diff --git a/cmd/qfs/main.go b/cmd/qfs/main.go
index 06e81a9..22d2109 100644
--- a/cmd/qfs/main.go
+++ b/cmd/qfs/main.go
@@ -996,8 +996,27 @@ func setupRouter(cfg *config.Config, local *localdb.LocalDB, connMgr *db.Connect
 					return
 				}
 
+				uuids := make([]string, len(cfgs))
+				for i, cfg := range cfgs {
+					uuids[i] = cfg.UUID
+				}
+				viewers, _ := syncService.ListActiveViewersByConfigUUIDs(uuids)
+
+				type cfgRow struct {
+					models.Configuration
+					Viewers []string `json:"viewers"`
+				}
+				rows := make([]cfgRow, len(cfgs))
+				for i, cfg := range cfgs {
+					v := viewers[cfg.UUID]
+					if v == nil {
+						v = []string{}
+					}
+					rows[i] = cfgRow{Configuration: cfg, Viewers: v}
+				}
+
 				c.JSON(http.StatusOK, gin.H{
-					"configurations": cfgs,
+					"configurations": rows,
 					"total":          total,
 					"page":           page,
 					"per_page":       perPage,
@@ -1332,6 +1351,16 @@ func setupRouter(cfg *config.Config, local *localdb.LocalDB, connMgr *db.Connect
 				}
 				c.JSON(http.StatusOK, config)
 			})
+
+			configs.POST("/:uuid/presence", func(c *gin.Context) {
+				_ = local.AddOpenConfigUUID(c.Param("uuid"))
+				c.JSON(http.StatusOK, gin.H{"ok": true})
+			})
+
+			configs.DELETE("/:uuid/presence", func(c *gin.Context) {
+				_ = local.RemoveOpenConfigUUID(c.Param("uuid"))
+				c.JSON(http.StatusOK, gin.H{"ok": true})
+			})
 		}
 
 		projects := api.Group("/projects")
@@ -1672,8 +1701,32 @@ func setupRouter(cfg *config.Config, local *localdb.LocalDB, connMgr *db.Connect
 					}
 					return
 				}
+
+				projUUIDs := make([]string, len(result.Configs))
+				for i, cfg := range result.Configs {
+					projUUIDs[i] = cfg.UUID
+				}
+				projViewers, _ := syncService.ListActiveViewersByConfigUUIDs(projUUIDs)
+
+				type projCfgRow struct {
+					models.Configuration
+					Viewers []string `json:"viewers"`
+				}
+				projRows := make([]projCfgRow, len(result.Configs))
+				for i, cfg := range result.Configs {
+					v := projViewers[cfg.UUID]
+					if v == nil {
+						v = []string{}
+					}
+					projRows[i] = projCfgRow{Configuration: cfg, Viewers: v}
+				}
+
 				c.Header("X-Config-Status", status)
-				c.JSON(http.StatusOK, result)
+				c.JSON(http.StatusOK, gin.H{
+					"project_uuid":   result.ProjectUUID,
+					"configurations": projRows,
+					"total":          result.Total,
+				})
 			})
 
 			projects.PATCH("/:uuid/configs/reorder", func(c *gin.Context) {
diff --git a/internal/localdb/localdb.go b/internal/localdb/localdb.go
index e35de47..0b47503 100644
--- a/internal/localdb/localdb.go
+++ b/internal/localdb/localdb.go
@@ -1235,6 +1235,67 @@ func (l *LocalDB) GetLastComponentSyncError() string {
 }
 
