⚡ Bolt: [performance improvement] Optimize collection operations in view models

.jules/bolt.md

@@ -28,3 +28,6 @@
 ## 2025-10-24 - Bulk Disk I/O Parallelization and Thread Pool Starvation
 **Learning:** Both `withTaskGroup` and `Task.detached` schedule their work on Swift's cooperative thread pool, which has only as many threads as the CPU has cores. Running synchronous blocking I/O (like `FileManager.removeItem`) directly inside such tasks ties up cooperative threads — when every thread is parked in a syscall there is nothing left to advance other Swift Concurrency work, which manifests as starvation and (with self-referential `await` chains) outright deadlock. `Task.detached` does not help here: "detached" means unstructured/independent, not "off the cooperative pool."
 **Action:** To parallelize bulk blocking I/O, combine a sliding-window `withThrowingTaskGroup` (e.g., `maxConcurrency` of 8) with a per-item handoff to a GCD queue: wrap the blocking call in `withCheckedThrowingContinuation` and dispatch it via `DispatchQueue.global(qos: .userInitiated).async { ... continuation.resume(...) }`. The cooperative-pool task only `await`s the continuation, so it never holds a thread while the syscall runs.
+## 2026-06-15 - Collection Processing and Memory Churn
+**Learning:** Eager `.filter` operations in SwiftUI computed properties (like checking `.isEmpty` on a filtered array or `.filter {}.count`) cause unnecessary intermediate array allocations on every render cycle. Checking `.isEmpty` on an eagerly filtered array is an O(N) memory allocation just to check for existence.
+**Action:** Chain `.lazy.filter` before `.reduce` or `.count` to prevent intermediate array allocations, and use `.contains(where:)` to short-circuit evaluation instead of `.isEmpty` on filtered arrays. Use eager `.filter` only when a concrete `Array` is strictly required (e.g., for `ForEach`).

Sources/Cacheout/ViewModels/CacheoutViewModel.swift

@@ -106,7 +106,7 @@ class CacheoutViewModel: ObservableObject {
     }
 
     var selectedSize: Int64 {
-        selectedResults.reduce(0) { $0 + $1.sizeBytes }
+        scanResults.lazy.filter(\.isSelected).reduce(0) { $0 + $1.sizeBytes }
     }
 
     var formattedSelectedSize: String {
@@ -118,7 +118,7 @@ class CacheoutViewModel: ObservableObject {
     }
 
     var hasResults: Bool { !scanResults.isEmpty || !nodeModulesItems.isEmpty }
-    var hasSelection: Bool { !selectedResults.isEmpty || selectedNodeModulesSize > 0 }
+    var hasSelection: Bool { scanResults.contains(where: \.isSelected) || selectedNodeModulesSize > 0 }
 
     // MARK: - Node Modules computed properties
 

Sources/Cacheout/Views/CleanConfirmation.swift

@@ -36,7 +36,7 @@ struct CleanConfirmationSheet: View {
             Text("Clean Selected Caches?")
                 .font(.title2.bold())
 
-            Text("This will remove \(viewModel.formattedTotalSelectedSize) from \(viewModel.selectedResults.count + viewModel.nodeModulesItems.filter(\.isSelected).count) items.")
+            Text("This will remove \(viewModel.formattedTotalSelectedSize) from \(viewModel.selectedResults.count + viewModel.nodeModulesItems.lazy.filter(\.isSelected).count) items.")
                 .font(.body)
                 .foregroundStyle(.secondary)
                 .multilineTextAlignment(.center)

Sources/Cacheout/Views/MenuBarView.swift

@@ -154,7 +154,7 @@ struct MenuBarView: View {
             Spacer()
             statPill(
                 label: "Categories",
-                value: "\(viewModel.scanResults.filter { !$0.isEmpty }.count)",
+                value: "\(viewModel.scanResults.lazy.filter { !$0.isEmpty }.count)",
                 color: .blue
             )
         }