diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
new file mode 100644
index 00000000..a34ea6aa
--- /dev/null
+++ b/.github/workflows/main.yml
@@ -0,0 +1,309 @@
+name: build xo-optionutil + dependencies
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+env:
+  # Customize the CMake build type here (Release, Debug, RelWithDebInfo, etc.)
+  BUILD_TYPE: Release
+
+jobs:
+  build:
+    # The CMake configure and build commands are platform agnostic and should work equally well on Windows or Mac.
+    # You can convert this to a matrix build if you need cross-platform coverage.
+    # See: https://docs.github.com/en/free-pro-team@latest/actions/learn-github-actions/managing-complex-workflows#using-a-build-matrix
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: checkout source
+      uses: actions/checkout@v3
+
+    - name: Install dependencies
+      run: |
+        echo "::group::install catch2"
+        # install catch2.  see
+        #   [[https://stackoverflow.com/questions/57982945/how-to-apt-get-install-in-a-github-actions-workflow]]
+        sudo apt-get install -y catch2
+        echo "::endgroup"
+
+        #echo "::group::install pybind11"
+        #sudo apt-get install -y pybind11-dev
+        #echo "::endgroup"
+
+    # ----------------------------------------------------------------
+
+    - name: clone xo-cmake
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/xo-cmake
+        path: repo/xo-cmake
+
+    - name: build xo-cmake
+      run: |
+        XONAME=xo-cmake
+        XOSRC=repo/${XONAME}
+        BUILDDIR=${{github.workspace}}/build_${XONAME}
+        PREFIX=${{github.workspace}}/local
+
+        echo "::group::configure ${XONAME}"
+        cmake -B ${BUILDDIR} -DCMAKE_INSTALL_PREFIX=${PREFIX} ${XOSRC}
+        echo "::endgroup"
+
+        echo "::group::compile ${XONAME}"
+        cmake --build ${BUILDDIR} --config ${{env.BUILD_TYPE}}
+        echo "::endgroup"
+
+        echo "::group::local install ${XONAME}"
+        cmake --install ${BUILDDIR}
+        echo "::endgroup"
+
+        echo "::group::local dir tree"
+        tree ${PREFIX}
+        echo "::endgroup"
+
+    # ----------------------------------------------------------------
+
+    - name: clone xo-indentlog
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/indentlog
+        path: repo/xo-indentlog
+
+    - name: build xo-indentlog
+      run: |
+        XONAME=xo-indentlog
+        XOSRC=repo/${XONAME}
+        BUILDDIR=${{github.workspace}}/build_${XONAME}
+        PREFIX=${{github.workspace}}/local
+
+        echo "::group::repo dir tree"
+        tree -L 2 repo
+        echo "::endgroup"
+
+        echo "::group::configure ${XONAME}"
+        cmake -B ${BUILDDIR} -DCMAKE_INSTALL_PREFIX=${PREFIX} ${XOSRC}
+        echo "::endgroup"
+
+        echo "::group::compile ${XONAME}"
+        cmake --build ${BUILDDIR} --config ${{env.BUILD_TYPE}} -j
+        echo "::endgroup"
+
+        echo "::group::local install ${XONAME}"
+        cmake --install ${BUILDDIR}
+        echo "::endgroup"
+
+        echo "::group::local dir tree"
+        tree -L 3 ${PREFIX}
+        echo "::endgroup"
+
+    # ----------------------------------------------------------------
+
+    - name: clone xo-refcnt
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/refcnt
+        path: repo/xo-refcnt
+
+    - name: build xo-refcnt
+      run: |
+        XONAME=xo-refcnt
+        XOSRC=repo/${XONAME}
+        BUILDDIR=${{github.workspace}}/build_${XONAME}
+        PREFIX=${{github.workspace}}/local
+
+        echo "::group::repo dir tree"
+        tree -L 2 repo
+        echo "::endgroup"
+
+        echo "::group::configure ${XONAME}"
+        cmake -B ${BUILDDIR} -DCMAKE_INSTALL_PREFIX=${PREFIX} ${XOSRC}
+        echo "::endgroup"
+
+        echo "::group::compile ${XONAME}"
+        cmake --build ${BUILDDIR} --config ${{env.BUILD_TYPE}} -j
+        echo "::endgroup"
+
+        echo "::group::local install ${XONAME}"
+        cmake --install ${BUILDDIR}
+        echo "::endgroup"
+
+        echo "::group::local dir tree"
+        tree -L 3 ${PREFIX}
+        echo "::endgroup"
+
+    # ----------------------------------------------------------------
+
+    - name: clone xo-subsys
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/subsys
+        path: repo/xo-subsys
+
+    - name: build xo-subsys
+      run: |
+        XONAME=xo-subsys
+        XOSRC=repo/${XONAME}
+        BUILDDIR=${{github.workspace}}/build_${XONAME}
+        PREFIX=${{github.workspace}}/local
+
+        echo "::group::repo dir tree"
+        tree -L 2 repo
+        echo "::endgroup"
+
+        echo "::group::configure ${XONAME}"
+        cmake -B ${BUILDDIR} -DCMAKE_INSTALL_PREFIX=${PREFIX} ${XOSRC}
+        echo "::endgroup"
+
+        echo "::group::compile ${XONAME}"
