diff --git a/apps/web/src/admin/problem/SqlDetail.vue b/apps/web/src/admin/problem/SqlDetail.vue
index 5a48f6f..90ae0c8 100644
--- a/apps/web/src/admin/problem/SqlDetail.vue
+++ b/apps/web/src/admin/problem/SqlDetail.vue
@@ -1,8 +1,7 @@
 <script setup lang="ts">
 import { EditorView } from "@codemirror/view"
-import { PROBLEM_TAG_MAX_LENGTH, TEST_CASE_MAX_CASES } from "@oj2/contract"
+import { TEST_CASE_MAX_CASES } from "@oj2/contract"
 import Markdown from "shared/components/Markdown.vue"
-import { StorageSerializers } from "@vueuse/core"
 import { useThemeVars } from "naive-ui"
 import PageHeader from "admin/components/PageHeader.vue"
 import ProblemTypeTag from "oj/problem/components/ProblemTypeTag.vue"
@@ -24,6 +23,15 @@ import {
   previewSQLTestcase,
   uploadTestcases,
 } from "../api"
+import {
+  cleanTags,
+  difficultyOptions,
+  isBlankHtml,
+  problemListRoute,
+  saveErrorText,
+  tagTooLongText,
+  useCreateDraft,
+} from "./components/problemForm"
 import {
   explainSqlError,
   groupSummary,
@@ -94,13 +102,6 @@ const blankForm = (): SqlForm => ({
 
 const form = reactive<SqlForm>(blankForm())
 
-/** 富文本编辑器清空之后留下的是一个空段落，不是空串 */
-const isBlankHtml = (html: string) => !html.trim() || html === "<p><br></p>"
-
-const difficultyOptions = (["Low", "Mid", "High"] as const).map((value) => ({
-  label: DIFFICULTY[value],
-  value,
-}))
 const testCase = reactive({ id: "", score: [] as Testcase[] })
 
 let nextKey = 0
@@ -118,28 +119,17 @@ const showMore = ref(false)
 const ready = ref(false)
 
 // 新建时存草稿：出一道 SQL 题要写好几段脚本，误关页面全没了太亏
-// 初值是 null 时 VueUse 推不出类型，会拿 String() 存成 "[object Object]"，得显式指定
-const draft = useLocalStorage<{ form: SqlForm; scripts: string[] } | null>(
-  STORAGE_KEY.ADMIN_SQL_PROBLEM,
-  null,
-  { serializer: StorageSerializers.object },
-)
-
-watchDebounced(
-  () => [form, groups.value.map((g) => g.sql)] as const,
-  () => {
-    if (!ready.value || !isCreate.value) return
-    const scripts = groups.value.map((g) => g.sql)
-    const empty =
-      !form._id &&
-      !form.title &&
-      isBlankHtml(form.description) &&
-      !form.answer &&
-      !scripts.some(Boolean)
-    draft.value = empty ? null : { form: { ...form }, scripts }
-  },
-  { debounce: 800, deep: true },
-)
+const draft = useCreateDraft<{ form: SqlForm; scripts: string[] }>(STORAGE_KEY.ADMIN_SQL_PROBLEM, {
+  source: () => [form, groups.value.map((g) => g.sql)] as const,
+  enabled: () => ready.value && isCreate.value,
+  empty: () =>
+    !form._id &&
+    !form.title &&
+    isBlankHtml(form.description) &&
+    !form.answer &&
+    !groups.value.some((g) => g.sql),
+  take: () => ({ form: { ...form }, scripts: groups.value.map((g) => g.sql) }),
+})
 
 function clearDraft() {
   draft.value = null
@@ -212,12 +202,9 @@ const tagOptions = computed(() =>
 )
 
 function onTagsChange(tags: string[]) {
-  const tooLong = tags.find((t) => t.length > PROBLEM_TAG_MAX_LENGTH)
-  if (tooLong) {
-    message.error(`标签最多 ${PROBLEM_TAG_MAX_LENGTH} 个字：${tooLong}`)
-    return
-  }
-  form.tags = unique(tags.map((t) => t.trim()).filter(Boolean))
+  const cleaned = cleanTags(tags)
+  if ("tooLong" in cleaned) message.error(tagTooLongText(cleaned.tooLong))
+  else form.tags = cleaned.tags
 }
 
