Moonshot AI's Kimi K3.1 Pro launches on API, weights to be opened on November 4
Kimi K3.1 Pro launches on the Kimi API today; weights are not yet open, and Moonshot AI promises to release the full model weights before November 4, 2026. Pricing is $2.00 per million input tokens and $10 per million output tokens, the same as GPT-6.1 Sol and half that of Claude Opus 5.5; a Highspeed version that is 2-3 times faster at double the price is also offered. Artificial Analysis gives Kimi a score of 55, higher than Claude Fable 5.1, GPT-6 Astra and Gemini 4 Argon at 53, and second only to Claude Opus 5.5 at 58. Simon Willison tested SVG generation via the Moonshot API at three reasoning effort levels: low, medium and max.
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The author tested Kimi K3.1 Pro's reasoning tiers and provides pricing and benchmark comparisons with frontier closed-source models.
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23rd October 2026 - Link Blog
Introducing Kimi K3.1 Pro (via) Kimi K3.1 Pro landed on the Kimi API today - it's not yet open weights, but Moonshot promise "Full model weights will be released by Nov 4, 2026".
They're also offering a "Highspeed" version that's 2-3x faster, at twice the price (except for input token cache hits, which are priced the same).
The US dollar pricing is $2.00/million tokens for input and $10/million for output - the same as GPT-6.1 Sol and half the price of Claude Opus 5.5.
Moonshot's own benchmarks show Kimi as approximately level with Opus 5.5 and GPT-6 Astra - beating them on a few benchmarks, coming close on others.
Artificial Analysis scored Kimi at 55 - ahead of Claude Fable 5.1, GPT-6 Astra, and Gemini 4 Argon (all at 53) and behind only Claude Opus 5.5 (58).
This is the first time a (soon-to-be) open weight model has scored this highly against the frontier.
I tried it out via the Moonshot API using the llm openai endpoint command I added to LLM 0.32 back in August:
llm openai endpoint \ https://api.moonshot.ai/v1 \ --key kimi \ -m kimi-k3.1-pro \ "Generate an SVG of a pelican riding a bicycle" \ --responses \ -o reasoning_effort low \ > kimi-k3.1-pro-pelican-low.stdout.txt \ 2> kimi-k3.1-pro-pelican-low.stderr.txt
llm openai endpoint can run prompts against any OpenAI-compatible endpoint but doesn't log the results, hence the extra options to save stdout and stderr (the reasoning trace).
Here are the pelicans I got for Kimi K3.1 Pro on the three reasoning levels it supports - low, medium, and max. This is max:
For comparison, I ran fresh pelicans against Kimi K3 on those three reasoning levels.
Posted 23rd October 2026 at 7:40 pm
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This is a link post by Simon Willison, posted on 23rd October 2026.
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