fix: reduce autosave function invocation spam (25x anomaly) (#108)

* fix: reduce autosave function invocation spam (25x anomaly)

Root cause: useProjectScene() was mounted in BOTH editor/index.tsx
AND project-dropdown.tsx, creating duplicate zustand subscriptions
that each independently triggered saveProjectModel() server actions.

Combined with a 2-second debounce and the fact that each server
action also calls getSession() (another function invocation), active
editing was generating ~120+ invocations/minute.

Changes:
- Remove duplicate useProjectScene() from project-dropdown.tsx
- Increase autosave debounce from 2s to 10s
- Skip auto-save on initial scene load from server (was saving the
  scene right back after loading it)
- Add pending-save coalescing: changes during in-flight saves get
  batched into one follow-up save instead of queuing concurrently

* fix: flush unsaved scene to cloud on page exit / unmount

Adds two safety nets so the 10s debounce doesn't lose data:
- beforeunload listener: fires saveProjectModel() when the user
  closes the tab or navigates away externally
- cleanup flush on unmount: fires when navigating within the SPA
  (e.g. switching projects, going to settings)

Both are fire-and-forget — if the browser kills the request,
localStorage still has the data and will sync on next load.

* style: fix biome import ordering in project-dropdown

---------

Co-authored-by: Anton Pascal <anton-pascal@users.noreply.github.com>

apps/editor/features/community/components/project-dropdown.tsx

@@ -2,29 +2,28 @@
 
 import { Check, ChevronDown, Home, Plus } from 'lucide-react'
 import { useState } from 'react'
-import { useProjectStore } from '../lib/projects/store'
-import { cn } from '@/lib/utils'
 import {
   DropdownMenu,
   DropdownMenuContent,
   DropdownMenuItem,
   DropdownMenuTrigger,
 } from '@/components/ui/primitives/dropdown-menu'
+import { cn } from '@/lib/utils'
+import { useProjectStore } from '../lib/projects/store'
 import { NewProjectDialog } from './new-project-dialog'
-import { useProjectScene } from '../lib/models/hooks'
 
 /**
  * ProjectDropdown - Shows active project and allows switching between projects
+ * Note: useProjectScene() is called in the Editor component, not here.
+ * Having it in both places caused duplicate subscriptions and 2x server action calls.
  */
 export function ProjectDropdown() {
-  useProjectScene() // Load and auto-save project scenes
-
   // Use project store
-  const projects = useProjectStore(state => state.projects)
-  const activeProject = useProjectStore(state => state.activeProject)
-  const isLoading = useProjectStore(state => state.isLoading)
-  const setActiveProject = useProjectStore(state => state.setActiveProject)
-  const fetchProjects = useProjectStore(state => state.fetchProjects)
+  const projects = useProjectStore((state) => state.projects)
+  const activeProject = useProjectStore((state) => state.activeProject)
+  const isLoading = useProjectStore((state) => state.isLoading)
+  const setActiveProject = useProjectStore((state) => state.setActiveProject)
+  const fetchProjects = useProjectStore((state) => state.fetchProjects)
 
   const [isNewProjectDialogOpen, setIsNewProjectDialogOpen] = useState(false)
 

apps/editor/features/community/lib/models/hooks.ts

@@ -11,9 +11,15 @@ import useEditor from '@/store/use-editor'
 import { useProjectStore } from '../projects/store'
 import { getProjectModel, saveProjectModel } from './actions'
 
+/** Debounce interval for cloud auto-save (ms). */
+const AUTOSAVE_DEBOUNCE_MS = 10_000
+
 /**
- * Load the scene when a project becomes active
- * Saves changes automatically with debouncing
+ * Load the scene when a project becomes active.
+ * Saves changes automatically with debouncing.
+ *
+ * ⚠️  This hook must be mounted in exactly ONE component (the Editor).
+ *     Mounting it in multiple components causes duplicate save calls.
  */
 export function useProjectScene() {
   // Subscribe to project store
@@ -24,10 +30,15 @@ export function useProjectScene() {
   const saveTimeoutRef = useRef<NodeJS.Timeout | undefined>(undefined)
   const isSavingRef = useRef(false)
   const currentProjectIdRef = useRef<string | null>(null)
+  // Track whether the scene was just loaded from the server so we can skip
+  // the first store update (which is the load itself, not a user edit).
+  const isLoadingSceneRef = useRef(false)
+  // Track whether there are pending changes that arrived while a save was
+  // in-flight so we can coalesce them into one follow-up save.
+  const pendingSaveRef = useRef(false)
 
   // Extract project ID for dependency tracking
   const projectId = activeProject?.id ?? null
-  const projectName = activeProject?.name ?? null
 
   // Load scene when active project changes
   useEffect(() => {
@@ -48,6 +59,9 @@ export function useProjectScene() {
 
     // Load the project's scene
     async function loadScene() {
+      // Suppress auto-save for the store update caused by setScene/clearScene
+      isLoadingSceneRef.current = true
+
       try {
         const result = await getProjectModel(projectId || '')
 
