perf(sidebar): index session ownership and narrow live subscriptions

Replace repeated project-by-session directory matching across sidebar hooks with a shared ownership index that resolves each unique directory once and exposes direct project and folder-scope buckets.

Gate destructive folder reconciliation on authoritative session data and topology readiness, preserve last-known worktrees after discovery failures, and retain nested-project, VS Code, active/archive dedupe, and Windows drive-root semantics.

Narrow cross-directory subscriptions to session and status slices so streaming deltas no longer trigger global aggregation. Reuse a cached session ID index for permission lineage checks instead of rebuilding it on every session switch.

On the reported 15-project, 67-worktree, 14,561-session shape, ownership indexing averages 3.81 ms versus roughly 450 ms for the cache-only hotfix.

Validation: 28 targeted tests, UI type-check, UI lint, and dead-code analysis.

packages/ui/src/sync/sync-refs.ts

@@ -14,6 +14,9 @@ let _childStores: ChildStoreManager | null = null
 let _directory: string = ""
 let _registerSessionDirectory: ((sessionID: string, directory: string) => void) | null = null
 const configListeners = new Set<(directory: string, config: Config) => void>()
+let cachedSessionManager: ChildStoreManager | null = null
+let cachedSessionSlices = new Map<string, State["session"]>()
+let cachedSessionsById = new Map<string, State["session"][number]>()
 
 export function setSyncRefs(
   _sdk: OpencodeClient,
@@ -22,6 +25,11 @@ export function setSyncRefs(
   registerSessionDirectory?: (sessionID: string, directory: string) => void,
 ) {
   _childStores = childStores
+  if (cachedSessionManager !== childStores) {
+    cachedSessionManager = null
+    cachedSessionSlices = new Map()
+    cachedSessionsById = new Map()
+  }
   _directory = directory
   if (registerSessionDirectory) {
     _registerSessionDirectory = registerSessionDirectory
@@ -76,17 +84,37 @@ export function getSyncSessions(directory?: string) {
 
 /** Read sessions across all initialized child stores */
 export function getAllSyncSessions() {
-  const stores = _childStores
-  if (!stores) return []
+  return Array.from(getAllSyncSessionMap().values())
+}
 
-  const deduped = new Map<string, State["session"][number]>()
-  for (const store of stores.children.values()) {
-    for (const session of store.getState().session) {
-      if (!session?.id) continue
-      deduped.set(session.id, session)
+/** Read the cached cross-directory session index, rebuilding only when a session slice changes. */
+export function getAllSyncSessionMap(): ReadonlyMap<string, State["session"][number]> {
+  const stores = _childStores
+  if (!stores) return cachedSessionsById
+
+  let changed = cachedSessionManager !== stores || cachedSessionSlices.size !== stores.children.size
+  for (const [directory, store] of stores.children) {
+    if (cachedSessionSlices.get(directory) !== store.getState().session) {
+      changed = true
+      break
     }
   }
-  return Array.from(deduped.values())
+  if (!changed) return cachedSessionsById
+
+  const nextSlices = new Map<string, State["session"]>()
+  const nextSessionsById = new Map<string, State["session"][number]>()
+  for (const [directory, store] of stores.children) {
+    const sessions = store.getState().session
+    nextSlices.set(directory, sessions)
+    for (const session of sessions) {
+      if (!session?.id) continue
+      nextSessionsById.set(session.id, session)
+    }
+  }
+  cachedSessionManager = stores
+  cachedSessionSlices = nextSlices
+  cachedSessionsById = nextSessionsById
+  return cachedSessionsById
 }
 
 /** Read messages for a session from current directory's child store */