diff --git a/EDITOR_LOCAL_STORAGE.md b/EDITOR_LOCAL_STORAGE.md
index c57499c..07b7af7 100644
--- a/EDITOR_LOCAL_STORAGE.md
+++ b/EDITOR_LOCAL_STORAGE.md
@@ -83,7 +83,7 @@ Nguồn: `const editor = useEditorState(initialData)`
 
 - `editor.draft: FeatureCollection`
   - **Single source of truth** cho geometry đang hiển thị + chỉnh sửa.
-  - Map render trực tiếp từ `draft` (hoặc bản “visibleDraft” đã filter theo timeline/binding).
+  - Map render trực tiếp từ `draft` (hoặc bản “visibleDraft” đã filter theo timeline/bound_with).
   - Đây chính là **store runtime của GEO** trong session.
 
 - `editor.changes: Map<id, Change>`
@@ -247,7 +247,7 @@ Khi bấm **Import** một geometry từ kết quả search:
 3. Nếu geometry chưa có trong `editor.draft`:
    - tạo `Feature` mới với `id = geometry.id`
    - set `properties.type` từ `geo_type` (map qua `geoTypeCodeToTypeKey`)
-   - set `time_start/time_end/binding`
+   - set `time_start/time_end/bound_with`
    - set denormalized `entity_id/entity_ids/entity_name/entity_names` để UI/joins hoạt động
 4. `editor.createFeature(feature)` và auto select feature đó.
 
diff --git a/src/app/editor/[id]/page.tsx b/src/app/editor/[id]/page.tsx
index f1044ad..60d779d 100644
--- a/src/app/editor/[id]/page.tsx
+++ b/src/app/editor/[id]/page.tsx
@@ -30,10 +30,14 @@ import {
 import { EditorMode } from "@/uhm/lib/editor/session/sessionTypes";
 import {
     getDefaultTypeIdForFeature,
-    normalizeFeatureBindingIds,
     normalizeFeatureEntityIds,
     uniqueEntityIds,
 } from "@/uhm/lib/editor/snapshot/editorSnapshot";
+import {
+    getDirectGeometryChildIds,
+    normalizeFeatureBoundWith,
+    wouldCreateGeometryBoundWithCycle,
+} from "@/uhm/lib/editor/geometry/geometryBinding";
 import {
     buildClientEntityId,
     mergeEntitySearchResults,
@@ -71,7 +75,7 @@ import {
     isFeatureVisibleAtYear,
     normalizeEntitiesForCompare,
     normalizeEntityWikiLinksForCompare,
-    normalizeGeoSearchBindingIds,
+    normalizeGeoSearchBoundWith,
     normalizeGeoSearchGeometry,
     normalizeReplaysForCompare,
     normalizeWikisForCompare,
@@ -630,11 +634,11 @@ function EditorPageContent() {
         return rows;
     }, [activeTimelineFilterEnabled, editor, mapRenderDraft.features]);
 
-    // Binding ids của geometry đại diện đang chọn.
-    const selectedGeometryBindingIds = useMemo(() => {
+    // Child ids bound to the selected geometry via child.properties.bound_with.
+    const selectedGeometryChildIds = useMemo(() => {
         if (!selectedFeature) return [];
-        return normalizeFeatureBindingIds(selectedFeature);
-    }, [selectedFeature]);
+        return getDirectGeometryChildIds(editor.draft, selectedFeature.properties.id);
+    }, [editor.draft, selectedFeature]);
 
     // Choices wiki dùng trong replay actions và binding panel.
     const wikiChoices = useMemo(() => {
@@ -1317,7 +1321,6 @@ function EditorPageContent() {
                 type_key: "",
                 time_start: "",
                 time_end: "",
-                binding: "",
             });
             setEntityFormStatus(null);
             lastSelectedFeatureIdRef.current = null;
@@ -1336,7 +1339,6 @@ function EditorPageContent() {
             type_key: nextTypeKey,
             time_start: timeStart != null ? String(timeStart) : "",
             time_end: timeEnd != null ? String(timeEnd) : "",
-            binding: normalizeFeatureBindingIds(selectedFeature).join(", "),
         });
         // Only clear status when switching to a different geometry, not when patching metadata/bindings
         // on the same selected geometry (otherwise messages will blink).
@@ -1518,58 +1520,55 @@ function EditorPageContent() {
         setSelectedGeometryEntityIds,
     ]);
 
-    // Bind/unbind geometry id vào trường binding của selected geometry.
+    // Bind/unbind geometry con vào selected geometry qua field child.bound_with.
     const handleToggleBindGeometryForSelectedGeometry = useCallback((geoId: string, nextChecked: boolean) => {
         if (!selectedFeatures || selectedFeatures.length === 0) {
             flashGeoBindingStatus("Chưa chọn geometry để bind.");
             return;
         }
+        if (selectedFeatures.length !== 1 || !selectedFeature) {
+            flashGeoBindingStatus("Chỉ bind geometry-geometry khi chọn đúng một geometry cha.");
+            return;
+        }
         if (!isMultiEditValid) {
             flashGeoBindingStatus("Không thể bind geometry cho nhiều geometry khác loại.");
             return;
         }
         const id = String(geoId || "").trim();
         if (!id) return;
-        if (selectedFeatures.some(f => String(f.properties.id) === id)) return;
-
-
+        const parentId = String(selectedFeature.properties.id);
+        if (parentId === id) return;
+        const childFeature = editor.draft.features.find((f) => String(f.properties.id) === id);
+        if (!childFeature) {
+            flashGeoBindingStatus("Không tìm thấy geometry con.");
+            return;
+        }
+        if (nextChecked && wouldCreateGeometryBoundWithCycle(editor.draft.features, id, parentId)) {
+            flashGeoBindingStatus("Không thể bind vì sẽ tạo vòng lặp bound_with.");
+            return;
+        }
 
         setIsEntitySubmitting(true);
         flashGeoBindingStatus(null, 0);
         try {
-            const bindingPatches = selectedFeatures.map((feature) => {
-                const prevBindingIds = normalizeFeatureBindingIds(feature);
-                const has = prevBindingIds.includes(id);
-                const nextBindingIds = (() => {
-                    if (nextChecked) {
-                        if (has) return prevBindingIds;
-                        return [...prevBindingIds, id];
-                    }
-                    if (!has) return prevBindingIds;
-                    return prevBindingIds.filter((x) => x !== id);
-                })();
-                return {
-                    id: feature.properties.id,
-                    patch: { binding: nextBindingIds },
-                };
-            });
+            const currentParentId = normalizeFeatureBoundWith(childFeature);
+            const nextBoundWith = nextChecked
+                ? parentId
+                : currentParentId === parentId
+                    ? null
+                    : currentParentId;
             editor.patchFeaturePropertiesBatch(
-                bindingPatches,
+                [{
+                    id: childFeature.properties.id,
+                    patch: { bound_with: nextBoundWith },
+                }],
                 nextChecked ? "Bind geometry vào GEO" : "Unbind geometry khỏi GEO"
             );
 
-            // Assume selectedFeature (the first one) reflects the representative binding in UI
-            const firstFeaturePrevBindings = normalizeFeatureBindingIds(selectedFeatures[0]);
-            const firstFeatureHas = firstFeaturePrevBindings.includes(id);
-            const nextBindingIdsForUI = (() => {
-                if (nextChecked) return firstFeatureHas ? firstFeaturePrevBindings : [...firstFeaturePrevBindings, id];
-                return firstFeatureHas ? firstFeaturePrevBindings.filter(x => x !== id) : firstFeaturePrevBindings;
-            })();
-            setGeometryMetaForm((prev) => ({ ...prev, binding: nextBindingIdsForUI.join(", ") }));
             flashGeoBindingStatus(
                 nextChecked
-                    ? "Đã bind geometry vào binding. Commit khi sẵn sàng."
-                    : "Đã gỡ binding geometry. Commit khi sẵn sàng.",
+                    ? "Đã set bound_with cho geometry con. Commit khi sẵn sàng."
+                    : "Đã gỡ bound_with khỏi geometry con. Commit khi sẵn sàng.",
                 3000
             );
         } finally {
@@ -1578,13 +1577,13 @@ function EditorPageContent() {
     }, [
         editor,
         flashGeoBindingStatus,
+        selectedFeature,
         selectedFeatures,
         isMultiEditValid,
-        setGeometryMetaForm,
         setIsEntitySubmitting,
     ]);
 
-    // Bind nhiều geometries vào target geometry.
+    // Bind nhiều geometries con vào target geometry.
     const handleBindGeometries = useCallback((targetId: string | number, sourceIds: (string | number)[]) => {
         const idStr = String(targetId).trim();
         if (!idStr) return;
@@ -1595,23 +1594,27 @@ function EditorPageContent() {
             return;
         }
 
-        const prevBindingIds = normalizeFeatureBindingIds(targetFeature);
+        const sourceFeatures = sourceIds
+            .map((sourceId) => editor.draft.features.find((f) => String(f.properties.id) === String(sourceId)))
+            .filter((feature): feature is Feature => Boolean(feature))
+            .filter((feature) => String(feature.properties.id) !== idStr)
+            .filter((feature) => !wouldCreateGeometryBoundWithCycle(editor.draft.features, feature.properties.id, idStr));
 
