diff --git a/apps/agor-ui/src/components/SessionCanvas/canvas/BoardObjectNodes.test.tsx b/apps/agor-ui/src/components/SessionCanvas/canvas/BoardObjectNodes.test.tsx
index d4919536a..f0acd5619 100644
--- a/apps/agor-ui/src/components/SessionCanvas/canvas/BoardObjectNodes.test.tsx
+++ b/apps/agor-ui/src/components/SessionCanvas/canvas/BoardObjectNodes.test.tsx
@@ -2,10 +2,19 @@ import { fireEvent, render, screen } from '@testing-library/react';
 import { App as AntApp } from 'antd';
 import type { ReactNode } from 'react';
 import { ReactFlowProvider } from 'reactflow';
-import { describe, expect, it, vi } from 'vitest';
+import { beforeEach, describe, expect, it, vi } from 'vitest';
 import { ConnectionProvider } from '../../../contexts/ConnectionContext';
 import { ZoneNode } from './BoardObjectNodes';
 
+const zoneConfigModalRenderSpy = vi.hoisted(() => vi.fn());
+
+vi.mock('./ZoneConfigModal', () => ({
+  ZoneConfigModal: (props: { zoneName: string }) => {
+    zoneConfigModalRenderSpy(props);
+    return <div data-testid="zone-config-modal">Configure Zone: {props.zoneName}</div>;
+  },
+}));
+
 const CONNECTED = {
   connected: true,
   connecting: false,
@@ -106,3 +115,21 @@ describe('ZoneNode layer toolbar', () => {
     expect(onReorder).not.toHaveBeenCalled();
   });
 });
+
+describe('ZoneNode config modal', () => {
+  beforeEach(() => {
+    zoneConfigModalRenderSpy.mockClear();
+  });
+
+  it('mounts the configuration modal only when the user opens it', () => {
+    renderZone(vi.fn(), CONNECTED);
+
+    expect(zoneConfigModalRenderSpy).not.toHaveBeenCalled();
+    expect(screen.queryByTestId('zone-config-modal')).not.toBeInTheDocument();
+
+    fireEvent.pointerUp(screen.getByTitle('Configure zone'));
+
+    expect(zoneConfigModalRenderSpy).toHaveBeenCalledTimes(1);
+    expect(screen.getByTestId('zone-config-modal')).toHaveTextContent('Configure Zone: My Zone');
+  });
+});
diff --git a/apps/agor-ui/src/components/SessionCanvas/canvas/BoardObjectNodes.tsx b/apps/agor-ui/src/components/SessionCanvas/canvas/BoardObjectNodes.tsx
index 2063f9e17..2c267c2f5 100644
--- a/apps/agor-ui/src/components/SessionCanvas/canvas/BoardObjectNodes.tsx
+++ b/apps/agor-ui/src/components/SessionCanvas/canvas/BoardObjectNodes.tsx
@@ -17,7 +17,7 @@ import {
 import { ColorPicker, theme } from 'antd';
 import type { Color } from 'antd/es/color-picker';
 import { AggregationColor } from 'antd/es/color-picker/color';
-import React, { useEffect, useRef, useState } from 'react';
+import React, { useEffect, useMemo, useRef, useState } from 'react';
 import { NodeResizer, useViewport } from 'reactflow';
 import { useMutationGate } from '../../../contexts/ConnectionContext';
 import { DeleteZoneModal } from './DeleteZoneModal';
@@ -49,27 +49,13 @@ const getColorPalette = (token: ReturnType<typeof theme.useToken>['token']) => [
   token.magenta6 || token.magenta, // magenta-6
 ];
 
+type ZoneBoardObject = Extract<BoardObject, { type: 'zone' }>;
+
 /**
  * ZoneNode - Resizable rectangle for organizing sessions visually
  */
-interface ZoneNodeData {
+interface ZoneNodeData extends Omit<ZoneBoardObject, 'type'> {
   objectId: string;
-  label: string;
-  width: number;
-  height: number;
-  borderColor?: string;
-  backgroundColor?: string;
-  /** @deprecated Use borderColor instead */
-  color?: string;
-  status?: string;
-  locked?: boolean;
-  /** Label/status font size in px. Falls back to the theme default when unset. */
-  fontSize?: number;
-  /** Effective base stacking order (persisted value or per-type default). */
-  zIndex?: number;
-  x: number;
-  y: number;
-  trigger?: BoardObject extends { type: 'zone'; trigger?: infer T } ? T : never;
   pinnedItemCount?: number;
   onUpdate?: (objectId: string, objectData: BoardObject) => void;
   onDelete?: (objectId: string, deleteAssociatedSessions: boolean) => void;
@@ -149,36 +135,43 @@ const ZoneNodeComponent = ({ data, selected }: { data: ZoneNodeData; selected?:
     }
   }, [isEditingLabel]);
 
