fix(moa): route native anthropic OAuth references through provider branch

MoA's _slot_runtime() whitelists providers that must keep their provider
identity (so call_llm runs their provider branch) instead of being treated
as a plain custom endpoint via forwarded base_url/api_key. Native anthropic
was missing from this set.

Native anthropic subscription OAuth setup-tokens (sk-ant-oat*) require Bearer
auth plus the 'anthropic-beta: oauth-*' header, which only the anthropic
provider branch adds. Without the whitelist entry, the slot's base_url/api_key
were forwarded and call_llm sent the OAuth token as x-api-key, which Anthropic
rejects with a bare 429 (rate_limit_error with no quota details). This made
anthropic references in MoA presets fail every time.

Add 'anthropic' to the whitelist so native anthropic reference/aggregator
slots route through the provider branch. Extends upstream 9229d0db1 which
added 'nous' for the same reason.

agent/moa_loop.py

@@ -99,7 +99,7 @@ def _slot_runtime(slot: dict[str, str]) -> dict[str, Any]:
         # provider-backed targets whose provider branch adds auth refresh,
         # request metadata, or request-shape adapters. Keep those providers
         # identified by name.
-        if resolved_provider in {"nous", "openai-codex", "xai-oauth"}:
+        if resolved_provider in {"nous", "anthropic", "openai-codex", "xai-oauth"}:
             return out
         # Pass the resolved endpoint through so call_llm builds the request for
         # the provider's actual API surface instead of auto-detecting. base_url

tests/run_agent/test_moa_loop_mode.py

@@ -678,3 +678,45 @@ def test_moa_facade_reruns_references_on_new_turn(monkeypatch, tmp_path):
 
     # 2 references × 2 distinct turns = 4 reference runs.
     assert len(ref_runs) == 4
+
+
+def test_slot_runtime_anthropic_oauth_routes_through_provider_branch(monkeypatch):
+    """Native anthropic slots must NOT forward base_url/api_key.
+
+    anthropic OAuth setup-tokens (sk-ant-oat*) require Bearer auth + the
+    ``anthropic-beta: oauth-*`` header, which only the provider branch of
+    call_llm adds. If _slot_runtime forwarded base_url/api_key, call_llm would
+    treat the slot as a plain custom endpoint and send the token as x-api-key,
+    which Anthropic rejects with a bare 429. So a whitelisted provider
+    (anthropic) returns only provider/model, while a non-whitelisted provider
+    (openrouter) forwards the resolved base_url/api_key.
+    """
+    from agent import moa_loop
+
+    def fake_resolve(*, requested, target_model=None):
+        return {
+            "provider": requested,
+            "base_url": "https://resolved.example/v1",
+            "api_key": "resolved-key",
+        }
+
+    monkeypatch.setattr(
+        "hermes_cli.runtime_provider.resolve_runtime_provider", fake_resolve
+    )
+
+    # Whitelisted: anthropic must skip base_url/api_key forwarding.
+    anthropic_rt = moa_loop._slot_runtime(
+        {"provider": "anthropic", "model": "claude-opus-4-8"}
+    )
+    assert anthropic_rt == {"provider": "anthropic", "model": "claude-opus-4-8"}
+    assert "base_url" not in anthropic_rt
+    assert "api_key" not in anthropic_rt
+
+    # Non-whitelisted: openrouter still forwards the resolved endpoint.
+    other_rt = moa_loop._slot_runtime(
+        {"provider": "openrouter", "model": "some-model"}
+    )
+    assert other_rt["provider"] == "openrouter"
+    assert other_rt["model"] == "some-model"
+    assert other_rt["base_url"] == "https://resolved.example/v1"
+    assert other_rt["api_key"] == "resolved-key"