-        // Merge prevBindingIds with sourceIds (which are strings of selected features)
-        // filter out targetId itself (we can't bind a geometry to itself)
-        const newSources = sourceIds.map(String).filter((x) => x !== idStr);
-        const merged = Array.from(new Set([...prevBindingIds, ...newSources]));
+        if (!sourceFeatures.length) {
+            flashGeoBindingStatus("Không có geometry con hợp lệ để bind.");
+            return;
+        }
 
         editor.patchFeaturePropertiesBatch(
-            [{
-                id: targetFeature.properties.id,
-                patch: { binding: merged },
-            }],
+            sourceFeatures.map((feature) => ({
+                id: feature.properties.id,
+                patch: { bound_with: idStr },
+            })),
             "Bind các geometry đã chọn vào GEO"
         );
 
         setSelectedFeatureIds([targetFeature.properties.id]);
-        flashGeoBindingStatus(`Đã bind ${newSources.length} geometry vào GEO này. Commit khi sẵn sàng.`, 3000);
+        flashGeoBindingStatus(`Đã set bound_with cho ${sourceFeatures.length} geometry con. Commit khi sẵn sàng.`, 3000);
     }, [editor, flashGeoBindingStatus, setSelectedFeatureIds]);
 
     // Focus/zoom tới geometry từ binding panel; nếu geo có time_start thì kéo year filter về năm đó.
@@ -1787,7 +1790,7 @@ function EditorPageContent() {
             return;
         }
 
-        const bindingIds = normalizeGeoSearchBindingIds(geo.binding);
+        const boundWith = normalizeGeoSearchBoundWith(geo.bound_with);
         const typeKey = geo.type || null;
 
         const feature: Feature = {
@@ -1797,7 +1800,7 @@ function EditorPageContent() {
                 type: typeKey,
                 time_start: normalizeTimelineYearValue(geo.time_start),
                 time_end: normalizeTimelineYearValue(geo.time_end),
-                binding: bindingIds.length ? bindingIds : undefined,
+                bound_with: boundWith,
                 entity_id: entityItem.entity_id,
                 entity_ids: [entityItem.entity_id],
                 entity_name: (entityItem.name || "").trim() || entityItem.entity_id,
@@ -2345,7 +2348,7 @@ function EditorPageContent() {
                                 <GeometryBindingPanel
                                     geometries={geometryChoices}
                                     selectedGeometryId={selectedFeature ? String(selectedFeature.properties.id) : null}
-                                    selectedGeometryBindingIds={selectedGeometryBindingIds}
+                                    selectedGeometryChildIds={selectedGeometryChildIds}
                                     onToggleBindGeometryForSelectedGeometry={handleToggleBindGeometryForSelectedGeometry}
                                     onFocusGeometry={handleFocusGeometryFromBindingPanel}
                                 />
diff --git a/src/uhm/api/geometries.ts b/src/uhm/api/geometries.ts
index 639b8a2..fc67ea5 100644
--- a/src/uhm/api/geometries.ts
+++ b/src/uhm/api/geometries.ts
@@ -10,7 +10,7 @@ export type EntityGeometrySearchGeo = {
     id: string;
     type: string | null;
     draw_geometry: Geometry;
-    binding?: string[];
+    bound_with?: string | null;
 
     time_start?: number | null;
     time_end?: number | null;
@@ -96,7 +96,7 @@ export async function searchGeometriesByEntityName(
                 id: geometry.id,
                 type: geoTypeCodeToTypeKey(geometry.geo_type) || null,
                 draw_geometry: geometry.draw_geometry,
-                binding: geometry.binding,
+                bound_with: normalizeBoundWith(geometry.bound_with),
                 time_start: geometry.time_start ?? null,
                 time_end: geometry.time_end ?? null,
             })),
@@ -108,7 +108,7 @@ type GeometryRow = {
     id: string;
     geo_type: number;
     draw_geometry: Geometry;
-    binding?: string[];
+    bound_with?: string | null;
 
     time_start?: number;
     time_end?: number;
@@ -127,7 +127,7 @@ function geometriesToFeatureCollection(rows: GeometryRow[]): FeatureCollection {
         const geometry = normalizeGeometry(row.draw_geometry);
         if (!geometry) continue;
 
-        const binding = normalizeBinding(row.binding);
+        const boundWith = normalizeBoundWith(row.bound_with);
         const typeKey = geoTypeCodeToTypeKey(row.geo_type) || null;
 
         const properties: FeatureProperties = {
@@ -135,7 +135,7 @@ function geometriesToFeatureCollection(rows: GeometryRow[]): FeatureCollection {
             type: typeKey,
             time_start: row.time_start ?? null,
             time_end: row.time_end ?? null,
-            binding: binding.length ? binding : undefined,
+            bound_with: boundWith,
         };
 
         features.push({
@@ -156,11 +156,9 @@ function normalizeGeometry(value: unknown): Geometry | null {
     return value as Geometry;
 }
 
-function normalizeBinding(value: unknown): string[] {
-    if (!value) return [];
-    if (Array.isArray(value)) {
-        return value.map((v) => String(v)).filter((v) => v.length > 0);
-    }
-    // Some deployments may return binding as an object; ignore it for FE properties.binding.
-    return [];
+function normalizeBoundWith(value: unknown): string | null {
+    if (value == null) return null;
+    if (typeof value !== "string" && typeof value !== "number") return null;
+    const id = String(value).trim();
+    return id.length ? id : null;
 }
diff --git a/src/uhm/components/editor/GeometryBindingPanel.tsx b/src/uhm/components/editor/GeometryBindingPanel.tsx
index e945acf..488db5e 100644
--- a/src/uhm/components/editor/GeometryBindingPanel.tsx
+++ b/src/uhm/components/editor/GeometryBindingPanel.tsx
@@ -29,7 +29,7 @@ type GeometryRow = Required<Pick<GeometryChoice, "id" | "label" | "isOrphan" | "
 type Props = {
   geometries: GeometryChoice[];
   selectedGeometryId?: string | null;
-  selectedGeometryBindingIds: string[];
+  selectedGeometryChildIds: string[];
   onToggleBindGeometryForSelectedGeometry?: (geometryId: string, nextChecked: boolean) => void;
   onFocusGeometry?: (geometryId: string) => void;
 };
@@ -37,7 +37,7 @@ type Props = {
 export default function GeometryBindingPanel({
   geometries,
   selectedGeometryId,
-  selectedGeometryBindingIds,
+  selectedGeometryChildIds,
   onToggleBindGeometryForSelectedGeometry,
   onFocusGeometry,
 }: Props) {
@@ -85,7 +85,7 @@ export default function GeometryBindingPanel({
     return cleaned;
   }, [geometries]);
 
-  const bindingSet = useMemo(() => new Set(selectedGeometryBindingIds || []), [selectedGeometryBindingIds]);
+  const childSet = useMemo(() => new Set(selectedGeometryChildIds || []), [selectedGeometryChildIds]);
   const selectedGeometry = useMemo(() => {
     if (!effectiveSelectedGeometryId) return null;
     return rows.find((g) => g.id === effectiveSelectedGeometryId) || null;
@@ -94,12 +94,12 @@ export default function GeometryBindingPanel({
     return rows
       .filter((g) => g.id !== effectiveSelectedGeometryId)
       .sort((a, b) => {
-        const aBound = bindingSet.has(a.id);
-        const bBound = bindingSet.has(b.id);
+        const aBound = childSet.has(a.id);
+        const bBound = childSet.has(b.id);
         if (aBound !== bBound) return aBound ? -1 : 1;
         return a.id.localeCompare(b.id);
       });
-  }, [bindingSet, effectiveSelectedGeometryId, rows]);
+  }, [childSet, effectiveSelectedGeometryId, rows]);
   const summary = useMemo(() => {
     let orphan = 0;
     let missingTime = 0;
@@ -247,7 +247,7 @@ export default function GeometryBindingPanel({
       {collapsed ? null : selectedGeometry ? (
         (() => {
           const isHidden = geometryVisibility[selectedGeometry.id] === false;
-          const isBound = bindingSet.has(selectedGeometry.id);
+          const isBound = childSet.has(selectedGeometry.id);
           const title = buildGeometryTitle(selectedGeometry, isHidden, isBound);
           return (
         <div
@@ -306,7 +306,7 @@ export default function GeometryBindingPanel({
         <div style={{ marginTop: "10px", display: "grid", gap: "6px", maxHeight: 250, overflowY: "auto", paddingRight: 4 }}>
           {visibleRows
             .map((g) => {
-              const isBound = bindingSet.has(g.id);
+              const isBound = childSet.has(g.id);
               const isHidden = geometryVisibility[g.id] === false;
               const title = buildGeometryTitle(g, isHidden, isBound);
               return (
diff --git a/src/uhm/components/editor/SelectedGeometryPanel.tsx b/src/uhm/components/editor/SelectedGeometryPanel.tsx
index 8e8b0bb..e95de34 100644
--- a/src/uhm/components/editor/SelectedGeometryPanel.tsx
+++ b/src/uhm/components/editor/SelectedGeometryPanel.tsx
@@ -58,10 +58,8 @@ export default function SelectedGeometryPanel({
             geometryMetaForm.type_key,
             geometryMetaForm.time_start,
             geometryMetaForm.time_end,
-            geometryMetaForm.binding,
         ].join("|");
     }, [
-        geometryMetaForm.binding,
         geometryMetaForm.time_end,
         geometryMetaForm.time_start,
         geometryMetaForm.type_key,
diff --git a/src/uhm/components/map/mapUtils.ts b/src/uhm/components/map/mapUtils.ts
index e8382d6..84f8ef0 100644
--- a/src/uhm/components/map/mapUtils.ts
+++ b/src/uhm/components/map/mapUtils.ts
@@ -13,6 +13,7 @@ import { PATH_RENDER_BY_TYPE } from "@/uhm/lib/map/styles/style";
 import { getBackgroundRasterSourceSpecification } from "@/uhm/api/tiles";
 import { newId } from "@/uhm/lib/utils/id";
 import { normalizeGeoTypeKey } from "@/uhm/lib/map/geo/geoTypeMap";
+import { normalizeBoundWithId, normalizeFeatureBoundWith } from "@/uhm/lib/editor/geometry/geometryBinding";
 import type { EntityLabelCandidate } from "@/uhm/types/geo";
 
