fix(downloads): route unknown checkpoint baseModels to diffusion models by default

CivitAI labels new DiT architectures (MiniMax H3, future Flux/Wan/Qwen
variants) as model.type "Checkpoint" with plain "Model" file entries,
so the DIFFUSION_MODEL_BASE_MODELS allowlist could never keep up and
such downloads were mis-routed to the checkpoint roots (e.g. model
2877206 / version 3374439). The set of true full-checkpoint families is
closed, so the baseModel fallback is inverted:

1. file type UNet/Diffusion Model -> unet (unchanged)
2. baseModel in DIFFUSION_MODEL_BASE_MODELS (now incl. MiniMax H3) -> unet
3. baseModel in new CHECKPOINT_BASE_MODELS (SD 1.x/2.x/3.x, SDXL, Pony,
   Illustrious, NoobAI) -> checkpoint
4. unknown/empty baseModel -> new unknown_base_model_routing setting,
   defaulting to diffusion models

The setting is exposed under Settings > Downloads, validated in
SettingsManager, and threaded into both the download manager and the
download routing endpoint so they keep agreeing.

locales/de.json

@@ -353,6 +353,14 @@
             "placeholder": "Leer lassen, um aria2c aus dem PATH zu verwenden"
         },
         "aria2HelpLink": "Erfahren Sie, wie Sie das aria2-Download-Backend einrichten",
+        "unknownBaseModelRouting": {
+            "label": "[TODO: Translate] Unknown base model routing",
+            "help": "[TODO: Translate] Decides where checkpoint downloads go when CivitAI reports a base model that is neither a known checkpoint (SD 1.x/2.x/3.x, SDXL, Pony, Illustrious, NoobAI) nor a known diffusion model. New diffusion architectures appear frequently, so routing them to diffusion models is usually correct.",
+            "options": {
+                "diffusionModel": "[TODO: Translate] Diffusion models (recommended)",
+                "checkpoint": "[TODO: Translate] Checkpoints"
+            }
+        },
         "civitaiHostBanner": {
             "title": "CivitAI-Host-Einstellung verfügbar",
             "content": "CivitAI verwendet jetzt civitai.com für SFW-Inhalte und civitai.red für uneingeschränkte Inhalte. In den Einstellungen können Sie ändern, welche Seite standardmäßig geöffnet wird.",

locales/en.json

@@ -353,6 +353,14 @@
       "placeholder": "Leave empty to use aria2c from PATH"
     },
     "aria2HelpLink": "Learn how to set up the aria2 download backend",
+    "unknownBaseModelRouting": {
+      "label": "Unknown base model routing",
+      "help": "Decides where checkpoint downloads go when CivitAI reports a base model that is neither a known checkpoint (SD 1.x/2.x/3.x, SDXL, Pony, Illustrious, NoobAI) nor a known diffusion model. New diffusion architectures appear frequently, so routing them to diffusion models is usually correct.",
+      "options": {
+        "diffusionModel": "Diffusion models (recommended)",
+        "checkpoint": "Checkpoints"
+      }
+    },
     "civitaiHostBanner": {
       "title": "CivitAI host preference available",
       "content": "CivitAI now uses civitai.com for SFW content and civitai.red for unrestricted content. You can change which site opens by default in Settings.",

locales/es.json

@@ -353,6 +353,14 @@
             "placeholder": "Déjalo vacío para usar aria2c desde el PATH"
         },
         "aria2HelpLink": "Aprende a configurar el backend de descarga aria2",
+        "unknownBaseModelRouting": {
+            "label": "[TODO: Translate] Unknown base model routing",
+            "help": "[TODO: Translate] Decides where checkpoint downloads go when CivitAI reports a base model that is neither a known checkpoint (SD 1.x/2.x/3.x, SDXL, Pony, Illustrious, NoobAI) nor a known diffusion model. New diffusion architectures appear frequently, so routing them to diffusion models is usually correct.",
+            "options": {
+                "diffusionModel": "[TODO: Translate] Diffusion models (recommended)",
+                "checkpoint": "[TODO: Translate] Checkpoints"
+            }
+        },
         "civitaiHostBanner": {
             "title": "Preferencia de host de CivitAI disponible",
             "content": "CivitAI ahora usa civitai.com para contenido SFW y civitai.red para contenido sin restricciones. Puedes cambiar en Ajustes qué sitio se abre por defecto.",

