diff --git a/frontend/src/api/submissionIntent.ts b/frontend/src/api/submissionIntent.ts
index 7298ed2..f5875de 100644
--- a/frontend/src/api/submissionIntent.ts
+++ b/frontend/src/api/submissionIntent.ts
@@ -1,7 +1,8 @@
 // No source is stored here. Fingerprints bind an immutable request and owner to a UUID.
+import type { components } from './generated/schema'
 export type SubmissionInput = {
   problem_version_id: string
-  language: 'c17' | 'cpp20'
+  language: components['schemas']['kf_oj__contracts__judging_v2__Language']
   source: string
 }
 type Intent = { fingerprint: string; key: string; submissionId?: string }
diff --git a/frontend/src/components/CodeEditor.vue b/frontend/src/components/CodeEditor.vue
index 228f03e..d8a0f83 100644
--- a/frontend/src/components/CodeEditor.vue
+++ b/frontend/src/components/CodeEditor.vue
@@ -10,6 +10,7 @@ import 'monaco-editor/features/linesOperations/register'
 import 'monaco-editor/features/wordOperations/register'
 import 'monaco-editor/languages/definitions/cpp/register'
 import 'monaco-editor/languages/definitions/python/register'
+import 'monaco-editor/languages/definitions/java/register'
 import 'monaco-editor/languages/definitions/rust/register'
 import EditorWorker from 'monaco-editor/editor/editor.worker?worker'
 const props = defineProps<{
diff --git a/frontend/src/components/JudgementStatus.vue b/frontend/src/components/JudgementStatus.vue
index 2146ab8..3ffda18 100644
--- a/frontend/src/components/JudgementStatus.vue
+++ b/frontend/src/components/JudgementStatus.vue
@@ -1,9 +1,11 @@
 <script setup lang="ts">
 import { computed } from 'vue'
 import type { components } from '../api/generated/schema'
+import { preparingStatus, type WireLanguage } from '../composables/judgingLanguage'
 const props = defineProps<{
   state: components['schemas']['SubmissionSummary']['state']
   verdict: components['schemas']['SubmissionSummary']['verdict']
+  language?: WireLanguage
 }>()
 const grades: Record<string, string> = {
   accepted: 'AC',
@@ -27,7 +29,11 @@ const states: Record<string, string> = {
   finished: '评测完成',
 }
 const label = computed(() =>
-  props.verdict ? (grades[props.verdict] ?? props.verdict) : states[props.state],
+  props.verdict
+    ? (grades[props.verdict] ?? props.verdict)
+    : props.state === 'compiling'
+      ? preparingStatus(props.language)
+      : states[props.state],
 )
 </script>
 <template>
diff --git a/frontend/src/composables/judgingLanguage.ts b/frontend/src/composables/judgingLanguage.ts
new file mode 100644
index 0000000..2ee87db
--- /dev/null
+++ b/frontend/src/composables/judgingLanguage.ts
@@ -0,0 +1,52 @@
+import type { components } from '../api/generated/schema'
+import type { Language } from './useCodeDraft'
+
+export type WireLanguage = components['schemas']['SubmissionSummary']['language']
+type ProblemCapability = Pick<
+  components['schemas']['ProblemDetail'],
+  'languages' | 'language_configurations' | 'run_limits'
+>
+const wire: Record<Language, WireLanguage | null> = {
+  c: 'c17',
+  cpp: 'cpp20',
+  python: 'python313',
+  java: 'java21',
+  rust: null,
+}
+
+export function languageCapability(problem: ProblemCapability | null, language: Language) {
+  const id = wire[language]
+  if (!problem || !id || !problem.languages.includes(id)) return null
+  const configuration = problem.language_configurations.find((c) => c.language === id)
+  if (configuration) {
+    const validEntry =
+      id === 'python313'
+        ? configuration.preparation_kind === 'syntax_check' &&
+          configuration.source_name === 'main.py' &&
+          configuration.entrypoint === 'main.py'
+        : id === 'java21'
+          ? configuration.preparation_kind === 'compile' &&
+            configuration.source_name === 'Main.java' &&
+            configuration.entrypoint === 'Main'
+          : configuration.preparation_kind === 'compile'
+    if (!validEntry || !configuration.runtime_version) return null
+    return { wire: id, configuration, runLimits: configuration.run_limits }
+  }
+  // Only legacy C/C++ versions expose one shared budget. A managed language
+  // without its server-provided configuration must not inherit that budget.
