diff --git a/server/internal/codes/paygrant.go b/server/internal/codes/paygrant.go
new file mode 100644
index 0000000..64b3a54
--- /dev/null
+++ b/server/internal/codes/paygrant.go
@@ -0,0 +1,31 @@
+package codes
+
+import (
+	"context"
+	"database/sql"
+	"encoding/json"
+	"fmt"
+	"time"
+)
+
+// GrantPaidSubscriptionTx 在调用方事务里执行支付驱动的订阅开通/续期。
+// 与兑换码走同一段叠加语义(applySubscription):同 plan 有活跃订阅则原地
+// 延长 max(expires,now)+days,否则新建 source='pay' 的一行。ref 为审计
+// 追踪串(如 "pay:<out_trade_no>"),审计写失败不影响事务(与兑换一致)。
+func (svc *Service) GrantPaidSubscriptionTx(
+	ctx context.Context, tx *sql.Tx, userID int64, plan PlanCode, days int, ref string,
+) (subID int64, expiresAt time.Time, err error) {
+	planID, err := svc.store.GetPlanIDTx(ctx, tx, plan)
+	if err != nil {
+		return 0, time.Time{}, err
+	}
+	subID, expiresAt, err = svc.applySubscription(ctx, tx, userID, planID, days, "pay")
+	if err != nil {
+		return 0, time.Time{}, err
+	}
+	meta, _ := json.Marshal(map[string]any{
+		"plan": string(plan), "duration_days": days, "sub_id": subID,
+	})
+	_ = svc.store.WriteAuditLog(ctx, tx, fmt.Sprintf("user:%d", userID), "pay_grant", ref, string(meta))
+	return subID, expiresAt, nil
+}
diff --git a/server/internal/codes/paygrant_sqlite_test.go b/server/internal/codes/paygrant_sqlite_test.go
new file mode 100644
index 0000000..1c67778
--- /dev/null
+++ b/server/internal/codes/paygrant_sqlite_test.go
@@ -0,0 +1,82 @@
+package codes_test
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/wangjia/pangolin/server/internal/codes"
+)
+
+// 新用户:GrantPaidSubscriptionTx 新建一行 source='pay',到期 = now+days。
+func TestGrantPaidSubscription_NewRow(t *testing.T) {
+	db := openMigratedSQLite(t)
+	seedUser(t, db, 1)
+	store := codes.NewStore(db)
+	svc := codes.NewService(store, nil, 5, time.Hour)
+	ctx := context.Background()
+
+	tx, err := store.BeginTx(ctx)
+	if err != nil {
+		t.Fatalf("BeginTx: %v", err)
+	}
+	subID, expiresAt, err := svc.GrantPaidSubscriptionTx(ctx, tx, 1, codes.PlanPro, 31, "order:test001")
+	if err != nil {
+		t.Fatalf("GrantPaidSubscriptionTx: %v", err)
+	}
+	if err := tx.Commit(); err != nil {
+		t.Fatalf("commit: %v", err)
+	}
+	if subID == 0 {
+		t.Fatal("subID = 0")
+	}
+	want := time.Now().UTC().AddDate(0, 0, 31)
+	if d := expiresAt.Sub(want); d > time.Minute || d < -time.Minute {
+		t.Errorf("expiresAt = %v, want ≈ %v", expiresAt, want)
+	}
+	var source string
+	if err := db.QueryRow(`SELECT source FROM subscriptions WHERE id = ?`, subID).Scan(&source); err != nil {
+		t.Fatalf("query source: %v", err)
+	}
+	if source != "pay" {
+		t.Errorf("source = %q, want pay", source)
+	}
+}
+
+// 已有同 plan 活跃订阅:原地延长(行数不变,expires 累加),复用兑换码同一段叠加语义。
+func TestGrantPaidSubscription_StacksOnActive(t *testing.T) {
+	db := openMigratedSQLite(t)
+	seedUser(t, db, 1)
+	store := codes.NewStore(db)
+	svc := codes.NewService(store, nil, 5, time.Hour)
+	ctx := context.Background()
+
+	grant := func(days int) time.Time {
+		tx, err := store.BeginTx(ctx)
+		if err != nil {
+			t.Fatalf("BeginTx: %v", err)
+		}
+		_, exp, err := svc.GrantPaidSubscriptionTx(ctx, tx, 1, codes.PlanPro, days, "order:test002")
+		if err != nil {
+			t.Fatalf("grant: %v", err)