 type Coordinate = [number, number];
@@ -149,9 +150,18 @@ export function filterDraftByBinding(
     }
 
     const childIds = new Set<string>();
+    const selectedChildren = new Set<string>();
+    const selectedParents = new Set<string>();
     for (const feature of fc.features) {
-        for (const id of normalizeBindingIds(feature.properties.binding)) {
-            childIds.add(id);
+        const featureId = String(feature.properties.id);
+        const parentId = normalizeFeatureBoundWith(feature);
+        if (!parentId) continue;
+        childIds.add(featureId);
+        if (selectedIds.has(parentId)) {
+            selectedChildren.add(featureId);
+        }
+        if (selectedIds.has(featureId)) {
+            selectedParents.add(parentId);
         }
     }
 
@@ -159,21 +169,13 @@ export function filterDraftByBinding(
         return { ...fc, features: fc.features.filter((f) => !childIds.has(String(f.properties.id))) };
     }
 
-    const selectedChildren = new Set<string>();
-    for (const feature of fc.features) {
-        if (selectedIds.has(String(feature.properties.id))) {
-            for (const id of normalizeBindingIds(feature.properties.binding)) {
-                selectedChildren.add(id);
-            }
-        }
-    }
-
     return {
         ...fc,
         features: fc.features.filter((feature) => {
             const featureId = String(feature.properties.id);
             if (selectedIds.has(featureId)) return true;
             if (selectedChildren.has(featureId)) return true;
+            if (selectedParents.has(featureId)) return true;
             return !childIds.has(featureId);
         }),
     };
@@ -200,20 +202,6 @@ export function filterDraftByGeometryVisibility(
     };
 }
 
-export function normalizeBindingIds(rawBinding: unknown): string[] {
-    if (!Array.isArray(rawBinding)) return [];
-    const deduped: string[] = [];
-    const seen = new Set<string>();
-    for (const rawId of rawBinding) {
-        if (typeof rawId !== "string" && typeof rawId !== "number") continue;
-        const id = String(rawId).trim();
-        if (!id || seen.has(id)) continue;
-        seen.add(id);
-        deduped.push(id);
-    }
-    return deduped;
-}
-
 export function splitDraftFeatures(fc: FeatureCollection) {
     const polygons = {
         type: "FeatureCollection",
@@ -683,21 +671,13 @@ function createFeatureLabelResolver(
     }
 
     for (const feature of fc.features) {
-        const parentLabel = directLabelsByFeatureId.get(String(feature.properties.id));
         const featureId = String(feature.properties.id);
-        const bindingIds = normalizeBindingIds(feature.properties.binding);
+        const parentId = normalizeBoundWithId(feature.properties.bound_with);
+        if (!parentId) continue;
 
+        const parentLabel = directLabelsByFeatureId.get(parentId);
         if (parentLabel) {
-            for (const childId of bindingIds) {
-                mergeInheritedFeatureLabel(inheritedLabelsByChildId, childId, parentLabel);
-            }
-        }
-
-        for (const parentId of bindingIds) {
-            const linkedParentLabel = directLabelsByFeatureId.get(parentId);
-            if (linkedParentLabel) {
-                mergeInheritedFeatureLabel(inheritedLabelsByChildId, featureId, linkedParentLabel);
-            }
+            mergeInheritedFeatureLabel(inheritedLabelsByChildId, featureId, parentLabel);
         }
     }
 
diff --git a/src/uhm/components/map/useMapInteraction.ts b/src/uhm/components/map/useMapInteraction.ts
index b56729a..f039ce0 100644
--- a/src/uhm/components/map/useMapInteraction.ts
+++ b/src/uhm/components/map/useMapInteraction.ts
@@ -135,7 +135,7 @@ export function useMapInteraction({
                         entity_ids: [],
                         entity_name: null,
                         entity_type_id: null,
-                        binding: [],
+                        bound_with: null,
                     },
                     geometry,
                 });
@@ -201,7 +201,7 @@ export function useMapInteraction({
                         entity_ids: [],
                         entity_name: null,
                         entity_type_id: null,
-                        binding: [],
+                        bound_with: null,
                     },
                     geometry,
                 });
@@ -223,7 +223,7 @@ export function useMapInteraction({
                         entity_ids: [],
                         entity_name: null,
                         entity_type_id: null,
-                        binding: [],
+                        bound_with: null,
                     },
                     geometry,
                 });
@@ -245,7 +245,7 @@ export function useMapInteraction({
                         entity_ids: [],
                         entity_name: null,
                         entity_type_id: null,
-                        binding: [],
+                        bound_with: null,
                     },
                     geometry,
                 });
@@ -267,7 +267,7 @@ export function useMapInteraction({
                         entity_ids: [],
                         entity_name: null,
                         entity_type_id: null,
-                        binding: [],
+                        bound_with: null,
                     },
                     geometry,
                 });
@@ -372,7 +372,7 @@ function buildDuplicatedFeatureShapeOnly(
             entity_ids: [],
             entity_name: null,
             entity_names: [],
-            binding: [],
+            bound_with: null,
         },
         geometry,
     };
diff --git a/src/uhm/doc/commit_snapshot.ts b/src/uhm/doc/commit_snapshot.ts
index 8b472d1..f1ca78d 100644
--- a/src/uhm/doc/commit_snapshot.ts
+++ b/src/uhm/doc/commit_snapshot.ts
@@ -47,7 +47,7 @@ export type FeatureProperties = {
     geometry_preset?: GeometryPreset | null;
     time_start?: number | null;
     time_end?: number | null;
-    binding?: string[];
+    bound_with?: string | null;
 
     // UI/editor-only denormalized fields.
     entity_id?: string | null;
@@ -103,7 +103,7 @@ export type GeometrySnapshot = {
     type?: string | null;
     draw_geometry?: Geometry;
     geometry?: Geometry;
-    binding?: string[];
+    bound_with?: string | null;
     time_start?: number | null;
     time_end?: number | null;
     bbox?: {
diff --git a/src/uhm/doc/developer_guide.md b/src/uhm/doc/developer_guide.md
index cf7b81b..5d0d574 100644
--- a/src/uhm/doc/developer_guide.md
+++ b/src/uhm/doc/developer_guide.md
@@ -76,7 +76,7 @@ Checklist an toàn:
    - `type`
    - `geometry_preset`
    - `entity_ids`
-   - `binding`
+   - `bound_with`
 6. Kiểm tra interaction cleanup khi chuyển mode.
 
 Nếu mode chưa được cleanup đúng, map rất dễ giữ preview cũ hoặc event listener cũ.
@@ -101,7 +101,7 @@ File quan trọng nhất là `editorSnapshot.ts`.
 
 - `normalizeEditorSnapshot(raw)`
   - đọc payload từ backend
-  - rehydrate fields UI như `entity_ids`, `entity_name`, `binding`, `time_start`, `time_end`
+  - rehydrate fields UI như `entity_ids`, `entity_name`, `bound_with`, `time_start`, `time_end`
 - `buildEditorSnapshot(options)`
   - strip các field generate-only khỏi `editor_feature_collection`
   - build `geometry_entity[]` và `entity_wiki[]`
@@ -175,7 +175,7 @@ Có thể do:
 
 - timeline filter
 - geometry visibility theo type
-- binding filter
+- bound_with filter
 
 Không phải lúc nào cũng là bug render layer.
 
diff --git a/src/uhm/doc/editor_data_roles.md b/src/uhm/doc/editor_data_roles.md
index b0e868c..65a2f37 100644
--- a/src/uhm/doc/editor_data_roles.md
+++ b/src/uhm/doc/editor_data_roles.md
@@ -94,9 +94,9 @@ Các link entity-wiki hiện tại của snapshot. Snapshot builder sẽ tự si
 
 Join table persist quan hệ geometry-entity trong snapshot commit. `feature.properties.entity_ids` chỉ là field denormalized cho UI.
 
