Anthropic employees clarified in HN comment threads that the API credits are in addition to the existing behavior and not a replacement. Other harnesses can still call the Claude Code CLI and use the subscription quota that way.

They need to stop clarifying on HN and X and MiGente / MySpace / Angelfire and whatever else and update their damn docs, I am not taking a risk on my account because of he said she said.

Tbh I think Thariq or one of the others passively hinted/suggested but didn't come out and make a categorical statement. I've seen anecdotal evidence of folks getting those extra data messages in various "not using the official harness" scenarios, but there's way more people like you who are not having issues.