fix(moa): persist named preset deletion without losing config

hermes_cli/web_routers/models.py

@@ -29,6 +29,7 @@ _config_profile_scope = late("_config_profile_scope", "hermes_cli.web_server_pro
 _profile_scope = late("_profile_scope", "hermes_cli.web_server_profiles")
 load_config = late("load_config", "hermes_cli.config")
 save_config = late("save_config", "hermes_cli.config")
+read_raw_config = late("read_raw_config", "hermes_cli.config")
 
 
 _EMPTY_MODEL_INFO: dict = {
@@ -309,7 +310,6 @@ def set_moa_models(body: MoaConfigPayload, profile: Optional[str] = None):
         # desktop's debounced PUT /api/config autosave races it, so the whole
         # span holds _CONFIG_MUTATION_LOCK or one of the two saves is dropped.
         with config_write_scope(body.profile or profile):
-            cfg = load_config()
             if body.presets:
                 raw = {
                     "default_preset": body.default_preset,
@@ -328,14 +328,18 @@ def set_moa_models(body: MoaConfigPayload, profile: Optional[str] = None):
             if problems:
                 raise HTTPException(status_code=422, detail="Invalid MoA config: " + "; ".join(problems))
             normalized = normalize_moa_config(raw)
-            # Merge, don't overwrite: hand-edited keys not in MoaConfigPayload (save_traces, trace_dir) survive.
-            # See issue #58819. Write ONLY the moa section (merge_existing deep-merges it over the
-            # on-disk raw file): saving the whole default-expanded ``cfg`` snapshot re-persisted
-            # every other section too, so a Desktop MoA autosave could wipe a chain another
-            # surface wrote meanwhile (#89184, ``fallback_providers: []``).
-            moa_section = dict(cfg.get("moa") or {})
+
+            # Read the raw profile file because the effective config contains defaults and
+            # ``merge_existing=True`` deep-merges dicts, which resurrects omitted preset names.
+            # Keep unknown MoA keys and sibling sections by rebuilding only the MoA section on
+            # the raw document, while treating the submitted named map as authoritative.
+            raw_cfg = read_raw_config()
+            moa_section = dict(raw_cfg.get("moa") or {})
             moa_section.update(normalized)
-            save_config({"moa": moa_section}, merge_existing=True)
+            if body.presets:
+                moa_section["presets"] = normalized["presets"]
+            raw_cfg["moa"] = moa_section
+            save_config(raw_cfg)
             return {"ok": True, **normalized}
 
 

