diff --git a/.github/workflows/custom-branch.yml b/.github/workflows/custom-branch.yml
new file mode 100644
index 00000000..f19df10e
--- /dev/null
+++ b/.github/workflows/custom-branch.yml
@@ -0,0 +1,90 @@
+name: Run tests on custom libsemigroups branch
+on:
+  workflow_dispatch:
+    inputs:
+      branch:
+        description: "The branch of libsemigroups to clone"
+        required: true
+        type: string
+      fork:
+        description: "The fork of libsemigroups to clone"
+        required: false
+        type: string
+        default: libsemigroups/libsemigroups
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  run-tests:
+    name: "${{ inputs.branch }}, ${{ matrix.os }}, Python 3.13"
+    strategy:
+      fail-fast: false
+      matrix:
+        os: ["ubuntu-latest", "macOS-latest"]
+        include:
+          - os: "ubuntu-latest"
+            compiler: "ccache g++"
+          - os: "macOS-latest"
+            compiler: "ccache clang++"
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@v4
+      - name: "Setup ccache . . ."
+        uses: Chocobo1/setup-ccache-action@v1
+        with:
+          update_packager_index: false
+          install_ccache: true
+      - name: "Create micromamba environment . . ."
+        uses: mamba-org/setup-micromamba@v2
+        with:
+          environment-name: libsemigroups
+          cache-environment: true
+          create-args: >-
+            python=3.13
+            pip
+            fmt
+            eigen
+      - name: "Set environment variables . . ."
+        run: |
+          echo "PKG_CONFIG_PATH=$MAMBA_ROOT_PREFIX/envs/libsemigroups/lib/pkgconfig:$MAMBA_ROOT_PREFIX/envs/libsemigroups/share/pkgconfig:/usr/local/lib/pkgconfig" >> $GITHUB_ENV
+          echo "LD_LIBRARY_PATH=$MAMBA_ROOT_PREFIX/envs/libsemigroups/lib:/usr/local/lib:$LD_LIBRARY_PATH" >> $GITHUB_ENV
+          echo "PATH=$MAMBA_ROOT_PREFIX/envs/libsemigroups/bin:$PATH" >> $GITHUB_ENV
+      - name: "Check Python version . . ."
+        run: |
+          python --version
+          pip --version
+      - name: "Install make requirements (Mac only) . . ."
+        if: ${{ matrix.os == 'macOS-latest' }}
+        run: brew install autoconf automake libtool
+      - name: "Install libsemigroups . . ."
+        run: |
+          git clone --depth 1 --branch ${{ inputs.branch }} https://github.com/${{ inputs.fork }}.git
+          cd libsemigroups
+          ./autogen.sh
+          ./configure CXX="${{ matrix.compiler }}" CXXFLAGS="-O2 -g" --disable-hpcombi --with-external-fmt --with-external-eigen
+          sudo make install -j8
+          ccache -s
+      - name: "Install requirements libsemigroups . . ."
+        run: pip install -r requirements.txt
+      - name: "Pip install libsemigroups_pybind11 . . ."
+        run: |
+          CXX="${{ matrix.compiler }}"  pip install . -v
+          ccache -s
+      - name: "Run tests . . ."
+        run: |
+          python -m pytest -vv tests/test_*.py
+      - name: "Run doc tests . . ."
+        run: |
+          etc/make-doc.sh  # so that all files are generated!
+          cd docs
+          python -m sphinx -b doctest -d _build/doctrees source _build/doctest
+      - name: "Pip install pylint + cpplint . . ."
+        run: |
+          pip install pylint cpplint
+      - name: "Run pylint and cpplint . . ."
+        run: |
+          python -m pylint setup.py tests/*.py libsemigroups_pybind11/*.py
+          python -m cpplint src/*.hpp src/*.cpp
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 1dfaa4b9..b9d43a1e 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -6,55 +6,51 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
-  ubuntu:
+  conda-version:
+    name: "Conda, ${{ matrix.os }}, Python ${{ matrix.python_version }}"
     strategy:
       fail-fast: false
       matrix:
         python_version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
-    runs-on: ubuntu-latest
+        os: ["ubuntu-latest", "macOS-latest"]
+        include:
+          - os: "ubuntu-latest"
+            compiler: "ccache g++"
+          - os: "macOS-latest"
+            compiler: "ccache clang++"
+    runs-on: ${{ matrix.os }}
     timeout-minutes: 15
-    defaults:
-      run:
-        shell: bash -l {0}
-    env:
-      CXX: "ccache g++"
-      CXXFLAGS: "-O2 -g"
     steps:
       - uses: actions/checkout@v4
-      - name: "Create micromamba environment"
-        uses: mamba-org/setup-micromamba@v1
+      - name: "Setup ccache . . ."
