fix: prevent mobile session resync flicker

Avoid unnecessary resync on clean initial stream connect
Skip no-op message snapshot writes during recovery
Only trigger mobile resume sync after real app resume

packages/ui/src/sync/sync-context.tsx

@@ -277,15 +277,18 @@ async function materializeSessionFromServer(
   if (options?.isStale?.()) return
 
   store.setState((state: DirectoryStore) => {
-    const materialized = materializeSessionSnapshots(
-      state,
-      sessionID,
+    const materialized = materializeSessionSnapshots(
+      state,
+      sessionID,
       records.map((record: { info: Message; parts?: Part[] }) => ({
         info: stripMessageDiffSnapshots(record.info),
         parts: record.parts ?? [],
-      })),
+      })),
       { skipPartTypes: RECONNECT_SKIP_PARTS },
     )
+    if (!materialized.messagesChanged && !materialized.partsChanged) {
+      return state
+    }
     return { message: materialized.message, part: materialized.part }
   })
 
@@ -1705,9 +1708,11 @@ export function SyncProvider(props: {
   const lastStatusPollAtByDirectoryRef = useRef(new Map<string, number>())
   const lastFullResyncAtByDirectoryRef = useRef(new Map<string, number>())
   const lastChildDiscoveryAtByDirectoryRef = useRef(new Map<string, number>())
-  const resyncingDirectoriesRef = useRef(new Set<string>())
-  const statusPollingDirectoriesRef = useRef(new Set<string>())
-  const pipelineReconnectRef = useRef<((reason?: string) => void) | null>(null)
+  const resyncingDirectoriesRef = useRef(new Set<string>())
+  const statusPollingDirectoriesRef = useRef(new Set<string>())
+  const pipelineReconnectRef = useRef<((reason?: string) => void) | null>(null)
+  const pipelineHasConnectedRef = useRef(false)
+  const pipelineDisconnectedBeforeFirstConnectRef = useRef(false)
 
   const system = useMemo<SyncSystem>(
     () => ({
@@ -1903,23 +1908,31 @@ export function SyncProvider(props: {
         }
         handleEvent(directory, payload, childStores, routingIndex)
       },
-      onReconnect: () => {
-        useConfigStore.setState({
-          isConnected: true,
-          hasEverConnected: true,
-          connectionPhase: "connected",
-        })
-        if (isRecentBoot()) {
-          return
-        }
+      onReconnect: () => {
+        useConfigStore.setState({
+          isConnected: true,
+          hasEverConnected: true,
+          connectionPhase: "connected",
+        })
+        const isFirstConnect = !pipelineHasConnectedRef.current
+        pipelineHasConnectedRef.current = true
+        if (isFirstConnect && !pipelineDisconnectedBeforeFirstConnectRef.current) {
+          return
+        }
+        if (isRecentBoot()) {
+          return
+        }
         for (const dir of childStores.children.keys()) {
           triggerDirectoryResync(dir, "stream-reconnect")
         }
-      },
-      onDisconnect: (reason) => {
-        const { hasEverConnected } = useConfigStore.getState()
-        useConfigStore.setState({
-          isConnected: false,
+      },
+      onDisconnect: (reason) => {
+        if (!pipelineHasConnectedRef.current) {
+          pipelineDisconnectedBeforeFirstConnectRef.current = true
+        }
+        const { hasEverConnected } = useConfigStore.getState()
+        useConfigStore.setState({
+          isConnected: false,
           connectionPhase: hasEverConnected ? "reconnecting" : "connecting",
           lastDisconnectReason: reason,
         })