 
+const openConfigUUIDsKey = "open_config_uuids"
+
+// GetOpenConfigUUIDs returns UUIDs of all configurations currently open in the configurator.
+func (l *LocalDB) GetOpenConfigUUIDs() []string {
+	value, ok := l.getAppSettingValue(openConfigUUIDsKey)
+	if !ok || value == "" {
+		return nil
+	}
+	var uuids []string
+	if err := json.Unmarshal([]byte(value), &uuids); err != nil {
+		return nil
+	}
+	return uuids
+}
+
+// AddOpenConfigUUID records that a configuration is open in the configurator.
+func (l *LocalDB) AddOpenConfigUUID(uuid string) error {
+	uuids := l.GetOpenConfigUUIDs()
+	for _, u := range uuids {
+		if u == uuid {
+			return nil
+		}
+	}
+	uuids = append(uuids, uuid)
+	raw, err := json.Marshal(uuids)
+	if err != nil {
+		return err
+	}
+	return l.db.Exec(`
+		INSERT INTO app_settings (key, value, updated_at)
+		VALUES (?, ?, ?)
+		ON CONFLICT(key) DO UPDATE SET value = excluded.value, updated_at = excluded.updated_at
+	`, openConfigUUIDsKey, string(raw), time.Now().Format(time.RFC3339)).Error
+}
+
+// RemoveOpenConfigUUID records that a configuration is no longer open in the configurator.
+func (l *LocalDB) RemoveOpenConfigUUID(uuid string) error {
+	uuids := l.GetOpenConfigUUIDs()
+	filtered := uuids[:0]
+	for _, u := range uuids {
+		if u != uuid {
+			filtered = append(filtered, u)
+		}
+	}
+	var raw []byte
+	var err error
+	if len(filtered) == 0 {
+		raw = []byte("[]")
+	} else {
+		raw, err = json.Marshal(filtered)
+		if err != nil {
+			return err
+		}
+	}
+	return l.db.Exec(`
+		INSERT INTO app_settings (key, value, updated_at)
+		VALUES (?, ?, ?)
+		ON CONFLICT(key) DO UPDATE SET value = excluded.value, updated_at = excluded.updated_at
+	`, openConfigUUIDsKey, string(raw), time.Now().Format(time.RFC3339)).Error
+}
+
 // CountLocalPricelists returns the number of local pricelists
 func (l *LocalDB) CountLocalPricelists() int64 {
 	var count int64
diff --git a/internal/services/sync/readiness.go b/internal/services/sync/readiness.go
index cd2c84d..1af9266 100644
--- a/internal/services/sync/readiness.go
+++ b/internal/services/sync/readiness.go
@@ -249,6 +249,13 @@ func (s *Service) reportClientSchemaState(mariaDB *gorm.DB, checkedAt time.Time)
 	pricelistItemsCount := s.localDB.CountAllPricelistItems()
 	componentsCount := s.localDB.CountComponents()
 	dbSizeBytes := s.localDB.DBFileSizeBytes()
+	openConfigUUIDs := s.localDB.GetOpenConfigUUIDs()
+	var openConfigUUIDsJSON *string
+	if len(openConfigUUIDs) > 0 {
+		raw, _ := json.Marshal(openConfigUUIDs)
+		s := string(raw)
+		openConfigUUIDsJSON = &s
+	}
 	return mariaDB.Exec(`
 		INSERT INTO qt_client_schema_state (
 			username, hostname, app_version,
@@ -257,9 +264,10 @@ func (s *Service) reportClientSchemaState(mariaDB *gorm.DB, checkedAt time.Time)
 			estimate_pricelist_version, warehouse_pricelist_version, competitor_pricelist_version,
 			last_sync_error_code, last_sync_error_text,
 			local_pricelist_count, pricelist_items_count, components_count, db_size_bytes,
+			open_config_uuids,
 			last_checked_at, updated_at
 		)
-		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
 		ON DUPLICATE KEY UPDATE
 			app_version = VALUES(app_version),
 			last_sync_at = VALUES(last_sync_at),
@@ -277,6 +285,7 @@ func (s *Service) reportClientSchemaState(mariaDB *gorm.DB, checkedAt time.Time)
 			pricelist_items_count = VALUES(pricelist_items_count),
 			components_count = VALUES(components_count),
 			db_size_bytes = VALUES(db_size_bytes),
+			open_config_uuids = VALUES(open_config_uuids),
 			last_checked_at = VALUES(last_checked_at),
 			updated_at = VALUES(updated_at)
 	`, username, hostname, appmeta.Version(),
@@ -285,6 +294,7 @@ func (s *Service) reportClientSchemaState(mariaDB *gorm.DB, checkedAt time.Time)
 		estimateVersion, warehouseVersion, competitorVersion,
 		lastSyncErrorCode, lastSyncErrorText,
 		localPricelistCount, pricelistItemsCount, componentsCount, dbSizeBytes,
+		openConfigUUIDsJSON,
 		checkedAt, checkedAt).Error
 }
 