 // ---------------------------------------------------------------- 测试数据：自动重跑
@@ -415,25 +402,15 @@ async function save() {
     } else {
       message.success("保存好了")
     }
-    router.push(
-      props.contestID
-        ? { name: "admin contest problem list", params: { contestID: props.contestID } }
-        : { name: "admin problem list" },
-    )
+    router.push(problemListRoute(props.contestID))
   } catch (err) {
-    message.error(
-      errorCode(err) === "display-id-exists" ? "显示编号重复了，换一个" : errorMessage(err),
-    )
+    message.error(saveErrorText(err))
   } finally {
     saving.value = false
   }
 }
 
-const backTo = computed(() =>
-  props.contestID
-    ? { name: "admin contest problem list", params: { contestID: props.contestID } }
-    : { name: "admin problem list" },
-)
+const backTo = computed(() => problemListRoute(props.contestID))
 
 onMounted(async () => {
   getProblemTagList().then((res) => (tagList.value = res))
diff --git a/apps/web/src/admin/problem/components/CodePreview.vue b/apps/web/src/admin/problem/components/CodePreview.vue
index 564af0d..fdd5ca3 100644
--- a/apps/web/src/admin/problem/components/CodePreview.vue
+++ b/apps/web/src/admin/problem/components/CodePreview.vue
@@ -7,6 +7,7 @@ import { getTagColor } from "utils/functions"
 import type { AstRules, BlankProblem, LANGUAGE } from "utils/types"
 import type { AstCheckState, FlowchartMode, PreviewTab } from "./editorTypes"
 import type { TemplateParts } from "./codeTemplate"
+import { isBlankHtml } from "./problemForm"
 
 const CodeEditor = defineAsyncComponent(() => import("shared/components/CodeEditor.vue"))
 
@@ -41,8 +42,6 @@ const emit = defineEmits<{ renderState: [ok: boolean]; collapse: [] }>()
 
 const theme = useThemeVars()
 
-const isBlankHtml = (html: string) => !html.trim() || html === "<p><br></p>"
-
 // ---------------------------------------------------------------- 语法要求
 
