Kimi K3 — Moonshot Ships 2.8T-Parameter "Largest Open Model Ever," Opus-Class Coding at Sonnet Pricing

Summary

Moonshot AI released Kimi K3, a 2.8-trillion-parameter (≈50B active) mixture-of-experts model billed as the largest open model released to date. Early reporting has it ranking #1 in frontend-coding benchmarks on Arena and scoring comparably to Claude Opus 4.8, while priced at roughly $3 / $15 per million input/output tokens — Sonnet-5-class economics for near-frontier capability. Simon Willison's coverage pairs the launch with his ongoing "pelican riding a bicycle" evaluation and a separate note