The backend toggle now cycles through configured roles (chat, coder,
research, distill, etc.) instead of backup model slots within the chat
role. Each role uses its own primary→backup chain from the registry.
- ChatRequest.slot replaced by chat_role (default "chat")
- GET /backend returns available_roles instead of chat_models
- _available_roles_for_toggle() builds list from defined_roles, excluding
orchestrator (which has its own Agent mode)
- Model label on responses now reflects the actual role's assigned model
- Toggle is inert when only one role is configured (avoids useless cycling)
- Add "Clear browser cache" button to Account Settings (Connected Accounts)
- Add _role_model_label() helper for cleaner response tag labeling
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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