini 4 row on it. So when a search result says "Gemini 4" and means a tier you can select, it is describing a name that the vendor has not attached to anything.

The Claude side is the opposite shape. Anthropic publishes four current models, each with its own rate card, context window, output ceiling, effort default and retirement commitment. Claude Opus 5.5 is the flagship of that set: 1M-token context, 128,000-token maximum output, adaptive thinking always on with a default effort of medium — the only model in the line that does not default to high effort — and a reliable knowledge cutoff of June 2026. Anthropic describes it as built for long-running agentic coding and knowledge work, and it replaces Claude Opus 5 as the generally available flagship while Opus 5 stays listed as legacy and remains served.

There is a documentation asymmetry here that is worth stating once rather than letting it quietly shape the page. We have 36 live articles that mention or centre Claude Opus 5.5 and 18 on the Gemini 4 stem, and of those 18, thirteen are comparisons against a model called Argon rather than four-tier explainers. That is a fact about our own coverage, not about the models, and a reader arriving from either direction should know which side has more material behind it.

The rate cards, and which number to plan against

Gemini 4 Argon launched at an introductory rate and the word introductory is doing real work. Per million tokens, both sides as the vendors publish them on 2026-10-14:

• Input — Gemini 4 Argon $2.00 introductory, rising to $4.00 on 2026-12-01 per G​oogle's pricing page, vs Claude Opus 5.5 $4.00 flat.

• Output — Gemini 4 Argon $10.00 introductory, rising to $20.00 on 2026-12-01, vs Claude Opus 5.5 $20.00.

• Cached input — Gemini 4 Argon $0.10 per million vs Claude Opus 5.5 $0.20. Argon is half the price on the line that dominates long agent runs, and G​oogle supports implicit caching only, not explicit.

• Batch — Gemini 4 Argon $1.00 / $5.00 vs Claude Opus 5.5 $2.00 / $10.00, both at half the standard rate.

• Cache write — Claude Opus 5.5 charges $5.00 per million for a five-minute cache write and $8.00 for the one-hour window. G​oogle's page publishes no separate cache-write rate for Argon, because it does not offer explicit caching.

• Context and output — 1M tokens of context on both. G​oogle publishes an output ceiling of 1M tokens for Argon; Anthropic publishes 128,000 for Opus 5.5.

Read the top two rows together and the pricing story is a countdown rather than a discount. Argon is half of Opus 5.5's price today and the same price in December. Anyone planning a migration on the $2 / $10 number is planning on a rate with a published expiry date, and Anthropic's rate card has no such step in it. That is not an argument for either model; it is the arithmetic a budget actually runs on, and it is the single most common thing readers get wrong about this pairing.

Both vendors' models are

third-party here, and the routing question is separate from the comparison. Claude Opus 5.5 is in our catalogue at its list price with no markup added, which is what the 0% pass-through means in practice — the provider's price reaches your invoice unchanged. Nothing on the Gemini 4 stem is in that catalogue as of 2026-10-14, so a reader who wants to run both through one key today cannot; a reader who is weighing Opus 5.5 against the rest of the Claude line can, without a second contract or a second SDK.

The one scoreboard both models appear on — and what it says

Artificial Analysis measures both on the same index, which makes this the closest thing to a matched comparison available. On Intelligence Index revision v4.3.2, which is built from ten evaluations, Gemini 4 Argon at high effort reads 52.56 and Claude Opus 5.5 at maximum effort reads 57.62. The leaderboard displays those as 53 and 58. That is a five-point gap in Anthropic's favour on a ten-evaluation composite.

The same comparison pages carry the rows behind it, and they are not uniform. Argon leads on exactly one listed evaluation — AutomationBench-AA at 78 per cent against Opus 5.5's 70. On everything else the ordering follows the index: Terminal-Bench 4.0 at 57 per cent against 60, SciCode 62 against 67, Humanity's Last Exam 57 against 61, GDP.pdf 22 against 26, CritPt 27 against 32, AA-Omniscience 42 against 46, AA-LCR v1.1 80 against 85. Two of those margins are narrow enough to be worth ignoring; the HumanEval-style coding and the graduate-level science rows are not.

Then there is the bill, which runs the other way. The same evaluator prices the run behind each score: $1.99 of pay-per-token cost per Intelligence Index task for Gemini 4 Argon against $5.98 for Claude Opus 5.5, with Argon emitting 62,000 output tokens per task against Opus 5.5's 119,000 and 36,000 reasoning tokens against 84,000. For a full index run that is $2,407 against $8,708. Argon is not cheaper because its tokens cost less, though they do — it is cheaper because it takes fewer of them to answer.

Two honest caveats belong on that paragraph. The first is the effort setting: Argon is measured at high and Opus 5.5 at maximum, and effort is not a neutral knob — the same models measured at matched effort will not necessarily hold this ordering. The second is speed, where the two Artificial Analysis comparison pages for Argon disagree with each other, listing 61 tokens per second on one page and 95 on another for what should be the same configuration. When a board contradicts itself on a figure, the figure is not evidence yet.

G​oogle also publishes its own benchmark table, in which Argon leads Claude Opus 5.5 on the majority of rows. That table is vendor-reported, and G​oogle's own methodology discloses that the non-G​oogle columns are the competitors' self-reported numbers rather than measurements G​oogle ran. It is a useful document about what G​oogle claims. It is not a controlled comparison, and the margins in it should be read accordingly.

What usually decides it

If your work is multi-step software engineering that runs long and you are optimising for the best answer rather than the cheapest one, Claude Opus 5.5 is the safer pick today: it is GA, it has a published retirement floor of September 2027, it is served from more places, and independent measurement puts it ahead on the coding and science rows that matter most for that work. The migration cost is real but knowable — effort levels are recalibrated across the Claude line, so an effort setting carried over from an older model should be re-swept rather than reused.

If your work is high-volume, or the per-task bill is the constraint rather than the last five index points, Gemini 4 Argon is the more interesting proposition right now, and the interesting part is specifically the gap between per-token price and per-task cost. Argon answers in roughly half the tokens, which means a workload that is mostly repetition and extraction can be cheaper on Argon even after the introductory rate expires. What it does not yet have is the thing Opus 5.5 has had since September: a tier structure around it. There is no cheaper Gemini 4 to fall back to when the flagship is overkill, and no dearer one to reach for when it is not enough.

The single fact that decides most of these evaluations in practice is the one at the top: you are not choosing between two comparable tiers. Claude Opus 5.5 is a flagship inside a line that prices four rungs; Gemini 4 Argon is the entire Gemini 4 line, at a rate that changes on 2026-12-01. Pick the side whose shape you can plan against.

Getting both models onto one key

Claude Opus 5.5 is served through OrcaRouter at Anthropic's list price with 0% markup on top, so a vendor price cut reaches your invoice the same day rather than after a repricing cycle, and the same key reaches Opus 5.5's siblings without a second contract. Gemini 4 Argon is not in that catalogue as of 2026-10-14, so it is not a second option on the same key today; a reader weighing the two has to keep G​oogle's own API in the path alongside ours.

The same key that reaches Claude Opus 5.5 reaches every model we carry, at list price. the rest of the catalogue Which is the reason the vendor list price is the number that lands on your invoice.

A model choice is also a question of what has gone wrong before: the documented AI incidents and agent failures for models of this class are collected in the OrcaRouter AI Incident Archive , where each entry carries its own sources, severity, confidence grade and disputed flag.