diff --git a/apps/web/src/oj/api.ts b/apps/web/src/oj/api.ts
index 90835ed..de96a68 100644
--- a/apps/web/src/oj/api.ts
+++ b/apps/web/src/oj/api.ts
@@ -1,54 +1,55 @@
 import {
   type AiAnalysisRecord,
-  type Contest as OjContest,
-  type ContestAccess,
-  type ContestList,
-  type ActivityRankItem,
   type FormatCodeResponse,
-  type Metrics,
   type TutorialSummary,
   type ClassComparisonResponse,
   type ClassRankItem,
   type ClassUserRank,
-  type UserRank,
-  type ProblemRank,
   type CreateSubmissionResponse,
   type ProblemAuthor,
-  type ProblemListItem,
   type YearlyAc,
   type CreateFlowchartResponse,
-  type FlowchartCurrent,
-  type FlowchartDetail,
-  type FlowchartList,
   type FlowchartSubmission,
   type AiDetail,
   type DurationData,
   type HeatmapItem,
   type LoginSummary,
   type SolvedList,
-  type ProblemSet,
-  type ProblemSetBadge,
-  type ProblemSetList,
-  type ProblemSetProblem,
-  type ProblemSetProgressList,
-  type UserBadge,
   problemDetailSchema,
   problemListSchema,
+  problemListItemSchema,
   submissionDetailSchema,
   submissionListSchema,
+  submissionStatisticsSchema,
+  submissionStatisticsItemsSchema,
   onlineCountSchema,
   websiteConfigSchema,
-  type FlowchartStatistics,
-  type SubmissionStatistics,
-  type SubmissionStatisticsItems,
+  contestListSchema,
+  contestSchema,
+  contestAccessSchema,
+  contestRankSchema,
+  announcementListSchema,
+  announcementSchema,
+  problemSetListSchema,
+  problemSetSchema,
+  problemSetBadgeSchema,
+  userBadgeSchema,
+  tutorialSchema,
+  metricsSchema,
+  activityRankItemSchema,
+  problemRankSchema,
+  userRankSchema,
+  flowchartListSchema,
+  flowchartDetailSchema,
+  flowchartCurrentSchema,
+  flowchartStatisticsSchema,
+  problemSetProgressListSchema,
+  problemSetProblemSchema,
 } from "@oj2/contract"
 import api from "utils/api"
 import { contract } from "utils/contract"
 import { filterResult } from "oj/transforms"
 import type {
-  Announcement,
-  AnnouncementListItem,
-  ContestRank,
   Profile,
   Message,
   Exercise,
@@ -57,7 +58,6 @@ import type {
   ReactionState,
   SubmissionListPayload,
   SubmitCodePayload,
-  Tutorial,
   TutorialProgress,
 } from "utils/types"
 
@@ -183,8 +183,13 @@ async function getSubmissionPage(
   )
 }
 
-export function getRankOfProblem(problemId: string) {
-  return api.get<ProblemRank>(`problems/${encodeURIComponent(problemId)}/rank`)
+export async function getRankOfProblem(problemId: string) {
+  const endpoint = `problems/${encodeURIComponent(problemId)}/rank`
+  return contract(
+    "GET /problems/:id/rank",
+    problemRankSchema,
+    await api.get<unknown>(endpoint),
+  )
 }
 
 export function getTodaySubmissionCount(language?: string) {
@@ -201,38 +206,56 @@ export function adminRejudge(id: string) {
  * 统计面板展开一行时拉这个人的明细。username 这里要**精确**到人，
  * 和上面那个按班级模糊匹配的不是一回事。
  */
-export function getSubmissionStatisticsItems(
+export async function getSubmissionStatisticsItems(
   duration: { start?: string; end: string },
   username: string,
   problemID?: string,
 ) {
-  return api.get<SubmissionStatisticsItems>("submissions/statistics/items", {
-    params: { ...duration, problemId: problemID, username },
-  })
+  const endpoint = "submissions/statistics/items"
+  return contract(
+    "GET /submissions/statistics/items",
+    submissionStatisticsItemsSchema,
+    await api.get<unknown>(endpoint, {
+      params: { ...duration, problemId: problemID, username },
+    }),
+  )
 }
 
