diff --git a/pybamm/parameters/parameter_values.py b/pybamm/parameters/parameter_values.py
index 5a6b992fd..5c782ec34 100644
--- a/pybamm/parameters/parameter_values.py
+++ b/pybamm/parameters/parameter_values.py
@@ -487,9 +487,12 @@ class ParameterValues:
                 # Scalar inherits name (for updating parameters) and domain (for
                 # Broadcast)
                 return pybamm.Scalar(value, name=symbol.name, domain=symbol.domain)
-            elif isinstance(value, pybamm.InputParameter):
-                value.domain = symbol.domain
-                return value
+            elif isinstance(value, pybamm.Symbol):
+                new_value = self.process_symbol(value)
+                new_value.domain = symbol.domain
+                return new_value
+            else:
+                raise TypeError("Cannot process parameter '{}'".format(value))
 
         elif isinstance(symbol, pybamm.FunctionParameter):
             new_children = [self.process_symbol(child) for child in symbol.children]
diff --git a/pybamm/simulation.py b/pybamm/simulation.py
index 9b9f58a08..7d7374ab5 100644
--- a/pybamm/simulation.py
+++ b/pybamm/simulation.py
@@ -422,6 +422,9 @@ class Simulation:
                 pybamm.logger.warning(
                     "Ignoring t_eval as solution times are specified by the experiment"
                 )
+            # Re-initialize solution, e.g. for solving multiple times with different
+            # inputs without having to build the simulation again
+            self._solution = None
             # Step through all experimental conditions
             inputs = inputs or {}
             pybamm.logger.info("Start running experiment")

Parameter fitting with simulation class
Trying to do parameter fitting directly with the simulation class doesn't work. It looks like the inputs don't get updated.
diff --git a/tests/unit/test_experiments/test_simulation_with_experiment.py b/tests/unit/test_experiments/test_simulation_with_experiment.py
index 511b4c354..1569969a3 100644
--- a/tests/unit/test_experiments/test_simulation_with_experiment.py
+++ b/tests/unit/test_experiments/test_simulation_with_experiment.py
@@ -2,6 +2,7 @@
 # Test setting up a simulation with an experiment
 #
 import pybamm
+import numpy as np
 import unittest
 
 
@@ -93,6 +94,27 @@ class TestSimulationExperiment(unittest.TestCase):
         pybamm.set_logging_level("WARNING")
         self.assertIn("event", sim._solution.termination)
 
+    def test_inputs(self):
+        experiment = pybamm.Experiment(
+            ["Discharge at C/2 for 1 hour", "Rest for 1 hour"]
+        )
+        model = pybamm.lithium_ion.SPM()
+
+        # Change a parameter to an input
+        param = pybamm.ParameterValues(chemistry=pybamm.parameter_sets.Marquis2019)
+        param["Negative electrode diffusivity [m2.s-1]"] = (
+            pybamm.InputParameter("Dsn") * 3.9e-14
+        )
+
+        # Solve a first time
+        sim = pybamm.Simulation(model, experiment=experiment, parameter_values=param)
+        sim.solve(inputs={"Dsn": 1})
+        np.testing.assert_array_equal(sim.solution.inputs["Dsn"], 1)
+
+        # Solve again, input should change
+        sim.solve(inputs={"Dsn": 2})
+        np.testing.assert_array_equal(sim.solution.inputs["Dsn"], 2)
+
 
 if __name__ == "__main__":
     print("Add -v for more debug output")
diff --git a/tests/unit/test_parameters/test_parameter_values.py b/tests/unit/test_parameters/test_parameter_values.py
index aa35fdecb..5c82a57ed 100644
--- a/tests/unit/test_parameters/test_parameter_values.py
+++ b/tests/unit/test_parameters/test_parameter_values.py
@@ -235,8 +235,25 @@ class TestParameterValues(unittest.TestCase):
             x = pybamm.Parameter("x")
             parameter_values.process_symbol(x)
 
