diff --git a/.github/workflows/merge.yaml b/.github/workflows/merge.yaml
index b06caaf4..71e1f134 100644
--- a/.github/workflows/merge.yaml
+++ b/.github/workflows/merge.yaml
@@ -30,3 +30,50 @@ jobs:
     with:
       doc_target: "simde_cxx_api"
     secrets: inherit
+
+  platform_matrix:
+    uses: NWChemEx/.github/.github/workflows/platform_matrix.yaml@master
+
+  build_pypi_dist:
+    needs: [tag-commit, platform_matrix]
+    strategy:
+      fail-fast: false
+      matrix:
+        include: ${{ fromJSON(needs.platform_matrix.outputs.release_matrix) }}
+    runs-on: ${{ matrix.os }}
+    steps:
+      - name: Build PyPI Distribution
+        uses: NWChemEx/.github/.github/actions/build_pypi_dist@master
+        with:
+          cibw_build: ${{ matrix.cibw_build }}
+          build_sdist: ${{ matrix.os == 'ubuntu-latest' && 'true' || 'false' }}
+          needs_mpi: "true"
+          needs_boost: "true"
+
+      - name: Upload Distribution Artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: dist-${{ matrix.os }}
+          path: dist/
+
+  # A separate, ubuntu-only publish job (rather than a publish step per
+  # build_pypi_dist leg) because pypa/gh-action-pypi-publish only runs on
+  # Linux, and because PyPI trusted publishing does not support reusable
+  # workflows (this job must be defined directly here, not delegated).
+  deploy_to_pypi:
+    needs: build_pypi_dist
+    runs-on: ubuntu-latest
+    permissions:
+      id-token: write
+    steps:
+      - name: Download All Distributions
+        uses: actions/download-artifact@v4
+        with:
+          pattern: dist-*
+          path: dist
+          merge-multiple: true
+
+      - name: Publish to PyPI
+        uses: pypa/gh-action-pypi-publish@release/v1
+        with:
+          packages-dir: dist/
diff --git a/.github/workflows/nightly.yaml b/.github/workflows/nightly.yaml
index 13a475e6..a751b3e8 100644
--- a/.github/workflows/nightly.yaml
+++ b/.github/workflows/nightly.yaml
@@ -14,13 +14,20 @@
 #
 
 name: Nightly Workflow
+# Re-runs the same build/test jobs pull_request.yaml runs, on a schedule, to
+# catch breakage that originates outside the repo (upstream dependency
+# releases, refreshed GitHub runner images) rather than from a code change.
+# Keep the job list below in sync with pull_request.yaml.
 
 on:
   schedule:
     - cron: "0 6 * * *" # Every day at 06:00 UTC (00:00 CST)
 
 jobs:
-  test_library:
-    uses: NWChemEx/.github/.github/workflows/test_nwx_library.yaml@master
+  test_cmake_build:
+    uses: NWChemEx/.github/.github/workflows/test_nwx_cmake_build.yaml@master
     with:
-      compilers: '["gcc-14", "clang-18"]'
+      run_python_tests: "true"
+
+  test_pip_build:
+    uses: NWChemEx/.github/.github/workflows/test_nwx_pip_build.yaml@master
diff --git a/.github/workflows/pull_request.yaml b/.github/workflows/pull_request.yaml
index 7a6060df..cd68ed1e 100644
--- a/.github/workflows/pull_request.yaml
+++ b/.github/workflows/pull_request.yaml
@@ -13,7 +13,7 @@
 # limitations under the License.
 #
 
-name: .github Pull Request Workflow
+name: Pull Request Workflow
 
 on:
   pull_request:
@@ -29,7 +29,10 @@ jobs:
     with:
       doc_target: "simde_cxx_api"
 
-  test_library:
-    uses: NWChemEx/.github/.github/workflows/test_nwx_library.yaml@master
+  test_cmake_build:
+    uses: NWChemEx/.github/.github/workflows/test_nwx_cmake_build.yaml@master
     with:
-      compilers: '["gcc-14", "clang-18"]'
+      run_python_tests: "true"
+
+  test_pip_build:
+    uses: NWChemEx/.github/.github/workflows/test_nwx_pip_build.yaml@master
diff --git a/.gitignore b/.gitignore
index 09e31b5a..dc56d3f4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -48,3 +48,9 @@ toolchain.cmake
 
