diff --git a/apps/api/src/routes/flowchart.ts b/apps/api/src/routes/flowchart.ts
index 790be9e..4e2af34 100644
--- a/apps/api/src/routes/flowchart.ts
+++ b/apps/api/src/routes/flowchart.ts
@@ -10,6 +10,7 @@ import {
   type FlowchartListItem,
   type FlowchartStatistics,
   type FlowchartSubmission,
+  NO_CLASS,
 } from "@oj2/contract"
 import { and, asc, count, desc, eq, inArray, isNull, sql, type SQL } from "drizzle-orm"
 import { Hono } from "hono"
@@ -27,6 +28,7 @@ import { buildWordFrequencies } from "../services/word-frequency"
 import { dayStart } from "../time"
 import { unknownDisplayIds } from "./submission-statistics"
 import {
+  classCondition,
   isAdminRole,
   matchedUsers,
   asRecord,
@@ -208,7 +210,7 @@ async function flowchartClassFilter(className: string) {
   const users = await db
     .select({ id: schema.user.id })
     .from(schema.user)
-    .where(eq(schema.user.className, className))
+    .where(classCondition(className))
   return users.length
     ? inArray(
         schema.flowchartSubmission.userId,
@@ -422,10 +424,13 @@ flowchartRoutes.get("/flowcharts/statistics", requireTeacher, async (c) => {
   }
   const where = and(...filters)
   // 花名册：只有指定了用户名才谈得上「班级人数」，不指定时分母无意义。
-  // 未禁用的普通用户才进分母，教师和管理员不算
-  const roster = scoped
-    ? matched.filter((row) => !row.isDisabled && row.adminType === "Regular User")
-    : []
+  // 未禁用的普通用户才进分母，教师和管理员不算。
+  // 「没填班级」不是一个真的班（两百来个夏令营、自己注册的号混在一起），「谁没做」列出来全是
+  // 不相干的人，当没有花名册
+  const roster =
+    scoped && c.req.query("className")?.trim() !== NO_CLASS
+      ? matched.filter((row) => !row.isDisabled && row.adminType === "Regular User")
+      : []
 
   /**
    * 五条查询，每条的代价都和窗口里的行数脱钩（词云那条卡了 limit）。
diff --git a/apps/api/src/routes/helpers.ts b/apps/api/src/routes/helpers.ts
index 0e48cd0..d64bf28 100644
--- a/apps/api/src/routes/helpers.ts
+++ b/apps/api/src/routes/helpers.ts
@@ -1,6 +1,6 @@
-import { ADMIN_ROLES, TEACHER_ROLES, type SampleUser } from "@oj2/contract"
+import { ADMIN_ROLES, NO_CLASS, TEACHER_ROLES, type SampleUser } from "@oj2/contract"
 
-import { and, count, eq, ilike, notInArray, sql } from "drizzle-orm"
+import { and, count, eq, ilike, isNull, notInArray, sql } from "drizzle-orm"
 
 import type { AuthUser } from "../auth/session"
 import { db, schema } from "../db"
@@ -159,6 +159,19 @@ export async function countFailedSubmissions(userId: number, problemId: number)
  * 代码提交和流程图两条统计都走这里。流程图那张表连冻结用户名都没有（只有
  * `user_id`），更是只能从这儿拿 id。
  */
+/**
+ * 「这个班的人」：`user.class_name` 精确匹配；NO_CLASS 是没填班级的学生（class_name 为 null）。
+ * 统计、提交列表、流程图按班级筛都走它，没填班级的才能和普通班一样被圈出来。
+ *
+ * NO_CLASS 只圈普通用户：老师、管理员的号本来就都不填班级，不挡的话老师自己试题的提交
+ * 会混进「没填班级」，还算进做完的人数里（切课那边也只算普通学生，两边口径一致）
+ */
+export function classCondition(className: string) {
+  return className === NO_CLASS
+    ? and(isNull(schema.user.className), eq(schema.user.adminType, "Regular User"))
+    : eq(schema.user.className, className)
+}
+
 /**
  * 统计接口「圈哪些人」：班级按 `user.class_name` **精确**匹配，学生名按包含匹配，两个都给
  * 就取交集，都没给返回 null（不圈人）。
@@ -179,7 +192,7 @@ export async function scopedUsers(username: string | undefined, className: strin
     .from(schema.user)
     .where(
       and(
-        className ? eq(schema.user.className, className) : undefined,
+        className ? classCondition(className) : undefined,
         username ? ilike(schema.user.username, `%${username}%`) : undefined,
       ),
     )
diff --git a/apps/api/src/routes/submission-statistics.ts b/apps/api/src/routes/submission-statistics.ts
index 5d3176c..b269902 100644
--- a/apps/api/src/routes/submission-statistics.ts
+++ b/apps/api/src/routes/submission-statistics.ts
@@ -7,6 +7,7 @@
  */
 
