diff --git a/invokeai/app/services/model_manager.py b/invokeai/app/services/model_manager.py
new file mode 100644
index 0000000000..044310fccb
--- /dev/null
+++ b/invokeai/app/services/model_manager.py
@@ -0,0 +1,179 @@
+# Copyright (c) 2023 Lincoln D. Stein and the InvokeAI Team
+
+from abc import ABC, abstractmethod
+from pathlib import Path
+from typing import Union, Callable
+
+from invokeai.backend import ModelManager, SDModelType, SDModelInfo
+
+class ModelManagerBase(ABC):
+    """Responsible for managing models on disk and in memory"""
+
+    @abstractmethod
+    def get(self, model_name: str, submodel: SDModelType=None)->SDModelInfo:
+        """Retrieve the indicated model. submodel can be used to get a
+        part (such as the vae) of a diffusers mode.l"""
+        pass
+
+    @abstractmethod
+    def valid_model(self, model_name: str) -> bool:
+        """
+        Given a model name, returns True if it is a valid
+        identifier.
+        """
+        pass
+
+    @abstractmethod
+    def default_model(self) -> Union[str,None]:
+        """
+        Returns the name of the default model, or None
+        if none is defined.
+        """
+        pass
+
+    @abstractmethod
+    def set_default_model(self, model_name:str):
+        """Sets the default model to the indicated name."""
+        pass
+
+    @abstractmethod
+    def model_info(self, model_name: str)->dict:
+        """
+        Given a model name returns a dict-like (OmegaConf) object describing it.
+        """
+        pass
+
+    @abstractmethod
+    def model_names(self)->list[str]:
+        """
+        Returns a list of all the model names known.
+        """
+        pass
+
+    @abstractmethod
+    def list_models(self)->dict:
+        """
+        Return a dict of models in the format:
+        { model_name1: {'status': ('active'|'cached'|'not loaded'),
+                        'description': description,
+                        'format': ('ckpt'|'diffusers'|'vae'|'text_encoder'|'tokenizer'|'lora'...),
+                       },
+          model_name2: { etc }
+        """
+        pass
+
+
+    @abstractmethod
+    def add_model(
+            self, model_name: str, model_attributes: dict, clobber: bool = False)->None:
+        """
+        Update the named model with a dictionary of attributes. Will fail with an
+        assertion error if the name already exists. Pass clobber=True to overwrite.
+        On a successful update, the config will be changed in memory. Will fail 
+        with an assertion error if provided attributes are incorrect or 
+        the model name is missing. Call commit() to write changes to disk.
+        """
+        pass
+
+    @abstractmethod
+    def del_model(self, model_name: str, delete_files: bool = False) -> None:
+        """
+        Delete the named model from configuration. If delete_files is true, 
+        then the underlying weight file or diffusers directory will be deleted 
+        as well. Call commit() to write to disk.
+        """
+        pass
+
+    @abstractmethod
+    def import_diffuser_model(
+        repo_or_path: Union[str, Path],
+        model_name: str = None,
+        description: str = None,
+        vae: dict = None,
+    ) -> bool:
+        """
+        Install the indicated diffuser model and returns True if successful.
+
+        "repo_or_path" can be either a repo-id or a path-like object corresponding to the
+        top of a downloaded diffusers directory.
+
+        You can optionally provide a model name and/or description. If not provided,
+        then these will be derived from the repo name. Call commit() to write to disk.
+        """
+        pass
+    
+    @abstractmethod
+    def import_lora(
+            self,
+            path: Path,
+            model_name: str=None,
+            description: str=None,
+    ):
+        """
+        Creates an entry for the indicated lora file. Call
+        mgr.commit() to write out the configuration to models.yaml
+        """
+        pass
+
+    @abstractmethod
+    def import_embedding(
+            self,
+            path: Path,
+            model_name: str=None,
+            description: str=None,
+    ):
+        """
+        Creates an entry for the indicated textual inversion embedding file. 
+        Call commit() to write out the configuration to models.yaml
+        """
+        pass
+
+    @abstractmethod
+    def heuristic_import(
+        self,
+        path_url_or_repo: str,
+        model_name: str = None,
+        description: str = None,
+        model_config_file: Path = None,
+        commit_to_conf: Path = None,
+        config_file_callback: Callable[[Path], Path] = None,
+    ) -> str:
+        """Accept a string which could be:
+           - a HF diffusers repo_id
+           - a URL pointing to a legacy .ckpt or .safetensors file
+           - a local path pointing to a legacy .ckpt or .safetensors file
+           - a local directory containing .ckpt and .safetensors files
+           - a local directory containing a diffusers model
+
+        After determining the nature of the model and downloading it
+        (if necessary), the file is probed to determine the correct
+        configuration file (if needed) and it is imported.
+
+        The model_name and/or description can be provided. If not, they will
+        be generated automatically.
+
+        If commit_to_conf is provided, the newly loaded model will be written
+        to the `models.yaml` file at the indicated path. Otherwise, the changes
+        will only remain in memory.
+
+        The routine will do its best to figure out the config file
+        needed to convert legacy checkpoint file, but if it can't it
+        will call the config_file_callback routine, if provided. The
+        callback accepts a single argument, the Path to the checkpoint
+        file, and returns a Path to the config file to use.
+
+        The (potentially derived) name of the model is returned on
+        success, or None on failure. When multiple models are added
+        from a directory, only the last imported one is returned.
+
+        """
+        pass
+
+    @abstractmethod
+    def commit(self, conf_file: Path=None) -> None:
+        """
+        Write current configuration out to the indicated file.
+        If no conf_file is provided, then replaces the
+        original file/database used to initialize the object.
+        """
+        pass
diff --git a/invokeai/backend/__init__.py b/invokeai/backend/__init__.py
index dc2eeca67a..e06e220ffe 100644
--- a/invokeai/backend/__init__.py
+++ b/invokeai/backend/__init__.py
@@ -10,7 +10,7 @@ from .generator import (
     Img2Img,
     Inpaint
 )
-from .model_management import ModelManager, ModelCache, ModelStatus, SDModelType
+from .model_management import ModelManager, ModelCache, ModelStatus, SDModelType, SDModelInfo
 from .safety_checker import SafetyChecker
 from .args import Args
 from .globals import Globals
diff --git a/invokeai/backend/model_management/__init__.py b/invokeai/backend/model_management/__init__.py
index 44b51e6a2a..89114d7de4 100644
--- a/invokeai/backend/model_management/__init__.py
+++ b/invokeai/backend/model_management/__init__.py
@@ -1,5 +1,5 @@
 """
 Initialization file for invokeai.backend.model_management
 """
-from .model_manager import ModelManager
+from .model_manager import ModelManager, SDModelInfo
 from .model_cache import ModelCache, ModelStatus, SDModelType
diff --git a/invokeai/backend/model_management/model_manager.py b/invokeai/backend/model_management/model_manager.py
index 8929d8cdd6..7c3c32c004 100644
--- a/invokeai/backend/model_management/model_manager.py
+++ b/invokeai/backend/model_management/model_manager.py
@@ -102,7 +102,7 @@ from omegaconf import OmegaConf
 from omegaconf.dictconfig import DictConfig
 
