C-Achard · Nov 13, 2026 · Nov 13, 2026 · Nov 13, 2026
diff --git a/deeplabcut/core/config/utils.py b/deeplabcut/core/config/utils.py
@@ -56,10 +56,12 @@ def get_yaml_dumper() -> YAML:
     return yaml
 
 
-def read_config_as_dict(config_path: str | Path) -> dict:
+def read_config_as_dict(config_path: str | Path, repair_project_path: bool = False) -> dict:
     """
     Args:
         config_path: the path to the configuration file to load
+        repair_project_path: if True, fix the config key ``project_path`` to match the parent
+        folder of ``config_path``. Only the return dict is updated, not persisted to disk.
 
     Returns:
         The configuration file with pure Python classes
@@ -75,6 +77,11 @@ def read_config_as_dict(config_path: str | Path) -> dict:
         raise ValueError(f"Config {config_path} is empty or null.")
     if not isinstance(cfg, dict):
         raise ValueError(f"Config {config_path} must be a YAML mapping at the top level, got {type(cfg).__name__}.")
+    if repair_project_path:
+        project_path = Path(config_path).parent.absolute()
+        if cfg.get("project_path") is None or Path(cfg["project_path"]).absolute() != project_path:
+            logger.info("project_path updated: %s -> %s", cfg.get("project_path"), project_path)
+            cfg["project_path"] = str(project_path)
     return cfg
 
 

diff --git a/deeplabcut/generate_training_dataset/frame_extraction.py b/deeplabcut/generate_training_dataset/frame_extraction.py
@@ -297,6 +297,7 @@ def extract_frames(
     from skimage import io
     from skimage.util import img_as_ubyte
 
+    from deeplabcut.core.config import read_config_as_dict
     from deeplabcut.utils import auxiliaryfunctions, frameselectiontools
 
     videos_list = None if videos_list is None else [Path(video) for video in videos_list]
@@ -506,7 +507,7 @@ def extract_frames(
         project_path = Path(config).parents[0]
         labels_path = project_path / "labeled-data"
         try:
-            cfg_3d = auxiliaryfunctions.read_config(config3d)
+            cfg_3d = read_config_as_dict(config3d, repair_project_path=True)
         except Exception as e:
             raise Exception(
                 "You must create a 3D project and edit the 3D config file before extracting matched frames. \n"

diff --git a/deeplabcut/pose_estimation_3d/camera_calibration.py b/deeplabcut/pose_estimation_3d/camera_calibration.py
@@ -17,6 +17,7 @@
 import matplotlib.pyplot as plt
 import numpy as np
 
+from deeplabcut.core.config import read_config_as_dict
 from deeplabcut.utils import auxiliaryfunctions, auxiliaryfunctions_3d
 from deeplabcut.utils.matplotlib_utils import silence_axes_logger
 
@@ -78,7 +79,7 @@ def calibrate_cameras(
     objp[:, :2] = np.mgrid[0:cbcol, 0:cbrow].T.reshape(-1, 2)
 
     # Read the config file
-    cfg_3d = auxiliaryfunctions.read_config(config)
+    cfg_3d = read_config_as_dict(config, repair_project_path=True)
     (
         img_path,
         path_corners,
@@ -281,7 +282,7 @@ def check_undistortion(config: str | Path, cbrow=8, cbcol=6, plot=True):
     """
     # Read the config file
     criteria = (cv2.TERM_CRITERIA_EPS + cv2.TERM_CRITERIA_MAX_ITER, 30, 0.001)
-    cfg_3d = auxiliaryfunctions.read_config(config)
+    cfg_3d = read_config_as_dict(config, repair_project_path=True)
     (
         img_path,
         path_corners,

diff --git a/deeplabcut/pose_estimation_3d/plotting3D.py b/deeplabcut/pose_estimation_3d/plotting3D.py
@@ -20,8 +20,8 @@
 from mpl_toolkits.mplot3d.art3d import Line3DCollection
 from tqdm import tqdm
 
