diff --git a/apps/api/src/routes/submission-statistics.ts b/apps/api/src/routes/submission-statistics.ts
index 7621d7f..52ae43d 100644
--- a/apps/api/src/routes/submission-statistics.ts
+++ b/apps/api/src/routes/submission-statistics.ts
@@ -296,6 +296,19 @@ async function astOnlyByUser(where: SQL | undefined, userIds: number[]) {
  * 快照实测 count 65ms → 0.6ms。`ks2` 这种匹配上千个账号的宽前缀退回扫表，30~50ms，
  * 和原来持平。
  */
+/**
+ * 用户名**精确**匹配。usernameFilter 是「包含」，学号互相包含是常态（ks24a1 包含在 ks24a10 里），
+ * 协作中老师看「这个学生」的提交时不能把别人的也捞进来。查无此人留恒假条件
+ */
+export async function exactUsernameFilter(username: string) {
+  const [row] = await db
+    .select({ id: schema.user.id })
+    .from(schema.user)
+    .where(eq(schema.user.username, username))
+    .limit(1)
+  return row ? eq(schema.submission.userId, row.id) : sql`false`
+}
+
 export async function usernameFilter(username: string) {
   const like = `%${username}%`
   const users = await db
diff --git a/apps/api/src/routes/submission.ts b/apps/api/src/routes/submission.ts
index aef4091..56a545e 100644
--- a/apps/api/src/routes/submission.ts
+++ b/apps/api/src/routes/submission.ts
@@ -32,7 +32,12 @@ import { problemSetJoinTimes } from "../services/problemset"
 import { consumeToken } from "../services/throttling"
 import { dayStart } from "../time"
 import { asFilterValue, asRecord, isAdminRole, queryInteger } from "./helpers"
-import { problemFilter, submissionStatisticsRoutes, usernameFilter } from "./submission-statistics"
+import {
+  exactUsernameFilter,
+  problemFilter,
+  submissionStatisticsRoutes,
+  usernameFilter,
+} from "./submission-statistics"
 
 export const submissionRoutes = new Hono<ContestEnv>()
 
