From 7933a3e4687cff18c811dff18e1a8d8bed024c9e Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Fri, 14 Nov 2025 18:07:23 +0000
Subject: [PATCH 01/20] Created persist-dir-cache.

---
 .../composite/persist-dir-cache/action.yml    | 42 +++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 .github/workflows/composite/persist-dir-cache/action.yml

diff --git a/.github/workflows/composite/persist-dir-cache/action.yml b/.github/workflows/composite/persist-dir-cache/action.yml
new file mode 100644
index 0000000000..5331bd3922
--- /dev/null
+++ b/.github/workflows/composite/persist-dir-cache/action.yml
@@ -0,0 +1,42 @@
+name: "persist-dir-cache"
+description: "Use caching to persist a directory across workflow runs"
+
+inputs:
+  cache_path:
+    description: "path to the directory to cache"
+    required: true
+
+env:
+  CACHE_BUILD: 0
+  CACHE_WEEKS: 2
+
+runs:
+  using: "composite"
+  steps:
+    - id: define-cache-period
+      run: echo "CACHE_PERIOD=$(date +%Y).$(expr $(date +%U) / ${{ env.CACHE_WEEKS }})" >> $GITHUB_OUTPUT
+
+    - id: sanitise-cache-path
+      run: echo "SANITISED_PATH=$(echo '${{ inputs.cache_path }}' | sed 's|/|_|g')" >> $GITHUB_OUTPUT
+
+    - id: define-cache-key
+      run: |
+        OS="${{ runner.os }}"
+        DIR_PATH="${{ steps.sanitise-cache-path.outputs.SANITISED_PATH }}"
+        PERIOD="${{ steps.define-cache-period.outputs.CACHE_PERIOD }}"
+        BUILD="${{ env.CACHE_BUILD }}"
+        CACHE_KEY="${OS}-${DIR_PATH}_cached-p${PERIOD}-b${BUILD}"
+        echo "CACHE_KEY=$CACHE_KEY" >> $GITHUB_ENV
+
+    - id: restore-dir-cache
+      uses: actions/cache/restore@v4
+      with:
+        path: ${{ inputs.cache_path }}
+        key: ${{ env.CACHE_KEY }}
+
+  post:
+    - id: save-dir-cache
+      uses: actions/cache/save@v4
+      with:
+        path: ${{ inputs.cache_path }}
+        key: ${{ env.CACHE_KEY }}

From e7b2fdfb768a3101e07b3e355bf74015a0f71d89 Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Mon, 17 Nov 2025 13:58:14 +0000
Subject: [PATCH 02/20] Refactor conda-pkg-cache.

---
 .github/workflows/ci-tests.yml                |  6 ++--
 .github/workflows/ci-wheels.yml               |  6 ++--
 .../composite/conda-pkg-cache/action.yml      | 32 ++++++++++---------
 .../composite/persist-dir-cache/action.yml    | 20 ++++++------
 4 files changed, 31 insertions(+), 33 deletions(-)

diff --git a/.github/workflows/ci-tests.yml b/.github/workflows/ci-tests.yml
index 5df55143bd..eefb2199b3 100644
--- a/.github/workflows/ci-tests.yml
+++ b/.github/workflows/ci-tests.yml
@@ -73,12 +73,10 @@ jobs:
           env_name: ${{ env.ENV_NAME }}
           version: ${{ env.IRIS_TEST_DATA_VERSION }}
 
+      # Note: this cache is shared across workflows, so sets its own cache period
+      #  and build number.
       - name: "conda package cache"
         uses: ./.github/workflows/composite/conda-pkg-cache
-        with:
-          cache_build: 6
-          cache_period: ${{ env.CACHE_PERIOD }}
-          env_name: ${{ env.ENV_NAME }}
 
       - name: "conda install"
         uses: conda-incubator/setup-miniconda@v3
diff --git a/.github/workflows/ci-wheels.yml b/.github/workflows/ci-wheels.yml
index 7d7eea830b..d84e87f3d3 100644
--- a/.github/workflows/ci-wheels.yml
+++ b/.github/workflows/ci-wheels.yml
@@ -74,12 +74,10 @@ jobs:
         echo "CACHE_PERIOD=$(date +%Y).$(expr $(date +%U) / ${CACHE_WEEKS})" >> ${GITHUB_ENV}
         echo "LOCK_FILE=requirements/locks/py$(echo ${{ matrix.python-version }} | tr -d '.')-linux-64.lock" >> ${GITHUB_ENV}
 
+    # Note: this cache is shared across workflows, so sets its own cache period
+    #  and build number.
     - name: "conda package cache"
       uses: ./.github/workflows/composite/conda-pkg-cache
-      with:
-        cache_build: 0
-        cache_period: ${{ env.CACHE_PERIOD }}
-        env_name: ${{ env.ENV_NAME }}
 
     - name: "conda install"
       uses: conda-incubator/setup-miniconda@v3
diff --git a/.github/workflows/composite/conda-pkg-cache/action.yml b/.github/workflows/composite/conda-pkg-cache/action.yml
index 48c4470e44..98b7e0734c 100644
--- a/.github/workflows/composite/conda-pkg-cache/action.yml
+++ b/.github/workflows/composite/conda-pkg-cache/action.yml
@@ -1,22 +1,24 @@
 name: "conda-pkg-cache"
-description: "cache the conda environment packages"
+description: "standardise conda package cache to ~/conda_pkgs_dir and cache across workflow runs"
 
