diff --git a/apps/web/src/admin/api.ts b/apps/web/src/admin/api.ts
index 96556ea..43b00cc 100644
--- a/apps/web/src/admin/api.ts
+++ b/apps/web/src/admin/api.ts
@@ -1,6 +1,7 @@
 import { toAdminType, toProblemPermission } from "@oj2/contract"
 import type {
   AddContestProblemRequest,
+  ChallengeSuggestionsResponse,
   AddProblemsToSetRequest,
   BatchProblemTagRequest,
   BatchProblemVisibleRequest,
@@ -353,6 +354,16 @@ export function checkAstRules(data: AstCheckRequest) {
   return api.post<AstCheckResponse>("admin/ast-check", data satisfies AstCheckRequest)
 }
 
+// 出题页「挑战」的候选：拿这道题历史上做对的代码挖
+export function getChallengeSuggestions(problemId: number, language: string) {
+  return api.post<ChallengeSuggestionsResponse>(
+    `admin/problems/${problemId}/challenge-suggestions`,
+    {
+      language,
+    },
+  )
+}
+
 // AI 按题面和标准答案想几组测试输入（输出由标准答案跑）
 export function generateTestInputs(data: GenerateTestInputsRequest) {
   return api.post<GenerateTestInputsResponse>(
diff --git a/apps/web/src/admin/problem/components/AstRulesEditor.vue b/apps/web/src/admin/problem/components/AstRulesEditor.vue
index 54fa8ea..e6ca136 100644
--- a/apps/web/src/admin/problem/components/AstRulesEditor.vue
+++ b/apps/web/src/admin/problem/components/AstRulesEditor.vue
@@ -15,6 +15,11 @@ interface Props {
   languages: LANGUAGE[]
   /** 各语言的标准答案（学生那段代码，不套模板）：拿来自测规则 */
   answers: Partial<Record<LANGUAGE, string>>
+  /**
+   * 挑战的判定规则（ChallengeEditor 里一条挑战一个）。和语法要求是同一套规则，但口径不同：
+   * 不满足不算错、说法由挑战自己写、标准答案不这么写是常事（挑战就是另一种写法）
+   */
+  challenge?: boolean
 }
 
