diff --git a/apps/api/src/routes/admin/lesson.ts b/apps/api/src/routes/admin/lesson.ts
index fe853ef..b7c84d9 100644
--- a/apps/api/src/routes/admin/lesson.ts
+++ b/apps/api/src/routes/admin/lesson.ts
@@ -161,10 +161,14 @@ adminLessonRoutes.put('/lessons/:id', requireTeacher, async (c) => {
   // 班级能改：原来那个班和新的班学生看到的都可能变，两边各比一次
   const classes = await affectedClasses(id, result.values.className)
   const before = await Promise.all(classes.map((className) => todayLessonSnapshot(className)))
+  // 时刻只填到分：没改时刻就留着原来带秒的那个。不然只改了做什么，这一节也被挪到这一分钟的开头，
+  // 排到同一分钟里后布置的那节前面去 —— 「今天最后一节」就换了人（先画流程图、紧接着再开一节写代码，常在同一分钟里）
+  const [current] = await db.select({ createdAt: schema.classLesson.createdAt }).from(schema.classLesson).where(eq(schema.classLesson.id, id))
+  const sameMinute = current && Math.floor(Date.parse(current.createdAt) / 60_000) * 60_000 === Date.parse(result.values.createdAt)
   // 布置的老师不换，和任务页上「改」一样认第一次
   const [row] = await db
     .update(schema.classLesson)
-    .set({ ...result.values, updatedAt: new Date().toISOString() })
+    .set({ ...result.values, createdAt: sameMinute ? current.createdAt : result.values.createdAt, updatedAt: new Date().toISOString() })
     .where(eq(schema.classLesson.id, id))
     .returning({ id: schema.classLesson.id })
   if (!row) return failure(c, 404, 'lesson-not-found', '这一节已经被删掉了')
diff --git a/apps/api/src/routes/submission-statistics.ts b/apps/api/src/routes/submission-statistics.ts
index e098cb7..67aa1e3 100644
--- a/apps/api/src/routes/submission-statistics.ts
+++ b/apps/api/src/routes/submission-statistics.ts
@@ -527,6 +527,11 @@ const LESSON_LIVE_MINUTES = 15
 /** 一次列多少节课。「一节课」「今天」一般一两行，「这学期」「全部」有几百节，先给最近的这些 */
 const LESSONS_DEFAULT = 50
 const LESSONS_MAX = 500
+/** 课只算学生（STUDENT_ROLES，学生管理员也算），老师试题的提交不算 */
+const studentRoles = sql.join(
+  STUDENT_ROLES.map((role) => sql`${role}`),
+  sql`, `,
+)
 
