diff --git a/apps/web/src/oj/classroom/board.vue b/apps/web/src/oj/classroom/board.vue
index 37e1e00..f3c6242 100644
--- a/apps/web/src/oj/classroom/board.vue
+++ b/apps/web/src/oj/classroom/board.vue
@@ -13,8 +13,9 @@ import type { ClassBoard, ClassBoardCell, ClassBoardStudent } from "utils/types"
  * 学生一道都没交（占三分之一），交了 3 次以上还没过的平均不到 1 个。所以排序是
  * 没交过 → 卡住 → 在做 → 做完，没交过的名单还单独摆在最上面，老师扫一眼就能走过去。
  *
- * 班级**不记本地**，默认由后端猜最近两小时在交题的班 —— 理由见 StatisticsPanel.vue
- * 那段注释（上一节课的班悄悄留在框里，老师看的整个是别人的班）。
+ * 班级**不记本地**，默认由后端猜最近两小时在交题的班 —— 记本地的话，上一节课的班会
+ * 悄悄留在框里，老师看的整个是别人的班。（提交统计弹窗是记一小时的，见 composables/statisticsQuery.ts，
+ * 那边是老师自己手选的查询；这里后端本来就猜得出，没必要冒这个险。）
  */
 
 /** 同一道题今天交了这么多次还没过，算卡住 */
diff --git a/apps/web/src/shared/components/FlowchartStatisticsPanel.vue b/apps/web/src/shared/components/FlowchartStatisticsPanel.vue
index 1baa769..4fe7900 100644
--- a/apps/web/src/shared/components/FlowchartStatisticsPanel.vue
+++ b/apps/web/src/shared/components/FlowchartStatisticsPanel.vue
@@ -142,9 +142,10 @@
 import { formatISO, sub, type Duration } from "date-fns"
 import type { FlowchartStatistics } from "@oj2/contract"
 import { getFlowchartStatistics } from "oj/api"
-import { PANEL_DURATION_OPTIONS, FLOWCHART_CRITERIA_ORDER } from "utils/constants"
+import { PANEL_DURATION_OPTIONS, FLOWCHART_CRITERIA_ORDER, STORAGE_KEY } from "utils/constants"
 import { durationFromValue } from "utils/functions"
 import { useHiddenStudents } from "../composables/hiddenStudents"
+import { useStatisticsQuery } from "../composables/statisticsQuery"
 import { Doughnut, Radar, Bar } from "vue-chartjs"
 import {
   Chart as ChartJS,
@@ -189,11 +190,8 @@ const message = useMessage()
 
 const durationOptions: SelectOption[] = [...PANEL_DURATION_OPTIONS]
 
-const query = reactive({
-  username: props.username,
-  problem: props.problem,
-  duration: durationOptions[0].value,
-})
+// 班级、题号、时间段记一小时，理由见 useStatisticsQuery
+const { query, save: saveQuery } = useStatisticsQuery(STORAGE_KEY.FLOWCHART_STATISTICS_QUERY, props)
 
 const data = reactive<FlowchartStatistics>({
   totalCount: 0,
@@ -447,6 +445,7 @@ async function handleStatistics() {
   try {
     const res = await getFlowchartStatistics(duration, query.problem, query.username)
     Object.assign(data, res)
+    saveQuery()
   } catch (error) {
     message.error("获取流程图统计失败")
     console.error("获取流程图统计失败:", error)
diff --git a/apps/web/src/shared/components/StatisticsPanel.vue b/apps/web/src/shared/components/StatisticsPanel.vue
index 64a66ec..3634479 100644
--- a/apps/web/src/shared/components/StatisticsPanel.vue
+++ b/apps/web/src/shared/components/StatisticsPanel.vue
@@ -157,9 +157,10 @@
 import { h } from "vue"
 import { formatISO, sub, type Duration } from "date-fns"
 import { getSubmissionStatistics, getSubmissionStatisticsItems } from "oj/api"
-import { PANEL_DURATION_OPTIONS } from "utils/constants"
+import { PANEL_DURATION_OPTIONS, STORAGE_KEY } from "utils/constants"
 import { useConfigStore } from "../store/config"
 import { useHiddenStudents } from "../composables/hiddenStudents"
+import { useStatisticsQuery } from "../composables/statisticsQuery"
 import { Doughnut } from "vue-chartjs"
 import { Chart as ChartJS, ArcElement, Title, Tooltip, Legend } from "chart.js"
 import { NFlex, NTag, NText, NTooltip, type DataTableRowKey } from "naive-ui"
@@ -385,19 +386,8 @@ const classOptions = computed<SelectOption[]>(
     })) ?? [],
 )
 
