Anthropic's model family, first released March 2023, trained with Constitutional AI and named in Haiku, Sonnet and Opus sizes since the Claude 3 generation.
Claude is Anthropic's model family, first released in March 2023. It is used through the Claude apps, the Anthropic API, the major cloud platforms and Claude Code, and it is trained with Constitutional AI, in which model outputs are critiqued against a written set of principles rather than only against human preference labels.
The Claude 3 family (March 2024) shipped as Haiku, Sonnet and Opus, a naming scheme kept since: Haiku tuned for latency, Sonnet for balance, Opus for the hardest work. Later generations added extended thinking, where the model spends additional tokens on reasoning before answering, and made tool use a first-class capability rather than a wrapper around text output.
Anthropic published the Model Context Protocol in November 2024, an open standard for connecting models to tools and data sources. It has since been adopted well beyond Claude, and it is the basis of the browser-side WebMCP proposal.
