diff --git a/api/config.py b/api/config.py
index bbd3dfae..e74fe911 100644
--- a/api/config.py
+++ b/api/config.py
@@ -6008,7 +6008,22 @@ def get_available_models(*, prefer_cache: bool = False, force_refresh: bool = Fa
                         str(_provider_cfg.get(_route_key) or "").strip()
                         for _route_key in ("api", "base_url", "api_key", "key_env")
                     )
-                if not (_is_known_provider or _has_provider_route):
+                # A models-only provider config (no api/base_url/api_key/key_env)
+                # is only admitted as evidence when it's the active/configured
+                # provider (e.g. the lmstudio-style custom shape from #1970).
+                # This must NOT re-open the door for a spurious duplicate alias
+                # of a known provider (e.g. ``copilot-2: {name: "copilot",
+                # models: {...}}`` from #644/dedup regression) — that case is
+                # still rejected because it isn't the active provider and it
+                # isn't a route-bearing config in its own right.
+                _has_models_only_active_route = (
+                    not _has_provider_route
+                    and _is_provider_config
+                    and isinstance(_provider_cfg.get("models"), (dict, list))
+                    and _provider_cfg["models"]
+                    and _canonical == _canonicalise_provider_id(active_provider)
+                )
+                if not (_is_known_provider or _has_provider_route or _has_models_only_active_route):
                     continue
 
                 _canonical_to_raw_provider_key.setdefault(_canonical, _pid_key)
diff --git a/tests/test_pr1970_lmstudio_base_url_fallback.py b/tests/test_pr1970_lmstudio_base_url_fallback.py
index c3951417..d8488dc2 100644
--- a/tests/test_pr1970_lmstudio_base_url_fallback.py
+++ b/tests/test_pr1970_lmstudio_base_url_fallback.py
@@ -417,6 +417,39 @@ def test_provider_catalog_preserves_dict_shaped_raw_key_lookup(monkeypatch):
     assert "another-model" in model_ids
 
 
+def test_provider_catalog_rejects_non_active_models_only_custom_provider(monkeypatch):
+    """A models-only custom provider config must NOT render when it is not the
+    active/configured provider (#5301 review finding: admitting any
+    models-only config re-opens the copilot-2 duplicate-alias regression)."""
+    _stub_hermes_cli(monkeypatch)
+    monkeypatch.setattr("socket.getaddrinfo", lambda *a, **k: [])
+
+    with _RestoreCfg():
+        _set_cfg({
+            "model": {
+                "default": "my-model",
+                "provider": "CLIPpoxy",
+            },
+            "providers": {
+                "CLIPpoxy": {
+                    "models": ["my-model"],
+                },
+                "OtherCustom": {
+                    "models": ["unrelated-model"],
+                },
+            },
+        })
+        config.invalidate_models_cache()
+
+        result = config.get_available_models()
+
+    groups = _groups_by_provider_id(result)
+    assert "clippoxy" in groups, f"Active models-only provider should render, got: {list(groups)}"
+    assert "othercustom" not in groups, (
+        f"Non-active models-only provider must not render as a phantom group, got: {list(groups)}"
+    )
+
+
 def test_provider_catalog_treats_malformed_provider_entry_as_unconfigured(monkeypatch):
     """Provider catalog raw-key lookup must ignore truth-y non-dict entries."""
     _stub_hermes_cli(monkeypatch)