How can I add custom HTTP headers or load a ModHeader-like extension in Cursor’s @Browser?

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1

’m using Cursor’s built-in @Browser to open a staging merchant admin web page and manually verify some behavior changes.

However, the browser opened by @Browser does not allow installing or loading any browser extensions (such as ModHeader or Requestly).
The entire flow is driven purely by the frontend page — there is no client code or API call that I can modify.

My requirement is to add a custom HTTP request header to all outgoing requests, for example:

trace-context: {“laneId”: “STAGING.hello_cursor”}

Is there any supported way to:

  • inject custom HTTP headers in Cursor’s @Browser, or

  • launch the browser with a custom extension / request interceptor, or

  • configure request headers globally for the @Browser session?

If this is not supported, is it an intentional limitation of Cursor’s browser architecture?

4

Hey, thanks for the question.

@Browser doesn’t support loading browser extensions or injecting custom HTTP headers. This is an architectural limitation. Browser runs as an isolated web view for security.

Workarounds:

  1. External browser: use regular Chrome with ModHeader for manual verification, and use @Browser for automated testing without custom headers.

  2. Proxy: set up a local proxy (mitmproxy, Charles) that adds the required headers to all requests.

  3. MCP server: if the staging API can be called directly, you can write a custom MCP that adds headers to fetch requests.

If this is critical for your workflow, please file a feature request in the Feature Requests category and describe your use case.

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