-export function getSubmissionStatistics(
+export async function getSubmissionStatistics(
   duration: { start?: string; end: string },
   problemID?: string,
   username?: string,
 ) {
-  return api.get<SubmissionStatistics>("submissions/statistics", {
-    params: { ...duration, problemId: problemID, username },
-  })
+  const endpoint = "submissions/statistics"
+  return contract(
+    "GET /submissions/statistics",
+    submissionStatisticsSchema,
+    await api.get<unknown>(endpoint, {
+      params: { ...duration, problemId: problemID, username },
+    }),
+  )
 }
 
 /**
  * 全服榜单。上限（100 名）由服务端定，调用方只管翻页 ——
  * 「全服 Top10」就是这个榜的第一页，取 limit=10 即可，不需要另一个上限参数。
  */
-export function getRank(offset: number, limit: number) {
-  return api.get<UserRank>("rankings/users", { params: { offset, limit } })
+export async function getRank(offset: number, limit: number) {
+  const endpoint = "rankings/users"
+  return contract(
+    "GET /rankings/users",
+    userRankSchema,
+    await api.get<unknown>(endpoint, { params: { offset, limit } }),
+  )
 }
 
-export function getActivityRank(start: string) {
-  return api.get<ActivityRankItem[]>("rankings/activity", {
-    params: { start },
-  })
+export async function getActivityRank(start: string) {
+  const endpoint = "rankings/activity"
+  return contract(
+    "GET /rankings/activity",
+    activityRankItemSchema.array(),
+    await api.get<unknown>(endpoint, { params: { start } }),
+  )
 }
 
 export function getClassRank(grade?: number | null) {
@@ -261,22 +284,37 @@ export function getClassPK(
   })
 }
 
-export function getContestList(query: {
+export async function getContestList(query: {
   offset: number
   limit: number
   keyword: string
   status: string
   tag: string
 }) {
-  return api.get<ContestList>("contests", { params: query })
+  const endpoint = "contests"
+  return contract(
+    "GET /contests",
+    contestListSchema,
+    await api.get<unknown>(endpoint, { params: query }),
+  )
 }
 
-export function getContest(id: string) {
-  return api.get<OjContest>(`contests/${encodeURIComponent(id)}`)
+export async function getContest(id: string) {
+  const endpoint = `contests/${encodeURIComponent(id)}`
+  return contract(
+    "GET /contests/:id",
+    contestSchema,
+    await api.get<unknown>(endpoint),
+  )
 }
 
-export function getContestAccess(id: string) {
-  return api.get<ContestAccess>(`contests/${encodeURIComponent(id)}/access`)
+export async function getContestAccess(id: string) {
+  const endpoint = `contests/${encodeURIComponent(id)}/access`
+  return contract(
+    "GET /contests/:id/access",
+    contestAccessSchema,
+    await api.get<unknown>(endpoint),
+  )
 }
 
 // 注意和 GET /access 不一样：这个返回裸 true，密码错是 403 走 catch
@@ -290,21 +328,29 @@ export function checkContestPassword(contestID: string, password: string) {
 }
 
 export async function getContestProblems(contestID: string) {
-  const res = await api.get<ProblemListItem[]>(
-    `contests/${encodeURIComponent(contestID)}/problems`,
+  const endpoint = `contests/${encodeURIComponent(contestID)}/problems`
+  // 用 problemListItemSchema.array()，不是契约的 contestProblemsSchema ——
+  // 后者是 `array(union([列表项, 详情]))`，联合类型会让 filterResult 的类型收窄
+  // 落到详情分支上，而且学生侧这条接口只下发列表项。
+  const res = contract(
+    "GET /contests/:id/problems",
+    problemListItemSchema.array(),
+    await api.get<unknown>(endpoint),
   )
   return res.map(filterResult)
 }
 
