diff --git a/README.md b/README.md
index 1f105f058..3dbc3bc5e 100644
--- a/README.md
+++ b/README.md
@@ -111,6 +111,11 @@ Hydro 用户群：1085853538
 <details>
 <summary><h2>更新日志（点击展开）</h2></summary>
 
+## Unreleased
+
+- judge: breaking: 不再支持在 checker 等的编译阶段读取选手代码
+
+
 ## Hydro 4.19.0 / UI 4.57.0
 
 - core&ui&judge: 添加通信题支持
diff --git a/packages/hydrojudge/src/compile.ts b/packages/hydrojudge/src/compile.ts
index 1e9f525f8..142a6c02a 100644
--- a/packages/hydrojudge/src/compile.ts
+++ b/packages/hydrojudge/src/compile.ts
@@ -1,7 +1,6 @@
 import { LangConfig } from '@hydrooj/utils/lib/lang';
 import { STATUS } from '@hydrooj/utils/lib/status';
-import { findFileSync } from '@hydrooj/utils/lib/utils';
-import { CompileError, FormatError } from './error';
+import { CompileError } from './error';
 import { Execute } from './interface';
 import {
     CopyIn, CopyInFile, del, runQueued,
@@ -46,25 +45,3 @@ export default async function compile(
         clean: () => Promise.resolve(null),
     };
 }
-
-const testlibFile = {
-    src: findFileSync('@hydrooj/hydrojudge/vendor/testlib/testlib.h'),
-};
-
-export async function compileLocalFile(
-    src: string, type: 'checker' | 'validator' | 'interactor' | 'generator' | 'manager' | 'std',
-    getLang, copyIn: CopyIn, withTestlib = true, next?: any,
-) {
-    const s = src.replace('@', '.').split('.');
-    let lang;
-    let langId = s.pop();
-    while (s.length) {
-        lang = getLang(langId, false);
-        if (lang) break;
-        langId = `${s.pop()}.${langId}`;
-    }
-    if (!lang) throw new FormatError(`Unknown ${type} language.`);
-    if (withTestlib) copyIn = { ...copyIn, 'testlib.h': testlibFile };
-    // TODO cache compiled binary
-    return await compile(lang, { src }, copyIn, next);
-}
diff --git a/packages/hydrojudge/src/hosts/vj4.ts b/packages/hydrojudge/src/hosts/vj4.ts
index 9dc449d44..b666789b6 100644
--- a/packages/hydrojudge/src/hosts/vj4.ts
+++ b/packages/hydrojudge/src/hosts/vj4.ts
@@ -26,7 +26,7 @@ export default class VJ4 implements Session {
     progress = 0;
     ws: WebSocket;
 
-    async fetchFile(): Promise<string> {
+    async fetchFile(): Promise<any> {
         throw new Error('not implemented');
     }
 
diff --git a/packages/hydrojudge/src/task.ts b/packages/hydrojudge/src/task.ts
index d3710b4b6..5c432dfa1 100644
--- a/packages/hydrojudge/src/task.ts
+++ b/packages/hydrojudge/src/task.ts
@@ -1,12 +1,12 @@
 import { basename, join } from 'path';
-import { fs } from '@hydrooj/utils';
+import { findFileSync, fs } from '@hydrooj/utils';
 import { STATUS } from '@hydrooj/utils/lib/status';
 import type {
-    FileInfo, JudgeMeta, JudgeResultBody, TestCase,
+    CompilableSource, FileInfo, JudgeMeta, JudgeResultBody, TestCase,
 } from 'hydrooj';
 import readCases from './cases';
 import checkers from './checkers';
-import compile, { compileLocalFile } from './compile';
+import compile from './compile';
 import { getConfig } from './config';
 import { CompileError, FormatError } from './error';
 import {
@@ -19,6 +19,10 @@ import { compilerText, Lock, md5 } from './utils';
 
 const logger = new Logger('judge');
 
+const testlibFile = {
+    src: findFileSync('@hydrooj/hydrojudge/vendor/testlib/testlib.h'),
+};
+
 export class JudgeTask {
     stat: Record<string, Date> = Object.create(null);
     source: string;
@@ -93,6 +97,8 @@ export class JudgeTask {
     }
 
     async cacheOpen(source: string, files: FileInfo[]) {
+        // Backward compatibility for vj4
+        if ((this.session as any).cacheOpen) return (this.session as any).cacheOpen(source, files);
         const lockKey = `${this.session.config?.host || 'local'}/${source}`;
         await Lock.acquire(lockKey);
         const filePath = join(getConfig('cache_dir'), lockKey);
@@ -165,19 +171,36 @@ export class JudgeTask {
         return result;
     }
 
-    async compileLocalFile(type: 'interactor' | 'validator' | 'checker' | 'generator' | 'manager' | 'std', file: string, checkerType?: string) {
+    async compileLocalFile(
+        type: 'interactor' | 'validator' | 'checker' | 'generator' | 'manager' | 'std',
+        source: CompilableSource,
+        checkerType?: string,
+    ) {
         if (type === 'checker' && ['default', 'strict'].includes(checkerType)) return { execute: '', copyIn: {}, clean: () => Promise.resolve(null) };
         if (type === 'checker' && !checkers[checkerType]) throw new FormatError('Unknown checker type {0}.', [checkerType]);
         const withTestlib = type !== 'std' && (type !== 'checker' || checkerType === 'testlib');
         const extra = type === 'std' ? this.config.user_extra_files : this.config.judge_extra_files;
         const copyIn = {
-            user_code: this.code,
             ...Object.fromEntries(
                 (extra || []).map((i) => [basename(i), { src: i }]),
             ),
+            ...(withTestlib ? { testlib: testlibFile } : {}),
         } as CopyIn;
+        let [file, langId] = typeof source === 'string' ? [source, 'auto'] : [source.file, source.lang];
         if (!file.startsWith('/')) file = join(this.folder, file);
-        const result = await compileLocalFile(file, type, this.session.getLang, copyIn, withTestlib, this.next);
+        let lang;
+        if (langId === 'auto') {
+            const s = file.replace('@', '.').split('.');
+            langId = s.pop();
+            while (s.length) {
+                lang = this.session.getLang(langId);
+                if (lang) break;
+                langId = `${s.pop()}.${langId}`;
+            }
+        } else lang = this.session.getLang(langId);
+        if (!lang) throw new FormatError(`Unknown ${type} language.`);
+        // TODO cache compiled binary
+        const result = await compile(lang, { src: file }, copyIn, this.next);
         this.clean.push(result.clean);
         return result;
     }