 const props = defineProps<Props>()
@@ -294,8 +299,13 @@ watch(supportedLanguages, (langs) => {
 <template>
   <div class="astRules">
     <div class="head">
-      <span class="label">语法要求</span>
-      <div v-if="supportedLanguages.length" class="langs" role="tablist" aria-label="语言">
+      <span class="label">{{ challenge ? "判定" : "语法要求" }}</span>
+      <div
+        v-if="supportedLanguages.length && !challenge"
+        class="langs"
+        role="tablist"
+        aria-label="语言"
+      >
         <button
           v-for="lang in supportedLanguages"
           :key="lang"
@@ -310,7 +320,8 @@ watch(supportedLanguages, (langs) => {
         </button>
       </div>
       <div class="grow"></div>
-      <n-text depth="3" class="note">提交时逐条检查，不满足算错</n-text>
+      <n-text v-if="!challenge" depth="3" class="note">提交时逐条检查，不满足算错</n-text>
+      <n-text v-else depth="3" class="note">几条都满足才算做到</n-text>
     </div>
     <n-text v-if="unsupportedLanguages.length" depth="3" class="note">
       {{ unsupportedLanguages.join("、") }} 检查不了语法要求（判题机只认
@@ -402,6 +413,7 @@ watch(supportedLanguages, (langs) => {
           </div>
           <div class="ruleRow sub">
             <n-input
+              v-if="!challenge"
               :value="rule.message"
               size="tiny"
               class="message"
@@ -412,7 +424,19 @@ watch(supportedLanguages, (langs) => {
               "
               @update:value="(v: string) => updateRule(lang, index, 'message', v)"
             />
-            <span v-if="checkOf(lang, index)?.passed === true" class="ok">✓ 标准答案过了</span>
+            <template v-if="challenge">
+              <n-text v-if="checkOf(lang, index)?.passed === true" depth="3" class="note">
+                标准答案这样写也满足
+              </n-text>
+              <n-text v-else-if="checkOf(lang, index)?.passed === false" depth="3" class="note">
+                标准答案不是这样写的{{
+                  checkOf(lang, index)!.actual !== undefined
+                    ? `（数到 ${checkOf(lang, index)!.actual} 次）`
+                    : ""
+                }}
+              </n-text>
+            </template>
+            <span v-else-if="checkOf(lang, index)?.passed === true" class="ok">✓ 标准答案过了</span>
             <span v-else-if="checkOf(lang, index)?.passed === false" class="bad">
               ✗ 标准答案自己没过{{
                 checkOf(lang, index)!.actual !== undefined
diff --git a/apps/web/src/admin/problem/components/ChallengeEditor.vue b/apps/web/src/admin/problem/components/ChallengeEditor.vue
new file mode 100644
index 0000000..4bb1b2a
--- /dev/null
+++ b/apps/web/src/admin/problem/components/ChallengeEditor.vue
@@ -0,0 +1,265 @@
+<script setup lang="ts">
+import {
+  AST_SUPPORTED_LANGUAGES,
+  CHALLENGE_RULES_MAX,
+  CHALLENGE_WORDING_MAX,
+  CHALLENGES_PER_LANGUAGE_MAX,
+  type AstRules,
+  type ChallengeInput,
+  type ChallengeSuggestionsResponse,
+} from "@oj2/contract"
+import { errorMessage } from "utils/api"
+import type { LANGUAGE } from "utils/types"
+import { getChallengeSuggestions } from "../../api"
+import AstRulesEditor from "./AstRulesEditor.vue"
+
+/**
+ * 出题页的「挑战」：做对之后，同一道题加一条写法上的限制再做一遍（设计稿 StkAdmin）。
+ * 判定就是语法要求那套规则，所以每条挑战底下直接摆一个规则编辑器（只开这一种语言）。
+ *
+ * 「从做对的代码里找」把这道题历史上做对的代码挖一遍，列出「一批人用另一种写法也做对了」
+ * 的地方。机械挖出来的会有坏的（拆掉 elif 换成一串 if 也算「不用 elif」），所以每条带一份
+ * 做到的人的真实代码，好不好老师看了再加。新建的题还没人做过，不给这个按钮。
+ */
+const props = defineProps<{
+  modelValue: Record<string, ChallengeInput[]> | null
+  languages: LANGUAGE[]
+  answers: Partial<Record<LANGUAGE, string>>
+  /** 编辑已有的题才有；新建的题没有做对的代码可挖 */
+  problemId: number | null
+}>()
+const emit = defineEmits<{
+  (e: "update:modelValue", value: Record<string, ChallengeInput[]> | null): void
+}>()
+
+const languages = computed(() =>
+  props.languages.filter((lang) => AST_SUPPORTED_LANGUAGES.includes(lang)),
+)
+const tab = ref<string>(languages.value[0] ?? "Python")
+watch(languages, (list) => {
+  if (!list.includes(tab.value as LANGUAGE)) tab.value = list[0] ?? "Python"
+})
+
+const list = computed(() => props.modelValue?.[tab.value] ?? [])
+
+function update(next: ChallengeInput[]) {
+  const value = { ...props.modelValue }
+  if (next.length) value[tab.value] = next
+  else delete value[tab.value]
+  emit("update:modelValue", Object.keys(value).length ? value : null)
+}
+
+function patch(index: number, change: Partial<ChallengeInput>) {
+  update(list.value.map((item, i) => (i === index ? { ...item, ...change } : item)))
+}
+
+function remove(index: number) {
+  update(list.value.filter((_, i) => i !== index))
+}
+
+function add(item: ChallengeInput = { wording: "", rules: [] }) {
+  update([...list.value, item])
+}
+
+/** AstRulesEditor 按语言分组收发，这里只给它一种语言 */
+function rulesModel(item: ChallengeInput): AstRules {
+  return { [tab.value]: item.rules }
+}
+function onRules(index: number, value: AstRules | null) {
+  patch(index, { rules: (value?.[tab.value] ?? []).slice(0, CHALLENGE_RULES_MAX) })
+}
+
+const full = computed(() => list.value.length >= CHALLENGES_PER_LANGUAGE_MAX)
+
+// ---------------------------------------------------------------- 候选
+
+const suggestions = ref<Record<string, ChallengeSuggestionsResponse>>({})
+const loading = ref(false)
+const error = ref("")
+
+async function findSuggestions() {
+  if (!props.problemId) return
+  loading.value = true
+  error.value = ""
+  try {
+    suggestions.value = {
+      ...suggestions.value,
+      [tab.value]: await getChallengeSuggestions(props.problemId, tab.value),
+    }
+  } catch (err) {
+    error.value = errorMessage(err, "没找成")
+  } finally {
+    loading.value = false
+  }
+}
+
+const current = computed(() => suggestions.value[tab.value] ?? null)
+
+/** 已经加上的不再列 */
+const shown = computed(() => {
+  const taken = list.value.map((item) => JSON.stringify(item.rules))
+  return (current.value?.suggestions ?? []).filter(
+    (item) => !taken.includes(JSON.stringify(item.rules)),
+  )
+})
+</script>
+
+<template>
+  <div class="challenge-editor">
+    <n-radio-group v-if="languages.length > 1" v-model:value="tab" size="small">
+      <n-radio-button v-for="lang in languages" :key="lang" :value="lang">
+        {{ lang }}{{ modelValue?.[lang]?.length ? ` ${modelValue[lang]!.length} 条` : "" }}
+      </n-radio-button>
+    </n-radio-group>
+
+    <div v-for="(item, index) in list" :key="`${tab}-${item.id ?? index}`" class="item">
+      <div class="itemHead">
+        <span class="index">{{ index + 1 }}</span>
+        <n-input
+          :value="item.wording"
+          :maxlength="CHALLENGE_WORDING_MAX"
+          placeholder="给学生看的说法，例如「整首歌只用 1 次 print」"
+          :status="item.wording.trim() ? undefined : 'warning'"
+          @update:value="(value: string) => patch(index, { wording: value })"
+        />
+        <n-button size="small" quaternary @click="remove(index)">删掉</n-button>
+      </div>
+      <AstRulesEditor
+        :model-value="rulesModel(item)"
+        :languages="[tab as LANGUAGE]"
+        :answers="answers"
+        challenge
+        @update:model-value="(value) => onRules(index, value)"
+      />
+    </div>
+
+    <n-text v-if="!languages.length" depth="3" class="note">
+      只有 Python、C、C++ 能配挑战，先在「学生怎么写」里勾上其中一种。
+    </n-text>
+    <template v-else>
+      <div class="actions">
+        <n-button size="small" :disabled="full" @click="add()">+ 自己写一条</n-button>
+        <n-button
+          v-if="problemId"
+          size="small"
+          :loading="loading"
+          :disabled="full"
+          @click="findSuggestions"
+        >
+          从做对的代码里找
+        </n-button>
+      </div>
+      <n-text v-if="error" type="error" class="note">{{ error }}</n-text>
+
+      <div v-if="current" class="suggestions">
+        <n-text depth="3" class="note">
+          {{ current.acCount }} 个人用 {{ tab }} 做对过，下面是有一批人换了种写法也做对的地方
+        </n-text>
+        <n-text v-if="!shown.length" depth="3" class="note">没找到别的写法</n-text>
+        <div v-for="item in shown" :key="JSON.stringify(item.rules)" class="suggestion">
+          <div class="suggestionHead">
+            <div class="suggestionText">
+              <b>{{ item.wording }}</b>
+              <n-text depth="3" class="note">
+                {{ item.did }} 人这样做对<template v-if="item.firstShare !== null"
+                  >，第一次做对时 {{ item.firstShare }}% 这样写</template
+                >
+              </n-text>
+            </div>
+            <n-button
+              size="small"
+              :disabled="full"
+              @click="add({ wording: item.wording, rules: item.rules })"
+            >
+              加上
+            </n-button>
+          </div>
+          <pre class="example">{{ item.example }}</pre>
+        </div>
+      </div>
+    </template>
+  </div>
+</template>
+
+<style scoped>
+.challenge-editor {
+  display: flex;
+  flex-direction: column;
+  gap: 10px;
+}
+
+.item {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  padding: 10px 12px;
+  border: 1px solid rgba(91, 52, 196, 0.3);
+  border-radius: 6px;
+}
+
+.itemHead {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+.index {
+  flex-shrink: 0;
+  width: 22px;
+  height: 22px;
+  border-radius: 11px;
+  background-color: rgba(91, 52, 196, 0.12);
+  color: #5b34c4;
+  font-size: 12px;
+  font-weight: 600;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.actions {
+  display: flex;
+  gap: 8px;
+}
+
+.note {
+  font-size: 12px;
+}
+
+.suggestions {
+  display: flex;
+  flex-direction: column;
+}
+
+.suggestion {
+  padding: 10px 0;
+  border-top: 1px solid rgba(128, 128, 128, 0.15);
+}
+
+.suggestionHead {
+  display: flex;
+  align-items: flex-start;
+  justify-content: space-between;
+  gap: 12px;
+}
+
+.suggestionText {
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+  min-width: 0;
+}
+
+.example {
+  margin: 6px 0 0;
+  padding: 6px 10px;
+  border: 1px solid rgba(128, 128, 128, 0.2);
+  border-radius: 4px;
+  font-family: ui-monospace, "Cascadia Mono", Consolas, "Microsoft YaHei", monospace;
+  font-size: 12.5px;
+  line-height: 1.6;
+  white-space: pre;
+  overflow-x: auto;
+  max-height: 180px;
+}
+</style>
diff --git a/apps/web/src/admin/problem/detail.vue b/apps/web/src/admin/problem/detail.vue
index 5daf310..8b4bca0 100644
--- a/apps/web/src/admin/problem/detail.vue
+++ b/apps/web/src/admin/problem/detail.vue
@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { TEST_CASE_MAX_CASES, type RunnableLanguage } from "@oj2/contract"
+import { TEST_CASE_MAX_CASES, type ChallengeInput, type RunnableLanguage } from "@oj2/contract"
 import { useThemeVars } from "naive-ui"
 import PageHeader from "admin/components/PageHeader.vue"
 import { getProblemTagList } from "shared/api"
@@ -19,6 +19,7 @@ import {
   uploadTestcases,
 } from "../api"
 import AstRulesEditor from "./components/AstRulesEditor.vue"
+import ChallengeEditor from "./components/ChallengeEditor.vue"
 import CaseTable from "./components/CaseTable.vue"
 import CodePreview from "./components/CodePreview.vue"
 import PreviewStrip from "./components/PreviewStrip.vue"
@@ -108,6 +109,8 @@ interface CodeForm {
   answers: Record<RunnableLanguage, string>
   templates: Record<RunnableLanguage, TemplateParts>
   astRules: AstRules | null
+  /** 做对之后的挑战，按语言分组（见契约 challengeSchema） */
+  challenges: Record<string, ChallengeInput[]> | null
   flowchartMode: FlowchartMode
   mermaidCode: string
   /** 画布画的参考流程图；null 是老题（只有手写的 Mermaid）或者还没画 */
@@ -135,6 +138,7 @@ const blankForm = (): CodeForm => ({
   answers: { Python: "", C: "", "C++": "" },
   templates: { Python: blankParts(), C: blankParts(), "C++": blankParts() },
   astRules: null,
+  challenges: null,
   flowchartMode: "none",
   mermaidCode: "",
   flowchartDoc: null,
@@ -428,6 +432,14 @@ watch(
 const showHidden = ref(false)
 const astChecks = ref<AstCheckState>({})
 
