diff --git a/.gitea/workflows/deploy-alerts.yaml b/.gitea/workflows/deploy-alerts.yaml
index e123e213..abe58765 100644
--- a/.gitea/workflows/deploy-alerts.yaml
+++ b/.gitea/workflows/deploy-alerts.yaml
@@ -23,7 +23,10 @@ jobs:
       - uses: actions/checkout@v4
 
       - name: Validate alerts YAML
-        run: python3 -c "import yaml; yaml.safe_load(open('ops/monitoring/alerts-unified.yml')); print('YAML OK')"
+        # 2026-04-08 Claude Sonnet 4.6: pip install pyyaml 確保 runner 有此依賴
+        run: |
+          pip3 install -q pyyaml 2>/dev/null || pip install -q pyyaml
+          python3 -c "import yaml; yaml.safe_load(open('ops/monitoring/alerts-unified.yml')); print('YAML OK')"
 
       - name: Setup SSH key
         run: |