+from deeplabcut.core.config import read_config_as_dict
 from deeplabcut.utils import (
-    auxiliaryfunctions,
     auxiliaryfunctions_3d,
     make_labeled_video,
 )
@@ -124,7 +124,7 @@ def create_labeled_video_3d(
             )
     """
     # Read the config file and related variables
-    cfg_3d = auxiliaryfunctions.read_config(config)
+    cfg_3d = read_config_as_dict(config, repair_project_path=True)
     cam_names = cfg_3d["camera_names"]
     pcutoff = cfg_3d["pcutoff"]
     markerSize = cfg_3d["dotsize"]

diff --git a/deeplabcut/pose_estimation_3d/triangulation.py b/deeplabcut/pose_estimation_3d/triangulation.py
@@ -16,6 +16,7 @@
 import numpy as np
 import pandas as pd
 
+from deeplabcut.core.config import read_config_as_dict
 from deeplabcut.core.trackingutils import TRACK_METHODS
 from deeplabcut.utils import auxfun_multianimal, auxiliaryfunctions, auxiliaryfunctions_3d
 
@@ -95,7 +96,7 @@ def triangulate(
     from deeplabcut.compat import analyze_videos
     from deeplabcut.post_processing import filtering
 
-    cfg_3d = auxiliaryfunctions.read_config(config)
+    cfg_3d = read_config_as_dict(config, repair_project_path=True)
     cam_names = cfg_3d["camera_names"]
     pcutoff = cfg_3d["pcutoff"]
     scorer_3d = cfg_3d["scorername_3d"]
@@ -500,7 +501,7 @@ def _undistort_views(df_view_pairs, stereo_params):
 
 
 def undistort_points(config, dataframe, camera_pair):
-    cfg_3d = auxiliaryfunctions.read_config(config)
+    cfg_3d = read_config_as_dict(config, repair_project_path=True)
     path_camera_matrix = auxiliaryfunctions_3d.Foldernames3Dproject(cfg_3d)[2]
     """path_undistort = destfolder filename_cam1 = Path(dataframe[0]).stem filename_cam2
     = Path(dataframe[1]).stem.

diff --git a/examples/testscript_3d.py b/examples/testscript_3d.py
@@ -29,6 +29,7 @@
 from pathlib import Path
 
 import deeplabcut
+from deeplabcut.core.config import read_config_as_dict
 
 if __name__ == "__main__":
     print("Imported DLC!")
@@ -113,7 +114,7 @@
     path_config_file = deeplabcut.create_new_project_3d(task, scorer, num_cameras)
 
     try:
-        cfg = deeplabcut.auxiliaryfunctions.read_config(path_config_file)
+        cfg = read_config_as_dict(path_config_file, repair_project_path=True)
         cfg["config_file_camera-1"] = config
         cfg["shuffle_camera-1"] = 1
 

