diff --git a/.github/workflows/extra.yml b/.github/workflows/extra.yml
index 9491bf4dd..8a0c329e1 100644
--- a/.github/workflows/extra.yml
+++ b/.github/workflows/extra.yml
@@ -11,24 +11,24 @@ jobs:
             matrix:
                 os: [ubuntu-latest]
                 mpi-version: [mpich]
-                python-version: ['3.10', '3.11', '3.12', '3.13']
+                python-version: ["py310e", "py311e", "py312e", "py313e", "py314e"]
                 comms-type: [m, l]
                 include:
                     - os: macos-latest
-                      python-version: '3.13'
+                      python-version: "py312e"
                       mpi-version: mpich
                       comms-type: m
                     - os: macos-latest
-                      python-version: '3.13'
+                      python-version: "py312e"
                       mpi-version: mpich
                       comms-type: l
                     - os: ubuntu-latest
-                      python-version: '3.12'
+                      python-version: "py312e"
                       mpi-version: mpich
                       comms-type: t
                     - os: ubuntu-latest
-                      mpi-version: 'openmpi'
-                      python-version: '3.12'
+                      mpi-version: openmpi
+                      python-version: "py312e"
                       comms-type: l
 
         env:
@@ -42,93 +42,58 @@ jobs:
 
         steps:
         - uses: actions/checkout@v6
-        - name: Setup conda - Python ${{ matrix.python-version }}
-          uses: conda-incubator/setup-miniconda@v3
           with:
-            activate-environment: condaenv
-            miniconda-version: 'latest'
-            python-version: ${{ matrix.python-version }}
-            channels: conda-forge
-            channel-priority: strict
-            auto-update-conda: true
-
-        - name: Force-update certifi
-          run: |
-            python --version
-            pip install -I --upgrade certifi
+            lfs: true
 
-        - name: Install Ubuntu compilers
-          if: matrix.os == 'ubuntu-latest'
-          run: |
-            conda install -c conda-forge gcc_linux-64
-            pip install nlopt==2.9.0
+        - name: Checkout lockfile
+          run: git lfs checkout
 
-        # Roundabout solution on macos for proper linking with mpicc
-        - name: Install macOS compilers
-          if: matrix.os == 'macos-latest'
-          run: |
-            conda install clang_osx-64
-            pip install nlopt==2.8.0
-
-        - name: Install mpi4py and MPI from conda
-          run: |
-            conda install mpi4py ${{ matrix.mpi-version }}
-
-        - name: Install generator dependencies
-          run: |
-            conda env update --file install/gen_deps_environment.yml
-
-        - name: Install gpcam and octave # Neither yet support 3.13
-          if: matrix.python-version <= '3.12'
-          run: |
-            pip install gpcam==8.1.13
-            conda install octave
-
-        - name: Install surmise and Tasmanian
-          if: matrix.os == 'ubuntu-latest'
-          run: |
-            pip install --upgrade git+https://github.com/bandframework/surmise.git
-            pip install Tasmanian --user
-
-        - name: Install generator dependencies for Ubuntu tests
-          if: matrix.os == 'ubuntu-latest' && matrix.python-version <= '3.12'
-          run: |
-            pip install scikit-build packaging
+        - uses: prefix-dev/setup-pixi@v0.9.2
+          with:
+            pixi-version: v0.55.0
+            cache: true
+            frozen: true
+            environments: ${{ matrix.python-version }}
+            activate-environment: ${{ matrix.python-version }}
 
         - name: Install other testing dependencies
           run: |
-            pip install -r install/testing_requirements.txt
-            pip install -r install/misc_feature_requirements.txt
-            source install/install_ibcdfo.sh
-            conda install numpy scipy
+            pixi run -e ${{ matrix.python-version }} install/install_ibcdfo.sh
 
         - name: Install libEnsemble, flake8, lock environment
           run: |
             pip install -e .
             flake8 libensemble
 