+  if (
+    (id === 'c17' || id === 'cpp20') &&
+    problem.language_configurations.length === 0 &&
+    problem.run_limits
+  )
+    return { wire: id, configuration: null, runLimits: problem.run_limits }
+  return null
+}
+
+export function preparationName(language?: WireLanguage) {
+  return language === 'python313' ? '语法检查' : '编译'
+}
+
+export function preparingStatus(language?: WireLanguage) {
+  return language === 'python313' ? '正在检查语法' : '正在编译'
+}
diff --git a/frontend/src/composables/useCodeDraft.ts b/frontend/src/composables/useCodeDraft.ts
index 8d55371..45ddef3 100644
--- a/frontend/src/composables/useCodeDraft.ts
+++ b/frontend/src/composables/useCodeDraft.ts
@@ -1,15 +1,17 @@
 import { computed, onScopeDispose, ref, watch } from 'vue'
-export type Language = 'c' | 'cpp' | 'python' | 'rust'
+export type Language = 'c' | 'cpp' | 'python' | 'java' | 'rust'
 export const languageLabels: Record<Language, string> = {
   c: 'C17',
   cpp: 'C++20',
-  python: 'Python',
+  python: 'Python 3.13',
+  java: 'Java 21',
   rust: 'Rust',
 }
 export const codeTemplates: Record<Language, string> = {
   c: '#include <stdio.h>\n\nint main(void) {\n    return 0;\n}\n',
   cpp: '#include <iostream>\nusing namespace std;\n\nint main() {\n    // 在这里编写你的解法\n    return 0;\n}\n',
   python: '# 在这里编写你的解法\n\n',
+  java: 'public class Main {\n    public static void main(String[] args) throws Exception {\n        // 在这里编写你的解法\n    }\n}\n',
   rust: 'use std::io::{self, Read};\n\nfn main() {\n    let mut input = String::new();\n    io::stdin().read_to_string(&mut input).unwrap();\n    // 在这里编写你的解法\n}\n',
 }
 export function useCodeDraft(problemId: string) {
@@ -32,11 +34,11 @@ export function useCodeDraft(problemId: string) {
         typeof saved.drafts === 'object'
       ) {
         const storedDrafts = saved.drafts as Record<string, unknown>
-        for (const lang of ['c', 'cpp', 'python', 'rust'] as const) {
+        for (const lang of Object.keys(codeTemplates) as Language[]) {
           const value = storedDrafts[lang]
           if (typeof value === 'string') drafts.value[lang] = value
         }
-        if ('language' in saved && ['c', 'cpp', 'python', 'rust'].includes(String(saved.language)))
+        if ('language' in saved && Object.hasOwn(codeTemplates, String(saved.language)))
           language.value = saved.language as Language
         state.value = 'saved'
       }
diff --git a/frontend/src/views/ProblemDetailView.vue b/frontend/src/views/ProblemDetailView.vue
index 3b52ac4..ee43698 100644
--- a/frontend/src/views/ProblemDetailView.vue
+++ b/frontend/src/views/ProblemDetailView.vue
@@ -8,6 +8,7 @@ import { submissionIntent, type SubmissionInput } from '../api/submissionIntent'
 import type { components } from '../api/generated/schema'
 import { useSession } from '../composables/useSession'
 import { useCodeDraft, codeTemplates, languageLabels } from '../composables/useCodeDraft'
+import { languageCapability, preparationName } from '../composables/judgingLanguage'
 import CodeEditor from '../components/CodeEditor.vue'
 import EmptyState from '../components/EmptyState.vue'
 import UiIcon from '../components/UiIcon.vue'
@@ -31,17 +32,10 @@ const workspace = ref<HTMLDivElement>()
 const request = new AbortController()
 let alive = true
 const intents = new Map<string, ReturnType<typeof submissionIntent>>()
-const wireLanguage = computed(() =>
-  language.value === 'c' ? 'c17' : language.value === 'cpp' ? 'cpp20' : null,
-)
-const supported = computed(
-  () => wireLanguage.value !== null && !!problem.value?.languages.includes(wireLanguage.value),
-)
-const runLimits = computed(
-  () =>
-    problem.value?.language_configurations?.find((c) => c.language === wireLanguage.value)
-      ?.run_limits ?? problem.value?.run_limits,
-)
+const capability = computed(() => languageCapability(problem.value, language.value))
+const wireLanguage = computed(() => capability.value?.wire ?? null)
+const supported = computed(() => capability.value !== null)
+const runLimits = computed(() => capability.value?.runLimits)
 const draftText = computed(
   () =>
     ({
@@ -102,7 +96,11 @@ function downloadCode() {
