diff --git a/Sources/Lithe/LitheApp.swift b/Sources/Lithe/LitheApp.swift
index b5d01dfc..1add71c3 100644
--- a/Sources/Lithe/LitheApp.swift
+++ b/Sources/Lithe/LitheApp.swift
@@ -60,6 +60,7 @@ struct LitheApp: App {
     @StateObject private var settings: AppSettings
     @StateObject private var projectSessions: ProjectSessionManager
     @StateObject private var memoryUsageMonitor: MemoryUsageMonitor
+    @StateObject private var frameRateMonitor = FrameRateMonitor()
     @StateObject private var updateChecker = UpdateChecker()
 
     init() {
@@ -122,6 +123,7 @@ struct LitheApp: App {
                 .environmentObject(projectSessions)
                 .environmentObject(settings)
                 .environmentObject(memoryUsageMonitor)
+                .environmentObject(frameRateMonitor)
                 .environmentObject(updateChecker)
                 .environment(\.locale, settings.language.locale)
                 // SwiftUI does not consistently re-resolve every existing
@@ -132,6 +134,7 @@ struct LitheApp: App {
                 .preferredColorScheme(settings.themePreference.preferredColorScheme)
                 .task {
                     memoryUsageMonitor.start()
+                    frameRateMonitor.start()
                 }
         }
         .defaultSize(
diff --git a/Sources/Lithe/Models/AppModel/AppModel+EditorIntelligence.swift b/Sources/Lithe/Models/AppModel/AppModel+EditorIntelligence.swift
index 61cf7624..3ec1a2db 100644
--- a/Sources/Lithe/Models/AppModel/AppModel+EditorIntelligence.swift
+++ b/Sources/Lithe/Models/AppModel/AppModel+EditorIntelligence.swift
@@ -1,6 +1,30 @@
 import Foundation
 
+struct LanguageSessionChromeSignature: Equatable {
+    var features: [String: LanguageServerFeatureSet]
+    var states: [String: LanguageServerSessionState]
+    var infos: [String: LanguageServerInfo]
+}
+
 extension AppModel {
+    func handleLanguageSessionChange() {
+        refreshEditorDiagnosticsStore()
+        let signature = LanguageSessionChromeSignature(
+            features: languageToolingSessionsIfActive?.languageServerFeatures ?? [:],
+            states: languageToolingSessionsIfActive?.languageServerStates ?? [:],
+            infos: languageToolingSessionsIfActive?.languageServerInfos ?? [:]
+        )
+        guard signature != languageSessionChromeSignature else { return }
+        languageSessionChromeSignature = signature
+        scheduleObjectWillChangeRelay()
+    }
+
+    func refreshEditorDiagnosticsStore() {
+        editorDiagnosticsStore.replace(
+            EditorDiagnostic.fromLanguageServerDiagnostics(languageDiagnostics)
+        )
+    }
+
     func refreshCodeVision(for fileURL: URL) async {
         let normalizedURL = fileURL.standardizedFileURL
         guard normalizedURL.pathExtension.lowercased() == "java",
diff --git a/Sources/Lithe/Models/AppModel/AppModel+FeatureState.swift b/Sources/Lithe/Models/AppModel/AppModel+FeatureState.swift
index 0f8b0548..0dd2aa30 100644
--- a/Sources/Lithe/Models/AppModel/AppModel+FeatureState.swift
+++ b/Sources/Lithe/Models/AppModel/AppModel+FeatureState.swift
@@ -49,16 +49,19 @@ extension AppModel {
     var isPendingProjectClose: Bool { documentFeature.isPendingProjectClose }
 
     var gitChanges: [GitChange] { gitFeatureIfActive?.gitChanges ?? [] }
+    var gitTreeStatusProjection: GitTreeStatusProjection {
+        gitFeatureIfActive?.gitTreeStatus ?? GitTreeStatusProjection(changes: [])
+    }
     func gitChange(for url: URL) -> GitChange? {
         guard let root = gitRepositoryRoot,
               let relativePath = workspaceRelativePath(for: url, root: root) else { return nil }
-        return GitTreeStatusProjection(changes: gitChanges).change(relativePath: relativePath)
+        return gitFeatureIfActive?.gitTreeStatus.change(relativePath: relativePath)
     }
 
     func gitTreeStatus(for url: URL, isDirectory: Bool) -> GitChangeKind? {
         guard let root = gitRepositoryRoot,
               let relativePath = workspaceRelativePath(for: url, root: root) else { return nil }
-        return GitTreeStatusProjection(changes: gitChanges).kind(
+        return gitFeatureIfActive?.gitTreeStatus.kind(
             relativePath: relativePath,
             isDirectory: isDirectory
         )
diff --git a/Sources/Lithe/Models/AppModel/AppModel.swift b/Sources/Lithe/Models/AppModel/AppModel.swift
index 8ea31ae7..332dff63 100644
--- a/Sources/Lithe/Models/AppModel/AppModel.swift
+++ b/Sources/Lithe/Models/AppModel/AppModel.swift
@@ -68,14 +68,25 @@ final class AppModel: ObservableObject, Identifiable {
     /// Replace in Project 面板的搜索选项（Preserve Case、文件掩码等）。
     @Published var projectReplaceOptions = ProjectSearchOptions.default
     @Published var selectedProjectReplacementPaths: Set<String> = []
+    let editorChrome = EditorChromeModel()
+    let editorDiagnosticsStore = EditorDiagnosticsStore()
     /// 编辑器当前选中的单行文本，供 Find/Replace in Files 预填查询词。
-    @Published var editorSelectedText = ""
+    var editorSelectedText: String {
+        get { editorChrome.selectedText }
+        set { editorChrome.update(selectedText: newValue) }
+    }
     /// 递增令牌：搜索侧栏观察它来把焦点移回输入框。
     @Published var searchSidebarFocusRequest = 0
-    @Published var isFindBarVisible = false
-    @Published var findBarQuery = ""
-    @Published private(set) var findMatchCount = 0
-    @Published private(set) var currentFindMatchIndex = 0
+    var isFindBarVisible: Bool {
+        get { editorChrome.isFindBarVisible }
+        set { editorChrome.setFindBarVisible(newValue) }
+    }
+    var findBarQuery: String {
+        get { editorChrome.findBarQuery }
+        set { editorChrome.setFindBarQuery(newValue) }
+    }
+    var findMatchCount: Int { editorChrome.findMatchCount }
+    var currentFindMatchIndex: Int { editorChrome.currentFindMatchIndex }
     var projectItemEditRequest: ProjectItemEditRequest? {
         get { workspaceFeature.projectItemEditRequest }
         set { workspaceFeature.projectItemEditRequest = newValue }
@@ -108,7 +119,10 @@ final class AppModel: ObservableObject, Identifiable {
     @Published var languageNavigationLocations: [LanguageNavigationLocation] = []
     @Published var languageNavigationResultKind: LanguageNavigationResultKind = .definitions
     @Published var isLoadingLanguageNavigation = false
-    @Published var editorCaret: EditorCaret?
+    var editorCaret: EditorCaret? {
+        get { editorChrome.caret }
+        set { editorChrome.update(caret: newValue) }
+    }
     @Published var editorNavigationTarget: EditorNavigationTarget?
     let navigationHistoryFeature: NavigationHistoryFeatureModel
     var virtualDocumentProviderIDs: [URL: String] = [:]
@@ -244,8 +258,9 @@ final class AppModel: ObservableObject, Identifiable {
         return combined
     }
     var editorDiagnostics: [URL: [EditorDiagnostic]] {
-        EditorDiagnostic.fromLanguageServerDiagnostics(languageDiagnostics)
+        editorDiagnosticsStore.diagnosticsByURL
     }
+    var languageSessionChromeSignature: LanguageSessionChromeSignature?
     private var workspaceFeatureObservation: AnyCancellable?
     private var githubFeatureObservation: AnyCancellable?
     private var runtimeFeatureObservation: AnyCancellable?
@@ -623,6 +638,7 @@ final class AppModel: ObservableObject, Identifiable {
             self?.scheduleObjectWillChangeRelay()
         }
         springFeatureObservation = springFeature.objectWillChange.sink { [weak self] _ in
+            self?.refreshEditorDiagnosticsStore()
             self?.scheduleObjectWillChangeRelay()
         }
         fileVisibilityRulesObserverID = settings.addFileVisibilityRulesObserver { [weak self] in
@@ -959,7 +975,8 @@ final class AppModel: ObservableObject, Identifiable {
         isRunVisible = false
         isTestsVisible = false
         isDebugVisible = false
-        editorCaret = nil
+        editorChrome.reset()
+        editorDiagnosticsStore.reset()
         editorNavigationTarget = nil
         navigationHistoryFeature.reset()
         virtualDocumentProviderIDs.removeAll()
@@ -1022,10 +1039,8 @@ final class AppModel: ObservableObject, Identifiable {
         projectReplaceQuery = ""
         projectReplaceText = ""
         selectedProjectReplacementPaths = []
-        isFindBarVisible = false
-        findBarQuery = ""
-        findMatchCount = 0
-        currentFindMatchIndex = 0
+        editorChrome.resetFindBar()
+        editorDiagnosticsStore.reset()
         projectHistoryFeatureIfActive?.reset()
         workspaceFeature.reset()
         gitFeatureIfActive?.reset()
@@ -1048,7 +1063,7 @@ final class AppModel: ObservableObject, Identifiable {
         genericDebugFeatureIfActive?.reset()
         javaFeature.stop()
         springFeature.reset()
-        editorCaret = nil
+        editorChrome.reset()
         editorNavigationTarget = nil
         navigationHistoryFeature.reset()
         virtualDocumentProviderIDs.removeAll()
@@ -1338,7 +1353,7 @@ final class AppModel: ObservableObject, Identifiable {
                     guard let capability = value as? LitheLanguageIntelligenceModule.LanguageIntelligenceCapability else { return }
                     self.cacheModuleCapability(capability, id: .languageIntelligence, moduleID: .languageIntelligence)
                     self.observeModuleFeature(.languageIntelligence, observation: capability.sessions.objectWillChange.sink { [weak self] _ in
-                        self?.scheduleObjectWillChangeRelay()
+                        self?.handleLanguageSessionChange()
                     })
                     capability.tools.onCandidatesChanged = { [weak self] providerID in
                         guard let self,
@@ -1391,14 +1406,11 @@ final class AppModel: ObservableObject, Identifiable {
 
