fix(providers): re-derive minimax api_mode to prevent stale /model-switch 404

[onepisYa]

What

MiniMax API-key providers (minimax, minimax-cn) now re-derive api_mode from the resolved base URL when the persisted config value belongs to a different provider family (e.g. a leftover chat_completions in model.yaml after switching away from opencode-go).

Why

8 historical subagent 404 incidents (5/16 → 6/12, up to 67% failure rate in 3-parallel subagent batches) — tracked in subagent-404-investigation board — traced in part to api_mode leaking across provider switches.

The MiniMax plugin lacked the same stale-api_mode protection that opencode-zen/opencode-go already has (Refs #16878) because:

1. Its base_url is hardcoded to the /anthropic suffix.
2. Its ProviderProfile explicitly sets api_mode="anthropic_messages".

Both mask the bug — until a user typo or a stale model.yaml surfaces it. Result: /chat/completions routed under /anthropic → the MiniMax gateway returns a bare nginx 404.

The existing minimax-oauth branch already protects OAuth via a similar force-anthropic_messages policy. This PR extends the same protection to API-key minimax/minimax-cn.

How

Extend the existing _resolve_runtime_from_pool_entry branch in hermes_cli/runtime_provider.py (the one that already protects opencode-zen/opencode-go, Refs #16878) to cover minimax/minimax-cn. Force anthropic_messages against the canonical /anthropic endpoint when all three of:

1. base_url is the provider default (/anthropic), not a user override
2. URL auto-detect (_detect_api_mode_for_url) returns anthropic_messages
3. The persisted api_mode is not a same-provider explicit value (_provider_supports_explicit_api_mode(provider, configured_provider) is False)

Honor explicit user intent for full backward compatibility:

• base_url: /v1 override → _detect_api_mode_for_url returns chat_completions → honored (preserves the test_minimax_v1_url_uses_chat_completions semantic for regions where /anthropic 404s).
• provider: minimax + api_mode: chat_completions (same provider family explicit) → honored (preserves test_minimax_explicit_api_mode_respected semantic).

Tests

Three new RED-then-GREEN tests in tests/hermes_cli/test_runtime_provider_resolution.py:

Test	Scenario	Expected
test_minimax_re_derives_stale_chat_completions_from_opencode_go	provider=minimax active, configured_provider=opencode-go stale + api_mode=chat_completions stale	anthropic_messages (forced)
test_minimax_cn_re_derives_stale_chat_completions_from_opencode_go	Same for minimax-cn	anthropic_messages (forced)
test_minimax_v1_override_still_uses_chat_completions	MINIMAX_BASE_URL=/v1 override + no explicit mode	chat_completions (honored)

All three FAIL on upstream main (verified locally) and PASS after the fix.

Regression verification

python -m pytest tests/hermes_cli/test_runtime_provider_resolution.py
# 132 passed
python -m pytest tests/hermes_cli/test_runtime_provider_resolution.py tests/hermes_cli/test_custom_provider_model_switch.py tests/hermes_cli/test_model_switch_opencode_anthropic.py
# 162 passed

Zero regressions in adjacent test files (model_switch_opencode_anthropic.py exercises the same path as the opencode-zen/opencode-go fix this PR mirrors).

Diff stats

hermes_cli/runtime_provider.py                          | 38 ++++++++-
tests/hermes_cli/test_runtime_provider_resolution.py   | 90 ++++++++++++++++++++++
2 files changed, 127 insertions(+), 1 deletion(-)

Net code change in runtime_provider.py: +37/-1 (one elif branch with extensive rationale comments).

Refs

• hermes-agent#16878 — original opencode-zen/go stale api_mode 404 bug
• hermes-agent PR fix(opencode): re-derive api_mode per target model on /model switch #16888 — the original opencode-zen/go fix this PR mirrors

🤖 Generated with Claude Code via Hermes Agent

[tonydwb]

Clean fix for MiniMax stale api_mode. Re-derives api_mode from URL when the persisted value comes from a different provider family, preventing /chat/completions routing under /anthropic (which returns nginx 404). Backward-compatible for users with explicit /v1 base_url overrides. Good test coverage. No issues found.