The provider is Anthropic; Claude is its model family. Models now take
the ant: prefix (e.g. ant:claude-opus-5-5), the provider value sent to
the proxy is "anthropic", and the key lives in anthropic_api_key /
USER.apiKeyAnthropic. No fallback for the old names.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>