     func showFindBar() {
         guard activeDocument != nil else { return }
-        isFindBarVisible = true
+        editorChrome.setFindBarVisible(true)
     }
 
     func hideFindBar() {
-        isFindBarVisible = false
-        findBarQuery = ""
-        findMatchCount = 0
-        currentFindMatchIndex = 0
+        editorChrome.resetFindBar()
         NotificationCenter.default.post(name: .litheFindDismiss, object: nil)
     }
 
@@ -1411,7 +1423,7 @@ final class AppModel: ObservableObject, Identifiable {
     }
 
     func setFindBarQuery(_ query: String) {
-        findBarQuery = query
+        editorChrome.setFindBarQuery(query)
         NotificationCenter.default.post(
             name: .litheFindQueryChanged,
             object: nil,
@@ -1428,9 +1440,7 @@ final class AppModel: ObservableObject, Identifiable {
     }
 
     func updateFindState(currentIndex: Int, count: Int) {
-        guard currentFindMatchIndex != currentIndex || findMatchCount != count else { return }
-        findMatchCount = count
-        currentFindMatchIndex = currentIndex
+        editorChrome.updateFindState(currentIndex: currentIndex, count: count)
     }
 
     func commitStagedChanges() async {
diff --git a/Sources/Lithe/Models/Editor/EditorChromeModel.swift b/Sources/Lithe/Models/Editor/EditorChromeModel.swift
new file mode 100644
index 00000000..9e5e7609
--- /dev/null
+++ b/Sources/Lithe/Models/Editor/EditorChromeModel.swift
@@ -0,0 +1,54 @@
+import Combine
+import Foundation
+
+/// Caret, selection, and Find in File chrome. These values change on arrow
+/// keys and query keystrokes, so they live off `AppModel` and must not
+/// republish the workbench tree.
+@MainActor
+final class EditorChromeModel: ObservableObject {
+    @Published private(set) var caret: EditorCaret?
+    @Published private(set) var selectedText = ""
+    @Published private(set) var isFindBarVisible = false
+    @Published private(set) var findBarQuery = ""
+    private(set) var findMatchCount = 0
+    private(set) var currentFindMatchIndex = 0
+
+    func update(caret: EditorCaret?) {
+        guard self.caret != caret else { return }
+        self.caret = caret
+    }
+
+    func update(selectedText: String) {
+        guard self.selectedText != selectedText else { return }
+        self.selectedText = selectedText
+    }
+
+    func setFindBarVisible(_ isVisible: Bool) {
+        guard isFindBarVisible != isVisible else { return }
+        isFindBarVisible = isVisible
+    }
+
+    func setFindBarQuery(_ query: String) {
+        guard findBarQuery != query else { return }
+        findBarQuery = query
+    }
+
+    func updateFindState(currentIndex: Int, count: Int) {
+        guard currentFindMatchIndex != currentIndex || findMatchCount != count else { return }
+        objectWillChange.send()
+        currentFindMatchIndex = currentIndex
+        findMatchCount = count
+    }
+
+    func resetFindBar() {
+        setFindBarVisible(false)
+        setFindBarQuery("")
+        updateFindState(currentIndex: 0, count: 0)
+    }
+
+    func reset() {
+        update(caret: nil)
+        update(selectedText: "")
+        resetFindBar()
+    }
+}
diff --git a/Sources/Lithe/Models/Editor/EditorDiagnosticsStore.swift b/Sources/Lithe/Models/Editor/EditorDiagnosticsStore.swift
new file mode 100644
index 00000000..54445c6d
--- /dev/null
+++ b/Sources/Lithe/Models/Editor/EditorDiagnosticsStore.swift
@@ -0,0 +1,22 @@
+import Combine
+import Foundation
+
+/// Latest editor diagnostics for the open workspace. Language-server publish
+/// storms stay on this object so the workbench tree does not rebuild.
+@MainActor
+final class EditorDiagnosticsStore: ObservableObject {
+    @Published private(set) var diagnosticsByURL: [URL: [EditorDiagnostic]] = [:]
+
+    func replace(_ diagnostics: [URL: [EditorDiagnostic]]) {
+        guard diagnosticsByURL != diagnostics else { return }
+        diagnosticsByURL = diagnostics
+    }
+
+    func reset() {
+        replace([:])
+    }
+
+    func diagnostics(for url: URL) -> [EditorDiagnostic] {
+        diagnosticsByURL[url.standardizedFileURL] ?? []
+    }
+}
diff --git a/Sources/Lithe/Models/Editor/EditorDocument.swift b/Sources/Lithe/Models/Editor/EditorDocument.swift
index 83bf418a..5be65e60 100644
--- a/Sources/Lithe/Models/Editor/EditorDocument.swift
+++ b/Sources/Lithe/Models/Editor/EditorDocument.swift
@@ -17,7 +17,11 @@ final class EditorDocument: ObservableObject, Identifiable, @unchecked Sendable
     private(set) var url: URL
     let isReadOnly: Bool
     let displayPath: String?
-    @Published var text: String
+    private var storedText: String
+    var text: String {
+        get { storedText }
+        set { replaceText(newValue, publish: true) }
+    }
     @Published private(set) var savedText: String
     @Published var hasExternalConflict = false
     private(set) var lastKnownModificationDate: Date?
@@ -32,7 +36,7 @@ final class EditorDocument: ObservableObject, Identifiable, @unchecked Sendable
         self.url = url
         self.isReadOnly = isReadOnly
         self.displayPath = displayPath
-        self.text = text
+        self.storedText = text
         self.savedText = text
         self.lastKnownModificationDate = modificationDate
     }
@@ -41,7 +45,22 @@ final class EditorDocument: ObservableObject, Identifiable, @unchecked Sendable
         displayPath?.split(separator: "/").last.map(String.init) ?? url.lastPathComponent
     }
 
