diff --git a/conftest.py b/conftest.py
index 16c68c85..fd5b288d 100644
--- a/conftest.py
+++ b/conftest.py
@@ -3,6 +3,8 @@
 Based on https://docs.pytest.org/en/latest/example/simple.html.
 """
 
+from __future__ import annotations
+
 import pytest
 
 
diff --git a/janus_core/__init__.py b/janus_core/__init__.py
index efaa8049..fd316051 100644
--- a/janus_core/__init__.py
+++ b/janus_core/__init__.py
@@ -1,5 +1,7 @@
 """Tools for machine learnt interatomic potentials."""
 
+from __future__ import annotations
+
 from importlib.metadata import version
 
 __version__ = version("janus-core")
diff --git a/janus_core/calculations/base.py b/janus_core/calculations/base.py
index bc3fccdf..7146ac5e 100644
--- a/janus_core/calculations/base.py
+++ b/janus_core/calculations/base.py
@@ -1,6 +1,8 @@
 """Prepare structures for MLIP calculations."""
 
-from typing import Any, Optional
+from __future__ import annotations
+
+from typing import Any
 
 from ase import Atoms
 
@@ -71,22 +73,22 @@ def __init__(
         self,
         *,
         calc_name: str = "base",
-        struct: Optional[MaybeSequence[Atoms]] = None,
-        struct_path: Optional[PathLike] = None,
+        struct: MaybeSequence[Atoms] | None = None,
+        struct_path: PathLike | None = None,
         arch: Architectures = "mace_mp",
         device: Devices = "cpu",
-        model_path: Optional[PathLike] = None,
-        read_kwargs: Optional[ASEReadArgs] = None,
+        model_path: PathLike | None = None,
+        read_kwargs: ASEReadArgs | None = None,
         sequence_allowed: bool = True,
-        calc_kwargs: Optional[dict[str, Any]] = None,
-        set_calc: Optional[bool] = None,
+        calc_kwargs: dict[str, Any] | None = None,
+        set_calc: bool | None = None,
         attach_logger: bool = False,
-        log_kwargs: Optional[dict[str, Any]] = None,
+        log_kwargs: dict[str, Any] | None = None,
         track_carbon: bool = True,
-        tracker_kwargs: Optional[dict[str, Any]] = None,
-        file_prefix: Optional[PathLike] = None,
-        additional_prefix: Optional[str] = None,
-        param_prefix: Optional[str] = None,
+        tracker_kwargs: dict[str, Any] | None = None,
+        file_prefix: PathLike | None = None,
+        additional_prefix: str | None = None,
+        param_prefix: str | None = None,
     ) -> None:
         """
         Read the structure being simulated and attach an MLIP calculator.
diff --git a/janus_core/calculations/descriptors.py b/janus_core/calculations/descriptors.py
index f8d4dd28..95425d15 100644
--- a/janus_core/calculations/descriptors.py
+++ b/janus_core/calculations/descriptors.py
@@ -1,7 +1,9 @@
 """Calculate MLIP descriptors for structures."""
 
+from __future__ import annotations
+
 from collections.abc import Sequence
-from typing import Any, Optional
+from typing import Any
 
 from ase import Atoms
 import numpy as np
@@ -73,23 +75,23 @@ class Descriptors(BaseCalculation):
 
     def __init__(
         self,
-        struct: Optional[MaybeSequence[Atoms]] = None,
-        struct_path: Optional[PathLike] = None,
+        struct: MaybeSequence[Atoms] | None = None,
+        struct_path: PathLike | None = None,
         arch: Architectures = "mace_mp",
         device: Devices = "cpu",
-        model_path: Optional[PathLike] = None,
-        read_kwargs: Optional[ASEReadArgs] = None,
-        calc_kwargs: Optional[dict[str, Any]] = None,
-        set_calc: Optional[bool] = None,
+        model_path: PathLike | None = None,
+        read_kwargs: ASEReadArgs | None = None,
+        calc_kwargs: dict[str, Any] | None = None,
+        set_calc: bool | None = None,
         attach_logger: bool = False,
-        log_kwargs: Optional[dict[str, Any]] = None,
+        log_kwargs: dict[str, Any] | None = None,
         track_carbon: bool = True,
-        tracker_kwargs: Optional[dict[str, Any]] = None,
+        tracker_kwargs: dict[str, Any] | None = None,
         invariants_only: bool = True,
         calc_per_element: bool = False,
         calc_per_atom: bool = False,
         write_results: bool = False,
-        write_kwargs: Optional[ASEWriteArgs] = None,
+        write_kwargs: ASEWriteArgs | None = None,
     ) -> None:
         """
         Initialise class.
diff --git a/janus_core/calculations/eos.py b/janus_core/calculations/eos.py
index fee3df43..1ddd3ee7 100644
--- a/janus_core/calculations/eos.py
+++ b/janus_core/calculations/eos.py
@@ -1,7 +1,9 @@
 """Equation of State."""
 
+from __future__ import annotations
+
 from copy import copy
-from typing import Any, Optional
+from typing import Any
 
 from ase import Atoms
 from ase.eos import EquationOfState
@@ -105,31 +107,31 @@ class EoS(BaseCalculation):
 
     def __init__(
         self,
-        struct: Optional[Atoms] = None,
-        struct_path: Optional[PathLike] = None,
+        struct: Atoms | None = None,
+        struct_path: PathLike | None = None,
         arch: Architectures = "mace_mp",
         device: Devices = "cpu",
-        model_path: Optional[PathLike] = None,
-        read_kwargs: Optional[ASEReadArgs] = None,
-        calc_kwargs: Optional[dict[str, Any]] = None,
-        set_calc: Optional[bool] = None,
+        model_path: PathLike | None = None,
+        read_kwargs: ASEReadArgs | None = None,
+        calc_kwargs: dict[str, Any] | None = None,
+        set_calc: bool | None = None,
         attach_logger: bool = False,
-        log_kwargs: Optional[dict[str, Any]] = None,
+        log_kwargs: dict[str, Any] | None = None,
         track_carbon: bool = True,
-        tracker_kwargs: Optional[dict[str, Any]] = None,
+        tracker_kwargs: dict[str, Any] | None = None,
         min_volume: float = 0.95,
         max_volume: float = 1.05,
         n_volumes: int = 7,
         eos_type: EoSNames = "birchmurnaghan",
         minimize: bool = True,
         minimize_all: bool = False,
-        minimize_kwargs: Optional[dict[str, Any]] = None,
+        minimize_kwargs: dict[str, Any] | None = None,
         write_results: bool = True,
         write_structures: bool = False,
-        write_kwargs: Optional[OutputKwargs] = None,
+        write_kwargs: OutputKwargs | None = None,
         plot_to_file: bool = False,
-        plot_kwargs: Optional[dict[str, Any]] = None,
-        file_prefix: Optional[PathLike] = None,
+        plot_kwargs: dict[str, Any] | None = None,
+        file_prefix: PathLike | None = None,
     ) -> None:
         """
         Initialise class.
diff --git a/janus_core/calculations/geom_opt.py b/janus_core/calculations/geom_opt.py
index 09b18d01..3f4c155e 100644
--- a/janus_core/calculations/geom_opt.py
+++ b/janus_core/calculations/geom_opt.py
@@ -1,6 +1,8 @@
 """Prepare and run geometry optimization."""
 