 # Commonly install to a subdirectory called install
 install/
+
+# These are MacOS files
+.DS_Store
+
+# Automatically installed in dev mode
+.pre-commit-config.yaml
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6713c36d..1cb14d95 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-# Copyright 2022 NWChemEx-Project
+# Copyright 2026 NWChemEx-Project
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -14,72 +14,39 @@
 
 cmake_minimum_required(VERSION 3.14)
 
-#Downloads common CMake modules used throughout NWChemEx
+# Downloads common CMake modules used throughout NWChemEx. Included before
+# project() so nwx_set_version() is available to compute the version.
 include(cmake/get_nwx_cmake.cmake)
 
-#Sets the version to whatever git thinks it is
-include(get_version_from_git)
-get_version_from_git(simde_version "${CMAKE_CURRENT_LIST_DIR}")
+# Version from scikit-build-core (wheels/sdists) or the latest git tag.
+include(nwx_set_version)
+nwx_set_version(simde_version "${CMAKE_CURRENT_LIST_DIR}")
 project(simde VERSION "${simde_version}" LANGUAGES CXX)
-set(CMAKE_CXX_STANDARD 20)
 
-include(get_cmaize)
-include(nwx_cxx_api_docs)
-
-### Paths ###
-set(SIMDE_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/src")
-set(SIMDE_INCLUDE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/include")
-set(SIMDE_TESTS_DIR "${CMAKE_CURRENT_SOURCE_DIR}/tests")
-set(SIMDE_EXP_DIR "${CMAKE_CURRENT_SOURCE_DIR}/experimental")
-
-nwx_cxx_api_docs("${SIMDE_SOURCE_DIR}" "${SIMDE_INCLUDE_DIR}")
-
-### Options ###
-cmaize_option_list(
-    BUILD_TESTING OFF "Should we build the tests?"
-    BUILD_PYBIND11_PYBINDINGS ON "Build pybind11 python3 bindings?"
-    ENABLE_SIGMA OFF "Should we enable Sigma for uncertainty tracking?"
-)
+include(disable_in_source_builds)
+include(set_default_nwx_options)
 
-include(get_chemist)
-
-include(get_pluginplay)
-
-cmaize_add_library(
-    ${PROJECT_NAME}
-    SOURCE_DIR "${SIMDE_SOURCE_DIR}/${PROJECT_NAME}"
-    INCLUDE_DIRS "${SIMDE_INCLUDE_DIR}/${PROJECT_NAME}"
-    DEPENDS chemist pluginplay
-)
-
-# N.B. this is a no-op if BUILD_PYBIND11_PYBINDINGS is not turned on
-include(nwx_pybind11)
-nwx_add_pybind11_module(
+# Documentation target
+include(nwx_cxx_api_docs)
+nwx_cxx_api_docs("cxx/include" "cxx/src")
+
+# Dependencies: simde is header-only; its C++ deps come from chemist+pluginplay
+include(get_dependencies)
+get_dependencies(chemist pluginplay)
+
+# Build the library (header-only → nwx_library creates INTERFACE target)
+include(nwx_library)
+nwx_library(${PROJECT_NAME} "cxx/include" "cxx/src"
+    chemist pluginplay)
+
+# Python module
+include(nwx_python_module)
+nwx_python_module(${PROJECT_NAME} "cxx/src")
+
+# C++ tests
+include(catch2_tests_from_dir)
+catch2_tests_from_dir(
+    "unit_test_${PROJECT_NAME}"
+    "tests/cxx/unit_tests"
     ${PROJECT_NAME}
-    SOURCE_DIR "${SIMDE_SOURCE_DIR}/python"
-    DEPENDS "${PROJECT_NAME}"
-)
-
-if("${BUILD_TESTING}")
-    set(CXX_TEST_DIR ${SIMDE_TESTS_DIR}/cxx)
-    set(PYTHON_TEST_DIR ${SIMDE_TESTS_DIR}/python)
-
-    include(get_catch2)
-
-    cmaize_add_tests(
-        test_unit_${PROJECT_NAME}
-        SOURCE_DIR "${CXX_TEST_DIR}/unit_tests"
-        INCLUDE_DIRS "${SIMDE_SOURCE_DIR}/${PROJECT_NAME}"
-        DEPENDS Catch2 ${PROJECT_NAME}
-    )
-
-    # N.B. these are no-ops if BUILD_PYBIND11_PYBINDINGS is not turned on
-    nwx_pybind11_tests(
-        py_simde "${PYTHON_TEST_DIR}/unit_tests/test_simde.py"
-        SUBMODULES pluginplay chemist tensorwrapper parallelzone
-    )
-endif()
-
-cmaize_add_package(
-    ${PROJECT_NAME} NAMESPACE nwx::
 )
diff --git a/cmake/get_nwx_cmake.cmake b/cmake/get_nwx_cmake.cmake
index c99674d9..9188ad48 100644
--- a/cmake/get_nwx_cmake.cmake
+++ b/cmake/get_nwx_cmake.cmake
@@ -1,4 +1,4 @@
-# Copyright 2024 NWChemEx-Project
+# Copyright 2024 NWChemEx Community
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -14,18 +14,66 @@
 