 import {
+  NO_CLASS,
   type ProblemLanguage,
   type SubmissionLessons,
   type SubmissionStatistics,
@@ -23,7 +24,14 @@ import { JudgeStatus, UNJUDGED_RESULTS, type JudgeStatusValue } from "../judge/s
 import { type ContestEnv } from "../services/contest"
 import { getBooleanOption } from "../services/options"
 import { dayStart, localTime } from "../time"
-import { isAdminRole, parseDisplayIds, rounded, scopedUsers, stripClassPrefix } from "./helpers"
+import {
+  classCondition,
+  isAdminRole,
+  parseDisplayIds,
+  rounded,
+  scopedUsers,
+  stripClassPrefix,
+} from "./helpers"
 
 export const submissionStatisticsRoutes = new Hono<ContestEnv>()
 
@@ -240,7 +248,7 @@ export async function classNameFilter(className: string) {
   const users = await db
     .select({ id: schema.user.id })
     .from(schema.user)
-    .where(eq(schema.user.className, className))
+    .where(classCondition(className))
   return users.length
     ? inArray(
         schema.submission.userId,
@@ -381,7 +389,7 @@ submissionStatisticsRoutes.get("/submissions/statistics", requireTeacher, async
   }
   const where = and(...filters)
   // 花名册：只有未禁用的普通用户算进班级人数和「谁没做」，教师和管理员不进分母
-  const rosterRows = matched.filter((row) => !row.isDisabled && row.adminType === "Regular User")
+  const enrolled = matched.filter((row) => !row.isDisabled && row.adminType === "Regular User")
 
   const acceptedFilter = sql`count(*) filter (where ${inArray(schema.submission.result, ACCEPTED_RESULTS)})`
   // 判题中的条数。要单独数出来，正确率的分母才能把它们摘掉
@@ -474,6 +482,13 @@ submissionStatisticsRoutes.get("/submissions/statistics", requireTeacher, async
   const doneCount = perUser.filter(isDone).length
 
   const submittedUserIds = new Set(perUser.map((row) => row.userId))
+  /**
+   * 「没填班级」不是一个真的班：两百来个夏令营、兴趣班、自己注册的号混在一起，「还没交」
+   * 列出来全是不相干的人，分母也跟着失真。花名册只取这段时间交过的人 —— 「交了没对」照常有，
+   * 「还没交」为空，和不选班时一样
+   */
+  const rosterRows =
+    className === NO_CLASS ? enrolled.filter((row) => submittedUserIds.has(row.id)) : enrolled
 
