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[ARTICLE · art-156356] src=simonwillison.net ↗ pub= topic=large-language-models verified=true sentiment=↑ positive

Introducing Kimi K3.1 Pro

Moonshot released Kimi K3.1 Pro, a soon-to-be open-weight model that Artificial Analysis scored at 55, ahead of Claude Fable 5.1, GPT-6 Astra and Gemini 4 Argon (all 53) and behind only Claude Opus 5.5 (58). Kimi K3.1 Pro is priced at $2.00 per million input tokens and $10.00 per million output tokens, the same as GPT-6.1 Sol and half the price of Claude Opus 5.5, with a "Highspeed" version running 2-3x faster at twice the price except for input token cache hits. Simon Willison tested Kimi K3.1 Pro through the Moonshot API using the `llm openai endpoint` command added to LLM 0.32, generating pelican-riding-a-bicycle SVGs at the low, medium and max reasoning levels and comparing them against fresh runs on Kimi K3.

read1 min views1 publishedOct 23, 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.

Via Hacker News

Tags: ai, generative-ai, llms, llm, llm-pricing, pelican-riding-a-bicycle, llm-release, ai-in-china, moonshot, kimi

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