diff --git a/launch.py b/launch.py
index f83820d2..10aa5463 100644
--- a/launch.py
+++ b/launch.py
@@ -41,6 +41,9 @@ def main():
     if args.test_server:
         configure_for_tests()
 
+    if args.forge_ref_a1111_home:
+        launch_utils.configure_forge_reference_checkout(args.forge_ref_a1111_home)
+
     start()
 
 
diff --git a/modules/cmd_args.py b/modules/cmd_args.py
index ef2ecd7b..0aa8ef78 100644
--- a/modules/cmd_args.py
+++ b/modules/cmd_args.py
@@ -2,6 +2,7 @@ import argparse
 import json
 import os
 from modules.paths_internal import models_path, script_path, data_path, extensions_dir, extensions_builtin_dir, sd_default_config, sd_model_file  # noqa: F401
+from pathlib import Path
 from ldm_patched.modules import args_parser
 
 parser = args_parser.parser
@@ -122,3 +123,23 @@ parser.add_argument('--timeout-keep-alive', type=int, default=30, help='set time
 parser.add_argument("--disable-all-extensions", action='store_true', help="prevent all extensions from running regardless of any other settings", default=False)
 parser.add_argument("--disable-extra-extensions", action='store_true', help="prevent all extensions except built-in from running regardless of any other settings", default=False)
 parser.add_argument("--skip-load-model-at-start", action='store_true', help="if load a model at web start, only take effect when --nowebui", )
+
+# Arguments added by forge.
+parser.add_argument(
+    '--forge-ref-a1111-home',
+    type=Path,
+    help="Look for models in an existing A1111 checkout's path",
+    default=None
+)
+parser.add_argument(
+    "--controlnet-dir",
+    type=Path,
+    help="Path to directory with ControlNet models",
+    default=None,
+)
+parser.add_argument(
+    "--controlnet-preprocessor-models-dir",
+    type=Path,
+    help="Path to directory with annotator model directories",
+    default=None,
+)
diff --git a/modules/launch_utils.py b/modules/launch_utils.py
index 409385a8..48be47f4 100644
--- a/modules/launch_utils.py
+++ b/modules/launch_utils.py
@@ -10,6 +10,8 @@ import importlib.metadata
 import platform
 import json
 from functools import lru_cache
+from typing import NamedTuple
+from pathlib import Path
 
 from modules import cmd_args, errors
 from modules.paths_internal import script_path, extensions_dir, extensions_builtin_dir
@@ -503,6 +505,37 @@ def configure_for_tests():
     os.environ['COMMANDLINE_ARGS'] = ""
 
 
+def configure_forge_reference_checkout(a1111_home: Path):
+    """Set model paths based on an existing A1111 checkout."""
+    class ModelRef(NamedTuple):
+        arg_name: str
+        relative_path: str
+
+    refs = [
+        ModelRef(arg_name="--ckpt-dir", relative_path="models/Stable-diffusion"),
+        ModelRef(arg_name="--vae-dir", relative_path="models/VAE"),
+        ModelRef(arg_name="--hypernetwork-dir", relative_path="models/hypernetworks"),
+        ModelRef(arg_name="--embeddings-dir", relative_path="models/embeddings"),
+        ModelRef(arg_name="--lora-dir", relative_path="models/lora"),
+        # Ref A1111 need to have sd-webui-controlnet installed.
+        ModelRef(arg_name="--controlnet-dir", relative_path="models/ControlNet"),
+        ModelRef(arg_name="--controlnet-preprocessor-models-dir", relative_path="extensions/sd-webui-controlnet/annotator/downloads"),
+    ]
+
+    for ref in refs:
+        target_path = a1111_home / ref.relative_path
+        if not target_path.exists():
+            print(f"Path {target_path} does not exist. Skip setting {ref.arg_name}")
+            continue
+
+        if ref.arg_name in sys.argv:
+            # Do not override existing dir setting.
+            continue
+
+        sys.argv.append(ref.arg_name)
+        sys.argv.append(str(target_path))
+
+
 def start():
     print(f"Launching {'API server' if '--nowebui' in sys.argv else 'Web UI'} with arguments: {' '.join(sys.argv[1:])}")
     import webui
diff --git a/modules_forge/shared.py b/modules_forge/shared.py
index 8b03e788..ec44c9a4 100644
--- a/modules_forge/shared.py
+++ b/modules_forge/shared.py
@@ -2,12 +2,18 @@ import os
 import ldm_patched.modules.utils
 
 from modules.paths_internal import models_path
+from modules.shared import cmd_opts
 
-
-controlnet_dir = os.path.join(models_path, 'ControlNet')
+if cmd_opts.controlnet_dir:
+    controlnet_dir = str(cmd_opts.controlnet_dir)
+else:
+    controlnet_dir = os.path.join(models_path, 'ControlNet')
 os.makedirs(controlnet_dir, exist_ok=True)
 
-preprocessor_dir = os.path.join(models_path, 'ControlNetPreprocessor')
+if cmd_opts.controlnet_preprocessor_models_dir:
+    preprocessor_dir = str(cmd_opts.controlnet_preprocessor_models_dir)
+else:
+    preprocessor_dir = os.path.join(models_path, 'ControlNetPreprocessor')
 os.makedirs(preprocessor_dir, exist_ok=True)
 
 diffusers_dir = os.path.join(models_path, 'diffusers')