diff --git a/.github/workflows/CI-integrationtests.yml b/.github/workflows/CI-integrationtests.yml
index f9a4df6d02..8bf985fc60 100644
--- a/.github/workflows/CI-integrationtests.yml
+++ b/.github/workflows/CI-integrationtests.yml
@@ -3,6 +3,13 @@ name: CI-integrationtests
 
 permissions: {}
 
+env:
+  CLONE_ATTEMPTS: 2
+  GIT_HTTP_CONNECT_TIMEOUT: 20
+  GIT_HTTP_LOW_SPEED_LIMIT: 1000
+  GIT_HTTP_LOW_SPEED_TIME: 30
+  RETRY_SLEEP_SECONDS: 60
+
 on:
   workflow_dispatch:
     inputs:
@@ -68,18 +75,67 @@ jobs:
       CORSIKA_TABLES: "v0.1.0"
 
     steps:
+      - name: Restore cached CORSIKA interaction tables
+        id: restore_interaction_tables
+        uses: actions/cache/restore@v5
+        with:
+          path: ${{ env.IT_NAME }}
+          key: corsika-interaction-tables-${{ env.CORSIKA_TABLES }}
+          restore-keys: |
+            corsika-interaction-tables-${{ env.CORSIKA_TABLES }}-
+
       - name: Clone CORSIKA interaction tables (exclude QGSJet tables)
         run: |
           REPO_URL=https://gitlab.cta-observatory.org/cta-computing/dpps/simpipe/simulation_software/${IT_NAME}
           export GIT_LFS_SKIP_SMUDGE=1  # disable automatic downloading of all LFS files
-          for attempt in 1 2 3; do
-            git clone --depth 1 --branch "$CORSIKA_TABLES" "$REPO_URL" "$IT_NAME" && break
-            echo "Clone attempt $attempt failed. Retrying in 120 seconds..."
-            rm -rf "$IT_NAME"
-            sleep 120
+
+          CLONE_DIR="${IT_NAME}-clone"
+          CACHE_DIR="$IT_NAME"
+          rm -rf "$CLONE_DIR"
+          CLONE_SUCCESS=false
+
+          for attempt in $(seq 1 "$CLONE_ATTEMPTS"); do
+            if git \
+              -c "http.connectTimeout=$GIT_HTTP_CONNECT_TIMEOUT" \
+              -c "http.lowSpeedLimit=$GIT_HTTP_LOW_SPEED_LIMIT" \
+              -c "http.lowSpeedTime=$GIT_HTTP_LOW_SPEED_TIME" \
+              clone --depth 1 --branch "$CORSIKA_TABLES" "$REPO_URL" "$CLONE_DIR"
+            then
+              git lfs install
+              if ! (cd "$CLONE_DIR" && git lfs pull --exclude="interaction-tables/qgsdat-II-04,interaction-tables/qgsdat-III"); then
+                echo "git lfs pull failed; will retry and/or fall back to the cache."
+                rm -rf "$CLONE_DIR"
+                continue
+              fi
+              rm -rf "$CACHE_DIR"
+              mv "$CLONE_DIR" "$CACHE_DIR"
+              echo "Successfully cloned CORSIKA interaction tables $CORSIKA_TABLES."
+              CLONE_SUCCESS=true
+              break
+            fi
+
+            rm -rf "$CLONE_DIR"
+            if [[ "$attempt" -lt "$CLONE_ATTEMPTS" ]]; then
+              echo "Clone attempt $attempt failed. Retrying in $RETRY_SLEEP_SECONDS seconds..."
+              sleep "$RETRY_SLEEP_SECONDS"
+            fi
           done
-          git lfs install
-          (cd "$IT_NAME" && git lfs pull --exclude="interaction-tables/qgsdat-II-04,interaction-tables/qgsdat-III")
+
+          if [ "$CLONE_SUCCESS" = false ] && [ ! -d "$CACHE_DIR" ]; then
+            echo "Failed to clone CORSIKA interaction tables $CORSIKA_TABLES and no cache is available."
+            exit 1
+          fi
+
+          if [ "$CLONE_SUCCESS" = false ]; then
+            echo "GitLab clone failed; using cached CORSIKA interaction tables $CORSIKA_TABLES."
+          fi
+
+      - name: Save cached CORSIKA interaction tables
+        if: steps.restore_interaction_tables.outputs.cache-hit != 'true'
+        uses: actions/cache/save@v5
+        with:
+          path: ${{ env.IT_NAME }}
+          key: corsika-interaction-tables-${{ env.CORSIKA_TABLES }}
 
