Summary
- Anthropic's current Claude lineup includes four generally available models: Haiku 5.5, Sonnet 5.5, Opus 5.5, and Fable 5.2, alongside specialized research models like Mythos 5.2.
- Opus 5.5 is recommended as the default starting model for most coding, knowledge work, and complex agentic tasks due to its balanced cost and capability.
- Haiku 5.5 serves high-volume, cost-sensitive tasks such as classification and routing, while Sonnet 5.5 handles everyday well-scoped work and chat sessions.
- Fable 5.2 is designed for the most demanding technical projects, major refactors, and scientific or quantitative analysis.
- Users can balance performance and expenditure by adjusting effort levels, utilizing prompt caching, and strategically mixing models across workflows.
Why it matters
Choosing the right Claude model and effort level allows engineering and AI professionals to optimize cost, latency, and accuracy across diverse development and automation tasks.