diff --git a/.github/dockerfiles/Dockerfile b/.github/dockerfiles/Dockerfile
new file mode 100644
index 000000000..729e42d07
--- /dev/null
+++ b/.github/dockerfiles/Dockerfile
@@ -0,0 +1,12 @@
+FROM ubuntu:25.04
+
+WORKDIR /esm/
+
+# Install build-time dependencies.
+RUN apt-get update && \
+    apt-get install --yes --no-install-suggests --no-install-recommends \
+      git \
+      locales \
+      libsqlite3-dev \
+      ca-certificates \
+
diff --git a/.github/workflows/esm_tests_computer_workflow.yml b/.github/workflows/esm_tests_computer_workflow.yml
index 12e0e62f3..57820d5fd 100644
--- a/.github/workflows/esm_tests_computer_workflow.yml
+++ b/.github/workflows/esm_tests_computer_workflow.yml
@@ -44,10 +44,12 @@ jobs:
         apt-get install -y git;
         apt-get install -y locales;
         apt-get install -y libsqlite3-dev;
-    - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v4
-      with:
-        python-version: ${{ matrix.python-version }}
+    - name: Install miniforge
+      run: |
+        wget "https://github.com/conda-forge/miniforge/releases/latest/download/Miniforge3-$(uname)-$(uname -m).sh"
+        bash Miniforge3-$(uname)-$(uname -m).sh;
+        mamba create -n esm_tools python=${{ matrix.python-version }};
+        conda activate esm_toolls
     - name: Set locale
       run: |
         locale-gen en_US.UTF-8;