Claude 3.7 Sonnet introduced visible extended thinking — showing reasoningStep-by-step logical thinking in AI models — chain-of-thought before answering hard problems. steps before answers — and stronger tool-use for coding agents. It competed with OpenAIAn AI research company — created GPT, ChatGPT, DALL-E, and the o-series reasoning models. o3 and GPTGenerative Pre-trained Transformer — OpenAI's family of large language models from GPT-1 through GPT-5.-4.1 for developer copilots and autonomous workflows.

Claude 3.7 made extended reasoningStep-by-step logical thinking in AI models — chain-of-thought before answering hard problems. a first-class product feature.

Visible thinking and tool use advanced agenticAI systems that plan and execute multi-step tasks autonomously — tools, browsing, and sub-agents. coding assistants.