       - name: Upload CORSIKA interaction tables
         uses: actions/upload-artifact@v7
@@ -103,6 +159,7 @@ jobs:
       - uses: actions/checkout@v6
 
       - name: Determine simulation model branch
+        id: simulation_model_branch
         env:
           HEAD_REF: ${{ github.head_ref }}
           REF_NAME: ${{ github.ref_name }}
@@ -126,17 +183,64 @@ jobs:
             BRANCH="$SIMTOOLS_DB_SIMULATION_MODEL_VERSION"
           fi
           echo "SIMTOOLS_DB_SIMULATION_MODEL_BRANCH=$BRANCH" >> "$GITHUB_ENV"
+          echo "branch=$BRANCH" >> "$GITHUB_OUTPUT"
+
+      - name: Restore cached simulation models repository
+        if: github.event_name != 'schedule'
+        id: restore_simulation_models
+        uses: actions/cache/restore@v5
+        with:
+          path: simulation-models
+          key: simulation-models-${{ steps.simulation_model_branch.outputs.branch }}-${{ github.run_id }}
+          restore-keys: |
+            simulation-models-${{ steps.simulation_model_branch.outputs.branch }}-
 
       - name: Clone simulation models repository
         if: github.event_name != 'schedule'
         run: |
-          for attempt in 1 2 3; do
-            git clone --depth 1 --branch "$SIMTOOLS_DB_SIMULATION_MODEL_BRANCH" "$SIM_MODELS_REPO" "simulation-models" && break
-            echo "Clone attempt $attempt failed. Retrying in 120 seconds..."
-            rm -rf simulation-models
-            sleep 120
+          CLONE_DIR="simulation-models-clone"
+          CACHE_DIR="simulation-models"
+          rm -rf "$CLONE_DIR"
+          CLONE_SUCCESS=false
+
+          for attempt in $(seq 1 "$CLONE_ATTEMPTS"); do
+            if git \
+              -c "http.connectTimeout=$GIT_HTTP_CONNECT_TIMEOUT" \
+              -c "http.lowSpeedLimit=$GIT_HTTP_LOW_SPEED_LIMIT" \
+              -c "http.lowSpeedTime=$GIT_HTTP_LOW_SPEED_TIME" \
+              clone --depth 1 --branch "$SIMTOOLS_DB_SIMULATION_MODEL_BRANCH" "$SIM_MODELS_REPO" "$CLONE_DIR"
+            then
+              rm -rf "$CACHE_DIR"
+              mv "$CLONE_DIR" "$CACHE_DIR"
+              echo "Successfully cloned simulation models branch $SIMTOOLS_DB_SIMULATION_MODEL_BRANCH."
+              CLONE_SUCCESS=true
+              break
+            fi
+
+            rm -rf "$CLONE_DIR"
+            if [[ "$attempt" -lt "$CLONE_ATTEMPTS" ]]; then
+              echo "Clone attempt $attempt failed. Retrying in $RETRY_SLEEP_SECONDS seconds..."
+              sleep "$RETRY_SLEEP_SECONDS"
+            fi
           done
 
