diff --git a/backend/cmd/server/main.go b/backend/cmd/server/main.go
index 06d0cfb..f77bbad 100644
--- a/backend/cmd/server/main.go
+++ b/backend/cmd/server/main.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"fmt"
 	"log"
 	"net/http"
@@ -9,6 +10,7 @@ import (
 	"strings"
 
 	"sql-platform/config"
+	"sql-platform/internal/handler"
 	"sql-platform/internal/middleware"
 	"sql-platform/internal/model"
 	"sql-platform/router"
@@ -75,8 +77,13 @@ func main() {
 	config.EnsureJWTSecret()
 
 	// Setup Gin
-	r := gin.Default()
-	r.Use(middleware.CORSMiddleware())
+	//
+	// 用 gin.New() 而不是 gin.Default()：Default 自带的是文本格式的 gin.Logger()，
+	// 这里换成结构化 JSON 访问日志（middleware.AccessLog），便于 Promtail→Loki 按字段过滤，
+	// 同时跳过健康检查/静态资源，避免探针轮询把日志量刷满。
+	// Recovery 必须显式加回来（Default 里包含它），否则 panic 会打挂整个进程。
+	r := gin.New()
+	r.Use(middleware.AccessLog(), gin.Recovery(), middleware.CORSMiddleware())
 
 	// Health check
 	r.GET("/health", func(c *gin.Context) {
@@ -86,6 +93,11 @@ func main() {
 	// Routes
 	router.Setup(r)
 
+	// 后台保留期清理：启动 2 分钟后跑第一次，之后每 24h 一次。
+	// 解决「只配了保留天数但没人执行」的问题 —— 之前审计日志/查询历史
+	// 只能靠管理员手动点「立即清理」，表会一直涨、SQLite 文件也不会缩。
+	handler.StartCleanupScheduler(context.Background())
+
 	// 单镜像部署:直接托管前端产物(DIST_DIR 为空则跳过,开发模式由 vite 独立提供)
 	if distDir := os.Getenv("DIST_DIR"); distDir != "" {
 		indexPath := filepath.Join(distDir, "index.html")
@@ -145,6 +157,10 @@ func seedDefaultSettings(db *gorm.DB) {
 		{Key: "audit_log_retention_days", Value: "365", ValueType: "number", Group: "cleanup", Label: "审计日志保留天数", Desc: strPtr("超过此天数的审计日志将被清理"), DefaultValue: strPtr("365"), SortOrder: 2},
 		{Key: "query_history_retention_days", Value: "90", ValueType: "number", Group: "cleanup", Label: "查询历史保留天数", Desc: strPtr("超过此天数的查询历史将被清理"), DefaultValue: strPtr("90"), SortOrder: 3},
 		{Key: "slow_log_retention_days", Value: "180", ValueType: "number", Group: "cleanup", Label: "慢日志保留天数", Desc: strPtr("超过此天数的慢查询日志将被清理"), DefaultValue: strPtr("180"), SortOrder: 4},
+		{Key: "operation_log_retention_days", Value: "365", ValueType: "number", Group: "cleanup", Label: "操作日志保留天数", Desc: strPtr("超过此天数的操作日志将被清理"), DefaultValue: strPtr("365"), SortOrder: 5},
+		{Key: "workflow_log_retention_days", Value: "180", ValueType: "number", Group: "cleanup", Label: "工单流程日志保留天数", Desc: strPtr("超过此天数的工单流程执行日志将被清理"), DefaultValue: strPtr("180"), SortOrder: 6},
+		{Key: "scheduled_log_retention_days", Value: "180", ValueType: "number", Group: "cleanup", Label: "定时任务日志保留天数", Desc: strPtr("超过此天数的定时任务执行日志将被清理"), DefaultValue: strPtr("180"), SortOrder: 7},
+		{Key: "cleanup_auto_enabled", Value: "true", ValueType: "boolean", Group: "cleanup", Label: "自动清理", Desc: strPtr("每天自动按上面的保留天数清理一次；关闭后仍可在本页点「立即清理」"), DefaultValue: strPtr("true"), SortOrder: 99},
 