-from typing import Any, Callable, Optional, Union
+from __future__ import annotations
+
+from typing import Any, Callable
 import warnings
 
 from ase import Atoms, filters, units
@@ -97,30 +99,30 @@ class GeomOpt(BaseCalculation):
 
     def __init__(
         self,
-        struct: Optional[Atoms] = None,
-        struct_path: Optional[PathLike] = None,
+        struct: Atoms | None = None,
+        struct_path: PathLike | None = None,
         arch: Architectures = "mace_mp",
         device: Devices = "cpu",
-        model_path: Optional[PathLike] = None,
-        read_kwargs: Optional[ASEReadArgs] = None,
-        calc_kwargs: Optional[dict[str, Any]] = None,
-        set_calc: Optional[bool] = None,
+        model_path: PathLike | None = None,
+        read_kwargs: ASEReadArgs | None = None,
+        calc_kwargs: dict[str, Any] | None = None,
+        set_calc: bool | None = None,
         attach_logger: bool = False,
-        log_kwargs: Optional[dict[str, Any]] = None,
+        log_kwargs: dict[str, Any] | None = None,
         track_carbon: bool = True,
-        tracker_kwargs: Optional[dict[str, Any]] = None,
+        tracker_kwargs: dict[str, Any] | None = None,
         fmax: float = 0.1,
         steps: int = 1000,
         symmetrize: bool = False,
         symmetry_tolerance: float = 0.001,
         angle_tolerance: float = -1.0,
-        filter_func: Optional[Union[Callable, str]] = FrechetCellFilter,
-        filter_kwargs: Optional[dict[str, Any]] = None,
-        optimizer: Union[Callable, str] = LBFGS,
-        opt_kwargs: Optional[ASEOptArgs] = None,
+        filter_func: Callable | str | None = FrechetCellFilter,
+        filter_kwargs: dict[str, Any] | None = None,
+        optimizer: Callable | str = LBFGS,
+        opt_kwargs: ASEOptArgs | None = None,
         write_results: bool = False,
-        write_kwargs: Optional[OutputKwargs] = None,
-        traj_kwargs: Optional[OutputKwargs] = None,
+        write_kwargs: OutputKwargs | None = None,
+        traj_kwargs: OutputKwargs | None = None,
     ) -> None:
         """
         Initialise GeomOpt class.
diff --git a/janus_core/calculations/md.py b/janus_core/calculations/md.py
index 0096ad17..4f17d883 100644
--- a/janus_core/calculations/md.py
+++ b/janus_core/calculations/md.py
@@ -1,5 +1,7 @@
 """Run molecular dynamics simulations."""
 
+from __future__ import annotations
+
 import datetime
 from functools import partial
 from itertools import combinations_with_replacement
@@ -7,7 +9,7 @@
 from os.path import getmtime
 from pathlib import Path
 import random
-from typing import Any, Optional, Union
+from typing import Any
 from warnings import warn
 
 from ase import Atoms, units
@@ -175,51 +177,51 @@ class MolecularDynamics(BaseCalculation):
 
     def __init__(
         self,
-        struct: Optional[Atoms] = None,
-        struct_path: Optional[PathLike] = None,
+        struct: Atoms | None = None,
+        struct_path: PathLike | None = None,
         arch: Architectures = "mace_mp",
         device: Devices = "cpu",
-        model_path: Optional[PathLike] = None,
-        read_kwargs: Optional[ASEReadArgs] = None,
-        calc_kwargs: Optional[dict[str, Any]] = None,
-        set_calc: Optional[bool] = None,
+        model_path: PathLike | None = None,
+        read_kwargs: ASEReadArgs | None = None,
+        calc_kwargs: dict[str, Any] | None = None,
+        set_calc: bool | None = None,
         attach_logger: bool = False,
-        log_kwargs: Optional[dict[str, Any]] = None,
+        log_kwargs: dict[str, Any] | None = None,
         track_carbon: bool = True,
-        tracker_kwargs: Optional[dict[str, Any]] = None,
-        ensemble: Optional[Ensembles] = None,
+        tracker_kwargs: dict[str, Any] | None = None,
+        ensemble: Ensembles | None = None,
         steps: int = 0,
         timestep: float = 1.0,
         temp: float = 300,
         equil_steps: int = 0,
         minimize: bool = False,
         minimize_every: int = -1,
-        minimize_kwargs: Optional[dict[str, Any]] = None,
+        minimize_kwargs: dict[str, Any] | None = None,
         rescale_velocities: bool = False,
         remove_rot: bool = False,
         rescale_every: int = 10,
-        file_prefix: Optional[PathLike] = None,
+        file_prefix: PathLike | None = None,
         restart: bool = False,
         restart_auto: bool = True,
-        restart_stem: Optional[PathLike] = None,
+        restart_stem: PathLike | None = None,
         restart_every: int = 1000,
         rotate_restart: bool = False,
         restarts_to_keep: int = 4,
-        final_file: Optional[PathLike] = None,
-        stats_file: Optional[PathLike] = None,
+        final_file: PathLike | None = None,
+        stats_file: PathLike | None = None,
         stats_every: int = 100,
-        traj_file: Optional[PathLike] = None,
+        traj_file: PathLike | None = None,
         traj_append: bool = False,
         traj_start: int = 0,
         traj_every: int = 100,
-        temp_start: Optional[float] = None,
-        temp_end: Optional[float] = None,
-        temp_step: Optional[float] = None,
-        temp_time: Optional[float] = None,
-        write_kwargs: Optional[OutputKwargs] = None,
-        post_process_kwargs: Optional[PostProcessKwargs] = None,
-        correlation_kwargs: Optional[list[CorrelationKwargs]] = None,
-        seed: Optional[int] = None,
+        temp_start: float | None = None,
+        temp_end: float | None = None,
+        temp_step: float | None = None,
+        temp_time: float | None = None,
+        write_kwargs: OutputKwargs | None = None,
+        post_process_kwargs: PostProcessKwargs | None = None,
+        correlation_kwargs: list[CorrelationKwargs] | None = None,
+        seed: int | None = None,
     ) -> None:
         """
         Initialise molecular dynamics simulation configuration.
@@ -493,7 +495,7 @@ def __init__(
                 "filemode": "a",
             }
 
-        self.dyn: Union[Langevin, VelocityVerlet, ASE_NPT]
+        self.dyn: Langevin | VelocityVerlet | ASE_NPT
         self.n_atoms = len(self.struct)
 
         self.offset = 0
@@ -633,7 +635,7 @@ def _optimize_structure(self) -> None:
             optimizer = GeomOpt(self.struct, **self.minimize_kwargs)
             optimizer.run()
 
-    def _set_param_prefix(self, file_prefix: Optional[PathLike] = None) -> str:
+    def _set_param_prefix(self, file_prefix: PathLike | None = None) -> str:
         """
         Set ensemble parameters for output files.
 