diff --git a/tests/generate_training_dataset/test_frame_extraction.py b/tests/generate_training_dataset/test_frame_extraction.py
@@ -133,3 +133,12 @@ def test_filter_config_videos_matches_string_to_path(self):
     def test_filter_config_videos_raises_for_empty_selection(self):
         with pytest.raises(ValueError, match="None of the selected videos matched"):
             _filter_config_videos(["video-a.mp4"], [])
+
+
+def test_extract_frames_match_reads_3d_config(valid_project, tmp_path):
+    """Regression test for #3585: mode="match" must read the 3D config without 2D validation."""
+    from deeplabcut.create_project.new_3d import create_new_project_3d
+
+    config_3d = create_new_project_3d("trial", "tester", num_cameras=2, working_directory=str(tmp_path / "3d"))
+
+    extract_frames(str(valid_project / "config.yaml"), mode="match", config3d=config_3d, userfeedback=False)
diff --git a/tests/test_3d_project_config.py b/tests/test_3d_project_config.py
@@ -0,0 +1,108 @@
+#
+# DeepLabCut Toolbox (deeplabcut.org)
+# © A. & M.W. Mathis Labs
+# https://github.com/DeepLabCut/DeepLabCut
+#
+# Please see AUTHORS for contributors.
+# https://github.com/DeepLabCut/DeepLabCut/blob/main/AUTHORS
+#
+# Licensed under GNU Lesser General Public License v3.0
+#
+"""Regression tests: 3D entry points must read a 3D config.yaml without 2D validation.
+
+See https://github.com/DeepLabCut/DeepLabCut/issues/3585. Each entry point is run on a
+freshly created 3D project; it must get past reading the config and fail later, on
+the data that a fresh project does not have yet.
+"""
+
+import shutil
+from pathlib import Path
+
+import pytest
+
+from deeplabcut.core.config import read_config_as_dict
+from deeplabcut.create_project.new_3d import create_new_project_3d
+from deeplabcut.pose_estimation_3d import camera_calibration, plotting3D, triangulation
+from deeplabcut.utils import auxiliaryfunctions
+
+
+@pytest.fixture
+def config_3d(tmp_path):
+    return create_new_project_3d("trial", "tester", num_cameras=2, working_directory=str(tmp_path))
+
+
+@pytest.mark.parametrize(
+    "run, error, match",
+    [
+        (
+            lambda cfg, tmp: camera_calibration.calibrate_cameras(cfg, cbrow=8, cbcol=6),
+            Exception,
+            "No calibration images found",
+        ),
+        (
+            lambda cfg, tmp: camera_calibration.check_undistortion(cfg, cbrow=8, cbcol=6),
+            FileNotFoundError,
+            "stereo_params.pickle",
+        ),
+        (
+            lambda cfg, tmp: triangulation.triangulate(cfg, str(tmp)),
+            Exception,
+            "config_file_camera-1 does not exist",
+        ),
+        (
+            lambda cfg, tmp: triangulation.undistort_points(cfg, [tmp / "a.h5", tmp / "b.h5"], None),
+            FileNotFoundError,
+            "Dataframe path",
+        ),
+        (
+            lambda cfg, tmp: plotting3D.create_labeled_video_3d(cfg, [str(tmp)]),
+            Exception,
+            "No corresponding video file",
+        ),
+    ],
+    ids=["calibrate_cameras", "check_undistortion", "triangulate", "undistort_points", "create_labeled_video_3d"],
+)
+def test_3d_entry_points_read_3d_config(config_3d, tmp_path, run, error, match):
+    with pytest.raises(error, match=match):
+        run(config_3d, tmp_path)
+
+
+def test_calibrate_cameras_keeps_3d_config_keys(config_3d):
+    before = auxiliaryfunctions.read_plainconfig(config_3d)
+
+    with pytest.raises(Exception, match="No calibration images found"):
+        camera_calibration.calibrate_cameras(config_3d, cbrow=8, cbcol=6)
+
+    assert auxiliaryfunctions.read_plainconfig(config_3d) == before
+
+
+@pytest.fixture
+def moved_config_3d(config_3d, tmp_path):
+    """Config of a moved 3D project; its project_path still points at the old location."""
+    return Path(shutil.move(Path(config_3d).parent, tmp_path / "moved")) / "config.yaml"
+
+
+def test_read_config_as_dict_repairs_project_path(moved_config_3d):
+    cfg = read_config_as_dict(moved_config_3d, repair_project_path=True)
+    assert Path(cfg["project_path"]) == moved_config_3d.parent
+
+
+@pytest.mark.parametrize(
+    "run, error, match",
+    [
+        (
+            lambda cfg: camera_calibration.calibrate_cameras(cfg, cbrow=8, cbcol=6),
+            Exception,
+            "No calibration images",
+        ),
+        (
+            lambda cfg: camera_calibration.check_undistortion(cfg, cbrow=8, cbcol=6),
+            FileNotFoundError,
+            r"moved\W+camera_matrix",
+        ),
+    ],
+    ids=["calibrate_cameras", "check_undistortion"],
+)
+def test_3d_entry_points_use_moved_project_folder(moved_config_3d, run, error, match):
+    with pytest.raises(error, match=match):
+        run(moved_config_3d)