Yesterday we tightened our safeguards against spoofing the Claude Code harness after accounts were banned for triggering abuse filters from third-party harnesses using Claude subscriptions.

Third-party harnesses using Claude subscriptions create problems for users and are prohibited by our Terms of Service. They generate unusual traffic patterns without any of the usual telemetry that the Claude Code harness provides, making it really hard for us to help debug when they have questions about rate limit usage or account bans and they don’t have any other avenue for this support.

This is why the supported way to use Claude in your own tools is via the API. We genuinely want people building on Claude, including other coding agents and harnesses, and we know developers have broad preferences for different tool ergonomics. If you're a maintainer of a third-party tool and want to chat about integration paths, my DMs are open.

We've also heard it wasn't clear enough to end users that this was a ToS violation, and that's on us. We'll make it clearer in the OAuth screen going forward.

We’ve lifted all bans we're aware of that were caused by this issue, please DM me your email if you were banned due to this and haven’t been reinstated.