-### `binding`
+### `bound_with`
 
-Field geometry-geometry binding trên feature. Binding này không tính là entity binding; geometry không có `entity_ids/entity_id` hợp lệ vẫn là orphan.
+Field geometry-geometry trên feature con, lưu id geometry cha mà nó nằm trong. `bound_with` không tính là entity binding; geometry không có `entity_ids/entity_id` hợp lệ vẫn là orphan.
 
 ### `geometryVisibility`
 
@@ -104,7 +104,7 @@ Map local visibility override. Key có thể là geometry id hoặc semantic geo
 
 ### `applyGeometryBindingFilter`
 
-Filter map theo selection/binding. Chỉ ảnh hưởng render trên map, không đổi draft và không đi snapshot.
+Filter map theo selection/bound_with. Chỉ ảnh hưởng render trên map, không đổi draft và không đi snapshot.
 
 ## Guard rails
 
diff --git a/src/uhm/doc/editor_features.md b/src/uhm/doc/editor_features.md
index ebb8e32..2c714ae 100644
--- a/src/uhm/doc/editor_features.md
+++ b/src/uhm/doc/editor_features.md
@@ -75,7 +75,7 @@ Geometry mới mặc định có:
 - `type: "country"`
 - `geometry_preset: "polygon"`
 - `entity_ids: []`
-- `binding: []`
+- `bound_with: null`
 
 ### Point (`add-point`)
 
@@ -143,7 +143,7 @@ Khi đang ở `select`, editor có thể sửa polygon/circle qua `editingEngine
 - `time_start`
 - `time_end`
 
-`binding` đang được hiển thị trong state form nhưng không có input edit trực tiếp trong panel; việc bind/unbind geometry hiện đi qua `GeometryBindingPanel`.
+`bound_with` không nằm trong form metadata; việc bind/unbind geometry hiện đi qua `GeometryBindingPanel`.
 
 Các ràng buộc đang có:
 
@@ -203,12 +203,12 @@ Panel `ProjectEntityRefsPanel` là nơi bind/unbind entity theo geometry đang c
 
 ### Geometry ↔ Geometry
 
-`GeometryBindingPanel` thao tác trên `feature.properties.binding`.
+`GeometryBindingPanel` thao tác trên `feature.properties.bound_with` của geometry con.
 
 - Chọn một geometry làm gốc.
-- Bind/unbind với geometry khác trong project.
+- Bind/unbind với geometry khác trong project bằng cách set/clear `bound_with` của geometry con.
 - Có nút focus để zoom vào geometry trong list binding.
-- Có toggle `Filter`: map chỉ hiển thị geometry liên quan tới selection nếu filter binding đang bật.
+- Có toggle `Filter`: map chỉ hiển thị geometry liên quan tới selection nếu filter bound_with đang bật.
 - Row geometry hiển thị chip trạng thái trong panel:
   - `no entity` nếu geometry chưa bind entity.
   - `no time` nếu thiếu cả `time_start` và `time_end`.
diff --git a/src/uhm/doc/editor_manual_test_checklist.md b/src/uhm/doc/editor_manual_test_checklist.md
index 3d13200..0d4102b 100644
--- a/src/uhm/doc/editor_manual_test_checklist.md
+++ b/src/uhm/doc/editor_manual_test_checklist.md
@@ -52,7 +52,7 @@ Checklist này dùng sau mỗi lần sửa editor. Không thay thế typecheck/l
 - Chọn một geometry, bind geometry khác trong `GeometryBindingPanel`.
 - Panel hiện chip `bound` cho geometry liên quan.
 - Toggle Filter: map chỉ hiện selection, selected children và parent/root phù hợp.
-- Undo bind/unbind geometry phải khôi phục `properties.binding`.
+- Undo bind/unbind geometry phải khôi phục `properties.bound_with`.
 - Bind geometry-geometry không làm mất chip `no entity` nếu geometry vẫn chưa bind entity.
 
 ## 6. Wiki và entity-wiki
@@ -69,7 +69,7 @@ Checklist này dùng sau mỗi lần sửa editor. Không thay thế typecheck/l
 ## 7. Replay
 
 - Chọn geometry có entity, bấm replay.
-- Replay mở với MAIN geo và các target ids liên quan binding.
+- Replay mở với MAIN geo và các target ids có `bound_with` trỏ tới MAIN.
 - Tạo stage, tạo step, đổi duration.
 - Thêm narrative action `set_title` và `set_descriptions`.
 - Thêm map action `set_time_filter`, `show_labels`, `hide_labels`.
diff --git a/src/uhm/doc/editor_operations.md b/src/uhm/doc/editor_operations.md
index de3bd43..2b78974 100644
--- a/src/uhm/doc/editor_operations.md
+++ b/src/uhm/doc/editor_operations.md
@@ -79,16 +79,16 @@ Một thao tác không cần undo nếu nó chỉ đổi trạng thái xem/đi
 | Ẩn/hiện geometry local | Eye button, map hide callback | `geometryVisibility` | Không | Không | Local UI only, không đi snapshot |
 | Geometry status panel | `GeometryBindingPanel` | Derived từ draft/timeline/visibility | Không | Không | Hiện `no entity`, `no time`, `partial time`, `timeline`, `out timeline`, `hidden`, `bound`, `new`; ID chỉ nằm trong tooltip |
 
-## 3. Geometry binding
+## 3. Geometry bound_with
 
 | Thao tác | Entry point | State đổi | Undo | Snapshot/commit | Ghi chú |
 | --- | --- | --- | --- | --- | --- |
 | Bind entity vào selected geometry | `ProjectEntityRefsPanel` checkbox | `entity_id`, `entity_ids`, `entity_name`, `entity_names` trên selected features | `properties` hoặc `group` | `geometry_entity[]` | Multi-select chỉ hợp lệ khi cùng shape type |
 | Unbind entity | `ProjectEntityRefsPanel` checkbox | Các field entity trên feature | `properties` hoặc `group` | `geometry_entity[]` delete delta nếu baseline có link | Commit/submit chặn geometry không còn entity |
-| Bind geometry-geometry | `GeometryBindingPanel` lock button | `feature.properties.binding` | `properties` hoặc `group` | `geometries[].binding` | Binding geometry không thay thế entity binding |
-| Unbind geometry-geometry | `GeometryBindingPanel` unlock button | `feature.properties.binding` | `properties` hoặc `group` | `geometries[].binding` | Không ảnh hưởng `geometry_entity[]` |
-| Bind nhiều geometry vào target | Map bind callback | `binding` của target geometry | `properties` | `geometries[].binding` | Tự bỏ target id khỏi source ids |
-| Toggle binding filter | `GeometryBindingPanel` filter checkbox | `geometryBindingFilterEnabled` | Không | Không | Chỉ lọc hiển thị map theo selection/binding |
+| Bind geometry-geometry | `GeometryBindingPanel` lock button | `child.properties.bound_with = selectedGeometryId` | `properties` | `geometries[].bound_with` | Geometry con lưu id cha; không thay thế entity binding |
+| Unbind geometry-geometry | `GeometryBindingPanel` unlock button | `child.properties.bound_with = null` | `properties` | `geometries[].bound_with` | Không ảnh hưởng `geometry_entity[]` |
+| Bind nhiều geometry vào target | Map bind callback | `bound_with` của từng source geometry | `properties` hoặc `group` | `geometries[].bound_with` | Tự bỏ target id khỏi source ids và chặn cycle |
+| Toggle binding filter | `GeometryBindingPanel` filter checkbox | `geometryBindingFilterEnabled` | Không | Không | Chỉ lọc hiển thị map theo selection/bound_with |
 
 ## 4. Entity snapshot
 
@@ -189,7 +189,7 @@ Khi một thao tác cần đi vào commit, kiểm output snapshot:
 - Wiki rows nằm trong `wikis[]`.
 - Entity-wiki rows nằm trong `entity_wiki[]`.
 - Replay script nằm trong `replays[]`, không lưu `replayDraft`.
-- Generate-only fields trên feature như `entity_id`, `entity_ids`, `entity_name`, `entity_names`, `entity_label_candidates`, `time_start`, `time_end`, `binding`, `type` được snapshot builder xử lý/loại bỏ đúng chỗ trước API payload.
+- Generate-only fields trên feature như `entity_id`, `entity_ids`, `entity_name`, `entity_names`, `entity_label_candidates`, `time_start`, `time_end`, `bound_with`, `type` được snapshot builder xử lý/loại bỏ đúng chỗ trước API payload.
 
