diff --git a/.claude/sweep-style-state.csv b/.claude/sweep-style-state.csv
index 157ca015e..797ac1649 100644
--- a/.claude/sweep-style-state.csv
+++ b/.claude/sweep-style-state.csv
@@ -4,6 +4,7 @@ contour,2026-05-29,2698,HIGH,3,"F821 line 557: contours() return annotation ""gp
 geotiff,2026-05-27,2481,HIGH,1;3;4,"Bundled 387 flake8 + ~30 isort fixes since #2285/#2430. F401 x9, F811 x6, F841 x3. E501 x250 (mostly wrapped, 3 file-scope imports keep noqa: E402+E501). E252 x62, blank-line cluster, E128/E127 indents. importorskip imports use # noqa: E402. Cat 5 grep clean."
 hydro-d8,2026-05-29,2705,HIGH,1;3;4,"flake8+isort over the 13 D8 files only (dinf/mfd out of scope). Cat 3 HIGH: F401 x2 (flow_length_d8 function-local _compute_accum_seeds never called; snap_pour_point_d8 module-level cuda_args unused) - both confirmed dead, no re-export. Cat 1: E127/E128 continuation-indent x90 (mostly multi-line def signatures); E302/E303 blank-line cluster in watershed_d8; E501 x4 (flow_path_d8 + snap_pour_point_d8, wrapped ternaries). Cat 4: isort import-block reordering on all 13 files. No Cat 2 (W-codes), no Cat 5 (grep clean: no bare except, mutable defaults, ==None/==True, or shadowed builtins). flake8+isort clean after fix; 385 D8 tests pass. flow_direction_d8 needed manual blank-line placement to satisfy both isort and E302."
 polygonize,2026-05-27,2534,HIGH,1;3;4,"F401 line 58 (is_cupy_array unused, not re-exported). E127 lines 83/88 (overload continuation indent in generated_jit). isort: 5-line .utils import block collapses to one line at 100-char limit. Cat 2 clean. Cat 5 grep clean."
+proximity,2026-05-29,2725,HIGH,1;3;4;5,"F841 line 1274 original_chunks dead local in unbounded dask+cupy branch (refactor leftover). Cat 5 mutable default target_values: list = [] in proximity/allocation/direction -> None sentinel, normalized to [] in body (never mutated, behaviour preserved). E128 line 291 np.where continuation under-indent in _vectorized_calc_direction. isort: re-sorted xrspatial import block + blank line after inline import cupy as cp. flake8+isort clean after fix; 69 proximity tests pass + new parametrized regression test. Pre-existing E127 (test_proximity.py 726/752) + test-file isort drift left untouched (out of module scope)."
 rasterize,2026-05-27,2503,HIGH,1;3,F401 line 15 + F811 line 1193 (paired: local import warnings shadowed unused module-level import); E306 line 1775 (nested @cuda.jit). isort clean. Cat 5 grep clean. Fix in PR #2507.
 resample,2026-05-27,2543,MEDIUM,4,isort drift only: 4 multi-line parenthesised imports collapsed to single/one-per-line under line_length=100 (top-of-file scipy.ndimage + xrspatial.utils; local cupyx imports in _nan_aware_interp_cupy and _interp_block_cupy); two blank-line nits after import math in _run_dask_numpy/_run_dask_cupy. flake8 clean. Cat 5 grep clean. 169 resample tests pass.
 viewshed,2026-05-29,2690,HIGH,1;4;5,"flake8 E127 x2 (L2013-2014 _viewshed_distance_sweep sig); isort .utils import reflow; shadowed builtin id->node_id (L1409,1474). Fixed via /rockout PR. No behavioural change."
diff --git a/xrspatial/proximity.py b/xrspatial/proximity.py
index 5bea23d75..329862913 100644
--- a/xrspatial/proximity.py
+++ b/xrspatial/proximity.py
@@ -24,13 +24,10 @@
     class cupy(object):
         ndarray = False
 
-from xrspatial.pathfinding import _available_memory_bytes
-from xrspatial.utils import (
-    _validate_raster,
-    cuda_args, has_cuda_and_cupy,
-    is_cupy_array, is_dask_cupy, ngjit,
-)
 from xrspatial.dataset_support import supports_dataset
+from xrspatial.pathfinding import _available_memory_bytes
+from xrspatial.utils import (_validate_raster, cuda_args, has_cuda_and_cupy, is_cupy_array,
+                             is_dask_cupy, ngjit)
 
