diff --git a/.github/actions/setup-llvm/action.yml b/.github/actions/setup-llvm/action.yml
new file mode 100644
index 000000000..d1ca04059
--- /dev/null
+++ b/.github/actions/setup-llvm/action.yml
@@ -0,0 +1,64 @@
+name: Set up LLVM
+description: Restore or build LLVM with assertions enabled
+
+inputs:
+  save-cache:
+    description: Save LLVM caches after a cache miss
+    required: false
+    default: "true"
+
+runs:
+  using: composite
+  steps:
+    - name: Restore LLVM source cache
+      uses: actions/cache/restore@v5
+      id: cache-llvm-source
+      with:
+        key: llvm-source-22-linux-ubuntu-24.04-asserts-v1-${{ hashFiles('llvm-version.txt') }}
+        path: |
+          llvm-project/clang/lib/Headers
+          llvm-project/clang/include
+          llvm-project/compiler-rt
+          llvm-project/lld/include
+          llvm-project/llvm/include
+    - name: Download LLVM source
+      if: steps.cache-llvm-source.outputs.cache-hit != 'true'
+      shell: bash
+      run: make llvm-source
+    - name: Save LLVM source cache
+      uses: actions/cache/save@v5
+      if: inputs.save-cache == 'true' && steps.cache-llvm-source.outputs.cache-hit != 'true'
+      with:
+        key: ${{ steps.cache-llvm-source.outputs.cache-primary-key }}
+        path: |
+          llvm-project/clang/lib/Headers
+          llvm-project/clang/include
+          llvm-project/compiler-rt
+          llvm-project/lld/include
+          llvm-project/llvm/include
+    - name: Restore LLVM build cache
+      uses: actions/cache/restore@v5
+      id: cache-llvm-build
+      with:
+        key: llvm-build-22-linux-ubuntu-24.04-asserts-v1-${{ hashFiles('llvm-version.txt') }}
+        path: llvm-build
+    - name: Install Ninja
+      if: steps.cache-llvm-build.outputs.cache-hit != 'true'
+      shell: bash
+      run: |
+        sudo apt-get update
+        sudo apt-get install --no-install-recommends ninja-build
+    - name: Build LLVM
+      if: steps.cache-llvm-build.outputs.cache-hit != 'true'
+      shell: bash
+      run: |
+        rm -rf llvm-project
+        make llvm-source
+        make llvm-build ASSERT=1
+        find llvm-build -name CMakeFiles -prune -exec rm -r '{}' \;
+    - name: Save LLVM build cache
+      uses: actions/cache/save@v5
+      if: inputs.save-cache == 'true' && steps.cache-llvm-build.outputs.cache-hit != 'true'
+      with:
+        key: ${{ steps.cache-llvm-build.outputs.cache-primary-key }}
+        path: llvm-build
diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index 3465f020d..95037acfb 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -220,7 +220,7 @@ jobs:
   assert-test-linux:
     # Run all tests that can run on Linux, with LLVM assertions enabled to catch
     # potential bugs.
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     steps:
       - name: Checkout
         uses: actions/checkout@v6
@@ -239,8 +239,7 @@ jobs:
               qemu-system-arm \
               qemu-system-riscv32 \
               qemu-user \
-              simavr \
-              ninja-build
+              simavr
       - name: Install Go
         uses: actions/setup-go@v6
         with:
@@ -264,53 +263,7 @@ jobs:
             "https://github.com/espressif/qemu/releases/download/$release/$archive"
           tar -xJf "$RUNNER_TEMP/$archive" -C "$RUNNER_TEMP"
           echo "$RUNNER_TEMP/qemu/bin" >> "$GITHUB_PATH"
-      - name: Restore LLVM source cache
-        uses: actions/cache/restore@v5
-        id: cache-llvm-source
-        with:
-          key: llvm-source-22-linux-asserts-v1-${{ hashFiles('llvm-version.txt') }}
-          path: |
-            llvm-project/clang/lib/Headers
-            llvm-project/clang/include
-            llvm-project/compiler-rt
-            llvm-project/lld/include
-            llvm-project/llvm/include
-      - name: Download LLVM source
-        if: steps.cache-llvm-source.outputs.cache-hit != 'true'
-        run: make llvm-source
-      - name: Save LLVM source cache
-        uses: actions/cache/save@v5
-        if: steps.cache-llvm-source.outputs.cache-hit != 'true'
-        with:
-          key: ${{ steps.cache-llvm-source.outputs.cache-primary-key }}
-          path: |
-            llvm-project/clang/lib/Headers
-            llvm-project/clang/include
-            llvm-project/compiler-rt
-            llvm-project/lld/include
-            llvm-project/llvm/include
-      - name: Restore LLVM build cache
-        uses: actions/cache/restore@v5
-        id: cache-llvm-build
-        with:
-          key: llvm-build-22-linux-asserts-v1-${{ hashFiles('llvm-version.txt') }}
-          path: llvm-build
-      - name: Build LLVM
-        if: steps.cache-llvm-build.outputs.cache-hit != 'true'
-        run: |
-          # fetch LLVM source
-          rm -rf llvm-project
-          make llvm-source
-          # build!
-          make llvm-build ASSERT=1
-          # Remove unnecessary object files (to reduce cache size).
-          find llvm-build -name CMakeFiles -prune -exec rm -r '{}' \;
-      - name: Save LLVM build cache
-        uses: actions/cache/save@v5
-        if: steps.cache-llvm-build.outputs.cache-hit != 'true'
-        with:
-          key: ${{ steps.cache-llvm-build.outputs.cache-primary-key }}
-          path: llvm-build
+      - uses: ./.github/actions/setup-llvm
       - name: Cache Binaryen
         uses: actions/cache@v5
         id: cache-binaryen