 ## 12. Các thao tác cần audit lại nếu editor đổi lớn
 
diff --git a/src/uhm/doc/editor_snapshot_contract.md b/src/uhm/doc/editor_snapshot_contract.md
index cc620f7..f2b8667 100644
--- a/src/uhm/doc/editor_snapshot_contract.md
+++ b/src/uhm/doc/editor_snapshot_contract.md
@@ -63,10 +63,12 @@ Mỗi feature trong `mainDraft.features` sinh một row:
 | `operation` | `"create"`, `"update"` hoặc `"reference"` theo baseline/diff |
 | `type` | FE type key trước `toApiEditorSnapshot()`, backend code string sau normalize API |
 | `draw_geometry` | `feature.geometry` |
-| `binding` | `normalizeFeatureBindingIds(feature)` |
+| `bound_with` | `normalizeFeatureBoundWith(feature)` |
 | `time_start` / `time_end` | `feature.properties.time_start/time_end ?? null` |
 | `bbox` | BBox tính từ geometry, hoặc `null` |
 
+Snapshot legacy có `binding: string[]` trên geometry cha được FE migrate khi load bằng cách invert sang `bound_with` trên từng geometry con.
+
 Geometry đã bị xóa sinh row:
 
 ```ts
@@ -93,7 +95,7 @@ Geometry đã bị xóa sinh row:
 - `type`
 - `time_start`
 - `time_end`
-- `binding`
+- `bound_with`
 - `entity_id`
 - `entity_ids`
 - `entity_name`
@@ -103,7 +105,7 @@ Geometry đã bị xóa sinh row:
 
 Các field này được lưu ở collection chuẩn hơn:
 
-- `type/time/binding` nằm ở `geometries[]`.
+- `type/time/bound_with` nằm ở `geometries[]`.
 - entity relation nằm ở `geometry_entity[]`.
 - entity label/name được hydrate lại từ `entities[]` và join table khi load.
 
@@ -125,7 +127,7 @@ Build rule:
 
 Rows được dedupe/sort theo `geometry_id`, rồi `entity_id`.
 
-Commit/submit hiện chặn nếu có geometry không có entity ids hợp lệ. Geometry-geometry `binding` không được tính là đã bind entity.
+Commit/submit hiện chặn nếu có geometry không có entity ids hợp lệ. Geometry-geometry `bound_with` không được tính là đã bind entity.
 
 ## 6. Entity contract
 
diff --git a/src/uhm/doc/editor_state_replay.md b/src/uhm/doc/editor_state_replay.md
index b15acca..d996560 100644
--- a/src/uhm/doc/editor_state_replay.md
+++ b/src/uhm/doc/editor_state_replay.md
@@ -82,7 +82,7 @@ Replay seed mới có dạng:
 
 - MAIN geo
 - toàn bộ bulk selection hiện tại
-- toàn bộ `binding` của MAIN geo trong `mainDraft`
+- toàn bộ geometry con có `bound_with` trỏ tới MAIN geo trong `mainDraft`
 
 Rule hiện tại:
 
@@ -110,7 +110,7 @@ Hydrate hiện tại:
 
 - lấy feature từ `mainDraft` theo đúng thứ tự `target_geometry_ids`
 - clone ra `FeatureCollection` mới
-- flatten `binding` thành `[]` để các geo trong replay bình đẳng với nhau
+- flatten `bound_with` thành `null` để các geo trong replay bình đẳng với nhau
 
 ## 6. Trong replay mode map đang đọc gì
 
diff --git a/src/uhm/doc/editor_states.md b/src/uhm/doc/editor_states.md
index df07224..52113a7 100644
--- a/src/uhm/doc/editor_states.md
+++ b/src/uhm/doc/editor_states.md
@@ -116,9 +116,8 @@ Editor hiện có `undo`, nhưng chưa có redo.
   - `type_key`
   - `time_start`
   - `time_end`
-  - `binding`
 
-`geometryMetaForm.binding` hiện chủ yếu là giá trị hiển thị/đồng bộ UI, còn chỉnh sửa binding thật đi qua `GeometryBindingPanel`.
+Geometry-geometry bound state không nằm trong `geometryMetaForm`; `GeometryBindingPanel` chỉnh trực tiếp `feature.properties.bound_with` của geometry con.
 
 ### 4.3. Replay state
 
@@ -324,5 +323,5 @@ Hiệu ứng:
 - có `undo`, chưa có `redo`
 - timeline state có `timelineYear`, nhưng page hiện dùng `timelineDraftYear` cho filtering
 - dirty count của commit không tương ứng một-một với số mutation backend
-- map selection, binding filter và timeline filter đều là state client-side
+- map selection, bound_with filter và timeline filter đều là state client-side
 - trạng thái orphan/time/timeline trong `GeometryBindingPanel` là derived từ draft + visibility, không phải field persist riêng
diff --git a/src/uhm/doc/export_json_replay.md b/src/uhm/doc/export_json_replay.md
index d613712..ac9630e 100644
--- a/src/uhm/doc/export_json_replay.md
+++ b/src/uhm/doc/export_json_replay.md
@@ -86,7 +86,7 @@ FE không còn export/persist cả `FeatureCollection` riêng của replay nữa
 
 - geo MAIN
 - các geo được đưa vào replay từ bulk select
-- binding của MAIN geo
+- các geometry con có `bound_with` trỏ tới MAIN geo
 
 Khi mở replay, FE sẽ hydrate lại `replayDraft` từ:
 
diff --git a/src/uhm/doc/map_engine.md b/src/uhm/doc/map_engine.md
index 5fdfea4..3cd40d1 100644
--- a/src/uhm/doc/map_engine.md
+++ b/src/uhm/doc/map_engine.md
@@ -88,7 +88,7 @@ Source này dùng cho:
 `useMapSync()` chịu trách nhiệm:
 
 1. nhận `renderDraft` đã được page áp timeline/replay/preview filter trước
-2. filter draft theo binding nếu `applyGeometryBindingFilter = true`
+2. filter draft theo `bound_with` nếu `applyGeometryBindingFilter = true`
 3. filter theo geometry visibility
 4. split feature thành nhóm polygon/line/point
 5. decorate line/polygon/point cho label rendering
@@ -100,7 +100,7 @@ Source này dùng cho:
 - data mà map render không phải raw `mainDraft` nguyên xi
 - `renderDraft` là nguồn quyết định geometry nào xuất hiện trên map
 - `labelContextDraft` chỉ dùng để lookup label/entity name, có thể chứa geometry đã bị timeline filter ẩn, và không được dùng để quyết định render
-- source MapLibre cuối cùng là `renderDraft` sau khi đã qua binding filter, geometry visibility và label decoration
+- source MapLibre cuối cùng là `renderDraft` sau khi đã qua bound_with filter, geometry visibility và label decoration
 
 ## 5. Map interaction layer
 
diff --git a/src/uhm/doc/map_styling.md b/src/uhm/doc/map_styling.md
index d868fb3..61dfdd3 100644
--- a/src/uhm/doc/map_styling.md
+++ b/src/uhm/doc/map_styling.md
@@ -144,7 +144,7 @@ Có ba lớp filter hiển thị trong runtime:
 
 1. background layer visibility
 2. geometry visibility theo type key từ panel phải
-3. binding filter / replay filter / timeline filter ở phía data trước khi set source
+3. bound_with filter / replay filter / timeline filter ở phía data trước khi set source
 
 Vì vậy khi một geometry "không hiện", có thể nguyên nhân nằm ở data filtering chứ không phải style layer.
 
@@ -170,6 +170,6 @@ Implementation hiện tại không làm vậy.
 Thay vào đó:
 
 - timeline filter đang chạy phía data trong `page.tsx`
-- binding filter và geometry visibility cũng chủ yếu chạy trước khi set source
+- bound_with filter và geometry visibility cũng chủ yếu chạy trước khi set source
 
 Tức là phần lớn filtering là `prepare data -> set source`, không phải `add layer filter expression per year`.
diff --git a/src/uhm/doc/project_workflow.md b/src/uhm/doc/project_workflow.md
index ee744a4..fd3e430 100644
--- a/src/uhm/doc/project_workflow.md
+++ b/src/uhm/doc/project_workflow.md
@@ -151,7 +151,7 @@ và sinh ra:
 Các điểm quan trọng:
 
 - geometry many-to-many với entity được persist ở `geometry_entity[]`
-- denormalized fields trên feature như `entity_ids`, `entity_name`, `binding`, `time_start` sẽ bị strip khỏi `editor_feature_collection` trước khi gửi API
+- denormalized fields trên feature như `entity_ids`, `entity_name`, `bound_with`, `time_start` sẽ bị strip khỏi `editor_feature_collection` trước khi gửi API
 - wiki/entity/link được chuẩn hóa lại thành `reference`, `binding`, `delete`, `create`, `update` tùy baseline
 - replay script được persist ở `replays[]`; `replayDraft` không được gửi
 
diff --git a/src/uhm/lib/editor/editorPageUtils.ts b/src/uhm/lib/editor/editorPageUtils.ts
index 110e3c6..78d5a09 100644
--- a/src/uhm/lib/editor/editorPageUtils.ts
+++ b/src/uhm/lib/editor/editorPageUtils.ts
@@ -126,17 +126,10 @@ export function normalizeGeoSearchGeometry(value: unknown): Geometry | null {
     return value as Geometry;
 }
 
-// Chuẩn hóa danh sách binding id từ API search GEO.
-export function normalizeGeoSearchBindingIds(value: unknown): string[] {
-    if (!Array.isArray(value)) return [];
-    const deduped: string[] = [];
-    const seen = new Set<string>();
-    for (const rawId of value) {
-        if (typeof rawId !== "string" && typeof rawId !== "number") continue;
-        const id = String(rawId).trim();
-        if (!id || seen.has(id)) continue;
-        seen.add(id);
-        deduped.push(id);
-    }
-    return deduped;
+// Chuẩn hóa parent id từ API search GEO.
+export function normalizeGeoSearchBoundWith(value: unknown): string | null {
+    if (value == null) return null;
+    if (typeof value !== "string" && typeof value !== "number") return null;
