Kimi K3.1 Pro vs Claude Opus 5.5

This is a cross-vendor comparison where, unusually, one head-to-head number actually exists: Moonshot AI's own tech blog reports Kimi K3.1 Pro scoring 65.7% on Terminal-Bench 4.0 — "narrowly behind" Claude Opus 5.5's 66.4% vendor claim. Read that twice, because both halves matter: the challenger's lab itself published a comparison where it loses by 0.7 points observed — and it is still a vendor-run benchmark, published by the party with every incentive to pick flattering tests, so it is a claim to track rather than a fact to cite analysis. No independent comparison exists as of our November 1, 2026 capture; benchmarks pending. What a careful comparison can settle today: positioning, openness, and the shape of your cost model. Labels: vendor claim / observed / analysis.

The one published number, in context

Moonshot's official blog reports this benchmark slate vendor claim: on Terminal-Bench 4.0 — which the blog describes as testing coding agents on realistic, resource-constrained terminal tasks with strict task-specific tests — Kimi K3.1 Pro scores 65.7%, ahead of GPT-6 Astra (58.2%) and narrowly behind Claude Opus 5.5 (66.4%). Moonshot also reports 61.2% on its internal Kimi Code Bench 3.0 Long-horizon, above Kimi K3's 55.95% vendor claim.

Three things to hold onto before quoting those numbers analysis:

• Who ran it. Moonshot ran the evaluation. A lab reporting that it loses to a competitor by 0.7 points is either unusually honest or has a reason to publish that specific framing — likely both; the point is you cannot separate the two from the blog post alone analysis.
• What it measures. Terminal-Bench is a coding-agent benchmark. It says nothing about long-context behavior at 1M tokens, financial research, 3D workflows, or any other task either vendor claims strength in analysis.
• What would settle it. Independent replication on the same harness, plus evaluations beyond coding agents. Benchmarks pending — this page ages with the evidence analysis.

Side by side: what each side officially states

	Kimi K3.1 Pro (Moonshot AI)	Claude Opus 5.5 (Anthropic)
Class	Frontier open-weight; "most capable 3T-class open-weight model to date" vendor claim	Flagship tier of the Claude family analysis
Context window	1 million tokens vendor claim	Per Anthropic's official documentation — not restated here analysis
Openness	Full model weights promised by November 4 vendor claim	Closed weights; API and subscription surfaces analysis
Availability	Kimi.com, Kimi Work, Kimi Code, Kimi API vendor claim	Anthropic's official surfaces and API analysis
Published head-to-head	Terminal-Bench 4.0: K3.1 Pro 65.7% vs Opus 5.5 66.4% — Moonshot-reported, not independently verified vendor claim
Independent benchmarks	None exist yet for this pairing analysis
Pricing	Not in the official pages we captured analysis	See Anthropic's official pricing pages; see also Opus 5.5 vs Sonnet 5.5 for tier context analysis

The structural difference benchmarks skip: weights or API

The benchmark table treats these two as interchangeable models. They are not analysis. K3.1 Pro is built to be downloaded — with full weights promised by November 4, a 1M-token context window, and Moonshot's API as one of several surfaces vendor claim. Opus 5.5 is built to be subscribed to — accessed through Anthropic's products and API, with the weights staying in Anthropic's hands analysis. That distinction decides things benchmarks never ask about: whether you can fine-tune, whether your data leaves your infrastructure, what happens to your stack if a vendor changes terms, and how your cost curve bends at very high volume analysis. A 0.7-point Terminal-Bench gap is smaller than any of those differences for most real deployments analysis.

What nobody can tell you yet

• Independent verification of the 65.7/66.4 result. Nobody outside Moonshot has published a replication analysis.
• Any comparison beyond coding agents. Long-context tasks, agentic workflows, financial research — no public head-to-head exists analysis.
• Cost at your volume. No first-hand K3.1 Pro pricing in our capture; model both patterns in our API cost calculator once rates are official analysis.
• Whether the weights actually ship by November 4. A promise with a date is still a promise; verify on release day analysis.

How to decide between them right now

• If openness is the constraint, the comparison is already over. Only one of these models plans to hand you weights observed. If you need self-hosting or fine-tuning, K3.1 Pro's November 4 delivery is the fact to watch — and its license terms, when published, are the fine print that matters analysis.
• If coding-agent performance is the constraint, demand replication. A 0.7-point vendor-run gap is within the noise of harness choices; wait for independent Terminal-Bench runs or run your own three-task trial analysis.
• Price the pattern, not the token. 1M-token contexts and long agentic sessions multiply consumption; put your realistic session shape into our API cost calculator before comparing rates analysis.
• Read both vendors' own pages. Moonshot's tech blog observed and Anthropic's model documentation are the primary sources; everything else — this page included — is commentary on top analysis.

Related pages

• Kimi K3.1 Pro — the model card, from Moonshot's official pages
• Opus 5.5 vs Sonnet 5.5 — Anthropic's same-family tier comparison
• Claude Code + Opus 5.5 — the Anthropic coding-agent scenario
• Gemini 4 Carbon vs GPT-6.1 Terra — the same launch week's other cross-vendor pairing

Kimi K3.1 Pro vs Opus 5.5 FAQ

Did Kimi K3.1 Pro beat Claude Opus 5.5?

No — not even by Moonshot's own account. Moonshot's blog reports K3.1 Pro at 65.7% on Terminal-Bench 4.0, "narrowly behind" Opus 5.5 at 66.4% vendor claim. It did report beating GPT-6 Astra (58.2%). Any page telling you Kimi "beat Opus" is misreading the one source that exists analysis.

Why would Moonshot publish a number where it loses?

Because "narrowly behind the incumbent flagship" is itself a strong claim for a new open-weight challenger — it positions K3.1 Pro as frontier-adjacent while looking candid analysis. That framing logic is exactly why vendor-run numbers, flattering or not, stay claims until replicated analysis.

Which should I use for coding work today?

The one you can access with the workflow you already run. Opus 5.5 is available now through Anthropic's surfaces analysis; K3.1 Pro is live on Kimi's surfaces with weights promised by November 4 vendor claim. Trial both on your own repo — three real tasks, count failures — and let your failure log, not a vendor table, make the call analysis.

Is the 0.7-point gap meaningful?

On a vendor-run benchmark with no published replication, a 0.7-point gap is within the range harness choices can produce analysis. It is a talking point, not a ranking analysis.

What would change this comparison?

Three things, in order of likelihood: independent Terminal-Bench replication; the November 4 weights release (which unlocks fine-tuning comparisons entirely); and first-hand pricing for K3.1 Pro's API. This page tracks all three analysis.

This page is descriptive and independent, built from a direct capture of Moonshot AI's official tech blog and Anthropic-related public documentation, last reviewed November 1, 2026. Not affiliated with Moonshot AI or Anthropic. "Kimi" and "Claude" are trademarks of their respective owners; benchmark figures are vendor-reported and labeled as such.