diff --git a/apps/api/src/services/test-case.ts b/apps/api/src/services/test-case.ts
index 780f45d..c18cb0a 100644
--- a/apps/api/src/services/test-case.ts
+++ b/apps/api/src/services/test-case.ts
@@ -4,6 +4,8 @@ import { resolve } from "node:path"
 
 import { unzipSync, zipSync } from "fflate"
 
+import { TEST_CASE_MAX_CASES } from "@oj2/contract"
+
 import { config } from "../config"
 
 /**
@@ -18,7 +20,7 @@ import { config } from "../config"
 const MAX_ENTRY_BYTES = 32 * 1024 * 1024
 /** 解压后总大小上限，防 zip bomb */
 const MAX_TOTAL_BYTES = 128 * 1024 * 1024
-/** 测试点数量上限 */
+/** 往后找连续编号最多找到几号。真正的上限是契约的 TEST_CASE_MAX_CASES，多出来的要报错而不是静默截掉 */
 const MAX_CASES = 500
 
 export class TestCaseError extends Error {}
@@ -132,6 +134,12 @@ export async function processTestCaseZip(
 
   const selected = options.sql ? collectSqlScripts(names) : collectPairs(names).flat()
   if (selected.length === 0) throw new TestCaseError("压缩包里没有找到从 1 开始连续编号的测试点")
+  const count = options.sql ? selected.length : selected.length / 2
+  if (count > TEST_CASE_MAX_CASES) {
+    throw new TestCaseError(
+      `测试数据最多 ${TEST_CASE_MAX_CASES} 组，这个压缩包里有 ${count} 组，挑有代表性的留下`,
+    )
+  }
   if (options.sql && selected.length < 2) {
     // 题目页会展示测试点 1 的期望结果，只有一个测试点时学生可以对照着硬编码 AC
     throw new TestCaseError("SQL 题至少需要 2 个数据不同的测试点，防止硬编码期望结果")
diff --git a/apps/web/src/admin/problem/SqlDetail.vue b/apps/web/src/admin/problem/SqlDetail.vue
index e113574..e518580 100644
--- a/apps/web/src/admin/problem/SqlDetail.vue
+++ b/apps/web/src/admin/problem/SqlDetail.vue
@@ -1,6 +1,6 @@
 <script setup lang="ts">
 import { EditorView } from "@codemirror/view"
-import { PROBLEM_TAG_MAX_LENGTH } from "@oj2/contract"
+import { PROBLEM_TAG_MAX_LENGTH, TEST_CASE_MAX_CASES } from "@oj2/contract"
 import { MdPreview } from "md-editor-v3"
 import "md-editor-v3/lib/preview.css"
 import { StorageSerializers } from "@vueuse/core"
@@ -275,7 +275,11 @@ watchDebounced(
   { debounce: 600, deep: true },
 )
 
+/** 测试数据加满了（见契约 TEST_CASE_MAX_CASES） */
+const groupsFull = computed(() => groups.value.length >= TEST_CASE_MAX_CASES)
+
 function addGroup() {
+  if (groupsFull.value) return
   groups.value.push(newGroup())
   selected.value = groups.value.length - 1
 }
@@ -288,6 +292,7 @@ function removeGroup(index: number) {
 const generating = ref(false)
 