+    const id = String(value).trim();
+    return id.length ? id : null;
 }
diff --git a/src/uhm/lib/editor/geometry/geometryBinding.ts b/src/uhm/lib/editor/geometry/geometryBinding.ts
new file mode 100644
index 0000000..0c58640
--- /dev/null
+++ b/src/uhm/lib/editor/geometry/geometryBinding.ts
@@ -0,0 +1,65 @@
+import type { Feature, FeatureCollection } from "@/uhm/types/geo";
+
+export function normalizeBoundWithId(value: unknown): string | null {
+    if (value == null) return null;
+    if (typeof value !== "string" && typeof value !== "number") return null;
+    const id = String(value).trim();
+    return id.length ? id : null;
+}
+
+export function normalizeFeatureBoundWith(feature: Feature): string | null {
+    return normalizeBoundWithId(feature.properties.bound_with);
+}
+
+export function normalizeLegacyGeometryBindingIds(value: unknown): string[] {
+    if (!Array.isArray(value)) return [];
+    const ids: string[] = [];
+    const seen = new Set<string>();
+    for (const rawId of value) {
+        const id = normalizeBoundWithId(rawId);
+        if (!id || seen.has(id)) continue;
+        seen.add(id);
+        ids.push(id);
+    }
+    return ids;
+}
+
+export function getDirectGeometryChildIds(
+    fc: FeatureCollection,
+    parentId: string | number | null | undefined
+): string[] {
+    const normalizedParentId = normalizeBoundWithId(parentId);
+    if (!normalizedParentId) return [];
+
+    return fc.features
+        .filter((feature) => normalizeFeatureBoundWith(feature) === normalizedParentId)
+        .map((feature) => String(feature.properties.id));
+}
+
+export function wouldCreateGeometryBoundWithCycle(
+    features: Feature[],
+    childId: string | number,
+    parentId: string | number
+): boolean {
+    const normalizedChildId = normalizeBoundWithId(childId);
+    const normalizedParentId = normalizeBoundWithId(parentId);
+    if (!normalizedChildId || !normalizedParentId) return false;
+
+    const parentByChild = new Map<string, string>();
+    for (const feature of features) {
+        const id = String(feature.properties.id);
+        const boundWith = normalizeFeatureBoundWith(feature);
+        if (boundWith) parentByChild.set(id, boundWith);
+    }
+
+    const seen = new Set<string>();
+    let cursor: string | null = normalizedParentId;
+    while (cursor) {
+        if (cursor === normalizedChildId) return true;
+        if (seen.has(cursor)) return false;
+        seen.add(cursor);
+        cursor = parentByChild.get(cursor) || null;
+    }
+
+    return false;
+}
diff --git a/src/uhm/lib/editor/geometry/geometryMetadata.ts b/src/uhm/lib/editor/geometry/geometryMetadata.ts
index 0e0d1d7..08d1b67 100644
--- a/src/uhm/lib/editor/geometry/geometryMetadata.ts
+++ b/src/uhm/lib/editor/geometry/geometryMetadata.ts
@@ -1,9 +1,6 @@
 import type { Feature, FeatureProperties } from "@/uhm/types/geo";
 import type { GeometryMetaFormState } from "@/uhm/lib/editor/session/sessionTypes";
-import {
-    normalizeFeatureBindingIds,
-    parseBindingInput,
-} from "@/uhm/lib/editor/snapshot/editorSnapshot";
+import { normalizeFeatureBoundWith } from "@/uhm/lib/editor/geometry/geometryBinding";
 
 export type GeometryMetadataPatch = {
     patch: Partial<FeatureProperties>;
@@ -18,27 +15,22 @@ export function buildGeometryMetadataPatch(form: GeometryMetaFormState): Geometr
         throw new Error("time_start phải <= time_end.");
     }
 
-    const bindingIds = parseBindingInput(form.binding);
     return {
         patch: {
             type: typeKey.length ? typeKey : undefined,
             time_start: timeStart,
             time_end: timeEnd,
-            binding: bindingIds,
         },
         formState: {
             type_key: typeKey,
             time_start: timeStart != null ? String(timeStart) : "",
             time_end: timeEnd != null ? String(timeEnd) : "",
-            binding: bindingIds.join(", "),
         },
     };
 }
 
-export function formatBindingIdsForDisplay(feature: Feature): string {
-    const bindingIds = normalizeFeatureBindingIds(feature);
-    if (!bindingIds.length) return "Không có";
-    return bindingIds.join(", ");
+export function formatBoundWithForDisplay(feature: Feature): string {
+    return normalizeFeatureBoundWith(feature) || "Không có";
 }
 
 function parseOptionalYearInput(raw: string, fieldName: string): number | null {
diff --git a/src/uhm/lib/editor/geometry/useFeatureCommands.ts b/src/uhm/lib/editor/geometry/useFeatureCommands.ts
index ae5fb88..b35e977 100644
--- a/src/uhm/lib/editor/geometry/useFeatureCommands.ts
+++ b/src/uhm/lib/editor/geometry/useFeatureCommands.ts
@@ -43,7 +43,7 @@ export function useFeatureCommands(options: Options) {
         setEntityFormStatus,
     } = options;
 
-    // Áp metadata GEO (type/time/binding) cho toàn bộ selectedFeatures.
+    // Áp metadata GEO (type/time) cho toàn bộ selectedFeatures.
     const applyGeometryMetadata = useCallback(async (): Promise<{ ok: boolean; error?: string }> => {
         if (!selectedFeatures || selectedFeatures.length === 0) {
             const msg = "Hãy chọn ít nhất một geometry trước.";
diff --git a/src/uhm/lib/editor/project/useProjectCommands.ts b/src/uhm/lib/editor/project/useProjectCommands.ts
index cde3376..53ba572 100644
--- a/src/uhm/lib/editor/project/useProjectCommands.ts
+++ b/src/uhm/lib/editor/project/useProjectCommands.ts
@@ -11,7 +11,6 @@ import {
 import {
     buildEditorSnapshot,
     normalizeEditorSnapshot,
-    normalizeFeatureEntityIds,
     toApiEditorSnapshot,
 } from "@/uhm/lib/editor/snapshot/editorSnapshot";
 import { normalizeTimelineYearValue } from "@/uhm/lib/utils/timeline";
@@ -230,7 +229,7 @@ export function useProjectCommands(options: Options) {
         } finally {
             state.setIsSubmitting(false);
         }
-    }, [options.editor.mainDraft, options.pendingSaveCount, options.store]);
+    }, [options.pendingSaveCount, options.store]);
 
     const restoreCommit = useCallback(async (commitId: string) => {
         const state = options.store.getState();
@@ -344,7 +343,7 @@ function toEditorSessionGeometries(input: EditorSnapshot["geometries"]): Geometr
                 type: g.type ?? undefined,
                 draw_geometry: g.draw_geometry,
                 geometry: g.geometry,
-                binding: Array.isArray(g.binding) ? [...g.binding] : undefined,
+                bound_with: g.bound_with ?? null,
                 time_start: normalizeTimelineYearValue(g.time_start) ?? undefined,
                 time_end: normalizeTimelineYearValue(g.time_end) ?? undefined,
                 bbox: g.bbox
diff --git a/src/uhm/lib/editor/session/sessionTypes.ts b/src/uhm/lib/editor/session/sessionTypes.ts
index 2023b2f..9c6618e 100644
--- a/src/uhm/lib/editor/session/sessionTypes.ts
+++ b/src/uhm/lib/editor/session/sessionTypes.ts
@@ -27,7 +27,6 @@ export type GeometryMetaFormState = {
     type_key: string;
     time_start: string;
     time_end: string;
-    binding: string;
 };
 
 export type PendingEntityCreate = {
diff --git a/src/uhm/lib/editor/session/useEntitySessionState.ts b/src/uhm/lib/editor/session/useEntitySessionState.ts
index 72fc036..604ee9b 100644
--- a/src/uhm/lib/editor/session/useEntitySessionState.ts
+++ b/src/uhm/lib/editor/session/useEntitySessionState.ts
@@ -25,12 +25,11 @@ export function useEntitySessionState() {
     });
     // Danh sách entity IDs đang chọn để bind vào geometry hiện tại.
     const [selectedGeometryEntityIds, setSelectedGeometryEntityIds] = useState<string[]>([]);
-    // Form metadata geometry (time range + binding ids).
+    // Form metadata geometry (type + time range).
     const [geometryMetaForm, setGeometryMetaForm] = useState<GeometryMetaFormState>({
         type_key: "",
         time_start: "",
         time_end: "",
-        binding: "",
     });
     // Cờ loading khi apply entity/metadata (local submit).
     const [isEntitySubmitting, setIsEntitySubmitting] = useState(false);
diff --git a/src/uhm/lib/editor/snapshot/editorSnapshot.ts b/src/uhm/lib/editor/snapshot/editorSnapshot.ts
index ef49ed7..1c935cf 100644
--- a/src/uhm/lib/editor/snapshot/editorSnapshot.ts
+++ b/src/uhm/lib/editor/snapshot/editorSnapshot.ts
@@ -2,6 +2,11 @@ import { DEFAULT_GEOMETRY_TYPE_ID } from "@/uhm/lib/map/geo/geometryTypeOptions"