+		}
+		if err := tx.Commit(); err != nil {
+			t.Fatalf("commit: %v", err)
+		}
+		return exp
+	}
+	first := grant(31)
+	second := grant(92)
+
+	want := first.AddDate(0, 0, 92)
+	if d := second.Sub(want); d > time.Minute || d < -time.Minute {
+		t.Errorf("stacked expiresAt = %v, want ≈ %v", second, want)
+	}
+	var n int
+	if err := db.QueryRow(`SELECT COUNT(*) FROM subscriptions WHERE user_id = 1`).Scan(&n); err != nil {
+		t.Fatalf("count: %v", err)
+	}
+	if n != 1 {
+		t.Errorf("subscription rows = %d, want 1(原地延长)", n)
+	}
+}
diff --git a/server/internal/codes/service.go b/server/internal/codes/service.go
index c9cf8f6..e4d7316 100644
--- a/server/internal/codes/service.go
+++ b/server/internal/codes/service.go
@@ -156,7 +156,7 @@ func (svc *Service) grantSubscription(userID int64) libcodes.GrantFunc[grantOutc
 		if err != nil {
 			return grantOutcome{}, err
 		}
-		subID, expiresAt, err := svc.applySubscription(ctx, tx, userID, planID, dur.Days)
+		subID, expiresAt, err := svc.applySubscription(ctx, tx, userID, planID, dur.Days, "code")
 		if err != nil {
 			return grantOutcome{}, err
 		}
@@ -177,10 +177,13 @@ func (svc *Service) grantSubscription(userID int64) libcodes.GrantFunc[grantOutc
 }
 
 // applySubscription:同 plan 有活跃订阅 → 取最晚到期那条 max(expires,now)+days
-// 原地延长;否则新建一行 max(now, latestSamePlan)+days。算法体与迁移前完全一致,
-// 仅签名从 (*CodeRow, *apierr.Error) 改为 (planID, days, error)。
+// 原地延长;否则新建一行 max(now, latestSamePlan)+days,source 记录新建行的
+// 创建者("code"=兑换码,"pay"=支付)。算法体与迁移前完全一致,仅签名从
+// (*CodeRow, *apierr.Error) 改为 (planID, days, source, error)。
+// ExtendSubscription 路径不看 source:延长的是既有行,行上的 source 仍是
+// 该行最初创建者,不因后续延长(不论来源)而改写——台账/审计保留完整出处。
 func (svc *Service) applySubscription(
-	ctx context.Context, tx *sql.Tx, userID, planID int64, durationDays int,
+	ctx context.Context, tx *sql.Tx, userID, planID int64, durationDays int, source string,
 ) (int64, time.Time, error) {
 	subs, err := svc.store.GetActiveSubscriptions(ctx, tx, userID)
 	if err != nil {
@@ -209,7 +212,7 @@ func (svc *Service) applySubscription(
 		}
 		return samePlanSub.ID, base.AddDate(0, 0, durationDays), nil
 	}
-	newSubID, err := svc.store.CreateSubscription(ctx, tx, userID, planID, durationDays, latestSamePlan)
+	newSubID, err := svc.store.CreateSubscription(ctx, tx, userID, planID, durationDays, latestSamePlan, source)
 	if err != nil {
 		return 0, time.Time{}, err
 	}
diff --git a/server/internal/codes/store.go b/server/internal/codes/store.go
index 455634b..f0ec605 100644
--- a/server/internal/codes/store.go
+++ b/server/internal/codes/store.go
@@ -158,6 +158,7 @@ func (s *Store) CreateSubscription(
 	userID, planID int64,
 	durationDays int,
 	latestSamePlan time.Time,
+	source string,
 ) (int64, error) {
 	now := time.Now().UTC()
 	base := now
@@ -168,8 +169,8 @@ func (s *Store) CreateSubscription(
 
 	res, err := tx.ExecContext(ctx,
 		`INSERT INTO subscriptions (user_id, plan_id, expires_at, source, created_at)
-		 VALUES (?, ?, ?, 'code', ?)`,
-		userID, planID, expiresAt, now)
+		 VALUES (?, ?, ?, ?, ?)`,
+		userID, planID, expiresAt, source, now)
 	if err != nil {
 		return 0, fmt.Errorf("store.CreateSubscription: %w", err)
 	}