 		// ── 执行器 ──
 		{Key: "executor_timeout", Value: "300", ValueType: "number", Group: "executor", Label: "执行超时(秒)", Desc: strPtr("工单中 SQL 语句执行的最大等待时间"), DefaultValue: strPtr("300"), SortOrder: 1},
diff --git a/backend/internal/handler/cleanup.go b/backend/internal/handler/cleanup.go
new file mode 100644
index 0000000..bfea43d
--- /dev/null
+++ b/backend/internal/handler/cleanup.go
@@ -0,0 +1,219 @@
+package handler
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"sql-platform/internal/middleware"
+	"sql-platform/internal/model"
+)
+
+// 保留期清理任务的调参。设计取舍：
+//   - 分批删（每批 5000）而不是一条 DELETE 全删：SQLite 是单写者，
+//     大事务会把整个库锁住，前端所有请求都会排队等锁。
+//   - 单表单轮最多删 20 万行：极端情况下（比如首次清理积压半年的审计日志），
+//     剩下的留给下一轮或手动跑，避免一次任务跑太久。
+//   - 删完看 freelist 比例决定要不要 VACUUM：SQLite 的 DELETE 只把页标记为空闲，
+//     文件不会自动变小，必须 VACUUM 才真正归还磁盘。
+const (
+	cleanupBatchSize   = 5000
+	cleanupMaxPerTable = 200000
+	cleanupInterval    = 24 * time.Hour
+	cleanupFirstDelay  = 2 * time.Minute
+	vacuumFreeRatio    = 0.25
+)
+
+// retentionRule 一条「按时间列保留 N 天」的清理规则
+type retentionRule struct {
+	Table   string
+	TimeCol string
+	DaysKey string // system_settings 里对应的保留天数 key
+	Default int
+}
+
+// 会无限增长的表清单。tickets 不在这里（要按状态过滤，单独处理）。
+var retentionRules = []retentionRule{
+	{"audit_logs", "created_at", "audit_log_retention_days", 365},
+	{"query_histories", "created_at", "query_history_retention_days", 90},
+	{"slow_logs", "created_at", "slow_log_retention_days", 180},
+	{"operation_logs", "created_at", "operation_log_retention_days", 365},
+	{"workflow_execution_logs", "created_at", "workflow_log_retention_days", 180},
+	{"scheduled_task_logs", "started_at", "scheduled_log_retention_days", 180},
+}
+
+// deleteInBatches 分批删除，返回实际删除行数。
+//
+// 用 `DELETE ... WHERE id IN (SELECT id ... LIMIT n)` 而不是 GORM 的 Delete：
+// GORM 不支持 Limit，一次性删会生成超大事务。
+func deleteInBatches(table, where string, args []any, maxRows int64) int64 {
+	var total int64
+	for total < maxRows {
+		params := make([]any, 0, len(args)+1)
+		params = append(params, args...)
+		params = append(params, cleanupBatchSize)
+
+		res := model.DB.Exec(
+			fmt.Sprintf("DELETE FROM %s WHERE id IN (SELECT id FROM %s WHERE %s LIMIT ?)",
+				table, table, where),
+			params...,
+		)
+		if res.Error != nil {
+			middleware.LogJSON(map[string]any{
+				"ts": time.Now().Format(time.RFC3339Nano), "level": "error", "type": "cleanup",
+				"msg": "删除失败", "table": table, "error": res.Error.Error(),
+			})
+			break
+		}
+		if res.RowsAffected == 0 {
+			break
+		}
+		total += res.RowsAffected
+		time.Sleep(50 * time.Millisecond) // 让出写锁，避免饿死业务请求
+	}
+	return total
+}
+
+// RunRetentionCleanup 执行一轮清理，返回 {表名: 删除行数}
+func RunRetentionCleanup() map[string]int64 {
+	now := time.Now()
+	deleted := map[string]int64{}
+
+	for _, r := range retentionRules {
+		days := getSettingInt(r.DaysKey, r.Default)
+		if days <= 0 {
+			continue // <=0 视为不清理，避免误配把数据全删
+		}
+		cutoff := now.AddDate(0, 0, -days)
+		n := deleteInBatches(r.Table, r.TimeCol+" < ?", []any{cutoff}, cleanupMaxPerTable)
+		if n > 0 {
+			deleted[r.Table] = n
+		}
+	}
+
+	// 工单：只删终态（success/failed/closed/rejected），进行中的不能动
+	ticketDays := getSettingInt("ticket_retention_days", 180)
+	if ticketDays > 0 {
+		n := deleteInBatches("tickets",
+			"status IN ('success','failed','closed','rejected') AND create_time < ?",
+			[]any{now.AddDate(0, 0, -ticketDays)}, cleanupMaxPerTable)
+		if n > 0 {
+			deleted["tickets"] = n
+		}
+	}
+
+	// 刷新令牌：过期/已吊销的直接清掉（按时间点，不是保留天数）
+	// 不清的话每次登录都会新增一行，永远不减少。
+	n := deleteInBatches("refresh_tokens", "expires_at < ?", []any{now}, 100000)
+	if n > 0 {
+		deleted["refresh_tokens"] = n
+	}
+
+	return deleted
+}
+
+// CleanupPreview 返回各表「按当前保留策略会被删掉多少行」
+func CleanupPreview() map[string]any {
+	now := time.Now()
+	out := map[string]any{}
+	count := func(table, where string, args ...any) int64 {
+		var n int64
+		model.DB.Raw(fmt.Sprintf("SELECT COUNT(*) FROM %s WHERE %s", table, where), args...).Scan(&n)
+		return n
+	}
+
+	for _, r := range retentionRules {
+		days := getSettingInt(r.DaysKey, r.Default)
+		out[r.Table] = map[string]any{
+			"days":  days,
+			"count": count(r.Table, r.TimeCol+" < ?", now.AddDate(0, 0, -days)),
+		}
+	}
+	ticketDays := getSettingInt("ticket_retention_days", 180)
+	out["tickets"] = map[string]any{
+		"days":  ticketDays,
+		"count": count("tickets", "status IN ('success','failed','closed','rejected') AND create_time < ?", now.AddDate(0, 0, -ticketDays)),
+	}
+	out["refresh_tokens"] = map[string]any{
+		"days":  0,
+		"count": count("refresh_tokens", "expires_at < ?", now),
+	}
+	return out
+}
+
+// VacuumIfNeeded 空闲页占比超过阈值时执行 VACUUM 回收磁盘，返回 (是否执行, 释放字节数)
+func VacuumIfNeeded() (bool, int64) {
+	var pageCount, freeList, pageSize int64
+	model.DB.Raw("PRAGMA page_count").Scan(&pageCount)
+	model.DB.Raw("PRAGMA freelist_count").Scan(&freeList)
+	model.DB.Raw("PRAGMA page_size").Scan(&pageSize)
+	if pageCount <= 0 || pageSize <= 0 {
+		return false, 0
+	}
+	if float64(freeList)/float64(pageCount) < vacuumFreeRatio {
+		return false, 0
+	}
+	before := pageCount * pageSize
+	if err := model.DB.Exec("VACUUM").Error; err != nil {
+		middleware.LogJSON(map[string]any{
+			"ts": time.Now().Format(time.RFC3339Nano), "level": "error", "type": "cleanup",
+			"msg": "VACUUM 失败", "error": err.Error(),
+		})
+		return false, 0
+	}
+	model.DB.Raw("PRAGMA page_count").Scan(&pageCount)
+	after := pageCount * pageSize
+	return true, before - after
+}
+
+// StartCleanupScheduler 启动后台清理：启动 2 分钟后跑一次，之后每 24h 一次。
+// 可通过系统设置 cleanup_auto_enabled=false 关掉（关掉后仍可手动点「立即清理」）。
+func StartCleanupScheduler(ctx context.Context) {
+	go func() {
+		select {
+		case <-time.After(cleanupFirstDelay):
+		case <-ctx.Done():
+			return
+		}
+		runScheduledCleanup()
+
+		ticker := time.NewTicker(cleanupInterval)
+		defer ticker.Stop()
+		for {
+			select {
+			case <-ticker.C:
+				runScheduledCleanup()
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+}
+
+func runScheduledCleanup() {
+	if getSetting("cleanup_auto_enabled", "true") != "true" {
+		return
+	}
+	start := time.Now()
+	deleted := RunRetentionCleanup()
+	vacuumed, freed := VacuumIfNeeded()
+
+	var total int64
+	for _, n := range deleted {
+		total += n
+	}
+	if total == 0 && !vacuumed {
+		return // 没什么可清的，不刷日志
+	}
+	middleware.LogJSON(map[string]any{
+		"ts":          time.Now().Format(time.RFC3339Nano),
+		"level":       "info",
+		"type":        "cleanup",
+		"msg":         "保留期清理完成",
+		"deleted":     deleted,
+		"total":       total,
+		"vacuumed":    vacuumed,
+		"freed_bytes": freed,
+		"cost_ms":     time.Since(start).Milliseconds(),
+	})
+}
diff --git a/backend/internal/handler/ghost.go b/backend/internal/handler/ghost.go
index 4595cbd..c291124 100644
--- a/backend/internal/handler/ghost.go
+++ b/backend/internal/handler/ghost.go
@@ -508,71 +508,33 @@ func UpdateSettings(c *gin.Context) {
 }
 