 import { normalizeGeoTypeKey, typeKeyToGeoTypeCode } from "@/uhm/lib/map/geo/geoTypeMap";
 import { normalizeTimelineYearValue } from "@/uhm/lib/utils/timeline";
 import type { Change } from "@/uhm/lib/editor/draft/editorTypes";
+import {
+    normalizeBoundWithId,
+    normalizeFeatureBoundWith,
+    normalizeLegacyGeometryBindingIds,
+} from "@/uhm/lib/editor/geometry/geometryBinding";
 import type { EntitySnapshot } from "@/uhm/types/entities";
 import type { EntitySnapshotOperation } from "@/uhm/types/entities";
 import type { Feature, FeatureCollection, GeometryEntitySnapshot, GeometrySnapshot } from "@/uhm/types/geo";
@@ -55,6 +60,8 @@ interface RawGeometryRow extends UnknownRecord {
     geo_type?: unknown;
     draw_geometry?: unknown;
     geometry?: unknown;
+    bound_with?: unknown;
+    // Legacy parent->children geometry binding, migrated to child.bound_with on load.
     binding?: unknown;
     time_start?: unknown;
     time_end?: unknown;
@@ -100,6 +107,35 @@ function normalizeApiTimeFields(row: UnknownRecord): void {
     if ("time_end" in row) row.time_end = normalizeTimelineYearValue(row.time_end);
 }
 
+function buildLegacyBoundWithByChildId(
+    geometriesRaw: unknown,
+    fc: FeatureCollection | undefined
+): Map<string, string> {
+    const boundWithByChildId = new Map<string, string>();
+
+    const ingestParentBinding = (parentId: unknown, rawBinding: unknown) => {
+        const normalizedParentId = normalizeBoundWithId(parentId);
+        if (!normalizedParentId) return;
+        for (const childId of normalizeLegacyGeometryBindingIds(rawBinding)) {
+            if (childId === normalizedParentId || boundWithByChildId.has(childId)) continue;
+            boundWithByChildId.set(childId, normalizedParentId);
+        }
+    };
+
+    if (Array.isArray(geometriesRaw)) {
+        for (const raw of geometriesRaw) {
+            if (!isRecord(raw)) continue;
+            ingestParentBinding(raw.id, raw.binding);
+        }
+    }
+
+    for (const feature of fc?.features || []) {
+        ingestParentBinding(feature.properties?.id, (feature.properties as unknown as UnknownRecord)?.binding);
+    }
+
+    return boundWithByChildId;
+}
+
 export function normalizeEditorSnapshot(raw: unknown): EditorSnapshot | null {
     if (!isRecord(raw)) return null;
     const snapshot = raw as UnknownRecord;
@@ -139,6 +175,7 @@ export function normalizeEditorSnapshot(raw: unknown): EditorSnapshot | null {
         : undefined;
 
     const geometriesRaw = snapshot.geometries;
+    const legacyBoundWithByChildId = buildLegacyBoundWithByChildId(geometriesRaw, fc);
     const geometries: GeometrySnapshot[] | undefined = Array.isArray(geometriesRaw)
         ? geometriesRaw
             .filter(isRecord)
@@ -153,6 +190,10 @@ export function normalizeEditorSnapshot(raw: unknown): EditorSnapshot | null {
                 const hasInlineGeometry = "draw_geometry" in row || "geometry" in row;
                 const source: "inline" | "ref" = existingSource || (refId || !hasInlineGeometry ? "ref" : "inline");
                 const typeKey = normalizeGeoTypeKey(row.type) || normalizeGeoTypeKey(row.geo_type);
+                const canonicalBoundWith = "bound_with" in row ? normalizeBoundWithId(row.bound_with) : undefined;
+                const boundWith = canonicalBoundWith !== undefined
+                    ? canonicalBoundWith
+                    : legacyBoundWithByChildId.get(id);
 
                 return {
                     id,
@@ -161,7 +202,7 @@ export function normalizeEditorSnapshot(raw: unknown): EditorSnapshot | null {
                     type: typeKey,
                     draw_geometry: row.draw_geometry as GeometrySnapshot["draw_geometry"],
                     geometry: row.geometry as GeometrySnapshot["geometry"],
-                    binding: Array.isArray(row.binding) ? row.binding as string[] : undefined,
+                    bound_with: boundWith,
                     time_start: normalizeTimelineYearValue(row.time_start) ?? undefined,
                     time_end: normalizeTimelineYearValue(row.time_end) ?? undefined,
                     bbox: isRecord(row.bbox)
@@ -299,6 +340,17 @@ export function normalizeEditorSnapshot(raw: unknown): EditorSnapshot | null {
             const gid = String(feature.properties.id);
             const entity_ids = byGeom.get(gid) || [];
             const p = feature.properties as unknown as UnknownRecord;
+            const existingBoundWith = "bound_with" in p ? normalizeBoundWithId(p.bound_with) : undefined;
+            const migratedBoundWith = legacyBoundWithByChildId.get(gid);
+            if (existingBoundWith !== undefined) {
+                p.bound_with = existingBoundWith;
+            } else if (migratedBoundWith !== undefined) {
+                p.bound_with = migratedBoundWith;
+            } else {
+                delete p.bound_with;
+            }
+            delete p.binding;
+
             const existingTimeStart = normalizeTimelineYearValue(p.time_start);
             const existingTimeEnd = normalizeTimelineYearValue(p.time_end);
             if (existingTimeStart !== null) {
@@ -351,7 +403,9 @@ export function normalizeEditorSnapshot(raw: unknown): EditorSnapshot | null {
                     || existingTypeKey
                     || fallbackTypeKey;
                 if (typeKey) p.type = typeKey;
-                if (Array.isArray(geo.binding) && geo.binding.length) p.binding = geo.binding;
+                if (geo.bound_with !== undefined) {
+                    p.bound_with = geo.bound_with;
+                }
                 const timeStart = normalizeTimelineYearValue(geo.time_start);
                 const timeEnd = normalizeTimelineYearValue(geo.time_end);
                 if (timeStart !== null) {
@@ -519,7 +573,7 @@ export function buildEditorSnapshot(options: {
             source: "inline",
             type: typeKey,
             draw_geometry: feature.geometry,
-            binding: normalizeFeatureBindingIds(feature),
+            bound_with: normalizeFeatureBoundWith(feature),
             time_start: timeStart,
             time_end: timeEnd,
             bbox: bbox
@@ -588,6 +642,7 @@ export function buildEditorSnapshot(options: {
         delete p.type;
         delete p.time_start;
         delete p.time_end;
+        delete p.bound_with;
         delete p.binding;
         delete p.entity_id;
         delete p.entity_ids;
@@ -1113,27 +1168,6 @@ export function normalizeFeatureEntityIds(feature: Feature): string[] {
     return [];
 }
 
-export function normalizeFeatureBindingIds(feature: Feature): string[] {
-    const rawBinding = feature.properties.binding;
-    if (!Array.isArray(rawBinding)) return [];
-    return uniqueEntityIds(rawBinding
-        .map((id) => {
-            if (typeof id !== "string" && typeof id !== "number") return "";
-            return String(id).trim();
-        })
-        .filter((id) => id.length > 0));
-}
-
-export function parseBindingInput(raw: string): string[] {
-    if (!raw.trim().length) return [];
-    return uniqueEntityIds(
-        raw
-            .split(/[,\n]/)
-            .map((item) => item.trim())
-            .filter((item) => item.length > 0)
-    );
-}
-
 export function uniqueEntityIds(ids: string[]): string[] {
     const deduped: string[] = [];
     const seen = new Set<string>();
diff --git a/src/uhm/lib/editor/state/useEditorState.ts b/src/uhm/lib/editor/state/useEditorState.ts
index 8ac9bab..f87e30f 100644
--- a/src/uhm/lib/editor/state/useEditorState.ts
+++ b/src/uhm/lib/editor/state/useEditorState.ts
@@ -14,7 +14,7 @@ import type { WikiSnapshot } from "@/uhm/types/wiki";
 import type { BattleReplay, EntityWikiLinkSnapshot } from "@/uhm/types/projects";
 import { EMPTY_FEATURE_COLLECTION } from "@/uhm/lib/map/geo/constants";
 import type { EditorMode } from "@/uhm/lib/editor/session/sessionTypes";
-import { newId } from "@/uhm/lib/utils/id";
+import { normalizeFeatureBoundWith } from "@/uhm/lib/editor/geometry/geometryBinding";
 
 export type { Feature, FeatureCollection, FeatureProperties, Geometry } from "@/uhm/types/geo";
 export type { Change, UndoAction } from "@/uhm/lib/editor/draft/editorTypes";
@@ -552,12 +552,25 @@ export function useEditorState(
         if (idx === -1) return;
 
         const feature = mainDraftRef.current.features[idx];