 include_guard()
 
+# Puts the shared NWXCMake modules on CMAKE_MODULE_PATH. This runs *before*
+# project() so factored helpers (e.g. nwx_set_version) are available to feed
+# project(VERSION ...).
+#
+# Resolution order:
+#   1. A pip-installed `nwxcmake` package (query it for its cmake/ dir). An
+#      editable install (`pip install -e /path/to/NWXCMake`) points at a local
+#      working copy, so NWXCMake edits are picked up with no git push.
+#   2. Fallback: FetchContent from github.com/NWChemEx/NWXCMake.
 macro(get_nwx_cmake)
-    include(FetchContent)
-    FetchContent_Declare(
-        nwx_cmake
-        GIT_REPOSITORY https://github.com/NWChemEx/NWXCMake
-    )
-    FetchContent_MakeAvailable(nwx_cmake)
-    set(
-        CMAKE_MODULE_PATH "${CMAKE_MODULE_PATH}" "${nwx_cmake_SOURCE_DIR}/cmake"
-        CACHE STRING ""
-        FORCE
-    )
+    if(NOT _NWX_CMAKE_MODULE_DIR)
+        # find_package(Python) needs no enabled language, so it is safe here,
+        # before project(). Request only the interpreter to avoid a dev/compiler
+        # probe this early.
+        find_package(Python QUIET COMPONENTS Interpreter)
+
+        set(_gnc_local_dir "")
+        if(Python_Interpreter_FOUND)
+            execute_process(
+                COMMAND "${Python_EXECUTABLE}" -c
+                    "import nwxcmake,sys;sys.stdout.write(nwxcmake.cmake_dir())"
+                OUTPUT_VARIABLE _gnc_local_dir
+                OUTPUT_STRIP_TRAILING_WHITESPACE
+                RESULT_VARIABLE _gnc_rc
+                ERROR_QUIET
+            )
+            if(NOT _gnc_rc EQUAL 0)
+                set(_gnc_local_dir "")
+            endif()
+        endif()
+
+        if(_gnc_local_dir AND IS_DIRECTORY "${_gnc_local_dir}")
+            message(STATUS
+                "NWXCMake: using local pip package at ${_gnc_local_dir}"
+            )
+            set(_gnc_resolved "${_gnc_local_dir}")
+        else()
+            message(STATUS
+                "NWXCMake: pip package not found; fetching from git"
+            )
+            include(FetchContent)
+            FetchContent_Declare(
+                nwx_cmake
+                GIT_REPOSITORY https://github.com/NWChemEx/NWXCMake
+            )
+            FetchContent_MakeAvailable(nwx_cmake)
+            set(_gnc_resolved "${nwx_cmake_SOURCE_DIR}/cmake")
+        endif()
+
+        # Cache the resolved directory (not CMAKE_MODULE_PATH itself) so
+        # reconfigures are stable. Clear this var (or the build dir) to
+        # re-resolve after switching between the pip and git sources.
+        set(_NWX_CMAKE_MODULE_DIR "${_gnc_resolved}"
+            CACHE INTERNAL "Resolved NWXCMake module directory"
+        )
+    endif()
+
+    # Prepend so NWXCMake modules win; set in the caller's scope (macro), do not
+    # FORCE-cache CMAKE_MODULE_PATH (avoids accumulating stale entries).
+    list(PREPEND CMAKE_MODULE_PATH "${_NWX_CMAKE_MODULE_DIR}")
 endmacro()
 