@@ -489,7 +494,11 @@ submissionRoutes.get("/submissions", optionalAuth, async (c) => {
   filters.push(
     ...(await Promise.all([
       displayId ? problemFilter(displayId, null) : undefined,
-      username ? usernameFilter(username) : undefined,
+      username
+        ? c.req.query("exactUsername") === "1"
+          ? exactUsernameFilter(username)
+          : usernameFilter(username)
+        : undefined,
     ])),
   )
   if (myself) filters.push(eq(schema.submission.userId, myself.id))
diff --git a/apps/web/src/oj/problem/components/CollabBar.vue b/apps/web/src/oj/problem/components/CollabBar.vue
new file mode 100644
index 0000000..3330b0b
--- /dev/null
+++ b/apps/web/src/oj/problem/components/CollabBar.vue
@@ -0,0 +1,77 @@
+<script setup lang="ts">
+import { storeToRefs } from "pinia"
+import { useProblemStore } from "oj/store/problem"
+import { useCollabStore } from "shared/store/collab"
+import { LANGUAGE_SHOW_VALUE } from "utils/constants"
+
+/**
+ * 老师协作时右栏顶上的一条：正在帮谁、他用什么语言、看他交过什么、结束协作。
+ *
+ * 原来这几样挤在工具栏里（一个标签 + 一个按钮），和老师自己的「提交」「课堂统计」混在一行，
+ * 一眼看不出「现在编辑器里是学生的代码」。学生那边不加横幅，省下编辑器的 40px。
+ */
+const collabStore = useCollabStore()
+const { problem } = storeToRefs(useProblemStore())
+const router = useRouter()
+
+/**
+ * 「看他交过什么」：只看这个学生、这道题。开新标签 —— 跳走这一页协作就断了。
+ * 原来工具栏的「本题提交」只带题号，老师得再手动筛一遍用户名
+ */
+function openHisSubmissions() {
+  const room = collabStore.room
+  if (!room || !problem.value) return
+  const target = router.resolve({
+    name: "submissions",
+    query: { problem: problem.value._id, username: room.peerName },
+  })
+  window.open(target.href, "_blank")
+}
+</script>
+
+<template>
+  <div v-if="collabStore.room" class="collab-bar" role="status">
+    <span class="who">
+      正在帮 <b>{{ collabStore.room.peerName }}</b> ·
+      {{ LANGUAGE_SHOW_VALUE[collabStore.room.language] }}
+    </span>
+    <n-button text class="link" @click="openHisSubmissions">看他交过什么 ↗</n-button>
+    <!-- 显式的「结束」：求助记录一并清掉。跳走页面发的是 leave("left")，
+         那边只是退回排队 —— 见 store 里 leave 的注释 -->
+    <n-button size="small" class="end" @click="collabStore.leave('done')">结束协作</n-button>
+  </div>
+</template>
+
+<style scoped>
+.collab-bar {
+  height: 40px;
+  flex: none;
+  display: flex;
+  align-items: center;
+  gap: 14px;
+  padding: 0 12px;
+  border-radius: 6px;
+  background-color: #2080f0;
+  color: #fff;
+  font-size: 14px;
+  white-space: nowrap;
+}
+
+.who {
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+.link {
+  --n-text-color: #fff !important;
+  --n-text-color-hover: rgba(255, 255, 255, 0.85) !important;
+  --n-text-color-pressed: rgba(255, 255, 255, 0.7) !important;
+  --n-text-color-focus: #fff !important;
+  text-decoration: underline;
+}
+
+.end {
+  margin-left: auto;
+}
+</style>
diff --git a/apps/web/src/oj/problem/components/EditorToolbar.vue b/apps/web/src/oj/problem/components/EditorToolbar.vue
index 694ffc6..dccf4b8 100644
--- a/apps/web/src/oj/problem/components/EditorToolbar.vue
+++ b/apps/web/src/oj/problem/components/EditorToolbar.vue
@@ -108,14 +108,14 @@ const showCollabBar = computed(() => collabHere.value && userStore.isTeacherOrAb
 const helpButtonText = computed(() => {
   if (collabStore.helpStatus === "active") {
     const name = collabStore.teacherName
-    return name ? `${name} 老师帮你中` : "老师正在帮你"
+    return name ? `${name} 老师在帮你` : "老师正在帮你"
   }
   if (collabStore.helpStatus === "pending") {
     return collabStore.queueAhead > 0
-      ? `已求助 · 前面 ${collabStore.queueAhead} 人`
-      : "已求助 · 待接入"
+      ? `已举手 · 前面 ${collabStore.queueAhead} 人`
+      : "已举手 · 老师马上来"
   }
-  return "求助"
+  return "举手求助"
 })
 
 const helpButtonType = computed(() => {
@@ -301,18 +301,6 @@ const goEdit = () => {
       <n-button :size="buttonSize">更多</n-button>
     </n-dropdown>
 
