Kimi K2 Thinking extends Moonshot AI's K2 series into a new tier of agentic, long-horizon reasoning. Built on the trillion-parameter Mixture-of-Experts architecture introduced in the Kimi K2 base, the model activates 32 billion parameters per forward pass, enabling deep step-by-step reasoning without sacrificing inference efficiency. The 256K-token context window supports complex, multi-turn workflows where hundreds of sequential actions—research, coding, writing—unfold coherently. It interleaves structured thinking with dynamic tool invocation, maintaining stable behavior through 200–300 tool calls in multi-agent scenarios, making it well-suited for autonomous agents that must plan, adapt, and execute across extended sessions.

The model leverages MuonClip optimization alongside its large-scale MoE design to combine reasoning depth with practical throughput, setting new open-source benchmarks on HLE, BrowseComp, SWE-Multilingual, and LiveCodeBench. Released as an open-weights model on Hugging Face in November 2025, it gives researchers and developers access to frontier-level reasoning capabilities under an open framework—a notable shift in the landscape of accessible, high-capability language models that can rival proprietary systems in sustained analytical and agentic work.