diff --git a/src/stores/aiChat.ts b/src/stores/aiChat.ts
index 195b4fd0..67f0709f 100644
--- a/src/stores/aiChat.ts
+++ b/src/stores/aiChat.ts
@@ -17,6 +17,7 @@ import { useSkillStore } from '@/stores/skill'
 import { useLLMStore } from '@/stores/llm'
 import type { TokenUsage, AgentRuntimeStatus, SerializedErrorInfo } from '@electron/shared/types'
 import { useAgentStreamService } from '@/services/ai-stream/service'
+import { buildSerializablePreprocessConfig, shouldEnsureDesensitizeRulesBeforeSerialize } from './aiPreprocessConfig'
 
 // 工具调用记录
 export interface ToolCallRecord {
@@ -811,7 +812,7 @@ export const useAIChatStore = defineStore('aiChatRuntime', () => {
           ? { platformId: state.ownerInfo.platformId, displayName: state.ownerInfo.displayName }
           : undefined,
         mentionedMembers: currentMentionedMembers.length > 0 ? currentMentionedMembers : undefined,
-        preprocessConfig: buildSerializablePreprocessConfig(),
+        preprocessConfig: await buildReadySerializablePreprocessConfig(),
         searchContextBefore: aiGlobalSettings.value.searchContextBefore,
         searchContextAfter: aiGlobalSettings.value.searchContextAfter,
       }
@@ -1096,30 +1097,13 @@ export const useAIChatStore = defineStore('aiChatRuntime', () => {
     }
   }
 
-  function buildSerializablePreprocessConfig() {
+  async function buildReadySerializablePreprocessConfig() {
     const preprocessConfig = settingsStore.aiPreprocessConfig
-    const hasPreprocess =
-      preprocessConfig.dataCleaning ||
-      preprocessConfig.mergeConsecutive ||
-      preprocessConfig.blacklistKeywords.length > 0 ||
-      preprocessConfig.denoise ||
-      preprocessConfig.desensitize ||
-      preprocessConfig.anonymizeNames
-
-    if (!hasPreprocess) return undefined
-    return {
-      dataCleaning: preprocessConfig.dataCleaning,
-      mergeConsecutive: preprocessConfig.mergeConsecutive,
-      mergeWindowSeconds: preprocessConfig.mergeWindowSeconds,
-      blacklistKeywords: [...preprocessConfig.blacklistKeywords],
-      denoise: preprocessConfig.denoise,
-      desensitize: preprocessConfig.desensitize,
-      desensitizeRules: preprocessConfig.desensitizeRules.map((rule) => ({
-        ...rule,
-        locales: [...rule.locales],
-      })),
-      anonymizeNames: preprocessConfig.anonymizeNames,
+    if (shouldEnsureDesensitizeRulesBeforeSerialize(preprocessConfig)) {
+      await settingsStore.ensureDesensitizeRules()
     }
+
+    return buildSerializablePreprocessConfig(settingsStore.aiPreprocessConfig)
   }
 
   function normalizeMentionLookupText(value: string): string {
@@ -1360,7 +1344,7 @@ export const useAIChatStore = defineStore('aiChatRuntime', () => {
           ? { platformId: state.ownerInfo.platformId, displayName: state.ownerInfo.displayName }
           : undefined,
         mentionedMembers: currentMentionedMembers.length > 0 ? currentMentionedMembers : undefined,
-        preprocessConfig: buildSerializablePreprocessConfig(),
+        preprocessConfig: await buildReadySerializablePreprocessConfig(),
         searchContextBefore: aiGlobalSettings.value.searchContextBefore,
         searchContextAfter: aiGlobalSettings.value.searchContextAfter,
       }
diff --git a/src/stores/aiPreprocessConfig.test.ts b/src/stores/aiPreprocessConfig.test.ts
new file mode 100644
index 00000000..eaab5eff
--- /dev/null
+++ b/src/stores/aiPreprocessConfig.test.ts
@@ -0,0 +1,65 @@
+import { describe, it } from 'node:test'
+import assert from 'node:assert/strict'
+import { shouldEnsureDesensitizeRulesBeforeSerialize } from './aiPreprocessConfig'
+
+describe('AI preprocess config serialization guards', () => {
+  it('requires built-in rules before serializing an enabled empty desensitize config', () => {
+    assert.equal(
+      shouldEnsureDesensitizeRulesBeforeSerialize({
+        desensitize: true,
+        desensitizeRules: [],
+      }),
+      true
+    )
+  })
+
+  it('requires built-in rules before serializing enabled custom-only desensitize rules', () => {
+    assert.equal(
+      shouldEnsureDesensitizeRulesBeforeSerialize({
+        desensitize: true,
+        desensitizeRules: [
+          {
+            id: 'custom_staff_id',
+            label: 'Staff ID',
+            pattern: 'EMP-\\d+',
+            replacement: '[Staff ID]',
+            enabled: true,
+            builtin: false,
+            locales: [],
+          },
+        ],
+      }),
+      true
+    )
+  })
+
+  it('does not require built-in rules when enabled rules already include a built-in rule', () => {
+    assert.equal(
+      shouldEnsureDesensitizeRulesBeforeSerialize({
+        desensitize: true,
+        desensitizeRules: [
+          {
+            id: 'email',
+            label: 'desensitize.rules.email',
+            pattern: '[^@\\s]+@[^@\\s]+',
+            replacement: '[Email]',
+            enabled: true,
+            builtin: true,
+            locales: [],
+          },
+        ],
+      }),
+      false
+    )
+  })
+
+  it('does not require built-in rules when masking is disabled', () => {
+    assert.equal(
+      shouldEnsureDesensitizeRulesBeforeSerialize({
+        desensitize: false,
+        desensitizeRules: [],
+      }),
+      false
+    )
+  })
+})
diff --git a/src/stores/aiPreprocessConfig.ts b/src/stores/aiPreprocessConfig.ts
new file mode 100644
index 00000000..b21121dc
--- /dev/null
+++ b/src/stores/aiPreprocessConfig.ts
@@ -0,0 +1,32 @@
+import type { PreprocessConfig } from '@electron/preload/index'
+
+export function shouldEnsureDesensitizeRulesBeforeSerialize(
+  config: Pick<PreprocessConfig, 'desensitize' | 'desensitizeRules'>
+): boolean {
+  return config.desensitize && !config.desensitizeRules.some((rule) => rule.builtin)
+}
+
+export function buildSerializablePreprocessConfig(config: PreprocessConfig) {
+  const hasPreprocess =
+    config.dataCleaning ||
+    config.mergeConsecutive ||
+    config.blacklistKeywords.length > 0 ||
+    config.denoise ||
+    config.desensitize ||
+    config.anonymizeNames
+
+  if (!hasPreprocess) return undefined
+  return {
+    dataCleaning: config.dataCleaning,
+    mergeConsecutive: config.mergeConsecutive,
+    mergeWindowSeconds: config.mergeWindowSeconds,
+    blacklistKeywords: [...config.blacklistKeywords],
+    denoise: config.denoise,
+    desensitize: config.desensitize,
+    desensitizeRules: config.desensitizeRules.map((rule) => ({
+      ...rule,
+      locales: [...rule.locales],
+    })),
+    anonymizeNames: config.anonymizeNames,
+  }
+}