Are you referencing the use of Claude subscription authentication (oauth) from non-Claude Code clients?
That’s already possible, nothing prevents you from doing it.
They are detecting it on their backend by profiling your API calls, not by guarding with some secret crypto stuff.
At least that’s how things worked last week xD
https://alex000kim.com/posts/2026-03-31-claude-code-source-l...
Ah, it seems that Bun itself signs the code. I don't understand how this can't be spoofed.
They are most likely using these as post-fact indicators and have automation they kicks in after a threshold is reached.
Now that the indicators have leaked, they will most likely be rotated.
They can't really do that. Now they have no way to distinguish "this is a user of a non updated Claude code" from "this is a user of a Claude code proxy".