@@ -1156,8 +1158,8 @@ def __init__(
         bulk_modulus: float = 2.0,
         pressure: float = 0.0,
         ensemble: Ensembles = "npt",
-        file_prefix: Optional[PathLike] = None,
-        ensemble_kwargs: Optional[dict[str, Any]] = None,
+        file_prefix: PathLike | None = None,
+        ensemble_kwargs: dict[str, Any] | None = None,
         **kwargs,
     ) -> None:
         """
@@ -1211,7 +1213,7 @@ def __init__(
             **ensemble_kwargs,
         )
 
-    def _set_param_prefix(self, file_prefix: Optional[PathLike] = None) -> str:
+    def _set_param_prefix(self, file_prefix: PathLike | None = None) -> str:
         """
         Set ensemble parameters for output files.
 
@@ -1297,7 +1299,7 @@ def __init__(
         *args,
         friction: float = 0.005,
         ensemble: Ensembles = "nvt",
-        ensemble_kwargs: Optional[dict[str, Any]] = None,
+        ensemble_kwargs: dict[str, Any] | None = None,
         **kwargs,
     ) -> None:
         """
@@ -1391,7 +1393,7 @@ def __init__(
         self,
         *args,
         ensemble: Ensembles = "nve",
-        ensemble_kwargs: Optional[dict[str, Any]] = None,
+        ensemble_kwargs: dict[str, Any] | None = None,
         **kwargs,
     ) -> None:
         """
@@ -1442,7 +1444,7 @@ def __init__(
         *args,
         thermostat_time: float = 50.0,
         ensemble: Ensembles = "nvt-nh",
-        ensemble_kwargs: Optional[dict[str, Any]] = None,
+        ensemble_kwargs: dict[str, Any] | None = None,
         **kwargs,
     ) -> None:
         """
@@ -1546,8 +1548,8 @@ def __init__(
         bulk_modulus: float = 2.0,
         pressure: float = 0.0,
         ensemble: Ensembles = "nph",
-        file_prefix: Optional[PathLike] = None,
-        ensemble_kwargs: Optional[dict[str, Any]] = None,
+        file_prefix: PathLike | None = None,
+        ensemble_kwargs: dict[str, Any] | None = None,
         **kwargs,
     ) -> None:
         """
diff --git a/janus_core/calculations/phonons.py b/janus_core/calculations/phonons.py
index 19fd6ce1..ffc3cfc5 100644
--- a/janus_core/calculations/phonons.py
+++ b/janus_core/calculations/phonons.py
@@ -1,7 +1,9 @@
 """Phonon calculations."""
 
+from __future__ import annotations
+
 from collections.abc import Sequence
-from typing import Any, Optional, get_args
+from typing import Any, get_args
 
 from ase import Atoms
 from numpy import ndarray
@@ -137,25 +139,25 @@ class Phonons(BaseCalculation):
 
     def __init__(
         self,
-        struct: Optional[Atoms] = None,
-        struct_path: Optional[PathLike] = None,
+        struct: Atoms | None = None,
+        struct_path: PathLike | None = None,
         arch: Architectures = "mace_mp",
         device: Devices = "cpu",
-        model_path: Optional[PathLike] = None,
-        read_kwargs: Optional[ASEReadArgs] = None,
-        calc_kwargs: Optional[dict[str, Any]] = None,
-        set_calc: Optional[bool] = None,
+        model_path: PathLike | None = None,
+        read_kwargs: ASEReadArgs | None = None,
+        calc_kwargs: dict[str, Any] | None = None,
+        set_calc: bool | None = None,
         attach_logger: bool = False,
-        log_kwargs: Optional[dict[str, Any]] = None,
+        log_kwargs: dict[str, Any] | None = None,
         track_carbon: bool = True,
-        tracker_kwargs: Optional[dict[str, Any]] = None,
+        tracker_kwargs: dict[str, Any] | None = None,
         calcs: MaybeSequence[PhononCalcs] = (),
         supercell: MaybeList[int] = 2,
         displacement: float = 0.01,
         mesh: tuple[int, int, int] = (10, 10, 10),
         symmetrize: bool = False,
         minimize: bool = False,
-        minimize_kwargs: Optional[dict[str, Any]] = None,
+        minimize_kwargs: dict[str, Any] | None = None,
         temp_min: float = 0.0,
         temp_max: float = 1000.0,
         temp_step: float = 50.0,
@@ -163,7 +165,7 @@ def __init__(
         plot_to_file: bool = False,
         write_results: bool = True,
         write_full: bool = True,
-        file_prefix: Optional[PathLike] = None,
+        file_prefix: PathLike | None = None,
         enable_progress_bar: bool = False,
     ) -> None:
         """
@@ -364,7 +366,7 @@ def calcs(self, value: MaybeSequence[PhononCalcs]) -> None:
         self._calcs = value
 
     def calc_force_constants(
-        self, write_force_consts: Optional[bool] = None, **kwargs
+        self, write_force_consts: bool | None = None, **kwargs
     ) -> None:
         """
         Calculate force constants and optionally write results.
@@ -437,9 +439,9 @@ def calc_force_constants(
     def write_force_constants(
         self,
         *,
-        phonopy_file: Optional[PathLike] = None,
-        force_consts_to_hdf5: Optional[bool] = None,
-        force_consts_file: Optional[PathLike] = None,
+        phonopy_file: PathLike | None = None,
+        force_consts_to_hdf5: bool | None = None,
+        force_consts_file: PathLike | None = None,
     ) -> None:
         """
         Write results of force constants calculations.
@@ -480,7 +482,7 @@ def write_force_constants(
                 phonon.force_constants, filename=force_consts_file
             )
 
-    def calc_bands(self, write_bands: Optional[bool] = None, **kwargs) -> None:
+    def calc_bands(self, write_bands: bool | None = None, **kwargs) -> None:
         """
         Calculate band structure and optionally write and plot results.
 
@@ -505,9 +507,9 @@ def calc_bands(self, write_bands: Optional[bool] = None, **kwargs) -> None:
     def write_bands(
         self,
         *,
-        bands_file: Optional[PathLike] = None,
-        save_plots: Optional[bool] = None,
-        plot_file: Optional[PathLike] = None,
+        bands_file: PathLike | None = None,
+        save_plots: bool | None = None,
+        plot_file: PathLike | None = None,
     ) -> None:
         """
         Write results of band structure calculations.
@@ -547,8 +549,8 @@ def write_bands(
 
     def calc_thermal_props(
         self,
-        mesh: Optional[tuple[int, int, int]] = None,
-        write_thermal: Optional[bool] = None,
+        mesh: tuple[int, int, int] | None = None,
+        write_thermal: bool | None = None,
         **kwargs,
     ) -> None:
         """
@@ -598,7 +600,7 @@ def calc_thermal_props(
         if write_thermal:
             self.write_thermal_props(**kwargs)
 
-    def write_thermal_props(self, thermal_file: Optional[PathLike] = None) -> None:
+    def write_thermal_props(self, thermal_file: PathLike | None = None) -> None:
         """
         Write results of thermal properties calculations.
 