 get_nwx_cmake()
diff --git a/include/simde/basis_set/atomic_basis_set.hpp b/cxx/include/simde/basis_set/atomic_basis_set.hpp
similarity index 100%
rename from include/simde/basis_set/atomic_basis_set.hpp
rename to cxx/include/simde/basis_set/atomic_basis_set.hpp
diff --git a/include/simde/basis_set/basis_set.hpp b/cxx/include/simde/basis_set/basis_set.hpp
similarity index 100%
rename from include/simde/basis_set/basis_set.hpp
rename to cxx/include/simde/basis_set/basis_set.hpp
diff --git a/include/simde/basis_set/molecular_basis_set.hpp b/cxx/include/simde/basis_set/molecular_basis_set.hpp
similarity index 100%
rename from include/simde/basis_set/molecular_basis_set.hpp
rename to cxx/include/simde/basis_set/molecular_basis_set.hpp
diff --git a/include/simde/chemical_system/Z_from_symbol.hpp b/cxx/include/simde/chemical_system/Z_from_symbol.hpp
similarity index 100%
rename from include/simde/chemical_system/Z_from_symbol.hpp
rename to cxx/include/simde/chemical_system/Z_from_symbol.hpp
diff --git a/include/simde/chemical_system/atom.hpp b/cxx/include/simde/chemical_system/atom.hpp
similarity index 100%
rename from include/simde/chemical_system/atom.hpp
rename to cxx/include/simde/chemical_system/atom.hpp
diff --git a/include/simde/chemical_system/atomic_density_matrix.hpp b/cxx/include/simde/chemical_system/atomic_density_matrix.hpp
similarity index 100%
rename from include/simde/chemical_system/atomic_density_matrix.hpp
rename to cxx/include/simde/chemical_system/atomic_density_matrix.hpp
diff --git a/include/simde/chemical_system/chemical_system.hpp b/cxx/include/simde/chemical_system/chemical_system.hpp
similarity index 100%
rename from include/simde/chemical_system/chemical_system.hpp
rename to cxx/include/simde/chemical_system/chemical_system.hpp
diff --git a/include/simde/chemical_system/molecule_from_string.hpp b/cxx/include/simde/chemical_system/molecule_from_string.hpp
similarity index 100%
rename from include/simde/chemical_system/molecule_from_string.hpp
rename to cxx/include/simde/chemical_system/molecule_from_string.hpp
diff --git a/include/simde/chemical_system/symbol_from_Z.hpp b/cxx/include/simde/chemical_system/symbol_from_Z.hpp
similarity index 100%
rename from include/simde/chemical_system/symbol_from_Z.hpp
rename to cxx/include/simde/chemical_system/symbol_from_Z.hpp
diff --git a/include/simde/density/density.hpp b/cxx/include/simde/density/density.hpp
similarity index 100%
rename from include/simde/density/density.hpp
rename to cxx/include/simde/density/density.hpp
diff --git a/include/simde/density/initial_density.hpp b/cxx/include/simde/density/initial_density.hpp
similarity index 100%
rename from include/simde/density/initial_density.hpp
rename to cxx/include/simde/density/initial_density.hpp
diff --git a/include/simde/derivative/derivative.hpp b/cxx/include/simde/derivative/derivative.hpp
similarity index 100%
rename from include/simde/derivative/derivative.hpp
rename to cxx/include/simde/derivative/derivative.hpp
diff --git a/include/simde/derivative/derivative_pt.hpp b/cxx/include/simde/derivative/derivative_pt.hpp
similarity index 100%
rename from include/simde/derivative/derivative_pt.hpp
rename to cxx/include/simde/derivative/derivative_pt.hpp
diff --git a/include/simde/derivative/nuclear.hpp b/cxx/include/simde/derivative/nuclear.hpp
similarity index 100%
rename from include/simde/derivative/nuclear.hpp
