_seed_from_singletons('anthropic') now checks
is_provider_explicitly_configured('anthropic') before reading
~/.claude/.credentials.json. Without this, the auxiliary client
fallback chain silently discovers and uses Claude Code tokens when
the user's primary provider key is invalid — consuming their Claude
Max subscription quota without consent.
Follows the same gating pattern as PR #4210 (setup wizard gate)
but applied to the credential pool seeding path.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2fafcf42e8