diff --git a/server/routes/vocabulary.ts b/server/routes/vocabulary.ts
index 800686b..cc6db99 100644
--- a/server/routes/vocabulary.ts
+++ b/server/routes/vocabulary.ts
@@ -929,13 +929,14 @@ router.post('/test-answer', authMiddleware, async (req, res) => {
   try {
     const { attemptId, questionToken, userAnswer, submittedAt, answerProof, interactions } = req.body;
     const userId = req.user?._id;
+    const softRiskFlags: string[] = [];
 
     if (!userId) {
       return res.status(401).json({ message: INVALID_CREDENTIAL_MESSAGE });
     }
 
     if (!isAllowedVocabularyOrigin(req)) {
-      return res.status(403).json({ message: INVALID_CREDENTIAL_MESSAGE });
+      softRiskFlags.push('invalid_origin');
     }
 
     if (!mongoose.isValidObjectId(attemptId)) {
@@ -957,9 +958,7 @@ router.post('/test-answer', authMiddleware, async (req, res) => {
     const now = Date.now();
 
     if (!Number.isFinite(expiresAt.getTime()) || expiresAt.getTime() < now) {
-      attemptAny.status = 'expired';
-      await attempt.save();
-      return res.status(410).json({ message: INVALID_CREDENTIAL_MESSAGE });
+      softRiskFlags.push('attempt_expired');
     }
 
     if (attemptAny.status !== 'active') {
@@ -985,16 +984,14 @@ router.post('/test-answer', authMiddleware, async (req, res) => {
 
     const submittedAtMs = Number.parseInt(String(submittedAt), 10);
     if (!Number.isFinite(submittedAtMs)) {
-      return res.status(400).json({ message: INVALID_CREDENTIAL_MESSAGE });
-    }
-
-    if (Math.abs(now - submittedAtMs) > 5 * 60 * 1000) {
-      return res.status(400).json({ message: INVALID_CREDENTIAL_MESSAGE });
+      softRiskFlags.push('invalid_submitted_at');
+    } else if (Math.abs(now - submittedAtMs) > 5 * 60 * 1000) {
+      softRiskFlags.push('submitted_at_out_of_sync');
     }
 
     const wordId = getObjectIdString(attemptAny.questionWordIds[tokenIndex]);
     if (!wordId || !verifyQuestionToken(token, attemptId.toString(), wordId, tokenIndex, issuedAt)) {
-      return res.status(400).json({ message: INVALID_CREDENTIAL_MESSAGE });
+      softRiskFlags.push('invalid_question_token');
     }
 
     let normalizedUserAnswer = String(userAnswer ?? '').trim().slice(0, 500);
@@ -1003,24 +1000,31 @@ router.post('/test-answer', authMiddleware, async (req, res) => {
       const optionTexts = attemptAny.optionTexts?.[tokenIndex] || [];
       const selectedOptionIndex = optionTokens.findIndex((optionToken: string) => safeEqualString(optionToken, normalizedUserAnswer));
       if (selectedOptionIndex < 0) {
-        return res.status(400).json({ message: INVALID_CREDENTIAL_MESSAGE });
+        softRiskFlags.push('invalid_option_token');
+        const fallbackOptionIndex = optionTexts.findIndex((text: string) => text === normalizedUserAnswer);
+        normalizedUserAnswer = fallbackOptionIndex >= 0
+          ? optionTexts[fallbackOptionIndex]
+          : String(userAnswer ?? '').trim().slice(0, 500);
+      } else {
+        normalizedUserAnswer = optionTexts[selectedOptionIndex] || '';
       }
-      normalizedUserAnswer = optionTexts[selectedOptionIndex] || '';
     }
 
     const expectedProof = buildAnswerProof(attemptId.toString(), token, String(userAnswer ?? '').trim().slice(0, 500), submittedAtMs);
     if (!safeEqualString(expectedProof, String(answerProof ?? ''))) {
-      return res.status(400).json({ message: INVALID_CREDENTIAL_MESSAGE });
+      softRiskFlags.push('invalid_answer_proof');
     }
 
     const questionShownAtMs = tokenIndex === 0
       ? issuedAt.getTime()
       : new Date(attemptAny.answers?.[tokenIndex - 1]?.submittedAt || issuedAt).getTime();
-    const duration = Math.max(0, (submittedAtMs - questionShownAtMs) / 1000);
+    const effectiveSubmittedAtMs = Number.isFinite(submittedAtMs) ? submittedAtMs : now;
+    const duration = Math.max(0, (effectiveSubmittedAtMs - questionShownAtMs) / 1000);
     const interactionSummary = summarizeInteractionEvents(interactions, questionShownAtMs);
     const riskFlags = Array.from(new Set([
       ...analyzeAnswerRisk(duration, interactionSummary, attemptAny.testType),
-      ...analyzeInputTraceRisk(interactions, normalizedUserAnswer, attemptAny.testType)
+      ...analyzeInputTraceRisk(interactions, normalizedUserAnswer, attemptAny.testType),
+      ...softRiskFlags
     ]));
 