rename to cxx/include/simde/derivative/nuclear.hpp
diff --git a/include/simde/derivative/traits.hpp b/cxx/include/simde/derivative/traits.hpp
similarity index 100%
rename from include/simde/derivative/traits.hpp
rename to cxx/include/simde/derivative/traits.hpp
diff --git a/include/simde/energy/ao_energy.hpp b/cxx/include/simde/energy/ao_energy.hpp
similarity index 100%
rename from include/simde/energy/ao_energy.hpp
rename to cxx/include/simde/energy/ao_energy.hpp
diff --git a/include/simde/energy/electrostatic_energy.hpp b/cxx/include/simde/energy/electrostatic_energy.hpp
similarity index 100%
rename from include/simde/energy/electrostatic_energy.hpp
rename to cxx/include/simde/energy/electrostatic_energy.hpp
diff --git a/include/simde/energy/energy.hpp b/cxx/include/simde/energy/energy.hpp
similarity index 100%
rename from include/simde/energy/energy.hpp
rename to cxx/include/simde/energy/energy.hpp
diff --git a/include/simde/energy/total_energy.hpp b/cxx/include/simde/energy/total_energy.hpp
similarity index 100%
rename from include/simde/energy/total_energy.hpp
rename to cxx/include/simde/energy/total_energy.hpp
diff --git a/include/simde/evaluate_braket/evaluate_braket.hpp b/cxx/include/simde/evaluate_braket/evaluate_braket.hpp
similarity index 100%
rename from include/simde/evaluate_braket/evaluate_braket.hpp
rename to cxx/include/simde/evaluate_braket/evaluate_braket.hpp
diff --git a/include/simde/integration_grids/collocation_matrix.hpp b/cxx/include/simde/integration_grids/collocation_matrix.hpp
similarity index 100%
rename from include/simde/integration_grids/collocation_matrix.hpp
rename to cxx/include/simde/integration_grids/collocation_matrix.hpp
diff --git a/include/simde/integration_grids/integration_grids.hpp b/cxx/include/simde/integration_grids/integration_grids.hpp
similarity index 100%
rename from include/simde/integration_grids/integration_grids.hpp
rename to cxx/include/simde/integration_grids/integration_grids.hpp
diff --git a/include/simde/integration_grids/molecular_grid.hpp b/cxx/include/simde/integration_grids/molecular_grid.hpp
similarity index 100%
rename from include/simde/integration_grids/molecular_grid.hpp
rename to cxx/include/simde/integration_grids/molecular_grid.hpp
diff --git a/include/simde/numerical_methods/eigen_solve.hpp b/cxx/include/simde/numerical_methods/eigen_solve.hpp
similarity index 100%
rename from include/simde/numerical_methods/eigen_solve.hpp
rename to cxx/include/simde/numerical_methods/eigen_solve.hpp
diff --git a/include/simde/numerical_methods/generalized_eigen_solve.hpp b/cxx/include/simde/numerical_methods/generalized_eigen_solve.hpp
similarity index 100%
rename from include/simde/numerical_methods/generalized_eigen_solve.hpp
rename to cxx/include/simde/numerical_methods/generalized_eigen_solve.hpp
diff --git a/include/simde/numerical_methods/numerical_methods.hpp b/cxx/include/simde/numerical_methods/numerical_methods.hpp
similarity index 100%
rename from include/simde/numerical_methods/numerical_methods.hpp
rename to cxx/include/simde/numerical_methods/numerical_methods.hpp
diff --git a/include/simde/optimize/optimize.hpp b/cxx/include/simde/optimize/optimize.hpp
similarity index 100%
rename from include/simde/optimize/optimize.hpp
rename to cxx/include/simde/optimize/optimize.hpp
diff --git a/include/simde/optimize/optimize_energy.hpp b/cxx/include/simde/optimize/optimize_energy.hpp
similarity index 100%