-export function getContestRank(
+export async function getContestRank(
   contestID: string,
   query: { limit: number; offset: number },
 ) {
   // submissionInfo 在契约里是 Record<string, unknown>（JSONB 原文），
   // 前端在这里收窄成 SubmissionInfo，见 utils/types 的 ContestRank
-  return api.get<{ results: ContestRank[]; total: number }>(
-    `contests/${encodeURIComponent(contestID)}/rank`,
-    { params: query },
+  const endpoint = `contests/${encodeURIComponent(contestID)}/rank`
+  return contract(
+    "GET /contests/:id/rank",
+    contestRankSchema,
+    await api.get<unknown>(endpoint, { params: query }),
   )
 }
 
@@ -320,14 +366,22 @@ export function updateProfile(data: { realName: string; mood: string }) {
   return api.put<Profile>("me/profile", data)
 }
 
-export function getAnnouncementList(offset = 0, limit = 10) {
-  return api.get<{ results: AnnouncementListItem[]; total: number }>("announcements", {
-    params: { limit, offset },
-  })
+export async function getAnnouncementList(offset = 0, limit = 10) {
+  const endpoint = "announcements"
+  return contract(
+    "GET /announcements",
+    announcementListSchema,
+    await api.get<unknown>(endpoint, { params: { limit, offset } }),
+  )
 }
 
-export function getAnnouncement(id: number) {
-  return api.get<Announcement>(`announcements/${id}`)
+export async function getAnnouncement(id: number) {
+  const endpoint = `announcements/${id}`
+  return contract(
+    "GET /announcements/:id",
+    announcementSchema,
+    await api.get<unknown>(endpoint),
+  )
 }
 
 export function getMessageList(offset = 0, limit = 10) {
@@ -345,12 +399,22 @@ export function setReaction(problemID: number, type: ReactionKey) {
   return api.post<ReactionState>(`problems/${problemID}/reaction`, { type })
 }
 
-export function getMetrics(userid: number) {
-  return api.get<Metrics>(`users/${userid}/metrics`)
+export async function getMetrics(userid: number) {
+  const endpoint = `users/${userid}/metrics`
+  return contract(
+    "GET /users/:id/metrics",
+    metricsSchema,
+    await api.get<unknown>(endpoint),
+  )
 }
 
-export function getTutorial(id: number) {
-  return api.get<Tutorial>(`tutorials/${id}`)
+export async function getTutorial(id: number) {
+  const endpoint = `tutorials/${id}`
+  return contract(
+    "GET /tutorials/:id",
+    tutorialSchema,
+    await api.get<unknown>(endpoint),
+  )
 }
 
 export function getTutorials(type: "python" | "c") {
@@ -399,10 +463,14 @@ export function getAIPinnedReport() {
 
 // ==================== 相似题目推荐 ====================
 
-export function getSimilarProblems(problemId: string) {
-  return api
-    .get<ProblemListItem[]>(`problems/${encodeURIComponent(problemId)}/similar`)
-    .then((response) => response.map(filterResult))
+export async function getSimilarProblems(problemId: string) {
+  const endpoint = `problems/${encodeURIComponent(problemId)}/similar`
+  const res = contract(
+    "GET /problems/:id/similar",
+    problemListItemSchema.array(),
+    await api.get<unknown>(endpoint),
+  )
+  return res.map(filterResult)
 }
 
 export type { YearlyAc as YearlyACData } from "@oj2/contract"
@@ -427,7 +495,7 @@ export function getFlowchartSubmission(id: string) {
   return api.get<FlowchartSubmission>(`flowcharts/${encodeURIComponent(id)}`)
 }
 
-export function getFlowchartSubmissions(params: {
+export async function getFlowchartSubmissions(params: {
   username?: string
   problemId?: string
   myself?: string
@@ -436,17 +504,27 @@ export function getFlowchartSubmissions(params: {
   today?: string
   grade?: string
 }) {
-  return api.get<FlowchartList>("flowcharts", { params })
+  const endpoint = "flowcharts"
+  return contract(
+    "GET /flowcharts",
+    flowchartListSchema,
+    await api.get<unknown>(endpoint, { params }),
+  )
 }
 