-    var isDirty: Bool { text != savedText }
+    var isDirty: Bool { storedText != savedText }
+
+    /// Keep the live NSTextView buffer in sync without waking SwiftUI on every
+    /// already-dirty keystroke. The first edit still publishes so the tab dirty
+    /// mark can appear.
+    func applyLiveEditorText(_ newText: String) {
+        replaceText(newText, publish: isDirty != (newText != savedText))
+    }
+
+    private func replaceText(_ newText: String, publish: Bool) {
+        guard storedText != newText else { return }
+        if publish {
+            objectWillChange.send()
+        }
+        storedText = newText
+    }
 
     func save() throws {
         guard !isReadOnly else { throw DocumentError.readOnly }
diff --git a/Sources/Lithe/Models/Workspace/ProjectSessionManager.swift b/Sources/Lithe/Models/Workspace/ProjectSessionManager.swift
index 51f39b11..5ca8e659 100644
--- a/Sources/Lithe/Models/Workspace/ProjectSessionManager.swift
+++ b/Sources/Lithe/Models/Workspace/ProjectSessionManager.swift
@@ -185,9 +185,14 @@ final class ProjectSessionManager: ObservableObject {
                 self.removeClosedSession(model)
             }
         )
-        modelObservations[model.id] = model.objectWillChange.sink { [weak self] _ in
-            self?.objectWillChange.send()
-        }
+        // Only workspace open/close should wake the window chrome. Relaying
+        // every AppModel tick rebuilds every mounted project session.
+        modelObservations[model.id] = model.$workspaceURL
+            .removeDuplicates()
+            .dropFirst()
+            .sink { [weak self] _ in
+                self?.objectWillChange.send()
+            }
     }
 
     private func removeClosedSession(_ model: AppModel) {
diff --git a/Sources/Lithe/Services/Monitoring/FrameRateMonitor.swift b/Sources/Lithe/Services/Monitoring/FrameRateMonitor.swift
new file mode 100644
index 00000000..6780727d
--- /dev/null
+++ b/Sources/Lithe/Services/Monitoring/FrameRateMonitor.swift
@@ -0,0 +1,81 @@
+import Combine
+import CoreVideo
+import Foundation
+import QuartzCore
+
+/// Counts vsync callbacks that reach the main thread so a hitch shows up as a
+/// lower FPS. The workbench must not observe this object; only the status-bar
+/// label should subscribe.
+@MainActor
+final class FrameRateMonitor: ObservableObject {
+    private(set) var framesPerSecond = 0
+
+    var framesPerSecondText: String {
+        "\(framesPerSecond) FPS"
+    }
+
+    private var displayLink: CVDisplayLink?
+    private var framesInWindow: UInt64 = 0
+    private var windowStartedAt: CFTimeInterval?
+    private var lastAcceptedFrameAt: CFTimeInterval?
+    private var displayedFramesPerSecond = -1
+    private let sampleWindow: CFTimeInterval
+
+    init(sampleWindow: TimeInterval = 0.5) {
+        self.sampleWindow = sampleWindow
+    }
+
+    deinit {
+        if let displayLink {
+            CVDisplayLinkStop(displayLink)
+        }
+    }
+
+    func start() {
+        guard displayLink == nil else { return }
+        windowStartedAt = CACurrentMediaTime()
+        lastAcceptedFrameAt = nil
+        var link: CVDisplayLink?
+        CVDisplayLinkCreateWithActiveCGDisplays(&link)
+        guard let link else { return }
+        displayLink = link
+        let context = Unmanaged.passUnretained(self).toOpaque()
+        CVDisplayLinkSetOutputCallback(link, { _, _, _, _, _, context in
+            guard let context else { return kCVReturnSuccess }
+            Task { @MainActor in
+                Unmanaged<FrameRateMonitor>.fromOpaque(context).takeUnretainedValue()
+                    .recordFrame(at: CACurrentMediaTime())
+            }
+            return kCVReturnSuccess
+        }, context)
+        CVDisplayLinkStart(link)
+    }
+
+    #if DEBUG
+    func recordFrameForTesting(at mediaTime: TimeInterval) {
+        recordFrame(at: mediaTime)
+    }
+    #endif
+
+    /// Display-link callbacks can pile up behind a hitch. Collapse ticks that
+    /// land in the same frame so a stall is not hidden by a later burst.
+    private func recordFrame(at mediaTime: CFTimeInterval) {
+        if let lastAcceptedFrameAt, mediaTime - lastAcceptedFrameAt < 0.008 {
+            return
+        }
+        lastAcceptedFrameAt = mediaTime
+        let windowStart = windowStartedAt ?? mediaTime
+        windowStartedAt = windowStart
+        framesInWindow += 1
+        let elapsed = mediaTime - windowStart
+        guard elapsed >= sampleWindow else { return }
+
+        let fps = Int((Double(framesInWindow) / elapsed).rounded())
+        framesInWindow = 0
+        windowStartedAt = mediaTime
+        guard fps != displayedFramesPerSecond else { return }
+        displayedFramesPerSecond = fps
+        framesPerSecond = fps
+        objectWillChange.send()
+    }
+}
diff --git a/Sources/Lithe/Views/App/RootView.swift b/Sources/Lithe/Views/App/RootView.swift
index ccde8c35..2b5c5f42 100644
--- a/Sources/Lithe/Views/App/RootView.swift
+++ b/Sources/Lithe/Views/App/RootView.swift
@@ -6,8 +6,6 @@ enum LitheWindowID {
 }
 
 struct RootView: View {
-    @Environment(\.openWindow) private var openWindow
-    @EnvironmentObject private var model: AppModel
     @EnvironmentObject private var projectSessions: ProjectSessionManager
     @EnvironmentObject private var updateChecker: UpdateChecker
     @State private var didStartAutomaticUpdateCheck = false
@@ -15,33 +13,18 @@ struct RootView: View {
     var body: some View {
         ZStack {
             ForEach(projectSessions.sessions) { session in
-                projectContent(for: session)
-                    .opacity(session.id == projectSessions.activeSessionID ? 1 : 0)
-                    .allowsHitTesting(session.id == projectSessions.activeSessionID)
-                    .accessibilityHidden(session.id != projectSessions.activeSessionID)
-                    .zIndex(session.id == projectSessions.activeSessionID ? 1 : 0)
+                ProjectSessionContent(
+                    session: session,
+                    isActive: session.id == projectSessions.activeSessionID
+                )
             }
+            ActiveSessionChrome()
         }
         .frame(
             minWidth: windowLayout.minimumContentSize.width,
             minHeight: windowLayout.minimumContentSize.height
         )
         .background(LitheTheme.window)
-        .background(
-            WindowCloseGuard(
-                projectSessions: projectSessions,
-                layout: windowLayout,
-                title: windowTitle
-            )
-        )
-        .onReceive(model.$isSettingsPresented) { isPresented in
-            guard isPresented else { return }
-            openWindow(id: LitheWindowID.settings)
-        }
-        .sheet(isPresented: $model.isCloneRepositoryPresented) {
-            CloneRepositoryView()
-                .environmentObject(model)
-        }
         .sheet(item: $projectSessions.pendingProjectOpen) { request in
             OpenProjectLocationDialog(request: request) { placement, doNotAskAgain in
                 projectSessions.resolvePendingOpen(
@@ -51,14 +34,6 @@ struct RootView: View {
                 )
             }
         }
-        .sheet(item: $model.localHistoryRequest) { request in
-            LocalHistoryView(request: request)
-                .environmentObject(model)
-        }
-        .sheet(item: $model.projectLocalHistoryRequest) { request in
-            ProjectLocalHistoryView(request: request)
-                .environmentObject(model)
-        }
         .alert(item: $updateChecker.notice) { notice in
             switch notice.action {
             case .install:
@@ -115,8 +90,27 @@ struct RootView: View {
         }
     }
 