rename from include/simde/optimize/optimize_energy.hpp
rename to cxx/include/simde/optimize/optimize_energy.hpp
diff --git a/include/simde/optimize/optimize_pt.hpp b/cxx/include/simde/optimize/optimize_pt.hpp
similarity index 100%
rename from include/simde/optimize/optimize_pt.hpp
rename to cxx/include/simde/optimize/optimize_pt.hpp
diff --git a/include/simde/quantum_mechanics/fock_operator.hpp b/cxx/include/simde/quantum_mechanics/fock_operator.hpp
similarity index 100%
rename from include/simde/quantum_mechanics/fock_operator.hpp
rename to cxx/include/simde/quantum_mechanics/fock_operator.hpp
diff --git a/include/simde/quantum_mechanics/initial_guess.hpp b/cxx/include/simde/quantum_mechanics/initial_guess.hpp
similarity index 100%
rename from include/simde/quantum_mechanics/initial_guess.hpp
rename to cxx/include/simde/quantum_mechanics/initial_guess.hpp
diff --git a/include/simde/quantum_mechanics/quantum_mechanics.hpp b/cxx/include/simde/quantum_mechanics/quantum_mechanics.hpp
similarity index 100%
rename from include/simde/quantum_mechanics/quantum_mechanics.hpp
rename to cxx/include/simde/quantum_mechanics/quantum_mechanics.hpp
diff --git a/include/simde/quantum_mechanics/update_guess.hpp b/cxx/include/simde/quantum_mechanics/update_guess.hpp
similarity index 100%
rename from include/simde/quantum_mechanics/update_guess.hpp
rename to cxx/include/simde/quantum_mechanics/update_guess.hpp
diff --git a/include/simde/simde.hpp b/cxx/include/simde/simde.hpp
similarity index 100%
rename from include/simde/simde.hpp
rename to cxx/include/simde/simde.hpp
diff --git a/include/simde/types.hpp b/cxx/include/simde/types.hpp
similarity index 100%
rename from include/simde/types.hpp
rename to cxx/include/simde/types.hpp
diff --git a/include/simde/utils/convert.hpp b/cxx/include/simde/utils/convert.hpp
similarity index 100%
rename from include/simde/utils/convert.hpp
rename to cxx/include/simde/utils/convert.hpp
diff --git a/src/python/basis_set/export_basis_set.hpp b/cxx/src/simde/basis_set/export_basis_set.hpp
similarity index 100%
rename from src/python/basis_set/export_basis_set.hpp
rename to cxx/src/simde/basis_set/export_basis_set.hpp
diff --git a/src/python/chemical_system/export_chemical_system.hpp b/cxx/src/simde/chemical_system/export_chemical_system.hpp
similarity index 100%
rename from src/python/chemical_system/export_chemical_system.hpp
rename to cxx/src/simde/chemical_system/export_chemical_system.hpp
diff --git a/src/python/derivative/export_derivative.hpp b/cxx/src/simde/derivative/export_derivative.hpp
similarity index 100%
rename from src/python/derivative/export_derivative.hpp
rename to cxx/src/simde/derivative/export_derivative.hpp
diff --git a/src/python/energy/export_energy.hpp b/cxx/src/simde/energy/export_energy.hpp
similarity index 100%
rename from src/python/energy/export_energy.hpp
rename to cxx/src/simde/energy/export_energy.hpp
diff --git a/src/python/evaluate_braket/export_evaluate_braket.hpp b/cxx/src/simde/evaluate_braket/export_evaluate_braket.hpp
similarity index 100%
rename from src/python/evaluate_braket/export_evaluate_braket.hpp
rename to cxx/src/simde/evaluate_braket/export_evaluate_braket.hpp
diff --git a/src/python/module.cpp b/cxx/src/simde/export_simde.cpp
similarity index 100%
rename from src/python/module.cpp
rename to cxx/src/simde/export_simde.cpp
diff --git a/src/python/export_simde.hpp b/cxx/src/simde/export_simde.hpp
