diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 48316f4..5b31494 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -12,7 +12,7 @@ ci:
 
 repos:
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.13.3
+    rev: v0.14.0
     hooks:
       - id: ruff
         args: ["--fix", "--output-format=full"]
diff --git a/pymc_bart/bart.py b/pymc_bart/bart.py
index 233d33e..1c99bce 100644
--- a/pymc_bart/bart.py
+++ b/pymc_bart/bart.py
@@ -16,7 +16,6 @@
 
 import warnings
 from multiprocessing import Manager
-from typing import Optional
 
 import numpy as np
 import numpy.typing as npt
@@ -130,9 +129,9 @@ def __new__(
         alpha: float = 0.95,
         beta: float = 2.0,
         response: str = "constant",
-        split_prior: Optional[npt.NDArray] = None,
-        split_rules: Optional[list[SplitRule]] = None,
-        separate_trees: Optional[bool] = False,
+        split_prior: npt.NDArray | None = None,
+        split_rules: list[SplitRule] | None = None,
+        separate_trees: bool | None = False,
         **kwargs,
     ):
         if response in ["linear", "mix"]:
diff --git a/pymc_bart/pgbart.py b/pymc_bart/pgbart.py
index 87bd36a..72764b2 100644
--- a/pymc_bart/pgbart.py
+++ b/pymc_bart/pgbart.py
@@ -12,7 +12,6 @@
 #   See the License for the specific language governing permissions and
 #   limitations under the License.
 
-from typing import Optional, Union
 
 import numpy as np
 import numpy.typing as npt
@@ -128,7 +127,7 @@ def __init__(  # noqa: PLR0912, PLR0915
         vars: list[pm.Distribution] | None = None,
         num_particles: int = 10,
         batch: tuple[float, float] = (0.1, 0.1),
-        model: Optional[Model] = None,
+        model: Model | None = None,
         initial_point: PointType | None = None,
         compile_kwargs: dict | None = None,
         **kwargs,  # Accept additional kwargs for compound sampling
@@ -445,7 +444,7 @@ def __init__(self, shape: tuple[int, ...]) -> None:
         self.mean = np.zeros(shape)  # running mean
         self.m_2 = np.zeros(shape)  # running second moment
 
-    def update(self, new_value: npt.NDArray) -> Union[float, npt.NDArray]:
+    def update(self, new_value: npt.NDArray) -> float | npt.NDArray:
         self.count = self.count + 1
         self.mean, self.m_2, std = _update(self.count, self.mean, self.m_2, new_value)
         return fast_mean(std)
@@ -457,7 +456,7 @@ def _update(
     mean: npt.NDArray,
     m_2: npt.NDArray,
     new_value: npt.NDArray,
-) -> tuple[npt.NDArray, npt.NDArray, Union[float, npt.NDArray]]:
+) -> tuple[npt.NDArray, npt.NDArray, float | npt.NDArray]:
     delta = new_value - mean
     mean += delta / count
     delta2 = new_value - mean
@@ -477,7 +476,7 @@ def __init__(self, alpha_vec: npt.NDArray) -> None:
         """
         self.enu = list(enumerate(np.cumsum(alpha_vec / alpha_vec.sum())))
 
-    def rvs(self) -> Union[int, tuple[int, float]]:
+    def rvs(self) -> int | tuple[int, float]:
         rnd: float = np.random.random()
         for i, val in self.enu:
             if rnd <= val:
@@ -587,7 +586,7 @@ def draw_leaf_value(
     norm: npt.NDArray,
     shape: int,
     response: str,
-) -> tuple[npt.NDArray, Optional[npt.NDArray]]:
+) -> tuple[npt.NDArray, npt.NDArray | None]:
     """Draw Gaussian distributed leaf values."""
     linear_params = None
     mu_mean: npt.NDArray
@@ -605,7 +604,7 @@ def draw_leaf_value(
 
 
 @njit
-def fast_mean(ari: npt.NDArray) -> Union[float, npt.NDArray]:
+def fast_mean(ari: npt.NDArray) -> float | npt.NDArray:
     """Use Numba to speed up the computation of the mean."""
     if ari.ndim == 1:
         count = ari.shape[0]
diff --git a/pymc_bart/tree.py b/pymc_bart/tree.py
index 61e5050..250e16b 100644
--- a/pymc_bart/tree.py
+++ b/pymc_bart/tree.py
@@ -14,7 +14,6 @@
 
 from collections.abc import Generator
 from functools import lru_cache
-from typing import Optional, Union
 
 import numpy as np
 import numpy.typing as npt
@@ -40,9 +39,9 @@ def __init__(
         self,
         value: npt.NDArray = np.array([-1.0]),
         nvalue: int = 0,
-        idx_data_points: Optional[npt.NDArray[np.int_]] = None,
+        idx_data_points: npt.NDArray[np.int_] | None = None,
         idx_split_variable: int = -1,
-        linear_params: Optional[list[npt.NDArray]] = None,
+        linear_params: list[npt.NDArray] | None = None,
     ) -> None:
         self.value = value
         self.nvalue = nvalue
@@ -55,9 +54,9 @@ def new_leaf_node(
         cls,
         value: npt.NDArray,
         nvalue: int = 0,
-        idx_data_points: Optional[npt.NDArray[np.int_]] = None,
+        idx_data_points: npt.NDArray[np.int_] | None = None,
         idx_split_variable: int = -1,
-        linear_params: Optional[list[npt.NDArray]] = None,
+        linear_params: list[npt.NDArray] | None = None,
     ) -> "Node":
         return cls(
             value=value,
@@ -124,7 +123,7 @@ def __init__(
         tree_structure: dict[int, Node],
         output: npt.NDArray,
         split_rules: list[SplitRule],
-        idx_leaf_nodes: Optional[list[int]] = None,
+        idx_leaf_nodes: list[int] | None = None,
     ) -> None:
         self.tree_structure = tree_structure
         self.idx_leaf_nodes = idx_leaf_nodes
@@ -135,7 +134,7 @@ def __init__(
     def new_tree(
         cls,
         leaf_node_value: npt.NDArray,
-        idx_data_points: Optional[npt.NDArray[np.int_]],
+        idx_data_points: npt.NDArray[np.int_] | None,
         num_observations: int,
         shape: int,
         split_rules: list[SplitRule],
@@ -234,7 +233,7 @@ def _predict(self) -> npt.NDArray:
     def predict(
         self,
         x: npt.NDArray,
-        excluded: Optional[list[int]] = None,
+        excluded: list[int] | None = None,
         shape: int = 1,
     ) -> npt.NDArray:
         """
@@ -260,8 +259,8 @@ def predict(
     def _traverse_tree(
         self,
         X: npt.NDArray,
-        excluded: Optional[list[int]] = None,
-        shape: Union[int, tuple[int, ...]] = 1,
+        excluded: list[int] | None = None,
+        shape: int | tuple[int, ...] = 1,
     ) -> npt.NDArray:
         """
         Traverse the tree starting from the root node given an (un)observed point.