Sonnet 5 became the default for free and Pro Claude users — planning, browsing, and terminal tool use that previously required Opus tiers. It shipped weeks before Claude Fable 5's export-control drama and narrowed the gap between mid-tier and frontier pricing.

Sonnet 5 brought agenticAI systems that plan and execute multi-step tasks autonomously — tools, browsing, and sub-agents. Opus-class behavior to AnthropicAn AI safety company — creators of the Claude family of language models.'s default tier.

Introductory pricing undercut GPTGenerative Pre-trained Transformer — OpenAI's family of large language models from GPT-1 through GPT-5.-5.x for high-volume agent workloads.