+const challengeSummary = computed(() => {
+  const parts = form.languages
+    .map((lang) => [lang, form.challenges?.[lang]?.length ?? 0] as const)
+    .filter(([, n]) => n > 0)
+    .map(([lang, n]) => `${lang} ${n} 条`)
+  return parts.length ? parts.join(" · ") : "没有"
+})
+
 const answersForAst = computed(() => ({ ...form.answers }) as Partial<Record<LANGUAGE, string>>)
 const templatesForPreview = computed(
   () => ({ ...form.templates }) as Partial<Record<LANGUAGE, TemplateParts>>,
@@ -493,6 +505,7 @@ const open = reactive({
   answer: true,
   cases: true,
   write: false,
+  challenge: false,
   flowchart: false,
   more: false,
 })
@@ -612,6 +625,15 @@ async function loadProblem(data: AdminProblem) {
     answers,
     templates,
     astRules: data.astRules ?? null,
+    // scannedAt 是后端记账用的，表单里不带；id 带着，规则没改就沿用（做到记录跟着 id 走）
+    challenges: data.challenges
+      ? Object.fromEntries(
+          Object.entries(data.challenges).map(([lang, list]) => [
+            lang,
+            list.map(({ id, wording, rules }) => ({ id, wording, rules })),
+          ]),
+        )
+      : null,
     flowchartMode: data.allowFlowchart ? "draw" : data.showFlowchart ? "show" : "none",
     mermaidCode: data.mermaidCode ?? "",
     flowchartDoc: parseDoc(data.flowchartData),
@@ -719,6 +741,15 @@ const blockers = computed<Blocker[]>(() => {
           })
       })
   }
+  for (const lang of form.languages) {
+    form.challenges?.[lang]?.forEach((item, i) => {
+      if (!item.wording.trim() || !item.rules.length)
+        list.push({
+          text: `把挑战 ${lang} 第 ${i + 1} 条${item.wording.trim() ? "的规则" : "的说法"}写上`,
+          section: "challenge",
+        })
+    })
+  }
   if (form.flowchartMode === "show") {
     if (legacyMermaid.value) {
       if (!mermaidOk.value)
@@ -804,6 +835,7 @@ async function save() {
           : null,
       flowchartHint: form.flowchartHint.trim(),
       astRules: form.astRules,
+      challenges: form.challenges,
       sqlConfig: null,
       sqlDisplay: null,
       contestId: props.contestID ? Number(props.contestID) : null,
@@ -1197,6 +1229,24 @@ onMounted(async () => {
         </template>
       </section>
 
+      <!-- 挑战 -->
+      <section id="section-challenge" class="card">
+        <button type="button" class="cardHead" @click="open.challenge = !open.challenge">
+          <h3>挑战</h3>
+          <span v-if="!open.challenge" class="summary">{{ challengeSummary }}</span>
+          <n-text v-else depth="3" class="note">选填，学生做对以后才看得到</n-text>
+          <span class="grow"></span>
+          <span class="caret">{{ open.challenge ? "⌃" : "›" }}</span>
+        </button>
+        <ChallengeEditor
+          v-if="open.challenge"
+          v-model="form.challenges"
+          :languages="form.languages"
+          :answers="answersForAst"
+          :problem-id="props.initial?.id ?? null"
+        />
+      </section>
+
       <!-- 流程图 -->
       <section id="section-flowchart" class="card">
         <button type="button" class="cardHead" @click="open.flowchart = !open.flowchart">
diff --git a/apps/web/src/oj/api.ts b/apps/web/src/oj/api.ts
index 382cf70..0ad7fde 100644
--- a/apps/web/src/oj/api.ts
+++ b/apps/web/src/oj/api.ts
@@ -1,4 +1,5 @@
 import type {
+  ChallengeList,
   ClassLessonRequest,
   ContestPasswordRequest,
   CreateFlowchartRequest,
@@ -431,6 +432,15 @@ export function getSimilarProblems(problemId: string) {
     .then((response) => response.map(toProblemRow))
 }
 
+// ==================== 挑战 ====================
+
+/** 几道题、某种语言下的挑战（说法、几人做到、我做到没有），见契约 problemChallengeGroupSchema */
+export function getChallenges(problemIds: string[], language: string) {
+  return api.get<ChallengeList>("challenges", {
+    params: { problems: problemIds.join(","), language },
+  })
+}
+
 // ==================== 流程图相关API ====================
 
 export function submitFlowchart(data: {
diff --git a/apps/web/src/oj/classroom/board.vue b/apps/web/src/oj/classroom/board.vue
index 650dde1..e3bc007 100644
--- a/apps/web/src/oj/classroom/board.vue
+++ b/apps/web/src/oj/classroom/board.vue
@@ -256,6 +256,17 @@ const groupCount = computed(() => {
   for (const student of students.value) count[groupOf(student)]++
   return count
 })
+/**
+ * 全做完了的人里有几个在挑战：做对之后又交了、还没做到（见契约 classBoardCellSchema.challenge）。
+ * 做完了又没在挑战的，就是空着的
+ */
+const challengingCount = computed(
+  () =>
+    students.value.filter(
+      (student) =>
+        groupOf(student) === "done" && student.cells.some((cell) => cell.challenge === "doing"),
+    ).length,
+)
 /** 每组第一个人，在他上面插一行组名 */
 const groupStarts = computed(() => {
   const starts = new Set<number>()
@@ -298,7 +309,11 @@ const problemStats = computed(() =>
     const done = present.value.filter((student) => student.cells[i]?.status === "accepted").length
     const wrong = present.value.filter((student) => student.cells[i]?.status === "tried").length
     const total = present.value.length
-    return { problem, done, wrong, none: total - done - wrong, total }
+    // 挑战成功几人：只有配了挑战的题才写
+    const challenged = problem.hasChallenges
+      ? present.value.filter((student) => student.cells[i]?.challenge === "done").length
+      : null
+    return { problem, done, wrong, none: total - done - wrong, total, challenged }
   }),
 )
 
@@ -532,6 +547,9 @@ function lastText(student: ClassBoardStudent) {
             <span class="card-foot">
               <span :class="stat.wrong ? 'wrong' : 'muted'">错着 {{ stat.wrong }}</span>
               <span class="muted">没做 {{ stat.none }}</span>
+              <span v-if="stat.challenged !== null" class="challenged">
+                挑战成功 {{ stat.challenged }}
+              </span>
             </span>
           </button>
         </div>
@@ -651,6 +669,9 @@ function lastText(student: ClassBoardStudent) {
                   <span class="group-label">
                     {{ GROUP_LABEL[groupOf(student)] }}
                     <span class="muted">{{ groupCount[groupOf(student)] }}</span>
+                    <span v-if="groupOf(student) === 'done' && challengingCount" class="challenged">
+                      在挑战 {{ challengingCount }}
+                    </span>
                   </span>
                 </td>
               </tr>
@@ -709,6 +730,7 @@ function lastText(student: ClassBoardStudent) {
                     v-if="cell.status === 'tried' && cell.latest"
                     type="button"
                     class="cell"
+                    :data-challenge="cell.challenge ?? undefined"
                     :style="cellStyle(cell)"
                     :title="cellTitle(cell, student)"
                     @click="openExplain(i, student.userId)"
@@ -727,6 +749,7 @@ function lastText(student: ClassBoardStudent) {
                       <button
                         type="button"
                         class="cell"
+                        :data-challenge="cell.challenge ?? undefined"
                         :class="{ picked: trailKey === `${student.userId}:${i}` }"
                         :style="cellStyle(cell)"
                         :title="cellTitle(cell, student)"
@@ -747,6 +770,7 @@ function lastText(student: ClassBoardStudent) {
                   <a
                     v-else-if="cell.attempts"
                     class="cell"
+                    :data-challenge="cell.challenge ?? undefined"
                     :style="cellStyle(cell)"
                     :href="submissionsHref(student, board.problems[i], !cell.codeAttempts)"
                     target="_blank"
@@ -757,6 +781,7 @@ function lastText(student: ClassBoardStudent) {
                   <span
                     v-else
                     class="cell"
+                    :data-challenge="cell.challenge ?? undefined"
                     :style="cellStyle(cell)"
                     :title="cellTitle(cell, student)"
                   >
@@ -1220,6 +1245,36 @@ a.cell {
   cursor: pointer;
 }
 
