Kimi K3.1 Pro ships now, with open weights promised by November 4

Moonshot calls K3.1 Pro its most capable "3T-class" open-weight model, with a 1-million-token context window, and says a Highspeed variant runs 2-3 times faster. Both are available today through the Kimi API and Kimi Code; the full weights are due "by Nov 4". On Terminal-Bench 4.0, run with the Claude Code harness, Moonshot reports 65.7%, against 58.2% for GPT-6 Astra and 66.4% for Claude Opus 5.5. On its own long-horizon coding benchmark it reports 61.2%, up from 55.95% for K3. All figures are the vendor's, and the competitor scores are copied from other published sources, not rerun.

The post also describes a training-time control. Moonshot says it found vulnerability-research skill rising with post-training scale, traced it to cyber-related data in the mid-training corpus and the reinforcement learning environments, and removed that data. On its in-house xdev-bench-hard exploit tasks, the checkpoint without the removal solves 90.5% at pass@3 and the released model solves 81.0%. It states the aim "not to release open weights that would extend the absolute frontier of cyber capability." Those numbers come from a benchmark only Moonshot has run.

Why it matters: If the weights arrive on schedule, teams that run agent harnesses on their own infrastructure get another long-context candidate to test, and Moonshot's own results are for the Claude Code harness, so a harness swap is plausible. Until the weights are out and someone outside Moonshot reproduces the coding and cyber numbers, treat them as claims.