diff --git a/.coveragerc b/.coveragerc
new file mode 100644
index 0000000..60bdfcb
--- /dev/null
+++ b/.coveragerc
@@ -0,0 +1,4 @@
+[run]
+omit =
+    src/python_osw_validation/version.py
+    src/python_osw_validation/example.py
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 265d434..593278f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Change log
 
+### 0.4.1 - 2026-05-28
+- Fixed misleading `Expecting value: line 1 column 1 (char 0)` failure when loading GeoJSON files containing `ext:*` extension properties with mixed value types across features (e.g. `ext:TextRotation` numeric in some features and string in others). Extension properties are now stripped before the internal GeoPandas load used for geometry and `_id` integrity checks; schema-level validation of `ext:*` properties is unchanged.
+- Added regression coverage for the mixed-type `ext:*` load path in `tests/unit_tests/test_helpers.py` and added `tests/assets/SDOT_lanewidth_osw.points.geojson.zip` as the reproducer dataset.
+- Excluded `version.py` from the coverage report via a new `.coveragerc`.
+
 ### 0.4.0 - 2026-04-30
 - Added geometry mapping consistency validation: `_u_id` and `_v_id` references in edges are now verified against the actual start/end coordinates of the referenced node geometries.
 - Added `_w_id` coordinate mapping validation for zones: each referenced node coordinate must be a vertex of the zone's polygon exterior ring, in order.
diff --git a/README.md b/README.md
index ba98dd9..547327a 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,8 @@
 # TDEI python lib OSW validation package
 
+[![Tests](https://github.com/TaskarCenterAtUW/TDEI-python-lib-osw-validation/actions/workflows/unit_tests.yml/badge.svg)](https://github.com/TaskarCenterAtUW/TDEI-python-lib-osw-validation/actions/workflows/unit_tests.yml)
+[![Coverage](https://img.shields.io/badge/coverage-92%25-brightgreen)](#)
+
 This package validates OSW GeoJSON datasets packaged as a ZIP file.
 
 ## System requirements
diff --git a/src/python_osw_validation/__init__.py b/src/python_osw_validation/__init__.py
index cac2a70..506cf51 100644
--- a/src/python_osw_validation/__init__.py
+++ b/src/python_osw_validation/__init__.py
@@ -14,6 +14,7 @@
     _err_kind,
     _feature_index_from_error,
     _pretty_message,
+    _read_geojson_without_ext,
 )
 
 SCHEMA_PATH = os.path.join(os.path.dirname(__file__), 'schema')
@@ -419,7 +420,7 @@ def _finalize(is_valid: bool, errors: Optional[List[str]] = None) -> ValidationR
                 osw_file = next((osw_key for osw_key in OSW_DATASET_FILES.keys()
                                  if osw_key in os.path.basename(file_path)), '')
                 try:
-                    gdf = gpd.read_file(file_path)
+                    gdf = _read_geojson_without_ext(file_path)
                 except Exception as e:
                     self.log_errors(
                         message=f"Failed to read '{os.path.basename(file_path)}' as GeoJSON: {e}",
@@ -557,7 +558,7 @@ def _finalize(is_valid: bool, errors: Optional[List[str]] = None) -> ValidationR
                 file_path = os.path.join(file)
                 file_name = os.path.basename(file)
                 try:
-                    extensionFile = gpd.read_file(file_path)
+                    extensionFile = _read_geojson_without_ext(file_path)
                 except Exception as e:
                     self.log_errors(
                         message=f"Failed to read extension '{file_name}' as GeoJSON: {e}",
diff --git a/src/python_osw_validation/helpers.py b/src/python_osw_validation/helpers.py
index 4f971b0..fc528f9 100644
--- a/src/python_osw_validation/helpers.py
+++ b/src/python_osw_validation/helpers.py
@@ -1,6 +1,30 @@
 from typing import Optional
+import json
 import re
 
+import geopandas as gpd
+
+
+def _read_geojson_without_ext(file_path: str) -> gpd.GeoDataFrame:
+    """Load a GeoJSON file into a GeoDataFrame with ext:* properties removed.
+
+    Why: pyogrio/GDAL infers a single dtype per property column when reading
+    GeoJSON. Extension tags (ext:*) are free-form by spec and may legitimately
+    mix numbers and strings across features, which breaks that inference and
+    surfaces as a confusing JSON parse error. Schema validation has already
+    accepted these properties; the GeoDataFrame is only used for geometry and
+    _id-based integrity checks, so dropping ext:* here is safe.
+    """
+    with open(file_path, 'r') as f:
+        data = json.load(f)
+    for feature in data.get('features', []):
+        props = feature.get('properties')
+        if isinstance(props, dict):
+            for key in [k for k in props if isinstance(k, str) and k.startswith('ext:')]:
+                del props[key]
+    crs = (data.get('crs') or {}).get('properties', {}).get('name')
+    return gpd.GeoDataFrame.from_features(data.get('features', []), crs=crs)
+
 _ADDITIONAL_PROPERTIES_RE = re.compile(
     r"Additional properties are not allowed \('(?P<tag>[^']+)' was unexpected\)"
 )
diff --git a/src/python_osw_validation/version.py b/src/python_osw_validation/version.py
index abeeedb..f0ede3d 100644
--- a/src/python_osw_validation/version.py
+++ b/src/python_osw_validation/version.py
@@ -1 +1 @@
-__version__ = '0.4.0'
+__version__ = '0.4.1'
diff --git a/tests/assets/SDOT_lanewidth_osw.points.geojson.zip b/tests/assets/SDOT_lanewidth_osw.points.geojson.zip
new file mode 100644
index 0000000..1721dd4
Binary files /dev/null and b/tests/assets/SDOT_lanewidth_osw.points.geojson.zip differ
diff --git a/tests/unit_tests/test_helpers.py b/tests/unit_tests/test_helpers.py
index 9e604b4..641b4de 100644
--- a/tests/unit_tests/test_helpers.py
+++ b/tests/unit_tests/test_helpers.py
@@ -1,4 +1,8 @@
+import json
+import os
+import tempfile
 import unittest
+
 import src.python_osw_validation.helpers as helpers
 
