From the system card [0]:

Claude Opus 4 - Knowledge Cutoff: Mar 2025 - Core Capabilities: Hybrid reasoning, visual analysis, computer use (agentic), tool use, adv. coding (autonomous), enhanced tool use & agentic workflows. - Thinking Mode: Std & "Extended Thinking Mode" Safety/Agency: ASL-3 (precautionary); higher initiative/agency than prev. models. 0/4 researchers believed that Claude Opus 4 could completely automate the work of a junior ML researcher.

Claude Sonnet 4 - Knowledge Cutoff: Mar 2025 - Core Capabilities: Hybrid reasoning - Thinking Mode: Std & "Extended Thinking Mode" - Safety: ASL-2.

[0] https://www-cdn.anthropic.com/4263b940cabb546aa0e3283f35b686...