Problem

Hermes users with minimax-oauth as their main provider see this on every CLI session:

⚠ Auxiliary title generation failed: HTTP 401: Invalid Authentication

The same root cause breaks kanban specify and any other auxiliary task that doesn't pin a fallback provider.

Root cause

hermes_cli/auth.py:301 declares MiniMax OAuth with auth_type="oauth_minimax". agent/auxiliary_client.py dispatches on pconfig.auth_type, but the OAuth provider branch was gated on {"oauth_device_code", "oauth_external"} — "oauth_minimax" was not in the set. The call therefore fell through to the generic warning at the bottom of the resolver and returned (None, None).

Fix

1. Add "oauth_minimax" to the OAuth provider dispatch gate (1 line).
2. Add a minimax-oauth case in the provider switch that delegates to a new builder, _build_minimax_oauth_aux_client() (12 lines).
3. The builder mirrors _try_anthropic() — MiniMax's inference endpoint is Anthropic-API compatible — but installs build_minimax_oauth_token_provider() as a per-request callable api_key, so MiniMax's 15-minute access-token TTL is auto-refreshed on every outbound request. Same pattern the main runtime uses (agent/agent_runtime_helpers.py:1460).

Tests

Four new tests in TestMiniMaxOAuthAuxiliaryClient:

• test_resolve_minimax_oauth_dispatches_to_anthropic_compat — happy path, asserts the builder is called with the right inference_base_url.
• test_resolve_minimax_oauth_uses_main_model_when_empty — universal fallback chain (Step 3 main-model) still works when no model is passed and there is no catalog default.
• test_resolve_minimax_oauth_returns_none_when_not_logged_in — swallowed AuthError returns (None, None) so the chain falls through to its next provider.
• test_builder_uses_anthropic_sdk_not_openai — regression guard for the previous fix attempt (PR fix: resolve minimax-oauth auxiliary client routing #35539) that wrapped an OpenAI client in AnthropicAuxiliaryClient and crashed at runtime.

Verification

• pytest tests/agent/test_auxiliary_client.py — 211 passed.
• pytest tests/agent/test_minimax_provider.py tests/agent/test_minimax_auxiliary_url.py tests/plugins/model_providers/test_minimax_profile.py — 276 passed total.
• End-to-end repro: call_llm(task='title_generation', ...) returns a real title (no HTTP 401, no 'unhandled auth_type' warning).

Notes

• The fix makes minimax-oauth work for ALL auxiliary tasks, not just title generation. The default model is the one registered on the provider profile (MiniMax-M2.7 per plugins/model-providers/minimax/__init__.py).
• AnthropicAuxiliaryClient already accepts a callable api_key (the bearer-hook machinery in agent/anthropic_adapter.py calls it per-request), so no upstream changes to the wrapper are needed.

Fixes #21521, #36091