-    @ViewBuilder
-    private func projectContent(for session: AppModel) -> some View {
+    private var windowLayout: LitheWindowLayout {
+        projectSessions.activeModel.workspaceURL == nil ? .welcome : .workspace
+    }
+
+    private var updatePromptPresented: Binding<Bool> {
+        Binding(
+            get: { updateChecker.updatePrompt != nil },
+            set: { isPresented in
+                if !isPresented {
+                    updateChecker.dismissUpdatePrompt()
+                }
+            }
+        )
+    }
+}
+
+private struct ProjectSessionContent: View {
+    @ObservedObject var session: AppModel
+    let isActive: Bool
+
+    var body: some View {
         Group {
             if session.workspaceURL == nil {
                 WelcomeView()
@@ -126,21 +120,52 @@ struct RootView: View {
             }
         }
         .environmentObject(session)
+        .environmentObject(session.editorChrome)
+        .environmentObject(session.editorDiagnosticsStore)
+        .opacity(isActive ? 1 : 0)
+        .allowsHitTesting(isActive)
+        .accessibilityHidden(!isActive)
+        .zIndex(isActive ? 1 : 0)
     }
+}
 
-    private var updatePromptPresented: Binding<Bool> {
-        Binding(
-            get: { updateChecker.updatePrompt != nil },
-            set: { isPresented in
-                if !isPresented {
-                    updateChecker.dismissUpdatePrompt()
-                }
+private struct ActiveSessionChrome: View {
+    @Environment(\.openWindow) private var openWindow
+    @EnvironmentObject private var model: AppModel
+    @EnvironmentObject private var projectSessions: ProjectSessionManager
+
+    var body: some View {
+        Color.clear
+            .frame(maxWidth: .infinity, maxHeight: .infinity)
+            .allowsHitTesting(false)
+            .accessibilityHidden(true)
+            .background(
+                WindowCloseGuard(
+                    projectSessions: projectSessions,
+                    layout: windowLayout,
+                    title: windowTitle
+                )
+            )
+            .onReceive(model.$isSettingsPresented) { isPresented in
+                guard isPresented else { return }
+                openWindow(id: LitheWindowID.settings)
+            }
+            .sheet(isPresented: $model.isCloneRepositoryPresented) {
+                CloneRepositoryView()
+                    .environmentObject(model)
+            }
+            .sheet(item: $model.localHistoryRequest) { request in
+                LocalHistoryView(request: request)
+                    .environmentObject(model)
+            }
+            .sheet(item: $model.projectLocalHistoryRequest) { request in
+                ProjectLocalHistoryView(request: request)
+                    .environmentObject(model)
             }
-        )
     }
 
     private var windowLayout: LitheWindowLayout {
-        projectSessions.activeModel.workspaceURL == nil ? .welcome : .workspace
+        model.workspaceURL == nil ? .welcome : .workspace
     }
 
     private var windowTitle: String? {
diff --git a/Sources/Lithe/Views/Editor/CodeEditorView.swift b/Sources/Lithe/Views/Editor/CodeEditorView.swift
index 2efdf418..d27a90aa 100644
--- a/Sources/Lithe/Views/Editor/CodeEditorView.swift
+++ b/Sources/Lithe/Views/Editor/CodeEditorView.swift
@@ -58,6 +58,8 @@ fileprivate struct CodeEditorPalette {
 struct CodeEditorView: NSViewRepresentable {
     @Environment(\.colorScheme) private var colorScheme
     @EnvironmentObject private var model: AppModel
+    @EnvironmentObject private var chrome: EditorChromeModel
+    @EnvironmentObject private var diagnosticsStore: EditorDiagnosticsStore
     @EnvironmentObject private var settings: AppSettings
     @ObservedObject var document: EditorDocument
     var debugService: JavaDebugFeatureModel?
@@ -221,31 +223,32 @@ struct CodeEditorView: NSViewRepresentable {
         context.coordinator.shouldFocus = shouldFocus
         context.coordinator.markdownScrollPosition = markdownScrollPosition
         if let scrollView = container.scrollView {
-            scrollView.backgroundColor = palette.background
+            if appearanceChanged {
+                scrollView.backgroundColor = palette.background
+            }
             context.coordinator.attachMarkdownScrollSync(to: scrollView)
             context.coordinator.attachMarkdownImagePasteMonitor(to: scrollView)
         }
         context.coordinator.isDarkAppearance = palette.isDark
         context.coordinator.colorTheme = settings.colorTheme
         context.coordinator.requestInitialFocusIfNeeded()
-        textView.font = LitheTheme.editorFont(size: settings.editorFontSize)
-        textView.defaultParagraphStyle = LitheTheme.editorParagraphStyle
-        if let codeTextView = textView as? CodeTextView {
-            codeTextView.applyAppearance(palette)
-            codeTextView.indentationWidth = settings.tabWidth
-            codeTextView.languageServerFeatures = model.languageToolingSessionsIfActive?.features(for: document.url) ?? []
-            codeTextView.isLanguageNavigationEnabled = !codeTextView.languageServerFeatures.intersection([
-                .definition, .references, .implementation
-            ]).isEmpty
-            codeTextView.isLanguageIntelligenceEnabled = !codeTextView.languageServerFeatures.intersection([
-                .hover, .completion, .rename, .formatting, .codeActions
-            ]).isEmpty
-        }
-        container.gutter?.applyAppearance(palette)
-        textView.isEditable = !document.isReadOnly
-        textView.isSelectable = true
+
+        let languageFeatures = model.languageToolingSessionsIfActive?.features(for: document.url) ?? []
+        let fontSize = settings.editorFontSize
+        let tabWidth = settings.tabWidth
+        let chromeChanged = context.coordinator.applyEditorChromeIfNeeded(
+            fontSize: fontSize,
+            tabWidth: tabWidth,
+            languageFeatures: languageFeatures,
+            isReadOnly: document.isReadOnly,
+            palette: palette,
+            textView: textView,
+            gutter: container.gutter
+        )
+
         // Keep IME marked text (for example, an active Chinese pinyin
         // composition) in the NSTextView until the input method commits it.
+        var textChanged = false
         if textView.string != document.text,
            !textView.hasMarkedText(),
            !context.coordinator.isApplyingEditorChange {
@@ -256,17 +259,27 @@ struct CodeEditorView: NSViewRepresentable {
             context.coordinator.highlight()
             (textView as? CodeTextView)?.updateEditorDecorations()
             container.gutter?.needsDisplay = true
+            textChanged = true
         }
         if appearanceChanged {
             context.coordinator.highlight()
             (textView as? CodeTextView)?.updateEditorDecorations()
+        } else if chromeChanged, !textChanged {
+            (textView as? CodeTextView)?.updateEditorDecorations()
         }
         context.coordinator.updateCodeVisionAndBlame()
         context.coordinator.updateGitLineChanges()
         context.coordinator.updateDiagnostics()
         context.coordinator.applyNavigationTargetIfNeeded()
         if let codeTextView = textView as? CodeTextView {
-            codeTextView.syncFindState(isVisible: model.isFindBarVisible, query: model.findBarQuery)
+            let findVisible = chrome.isFindBarVisible
+            let findQuery = chrome.findBarQuery
+            if context.coordinator.lastFindVisible != findVisible
+                || context.coordinator.lastFindQuery != findQuery {
+                context.coordinator.lastFindVisible = findVisible
+                context.coordinator.lastFindQuery = findQuery
+                codeTextView.syncFindState(isVisible: findVisible, query: findQuery)
+            }
         }
         context.coordinator.applySynchronizedMarkdownScrollIfNeeded(to: container.scrollView)
     }
@@ -290,6 +303,26 @@ struct CodeEditorView: NSViewRepresentable {
         var appliedNavigationTargetID: UUID?
         var foldRegions: [JavaFoldRegion] = []
         var collapsedFoldIDs: Set<String> = []
+        var lastFindVisible = false
+        var lastFindQuery = ""
+        private var pendingHighlightRange: NSRange?
+        private var pendingReplacedRange: NSRange?
+        private var pendingReplacement: String?
+        private var foldRefreshTask: Task<Void, Never>?
+        private var decorationRefreshTask: Task<Void, Never>?
+        private var documentChangeTask: Task<Void, Never>?
+        private var remainingHighlightTask: Task<Void, Never>?
+        private var appliedFontSize: CGFloat?
+        private var appliedTabWidth: Int?
+        private var appliedLanguageFeatures: LanguageServerFeatureSet?
+        private var appliedReadOnly: Bool?
+        private var appliedCodeVisionHints: [JavaCodeVisionHint]?
+        private var appliedInlayHints: [JavaInlayHint]?
+        private var appliedBlameVisible = false
+        private var appliedBlameLines: [GitBlameLine] = []
+        private var appliedDebugBreakpointLines = Set<Int>()
+        private var appliedGitMarkers: [GitLineChangeMarker]?
+        private var appliedDiagnostics: [EditorDiagnostic]?
         private var markdownImagePasteMonitor: Any?
         private weak var markdownScrollView: NSScrollView?
         private var markdownScrollObserver: NSObjectProtocol?
@@ -311,6 +344,10 @@ struct CodeEditorView: NSViewRepresentable {
         }
 
