Moonshot AI's Kimi K3.1 Pro Closes Gap with Claude Opus 5.5

A new Chinese AI model from Moonshot AI, called Kimi K3.1 Pro, has moved up to fourth place on the Artificial Analysis Intelligence Index, just behind Claude Opus 5.5. This model shows major gains in agentic tasks, coding, and 3D modeling, while keeping the same parameter count as its predecessor. API prices have dropped by 33 percent, and the company plans to release the model weights by November 2026.

Kimi K3.1 Pro scored 55 points on the Artificial Analysis Intelligence Index, an 11-point increase from its predecessor, Kimi K3, which placed it in fourth position. Only Claude Opus 5.5, Claude Sonnet 5.5, and Muse Wonder Full rank higher, according to Artificial Analysis. If Moonshot releases the model weights as planned by November 4, 2026, it would become the highest-scoring open-weights model available, reducing the gap between open and proprietary models from 12 to just 3 points.

Alongside Kimi K3.1 Pro, Moonshot is also releasing a variant called Kimi K3.1 Pro Highspeed that runs two to three times faster, according to the company. Both are available now through Kimi.ai, Kimi Work, Kimi Code, and the Kimi API.

Kimi K3.1 Pro's strongest improvements show up in agentic tasks. On the GDPval-AA benchmark, it reaches 1,846 Elo, 312 points above Kimi K3. That puts it just behind Claude Opus 5.5 (1,866) and Muse Wonder Full (1,857). On Terminal-Bench 4.0, Moonshot reports 65.7 percent, ahead of GPT-6 Astra (58.2 percent) and barely behind Claude Opus 5.5 (66.4 percent). Kimi K3 managed only 13 percent on the same test.

Hallucination rates dropped sharply too. On Moonshot's internal Kimi Hallu Bench Hard, claim-level hallucinations fell from 23.4 percent with Kimi K3 to 8.3 percent, according to the company. Moonshot says this is a stress test, not a measure of general error rates. GPT-6 Astra hits 5.5 percent on the same benchmark, so it still has an edge.