fix(moa): restore a valid preset after fallback model drift

build_moa_facade() reused agent.model as the preset name; a session
that had drifted to a fallback model crashed on restore with
MoAPresetNotFoundError. Validate the resolved preset against the
configured presets and fall back to the default preset.

Salvaged from PR #74903 by @liusencomic-cyber.

agent/moa_loop.py

@@ -2230,8 +2230,24 @@ def build_moa_facade(agent, preset_name: Any = None) -> MoAClient:
         except Exception:
             pass
 
+    resolved_preset = preset_name
+    if resolved_preset is None and getattr(agent, "provider", None) == "moa":
+        resolved_preset = getattr(agent, "model", None)
+
+    resolved_preset = str(resolved_preset or "default")
+    try:
+        from hermes_cli.config import load_config
+        from hermes_cli.moa_config import normalize_moa_config
+
+        moa_cfg = normalize_moa_config(load_config().get("moa") or {})
+        presets = moa_cfg.get("presets") or {}
+        if resolved_preset not in presets:
+            resolved_preset = moa_cfg.get("default_preset") or "default"
+    except Exception:
+        resolved_preset = "default"
+
     return MoAClient(
-        str(preset_name or getattr(agent, "model", None) or "default"),
+        resolved_preset,
         reference_callback=_moa_reference_relay,
         # Thread the agent through so the reference fan-out wait can be
         # aborted on a user interrupt (see _run_references_parallel).

tests/run_agent/test_moa_streaming.py

@@ -90,6 +90,29 @@ def test_create_streams_aggregator_when_requested(monkeypatch, tmp_path):
     assert agg["tools"] is not None
 
 
+def test_build_moa_facade_ignores_fallback_model_name_when_restoring(monkeypatch, tmp_path):
+    """A fallback restore must not turn the temporary fallback model name into
+    a MoA preset. Sessions that drifted to e.g. deepseek-v4-flash previously
+    crashed on restore with MoAPresetNotFoundError because build_moa_facade()
+    reused agent.model as the preset (#MoA restore path).
+    """
+    home = tmp_path / ".hermes"
+    _write_cfg(home)
+    monkeypatch.setenv("HERMES_HOME", str(home))
+
+    from agent.moa_loop import build_moa_facade
+
+    agent = SimpleNamespace(
+        provider="moa",
+        model="deepseek-v4-flash",
+        tool_progress_callback=None,
+    )
+
+    client = build_moa_facade(agent, None)
+
+    assert client.chat.completions.preset_name == "review"
+
+
 def test_create_wraps_completed_aggregator_response_as_delta_chunk(monkeypatch, tmp_path):
     """When an aggregator adapter returns a completed response despite
     stream=True (Codex Responses compatibility shape), MoA must return a