diff --git a/.github/workflows/run_tests.yml b/.github/workflows/run_tests.yml
index 330cdeb..1fee02d 100644
--- a/.github/workflows/run_tests.yml
+++ b/.github/workflows/run_tests.yml
@@ -44,7 +44,7 @@ jobs:
         apt-get update && apt-get install -y git-lfs
         git lfs install
         pip install --upgrade pip
-        pip install -e .[test]
+        pip install -e ".[all,test]"
     - name: Test with pytest
       run: |
         py.test --durations=0 tests/
diff --git a/pyproject.toml b/pyproject.toml
index 5d64209..56c5d0f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -38,16 +38,27 @@ classifiers = [
 ]
 requires-python = ">=3.9,<3.12"
 dependencies = [
-    "py_wake>=2.6.5",
-    "foxes>=1.6.2",
     "windIO @ git+https://github.com/EUFlow/windIO.git",
-    "wayve @ git+https://gitlab.kuleuven.be/TFSO-software/wayve@dev_foxes",
-    "floris @ git+https://github.com/lejeunemax/floris.git@windIO",
     "xarray>=2022.0.0,<2025",
-    "mpmath",
+    "scipy",
+    "pyyaml",
 ]
 
 [project.optional-dependencies]
+pywake = ["py_wake>=2.6.5"]
+foxes = ["foxes>=1.6.2"]
+floris = ["floris @ git+https://github.com/lejeunemax/floris.git@windIO"]
+wayve = [
+    "wayve @ git+https://gitlab.kuleuven.be/TFSO-software/wayve",
+    "mpmath",
+]
+cs = []  # code_saturne is a subprocess, no pip dependency
+all = [
+    "wifa[pywake]",
+    "wifa[foxes]",
+    "wifa[floris]",
+    "wifa[wayve]",
+]
 test = [
     "pytest",
     "pytest-cov",
diff --git a/tests/test_floris.py b/tests/test_floris.py
index 2f8cd8e..1495535 100644
--- a/tests/test_floris.py
+++ b/tests/test_floris.py
@@ -9,12 +9,21 @@
 
 import os
 import shutil
+import sys
 from pathlib import Path
 
-import floris
 import numpy as np
 import pytest
 import xarray as xr
+
+if sys.version_info < (3, 10):
+    pytest.skip("floris requires Python >= 3.10", allow_module_level=True)
+
+pytest.importorskip(
+    "floris", reason="floris not installed, install with: pip install wifa[floris]"
+)
+
+import floris
 from floris.turbine_library import build_cosine_loss_turbine_dict
 from windIO import __path__ as wiop
 from windIO import load_yaml
diff --git a/tests/test_foxes.py b/tests/test_foxes.py
index deb17de..54791a3 100644
--- a/tests/test_foxes.py
+++ b/tests/test_foxes.py
@@ -3,6 +3,12 @@
 from shutil import rmtree
 
 import numpy as np
+import pytest
+
+pytest.importorskip(
+    "foxes", reason="foxes not installed, install with: pip install wifa[foxes]"
+)
+
 from windIO import __path__ as wiop
 from windIO import validate as validate_yaml
 
diff --git a/tests/test_pywake.py b/tests/test_pywake.py
index 3c01eb2..5bd4003 100644
--- a/tests/test_pywake.py
+++ b/tests/test_pywake.py
@@ -4,6 +4,11 @@
 import numpy as np
 import pytest
 import xarray as xr
+
+pytest.importorskip(
+    "py_wake", reason="py_wake not installed, install with: pip install wifa[pywake]"
+)
+
 from py_wake.deficit_models.gaussian import BastankhahGaussian
 from py_wake.examples.data.dtu10mw._dtu10mw import DTU10MW
 from py_wake.examples.data.hornsrev1 import Hornsrev1Site
diff --git a/tests/test_wayve.py b/tests/test_wayve.py
index 902edf0..4957f04 100644
--- a/tests/test_wayve.py
+++ b/tests/test_wayve.py
@@ -1,6 +1,12 @@
 import os
 from pathlib import Path
 
+import pytest
+
+pytest.importorskip(
+    "wayve", reason="wayve not installed, install with: pip install wifa[wayve]"
+)
+
 from windIO import __path__ as wiop
 from windIO import validate as validate_yaml
 
diff --git a/wifa/__init__.py b/wifa/__init__.py
index 88be468..005a376 100644
--- a/wifa/__init__.py
+++ b/wifa/__init__.py
@@ -1,6 +1,7 @@
 # __init__.py
 
 from .cs_api.cs_modules.csLaunch.cs_run_function import run_code_saturne
+from .floris_api import run_floris
 from .foxes_api import run_foxes
 from .main_api import run_api
 from .pywake_api import run_pywake
diff --git a/wifa/_optional.py b/wifa/_optional.py
new file mode 100644
index 0000000..0870f42
--- /dev/null
+++ b/wifa/_optional.py
@@ -0,0 +1,10 @@
+import importlib.util
+
+
+def require(package_name: str, extra_name: str) -> None:
+    """Raise a clear ImportError if an optional dependency is missing."""
+    if importlib.util.find_spec(package_name) is None:
+        raise ImportError(
+            f"'{package_name}' is required for this functionality but is not installed. "
+            f"Install it with: pip install wifa[{extra_name}]"
+        )
diff --git a/wifa/floris_api.py b/wifa/floris_api.py
index b5d5812..7a23c94 100644
--- a/wifa/floris_api.py
+++ b/wifa/floris_api.py
@@ -5,6 +5,8 @@
 import windIO
 from windIO import load_yaml
 
