Kimi unveiled Kimi K3.1 Pro, its most capable 3T-class open-weight model to date, built around a 1-million-token context window. The Chinese AI company also launched Kimi K3.1 Pro Highspeed, a faster variant that delivers two to three times the speed of K3.1 Pro for more responsive interactions.
Both models are available today on Kimi.ai, Kimi Work, Kimi Code and the Kimi API, with the full model weights set to be released by November 4. The launch puts an open-weight challenger directly against the strongest proprietary models from OpenAI and Anthropic.
Kimi K3.1 Pro specs and benchmarks
K3.1 Pro is a post-trained version of Kimi K3, trained with substantially larger post-training compute. Kimi says it optimized every layer of its stack — the reinforcement learning framework, long-context inference, training efficiency, sandbox infrastructure, rollout scheduling and environment quality checks — to run large-scale joint RL across hundreds of downstream domains.
On Terminal-Bench 4.0, which tests coding agents on realistic, resource-constrained terminal tasks, K3.1 Pro scored 65.7% — ahead of GPT-6 Astra at 58.2% and narrowly behind Claude Opus 5.5 at 66.4%. On Kimi Code Bench 3.0 Long-horizon, an internal benchmark for multi-step execution, tool use and end-to-end problem solving, it scored 61.2%, up from K3's 55.95%.
- 3T-class open-weight model with a 1M-token context window
- K3.1 Pro Highspeed: 2–3× faster than K3.1 Pro
- Terminal-Bench 4.0: 65.7% vs GPT-6 Astra (58.2%) and Claude Opus 5.5 (66.4%)
