diff --git a/src/main/java/org/ezcode/codetest/application/submission/dto/request/submission/CodeSubmitRequest.java b/src/main/java/org/ezcode/codetest/application/submission/dto/request/submission/CodeSubmitRequest.java
index 2342c8b6..38cce0bd 100644
--- a/src/main/java/org/ezcode/codetest/application/submission/dto/request/submission/CodeSubmitRequest.java
+++ b/src/main/java/org/ezcode/codetest/application/submission/dto/request/submission/CodeSubmitRequest.java
@@ -16,7 +16,10 @@ public record CodeSubmitRequest(
         example = "public class Main { public static void main(String[] args) { System.out.println(\"Hello World\"); } }"
     )
     @NotBlank(message = "소스 코드는 필수 입력 값입니다.")
-    String sourceCode
+    String sourceCode,
+
+    @NotBlank(message = "세션 키는 필수 입력 값입니다.")
+    String sessionKey
 
 ) {
 }
diff --git a/src/main/java/org/ezcode/codetest/application/submission/service/SubmissionService.java b/src/main/java/org/ezcode/codetest/application/submission/service/SubmissionService.java
index 0286e47a..72526eb6 100644
--- a/src/main/java/org/ezcode/codetest/application/submission/service/SubmissionService.java
+++ b/src/main/java/org/ezcode/codetest/application/submission/service/SubmissionService.java
@@ -55,8 +55,7 @@ public class SubmissionService {
     private final JudgementService judgementService;
     private final GitHubPushService gitHubPushService;
 
-    public SubmitResponse enqueueCodeSubmission(Long problemId, CodeSubmitRequest request, AuthUser authUser) {
-
+    public SubmitResponse prepareSubmission(Long problemId, AuthUser authUser) {
         boolean acquired = lockManager.tryLock("submission", authUser.getId(), problemId);
         if (!acquired) {
             throw new SubmissionException(SubmissionExceptionCode.ALREADY_JUDGING);
@@ -65,11 +64,13 @@ public SubmitResponse enqueueCodeSubmission(Long problemId, CodeSubmitRequest re
         String sessionKey = authUser.getId() + "_" + UUID.randomUUID();
         List<Testcase> testcaseList = testcaseDomainService.getTestcaseListByProblemId(problemId);
 
+        return SubmitResponse.of(sessionKey, testcaseList);
+    }
+
+    public void enqueueCodeSubmission(Long problemId, CodeSubmitRequest request, AuthUser authUser) {
         queueProducer.enqueue(
-            new SubmissionMessage(sessionKey, problemId, request.languageId(), authUser.getId(), request.sourceCode())
+            SubmissionMessage.of(request, problemId, authUser.getId())
         );
-
-        return SubmitResponse.of(sessionKey, testcaseList);
     }
 
     @Async("judgeSubmissionExecutor")
diff --git a/src/main/java/org/ezcode/codetest/infrastructure/event/dto/submission/SubmissionMessage.java b/src/main/java/org/ezcode/codetest/infrastructure/event/dto/submission/SubmissionMessage.java
index 1a8af3a4..f9ff0dad 100644
--- a/src/main/java/org/ezcode/codetest/infrastructure/event/dto/submission/SubmissionMessage.java
+++ b/src/main/java/org/ezcode/codetest/infrastructure/event/dto/submission/SubmissionMessage.java
@@ -1,5 +1,7 @@
 package org.ezcode.codetest.infrastructure.event.dto.submission;
 
+import org.ezcode.codetest.application.submission.dto.request.submission.CodeSubmitRequest;
+
 public record SubmissionMessage(
 
     String sessionKey,
@@ -13,4 +15,13 @@ public record SubmissionMessage(
     String sourceCode
 
 ) {
+    public static SubmissionMessage of(CodeSubmitRequest request, Long problemId, Long userId) {
+        return new SubmissionMessage(
+            request.sessionKey(),
+            problemId,
+            request.languageId(),
+            userId,
+            request.sourceCode()
+        );
+    }
 }
diff --git a/src/main/java/org/ezcode/codetest/presentation/submission/SubmissionController.java b/src/main/java/org/ezcode/codetest/presentation/submission/SubmissionController.java
index f14531d0..aebe4664 100644
--- a/src/main/java/org/ezcode/codetest/presentation/submission/SubmissionController.java
+++ b/src/main/java/org/ezcode/codetest/presentation/submission/SubmissionController.java
@@ -32,37 +32,46 @@ public class SubmissionController {
 
     private final SubmissionService submissionService;
 