+from wifa._optional import require
+
 if TYPE_CHECKING:
     from floris import FlorisModel
 
@@ -30,6 +32,7 @@ def run_floris(yaml_input):
     - Some advanced windIO properties may not be fully supported. These include:
       blockage_model, rotor_averaging, and axial_induction_model.
     """
+    require("floris", "floris")
 
     from floris import FlorisModel
     from floris.read_windio import TrackedDict
diff --git a/wifa/foxes_api.py b/wifa/foxes_api.py
index 8c97417..09f240a 100644
--- a/wifa/foxes_api.py
+++ b/wifa/foxes_api.py
@@ -3,6 +3,8 @@
 
 from windIO import load_yaml
 
+from wifa._optional import require
+
 
 def run_foxes(
     input_yaml,
@@ -54,6 +56,7 @@ def run_foxes(
         foxes output class
 
     """
+    require("foxes", "foxes")
 
     from foxes.input.yaml import run_dict
     from foxes.input.yaml.windio import read_windio_dict
diff --git a/wifa/pywake_api.py b/wifa/pywake_api.py
index 703f5dd..2f3c02f 100644
--- a/wifa/pywake_api.py
+++ b/wifa/pywake_api.py
@@ -11,6 +11,8 @@
 from windIO import dict_to_netcdf, load_yaml
 from windIO import validate as validate_yaml
 
+from wifa._optional import require
+
 # Define default values for wind_deficit_model parameters
 DEFAULTS = {
     "wind_deficit_model": {
@@ -1052,6 +1054,8 @@ def run_pywake(yaml_input, output_dir="output"):
         float: Total AEP in GWh
     """
     # Step 1: Load and validate configuration
+    require("py_wake", "pywake")
+
     system_dat, output_dir = load_and_validate_config(yaml_input, output_dir)
 
     # Step 2: Create turbine objects
diff --git a/wifa/wayve_api.py b/wifa/wayve_api.py
index 768df92..b933d59 100644
--- a/wifa/wayve_api.py
+++ b/wifa/wayve_api.py
@@ -3,16 +3,18 @@
 import warnings
 from pathlib import Path
 
-import matplotlib.pyplot as plt
-import mpmath
 import numpy as np
 import xarray as xr
 from scipy.interpolate import interp1d
 from scipy.special import gamma as scipy_gamma
 from windIO import load_yaml
 
+from wifa._optional import require
+
 
 def run_wayve(yamlFile, output_dir="output", debug_mode=False):
+    require("wayve", "wayve")
+
     # General APM setup
     from wayve.apm import APM
     from wayve.grid.grid import Stat2Dgrid
@@ -271,6 +273,8 @@ def run_wayve(yamlFile, output_dir="output", debug_mode=False):
 
 def nieuwstadt83_profiles(zh, v, wd, z0=1.0e-1, h=1.5e3, fc=1.0e-4, ust=0.666):
     """Set up the cubic analytical profile from Nieuwstadt (1983), based on hub height velocity information"""
+    import mpmath
+
     # Atmospheric state setup
     from wayve.abl.abl_tools import Cg_cubic, alpha_cubic
 
@@ -393,6 +397,8 @@ def rotate_xy_arrays(xs, ys, angle):
 def ci_fitting(
     zs, ths, l_mo=5.0e3, blh=1.0e3, dh_max=300.0, serz=True, plot_fits=False
 ):
+    import matplotlib.pyplot as plt
+
     # Atmospheric state setup
     from wayve.abl import ci_methods
 
@@ -638,8 +644,6 @@ def wm_coupling_setup(analysis_dat, wake_model):
 
 
 def wake_model_setup(analysis_dat, debug_mode=False):
-    # WAYVE imports
-    from wayve.couplings.foxes_coupling import FoxesWakeModel
     from wayve.forcing.wind_farms.wake_model_coupling.wake_models.lanzilao_merging import (
         Lanzilao,
     )
@@ -666,9 +670,11 @@ def wake_model_setup(analysis_dat, debug_mode=False):
         # Use wake merging method of Lanzilao and Meyers (2021)
         wake_model = Lanzilao(ka=k_a, kb=k_b, eps_beta=ceps)
     elif wake_tool == "foxes":
+        require("foxes", "foxes")
         from foxes import ModelBook
         from foxes.input.yaml.windio.read_attributes import _read_analysis
         from foxes.utils import Dict
+        from wayve.couplings.foxes_coupling import FoxesWakeModel
 
         verbosity = 1 if debug_mode else 0
 
@@ -824,8 +830,9 @@ def flow_io_abl(wind_resource_dat, time_index, zh, h1, dh_max=None, serz=True):
             )
         # Geostrophic wind speed
         z = np.linspace(h, 15.0e3, 1000)
-        U3 = np.trapz(np.interp(z, zs, us), z) / (15.0e3 - h)
-        V3 = np.trapz(np.interp(z, zs, vs), z) / (15.0e3 - h)
+        _trapz = getattr(np, "trapezoid", np.trapz)
+        U3 = _trapz(np.interp(z, zs, us), z) / (15.0e3 - h)
+        V3 = _trapz(np.interp(z, zs, vs), z) / (15.0e3 - h)
     # Upper layer thickness
     h2 = h - h1
     if (