-export function getFlowchartStatistics(
+export async function getFlowchartStatistics(
   duration: { start?: string; end: string },
   problemID?: string,
   username?: string,
 ) {
-  return api.get<FlowchartStatistics>("flowcharts/statistics", {
-    params: { ...duration, problemId: problemID, username },
-  })
+  const endpoint = "flowcharts/statistics"
+  return contract(
+    "GET /flowcharts/statistics",
+    flowchartStatisticsSchema,
+    await api.get<unknown>(endpoint, {
+      params: { ...duration, problemId: problemID, username },
+    }),
+  )
 }
 
 export function retryFlowchartSubmission(submissionId: string) {
@@ -455,36 +533,59 @@ export function retryFlowchartSubmission(submissionId: string) {
   )
 }
 
-export function getCurrentProblemFlowchartSubmission(problemId: number) {
-  return api.get<FlowchartCurrent>(`problems/${problemId}/flowchart/current`)
+export async function getCurrentProblemFlowchartSubmission(problemId: number) {
+  const endpoint = `problems/${problemId}/flowchart/current`
+  return contract(
+    "GET /problems/:id/flowchart/current",
+    flowchartCurrentSchema,
+    await api.get<unknown>(endpoint),
+  )
 }
 
-export function getFlowchartSubmissionDetail(problemId: number, page = 0) {
-  return api.get<FlowchartDetail>(`problems/${problemId}/flowchart/history`, {
-    params: { page },
-  })
+export async function getFlowchartSubmissionDetail(problemId: number, page = 0) {
+  const endpoint = `problems/${problemId}/flowchart/history`
+  return contract(
+    "GET /problems/:id/flowchart/history",
+    flowchartDetailSchema,
+    await api.get<unknown>(endpoint, { params: { page } }),
+  )
 }
 
 // ==================== 题单相关API ====================
 
-export function getProblemSetList(
+export async function getProblemSetList(
   offset = 0,
   limit = 10,
   keyword = "",
   difficulty = "",
   status = "",
 ) {
-  return api.get<ProblemSetList>("problem-sets", {
-    params: { offset, limit, keyword, difficulty, status },
-  })
+  const endpoint = "problem-sets"
+  return contract(
+    "GET /problem-sets",
+    problemSetListSchema,
+    await api.get<unknown>(endpoint, {
+      params: { offset, limit, keyword, difficulty, status },
+    }),
+  )
 }
 
-export function getProblemSetDetail(id: number) {
-  return api.get<ProblemSet>(`problem-sets/${id}`)
+export async function getProblemSetDetail(id: number) {
+  const endpoint = `problem-sets/${id}`
+  return contract(
+    "GET /problem-sets/:id",
+    problemSetSchema,
+    await api.get<unknown>(endpoint),
+  )
 }
 
-export function getProblemSetProblems(problemSetId: number) {
-  return api.get<ProblemSetProblem[]>(`problem-sets/${problemSetId}/problems`)
+export async function getProblemSetProblems(problemSetId: number) {
+  const endpoint = `problem-sets/${problemSetId}/problems`
+  return contract(
+    "GET /problem-sets/:id/problems",
+    problemSetProblemSchema.array(),
+    await api.get<unknown>(endpoint),
+  )
 }
 
 export function joinProblemSet(problemSetId: number) {
@@ -503,17 +604,25 @@ export function updateProblemSetProgress(
   })
 }
 
-export function getUserBadges(username?: string) {
-  return api.get<UserBadge[]>(
-    `users/${encodeURIComponent(username ?? "me")}/badges`,
+export async function getUserBadges(username?: string) {
+  const endpoint = `users/${encodeURIComponent(username ?? "me")}/badges`
+  return contract(
+    "GET /users/:username/badges",
+    userBadgeSchema.array(),
+    await api.get<unknown>(endpoint),
   )
 }
 
