test(plugins): cover _discover_all_plugins recursion + cross-link loader

Add a TestDiscoverAllPlugins class covering the six cases the recursive
scan needs to handle:

- flat plugin uses its manifest ``name:`` as the key
- category-namespaced plugin keys off ``<category>/<dirname>`` even when
  the manifest ``name:`` is bare (regression test for the original bug —
  ``plugins/observability/langfuse/`` with ``name: langfuse`` must
  surface as ``observability/langfuse``, not ``langfuse``)
- user-installed plugin overrides bundled on key collision
- depth cap: anything below ``<root>/<category>/<plugin>/`` is ignored
- bundled ``memory/`` and ``context_engine/`` are skipped (they have
  their own loaders), but user plugins under those category names are
  still scanned

Also add an in-source comment next to the key derivation pointing at the
loader's matching line (``PluginManager._parse_manifest`` in
plugins.py:1027-1028), so future renames of one site flag the other.

Both items raised in Copilot review on #27161.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/hermes_cli/test_plugins_cmd.py

@@ -396,6 +396,117 @@ class TestCmdList:
         cmd_list()
 
 
+# ── _discover_all_plugins tests ───────────────────────────────────────────────
+
+
+class TestDiscoverAllPlugins:
+    """Exercise the recursive scan that powers ``hermes plugins list``.
+
+    Mirrors the layouts the runtime loader handles
+    (:meth:`PluginManager._scan_directory_level`): flat plugins at the root,
+    category-namespaced plugins one level deeper, and user-overrides-bundled
+    on key collision.
+    """
+
+    @staticmethod
+    def _write_plugin(root: Path, segments: list, manifest_name: str = None) -> None:
+        plugin_dir = root
+        for seg in segments:
+            plugin_dir = plugin_dir / seg
+        plugin_dir.mkdir(parents=True, exist_ok=True)
+        manifest = {
+            "name": manifest_name or segments[-1],
+            "version": "0.1.0",
+            "description": f"Test plugin {'/'.join(segments)}",
+        }
+        (plugin_dir / "plugin.yaml").write_text(yaml.dump(manifest))
+
+    def _entries_by_key(self, tmp_path, monkeypatch) -> dict:
+        from hermes_cli import plugins_cmd
+        bundled = tmp_path / "bundled"
+        user = tmp_path / "user"
+        bundled.mkdir()
+        user.mkdir()
+        monkeypatch.setattr(
+            "hermes_cli.plugins.get_bundled_plugins_dir", lambda: bundled
+        )
+        monkeypatch.setattr(plugins_cmd, "_plugins_dir", lambda: user)
+        return bundled, user, lambda: {
+            e[0]: e for e in plugins_cmd._discover_all_plugins()
+        }
+
+    def test_flat_plugin_uses_manifest_name_as_key(self, tmp_path, monkeypatch):
+        bundled, _, discover = self._entries_by_key(tmp_path, monkeypatch)
+        self._write_plugin(bundled, ["disk-cleanup"])
+
+        entries = discover()
+        assert "disk-cleanup" in entries
+        assert entries["disk-cleanup"][3] == "bundled"
+
+    def test_category_namespaced_plugin_uses_path_derived_key(
+        self, tmp_path, monkeypatch
+    ):
+        """Regression test for the original bug — ``observability/langfuse``
+        and ``image_gen/openai`` must surface under their path-derived key,
+        not vanish because the category directory has no ``plugin.yaml``."""
+        bundled, _, discover = self._entries_by_key(tmp_path, monkeypatch)
+        # langfuse's real manifest declares ``name: langfuse`` (bare), but it
+        # lives under ``observability/`` — the key must reflect the path.
+        self._write_plugin(
+            bundled, ["observability", "langfuse"], manifest_name="langfuse"
+        )
+        self._write_plugin(bundled, ["image_gen", "openai"])
+
+        entries = discover()
+        assert "observability/langfuse" in entries
+        assert "image_gen/openai" in entries
+        # Bare manifest name must NOT leak through as a top-level key.
+        assert "langfuse" not in entries
+        assert "openai" not in entries
+
+    def test_user_overrides_bundled_on_key_collision(self, tmp_path, monkeypatch):
+        bundled, user, discover = self._entries_by_key(tmp_path, monkeypatch)
+        self._write_plugin(bundled, ["observability", "langfuse"])
+        self._write_plugin(user, ["observability", "langfuse"])
+
+        entries = discover()
+        assert entries["observability/langfuse"][3] == "user"
+
+    def test_depth_cap_skips_third_level(self, tmp_path, monkeypatch):
+        """Anything deeper than ``<root>/<category>/<plugin>/`` is ignored,
+        matching the loader's depth cap."""
+        bundled, _, discover = self._entries_by_key(tmp_path, monkeypatch)
+        # plugins/a/b/c/plugin.yaml — too deep, must NOT be discovered.
+        self._write_plugin(bundled, ["a", "b", "c"])
+
+        entries = discover()
+        assert not any(k.startswith("a/") for k in entries), entries
+
+    def test_bundled_memory_and_context_engine_skipped(self, tmp_path, monkeypatch):
+        """``plugins/memory/`` and ``plugins/context_engine/`` use their own
+        loaders; bundled entries inside them must not appear in the general
+        list (matches the pre-refactor skip set)."""
+        bundled, _, discover = self._entries_by_key(tmp_path, monkeypatch)
+        self._write_plugin(bundled, ["memory", "honcho"])
+        self._write_plugin(bundled, ["context_engine", "compressor"])
+        self._write_plugin(bundled, ["observability", "langfuse"])
+
+        entries = discover()
+        assert "memory/honcho" not in entries
+        assert "context_engine/compressor" not in entries
+        assert "observability/langfuse" in entries
+
+    def test_user_memory_subdir_is_still_scanned(self, tmp_path, monkeypatch):
+        """The memory/context_engine skip only applies to *bundled* — a user
+        plugin at ``~/.hermes/plugins/memory/<x>/`` should still be discovered
+        so the user can see what they installed."""
+        bundled, user, discover = self._entries_by_key(tmp_path, monkeypatch)
+        self._write_plugin(user, ["memory", "my-custom-store"])
+
+        entries = discover()
+        assert "memory/my-custom-store" in entries
+
+
 # ── _copy_example_files tests ─────────────────────────────────────────────────