fix: Prevent corruption of workflow data due to checkState during graph loading (#9531)

## Summary

During workflow loading, the workflow data & active workflow object can
be out of sync, meaning any checkState calls will overwrite data into
the wrong workflow.

Recreation steps:
* Open 2-3 workflows
* Enter builder mode > select step
* Select some different inputs on each
* Quickly tap the shift key (this triggers checkState) while switching
tabs
* After a while, you'll see the wrong inputs on the workflows

Alternatively, register an extension that guarantees to call checkState
during the bad phase, run this in browser devtools and switch tabs:
```
window.app.registerExtension({
  name: 'bad',
  async afterConfigureGraph() {
    window.app.extensionManager.workflow.activeWorkflow.changeTracker.checkState()
  }
})
```

## Changes

- **What**: 
- Add loading graph flag
- Prevent checkState calls while loading
- Prevent app mode data sync while loading

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9531-fix-Prevent-corruption-of-workflow-data-due-to-checkState-during-graph-loading-31c6d73d365081e2ab91d9145bf1d025)
by [Unito](https://www.unito.io)

src/scripts/app.ts

@@ -9,6 +9,7 @@ import { layoutStore } from '@/renderer/core/layout/store/layoutStore'
 import { flushScheduledSlotLayoutSync } from '@/renderer/extensions/vueNodes/composables/useSlotElementTracking'
 
 import { st, t } from '@/i18n'
+import { ChangeTracker } from '@/scripts/changeTracker'
 import type { IContextMenuValue } from '@/lib/litegraph/src/interfaces'
 import {
   LGraph,
@@ -1306,6 +1307,8 @@ export class ComfyApp {
       }
     }
 
+    ChangeTracker.isLoadingGraph = true
+    try {
       try {
         // @ts-expect-error Discrepancies between zod and litegraph - in progress
         this.rootGraph.configure(graphData)
@@ -1376,7 +1379,9 @@ export class ComfyApp {
                 values.length > 0 &&
                 (widget.value == null ||
                   (reset_invalid_values &&
-                  !values.includes(widget.value as string | number | boolean)))
+                    !values.includes(
+                      widget.value as string | number | boolean
+                    )))
               ) {
                 widget.value = values[0]
               }
@@ -1436,6 +1441,9 @@ export class ComfyApp {
       requestAnimationFrame(() => {
         this.canvas.setDirty(true, true)
       })
+    } finally {
+      ChangeTracker.isLoadingGraph = false
+    }
   }
 
   async graphToPrompt(graph = this.rootGraph) {

src/scripts/changeTracker.ts

@@ -28,6 +28,14 @@ logger.setLevel('info')
 
 export class ChangeTracker {
   static MAX_HISTORY = 50
+  /**
+   * Guard flag to prevent checkState from running during loadGraphData.
+   * Between rootGraph.configure() and afterLoadNewGraph(), the rootGraph
+   * contains the NEW workflow's data while activeWorkflow still points to
+   * the OLD workflow. Any checkState call in that window would serialize
+   * the wrong graph into the old workflow's activeState, corrupting it.
+   */
+  static isLoadingGraph = false
   /**
    * The active state of the workflow.
    */
@@ -131,7 +139,7 @@ export class ChangeTracker {
   }
 
   checkState() {
-    if (!app.graph || this.changeCount) return
+    if (!app.graph || this.changeCount || ChangeTracker.isLoadingGraph) return
     const currentState = clone(app.rootGraph.serialize()) as ComfyWorkflowJSON
     if (!this.activeState) {
       this.activeState = currentState

src/stores/appModeStore.ts

@@ -9,6 +9,7 @@ import { useCanvasStore } from '@/renderer/core/canvas/canvasStore'
 import { useWorkflowStore } from '@/platform/workflow/management/stores/workflowStore'
 import { useSidebarTabStore } from '@/stores/workspace/sidebarTabStore'
 import { app } from '@/scripts/app'
+import { ChangeTracker } from '@/scripts/changeTracker'
 import { resolveNode } from '@/utils/litegraphUtil'
 
 export const useAppModeStore = defineStore('appMode', () => {
@@ -77,7 +78,7 @@ export const useAppModeStore = defineStore('appMode', () => {
         ? { inputs: selectedInputs, outputs: selectedOutputs }
         : null,
     (data) => {
-      if (!data) return
+      if (!data || ChangeTracker.isLoadingGraph) return
       const graph = app.rootGraph
       if (!graph) return
       const extra = (graph.extra ??= {})