-export function getProblemSetBadges(problemSetId: number) {
-  return api.get<ProblemSetBadge[]>(`problem-sets/${problemSetId}/badges`)
+export async function getProblemSetBadges(problemSetId: number) {
+  const endpoint = `problem-sets/${problemSetId}/badges`
+  return contract(
+    "GET /problem-sets/:id/badges",
+    problemSetBadgeSchema.array(),
+    await api.get<unknown>(endpoint),
+  )
 }
 
-export function getProblemSetUserProgress(
+export async function getProblemSetUserProgress(
   problemSetId: number,
   params?: {
     limit?: number
@@ -522,9 +631,11 @@ export function getProblemSetUserProgress(
     completionStatus?: "" | "completed" | "in_progress" | "not_started"
   },
 ) {
-  return api.get<ProblemSetProgressList>(
-    `problem-sets/${problemSetId}/user-progress`,
-    { params },
+  const endpoint = `problem-sets/${problemSetId}/user-progress`
+  return contract(
+    "GET /problem-sets/:id/user-progress",
+    problemSetProgressListSchema,
+    await api.get<unknown>(endpoint, { params }),
   )
 }
 
diff --git a/apps/web/src/utils/types.ts b/apps/web/src/utils/types.ts
index a847adf..b9a73f4 100644
--- a/apps/web/src/utils/types.ts
+++ b/apps/web/src/utils/types.ts
@@ -113,17 +113,18 @@ export type { UploadTestCaseResponse } from "@oj2/contract"
 export type { ProblemTestCaseScore as Testcase } from "@oj2/contract"
 
 /**
- * 题目详情。以契约的 ProblemDetail 为准，只在这里补两处前端自己的窄化：
- * - `languages` / `template` 的键窄化成 LANGUAGE，组件按语言查模板要靠它
+ * 题目详情。**直接取契约** —— `languages` / `template` 的收窄已经搬进
+ * `problemDetailSchema`（`z.array(problemLanguageSchema)` 与
+ * `z.partialRecord(problemLanguageSchema, …)`），这里原来那份
+ * `Omit<ProblemDetail, "languages" | "template"> & {...}` 与契约**双向可赋值**，
+ * 即完全等价，是一层没有内容的重复（已用类型探针验证）。
+ *
+ * 原来它还多挂三个可选字段（`hasAstRules` / `visible` / `answers`）。它们在
+ * 契约里**本来就有**（`hasAstRules` 在题目列表项上、`ProblemDetail` 带的是
+ * `astRequirements`），少数管理端调用点需要补充时应该就地声明自己的类型，
+ * 不该让一个全局别名对所有调用方声称这些字段存在。
  */
-export type Problem = Omit<ProblemDetail, "languages" | "template"> & {
-  languages: LANGUAGE[]
-  template: { [key in LANGUAGE]?: string }
-  // oj 侧不下发 astRules 原文，只有 astRequirements（契约里就有）
-  hasAstRules?: boolean
-  visible?: boolean
-  answers?: { language: LANGUAGE; code: string }[]
-}
+export type Problem = ProblemDetail
 
 /**
  * AST 代码要求。原来这里手抄的那份少了 label / exact / outer / inner ——
@@ -327,27 +328,16 @@ export type BlankContest = Omit<
 >
 
 /**
- * acm_contest_rank.submission_info 的 JSONB 内容。**键名保持 snake_case** ——
- * 判题按这套键名写进去，历史比赛的榜单行也是这个形状，不能跟着响应字段一起改名。
+ * `acm_contest_rank.submission_info` 的 JSONB 内容。**形状已搬进契约**
+ * （`contestSubmissionInfoSchema`），这里保留别名给既有调用点。
  */
-export interface SubmissionInfo {
-  is_ac: boolean
-  ac_time: number
-  is_first_ac: boolean
-  error_number: number
-  checked?: boolean
-}
+export type { ContestSubmissionInfo as SubmissionInfo } from "@oj2/contract"
 