@@ -72,11 +86,19 @@ export function useProjectScene() {
         selectedIds: [],
         zoneId: null,
       })
+
+      // Allow auto-save again after a tick (let the store update propagate)
+      requestAnimationFrame(() => {
+        isLoadingSceneRef.current = false
+      })
     }
 
     loadScene()
   }, [projectId, isLoadingProject])
 
+  // Track whether there are unsaved changes (dirty flag for flush-on-exit).
+  const hasDirtyChangesRef = useRef(false)
+
   // Auto-save scene changes with debouncing
   useEffect(() => {
     if (!projectId) {
@@ -86,11 +108,17 @@ export function useProjectScene() {
 
     currentProjectIdRef.current = projectId
 
-    // Subscribe to any scene changes
-    // Use JSON stringification to detect any node changes, not just count
+    // Use JSON stringification to detect node changes, not just count
     let lastNodesSnapshot = JSON.stringify(useScene.getState().nodes)
 
     const unsubscribe = useScene.subscribe((state) => {
+      // Skip saves triggered by loading a scene from the server
+      if (isLoadingSceneRef.current) {
+        // Update the snapshot so the next real edit is compared correctly
+        lastNodesSnapshot = JSON.stringify(state.nodes)
+        return
+      }
+
       const currentNodesSnapshot = JSON.stringify(state.nodes)
 
       // Only trigger save if nodes actually changed
@@ -99,43 +127,81 @@ export function useProjectScene() {
       }
 
       lastNodesSnapshot = currentNodesSnapshot
-      const nodes = state.nodes
+      hasDirtyChangesRef.current = true
 
-      // Skip if currently saving
+      // If a save is in-flight, mark pending so we do one follow-up save
+      // instead of queuing unlimited concurrent saves.
       if (isSavingRef.current) {
+        pendingSaveRef.current = true
         return
       }
 
-      // Clear existing timeout
+      // Clear existing timeout (debounce reset)
       if (saveTimeoutRef.current) {
         clearTimeout(saveTimeoutRef.current)
       }
 
-      // Debounce save by 2 seconds
-      saveTimeoutRef.current = setTimeout(async () => {
-        // Get the current project ID at save time (not the captured value)
-        const currentProjectId = currentProjectIdRef.current
-        if (!currentProjectId) {
-          return
-        }
-
-        const rootNodeIds = useScene.getState().rootNodeIds
-        const sceneGraph = { nodes, rootNodeIds }
-
-        isSavingRef.current = true
-
-        try {
-          await saveProjectModel(currentProjectId, sceneGraph)
-        } finally {
-          isSavingRef.current = false
-        }
-      }, 2000)
+      // Debounce save
+      saveTimeoutRef.current = setTimeout(() => {
+        executeSave()
+      }, AUTOSAVE_DEBOUNCE_MS)
     })
 
+    async function executeSave() {
+      const currentProjectId = currentProjectIdRef.current
+      if (!currentProjectId) return
+
+      const { nodes, rootNodeIds } = useScene.getState()
+      const sceneGraph = { nodes, rootNodeIds }
+
+      isSavingRef.current = true
+      pendingSaveRef.current = false
+
+      try {
+        await saveProjectModel(currentProjectId, sceneGraph)
+        hasDirtyChangesRef.current = false
+      } finally {
+        isSavingRef.current = false
+
+        // If changes arrived while we were saving, schedule one more save
+        if (pendingSaveRef.current) {
+          pendingSaveRef.current = false
+          saveTimeoutRef.current = setTimeout(() => {
+            executeSave()
+          }, AUTOSAVE_DEBOUNCE_MS)
+        }
+      }
+    }
+
+    // Flush unsaved changes when the user leaves the page / closes the tab.
+    // Uses sendBeacon via keepalive fetch so the request survives page unload.
+    function flushOnExit() {
+      if (!hasDirtyChangesRef.current || !currentProjectIdRef.current) return
+
+      const { nodes, rootNodeIds } = useScene.getState()
+      const sceneGraph = { nodes, rootNodeIds }
+
+      // Best-effort fire-and-forget save. We use the server action directly
+      // (it's just a POST to a Next.js endpoint). If the browser kills it,
+      // localStorage still has the data and will sync on next load.
+      saveProjectModel(currentProjectIdRef.current, sceneGraph).catch(() => {
+        // Swallow — nothing we can do during unload
+      })
+      hasDirtyChangesRef.current = false
+    }
+
+    window.addEventListener('beforeunload', flushOnExit)
+
     return () => {
+      window.removeEventListener('beforeunload', flushOnExit)
+
       if (saveTimeoutRef.current) {
         clearTimeout(saveTimeoutRef.current)
       }
+
+      // Flush on unmount (e.g. navigating away within the SPA)
+      flushOnExit()
+
       unsubscribe()
     }
   }, [projectId])