Claude Opus 5.5
Claude Opus 5.5 is Anthropic's recommended starting model for most workloads, built for long-running agentic coding and knowledge work, and available through the Claude API and major cloud platforms.
Key functions
- Adaptive thinking that is always on and steered by the effort parameter
- Text and image input with a one-million-token context
- Tool use and up to 128,000 output tokens
Compared with Mistral Medium 3.5
- Names 3 security certificates, Mistral Medium 3.5 1.
- States no EU hosting option; Mistral Medium 3.5 has one.
- Starts higher: from $4 usage-based, Mistral Medium 3.5 from $1.50 usage-based.
Check before buying: Billing is per token, with batch requests at half price and cached prompts much cheaper. On the Claude API, workspace data is stored in the US; inference can be pinned to the US for 1.1 times the price, while the global default may run anywhere. Amazon Bedrock and Google Cloud offer their own regional endpoints. In the US, check Colorado and Illinois rules if outputs feed decisions about people.