@@ -629,8 +631,8 @@ def write_thermal_props(self, thermal_file: Optional[PathLike] = None) -> None:
     def calc_dos(
         self,
         *,
-        mesh: Optional[tuple[int, int, int]] = None,
-        write_dos: Optional[bool] = None,
+        mesh: tuple[int, int, int] | None = None,
+        write_dos: bool | None = None,
         **kwargs,
     ) -> None:
         """
@@ -677,11 +679,11 @@ def calc_dos(
     def write_dos(
         self,
         *,
-        dos_file: Optional[PathLike] = None,
-        plot_to_file: Optional[bool] = None,
-        plot_file: Optional[PathLike] = None,
+        dos_file: PathLike | None = None,
+        plot_to_file: bool | None = None,
+        plot_file: PathLike | None = None,
         plot_bands: bool = False,
-        plot_bands_file: Optional[PathLike] = None,
+        plot_bands_file: PathLike | None = None,
     ) -> None:
         """
         Write results of DOS calculation.
@@ -736,8 +738,8 @@ def write_dos(
     def calc_pdos(
         self,
         *,
-        mesh: Optional[tuple[int, int, int]] = None,
-        write_pdos: Optional[bool] = None,
+        mesh: tuple[int, int, int] | None = None,
+        write_pdos: bool | None = None,
         **kwargs,
     ) -> None:
         """
@@ -786,9 +788,9 @@ def calc_pdos(
     def write_pdos(
         self,
         *,
-        pdos_file: Optional[PathLike] = None,
-        plot_to_file: Optional[bool] = None,
-        plot_file: Optional[PathLike] = None,
+        pdos_file: PathLike | None = None,
+        plot_to_file: bool | None = None,
+        plot_file: PathLike | None = None,
     ) -> None:
         """
         Write results of PDOS calculation.
diff --git a/janus_core/calculations/single_point.py b/janus_core/calculations/single_point.py
index a4171f54..a182e530 100644
--- a/janus_core/calculations/single_point.py
+++ b/janus_core/calculations/single_point.py
@@ -1,7 +1,9 @@
 """Prepare and perform single point calculations."""
 
+from __future__ import annotations
+
 from collections.abc import Sequence
-from typing import Any, Optional, get_args
+from typing import Any, get_args
 
 from ase import Atoms
 from numpy import ndarray
@@ -80,21 +82,21 @@ class SinglePoint(BaseCalculation):
     def __init__(
         self,
         *,
-        struct: Optional[MaybeSequence[Atoms]] = None,
-        struct_path: Optional[PathLike] = None,
+        struct: MaybeSequence[Atoms] | None = None,
+        struct_path: PathLike | None = None,
         arch: Architectures = "mace_mp",
         device: Devices = "cpu",
-        model_path: Optional[PathLike] = None,
-        read_kwargs: Optional[ASEReadArgs] = None,
-        calc_kwargs: Optional[dict[str, Any]] = None,
-        set_calc: Optional[bool] = None,
+        model_path: PathLike | None = None,
+        read_kwargs: ASEReadArgs | None = None,
+        calc_kwargs: dict[str, Any] | None = None,
+        set_calc: bool | None = None,
         attach_logger: bool = False,
-        log_kwargs: Optional[dict[str, Any]] = None,
+        log_kwargs: dict[str, Any] | None = None,
         track_carbon: bool = True,
-        tracker_kwargs: Optional[dict[str, Any]] = None,
+        tracker_kwargs: dict[str, Any] | None = None,
         properties: MaybeSequence[Properties] = (),
         write_results: bool = False,
-        write_kwargs: Optional[OutputKwargs] = None,
+        write_kwargs: OutputKwargs | None = None,
     ) -> None:
         """
         Read the structure being simulated and attach an MLIP calculator.
diff --git a/janus_core/cli/descriptors.py b/janus_core/cli/descriptors.py
index a81a3f25..dbebd3ce 100644
--- a/janus_core/cli/descriptors.py
+++ b/janus_core/cli/descriptors.py
@@ -1,5 +1,10 @@
+# ruff: noqa: I002, FA100
 """Set up MLIP descriptors commandline interface."""
 
+# Issues with future annotations and typer
+# c.f. https://github.com/fastapi/typer/discussions/802
+# from __future__ import annotations
+
 from pathlib import Path
 from typing import Annotated, Optional
 
diff --git a/janus_core/cli/eos.py b/janus_core/cli/eos.py
index c55be86e..33d7387f 100644
--- a/janus_core/cli/eos.py
+++ b/janus_core/cli/eos.py
@@ -1,5 +1,10 @@
+# ruff: noqa: I002, FA100
 """Set up eos commandline interface."""
 
+# Issues with future annotations and typer
+# c.f. https://github.com/fastapi/typer/discussions/802
+# from __future__ import annotations
+
 from pathlib import Path
 from typing import Annotated, Optional, get_args
 
diff --git a/janus_core/cli/geomopt.py b/janus_core/cli/geomopt.py
index 5b76a529..de218804 100644
--- a/janus_core/cli/geomopt.py
+++ b/janus_core/cli/geomopt.py
@@ -1,5 +1,10 @@
+# ruff: noqa: I002, FA100
 """Set up geomopt commandline interface."""
 
+# Issues with future annotations and typer
+# c.f. https://github.com/fastapi/typer/discussions/802
+# from __future__ import annotations
+
 from pathlib import Path
 from typing import Annotated, Any, Optional
 
diff --git a/janus_core/cli/janus.py b/janus_core/cli/janus.py
index ecb3dcd1..9d33da80 100644
--- a/janus_core/cli/janus.py
+++ b/janus_core/cli/janus.py
@@ -1,5 +1,10 @@
+# ruff: noqa: I002, FA100
 """Set up commandline interface."""
 
+# Issues with future annotations and typer
+# c.f. https://github.com/fastapi/typer/discussions/802
+# from __future__ import annotations
+
 from typing import Annotated
 
 from typer import Exit, Option, Typer
diff --git a/janus_core/cli/md.py b/janus_core/cli/md.py
index 5bab22ef..74845d26 100644
--- a/janus_core/cli/md.py
+++ b/janus_core/cli/md.py
@@ -1,5 +1,10 @@
+# ruff: noqa: I002, FA100
 """Set up md commandline interface."""
 