-    @PostMapping("/problems/{problemId}/submit-ws")
+    @PostMapping("/problems/{problemId}/submit-prepare")
+    public ResponseEntity<SubmitResponse> prepareSubmission(
+        @PathVariable Long problemId,
+        @AuthenticationPrincipal AuthUser authUser
+    ) {
+        return ResponseEntity
+            .status(HttpStatus.OK)
+            .body(submissionService.prepareSubmission(problemId, authUser));
+    }
+
+    @PostMapping("/problems/{problemId}/submit-ready")
     @Operation(
         summary = "코드 제출 (WebSocket)",
         description = """
-        문제에 대한 코드를 제출하면 채점 큐에 등록되고,
-        서버는 WebSocket(STOMP)을 통해 채점 결과를 실시간으로 전송합니다.
-
-        반환된 sessionKey를 사용해 다음 경로로 구독하세요.
- 
-        • /user/queue/submission/{sessionKey}/case
-        
-        • /user/queue/submission/{sessionKey}/final
-        
-        • /topic/submission/{sessionKey}/error
-        
-        • /user/queue/submission/{sessionKey}/git-status
-        """
+            문제에 대한 코드를 제출하면 채점 큐에 등록되고,
+            서버는 WebSocket(STOMP)을 통해 채점 결과를 실시간으로 전송합니다.
+            
+            반환된 sessionKey를 사용해 다음 경로로 구독하세요.
+            
+            • /user/queue/submission/{sessionKey}/case
+            
+            • /user/queue/submission/{sessionKey}/final
+            
+            • /topic/submission/{sessionKey}/error
+            
+            • /user/queue/submission/{sessionKey}/git-status
+            """
     )
     @ApiResponses({
         @ApiResponse(responseCode = "200", description = "코드 제출 성공 및 sessionKey 반환"),
         @ApiResponse(responseCode = "400", description = "유효하지 않은 요청 데이터"),
         @ApiResponse(responseCode = "409", description = "이미 해당 문제를 채점 중인 경우"),
     })
-    public ResponseEntity<SubmitResponse> submitCodeStream(
+    public ResponseEntity<Void> submitCodeStream(
         @Parameter(description = "제출할 문제 ID", required = true) @PathVariable Long problemId,
         @RequestBody @Valid CodeSubmitRequest request,
         @AuthenticationPrincipal AuthUser authUser
     ) {
-        return ResponseEntity
-            .status(HttpStatus.OK)
-            .body(submissionService.enqueueCodeSubmission(problemId, request, authUser));
+        submissionService.enqueueCodeSubmission(problemId, request, authUser);
+        return ResponseEntity.status(HttpStatus.OK).build();
     }
 
     @Operation(
diff --git a/src/main/resources/templates/test-submit.html b/src/main/resources/templates/test-submit.html
index 665181fa..d66e9c9c 100644
--- a/src/main/resources/templates/test-submit.html
+++ b/src/main/resources/templates/test-submit.html
@@ -953,7 +953,6 @@ <h3>채점 결과</h3>
             const pid = window.problemId;
             const languageId = +document.getElementById('language').value;
             const sourceCode = window.getEditorCode();
-            const payload = { languageId, sourceCode };
             const judgeEl = document.getElementById('judgeResult');
             judgeEl.innerHTML = '';
             reviewBox.style.display = 'none';
@@ -961,24 +960,38 @@ <h3>채점 결과</h3>
             finalIsCorrect = null;
 