similarity index 100%
rename from src/python/export_simde.hpp
rename to cxx/src/simde/export_simde.hpp
diff --git a/src/python/numerical_methods/export_numerical_methods.hpp b/cxx/src/simde/numerical_methods/export_numerical_methods.hpp
similarity index 100%
rename from src/python/numerical_methods/export_numerical_methods.hpp
rename to cxx/src/simde/numerical_methods/export_numerical_methods.hpp
diff --git a/src/python/optimize/export_optimize.hpp b/cxx/src/simde/optimize/export_optimize.hpp
similarity index 100%
rename from src/python/optimize/export_optimize.hpp
rename to cxx/src/simde/optimize/export_optimize.hpp
diff --git a/src/python/quantum_mechanics/export_quantum_mechanics.hpp b/cxx/src/simde/quantum_mechanics/export_quantum_mechanics.hpp
similarity index 100%
rename from src/python/quantum_mechanics/export_quantum_mechanics.hpp
rename to cxx/src/simde/quantum_mechanics/export_quantum_mechanics.hpp
diff --git a/src/python/utils/export_utils.hpp b/cxx/src/simde/utils/export_utils.hpp
similarity index 100%
rename from src/python/utils/export_utils.hpp
rename to cxx/src/simde/utils/export_utils.hpp
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 00000000..4557adf4
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,52 @@
+# Copyright 2026 NWChemEx-Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+[build-system]
+requires = [
+    "scikit-build-core>=0.10",
+    "setuptools-scm>=8",
+]
+build-backend = "scikit_build_core.build"
+
+[project]
+name = "nwchemex-simde"
+dynamic = ["version"]
+description = "Simulation Domain Extensions for the NWChemEx ecosystem"
+license = { text = "Apache-2.0" }
+requires-python = ">=3.8"
+dependencies = [
+    "pybind11",
+    "nwchemex-nwxcmake>=0.1.0",
+    "nwchemex-pluginplay>=1.0.63",
+    "nwchemex-chemist>=1.3.44",
+]
+
+[project.optional-dependencies]
+dev = ["pytest", "pre-commit"]
+
+[tool.scikit-build]
+metadata.version.provider = "scikit_build_core.metadata.setuptools_scm"
+cmake.build-type = "Release"
+cmake.args = ["-DBUILD_PYBIND11_BINDINGS=ON", "-DBUILD_TESTING=OFF"]
+# All installed content comes from the CMake install; no pure-Python packages.
+wheel.packages = []
+build-dir = "build"
+
+[tool.setuptools_scm]
+fallback_version = "0.0.0"
+
+# For editable (developer) installs, also build the tests.
+[[tool.scikit-build.overrides]]
+if.state = "editable"
+cmake.args = ["-DDEVELOPER_SETUP=ON"]
diff --git a/tests/python/conftest.py b/tests/python/conftest.py
new file mode 100644
index 00000000..d9c5a96e
--- /dev/null
+++ b/tests/python/conftest.py
@@ -0,0 +1,35 @@
+#
+# Copyright 2026 NWChemEx-Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+import parallelzone as pz
+import pytest
+
+
+@pytest.fixture(scope="session", autouse=True)
+def _session_runtime_view():
+    """
+    Holds a single RuntimeView for the whole pytest session.
+
+    MPI may only be initialized/finalized once per process. The first
+    RuntimeView constructed owns that responsibility; individual test
+    modules construct their own RuntimeView per test (e.g. in setUp),
+    which is safe only as long as this session-scoped instance is still
+    alive to keep MPI initialized in between. Without this, pytest would
+    run each test module independently and MPI would be finalized after
+    the first module's tests finished, breaking every module after it.
+    """
+    rv = pz.runtime.RuntimeView()
+    yield rv