   const data = perUser.map((row) => ({
     username: row.username,
@@ -755,7 +770,7 @@ submissionStatisticsRoutes.get("/submissions/statistics/lessons", requireTeacher
       select class_name, day, sid
       from (
         select class_name, day, sid, problem_id, count(distinct user_id) as n
-        from seg where class_name is not null
+        from seg
         group by class_name, day, sid, problem_id
       ) p
       group by class_name, day, sid
@@ -765,7 +780,8 @@ submissionStatisticsRoutes.get("/submissions/statistics/lessons", requireTeacher
       select seg.*, (l.sid is not null) as lesson
       from seg
       left join lesson_seg l
-        on l.class_name = seg.class_name and l.day = seg.day and l.sid = seg.sid
+        -- 没填班级的号（class_name 为 null）合在一起当一个班切，= 会把它们全漏掉
+        on l.class_name is not distinct from seg.class_name and l.day = seg.day and l.sid = seg.sid
     )
     select grouping(class_name, day, sid, problem_id, result, lesson) as level,
       class_name, day, sid::int as sid, problem_id, result, lesson,
@@ -866,7 +882,9 @@ submissionStatisticsRoutes.get("/submissions/statistics/lessons", requireTeacher
     : []
   const problemById = new Map(problems.map((row) => [row.id, row]))
 
-  const lessonClasses = [...new Set(picked.map((row) => row.class_name!))]
+  const lessonClasses = [
+    ...new Set(picked.flatMap((row) => (row.class_name === null ? [] : [row.class_name]))),
+  ]
   const sizes = lessonClasses.length
     ? await db
         .select({ className: schema.user.className, value: count() })
@@ -889,12 +907,16 @@ submissionStatisticsRoutes.get("/submissions/statistics/lessons", requireTeacher
     const hardest = [...own].sort((a, b) => failedOf(b) - failedOf(a))[0]
     const hardestProblem = hardest ? problemById.get(hardest.problem_id!) : undefined
     return {
-      className: lesson.class_name!,
+      className: lesson.class_name,
       day: lesson.day!,
       start: lesson.first,
       end: lesson.last,
       userCount: lesson.users,
-      classSize: sizes.find((row) => row.className === lesson.class_name)?.value ?? 0,
+      // 没填班级的谈不上花名册，给 0（界面上就只写「几人」）
+      classSize:
+        lesson.class_name === null
+          ? 0
+          : (sizes.find((row) => row.className === lesson.class_name)?.value ?? 0),
       // 点进去就拿这几道去筛：统计接口只认公开题，一次最多 20 道
       problems: own
         .map((row) => problemById.get(row.problem_id!))
diff --git a/apps/web/src/oj/statistics/components/ByClass.vue b/apps/web/src/oj/statistics/components/ByClass.vue
index 2bbd846..0ecf9d8 100644
--- a/apps/web/src/oj/statistics/components/ByClass.vue
+++ b/apps/web/src/oj/statistics/components/ByClass.vue
@@ -1,6 +1,6 @@
 <script setup lang="ts">
 import { useThemeVars } from "naive-ui"
-import type { SubmissionStatisticsGrid } from "@oj2/contract"
+import { NO_CLASS, type SubmissionStatisticsGrid } from "@oj2/contract"
 import { SubmissionStatus } from "utils/constants"
 import { useTone } from "oj/submission/composables/tone"
 import { classLabel, submissionDayText } from "oj/submission/utils"
@@ -27,7 +27,7 @@ const classes = computed(() => {
   const need = props.grid.problems.map((problem) => problem.problemDisplayId)
   const groups = new Map<string, SubmissionStatisticsGrid["rows"]>()
   for (const row of props.grid.rows) {
-    const key = row.className ?? ""
+    const key = row.className ?? NO_CLASS
     groups.set(key, [...(groups.get(key) ?? []), row])
   }
   return (
@@ -56,7 +56,7 @@ const classes = computed(() => {
         const size = props.grid.classSizes[className] ?? rows.length
         return {
           className,
-          label: className ? classLabel(className) : "没有班级",
+          label: classLabel(className),
           size,
           done,
           tried: rows.length - done,
@@ -101,13 +101,7 @@ const classes = computed(() => {
         <span class="c-n muted">{{ row.rate }}</span>
         <span class="c-last muted">{{ row.last ? submissionDayText(row.last) : "—" }}</span>
         <span class="spacer"></span>
-        <n-button
-          v-if="row.className"
-          size="small"
-          text
-          type="primary"
-          @click="emit('pick', row.className)"
-        >
+        <n-button size="small" text type="primary" @click="emit('pick', row.className)">
           看这个班 →
         </n-button>
       </div>
diff --git a/apps/web/src/oj/statistics/components/Lessons.vue b/apps/web/src/oj/statistics/components/Lessons.vue
index a8a21c0..b0f268a 100644
--- a/apps/web/src/oj/statistics/components/Lessons.vue
+++ b/apps/web/src/oj/statistics/components/Lessons.vue
@@ -8,6 +8,7 @@ import { classLabel } from "oj/submission/utils"
 import { resultName, useResultColor } from "../results"
 