-    <template v-if="showCollabBar">
-      <n-tag type="success" :size="buttonSize">
-        正在帮 {{ collabStore.room!.peerName }} ·
-        {{ LANGUAGE_SHOW_VALUE[collabStore.room!.language] }}
-      </n-tag>
-      <!-- 显式的「结束」：求助记录一并清掉。跳走页面发的是 leave("left")，
-           那边只是退回排队 —— 见 store 里 leave 的注释 -->
-      <n-button :size="buttonSize" type="primary" @click="collabStore.leave('done')">
-        结束协作
-      </n-button>
-    </template>
-
     <n-button
       v-if="showHelpButton"
       :size="buttonSize"
diff --git a/apps/web/src/oj/problem/components/PeerLatest.vue b/apps/web/src/oj/problem/components/PeerLatest.vue
new file mode 100644
index 0000000..979e808
--- /dev/null
+++ b/apps/web/src/oj/problem/components/PeerLatest.vue
@@ -0,0 +1,75 @@
+<script setup lang="ts">
+import { storeToRefs } from "pinia"
+import { getSubmission, getSubmissions } from "oj/api"
+import { useProblemStore } from "oj/store/problem"
+import { useCollabStore } from "shared/store/collab"
+import { parseTime } from "utils/functions"
+import type { Submission } from "utils/types"
+
+/**
+ * 老师接单之后落在题目页，「结果」页签原来是空的 —— 学生多半是交了几次没过才举的手，
+ * 老师最先想知道的就是「他交上去是什么结果」。这里摆出学生最近一次交的（设计文档第 9 节）。
+ * 管理员角色本来就能看任何人的提交，不需要新接口。
+ */
+const SubmissionResult = defineAsyncComponent(() => import("./SubmissionResult.vue"))
+
+const collabStore = useCollabStore()
+const { problem } = storeToRefs(useProblemStore())
+
+const loading = ref(false)
+const failed = ref(false)
+const latest = ref<Submission | null>(null)
+const checked = ref(false)
+
+const peer = computed(() => collabStore.room?.peerName ?? "")
+
+async function load() {
+  if (!peer.value || !problem.value) return
+  loading.value = true
+  failed.value = false
+  try {
+    const list = await getSubmissions({
+      username: peer.value,
+      exactUsername: "1",
+      problemDisplayId: problem.value._id,
+      limit: 1,
+      offset: 0,
+    })
+    const row = list.results[0]
+    latest.value = row ? await getSubmission(row.id) : null
+    checked.value = true
+  } catch {
+    failed.value = true
+  } finally {
+    loading.value = false
+  }
+}
+
+watch([peer, () => problem.value?._id], load, { immediate: true })
+</script>
+
+<template>
+  <div class="peer-latest">
+    <n-flex align="center" justify="space-between" class="head">
+      <span>
+        <b>{{ peer }}</b> 最近一次交的
+        <n-text v-if="latest" depth="3">· {{ parseTime(latest.createTime, "HH:mm:ss") }}</n-text>
+      </span>
+      <n-button size="small" :loading="loading" @click="load">刷新</n-button>
+    </n-flex>
+
+    <n-text v-if="failed" type="error">读不出他的提交，点「刷新」再试</n-text>
+    <SubmissionResult v-else-if="latest" :submission="latest" peer />
+    <n-empty v-else-if="checked" class="empty" description="他还没交过这道题" />
+  </div>
+</template>
+
+<style scoped>
+.head {
+  margin-bottom: 12px;
+}
+
+.empty {
+  margin-top: 32px;
+}
+</style>
diff --git a/apps/web/src/oj/problem/components/ProblemDrawer.vue b/apps/web/src/oj/problem/components/ProblemDrawer.vue
index eb2a7a4..abb95f2 100644
--- a/apps/web/src/oj/problem/components/ProblemDrawer.vue
+++ b/apps/web/src/oj/problem/components/ProblemDrawer.vue
@@ -1,13 +1,13 @@
 <script setup lang="ts">
 import { storeToRefs } from "pinia"
 import { useProblemStore } from "oj/store/problem"
-import { useCollabStore } from "shared/store/collab"
 import { useUserStore } from "shared/store/user"
 import {
   DRAWER_TITLE,
   useProblemPageContext,
   type ProblemDrawer,
 } from "../composables/problemPageContext"
+import { useTeacherCollab } from "../composables/teacherCollab"
 
 /**
  * 统计 / 点评 / 我的提交。原来是左栏的三个页签，课上几乎没人点，却和「题目」挤在一排；
@@ -30,7 +30,6 @@ const ctx = useProblemPageContext()
 const route = useRoute()
 const router = useRouter()
 const userStore = useUserStore()
-const collabStore = useCollabStore()
 const { problem } = storeToRefs(useProblemStore())
 
 const show = computed({
@@ -55,6 +54,14 @@ watch(
   },
 )
 