         deinit {
+            foldRefreshTask?.cancel()
+            decorationRefreshTask?.cancel()
+            documentChangeTask?.cancel()
+            remainingHighlightTask?.cancel()
             if let markdownImagePasteMonitor {
                 NSEvent.removeMonitor(markdownImagePasteMonitor)
             }
@@ -468,44 +505,194 @@ struct CodeEditorView: NSViewRepresentable {
             return true
         }
 
+        func textView(_ textView: NSTextView, shouldChangeTextIn affectedCharRange: NSRange, replacementString: String?) -> Bool {
+            let inserted = replacementString ?? ""
+            pendingReplacement = inserted
+            pendingReplacedRange = affectedCharRange
+            pendingHighlightRange = NSRange(location: affectedCharRange.location, length: (inserted as NSString).length)
+            return true
+        }
+
         func textDidChange(_ notification: Notification) {
             guard let textView else { return }
             guard document?.isReadOnly != true else { return }
-            (textView as? CodeTextView)?.rebuildLineIndex()
+            let codeTextView = textView as? CodeTextView
+            if let replacedRange = pendingReplacedRange, let replacement = pendingReplacement {
+                codeTextView?.applyLineIndexEdit(replacedRange: replacedRange, replacement: replacement)
+            } else {
+                codeTextView?.rebuildLineIndex()
+            }
             isApplyingEditorChange = true
-            document?.text = textView.string
+            document?.applyLiveEditorText(textView.string)
             if let document {
-                model?.documentDidChange(document)
+                scheduleDocumentChange(document)
             }
-            highlight()
-            let codeTextView = textView as? CodeTextView
-            if let codeTextView, let model, model.isFindBarVisible, !model.findBarQuery.isEmpty {
-                // 先按新文本重算匹配再统一刷新装饰，避免旧 range 越界
-                codeTextView.updateFindMatches(query: model.findBarQuery)
+            highlight(in: pendingHighlightRange)
+            let findReplacedRange = pendingReplacedRange
+            let findInsertedLength = pendingHighlightRange?.length ?? 0
+            pendingHighlightRange = nil
+            pendingReplacedRange = nil
+            pendingReplacement = nil
+            if let codeTextView,
+               let findReplacedRange,
+               model?.editorChrome.isFindBarVisible == true,
+               let query = model?.editorChrome.findBarQuery,
+               !query.isEmpty {
+                codeTextView.applyFindEdit(
+                    replacedRange: findReplacedRange,
+                    insertedLength: findInsertedLength,
+                    query: query
+                )
+                codeTextView.updateCaretDecorations()
+            } else if model?.editorChrome.isFindBarVisible == true,
+                      !(model?.editorChrome.findBarQuery.isEmpty ?? true) {
+                scheduleDecorationRefresh()
             } else {
-                codeTextView?.updateEditorDecorations()
+                codeTextView?.updateCaretDecorations()
+                scheduleDecorationRefresh()
             }
-            refreshFoldRegions(useDefaultImportFold: false)
+            scheduleFoldRefresh()
             gutter?.needsDisplay = true
             isApplyingEditorChange = false
             updateCaret()
         }
 
         func textViewDidChangeSelection(_ notification: Notification) {
-            (textView as? CodeTextView)?.updateEditorDecorations()
+            // Typing already refreshed caret chrome in textDidChange. A second
+            // full pass here is what dropped the frame rate into the 30s.
+            guard !isApplyingEditorChange else { return }
+            (textView as? CodeTextView)?.updateCaretDecorations()
             textView?.needsDisplay = true
             gutter?.needsDisplay = true
             updateCaret()
         }
 