+    def test_process_parameter_in_parameter(self):
+        parameter_values = pybamm.ParameterValues(
+            {"a": 2, "2a": pybamm.Parameter("a") * 2, "b": np.array([1, 2, 3])}
+        )
+
+        # process 2a parameter
+        a = pybamm.Parameter("2a")
+        processed_a = parameter_values.process_symbol(a)
+        self.assertEqual(processed_a.evaluate(), 4)
+
+        # case where parameter can't be processed
+        b = pybamm.Parameter("b")
+        with self.assertRaisesRegex(TypeError, "Cannot process parameter"):
+            parameter_values.process_symbol(b)
+
     def test_process_input_parameter(self):
-        parameter_values = pybamm.ParameterValues({"a": "[input]", "b": 3})
+        parameter_values = pybamm.ParameterValues(
+            {"a": "[input]", "b": 3, "c times 2": pybamm.InputParameter("c") * 2}
+        )
         # process input parameter
         a = pybamm.Parameter("a")
         processed_a = parameter_values.process_symbol(a)
@@ -252,6 +269,11 @@ class TestParameterValues(unittest.TestCase):
         self.assertIsInstance(processed_add.children[1], pybamm.Scalar)
         self.assertEqual(processed_add.evaluate(inputs={"a": 4}), 7)
 
+        # process complex input parameter
+        c = pybamm.Parameter("c times 2")
+        processed_c = parameter_values.process_symbol(c)
+        self.assertEqual(processed_c.evaluate(inputs={"c": 5}), 10)
+
     def test_process_function_parameter(self):
         parameter_values = pybamm.ParameterValues(
             {

pip install -e .[dev,docs]
parse_log_pytest
requirements.txt
flake8 coverage pytest
apt-get update apt-get install -y gfortran gcc libopenblas-dev liblapack-dev
3.7
requirements.txt
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
aiofiles==22.1.0
aiosqlite==0.19.0
alabaster==0.7.13
anyio==3.7.1
anytree==2.12.1
argon2-cffi==23.1.0
argon2-cffi-bindings==21.2.0
arrow==1.2.3
attrs==24.2.0
autograd==1.6.2
Babel==2.14.0
backcall==0.2.0
beautifulsoup4==4.13.3
black==23.3.0
bleach==6.0.0
cached-property==1.5.2
casadi==3.7.0
certifi @ file:///croot/certifi_1671487769961/work/certifi
cffi==1.15.1
charset-normalizer==3.4.1
click==8.1.8
comm==0.1.4
coverage==7.2.7
cycler==0.11.0
debugpy==1.7.0
decorator==5.1.1
defusedxml==0.7.1
docutils==0.17.1
entrypoints==0.4
exceptiongroup==1.2.2
fastjsonschema==2.21.1
flake8==5.0.4
fonttools==4.38.0
fqdn==1.5.1
future==1.0.0
guzzle-sphinx-theme==0.7.11
idna==3.10
imagesize==1.4.1
importlib-metadata==4.2.0
importlib-resources==5.12.0
iniconfig==2.0.0
ipykernel==6.16.2
ipython==7.34.0
ipython-genutils==0.2.0
ipywidgets==8.1.5
isoduration==20.11.0
jedi==0.19.2
Jinja2==3.1.6
json5==0.9.16
jsonpointer==3.0.0
jsonschema==4.17.3
jupyter==1.1.1
jupyter-console==6.6.3
jupyter-events==0.6.3
jupyter-server==1.24.0
jupyter-ydoc==0.2.5
jupyter_client==7.4.9
jupyter_core==4.12.0
jupyter_server_fileid==0.9.3
jupyter_server_ydoc==0.8.0
jupyterlab==3.5.3
jupyterlab-pygments==0.2.2
jupyterlab_server==2.15.2
jupyterlab_widgets==3.0.13
kiwisolver==1.4.5
MarkupSafe==2.1.5
matplotlib==3.5.3
matplotlib-inline==0.1.6
mccabe==0.7.0
mistune==3.0.2
mypy-extensions==1.0.0
nbclassic==1.2.0
nbclient==0.7.4
nbconvert==7.6.0
nbformat==5.8.0
nest-asyncio==1.6.0
notebook==6.5.7
notebook_shim==0.2.4
numpy==1.21.6
packaging==24.0
pandas==1.3.5
pandocfilters==1.5.1
parso==0.8.4
pathspec==0.11.2
pexpect==4.9.0
pickleshare==0.7.5
Pillow==9.5.0
pkgutil_resolve_name==1.3.10
platformdirs==4.0.0
pluggy==1.2.0
prometheus-client==0.17.1
prompt_toolkit==3.0.48
psutil==7.0.0
ptyprocess==0.7.0
-e git+https://github.com/pybamm-team/PyBaMM.git@8f0a6d82e26c19f5735ed81b55671574af29eb16#egg=pybamm
pycodestyle==2.9.1
pycparser==2.21
pyflakes==2.5.0
Pygments==2.17.2
pyparsing==3.1.4
pyrsistent==0.19.3
pytest==7.4.4
python-dateutil==2.9.0.post0
python-json-logger==3.0.1
pytz==2025.2
PyYAML==6.0.1
pyzmq==26.2.1
requests==2.31.0
rfc3339-validator==0.1.4
rfc3986-validator==0.1.1
scikit-fem==8.1.0
scipy==1.7.3
Send2Trash==1.8.3
six==1.17.0
sniffio==1.3.1
snowballstemmer==2.2.0
soupsieve==2.4.1
Sphinx==4.3.2
sphinxcontrib-applehelp==1.0.2
sphinxcontrib-devhelp==1.0.2
sphinxcontrib-htmlhelp==2.0.0
sphinxcontrib-jsmath==1.0.1
sphinxcontrib-qthelp==1.0.3
sphinxcontrib-serializinghtml==1.1.5
terminado==0.17.1
tinycss2==1.2.1
tomli==2.0.1
tornado==6.2
traitlets==5.9.0
typed-ast==1.5.5
typing_extensions==4.7.1
uri-template==1.3.0
urllib3==2.0.7
wcwidth==0.2.13
webcolors==1.13
webencodings==0.5.1
websocket-client==1.6.1
widgetsnbextension==4.0.13
y-py==0.6.2
ypy-websocket==0.8.4
zipp==3.15.0

