diff --git a/openspec/changes/cloud-control-plane-integration/tasks.md b/openspec/changes/cloud-control-plane-integration/tasks.md
index ebf55b5..3b3e06e 100644
--- a/openspec/changes/cloud-control-plane-integration/tasks.md
+++ b/openspec/changes/cloud-control-plane-integration/tasks.md
@@ -31,7 +31,7 @@
 - [x] 4.2 Add public scopes for task submission/read, pool read, plugin read, and plugin administration and enforce them on every `/v1` route.
 - [x] 4.3 Add host principals bound to one `host_id` and reject cross-host heartbeat, claim, renewal, or result operations.
 - [x] 4.4 Make missing production credentials a startup/readiness failure and permit anonymous mode only through the explicit non-production override.
-- [ ] 4.5 Add authentication tests covering invalid tokens, missing scopes, host impersonation, plugin administration, and secret redaction.
+- [x] 4.5 Add authentication tests covering invalid tokens, missing scopes, host impersonation, plugin administration, and secret redaction.
 
 ## 5. Host Agent Internal API
 
diff --git a/tests/test_cloud_auth.py b/tests/test_cloud_auth.py
index aeaf07c..56c1dc2 100644
--- a/tests/test_cloud_auth.py
+++ b/tests/test_cloud_auth.py
@@ -147,3 +147,18 @@ def test_public_principal_cannot_act_as_host() -> None:
     assert principal is not None
     with pytest.raises(HostPrincipalRequiredError):
         principal.require_host("host-a")
+
+
+def test_authentication_failure_does_not_log_bearer_secret(caplog) -> None:
+    provider = ConfiguredBearerAuthProvider(
+        [BearerCredential(principal_id="integrator", token="valid-secret")]
+    )
+
+    assert (
+        provider.authenticate(
+            _Request(headers={"authorization": "Bearer invalid-secret"})
+        )
+        is None
+    )
+    assert "invalid-secret" not in caplog.text
+    assert "valid-secret" not in caplog.text
diff --git a/tests/test_cloud_sdk_api.py b/tests/test_cloud_sdk_api.py
index d8d9995..d35b46d 100644
--- a/tests/test_cloud_sdk_api.py
+++ b/tests/test_cloud_sdk_api.py
@@ -287,3 +287,56 @@ def test_every_public_route_enforces_its_scope(
     assert unauthorized.headers["www-authenticate"] == "Bearer"
     assert forbidden.status_code == 403
     assert authorized.status_code not in {401, 403}
+
+
+def test_plugin_admin_scope_is_checked_before_registration(
+    tmp_path,
+    monkeypatch,
+) -> None:
+    provider = ConfiguredBearerAuthProvider(
+        [
+            BearerCredential(
+                principal_id="plugin-reader",
+                token="reader-token",
+                scopes=frozenset({"plugins:read"}),
+            )
+        ]
+    )
+    app, _, _, plugin_registry = _build_app(tmp_path, auth_provider=provider)
+    registration_called = False
+
+    def fail_if_called(_manifest) -> None:
+        nonlocal registration_called
+        registration_called = True
+        raise AssertionError("plugin registration must not run before authorization")
+
+    monkeypatch.setattr(plugin_registry, "register", fail_if_called)
+    response = _client_for(app).post(
+        "/v1/plugins",
+        headers={"Authorization": "Bearer reader-token"},
+        json={
+            "name": "forbidden-plugin",
+            "version": "1.0.0",
+            "entry_point_kind": "driver",
+            "target": "secret.module:builder",
+        },
+    )
+
+    assert response.status_code == 403
+    assert registration_called is False
+    assert "secret.module" not in response.text
+
+
+def test_invalid_token_is_rejected_by_public_router(tmp_path) -> None:
+    provider = ConfiguredBearerAuthProvider(
+        [BearerCredential(principal_id="integrator", token="valid-token")]
+    )
+    app, _, _, _ = _build_app(tmp_path, auth_provider=provider)
+
+    response = _client_for(app).get(
+        "/v1/devices",
+        headers={"Authorization": "Bearer invalid-token"},
+    )
+
+    assert response.status_code == 401
+    assert response.headers["www-authenticate"] == "Bearer"