diff --git a/internal/store/host_repo_stats_history.go b/internal/store/host_repo_stats_history.go
new file mode 100644
index 0000000..79a1433
--- /dev/null
+++ b/internal/store/host_repo_stats_history.go
@@ -0,0 +1,98 @@
+package store
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"fmt"
+	"time"
+)
+
+// RepoStatsHistoryPoint is one (day, host) point for the trend chart.
+// Both metric pointers may be nil — a row exists as soon as either
+// metric was reported on that day.
+type RepoStatsHistoryPoint struct {
+	Day            time.Time // 00:00:00 UTC
+	TotalSizeBytes *int64
+	SnapshotCount  *int64
+}
+
+// UpsertHostRepoStatsHistory records the metrics carried by a
+// repo.stats patch into the daily history table. Only the non-nil
+// fields of patch.TotalSizeBytes / patch.SnapshotCount are written;
+// existing values in the row are preserved via COALESCE so a
+// prune-only or check-only patch does not null out a backup-time
+// size we already captured earlier the same day.
+func (s *Store) UpsertHostRepoStatsHistory(
+	ctx context.Context, hostID, day string, patch HostRepoStats, recordedAt time.Time,
+) error {
+	_, err := s.db.ExecContext(ctx, `
+		INSERT INTO host_repo_stats_history
+		  (host_id, day, total_size_bytes, snapshot_count, recorded_at)
+		VALUES (?, ?, ?, ?, ?)
+		ON CONFLICT(host_id, day) DO UPDATE SET
+		  total_size_bytes = COALESCE(excluded.total_size_bytes, host_repo_stats_history.total_size_bytes),
+		  snapshot_count   = COALESCE(excluded.snapshot_count,   host_repo_stats_history.snapshot_count),
+		  recorded_at      = excluded.recorded_at`,
+		hostID, day,
+		nullableInt64(patch.TotalSizeBytes),
+		nullableInt64(patch.SnapshotCount),
+		recordedAt.UTC().Format(time.RFC3339Nano),
+	)
+	if err != nil {
+		return fmt.Errorf("store: upsert host_repo_stats_history: %w", err)
+	}
+	return nil
+}
+
+// ListHostRepoStatsHistory returns all points for hostID with day
+// >= since (UTC), ordered ascending. Pass time.Time{} to fetch the
+// full history.
+func (s *Store) ListHostRepoStatsHistory(
+	ctx context.Context, hostID string, since time.Time,
+) ([]RepoStatsHistoryPoint, error) {
+	sinceStr := ""
+	if !since.IsZero() {
+		sinceStr = since.UTC().Format("2006-01-02")
+	}
+	rows, err := s.db.QueryContext(ctx, `
+		SELECT day, total_size_bytes, snapshot_count
+		FROM host_repo_stats_history
+		WHERE host_id = ? AND day >= ?
+		ORDER BY day ASC`,
+		hostID, sinceStr)
+	if err != nil {
+		return nil, fmt.Errorf("store: list host_repo_stats_history: %w", err)
+	}
+	defer func() { _ = rows.Close() }()
+
+	var out []RepoStatsHistoryPoint
+	for rows.Next() {
+		var (
+			dayStr  string
+			total   sql.NullInt64
+			snapCnt sql.NullInt64
+		)
+		if err := rows.Scan(&dayStr, &total, &snapCnt); err != nil {
+			return nil, fmt.Errorf("store: scan history row: %w", err)
+		}
+		d, perr := time.Parse("2006-01-02", dayStr)
+		if perr != nil {
+			return nil, fmt.Errorf("store: parse history day %q: %w", dayStr, perr)
+		}
+		p := RepoStatsHistoryPoint{Day: d}
+		if total.Valid {
+			v := total.Int64
+			p.TotalSizeBytes = &v
+		}
+		if snapCnt.Valid {
+			v := snapCnt.Int64
+			p.SnapshotCount = &v
+		}
+		out = append(out, p)
+	}
+	if err := rows.Err(); err != nil && !errors.Is(err, sql.ErrNoRows) {
+		return nil, fmt.Errorf("store: iterate history rows: %w", err)
+	}
+	return out, nil
+}
diff --git a/internal/store/host_repo_stats_history_test.go b/internal/store/host_repo_stats_history_test.go
new file mode 100644
index 0000000..cd70b13
--- /dev/null
+++ b/internal/store/host_repo_stats_history_test.go
@@ -0,0 +1,120 @@
+package store
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+func TestHostRepoStatsHistory_PartialUpsertPreservesPriorValues(t *testing.T) {
+	t.Parallel()
+	s := openTestStore(t)
+	ctx := context.Background()
+
+	const hostID = "h-history-1"
+	seedHost(t, s, hostID)
+
+	day := "2026-05-07"
+	now := time.Now().UTC()
+
+	// 1. First write of the day: total_size only.