 type Lesson = SubmissionLessons["lessons"][number]
+type Scattered = SubmissionLessons["scattered"][number]
 
 /**
  * 统计「一行一节课」的总览（设计稿「统计合二为一」B）。没选班、没填学生和题号时用它：
@@ -24,6 +25,8 @@ const props = defineProps<{
 }>()
 const emit = defineEmits<{
   pick: [lesson: Lesson]
+  /** 点某天的零散提交：那个班（或没填班级的）那一天 */
+  scattered: [item: Scattered]
   /** 点「错得最多的题」里的一道：只看这道（按班级汇总） */
   problem: [displayId: string]
   more: []
@@ -49,27 +52,23 @@ function dayText(day: string) {
 
 /** 按天分组，天和天里的课都是从近到远，零散提交挂在对应那天下面 */
 const days = computed(() => {
-  const map = new Map<string, { lessons: Lesson[]; scattered: string }>()
+  const map = new Map<string, Lesson[]>()
   for (const lesson of props.data.lessons) {
-    const entry = map.get(lesson.day) ?? { lessons: [], scattered: "" }
-    entry.lessons.push(lesson)
-    map.set(lesson.day, entry)
+    map.set(lesson.day, [...(map.get(lesson.day) ?? []), lesson])
   }
-  const scatteredByDay = new Map<string, string[]>()
+  const scatteredByDay = new Map<string, Scattered[]>()
   for (const item of props.data.scattered) {
-    const name = item.className ? classLabel(item.className) : "没填班级的"
-    const text = `${name} ${item.userCount} 人 ${item.total} 次`
-    scatteredByDay.set(item.day, [...(scatteredByDay.get(item.day) ?? []), text])
-    if (!map.has(item.day)) map.set(item.day, { lessons: [], scattered: "" })
+    scatteredByDay.set(item.day, [...(scatteredByDay.get(item.day) ?? []), item])
+    if (!map.has(item.day)) map.set(item.day, [])
   }
   return [...map.entries()]
     .sort((a, b) => b[0].localeCompare(a[0]))
-    .map(([day, entry]) => ({
+    .map(([day, lessons]) => ({
       day,
       label: dayText(day),
       // 最近的一节在最上面（用户说的）：打开就看到这节课，往下是更早的
-      lessons: [...entry.lessons].sort((a, b) => b.start.localeCompare(a.start)),
-      scattered: (scatteredByDay.get(day) ?? []).join(" · "),
+      lessons: [...lessons].sort((a, b) => b.start.localeCompare(a.start)),
+      scattered: scatteredByDay.get(day) ?? [],
     }))
 })
 
@@ -157,7 +156,7 @@ function percent(value: number, total: number) {
       <div class="day">{{ group.label }}</div>
       <a
         v-for="lesson in group.lessons"
-        :key="lesson.className + lesson.start"
+        :key="`${lesson.className}|${lesson.start}`"
         href="#"
         class="row"
         @click.prevent="emit('pick', lesson)"
@@ -192,8 +191,14 @@ function percent(value: number, total: number) {
         </span>
         <span class="c-go">看这节课<Icon icon="ph:caret-right-bold" :width="12" /></span>
       </a>
-      <div v-if="group.scattered" class="scattered">
-        {{ group.lessons.length ? "另有零散提交：" : "零散提交：" }}{{ group.scattered }}
+      <div v-if="group.scattered.length" class="scattered">
+        {{ group.lessons.length ? "另有零散提交：" : "零散提交：" }}
+        <template v-for="(item, index) in group.scattered" :key="item.className ?? ''">
+          <template v-if="index"> · </template>
+          <a href="#" title="看这个班这一天的提交" @click.prevent="emit('scattered', item)"
+            >{{ classLabel(item.className) }} {{ item.userCount }} 人 {{ item.total }} 次</a
+          >
+        </template>
       </div>
     </template>
 
