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Kimi K3.1 Pro is Moonshot AI’s flagship 3T-class open-weight model in the K3.1 series, with a 1-million-token context window. Moonshot’s blog (opened for this article) also ships Kimi K3.1 Pro Highspeed at about 2–3× the speed of the standard model. Both are live on Kimi.ai, Kimi Work, Kimi Code, and the Kimi API. Full model weights are scheduled for release by November 4, 2026. This page sticks to that blog, the API quickstart, and the pricing page—no invented parameter counts.

What Moonshot Claims

Official copy describes K3.1 Pro as a post-trained Kimi K3 with much larger post-training compute, aimed at coding, 3D creation, financial research, and other agent workflows. On Terminal-Bench 4.0, the blog reports 65.7% for K3.1 Pro (Claude-Code harness in the footnotes), ahead of the GPT-6 Astra figure they cite (58.2%) and just behind Claude Opus 5.5 (66.4%). On internal Kimi Code Bench 3.0 Long-horizon, it scores 61.2% versus K3’s 55.95%. On BenchCAD with tools, the blog lists 92.7%. On OfficeQA Pro v2, it lists 64.4. Footnotes say default eval settings used reasoning effort max, temperature 1.0, top-p 0.95 unless noted.

Moonshot writes “3T-class” / most capable 3T-class open-weight model—not a more precise parameter count. Do not treat “2.8 trillion” style figures from secondary posts as official.

API IDs and Limits

From the platform quickstart:

  • Model IDs: kimi-k3.1-pro and kimi-k3.1-pro-highspeed
  • Base URL example: https://api.moonshot.ai/v1
  • Context: 1,048,576 tokens (pricing page)
  • Thinking is always on; reasoning_effort supports low / high / max (default max)
  • max_completion_tokens defaults to 131072, up to 1048576
  • Flagship unlock: successful top-up (minimum $1) per the quickstart access note

API Pricing (USD / 1M tokens)

Copied from https://www.kimi.ai/resources/kimi-k3-1-pro-pricing (page notes rates checked October 24, 2026; taxes extra):

Model Input Output Cached input Cache write 5m Cache write 1h
kimi-k3.1-pro $2.00 $10.00 $0.20 $2.00 $4.00
kimi-k3.1-pro-highspeed $4.00 $20.00 $0.20 $4.00 $8.00

Membership tiers (Free / Plus / Pro / Max / Ultra) and Highspeed product access are tabled on the same pricing page; API billing is separate from membership.

Open Weights and Cyber Notes

Weights: by November 4, 2026, per the blog. The same post describes cyber-data filtering for the open-weight release and reports internal xdev-bench-hard pass@3 of 81.0% after controls versus 90.5% on an unfiltered checkpoint. Those are Moonshot’s own figures.

FAQ

What is the Kimi K3.1 Pro API id?

kimi-k3.1-pro (and kimi-k3.1-pro-highspeed for the faster SKU).

How big is the context window?

1M tokens (1,048,576 on the pricing page).

When do open weights ship?

Moonshot says by November 4, 2026.

Sources