Describe the Bug
Cursor sends Anthropic-style payloads to the OpenAI endpoint when Claude 4 is chosen, causing 400 errors.
The only way to obtain a valid OpenAI-style payload is to rename the model to something that starts with “gpt” (e.g. gpt-4.1 mapped to claude-4-sonnet). This aliasing forces Cursor to build the correct OpenAI body but obviously hides the real model identity and is not a viable long-term fix.
Steps to Reproduce
With an OpenAI API key configured, selecting Claude 4 in Cursor’s model picker causes every request to be routed to
https://xxxx/v1/chat/completions, but the JSON body follows Anthropic’s schema
Operating System
MacOS
Current Cursor Version (Menu → About Cursor → Copy)
Version: 1.1.3 (Universal)
VSCode Version: 1.96.2
Commit: 979ba33804ac150108481c14e0b5cb970bda3260
Date: 2025-06-15T06:37:17.379Z
Electron: 34.5.1
Chromium: 132.0.6834.210
Node.js: 20.19.0
V8: 13.2.152.41-electron.0
OS: Darwin arm64 24.4.0
Does this stop you from using Cursor
No - Cursor works, but with this issue