   const link = document.createElement('a')
   link.href = url
   link.download =
-    'solution-' + id + '.' + { c: 'c', cpp: 'cpp', python: 'py', rust: 'rs' }[language.value]
+    language.value === 'java'
+      ? 'Main.java'
+      : language.value === 'python'
+        ? 'main.py'
+        : 'solution-' + id + '.' + { c: 'c', cpp: 'cpp', rust: 'rs' }[language.value]
   link.click()
   setTimeout(() => URL.revokeObjectURL(url), 1000)
 }
@@ -289,7 +287,21 @@ onBeforeUnmount(() => {
       </div>
       <div class="editor-testing">
         <p v-if="!supported" class="notice-strip">
-          当前语言暂不支持提交，草稿仍会保存。可切换到题目支持的 C17 / C++20。
+          当前题目版本不支持此语言，草稿仍会保存。请选择题目公布的可用语言。
+        </p>
+        <p
+          v-else-if="capability?.configuration"
+          class="notice-strip"
+          data-testid="language-capability"
+        >
+          {{ languageLabels[language] }} · {{ capability.configuration.runtime_version }} ·
+          {{ preparationName(capability.wire) }}后逐点运行。
+          <template v-if="capability.wire === 'java21'">
+            默认包 Main.java，入口为 public static void main(String[])。
+          </template>
+          <template v-else-if="capability.wire === 'python313'">
+            单文件 main.py，仅标准库。
+          </template>
         </p>
         <p v-if="submitError" role="alert">
           {{ submitError }}
diff --git a/frontend/src/views/SubmissionDetailView.vue b/frontend/src/views/SubmissionDetailView.vue
index e508a9f..6a13e6e 100644
--- a/frontend/src/views/SubmissionDetailView.vue
+++ b/frontend/src/views/SubmissionDetailView.vue
@@ -9,6 +9,7 @@ import type { components } from '../api/generated/schema'
 import PageHeading from '../components/PageHeading.vue'
 import PanelCard from '../components/PanelCard.vue'
 import JudgementStatus from '../components/JudgementStatus.vue'
+import { preparationName } from '../composables/judgingLanguage'
 const route = useRoute()
 const id = String(route.params.id)
 const submission = ref<components['schemas']['SubmissionDetail'] | null>(null)
@@ -120,7 +121,11 @@ onBeforeUnmount(() => {
 </script>
 <template>
   <PageHeading :title="'提交 ' + id" description="个人提交的持久化评测状态"
-    ><JudgementStatus v-if="submission" :state="submission.state" :verdict="submission.verdict"
+    ><JudgementStatus
+      v-if="submission"
+      :state="submission.state"
+      :verdict="submission.verdict"
+      :language="submission.language"
   /></PageHeading>
   <p v-if="error" role="alert">
     {{ error }}
@@ -169,13 +174,17 @@ onBeforeUnmount(() => {
     <PanelCard title="评测详情" icon="submissions">
       <p v-if="submission.failure_code" role="alert">系统原因：{{ submission.failure_code }}</p>
       <template v-if="submission.result">
-        <p>编译状态：{{ submission.result.compilation_status }}</p>
+        <p>
+          {{ preparationName(submission.language) }}状态：{{ submission.result.compilation_status }}
+        </p>
         <pre
           v-if="submission.result.diagnostics"
           class="sample-block"
           data-testid="compiler-diagnostics"
           >{{ submission.result.diagnostics }}</pre>
-        <p v-if="submission.result.diagnostics_truncated">编译诊断已截断。</p>
+        <p v-if="submission.result.diagnostics_truncated">
+          {{ preparationName(submission.language) }}诊断已截断。
+        </p>
         <p v-if="!submission.result.cleanup_complete" role="alert">
           资源清理未确认，服务保留该任务并隔离容量。
         </p>
diff --git a/frontend/src/views/SubmissionsView.vue b/frontend/src/views/SubmissionsView.vue
index ead4f71..1c270d3 100644
--- a/frontend/src/views/SubmissionsView.vue
+++ b/frontend/src/views/SubmissionsView.vue
@@ -91,7 +91,10 @@ onBeforeUnmount(() => {
         label="状态"
         min-width="130"
         ><template #default="{ row }"
-          ><JudgementStatus :state="row.state" :verdict="row.verdict" /></template></el-table-column
+          ><JudgementStatus
+            :state="row.state"
+            :verdict="row.verdict"
+            :language="row.language" /></template></el-table-column
       ><el-table-column prop="created_at" label="提交时间" min-width="180" />
     </el-table>
     <div class="pagination-row">