 type StatisticsRange = { start: string | null; end: string }
 
@@ -599,7 +604,7 @@ async function assignedLessons(plans: LessonPlan[], range: StatisticsRange) {
         where s.contest_id is null and p.mode <> 'flowchart'
           and s.create_time <= ${range.end}
           ${range.start ? sql`and s.create_time >= ${range.start}` : sql``}
-          and u.admin_type = 'Regular User' and u.is_disabled = false
+          and u.admin_type in (${studentRoles}) and u.is_disabled = false
         union all
         select p.k, f.user_id, f.problem_id, (f.status = 2 and coalesce(f.ai_grade in (${sql.join(
           FLOWCHART_PASS_GRADES.map((grade) => sql`${grade}`),
@@ -612,7 +617,7 @@ async function assignedLessons(plans: LessonPlan[], range: StatisticsRange) {
         where p.mode <> 'code'
           and f.create_time <= ${range.end}
           ${range.start ? sql`and f.create_time >= ${range.start}` : sql``}
-          and u.admin_type = 'Regular User' and u.is_disabled = false
+          and u.admin_type in (${studentRoles}) and u.is_disabled = false
       )
       select k, problem_id,
         count(distinct user_id)::int as users,
@@ -721,8 +726,8 @@ submissionStatisticsRoutes.get('/submissions/statistics/lessons', requireTeacher
       where s.contest_id is null
         and s.create_time <= ${range.end}
         ${range.start ? sql`and s.create_time >= ${range.start}` : sql``}
-        -- 只算普通学生：老师试题的提交不该把一段拼成「一节课」
-        and u.admin_type = 'Regular User' and u.is_disabled = false
+        -- 只算学生（学生管理员也是学生）：老师试题的提交不该把一段拼成「一节课」
+        and u.admin_type in (${studentRoles}) and u.is_disabled = false
     ),
     g as (
       select *,
diff --git a/apps/web/src/oj/home/student.vue b/apps/web/src/oj/home/student.vue
index 2a98e55..3c4bfc3 100644
--- a/apps/web/src/oj/home/student.vue
+++ b/apps/web/src/oj/home/student.vue
@@ -7,6 +7,7 @@ import { getClassActivity } from 'shared/api'
 import SubmissionResultTag from 'shared/components/SubmissionResultTag.vue'
 import { pickHeadline, type Headline } from 'oj/user/knowledge'
 import { useUserStore } from 'shared/store/user'
+import { activityMode } from 'shared/store/lesson'
 import { ContestStatus, CONTEST_STATUS, JUDGE_STATUS, LANGUAGE_SHOW_VALUE } from 'utils/constants'
 import { duration, parseTime, zonedParts, zonedYear } from 'utils/functions'
 import type { AnnouncementListItem, ClassActivity, ClassActivityProblem, Contest, LastVisit, SubmissionListItem, WeeklyRank } from 'utils/types'
@@ -191,7 +192,7 @@ const classActivityTitle = computed(() => {
   // 老师在课堂任务布置的，说成「老师布置的」，比「班里在做」更让人知道该做这几道
   if (classActivity.value?.source === 'teacher') {
     const language = classActivity.value.language
-    const mode = classActivity.value.mode
+    const mode = activityMode(classActivity.value)
     if (mode === 'flowchart') return '这节课 · 画流程图'
     if (mode === 'both') return `这节课 · 先画流程图，再${language ? `用${LANGUAGE_SHOW_VALUE[language]}` : ''}写代码`
     return `这节课${language ? ` · 用${LANGUAGE_SHOW_VALUE[language]}做` : ''}`
diff --git a/apps/web/src/oj/problem/components/ProblemEditor.vue b/apps/web/src/oj/problem/components/ProblemEditor.vue
index 570c517..ecbdac7 100644
--- a/apps/web/src/oj/problem/components/ProblemEditor.vue
+++ b/apps/web/src/oj/problem/components/ProblemEditor.vue
@@ -182,16 +182,25 @@ watch(
  * 没有画这一步的课，画着流程图时不动他
  */
 const lessonStore = useLessonStore()
-let lessonLanguageFor: string | null = null
+/**
+ * 换过的（题 + 这一节 + 该做的那一步）都记下：换到别的题再回来，同一步不再换第二次。
+ * 编辑器在换题时不重新挂载（detail.vue 只重新 init），只记最后一个的话一回来又被拽回去
+ */
+const lessonSwitched = new Set<string>()
+let lessonViewing: string | null = null
 watch(
   () => [problem.value?._id, lessonStore.activity] as const,
   ([id, activity]) => {
     if (!id || !activity) return
-    const key = [id, activity.day, activity.mode, activity.language].join('|')
-    if (lessonLanguageFor === key) return
-    lessonLanguageFor = key
-    if (ctx.value.entry !== 'problem' || teacherCollab.value) return
+    const lesson = [id, activity.day, activity.mode, activity.language].join('|')
     const item = lessonStore.find(id)
+    const key = [lesson, item?.draw && item.draw !== 'accepted' ? 'draw' : 'code'].join('|')
+    // 停在这道题上、只是课堂状态刷新了（比如刚画对图）：不跟着换，也不记，下回打开这道题再换
+    const stay = lessonViewing === lesson
+    lessonViewing = lesson
+    if (lessonSwitched.has(key) || stay) return
+    lessonSwitched.add(key)
+    if (ctx.value.entry !== 'problem' || teacherCollab.value) return
     if (!item) return
     if (item.draw && item.draw !== 'accepted') {
       if (problemStore.canDraw && codeStore.code.language !== 'Flowchart') problemStore.switchLanguage('Flowchart')
diff --git a/apps/web/src/oj/task/index.vue b/apps/web/src/oj/task/index.vue
index 1e1ca50..fa7d94e 100644
--- a/apps/web/src/oj/task/index.vue
+++ b/apps/web/src/oj/task/index.vue
@@ -408,10 +408,14 @@ const explainShow = ref(false)
 const explainIndex = ref(0)
 const explainProblemIndex = ref(-1)
 const explainProblem = computed(() => board.value?.problems[explainProblemIndex.value] ?? null)
-/** 弹层顶上那排人：这道题错着的人，顺序和错法堆一样 */
-const explainPeople = computed<ExplainPerson[]>(() => {
-  if (explainProblemIndex.value < 0) return []
-  const people = wrongOf(explainProblemIndex.value).filter((person) => person.explain)
+/**
+ * 弹层顶上那排人：这道题错着的人，顺序和错法堆一样。打开那一刻定下来，开着时不跟 15 秒的刷新变：
+ * 弹层记的是第几个人，名单一变（有人改对了、图评完了回到名单里）就成了讲着讲着换了个人
+ */
+const explainPeople = ref<ExplainPerson[]>([])
+function explainPeopleOf(problemIndex: number): ExplainPerson[] {
+  if (problemIndex < 0) return []
+  const people = wrongOf(problemIndex).filter((person) => person.explain)
   const order = new Map<string, number>()
   for (const person of people) {
     order.set(person.kind.key, (order.get(person.kind.key) ?? 0) + 1)
@@ -423,10 +427,11 @@ const explainPeople = computed<ExplainPerson[]>(() => {
         ? { userId: person.student.userId, username: person.student.username, flowchartId: person.cell.flowchart!.latest!.id, label: person.kind.label }
         : { userId: person.student.userId, username: person.student.username, submissionId: person.cell.latest!.submissionId, label: person.kind.label },
     )
-})
+}
 
