diff --git a/.gitea/workflows/ci.yml b/.gitea/workflows/ci.yml
index bfd1ae7a..7418145d 100644
--- a/.gitea/workflows/ci.yml
+++ b/.gitea/workflows/ci.yml
@@ -94,9 +94,10 @@ jobs:
             exit 1
           fi
 
+      # Gitea Actions (act_runner) does not implement upload-artifact v4 protocol — pinned per ADR-014. Do NOT upgrade. See #557.
       - name: Upload coverage reports
         if: always()
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v3
         with:
           name: coverage-reports
           path: |
@@ -130,9 +131,10 @@ jobs:
             || { echo "FAIL: /hilfe/transkription.html missing from prerender output"; exit 1; }
           echo "PASS: only /hilfe/transkription.html prerendered."
 
+      # Gitea Actions (act_runner) does not implement upload-artifact v4 protocol — pinned per ADR-014. Do NOT upgrade. See #557.
       - name: Upload screenshots
         if: always()
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v3
         with:
           name: unit-test-screenshots
           path: frontend/test-results/screenshots/
diff --git a/.gitea/workflows/coverage-flake-probe.yml b/.gitea/workflows/coverage-flake-probe.yml
index 0258ba7a..0af5a805 100644
--- a/.gitea/workflows/coverage-flake-probe.yml
+++ b/.gitea/workflows/coverage-flake-probe.yml
@@ -56,9 +56,10 @@ jobs:
             exit 1
           fi
 
+      # Gitea Actions (act_runner) does not implement upload-artifact v4 protocol — pinned per ADR-014. Do NOT upgrade. See #557.
       - name: Upload coverage log on failure
         if: failure()
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v3
         with:
           name: coverage-log-run-${{ matrix.run }}
           path: /tmp/coverage-test-${{ github.run_id }}-${{ matrix.run }}.log