 
@@ -179,5 +183,97 @@ def test_tiebreaker_shorter_message_is_better(self):
         self.assertLess(helpers._rank_for(e_short), helpers._rank_for(e_long))
 
 
+class TestReadGeojsonWithoutExt(unittest.TestCase):
+    def _write_geojson(self, payload):
+        fd, path = tempfile.mkstemp(suffix=".geojson")
+        os.close(fd)
+        with open(path, "w") as f:
+            json.dump(payload, f)
+        self.addCleanup(os.remove, path)
+        return path
+
+    def test_drops_ext_properties_with_mixed_types(self):
+        """The bug we're fixing: ext:* values mixing numeric and string across
+        features causes pyogrio dtype inference to fail. After stripping, the
+        load should succeed and the ext:* column should not be present."""
+        payload = {
+            "type": "FeatureCollection",
+            "features": [
+                {
+                    "type": "Feature",
+                    "properties": {"_id": "a", "ext:TextRotation": 310.0, "name": "n1"},
+                    "geometry": {"type": "Point", "coordinates": [0, 0]},
+                },
+                {
+                    "type": "Feature",
+                    "properties": {"_id": "b", "ext:TextRotation": "not_appl", "name": "n2"},
+                    "geometry": {"type": "Point", "coordinates": [1, 1]},
+                },
+            ],
+        }
+        path = self._write_geojson(payload)
+        gdf = helpers._read_geojson_without_ext(path)
+
+        self.assertEqual(len(gdf), 2)
+        self.assertNotIn("ext:TextRotation", gdf.columns)
+        # Non-ext columns must be preserved for downstream integrity checks.
+        self.assertIn("_id", gdf.columns)
+        self.assertIn("name", gdf.columns)
+        self.assertEqual(sorted(gdf["_id"].tolist()), ["a", "b"])
+
+    def test_preserves_non_ext_properties(self):
+        payload = {
+            "type": "FeatureCollection",
+            "features": [
+                {
+                    "type": "Feature",
+                    "properties": {"_id": "x", "highway": "footway", "ext:foo": 1},
+                    "geometry": {"type": "Point", "coordinates": [0, 0]},
+                }
+            ],
+        }
+        gdf = helpers._read_geojson_without_ext(self._write_geojson(payload))
+        self.assertIn("highway", gdf.columns)
+        self.assertNotIn("ext:foo", gdf.columns)
+        self.assertEqual(gdf["highway"].iloc[0], "footway")
+
+    def test_no_ext_properties_is_noop(self):
+        payload = {
+            "type": "FeatureCollection",
+            "features": [
+                {
+                    "type": "Feature",
+                    "properties": {"_id": "x", "highway": "footway"},
+                    "geometry": {"type": "Point", "coordinates": [2, 3]},
+                }
+            ],
+        }
+        gdf = helpers._read_geojson_without_ext(self._write_geojson(payload))
+        self.assertEqual(len(gdf), 1)
+        self.assertEqual(gdf["highway"].iloc[0], "footway")
+        self.assertEqual(gdf.geometry.iloc[0].x, 2)
+        self.assertEqual(gdf.geometry.iloc[0].y, 3)
+
+    def test_empty_feature_collection(self):
+        payload = {"type": "FeatureCollection", "features": []}
+        gdf = helpers._read_geojson_without_ext(self._write_geojson(payload))
+        self.assertEqual(len(gdf), 0)
+
+    def test_crs_is_propagated_when_present(self):
+        payload = {
+            "type": "FeatureCollection",
+            "crs": {"type": "name", "properties": {"name": "EPSG:4326"}},
+            "features": [
+                {
+                    "type": "Feature",
+                    "properties": {"_id": "x"},
+                    "geometry": {"type": "Point", "coordinates": [0, 0]},
+                }
+            ],
+        }
+        gdf = helpers._read_geojson_without_ext(self._write_geojson(payload))
+        self.assertIsNotNone(gdf.crs)
+
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/tests/unit_tests/test_osw_validation_extras.py b/tests/unit_tests/test_osw_validation_extras.py
index b136bb3..14b2961 100644
--- a/tests/unit_tests/test_osw_validation_extras.py
+++ b/tests/unit_tests/test_osw_validation_extras.py
@@ -16,7 +16,7 @@
 _PATCH_UNIQUE = f"{_PATCH_PREFIX}.OSWValidation.are_ids_unique"
 _PATCH_ZIP = f"{_PATCH_PREFIX}.ZipFileHandler"
 _PATCH_EV = f"{_PATCH_PREFIX}.ExtractedDataValidator"
-_PATCH_READ_FILE = f"{_PATCH_PREFIX}.gpd.read_file"
+_PATCH_READ_FILE = f"{_PATCH_PREFIX}._read_geojson_without_ext"
 _PATCH_VALIDATE = f"{_PATCH_PREFIX}.OSWValidation.validate_osw_errors"
 _PATCH_DATASET_FILES = f"{_PATCH_PREFIX}.OSW_DATASET_FILES"