Good question. There's 2 points to consider.

• For both Kimi K2 and for Sonnet, there's a non-thinking and a thinking version. Sonnet 4.5 Thinking is better than Kimi K2 non-thinking, but the K2 Thinking model came out recently, and beats it on all comparable pure-coding benchmarks I know: OJ-Bench (Sonnet: 30.4% < K2: 48.7%), LiveCodeBench (Sonnet: 64% < K2: 83%), they tie at SciCode at 44.8%. It is a finding shared by ArtificialAnalysis: https://artificialanalysis.ai/models/capabilities/coding

• The reason developers love Sonnet 4.5 for coding, though, is not just the quality of the code. They use Cursor, Claude Code, or some other system such as Github Copilot, which are increasingly agentic. On the Agentic Coding criteria, Sonnet 4.5 Thinking is much higher.

By the way, you can look at the Table tab to see all known and predicted results on benchmarks.