locales/fr.json

@@ -353,6 +353,14 @@
             "placeholder": "Laisser vide pour utiliser aria2c depuis le PATH"
         },
         "aria2HelpLink": "Apprenez à configurer le backend de téléchargement aria2",
+        "unknownBaseModelRouting": {
+            "label": "[TODO: Translate] Unknown base model routing",
+            "help": "[TODO: Translate] Decides where checkpoint downloads go when CivitAI reports a base model that is neither a known checkpoint (SD 1.x/2.x/3.x, SDXL, Pony, Illustrious, NoobAI) nor a known diffusion model. New diffusion architectures appear frequently, so routing them to diffusion models is usually correct.",
+            "options": {
+                "diffusionModel": "[TODO: Translate] Diffusion models (recommended)",
+                "checkpoint": "[TODO: Translate] Checkpoints"
+            }
+        },
         "civitaiHostBanner": {
             "title": "Préférence d’hôte CivitAI disponible",
             "content": "CivitAI utilise désormais civitai.com pour le contenu SFW et civitai.red pour le contenu sans restriction. Vous pouvez modifier dans les paramètres le site ouvert par défaut.",

locales/he.json

@@ -353,6 +353,14 @@
             "placeholder": "השאר ריק כדי להשתמש ב-aria2c מתוך ה-PATH"
         },
         "aria2HelpLink": "למד כיצד להגדיר את מנוע ההורדה aria2",
+        "unknownBaseModelRouting": {
+            "label": "[TODO: Translate] Unknown base model routing",
+            "help": "[TODO: Translate] Decides where checkpoint downloads go when CivitAI reports a base model that is neither a known checkpoint (SD 1.x/2.x/3.x, SDXL, Pony, Illustrious, NoobAI) nor a known diffusion model. New diffusion architectures appear frequently, so routing them to diffusion models is usually correct.",
+            "options": {
+                "diffusionModel": "[TODO: Translate] Diffusion models (recommended)",
+                "checkpoint": "[TODO: Translate] Checkpoints"
+            }
+        },
         "civitaiHostBanner": {
             "title": "העדפת מארח CivitAI זמינה",
             "content": "CivitAI משתמש כעת ב-civitai.com עבור תוכן SFW וב-civitai.red עבור תוכן ללא הגבלות. ניתן לשנות בהגדרות איזה אתר ייפתח כברירת מחדל.",

locales/ja.json

@@ -353,6 +353,14 @@
             "placeholder": "空欄のままにすると PATH 上の aria2c を使用します"
         },
         "aria2HelpLink": "aria2 ダウンロードバックエンドの設定方法",
+        "unknownBaseModelRouting": {
+            "label": "[TODO: Translate] Unknown base model routing",
+            "help": "[TODO: Translate] Decides where checkpoint downloads go when CivitAI reports a base model that is neither a known checkpoint (SD 1.x/2.x/3.x, SDXL, Pony, Illustrious, NoobAI) nor a known diffusion model. New diffusion architectures appear frequently, so routing them to diffusion models is usually correct.",
+            "options": {
+                "diffusionModel": "[TODO: Translate] Diffusion models (recommended)",
+                "checkpoint": "[TODO: Translate] Checkpoints"
+            }
+        },
         "civitaiHostBanner": {
             "title": "CivitAI ホスト設定を利用できます",
             "content": "CivitAI は現在、SFW コンテンツには civitai.com、制限なしコンテンツには civitai.red を使用しています。設定で既定で開くサイトを変更できます。",

locales/ko.json

@@ -353,6 +353,14 @@
             "placeholder": "비워 두면 PATH의 aria2c를 사용합니다"
         },
         "aria2HelpLink": "aria2 다운로드 백엔드 설정 방법 알아보기",
+        "unknownBaseModelRouting": {
+            "label": "[TODO: Translate] Unknown base model routing",
+            "help": "[TODO: Translate] Decides where checkpoint downloads go when CivitAI reports a base model that is neither a known checkpoint (SD 1.x/2.x/3.x, SDXL, Pony, Illustrious, NoobAI) nor a known diffusion model. New diffusion architectures appear frequently, so routing them to diffusion models is usually correct.",
+            "options": {
+                "diffusionModel": "[TODO: Translate] Diffusion models (recommended)",
+                "checkpoint": "[TODO: Translate] Checkpoints"
+            }
+        },
         "civitaiHostBanner": {
             "title": "CivitAI 호스트 기본 설정 사용 가능",
             "content": "이제 CivitAI는 SFW 콘텐츠에 civitai.com을, 무제한 콘텐츠에 civitai.red를 사용합니다. 설정에서 기본으로 열 사이트를 변경할 수 있습니다.",

