Cursor Cloud Agent launch failed with status 400. Response: {"error":"Model 'claude-4.6-sonnet-high-thinking' is not available or invalid."}

[Francisco_Macario]

Where does the bug appear (feature/product)?

Somewhere else…

Describe the Bug

I’m frequently getting the following error: Cursor Cloud Agent launch failed with status 400. Response: {“error”:“Model ‘claude-4.6-sonnet-high-thinking’ is not available or invalid.”}.

I’m launching the Cursor Cloud Agent. I’m not passing the model in the request since it’s optional and Cursor will use the default from the settings. This error shouldn’t happen.

Steps to Reproduce

Using the Cursor Cloud Agent API. Launch an Agent. Don’t include the model in the payload, so Cursor will use the default one.

Expected Behavior

Trigger an Agent

Operating System

MacOS

Version Information

Cursor Cloud

Does this stop you from using Cursor

Sometimes - I can sometimes use Cursor

[deanrie]

Hey, thanks for the report. This is a known issue: the claude-4.6-sonnet-high-thinking model fails backend validation when starting Cloud Agent, even though it shows up in settings.

The team is aware, but we don’t have an ETA for a fix yet. Your report helps with prioritization.

As a workaround, try explicitly passing the model in the API request payload, for example claude-4.6-sonnet or another available model. This should bypass the default model issue.

Let me know if that helps.