diff --git a/internal/services/sync/service.go b/internal/services/sync/service.go
index 53bd30b..f5ed695 100644
--- a/internal/services/sync/service.go
+++ b/internal/services/sync/service.go
@@ -630,6 +630,56 @@ func (s *Service) backfillUsedPricelistItemCategories(pricelistRepo *repository.
 	}
 }
 
+// ListActiveViewersByConfigUUIDs returns a map of configUUID → []username for users
+// who currently have those configs open (based on the last two sync cycles).
+func (s *Service) ListActiveViewersByConfigUUIDs(uuids []string) (map[string][]string, error) {
+	if len(uuids) == 0 {
+		return map[string][]string{}, nil
+	}
+	mariaDB, err := s.getDB()
+	if err != nil || mariaDB == nil {
+		return map[string][]string{}, nil
+	}
+	selfUsername := strings.ToLower(strings.TrimSpace(s.localDB.GetDBUser()))
+
+	type row struct {
+		Username       string `gorm:"column:username"`
+		OpenConfigJSON string `gorm:"column:open_config_uuids"`
+	}
+	var rows []row
+	if err := mariaDB.Raw(`
+		SELECT username, open_config_uuids
+		FROM qt_client_schema_state
+		WHERE open_config_uuids IS NOT NULL
+		  AND open_config_uuids != '[]'
+		  AND last_checked_at > NOW() - INTERVAL 10 MINUTE
+	`).Scan(&rows).Error; err != nil {
+		return map[string][]string{}, nil
+	}
+
+	wantSet := make(map[string]struct{}, len(uuids))
+	for _, u := range uuids {
+		wantSet[u] = struct{}{}
+	}
+
+	result := make(map[string][]string)
+	for _, r := range rows {
+		if strings.ToLower(strings.TrimSpace(r.Username)) == selfUsername {
+			continue
+		}
+		var openUUIDs []string
+		if err := json.Unmarshal([]byte(r.OpenConfigJSON), &openUUIDs); err != nil {
+			continue
+		}
+		for _, ou := range openUUIDs {
+			if _, ok := wantSet[ou]; ok {
+				result[ou] = append(result[ou], r.Username)
+			}
+		}
+	}
+	return result, nil
+}
+
 // ListUserSyncStatuses returns users who have recorded a client schema state check.
 func (s *Service) ListUserSyncStatuses(onlineThreshold time.Duration) ([]UserSyncStatus, error) {
 	mariaDB, err := s.getDB()
diff --git a/web/templates/configs.html b/web/templates/configs.html
index b9a7d6e..2b47641 100644
--- a/web/templates/configs.html
+++ b/web/templates/configs.html
@@ -242,6 +242,7 @@ function renderConfigs(configs) {
     html += '<th class="px-4 py-3 text-left text-xs font-medium text-gray-500 uppercase">Цена (за 1 шт)</th>';
     html += '<th class="px-4 py-3 text-left text-xs font-medium text-gray-500 uppercase">Кол-во</th>';
     html += '<th class="px-4 py-3 text-right text-xs font-medium text-gray-500 uppercase">Сумма</th>';
+    html += '<th class="px-2 py-3 w-8"></th>';
     html += '<th class="px-4 py-3 text-right text-xs font-medium text-gray-500 uppercase">Действия</th>';
     html += '</tr></thead><tbody class="divide-y">';
 