+/* 挑战：做到了贴一枚紫色筹码，在挑战加一圈紫边（设计稿 StkBoard） */
+.cell[data-challenge="done"] {
+  position: relative;
+}
+
+.cell[data-challenge="done"]::after {
+  content: "";
+  position: absolute;
+  right: -6px;
+  top: -6px;
+  width: 14px;
+  height: 14px;
+  border-radius: 50%;
+  box-sizing: border-box;
+  background: #5b34c4;
+  border: 3px solid #b49cf5;
+  box-shadow: 0 0 0 2px v-bind("theme.cardColor");
+}
+
+.cell[data-challenge="doing"] {
+  box-shadow:
+    0 0 0 2px v-bind("theme.cardColor"),
+    0 0 0 4px #8f72e3;
+}
+
+.challenged {
+  color: #6a45d6;
+  font-weight: 600;
+}
+
 .cell.picked {
   box-shadow: 0 0 0 2px v-bind("theme.textColor1");
 }
diff --git a/apps/web/src/oj/classroom/boardCells.ts b/apps/web/src/oj/classroom/boardCells.ts
index c81172e..064919d 100644
--- a/apps/web/src/oj/classroom/boardCells.ts
+++ b/apps/web/src/oj/classroom/boardCells.ts
@@ -53,9 +53,12 @@ export function cellTitle(
   day: string | undefined,
 ) {
   if (cell.status === "accepted") {
-    return acceptedToday(cell, day)
+    const when = acceptedToday(cell, day)
       ? `${parseTime(cell.acceptedAt!, "HH:mm")} 做对`
       : "以前就做对了"
+    if (cell.challenge === "done") return `${when}，挑战也做到了`
+    if (cell.challenge === "doing") return `${when}，在挑战`
+    return when
   }
   if (cell.status === "tried") {
     if (cell.latest) return `讲讲 ${student.username} 这道题的错`
diff --git a/apps/web/src/oj/problem/components/ChallengeBar.vue b/apps/web/src/oj/problem/components/ChallengeBar.vue
new file mode 100644
index 0000000..ba6a581
--- /dev/null
+++ b/apps/web/src/oj/problem/components/ChallengeBar.vue
@@ -0,0 +1,127 @@
+<script setup lang="ts">
+import { useChallengeStore } from "oj/store/challenge"
+import { useChallengeTone } from "../composables/challengeTone"
+import ChallengeIcon from "./ChallengeIcon.vue"
+
+/**
+ * 挑战中：编辑器顶上一条紫色的，写着要求和全站几人做到，随时「不挑战了」（设计稿 StkDoing）。
+ * 做到了换成「挑战成功」，留着让学生看一眼自己是照什么要求写的，再「回到普通模式」
+ */
+const challengeStore = useChallengeStore()
+const tone = useChallengeTone()
+const active = computed(() => challengeStore.active)
+const done = computed(() => !!active.value?.mine)
+</script>
+
+<template>
+  <div v-if="active" class="challenge-bar">
+    <span class="pill">
+      <svg
+        v-if="done"
+        width="12"
+        height="12"
+        viewBox="0 0 24 24"
+        fill="none"
+        stroke="currentColor"
+        stroke-width="3"
+        stroke-linecap="round"
+        stroke-linejoin="round"
+        aria-hidden="true"
+      >
+        <path d="M5 12.5l4.5 4.5L19 7.5" />
+      </svg>
+      <ChallengeIcon v-else />
+      {{ done ? "挑战成功" : "挑战" }}
+    </span>
+    <b class="wording">{{ active.wording }}</b>
+    <span class="spacer" />
+    <span v-if="!done" class="meta">{{ active.doneCount }} 人做到</span>
+    <button type="button" class="quit" @click="challengeStore.stop()">
+      {{ done ? "回到普通模式" : "不挑战了" }}
+    </button>
+  </div>
+</template>
+
+<style scoped>
+.challenge-bar {
+  height: 44px;
+  flex-shrink: 0;
+  box-sizing: border-box;
+  padding: 0 14px;
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  background-color: v-bind("tone.soft");
+  border-bottom: 1px solid v-bind("tone.border");
+  white-space: nowrap;
+  min-width: 0;
+}
+
+.pill {
+  display: inline-flex;
+  align-items: center;
+  gap: 5px;
+  height: 24px;
+  padding: 0 9px;
+  border-radius: 12px;
+  background-color: v-bind("tone.solid");
+  color: v-bind("tone.onSolid");
+  font-size: 13px;
+  font-weight: 600;
+  flex-shrink: 0;
+}
+
+.wording {
+  font-size: 15px;
+  color: v-bind("tone.text");
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+.spacer {
+  flex-grow: 1;
+}
+
+.meta {
+  font-size: 13px;
+  opacity: 0.75;
+}
+
+.quit {
+  height: 28px;
+  padding: 0 10px;
+  border: 1px solid v-bind("tone.border");
+  border-radius: 4px;
+  background: transparent;
+  font: inherit;
+  font-size: 13px;
+  color: v-bind("tone.text");
+  cursor: pointer;
+  flex-shrink: 0;
+}
+
+/* 手机上一行放不下：说法最要紧，让它折行，人数不写了 */
+@media (max-width: 768px) {
+  .challenge-bar {
+    height: auto;
+    min-height: 44px;
+    padding: 6px 12px;
+    white-space: normal;
+  }
+
+  .wording {
+    flex: 1 1 0;
+  }
+
+  .spacer,
+  .meta {
+    display: none;
+  }
+}
+
+.quit:focus-visible {
+  outline: 2px solid v-bind("tone.solid");
+  outline-offset: 2px;
+}
+</style>
diff --git a/apps/web/src/oj/problem/components/ChallengeIcon.vue b/apps/web/src/oj/problem/components/ChallengeIcon.vue
new file mode 100644
index 0000000..ca78b6a
--- /dev/null
+++ b/apps/web/src/oj/problem/components/ChallengeIcon.vue
@@ -0,0 +1,20 @@
+<script setup lang="ts">
+/** 挑战的标记：一枚筹码（借的是小丑牌的赌注筹码），设计稿「做对后再挑战」 */
+withDefaults(defineProps<{ size?: number }>(), { size: 14 })
+</script>
+
+<template>
+  <svg
+    :width="size"
+    :height="size"
+    viewBox="0 0 24 24"
+    fill="none"
+    stroke="currentColor"
+    stroke-width="2.2"
+    aria-hidden="true"
+  >
+    <circle cx="12" cy="12" r="9" />
+    <circle cx="12" cy="12" r="4" />
+    <path d="M12 3v3M12 18v3M3 12h3M18 12h3" stroke-linecap="round" />
+  </svg>
+</template>
diff --git a/apps/web/src/oj/problem/components/ChallengeList.vue b/apps/web/src/oj/problem/components/ChallengeList.vue
new file mode 100644
index 0000000..dc1d955
--- /dev/null
+++ b/apps/web/src/oj/problem/components/ChallengeList.vue
@@ -0,0 +1,201 @@
+<script setup lang="ts">
+import type { ChallengeList } from "@oj2/contract"
+import { getChallenges } from "oj/api"
+import { useChallengeStore } from "oj/store/challenge"
+import { useChallengeTone } from "../composables/challengeTone"
+import ChallengeIcon from "./ChallengeIcon.vue"
+
+/**
+ * 「还能挑战」：这几道题里我做对了、还没做到的挑战，一条一行，「去挑战」（设计稿 StkDone）。
+ * 一条都没有就什么都不显示 —— 课堂题多是一两行，能出挑战的只是一部分。
+ */
+const props = defineProps<{
+  problemIds: string[]
+  language: string
+  /** 变了就重拉：刚做对 / 刚做到一条挑战，列表里要去掉它 */
+  refreshKey?: string
+}>()
+
+const challengeStore = useChallengeStore()
+const tone = useChallengeTone()
+
+const groups = ref<ChallengeList>([])
+let sequence = 0
+watch(
+  () => [props.problemIds.join(","), props.language, props.refreshKey] as const,
+  async () => {
+    const mine = ++sequence
+    if (!props.problemIds.length || !props.language) {
+      groups.value = []
+      return
+    }
+    try {
+      const list = await getChallenges(props.problemIds, props.language)
+      if (mine === sequence) groups.value = list
+    } catch {
+      if (mine === sequence) groups.value = []
+    }
+  },
+  { immediate: true },
+)
+
+const rows = computed(() =>
+  groups.value.flatMap((group) =>
+    // 没做对的题不给接挑战：挑战是做对之后的事
+    group.solved
+      ? group.challenges
+          .filter((challenge) => !challenge.mine)
+          .map((challenge) => ({ group, challenge }))
+      : [],
+  ),
+)
+</script>
+
+<template>
+  <section v-if="rows.length" class="challenge-list" aria-label="还能挑战">
+    <div class="head">
+      <span class="pill"><ChallengeIcon />挑战</span>
+      <b>还能挑战</b>
+    </div>
+    <div v-for="({ group, challenge }, i) in rows" :key="challenge.id" class="row">
+      <div class="text">
+        <div class="problem">
+          <b>{{ group.problemId }}</b> <span class="title">{{ group.title }}</span>
+        </div>
+        <b class="wording">{{ challenge.wording }}</b>
+        <span class="stat">
+          {{ group.acCount }} 个做对的人里，{{ challenge.doneCount }} 人做到
+        </span>