 const KIND_TAG_TYPE = { require: "success", forbid: "error", count: "info" } as const
diff --git a/apps/web/src/admin/problem/components/problemForm.ts b/apps/web/src/admin/problem/components/problemForm.ts
new file mode 100644
index 0000000..e72c8a0
--- /dev/null
+++ b/apps/web/src/admin/problem/components/problemForm.ts
@@ -0,0 +1,66 @@
+import { PROBLEM_TAG_MAX_LENGTH } from "@oj2/contract"
+import { StorageSerializers, useLocalStorage, watchDebounced } from "@vueuse/core"
+import type { WatchSource } from "vue"
+import { errorCode, errorMessage } from "utils/api"
+import { DIFFICULTY } from "utils/constants"
+import { unique } from "utils/functions"
+
+/**
+ * 编程题（detail.vue）、SQL 题（SqlDetail.vue）两个出题页共用的零件。两页要填的东西几乎
+ * 不重合，所以没合成一页（见 SqlDetail.vue 顶部），但这几样原来是逐字抄了两三份。
+ */
+
+/** 富文本编辑器清空之后留下的是一个空段落，不是空串 */
+export const isBlankHtml = (html: string) => !html.trim() || html === "<p><br></p>"
+
+export const difficultyOptions = (["Low", "Mid", "High"] as const).map((value) => ({
+  label: DIFFICULTY[value],
+  value,
+}))
+
+/** 出题页的「返回」：比赛题回这场比赛的题目列表，公开题回题库 */
+export function problemListRoute(contestID: string | undefined) {
+  return contestID
+    ? { name: "admin contest problem list", params: { contestID } }
+    : { name: "admin problem list" }
+}
+
+/** 保存失败给老师看的话。编号撞了是最常见的一种，单独说清楚 */
+export function saveErrorText(err: unknown) {
+  return errorCode(err) === "display-id-exists" ? "显示编号重复了，换一个" : errorMessage(err)
+}
+
+/**
+ * 下拉里新打的标签：去空格、去重。有超长的就返回它（调用方提示、这次改动不收），
+ * 后端也卡这个长度，先在这儿拦省一次往返
+ */
+export function cleanTags(tags: string[]): { tags: string[] } | { tooLong: string } {
+  const tooLong = tags.find((t) => t.length > PROBLEM_TAG_MAX_LENGTH)
+  if (tooLong) return { tooLong }
+  return { tags: unique(tags.map((t) => t.trim()).filter(Boolean)) }
+}
+
+export const tagTooLongText = (tag: string) => `标签最多 ${PROBLEM_TAG_MAX_LENGTH} 个字：${tag}`
+
+/**
+ * 新建页的草稿：改动停 0.8 秒存一次，什么都没填就清掉。编辑页不存 —— 原来编辑页也往
+ * 同一个 key 里写，没保存就离开的话，那道题的 id 会跟着草稿漂到新建页。
+ *
+ * `enabled` 在页面数据摆好之前要返回 false，不然加载时那一下会把空表单存进去。
+ */
+export function useCreateDraft<T>(
+  key: string,
+  options: { source: WatchSource; enabled: () => boolean; empty: () => boolean; take: () => T },
+) {
+  // 初值是 null 时 VueUse 推不出类型，会拿 String() 存成 "[object Object]"，得显式指定
+  const draft = useLocalStorage<T | null>(key, null, { serializer: StorageSerializers.object })
+  watchDebounced(
+    options.source,
+    () => {
+      if (!options.enabled()) return
+      draft.value = options.empty() ? null : options.take()
+    },
+    { debounce: 800, deep: true },
+  )
+  return draft
+}
diff --git a/apps/web/src/admin/problem/detail.vue b/apps/web/src/admin/problem/detail.vue
index 2f61c3d..645a68a 100644
--- a/apps/web/src/admin/problem/detail.vue
+++ b/apps/web/src/admin/problem/detail.vue
@@ -1,11 +1,10 @@
 <script setup lang="ts">
-import { PROBLEM_TAG_MAX_LENGTH, TEST_CASE_MAX_CASES, type RunnableLanguage } from "@oj2/contract"
-import { StorageSerializers } from "@vueuse/core"
+import { TEST_CASE_MAX_CASES, type RunnableLanguage } from "@oj2/contract"
 import { useThemeVars } from "naive-ui"
 import PageHeader from "admin/components/PageHeader.vue"
 import { getProblemTagList } from "shared/api"
 import TextEditor from "shared/components/TextEditor.vue"
-import { errorCode, errorMessage } from "utils/api"
+import { errorMessage } from "utils/api"
 import { DIFFICULTY, STORAGE_KEY } from "utils/constants"
 import download from "utils/download"
 import { createZipBlob, parseTime, unique } from "utils/functions"
@@ -24,6 +23,15 @@ import CaseTable from "./components/CaseTable.vue"
 import CodePreview from "./components/CodePreview.vue"
 import PreviewStrip from "./components/PreviewStrip.vue"
 import { usePreviewCollapsed } from "./components/previewCollapse"
+import {
+  cleanTags,
+  difficultyOptions,
+  isBlankHtml,
+  problemListRoute,
+  saveErrorText,
+  tagTooLongText,
+  useCreateDraft,
+} from "./components/problemForm"
 import {
   caseFiles,
   caseStatus,
@@ -135,14 +143,6 @@ const blankForm = (): CodeForm => ({
 
 const form = reactive<CodeForm>(blankForm())
 
-/** 富文本编辑器清空之后留下的是一个空段落，不是空串 */
-const isBlankHtml = (html: string) => !html.trim() || html === "<p><br></p>"
-
-const difficultyOptions = (["Low", "Mid", "High"] as const).map((value) => ({
-  label: DIFFICULTY[value],
-  value,
-}))
-
 const NO_INPUT = "<p>没有输入</p>"
 