@@ -244,7 +249,7 @@ function percent(value: number, total: number) {
               </a>
             </td>
             <td>
-              <n-text depth="2">{{ item.className ? classLabel(item.className) : "—" }}</n-text>
+              <n-text depth="2">{{ classLabel(item.className) }}</n-text>
             </td>
             <td>{{ item.total }} 次</td>
             <td>
@@ -465,6 +470,16 @@ function percent(value: number, total: number) {
   border-bottom: 1px solid v-bind("theme.dividerColor");
 }
 
+.scattered a {
+  color: v-bind("theme.textColor2");
+  text-decoration: underline dotted;
+  text-underline-offset: 3px;
+}
+
+.scattered a:hover {
+  color: v-bind("theme.primaryColor");
+}
+
 .more {
   padding: 12px 20px 0;
 }
diff --git a/apps/web/src/oj/statistics/components/StatisticsView.vue b/apps/web/src/oj/statistics/components/StatisticsView.vue
index 246ba6f..7500f6c 100644
--- a/apps/web/src/oj/statistics/components/StatisticsView.vue
+++ b/apps/web/src/oj/statistics/components/StatisticsView.vue
@@ -1,11 +1,12 @@
 <script setup lang="ts">
 import { Icon } from "@iconify/vue"
 import { useThemeVars } from "naive-ui"
-import type {
-  FlowchartStatistics,
-  SubmissionLessons,
-  SubmissionStatistics,
-  SubmissionStatisticsGrid,
+import {
+  NO_CLASS,
+  type FlowchartStatistics,
+  type SubmissionLessons,
+  type SubmissionStatistics,
+  type SubmissionStatisticsGrid,
 } from "@oj2/contract"
 import {
   getFlowchartStatistics,
@@ -16,8 +17,8 @@ import {
 import { useConfigStore } from "shared/store/config"
 import { fromPickerValue, toPickerValue } from "utils/functions"
 import { useTone } from "oj/submission/composables/tone"
-import { classLabel } from "oj/submission/utils"
-import { DEFAULT_PERIOD, PERIOD_OPTIONS, periodRange, type Period } from "../period"
+import { classSelectOptions } from "oj/submission/utils"
+import { DEFAULT_PERIOD, PERIOD_OPTIONS, dayStartOfDate, periodRange, type Period } from "../period"
 import { resultName, useResultColor } from "../results"
 import ByClass from "./ByClass.vue"
 import CodeStats from "./CodeStats.vue"
@@ -106,11 +107,9 @@ function pickDates(value: [number, number] | null) {
 /** 学生框：包含匹配。班级另外单独传（按 class_name 精确匹配，见后端 scopedUsers） */
 const studentParam = computed(() => username.value.trim())
 
-const classOptions = computed(() => {
-  const list = configStore.config?.classList ?? []
-  const all = className.value && !list.includes(className.value) ? [className.value, ...list] : list
-  return all.map((item) => ({ label: classLabel(item), value: item }))
-})
+const classOptions = computed(() =>
+  classSelectOptions(configStore.config?.classList ?? [], className.value),
+)
 