+// 协作中的老师看的是学生的提交（ProblemSubmission 里按学生用户名查）
+const teacherCollab = useTeacherCollab()
+const drawerTitle = computed(() =>
+  lastOpened.value === "submission" && teacherCollab.value
+    ? "他的提交"
+    : DRAWER_TITLE[lastOpened.value],
+)
+
 /**
  * 「看这道题所有人的提交」，原来是工具栏上的「本题提交」。可见条件照旧：
  * 比赛里总给（看的是这场比赛的提交），题库里要管理员或者开着提交列表。
@@ -72,11 +79,7 @@ function goAllSubmissions() {
   // 协作中走新标签：教师端「页面即协作现场」，跳走这一页协作就结束了
   // （求助会退回排队，但老师还得再接一次）。而「看看这学生都交了什么」恰好是
   // 协作时最常点的一个
-  const collabHere =
-    collabStore.room !== null &&
-    collabStore.room.problemId === problem.value?._id &&
-    userStore.isTeacherOrAbove
-  if (collabHere) {
+  if (teacherCollab.value) {
     window.open(router.resolve(target).href, "_blank")
     return
   }
@@ -94,7 +97,7 @@ function goAllSubmissions() {
     :trap-focus="false"
     :block-scroll="!props.to"
   >
-    <n-drawer-content :title="DRAWER_TITLE[lastOpened]" closable :native-scrollbar="false">
+    <n-drawer-content :title="drawerTitle" closable :native-scrollbar="false">
       <ProblemInfo v-if="lastOpened === 'info'" />
       <ProblemReaction v-else-if="lastOpened === 'reaction'" />
       <template v-else>
diff --git a/apps/web/src/oj/problem/components/ProblemEditor.vue b/apps/web/src/oj/problem/components/ProblemEditor.vue
index 8793fdb..48a5227 100644
--- a/apps/web/src/oj/problem/components/ProblemEditor.vue
+++ b/apps/web/src/oj/problem/components/ProblemEditor.vue
@@ -11,6 +11,7 @@ import type { LANGUAGE } from "utils/types"
 import { beginEditTrace, editTraceExtensions } from "oj/problem/utils/editTrace"
 import { errorMarkExtensions } from "oj/problem/utils/errorMark"
 import EditorToolbar from "./EditorToolbar.vue"
+import CollabBar from "./CollabBar.vue"
 import { useFlowchartStore } from "oj/store/flowchart"
 
 const FlowchartEditor = defineAsyncComponent(
@@ -97,9 +98,11 @@ const storageKey = computed(() =>
     : `problem_${problem.value!._id}_contest_${contestID}_lang_${codeStore.code.language}`,
 )
 
-const editorHeight = computed(() =>
-  isDesktop.value ? "calc(100vh - 133px)" : "calc(100vh - 172px)",
-)
+// 协作条 40px + 和工具栏之间的 12px 间距，要从编辑器里让出来，不然页面底下多出一截滚动条
+const editorHeight = computed(() => {
+  const base = isDesktop.value ? 133 : 172
+  return `calc(100vh - ${base + (teacherCollab.value ? 52 : 0)}px)`
+})
 
 function loadCode() {
   codeStore.code.language = problemStore.supportedLanguage(codeStore.code.language)
@@ -166,6 +169,7 @@ provide("flowchartEditorRef", flowchartEditorRef)
 
 <template>
   <n-flex vertical>
+    <CollabBar v-if="teacherCollab" />
     <EditorToolbar :storage-key="storageKey" @change-language="changeLanguage" />
     <!--
       协作中教师这边不会落到流程图分支：上面那个 watch 已经把他的语言换成了学生的，
diff --git a/apps/web/src/oj/problem/components/ProblemSubmission.vue b/apps/web/src/oj/problem/components/ProblemSubmission.vue
index 49f27b5..4694f4c 100644
--- a/apps/web/src/oj/problem/components/ProblemSubmission.vue
+++ b/apps/web/src/oj/problem/components/ProblemSubmission.vue
@@ -1,8 +1,6 @@
 <script lang="ts" setup>
-import { storeToRefs } from "pinia"
 import { getRankOfProblem, getSubmission, getSubmissions } from "oj/api"
 import { useCodeStore } from "oj/store/code"
-import { useProblemStore } from "oj/store/problem"
 import Pagination from "shared/components/Pagination.vue"
 import SubmissionResultTag from "shared/components/SubmissionResultTag.vue"
 import { useCollabStore } from "shared/store/collab"
@@ -12,6 +10,7 @@ import { copyToClipboard, parseTime } from "utils/functions"
 import type { ProblemRank } from "@oj2/contract"
 import type { LANGUAGE, SubmissionListItem } from "utils/types"
 import { useProblemPageContext } from "../composables/problemPageContext"
+import { useTeacherCollab } from "../composables/teacherCollab"
 