diff --git a/frontend/tests/judgingLanguage.test.ts b/frontend/tests/judgingLanguage.test.ts
new file mode 100644
index 0000000..04e8afc
--- /dev/null
+++ b/frontend/tests/judgingLanguage.test.ts
@@ -0,0 +1,105 @@
+import assert from 'node:assert/strict'
+import { test } from 'node:test'
+import type { components } from '../src/api/generated/schema'
+import {
+  languageCapability,
+  preparationName,
+  preparingStatus,
+} from '../src/composables/judgingLanguage.ts'
+
+const limits: components['schemas']['RunLimits'] = {
+  cpu_time_us: 1_000_000,
+  wall_time_us: 3_000_000,
+  memory_bytes: 67_108_864,
+  file_bytes: 16_777_216,
+  open_files: 64,
+  processes: 8,
+  stack_bytes: 8_388_608,
+  stderr_bytes: 1_048_576,
+  stdout_bytes: 1_048_576,
+  workdir_bytes: 67_108_864,
+}
+const python: components['schemas']['PublicLanguageConfiguration'] = {
+  language: 'python313',
+  runtime_version: '3.13.16',
+  source_name: 'main.py',
+  entrypoint: 'main.py',
+  preparation_kind: 'syntax_check',
+  compile_limits: limits,
+  run_limits: { ...limits, cpu_time_us: 2_000_000 },
+  job_wall_time_us: 12_000_000,
+}
+const java: components['schemas']['PublicLanguageConfiguration'] = {
+  language: 'java21',
+  runtime_version: '21.0.12.1+1-LTS',
+  source_name: 'Main.java',
+  entrypoint: 'Main',
+  preparation_kind: 'compile',
+  compile_limits: limits,
+  run_limits: { ...limits, memory_bytes: 134_217_728 },
+  job_wall_time_us: 12_000_000,
+}
+type Problem = Parameters<typeof languageCapability>[0]
+
+test('server capability controls managed submission and the selected version/budget; legacy C stays supported', () => {
+  const legacy: Problem = {
+    languages: ['c17', 'cpp20'],
+    language_configurations: [],
+    run_limits: limits,
+  }
+  assert.equal(languageCapability(legacy, 'c')?.wire, 'c17')
+  assert.equal(languageCapability(legacy, 'cpp')?.runLimits, limits)
+  assert.equal(languageCapability(legacy, 'python'), null)
+  assert.equal(languageCapability(legacy, 'java'), null)
+  assert.equal(languageCapability(legacy, 'rust'), null)
+  const current: Problem = {
+    languages: ['python313', 'java21'],
+    language_configurations: [python, java],
+    run_limits: null,
+  }
+  assert.equal(
+    languageCapability(current, 'python')?.configuration?.runtime_version,
+    python.runtime_version,
+  )
+  assert.equal(languageCapability(current, 'python')?.runLimits.cpu_time_us, 2_000_000)
+  assert.equal(languageCapability(current, 'java')?.runLimits.memory_bytes, 134_217_728)
+  assert.equal(languageCapability(current, 'java')?.configuration?.entrypoint, 'Main')
+  assert.equal(languageCapability(current, 'c'), null)
+  assert.equal(languageCapability(null, 'python'), null)
+})
+
+test('managed language with absent or invalid fixed entry capability cannot inherit legacy budget', () => {
+  const missing: Problem = {
+    languages: ['python313', 'java21'],
+    language_configurations: [],
+    run_limits: limits,
+  }
+  assert.equal(languageCapability(missing, 'python'), null)
+  assert.equal(languageCapability(missing, 'java'), null)
+  for (const invalid of [
+    { ...python, preparation_kind: 'compile' as const },
+    { ...python, source_name: 'main.pyc' },
+    { ...java, entrypoint: 'Other' },
+    { ...java, source_name: 'package/Main.java' },
+    { ...java, runtime_version: '' },
+  ]) {
+    const problem: Problem = {
+      languages: [invalid.language],
+      language_configurations: [invalid],
+      run_limits: limits,
+    }
+    assert.equal(
+      languageCapability(problem, invalid.language === 'python313' ? 'python' : 'java'),
+      null,
+    )
+  }
+})
+
+test('Python preparation is displayed as syntax checking while Java and old C/C++ compile', () => {
+  assert.equal(preparingStatus('python313'), '正在检查语法')
+  assert.equal(preparationName('python313'), '语法检查')
+  for (const language of ['c17', 'cpp20', 'java21'] as const) {
+    assert.equal(preparingStatus(language), '正在编译')
+    assert.equal(preparationName(language), '编译')
+  }
+})
diff --git a/frontend/tests/submissionFlow.test.ts b/frontend/tests/submissionFlow.test.ts
index 24734de..66ffc62 100644
--- a/frontend/tests/submissionFlow.test.ts