name: PyBaMM
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
  - certifi=2022.12.7=py37h06a4308_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=1.1.1w=h7f8727e_0
  - pip=22.3.1=py37h06a4308_0
  - python=3.7.16=h7a1cb2a_0
  - readline=8.2=h5eee18b_0
  - setuptools=65.6.3=py37h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - wheel=0.38.4=py37h06a4308_0
  - xz=5.6.4=h5eee18b_1
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - aiofiles==22.1.0
      - aiosqlite==0.19.0
      - alabaster==0.7.13
      - anyio==3.7.1
      - anytree==2.12.1
      - argon2-cffi==23.1.0
      - argon2-cffi-bindings==21.2.0
      - arrow==1.2.3
      - attrs==24.2.0
      - autograd==1.6.2
      - babel==2.14.0
      - backcall==0.2.0
      - beautifulsoup4==4.13.3
      - black==23.3.0
      - bleach==6.0.0
      - cached-property==1.5.2
      - casadi==3.7.0
      - cffi==1.15.1
      - charset-normalizer==3.4.1
      - click==8.1.8
      - comm==0.1.4
      - coverage==7.2.7
      - cycler==0.11.0
      - debugpy==1.7.0
      - decorator==5.1.1
      - defusedxml==0.7.1
      - docutils==0.17.1
      - entrypoints==0.4
      - exceptiongroup==1.2.2
      - fastjsonschema==2.21.1
      - flake8==5.0.4
      - fonttools==4.38.0
      - fqdn==1.5.1
      - future==1.0.0
      - guzzle-sphinx-theme==0.7.11
      - idna==3.10
      - imagesize==1.4.1
      - importlib-metadata==4.2.0
      - importlib-resources==5.12.0
      - iniconfig==2.0.0
      - ipykernel==6.16.2
      - ipython==7.34.0
      - ipython-genutils==0.2.0
      - ipywidgets==8.1.5
      - isoduration==20.11.0
      - jedi==0.19.2
      - jinja2==3.1.6
      - json5==0.9.16
      - jsonpointer==3.0.0
      - jsonschema==4.17.3
      - jupyter==1.1.1
      - jupyter-client==7.4.9
      - jupyter-console==6.6.3
      - jupyter-core==4.12.0
      - jupyter-events==0.6.3
      - jupyter-server==1.24.0
      - jupyter-server-fileid==0.9.3
      - jupyter-server-ydoc==0.8.0
      - jupyter-ydoc==0.2.5
      - jupyterlab==3.5.3
      - jupyterlab-pygments==0.2.2
      - jupyterlab-server==2.15.2
      - jupyterlab-widgets==3.0.13
      - kiwisolver==1.4.5
      - markupsafe==2.1.5
      - matplotlib==3.5.3
      - matplotlib-inline==0.1.6
      - mccabe==0.7.0
      - mistune==3.0.2
      - mypy-extensions==1.0.0
      - nbclassic==1.2.0
      - nbclient==0.7.4
      - nbconvert==7.6.0
      - nbformat==5.8.0
      - nest-asyncio==1.6.0
      - notebook==6.5.7
      - notebook-shim==0.2.4
      - numpy==1.21.6
      - packaging==24.0
      - pandas==1.3.5
      - pandocfilters==1.5.1
      - parso==0.8.4
      - pathspec==0.11.2
      - pexpect==4.9.0
      - pickleshare==0.7.5
      - pillow==9.5.0
      - pkgutil-resolve-name==1.3.10
      - platformdirs==4.0.0
      - pluggy==1.2.0
      - prometheus-client==0.17.1
      - prompt-toolkit==3.0.48
      - psutil==7.0.0
      - ptyprocess==0.7.0
      - pycodestyle==2.9.1
      - pycparser==2.21
      - pyflakes==2.5.0
      - pygments==2.17.2
      - pyparsing==3.1.4
      - pyrsistent==0.19.3
      - pytest==7.4.4
      - python-dateutil==2.9.0.post0
      - python-json-logger==3.0.1
      - pytz==2025.2
