DeepSeek: deepseek-reasoner:free

deepseek-reasoner is the specialized reasoning API alias from DeepSeek, designed to tackle complex logic, mathematics, programming, and long-horizon planning. Unlike the conversation-oriented deepseek-chat, it mandates the generation of a Chain of Thought (CoT) before delivering the final answer. As of early 2026, this endpoint primarily powers the DeepSeek-R1 flagship, refined through massive Reinforcement Learning (RL). Rivaling OpenAI o1/o3 in benchmarks like AIME and Codeforces, it features an "autonomous reflection" mechanism to self-correct reasoning errors. It is the premier choice for building R&D automation, scientific computing, and high-complexity AI agents.