feat(backend): gate Other Models behind opt-in management toggles

Other Models management is now opt-in: enable_other_models (default false)
plus the enabled_other_sub_types allow-list replace the unreleased additive
enabled_other_folders key.

- config._get_enabled_other_folder_keys() is the single scan gate; a new
  refresh_other_roots() rebuilds roots and preview roots on toggle.
- ModelScanner gains a _should_keep_cached_entry() hydration hook and
  on_library_changed(reconcile=...) so switching a sub_type off drops its
  entries (and hash/autov3 rows) at load time and switching it on rescans.
- OtherScanner filters location-derived entries accordingly.
- Other routes reject every other type while off (or a disabled sub_type) and
  expose an "other_disabled" page flag; download routing returns a disabled
  marker instead of guessing; the download manager refuses other-type
  downloads and default-path routing for switched-off sub_types.
- Doctor / init-status / refresh-all skip the other scanner while off; the
  scanner stays registered so staged pending-deletes still merge.
- Tests updated with explicit opt-in fixtures plus new gating coverage.

py/routes/handlers/download_routing_handlers.py

@@ -56,11 +56,38 @@ class DownloadRoutingHandler:
             )
 
         if model_type.lower() in VALID_OTHER_CIVITAI_TYPES:
+            from ...services.settings_manager import get_settings_manager
+
+            settings = get_settings_manager()
+            if not settings.is_other_models_enabled():
+                # Opt-in feature is off: never auto-route, the UI falls back to
+                # manual folder selection and the download manager rejects it.
+                return web.json_response(
+                    {
+                        "success": True,
+                        "root_kind": "other",
+                        "sub_type": None,
+                        "disabled": True,
+                        "reason": "other_models_disabled",
+                    }
+                )
+
             sub_type = resolve_other_download_sub_type(
                 model_type,
                 file_types=(str(t) for t in file_types),
                 selected_file_type=selected_file_type,
             )
+            if sub_type and not settings.is_other_sub_type_enabled(sub_type):
+                return web.json_response(
+                    {
+                        "success": True,
+                        "root_kind": "other",
+                        "sub_type": None,
+                        "disabled": True,
+                        "reason": "other_sub_type_disabled",
+                        "requested_sub_type": sub_type,
+                    }
+                )
             return web.json_response(
                 {
                     "success": True,

py/routes/handlers/misc_handlers.py

@@ -663,6 +663,17 @@ class HealthCheckHandler:
             "recipe": ServiceRegistry.get_recipe_scanner,
         }
 
+    def _active_scanner_getters(
+        self,
+    ) -> Mapping[str, Callable[[], Awaitable[Any]]]:
+        """Drop the opt-in other scanner while Other Models is disabled."""
+        getters = self._scanner_getters
+        if "other" not in getters:
+            return getters
+        if get_settings_manager().is_other_models_enabled():
+            return getters
+        return {name: getter for name, getter in getters.items() if name != "other"}
+
     async def health_check(self, request: web.Request) -> web.Response:
         return web.json_response({"status": "ok"})
 
@@ -674,7 +685,7 @@ class HealthCheckHandler:
         page accepts the update and only reloads once all scanners are done.
         """
         pending: list[str] = []
-        for name, getter in self._scanner_getters.items():
+        for name, getter in self._active_scanner_getters().items():
             try:
                 scanner = await getter()
             except Exception:
@@ -764,6 +775,14 @@ class DoctorHandler:
         )
         self._app_version_getter = app_version_getter
 
+    def _active_scanner_factories(
+        self,
+    ) -> Sequence[tuple[str, str, Callable[[], Awaitable[Any]]]]:
+        """Drop the opt-in other scanner while Other Models is disabled."""
+        if self._settings.is_other_models_enabled():
+            return self._scanner_factories
+        return tuple(entry for entry in self._scanner_factories if entry[0] != "other")
+
     async def get_doctor_diagnostics(self, request: web.Request) -> web.Response:
         try:
             client_version = (request.query.get("clientVersion") or "").strip()
@@ -811,7 +830,7 @@ class DoctorHandler:
         repaired: list[dict[str, Any]] = []
         failures: list[dict[str, str]] = []
 
-        for model_type, label, factory in self._scanner_factories:
+        for model_type, label, factory in self._active_scanner_factories():
             try:
                 scanner = await factory()
                 await scanner.get_cached_data(force_refresh=True, rebuild_cache=True)
@@ -843,7 +862,7 @@ class DoctorHandler:
         renamed: list[dict[str, Any]] = []
 
         try:
-            for model_type, label, factory in self._scanner_factories:
+            for model_type, label, factory in self._active_scanner_factories():
                 try:
                     scanner = await factory()
                     hash_index = getattr(scanner, "_hash_index", None)
@@ -1075,7 +1094,7 @@ class DoctorHandler:
         overall_status = "ok"
         summary = "All model caches look healthy."
 
-        for model_type, label, factory in self._scanner_factories:
+        for model_type, label, factory in self._active_scanner_factories():
             try:
                 scanner = await factory()
                 persisted = None
@@ -1160,7 +1179,7 @@ class DoctorHandler:
         total_conflict_groups = 0
         total_conflict_files = 0
 
-        for model_type, label, factory in self._scanner_factories:
+        for model_type, label, factory in self._active_scanner_factories():
             # Duplicate filename detection targets LoRAs which use basename-only
             # syntax (<lora:name:strength>). Checkpoints/embeddings reference
             # models via relative paths with extensions, so conflicts there would
@@ -2797,6 +2816,8 @@ class ModelLibraryHandler:
 
             # Acquire the other scanner lazily so adapters without it only
             # fail when the payload actually contains other-type models.
+            # While the opt-in feature is off the scanner still exists (its
+            # cache is empty), so other types simply report inLibrary=False.
             needs_other_scanner = any(
                 isinstance(model, dict)
                 and str(model.get("type", "")).lower() in other_type_aliases

py/routes/handlers/model_handlers.py

@@ -90,6 +90,7 @@ class ModelPageView:
         settings_service: SettingsManager,
         server_i18n,
         logger: logging.Logger,
+        page_context_provider: Callable[[web.Request], Dict[str, Any]] | None = None,
     ) -> None:
         self._template_env = template_env
         self._template_name = template_name
@@ -97,6 +98,7 @@ class ModelPageView:
         self._settings = settings_service
         self._server_i18n = server_i18n
         self._logger = logger
+        self._page_context_provider = page_context_provider
 
     def _load_supporters(self) -> dict[str, Any]:
         """Load supporters data from JSON file."""
@@ -210,6 +212,16 @@ class ModelPageView:
                     self._logger.error("Error loading cache data: %s", cache_error)
                     template_context["is_initializing"] = True
 
+            if self._page_context_provider is not None:
+                try:
+                    extra_context = self._page_context_provider(request)
+                    if isinstance(extra_context, dict):
+                        template_context.update(extra_context)
+                except Exception as context_error:  # pragma: no cover - logging path
+                    self._logger.error(
+                        "Error building page context: %s", context_error
+                    )
+
             rendered = self._template_env.get_template(self._template_name).render(
                 **template_context
             )