diff --git a/backend/internal/middleware/rate_limiter.go b/backend/internal/middleware/rate_limiter.go
index 13b71683..819d74c2 100644
--- a/backend/internal/middleware/rate_limiter.go
+++ b/backend/internal/middleware/rate_limiter.go
@@ -2,7 +2,10 @@ package middleware
 
 import (
 	"context"
+	"fmt"
+	"log"
 	"net/http"
+	"strconv"
 	"time"
 
 	"github.com/gin-gonic/gin"
@@ -25,15 +28,34 @@ type RateLimitOptions struct {
 var rateLimitScript = redis.NewScript(`
 local current = redis.call('INCR', KEYS[1])
 local ttl = redis.call('PTTL', KEYS[1])
-if current == 1 or ttl == -1 then
+local repaired = 0
+if current == 1 then
   redis.call('PEXPIRE', KEYS[1], ARGV[1])
+elseif ttl == -1 then
+  redis.call('PEXPIRE', KEYS[1], ARGV[1])
+  repaired = 1
 end
-return current
+return {current, repaired}
 `)
 
 // rateLimitRun 允许测试覆写脚本执行逻辑
-var rateLimitRun = func(ctx context.Context, client *redis.Client, key string, windowMillis int64) (int64, error) {
-	return rateLimitScript.Run(ctx, client, []string{key}, windowMillis).Int64()
+var rateLimitRun = func(ctx context.Context, client *redis.Client, key string, windowMillis int64) (int64, bool, error) {
+	values, err := rateLimitScript.Run(ctx, client, []string{key}, windowMillis).Slice()
+	if err != nil {
+		return 0, false, err
+	}
+	if len(values) < 2 {
+		return 0, false, fmt.Errorf("rate limit script returned %d values", len(values))
+	}
+	count, err := parseInt64(values[0])
+	if err != nil {
+		return 0, false, err
+	}
+	repaired, err := parseInt64(values[1])
+	if err != nil {
+		return 0, false, err
+	}
+	return count, repaired == 1, nil
 }
 
 // RateLimiter Redis 速率限制器
@@ -74,8 +96,9 @@ func (r *RateLimiter) LimitWithOptions(key string, limit int, window time.Durati
 		windowMillis := windowTTLMillis(window)
 
 		// 使用 Lua 脚本原子操作增加计数并设置过期
-		count, err := rateLimitRun(ctx, r.redis, redisKey, windowMillis)
+		count, repaired, err := rateLimitRun(ctx, r.redis, redisKey, windowMillis)
 		if err != nil {
+			log.Printf("[RateLimit] redis error: key=%s mode=%s err=%v", redisKey, failureModeLabel(failureMode), err)
 			if failureMode == RateLimitFailClose {
 				abortRateLimit(c)
 				return
@@ -84,6 +107,9 @@ func (r *RateLimiter) LimitWithOptions(key string, limit int, window time.Durati
 			c.Next()
 			return
 		}
+		if repaired {
+			log.Printf("[RateLimit] ttl repaired: key=%s window_ms=%d", redisKey, windowMillis)
+		}
 
 		// 超过限制
 		if count > int64(limit) {
@@ -109,3 +135,27 @@ func abortRateLimit(c *gin.Context) {
 		"message": "Too many requests, please try again later",
 	})
 }
+
+func failureModeLabel(mode RateLimitFailureMode) string {
+	if mode == RateLimitFailClose {
+		return "fail-close"
+	}
+	return "fail-open"
+}
+
+func parseInt64(value any) (int64, error) {
+	switch v := value.(type) {
+	case int64:
+		return v, nil
+	case int:
+		return int64(v), nil
+	case string:
+		parsed, err := strconv.ParseInt(v, 10, 64)
+		if err != nil {
+			return 0, err
+		}
+		return parsed, nil
+	default:
+		return 0, fmt.Errorf("unexpected value type %T", value)
+	}
+}
diff --git a/backend/internal/middleware/rate_limiter_test.go b/backend/internal/middleware/rate_limiter_test.go
index 7c72e5be..0c379c0f 100644
--- a/backend/internal/middleware/rate_limiter_test.go
+++ b/backend/internal/middleware/rate_limiter_test.go
@@ -66,13 +66,13 @@ func TestRateLimiterSuccessAndLimit(t *testing.T) {
 	originalRun := rateLimitRun
 	counts := []int64{1, 2}
 	callIndex := 0
-	rateLimitRun = func(ctx context.Context, client *redis.Client, key string, windowMillis int64) (int64, error) {
+	rateLimitRun = func(ctx context.Context, client *redis.Client, key string, windowMillis int64) (int64, bool, error) {
 		if callIndex >= len(counts) {
-			return counts[len(counts)-1], nil
+			return counts[len(counts)-1], false, nil
 		}
 		value := counts[callIndex]
 		callIndex++
-		return value, nil
+		return value, false, nil
 	}
 	t.Cleanup(func() {
 		rateLimitRun = originalRun