tests/hermes_cli/test_moa_preset_deletion.py

@@ -0,0 +1,128 @@
+"""A MoA preset dropped from the payload must leave config.yaml.
+
+``PUT /api/model/moa`` expresses a deletion by OMITTING the preset from
+``presets``. The save used ``save_config(..., merge_existing=True)``, whose
+``_deep_merge`` recurses dict-over-dict and therefore restored every omitted
+preset from disk — the GUI's delete button returned ok while the preset stayed
+in config.yaml forever. ``presets`` is authoritative on write; undeclared
+sibling keys (``save_traces``, ``trace_dir``) must still survive (#58819), and
+other config sections must not be clobbered (#89184).
+
+Real config pipeline against a temp HERMES_HOME — a mocked save cannot show the
+merge that caused the bug.
+"""
+
+from __future__ import annotations
+
+import yaml
+
+from hermes_cli.web_models import MoaConfigPayload, MoaModelSlot, MoaPresetPayload
+from hermes_cli.web_routers.models import set_moa_models
+
+
+def _preset(model: str) -> MoaPresetPayload:
+    return MoaPresetPayload(
+        reference_models=[MoaModelSlot(provider="openai-codex", model=model)],
+        aggregator=MoaModelSlot(provider="anthropic", model="claude-opus-5"),
+        enabled=True,
+    )
+
+
+def _on_disk(home) -> dict:
+    return yaml.safe_load((home / "config.yaml").read_text(encoding="utf-8")) or {}
+
+
+def _seed(home, monkeypatch, moa: dict, **sections) -> None:
+    monkeypatch.setenv("HERMES_HOME", str(home))
+    (home / "config.yaml").write_text(yaml.safe_dump({"moa": moa, **sections}), encoding="utf-8")
+
+
+def _three_presets() -> dict:
+    return {
+        "default_preset": "keep_a",
+        "presets": {
+            "keep_a": {
+                "reference_models": [{"provider": "openai-codex", "model": "gpt-5.5"}],
+                "aggregator": {"provider": "anthropic", "model": "claude-opus-5"},
+                "enabled": True,
+            },
+            "doomed": {
+                "reference_models": [{"provider": "openai-codex", "model": "gpt-5.6-luna"}],
+                "aggregator": {"provider": "anthropic", "model": "claude-opus-5"},
+                "enabled": True,
+            },
+            "keep_b": {
+                "reference_models": [{"provider": "openai-codex", "model": "gpt-5.7"}],
+                "aggregator": {"provider": "anthropic", "model": "claude-opus-5"},
+                "enabled": True,
+            },
+        },
+    }
+
+
+def test_omitted_preset_is_deleted_from_disk(tmp_path, monkeypatch):
+    """The whole point: a preset the payload omits must not survive the save."""
+    home = tmp_path / ".hermes"
+    home.mkdir()
+    _seed(home, monkeypatch, _three_presets())
+
+    # The GUI re-sends the surviving presets; "doomed" is simply absent.
+    set_moa_models(
+        MoaConfigPayload(
+            default_preset="keep_a",
+            active_preset="",
+            presets={"keep_a": _preset("gpt-5.5"), "keep_b": _preset("gpt-5.7")},
+        )
+    )
+
+    presets = _on_disk(home)["moa"]["presets"]
+    assert "doomed" not in presets, "deleted preset was restored by the merge"
+    assert set(presets) == {"keep_a", "keep_b"}
+
+
+def test_deletion_preserves_undeclared_moa_keys_and_other_sections(tmp_path, monkeypatch):
+    """Authoritative presets must not cost us #58819 (save_traces) or #89184 (siblings)."""
+    home = tmp_path / ".hermes"
+    home.mkdir()
+    moa = _three_presets()
+    moa.update(save_traces=True, trace_dir="/custom/traces")
+    chain = [{"provider": "custom", "model": "glm-5.08", "base_url": "http://gw:8080/v1"}]
+    _seed(home, monkeypatch, moa, fallback_providers=chain)
+
+    set_moa_models(
+        MoaConfigPayload(
+            default_preset="keep_a",
+            active_preset="",
+            presets={"keep_a": _preset("gpt-5.5"), "keep_b": _preset("gpt-5.7")},
+        )
+    )
+
+    on_disk = _on_disk(home)
+    assert "doomed" not in on_disk["moa"]["presets"]
+    assert on_disk["moa"]["save_traces"] is True, "save_traces dropped (#58819)"
+    assert on_disk["moa"]["trace_dir"] == "/custom/traces", "trace_dir dropped (#58819)"
+    assert on_disk["fallback_providers"] == chain, "MoA save clobbered fallback_providers (#89184)"
+
+
+def test_adding_a_preset_still_works(tmp_path, monkeypatch):
+    """Authoritative writes must not break the add/edit path."""
+    home = tmp_path / ".hermes"
+    home.mkdir()
+    _seed(home, monkeypatch, _three_presets())
+
+    set_moa_models(
+        MoaConfigPayload(
+            default_preset="keep_a",
+            active_preset="",
+            presets={
+                "keep_a": _preset("gpt-5.5"),
+                "doomed": _preset("gpt-5.6-luna"),
+                "keep_b": _preset("gpt-5.7"),
+                "fresh": _preset("gpt-5.9"),
+            },
+        )
+    )
+
+    presets = _on_disk(home)["moa"]["presets"]
+    assert set(presets) == {"keep_a", "doomed", "keep_b", "fresh"}
+    assert presets["fresh"]["reference_models"][0]["model"] == "gpt-5.9"

tests/hermes_cli/test_moa_set_models_preserves_extra_keys.py

@@ -58,7 +58,7 @@ class TestSetMoaModelsPreservesUndeclaredKeys:
 
         saved_cfg = {}
 
-        def fake_load_config():
+        def fake_read_raw_config():
             return dict(existing_cfg)  # shallow copy
 
         def fake_save_config(cfg, **_kwargs):
@@ -67,7 +67,7 @@ class TestSetMoaModelsPreservesUndeclaredKeys:
         payload = _base_payload()
 
         with (
-            patch("hermes_cli.config.load_config", side_effect=fake_load_config),
+            patch("hermes_cli.config.read_raw_config", side_effect=fake_read_raw_config),
             patch("hermes_cli.config.save_config", side_effect=fake_save_config),
             patch("hermes_cli.web_server_profiles._profile_scope"),
         ):