Kimi K3, an open-weight model from Moonshot AI, achieves performance comparable to Anthropic's Claude Fable 5 on the DeepSWE benchmark while costing significantly less per task. In a July 16, 2026 evaluation, Kimi K3 reached 68.5% pass@1 compared to Fable 5's 69.9%, but surpassed it in multi-attempt scenarios and offered superior cost efficiency.
- Kimi K3 costs $4.65 per rollout versus $13.41 for Claude Fable 5, delivering 2.8x more solved tasks per dollar.
- While Fable 5 leads on single-attempt reliability (69.9% vs 68.5%), Kimi K3 wins pass@2 (82.0% vs 80.2%) and pass@4 (89.4% vs 88.5%).
- Kimi K3 covers a wider range of tasks, solving 101 unique tasks compared to Fable 5's 107, with strong performance in Go.
- The models show high correlation (0.72) and similar failure patterns, meaning they do not provide significant diversity when paired.
Kimi K3 is positioned as a rational default for high-volume or retry-tolerant agent work due to its open-weight nature and lower cost, despite Fable 5's slight edge in single-attempt reliability.