refactor(moa): unify slot provider-identity on the single call_llm chokepoint

[hashbender]

Summary

MoA slot provider-identity is now decided in one place. _slot_runtime forwards the resolved endpoint for every slot; _resolve_task_provider_model is the single chokepoint that keeps a first-class provider's identity instead of collapsing an explicit base_url to the generic custom route.

This retires the hand-maintained name-preservation whitelist in agent/moa_loop.py that had to be extended by hand for every provider with custom auth/signing — the exact drift that produced the recent anthropic (NousResearch#54609) and bedrock (NousResearch#54912) breakages.

Root cause of the duplication

Two guards were enforcing the same invariant:

• moa_loop.py::_slot_runtime — a fixed set {nous, anthropic, openai-codex, xai-oauth, bedrock} that returned bare provider+model so call_llm never saw a base_url to collapse.
• auxiliary_client.py::_resolve_task_provider_model — _preserve_provider_with_base_url(provider), a provider-catalog capability check that keeps identity for any first-class provider even when a base_url is present.

The second is strictly more general (auto-tracks the catalog); the first was a manual denylist of the collapse that drifted out of sync.

Change

• _slot_runtime forwards base_url/api_key/api_mode unconditionally; whitelist removed.
• Tests updated to assert the pipeline invariant (_slot_runtime → _resolve_task_provider_model preserves identity) against the real resolver, instead of the whitelist's bare-return shape.

Why it's behaviorally safe

The five providers' resolve_provider_client branches re-resolve their own credentials by name and ignore a forwarded base_url/api_key:

• openai-codex → _read_codex_access_token() (Responses wrap + Cloudflare headers)
• xai-oauth → _build_xai_oauth_aux_client()
• bedrock (aws_sdk) → boto3 credential chain + SigV4 signing; forwarded placeholder "aws-sdk" key is ignored
• anthropic → _try_anthropic() (OAuth-token detection → Bearer + anthropic-beta)
• nous → catalog api_key provider, re-resolves the same endpoint

Validation

	Result
Real-import E2E: _slot_runtime → _resolve_task_provider_model for openai-codex / xai-oauth / bedrock / anthropic / nous (+openrouter control)	6/6 preserve identity, 0 collapse to custom
tests/run_agent/test_moa_loop_mode.py	20/20 pass
tests/agent/test_auxiliary_client.py	274/274 pass

Infographic

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Mirror-of: NousResearch#55991
NousResearch#55991

[tenki-reviewer]

Review Complete

Risk: 🟡 Medium (35/100) — 1 medium finding · 99 LOC across 2 files

Files Reviewed: 2
Findings: 1

By Severity:

• 🟡 Medium: 1

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The PR refactors MoA loop slot resolution, removing a duplicate provider whitelist from moa_loop.py and delegating all identity preservation to _preserve_provider_with_base_url. One defense-in-depth gap noted: the hardcoded fallback set in auxiliary_client.py omits 'bedrock', which was previously covered by the removed whitelist.

Files Reviewed (2 files)

agent/moa_loop.py
tests/run_agent/test_moa_loop_mode.py