-inputs:
-  cache_build:
-    description: "conda environment cache build number"
-    required: false
-    default: "0"
-  cache_period:
-    description: "conda environment cache timestamp"
-    required: true
-  env_name:
-    description: "environment name"
-    required: true
+env:
+  # Lets us manually bump the cache to rebuild.
+  CACHE_BUILD: 0
+  # Maximum cache period (in weeks) before forcing a cache refresh.
+  CACHE_WEEKS: 2
 
 runs:
   using: "composite"
   steps:
-    - uses: actions/cache@v4
+    - id: set-pkg-dir
+      run: conda config --add pkgs_dirs ~/conda_pkgs_dir
+
+    - id: set-cache-period
+      run: echo "CACHE_PERIOD=$(date +%Y).$(expr $(date +%U) / ${{ env.CACHE_WEEKS }})" >> $GITHUB_OUTPUT
+
+    - id: conda-pkg-cache
+      uses: ./.github/workflows/composite/persist-dir-cache
       with:
-        path: ~/conda_pkgs_dir
-        key: ${{ runner.os }}-conda-pkgs-${{ inputs.env_name }}-p${{ inputs.cache_period }}-b${{ inputs.cache_build }}
+        cache_path: ~/conda_pkgs_dir
+        cache_build: ${{ env.CACHE_BUILD }}
+        cache_period: ${{ steps.set-cache-period.outputs.CACHE_PERIOD }}
diff --git a/.github/workflows/composite/persist-dir-cache/action.yml b/.github/workflows/composite/persist-dir-cache/action.yml
index 5331bd3922..078214d1a9 100644
--- a/.github/workflows/composite/persist-dir-cache/action.yml
+++ b/.github/workflows/composite/persist-dir-cache/action.yml
@@ -5,17 +5,17 @@ inputs:
   cache_path:
     description: "path to the directory to cache"
     required: true
-
-env:
-  CACHE_BUILD: 0
-  CACHE_WEEKS: 2
+  cache_build:
+    description: "persist dir cache build number"
+    required: false
+    default: "0"
+  cache_period:
+    description: "persist dir cache timestamp"
+    required: true
 
 runs:
   using: "composite"
   steps:
-    - id: define-cache-period
-      run: echo "CACHE_PERIOD=$(date +%Y).$(expr $(date +%U) / ${{ env.CACHE_WEEKS }})" >> $GITHUB_OUTPUT
-
     - id: sanitise-cache-path
       run: echo "SANITISED_PATH=$(echo '${{ inputs.cache_path }}' | sed 's|/|_|g')" >> $GITHUB_OUTPUT
 
@@ -23,9 +23,9 @@ runs:
       run: |
         OS="${{ runner.os }}"
         DIR_PATH="${{ steps.sanitise-cache-path.outputs.SANITISED_PATH }}"
-        PERIOD="${{ steps.define-cache-period.outputs.CACHE_PERIOD }}"
-        BUILD="${{ env.CACHE_BUILD }}"
-        CACHE_KEY="${OS}-${DIR_PATH}_cached-p${PERIOD}-b${BUILD}"
+        PERIOD="${{ inputs.cache_period }}"
+        BUILD="${{ inputs.cache_build }}"
+        CACHE_KEY="${DIR_PATH}_cached-${OS}-p${PERIOD}-b${BUILD}"
         echo "CACHE_KEY=$CACHE_KEY" >> $GITHUB_ENV
 
     - id: restore-dir-cache

From 4ae11cd7b3ad27d4b43d572bfd5d7fc659973c50 Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Mon, 17 Nov 2025 14:28:38 +0000
Subject: [PATCH 03/20] More sensible Conda caching in all workflows.

---
 .github/workflows/benchmarks_run.yml          | 14 +++-----
 .github/workflows/benchmarks_validate.yml     | 17 +++------
 .github/workflows/ci-tests.yml                | 16 ++-------
 .github/workflows/ci-wheels.yml               | 16 ++-------
 .../composite/conda-env-cache/action.yml      | 35 -------------------
 .../workflows/composite/nox-cache/action.yml  | 22 ------------
 6 files changed, 12 insertions(+), 108 deletions(-)
 delete mode 100644 .github/workflows/composite/conda-env-cache/action.yml
 delete mode 100644 .github/workflows/composite/nox-cache/action.yml

diff --git a/.github/workflows/benchmarks_run.yml b/.github/workflows/benchmarks_run.yml
index c91e7841a1..36e7c5e0fb 100644
--- a/.github/workflows/benchmarks_run.yml
+++ b/.github/workflows/benchmarks_run.yml
@@ -66,7 +66,6 @@ jobs:
       IRIS_TEST_DATA_PATH: benchmarks/iris-test-data
       IRIS_TEST_DATA_VERSION: "2.28"
       # Lets us manually bump the cache to rebuild
-      ENV_CACHE_BUILD: "0"
       TEST_DATA_CACHE_BUILD: "2"
 
     steps:
@@ -79,15 +78,10 @@ jobs:
       - name: Install run dependencies
         run: pip install asv nox!=2025.05.01
 
-      - name: Cache environment directories
-        id: cache-env-dir
-        uses: actions/cache@v4
-        with:
-          path: |
-            .nox
-            benchmarks/.asv/env
-            $CONDA/pkgs
-          key: ${{ runner.os }}-${{ hashFiles('requirements/') }}-${{ env.ENV_CACHE_BUILD }}
+      # Note: this cache is shared across workflows, so sets its own cache period
+      #  and build number.
+      - name: Cache Conda package directory
+        uses: ./.github/workflows/composite/conda-pkg-cache
 
       - name: Cache test data directory
         id: cache-test-data
diff --git a/.github/workflows/benchmarks_validate.yml b/.github/workflows/benchmarks_validate.yml
index e3f090b32c..26930b501d 100644
--- a/.github/workflows/benchmarks_validate.yml
+++ b/.github/workflows/benchmarks_validate.yml
@@ -21,10 +21,6 @@ jobs:
   validate:
     runs-on: ubuntu-latest
 
-    env:
-      # Lets us manually bump the cache to rebuild
-      ENV_CACHE_BUILD: "0"
-
     steps:
       - name: Checkout repo
         uses: actions/checkout@v5
@@ -34,15 +30,10 @@ jobs:
       - name: Install run dependencies
         run: pip install asv nox!=2025.05.01
 
-      - name: Cache environment directories
-        id: cache-env-dir
-        uses: actions/cache@v4
-        with:
-          path: |
-            .nox
-            benchmarks/.asv/env
-            $CONDA/pkgs
-          key: ${{ runner.os }}-${{ hashFiles('requirements/') }}-${{ env.ENV_CACHE_BUILD }}
+      # Note: this cache is shared across workflows, so sets its own cache period
+      #  and build number.
+      - name: Cache Conda package directory
+        uses: ./.github/workflows/composite/conda-pkg-cache
 