locales/ru.json

@@ -353,6 +353,14 @@
             "placeholder": "Оставьте пустым, чтобы использовать aria2c из PATH"
         },
         "aria2HelpLink": "Узнайте, как настроить сервер загрузки aria2",
+        "unknownBaseModelRouting": {
+            "label": "[TODO: Translate] Unknown base model routing",
+            "help": "[TODO: Translate] Decides where checkpoint downloads go when CivitAI reports a base model that is neither a known checkpoint (SD 1.x/2.x/3.x, SDXL, Pony, Illustrious, NoobAI) nor a known diffusion model. New diffusion architectures appear frequently, so routing them to diffusion models is usually correct.",
+            "options": {
+                "diffusionModel": "[TODO: Translate] Diffusion models (recommended)",
+                "checkpoint": "[TODO: Translate] Checkpoints"
+            }
+        },
         "civitaiHostBanner": {
             "title": "Доступна настройка хоста CivitAI",
             "content": "Теперь CivitAI использует civitai.com для контента SFW и civitai.red для контента без ограничений. В настройках можно изменить, какой сайт открывать по умолчанию.",

locales/zh-CN.json

@@ -353,6 +353,14 @@
             "placeholder": "留空则使用 PATH 中的 aria2c"
         },
         "aria2HelpLink": "了解如何配置 aria2 下载后端",
+        "unknownBaseModelRouting": {
+            "label": "[TODO: Translate] Unknown base model routing",
+            "help": "[TODO: Translate] Decides where checkpoint downloads go when CivitAI reports a base model that is neither a known checkpoint (SD 1.x/2.x/3.x, SDXL, Pony, Illustrious, NoobAI) nor a known diffusion model. New diffusion architectures appear frequently, so routing them to diffusion models is usually correct.",
+            "options": {
+                "diffusionModel": "[TODO: Translate] Diffusion models (recommended)",
+                "checkpoint": "[TODO: Translate] Checkpoints"
+            }
+        },
         "civitaiHostBanner": {
             "title": "已提供 CivitAI 站点偏好设置",
             "content": "CivitAI 现在使用 civitai.com 提供 SFW 内容，使用 civitai.red 提供无限制内容。你可以在设置中更改默认打开的站点。",

locales/zh-TW.json

@@ -353,6 +353,14 @@
             "placeholder": "留空則使用 PATH 中的 aria2c"
         },
         "aria2HelpLink": "了解如何設定 aria2 下載後端",
+        "unknownBaseModelRouting": {
+            "label": "[TODO: Translate] Unknown base model routing",
+            "help": "[TODO: Translate] Decides where checkpoint downloads go when CivitAI reports a base model that is neither a known checkpoint (SD 1.x/2.x/3.x, SDXL, Pony, Illustrious, NoobAI) nor a known diffusion model. New diffusion architectures appear frequently, so routing them to diffusion models is usually correct.",
+            "options": {
+                "diffusionModel": "[TODO: Translate] Diffusion models (recommended)",
+                "checkpoint": "[TODO: Translate] Checkpoints"
+            }
+        },
         "civitaiHostBanner": {
             "title": "已提供 CivitAI 站點偏好設定",
             "content": "CivitAI 現在使用 civitai.com 提供 SFW 內容，使用 civitai.red 提供無限制內容。您可以在設定中變更預設開啟的站點。",

py/routes/handlers/download_routing_handlers.py

@@ -96,10 +96,15 @@ class DownloadRoutingHandler:
                 }
             )
 
+        from ...services.settings_manager import get_settings_manager
+
         is_diffusion = is_diffusion_model_download(
             model_type,
             file_types=(str(t) for t in file_types),
             base_model=base_model,
+            unknown_base_model_default=get_settings_manager().get(
+                "unknown_base_model_routing", "diffusion_model"
+            ),
         )
         return web.json_response(
             {

py/services/download_manager.py

@@ -1670,6 +1670,9 @@ class DownloadManager:
                 model_type,
                 file_types=(f.get("type", "") for f in version_info.get("files", [])),
                 base_model=base_model_value,
+                unknown_base_model_default=get_settings_manager().get(
+                    "unknown_base_model_routing", "diffusion_model"
+                ),
             )
 