 async function generateGroup() {
+  if (groupsFull.value && groups.value.every((g) => g.sql.trim())) return
   generating.value = true
   try {
     const res = await generateSQLTestcase({ refSql: form.answer, mode: form.sqlConfig.mode })
@@ -318,6 +323,8 @@ const blocker = computed(() => {
   if (!form.tags.length) return "至少要有一个标签"
   if (!form.answer.trim()) return "标准答案还没写"
   if (groups.value.length < 2) return "测试数据至少要 2 组"
+  if (groups.value.length > TEST_CASE_MAX_CASES)
+    return `测试数据最多 ${TEST_CASE_MAX_CASES} 组，删掉 ${groups.value.length - TEST_CASE_MAX_CASES} 组`
   for (const [i, g] of groups.value.entries()) {
     if (!g.sql.trim()) return `第 ${i + 1} 组还是空的，写上或删掉`
   }
@@ -557,18 +564,30 @@ onMounted(async () => {
       <section class="card">
         <div class="cardHead">
           <h3>测试数据</h3>
-          <n-text depth="3" class="note">至少 2 组，数据要不一样</n-text>
+          <n-text depth="3" class="note">{{ `2～${TEST_CASE_MAX_CASES} 组，数据要不一样` }}</n-text>
           <div class="grow"></div>
           <n-button
             size="tiny"
             :loading="generating"
-            :disabled="!form.answer.trim()"
-            :title="form.answer.trim() ? '按标准答案用到的表，让 AI 编一组数据' : '先写标准答案'"
+            :disabled="!form.answer.trim() || (groupsFull && groups.every((g) => g.sql.trim()))"
+            :title="
+              groupsFull && groups.every((g) => g.sql.trim())
+                ? `最多 ${TEST_CASE_MAX_CASES} 组，已经满了`
+                : form.answer.trim()
+                  ? '按标准答案用到的表，让 AI 编一组数据'
+                  : '先写标准答案'
+            "
             @click="generateGroup"
           >
             AI 再写一组
           </n-button>
-          <n-button size="tiny" @click="addGroup">+ 加一组</n-button>
+          <n-button
+            size="tiny"
+            :disabled="groupsFull"
+            :title="groupsFull ? `最多 ${TEST_CASE_MAX_CASES} 组，已经满了` : undefined"
+            @click="addGroup"
+            >+ 加一组</n-button
+          >
         </div>
         <n-alert v-if="loadError" type="error" :show-icon="false">{{ loadError }}</n-alert>
         <div class="groups" role="listbox" aria-label="测试数据">
diff --git a/apps/web/src/admin/problem/components/caseRows.ts b/apps/web/src/admin/problem/components/caseRows.ts
index b2146f8..cfe4a38 100644
--- a/apps/web/src/admin/problem/components/caseRows.ts
+++ b/apps/web/src/admin/problem/components/caseRows.ts
@@ -1,4 +1,8 @@
-import { TEST_CASE_EDIT_MAX_CASES, TEST_CASE_EDIT_MAX_FILE_BYTES } from "@oj2/contract"
+import {
+  TEST_CASE_EDIT_MAX_CASES,
+  TEST_CASE_EDIT_MAX_FILE_BYTES,
+  TEST_CASE_MAX_CASES,
+} from "@oj2/contract"
 import type { RunnableLanguage } from "@oj2/contract"
 import { strFromU8, unzipSync } from "fflate"
 import type { Ref } from "vue"
@@ -186,6 +190,11 @@ export function readCaseZip(
   }
   if (!cases.length)
     return { ok: false, reason: "压缩包里没有从 1.in / 1.out 开始连续编号的测试点" }
+  if (cases.length > TEST_CASE_MAX_CASES)
+    return {
+      ok: false,
+      reason: `测试数据最多 ${TEST_CASE_MAX_CASES} 组，这个压缩包里有 ${cases.length} 组，挑有代表性的留下`,
+    }
   if (cases.length > TEST_CASE_EDIT_MAX_CASES) return { ok: false, reason: "too-large" }
   return { ok: true, cases }
 }
diff --git a/apps/web/src/admin/problem/detail.vue b/apps/web/src/admin/problem/detail.vue
index 24085e8..7cf298f 100644
--- a/apps/web/src/admin/problem/detail.vue
+++ b/apps/web/src/admin/problem/detail.vue
@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { PROBLEM_TAG_MAX_LENGTH, type RunnableLanguage } from "@oj2/contract"
+import { PROBLEM_TAG_MAX_LENGTH, TEST_CASE_MAX_CASES, type RunnableLanguage } from "@oj2/contract"
 import { StorageSerializers } from "@vueuse/core"
 import { useThemeVars } from "naive-ui"
 import PageHeader from "admin/components/PageHeader.vue"
@@ -287,7 +287,11 @@ function formatBytes(bytes: number) {
   return `${(bytes / 1024 / 1024).toFixed(1)}MB`
 }
 