       - name: Validate setup
         run: nox -s benchmarks -- validate
diff --git a/.github/workflows/ci-tests.yml b/.github/workflows/ci-tests.yml
index eefb2199b3..1f22319332 100644
--- a/.github/workflows/ci-tests.yml
+++ b/.github/workflows/ci-tests.yml
@@ -86,13 +86,8 @@ jobs:
           activate-environment: ${{ env.ENV_NAME }}
           auto-update-conda: false
 
-      - name: "conda environment cache"
-        uses: ./.github/workflows/composite/conda-env-cache
-        with:
-          cache_build: 6
-          cache_period: ${{ env.CACHE_PERIOD }}
-          env_name: ${{ env.ENV_NAME }}
-          install_packages: "cartopy nox pip"
+      - name: "install cartopy + nox + pip"
+        run: conda install --quiet --name ${{ env.ENV_NAME }} cartopy nox pip
 
       - name: "conda info"
         run: |
@@ -106,13 +101,6 @@ jobs:
           cache_period: ${{ env.CACHE_PERIOD }}
           env_name: ${{ env.ENV_NAME }}
 
-      - name: "nox cache"
-        uses: ./.github/workflows/composite/nox-cache
-        with:
-          cache_build: 6
-          env_name: ${{ env.ENV_NAME }}
-          lock_file: ${{ env.LOCK_FILE }}
-
       # TODO: drop use of site.cfg and explicit use of mplrc
       - name: "iris configure"
         env:
diff --git a/.github/workflows/ci-wheels.yml b/.github/workflows/ci-wheels.yml
index d84e87f3d3..c7339ee0ea 100644
--- a/.github/workflows/ci-wheels.yml
+++ b/.github/workflows/ci-wheels.yml
@@ -88,20 +88,8 @@ jobs:
         auto-update-conda: false
         use-only-tar-bz2: true
 
-    - name: "conda environment cache"
-      uses: ./.github/workflows/composite/conda-env-cache
-      with:
-        cache_build: 0
-        cache_period: ${{ env.CACHE_PERIOD }}
-        env_name: ${{ env.ENV_NAME }}
-        install_packages: "nox pip"
-
-    - name: "nox cache"
-      uses: ./.github/workflows/composite/nox-cache
-      with:
-        cache_build: 1
-        env_name: ${{ env.ENV_NAME }}
-        lock_file: ${{ env.LOCK_FILE }}
+    - name: "install nox + pip"
+      run: conda install --quiet --name ${{ env.ENV_NAME }} nox pip
 
     - name: "nox install and test wheel"
       env:
diff --git a/.github/workflows/composite/conda-env-cache/action.yml b/.github/workflows/composite/conda-env-cache/action.yml
deleted file mode 100644
index 15eaaec63c..0000000000
--- a/.github/workflows/composite/conda-env-cache/action.yml
+++ /dev/null
@@ -1,35 +0,0 @@
-name: "conda-env-cache"
-description: "create and cache the conda environment"
-
-#
-# Assumes the environment contains the following variables:
-#   - CONDA
-#
-inputs:
-  cache_build:
-    description: "conda environment cache build number"
-    required: false
-    default: "0"
-  cache_period:
-    description: "conda environment cache timestamp"
-    required: true
-  env_name:
-    description: "environment name"
-    required: true
-  install_packages:
-    description: "conda packages to install into environment"
-    required: true
-
-runs:
-  using: "composite"
-  steps:
-    - uses: actions/cache@v4
-      id: conda-env-cache
-      with:
-        path: ${{ env.CONDA }}/envs/${{ inputs.env_name }}
-        key: ${{ runner.os }}-conda-env-${{ inputs.env_name }}-p${{ inputs.cache_period }}-b${{ inputs.cache_build }}
-
-    - if: steps.conda-env-cache.outputs.cache-hit != 'true'
-      shell: bash
-      run: |
-        conda install --quiet --name ${{ inputs.env_name }} ${{ inputs.install_packages }}
diff --git a/.github/workflows/composite/nox-cache/action.yml b/.github/workflows/composite/nox-cache/action.yml
deleted file mode 100644
index 00387331e7..0000000000
--- a/.github/workflows/composite/nox-cache/action.yml
+++ /dev/null
@@ -1,22 +0,0 @@
-name: "nox cache"
-description: "cache the nox test environments"
-
-inputs:
-  cache_build:
-    description: "nox cache build number"
-    required: false
-    default: "0"
-  env_name:
-    description: "environment name"
-    required: true
-  lock_file:
-    description: "conda-lock environment requirements filename"
-    required: true
-
-runs:
-  using: "composite"
-  steps:
-    - uses: actions/cache@v4
-      with:
-        path: ${{ github.workspace }}/.nox
-        key: ${{ runner.os }}-nox-${{ inputs.env_name }}-s${{ matrix.session }}-py${{ matrix.python-version }}-b${{ inputs.cache_build }}-${{ hashFiles(inputs.lock_file) }}

From 49fdf42882df2890b3e4c3b87183a50f9ae5bb0a Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Mon, 17 Nov 2025 15:30:11 +0000
Subject: [PATCH 04/20] Include missing shell keys.