+	if err := s.UpsertHostRepoStatsHistory(ctx, hostID, day,
+		HostRepoStats{TotalSizeBytes: int64ptr(100)}, now); err != nil {
+		t.Fatalf("upsert 1: %v", err)
+	}
+
+	// 2. Second write: snapshot_count only — total_size MUST survive.
+	if err := s.UpsertHostRepoStatsHistory(ctx, hostID, day,
+		HostRepoStats{SnapshotCount: int64ptr(7)}, now.Add(time.Minute)); err != nil {
+		t.Fatalf("upsert 2: %v", err)
+	}
+
+	// 3. Third write: a prune-only patch (no size, no count). Both
+	//    prior values must survive.
+	if err := s.UpsertHostRepoStatsHistory(ctx, hostID, day,
+		HostRepoStats{}, now.Add(2*time.Minute)); err != nil {
+		t.Fatalf("upsert 3: %v", err)
+	}
+
+	pts, err := s.ListHostRepoStatsHistory(ctx, hostID, time.Time{})
+	if err != nil {
+		t.Fatalf("list: %v", err)
+	}
+	if len(pts) != 1 {
+		t.Fatalf("want 1 point, got %d", len(pts))
+	}
+	p := pts[0]
+	if p.TotalSizeBytes == nil || *p.TotalSizeBytes != 100 {
+		t.Errorf("TotalSizeBytes: want 100, got %v", p.TotalSizeBytes)
+	}
+	if p.SnapshotCount == nil || *p.SnapshotCount != 7 {
+		t.Errorf("SnapshotCount: want 7, got %v", p.SnapshotCount)
+	}
+}
+
+func TestHostRepoStatsHistory_OrderingAndSinceFilter(t *testing.T) {
+	t.Parallel()
+	s := openTestStore(t)
+	ctx := context.Background()
+
+	const hostID = "h-history-2"
+	seedHost(t, s, hostID)
+
+	now := time.Now().UTC()
+	for i, day := range []string{"2026-05-01", "2026-05-02", "2026-05-04", "2026-05-07"} {
+		v := int64(100 + i*10)
+		if err := s.UpsertHostRepoStatsHistory(ctx, hostID, day,
+			HostRepoStats{TotalSizeBytes: &v}, now); err != nil {
+			t.Fatalf("upsert %s: %v", day, err)
+		}
+	}
+
+	all, err := s.ListHostRepoStatsHistory(ctx, hostID, time.Time{})
+	if err != nil {
+		t.Fatalf("list all: %v", err)
+	}
+	if len(all) != 4 {
+		t.Fatalf("want 4 points, got %d", len(all))
+	}
+	wantDays := []string{"2026-05-01", "2026-05-02", "2026-05-04", "2026-05-07"}
+	for i, p := range all {
+		got := p.Day.Format("2006-01-02")
+		if got != wantDays[i] {
+			t.Errorf("point %d: want day %s, got %s", i, wantDays[i], got)
+		}
+	}
+
+	since, _ := time.Parse("2006-01-02", "2026-05-03")
+	recent, err := s.ListHostRepoStatsHistory(ctx, hostID, since)
+	if err != nil {
+		t.Fatalf("list since: %v", err)
+	}
+	if len(recent) != 2 {
+		t.Fatalf("since 2026-05-03: want 2 points, got %d", len(recent))
+	}
+}
+
+func TestHostRepoStatsHistory_CascadeOnHostDelete(t *testing.T) {
+	t.Parallel()
+	s := openTestStore(t)
+	ctx := context.Background()
+
+	const hostID = "h-history-3"
+	seedHost(t, s, hostID)
+	if err := s.UpsertHostRepoStatsHistory(ctx, hostID, "2026-05-07",
+		HostRepoStats{TotalSizeBytes: int64ptr(42)}, time.Now().UTC()); err != nil {
+		t.Fatalf("upsert: %v", err)
+	}
+
+	if err := s.DeleteHost(ctx, hostID); err != nil {
+		t.Fatalf("delete host: %v", err)
+	}
+
+	pts, err := s.ListHostRepoStatsHistory(ctx, hostID, time.Time{})
+	if err != nil {
+		t.Fatalf("list after delete: %v", err)
+	}
+	if len(pts) != 0 {
+		t.Fatalf("want 0 points after host delete, got %d", len(pts))
+	}
+}