+++ b/frontend/tests/submissionFlow.test.ts
@@ -22,13 +22,45 @@ const flush = async () => {
   await new Promise<void>((resolve) => setImmediate(resolve))
 }
 
+test('Python and Java retries preserve UUID and language/content changes create a new intent', async () => {
+  const storage = memory()
+  const keys: string[] = []
+  for (const language of ['python313', 'java21'] as const) {
+    const managed = { ...input, language }
+    await assert.rejects(
+      submissionIntent(storage, 'owner').submit(managed, async (key) => {
+        keys.push(key)
+        throw new Error('uncertain delivery')
+      }),
+    )
+    const failedKey = keys.at(-1)
+    await submissionIntent(storage, 'owner').submit(managed, async (key) => {
+      assert.equal(key, failedKey)
+      return 'saved-' + language
+    })
+  }
+  assert.notEqual(keys[0], keys[1])
+  await submissionIntent(storage, 'owner').submit(
+    { ...input, language: 'java21', source: 'changed Java' },
+    async (key) => {
+      assert.notEqual(key, keys[1])
+      return 'changed-id'
+    },
+  )
+})
+
 test('timeout and reload reuse persisted key; double click has one flight; content and owner change key', async () => {
   const storage = memory()
   const keys: string[] = []
   const intent = submissionIntent(storage, 'owner-a')
   let respond: (id: string) => void = () => {}
+  let sent: () => void = () => {}
+  const sending = new Promise<void>((resolve) => {
+    sent = resolve
+  })
   const send = async (key: string) => {
     keys.push(key)
+    sent()
     return new Promise<string>((resolve) => {
       respond = resolve
     })
@@ -36,7 +68,7 @@ test('timeout and reload reuse persisted key; double click has one flight; conte
   const a = intent.submit(input, send)
   const b = intent.submit(input, send)
   assert.equal(a, b)
-  await flush()
+  await sending
   assert.equal(keys.length, 1)
   respond('real-id')
   assert.equal(await a, 'real-id')
diff --git a/frontend/tests/useCodeDraft.test.ts b/frontend/tests/useCodeDraft.test.ts
index d815dae..9cbf3a7 100644
--- a/frontend/tests/useCodeDraft.test.ts
+++ b/frontend/tests/useCodeDraft.test.ts
@@ -142,6 +142,7 @@ test('pagehide preserves the selected language and keeps problem drafts separate
       c: codeTemplates.c,
       cpp: '// C++ draft',
       python: '# Python draft',
+      java: codeTemplates.java,
       rust: codeTemplates.rust,
     },
   })
@@ -190,3 +191,44 @@ test('old Python/Rust drafts survive adding C17; C and C++ retain separate conte
   assert.equal(env.read()?.drafts.python, '# original Python')
   assert.equal(env.read()?.drafts.rust, '// original Rust')
 })
+
+test('old drafts acquire Java without replacing their contents; four languages survive reload and version changes', (t) => {
+  const env = browser(t)
+  env.storage.items.set(
+    'kf-oj:code-draft:version-a',
+    JSON.stringify({
+      version: 1,
+      language: 'python',
+      drafts: { python: '# old Python', cpp: '// old C++', rust: '// old Rust' },
+    }),
+  )
+  const draft = env.open('version-a')
+  assert.equal(draft.code.value, '# old Python')
+  draft.language.value = 'java'
+  assert.equal(draft.code.value, codeTemplates.java)
+  draft.code.value = '// Java draft'
+  draft.language.value = 'c'
+  draft.code.value = '// C draft'
+  draft.language.value = 'java'
+  env.page.dispatchEvent(new Event('pagehide'))
+  draft.scope.stop()
+  const restored = env.open('version-a')
+  assert.equal(restored.language.value, 'java')
+  assert.equal(restored.code.value, '// Java draft')
+  for (const [language, contents] of [
+    ['c', '// C draft'],
+    ['cpp', '// old C++'],
+    ['python', '# old Python'],
+    ['rust', '// old Rust'],
+  ] as const) {
+    restored.language.value = language
+    assert.equal(restored.code.value, contents)
+  }
+  const other = env.open('version-b')
+  other.language.value = 'java'
+  assert.equal(other.code.value, codeTemplates.java)
+  other.code.value = '// other version Java'
+  other.save()
+  assert.equal(env.read('version-a')?.drafts.java, '// Java draft')
+  assert.equal(env.read('version-b')?.drafts.java, '// other version Java')
+})