---
 .github/workflows/composite/conda-pkg-cache/action.yml   | 2 ++
 .github/workflows/composite/persist-dir-cache/action.yml | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/.github/workflows/composite/conda-pkg-cache/action.yml b/.github/workflows/composite/conda-pkg-cache/action.yml
index 98b7e0734c..2aa5a74daf 100644
--- a/.github/workflows/composite/conda-pkg-cache/action.yml
+++ b/.github/workflows/composite/conda-pkg-cache/action.yml
@@ -11,9 +11,11 @@ runs:
   using: "composite"
   steps:
     - id: set-pkg-dir
+      shell: bash
       run: conda config --add pkgs_dirs ~/conda_pkgs_dir
 
     - id: set-cache-period
+      shell: bash
       run: echo "CACHE_PERIOD=$(date +%Y).$(expr $(date +%U) / ${{ env.CACHE_WEEKS }})" >> $GITHUB_OUTPUT
 
     - id: conda-pkg-cache
diff --git a/.github/workflows/composite/persist-dir-cache/action.yml b/.github/workflows/composite/persist-dir-cache/action.yml
index 078214d1a9..a794b9b85d 100644
--- a/.github/workflows/composite/persist-dir-cache/action.yml
+++ b/.github/workflows/composite/persist-dir-cache/action.yml
@@ -17,9 +17,11 @@ runs:
   using: "composite"
   steps:
     - id: sanitise-cache-path
+      shell: bash
       run: echo "SANITISED_PATH=$(echo '${{ inputs.cache_path }}' | sed 's|/|_|g')" >> $GITHUB_OUTPUT
 
     - id: define-cache-key
+      shell: bash
       run: |
         OS="${{ runner.os }}"
         DIR_PATH="${{ steps.sanitise-cache-path.outputs.SANITISED_PATH }}"

From 0d55c0600a72f41e0e441e9710b25c00635b2783 Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Mon, 17 Nov 2025 16:32:05 +0000
Subject: [PATCH 05/20] New approach that is Python specific and copes with
 unavailable post: syntax.

---
 .github/workflows/ci-tests.yml                |  2 ++
 .github/workflows/ci-wheels.yml               |  2 ++
 .../composite/conda-pkg-cache/action.yml      |  6 +++++
 .../composite/persist-dir-cache/action.yml    | 27 +++++++++++--------
 lib/iris/tests/test_coding_standards.py       |  2 ++
 5 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/.github/workflows/ci-tests.yml b/.github/workflows/ci-tests.yml
index 1f22319332..6f33fad585 100644
--- a/.github/workflows/ci-tests.yml
+++ b/.github/workflows/ci-tests.yml
@@ -77,6 +77,8 @@ jobs:
       #  and build number.
       - name: "conda package cache"
         uses: ./.github/workflows/composite/conda-pkg-cache
+        with:
+          python_version: ${{ matrix.python-version }}
 
       - name: "conda install"
         uses: conda-incubator/setup-miniconda@v3
diff --git a/.github/workflows/ci-wheels.yml b/.github/workflows/ci-wheels.yml
index c7339ee0ea..968361ea87 100644
--- a/.github/workflows/ci-wheels.yml
+++ b/.github/workflows/ci-wheels.yml
@@ -78,6 +78,8 @@ jobs:
     #  and build number.
     - name: "conda package cache"
       uses: ./.github/workflows/composite/conda-pkg-cache
+      with:
+        python_version: ${{ matrix.python-version }}
 
     - name: "conda install"
       uses: conda-incubator/setup-miniconda@v3
diff --git a/.github/workflows/composite/conda-pkg-cache/action.yml b/.github/workflows/composite/conda-pkg-cache/action.yml
index 2aa5a74daf..2376c9432d 100644
--- a/.github/workflows/composite/conda-pkg-cache/action.yml
+++ b/.github/workflows/composite/conda-pkg-cache/action.yml
@@ -1,6 +1,12 @@
 name: "conda-pkg-cache"
 description: "standardise conda package cache to ~/conda_pkgs_dir and cache across workflow runs"
 
+inputs:
+  python_version:
+    description: "conda package cache python version"
+    required: false
+    default: "3.13"
+
 env:
   # Lets us manually bump the cache to rebuild.
   CACHE_BUILD: 0
diff --git a/.github/workflows/composite/persist-dir-cache/action.yml b/.github/workflows/composite/persist-dir-cache/action.yml
index a794b9b85d..51e54c62bf 100644
--- a/.github/workflows/composite/persist-dir-cache/action.yml
+++ b/.github/workflows/composite/persist-dir-cache/action.yml
@@ -12,6 +12,10 @@ inputs:
   cache_period:
     description: "persist dir cache timestamp"
     required: true
+  key_suffix:
+    description: "optional suffix to append to the cache key"
+    required: false
+    default: ""
 
 runs:
   using: "composite"
@@ -27,18 +31,19 @@ runs:
         DIR_PATH="${{ steps.sanitise-cache-path.outputs.SANITISED_PATH }}"
         PERIOD="${{ inputs.cache_period }}"
         BUILD="${{ inputs.cache_build }}"
-        CACHE_KEY="${DIR_PATH}_cached-${OS}-p${PERIOD}-b${BUILD}"
+        SUFFIX="${{ inputs.key_suffix }}"
+        CACHE_KEY="${DIR_PATH}_cached-${OS}-p${PERIOD}-b${BUILD}-${SUFFIX}"
         echo "CACHE_KEY=$CACHE_KEY" >> $GITHUB_ENV
 
-    - id: restore-dir-cache
-      uses: actions/cache/restore@v4
-      with:
-        path: ${{ inputs.cache_path }}
-        key: ${{ env.CACHE_KEY }}
-
-  post:
-    - id: save-dir-cache
-      uses: actions/cache/save@v4
+    - id: dir-cache
+      uses: actions/cache@v4
       with:
         path: ${{ inputs.cache_path }}
-        key: ${{ env.CACHE_KEY }}
+        # This pattern allows continual updating of the cache_path with each new
+        #  commit. The most recent cache matching CACHE_KEY will be used, while
+        #  any updates will create a new cache entry specific to the commit SHA,
+        #  which will then be available to the next run as the new most-recent
+        #  cache.
+        key: ${{ env.CACHE_KEY }}-{{ github.sha }}
+        restore-keys: |
+          ${{ env.CACHE_KEY }}
diff --git a/lib/iris/tests/test_coding_standards.py b/lib/iris/tests/test_coding_standards.py
index f51a531721..13abceb858 100644
--- a/lib/iris/tests/test_coding_standards.py
+++ b/lib/iris/tests/test_coding_standards.py
@@ -83,6 +83,7 @@ def test_python_versions():
     nox_file = root_dir / "noxfile.py"
     ci_wheels_file = workflows_dir / "ci-wheels.yml"
     ci_tests_file = workflows_dir / "ci-tests.yml"
+    ci_pkg_cache_file = workflows_dir / "composite" / "conda-pkg-cache" / "action.yml"
     benchmark_runner_file = benchmarks_dir / "bm_runner.py"
 
     text_searches: List[Tuple[Path, str]] = [
@@ -107,6 +108,7 @@ def test_python_versions():
                 f'{" " * 8}session: ["doctest", "gallery"]'
             ),
         ),
+        (ci_pkg_cache_file, f'default: "{latest_supported}"'),
         (benchmark_runner_file, f'python_version = "{latest_supported}"'),
     ]
 

From 40a0f529eb5de7edd901972fb3b265338422b80f Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Mon, 17 Nov 2025 16:35:51 +0000
Subject: [PATCH 06/20] Use Python version as key_suffix.