+/** 测试数据加满了（见契约 TEST_CASE_MAX_CASES） */
+const casesFull = computed(() => rows.value.length >= TEST_CASE_MAX_CASES)
+
 function addRow() {
+  if (casesFull.value) return
   // 空着的第一组（新建页）直接用掉；例子一组都还没勾时，新加的这组先勾上
   const noExample = !rows.value.some((r) => r.example)
   rows.value.push(newRow("", "", noExample))
@@ -311,14 +315,23 @@ async function aiInputs() {
       message.info("AI 没想出新的输入")
       return
     }
-    // 空着的行先填掉
+    // 空着的行先填掉，再往后加，加到上限为止
     const blanks = rows.value.filter((r) => !r.input.trim() && !r.output.trim())
-    for (const input of res.inputs) {
+    const inputs = res.inputs.slice(0, blanks.length + TEST_CASE_MAX_CASES - rows.value.length)
+    if (!inputs.length) {
+      message.info(`测试数据最多 ${TEST_CASE_MAX_CASES} 组，已经满了`)
+      return
+    }
+    for (const input of inputs) {
       const blank = blanks.shift()
       if (blank) blank.input = input
       else rows.value.push(newRow(input))
     }
-    message.success(`加了 ${res.inputs.length} 组，输出马上跑出来`)
+    message.success(
+      inputs.length < res.inputs.length
+        ? `加了 ${inputs.length} 组，到 ${TEST_CASE_MAX_CASES} 组的上限了`
+        : `加了 ${inputs.length} 组，输出马上跑出来`,
+    )
   } catch (err) {
     message.error(errorMessage(err, "AI 没想出来，稍后再试"))
   } finally {
@@ -651,6 +664,12 @@ const blockers = computed<Blocker[]>(() => {
 
   const caseRows = big.value ? exampleRows.value : rows.value
   if (!big.value && !rows.value.length) list.push({ text: "加一组测试数据", section: "cases" })
+  if (!big.value && rows.value.length > TEST_CASE_MAX_CASES)
+    list.push({
+      text: `删掉 ${rows.value.length - TEST_CASE_MAX_CASES} 组测试数据（最多 ${TEST_CASE_MAX_CASES} 组）`,
+      section: "cases",
+      severe: true,
+    })
   if (caseRows.some((r) => caseStatus(r, source.value) === "running"))
     list.push({ text: "等测试数据跑完", section: "cases" })
   caseRows.forEach((r, i) => {
@@ -997,13 +1016,25 @@ onMounted(async () => {
               <n-button
                 size="tiny"
                 :loading="generatingInputs"
-                :disabled="!source"
-                :title="source ? '按题面和标准答案，让 AI 想几组边界情况' : '先写标准答案'"
+                :disabled="!source || casesFull"
+                :title="
+                  casesFull
+                    ? `最多 ${TEST_CASE_MAX_CASES} 组，已经满了`
+                    : source
+                      ? '按题面和标准答案，让 AI 想几组边界情况'
+                      : '先写标准答案'
+                "
                 @click="aiInputs"
               >
                 AI 想几组输入
               </n-button>
-              <n-button size="tiny" @click="addRow">+ 加一组</n-button>
+              <n-button
+                size="tiny"
+                :disabled="casesFull"
+                :title="casesFull ? `最多 ${TEST_CASE_MAX_CASES} 组，已经满了` : undefined"
+                @click="addRow"
+                >+ 加一组</n-button
+              >
             </template>
             <span class="grow"></span>
             <n-button
diff --git a/packages/contract/src/admin.ts b/packages/contract/src/admin.ts
index 93ac062..ab6a07e 100644
--- a/packages/contract/src/admin.ts
+++ b/packages/contract/src/admin.ts
@@ -822,6 +822,13 @@ export const generateSqlTestCaseRequestSchema = z.object({
 
 export const generateSqlTestCaseResponseSchema = z.object({ sql: z.string() })
 
+/**
+ * 一道题最多几组测试数据（编程题的 N.in / N.out、SQL 题的 N.sql 都算）。
+ * 提交详情要把每组的结果一行行列出来，几百组的题截图截不下；
+ * 2026-10 线上超过 20 组的题已经全部缩到 20 组。
+ */
+export const TEST_CASE_MAX_CASES = 20
+
 /**
  * 编程题出题页回显已有的测试点（N.in / N.out 原文）。太大的不展开 —— 页面上要一组一组
  * 摆出来、改了还要整包重跑一遍标准答案，几百组或者几 MB 的数据摆不下也跑不动，