+        uses: Chocobo1/setup-ccache-action@v1
+        with:
+          update_packager_index: false
+          install_ccache: true
+      - name: "Create micromamba environment . . ."
+        uses: mamba-org/setup-micromamba@v2
         with:
           environment-name: libsemigroups
+          cache-environment: true
           create-args: >-
             python=${{ matrix.python_version }}
-            fmt
+            pip
+            libsemigroups
       - name: "Set environment variables . . ."
         run: |
           echo "PKG_CONFIG_PATH=$MAMBA_ROOT_PREFIX/envs/libsemigroups/lib/pkgconfig:$MAMBA_ROOT_PREFIX/envs/libsemigroups/share/pkgconfig:/usr/local/lib/pkgconfig" >> $GITHUB_ENV
-          echo "LD_LIBRARY_PATH=$MAMBA_ROOT_PREFIX/envs/libsemigroups/lib:/usr/local/lib" >> $GITHUB_ENV
-      - name: "Setup ccache . . ."
-        uses: Chocobo1/setup-ccache-action@v1
-        with:
-          update_packager_index: false
-          install_ccache: true
-      - name: "Install libsemigroups . . ."
-        run: |
-          git clone --depth 1 --branch stable-3.0 https://github.com/libsemigroups/libsemigroups.git
-          cd libsemigroups
-          ./autogen.sh && ./configure CXX="$CXX" CXXFLAGS="$CXXFLAGS" --disable-hpcombi --with-external-fmt && sudo make install -j8
-          ccache -s
-      - name: "Python version . . ."
+          echo "PATH=$MAMBA_ROOT_PREFIX/envs/libsemigroups/bin:$PATH" >> $GITHUB_ENV
+      - name: "Check Python version . . ."
         run: |
           python --version
-          pip3 --version
-      - name: "Pip installing requirements.txt . . ."
-        run: |
-          pip3 install -r requirements.txt
-      - name: "Pip3 installing libsemigroups_pybind11 . . ."
+          pip --version
+      - name: "Install requirements . . ."
+        run: pip install -r requirements.txt
+      - name: "Pip install libsemigroups_pybind11 . . ."
         run: |
-          echo $PKG_CONFIG_PATH
-          pip3 install . -v
-      - name: "python -m pytest -vv tests/test_*.py . . ."
+          CXX="${{ matrix.compiler }}"  pip install . -v
+          ccache -s
+      - name: "Run tests . . ."
         run: |
           python -m pytest -vv tests/test_*.py
       - name: "Run doc tests . . ."
@@ -62,64 +58,70 @@ jobs:
           etc/make-doc.sh  # so that all files are generated!
           cd docs
           python -m sphinx -b doctest -d _build/doctrees source _build/doctest
-      - name: "Pip3 installing pylint + cpplint . . ."
+      - name: "Pip install pylint + cpplint . . ."
         run: |
           pip3 install pylint cpplint
-      - name: "Running pylint and cpplint . . ."
+      - name: "Run pylint and cpplint . . ."
         run: |
           python -m pylint setup.py tests/*.py libsemigroups_pybind11/*.py
           python -m cpplint src/*.hpp src/*.cpp
-  macosx:
+  main-branch:
+    name: "Main, ${{ matrix.os }}, Python 3.13"
     strategy:
       fail-fast: false
       matrix:
-        python_version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
-    runs-on: macOS-latest
+        os: ["ubuntu-latest", "macOS-latest"]
+        include:
+          - os: "ubuntu-latest"
+            compiler: "ccache g++"
+          - os: "macOS-latest"
+            compiler: "ccache clang++"
+    runs-on: ${{ matrix.os }}
     timeout-minutes: 15
-    env:
-      CXX: "ccache clang++"
-      CXXFLAGS: "-O2 -g"
     steps:
       - uses: actions/checkout@v4
-      - name: "Create micromamba environment"
-        uses: mamba-org/setup-micromamba@v1
+      - name: "Setup ccache . . ."