---
 .github/workflows/composite/conda-pkg-cache/action.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.github/workflows/composite/conda-pkg-cache/action.yml b/.github/workflows/composite/conda-pkg-cache/action.yml
index 2376c9432d..671b22eb8d 100644
--- a/.github/workflows/composite/conda-pkg-cache/action.yml
+++ b/.github/workflows/composite/conda-pkg-cache/action.yml
@@ -30,3 +30,4 @@ runs:
         cache_path: ~/conda_pkgs_dir
         cache_build: ${{ env.CACHE_BUILD }}
         cache_period: ${{ steps.set-cache-period.outputs.CACHE_PERIOD }}
+        key_suffix: "py${{ inputs.python_version }}"

From 2d18e4674a9ecbc8a8f7758972a34e38d2e88314 Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Mon, 17 Nov 2025 16:38:38 +0000
Subject: [PATCH 07/20] Minor corrections.

---
 .github/workflows/composite/conda-pkg-cache/action.yml   | 2 +-
 .github/workflows/composite/persist-dir-cache/action.yml | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/composite/conda-pkg-cache/action.yml b/.github/workflows/composite/conda-pkg-cache/action.yml
index 671b22eb8d..717e305451 100644
--- a/.github/workflows/composite/conda-pkg-cache/action.yml
+++ b/.github/workflows/composite/conda-pkg-cache/action.yml
@@ -9,7 +9,7 @@ inputs:
 
 env:
   # Lets us manually bump the cache to rebuild.
-  CACHE_BUILD: 0
+  CACHE_BUILD: "0"
   # Maximum cache period (in weeks) before forcing a cache refresh.
   CACHE_WEEKS: 2
 
diff --git a/.github/workflows/composite/persist-dir-cache/action.yml b/.github/workflows/composite/persist-dir-cache/action.yml
index 51e54c62bf..ae521754b5 100644
--- a/.github/workflows/composite/persist-dir-cache/action.yml
+++ b/.github/workflows/composite/persist-dir-cache/action.yml
@@ -44,6 +44,6 @@ runs:
         #  any updates will create a new cache entry specific to the commit SHA,
         #  which will then be available to the next run as the new most-recent
         #  cache.
-        key: ${{ env.CACHE_KEY }}-{{ github.sha }}
+        key: ${{ env.CACHE_KEY }}-${{ github.sha }}
         restore-keys: |
           ${{ env.CACHE_KEY }}

From d286c762788315df7cb866d0be1a6588252ad9a5 Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Mon, 17 Nov 2025 16:45:30 +0000
Subject: [PATCH 08/20] Fix CACHE_BUILD and CACHE_WEEKS handling.

---
 .../workflows/composite/conda-pkg-cache/action.yml    | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/composite/conda-pkg-cache/action.yml b/.github/workflows/composite/conda-pkg-cache/action.yml
index 717e305451..f0aa2ef88e 100644
--- a/.github/workflows/composite/conda-pkg-cache/action.yml
+++ b/.github/workflows/composite/conda-pkg-cache/action.yml
@@ -8,8 +8,6 @@ inputs:
     default: "3.13"
 
 env:
-  # Lets us manually bump the cache to rebuild.
-  CACHE_BUILD: "0"
   # Maximum cache period (in weeks) before forcing a cache refresh.
   CACHE_WEEKS: 2
 
@@ -22,12 +20,17 @@ runs:
 
     - id: set-cache-period
       shell: bash
-      run: echo "CACHE_PERIOD=$(date +%Y).$(expr $(date +%U) / ${{ env.CACHE_WEEKS }})" >> $GITHUB_OUTPUT
+      env:
+        CACHE_WEEKS: ${{ env.CACHE_WEEKS }}
+      run: echo "CACHE_PERIOD=$(date +%Y).$(expr $(date +%U) / ${CACHE_WEEKS})" >> $GITHUB_OUTPUT
 
     - id: conda-pkg-cache
       uses: ./.github/workflows/composite/persist-dir-cache
+      env:
+        CACHE_BUILD: ${{ env.CACHE_BUILD }}
       with:
         cache_path: ~/conda_pkgs_dir
-        cache_build: ${{ env.CACHE_BUILD }}
+        # Lets us manually bump the cache to rebuild.
+        cache_build: 0
         cache_period: ${{ steps.set-cache-period.outputs.CACHE_PERIOD }}
         key_suffix: "py${{ inputs.python_version }}"

From 210f953e024c559a3011c204ac928267cb4f985f Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Mon, 17 Nov 2025 16:49:40 +0000
Subject: [PATCH 09/20] More fixes for CACHE_WEEKS.

---
 .github/workflows/composite/conda-pkg-cache/action.yml | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/.github/workflows/composite/conda-pkg-cache/action.yml b/.github/workflows/composite/conda-pkg-cache/action.yml
index f0aa2ef88e..b4ac914414 100644
--- a/.github/workflows/composite/conda-pkg-cache/action.yml
+++ b/.github/workflows/composite/conda-pkg-cache/action.yml
@@ -7,10 +7,6 @@ inputs:
     required: false
     default: "3.13"
 
-env:
-  # Maximum cache period (in weeks) before forcing a cache refresh.
-  CACHE_WEEKS: 2
-
 runs:
   using: "composite"
   steps:
@@ -21,7 +17,8 @@ runs:
     - id: set-cache-period
       shell: bash
       env:
-        CACHE_WEEKS: ${{ env.CACHE_WEEKS }}
+        # Maximum cache period (in weeks) before forcing a cache refresh.
+        CACHE_WEEKS: 2
       run: echo "CACHE_PERIOD=$(date +%Y).$(expr $(date +%U) / ${CACHE_WEEKS})" >> $GITHUB_OUTPUT
 
     - id: conda-pkg-cache

From fea533a93b57c59ea3f699d82db3d3a68a7d5d76 Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Mon, 17 Nov 2025 17:04:07 +0000
Subject: [PATCH 10/20] Work around actions/runner#2009 .

