Reduce remaining UI stalls

- Add lightweight git status reloads for index polling

- Avoid blocking main thread on shell env load

- Fix single-file diff to not compute full-repo diff

- Truncate huge diffs and reduce diff reload churn

Author: wiedymi

aizen/Services/Git/Domain/GitStatusService.swift

@@ -21,11 +21,15 @@ struct DetailedGitStatus {
 
 actor GitStatusService {
 
-    func getDetailedStatus(at path: String) async throws -> DetailedGitStatus {
+    func getDetailedStatus(
+        at path: String,
+        includeUntracked: Bool = true,
+        includeDiffStats: Bool = true
+    ) async throws -> DetailedGitStatus {
         // Run libgit2 operations on background thread to avoid blocking
         return try await Task.detached(priority: .utility) {
             let repo = try Libgit2Repository(path: path)
-            let status = try repo.status()
+            let status = try repo.status(includeUntracked: includeUntracked)
 
             // Get current branch name
             let currentBranch = try? repo.currentBranchName()
@@ -35,8 +39,13 @@ actor GitStatusService {
             let aheadBy = aheadBehind.ahead
             let behindBy = aheadBehind.behind
 
-            // Calculate additions/deletions from diff
-            let diffStats = try repo.diffStats()
+            // Calculate additions/deletions from diff (can be expensive on large repos)
+            let diffStats: Libgit2DiffStats
+            if includeDiffStats {
+                diffStats = (try? repo.diffStats()) ?? Libgit2DiffStats(filesChanged: 0, insertions: 0, deletions: 0)
+            } else {
+                diffStats = Libgit2DiffStats(filesChanged: 0, insertions: 0, deletions: 0)
+            }
 
             // Map entries to file paths
             let stagedFiles = status.staged.map { $0.path }
@@ -59,7 +68,7 @@ actor GitStatusService {
     }
 
     func getCurrentBranch(at path: String) async throws -> String {
-        return try await Task.detached {
+        return try await Task.detached(priority: .utility) {
             let repo = try Libgit2Repository(path: path)
             guard let branch = try repo.currentBranchName() else {
                 throw Libgit2Error.referenceNotFound("HEAD")

aizen/Services/Git/GitRepositoryService.swift

@@ -27,6 +27,7 @@ class GitRepositoryService: ObservableObject {
     private var isStatusReloadPending = false
     private let statusReloadDebounceInterval: TimeInterval = 0.3
     private var inFlightStatusTask: Task<Void, Never>?
+    private var pendingReloadIsLightweight = true
 
     init(worktreePath: String) {
         self.worktreePath = worktreePath
@@ -328,16 +329,16 @@ class GitRepositoryService: ObservableObject {
 
     // MARK: - Status Loading
 
-    func reloadStatus() {
+    func reloadStatus(lightweight: Bool = false) {
         Task { @MainActor [weak self] in
-            self?.reloadStatusDebouncedOnMain()
+            self?.reloadStatusDebouncedOnMain(lightweight: lightweight)
         }
     }
 
     /// Force immediate status reload without debouncing (for use after operations)
     private func reloadStatusImmediate() {
         Task { @MainActor [weak self] in
-            await self?.reloadStatusNowOnMain()
+            await self?.reloadStatusNowOnMain(lightweight: false)
         }
     }
 
@@ -347,7 +348,7 @@ class GitRepositoryService: ObservableObject {
             guard newPath != self.worktreePath else { return }
             self.worktreePath = newPath
             self.currentStatus = .empty
-            self.reloadStatusDebouncedOnMain()
+            self.reloadStatusDebouncedOnMain(lightweight: true)
         }
     }
 
