diff --git a/apps/web/src/oj/problem/components/EditorToolbar.vue b/apps/web/src/oj/problem/components/EditorToolbar.vue
index dccf4b8..f477e18 100644
--- a/apps/web/src/oj/problem/components/EditorToolbar.vue
+++ b/apps/web/src/oj/problem/components/EditorToolbar.vue
@@ -269,8 +269,9 @@ const goEdit = () => {
       @update:value="changeLanguage"
     />
 
+    <!-- 手机上「运行例子」「提交」在屏幕底部那条（MobileActionBar），三个页签都在 -->
     <n-button
-      v-if="canRunSamples"
+      v-if="canRunSamples && isDesktop"
       :size="buttonSize"
       :loading="samplesRunning"
       :disabled="!codeStore.code.value.trim()"
@@ -281,7 +282,7 @@ const goEdit = () => {
 
     <SubmitFlowchart v-if="codeStore.code.language === 'Flowchart'" />
 
-    <SubmitCode v-else />
+    <SubmitCode v-else-if="isDesktop" />
 
     <n-button
       v-if="isDesktop && userStore.isTeacherOrAbove"
diff --git a/apps/web/src/oj/problem/components/MobileActionBar.vue b/apps/web/src/oj/problem/components/MobileActionBar.vue
new file mode 100644
index 0000000..9b94041
--- /dev/null
+++ b/apps/web/src/oj/problem/components/MobileActionBar.vue
@@ -0,0 +1,70 @@
+<script setup lang="ts">
+import { useThemeVars } from "naive-ui"
+import { storeToRefs } from "pinia"
+import { useCodeStore } from "oj/store/code"
+import { useProblemStore } from "oj/store/problem"
+import { useSubmissionStore } from "oj/store/submission"
+import SubmitCode from "./SubmitCode.vue"
+
+/**
+ * 手机上屏幕底部固定的「运行例子 / 提交」（设计文档 5.6）。原来这两个按钮在「代码」页签
+ * 顶上，和语言、更多挤成两行；看着题面想交一次，还得先切回代码页签。
+ * 提交状态、代码都在 store 里，编辑器没挂着也能交。
+ */
+const theme = useThemeVars()
+const codeStore = useCodeStore()
+const submissionStore = useSubmissionStore()
+const { samplesRunning } = submissionStore.trial
+const { problem } = storeToRefs(useProblemStore())
+
+// 和工具栏同一个条件：Judge0 跑不了 SQL，流程图没得跑，没有例子的题不给
+const canRunSamples = computed(
+  () =>
+    !!problem.value?.samples.length &&
+    codeStore.code.language !== "Flowchart" &&
+    codeStore.code.language !== "SQL",
+)
+</script>
+
+<template>
+  <div class="mobile-actions">
+    <n-button
+      v-if="canRunSamples"
+      size="large"
+      class="action"
+      :loading="samplesRunning"
+      :disabled="!codeStore.code.value.trim()"
+      @click="submissionStore.runSamples()"
+    >
+      运行例子
+    </n-button>
+    <div class="action">
+      <SubmitCode size="large" block />
+    </div>
+  </div>
+</template>
+
+<style scoped>
+.mobile-actions {
+  position: fixed;
+  left: 0;
+  right: 0;
+  bottom: 0;
+  z-index: 10;
+  display: flex;
+  gap: 10px;
+  padding: 8px 16px calc(8px + env(safe-area-inset-bottom));
+  background-color: v-bind("theme.bodyColor");
+  border-top: 1px solid rgba(128, 128, 128, 0.2);
+  backdrop-filter: blur(8px);
+}
+
+.action {
+  flex: 1;
+  min-width: 0;
+}
+
+.mobile-actions :deep(.n-button) {
+  height: 44px;
+}
+</style>
diff --git a/apps/web/src/oj/problem/components/ProblemEditor.vue b/apps/web/src/oj/problem/components/ProblemEditor.vue
index 48a5227..0bdea88 100644
--- a/apps/web/src/oj/problem/components/ProblemEditor.vue
+++ b/apps/web/src/oj/problem/components/ProblemEditor.vue
@@ -98,9 +98,10 @@ const storageKey = computed(() =>
     : `problem_${problem.value!._id}_contest_${contestID}_lang_${codeStore.code.language}`,
 )
 
