A head-to-head benchmark comparison of Kimi K3 and Claude Fable 5 on DeepSWE, covering 452 rollouts across 113 real software engineering tasks. Claude Fable 5 leads pass@1 by 1.4 points (69.9% vs 68.5%), but Kimi K3 overtakes it at pass@2 and pass@4 (89.4% vs 88.5%). The cost difference is significant: Kimi K3 costs $4.65 per rollout versus $13.41 for Fable, delivering 2.8x more solved tasks per dollar. Kimi K3 excels at Go tasks while Fable leads Python, JavaScript, TypeScript, and Rust. The two models show unusually high cross-vendor similarity (0.72 correlation), meaning combining them yields little diversity benefit. Kimi K3 is positioned as the value default for retry-tolerant or high-volume agent workloads, especially once open weights enable self-hosting.