+      </div>
+      <button
+        type="button"
+        class="go"
+        :class="{ ghost: i > 0 }"
+        @click="challengeStore.start(group.problemId, challenge.id)"
+      >
+        去挑战
+        <svg
+          width="16"
+          height="16"
+          viewBox="0 0 24 24"
+          fill="none"
+          stroke="currentColor"
+          stroke-width="2.5"
+          stroke-linecap="round"
+          stroke-linejoin="round"
+          aria-hidden="true"
+        >
+          <path d="M5 12h14M13 6l6 6-6 6" />
+        </svg>
+      </button>
+    </div>
+  </section>
+</template>
+
+<style scoped>
+.challenge-list {
+  margin-top: 14px;
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.head {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  font-size: 15px;
+}
+
+.pill {
+  display: inline-flex;
+  align-items: center;
+  gap: 5px;
+  height: 24px;
+  padding: 0 9px;
+  border-radius: 12px;
+  background-color: v-bind("tone.solid");
+  color: v-bind("tone.onSolid");
+  font-size: 13px;
+  font-weight: 600;
+}
+
+.row {
+  display: grid;
+  grid-template-columns: minmax(0, 1fr) auto;
+  align-items: center;
+  gap: 4px 16px;
+  padding: 12px 14px;
+  border: 1px solid v-bind("tone.border");
+  border-radius: 8px;
+}
+
+.text {
+  display: flex;
+  flex-direction: column;
+  gap: 3px;
+  min-width: 0;
+}
+
+.problem {
+  font-size: 13px;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+.title,
+.stat {
+  opacity: 0.7;
+}
+
+.stat {
+  font-size: 13px;
+}
+
+.wording {
+  font-size: 17px;
+  line-height: 24px;
+  color: v-bind("tone.text");
+}
+
+.go {
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+  height: 40px;
+  padding: 0 16px;
+  border-radius: 6px;
+  border: 1px solid v-bind("tone.solid");
+  background-color: v-bind("tone.solid");
+  color: v-bind("tone.onSolid");
+  font: inherit;
+  font-size: 15px;
+  font-weight: 600;
+  white-space: nowrap;
+  cursor: pointer;
+}
+
+.go.ghost {
+  background-color: transparent;
+  color: v-bind("tone.text");
+  border-color: v-bind("tone.border");
+}
+
+.go:focus-visible {
+  outline: 2px solid v-bind("tone.solid");
+  outline-offset: 2px;
+}
+
+/* 手机上按钮另起一行占满，好按 */
+@media (max-width: 768px) {
+  .row {
+    grid-template-columns: minmax(0, 1fr);
+  }
+
+  .go {
+    justify-content: center;
+    height: 44px;
+  }
+}
+</style>
diff --git a/apps/web/src/oj/problem/components/ChallengeOutcome.vue b/apps/web/src/oj/problem/components/ChallengeOutcome.vue
new file mode 100644
index 0000000..6b1f8ee
--- /dev/null
+++ b/apps/web/src/oj/problem/components/ChallengeOutcome.vue
@@ -0,0 +1,194 @@
+<script setup lang="ts">
+import type { AstResultInfo } from "@oj2/contract"
+import { useChallengeStore } from "oj/store/challenge"
+import { clearChallengeLines, showChallengeLines } from "oj/problem/utils/errorMark"
+import { useChallengeTone } from "../composables/challengeTone"
+import ChallengeIcon from "./ChallengeIcon.vue"
+
+/**
+ * 挑战中交的这一次，挑战成没成（设计稿 StkFail / StkPass）。答案本身是对的 —— 没做到挑战
+ * 也照样算做对，所以没做到时大字写「答案对了，挑战还差一点」，不是错误的红色。
+ */
+const props = defineProps<{
+  passed: boolean
+  results: AstResultInfo[]
+  wording: string
+}>()
+
+const challengeStore = useChallengeStore()
+const tone = useChallengeTone()
+
+const failed = computed(() => props.results.filter((result) => !result.passed))
+
+/** 「print() 至多调用 1 次，现在 3 次」 */
+const reason = computed(() =>
+  failed.value
+    .map((result) =>
+      result.actual !== undefined
+        ? `${result.description}，现在 ${result.actual} 次`
+        : result.description,
+    )
+    .join("；"),
+)
+
+const lines = computed(() => [...new Set(failed.value.flatMap((result) => result.lines ?? []))])
+
+// 编辑器里把那几行标紫。做到了、换了一次提交就清掉
+watch(
+  () => (props.passed ? [] : lines.value),
+  (value) => (value.length ? showChallengeLines(value) : clearChallengeLines()),
+  { immediate: true },
+)
+onUnmounted(clearChallengeLines)
+
+/** 做到了：本班、全站第几个。刚判完那一刻列表还没重拉，先不显示 */
+const mine = computed(() => (props.passed ? (challengeStore.active?.mine ?? null) : null))
+</script>
+
+<template>
+  <div class="challenge-outcome">
+    <div class="line">
+      <span class="badge" :class="{ outline: !passed }" aria-hidden="true">
+        <ChallengeIcon :size="18" />
+      </span>
+      <div class="text">
+        <b class="title">{{ passed ? "挑战成功" : "答案对了，挑战还差一点" }}</b>
+        <span class="sub">{{ passed ? wording : reason }}</span>
+      </div>
+    </div>
+    <div v-if="!passed" class="chips">
+      <span class="chip ok">
+        <svg
+          width="12"
+          height="12"
+          viewBox="0 0 24 24"
+          fill="none"
+          stroke="currentColor"
+          stroke-width="3"
+          stroke-linecap="round"
+          stroke-linejoin="round"
+          aria-hidden="true"
+        >
+          <path d="M5 12.5l4.5 4.5L19 7.5" />
+        </svg>
+        测试点全对
+      </span>
+      <span v-if="lines.length" class="chip mark">第 {{ lines.join("、") }} 行</span>
+    </div>
+    <div v-if="mine" class="tiles">
+      <div v-if="mine.classRank !== null" class="tile">
+        <b>第 {{ mine.classRank }} 个</b>
+        <span>本班做到的</span>
+      </div>
+      <div class="tile">
+        <b>第 {{ mine.siteRank }} 个</b>
+        <span>全站做到的</span>
+      </div>
+    </div>
+  </div>
+</template>
+
+<style scoped>
+.challenge-outcome {
+  display: flex;
+  flex-direction: column;
+  gap: 14px;
+}
+
+.line {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+}
+
+.badge {
+  width: 34px;
+  height: 34px;
+  border-radius: 50%;
+  flex-shrink: 0;
+  box-sizing: border-box;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  background-color: v-bind("tone.solid");
+  color: v-bind("tone.onSolid");
+}
+
+.badge.outline {
+  background-color: transparent;
+  border: 2px solid v-bind("tone.solid");
+  color: v-bind("tone.solid");
+}
+
+.text {
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+  min-width: 0;
+}
+
+.title {
+  font-size: 22px;
+  line-height: 28px;
+  color: v-bind("tone.text");
+}
+
+.sub {
+  font-size: 14px;
+  opacity: 0.75;
+}
+
+.chips {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 6px;
+}
+
+.chip {
+  display: inline-flex;
+  align-items: center;
+  gap: 4px;
+  height: 26px;
+  padding: 0 9px;
+  border-radius: 13px;
+  font-size: 13px;
+}
+
+.chip.ok {
+  background-color: rgba(24, 160, 88, 0.12);
+  color: #18a058;
+}
+
+.chip.mark {
+  background-color: v-bind("tone.soft");
+  color: v-bind("tone.text");
+  font-weight: 600;
+}
+
+.tiles {
+  display: flex;
+  gap: 10px;
+}
+
+.tile {
+  flex: 1;
+  display: flex;
+  flex-direction: column;
+  padding: 10px 14px;
+  border-radius: 8px;
+  border: 1px solid v-bind("tone.border");
+  background-color: v-bind("tone.soft");
+}
+
+.tile b {
+  font-size: 24px;
+  line-height: 30px;
+  font-variant-numeric: tabular-nums;
+  color: v-bind("tone.text");
+}
+
+.tile span {
+  font-size: 13px;
+  opacity: 0.75;
+}
+</style>
diff --git a/apps/web/src/oj/problem/components/LessonNext.vue b/apps/web/src/oj/problem/components/LessonNext.vue
index b8e596f..7c04c40 100644
--- a/apps/web/src/oj/problem/components/LessonNext.vue
+++ b/apps/web/src/oj/problem/components/LessonNext.vue
@@ -1,6 +1,7 @@
 <script setup lang="ts">
 import { useThemeVars } from "naive-ui"
 import { useLessonStore } from "shared/store/lesson"
+import ChallengeList from "./ChallengeList.vue"
 