             # Existence check after the metadata fetch (#1058):

py/services/download_routing.py

@@ -13,6 +13,7 @@ import logging
 from typing import Iterable, Optional
 
 from ..utils.constants import (
+    CHECKPOINT_BASE_MODELS,
     CIVITAI_FILE_TYPE_TO_OTHER_SUB_TYPE,
     CIVITAI_TYPE_TO_OTHER_SUB_TYPE,
     DIFFUSION_MODEL_BASE_MODELS,
@@ -24,17 +25,27 @@ logger = logging.getLogger(__name__)
 # model (loaded via UNETLoader in ComfyUI) rather than a full checkpoint.
 DIFFUSION_FILE_TYPES = frozenset({"UNet", "Diffusion Model"})
 
+# Allowed values for the "unknown_base_model_routing" setting / the
+# unknown_base_model_default parameter below.
+ROUTING_DIFFUSION_MODEL = "diffusion_model"
+ROUTING_CHECKPOINT = "checkpoint"
+
 
 def is_diffusion_model_download(
     model_type: str,
     file_types: Iterable[str] = (),
     base_model: str = "",
+    unknown_base_model_default: str = ROUTING_DIFFUSION_MODEL,
 ) -> bool:
     """Return True when a download should be routed to the unet roots.
 
     Only applies to downloads initiated from the checkpoint library.
     Priority: (1) any file has type "UNet" or "Diffusion Model" (the more
-    direct signal from CivitAI), (2) baseModel is a known diffusion model.
+    direct signal from CivitAI), (2) baseModel is a known diffusion model,
+    (3) baseModel is a known full checkpoint -> not diffusion, (4) unknown
+    or empty baseModel -> the ``unknown_base_model_default`` setting, which
+    defaults to diffusion because the set of true checkpoint families is
+    closed while new DiT base models appear all the time.
     """
     if model_type != "checkpoint":
         return False
@@ -54,7 +65,16 @@ def is_diffusion_model_download(
         )
         return True
 
-    return False
+    if base_model in CHECKPOINT_BASE_MODELS:
+        return False
+
+    is_diffusion = unknown_base_model_default != ROUTING_CHECKPOINT
+    logger.info(
+        "baseModel '%s' is unknown, routing to %s folder (unknown_base_model_routing)",
+        base_model,
+        "unet" if is_diffusion else "checkpoint",
+    )
+    return is_diffusion
 
 
 def resolve_other_download_sub_type(

py/services/settings_manager.py

@@ -130,6 +130,9 @@ DEFAULT_SETTINGS: Dict[str, Any] = {
     "metadata_refresh_skip_paths": [],
     "skip_previously_downloaded_model_versions": False,
     "download_skip_base_models": [],
+    # Routing target for checkpoint downloads whose baseModel is neither a
+    # known diffusion model nor a known full checkpoint (CHECKPOINT_BASE_MODELS).
+    "unknown_base_model_routing": "diffusion_model",
     "backup_auto_enabled": True,
     "backup_retention_count": 5,
     "use_new_license_icons": True,
@@ -1628,6 +1631,16 @@ class SettingsManager:
                 return normalized
         return "alongside"
 
+    @staticmethod
+    def _normalize_unknown_base_model_routing(value: Any) -> str:
+        """Return a valid unknown-base-model routing target, falling back to ``diffusion_model``."""
+
+        if isinstance(value, str):
+            normalized = value.strip().lower()
+            if normalized in ("diffusion_model", "checkpoint"):
+                return normalized
+        return "diffusion_model"
+
     def _refresh_sidecar_storage_config(self) -> None:
         """Rebuild dependent config state after sidecar storage settings change."""
 
@@ -1840,6 +1853,8 @@ class SettingsManager:
             self._migrate_recipes_directory(current_recipes_dir, target_recipes_dir)
         elif key == "sidecar_storage_mode":
             value = self._normalize_sidecar_storage_mode(value)
+        elif key == "unknown_base_model_routing":
+            value = self._normalize_unknown_base_model_routing(value)
         elif key == "sidecar_storage_path":
             value = self._normalize_recipes_path_value(value)
         self.settings[key] = value

py/utils/constants.py

@@ -371,6 +371,7 @@ DIFFUSION_MODEL_BASE_MODELS = frozenset(
         # Other diffusion models
         "Ernie",
         "Ernie Turbo",
+        "MiniMax H3",
         "Nucleus",
         "Qwen",
         "ZImageBase",
@@ -380,6 +381,39 @@ DIFFUSION_MODEL_BASE_MODELS = frozenset(
     ]
 )
 