 /**
- * 榜单行。`submissionInfo` 的**内容**仍是 snake_case —— 它是 acm_contest_rank
- * 表的 JSONB 原文，见 SubmissionInfo。
+ * 榜单行。`submissionInfo` 的收窄（JSONB 原文的 snake_case 形状）已经搬进
+ * `contestRankItemSchema`，这里不再需要 Omit + 覆盖。
  */
-export type ContestRank = Omit<
-  import("@oj2/contract").ContestRankItem,
-  "submissionInfo"
-> & {
-  submissionInfo: { [key: string]: SubmissionInfo }
-}
+export type ContestRank = import("@oj2/contract").ContestRankItem
 
 export type { WebsiteConfig, OnlineCount } from "@oj2/contract"
 
@@ -399,12 +389,12 @@ export type {
 export type AnnouncementEdit = CreateAnnouncementRequest & { id: number }
 
 /**
- * 站内信。取契约的形状，只把 `submission` 换成前端窄化过的那个
- * （statisticInfo / language 在契约里是 unknown，见 EmbeddedSubmission）。
+ * 站内信。**直接取契约** —— 原来这里把 `submission` 换成前端窄化过的
+ * `EmbeddedSubmission`，但那个窄化已经搬进 `embeddedSubmissionSchema`
+ * （statisticInfo / language 在契约里不再是 unknown），两者双向可赋值、
+ * 完全等价，这层 Omit 已经没有内容。
  */
-export type Message = Omit<ContractMessage, "submission"> & {
-  submission: EmbeddedSubmission
-}
+export type Message = ContractMessage
 
 /**
  * 题目表情。三个类型都直接取自契约 —— 语义 key 必须与后端 reaction/models.py
diff --git a/packages/contract/src/contest.ts b/packages/contract/src/contest.ts
index fecd661..b73034b 100644
--- a/packages/contract/src/contest.ts
+++ b/packages/contract/src/contest.ts
@@ -29,13 +29,32 @@ export const contestPasswordRequestSchema = z.object({
 export const contestAccessSchema = z.object({ access: z.boolean() })
 export const contestProblemsSchema = z.array(z.union([problemListItemSchema, problemDetailSchema]))
 
+/**
+ * `acm_contest_rank.submission_info` 的 JSONB 原文。
+ *
+ * 键名是**判题链路写进去的 snake_case**（历史比赛的榜单行也是这个形状），
+ * 不要跟着响应字段一起改成 camelCase。字段全部可选：只有真正提交过的题目键
+ * 才会出现，`checked` 更是前端在本地标「已看」时补的。
+ *
+ * 原来契约这里是 `z.record(z.string(), z.unknown())`，于是前端不得不
+ * 自己再声明一份 `SubmissionInfo` 去覆盖它（utils/types 的 ContestRank）。
+ * 形状搬进来之后那个覆盖就没有内容了。
+ */
+export const contestSubmissionInfoSchema = z.object({
+  is_ac: z.boolean(),
+  ac_time: z.number(),
+  is_first_ac: z.boolean(),
+  error_number: z.number().int(),
+  checked: z.boolean().optional(),
+})
+
 export const contestRankItemSchema = z.object({
   id: z.number().int(),
   user: sampleUserSchema,
   submissionNumber: z.number().int(),
   acceptedNumber: z.number().int(),
   totalTime: z.number().int(),
-  submissionInfo: z.record(z.string(), z.unknown()),
+  submissionInfo: z.record(z.string(), contestSubmissionInfoSchema),
   contestId: z.number().int(),
 })
 
@@ -46,6 +65,7 @@ export type ContestList = z.infer<typeof contestListSchema>
 export type ContestRankItem = z.infer<typeof contestRankItemSchema>
 export type ContestRank = z.infer<typeof contestRankSchema>
 export type ContestAccess = z.infer<typeof contestAccessSchema>
+export type ContestSubmissionInfo = z.infer<typeof contestSubmissionInfoSchema>
 
 export type ContestStatus = z.infer<typeof contestStatusSchema>
 export type ContestPasswordRequest = z.infer<typeof contestPasswordRequestSchema>