---
 .github/workflows/composite/persist-dir-cache/action.yml | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/composite/persist-dir-cache/action.yml b/.github/workflows/composite/persist-dir-cache/action.yml
index ae521754b5..831df36212 100644
--- a/.github/workflows/composite/persist-dir-cache/action.yml
+++ b/.github/workflows/composite/persist-dir-cache/action.yml
@@ -20,6 +20,12 @@ inputs:
 runs:
   using: "composite"
   steps:
+    # Work around bug where inputs.cache_path is unavailable for the post-cache
+    #  step. https://github.com/actions/runner/issues/2009
+    - id: store-path
+      shell: bash
+      run: echo "CACHE_PATH=${{ inputs.cache_path }}" >> $GITHUB_ENV
+
     - id: sanitise-cache-path
       shell: bash
       run: echo "SANITISED_PATH=$(echo '${{ inputs.cache_path }}' | sed 's|/|_|g')" >> $GITHUB_OUTPUT
@@ -38,7 +44,7 @@ runs:
     - id: dir-cache
       uses: actions/cache@v4
       with:
-        path: ${{ inputs.cache_path }}
+        path: ${{ env.CACHE_PATH }}
         # This pattern allows continual updating of the cache_path with each new
         #  commit. The most recent cache matching CACHE_KEY will be used, while
         #  any updates will create a new cache entry specific to the commit SHA,

From 8e3ffc721143afd4de6a67d31ad5fd9274c2d1f0 Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Mon, 17 Nov 2025 17:37:28 +0000
Subject: [PATCH 11/20] More traditional hashing solution.

---
 .../composite/conda-pkg-cache/action.yml      | 33 +++++++----
 .../composite/persist-dir-cache/action.yml    | 55 -------------------
 2 files changed, 21 insertions(+), 67 deletions(-)
 delete mode 100644 .github/workflows/composite/persist-dir-cache/action.yml

diff --git a/.github/workflows/composite/conda-pkg-cache/action.yml b/.github/workflows/composite/conda-pkg-cache/action.yml
index b4ac914414..4719bb6aa9 100644
--- a/.github/workflows/composite/conda-pkg-cache/action.yml
+++ b/.github/workflows/composite/conda-pkg-cache/action.yml
@@ -10,10 +10,6 @@ inputs:
 runs:
   using: "composite"
   steps:
-    - id: set-pkg-dir
-      shell: bash
-      run: conda config --add pkgs_dirs ~/conda_pkgs_dir
-
     - id: set-cache-period
       shell: bash
       env:
@@ -21,13 +17,26 @@ runs:
         CACHE_WEEKS: 2
       run: echo "CACHE_PERIOD=$(date +%Y).$(expr $(date +%U) / ${CACHE_WEEKS})" >> $GITHUB_OUTPUT
 
-    - id: conda-pkg-cache
-      uses: ./.github/workflows/composite/persist-dir-cache
+    - id: define-cache-key
+      shell: bash
       env:
-        CACHE_BUILD: ${{ env.CACHE_BUILD }}
-      with:
-        cache_path: ~/conda_pkgs_dir
         # Lets us manually bump the cache to rebuild.
-        cache_build: 0
-        cache_period: ${{ steps.set-cache-period.outputs.CACHE_PERIOD }}
-        key_suffix: "py${{ inputs.python_version }}"
+        CACHE_BUILD: "0"
+      run: |
+        OS="${{ runner.os }}"
+        PERIOD="${{ steps.set-cache-period.outputs.CACHE_PERIOD }}"
+        BUILD="${{ env.CACHE_BUILD }}"
+        PY="${{ inputs.python_version }}"
+        REQ="${{ hashFiles('requirements/locks/**') }}"
+        CACHE_KEY="$conda_pkgs_dir-${OS}-p${PERIOD}-b${BUILD}-py${PY}-${REQ}"
+        echo "CACHE_KEY=$CACHE_KEY" >> $GITHUB_ENV
+
+    - id: set-pkg-dir
+      shell: bash
+      run: conda config --add pkgs_dirs ~/conda_pkgs_dir
+
+    - id: conda-pkg-cache
+      uses: actions/cache@v4
+      with:
+        path: ~/conda_pkgs_dir
+        key: ${{ env.CACHE_KEY }}
diff --git a/.github/workflows/composite/persist-dir-cache/action.yml b/.github/workflows/composite/persist-dir-cache/action.yml
deleted file mode 100644
index 831df36212..0000000000
--- a/.github/workflows/composite/persist-dir-cache/action.yml
+++ /dev/null
@@ -1,55 +0,0 @@
-name: "persist-dir-cache"
-description: "Use caching to persist a directory across workflow runs"
-
-inputs:
-  cache_path:
-    description: "path to the directory to cache"
-    required: true
-  cache_build:
-    description: "persist dir cache build number"
-    required: false
-    default: "0"
-  cache_period:
-    description: "persist dir cache timestamp"
-    required: true
-  key_suffix:
-    description: "optional suffix to append to the cache key"
-    required: false
-    default: ""
-
-runs:
-  using: "composite"
-  steps:
-    # Work around bug where inputs.cache_path is unavailable for the post-cache
-    #  step. https://github.com/actions/runner/issues/2009
-    - id: store-path
-      shell: bash
-      run: echo "CACHE_PATH=${{ inputs.cache_path }}" >> $GITHUB_ENV
-
-    - id: sanitise-cache-path
-      shell: bash
-      run: echo "SANITISED_PATH=$(echo '${{ inputs.cache_path }}' | sed 's|/|_|g')" >> $GITHUB_OUTPUT
-
-    - id: define-cache-key
-      shell: bash
-      run: |
-        OS="${{ runner.os }}"
-        DIR_PATH="${{ steps.sanitise-cache-path.outputs.SANITISED_PATH }}"
-        PERIOD="${{ inputs.cache_period }}"
-        BUILD="${{ inputs.cache_build }}"
-        SUFFIX="${{ inputs.key_suffix }}"
-        CACHE_KEY="${DIR_PATH}_cached-${OS}-p${PERIOD}-b${BUILD}-${SUFFIX}"
-        echo "CACHE_KEY=$CACHE_KEY" >> $GITHUB_ENV
-
-    - id: dir-cache
-      uses: actions/cache@v4
-      with:
-        path: ${{ env.CACHE_PATH }}
-        # This pattern allows continual updating of the cache_path with each new
-        #  commit. The most recent cache matching CACHE_KEY will be used, while
-        #  any updates will create a new cache entry specific to the commit SHA,
-        #  which will then be available to the next run as the new most-recent
-        #  cache.
-        key: ${{ env.CACHE_KEY }}-${{ github.sha }}
-        restore-keys: |
-          ${{ env.CACHE_KEY }}