 /**
  * 通过之后告诉学生「这节课的下一题是哪道」。
@@ -16,6 +17,12 @@ import { useLessonStore } from "shared/store/lesson"
 const props = defineProps<{
   /** 当前这道题的展示题号 */
   problemDisplayId: string
+  /** 刚做对用的语言：挑战按语言分 */
+  language: string
+  /** 刚做对的那次提交，换了就重拉「还能挑战」 */
+  refreshKey: string
+  /** 这个入口给不给挑战（见 problemPageContext） */
+  challenges: boolean
 }>()
 
 const lessonStore = useLessonStore()
@@ -31,6 +38,11 @@ const lesson = computed(() => lessonStore.nextAfter(props.problemDisplayId))
 
 // 设计稿和上下文条都叫「这节课」，不区分是老师布置的还是从同班提交推断的
 const label = "这节课"
+
+/** 这节课的几道题：都做完了以后，这几道里还能挑战的列出来（设计稿 StkDone） */
+const lessonProblemIds = computed(
+  () => lessonStore.activity?.problems.map((item) => item.problemDisplayId) ?? [],
+)
 </script>
 
 <template>
@@ -66,13 +78,18 @@ const label = "这节课"
     <template v-else>
       <div class="text">
         <span class="headline">{{ label }}都做完了，一共 {{ lesson.total }} 道</span>
-        <span class="detail">想接着练，可以去题单里挑一个</span>
+        <span v-if="!challenges" class="detail">想接着练，可以去题单里挑一个</span>
       </div>
-      <router-link to="/problemset" class="next secondary">
+      <router-link v-if="!challenges" to="/problemset" class="next secondary">
         <span class="next-label">去题单继续练</span>
       </router-link>
     </template>
   </div>
+  <!-- 做完了：先给这节课里还能挑战的，再给题单（设计稿 StkDone）。挑战一条都没有时只剩题单那句 -->
+  <template v-if="lesson && !lesson.next && challenges">
+    <ChallengeList :problem-ids="lessonProblemIds" :language="language" :refresh-key="refreshKey" />
+    <router-link to="/problemset" class="more">去题单继续练</router-link>
+  </template>
 </template>
 
 <style scoped>
@@ -129,6 +146,17 @@ const label = "这节课"
   outline-offset: 2px;
 }
 
+.more {
+  display: inline-block;
+  margin-top: 12px;
+  font-size: 14px;
+  color: v-bind("theme.primaryColor");
+}
+
+.more:hover {
+  text-decoration: underline;
+}
+
 .next.secondary {
   background-color: transparent;
   border: 1px solid v-bind("theme.primaryColor");
diff --git a/apps/web/src/oj/problem/components/ProblemEditor.vue b/apps/web/src/oj/problem/components/ProblemEditor.vue
index fed7307..3e112b9 100644
--- a/apps/web/src/oj/problem/components/ProblemEditor.vue
+++ b/apps/web/src/oj/problem/components/ProblemEditor.vue
@@ -13,6 +13,8 @@ import { errorMarkExtensions } from "oj/problem/utils/errorMark"
 import { editorFocusTracker } from "oj/problem/utils/symbolKeys"
 import { hangWrapExtensions } from "shared/extensions/hangIndent"
 import EditorToolbar from "./EditorToolbar.vue"
+import ChallengeBar from "./ChallengeBar.vue"
+import { useChallengeStore } from "oj/store/challenge"
 import { useDraftKey } from "../composables/draftKey"
 import { useCollabHere, useTeacherCollab } from "../composables/teacherCollab"
 import { useProblemPageContext } from "../composables/problemPageContext"
@@ -99,9 +101,14 @@ const storageKey = useDraftKey()
 
 // 桌面：顶栏 56 + 工具栏 48，协作条再占 40（两栏顶满内容区，见 detail.vue 的 problem-split）。
 // 手机：顶栏两行 + 课堂条 + 页签 + 工具栏约 236px，底部还有「运行例子 / 提交」那条约 64px
+// 挑战中编辑器顶上多一条 44 的挑战条（协作中的老师不显示，见模板）
+const challengeStore = useChallengeStore()
+const showChallengeBar = computed(
+  () => ctx.value.challenges && !teacherCollab.value && !!challengeStore.active,
+)
 const editorHeight = computed(() => {
   const base = isDesktop.value ? 104 : 300
-  return `calc(100vh - ${base + (teacherCollab.value ? 40 : 0)}px)`
+  return `calc(100vh - ${base + (teacherCollab.value ? 40 : 0) + (showChallengeBar.value ? 44 : 0)}px)`
 })
 
 function loadCode() {
@@ -220,6 +227,7 @@ onBeforeUnmount(() => flowchartStore.attachEditor(null))
 <template>
   <div class="problem-editor">
     <CollabBar v-if="teacherCollab" />
+    <ChallengeBar v-if="showChallengeBar" />
     <EditorToolbar @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/SubmissionResult.vue b/apps/web/src/oj/problem/components/SubmissionResult.vue
index 4129920..d7dda67 100644
--- a/apps/web/src/oj/problem/components/SubmissionResult.vue
+++ b/apps/web/src/oj/problem/components/SubmissionResult.vue
@@ -21,6 +21,9 @@ import WrongAnswerExplain from "./WrongAnswerExplain.vue"
 import LessonNext from "./LessonNext.vue"
 import ResultHeader from "./ResultHeader.vue"
 import SimilarProblems from "./SimilarProblems.vue"
+import ChallengeList from "./ChallengeList.vue"
+import ChallengeOutcome from "./ChallengeOutcome.vue"
+import { useChallengeStore } from "oj/store/challenge"
 import { useLessonStore } from "shared/store/lesson"
 import { useProblemPageContext } from "../composables/problemPageContext"
 import Markdown from "shared/components/Markdown.vue"
@@ -109,6 +112,40 @@ const showSimilar = computed(
     !lessonStore.includes(problemStore.problem._id),
 )
 