 // ---------- 取数 ----------
 
@@ -306,7 +305,7 @@ function pickClass(value: string) {
 /** 点一节课：这个班、这节课的题、这节课第一条到最后一条（多留 1 秒：库里存到微秒，转成毫秒会截掉零头） */
 function pickLesson(lesson: SubmissionLessons["lessons"][number]) {
   remember()
-  className.value = lesson.className
+  className.value = lesson.className ?? NO_CLASS
   username.value = ""
   problem.value = lesson.problems.join(" ")
   from.value = String(Date.parse(lesson.start))
@@ -314,6 +313,18 @@ function pickLesson(lesson: SubmissionLessons["lessons"][number]) {
   period.value = "lesson"
 }
 
+/** 点某天的零散提交：这个班（或没填班级的）那一整天，题号不限 —— 补做、课后练的都在里面 */
+function pickScattered(item: SubmissionLessons["scattered"][number]) {
+  remember()
+  className.value = item.className ?? NO_CLASS
+  username.value = ""
+  problem.value = ""
+  const day = String(dayStartOfDate(item.day))
+  from.value = day
+  to.value = day
+  period.value = "custom"
+}
+
 /** 点「错得最多的题」里的一道：只看这道，按班级汇总 */
 function pickProblem(displayId: string) {
   remember()
@@ -478,6 +489,7 @@ function resultWidth(value: number) {
         :timeline="shown.withinToday"
         :loading-more="loadingMore"
         @pick="pickLesson"
+        @scattered="pickScattered"
         @problem="pickProblem"
         @more="loadMore"
       />
diff --git a/apps/web/src/oj/statistics/period.ts b/apps/web/src/oj/statistics/period.ts
index d751ba2..888e54e 100644
--- a/apps/web/src/oj/statistics/period.ts
+++ b/apps/web/src/oj/statistics/period.ts
@@ -34,6 +34,12 @@ function dayStartOf(year: number, month: number, day: number) {
   return Date.UTC(year, month - 1, day) - OFFSET_MS
 }
 
+/** 东八区某天（`2026-09-29`）0 点的真实时刻，毫秒 —— 点零散提交时拿它当「自己选日子」的起止 */
+export function dayStartOfDate(day: string) {
+  const [year, month, date] = day.split("-").map(Number) as [number, number, number]
+  return dayStartOf(year, month, date)
+}
+
 /** 东八区「现在」这一天的 0 点 */
 function todayStart(now: number) {
   const p = zonedParts(new Date(now))!
diff --git a/apps/web/src/oj/submission/list.vue b/apps/web/src/oj/submission/list.vue
index e0b4d27..6ad814d 100644
--- a/apps/web/src/oj/submission/list.vue
+++ b/apps/web/src/oj/submission/list.vue
@@ -31,7 +31,7 @@ import FlowchartState from "./components/FlowchartState.vue"
 import StatusPill from "./components/StatusPill.vue"
 import UserName from "./components/UserName.vue"
 import { useTone } from "./composables/tone"
-import { classLabel, submissionClockText, submissionDayText } from "./utils"
+import { classLabel, classSelectOptions, submissionClockText, submissionDayText } from "./utils"
 
 /**
  * 提交列表（设计稿「提交列表重设计 · 定稿」）：左边列表、右边常驻选中那条的代码。
@@ -448,12 +448,9 @@ const languageOptions = [
   { label: "SQL", value: "SQL" },
 ]
 
-const classOptions = computed(() => {
-  const list = configStore.config?.classList ?? []
-  // 带进来的班级不在配置里（老班、手打的）也要显示得出来，不然框里是空的却在筛
-  const all = query.className && !list.includes(query.className) ? [query.className, ...list] : list
-  return all.map((item) => ({ label: classLabel(item), value: item }))
-})
+const classOptions = computed(() =>
+  classSelectOptions(configStore.config?.classList ?? [], query.className),
+)
 
 const contestProblemOptions = computed(() => [
   { label: "全部题目", value: "" },
diff --git a/apps/web/src/oj/submission/utils.ts b/apps/web/src/oj/submission/utils.ts
index 60edc43..def2750 100644
--- a/apps/web/src/oj/submission/utils.ts
+++ b/apps/web/src/oj/submission/utils.ts
@@ -1,3 +1,4 @@
+import { NO_CLASS } from "@oj2/contract"
 import { parseTime } from "utils/functions"
 
