I agree with everything already said by @Jean85: first of all, I don’t understand the reason to have our own HttpClientInterface instead of just using the PSR-18 one. There is no benefit I can think of, it would be just another layer that needs to be implemented by the end user. Second, and more importantly, I don’t understand why we are reimplementing a full cURL client, which we have to maintain and for which there is no benefit because it’s a lot simpler and less customizable than any other out of here. Moreover, what’s happening here is that we are reinventing the wheel: I can understand that this SDK has to ship with a default client, even though I don’t agree, but at least choose one reliable client instead of reinventing the wheel. We had our own HTTP client in the past, and it was full of issues. Given that the SDK is integrated with both Laravel and Symfony, it would be wise to choose symfony/http-client which is common for both

Merging now to unblock other features. The remaining ToDos are documented in #1595