+  const zoneData = useMemo<ZoneBoardObject>(
+    () => ({
+      type: 'zone',
+      x: data.x,
+      y: data.y,
+      width: data.width,
+      height: data.height,
+      label: data.label,
+      borderColor: data.borderColor,
+      backgroundColor: data.backgroundColor,
+      color: data.color,
+      status: data.status,
+      locked: data.locked,
+      fontSize: data.fontSize,
+      zIndex: data.zIndex,
+      trigger: data.trigger,
+    }),
+    [
+      data.x,
+      data.y,
+      data.width,
+      data.height,
+      data.label,
+      data.borderColor,
+      data.backgroundColor,
+      data.color,
+      data.status,
+      data.locked,
+      data.fontSize,
+      data.zIndex,
+      data.trigger,
+    ]
+  );
+
   // Helper to create full object data with current values
-  const createObjectData = (
-    overrides: Partial<{
-      width: number;
-      height: number;
-      label: string;
-      borderColor?: string;
-      backgroundColor?: string;
-      color?: string;
-      status?: string;
-      locked?: boolean;
-      fontSize?: number;
-      zIndex?: number;
-      trigger?: BoardObject extends { type: 'zone'; trigger?: infer T } ? T : never;
-    }>
-  ): BoardObject => ({
-    type: 'zone',
-    x: data.x,
-    y: data.y,
-    width: data.width,
-    height: data.height,
-    label: data.label,
-    borderColor: data.borderColor,
-    backgroundColor: data.backgroundColor,
-    color: data.color,
-    status: data.status,
-    locked: data.locked,
-    fontSize: data.fontSize,
-    zIndex: data.zIndex,
-    trigger: data.trigger,
+  const createObjectData = (overrides: Partial<Omit<ZoneBoardObject, 'type'>>): BoardObject => ({
+    ...zoneData,
     ...overrides,
   });
 
