Cookie is sent only for certain requests

[kAlvaro]

Unless I'm missing something, the XDEBUG_SESSION cookie is sent only for GET and POST requests. That means it is not possible to step debug end-points that use e.g. PATCH or PUT. That's very typical when working with single-page applications and RESTful APIs in general.

Also, I'd say the cookie seems to be lost for GET/POST as well when the browser submits an AJAX request that uses some other method. (I'm not fully sure about this).

Edit: In my case, these requests are initiated by using the Fetch API rather than XMLHttpRequest. Perhaps that's the relevant factor rather than the HTTP method being used.