-        func highlight() {
+        fileprivate func applyEditorChromeIfNeeded(
+            fontSize: CGFloat,
+            tabWidth: Int,
+            languageFeatures: LanguageServerFeatureSet,
+            isReadOnly: Bool,
+            palette: CodeEditorPalette,
+            textView: NSTextView,
+            gutter: LineNumberGutterView?
+        ) -> Bool {
+            var changed = false
+            if appliedFontSize != fontSize {
+                textView.font = LitheTheme.editorFont(size: fontSize)
+                textView.defaultParagraphStyle = LitheTheme.editorParagraphStyle
+                appliedFontSize = fontSize
+                changed = true
+            }
+            if let codeTextView = textView as? CodeTextView {
+                codeTextView.applyAppearance(palette)
+                if appliedTabWidth != tabWidth {
+                    codeTextView.indentationWidth = tabWidth
+                    appliedTabWidth = tabWidth
+                    changed = true
+                }
+                if appliedLanguageFeatures != languageFeatures {
+                    codeTextView.languageServerFeatures = languageFeatures
+                    codeTextView.isLanguageNavigationEnabled = !languageFeatures.intersection([
+                        .definition, .references, .implementation
+                    ]).isEmpty
+                    codeTextView.isLanguageIntelligenceEnabled = !languageFeatures.intersection([
+                        .hover, .completion, .rename, .formatting, .codeActions
+                    ]).isEmpty
+                    appliedLanguageFeatures = languageFeatures
+                    changed = true
+                }
+            }
+            gutter?.applyAppearance(palette)
+            if appliedReadOnly != isReadOnly {
+                textView.isEditable = !isReadOnly
+                textView.isSelectable = true
+                appliedReadOnly = isReadOnly
+                changed = true
+            }
+            return changed
+        }
+
+        func highlight(in editedRange: NSRange? = nil) {
             guard let textView, let textStorage = textView.textStorage else { return }
+            if let editedRange {
+                SyntaxHighlighter.apply(
+                    to: textStorage,
+                    font: textView.font ?? LitheTheme.editorFont(size: 13),
+                    fileExtension: fileExtension,
+                    isDark: isDarkAppearance,
+                    range: editedRange
+                )
+                return
+            }
+            let visible = (textView as? CodeTextView)?.visibleCharacterRange()
+                ?? NSRange(location: 0, length: min(8_192, textStorage.length))
             SyntaxHighlighter.apply(
                 to: textStorage,
                 font: textView.font ?? LitheTheme.editorFont(size: 13),
                 fileExtension: fileExtension,
-                isDark: isDarkAppearance
+                isDark: isDarkAppearance,
+                range: visible
             )
+            scheduleRemainingHighlight(skipping: visible)
+        }
+
+        func scheduleRemainingHighlight(skipping alreadyColored: NSRange) {
+            remainingHighlightTask?.cancel()
+            remainingHighlightTask = Task { @MainActor [weak self] in
+                try? await Task.sleep(for: .milliseconds(16))
+                guard !Task.isCancelled, let self, let textView = self.textView,
+                      let storage = textView.textStorage else { return }
+                let font = textView.font ?? LitheTheme.editorFont(size: 13)
+                let chunk = 16_384
+                var location = 0
+                while location < storage.length {
+                    if Task.isCancelled { return }
+                    let length = min(chunk, storage.length - location)
+                    let range = NSRange(location: location, length: length)
+                    if NSIntersectionRange(range, alreadyColored) != range {
+                        SyntaxHighlighter.apply(
+                            to: storage,
+                            font: font,
+                            fileExtension: self.fileExtension,
+                            isDark: self.isDarkAppearance,
+                            range: range
+                        )
+                    }
+                    location += chunk
+                    await Task.yield()
+                }
+            }
+        }
+
+        func scheduleFoldRefresh() {
+            foldRefreshTask?.cancel()
+            foldRefreshTask = Task { @MainActor [weak self] in
+                try? await Task.sleep(for: .milliseconds(80))
+                guard !Task.isCancelled, let self else { return }
+                self.refreshFoldRegions(useDefaultImportFold: false)
+            }
+        }
+
+        func scheduleDecorationRefresh() {
+            decorationRefreshTask?.cancel()
+            decorationRefreshTask = Task { @MainActor [weak self] in
+                try? await Task.sleep(for: .milliseconds(80))
+                guard !Task.isCancelled, let self, let textView = self.textView as? CodeTextView else { return }
+                if let model = self.model, model.isFindBarVisible, !model.findBarQuery.isEmpty {
+                    textView.updateFindMatches(query: model.findBarQuery)
+                } else {
+                    textView.updateEditorDecorations()
+                }
+            }
+        }
+
+        func scheduleDocumentChange(_ document: EditorDocument) {
+            documentChangeTask?.cancel()
+            documentChangeTask = Task { @MainActor [weak self, weak document] in
+                try? await Task.sleep(for: .milliseconds(80))
+                guard !Task.isCancelled, let document else { return }
+                self?.model?.documentDidChange(document)
+            }
         }
 
         func refreshFoldRegions(useDefaultImportFold: Bool) {
@@ -569,19 +756,26 @@ struct CodeEditorView: NSViewRepresentable {
             guard let document, let model else { return }
             let url = document.url.standardizedFileURL
             let hints = model.settings.showCodeVision ? model.javaCodeVisionHints[url] ?? [] : []
-            codeVisionOverlay?.update(
-                hints: hints,
-                onUsages: { [weak model] hint in model?.findUsages(for: hint, in: url) },
-                onImplementations: { [weak model] hint in
-                    model?.findJavaImplementations(
-                        line: hint.line,
-                        utf16Column: hint.utf16Column,
-                        in: url
-                    )
-                },
-                onAuthor: { [weak model] in model?.showBlame(for: url) }
-            )
-            inlayHintOverlay?.update(hints: model.javaInlayHints[url] ?? [])
+            if appliedCodeVisionHints != hints {
+                appliedCodeVisionHints = hints
+                codeVisionOverlay?.update(
+                    hints: hints,
+                    onUsages: { [weak model] hint in model?.findUsages(for: hint, in: url) },
+                    onImplementations: { [weak model] hint in
+                        model?.findJavaImplementations(
+                            line: hint.line,
+                            utf16Column: hint.utf16Column,
+                            in: url
+                        )
+                    },
+                    onAuthor: { [weak model] in model?.showBlame(for: url) }
+                )
+            }
+            let inlayHints = model.javaInlayHints[url] ?? []
+            if appliedInlayHints != inlayHints {
+                appliedInlayHints = inlayHints
+                inlayHintOverlay?.update(hints: inlayHints)
+            }
 
             let isBlameVisible = model.blameVisibleURL == url
             let blameLines = model.gitBlameLines[url] ?? []
@@ -592,12 +786,19 @@ struct CodeEditorView: NSViewRepresentable {
                 $0.fileURL.standardizedFileURL == url
             }.map(\.line)
             let debugBreakpointLines = Set(javaBreakpointLines + genericBreakpointLines)
-            container?.gutterWidthConstraint?.constant = isBlameVisible ? 224 : 52
-            gutter?.update(blameLines: blameLines, isVisible: isBlameVisible) { [weak model] blame in
-                Task { await model?.showGitCommit(blame.commitHash) }
-            }
-            gutter?.updateDebugBreakpointLines(debugBreakpointLines) { [weak model] line in
-                model?.toggleDebugBreakpoint(fileURL: url, line: line)
+            if appliedBlameVisible != isBlameVisible
+                || appliedBlameLines != blameLines
+                || appliedDebugBreakpointLines != debugBreakpointLines {
+                appliedBlameVisible = isBlameVisible
+                appliedBlameLines = blameLines
+                appliedDebugBreakpointLines = debugBreakpointLines
+                container?.gutterWidthConstraint?.constant = isBlameVisible ? 224 : 52
+                gutter?.update(blameLines: blameLines, isVisible: isBlameVisible) { [weak model] blame in
+                    Task { await model?.showGitCommit(blame.commitHash) }
+                }
+                gutter?.updateDebugBreakpointLines(debugBreakpointLines) { [weak model] line in
+                    model?.toggleDebugBreakpoint(fileURL: url, line: line)
+                }
             }
         }
 
@@ -606,6 +807,8 @@ struct CodeEditorView: NSViewRepresentable {
             let url = document.url.standardizedFileURL
             if let markers = model.gitLineChangeMarkers(for: url) {
                 isLoadingGitLineChanges = false
+                guard appliedGitMarkers != markers else { return }
+                appliedGitMarkers = markers
                 let change = model.gitChange(for: url)
                 gutter.updateGitLineChanges(
                     markers,
@@ -627,7 +830,10 @@ struct CodeEditorView: NSViewRepresentable {
                 return
             }
 