@@ -905,26 +898,30 @@ const ZoneNodeComponent = ({ data, selected }: { data: ZoneNodeData; selected?:
           </div>
         )}
       </div>
-      <ZoneConfigModal
-        open={configModalOpen}
-        onCancel={() => setConfigModalOpen(false)}
-        zoneName={data.label}
-        objectId={data.objectId}
-        onUpdate={data.onUpdate || (() => {})}
-        zoneData={createObjectData({})}
-      />
-      <DeleteZoneModal
-        open={deleteModalOpen}
-        onCancel={() => setDeleteModalOpen(false)}
-        onConfirm={(deleteAssociatedSessions) => {
-          setDeleteModalOpen(false);
-          if (data.onDelete) {
-            data.onDelete(data.objectId, deleteAssociatedSessions);
-          }
-        }}
-        zoneName={data.label}
-        pinnedItemCount={data.pinnedItemCount || 0}
-      />
+      {configModalOpen && (
+        <ZoneConfigModal
+          open={configModalOpen}
+          onCancel={() => setConfigModalOpen(false)}
+          zoneName={data.label}
+          objectId={data.objectId}
+          onUpdate={data.onUpdate || (() => {})}
+          zoneData={zoneData}
+        />
+      )}
+      {deleteModalOpen && (
+        <DeleteZoneModal
+          open={deleteModalOpen}
+          onCancel={() => setDeleteModalOpen(false)}
+          onConfirm={(deleteAssociatedSessions) => {
+            setDeleteModalOpen(false);
+            if (data.onDelete) {
+              data.onDelete(data.objectId, deleteAssociatedSessions);
+            }
+          }}
+          zoneName={data.label}
+          pinnedItemCount={data.pinnedItemCount || 0}
+        />
+      )}
     </>
   );
 };
diff --git a/apps/agor-ui/src/components/SessionCanvas/canvas/ZoneConfigModal.test.tsx b/apps/agor-ui/src/components/SessionCanvas/canvas/ZoneConfigModal.test.tsx
new file mode 100644
index 000000000..d5237c805
--- /dev/null
+++ b/apps/agor-ui/src/components/SessionCanvas/canvas/ZoneConfigModal.test.tsx
@@ -0,0 +1,44 @@
+import type { BoardObject } from '@agor-live/client';
+import { fireEvent, render, screen } from '@testing-library/react';
+import { describe, expect, it } from 'vitest';
+import { ZoneConfigModal } from './ZoneConfigModal';
+
+const zoneData = (label: string): BoardObject => ({
+  type: 'zone',
+  x: 0,
+  y: 0,
+  width: 400,
+  height: 600,
+  label,
+});
+
+describe('ZoneConfigModal', () => {
+  it('does not reset in-progress edits during parent rerenders while open', () => {
+    const { rerender } = render(
+      <ZoneConfigModal
+        open
+        onCancel={() => {}}
+        zoneName="Zone"
+        objectId="zone-1"
+        onUpdate={() => {}}
+        zoneData={zoneData('Zone')}
+      />
+    );
+
+    const nameInput = screen.getByLabelText('Zone Name');
+    fireEvent.change(nameInput, { target: { value: 'Draft name' } });
+
+    rerender(
+      <ZoneConfigModal
+        open
+        onCancel={() => {}}
+        zoneName="Zone"
+        objectId="zone-1"
+        onUpdate={() => {}}
+        zoneData={zoneData('Zone')}
+      />
+    );
+
+    expect(nameInput).toHaveValue('Draft name');
+  });
+});
diff --git a/apps/agor-ui/src/components/SessionCanvas/canvas/ZoneConfigModal.tsx b/apps/agor-ui/src/components/SessionCanvas/canvas/ZoneConfigModal.tsx
index 61de53996..d5b18c9bd 100644
--- a/apps/agor-ui/src/components/SessionCanvas/canvas/ZoneConfigModal.tsx
+++ b/apps/agor-ui/src/components/SessionCanvas/canvas/ZoneConfigModal.tsx
@@ -47,17 +47,26 @@ export const ZoneConfigModal = ({
 
   const triggerBehavior = Form.useWatch('triggerBehavior', form);
 
-  // Reset form when modal opens (prevent WebSocket updates from erasing user input)
+  const zoneTrigger = zoneData.type === 'zone' ? zoneData.trigger : undefined;
+  const hasZoneTrigger = Boolean(zoneTrigger);
+  const zoneTriggerBehavior = zoneTrigger?.behavior;
+  const zoneTriggerTemplate = zoneTrigger?.template;
+  const zoneTriggerAgent = zoneTrigger?.agent;
+
+  // Reset form when modal opens (prevent WebSocket updates from erasing user input).
+  // Keep dependencies to stable primitive fields: ZoneNode re-renders often, and
+  // passing a freshly-created zone object through this effect used to make AntD's
+  // Form/Modal tree re-run initialization work unnecessarily while open.
   useEffect(() => {
     if (open && !isInitializingRef.current) {
       isInitializingRef.current = true;
-      if (zoneData.type === 'zone' && zoneData.trigger) {
+      if (hasZoneTrigger) {
         form.setFieldsValue({
           name: zoneName,
-          triggerBehavior: zoneData.trigger.behavior,
-          triggerTemplate: zoneData.trigger.template,
+          triggerBehavior: zoneTriggerBehavior,
+          triggerTemplate: zoneTriggerTemplate,
         });
-        setTriggerAgent(zoneData.trigger.agent || 'claude-code');
+        setTriggerAgent(zoneTriggerAgent || 'claude-code');
       } else {
         form.setFieldsValue({
           name: zoneName,
@@ -69,7 +78,15 @@ export const ZoneConfigModal = ({
     } else if (!open) {
       isInitializingRef.current = false;
     }
-  }, [open, zoneName, zoneData, form]);
+  }, [
+    open,
+    zoneName,
+    hasZoneTrigger,
+    zoneTriggerBehavior,
+    zoneTriggerTemplate,
+    zoneTriggerAgent,
+    form,
+  ]);
 
   const handleSave = async () => {
     if (!mutationGate.canMutate) return;