+          if [ "$CLONE_SUCCESS" = false ] && [ ! -d "$CACHE_DIR" ]; then
+            echo "Failed to clone simulation models branch $SIMTOOLS_DB_SIMULATION_MODEL_BRANCH and no cache is available."
+            exit 1
+          fi
+
+          if [ "$CLONE_SUCCESS" = false ]; then
+            echo "GitLab clone failed; using cached simulation models branch $SIMTOOLS_DB_SIMULATION_MODEL_BRANCH."
+          fi
+
+
+      - name: Save cached simulation models repository
+        if: github.event_name != 'schedule' && steps.restore_simulation_models.outputs.cache-hit != 'true'
+        uses: actions/cache/save@v5
+        with:
+          path: simulation-models
+          key: simulation-models-${{ steps.simulation_model_branch.outputs.branch }}-${{ github.run_id }}
+
       - name: Upload simulation models repository
         if: github.event_name != 'schedule'
         uses: actions/upload-artifact@v7
diff --git a/.github/workflows/CI-unittests.yml b/.github/workflows/CI-unittests.yml
index b7f86e0be5..434539e108 100644
--- a/.github/workflows/CI-unittests.yml
+++ b/.github/workflows/CI-unittests.yml
@@ -1,6 +1,6 @@
 ---
 name: CI-unittests
-# Unit tests (includes CTAO-SonarQube)
+# Unit tests and CTAO-SonarQube
 
 on:
   workflow_dispatch:
@@ -72,7 +72,7 @@ jobs:
 
           - os: ubuntu-latest
             python-version: "3.13"
-            extra-args: ["sonarqube", "random-order"]
+            extra-args: ["random-order"]
 
           - os: ubuntu-latest
             python-version: "3.14"
@@ -115,20 +115,14 @@ jobs:
           pytest --durations=10 --color=yes -n 4 --dist loadscope \
             --cov=simtools --cov-report=xml --retries 2 --retry-delay 5
 
-      # CTAO-DPPS-SonarQube
-      - uses: SonarSource/sonarqube-scan-action@v8.1.0
-        if: contains(matrix.extra-args, 'sonarqube')
-        env:
-          SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}
+      - name: Upload coverage report
+        if: matrix.python-version == '3.13'
+        uses: actions/upload-artifact@v7
         with:
-          args: >
-            -Dsonar.projectKey=gammasim_simtools_0d23837b-8b2d-4e54-9a98-2f1bde681f14
-            -Dsonar.host.url=https://sonar-ctao.zeuthen.desy.de
-            -Dsonar.qualitygate.wait=true
-            -Dsonar.python.coverage.reportPaths=coverage.xml
-            -Dsonar.python.version=${{ matrix.python-version }}
-            -Dsonar.exclusions=**/docs/**,src/simtools/applications/**,**/__init__.py
-            -Dsonar.coverage.exclusions=**/tests/**,src/simtools/applications/**
+          name: coverage-python-3.13
+          path: coverage.xml
+          if-no-files-found: error
+          retention-days: 3
 