-            gutter.updateGitLineChanges([], onShow: { _ in })
+            if appliedGitMarkers != [] {
+                appliedGitMarkers = []
+                gutter.updateGitLineChanges([], onShow: { _ in })
+            }
             guard !isLoadingGitLineChanges else { return }
             isLoadingGitLineChanges = true
             Task { @MainActor [weak self, weak model] in
@@ -637,11 +843,12 @@ struct CodeEditorView: NSViewRepresentable {
         }
 
         func updateDiagnostics() {
-            guard let document, let model,
+            guard let document,
                   let textView = textView as? CodeTextView else { return }
-            textView.updateDiagnostics(
-                model.editorDiagnostics[document.url.standardizedFileURL] ?? []
-            )
+            let diagnostics = model?.editorDiagnosticsStore.diagnostics(for: document.url) ?? []
+            guard appliedDiagnostics != diagnostics else { return }
+            appliedDiagnostics = diagnostics
+            textView.updateDiagnostics(diagnostics)
         }
 
         func applyNavigationTargetIfNeeded() {
@@ -671,12 +878,21 @@ struct CodeEditorView: NSViewRepresentable {
             let text = textView.string as NSString
             updateSelectedText(in: text, range: textView.selectedRange())
             let location = min(textView.selectedRange().location, text.length)
-            let prefix = text.substring(to: location) as NSString
-            var line = 0
-            var lineStart = 0
-            for index in 0..<prefix.length where prefix.character(at: index) == 10 {
-                line += 1
-                lineStart = index + 1
+            let line: Int
+            let lineStart: Int
+            if let codeTextView = textView as? CodeTextView {
+                line = codeTextView.lineNumber(at: location, in: text)
+                lineStart = codeTextView.characterOffset(forLine: line, in: text)
+            } else {
+                let prefix = text.substring(to: location) as NSString
+                var scannedLine = 0
+                var scannedStart = 0
+                for index in 0..<prefix.length where prefix.character(at: index) == 10 {
+                    scannedLine += 1
+                    scannedStart = index + 1
+                }
+                line = scannedLine
+                lineStart = scannedStart
             }
             model?.editorCaret = EditorCaret(
                 url: document.url.standardizedFileURL,
@@ -703,8 +919,8 @@ struct CodeEditorView: NSViewRepresentable {
 }
 
 private struct TextLineIndex {
-    let textLength: Int
-    let starts: [Int]
+    var textLength: Int
+    var starts: [Int]
 
     init(source: NSString) {
         textLength = source.length
@@ -723,6 +939,22 @@ private struct TextLineIndex {
         self.starts = starts
     }
 
+    /// Shift line starts after a single-line insert/delete. Returns false when
+    /// the replaced range crossed a line break and the index must be rebuilt.
+    mutating func applySingleLineEdit(replacedRange: NSRange, insertedLength: Int) -> Bool {
+        let replacedEnd = NSMaxRange(replacedRange)
+        if starts.contains(where: { $0 > replacedRange.location && $0 <= replacedEnd }) {
+            return false
+        }
+        let delta = insertedLength - replacedRange.length
+        guard delta != 0 else { return true }
+        textLength = max(0, textLength + delta)
+        for index in starts.indices where starts[index] > replacedRange.location {
+            starts[index] += delta
+        }
+        return true
+    }
+
     var lineCount: Int {
         guard textLength > 0, starts.last == textLength else { return starts.count }
         return max(1, starts.count - 1)
@@ -780,6 +1012,7 @@ final class CodeTextView: NSTextView, NSLayoutManagerDelegate {
     private var findMatchRanges: [NSRange] = []
     private var currentFindMatchIndex = 0
     private var lastReportedFindState: (index: Int, count: Int)?
+    private var lastCaretBackgroundRanges: [NSRange] = []
     private var completionItemsByID: [String: LanguageServerCompletionItem] = [:]
     private var languageHoverPopover: NSPopover?
 
@@ -856,6 +1089,88 @@ final class CodeTextView: NSTextView, NSLayoutManagerDelegate {
         lineIndex = TextLineIndex(source: string as NSString)
     }
 
+    func applyLineIndexEdit(replacedRange: NSRange, replacement: String) {
+        if replacement.contains("\n") || replacement.contains("\r")
+            || !lineIndex.applySingleLineEdit(replacedRange: replacedRange, insertedLength: (replacement as NSString).length) {
+            rebuildLineIndex()
+        }
+    }
+
+    func visibleCharacterRange() -> NSRange? {
+        guard let layoutManager,
+              let textContainer,
+              let scrollView = enclosingScrollView else { return nil }
+        let visibleRect = scrollView.documentVisibleRect
+        let textContainerVisibleRect = NSRect(
+            x: visibleRect.minX - textContainerOrigin.x,
+            y: visibleRect.minY - textContainerOrigin.y,
+            width: visibleRect.width,
+            height: visibleRect.height
+        )
+        let glyphRange = layoutManager.glyphRange(
+            forBoundingRect: textContainerVisibleRect,
+            in: textContainer
+        )
+        guard glyphRange.length > 0 else { return nil }
+        return layoutManager.characterRange(forGlyphRange: glyphRange, actualGlyphRange: nil)
+    }
+
+    #if DEBUG
+    var currentFindMatchCountForTesting: Int { findMatchRanges.count }
+    var findMatchLocationsForTesting: [Int] { findMatchRanges.map(\.location) }
+    #endif
+
+    func applyFindEdit(replacedRange: NSRange, insertedLength: Int, query: String) {
+        guard !query.isEmpty else {
+            clearFindHighlights()
+            return
+        }
+        let source = string as NSString
+        let delta = insertedLength - replacedRange.length
+        let replacedEnd = NSMaxRange(replacedRange)
+        findMatchRanges = findMatchRanges.compactMap { range in
+            if NSMaxRange(range) <= replacedRange.location { return range }
+            if range.location >= replacedEnd {
+                return NSRange(location: range.location + delta, length: range.length)
+            }
+            return nil
+        }
+        let safeLocation = min(replacedRange.location, max(0, source.length - 1))
+        let lineRange = source.length == 0
+            ? NSRange(location: 0, length: 0)
+            : source.lineRange(for: NSRange(location: safeLocation, length: 0))
+        let searchEnd = min(source.length, max(NSMaxRange(lineRange), replacedRange.location + insertedLength))
+        let searchRange = NSRange(
+            location: lineRange.location,
+            length: max(0, searchEnd - lineRange.location)
+        )
+        findMatchRanges.removeAll { range in
+            NSIntersectionRange(range, searchRange).length > 0
+                || (range.location >= searchRange.location && range.location < NSMaxRange(searchRange))
+        }
+        if searchRange.length > 0, !query.isEmpty {
+            var cursor = searchRange
+            while cursor.length > 0 {
+                let found = source.range(
+                    of: query,
+                    options: [.caseInsensitive, .diacriticInsensitive],
+                    range: cursor
+                )
+                if found.location == NSNotFound { break }
+                findMatchRanges.append(found)
+                let nextLocation = NSMaxRange(found)
+                cursor = NSRange(location: nextLocation, length: NSMaxRange(searchRange) - nextLocation)
+            }
+            findMatchRanges.sort { $0.location < $1.location }
+        }
+        currentFindMatchIndex = min(currentFindMatchIndex, max(0, findMatchRanges.count - 1))
+        applyFindHighlights()
+        reportFindState(
+            index: findMatchRanges.isEmpty ? -1 : currentFindMatchIndex,
+            count: findMatchRanges.count
+        )
+    }
+
     func characterOffset(forLine targetLine: Int, in _: NSString) -> Int {
         lineIndex.characterOffset(forLine: targetLine)
     }
@@ -873,6 +1188,53 @@ final class CodeTextView: NSTextView, NSLayoutManagerDelegate {
         updateEditorDecorations()
     }
 