+# Issues with future annotations and typer
+# c.f. https://github.com/fastapi/typer/discussions/802
+# from __future__ import annotations
+
 from pathlib import Path
 from typing import Annotated, Optional, get_args
 
diff --git a/janus_core/cli/phonons.py b/janus_core/cli/phonons.py
index 03dbf309..64a362df 100644
--- a/janus_core/cli/phonons.py
+++ b/janus_core/cli/phonons.py
@@ -1,5 +1,10 @@
+# ruff: noqa: I002, FA100
 """Set up phonons commandline interface."""
 
+# Issues with future annotations and typer
+# c.f. https://github.com/fastapi/typer/discussions/802
+# from __future__ import annotations
+
 from pathlib import Path
 from typing import Annotated, Optional
 
diff --git a/janus_core/cli/singlepoint.py b/janus_core/cli/singlepoint.py
index ead77ed7..602f5adf 100644
--- a/janus_core/cli/singlepoint.py
+++ b/janus_core/cli/singlepoint.py
@@ -1,5 +1,10 @@
+# ruff: noqa: I002, FA100
 """Set up singlepoint commandline interface."""
 
+# Issues with future annotations and typer
+# c.f. https://github.com/fastapi/typer/discussions/802
+# from __future__ import annotations
+
 from pathlib import Path
 from typing import Annotated, Optional
 
diff --git a/janus_core/cli/train.py b/janus_core/cli/train.py
index 6098e63c..1608c89b 100644
--- a/janus_core/cli/train.py
+++ b/janus_core/cli/train.py
@@ -1,5 +1,10 @@
+# noqa: I002, FA102
 """Set up MLIP training commandline interface."""
 
+# Issues with future annotations and typer
+# c.f. https://github.com/fastapi/typer/discussions/802
+# from __future__ import annotations
+
 from pathlib import Path
 from typing import Annotated
 
diff --git a/janus_core/helpers/janus_types.py b/janus_core/helpers/janus_types.py
index 8adc3400..708c7845 100644
--- a/janus_core/helpers/janus_types.py
+++ b/janus_core/helpers/janus_types.py
@@ -1,5 +1,7 @@
 """Module containing types used in Janus-Core."""
 
+from __future__ import annotations
+
 from collections.abc import Collection, Sequence
 from enum import Enum
 import logging
@@ -35,9 +37,9 @@
 class ASEReadArgs(TypedDict, total=False):
     """Main arguments for ase.io.read."""
 
-    filename: Union[str, PurePath, IO]
-    index: Union[int, slice, str]
-    format: Optional[str]
+    filename: str | PurePath | IO
+    index: int | slice | str
+    format: str | None
     parallel: bool
     do_not_split_by_at_sign: bool
 
@@ -45,9 +47,9 @@ class ASEReadArgs(TypedDict, total=False):
 class ASEWriteArgs(TypedDict, total=False):
     """Main arguments for ase.io.write."""
 
-    filename: Union[str, PurePath, IO]
+    filename: str | PurePath | IO
     images: MaybeSequence[Atoms]
-    format: Optional[str]
+    format: str | None
     parallel: bool
     append: bool
 
@@ -55,9 +57,9 @@ class ASEWriteArgs(TypedDict, total=False):
 class ASEOptArgs(TypedDict, total=False):
     """Main arguments for ase optimisers."""
 
-    restart: Optional[bool]
-    logfile: Optional[PathLike]
-    trajectory: Optional[str]
+    restart: bool | None
+    logfile: PathLike | None
+    trajectory: str | None
 
 
 class PostProcessKwargs(TypedDict, total=False):
@@ -67,21 +69,21 @@ class PostProcessKwargs(TypedDict, total=False):
     rdf_compute: bool
     rdf_rmax: float
     rdf_nbins: int
-    rdf_elements: MaybeSequence[Union[str, int]]
+    rdf_elements: MaybeSequence[str | int]
     rdf_by_elements: bool
     rdf_start: int
-    rdf_stop: Optional[int]
+    rdf_stop: int | None
     rdf_step: int
-    rdf_output_file: Optional[str]
+    rdf_output_file: str | None
     # VAF
     vaf_compute: bool
     vaf_velocities: bool
     vaf_fft: bool
     vaf_atoms: Sequence[Sequence[int]]
     vaf_start: int
-    vaf_stop: Optional[int]
+    vaf_stop: int | None
     vaf_step: int
-    vaf_output_file: Optional[PathLike]
+    vaf_output_file: PathLike | None
 
 
 @runtime_checkable
@@ -107,9 +109,9 @@ class CorrelationKwargs(TypedDict, total=True):
     """Arguments for on-the-fly correlations <ab>."""
 
     #: observable a in <ab>, with optional args and kwargs
-    a: Union[Observable, tuple[Observable, tuple, dict]]
+    a: Observable | tuple[Observable, tuple, dict]
     #: observable b in <ab>, with optional args and kwargs
-    b: Union[Observable, tuple[Observable, tuple, dict]]
+    b: Observable | tuple[Observable, tuple, dict]
     #: name used for correlation in output
     name: str
     #: blocks used in multi-tau algorithm
diff --git a/janus_core/helpers/log.py b/janus_core/helpers/log.py
index c61ee35e..cfa9845d 100644
--- a/janus_core/helpers/log.py
+++ b/janus_core/helpers/log.py
@@ -1,8 +1,10 @@
 """Configure logger with yaml-styled format."""
 
+from __future__ import annotations
+
 import json
 import logging
-from typing import Literal, Optional
+from typing import Literal
 
 from codecarbon import OfflineEmissionsTracker
 from codecarbon.output import LoggerOutput
@@ -98,12 +100,12 @@ def format(self, record: logging.LogRecord) -> str:
 
 def config_logger(
     name: str,
-    filename: Optional[str] = None,
+    filename: str | None = None,
     level: LogLevel = logging.INFO,
     capture_warnings: bool = True,
     filemode: Literal["r", "w", "a", "x", "r+", "w+", "a+", "x+"] = "w",
     force: bool = True,
-) -> Optional[logging.Logger]:
+) -> logging.Logger | None:
     """
     Configure logger with yaml-styled format.
 
@@ -152,13 +154,13 @@ def config_logger(
 
 
 def config_tracker(
-    janus_logger: Optional[logging.Logger],
+    janus_logger: logging.Logger | None,
     track_carbon: bool = True,
     *,
     country_iso_code: str = "GBR",
     save_to_file: bool = False,
     log_level: Literal["debug", "info", "warning", "error", "critical"] = "critical",
-) -> Optional[OfflineEmissionsTracker]:
+) -> OfflineEmissionsTracker | None:
     """
     Configure codecarbon tracker to log outputs.
 
diff --git a/janus_core/helpers/stats.py b/janus_core/helpers/stats.py
index 14ed89cc..f0f5fbb4 100644
--- a/janus_core/helpers/stats.py
+++ b/janus_core/helpers/stats.py
@@ -1,5 +1,7 @@
 """Module that reads the md stats output timeseries."""
 
