@@ -195,3 +195,13 @@ class DiscoveryDiff:
     unchanged: list[str]
     states: dict[str, PluginState]
     errors: list[PluginError]
+
+    def by_filter_reason(self, reason: FilterReason) -> list[str]:
+        """Return plugin names whose filter_reason matches.
+
+        Parity helper with DiscoveryResult.by_filter_reason. Consumers that
+        rediscover() periodically and group newly-filtered plugins by reason
+        (Settings UI surfaces, audit logs) get the same one-line accessor
+        instead of iterating states.items() and grouping by hand.
+        """
+        return [name for name, s in self.states.items() if s.filter_reason == reason]
@@ -200,6 +200,35 @@ def test_new_plugin_not_in_enabled_list_is_filtered(self, tmp_path: Path) -> Non
         assert diff.states["beta"].filter_reason == "not_enabled"
 
 
+class TestDiscoveryDiffHelpers:
+    def test_by_filter_reason(self, tmp_path: Path) -> None:
+        """Parity with DiscoveryResult.by_filter_reason: newly-discovered
+        plugins not in the enabled list show up under 'not_enabled'."""
+        cfg = _write_config(tmp_path, enabled=["alpha"])
+        pm = PluginManager(config_path=str(cfg))
+
+        with patch(
+            "pluginforge.manager.discover_entry_points",
+            return_value={"alpha": AlphaPlugin},
+        ):
+            pm.discover_plugins()
+
+        # Beta + gamma appear but aren't in the enabled list.
+        with patch(
+            "pluginforge.manager.discover_entry_points",
+            return_value={
+                "alpha": AlphaPlugin,
+                "beta": BetaPlugin,
+                "gamma": GammaPlugin,
+            },
+        ):
+            diff = pm.rediscover()
+
+        not_enabled = diff.by_filter_reason("not_enabled")
+        assert sorted(not_enabled) == ["beta", "gamma"]
+        assert "alpha" not in not_enabled
+
+
 class TestCacheInvalidation:
     def test_invalidate_caches_is_called(self, tmp_path: Path) -> None:
         cfg = _write_config(tmp_path)