             try {
-                const res = await fetch(`/api/problems/${pid}/submit-ws`, {
+                const res = await fetch(`/api/problems/${pid}/submit-prepare`, {
                     method: 'POST',
                     headers: {
                         'Content-Type': 'application/json',
                         ...tokenHeader()
                     },
-                    body: JSON.stringify(payload)
                 });
                 const resp = await res.json();
                 console.log('[DEBUG] 전체 응답:', resp);
                 console.log('[DEBUG] result:', resp.result);
                 if (!resp.success) {
-                    judgeEl.textContent = `Error: ${resp.message}`;
+                    judgeEl.textContent = `${resp.message}`;
                     return;
                 }
                 const { sessionKey, testcaseIds } = resp.result;
-                initWebSocket(sessionKey);
-                renderInitSlots(testcaseIds);
+
+                initWebSocket(sessionKey, async () => {
+                    renderInitSlots(testcaseIds);
+
+                    await fetch(`/api/problems/${pid}/submit-ready`, {
+                        method: 'POST',
+                        headers: {
+                            'Content-Type': 'application/json',
+                            ...tokenHeader()
+                        },
+                        body: JSON.stringify({
+                            sessionKey,
+                            languageId,
+                            sourceCode
+                        })
+                    });
+                });
             } catch (err) {
                 console.error(err);
                 judgeEl.textContent = '채점 요청 실패';
@@ -1058,7 +1071,7 @@ <h3>채점 결과</h3>
         // submitCode() 에서 호출할 함수
         window.getEditorCode = () => editor.getValue();
 
-        function initWebSocket(sessionKey) {
+        function initWebSocket(sessionKey, onReady) {
             const tokenOnly = (sessionStorage.getItem('accessToken') || '').replace(/^Bearer /, '');
             const socket = new SockJS(`/ws?token=${encodeURIComponent(tokenOnly)}`);
             stompClient = Stomp.over(socket);
@@ -1082,7 +1095,13 @@ <h3>채점 결과</h3>
                     else if (status === 'FAILED') gitDot.style.backgroundColor = '#ff4d4d';
                     else gitDot.style.backgroundColor = 'gray';
                 });
-            }, err => console.error('[STOMP] 연결 오류:', err));
+
+                if (typeof onReady === 'function') {
+                    onReady();
+                }
+            }, err => {
+                console.error('[STOMP] 연결 오류:', err);
+            });
         }
 
         function handleCase(data) {
@@ -1431,7 +1450,7 @@ <h3>채점 결과</h3>
                     if (res.ok) {
                         // 성공: 목록 새로고침
                         if (item.classList.contains('discussion-item')) {
-                            loadDiscussions(window.problemId, 0, 10, document.getElementById('discussion-sort')?.value || 'best');
+                            await loadDiscussions(window.problemId, 0, 10, document.getElementById('discussion-sort')?.value || 'best');
                         } else {
                             const discussionId = item.closest('.discussion-item').dataset.discussionId;
                             const container = document.getElementById(`replies-for-${discussionId}`);
@@ -1457,7 +1476,7 @@ <h3>채점 결과</h3>
                     const discussionId = item.closest('.discussion-item').dataset.discussionId;
                     url = `/api/problems/${window.problemId}/discussions/${discussionId}/replies/${e.target.dataset.id}`;
                 }
-                (async () => {
+                await (async () => {
                     const res = await fetch(url, {
                         method,
                         headers: {
@@ -1466,7 +1485,7 @@ <h3>채점 결과</h3>
                     });
                     if (res.ok) {
                         if (item.classList.contains('discussion-item')) {
-                            loadDiscussions(window.problemId, 0, 10, document.getElementById('discussion-sort')?.value || 'best');
+                            await loadDiscussions(window.problemId, 0, 10, document.getElementById('discussion-sort')?.value || 'best');
                         } else {
                             const discussionId = item.closest('.discussion-item').dataset.discussionId;
                             const container = document.getElementById(`replies-for-${discussionId}`);
@@ -1493,7 +1512,7 @@ <h3>채점 결과</h3>
                 body: JSON.stringify({ voteType })
             });
             if (res.ok) {
-                updateDiscussionVoteUI(discussionId);
+                await updateDiscussionVoteUI(discussionId);
             } else {
                 alert('추천/비추천에 실패했습니다.');
             }
@@ -1534,7 +1553,7 @@ <h3>채점 결과</h3>
                 body: JSON.stringify({ voteType })
             });
             if (res.ok) {
-                updateReplyVoteUI(discussionId, replyId);
+                await updateReplyVoteUI(discussionId, replyId);
             } else {
                 alert('추천/비추천에 실패했습니다.');
             }
diff --git a/src/test/java/org/ezcode/codetest/application/submission/SubmissionServiceTest.java b/src/test/java/org/ezcode/codetest/application/submission/SubmissionServiceTest.java
index d8f29005..1dbb7eb6 100644
--- a/src/test/java/org/ezcode/codetest/application/submission/SubmissionServiceTest.java
+++ b/src/test/java/org/ezcode/codetest/application/submission/SubmissionServiceTest.java
@@ -26,6 +26,7 @@
 import org.ezcode.codetest.domain.language.service.LanguageDomainService;
 import org.ezcode.codetest.domain.problem.model.ProblemInfo;
 import org.ezcode.codetest.domain.problem.model.entity.Problem;
+import org.ezcode.codetest.domain.problem.model.entity.Testcase;
 import org.ezcode.codetest.domain.problem.service.ProblemDomainService;
 import org.ezcode.codetest.domain.problem.service.TestcaseDomainService;
 import org.ezcode.codetest.domain.submission.exception.SubmissionException;
@@ -125,28 +126,44 @@ void setup() {
     class SuccessCases {
 