      - pyyaml==6.0.1
      - pyzmq==26.2.1
      - requests==2.31.0
      - rfc3339-validator==0.1.4
      - rfc3986-validator==0.1.1
      - scikit-fem==8.1.0
      - scipy==1.7.3
      - send2trash==1.8.3
      - six==1.17.0
      - sniffio==1.3.1
      - snowballstemmer==2.2.0
      - soupsieve==2.4.1
      - sphinx==4.3.2
      - sphinxcontrib-applehelp==1.0.2
      - sphinxcontrib-devhelp==1.0.2
      - sphinxcontrib-htmlhelp==2.0.0
      - sphinxcontrib-jsmath==1.0.1
      - sphinxcontrib-qthelp==1.0.3
      - sphinxcontrib-serializinghtml==1.1.5
      - terminado==0.17.1
      - tinycss2==1.2.1
      - tomli==2.0.1
      - tornado==6.2
      - traitlets==5.9.0
      - typed-ast==1.5.5
      - typing-extensions==4.7.1
      - uri-template==1.3.0
      - urllib3==2.0.7
      - wcwidth==0.2.13
      - webcolors==1.13
      - webencodings==0.5.1
      - websocket-client==1.6.1
      - widgetsnbextension==4.0.13
      - y-py==0.6.2
      - ypy-websocket==0.8.4
      - zipp==3.15.0
prefix: /opt/conda/envs/PyBaMM

tests/unit/test_experiments/test_simulation_with_experiment.py::TestSimulationExperiment::test_inputs tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_process_input_parameter tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_process_parameter_in_parameter
tests/unit/test_experiments/test_simulation_with_experiment.py::TestSimulationExperiment::test_run_experiment tests/unit/test_experiments/test_simulation_with_experiment.py::TestSimulationExperiment::test_run_experiment_breaks_early tests/unit/test_experiments/test_simulation_with_experiment.py::TestSimulationExperiment::test_set_up tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_check_parameter_values tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_evaluate tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_init tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_inplace tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_interpolant_against_function tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_multi_var_function_parameter tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_multi_var_function_with_parameters tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_process_complex_expression tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_process_empty_model tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_process_function_parameter tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_process_inline_function_parameters tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_process_interpolant tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_process_model tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_process_symbol tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_read_parameters_csv tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_repr tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_update tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_update_from_chemistry tests/unit/test_parameters/test_parameter_values.py::TestParameterValues::test_update_model
pybamm/parameters/parameter_values.py pybamm/simulation.py
pybamm/parameters/parameter_values.py pybamm/simulation.py