Non-Claude client access is not permitted in the terms and conditions, except via API key.

The correct implementation of this condition by Anthropic on the server side would be to block usage by non-Claude apps via Claude's authentication mechanism, and allow it via the per-token API key billing.

Instead of a simple 403 error, which would block usage, they silently redirect to a different billing bucket, which is not ethical behaviour especially since it is based on fuzzy heuristics.