Kimi K3.1 Pro vs Claude Opus 5.5

Pyyan / Compare / Kimi K3.1 Pro vs Claude Opus 5.5

2 of 5

Language Models · verified 26 Oct 2026

Kimi K3.1 ProMoonshot AIcurrent

Claude Opus 5.5Anthropiccurrent

Add another3 slots left

Specification	Kimi K3.1 Pro	Claude Opus 5.5
Summary	Frontier coding numbers at a fifth of the price, with the weights promised for November.	Fable 5.1's level of work on most tasks, at 40% less to run than Opus 5.
Context	1M	1M
Input ($/Mtok)	$2	$4
Output ($/Mtok)	$10	$20
Licence	Closed for now, weights promised 4 Nov 2026	Proprietary
Max output	944K	128K
Parameters	3T class, exact count not published	Not published
Released	23 Oct 2026	22 Sep 2026
Model ID	kimi-k3.1-pro	claude-opus-5-5
Category	Language Models	Language Models
Official	Moonshot AI ↗	Anthropic ↗

Highlighted rows are where these differ.

65.7% on Terminal-Bench 4.0 in Moonshot's own table, against 66.4% for Claude Opus 5.5 and 58.2% for GPT-6 Astra
Claim-level hallucination rate down from 23.4% on K3 to 8.3%
Cyber training data deliberately removed, which Moonshot says costs about nine points on xdev-bench-hard
Full weights promised by 4 November 2026, so the licence is not yet knowable

Best for long-horizon coding when the budget is the constraint.

66.4% on Terminal-Bench 4.0 against 52.3% for Opus 5, on Anthropic's own harness
Cache reads cut 60% to $0.20, and output more than 30% faster than Opus 5
Attempts to work around its boundaries 85% less often than Opus 5, Anthropic reports

Best for agentic coding at flagship quality.