 /**
  * 「我的提交」抽屉：这道题自己交过的每一次。
@@ -24,7 +23,6 @@ import { useProblemPageContext } from "../composables/problemPageContext"
 const userStore = useUserStore()
 const codeStore = useCodeStore()
 const collabStore = useCollabStore()
-const { problem } = storeToRefs(useProblemStore())
 const ctx = useProblemPageContext()
 const route = useRoute()
 const router = useRouter()
@@ -36,12 +34,10 @@ const problemDisplayId = computed(() => String(route.params.problemID ?? ""))
  * 协作中的教师：编辑器里是学生的代码，「放回编辑器」会经 Yjs 直接盖掉学生正在写的
  * 那一份，所以不给（设计文档第 9 节）。
  */
-const teacherCollab = computed(
-  () =>
-    userStore.isTeacherOrAbove &&
-    collabStore.room !== null &&
-    collabStore.room.problemId === problem.value?._id,
-)
+const teacherCollab = useTeacherCollab()
+
+/** 协作中看的是学生的提交（设计文档第 9 节）：房间里的 peerName 就是学生的用户名 */
+const peer = computed(() => (teacherCollab.value ? (collabStore.room?.peerName ?? null) : null))
 
 // ==================== 班上第几个做对的 ====================
 // 只在题库入口给：比赛有自己的排名，题单里整个抽屉都不出现
@@ -98,7 +94,9 @@ const blocked = computed(() => {
 async function listSubmissions() {
   const res = await getSubmissions({
     ...query,
-    myself: "1",
+    ...(peer.value
+      ? { username: peer.value, exactUsername: "1" as const }
+      : { myself: "1" as const }),
     offset: query.limit * (query.page - 1),
     problemDisplayId: problemDisplayId.value,
     contestId: ctx.value.contestId,
@@ -165,7 +163,8 @@ function openDetail(id: string) {
 onMounted(() => {
   if (blocked.value) return
   listSubmissions()
-  if (ctx.value.entry === "problem") {
+  // 排名是按当前登录的人算的，协作中那是老师自己的，不给
+  if (ctx.value.entry === "problem" && !peer.value) {
     getRankOfProblem(problemDisplayId.value)
       .then((res) => {
         rank.value = res
@@ -190,7 +189,11 @@ watch(query, () => {
       </n-button>
     </div>
 
-    <n-empty v-if="listed && !submissions.length" class="empty" description="这道题你还没有交过" />
+    <n-empty
+      v-if="listed && !submissions.length"
+      class="empty"
+      :description="peer ? '他还没有交过这道题' : '这道题你还没有交过'"
+    />
 
     <ul v-else class="list">
       <li v-for="(row, index) in submissions" :key="row.id" class="item">
diff --git a/apps/web/src/oj/problem/components/ResultPane.vue b/apps/web/src/oj/problem/components/ResultPane.vue
index 6e4b457..7c5ccf5 100644
--- a/apps/web/src/oj/problem/components/ResultPane.vue
+++ b/apps/web/src/oj/problem/components/ResultPane.vue
@@ -3,6 +3,7 @@ import { storeToRefs } from "pinia"
 import { useProblemStore } from "oj/store/problem"
 import { useSubmissionStore } from "oj/store/submission"
 import { useCodeStore } from "oj/store/code"
+import { useTeacherCollab } from "../composables/teacherCollab"
 
 /**
  * 左栏「结果」页签：三段 —— 提交结果 / 运行例子 / 自己输入。
@@ -19,12 +20,16 @@ const PythonErrorExplain = defineAsyncComponent(() => import("./PythonErrorExpla
 const SampleRunResult = defineAsyncComponent(() => import("./SampleRunResult.vue"))
 const CustomRun = defineAsyncComponent(() => import("./CustomRun.vue"))
 const FlowchartResult = defineAsyncComponent(() => import("./FlowchartResult.vue"))
+const PeerLatest = defineAsyncComponent(() => import("./PeerLatest.vue"))
 
 const submissionStore = useSubmissionStore()
 const { submission, syntaxErrorInfo, resultSegment } = storeToRefs(submissionStore)
 const { problem } = storeToRefs(useProblemStore())
 const codeStore = useCodeStore()
 