+        uses: Chocobo1/setup-ccache-action@v1
+        with:
+          update_packager_index: false
+          install_ccache: true
+      - name: "Create micromamba environment . . ."
+        uses: mamba-org/setup-micromamba@v2
         with:
           environment-name: libsemigroups
+          cache-environment: true
           create-args: >-
-            python=${{ matrix.python_version }}
+            python=3.13
+            pip
             fmt
+            eigen
       - name: "Set environment variables . . ."
         run: |
           echo "PKG_CONFIG_PATH=$MAMBA_ROOT_PREFIX/envs/libsemigroups/lib/pkgconfig:$MAMBA_ROOT_PREFIX/envs/libsemigroups/share/pkgconfig:/usr/local/lib/pkgconfig" >> $GITHUB_ENV
-          echo "LD_LIBRARY_PATH=$MAMBA_ROOT_PREFIX/envs/libsemigroups/lib:/usr/local/lib" >> $GITHUB_ENV
+          echo "LD_LIBRARY_PATH=$MAMBA_ROOT_PREFIX/envs/libsemigroups/lib:/usr/local/lib:$LD_LIBRARY_PATH" >> $GITHUB_ENV
           echo "PATH=$MAMBA_ROOT_PREFIX/envs/libsemigroups/bin:$PATH" >> $GITHUB_ENV
-      - name: "Install libsemigroups dependencies . . ."
+      - name: "Check Python version . . ."
+        run: |
+          python --version
+          pip --version
+      - name: "Install make requirements (Mac only) . . ."
+        if: ${{ matrix.os == 'macOS-latest' }}
         run: brew install autoconf automake libtool
-      - name: "Setup ccache . . ."
-        uses: Chocobo1/setup-ccache-action@v1
-        with:
-          update_packager_index: false
-          install_ccache: true
       - name: "Install libsemigroups . . ."
         run: |
-          git clone --depth 1 --branch stable-3.0 https://github.com/libsemigroups/libsemigroups.git
+          git clone --depth 1 --branch main https://github.com/libsemigroups/libsemigroups.git
           cd libsemigroups
-          ./autogen.sh 
-          ./configure CXX="$CXX" CXXFLAGS="$CXXFLAGS" --disable-hpcombi --with-external-fmt
+          ./autogen.sh
+          ./configure CXX="${{ matrix.compiler }}" CXXFLAGS="-O2 -g" --disable-hpcombi --with-external-fmt --with-external-eigen
           sudo make install -j8
           ccache -s
-      - name: "Python version . . ."
+      - name: "Install requirements libsemigroups . . ."
+        run: pip install -r requirements.txt
+      - name: "Pip install libsemigroups_pybind11 . . ."
         run: |
-          python --version
-          pip3 --version
-      - name: "Pip installing requirements.txt . . ."
-        run: |
-          pip3 install -r requirements.txt
-      - name: "Pip3 installing libsemigroups_pybind11 . . ."
-        run: |
-          echo $PKG_CONFIG_PATH
-          pip3 install . -v
-      - name: "python -m pytest -vv tests/test_*.py . . ."
+          CXX="${{ matrix.compiler }}"  pip install . -v
+          ccache -s
+      - name: "Run tests . . ."
         run: |
           python -m pytest -vv tests/test_*.py
       - name: "Run doc tests . . ."
@@ -127,10 +129,10 @@ jobs:
           etc/make-doc.sh  # so that all files are generated!
           cd docs
           python -m sphinx -b doctest -d _build/doctrees source _build/doctest
-      - name: "Pip3 installing pylint + cpplint . . ."
+      - name: "Pip install pylint + cpplint . . ."
         run: |
-          pip3 install pylint cpplint
-      - name: "Running pylint and cpplint . . ."
+          pip install pylint cpplint
+      - name: "Run pylint and cpplint . . ."
         run: |
           python -m pylint setup.py tests/*.py libsemigroups_pybind11/*.py
           python -m cpplint src/*.hpp src/*.cpp