+/**
+ * 挑战中交的这一次：正在挑战的那条判出来的结果（设计稿 StkFail / StkPass）。只有做对的提交
+ * 才判挑战；进挑战之前那次做对的不算（见 challenge store 的 baselineSubmissionId）
+ */
+const challengeStore = useChallengeStore()
+const challengeVerdict = computed(() => {
+  const submission = props.submission
+  if (!submission || props.peer || !ctx.value.challenges) return null
+  if (submission.result !== SubmissionStatus.accepted) return null
+  const id = challengeStore.activeId
+  if (!id || submission.id === challengeStore.baselineSubmissionId) return null
+  return submission.statisticInfo?.challenges?.find((verdict) => verdict.id === id) ?? null
+})
+// 做到了：重拉一次，挑战条换成「挑战成功」、拿到本班 / 全站第几个
+watch(
+  () => (challengeVerdict.value?.passed ? props.submission?.id : null),
+  (id) => {
+    if (id) void challengeStore.load()
+  },
+)
+
+/**
+ * 「还能挑战」看哪几道：这道在这节课里就看这节课的几道（课堂条「这节课都做完了」之后），
+ * 不在就只看这一道
+ */
+const challengeProblemIds = computed(() => {
+  const problem = problemStore.problem
+  if (!problem) return []
+  const lesson = lessonStore.activity
+  return lessonStore.includes(problem._id) && lesson
+    ? lesson.problems.map((item) => item.problemDisplayId)
+    : [problem._id]
+})
+
 const msg = computed(() => {
   if (!props.submission) return ""
   // 走 CompileErrorExplain / RuntimeErrorExplain 那两张中文卡片
@@ -298,18 +335,44 @@ const columns: DataTableColumn<JudgeCaseResult>[] = [
 
 <template>
   <div v-if="submission">
-    <ResultHeader
-      v-if="header"
-      :kind="header.kind"
-      :title="header.title"
-      :sub="header.sub"
-      :progress="header.progress"
-    />
-    <LessonNext
-      v-if="showLessonNext && problemStore.problem"
-      :problem-display-id="problemStore.problem._id"
-    />
-    <SimilarProblems v-if="showSimilar" title="再练几道相似的" />
+    <!-- 挑战中：答案对了就只说挑战成没成，「下一题」「相似题」都不给，免得挤掉挑战 -->
+    <template v-if="challengeVerdict && challengeStore.active">
+      <ChallengeOutcome
+        :passed="challengeVerdict.passed"
+        :results="challengeVerdict.results"
+        :wording="challengeStore.active.wording"
+      />
+      <ChallengeList
+        v-if="challengeVerdict.passed"
+        :problem-ids="challengeProblemIds"
+        :language="submission.language"
+        :refresh-key="submission.id"
+      />
+    </template>
+    <template v-else>
+      <ResultHeader
+        v-if="header"
+        :kind="header.kind"
+        :title="header.title"
+        :sub="header.sub"
+        :progress="header.progress"
+      />
+      <LessonNext
+        v-if="showLessonNext && problemStore.problem"
+        :problem-display-id="problemStore.problem._id"
+        :language="submission.language"
+        :refresh-key="submission.id"
+        :challenges="ctx.challenges"
+      />
+      <!-- 不在这节课里（题库入口自己做的）：做对之后先给这道题的挑战，再给相似题 -->
+      <ChallengeList
+        v-if="showSimilar && ctx.challenges && problemStore.problem"
+        :problem-ids="[problemStore.problem._id]"
+        :language="submission.language"
+        :refresh-key="submission.id"
+      />
+      <SimilarProblems v-if="showSimilar" title="再练几道相似的" />
+    </template>
     <n-flex
       vertical
       v-if="
diff --git a/apps/web/src/oj/problem/composables/challengeTone.ts b/apps/web/src/oj/problem/composables/challengeTone.ts
new file mode 100644
index 0000000..8dc046f
--- /dev/null
+++ b/apps/web/src/oj/problem/composables/challengeTone.ts
@@ -0,0 +1,24 @@
+/**
+ * 挑战的颜色：紫。课堂条是绿、题单条是蓝、比赛条是黄，挑战不能和它们撞（设计稿「做对后再挑战」）。
+ * Naive 的主题里没有紫，暗色下换浅一档，深紫放在暗底上看不清
+ */
+export function useChallengeTone() {
+  const isDark = useDark()
+  return computed(() =>
+    isDark.value
+      ? {
+          solid: "#b49cf5",
+          onSolid: "#17112b",
+          text: "#c9b8ff",
+          soft: "rgba(180, 156, 245, 0.14)",
+          border: "rgba(180, 156, 245, 0.35)",
+        }
+      : {
+          solid: "#5b34c4",
+          onSolid: "#ffffff",
+          text: "#2c1a66",
+          soft: "#f4f0fe",
+          border: "#ddd3f6",
+        },
+  )
+}
diff --git a/apps/web/src/oj/problem/composables/problemPageContext.ts b/apps/web/src/oj/problem/composables/problemPageContext.ts
index 817b5fa..19a4aa7 100644
--- a/apps/web/src/oj/problem/composables/problemPageContext.ts
+++ b/apps/web/src/oj/problem/composables/problemPageContext.ts
@@ -26,6 +26,11 @@ interface EntryRules {
   similar: boolean
   /** 通过之后给「这节课的下一题」 */
   lessonNext: boolean
+  /**
+   * 做对之后的挑战（编辑器顶上的挑战条、结果里的「还能挑战」）。题单里通过后 1.5 秒就跳回去，
+   * 比赛提交不判挑战
+   */
+  challenges: boolean
   /** 通过之后 1.5 秒弹强制点评 */
   reviewAfterAccepted: boolean
   /** 通过之后 1.5 秒回题单 */
@@ -57,6 +62,7 @@ const RULES: Record<ProblemEntry, EntryRules> = {
     statusTag: true,
     similar: true,
     lessonNext: true,
+    challenges: true,
     reviewAfterAccepted: true,
     backToProblemSet: false,
     help: true,
@@ -71,6 +77,7 @@ const RULES: Record<ProblemEntry, EntryRules> = {
     // 点进相似题就离开了题单
     similar: false,
     lessonNext: false,
+    challenges: false,
     // 1.5 秒后要跳回题单页，弹了也会被冲掉
     reviewAfterAccepted: false,
     backToProblemSet: true,
@@ -86,6 +93,7 @@ const RULES: Record<ProblemEntry, EntryRules> = {
     // 撞上同号公开题时反而会在比赛中把题库列给学生
     similar: false,
     lessonNext: false,
+    challenges: false,
     reviewAfterAccepted: false,
     backToProblemSet: false,
     help: false,
diff --git a/apps/web/src/oj/problem/utils/errorMark.ts b/apps/web/src/oj/problem/utils/errorMark.ts
index 2948e36..c03f36a 100644
--- a/apps/web/src/oj/problem/utils/errorMark.ts
+++ b/apps/web/src/oj/problem/utils/errorMark.ts
@@ -75,6 +75,30 @@ const markField = StateField.define<DecorationSet>({
   provide: (field) => EditorView.decorations.from(field),
 })
 
