diff --git a/.github/actions/install-qt/action.yml b/.github/actions/install-qt/action.yml
new file mode 100644
index 000000000..50c823128
--- /dev/null
+++ b/.github/actions/install-qt/action.yml
@@ -0,0 +1,61 @@
+name: Install Qt
+description: >-
+  Install the Qt 5 archives that Plus needs with jurplel/install-qt-action,
+  restored from the actions cache when an entry exists. Shared by the VTK and
+  Plus build workflows so that both use the same archive list and therefore
+  the same cache key.
+
+inputs:
+  arch:
+    description: Build architecture, x64 or Win32
+    required: true
+  version:
+    description: Qt version to install
+    required: false
+    default: '5.15.0'
+
+runs:
+  using: composite
+  steps:
+    # aqtinstall downloads each archive from a geo-selected mirror and, on a
+    # timeout, tries exactly one random fallback mirror before giving up. Give
+    # slow mirrors more time, skip the mirrors that have failed nightly builds
+    # (ftp1/ftp2.nluug.nl serve a certificate for a different hostname), and
+    # avoid the slow mirror that download.qt.io redirects the runners to.
+    - name: Configure aqtinstall
+      shell: bash
+      run: |
+        cat > "$RUNNER_TEMP/aqt.ini" <<'EOF'
+        [requests]
+        connection_timeout : 10
+        response_timeout : 120
+        max_retries_on_connection_error : 10
+        [mirrors]
+        blacklist :
+            https://mirror.ossplanet.net
+        fallbacks :
+            https://ftp.fau.de/qtproject/
+            https://mirror.netcologne.de/qtproject/
+            https://mirrors.dotsrc.org/qtproject/
+            https://master.qt.io/
+            https://qt.mirror.constant.com/
+            https://mirrors.ukfast.co.uk/sites/qt.io/
+        EOF
+        echo "AQT_CONFIG=$RUNNER_TEMP/aqt.ini" >> "$GITHUB_ENV"
+
+    - name: Install Qt
+      uses: jurplel/install-qt-action@v4
+      with:
+        dir: ${{ github.workspace }}/Qt
+        version: ${{ inputs.version }}
+        arch: ${{ inputs.arch == 'x64' && 'win64_msvc2019_64' || 'win32_msvc2019' }}
+        # Only the archives Plus links against (Core/Gui/Widgets/OpenGL/Sql/
+        # Concurrent/Network/Test/Xml come from qtbase; Designer from qttools;
+        # Quick/Qml from qtdeclarative for VTK's GUISupportQtQuick module, which
+        # find_package(VTK) requires even though Plus does not use it) plus what
+        # windeployqt bundles. Cuts the download from 27 archives to 9 and keeps
+        # the cache entry small.
+        archives: qtbase qttools qtxmlpatterns qtmultimedia qtdeclarative qttranslations d3dcompiler_47 opengl32sw
+        # Restore the Qt directory from the actions cache so that only the first
+        # job per architecture downloads Qt at all.
+        cache: true
diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index 79d1174ef..8a67b18eb 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -3,7 +3,11 @@
 version: 2
 updates:
   - package-ecosystem: "github-actions"
-    directory: "/"
+    # "/" only covers .github/workflows; local composite actions have to be
+    # listed separately for their "uses:" lines to be updated too.
+    directories:
+      - "/"
+      - "/.github/actions/*"
     schedule:
       # Check for updates to GitHub Actions every week
       interval: "weekly"
diff --git a/.github/workflows/build-plus.yml b/.github/workflows/build-plus.yml
index cc3414aec..adaba75c7 100644
--- a/.github/workflows/build-plus.yml
+++ b/.github/workflows/build-plus.yml
@@ -133,12 +133,19 @@ jobs:
       with:
         cmakeVersion: 4.3.4
 
+    # The job never checks out PlusLib itself (the superbuild clones it), so
+    # fetch just the local actions used below.
+    - name: Checkout CI actions
+      uses: actions/checkout@v7
+      with:
+        sparse-checkout: .github/actions
+        path: pluslib-ci
+
     - name: Install Qt
-      uses: jurplel/install-qt-action@v4
+      uses: ./pluslib-ci/.github/actions/install-qt
       with:
-        dir: ${{ github.workspace }}/Qt
+        arch: ${{ inputs.arch }}
         version: ${{ inputs.qt-version }}
-        arch: ${{ inputs.arch == 'x64' && 'win64_msvc2019_64' || 'win32_msvc2019' }}
 
     - name: Install NSIS
       uses: repolevedavaj/install-nsis@v1.3.0
@@ -183,11 +190,22 @@ jobs:
         }
         # -M/-T is used instead of -D so that the Nightly model does not run an
         # Update step, which would move the checkout to the nightly start time.
-        ctest -C Release -M ${{ inputs.dashboard-model }} -T Start -T Configure -T Build -T Test -T Submit -V
+        ctest -C Release -M ${{ inputs.dashboard-model }} -T Start -T Configure -T Build -T Test -V
         if ($LASTEXITCODE -ne 0) {
           throw "CTest failed with exit code $LASTEXITCODE"
         }
 
+    # Separate from the build step so that a CDash outage cannot fail the job.
+    - name: Submit build results to CDash
+      continue-on-error: true
+      shell: pwsh
+      working-directory: ${{ github.workspace }}/build
+      run: |
+        ctest -M ${{ inputs.dashboard-model }} -T Submit
+        if ($LASTEXITCODE -ne 0) {
+          throw "CDash submission failed with exit code $LASTEXITCODE"
+        }
+
     # The runners have no GPU, so VTK cannot create a render window. Tests that
     # generate report plots (the calibration algorithm tests) crash without a
     # software OpenGL implementation. This installs Mesa system-wide.
diff --git a/.github/workflows/build-vtk.yml b/.github/workflows/build-vtk.yml
index 42f95fe21..d7682a48b 100644
--- a/.github/workflows/build-vtk.yml
+++ b/.github/workflows/build-vtk.yml
@@ -59,13 +59,21 @@ jobs:
         with:
           cmakeVersion: 4.3.4
 
+      # The job never checks out PlusLib itself (the superbuild clones it), so
+      # fetch just the local actions used below.
+      - name: Checkout CI actions
+        if: steps.cache-vtk.outputs.cache-hit != 'true'
+        uses: actions/checkout@v7
+        with:
+          sparse-checkout: .github/actions
+          path: pluslib-ci
+
       - name: Install Qt
         if: steps.cache-vtk.outputs.cache-hit != 'true'
-        uses: jurplel/install-qt-action@v4
+        uses: ./pluslib-ci/.github/actions/install-qt
         with:
-          dir: ${{github.workspace}}/Qt
+          arch: ${{ inputs.arch }}
           version: '5.15.0'
-          arch: ${{ inputs.arch == 'x64' && 'win64_msvc2019_64' || 'win32_msvc2019' }}
 
       - name: Clone VTK
         if: steps.cache-vtk.outputs.cache-hit != 'true'