Claude is a family of state-of-the-art large language models developed by Anthropic, built using Constitutional AI (CAI)—a safety-first training approach that embeds ethical principles directly into the model during both pre-training and fine-tuning. Unlike traditional RLHF-only methods, Constitutional AI uses AI feedback to self-critique and revise responses before human evaluation, creating models that are helpful, harmless, and honest by design. Claude excels at complex reasoning, coding, multimodal understanding, and agentic workflows, offering context windows up to 1 million tokens (Opus 4.6, Sonnet 4.6) and specialized features like extended thinking, prompt caching, and tool use that make it uniquely suited for production-scale applications requiring both high intelligence and reliable safety alignment.