+# baseModel values from CivitAI that are true full checkpoints (loaded via
+# CheckpointLoaderSimple in ComfyUI). New DiT families appear on CivitAI all
+# the time, so download routing inverts the fallback: anything NOT in this
+# closed set (and not a known diffusion model) is treated as a diffusion
+# model by default (see py/services/download_routing.py).
+# "Pony V7" is deliberately excluded: it is not an SDXL-derivative full
+# checkpoint, so it follows the unknown-base-model default (diffusion).
+CHECKPOINT_BASE_MODELS = frozenset(
+    [
+        # Stable Diffusion 1.x
+        "SD 1.4",
+        "SD 1.5",
+        "SD 1.5 LCM",
+        "SD 1.5 Hyper",
+        # Stable Diffusion 2.x
+        "SD 2.0",
+        "SD 2.1",
+        # Stable Diffusion 3.x
+        "SD 3",
+        "SD 3.5",
+        "SD 3.5 Medium",
+        "SD 3.5 Large",
+        "SD 3.5 Large Turbo",
+        # SDXL and its full-checkpoint derivatives
+        "SDXL 1.0",
+        "SDXL Lightning",
+        "SDXL Hyper",
+        "Pony",
+        "Illustrious",
+        "NoobAI",
+    ]
+)
+
 # Supported baseModel values for download exclusion settings.
 # Keep this aligned with static/js/utils/constants.js, excluding the generic "Other" value.
 SUPPORTED_DOWNLOAD_SKIP_BASE_MODELS = frozenset(

static/js/managers/SettingsManager.js

@@ -1053,6 +1053,11 @@ export class SettingsManager {
             downloadBackendSelect.value = state.global.settings.download_backend || 'python';
         }
 
+        const unknownBaseModelRoutingSelect = document.getElementById('unknownBaseModelRouting');
+        if (unknownBaseModelRoutingSelect) {
+            unknownBaseModelRoutingSelect.value = state.global.settings.unknown_base_model_routing || 'diffusion_model';
+        }
+
         const aria2cPathInput = document.getElementById('aria2cPath');
         if (aria2cPathInput) {
             aria2cPathInput.value = state.global.settings.aria2c_path || '';

static/js/state/index.js

@@ -60,6 +60,7 @@ const DEFAULT_SETTINGS_BASE = Object.freeze({
     metadata_refresh_skip_paths: [],
     skip_previously_downloaded_model_versions: false,
     download_skip_base_models: [],
+    unknown_base_model_routing: 'diffusion_model',
     backup_auto_enabled: true,
     backup_retention_count: 5,
     sidecar_storage_mode: 'alongside',

templates/components/modals/settings/general.html

@@ -146,6 +146,10 @@
                 </div>
             </div>
         </div>
+        {{ sm.setting_select('unknownBaseModelRouting', 'unknown_base_model_routing', 'settings.unknownBaseModelRouting.label', [
+            ('diffusion_model', 'settings.unknownBaseModelRouting.options.diffusionModel'),
+            ('checkpoint', 'settings.unknownBaseModelRouting.options.checkpoint'),
+        ], 'settings.unknownBaseModelRouting.help') }}
     </div>
 
     <!-- AI Provider Configuration (BYOK) -->

tests/routes/test_download_routing_handlers.py

@@ -73,6 +73,42 @@ async def test_regular_checkpoint_stays_on_checkpoint_root():
     assert payload["root_kind"] == "checkpoint"
 
 
+@pytest.mark.asyncio
+async def test_unknown_base_model_routes_to_unet_by_default():
+    handler = DownloadRoutingHandler()
+    response = await handler.get_download_routing(
+        FakeRequest(
+            {
+                "model_type": "checkpoint",
+                "base_model": "Brand New Arch",
+                "file_types": ["Model"],
+            }
+        )
+    )
+    payload = json.loads(response.text)
+    assert payload["is_diffusion_model"] is True
+    assert payload["root_kind"] == "unet"
+
+
+@pytest.mark.asyncio
+async def test_unknown_base_model_honors_checkpoint_routing_setting():
+    get_settings_manager().settings["unknown_base_model_routing"] = "checkpoint"
+
+    handler = DownloadRoutingHandler()
+    response = await handler.get_download_routing(
+        FakeRequest(
+            {
+                "model_type": "checkpoint",
+                "base_model": "Brand New Arch",
+                "file_types": ["Model"],
+            }
+        )
+    )
+    payload = json.loads(response.text)
+    assert payload["is_diffusion_model"] is False
+    assert payload["root_kind"] == "checkpoint"
+
+
 @pytest.mark.asyncio
 async def test_lora_is_never_diffusion():
     handler = DownloadRoutingHandler()