@@ -298,6 +299,16 @@ function renderConfigs(configs) {
         html += '<td class="px-4 py-3 text-sm text-gray-500">' + pricePerUnit + '</td>';
         html += '<td class="px-4 py-3 text-sm text-gray-500">' + serverCount + '</td>';
         html += '<td class="px-4 py-3 text-sm text-right">' + total + '</td>';
+        const viewers = c.viewers || [];
+        if (viewers.length > 0) {
+            const names = viewers.map(escapeHtml).join(', ');
+            html += '<td class="px-2 py-3 text-center w-8">';
+            html += '<span title="Открыта: ' + names + '" class="inline-flex items-center justify-center text-blue-500 cursor-default">';
+            html += '<svg class="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M15 12a3 3 0 11-6 0 3 3 0 016 0z"></path><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M2.458 12C3.732 7.943 7.523 5 12 5c4.478 0 8.268 2.943 9.542 7-1.274 4.057-5.064 7-9.542 7-4.477 0-8.268-2.943-9.542-7z"></path></svg>';
+            html += '</span></td>';
+        } else {
+            html += '<td class="px-2 py-3 w-8"></td>';
+        }
         html += '<td class="px-4 py-3 text-sm text-right space-x-2">';
         if (configStatusMode === 'archived') {
             html += '<button onclick="reactivateConfig(\'' + c.uuid + '\')" class="text-emerald-600 hover:text-emerald-800" title="Восстановить">';
diff --git a/web/templates/index.html b/web/templates/index.html
index df71cd8..f659a9a 100644
--- a/web/templates/index.html
+++ b/web/templates/index.html
@@ -985,6 +985,16 @@ document.addEventListener('DOMContentLoaded', async function() {
     if (configUUID) {
         loadVendorSpec(configUUID);
     }
+
+    // Presence: announce that this config is open and keep renewing every 4 min
+    if (configUUID) {
+        const sendPresence = () => fetch('/api/configs/' + configUUID + '/presence', {method: 'POST'}).catch(() => {});
+        sendPresence();
+        setInterval(sendPresence, 4 * 60 * 1000);
+        window.addEventListener('beforeunload', () => {
+            fetch('/api/configs/' + configUUID + '/presence', {method: 'DELETE', keepalive: true}).catch(() => {});
+        });
+    }
 });
 
 async function loadAllComponents() {
diff --git a/web/templates/project_detail.html b/web/templates/project_detail.html
index 17195ea..ab655e2 100644
--- a/web/templates/project_detail.html
+++ b/web/templates/project_detail.html
@@ -518,7 +518,16 @@ function renderConfigs(configs) {
             html += '<td class="px-4 py-3 text-sm text-gray-500"><input type="number" min="1" value="' + serverCount + '" class="w-16 px-1 py-0.5 border rounded text-center text-sm" data-uuid="' + c.uuid + '" data-prev="' + serverCount + '" onchange="updateConfigServerCount(this)"></td>';
         }
         html += '<td class="px-4 py-3 text-sm text-right" data-total-uuid="' + c.uuid + '">' + formatMoneyNoDecimals(total) + '</td>';
-        html += '<td class="px-2 py-3 text-sm text-center text-gray-500 w-12">main</td>';
+        const projViewers = c.viewers || [];
+        if (projViewers.length > 0) {
+            const projNames = projViewers.map(escapeHtml).join(', ');
+            html += '<td class="px-2 py-3 text-center w-12">';
+            html += '<span title="Открыта: ' + projNames + '" class="inline-flex items-center justify-center text-blue-500 cursor-default">';
+            html += '<svg class="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M15 12a3 3 0 11-6 0 3 3 0 016 0z"></path><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M2.458 12C3.732 7.943 7.523 5 12 5c4.478 0 8.268 2.943 9.542 7-1.274 4.057-5.064 7-9.542 7-4.477 0-8.268-2.943-9.542-7z"></path></svg>';
+            html += '</span></td>';
+        } else {
+            html += '<td class="px-2 py-3 w-12"></td>';
+        }
         html += '<td class="px-4 py-3 text-sm text-right whitespace-nowrap"><div class="inline-flex items-center justify-end gap-2">';
         if (configStatusMode === 'archived') {
             html += '<button onclick="reactivateConfig(\'' + c.uuid + '\')" class="text-emerald-600 hover:text-emerald-800" title="Восстановить">';