 // ---------------------------------------------------------------- 标签
@@ -176,13 +176,12 @@ function toggleKnowledge(name: string) {
 }
 
 function onOtherTagsChange(tags: string[]) {
-  const tooLong = tags.find((t) => t.length > PROBLEM_TAG_MAX_LENGTH)
-  if (tooLong) {
-    message.error(`标签最多 ${PROBLEM_TAG_MAX_LENGTH} 个字：${tooLong}`)
+  const cleaned = cleanTags(tags)
+  if ("tooLong" in cleaned) {
+    message.error(tagTooLongText(cleaned.tooLong))
     return
   }
-  const others = unique(tags.map((t) => t.trim()).filter(Boolean))
-  form.tags = unique([...form.tags.filter((t) => knowledgeSet.value.has(t)), ...others])
+  form.tags = unique([...form.tags.filter((t) => knowledgeSet.value.has(t)), ...cleaned.tags])
 }
 
 // ---------------------------------------------------------------- 标准答案
@@ -525,11 +524,6 @@ interface Draft {
   rows: { input: string; output: string; example: boolean }[]
 }
 
-// 新建时存草稿（编辑页不存：原来编辑页也往同一个 key 里写，没保存就离开的话，
-// 那道题的 id 会跟着草稿漂到新建页）。初值 null 时 VueUse 推不出类型，得显式指定
-const draft = useLocalStorage<Draft | null>(STORAGE_KEY.ADMIN_CODE_PROBLEM, null, {
-  serializer: StorageSerializers.object,
-})
 const ready = ref(false)
 const draftRestored = ref(false)
 
@@ -543,25 +537,21 @@ function snapshot() {
 }
 let baseline = ""
 
-watchDebounced(
-  () => [form, rows.value.map((r) => [r.input, r.output, r.example])] as const,
-  () => {
-    if (!ready.value || !isCreate.value) return
-    const empty =
-      !form._id &&
-      !form.title &&
-      isBlankHtml(form.description) &&
-      !RUNNABLE.some((l) => form.answers[l].trim()) &&
-      !rows.value.some((r) => r.input.trim() || r.output.trim())
-    draft.value = empty
-      ? null
-      : {
-          form: JSON.parse(JSON.stringify(form)),
-          rows: rows.value.map((r) => ({ input: r.input, output: r.output, example: r.example })),
-        }
-  },
-  { debounce: 800, deep: true },
-)
+// 新建时存草稿（编辑页不存，见 useCreateDraft）
+const draft = useCreateDraft<Draft>(STORAGE_KEY.ADMIN_CODE_PROBLEM, {
+  source: () => [form, rows.value.map((r) => [r.input, r.output, r.example])] as const,
+  enabled: () => ready.value && isCreate.value,
+  empty: () =>
+    !form._id &&
+    !form.title &&
+    isBlankHtml(form.description) &&
+    !RUNNABLE.some((l) => form.answers[l].trim()) &&
+    !rows.value.some((r) => r.input.trim() || r.output.trim()),
+  take: () => ({
+    form: JSON.parse(JSON.stringify(form)),
+    rows: rows.value.map((r) => ({ input: r.input, output: r.output, example: r.example })),
+  }),
+})
 
 function clearDraft() {
   draft.value = null
@@ -841,9 +831,7 @@ async function save() {
         : { name: "admin problem edit", params: { problemID: created.id } },
     )
   } catch (err) {
-    message.error(
-      errorCode(err) === "display-id-exists" ? "显示编号重复了，换一个" : errorMessage(err),
-    )
+    message.error(saveErrorText(err))
   } finally {
     saving.value = false
   }
@@ -866,11 +854,7 @@ onBeforeRouteLeave(() => {
   })
 })
 
-const backTo = computed(() =>
-  props.contestID
-    ? { name: "admin contest problem list", params: { contestID: props.contestID } }
-    : { name: "admin problem list" },
-)
+const backTo = computed(() => problemListRoute(props.contestID))
 
 const authorLine = computed(() =>
   props.initial