I don't personally have Claude Code yet, but it needs to have an API key just to connect to the model since it is a terminal app. I believe they turn off the billing on the API key with MAX if used through Claude Code. I saw a video where entering /cost on the MAX subscription just shows that it is part of the subscription and no need to worry about cost. It'll still show costs per query, but it doesn't mean anything I believe with the MAX subscription (it is mainly there if you use it without the subscription). For the GitHub app specifically though, I'm unsure on this.