+from __future__ import annotations
+
 from collections.abc import Iterator
 from functools import singledispatchmethod
 import re
diff --git a/janus_core/helpers/struct_io.py b/janus_core/helpers/struct_io.py
index 87e4049f..bf877610 100644
--- a/janus_core/helpers/struct_io.py
+++ b/janus_core/helpers/struct_io.py
@@ -1,10 +1,12 @@
 """Module for functions for input and output of structures."""
 
+from __future__ import annotations
+
 from collections.abc import Collection, Sequence
 from copy import copy
 import logging
 from pathlib import Path
-from typing import Any, Optional, get_args
+from typing import Any, get_args
 
 from ase import Atoms
 from ase.io import read, write
@@ -67,8 +69,8 @@ def attach_calculator(
     *,
     arch: Architectures = "mace_mp",
     device: Devices = "cpu",
-    model_path: Optional[PathLike] = None,
-    calc_kwargs: Optional[dict[str, Any]] = None,
+    model_path: PathLike | None = None,
+    calc_kwargs: dict[str, Any] | None = None,
 ) -> None:
     """
     Configure calculator and attach to structure(s).
@@ -103,17 +105,17 @@ def attach_calculator(
 
 
 def input_structs(
-    struct: Optional[MaybeSequence[Atoms]] = None,
+    struct: MaybeSequence[Atoms] | None = None,
     *,
-    struct_path: Optional[PathLike] = None,
-    read_kwargs: Optional[ASEReadArgs] = None,
+    struct_path: PathLike | None = None,
+    read_kwargs: ASEReadArgs | None = None,
     sequence_allowed: bool = True,
     arch: Architectures = "mace_mp",
     device: Devices = "cpu",
-    model_path: Optional[PathLike] = None,
-    calc_kwargs: Optional[dict[str, Any]] = None,
-    set_calc: Optional[bool] = None,
-    logger: Optional[logging.Logger] = None,
+    model_path: PathLike | None = None,
+    calc_kwargs: dict[str, Any] | None = None,
+    set_calc: bool | None = None,
+    logger: logging.Logger | None = None,
 ) -> MaybeSequence[Atoms]:
     """
     Read input structures and/or attach MLIP calculators.
@@ -216,12 +218,12 @@ def input_structs(
 def output_structs(
     images: MaybeSequence[Atoms],
     *,
-    struct_path: Optional[PathLike] = None,
+    struct_path: PathLike | None = None,
     set_info: bool = True,
     write_results: bool = False,
     properties: Collection[Properties] = (),
     invalidate_calc: bool = False,
-    write_kwargs: Optional[ASEWriteArgs] = None,
+    write_kwargs: ASEWriteArgs | None = None,
 ) -> None:
     """
     Copy or move calculated results to Atoms.info dict and/or write structures to file.
diff --git a/janus_core/helpers/utils.py b/janus_core/helpers/utils.py
index 08557257..46f140a1 100644
--- a/janus_core/helpers/utils.py
+++ b/janus_core/helpers/utils.py
@@ -1,10 +1,12 @@
 """Utility functions for janus_core."""
 
+from __future__ import annotations
+
 from abc import ABC
 from collections.abc import Generator, Iterable, Sequence
 from io import StringIO
 from pathlib import Path
-from typing import Any, Literal, Optional, TextIO, Union
+from typing import Any, Literal, TextIO
 
 from ase import Atoms
 from rich.progress import (
@@ -28,9 +30,9 @@ class FileNameMixin(ABC):  # noqa: B024 (abstract-base-class-without-abstract-me
     struct : MaybeSequence[Atoms]
         Structure from which to derive the default name. If `struct` is a sequence,
         the first structure will be used.
-    struct_path : Optional[PathLike]
+    struct_path : PathLike | None
         Path to file containing structures.
-    file_prefix : Optional[PathLike]
+    file_prefix : PathLike | None
         Default prefix to use.
     *additional
         Components to add to default file_prefix (joined by hyphens).
@@ -47,8 +49,8 @@ class FileNameMixin(ABC):  # noqa: B024 (abstract-base-class-without-abstract-me
     def __init__(
         self,
         struct: MaybeSequence[Atoms],
-        struct_path: Optional[PathLike],
-        file_prefix: Optional[PathLike],
+        struct_path: PathLike | None,
+        file_prefix: PathLike | None,
         *additional,
     ) -> None:
         """
@@ -59,9 +61,9 @@ def __init__(
         struct : MaybeSequence[Atoms]
             Structure(s) from which to derive the default name. If `struct` is a
             sequence, the first structure will be used.
-        struct_path : Optional[PathLike]
+        struct_path : PathLike | None
             Path to file structures were read from. Used as default prefix is not None.
-        file_prefix : Optional[PathLike]
+        file_prefix : PathLike | None
             Default prefix to use.
         *additional
             Components to add to default file_prefix (joined by hyphens).
@@ -72,9 +74,9 @@ def __init__(
 
     @staticmethod
     def _get_default_prefix(
-        file_prefix: Optional[PathLike],
+        file_prefix: PathLike | None,
         struct: MaybeSequence[Atoms],
-        struct_path: Optional[PathLike],
+        struct_path: PathLike | None,
         *additional,
     ) -> str:
         """
@@ -82,12 +84,12 @@ def _get_default_prefix(
 
         Parameters
         ----------
-        file_prefix : Optional[PathLike]
+        file_prefix : PathLike | None
             Given file_prefix.
         struct : MaybeSequence[Atoms]
             Structure(s) from which to derive the default name. If `struct` is a
             sequence, the first structure will be used.
-        struct_path : Optional[PathLike]
+        struct_path : PathLike | None
             Path to file containing structures.
         *additional
             Components to add to default file_prefix (joined by hyphens).
@@ -114,8 +116,8 @@ def _build_filename(
         self,
         suffix: str,
         *additional,
-        filename: Optional[PathLike] = None,
-        prefix_override: Optional[str] = None,
+        filename: PathLike | None = None,
+        prefix_override: str | None = None,
     ) -> Path:
         """
         Set filename using the file prefix and suffix if not specified otherwise.
@@ -126,7 +128,7 @@ def _build_filename(
             Default suffix to use if `filename` is not specified.
         *additional
             Extra components to add to suffix (joined with hyphens).
-        filename : Optional[PathLike]
+        filename : PathLike | None
             Filename to use, if specified. Default is None.
         prefix_override : Optional[str]
             Replace file_prefix if not None.
@@ -149,7 +151,7 @@ def _build_filename(
         return built_filename
 
 
-def none_to_dict(dictionaries: Sequence[Optional[dict]]) -> Generator[dict, None, None]:
+def none_to_dict(dictionaries: Sequence[dict | None]) -> Generator[dict, None, None]:
     """
     Ensure dictionaries that may be None are dictionaries.
 
@@ -168,13 +170,13 @@ def none_to_dict(dictionaries: Sequence[Optional[dict]]) -> Generator[dict, None
 
 def write_table(
     fmt: Literal["ascii", "csv"],
-    file: Optional[TextIO] = None,
-    units: Optional[dict[str, str]] = None,
-    formats: Optional[dict[str, str]] = None,
+    file: TextIO | None = None,
+    units: dict[str, str] | None = None,
+    formats: dict[str, str] | None = None,
     *,
     print_header: bool = True,
     **columns,
-) -> Optional[StringIO]:
+) -> StringIO | None:
     """
     Dump a table in a standard format.
 