 EUCLIDEAN = 0
 GREAT_CIRCLE = 1
@@ -288,7 +285,7 @@ def _vectorized_calc_direction(x1, x2, y1, y2):
     dy = y2 - y1
     d = np.arctan2(-dy, dx) * 57.29578
     result = np.where(d < 0, 90.0 - d,
-             np.where(d > 90.0, 360.0 - d + 90.0, 90.0 - d))
+                      np.where(d > 90.0, 360.0 - d + 90.0, 90.0 - d))
     result[(x1 == x2) & (y1 == y2)] = 0.0
     return result.astype(np.float32)
 
@@ -1294,9 +1291,9 @@ def _process_dask(raster, xs, ys):
             was_dask_cupy = has_cuda_and_cupy() and is_dask_cupy(raster)
             if was_dask_cupy:
                 import cupy as cp
+
                 # Unbounded: convert to dask+numpy for KDTree/line-sweep
                 # (KDTree is CPU-only; O(N log T) beats brute-force O(NT))
-                original_chunks = raster.data.chunks
                 raster = raster.copy(
                     data=raster.data.map_blocks(
                         lambda x: x.get(), dtype=raster.dtype,
@@ -1369,7 +1366,7 @@ def proximity(
     raster: xr.DataArray,
     x: str = "x",
     y: str = "y",
-    target_values: list = [],
+    target_values: list = None,
     max_distance: float = np.inf,
     distance_metric: str = "EUCLIDEAN",
 ) -> xr.DataArray:
@@ -1485,6 +1482,9 @@ def proximity(
           * x        (x) int64 0 1 2 3 4
     """
 
+    if target_values is None:
+        target_values = []
+
     _validate_raster(raster, func_name='proximity', name='raster')
 
     proximity_img = _process(
@@ -1514,7 +1514,7 @@ def allocation(
     raster: xr.DataArray,
     x: str = "x",
     y: str = "y",
-    target_values: list = [],
+    target_values: list = None,
     max_distance: float = np.inf,
     distance_metric: str = "EUCLIDEAN",
 ) -> xr.DataArray:
@@ -1627,6 +1627,9 @@ def allocation(
           * x        (x) int64 0 1 2 3 4
     """
 
+    if target_values is None:
+        target_values = []
+
     _validate_raster(raster, func_name='allocation', name='raster')
 
     allocation_img = _process(
@@ -1656,7 +1659,7 @@ def direction(
     raster: xr.DataArray,
     x: str = "x",
     y: str = "y",
-    target_values: list = [],
+    target_values: list = None,
     max_distance: float = np.inf,
     distance_metric: str = "EUCLIDEAN",
 ) -> xr.DataArray:
@@ -1775,6 +1778,9 @@ def direction(
           * x        (x) int64 0 1 2 3 4
     """
 
+    if target_values is None:
+        target_values = []
+
     _validate_raster(raster, func_name='direction', name='raster')
 
     direction_img = _process(
diff --git a/xrspatial/tests/test_proximity.py b/xrspatial/tests/test_proximity.py
index f3c41b8c5..d02b34be6 100644
--- a/xrspatial/tests/test_proximity.py
+++ b/xrspatial/tests/test_proximity.py
@@ -1311,3 +1311,26 @@ def test_proximity_res_attr_drives_bounded_dask_padding():
     assert isinstance(result.data, da.Array)
     np.testing.assert_allclose(
         result.values, expected, equal_nan=True, rtol=1e-5)
+
+
+@pytest.mark.parametrize("func", [proximity, allocation, direction])
+def test_target_values_none_default_matches_empty_list(func):
+    # target_values default switched from [] to a None sentinel; passing
+    # None (the default) must behave exactly like passing an empty list.
+    data = np.asarray([[0., 0., 0., 0., 0.],
+                       [0., 0., 0., 1., 0.],
+                       [0., 0., 0., 0., 0.],
+                       [0., 0., 2., 0., 0.],
+                       [0., 0., 0., 0., 0.]])
+    n, m = data.shape
+    raster = xr.DataArray(data, dims=['y', 'x'])
+    raster['y'] = np.arange(n)[::-1]
+    raster['x'] = np.arange(m)
+
+    default_result = func(raster)
+    explicit_result = func(raster, target_values=[])
+
+    np.testing.assert_array_equal(
+        np.nan_to_num(default_result.data),
+        np.nan_to_num(explicit_result.data),
+    )