 // GET /api/v1/settings/cleanup/preview
+//
+// 统计口径统一收敛到 CleanupPreview()（handler/cleanup.go），
+// 与后台定时清理共用同一份规则表，避免「预览说有、真跑不删」这类漂移。
 func SettingsCleanupPreview(c *gin.Context) {
-	now := time.Now()
-	stats := gin.H{}
-
-	// Tickets
-	ticketDays := getSettingInt("ticket_retention_days", 180)
-	var ticketCount int64
-	model.DB.Model(&model.Ticket{}).
-		Where("status IN ? AND create_time < ?", []string{"success", "failed", "closed", "rejected"}, now.AddDate(0, 0, -ticketDays)).
-		Count(&ticketCount)
-	stats["tickets"] = gin.H{"days": ticketDays, "count": ticketCount}
-
-	// Query history
-	queryDays := getSettingInt("query_history_retention_days", 90)
-	var queryCount int64
-	model.DB.Model(&model.QueryHistory{}).
-		Where("created_at < ?", now.AddDate(0, 0, -queryDays)).
-		Count(&queryCount)
-	stats["query_history"] = gin.H{"days": queryDays, "count": queryCount}
-
-	// Slow logs
-	slowDays := getSettingInt("slow_log_retention_days", 180)
-	var slowCount int64
-	model.DB.Model(&model.SlowLog{}).
-		Where("created_at < ?", now.AddDate(0, 0, -slowDays)).
-		Count(&slowCount)
-	stats["slow_logs"] = gin.H{"days": slowDays, "count": slowCount}
-
-	// Audit logs — skip if no AuditLog model; use raw SQL
-	auditDays := getSettingInt("audit_log_retention_days", 365)
-	var auditCount int64
-	model.DB.Raw("SELECT COUNT(*) FROM audit_logs WHERE created_at < ?", now.AddDate(0, 0, -auditDays)).Scan(&auditCount)
-	stats["audit_logs"] = gin.H{"days": auditDays, "count": auditCount}
-
-	c.JSON(http.StatusOK, stats)
+	c.JSON(http.StatusOK, CleanupPreview())
 }
 
