diff --git a/backend/services/daily_volume.go b/backend/services/daily_volume.go
index 76a2793..3fe1b51 100644
--- a/backend/services/daily_volume.go
+++ b/backend/services/daily_volume.go
@@ -301,24 +301,49 @@ func CaptureRecentDailyVolumes() {
 	pruneDailyVolumeSnapshots()
 }
 
-// pruneDailyVolumeSnapshots 丢弃超过保留期的历史。
+// pruneDailyVolumeSnapshots 丢弃超过保留期的历史，并修正历史遗留的 partial 标记。
 func pruneDailyVolumeSnapshots() {
 	db := repository.GetDB()
 	if db == nil {
 		return
 	}
 	cutoff := dateKey(time.Now().AddDate(0, 0, -dailyVolumeRetentionDays))
+	today := dateKey(time.Now())
 	db.Lock()
 	defer db.Unlock()
+	changed := false
 	kept := make([]models.DailyVolumeSnapshot, 0, len(db.DailyVolumeSnapshots))
 	for _, snap := range db.DailyVolumeSnapshots {
-		if snap.Date >= cutoff {
-			kept = append(kept, snap)
+		if snap.Date < cutoff {
+			continue
 		}
+		kept = append(kept, snap)
 	}
 	if len(kept) != len(db.DailyVolumeSnapshots) {
 		log.Printf("[daily-volume] 清理过期快照 %d 条", len(db.DailyVolumeSnapshots)-len(kept))
 		db.DailyVolumeSnapshots = kept
+		changed = true
+	}
+
+	// 历史遗留修正：**过去的天不可能"还在进行中"**。
+	// 早期版本把「起点超出 24h」也当成 partial，于是昨天/前天的柱子一直是虚线空心，
+	// 看起来像"每天都在采样中"。只有当快照是在那天**结束之后**才抓的
+	// （说明抓的是完整一天）才改成完整；当天中途抓到的继续保持 partial —— 那时确实只有半天。
+	for i := range db.DailyVolumeSnapshots {
+		snap := &db.DailyVolumeSnapshots[i]
+		if !snap.Partial || snap.Date >= today {
+			continue
+		}
+		day, err := time.ParseInLocation("2006-01-02", snap.Date, time.Local)
+		if err != nil {
+			continue
+		}
+		if _, dayEnd := dayRange(day); snap.CapturedAt.UnixNano() >= dayEnd {
+			snap.Partial = false
+			changed = true
+		}
+	}
+	if changed {
 		db.RequestSave()
 	}
 }
diff --git a/backend/services/daily_volume_test.go b/backend/services/daily_volume_test.go
new file mode 100644
index 0000000..efac0bb
--- /dev/null
+++ b/backend/services/daily_volume_test.go
@@ -0,0 +1,136 @@
+package services
+
+import (
+	"testing"
+	"time"
+
+	"lokistack/models"
+	"lokistack/repository"
+)
+
+func setupDailyVolumeDB(t *testing.T) {
+	t.Helper()
+	t.Setenv("DATA_DIR", t.TempDir())
+	t.Setenv("JWT_SECRET", "test-jwt-secret-with-at-least-32-characters")
+	t.Setenv("ENCRYPTION_KEY", "test-encryption-key-with-at-least-32-characters")
+	if err := repository.InitDB(); err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = repository.Shutdown() })
+}
+
+func snapshotsByDate(t *testing.T) map[string]models.DailyVolumeSnapshot {
+	t.Helper()
+	got := map[string]models.DailyVolumeSnapshot{}
+	db := repository.GetDB()
+	db.RLock()
+	defer db.RUnlock()
+	for _, snap := range db.DailyVolumeSnapshots {
+		got[snap.Date] = snap
+	}
+	return got
+}
+
+// 过去的天不可能"还在进行中"：只有在那天结束之后才抓的快照才算完整一天，
+// 当天中途抓到的必须保持 partial —— 否则会把"只抓到半天"伪装成完整数据。
+func TestPruneDailyVolumeNormalizesPartialAndDropsExpired(t *testing.T) {
+	setupDailyVolumeDB(t)
+	now := time.Now()
+	midday := func(d time.Time) time.Time {
+		return time.Date(d.Year(), d.Month(), d.Day(), 12, 0, 0, 0, time.Local)
+	}
+	yesterday := now.AddDate(0, 0, -1)