+        const deletedId = String(feature.properties.id);
         const nextFeatures = [...mainDraftRef.current.features];
         nextFeatures.splice(idx, 1);
 
         const undoActions: UndoAction[] = [];
         const replayUndoAction = pruneReplaysForDeletedGeometryIds([feature.properties.id], `Xóa replay theo GEO #${feature.properties.id}`);
         if (replayUndoAction) undoActions.push(replayUndoAction);
+        for (let i = 0; i < nextFeatures.length; i += 1) {
+            if (normalizeFeatureBoundWith(nextFeatures[i]) !== deletedId) continue;
+            const prevProperties = deepClone(nextFeatures[i].properties);
+            nextFeatures[i] = {
+                ...nextFeatures[i],
+                properties: {
+                    ...nextFeatures[i].properties,
+                    bound_with: null,
+                },
+            };
+            undoActions.push({ type: "properties", id: nextFeatures[i].properties.id, prevProperties });
+        }
         undoActions.push({ type: "delete", feature: deepClone(feature), index: idx });
         pushMainUndo(
             undoActions.length === 1
@@ -574,28 +587,45 @@ export function useEditorState(
 
         const idsSet = new Set(ids.map(String));
         const nextFeatures: Feature[] = [];
-        const undoActions: UndoAction[] = [];
+        const deleteUndoActions: UndoAction[] = [];
+        const boundWithUndoActions: UndoAction[] = [];
 
         mainDraftRef.current.features.forEach((feature, index) => {
             if (idsSet.has(String(feature.properties.id))) {
-                undoActions.push({ type: "delete", feature: deepClone(feature), index });
+                deleteUndoActions.push({ type: "delete", feature: deepClone(feature), index });
             } else {
-                nextFeatures.push(feature);
+                const parentId = normalizeFeatureBoundWith(feature);
+                if (parentId && idsSet.has(parentId)) {
+                    boundWithUndoActions.push({
+                        type: "properties",
+                        id: feature.properties.id,
+                        prevProperties: deepClone(feature.properties),
+                    });
+                    nextFeatures.push({
+                        ...feature,
+                        properties: {
+                            ...feature.properties,
+                            bound_with: null,
+                        },
+                    });
+                } else {
+                    nextFeatures.push(feature);
+                }
             }
         });
 
-        if (undoActions.length === 0) return;
+        if (deleteUndoActions.length === 0) return;
 
-        const replayUndoAction = pruneReplaysForDeletedGeometryIds(ids, `Xóa replay theo ${undoActions.length} GEO`);
+        const replayUndoAction = pruneReplaysForDeletedGeometryIds(ids, `Xóa replay theo ${deleteUndoActions.length} GEO`);
         const groupedActions = replayUndoAction
-            ? [replayUndoAction, ...undoActions.slice().reverse()]
-            : undoActions.length === 1
-                ? undoActions
-                : undoActions.slice().reverse();
+            ? [replayUndoAction, ...boundWithUndoActions, ...deleteUndoActions.slice().reverse()]
+            : deleteUndoActions.length === 1 && boundWithUndoActions.length === 0
+                ? deleteUndoActions
+                : [...boundWithUndoActions, ...deleteUndoActions.slice().reverse()];
         pushMainUndo(
             groupedActions.length === 1
                 ? groupedActions[0]
-                : { type: "group", label: `Xóa ${undoActions.length} geometry`, actions: groupedActions }
+                : { type: "group", label: `Xóa ${deleteUndoActions.length} geometry`, actions: groupedActions }
         );
         commitMainDraft({ ...mainDraftRef.current, features: nextFeatures });
     }
@@ -620,6 +650,21 @@ export function useEditorState(
         };
         nextFeatures[idx] = newFeature;
 
+        const boundWithUndoActions: UndoAction[] = [];
+        for (let i = 0; i < nextFeatures.length; i += 1) {
+            if (i === idx) continue;
+            if (normalizeFeatureBoundWith(nextFeatures[i]) !== String(oldId)) continue;
+            const prevProperties = deepClone(nextFeatures[i].properties);
+            nextFeatures[i] = {
+                ...nextFeatures[i],
+                properties: {
+                    ...nextFeatures[i].properties,
+                    bound_with: String(newId),
+                },
+            };
+            boundWithUndoActions.push({ type: "properties", id: nextFeatures[i].properties.id, prevProperties });
+        }
+
         // Cập nhật replays nếu có
         const prevReplays = replaysRef.current || [];
         const nextReplays = prevReplays.map((replay) => {
@@ -640,6 +685,7 @@ export function useEditorState(
             type: "group",
             label: `Đổi ID GEO #${oldId} -> #${newId}`,
             actions: [
+                ...boundWithUndoActions,
                 { type: "replays", label: "Phục hồi replay cũ", prevReplays: deepClone(prevReplays) },
                 { type: "create", id: newId },
                 { type: "delete", feature: deepClone(prevFeature), index: idx },
@@ -910,7 +956,7 @@ function createReplaySessionSeed(
         id: geometryId,
         geometry_id: geometryId,
         target_geometry_ids: buildReplaySeedTargetIds(
-            sourceDraft.features.find((feature) => String(feature.properties.id) === geometryId),
+            sourceDraft,
             geometryId,
             selectedIds
         ),
@@ -926,8 +972,7 @@ function normalizeReplaySessionSeed(
 ): BattleReplay {
     const nextReplay = deepClone(replay);
     nextReplay.id = geometryId;
-    const triggerFeature = sourceDraft.features.find((feature) => String(feature.properties.id) === geometryId);
-    const seedTargetIds = buildReplaySeedTargetIds(triggerFeature, geometryId, selectedIds);
+    const seedTargetIds = buildReplaySeedTargetIds(sourceDraft, geometryId, selectedIds);
     nextReplay.target_geometry_ids = normalizeReplayTargetGeometryIds(
         nextReplay.target_geometry_ids,
         geometryId,
@@ -937,7 +982,7 @@ function normalizeReplaySessionSeed(
 }
 
 function buildReplaySeedTargetIds(
-    triggerFeature: Feature | undefined,
+    sourceDraft: FeatureCollection,
     featureId: string,
     selectedIds: (string | number)[]
 ) {
@@ -958,9 +1003,9 @@ function buildReplaySeedTargetIds(
         pushId(rawId);
     }
 
-    if (Array.isArray(triggerFeature?.properties?.binding)) {
-        for (const rawId of triggerFeature.properties.binding) {
-            pushId(rawId);
+    for (const feature of sourceDraft.features) {
+        if (normalizeFeatureBoundWith(feature) === featureId) {
+            pushId(feature.properties.id);
         }
     }
 
@@ -1020,7 +1065,7 @@ function sanitizeReplayFeature(feature: Feature): Feature {
         ...feature,
         properties: {
             ...feature.properties,
-            binding: [],
+            bound_with: null,
         },
     };
 }
diff --git a/src/uhm/store/editorStore.tsx b/src/uhm/store/editorStore.tsx
index 95dd745..8ede540 100644
--- a/src/uhm/store/editorStore.tsx
+++ b/src/uhm/store/editorStore.tsx
@@ -257,7 +257,6 @@ export function createEditorStore(options: EditorStoreOptions): EditorStoreApi {
                 type_key: "",
                 time_start: "",
                 time_end: "",
-                binding: "",
             },
             isEntitySubmitting: false,
             entityFormStatus: null,
diff --git a/src/uhm/types/geo.ts b/src/uhm/types/geo.ts
index 43720d2..c2726f7 100644
--- a/src/uhm/types/geo.ts
+++ b/src/uhm/types/geo.ts
@@ -21,7 +21,7 @@ export type FeatureProperties = {
     geometry_preset?: GeometryPreset | null;
     time_start?: number | null;
     time_end?: number | null;
-    binding?: string[];
+    bound_with?: string | null;
     entity_id?: string | null;
     entity_ids?: string[];
     entity_name?: string | null;
@@ -60,7 +60,7 @@ export type GeometrySnapshot = {
     type?: string | null;
     draw_geometry?: Geometry;
     geometry?: Geometry;
-    binding?: string[];
+    bound_with?: string | null;
     time_start?: number | null;
     time_end?: number | null;
     bbox?: {