 function openExplain(problemIndex: number, userId: number) {
   explainProblemIndex.value = problemIndex
+  explainPeople.value = explainPeopleOf(problemIndex)
   explainIndex.value = Math.max(
     0,
     explainPeople.value.findIndex((person) => person.userId === userId),
@@ -532,7 +537,8 @@ function lastText(student: TaskBoardStudent) {
       />
       <div v-else-if="board?.problems.length && !needLesson" class="lesson">
         <span class="lesson-label">{{ board.source === 'teacher' ? '这节课' : '今天在做' }}</span>
-        <span v-if="board.mode && board.mode !== 'code'" class="chip lang">{{ LESSON_MODE_LABEL[board.mode] }}</span>
+        <!-- 写代码也写出来：只写「Python」的话，看不出这节是写代码还是先画再写 -->
+        <span v-if="board.mode" class="chip lang">{{ LESSON_MODE_LABEL[board.mode] }}</span>
         <span v-if="board.language" class="chip lang">{{ LANGUAGE_SHOW_VALUE[board.language] }}</span>
         <span v-for="problem in board.problems" :key="problem.problemId" class="chip">
           {{ problem.problemDisplayId }}
diff --git a/apps/web/src/shared/components/LessonUpdateNotice.vue b/apps/web/src/shared/components/LessonUpdateNotice.vue
index 3952aa0..264ea8e 100644
--- a/apps/web/src/shared/components/LessonUpdateNotice.vue
+++ b/apps/web/src/shared/components/LessonUpdateNotice.vue
@@ -17,9 +17,12 @@ function names(list: Item[]) {
   return list.map((item) => `${item.problemDisplayId} ${item.title}`).join('、')
 }
 