+	dayBefore := now.AddDate(0, 0, -2)
+	expired := now.AddDate(0, 0, -(dailyVolumeRetentionDays + 5))
+
+	db := repository.GetDB()
+	db.Lock()
+	db.DailyVolumeSnapshots = []models.DailyVolumeSnapshot{
+		// 昨天结束之后（次日 12:00）抓的 → 完整一天
+		{ID: 1, Date: dateKey(yesterday), SourceID: 1, Bytes: 100, Entries: 7,
+			Partial: true, CapturedAt: midday(now)},
+		// 前天中午抓的 → 只有半天，保持 partial
+		{ID: 2, Date: dateKey(dayBefore), SourceID: 1, Bytes: 50,
+			Partial: true, CapturedAt: midday(dayBefore)},
+		// 今天 → 永远 partial
+		{ID: 3, Date: dateKey(now), SourceID: 1, Bytes: 10, Partial: true},
+		// 超过留存期 → 必须被清理
+		{ID: 4, Date: dateKey(expired), SourceID: 1, Bytes: 999},
+	}
+	db.Unlock()
+
+	pruneDailyVolumeSnapshots()
+
+	got := snapshotsByDate(t)
+	if _, ok := got[dateKey(expired)]; ok {
+		t.Error("超过留存期的快照没有被清理")
+	}
+	if snap := got[dateKey(yesterday)]; snap.Partial {
+		t.Error("昨天结束之后抓的快照应标记为完整（partial=false）")
+	}
+	if snap := got[dateKey(dayBefore)]; !snap.Partial {
+		t.Error("当天中途抓的快照必须保持 partial=true")
+	}
+	if snap := got[dateKey(now)]; !snap.Partial {
+		t.Error("今天必须保持 partial=true")
+	}
+	if snap := got[dateKey(yesterday)]; snap.Entries != 7 {
+		t.Errorf("条数不应被清理流程清空，得到 %d", snap.Entries)
+	}
+}
+
+// 刷新体积不能把已经抓到的条数（贵、每天最多 3 次）冲掉。
+func TestUpsertVolumeSnapshotKeepsEntries(t *testing.T) {
+	setupDailyVolumeDB(t)
+
+	db := repository.GetDB()
+	db.Lock()
+	db.DailyVolumeSnapshots = []models.DailyVolumeSnapshot{
+		{ID: 1, Date: "2026-10-01", SourceID: 1, Bytes: 111, Entries: 42, Partial: true},
+	}
+	db.Unlock()
+
+	if err := upsertVolumeSnapshot(1, "2026-10-01", 1000, false); err != nil {
+		t.Fatal(err)
+	}
+	got := snapshotsByDate(t)["2026-10-01"]
+	if got.Bytes != 1000 || got.Entries != 42 || got.Partial {
+		t.Fatalf("更新后 bytes=%d entries=%d partial=%v；期望 1000/42/false", got.Bytes, got.Entries, got.Partial)
+	}
+
+	if err := upsertVolumeSnapshot(1, "2026-10-02", 2000, true); err != nil {
+		t.Fatal(err)
+	}
+	if got := snapshotsByDate(t); len(got) != 2 {
+		t.Fatalf("新增一天后应有 2 条快照，得到 %d", len(got))
+	}
+}
+
+// 接口必须始终返回 days 个点，缺的标 Missing（"不知道"），绝不伪造 0（"确实没日志"）。
+func TestGetDailyVolumeHistoryReturnsAllDaysWithMissing(t *testing.T) {
+	setupDailyVolumeDB(t)
+	now := time.Now()
+
+	db := repository.GetDB()
+	db.Lock()
+	db.DailyVolumeSnapshots = []models.DailyVolumeSnapshot{
+		{ID: 1, Date: dateKey(now), SourceID: 1, Bytes: 123, Partial: true},
+		{ID: 2, Date: dateKey(now), SourceID: 2, Bytes: 999}, // 别的数据源，不应混进来
+	}
+	db.Unlock()
+
+	points := GetDailyVolumeHistory(1, 7)
+	if len(points) != 7 {
+		t.Fatalf("期望 7 个点，得到 %d", len(points))
+	}
+	today := points[len(points)-1]
+	if today.Missing || today.Bytes != 123 || !today.Partial {
+		t.Errorf("今天应命中快照：missing=%v bytes=%d partial=%v", today.Missing, today.Bytes, today.Partial)
+	}
+	for i := 0; i < len(points)-1; i++ {
+		if !points[i].Missing || points[i].Bytes != 0 {
+			t.Errorf("%s 应标记 Missing 且 bytes=0，得到 missing=%v bytes=%d",
+				points[i].Date, points[i].Missing, points[i].Bytes)
+		}
+	}
+}