+        cmake --build ${BUILDDIR} --config ${{env.BUILD_TYPE}} -j
+        echo "::endgroup"
+
+        echo "::group::local install ${XONAME}"
+        cmake --install ${BUILDDIR}
+        echo "::endgroup"
+
+        echo "::group::local dir tree"
+        tree -L 3 ${PREFIX}
+        echo "::endgroup"
+
+    # ----------------------------------------------------------------
+
+    - name: clone xo-reflect
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/reflect
+        path: repo/xo-reflect
+
+    - name: build xo-reflect
+      run: |
+        XONAME=xo-reflect
+        XOSRC=repo/${XONAME}
+        BUILDDIR=${{github.workspace}}/build_${XONAME}
+        PREFIX=${{github.workspace}}/local
+
+        echo "::group::repo dir tree"
+        tree -L 2 repo
+        echo "::endgroup"
+
+        echo "::group::configure ${XONAME}"
+        cmake -B ${BUILDDIR} -DCMAKE_INSTALL_PREFIX=${PREFIX} ${XOSRC}
+        echo "::endgroup"
+
+        echo "::group::compile ${XONAME}"
+        cmake --build ${BUILDDIR} --config ${{env.BUILD_TYPE}} -j
+        echo "::endgroup"
+
+        echo "::group::local install ${XONAME}"
+        cmake --install ${BUILDDIR}
+        echo "::endgroup"
+
+        echo "::group::local dir tree"
+        tree -L 3 ${PREFIX}
+        echo "::endgroup"
+
+    # ----------------------------------------------------------------
+
+#    - name: clone xo-callback
+#      uses: actions/checkout@v3
+#      with:
+#        repository: Rconybea/xo-callback
+#        path: repo/xo-callback
+#
+#    - name: build xo-callback
+#      run: |
+#        XONAME=xo-callback
+#        XOSRC=repo/${XONAME}
+#        BUILDDIR=${{github.workspace}}/build_${XONAME}
+#        PREFIX=${{github.workspace}}/local
+#
+#        echo "::group::repo dir tree"
+#        tree -L 2 repo
+#        echo "::endgroup"
+#
+#        echo "::group::configure ${XONAME}"
+#        cmake -B ${BUILDDIR} -DCMAKE_INSTALL_PREFIX=${PREFIX} ${XOSRC}
+#        echo "::endgroup"
+#
+#        echo "::group::compile ${XONAME}"
+#        cmake --build ${BUILDDIR} --config ${{env.BUILD_TYPE}} -j
+#        echo "::endgroup"
+#
+#        echo "::group::local install ${XONAME}"
+#        cmake --install ${BUILDDIR}
+#        echo "::endgroup"
+#
+#        echo "::group::local dir tree"
+#        tree -L 3 ${PREFIX}
+#        echo "::endgroup"
+
+    # ----------------------------------------------------------------
+
+    - name: clone xo-printjson
+      uses: actions/checkout@v3
+      with:
+        repository: Rconybea/xo-printjson
+        path: repo/xo-printjson
+
+    - name: build xo-printjson
+      run: |
+        XONAME=xo-printjson
+        XOSRC=repo/${XONAME}
+        BUILDDIR=${{github.workspace}}/build_${XONAME}
+        PREFIX=${{github.workspace}}/local
+
+        echo "::group::repo dir tree"
+        tree -L 2 repo
+        echo "::endgroup"
+
+        echo "::group::configure ${XONAME}"
+        cmake -B ${BUILDDIR} -DCMAKE_INSTALL_PREFIX=${PREFIX} ${XOSRC}
+        echo "::endgroup"
+
+        echo "::group::compile ${XONAME}"
+        cmake --build ${BUILDDIR} --config ${{env.BUILD_TYPE}} -j
+        echo "::endgroup"
+
+        echo "::group::local install ${XONAME}"
+        cmake --install ${BUILDDIR}
+        echo "::endgroup"
+
+        echo "::group::local dir tree"
+        tree -L 3 ${PREFIX}
+        echo "::endgroup"
+
+    # ----------------------------------------------------------------
+
+    - name: Configure self (kalmanfilter)
+      # Configure CMake in a 'build' subdirectory. `CMAKE_BUILD_TYPE` is only required if you are using a single-configuration generator such as make.
+      # See https://cmake.org/cmake/help/latest/variable/CMAKE_BUILD_TYPE.html?highlight=cmake_build_type
+      run: |
+        XONAME=xo-kalmanfilter
+        BUILDDIR=${{github.workspace}}/build_${XONAME}
+        PREFIX=${{github.workspace}}/local
+
+        echo "::group::repo dir tree"
+        tree -L 2 repo
+        echo "::endgroup"
+
+        echo "::group::configure ${XONAME}"
+        cmake -B ${BUILDDIR} -DCMAKE_MODULE_PATH=${PREFIX}/share/cmake -DCMAKE_PREFIX_PATH=${PREFIX} -DCMAKE_INSTALL_PREFIX=${PREFIX} -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}}
+        echo "::endgroup"
+
+        echo "::group::compile ${XONAME}"
+        cmake --build ${BUILDDIR} --config ${{env.BUILD_TYPE}}
+        echo "::endgroup"
+
+        echo "::group::local install ${XONAME}"
+        cmake --install ${BUILDDIR}
+        echo "::endgroup"
+
+        echo "::group::local dir tree"
+        tree -L 3 ${PREFIX}
+        echo "::endgroup"
+
+        # Execute tests defined by the CMake configuration.
+        # See https://cmake.org/cmake/help/latest/manual/ctest.1.html for more detail
+        (cd ${BUILDDIR} && ctest -C ${{env.BUILD_TYPE}})