 /**
@@ -30,7 +31,20 @@ export function submissionDayText(time: string) {
   return parseTime(time, "YYYY年M月D日")
 }
 
-/** 班级下拉的标签：`253` → `25计算机3班`，和统计面板、班级 PK 同一个写法 */
-export function classLabel(className: string) {
+/**
+ * 班级下拉的标签：`253` → `25计算机3班`，和统计面板、班级 PK 同一个写法。
+ * null（接口里没填班级的号）和 NO_CLASS（筛选里的「没填班级」）都写成「没填班级」
+ */
+export function classLabel(className: string | null) {
+  if (className === null || className === NO_CLASS) return "没填班级"
   return `${className.slice(0, 2)}计算机${className.slice(2)}班`
 }
+
+/**
+ * 班级下拉的选项：配置里的班，最后一项「没填班级」（这批号也要能和普通班一样圈出来看）。
+ * 带进来的班不在配置里（老班、手打的）也要显示得出来，不然框里是空的却在筛
+ */
+export function classSelectOptions(list: string[], current: string) {
+  const all = current && current !== NO_CLASS && !list.includes(current) ? [current, ...list] : list
+  return [...all, NO_CLASS].map((item) => ({ label: classLabel(item), value: item }))
+}
diff --git a/packages/contract/src/submission.ts b/packages/contract/src/submission.ts
index a0b2297..59d11fe 100644
--- a/packages/contract/src/submission.ts
+++ b/packages/contract/src/submission.ts
@@ -405,12 +405,20 @@ export const submissionStatisticsSchema = z.object({
   results: z.array(z.object({ result: judgeStatusSchema, count: z.number().int() })),
 })
 
+/**
+ * 班级筛选（统计、提交列表、流程图的 `className` 参数）里代表「没填班级」的取值：
+ * 这批号（夏令营、兴趣班、自己注册的）`user.class_name` 是 null，当成一个班来看。
+ * 真班名全是数字（`253`、`2511`），撞不上
+ */
+export const NO_CLASS = "none"
+
 /**
  * 统计「一行一节课」的总览（GET /submissions/statistics/lessons，设计稿「统计合二为一」B）。
  * 没选班、没填学生、没填题号时用它；原来「今日统计」老师那一版并进来了，换成任意时间段。
  *
  * **一节课怎么切**：只算普通学生（和方块串同一个口径），按「班 + 东八区哪一天」分组，
  * 相邻两条提交隔 30 分钟以上就切开；切出来的一段里有一道题 5 人以上做过，才算一节课。
+ * 没填班级的号合在一起当一个班切（`className` 为 null）。
  * 其余的是零散提交（补做、课后自己练）。这样 26计算机0班 9 月 29 日是 14:04–15:38，
  * 不会被 16:24、18:42 那两条课后提交拖成「14:04–18:42」。
  */
@@ -420,14 +428,15 @@ export const submissionLessonsSchema = z.object({
   /** 最近的 N 节课，按开始时间倒序（界面上按天分组，这节课在最上面） */
   lessons: z.array(
     z.object({
-      className: z.string(),
+      /** null = 没填班级的那批号，点进去按 NO_CLASS 筛 */
+      className: z.string().nullable(),
       /** 东八区的日子，`2026-09-29` */
       day: z.string(),
       /** 这一段第一条、最后一条提交 */
       start: z.string(),
       end: z.string(),
       userCount: z.number().int(),
-      /** 班里的学生数（未禁用的普通用户） */
+      /** 班里的学生数（未禁用的普通用户）。没填班级的谈不上花名册，给 0 */
       classSize: z.number().int(),
       /** 这节课做的题（这一段里 5 人以上做过的），做的人多的在前，最多 20 道 —— 点进去就筛这几道 */
       problems: z.array(z.string()),