@@ -368,7 +370,7 @@ def _dump_csv(
         print(",".join(map(format, cols, formats)), file=file)
 
 
-def track_progress(sequence: Union[Sequence, Iterable], description: str) -> Iterable:
+def track_progress(sequence: Sequence | Iterable, description: str) -> Iterable:
     """
     Track the progress of iterating over a sequence.
 
diff --git a/janus_core/processing/correlator.py b/janus_core/processing/correlator.py
index f38e1241..39752a82 100644
--- a/janus_core/processing/correlator.py
+++ b/janus_core/processing/correlator.py
@@ -1,7 +1,8 @@
 """Module to correlate scalar data on-the-fly."""
 
+from __future__ import annotations
+
 from collections.abc import Iterable
-from typing import Union
 
 from ase import Atoms
 import numpy as np
@@ -196,8 +197,8 @@ class Correlation:
 
     def __init__(
         self,
-        a: Union[Observable, tuple[Observable, tuple, dict]],
-        b: Union[Observable, tuple[Observable, tuple, dict]],
+        a: Observable | tuple[Observable, tuple, dict],
+        b: Observable | tuple[Observable, tuple, dict],
         name: str,
         blocks: int,
         points: int,
diff --git a/janus_core/processing/observables.py b/janus_core/processing/observables.py
index daec7840..32eee246 100644
--- a/janus_core/processing/observables.py
+++ b/janus_core/processing/observables.py
@@ -1,5 +1,7 @@
 """Module for built-in correlation observables."""
 
+from __future__ import annotations
+
 from ase import Atoms, units
 
 
diff --git a/janus_core/processing/post_process.py b/janus_core/processing/post_process.py
index 9fe7edf0..08af0e8d 100644
--- a/janus_core/processing/post_process.py
+++ b/janus_core/processing/post_process.py
@@ -1,8 +1,9 @@
 """Module for post-processing trajectories."""
 
+from __future__ import annotations
+
 from collections.abc import Sequence
 from itertools import combinations_with_replacement
-from typing import Optional, Union
 
 from ase import Atoms
 from ase.geometry.analysis import Analysis
@@ -45,17 +46,17 @@ def _process_index(index: SliceLike) -> StartStopStep:
 
 def compute_rdf(
     data: MaybeSequence[Atoms],
-    ana: Optional[Analysis] = None,
+    ana: Analysis | None = None,
     /,
     *,
-    filenames: Optional[MaybeSequence[PathLike]] = None,
+    filenames: MaybeSequence[PathLike] | None = None,
     by_elements: bool = False,
     rmax: float = 2.5,
     nbins: int = 50,
-    elements: Optional[MaybeSequence[Union[int, str]]] = None,
+    elements: MaybeSequence[int | str] | None = None,
     index: SliceLike = (0, None, 1),
-    volume: Optional[float] = None,
-) -> Union[NDArray[float64], dict[tuple[str, str], NDArray[float64]]]:
+    volume: float | None = None,
+) -> NDArray[float64] | dict[tuple[str, str] | NDArray[float64]]:
     """
     Compute the rdf of data.
 
@@ -184,12 +185,12 @@ def compute_rdf(
 
 def compute_vaf(
     data: Sequence[Atoms],
-    filenames: Optional[MaybeSequence[PathLike]] = None,
+    filenames: MaybeSequence[PathLike] | None = None,
     *,
     use_velocities: bool = False,
     fft: bool = False,
     index: SliceLike = (0, None, 1),
-    filter_atoms: MaybeSequence[MaybeSequence[Optional[int]]] = ((None),),
+    filter_atoms: MaybeSequence[MaybeSequence[int | None]] = ((None),),
     time_step: float = 1.0,
 ) -> tuple[NDArray[float64], list[NDArray[float64]]]:
     """
diff --git a/janus_core/processing/symmetry.py b/janus_core/processing/symmetry.py
index 058e2d38..1adb332b 100644
--- a/janus_core/processing/symmetry.py
+++ b/janus_core/processing/symmetry.py
@@ -1,5 +1,7 @@
 """Module for functions operating on structure symmetry."""
 
+from __future__ import annotations
+
 from ase import Atoms
 from ase.spacegroup.symmetrize import refine_symmetry
 from spglib import get_spacegroup
diff --git a/janus_core/training/train.py b/janus_core/training/train.py
index 6f9f1d20..6962fce6 100644
--- a/janus_core/training/train.py
+++ b/janus_core/training/train.py
@@ -1,7 +1,9 @@
 """Train MLIP."""
 
+from __future__ import annotations
+
 from pathlib import Path
-from typing import Any, Optional
+from typing import Any
 
 try:
     from mace.cli.run_train import run as run_train
@@ -40,11 +42,11 @@ def check_files_exist(config: dict, req_file_keys: list[PathLike]) -> None:
 
 def train(
     mlip_config: PathLike,
-    req_file_keys: Optional[list[PathLike]] = None,
+    req_file_keys: list[PathLike] | None = None,
     attach_logger: bool = False,
-    log_kwargs: Optional[dict[str, Any]] = None,
+    log_kwargs: dict[str, Any] | None = None,
     track_carbon: bool = True,
-    tracker_kwargs: Optional[dict[str, Any]] = None,
+    tracker_kwargs: dict[str, Any] | None = None,
 ) -> None:
     """
     Run training for MLIP by passing a configuration file to the MLIP's CLI.
diff --git a/pyproject.toml b/pyproject.toml
index 2f5451c5..5beba1b3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -115,7 +115,7 @@ select = [
     # pycodestyle
     "E", "W",
     # Pyflakes
-    "F",
+    "F", "FA",
     # pyupgrade
     "I",
     # pep8-naming
@@ -126,6 +126,7 @@ select = [
 
 [tool.ruff.lint.isort]
 force-sort-within-sections = true
+required-imports = ["from __future__ import annotations"]
 
 [tool.ruff.lint.pydocstyle]
 convention = "numpy"
diff --git a/tests/__init__.py b/tests/__init__.py
index 431588a3..647c1f33 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -1,5 +1,7 @@
 """Tests for janus_core."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 TEST_DIR = Path(__file__).resolve().parent
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 9330d586..d8fe5ce1 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -1,5 +1,7 @@
 """Test commandline interface with no sub-commands."""
 
+from __future__ import annotations
+
 from typer.testing import CliRunner
 
 from janus_core.cli.janus import app
diff --git a/tests/test_correlator.py b/tests/test_correlator.py
index 39bdeaf5..91b390e5 100644
--- a/tests/test_correlator.py
+++ b/tests/test_correlator.py
@@ -1,5 +1,7 @@
 """Test the Correlator."""
 