+/** 协作中的老师自己还没交过：先摆学生最近一次交的 */
+const teacherCollab = useTeacherCollab()
+
 /** 正在画流程图：结果就是 AI 的点评，没有例子可跑 */
 const drawing = computed(() => codeStore.code.language === "Flowchart")
 
@@ -51,6 +56,7 @@ const canTrial = computed(() => {
         <PythonErrorExplain :err-info="syntaxErrorInfo" />
       </n-flex>
       <SubmissionResult v-else-if="submission" :submission="submission" />
+      <PeerLatest v-else-if="teacherCollab" />
       <n-empty
         v-else
         class="empty"
diff --git a/apps/web/src/oj/problem/components/SubmissionResult.vue b/apps/web/src/oj/problem/components/SubmissionResult.vue
index 5fbdde6..6e3c448 100644
--- a/apps/web/src/oj/problem/components/SubmissionResult.vue
+++ b/apps/web/src/oj/problem/components/SubmissionResult.vue
@@ -26,6 +26,11 @@ import { useDark } from "@vueuse/core"
 
 const props = defineProps<{
   submission?: Submission
+  /**
+   * 看的是别人的提交（协作中的老师看学生最近一次交的）：不给 AI 提示 —— 那是按登录的人
+   * 自己的失败次数解锁的 —— 也不给「这节课的下一题」
+   */
+  peer?: boolean
 }>()
 
 const isDark = useDark()
@@ -89,7 +94,8 @@ const sampleCheck = computed(() => {
  */
 const ctx = useProblemPageContext()
 const showLessonNext = computed(
-  () => props.submission?.result === SubmissionStatus.accepted && ctx.value.lessonNext,
+  () =>
+    !props.peer && props.submission?.result === SubmissionStatus.accepted && ctx.value.lessonNext,
 )
 
 const msg = computed(() => {
@@ -130,7 +136,7 @@ const partialCases = computed(() => submissionPartialCases(props.submission))
 // system_error 也要排掉：那是判题机自己崩了，学生代码没毛病，让 AI 去分析
 // 只会瞎编一通，后端的失败计数同样不认这个状态。
 const showAIHint = computed(() => {
-  if (!props.submission) return false
+  if (!props.submission || props.peer) return false
   // 比赛题不给提示，和「求助」按钮一致。用 problem.contestId 而不是路由参数：
   // 带 contestId 的题目只可能从比赛入口进来（题库列表按 contest_id is null 过滤）。
   if (problemStore.problem?.contestId != null) return false
diff --git a/apps/web/src/oj/problem/composables/teacherCollab.ts b/apps/web/src/oj/problem/composables/teacherCollab.ts
new file mode 100644
index 0000000..79b2a73
--- /dev/null
+++ b/apps/web/src/oj/problem/composables/teacherCollab.ts
@@ -0,0 +1,19 @@
+import { useProblemStore } from "oj/store/problem"
+import { useCollabStore } from "shared/store/collab"
+import { useUserStore } from "shared/store/user"
+
+/**
+ * 老师正在这道题上协作：编辑器里是**学生的**代码，「我的提交」看的是学生的，
+ * 跳走这一页协作就断了（所以跳转都开新标签，设计文档第 9 节）。
+ */
+export function useTeacherCollab() {
+  const userStore = useUserStore()
+  const collabStore = useCollabStore()
+  const problemStore = useProblemStore()
+  return computed(
+    () =>
+      userStore.isTeacherOrAbove &&
+      collabStore.room !== null &&
+      collabStore.room.problemId === problemStore.problem?._id,
+  )
+}
diff --git a/apps/web/src/oj/problem/detail.vue b/apps/web/src/oj/problem/detail.vue
index 067936e..db6f1cb 100644
--- a/apps/web/src/oj/problem/detail.vue
+++ b/apps/web/src/oj/problem/detail.vue
@@ -8,6 +8,8 @@ import { useMyFlowchartStore } from "shared/store/myFlowchart"
 import { useUserStore } from "shared/store/user"
 import { useSubmissionStore } from "oj/store/submission"
 import { useFlowchartStore } from "oj/store/flowchart"
+import { useCollabStore } from "shared/store/collab"
+import type { RouteLocationNormalized } from "vue-router"
 // 判完之后该发生的事（烟花、点评、回题单）。静态引入：它得在第一次判完之前就挂好
 import SubmissionEffects from "./components/SubmissionEffects.vue"
 import ResultTabLabel from "./components/ResultTabLabel.vue"
@@ -17,6 +19,7 @@ import {
   useProblemPageContext,
   type ProblemDrawer as DrawerKey,
 } from "./composables/problemPageContext"
+import { useTeacherCollab } from "./composables/teacherCollab"
 