-/** 「画流程图」「先画再写 · C语言」「C语言」：写代码是默认的，不写出来 */
-function languageText(value: LessonUpdate) {
-  const mode = value.mode && value.mode !== 'code' ? LESSON_MODE_LABEL[value.mode] : ''
+/**
+ * 「画流程图」「先画再写 · C语言」「C语言」。新布置的一节写代码是默认的，不写出来（前面配「用」）；
+ * 改了做法时 `spellCode` 把「写代码」也写出来 —— 从画流程图改成写 C，只说「C语言」学生看不出不用画了
+ */
+function languageText(value: LessonUpdate, spellCode = false) {
+  const mode = value.mode && (spellCode || value.mode !== 'code') ? LESSON_MODE_LABEL[value.mode] : ''
   return [mode, value.language ? LANGUAGE_SHOW_VALUE[value.language] : ''].filter(Boolean).join(' · ')
 }
 
@@ -44,8 +47,9 @@ const lines = computed(() => {
   if (value.added.length) result.push({ label: '加了', text: names(value.added) })
   if (value.removed.length) result.push({ label: '去掉了', text: names(value.removed) })
   if (value.languageChanged) {
-    const text = languageText(value)
-    result.push({ label: value.mode && value.mode !== 'code' ? '做法' : '语言', text: text ? `改成 ${text}` : value.mode === 'code' ? '改成写代码' : '不限了' })
+    // languageChanged 连做法一起算，分不出改的是哪样：一律写「做法」，连写代码带语言一起说
+    const text = languageText(value, true)
+    result.push({ label: '做法', text: text ? `改成 ${text}` : '不限了' })
   }
   if (value.reordered) result.push({ label: '', text: '换了题目的顺序' })
   return result
diff --git a/apps/web/src/shared/store/lesson.ts b/apps/web/src/shared/store/lesson.ts
index 4db8d9c..7c451ea 100644
--- a/apps/web/src/shared/store/lesson.ts
+++ b/apps/web/src/shared/store/lesson.ts
@@ -1,9 +1,22 @@
-import { LESSON_MODE_LABEL } from '@oj2/contract'
+import { LESSON_MODE_LABEL, type LessonMode } from '@oj2/contract'
 import { defineStore } from 'pinia'
 import { getClassActivity } from 'shared/api'
 import { LANGUAGE_SHOW_VALUE } from 'utils/constants'
 import type { ClassActivity, ClassActivityProblem } from 'utils/types'
 
+/**
+ * 学生这边这节课做什么：按每道题合起来的要求算（后端 todaySteps 把今天几节里同一道题的要求并在一起），
+ * 不直接用 `mode` —— 那是今天最后布置的那一节的。先布置画流程图、再「用这几道题写代码」，
+ * 最后一节是写代码，但还没画完的照样要画，标题只写「用 C语言做」就漏了画图。
+ * 推断出来的课为 null
+ */
+export function activityMode(activity: ClassActivity | null | undefined): LessonMode | null {
+  if (!activity?.mode) return null
+  const draw = activity.problems.some((item) => item.draw !== null)
+  const code = activity.problems.some((item) => item.code !== null)
+  return draw && code ? 'both' : draw ? 'flowchart' : code ? 'code' : activity.mode
+}
+
 /** 同一节课里来回换题不用每次都重拉；过了这么久再进题目页就重拉一次 */
 const STALE_MS = 2 * 60 * 1000
 
@@ -89,8 +102,8 @@ export const useLessonStore = defineStore('lesson', () => {
    * 以前布置的）为空。写代码是默认的，不写出来
    */
   const languageText = computed(() => {
-    const mode = activity.value?.mode
-    const language = activity.value?.language
+    const mode = activityMode(activity.value)
+    const language = mode === 'flowchart' ? null : activity.value?.language
     return [mode && mode !== 'code' ? LESSON_MODE_LABEL[mode] : '', language ? LANGUAGE_SHOW_VALUE[language] : ''].filter(Boolean).join(' · ')
   })