diff --git a/src/oj/problem/components/SubmitFlowchart.vue b/src/oj/problem/components/SubmitFlowchart.vue
index 78d9e6e..f407dc6 100644
--- a/src/oj/problem/components/SubmitFlowchart.vue
+++ b/src/oj/problem/components/SubmitFlowchart.vue
@@ -106,7 +106,7 @@ async function submitFlowchartData(flowchartEditorRef: any) {
   // 获取流程图的JSON数据
   const flowchartData = flowchartEditorRef.value.getFlowchartData()
 
-  if (flowchartData.nodes.length === 0 || flowchartData.edges.length === 0) {
+  if (!flowchartData?.nodes?.length || !flowchartData?.edges?.length) {
     message.error("流程图节点或边不能为空")
     return
   }
diff --git a/src/oj/problem/composables/useMermaidConverter.ts b/src/oj/problem/composables/useMermaidConverter.ts
index 1a0372a..b5641c5 100644
--- a/src/oj/problem/composables/useMermaidConverter.ts
+++ b/src/oj/problem/composables/useMermaidConverter.ts
@@ -11,9 +11,17 @@ export function useMermaidConverter() {
 
     let mermaid = "graph TD\n"
 
+    // Build safe ID mapping to prevent Mermaid syntax errors from special characters
+    const idMap = new Map<string, string>()
+    nodes.forEach((node: any, index: number) => {
+      idMap.set(node.id, `node_${index}`)
+    })
+    const safeId = (id: string) =>
+      idMap.get(id) || id.replace(/[^a-zA-Z0-9_]/g, "_")
+
     // 处理节点 - 根据原始类型和自定义标签
     nodes.forEach((node: any) => {
-      const nodeId = node.id
+      const nodeId = safeId(node.id)
       const label = node.data?.customLabel || node.data?.label || "节点"
       const originalType = node.data?.originalType || node.type
 
@@ -50,8 +58,8 @@ export function useMermaidConverter() {
 
     // 处理边
     edges.forEach((edge: any) => {
-      const source = edge.source
-      const target = edge.target
+      const source = safeId(edge.source)
+      const target = safeId(edge.target)
       const label = edge.label ?? ""
 
       if (label && label.trim() !== "") {
@@ -77,7 +85,7 @@ export function useMermaidConverter() {
 
     // 为节点应用样式
     nodes.forEach((node: any) => {
-      const nodeId = node.id
+      const nodeId = safeId(node.id)
       const originalType = node.data?.originalType || node.type
 
       switch (originalType) {
diff --git a/src/shared/components/FlowchartEditor/index.vue b/src/shared/components/FlowchartEditor/index.vue
index 81ccffd..0b7bf60 100644
--- a/src/shared/components/FlowchartEditor/index.vue
+++ b/src/shared/components/FlowchartEditor/index.vue
@@ -114,7 +114,11 @@ const handleClear = () => {
 
 // 键盘事件
 const handleKeyDown = (event: KeyboardEvent) => {
-  if (event.target instanceof HTMLInputElement) return
+  if (
+    event.target instanceof HTMLInputElement ||
+    event.target instanceof HTMLTextAreaElement
+  )
+    return
 
   if (event.key === "Delete" || event.key === "Backspace") {
     deleteSelected()
diff --git a/src/shared/components/MermaidEditor.vue b/src/shared/components/MermaidEditor.vue
index 36b95a9..6c8b65d 100644
--- a/src/shared/components/MermaidEditor.vue
+++ b/src/shared/components/MermaidEditor.vue
@@ -22,7 +22,7 @@ const loadMermaid = async () => {
     mermaid = mermaidModule.default
     mermaid.initialize({
       startOnLoad: false,
-      securityLevel: "loose",
+      securityLevel: "strict",
       theme: "default",
     })
   }
@@ -72,12 +72,17 @@ const renderMermaid = async () => {
     const errorMessage = error?.message || "请检查代码语法"
     renderSuccess.value = false
 
-    mermaidContainer.value.innerHTML = `
-      <div style="color: #ff4d4f; padding: 20px; text-align: center; border: 1px dashed #ff4d4f; border-radius: 4px;">
-        <p>❌ Mermaid语法错误</p>
-        <p style="font-size: 12px; color: #666;">${errorMessage}</p>
-      </div>
-    `
+    const errorDiv = document.createElement("div")
+    errorDiv.style.cssText = "color: #ff4d4f; padding: 20px; text-align: center; border: 1px dashed #ff4d4f; border-radius: 4px;"
+    const titleP = document.createElement("p")
+    titleP.textContent = "Mermaid语法错误"
+    const detailP = document.createElement("p")
+    detailP.style.cssText = "font-size: 12px; color: #666;"
+    detailP.textContent = errorMessage
+    errorDiv.appendChild(titleP)
+    errorDiv.appendChild(detailP)
+    mermaidContainer.value.innerHTML = ""
+    mermaidContainer.value.appendChild(errorDiv)
   }
 }
 
diff --git a/src/shared/composables/useMermaid.ts b/src/shared/composables/useMermaid.ts
index 5919800..69d9db7 100644
--- a/src/shared/composables/useMermaid.ts
+++ b/src/shared/composables/useMermaid.ts
@@ -14,7 +14,7 @@ export function useMermaid() {
       mermaid = mermaidModule.default
       mermaid.initialize({
         startOnLoad: false,
-        securityLevel: "loose",
+        securityLevel: "strict",
         theme: "default",
       })
     }