 // 抽成具名 loader，便于进页面时与接口并行预取编辑器 chunk。
 // 题库、比赛、题单三种入口用的是同一个编辑器：原来比赛和题单用的是另一个精简版，
@@ -88,12 +91,17 @@ watch(
 
 const drawer = ref<DrawerKey | null>(null)
 
+// 协作中的老师看的是学生的提交
+const teacherCollab = useTeacherCollab()
+const drawerLabel = (key: DrawerKey) =>
+  key === "submission" && teacherCollab.value ? "他的提交" : DRAWER_TITLE[key]
+
 function toggleDrawer(key: DrawerKey) {
   drawer.value = drawer.value === key ? null : key
 }
 
 const drawerMenu = computed<DropdownOption[]>(() =>
-  ctx.value.drawers.map((key) => ({ label: DRAWER_TITLE[key], key })),
+  ctx.value.drawers.map((key) => ({ label: drawerLabel(key), key })),
 )
 
 // 交上去、或者语法检查没过：切到「结果」，抽屉开着就先关掉。提交按钮在编辑器那边，页签归这一页管
@@ -106,6 +114,35 @@ watch(
   },
 )
 
+/**
+ * 学生正在排队求助、或者老师正在帮他时换题：协作是开在这道题上的，换题就断了
+ * （SyncCodeEditor 的 detach），排队的求助也跟着撤掉。先问一句，别让他一点「下一题」
+ * 就把正在帮他的老师踢出去。只拦「离开这道题」，切页签改 `?tab=` 不算
+ */
+const collabStore = useCollabStore()
+const dialog = useDialog()
+function confirmLeavingHelp(to: RouteLocationNormalized, from: RouteLocationNormalized) {
+  if (collabStore.isTeacher || collabStore.helpStatus === "idle") return true
+  if (to.name === from.name && to.params.problemID === from.params.problemID) return true
+  const active = collabStore.helpStatus === "active"
+  return new Promise<boolean>((resolve) => {
+    dialog.warning({
+      title: active ? "老师正在帮你看这道题" : "你正在排队等老师",
+      content: active
+        ? "换题之后，老师那边的协作就断了。确定要换吗？"
+        : "换题之后这次举手就撤掉了，要在新的题目里重新举手。确定要换吗？",
+      positiveText: "换题",
+      negativeText: "留在这道题",
+      onPositiveClick: () => resolve(true),
+      onNegativeClick: () => resolve(false),
+      onClose: () => resolve(false),
+      onMaskClick: () => resolve(false),
+    })
+  })
+}
+onBeforeRouteUpdate(confirmLeavingHelp)
+onBeforeRouteLeave(confirmLeavingHelp)
+
 // 结果页签的标题带状态图标（ResultTabLabel），n-tab-pane 的 tab 接受渲染函数
 const resultTab = () => h(ResultTabLabel)
 
@@ -187,7 +224,7 @@ onBeforeUnmount(() => {
                 :secondary="drawer === key"
                 @click="toggleDrawer(key)"
               >
-                {{ DRAWER_TITLE[key] }}
+                {{ drawerLabel(key) }}
               </n-button>
             </n-flex>
           </div>
diff --git a/apps/web/src/utils/types.ts b/apps/web/src/utils/types.ts
index 83af2d8..bb74a2a 100644
--- a/apps/web/src/utils/types.ts
+++ b/apps/web/src/utils/types.ts
@@ -266,6 +266,8 @@ export interface SubmissionListPayload {
   myself?: "1" | "0"
   result?: string
   username?: string
+  /** "1" = username 精确匹配（默认是「包含」）。协作中老师看某个学生的提交用 */
+  exactUsername?: "1"
   contestId?: string
   problemDisplayId?: string
   language: LANGUAGE | ""