diff --git a/pulp_rust/app/views.py b/pulp_rust/app/views.py
index 482039c..9f661fb 100644
--- a/pulp_rust/app/views.py
+++ b/pulp_rust/app/views.py
@@ -27,6 +27,7 @@
 
 from pulp_rust.app.auth import CargoTokenAuthentication
 from pulp_rust.app.models import (
+    RustCargoToken,
     RustContent,
     RustDistribution,
     RustPackageYank,
@@ -86,6 +87,10 @@ def token_scope_error(token, action, distro):
     Scopes only narrow what a token can do, so this runs in addition to the RBAC check
     rather than in place of it. An empty scope means the token is not narrowed at all.
     """
+    if not isinstance(token, RustCargoToken):
+        # Credentials other than a Cargo token carry no scopes.
+        return None
+
     if token.actions and action not in token.actions:
         return cargo_error(f"this token is not scoped for the {action} action", status=403)
 
@@ -322,12 +327,23 @@ def retrieve(self, request, repo):
         data = {
             "dl": self.base_download_url,
             "api": self.base_api_url,
-            "auth-required": False,
+            "auth-required": bool(self.distribution.content_guard_id),
         }
         return HttpResponse(json.dumps(data), content_type="application/json")
 
 
-class CargoMeApiView(APIView):
+class CargoAuthMixin:
+    """Try the Cargo token first, then the instance's default authentication classes.
+
+    This keeps `cargo login` tokens working while still accepting the other credentials
+    the deployment is configured for (e.g. HTTP Basic).
+    """
+
+    def get_authenticators(self):
+        return [CargoTokenAuthentication(), *super().get_authenticators()]
+
+
+class CargoMeApiView(CargoAuthMixin, APIView):
     """
     Auth verification endpoint for ``cargo login``.
 
@@ -335,7 +351,6 @@ class CargoMeApiView(APIView):
     See: https://doc.rust-lang.org/cargo/reference/registry-web-api.html
     """
 
-    authentication_classes = [CargoTokenAuthentication]
     permission_classes = [IsAuthenticated]
     renderer_classes = [JSONRenderer]
 
@@ -343,7 +358,7 @@ def get(self, request, **kwargs):
         return HttpResponse(json.dumps({"ok": True}), content_type="application/json")
 
 
-class CargoPublishApiView(APIView):
+class CargoPublishApiView(CargoAuthMixin, APIView):
     """
     View for Cargo's crate publish endpoint (PUT /api/v1/crates/new).
 
@@ -353,7 +368,6 @@ class CargoPublishApiView(APIView):
     See: https://doc.rust-lang.org/cargo/reference/registry-web-api.html#publish
     """
 
-    authentication_classes = [CargoTokenAuthentication]
     permission_classes = [IsAuthenticated]
     renderer_classes = [JSONRenderer]
 
@@ -449,12 +463,11 @@ def put(self, request, **kwargs):
         )
 
 
-class CargoDownloadApiView(APIView):
+class CargoDownloadApiView(CargoAuthMixin, APIView):
     """
     View for Cargo's crate download, readme, yank, and unyank endpoints.
     """
 
-    authentication_classes = [CargoTokenAuthentication]
     renderer_classes = [PlainTextRenderer, JSONRenderer]
 
     def get_permissions(self):
diff --git a/pulp_rust/tests/functional/api/test_auth.py b/pulp_rust/tests/functional/api/test_auth.py
index b75ebdf..8e37d37 100644
--- a/pulp_rust/tests/functional/api/test_auth.py
+++ b/pulp_rust/tests/functional/api/test_auth.py
@@ -1,5 +1,7 @@
 """Tests for Cargo token authentication on Cargo API endpoints."""
 
+import base64
+import uuid
 from urllib.parse import urljoin
 
 from pulp_rust.tests.functional.utils import (
@@ -267,3 +269,89 @@ def test_yank_requires_distribution_permission(
     # Now Alice can yank
     response = cargo_yank(base_url, "itoa", "1.0.0", headers=headers)
     assert response.status_code == 200
+
+
+# --- Non-Cargo-token authenticators (the instance's default auth stack) ---
+
+
+def test_me_with_basic_auth_succeeds(
+    rust_repo_factory,
+    rust_distribution_factory,
+    cargo_registry_url,
+    gen_user,
+):
+    """A non-Cargo credential (HTTP Basic) must authenticate too.
+
+    The Cargo endpoints prepend the Cargo token to the instance's configured
+    authenticators instead of replacing them, so any deployment auth reaches them.
+    """
+    repository = rust_repo_factory()
+    distribution = rust_distribution_factory(repository=repository.pulp_href)
+    base = cargo_registry_url(distribution.base_path)
+
+    user = gen_user()
+    creds = base64.b64encode(f"{user.username}:{user.password}".encode()).decode()
+
+    response = cargo_api_request(
+        "GET", urljoin(base, "me"), headers={"Authorization": f"Basic {creds}"}
+    )
+    assert response.status_code == 200
+    assert response.json()["ok"] is True
+
+
+def test_yank_with_basic_auth_succeeds(
+    gen_user,
+    rust_distro_api_client,
+    populated_repo,
+):
+    """Token scopes only apply to Cargo tokens, so a Basic-authenticated yank goes through."""
+    alice = gen_user()
+    rust_distro_api_client.add_role(
+        populated_repo["distribution"].pulp_href,
+        {"role": "rust.rustdistribution_publisher", "users": [alice.username]},
+    )
+    creds = base64.b64encode(f"{alice.username}:{alice.password}".encode()).decode()
+
+    response = cargo_yank(
+        populated_repo["base_url"], "itoa", "1.0.0", headers={"Authorization": f"Basic {creds}"}
+    )
+    assert response.status_code == 200
+
+
+# --- config.json auth-required reflects the content guard ---
+
+
+def test_config_json_auth_required_false_without_guard(
+    rust_repo_factory,
+    rust_distribution_factory,
+    cargo_registry_url,
+):
+    """An unguarded distribution advertises auth-required: false."""
+    repository = rust_repo_factory()
+    distribution = rust_distribution_factory(repository=repository.pulp_href)
+    config_url = urljoin(cargo_registry_url(distribution.base_path), "config.json")
+
+    response = cargo_api_request("GET", config_url)
+    assert response.json()["auth-required"] is False
+
+
+def test_config_json_auth_required_true_with_guard(
+    rust_repo_factory,
+    rust_distribution_factory,
+    cargo_registry_url,
+    pulpcore_bindings,
+    gen_object_with_cleanup,
+):
+    """A guarded distribution advertises auth-required: true, so cargo sends its
+    credentials on the index and downloads, not only on the write API."""
+    guard = gen_object_with_cleanup(
+        pulpcore_bindings.ContentguardsRbacApi, {"name": str(uuid.uuid4())}
+    )
+    repository = rust_repo_factory()
+    distribution = rust_distribution_factory(
+        repository=repository.pulp_href, content_guard=guard.pulp_href
+    )
+    config_url = urljoin(cargo_registry_url(distribution.base_path), "config.json")
+
+    response = cargo_api_request("GET", config_url)
+    assert response.json()["auth-required"] is True