-        - name: Remove test using octave, gpcam on Python 3.13
-          if: matrix.python-version >= '3.13'
+        - name: Install gpcam
+          if: matrix.python-version != 'py313e' && matrix.python-version != 'py314e'
+          run: |
+            pixi run -e ${{ matrix.python-version }} pip install gpcam==8.1.13
+
+        - name: Remove test using octave, gpcam, globus-compute on Python 3.13
+          if: matrix.python-version == 'py313e' || matrix.python-version == 'py314e'
           run: |
+            rm ./libensemble/tests/unit_tests/test_ufunc_runners.py # needs globus-compute
             rm ./libensemble/tests/regression_tests/test_persistent_fd_param_finder.py # needs octave, which doesn't yet support 3.13
             rm ./libensemble/tests/regression_tests/test_persistent_aposmm_external_localopt.py # needs octave, which doesn't yet support 3.13
             rm ./libensemble/tests/regression_tests/test_gpCAM.py # needs gpcam, which doesn't build on 3.13
 
-        - name: Install redis/proxystore
-          run: |
-            pip install redis
-            pip install proxystore==0.7.0
-
         - name: Start Redis
           if: matrix.os == 'ubuntu-latest'
           uses: supercharge/redis-github-action@v2
           with:
             redis-version: 7
 
-        - name: Run extensive tests
+        - name: Run extensive tests, Ubuntu
+          if: matrix.os == 'ubuntu-latest'
           run: |
            ./libensemble/tests/run_tests.py -e -${{ matrix.comms-type }}
 
+        - name: Run extensive tests, macOS
+          if: matrix.os == 'macos-latest'
+          run: |
+           pixi run -e ${{ matrix.python-version }} ./libensemble/tests/run_tests.py -e -${{ matrix.comms-type }}
+
         - name: Merge coverage
           run: |
             mv libensemble/tests/.cov* .
diff --git a/pixi.lock b/pixi.lock
index d019ac56e..b041bbaf2 100644
--- a/pixi.lock
+++ b/pixi.lock
@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:a758e95c16d5e476bec89fd4351a7dc614057b22b7bd2c65cf982604ab45d4c5
-size 1087911
+oid sha256:633eb036d22ceed4164edea8a3c13870a606c5d04206ef8717fe3ad5792b4f04
+size 1091134
diff --git a/pyproject.toml b/pyproject.toml
index 4549355b6..d9932d722 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -143,6 +143,9 @@ packaging = "*"
 octave = ">=9.4.0,<11"
 pyzmq = ">=26.4.0,<28"
 
+[tool.pixi.feature.extra.target.linux-64.pypi-dependencies]
+tasmanian = ">=8.2, <9"
+
 # Python versions
 [tool.pixi.feature.py310.dependencies]
 python = "3.10.*"
@@ -157,25 +160,25 @@ python = "3.14.*"
 
 # ax-platform only works up to 3.13 on Linux
 [tool.pixi.feature.py310e.target.linux-64.dependencies]
-ax-platform = ">=1.2.1,<2"
+ax-platform = "==0.5.0"
 
 [tool.pixi.feature.py310e.dependencies]
 globus-compute-sdk = ">=4.3.0,<5"
 
 [tool.pixi.feature.py311e.target.linux-64.dependencies]
-ax-platform = ">=1.2.1,<2"
+ax-platform = "==0.5.0"
 
 [tool.pixi.feature.py311e.dependencies]
 globus-compute-sdk = ">=4.3.0,<5"
 
 [tool.pixi.feature.py312e.target.linux-64.dependencies]
-ax-platform = ">=1.2.1,<2"
+ax-platform = "==0.5.0"
 
 [tool.pixi.feature.py312e.dependencies]
 globus-compute-sdk = ">=4.3.0,<5"
 
 [tool.pixi.feature.py313e.target.linux-64.dependencies]
-ax-platform = ">=0.5.0,<0.6"
+ax-platform = "==0.5.0"
 
 [tool.pixi.feature.py314e]
 
@@ -206,6 +209,7 @@ extra = [
   "enchant>=0.0.1,<0.0.2",
   "proxystore>=0.8.3,<0.9",
   "redis>=7.1.0,<8",
+  "surmise>=0.3.0,<0.4",
 ]
 dev = ["wat>=0.7.0,<0.8"]