ERROR_OPENAI: “Missing required parameter: ‘tools[10].custom’” when using Plan Mode with Azure GPT-5

[Pedro_Maia]

Yep — confirming: after updating to Cursor v2.3, the ERROR_OPENAI: Missing required parameter: ‘tools[10].custom’ issue is fixed on my side. Thanks for the quick turnaround.

However, there are still Azure-specific issues, and they seem to be concentrated around file modification / Apply / Agent edits (chat works, but edits don’t):

Apply / patch fails (often 404 / “Resource not found”) — looks like an endpoint routing mismatch, as if Cursor is still hitting an OpenAI-style /v1/responses route instead of Azure’s required deployment routing for edit/apply operations:

Azure OpenAI Chat Works, but Cursor “Apply” Fails (404) Due to Hardcoded /v1/responses Endpoint Mismatch

Hey, thanks for the detailed report. This is a known issue - Azure OpenAI endpoints use different routing for the Responses API compared to standard OpenAI, and Cursor’s Apply/Agent features currently send requests in a format that causes 404s on Azure. The team is aware and working on improving Azure BYOK compatibility. As a workaround for now, you’ll need to use Cursor’s built-in models for Apply/Agent Mode operations. Related thread with same issue: Cursor Agent Mode cannot modify files wh…

Agent mode cannot modify files with Azure-deployed GPT-5-mini — communication works, but any file editing/modification flow fails / never applies changes:

Cursor Agent Mode cannot modify files when using Azure-deployed GPT-5 mini (communication works but no file editing)

Where does the bug appear (feature/product)? Somewhere else… Describe the Bug I connected Cursor to Azure using a GPT-5 mini deployment. The model responds normally and communication works, but when switching to Agent Mode, it is unable to modify or write to project files. The agent produces responses, but no edits are applied to the workspace. There is no error message indicating a local permission problem, and the issue only occurs when using the Azure deployment of GPT-5 mini. When using a…

Happy to provide request IDs, network traces, and exact endpoint paths being called during Apply/Agent edit attempts if that helps isolate what’s still hardcoded or misrouted for Azure.