From 1f0a11321f6ca36284322992e9e247b0bd4177d1 Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Mon, 17 Nov 2025 17:39:16 +0000
Subject: [PATCH 12/20] Fix typo.

---
 .github/workflows/composite/conda-pkg-cache/action.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/composite/conda-pkg-cache/action.yml b/.github/workflows/composite/conda-pkg-cache/action.yml
index 4719bb6aa9..2feece7da2 100644
--- a/.github/workflows/composite/conda-pkg-cache/action.yml
+++ b/.github/workflows/composite/conda-pkg-cache/action.yml
@@ -28,7 +28,7 @@ runs:
         BUILD="${{ env.CACHE_BUILD }}"
         PY="${{ inputs.python_version }}"
         REQ="${{ hashFiles('requirements/locks/**') }}"
-        CACHE_KEY="$conda_pkgs_dir-${OS}-p${PERIOD}-b${BUILD}-py${PY}-${REQ}"
+        CACHE_KEY="conda_pkgs_dir-${OS}-p${PERIOD}-b${BUILD}-py${PY}-${REQ}"
         echo "CACHE_KEY=$CACHE_KEY" >> $GITHUB_ENV
 
     - id: set-pkg-dir

From 45dc2735b304e6fb7249cd49320071079852e892 Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Mon, 17 Nov 2025 17:52:51 +0000
Subject: [PATCH 13/20] Dummy commit to demonstrate Conda package caching.

---
 .github/workflows/composite/conda-pkg-cache/action.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/composite/conda-pkg-cache/action.yml b/.github/workflows/composite/conda-pkg-cache/action.yml
index 2feece7da2..616c76df96 100644
--- a/.github/workflows/composite/conda-pkg-cache/action.yml
+++ b/.github/workflows/composite/conda-pkg-cache/action.yml
@@ -13,7 +13,7 @@ runs:
     - id: set-cache-period
       shell: bash
       env:
-        # Maximum cache period (in weeks) before forcing a cache refresh.
+        # Maximum cache period (in weeks) before forcing a cache refresh..
         CACHE_WEEKS: 2
       run: echo "CACHE_PERIOD=$(date +%Y).$(expr $(date +%U) / ${CACHE_WEEKS})" >> $GITHUB_OUTPUT
 

From 20d3b372a8213b0b4c8c7bf3dc65b93891aa9281 Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Fri, 28 Nov 2025 10:03:31 +0000
Subject: [PATCH 14/20] Align GHA Python versions for better caching.

---
 .github/workflows/ci-tests.yml  | 3 +++
 .github/workflows/ci-wheels.yml | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/.github/workflows/ci-tests.yml b/.github/workflows/ci-tests.yml
index 6f33fad585..9cb036031d 100644
--- a/.github/workflows/ci-tests.yml
+++ b/.github/workflows/ci-tests.yml
@@ -87,6 +87,9 @@ jobs:
           channels: conda-forge
           activate-environment: ${{ env.ENV_NAME }}
           auto-update-conda: false
+          # This aligns the top-level env with the env that Nox will create
+          #  below - meaning optimal use of package caching.
+          python-version: ${{ matrix.python-version }}
 
       - name: "install cartopy + nox + pip"
         run: conda install --quiet --name ${{ env.ENV_NAME }} cartopy nox pip
diff --git a/.github/workflows/ci-wheels.yml b/.github/workflows/ci-wheels.yml
index 968361ea87..a0ab79d1d8 100644
--- a/.github/workflows/ci-wheels.yml
+++ b/.github/workflows/ci-wheels.yml
@@ -89,6 +89,9 @@ jobs:
         activate-environment: ${{ env.ENV_NAME }}
         auto-update-conda: false
         use-only-tar-bz2: true
+        # This aligns the top-level env with the env that Nox will create
+        #  below - meaning optimal use of package caching.
+        python-version: ${{ matrix.python-version }}
 
     - name: "install nox + pip"
       run: conda install --quiet --name ${{ env.ENV_NAME }} nox pip

From 7635adb27310385c7c6dee16149dc2c6af5962b2 Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Fri, 28 Nov 2025 10:15:41 +0000
Subject: [PATCH 15/20] Remove defaults channel from ci-wheels.

---
 .github/workflows/ci-wheels.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/ci-wheels.yml b/.github/workflows/ci-wheels.yml
index a0ab79d1d8..c5d08c3bd6 100644
--- a/.github/workflows/ci-wheels.yml
+++ b/.github/workflows/ci-wheels.yml
@@ -85,7 +85,7 @@ jobs:
       uses: conda-incubator/setup-miniconda@v3
       with:
         miniforge-version: latest
-        channels: conda-forge,defaults
+        channels: conda-forge
         activate-environment: ${{ env.ENV_NAME }}
         auto-update-conda: false
         use-only-tar-bz2: true

From 20ed16cff8a5e74613f020574693039111b031c0 Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Fri, 28 Nov 2025 10:22:21 +0000
Subject: [PATCH 16/20] No longer need to use miniforge.