-// 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
+// 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。
+// 手机上：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
 const editorHeight = computed(() => {
-  const base = isDesktop.value ? 133 : 172
+  const base = isDesktop.value ? 133 : 300
   return `calc(100vh - ${base + (teacherCollab.value ? 52 : 0)}px)`
 })
 
diff --git a/apps/web/src/oj/problem/components/SubmitCode.vue b/apps/web/src/oj/problem/components/SubmitCode.vue
index f7b98cb..5a876c1 100644
--- a/apps/web/src/oj/problem/components/SubmitCode.vue
+++ b/apps/web/src/oj/problem/components/SubmitCode.vue
@@ -12,6 +12,9 @@ import { useUserStore } from "shared/store/user"
  * 这个组件在编辑器的工具栏里，编辑器卸载时它也跟着卸载，所以什么都不能只存在这里。
  */
 
+/** 手机底部那条操作栏里用大号、占满半宽 */
+const props = defineProps<{ size?: "small" | "medium" | "large"; block?: boolean }>()
+
 const userStore = useUserStore()
 const codeStore = useCodeStore()
 const submissionStore = useSubmissionStore()
@@ -41,7 +44,8 @@ function submit() {
 
 <template>
   <n-button
-    :size="isDesktop ? 'medium' : 'small'"
+    :size="props.size ?? (isDesktop ? 'medium' : 'small')"
+    :block="props.block"
     type="primary"
     :disabled="buttonState.disabled"
     @click="submit"
diff --git a/apps/web/src/oj/problem/detail.vue b/apps/web/src/oj/problem/detail.vue
index db6f1cb..3181255 100644
--- a/apps/web/src/oj/problem/detail.vue
+++ b/apps/web/src/oj/problem/detail.vue
@@ -30,6 +30,7 @@ const ProblemEditor = defineAsyncComponent(loadProblemEditor)
 const ProblemContent = defineAsyncComponent(() => import("./components/ProblemContent.vue"))
 const ProblemDrawer = defineAsyncComponent(() => import("./components/ProblemDrawer.vue"))
 const ResultPane = defineAsyncComponent(() => import("./components/ResultPane.vue"))
+const MobileActionBar = defineAsyncComponent(() => import("./components/MobileActionBar.vue"))
 
 interface Props {
   problemID: string
@@ -256,14 +257,18 @@ onBeforeUnmount(() => {
       </template>
     </n-split>
 
-    <!-- Mobile -->
-    <template v-else>
+    <!-- Mobile：底部固定「运行例子 / 提交」，内容底下留出它的高度 -->
+    <div v-else class="mobile">
       <ContextBar />
       <n-tabs v-model:value="currentTab" type="segment">
         <n-tab-pane name="content" tab="题目">
           <ProblemContent />
         </n-tab-pane>
-        <n-tab-pane name="editor" tab="代码">
+        <!--
+          编辑器一直挂着（show，不是默认的 if）：底部的「提交」在三个页签下都能点，
+          没切到过「代码」页签的话草稿就没读进来、按钮是灰的；切走就卸载还会丢掉撤销历史
+        -->
+        <n-tab-pane name="editor" tab="代码" display-directive="show">
           <ProblemEditor />
         </n-tab-pane>
         <n-tab-pane name="result" :tab="resultTab" display-directive="show:lazy">
@@ -276,12 +281,17 @@ onBeforeUnmount(() => {
         </template>
       </n-tabs>
       <ProblemDrawer v-model="drawer" />
-    </template>
+      <MobileActionBar />
+    </div>
   </template>
   <n-empty v-else :description="errMsg"></n-empty>
 </template>
 
 <style scoped>
+.mobile {
+  padding-bottom: calc(72px + env(safe-area-inset-bottom));
+}
+
 .left-pane {
   position: relative;
   height: 100%;
diff --git a/docs/specs/2026-09-28-problem-page-redesign-design.md b/docs/specs/2026-09-28-problem-page-redesign-design.md
index 0946955..efb6d67 100644
--- a/docs/specs/2026-09-28-problem-page-redesign-design.md
+++ b/docs/specs/2026-09-28-problem-page-redesign-design.md
@@ -1,7 +1,7 @@
 # OJ2 设计文档：题目详情页重设计
 
 日期：2026-09-28
-状态：**设计已定，第 14 节的 1–5 步和第 7 节已实施**（剩第 6 步：协作的几处规则、手机版）。效果图在 claude.ai 的私有画布「题目详情页重设计」里（「机房（方案 B）」
+状态：**第 14 节的 6 步和第 7 节都已实施**（2026-09-28）。和本文有出入的地方：手机上「⋯」只收了统计 / 点评 / 我的提交，去自测猫、复制、重置还在「代码」页签的「更多」里；协作中上下文条的跳转没有改成开新标签（老师不在课堂名单里，题库入口下这一条本来就不出现）。效果图在 claude.ai 的私有画布「题目详情页重设计」里（「机房（方案 B）」
 那一页是定稿，「初稿 1280×800」那一页已作废，只留着对照）。效果图表达不了的规则都写在这里，
 **实施时以本文为准**。