 // POST /api/v1/settings/cleanup/run
+//
+// 手动触发：与后台定时任务走同一套分批删除 + VACUUM 逻辑。
 func SettingsCleanupRun(c *gin.Context) {
-	now := time.Now()
-	stats := gin.H{}
+	start := time.Now()
+	deleted := RunRetentionCleanup()
+	vacuumed, freed := VacuumIfNeeded()
 
-	// Tickets
-	ticketDays := getSettingInt("ticket_retention_days", 180)
-	ticketResult := model.DB.Where("status IN ? AND create_time < ?",
-		[]string{"success", "failed", "closed", "rejected"}, now.AddDate(0, 0, -ticketDays)).
-		Delete(&model.Ticket{})
-	stats["tickets_deleted"] = ticketResult.RowsAffected
-
-	// Query history
-	queryDays := getSettingInt("query_history_retention_days", 90)
-	queryResult := model.DB.Where("created_at < ?", now.AddDate(0, 0, -queryDays)).Delete(&model.QueryHistory{})
-	stats["query_history_deleted"] = queryResult.RowsAffected
-
-	// Slow logs
-	slowDays := getSettingInt("slow_log_retention_days", 180)
-	slowResult := model.DB.Where("created_at < ?", now.AddDate(0, 0, -slowDays)).Delete(&model.SlowLog{})
-	stats["slow_logs_deleted"] = slowResult.RowsAffected
-
-	// Audit logs
-	auditDays := getSettingInt("audit_log_retention_days", 365)
-	auditResult := model.DB.Exec("DELETE FROM audit_logs WHERE created_at < ?", now.AddDate(0, 0, -auditDays))
-	stats["audit_logs_deleted"] = auditResult.RowsAffected
-
-	c.JSON(http.StatusOK, gin.H{"message": "Cleanup completed", "stats": stats})
+	var total int64
+	for _, n := range deleted {
+		total += n
+	}
+	c.JSON(http.StatusOK, gin.H{
+		"message":     "Cleanup completed",
+		"deleted":     deleted,
+		"total":       total,
+		"vacuumed":    vacuumed,
+		"freed_bytes": freed,
+		"cost_ms":     time.Since(start).Milliseconds(),
+	})
 }
 