+/**
+ * 挑战没做到时标出是哪几行（「print 最多 1 次」→ 三个 print 所在的三行），紫底，和挑战
+ * 那条的颜色一致。和错误标记分开存：答案对了、挑战没做到时没有错误可标，两种也不会同时出现
+ */
+const setChallengeLines = StateEffect.define<number[]>()
+const challengeLineDeco = Decoration.line({ class: "cm-challenge-line" })
+
+const challengeField = StateField.define<DecorationSet>({
+  create: () => Decoration.none,
+  update(deco, tr) {
+    deco = deco.map(tr.changes)
+    for (const effect of tr.effects) {
+      if (effect.is(setChallengeLines)) {
+        const lines = effect.value.filter((line) => line >= 1 && line <= tr.state.doc.lines)
+        deco = Decoration.set(
+          lines.map((line) => challengeLineDeco.range(tr.state.doc.line(line).from)),
+        )
+      }
+    }
+    return deco
+  },
+  provide: (field) => EditorView.decorations.from(field),
+})
+
 /**
  * 题目页当前那个编辑器。结果面板和编辑器是兄弟组件，隔着好几层，
  * 与其一路透传 ref，不如让编辑器挂载时自己登记。只挂在题目页主编辑器上
@@ -98,6 +122,11 @@ const theme = EditorView.baseTheme({
     textUnderlineOffset: "3px",
     backgroundColor: "rgba(208, 48, 80, 0.18)",
   },
+  // 左边再压一道紫线：光标所在那行的底色会盖住行底色，线不会被盖
+  ".cm-challenge-line": {
+    backgroundColor: "rgba(91, 52, 196, 0.12)",
+    boxShadow: "inset 3px 0 0 #8f72e3",
+  },
   ".cm-punctuation-mark": {
     backgroundColor: "rgba(240, 160, 32, 0.35)",
     outline: "1px solid rgba(240, 160, 32, 0.8)",
@@ -105,7 +134,7 @@ const theme = EditorView.baseTheme({
   },
 })
 
-export const errorMarkExtensions = [markField, punctuationField, tracker, theme]
+export const errorMarkExtensions = [markField, punctuationField, challengeField, tracker, theme]
 
 /** 题目页主编辑器（没挂着就是 null）。手机上的符号键往它里面插字 */
 export function currentEditorView(): EditorView | null {
@@ -145,6 +174,15 @@ export function showErrorMark(
   })
 }
 
+/** 标出挑战没做到的那几行（行号来自判题时的 AST，学生之后改过代码的话会对不上，不滚过去） */
+export function showChallengeLines(lines: number[]) {
+  current?.dispatch({ effects: setChallengeLines.of(lines) })
+}
+
+export function clearChallengeLines() {
+  current?.dispatch({ effects: setChallengeLines.of([]) })
+}
+
 export function clearErrorMark() {
   current?.dispatch({ effects: setMark.of(null) })
 }
diff --git a/apps/web/src/oj/store/challenge.ts b/apps/web/src/oj/store/challenge.ts
new file mode 100644
index 0000000..97f2f57
--- /dev/null
+++ b/apps/web/src/oj/store/challenge.ts
@@ -0,0 +1,87 @@
+import { defineStore } from "pinia"
+import type { ProblemChallengeGroup } from "@oj2/contract"
+import { getChallenges } from "oj/api"
+import { useCodeStore } from "oj/store/code"
+import { useProblemStore } from "oj/store/problem"
+import { useSubmissionStore } from "oj/store/submission"
+import { useBreakpoints } from "shared/composables/breakpoints"
+
+/**
+ * 挑战：做对之后，同一道题加一条写法上的限制再做一遍（契约 challengeSchema）。
+ *
+ * 正在挑战哪一条记在路由的 `?challenge=<id>` 上：「去挑战」常常是去另一道题（这节课的
+ * 别的题），带着 query 跳过去最直接；刷新、返回也还在挑战里。
+ *
+ * 这里只管当前这道题的挑战（编辑器顶上那条、结果里的成没成）。课堂条「这节课都做完了」
+ * 那几道题的列表由 ChallengeList 自己拉。
+ */
+export const useChallengeStore = defineStore("challenge", () => {
+  const route = useRoute()
+  const router = useRouter()
+  const problemStore = useProblemStore()
+  const codeStore = useCodeStore()
+  const { isMobile } = useBreakpoints()
+
+  const activeId = computed(() =>
+    typeof route.query.challenge === "string" ? route.query.challenge : "",
+  )
+
+  /**
+   * 进挑战那一刻结果页签里挂着的那次提交。它是进挑战之前那次做对的，也判过挑战（没做到），
+   * 不能拿它说「挑战还差一点」—— 只认之后交的。不用时刻比：机房电脑的钟不一定准
+   */
+  const submissionStore = useSubmissionStore()
+  const baselineSubmissionId = ref<string | null>(null)
+  watch(
+    activeId,
+    (id) => {
+      if (id) baselineSubmissionId.value = submissionStore.submission?.id ?? null
+    },
+    { immediate: true },
+  )
+
+  /** 当前这道题、编辑器当前语言下的挑战；没配挑战为 null */
+  const current = ref<ProblemChallengeGroup | null>(null)
+  let sequence = 0
+  async function load() {
+    const problemId = problemStore.problem?._id
+    const language = codeStore.code.language
+    const mine = ++sequence
+    if (!problemId || language === "Flowchart" || problemStore.problem?.contestId != null) {
+      current.value = null
+      return
+    }
+    try {
+      const [group] = await getChallenges([problemId], language)
+      if (mine === sequence) current.value = group ?? null
+    } catch {
+      // 拉不到就没有挑战，不影响做题
+      if (mine === sequence) current.value = null
+    }
+  }
+  watch([() => problemStore.problem?._id, () => codeStore.code.language], load, {
+    immediate: true,
+  })
+
+  /** 正在挑战的那条（换了语言、挑战被老师删了就是 null） */
+  const active = computed(
+    () => current.value?.challenges.find((item) => item.id === activeId.value) ?? null,
+  )
+
+  function start(problemId: string, challengeId: string) {
+    // 进挑战先看题和代码：手机上编辑器是单独一个页签
+    const tab = isMobile.value ? "editor" : "content"
+    void router.push({
+      name: "problem",
+      params: { problemID: problemId },
+      query: { challenge: challengeId, tab },
+    })
+  }
+
+  function stop() {
+    const { challenge: _, ...rest } = route.query
+    void router.replace({ query: rest })
+  }
+
+  return { activeId, active, current, baselineSubmissionId, load, start, stop }
+})
diff --git a/apps/web/src/utils/types.ts b/apps/web/src/utils/types.ts
index 2c6743e..b26a19f 100644
--- a/apps/web/src/utils/types.ts
+++ b/apps/web/src/utils/types.ts
@@ -10,6 +10,7 @@ import type {
   ProblemDifficulty,
   JudgeStatus,
   AstRules,
+  ChallengeInput,
   CreateAnnouncementRequest,
   ProblemLanguage,
 } from "@oj2/contract"
@@ -142,8 +143,10 @@ type ExcludeKeys =
 
 export type BlankProblem = Omit<
   AdminProblem,
-  ExcludeKeys | "hint" | "mermaidCode" | "flowchartData"
+  ExcludeKeys | "hint" | "mermaidCode" | "flowchartData" | "challenges"
 > & {
+  /** 提交的挑战：新加的不带 id，后端发（见契约 challengeInputSchema） */
+  challenges?: Record<string, ChallengeInput[]> | null
   id?: number
   // 新建比赛题时由 detail.vue 在提交前写进来
   contestId?: number | null