@@ -359,7 +360,7 @@ class GitRepositoryService: ObservableObject {
                 await MainActor.run { original?() }
                 return
             }
-            await self.reloadStatusNow()
+            await self.reloadStatusNow(lightweight: false)
             await MainActor.run {
                 original?()
             }
@@ -390,12 +391,16 @@ class GitRepositoryService: ObservableObject {
     }
 
     private func reloadStatusInternal() async {
-        await reloadStatusNow()
+        await reloadStatusNow(lightweight: false)
     }
 
     nonisolated
-    private func loadGitStatus(at path: String) async throws -> GitStatus {
-        let detailedStatus = try await statusService.getDetailedStatus(at: path)
+    private func loadGitStatus(at path: String, lightweight: Bool) async throws -> GitStatus {
+        let detailedStatus = try await statusService.getDetailedStatus(
+            at: path,
+            includeUntracked: !lightweight,
+            includeDiffStats: !lightweight
+        )
 
         return GitStatus(
             stagedFiles: detailedStatus.stagedFiles,
@@ -410,18 +415,19 @@ class GitRepositoryService: ObservableObject {
         )
     }
 
-    private func reloadStatusNow() async {
+    private func reloadStatusNow(lightweight: Bool) async {
         let task = await MainActor.run { () -> Task<Void, Never>? in
             statusReloadTask?.cancel()
             isStatusReloadPending = false
+            pendingReloadIsLightweight = true
 
             let path = worktreePath
 
             inFlightStatusTask?.cancel()
             let task = Task(priority: .utility) { [weak self] in
                 guard let self else { return }
                 do {
-                    let status = try await self.loadGitStatus(at: path)
+                    let status = try await self.loadGitStatus(at: path, lightweight: lightweight)
                     guard !Task.isCancelled else { return }
                     await MainActor.run {
                         // Guard against path changes while loading (e.g. worktree switch).
@@ -439,11 +445,17 @@ class GitRepositoryService: ObservableObject {
     }
 
     @MainActor
-    private func reloadStatusDebouncedOnMain() {
+    private func reloadStatusDebouncedOnMain(lightweight: Bool) {
         if isStatusReloadPending {
+            // Upgrade pending lightweight reload to full if requested.
+            if pendingReloadIsLightweight && !lightweight {
+                pendingReloadIsLightweight = false
+            }
             return
         }
+
         isStatusReloadPending = true
+        pendingReloadIsLightweight = lightweight
 
         statusReloadTask?.cancel()
         statusReloadTask = Task { [weak self] in
@@ -458,12 +470,13 @@ class GitRepositoryService: ObservableObject {
             await MainActor.run {
                 self.isStatusReloadPending = false
             }
-            await self.reloadStatusNow()
+            let doLightweight = await MainActor.run { self.pendingReloadIsLightweight }
+            await self.reloadStatusNow(lightweight: doLightweight)
         }
     }
 
     @MainActor
-    private func reloadStatusNowOnMain() async {
-        await reloadStatusNow()
+    private func reloadStatusNowOnMain(lightweight: Bool) async {
+        await reloadStatusNow(lightweight: lightweight)
     }
 }

aizen/Services/Git/Libgit2/Libgit2Diff.swift

@@ -443,6 +443,8 @@ extension Libgit2Repository {
     /// Format libgit2 diff as unified diff string
     private func formatDiffAsUnified(_ diff: OpaquePointer) -> String {
         var output = ""
+        let maxBytes = 4_000_000
+        var bytesWritten = 0
 
         let numDeltas = git_diff_num_deltas(diff)
         for i in 0..<numDeltas {
@@ -457,7 +459,21 @@ extension Libgit2Repository {
             defer { git_buf_dispose(&buf) }
 
             if git_patch_to_buf(&buf, p) == 0, let ptr = buf.ptr {
-                output += String(cString: ptr)
+                let remaining = maxBytes - bytesWritten
+                if remaining <= 0 {
+                    output += "\n... diff truncated (too large) ...\n"
+                    break
+                }
+
+                let take = min(Int(buf.size), remaining)
+                let raw = UnsafeRawBufferPointer(start: ptr, count: take)
+                output += String(decoding: raw, as: UTF8.self)
+                bytesWritten += take
+
+                if take < Int(buf.size) {
+                    output += "\n... diff truncated (too large) ...\n"
+                    break
+                }
             }
         }
 

aizen/Utilities/ShellEnvironment.swift

@@ -23,6 +23,15 @@ enum ShellEnvironment {
             return cached
         }
 
+        // Never block the UI thread on a login-shell spawn.
+        // Return a best-effort environment immediately and warm the cache asynchronously.
+        if Thread.isMainThread {
+            DispatchQueue.global(qos: .utility).async {
+                _ = loadUserShellEnvironment()
+            }
+            return ProcessInfo.processInfo.environment
+        }
+
         let env = loadEnvironmentFromShell()
         cachedEnvironment = env
         return env