         @Test
-        @DisplayName("락 획득 성공 -> 메세지 큐에 전송하고 sessionKey 반환")
+        @DisplayName("락 획득 성공 -> sessionKey, testcaseList 반환")
+        void prepareSubmissionSuccess() {
+
+            // given
+            given(authUser.getId()).willReturn(userId);
+            given(lockManager.tryLock("submission", userId, problemId)).willReturn(true);
+
+            List<Testcase> testcaseList = List.of(mock(Testcase.class), mock(Testcase.class));
+            given(testcaseDomainService.getTestcaseListByProblemId(problemId)).willReturn(testcaseList);
+
+            // when
+            SubmitResponse result = submissionService.prepareSubmission(problemId, authUser);
+
+            // then
+            assertThat(result.sessionKey()).startsWith(userId + "_");
+            assertThat(result.testcaseIds()).hasSize(2);
+            then(lockManager).should().tryLock("submission", userId, problemId);
+            then(testcaseDomainService).should().getTestcaseListByProblemId(problemId);
+        }
+
+        @Test
+        @DisplayName("큐에 메세지 전송 확인")
         void enqueueCodeSubmissionSucceeds() {
 
             // given
             given(authUser.getId()).willReturn(userId);
             given(request.languageId()).willReturn(languageId);
             given(request.sourceCode()).willReturn(sourceCode);
-            given(lockManager.tryLock("submission", authUser.getId(), problemId))
-                .willReturn(true);
-            given(testcaseDomainService.getTestcaseListByProblemId(problemId)).willReturn(List.of());
 
             // when
-            SubmitResponse result = submissionService.enqueueCodeSubmission(problemId, request, authUser);
+            submissionService.enqueueCodeSubmission(problemId, request, authUser);
 
             then(queueProducer).should()
                 .enqueue(argThat(msg ->
-                    msg.sessionKey().startsWith(sessionKey) &&
                         msg.problemId().equals(problemId) &&
                         msg.languageId().equals(languageId) &&
                         msg.sourceCode().equals(sourceCode)
                 ));
-            assertThat(result.sessionKey()).startsWith(sessionKey);
         }
 
         @Test
@@ -251,7 +268,7 @@ class FailureCases {
 
         @Test
         @DisplayName("락 획득 실패 -> ALREADY_JUDGING 예외")
-        void enqueueCodeSubmissionFailed() {
+        void prepareSubmissionFailed() {
 
             // given
             given(authUser.getId()).willReturn(userId);
@@ -260,7 +277,7 @@ void enqueueCodeSubmissionFailed() {
 
             // when & then
             assertThatThrownBy(() ->
-                submissionService.enqueueCodeSubmission(problemId, request, authUser)
+                submissionService.prepareSubmission(problemId, authUser)
             )
                 .isInstanceOf(SubmissionException.class)
                 .hasMessage(SubmissionExceptionCode.ALREADY_JUDGING.getMessage());