---
 .github/workflows/ci-tests.yml  | 1 -
 .github/workflows/ci-wheels.yml | 1 -
 2 files changed, 2 deletions(-)

diff --git a/.github/workflows/ci-tests.yml b/.github/workflows/ci-tests.yml
index 9cb036031d..7bad98c946 100644
--- a/.github/workflows/ci-tests.yml
+++ b/.github/workflows/ci-tests.yml
@@ -83,7 +83,6 @@ jobs:
       - name: "conda install"
         uses: conda-incubator/setup-miniconda@v3
         with:
-          miniforge-version: latest
           channels: conda-forge
           activate-environment: ${{ env.ENV_NAME }}
           auto-update-conda: false
diff --git a/.github/workflows/ci-wheels.yml b/.github/workflows/ci-wheels.yml
index c5d08c3bd6..920ed085dc 100644
--- a/.github/workflows/ci-wheels.yml
+++ b/.github/workflows/ci-wheels.yml
@@ -84,7 +84,6 @@ jobs:
     - name: "conda install"
       uses: conda-incubator/setup-miniconda@v3
       with:
-        miniforge-version: latest
         channels: conda-forge
         activate-environment: ${{ env.ENV_NAME }}
         auto-update-conda: false

From 0a8cbcf45d04744491d50b269664c77a9dc87df0 Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Fri, 28 Nov 2025 10:27:07 +0000
Subject: [PATCH 17/20] Revert "No longer need to use miniforge."

This reverts commit 20ed16cff8a5e74613f020574693039111b031c0.
---
 .github/workflows/ci-tests.yml  | 1 +
 .github/workflows/ci-wheels.yml | 1 +
 2 files changed, 2 insertions(+)

diff --git a/.github/workflows/ci-tests.yml b/.github/workflows/ci-tests.yml
index 7bad98c946..9cb036031d 100644
--- a/.github/workflows/ci-tests.yml
+++ b/.github/workflows/ci-tests.yml
@@ -83,6 +83,7 @@ jobs:
       - name: "conda install"
         uses: conda-incubator/setup-miniconda@v3
         with:
+          miniforge-version: latest
           channels: conda-forge
           activate-environment: ${{ env.ENV_NAME }}
           auto-update-conda: false
diff --git a/.github/workflows/ci-wheels.yml b/.github/workflows/ci-wheels.yml
index 920ed085dc..c5d08c3bd6 100644
--- a/.github/workflows/ci-wheels.yml
+++ b/.github/workflows/ci-wheels.yml
@@ -84,6 +84,7 @@ jobs:
     - name: "conda install"
       uses: conda-incubator/setup-miniconda@v3
       with:
+        miniforge-version: latest
         channels: conda-forge
         activate-environment: ${{ env.ENV_NAME }}
         auto-update-conda: false

From 7b780a14c6b97fc09bef8421ce43ca8f98a1268d Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Fri, 28 Nov 2025 10:28:42 +0000
Subject: [PATCH 18/20] ci-wheels Nox minimum pin.

---
 .github/workflows/ci-wheels.yml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/ci-wheels.yml b/.github/workflows/ci-wheels.yml
index c5d08c3bd6..45e4fcaba1 100644
--- a/.github/workflows/ci-wheels.yml
+++ b/.github/workflows/ci-wheels.yml
@@ -94,7 +94,8 @@ jobs:
         python-version: ${{ matrix.python-version }}
 
     - name: "install nox + pip"
-      run: conda install --quiet --name ${{ env.ENV_NAME }} nox pip
+      # Nox minimum pin is just to help avoid a solver bug.
+      run: conda install --quiet --name ${{ env.ENV_NAME }} "nox>=2025" pip
 
     - name: "nox install and test wheel"
       env:

From 6d3d00f668748745a9b22f2d4a8f0952f2bf5e18 Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Fri, 28 Nov 2025 11:29:28 +0000
Subject: [PATCH 19/20] Revert "ci-wheels Nox minimum pin."

This reverts commit 7b780a14c6b97fc09bef8421ce43ca8f98a1268d.
---
 .github/workflows/ci-wheels.yml | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/.github/workflows/ci-wheels.yml b/.github/workflows/ci-wheels.yml
index 45e4fcaba1..c5d08c3bd6 100644
--- a/.github/workflows/ci-wheels.yml
+++ b/.github/workflows/ci-wheels.yml
@@ -94,8 +94,7 @@ jobs:
         python-version: ${{ matrix.python-version }}
 
     - name: "install nox + pip"
-      # Nox minimum pin is just to help avoid a solver bug.
-      run: conda install --quiet --name ${{ env.ENV_NAME }} "nox>=2025" pip
+      run: conda install --quiet --name ${{ env.ENV_NAME }} nox pip
 
     - name: "nox install and test wheel"
       env:

From 957dc9f92a23c41b06d240319da7bec90f936827 Mon Sep 17 00:00:00 2001
From: Martin Yeo <martin.yeo@metoffice.gov.uk>
Date: Fri, 28 Nov 2025 11:31:52 +0000
Subject: [PATCH 20/20] Remove bz2 only line - this was a legacy workaround, no
 longer necessary.

---
 .github/workflows/ci-wheels.yml | 1 -
 1 file changed, 1 deletion(-)

diff --git a/.github/workflows/ci-wheels.yml b/.github/workflows/ci-wheels.yml
index c5d08c3bd6..24342c3db4 100644
--- a/.github/workflows/ci-wheels.yml
+++ b/.github/workflows/ci-wheels.yml
@@ -88,7 +88,6 @@ jobs:
         channels: conda-forge
         activate-environment: ${{ env.ENV_NAME }}
         auto-update-conda: false
-        use-only-tar-bz2: true
         # This aligns the top-level env with the env that Nox will create
         #  below - meaning optimal use of package caching.
         python-version: ${{ matrix.python-version }}