+from __future__ import annotations
+
 from collections.abc import Iterable
 from pathlib import Path
 
diff --git a/tests/test_descriptors.py b/tests/test_descriptors.py
index c1e1ddc6..2006b30d 100644
--- a/tests/test_descriptors.py
+++ b/tests/test_descriptors.py
@@ -1,5 +1,7 @@
 """Test MLIP desriptors calculations."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 from ase import Atoms
diff --git a/tests/test_descriptors_cli.py b/tests/test_descriptors_cli.py
index 3215770e..cbec3b31 100644
--- a/tests/test_descriptors_cli.py
+++ b/tests/test_descriptors_cli.py
@@ -1,5 +1,7 @@
 """Test descriptors commandline interface."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 from ase.io import read
diff --git a/tests/test_eos.py b/tests/test_eos.py
index 804d4949..d02cd658 100644
--- a/tests/test_eos.py
+++ b/tests/test_eos.py
@@ -1,5 +1,7 @@
 """Test equation of state calculations."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 from ase.eos import EquationOfState
diff --git a/tests/test_eos_cli.py b/tests/test_eos_cli.py
index 6e059100..2a21387d 100644
--- a/tests/test_eos_cli.py
+++ b/tests/test_eos_cli.py
@@ -1,5 +1,7 @@
 """Test eos commandline interface."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 from ase.io import read
diff --git a/tests/test_filenamemixin.py b/tests/test_filenamemixin.py
index 11b15f2e..2de75d91 100644
--- a/tests/test_filenamemixin.py
+++ b/tests/test_filenamemixin.py
@@ -1,5 +1,7 @@
 """Test FileNameMixin functions."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 from ase.io import read
diff --git a/tests/test_geom_opt.py b/tests/test_geom_opt.py
index c42a7641..a37621f3 100644
--- a/tests/test_geom_opt.py
+++ b/tests/test_geom_opt.py
@@ -1,5 +1,7 @@
 """Test geometry optimization."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 from ase.filters import FrechetCellFilter, UnitCellFilter
diff --git a/tests/test_geomopt_cli.py b/tests/test_geomopt_cli.py
index 9b25a265..dd2769f6 100644
--- a/tests/test_geomopt_cli.py
+++ b/tests/test_geomopt_cli.py
@@ -1,5 +1,7 @@
 """Test geomopt commandline interface."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 from ase import Atoms
diff --git a/tests/test_janus.py b/tests/test_janus.py
index 7172f147..ae54e012 100644
--- a/tests/test_janus.py
+++ b/tests/test_janus.py
@@ -1,5 +1,7 @@
 """Test importing janus_core."""
 
+from __future__ import annotations
+
 import janus_core
 
 
diff --git a/tests/test_log.py b/tests/test_log.py
index 5a176272..63a9593c 100644
--- a/tests/test_log.py
+++ b/tests/test_log.py
@@ -1,5 +1,7 @@
 """Test logging module."""
 
+from __future__ import annotations
+
 import yaml
 
 from janus_core.helpers.log import config_logger
diff --git a/tests/test_md.py b/tests/test_md.py
index ef815767..2373c52f 100644
--- a/tests/test_md.py
+++ b/tests/test_md.py
@@ -1,5 +1,7 @@
 """Test molecular dynamics."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 from ase import Atoms
diff --git a/tests/test_md_cli.py b/tests/test_md_cli.py
index 5c6d441a..ef6bfe20 100644
--- a/tests/test_md_cli.py
+++ b/tests/test_md_cli.py
@@ -1,5 +1,7 @@
 """Test md commandline interface."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 from ase import Atoms
diff --git a/tests/test_mlip_calculators.py b/tests/test_mlip_calculators.py
index 6d1c7754..b7c21d23 100644
--- a/tests/test_mlip_calculators.py
+++ b/tests/test_mlip_calculators.py
@@ -1,5 +1,7 @@
 """Test configuration of MLIP calculators."""
 
+from __future__ import annotations
+
 from pathlib import Path
 from zipfile import BadZipFile
 
diff --git a/tests/test_phonons.py b/tests/test_phonons.py
index 9644ce01..f36bc625 100644
--- a/tests/test_phonons.py
+++ b/tests/test_phonons.py
@@ -1,5 +1,7 @@
 """Test phonons calculations."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 from ase.io import read
diff --git a/tests/test_phonons_cli.py b/tests/test_phonons_cli.py
index 4764ebbb..e15dd66a 100644
--- a/tests/test_phonons_cli.py
+++ b/tests/test_phonons_cli.py
@@ -1,5 +1,7 @@
 """Test phonons commandline interface."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 import pytest
diff --git a/tests/test_post_process.py b/tests/test_post_process.py
index b1a3a600..5858627a 100644
--- a/tests/test_post_process.py
+++ b/tests/test_post_process.py
@@ -1,5 +1,7 @@
 """Test post processing."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 from ase.io import read
diff --git a/tests/test_single_point.py b/tests/test_single_point.py
index cf998d8d..c2bc538d 100644
--- a/tests/test_single_point.py
+++ b/tests/test_single_point.py
@@ -1,5 +1,7 @@
 """Test configuration of MLIP calculators."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 from ase.io import read
diff --git a/tests/test_singlepoint_cli.py b/tests/test_singlepoint_cli.py
index b5f89958..f3efde63 100644
--- a/tests/test_singlepoint_cli.py
+++ b/tests/test_singlepoint_cli.py
@@ -1,5 +1,7 @@
 """Test singlepoint commandline interface."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 from ase import Atoms
diff --git a/tests/test_stats.py b/tests/test_stats.py
index 443a180d..c11b1f09 100644
--- a/tests/test_stats.py
+++ b/tests/test_stats.py
@@ -1,5 +1,7 @@
 """Test stats reader."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 import pytest
diff --git a/tests/test_train_cli.py b/tests/test_train_cli.py
index ddde4d20..1db86763 100644
--- a/tests/test_train_cli.py
+++ b/tests/test_train_cli.py
@@ -1,5 +1,7 @@
 """Test train commandline interface."""
 
+from __future__ import annotations
+
 import logging
 from pathlib import Path
 import shutil
diff --git a/tests/test_utils.py b/tests/test_utils.py
index a4130834..c000b6af 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -1,5 +1,7 @@
 """Test utility functions."""
 
+from __future__ import annotations
+
 from pathlib import Path
 
 from ase import Atoms
diff --git a/tests/utils.py b/tests/utils.py
index fd26eaee..acd0188b 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -1,9 +1,10 @@
 """Utility functions for tests."""
 
+from __future__ import annotations
+
 import logging
 from pathlib import Path
 import re
-from typing import Union
 
 from ase import Atoms
 from ase.io import read
@@ -12,7 +13,7 @@
 from janus_core.helpers.janus_types import MaybeSequence, PathLike
 
 
-def read_atoms(path: Path) -> Union[Atoms, None]:
+def read_atoms(path: Path) -> Atoms | None:
     """
     Read Atoms structure file, and delete file regardless of success.