aizen/Views/Worktree/Components/Git/DiffView.swift

@@ -373,10 +373,21 @@ struct DiffView: NSViewRepresentable {
 
         private static func parseDiffOutput(diffOutput: String, showFileHeaders: Bool) -> ParsedDiffMetadata {
             var rawLines: [String] = []
-            rawLines.reserveCapacity(max(128, diffOutput.count / 48))
-            diffOutput.enumerateLines { line, _ in
+            let maxRawLines = 200_000
+            rawLines.reserveCapacity(min(max(128, diffOutput.count / 48), maxRawLines))
+            var didTruncate = false
+
+            diffOutput.enumerateLines { line, stop in
+                if rawLines.count >= maxRawLines {
+                    didTruncate = true
+                    stop = true
+                    return
+                }
                 rawLines.append(line)
             }
+            if didTruncate {
+                rawLines.append("@@ ... diff view truncated (too many lines) ... @@")
+            }
 
             var rowKinds: [RowKind] = []
             rowKinds.reserveCapacity(rawLines.count)

aizen/Views/Worktree/Components/Git/GitDiffViewModel.swift

@@ -211,7 +211,22 @@ class GitDiffViewModel: ObservableObject {
     /// Get unified diff output using libgit2
     private func runGitDiff(_ args: [String]) async -> String? {
         let path = repoPath
-        return await Task.detached {
+
+        // For single-file diffs, use the git CLI so we don't compute a full-repo diff.
+        if args.contains("--") {
+            do {
+                let result = try await ProcessExecutor.shared.executeWithOutput(
+                    executable: "/usr/bin/git",
+                    arguments: args,
+                    workingDirectory: path
+                )
+                return result.succeeded ? result.stdout : nil
+            } catch {
+                return nil
+            }
+        }
+
+        return await Task.detached(priority: .utility) {
             do {
                 let repo = try Libgit2Repository(path: path)
                 // Check if this is a HEAD diff or unstaged diff

aizen/Views/Worktree/Components/Git/GitPanelWindowContent.swift

@@ -101,8 +101,10 @@ struct GitPanelWindowContent: View {
             gitIndexWatchToken = nil
         }
         .onChange(of: gitStatus) { _ in
-            updateChangedFilesCache()
-            reloadDiffDebounced()
+            let changed = updateChangedFilesCache()
+            if changed {
+                reloadDiffDebounced()
+            }
         }
         .onChange(of: selectedHistoryCommit) { commit in
             Task {
@@ -384,7 +386,7 @@ struct GitPanelWindowContent: View {
         Task {
             let token = await GitIndexWatchCenter.shared.addSubscriber(worktreePath: worktreePath) { [weak gitRepositoryService] in
                 Task { @MainActor in
-                    gitRepositoryService?.reloadStatus()
+                    gitRepositoryService?.reloadStatus(lightweight: true)
                 }
             }
             await MainActor.run {
@@ -393,7 +395,7 @@ struct GitPanelWindowContent: View {
         }
     }
 
-    private func updateChangedFilesCache() {
+    private func updateChangedFilesCache() -> Bool {
         var files = Set<String>()
         files.formUnion(gitStatus.stagedFiles)
         files.formUnion(gitStatus.modifiedFiles)
@@ -403,7 +405,9 @@ struct GitPanelWindowContent: View {
         let sortedFiles = files.sorted()
         if sortedFiles != cachedChangedFiles {
             cachedChangedFiles = sortedFiles
+            return true
         }
+        return false
     }
 
     private func validateCommentsAgainstDiff() {

aizen/Views/Worktree/WorktreeDetailView.swift

@@ -556,7 +556,7 @@ struct WorktreeDetailView: View {
 
         let token = await GitIndexWatchCenter.shared.addSubscriber(worktreePath: worktreePath) { [weak gitRepositoryService] in
             Task { @MainActor in
-                gitRepositoryService?.reloadStatus()
+                gitRepositoryService?.reloadStatus(lightweight: true)
             }
         }
         gitIndexWatchToken = token