Claude Opus 5 vs Kimi K3

Claude Opus 5 and Kimi K3 are both available through FastRouter's OpenAI-compatible API, so switching between them is a change of model id, not a new integration.

Claude Opus 5, from Anthropic, has a 1,000,000-token context window, costs from $5.00/1M input and $25.00/1M output tokens across 3 providers and scores 48.1 on the Artificial Analysis Intelligence Index.

Kimi K3, from MoonshotAI, has a 1,048,576-token context window, costs from $2.70/1M input and $13.50/1M output tokens across 4 providers and scores 43.6 on the Artificial Analysis Intelligence Index.

Kimi K3 is the cheapest on input, 1.9× cheaper than the next model, Kimi K3 has the largest context window, Claude Opus 5 scores highest for intelligence, Claude Opus 5 leads on coding and Claude Opus 5 has the highest throughput.