Transcript Incremental Projection

Nucleic-Session: 0FFD007B-0696-4517-9429-129C7B0FD5AC
Co-authored-by: Nucleic <[email protected]>

NucleicRemote/NucleicRemote/Models/RemoteStore.swift

@@ -725,41 +725,54 @@ final class RemoteStore: ObservableObject {
     /// or a representative one. No-op in demo, which seeds the aggregate directly.
     private func rebuildAggregate() {
         guard !demoMode else { return }
+        // Every assignment below goes through `setIfChanged`: `didUpdate` fires on *every* wire
+        // frame from *any* host (session churn, dashboard refresh, diff-stat ticks), and a plain
+        // `@Published` assignment fires `objectWillChange` even when the value is identical —
+        // re-evaluating every view observing the store for nothing. Equality checks over these
+        // small aggregates are far cheaper than a whole-tree SwiftUI invalidation.
         let live = aggregatedSessions()
         if !live.isEmpty {
-            sessions = live
-            cachedSummaries = live
-            persistSummaries(live)
+            if sessions != live {
+                sessions = live
+                cachedSummaries = live
+                persistSummaries(live)
+            }
         } else if connections.values.contains(where: { $0.connectivity.isLive }) {
             // Connected, but the host genuinely has no sessions — reflect that honestly.
-            sessions = []
+            setIfChanged(\.sessions, [])
         } else {
             // Offline: keep showing the saved history rather than blanking the list.
-            sessions = cachedSummaries
+            setIfChanged(\.sessions, cachedSummaries)
         }
-        dashboard = DashboardSnapshot.merged(connections.values.map(\.dashboard))
-        meshPeers = connections.values.flatMap(\.meshPeers)
+        setIfChanged(\.dashboard, DashboardSnapshot.merged(connections.values.map(\.dashboard)))
+        setIfChanged(\.meshPeers, connections.values.flatMap(\.meshPeers))
 
         let ctx = contextConnection
-        hostName = ctx?.hostName ?? ""
-        capabilities = ctx?.capabilities
-            ?? WireCapabilities(canModifyToolInput: false, allowAlwaysScopes: [])
-        modelCatalog = ctx?.modelCatalog ?? .empty
+        setIfChanged(\.hostName, ctx?.hostName ?? "")
+        setIfChanged(\.capabilities, ctx?.capabilities
+            ?? WireCapabilities(canModifyToolInput: false, allowAlwaysScopes: []))
+        setIfChanged(\.modelCatalog, ctx?.modelCatalog ?? .empty)
 
         if let id = openSessionHostID, let conn = connections[id] {
             // While a transcript is open, the composer/controls act on *that* Mac — its connectivity
             // gates send and its scope drives the control affordances.
-            connectivity = conn.connectivity
-            grantedScope = conn.grantedScope
+            setIfChanged(\.connectivity, conn.connectivity)
+            setIfChanged(\.grantedScope, conn.grantedScope)
         } else {
-            connectivity = aggregateConnectivity()
+            setIfChanged(\.connectivity, aggregateConnectivity())
             // Optimistic new-chat gating: enabled if *any* Mac grants control (the owning Mac still
             // enforces scope when the intent lands there).
-            grantedScope = connections.values
-                .filter { $0.connectivity.isLive }.map(\.grantedScope).max() ?? .approve
+            setIfChanged(\.grantedScope, connections.values
+                .filter { $0.connectivity.isLive }.map(\.grantedScope).max() ?? .approve)
         }
     }
 
+    /// Assign a `@Published` property only when the value actually differs, so a no-op rebuild
+    /// doesn't fire `objectWillChange` (and with it a whole-tree view re-evaluation).
+    private func setIfChanged<T: Equatable>(_ keyPath: ReferenceWritableKeyPath<RemoteStore, T>, _ value: T) {
+        if self[keyPath: keyPath] != value { self[keyPath: keyPath] = value }
+    }
+
     /// Merge transcript events by `seq` (monotonic, globally unique within a session), keeping the
     /// union sorted. Lets a reconnect's snapshot fold its events into the transcript already on
     /// screen without duplicating what's shown or dropping history outside the host's tail window.