 // GET /api/v1/notifications/channels
diff --git a/backend/internal/middleware/accesslog.go b/backend/internal/middleware/accesslog.go
new file mode 100644
index 0000000..4f221f4
--- /dev/null
+++ b/backend/internal/middleware/accesslog.go
@@ -0,0 +1,134 @@
+package middleware
+
+import (
+	"bytes"
+	"encoding/json"
+	"os"
+	"sort"
+	"strings"
+	"time"
+
+	"github.com/gin-gonic/gin"
+)
+
+// LogJSON 输出一行 JSON 到标准输出（stdout）。
+//
+// 统一走 stdout 的原因：容器里日志由容器运行时接管（kubelet 侧
+// containerLogMaxSize=10Mi / containerLogMaxFiles=5 自动轮转），
+// 应用自己写文件会绕过这套轮转、把磁盘写爆。
+//
+// 关键细节：Go 的 map 序列化是**按 key 字母序**输出，ts 会排到最后，
+// kubectl logs 里一行以 {"bytes":... 开头完全看不出时间。
+// 这里手工拼装，把 ts/level/type/msg 固定在最前面，其余字段排序输出。
+func LogJSON(fields map[string]any) {
+	head := []string{"ts", "level", "type", "msg"}
+
+	var buf bytes.Buffer
+	buf.WriteByte('{')
+	first := true
+	write := func(k string) {
+		v, ok := fields[k]
+		if !ok {
+			return
+		}
+		kb, err := json.Marshal(k)
+		if err != nil {
+			return
+		}
+		vb, err := json.Marshal(v)
+		if err != nil {
+			return
+		}
+		if !first {
+			buf.WriteByte(',')
+		}
+		buf.Write(kb)
+		buf.WriteByte(':')
+		buf.Write(vb)
+		first = false
+	}
+	for _, k := range head {
+		write(k)
+	}
+	rest := make([]string, 0, len(fields))
+	for k := range fields {
+		switch k {
+		case "ts", "level", "type", "msg":
+			continue
+		}
+		rest = append(rest, k)
+	}
+	sort.Strings(rest)
+	for _, k := range rest {
+		write(k)
+	}
+	buf.WriteString("}\n")
+
+	_, _ = os.Stdout.Write(buf.Bytes())
+}
+
+// AccessLog 结构化访问日志，替代 gin.Default() 自带的文本 Logger。
+//
+// 与 gin.Logger() 的差异：
+//   - 一行一个 JSON 对象，字段可直接在 Loki 里过滤（status>=500、latency_ms>1000）
+//   - 按状态码自动分级：5xx=error / 4xx=warn / 其余=info
+//   - 健康检查与静态资源不打日志（K8s 探针每 10s 一次，纯噪音）
+func AccessLog() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		start := time.Now()
+		path := c.Request.URL.Path
+
+		c.Next()
+
+		if isQuietPath(path) {
+			return
+		}
+
+		status := c.Writer.Status()
+		level := "info"
+		switch {
+		case status >= 500:
+			level = "error"
+		case status >= 400:
+			level = "warn"
+		}
+
+		entry := map[string]any{
+			"ts":         time.Now().Format(time.RFC3339Nano),
+			"level":      level,
+			"type":       "access",
+			"method":     c.Request.Method,
+			"path":       path,
+			"status":     status,
+			"latency_ms": float64(time.Since(start).Microseconds()) / 1000.0,
+			"bytes":      c.Writer.Size(),
+			"ip":         c.ClientIP(),
+		}
+		if q := c.Request.URL.RawQuery; q != "" {
+			entry["query"] = q
+		}
+		if ua := c.Request.UserAgent(); ua != "" {
+			entry["ua"] = ua
+		}
+		// 鉴权中间件把用户信息放在 context 里，日志带上便于审计
+		if uid, ok := c.Get("userId"); ok {
+			entry["user_id"] = uid
+		}
+		if uname, ok := c.Get("username"); ok {
+			entry["username"] = uname
+		}
+		if len(c.Errors) > 0 {
+			entry["error"] = c.Errors.String()
+		}
+		LogJSON(entry)
+	}
+}
+
+// isQuietPath 探针/静态资源不记访问日志，避免日志量被轮询请求淹没
+func isQuietPath(p string) bool {
+	switch p {
+	case "/health", "/api/v1/health", "/favicon.ico", "/favicon.svg", "/robots.txt":
+		return true
+	}
+	return strings.HasPrefix(p, "/assets/")
+}