Hey, thanks for the report. This is a known limitation with Azure Anthropic models (including claude-opus-4-5).
Cursor’s Azure integration currently only supports the Azure OpenAI API format, but Anthropic models in Azure AI Foundry use a different API format. This affects all Anthropic Claude models on Azure, not just Opus 4.5.
The team is already tracking this issue in their backlog: Azure Claude 4.5 Sonnet Error
We’ll update the community when Azure Anthropic support becomes available. Let me know if you have any other questions!