diff --git a/gerrychain/partition/partition.py b/gerrychain/partition/partition.py
index 83c4b9a..b893aee 100644
--- a/gerrychain/partition/partition.py
+++ b/gerrychain/partition/partition.py
@@ -6,6 +6,7 @@ from ..graph import Graph
 from ..updaters import compute_edge_flows, flows_from_changes
 from .assignment import get_assignment
 from .subgraphs import SubgraphView
+from ..updaters import cut_edges
 
 
 class Partition:
@@ -15,7 +16,9 @@ class Partition:
     aggregations and calculations that we want to optimize.
     """
 
-    default_updaters = {}
+    default_updaters = {
+        "cut_edges": cut_edges
+    }
 
     def __init__(
         self, graph=None, assignment=None, updaters=None, parent=None, flips=None
@@ -46,6 +49,7 @@ class Partition:
 
         if updaters is None:
             updaters = dict()
+
         self.updaters = self.default_updaters.copy()
         self.updaters.update(updaters)
 

Four of six default proposal functions require a `cut_edges` updater
The `propose_chunk_flip`, `propose_random_flip`, `slow_reversible_propose_bi`, and `slow_reversible_propose` proposal functions all require that a `cut_edges` updater is present on the `partition` parameter passed to the function.

Returns a `KeyError`.
diff --git a/tests/partition/test_partition.py b/tests/partition/test_partition.py
index 6b44a41..56b0b16 100644
--- a/tests/partition/test_partition.py
+++ b/tests/partition/test_partition.py
@@ -137,6 +137,16 @@ def districtr_plan_file():
             json.dump(districtr_plan, f)
         yield filename
 
-
 def test_repr(example_partition):
     assert repr(example_partition) == "<Partition [2 parts]>"
+
+def test_partition_has_default_updaters(example_partition):
+    partition = example_partition
+    default_updaters = partition.default_updaters
+    should_have_updaters = {
+        "cut_edges": cut_edges
+    }
+
+    for updater in should_have_updaters:
+        assert default_updaters.get(updater, None) is not None
+        assert should_have_updaters[updater](partition) == partition[updater]

pip install -e .[dev]
parse_log_pytest
requirements.txt
pytest pytest-cov
apt-get update apt-get install -y gcc
3.9
requirements/base.txt
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
certifi==2025.1.31
contourpy==1.3.0
coverage==7.8.0
cycler==0.12.1
exceptiongroup==1.2.2
fonttools==4.56.0
geopandas==1.0.1
-e git+https://github.com/mggg/GerryChain.git@0ac0c6ac09c618c6c834223c5aca6d8a192d7b75#egg=gerrychain
importlib_resources==6.5.2
iniconfig==2.1.0
kiwisolver==1.4.7
matplotlib==3.9.4
networkx==3.2.1
numpy==2.0.2
packaging==24.2
pandas==2.2.3
pillow==11.1.0
pluggy==1.5.0
pyogrio==0.10.0
pyparsing==3.2.3
pyproj==3.6.1
pytest==8.3.5
pytest-cov==6.0.0
python-dateutil==2.9.0.post0
pytz==2025.2
scipy==1.13.1
shapely==2.0.7
six==1.17.0
tomli==2.2.1
tzdata==2025.2
zipp==3.21.0

name: GerryChain
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - ca-certificates=2025.2.25=h06a4308_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.4.4=h6a678d5_1
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - ncurses=6.4=h6a678d5_0
  - openssl=3.0.16=h5eee18b_0
  - pip=25.0=py39h06a4308_0
  - python=3.9.21=he870216_1
  - readline=8.2=h5eee18b_0
  - setuptools=75.8.0=py39h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - wheel=0.45.1=py39h06a4308_0
  - xz=5.6.4=h5eee18b_1
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - certifi==2025.1.31
      - contourpy==1.3.0
      - coverage==7.8.0
      - cycler==0.12.1
      - exceptiongroup==1.2.2
      - fonttools==4.56.0
      - geopandas==1.0.1
      - importlib-resources==6.5.2
      - iniconfig==2.1.0
      - kiwisolver==1.4.7
      - matplotlib==3.9.4
      - networkx==3.2.1
      - numpy==2.0.2
      - packaging==24.2
      - pandas==2.2.3
      - pillow==11.1.0
      - pluggy==1.5.0
      - pyogrio==0.10.0
      - pyparsing==3.2.3
      - pyproj==3.6.1
      - pytest==8.3.5
      - pytest-cov==6.0.0
      - python-dateutil==2.9.0.post0
      - pytz==2025.2
      - scipy==1.13.1
      - shapely==2.0.7
      - six==1.17.0
      - tomli==2.2.1
      - tzdata==2025.2
      - zipp==3.21.0
prefix: /opt/conda/envs/GerryChain

tests/partition/test_partition.py::test_partition_has_default_updaters
tests/partition/test_partition.py::test_Partition_can_be_flipped tests/partition/test_partition.py::test_Partition_misnamed_vertices_raises_keyerror tests/partition/test_partition.py::test_Partition_unlabelled_vertices_raises_keyerror tests/partition/test_partition.py::test_Partition_knows_cut_edges_K3 tests/partition/test_partition.py::test_propose_random_flip_proposes_a_partition tests/partition/test_partition.py::test_Partition_parts_is_a_dictionary_of_parts_to_nodes tests/partition/test_partition.py::test_Partition_has_subgraphs tests/partition/test_partition.py::test_Partition_caches_subgraphs tests/partition/test_partition.py::test_partition_implements_getattr_for_updater_access tests/partition/test_partition.py::test_can_be_created_from_a_districtr_file tests/partition/test_partition.py::test_from_districtr_plan_raises_if_id_column_missing tests/partition/test_partition.py::test_repr
gerrychain/partition/partition.py
gerrychain/partition/partition.py