fix(files): chain autosave unmount flush after in-flight save

The unmount flush no longer fires a concurrent PUT alongside an in-flight save; it awaits the in-flight save and then writes the latest content sequentially, so an out-of-order completion can't clobber newer edits with a stale snapshot (addresses Cursor Bugbot).

Author: waleedlatif1

apps/sim/hooks/use-autosave.ts

@@ -46,6 +46,8 @@ export function useAutosave({
 
   const isDirty = content !== savedContent
   const savingStartRef = useRef(0)
+  const inFlightRef = useRef<Promise<void> | null>(null)
+  const unmountedRef = useRef(false)
   const MIN_SAVING_DISPLAY_MS = 600
 
   const save = useCallback(async () => {
@@ -58,25 +60,33 @@ export function useAutosave({
     }
     savingRef.current = true
     savingStartRef.current = Date.now()
-    setSaveStatus('saving')
-    let nextStatus: SaveStatus = 'saved'
-    try {
-      await onSaveRef.current()
-    } catch {
-      nextStatus = 'error'
-    } finally {
-      const elapsed = Date.now() - savingStartRef.current
-      const remaining = Math.max(0, MIN_SAVING_DISPLAY_MS - elapsed)
-      displayTimerRef.current = setTimeout(() => {
-        setSaveStatus(nextStatus)
-        clearTimeout(idleTimerRef.current)
-        idleTimerRef.current = setTimeout(() => setSaveStatus('idle'), 2000)
-        savingRef.current = false
-        if (nextStatus !== 'error' && contentRef.current !== savedContentRef.current) {
-          save()
+    if (!unmountedRef.current) setSaveStatus('saving')
+    const run = (async () => {
+      let nextStatus: SaveStatus = 'saved'
+      try {
+        await onSaveRef.current()
+      } catch {
+        nextStatus = 'error'
+      } finally {
+        if (unmountedRef.current) {
+          savingRef.current = false
+        } else {
+          const elapsed = Date.now() - savingStartRef.current
+          const remaining = Math.max(0, MIN_SAVING_DISPLAY_MS - elapsed)
+          displayTimerRef.current = setTimeout(() => {
+            setSaveStatus(nextStatus)
+            clearTimeout(idleTimerRef.current)
+            idleTimerRef.current = setTimeout(() => setSaveStatus('idle'), 2000)
+            savingRef.current = false
+            if (nextStatus !== 'error' && contentRef.current !== savedContentRef.current) {
+              save()
+            }
+          }, remaining)
         }
-      }, remaining)
-    }
+      }
+    })()
+    inFlightRef.current = run
+    await run
   }, [])
 
   useEffect(() => {
@@ -88,15 +98,20 @@ export function useAutosave({
 
   useEffect(() => {
     return () => {
+      unmountedRef.current = true
       clearTimeout(timerRef.current)
       clearTimeout(idleTimerRef.current)
       clearTimeout(displayTimerRef.current)
-      // Flush the latest content on unmount even if a save is mid-flight: that in-flight save
-      // captured an older snapshot, so skipping here would terminally drop any edit typed since.
-      // The duplicate PUT is idempotent.
-      if (enabledRef.current && contentRef.current !== savedContentRef.current) {
-        onSaveRef.current().catch(() => {})
-      }
+      if (!enabledRef.current || contentRef.current === savedContentRef.current) return
+      // Flush the latest content on unmount, but chain it AFTER any in-flight save rather than
+      // firing a concurrent PUT: the in-flight save captured an older snapshot, so writing the
+      // latest sequentially (last) prevents an out-of-order completion from clobbering it.
+      void (async () => {
+        await inFlightRef.current
+        if (contentRef.current !== savedContentRef.current) {
+          await onSaveRef.current().catch(() => {})
+        }
+      })()
     }
   }, [])