       - name: Random order
         if: github.event_name == 'schedule' && contains(matrix.extra-args, 'random-order')
@@ -139,3 +133,116 @@ jobs:
         run: |
           pytest --color=yes -n 4 --dist loadscope --count 5 --random-order \
            --retries 2 --retry-delay 5
+
+  sonarqube:
+    needs: unit_tests
+    runs-on: ubuntu-latest
+    env:
+      SONAR_SCANNER_VERSION: 8.1.0.6389
+      SONAR_SCANNER_PLATFORM: linux-x64
+      SONAR_SCANNER_CACHE_DIR: .sonar/sonar-scanner
+
+    defaults:
+      run:
+        shell: bash -leo pipefail {0}
+
+    steps:
+      - name: checkout
+        uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+
+      - name: Download coverage report
+        uses: actions/download-artifact@v8
+        with:
+          name: coverage-python-3.13
+          path: .
+
+      # CTAO-DPPS-SonarQube
+      - name: Restore Sonar scanner cache
+        id: sonar_scanner_cache
+        uses: actions/cache@v5
+        with:
+          path: ${{ env.SONAR_SCANNER_CACHE_DIR }}
+          key: sonar-scanner-${{ runner.os }}-${{ runner.arch }}-${{ env.SONAR_SCANNER_VERSION }}
+
+      - name: Install Sonar scanner
+        if: steps.sonar_scanner_cache.outputs.cache-hit != 'true'
+        run: |
+          mkdir -p "$SONAR_SCANNER_CACHE_DIR"
+          curl --fail --location --retry 5 --retry-delay 20 --retry-all-errors \
+            "https://binaries.sonarsource.com/Distribution/sonar-scanner-cli/sonar-scanner-cli-${SONAR_SCANNER_VERSION}-${SONAR_SCANNER_PLATFORM}.zip" \
+            --output sonar-scanner.zip
+          unzip -q sonar-scanner.zip -d "$SONAR_SCANNER_CACHE_DIR"
+
+      - name: Run Sonar scanner
+        id: sonar_scan
+        # Soft fail for draft PRs (unstable network connections)
+        continue-on-error: ${{ github.event.pull_request.draft == true }}
+        env:
+          SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}
+        run: |
+          set +e
+          for attempt in 1 2 3; do
+            scanner_log="sonar-scanner-attempt-${attempt}.log"
+            "${SONAR_SCANNER_CACHE_DIR}/sonar-scanner-${SONAR_SCANNER_VERSION}-${SONAR_SCANNER_PLATFORM}/bin/sonar-scanner" \
+              -Dsonar.projectKey=gammasim_simtools_0d23837b-8b2d-4e54-9a98-2f1bde681f14 \
+              -Dsonar.host.url=https://sonar-ctao.zeuthen.desy.de \
+              -Dsonar.qualitygate.wait=true \
+              -Dsonar.scanner.connectTimeout=60 \
+              -Dsonar.scanner.socketTimeout=120 \
+              -Dsonar.scanner.responseTimeout=120 \
+              -Dsonar.plugins.download.timeout=600 \
+              -Dsonar.python.coverage.reportPaths=coverage.xml \
+              -Dsonar.python.version=3.13 \
+              -Dsonar.exclusions=**/docs/**,src/simtools/applications/**,**/__init__.py \
+              -Dsonar.coverage.exclusions=**/tests/**,src/simtools/applications/** \
+              2>&1 | tee "$scanner_log"
+            status=${PIPESTATUS[0]}
+
+            echo "Sonar scanner attempt $attempt exited with status $status."
+
+            if [[ "$status" -eq 0 ]]; then
+              echo "Sonar scanner succeeded."
+              exit 0
+            fi
+
+            if grep -Eqi "QUALITY GATE STATUS: FAILED|quality gate failed" "$scanner_log"; then
+              echo "Sonar quality gate failed; not retrying."
+              exit "$status"
+            fi
+
+            if ! grep -Eqi "HTTP connect timed out|connect timed out|Connection refused|Connection reset|Failed to query server version|Failed to upload report|Failed to request|timeout|timed out|temporarily unavailable|502|503|504" "$scanner_log"; then
+              echo "Sonar scanner failed with a non-transient error; not retrying."
+              exit "$status"
+            fi
+
+            if [[ "$attempt" -lt 3 ]]; then
+              delay=$((attempt * 60))
+              echo "Sonar scanner attempt $attempt failed. Retrying in $delay seconds..."
+              sleep "$delay"
+            fi
+          done
+
+          echo "Sonar scanner failed after 3 attempts."
+          exit 1
+
+      - name: Report soft-failed Sonar scan
+        if: always() && github.event.pull_request.draft == true && steps.sonar_scan.outcome == 'failure'
+        run: |
+          echo "::warning::Sonar scan failed but was allowed to continue because this is a draft PR."
+          {
+            echo "## Sonar scan soft failure"
+            echo
+            echo "The Sonar scan failed, but the workflow continued because this is a draft PR."
+            echo "Open the \`Run Sonar scanner\` step logs for details."
+          } >> "$GITHUB_STEP_SUMMARY"
+
+      - name: Upload soft-failed Sonar logs
+        if: always() && github.event.pull_request.draft == true && steps.sonar_scan.outcome == 'failure'
+        uses: actions/upload-artifact@v7
+        with:
+          name: sonar-scanner-logs
+          path: sonar-scanner-attempt-*.log
+          if-no-files-found: ignore
+          retention-days: 7
diff --git a/docs/changes/2239.maintenance.md b/docs/changes/2239.maintenance.md
new file mode 100644
index 0000000000..d76a289c85
--- /dev/null
+++ b/docs/changes/2239.maintenance.md
@@ -0,0 +1 @@
+Increase robustness of CI unit and integration tests. Add caching steps for CORSIKA interaction tables, simulation models, and sonar binary as a fallback.