fix(model-switch): prevent custom-provider misattribution in model picker (#48305)

When the current provider is a custom endpoint (custom or custom:*), the model
switch pipeline must NOT auto-switch to a native provider/OpenRouter based on a
static-catalog match. The user explicitly configured their own endpoint and the
same model name may be served there; silently rewriting model.provider destroys
their config.

- detect_static_provider_for_model(): skip the static-catalog scan when the
  current provider is custom/custom:*
- switch_model() Step e: extend is_custom to cover custom:* so the
  detect_provider_for_model() last-resort fallback cannot fire

Salvaged from #48351 by Elshayib (authorship preserved).

Fixes #48305

hermes_cli/model_switch.py

@@ -1057,8 +1057,10 @@ def switch_model(
 
         # --- Step e: detect_provider_for_model() as last resort ---
         _base = current_base_url or ""
-        is_custom = current_provider in {"custom", "local"} or (
-            "localhost" in _base or "127.0.0.1" in _base
+        is_custom = (
+            current_provider in {"custom", "local"}
+            or current_provider.startswith("custom:")
+            or ("localhost" in _base or "127.0.0.1" in _base)
         )
 
         if (

hermes_cli/models.py

@@ -1882,6 +1882,14 @@ def detect_static_provider_for_model(
         return None
 
     # --- Step 1: check static provider catalogs for a direct match ---
+    # If the current provider is a custom endpoint (custom or custom:*), never
+    # auto-switch away from it based on a static catalog match — the user
+    # explicitly configured their own endpoint and the same model name may be
+    # served there (#48305).
+    _is_custom_current = (
+        current_provider == "custom"
+        or current_provider.startswith("custom:")
+    )
     for pid, models in _PROVIDER_MODELS.items():
         if (
             pid in current_keys
@@ -1889,6 +1897,8 @@ def detect_static_provider_for_model(
             or pid in _BORROWED_MODEL_PROVIDERS
         ):
             continue
+        if _is_custom_current:
+            continue
         if any(name_lower == m.lower() for m in models):
             return (pid, name)
 

tests/hermes_cli/test_models.py

@@ -301,6 +301,26 @@ class TestDetectProviderForModel:
         assert result is not None
         assert result[0] not in {"nous",}  # nous has claude models but shouldn't be suggested
 
+    def test_custom_provider_not_overridden_by_static_catalog(self):
+        """When current provider is custom:*, a static-catalog match must NOT
+        override it — otherwise a model served by the user's own endpoint gets
+        misattributed to a native provider, rewriting model.provider (#48305).
+
+        `gpt-5.4` is in the static openai catalog; with current=custom:foo,
+        detection must return None instead of switching to openai.
+        """
+        assert detect_provider_for_model("gpt-5.4", "custom:foo") is None
+
+    def test_bare_custom_provider_not_overridden_by_static_catalog(self):
+        """Same protection for the bare 'custom' provider."""
+        assert detect_provider_for_model("gpt-5.4", "custom") is None
+
+    def test_non_custom_provider_detection_unaffected(self):
+        """The custom-provider guard must NOT change detection for non-custom
+        current providers — a static-catalog model still routes normally."""
+        result = detect_provider_for_model("gpt-5.4", "openrouter")
+        assert result is not None and result[0] == "openai"
+
 
 class TestIsNousFreeTier:
     """Tests for is_nous_free_tier — account tier detection."""