diff --git a/internal/web/service/client_bulk.go b/internal/web/service/client_bulk.go
index 89b241dc8..f6fe94586 100644
--- a/internal/web/service/client_bulk.go
+++ b/internal/web/service/client_bulk.go
@@ -30,6 +30,7 @@ type BulkAttachResult struct {
 // all clients to a target in a single AddInboundClient call, and reports clients already
 // present on a target as skipped.
 func (s *ClientService) BulkAttach(inboundSvc *InboundService, emails []string, inboundIds []int) (*BulkAttachResult, bool, error) {
+	inboundIds = uniqueInts(inboundIds)
 	result := &BulkAttachResult{}
 	if len(emails) == 0 || len(inboundIds) == 0 {
 		return result, false, nil
@@ -1357,7 +1358,7 @@ func (s *ClientService) bulkCreate(inboundSvc *InboundService, payloads []Client
 		seenEmail[le] = struct{}{}
 		seenSubID[client.SubID] = le
 
-		prep = append(prep, prepared{client: client, inboundIds: payloads[i].InboundIds, limitHwid: payloads[i].LimitHwid, payloadIdx: i})
+		prep = append(prep, prepared{client: client, inboundIds: uniqueInts(payloads[i].InboundIds), limitHwid: payloads[i].LimitHwid, payloadIdx: i})
 		emails = append(emails, email)
 		subIDs = append(subIDs, client.SubID)
 	}
diff --git a/internal/web/service/client_create_fanout_test.go b/internal/web/service/client_create_fanout_test.go
index 1d3b63d52..1d7dc57bc 100644
--- a/internal/web/service/client_create_fanout_test.go
+++ b/internal/web/service/client_create_fanout_test.go
@@ -3,6 +3,8 @@ package service
 import (
 	"context"
 	"fmt"
+	goruntime "runtime"
+	"slices"
 	"strings"
 	"sync/atomic"
 	"testing"
@@ -338,3 +340,54 @@ func TestFanoutReportsEveryFailingInbound(t *testing.T) {
 		}
 	})
 }
+
+// An inbound id costs two bytes of request body, so a repeated one must not cost
+// the panel another copy of the client: 2000 ids x 8 MB of comment was 16 GB.
+func TestRepeatedInboundIdCostsOneCopyOfTheClient(t *testing.T) {
+	const commentBytes = 1 << 20
+	client := func(email string) model.Client {
+		return model.Client{Email: email, Comment: strings.Repeat("x", commentBytes), Enable: true}
+	}
+
+	cases := map[string]func(svc *ClientService, inboundSvc *InboundService, spare int, ids []int) error{
+		"Create": func(svc *ClientService, inboundSvc *InboundService, _ int, ids []int) error {
+			_, err := svc.Create(inboundSvc, &ClientCreatePayload{Client: client("repeated@x"), InboundIds: ids})
+			return err
+		},
+		"BulkCreate": func(svc *ClientService, inboundSvc *InboundService, _ int, ids []int) error {
+			res, _, err := svc.BulkCreate(inboundSvc, []ClientCreatePayload{{Client: client("repeated@x"), InboundIds: ids}})
+			if err == nil && res.Created != 1 {
+				t.Fatalf("bulk create: created %d, skipped %+v", res.Created, res.Skipped)
+			}
+			return err
+		},
+		"Attach": func(svc *ClientService, inboundSvc *InboundService, spare int, ids []int) error {
+			if _, err := svc.CreateOne(inboundSvc, spare, client("repeated@x")); err != nil {
+				return err
+			}
+			_, err := svc.AttachByEmail(inboundSvc, "repeated@x", ids)
+			return err
+		},
+	}
+	for name, run := range cases {
+		t.Run(name, func(t *testing.T) {
+			setupBulkDB(t)
+			ib := mkInbound(t, 21011, model.VLESS, `{"clients":[]}`)
+			spare := mkInbound(t, 21012, model.VLESS, `{"clients":[]}`)
+
+			var before, after goruntime.MemStats
+			goruntime.ReadMemStats(&before)
+			if err := run(&ClientService{}, &InboundService{}, spare.Id, slices.Repeat([]int{ib.Id}, 300)); err != nil {
+				t.Fatal(err)
+			}
+			goruntime.ReadMemStats(&after)
+
+			if allocated := after.TotalAlloc - before.TotalAlloc; allocated > 100*commentBytes {
+				t.Fatalf("allocated %d MiB for a 1 MiB client named on one inbound", allocated>>20)
+			}
+			if emails := settingsClientEmails(t, ib.Id); len(emails) != 1 {
+				t.Fatalf("clients on the inbound = %v, want the one", emails)
+			}
+		})
+	}
+}
diff --git a/internal/web/service/client_crud.go b/internal/web/service/client_crud.go
index eb1135b9a..904f93037 100644
--- a/internal/web/service/client_crud.go
+++ b/internal/web/service/client_crud.go
@@ -191,6 +191,8 @@ func (s *ClientService) Create(inboundSvc *InboundService, payload *ClientCreate
 	if payload == nil {
 		return false, common.NewError("empty payload")
 	}
+	// A repeated id adds nothing but another copy of the client held through the fan-out.
+	payload.InboundIds = uniqueInts(payload.InboundIds)
 	client := payload.Client
 	if strings.TrimSpace(client.Email) == "" {
 		return false, common.NewError("client email is required")
@@ -1138,6 +1140,7 @@ func addressesFitAmneziaWGInbound(addrs []string, ib *model.Inbound) bool {
 // Attach applies the client to every requested inbound: one failing inbound no
 // longer aborts the others, so the error can name several and needRestart holds.
 func (s *ClientService) Attach(inboundSvc *InboundService, id int, inboundIds []int) (bool, error) {
+	inboundIds = uniqueInts(inboundIds)
 	existing, err := s.GetByID(id)
 	if err != nil {
 		return false, err
diff --git a/internal/web/service/inbound_node.go b/internal/web/service/inbound_node.go
index 986e16e2f..ba846a053 100644
--- a/internal/web/service/inbound_node.go
+++ b/internal/web/service/inbound_node.go
@@ -84,7 +84,7 @@ func (s *InboundService) AnyNodePending(inboundIds []int) bool {
 		return false
 	}
 	nodeSvc := NodeService{}
-	for _, id := range inboundIds {
+	for _, id := range uniqueInts(inboundIds) {
 		ib, err := s.GetInbound(id)
 		if err != nil || ib.NodeID == nil {
 			continue