diff --git a/.gitea/workflows/docker-build.yml b/.gitea/workflows/docker-build.yml
index f2ce4b1..6541e97 100644
--- a/.gitea/workflows/docker-build.yml
+++ b/.gitea/workflows/docker-build.yml
@@ -33,14 +33,30 @@ jobs:
           REG_USER: ${{ secrets.REGISTRY_USER || github.repository_owner }}
           REG_TOKEN: ${{ secrets.REGISTRY_TOKEN }}
         run: |
+          IMAGE_LOWER=$(echo "${IMAGE_NAME}" | tr '[:upper:]' '[:lower:]')
           echo "Registry:      ${REGISTRY}"
           echo "Username:       '${REG_USER}'  (Laenge: ${#REG_USER})"
           echo "Token gesetzt:  $([ -n "${REG_TOKEN}" ] && echo ja || echo NEIN)  (Laenge: ${#REG_TOKEN})"
-          echo "--- Test 1: /v2/ mit Basic-Auth ---"
-          curl -s -o /dev/null -w "HTTP %{http_code}\n" -u "${REG_USER}:${REG_TOKEN}" "https://${REGISTRY}/v2/"
-          echo "--- Test 2: Token-Endpoint (Bearer-Flow) ---"
-          curl -s -o /dev/null -w "HTTP %{http_code}\n" -u "${REG_USER}:${REG_TOKEN}" \
-            "https://${REGISTRY}/v2/token?scope=repository:${IMAGE_NAME}:pull,push&service=container_registry" || true
+          echo "Image (lower):  ${IMAGE_LOWER}"
+
+          echo "--- API-Test: /api/v1/user (Basic-Auth gueltig?) ---"
+          curl -s -o /dev/null -w "HTTP %{http_code}\n" -u "${REG_USER}:${REG_TOKEN}" "https://${REGISTRY}/api/v1/user"
+
+          echo "--- /v2/ Challenge (WWW-Authenticate) ---"
+          HDR=$(curl -s -D - -o /dev/null "https://${REGISTRY}/v2/")
+          AUTH=$(printf '%s' "$HDR" | tr -d '\r' | grep -i '^www-authenticate:' || true)
+          echo "${AUTH:-(keine WWW-Authenticate Zeile)}"
+          REALM=$(printf '%s' "$AUTH" | sed -n 's/.*realm="\([^"]*\)".*/\1/p')
+          SERVICE=$(printf '%s' "$AUTH" | sed -n 's/.*service="\([^"]*\)".*/\1/p')
+          echo "realm='${REALM}'  service='${SERVICE}'"
+
+          if [ -n "${REALM}" ]; then
+            echo "--- Token-Request am echten realm ---"
+            CODE=$(curl -s -o /tmp/tok.json -w "%{http_code}" -u "${REG_USER}:${REG_TOKEN}" \
+              "${REALM}?service=${SERVICE}&scope=repository:${IMAGE_LOWER}:pull,push")
+            echo "HTTP ${CODE}"
+            echo "Antwort (gekuerzt): $(head -c 300 /tmp/tok.json)"
+          fi
 
       - name: An Gitea Container Registry anmelden
         uses: docker/login-action@v3