     const word = await Word.findOne({
@@ -1042,7 +1046,7 @@ router.post('/test-answer', authMiddleware, async (req, res) => {
         userAnswer: evaluation.userAnswer,
         correctAnswer: evaluation.correctAnswer,
         isCorrect: evaluation.isCorrect,
-        submittedAt: new Date(submittedAtMs),
+        submittedAt: new Date(effectiveSubmittedAtMs),
         duration,
         riskFlags,
         interactionSummary
@@ -1148,13 +1152,14 @@ router.post('/test-record', authMiddleware, async (req, res) => {
   try {
     const { attemptId } = req.body;
     const userId = req.user?._id;
+    const finalRiskFlags: string[] = [];
 
     if (!userId) {
       return res.status(401).json({ message: INVALID_CREDENTIAL_MESSAGE });
     }
 
     if (!isAllowedVocabularyOrigin(req)) {
-      return res.status(403).json({ message: INVALID_CREDENTIAL_MESSAGE });
+      finalRiskFlags.push('invalid_origin');
     }
 
     if (!mongoose.isValidObjectId(attemptId)) {
@@ -1176,9 +1181,7 @@ router.post('/test-record', authMiddleware, async (req, res) => {
     const now = Date.now();
 
     if (!Number.isFinite(expiresAt.getTime()) || expiresAt.getTime() < now) {
-      attemptAny.status = 'expired';
-      await attempt.save();
-      return res.status(410).json({ message: INVALID_CREDENTIAL_MESSAGE });
+      finalRiskFlags.push('attempt_expired');
     }
 
     if (attemptAny.status !== 'active') {
@@ -1196,7 +1199,7 @@ router.post('/test-record', authMiddleware, async (req, res) => {
       const elapsedSeconds = Math.max(0, (lastSubmittedAtMs - issuedAt.getTime()) / 1000);
       const minimumSeconds = Math.max(2, attemptAny.questionTokens.length * MIN_SECONDS_PER_QUESTION);
       if (elapsedSeconds < minimumSeconds) {
-        return res.status(400).json({ message: INVALID_CREDENTIAL_MESSAGE });
+        finalRiskFlags.push('too_fast');
       }
     }
 
@@ -1221,6 +1224,7 @@ router.post('/test-record', authMiddleware, async (req, res) => {
     const totalWords = evaluatedResults.length;
     const originallyCorrectWords = evaluatedResults.filter(result => result.isCorrect).length;
     const batchRiskFlags = [
+      ...finalRiskFlags,
       ...(isMultipleChoiceAttempt ? [] : analyzeBatchRisk(attemptAny.answerDurations || [])),
       ...analyzeVocabularyAttemptResultRisk({
         testType: attemptAny.testType,
diff --git a/server/utils/vocabularyRisk.ts b/server/utils/vocabularyRisk.ts
index 7d11976..09653cf 100644
--- a/server/utils/vocabularyRisk.ts
+++ b/server/utils/vocabularyRisk.ts
@@ -4,8 +4,16 @@ export const DEFAULT_VOCABULARY_FULL_CORRECT_WORD_THRESHOLD = 50;
 export const VOCABULARY_FULL_CORRECT_RISK_FLAG = 'large_batch_all_correct';
 
 export const INVALIDATING_VOCABULARY_RISK_FLAGS: string[] = [
+  'invalid_origin',
+  'invalid_answer_proof',
+  'invalid_question_token',
+  'invalid_option_token',
+  'invalid_submitted_at',
+  'submitted_at_out_of_sync',
+  'attempt_expired',
   'too_fast',
   'too_slow',
+  'missing_choice_interaction',
   'missing_input_value_trace',
   'input_value_mismatch',
   'uniform_answer_intervals',
diff --git a/src/components/VocabularyStudy.tsx b/src/components/VocabularyStudy.tsx
index a1d9b87..6ca4cc9 100644
--- a/src/components/VocabularyStudy.tsx
+++ b/src/components/VocabularyStudy.tsx
@@ -619,7 +619,7 @@ const VocabularyStudy: React.FC = () => {
       ));
       setUserAnswer(response.optionToken);
     } catch (error) {
-      message.error(INVALID_CREDENTIAL_MESSAGE);
+      setUserAnswer(option.text);
     }
   };
 
@@ -647,7 +647,10 @@ const VocabularyStudy: React.FC = () => {
       answerSubmittingRef.current = false;
       return;
     }
-    if (testType === 'multiple-choice' && options.length > 0 && options.every(option => option.token !== normalizedUserAnswer)) {
+    const isKnownMultipleChoiceAnswer = options.some(option =>
+      option.token === normalizedUserAnswer || option.text === normalizedUserAnswer
+    );
+    if (testType === 'multiple-choice' && options.length > 0 && !isKnownMultipleChoiceAnswer) {
       answerSubmittingRef.current = false;
       message.warning('请选择一个选项后再提交');
       return;