tests/services/test_download_manager_basic.py

@@ -2209,7 +2209,7 @@ async def test_download_falls_back_to_rest_name_when_mini_fails(
     metadata_provider.payload = {
         "id": 42,
         "model": {"type": "Checkpoint", "tags": ["fantasy"]},
-        "baseModel": "BaseModel",
+        "baseModel": "SDXL 1.0",
         "creator": {"username": "Author"},
         "files": [
             {

tests/services/test_download_routing.py

@@ -20,9 +20,47 @@ def test_base_model_fallback_routes_to_unet():
     )
 
 
-def test_regular_checkpoint_stays_on_checkpoint_roots():
+def test_minimax_h3_routes_to_unet():
+    """CivitAI model 2877206: type "Checkpoint", baseModel "MiniMax H3",
+    all file entries typed "Model"."""
+    assert is_diffusion_model_download(
+        "checkpoint", file_types=["Model"], base_model="MiniMax H3"
+    )
+
+
+@pytest.mark.parametrize("base_model", ["SDXL 1.0", "Illustrious", "SD 1.5", "SD 3.5 Large"])
+def test_known_checkpoint_base_models_stay_on_checkpoint_roots(base_model):
+    """CHECKPOINT_BASE_MODELS members never route to unet, even when the
+    unknown-base-model default is diffusion."""
     assert not is_diffusion_model_download(
-        "checkpoint", file_types=["Model"], base_model="SDXL 1.0"
+        "checkpoint", file_types=["Model"], base_model=base_model
+    )
+
+
+def test_unknown_base_model_defaults_to_unet():
+    """New DiT families appear faster than the allowlist can track them, so
+    unknown baseModels route to unet by default."""
+    assert is_diffusion_model_download(
+        "checkpoint", file_types=["Model"], base_model="Brand New Arch"
+    )
+
+
+def test_unknown_base_model_honors_checkpoint_setting():
+    assert not is_diffusion_model_download(
+        "checkpoint",
+        file_types=["Model"],
+        base_model="Brand New Arch",
+        unknown_base_model_default="checkpoint",
+    )
+
+
+def test_unknown_base_model_checkpoint_setting_still_loses_to_file_type():
+    """The file-type signal stays first regardless of the setting."""
+    assert is_diffusion_model_download(
+        "checkpoint",
+        file_types=["Diffusion Model"],
+        base_model="SDXL 1.0",
+        unknown_base_model_default="checkpoint",
     )
 
 
@@ -35,9 +73,15 @@ def test_non_checkpoint_types_never_route_to_unet():
     )
 
 
-def test_empty_inputs_stay_on_checkpoint_roots():
+def test_empty_base_model_follows_unknown_default():
-    assert not is_diffusion_model_download("checkpoint")
+    assert is_diffusion_model_download("checkpoint")
-    assert not is_diffusion_model_download("checkpoint", file_types=[], base_model="")
+    assert is_diffusion_model_download("checkpoint", file_types=[], base_model="")
+    assert not is_diffusion_model_download(
+        "checkpoint",
+        file_types=[],
+        base_model="",
+        unknown_base_model_default="checkpoint",
+    )
 
 
 from py.services.download_routing import resolve_other_download_sub_type

tests/services/test_settings_manager.py

@@ -1300,6 +1300,21 @@ def test_setting_download_skip_base_models_normalizes_string_input(manager):
     assert manager.get("download_skip_base_models") == ["SDXL 1.0", "Pony"]
 
 
+def test_unknown_base_model_routing_defaults_to_diffusion_model(manager):
+    assert manager.get("unknown_base_model_routing") == "diffusion_model"
+
+
+def test_unknown_base_model_routing_is_normalized(manager):
+    manager.set("unknown_base_model_routing", "CHECKPOINT")
+    assert manager.get("unknown_base_model_routing") == "checkpoint"
+
+    manager.set("unknown_base_model_routing", "bogus")
+    assert manager.get("unknown_base_model_routing") == "diffusion_model"
+
+    manager.set("unknown_base_model_routing", None)
+    assert manager.get("unknown_base_model_routing") == "diffusion_model"
+
+
 def test_skip_previously_downloaded_model_versions_defaults_false(manager):
     assert manager.get_skip_previously_downloaded_model_versions() is False