 from invokeai.backend.globals import Globals, global_cache_dir, global_resolve_path
-from .model_cache import ModelClass, ModelCache, ModelLocker, SDModelType, ModelStatus, LegacyInfo
+from .model_cache import ModelCache, ModelLocker, SDModelType, ModelStatus, LegacyInfo
 
 from ..util import CUDA_DEVICE
 
@@ -267,7 +267,7 @@ class ModelManager(object):
             _cache = self.cache
         )
 
-    def default_model(self) -> str | None:
+    def default_model(self) -> Union[str,None]:
         """
         Returns the name of the default model, or None
         if none is defined.
@@ -541,7 +541,7 @@ class ModelManager(object):
         self.add_model(model_name,
                        dict(
                            format="textual_inversion",
-                           weights=str(path),
+                           weights=str(weights),
                            description=model_description,
                            ),
                        True
@@ -865,12 +865,12 @@ class ModelManager(object):
 
         return search_folder, found_models
 
-    def commit(self) -> None:
+    def commit(self, conf_file: Path=None) -> None:
         """
         Write current configuration out to the indicated file.
         """
         yaml_str = OmegaConf.to_yaml(self.config)
-        config_file_path = self.config_path
+        config_file_path = conf_file or self.config_path
         tmpfile = os.path.join(os.path.dirname(config_file_path), "new_config.tmp")
         with open(tmpfile, "w", encoding="utf-8") as outfile:
             outfile.write(self.preamble())