-/**
- * 班级/用户**不记本地**：这个选择框每次打开都从空的开始。
- *
- * 曾经把上次的班级写进 localStorage（statisticsClass），下次打开自动带上。但那正是
- * 最危险的地方 —— 下课换了班、或者换个人坐这台机器，上一个人查的班悄悄留在框里，
- * 老师没注意就按了「统计」，看到的整个是别人的班。宁可多选一次。
- * 登录框那份 LOGIN_CLASS 是另一回事：那记的是这台机器的身份，不是一次临时查询。
- */
-const query = reactive({
-  username: props.username,
-  problem: props.problem,
-  duration: options[0].value,
-})
+// 班级、题号、时间段记一小时，理由见 useStatisticsQuery
+const { query, save: saveQuery } = useStatisticsQuery(STORAGE_KEY.STATISTICS_QUERY, props)
 
 const count = reactive({
   total: 0,
@@ -675,6 +665,7 @@ async function fetchStatistics() {
     .map((item) => item.trim())
     .filter(Boolean)
   const res = await getSubmissionStatistics(duration, query.problem, query.username)
+  saveQuery()
   queriedProblemCount.value = new Set(problems.map((p) => p.toLowerCase())).size
   count.total = res.submissionCount
   count.accepted = res.acceptedCount
diff --git a/apps/web/src/shared/composables/statisticsQuery.ts b/apps/web/src/shared/composables/statisticsQuery.ts
new file mode 100644
index 0000000..436c264
--- /dev/null
+++ b/apps/web/src/shared/composables/statisticsQuery.ts
@@ -0,0 +1,65 @@
+import { reactive } from "vue"
+import { PANEL_DURATION_OPTIONS } from "utils/constants"
+import storage from "utils/storage"
+
+/**
+ * 统计面板的查询条件（班级/用户、题号、时间段），**记一小时**：一小时内再打开，
+ * 框里是上次查的那一组。
+ *
+ * 老师一节课里会反复开关这个弹窗（看一眼、关掉、走下去辅导、回来再开），每次都从空的
+ * 选班级、敲题号很烦。但也不能一直记着 —— 曾经把上次的班级永久写进 localStorage，
+ * 下课换了班、或者换个人坐这台机器，上一个人查的班悄悄留在框里，老师没注意就按了
+ * 「统计」，看到的整个是别人的班。一小时是折中：一节课够用，隔一节课就自己清掉。
+ * 注意**连堂**时下一节仍在一小时内，框里会是上一个班，这一点是接受了的。
+ *
+ * 一小时从「最后一次查询」算起（调用方在每次查完后调 `save`，自动刷新也算），
+ * 开着面板盯一整节课不会中途过期。
+ *
+ * 调用方传进来的初值优先：题目页固定是这道题、提交列表带着自己的筛选条件，
+ * 那是比缓存更明确的上下文；为空的那几项才用缓存补上。
+ * 登录框那份 LOGIN_CLASS 是另一回事：那记的是这台机器的身份，不是一次临时查询。
+ *
+ * @param storageKey localStorage 的键。**两个面板各用各的** —— 流程图题和代码题的
+ *   题号不是一批，互相带过去只会查出一片空。
+ */
+export function useStatisticsQuery(
+  storageKey: string,
+  initial: { username: string; problem: string },
+) {
+  const TTL = 60 * 60 * 1000
+
+  type Cached = { username: string; problem: string; duration: string; savedAt: number }
+
+  function load(): Partial<Cached> {
+    try {
+      const cached: Cached | null = storage.get(storageKey)
+      if (!cached || Date.now() - cached.savedAt > TTL) return {}
+      return cached
+    } catch {
+      return {}
+    }
+  }
+
+  const cached = load()
+
+  const query = reactive({
+    username: initial.username || cached.username || "",
+    problem: initial.problem || cached.problem || "",
+    // 选项表改过之后旧缓存里的值可能已经不在里面了，认不出来就回到第一档
+    duration: PANEL_DURATION_OPTIONS.some((option) => option.value === cached.duration)
+      ? cached.duration!
+      : PANEL_DURATION_OPTIONS[0].value,
+  })
+
+  function save() {
+    storage.set(storageKey, {
+      // 选择框点了清除是 null，不是空串
+      username: query.username ?? "",
+      problem: query.problem ?? "",
+      duration: query.duration,
+      savedAt: Date.now(),
+    } satisfies Cached)
+  }
+
+  return { query, save }
+}
diff --git a/apps/web/src/utils/constants.ts b/apps/web/src/utils/constants.ts
index d095327..79fcb44 100644
--- a/apps/web/src/utils/constants.ts
+++ b/apps/web/src/utils/constants.ts
@@ -156,6 +156,8 @@ export const STORAGE_KEY = {
   ADMIN_SIDER_COLLAPSED: "adminSiderCollapsed",
   DEMO_MODE: "demoMode",
   LOGIN_CLASS: "loginClass",
+  STATISTICS_QUERY: "statisticsQuery",
+  FLOWCHART_STATISTICS_QUERY: "flowchartStatisticsQuery",
 }
 
 export const DIFFICULTY = {