+    func updateCaretDecorations() {
+        guard let layoutManager else { return }
+        let fullLength = (string as NSString).length
+        for range in lastCaretBackgroundRanges where NSMaxRange(range) <= fullLength {
+            layoutManager.removeTemporaryAttribute(.backgroundColor, forCharacterRange: range)
+        }
+        lastCaretBackgroundRanges = []
+        guard fullLength > 0 else { return }
+
+        let source = string as NSString
+        let caret = min(selectedRange().location, source.length)
+        let lineRange = source.lineRange(for: NSRange(location: caret, length: 0))
+        layoutManager.addTemporaryAttribute(
+            .backgroundColor,
+            value: currentLineColor,
+            forCharacterRange: lineRange
+        )
+        lastCaretBackgroundRanges.append(lineRange)
+
+        for range in matchingBracketRanges(in: source, caret: caret) {
+            layoutManager.addTemporaryAttribute(.backgroundColor, value: bracketColor, forCharacterRange: range)
+            lastCaretBackgroundRanges.append(range)
+        }
+
+        if isLanguageNavigationEnabled,
+           let symbol = identifier(at: caret, in: source),
+           let scope = enclosingCodeScope(at: caret, in: source) {
+            let escaped = NSRegularExpression.escapedPattern(for: symbol.text)
+            if let expression = try? NSRegularExpression(pattern: "\\b\(escaped)\\b") {
+                expression.enumerateMatches(in: string, range: scope) { [weak layoutManager] match, _, _ in
+                    guard let match else { return }
+                    layoutManager?.addTemporaryAttribute(
+                        .backgroundColor,
+                        value: self.symbolColor,
+                        forCharacterRange: match.range
+                    )
+                    self.lastCaretBackgroundRanges.append(match.range)
+                }
+            }
+        }
+
+        if !findMatchRanges.isEmpty {
+            applyFindHighlights()
+        }
+        applyLinkHighlight()
+    }
+
     func updateEditorDecorations() {
         guard let layoutManager else { return }
         let fullRange = NSRange(location: 0, length: string.utf16.count)
@@ -887,6 +1249,7 @@ final class CodeTextView: NSTextView, NSLayoutManagerDelegate {
             return
         }
 
+        lastCaretBackgroundRanges = []
         let source = string as NSString
         let caret = min(selectedRange().location, source.length)
         let lineRange = source.lineRange(for: NSRange(location: caret, length: 0))
@@ -895,9 +1258,11 @@ final class CodeTextView: NSTextView, NSLayoutManagerDelegate {
             value: currentLineColor,
             forCharacterRange: lineRange
         )
+        lastCaretBackgroundRanges.append(lineRange)
 
         for range in matchingBracketRanges(in: source, caret: caret) {
             layoutManager.addTemporaryAttribute(.backgroundColor, value: bracketColor, forCharacterRange: range)
+            lastCaretBackgroundRanges.append(range)
         }
 
         if isLanguageNavigationEnabled,
@@ -912,6 +1277,7 @@ final class CodeTextView: NSTextView, NSLayoutManagerDelegate {
                         value: self.symbolColor,
                         forCharacterRange: match.range
                     )
+                    self.lastCaretBackgroundRanges.append(match.range)
                 }
             }
         }
@@ -2806,9 +3172,37 @@ private final class ClosureButton: NSButton {
 
 @MainActor
 private enum SyntaxHighlighter {
-    static func apply(to storage: NSTextStorage, font: NSFont, fileExtension: String, isDark: Bool) {
+    private static let keywordExpression = try! NSRegularExpression(
+        pattern: #"\b(class|struct|enum|protocol|extension|func|let|var|if|else|guard|switch|case|for|while|return|throw|throws|try|catch|async|await|public|private|internal|protected|static|final|new|import|package|interface|implements|extends|void|boolean|int|long|const|function|def|in|from|as|true|false|null|nil|self|this)\b"#
+    )
+    private static let annotationExpression = try! NSRegularExpression(
+        pattern: #"@[A-Za-z_][A-Za-z0-9_]*"#
+    )
+    private static let typeExpression = try! NSRegularExpression(
+        pattern: #"\b[A-Z][A-Za-z0-9_]*\b"#
+    )
+    private static let numberExpression = try! NSRegularExpression(
+        pattern: #"\b\d+(?:\.\d+)?\b"#
+    )
+    private static let stringExpression = try! NSRegularExpression(
+        pattern: #"\"(?:\\.|[^\"\\])*\"|'(?:\\.|[^'\\])*'"#
+    )
+    private static let commentExpression = try! NSRegularExpression(
+        pattern: #"//.*$|#.*$|/\*[\s\S]*?\*/"#,
+        options: [.anchorsMatchLines]
+    )
+
+    static func apply(
+        to storage: NSTextStorage,
+        font: NSFont,
+        fileExtension: String,
+        isDark: Bool,
+        range: NSRange? = nil
+    ) {
         let fullRange = NSRange(location: 0, length: storage.length)
         guard fullRange.length > 0 else { return }
+        let target = expandedRange(range, in: storage.string as NSString, limit: fullRange)
+        guard target.length > 0 else { return }
         let palette = CodeEditorPalette(isDark: isDark, theme: LitheTheme.activeTheme)
 
         storage.beginEditing()
@@ -2817,28 +3211,51 @@ private enum SyntaxHighlighter {
             .paragraphStyle: LitheTheme.editorParagraphStyle,
             .ligature: 0,
             .foregroundColor: palette.text
-        ], range: fullRange)
-
-        apply(pattern: #"\b(class|struct|enum|protocol|extension|func|let|var|if|else|guard|switch|case|for|while|return|throw|throws|try|catch|async|await|public|private|internal|protected|static|final|new|import|package|interface|implements|extends|void|boolean|int|long|const|function|def|in|from|as|true|false|null|nil|self|this)\b"#, color: palette.keyword, storage: storage)
-        apply(pattern: #"@[A-Za-z_][A-Za-z0-9_]*"#, color: palette.annotation, storage: storage)
-        apply(pattern: #"\b[A-Z][A-Za-z0-9_]*\b"#, color: palette.type, storage: storage)
-        apply(pattern: #"\b\d+(?:\.\d+)?\b"#, color: palette.number, storage: storage)
-        apply(pattern: #"\"(?:\\.|[^\"\\])*\"|'(?:\\.|[^'\\])*'"#, color: palette.string, storage: storage)
-        apply(pattern: #"//.*$|#.*$|/\*[\s\S]*?\*/"#, options: [.anchorsMatchLines], color: palette.comment, storage: storage)
+        ], range: target)
+
+        apply(keywordExpression, color: palette.keyword, storage: storage, range: target)
+        apply(annotationExpression, color: palette.annotation, storage: storage, range: target)
+        apply(typeExpression, color: palette.type, storage: storage, range: target)
+        apply(numberExpression, color: palette.number, storage: storage, range: target)
+        apply(stringExpression, color: palette.string, storage: storage, range: target)
+        apply(commentExpression, color: palette.comment, storage: storage, range: target)
         storage.endEditing()
     }
 
     private static func apply(
-        pattern: String,
-        options: NSRegularExpression.Options = [],
+        _ expression: NSRegularExpression,
         color: NSColor,
-        storage: NSTextStorage
+        storage: NSTextStorage,
+        range: NSRange
     ) {
-        guard let expression = try? NSRegularExpression(pattern: pattern, options: options) else { return }
-        let range = NSRange(location: 0, length: storage.length)
         expression.enumerateMatches(in: storage.string, range: range) { match, _, _ in
             guard let match else { return }
             storage.addAttribute(.foregroundColor, value: color, range: match.range)
         }
     }
+
+    /// Re-color the edited lines plus a small pad so a token that crosses the
+    /// caret, or a nearby block comment, is not left half-styled.
+    private static func expandedRange(_ range: NSRange?, in source: NSString, limit: NSRange) -> NSRange {
+        guard let range else { return limit }
+        let safe = NSIntersectionRange(range, limit)
+        guard source.length > 0 else { return safe }
+        let startLine = source.lineRange(for: NSRange(location: safe.location, length: 0))
+        let endIndex = max(safe.location, NSMaxRange(safe) > 0 ? NSMaxRange(safe) - 1 : 0)
+        let endLine = source.lineRange(for: NSRange(location: min(endIndex, source.length - 1), length: 0))
+        var combined = NSUnionRange(startLine, endLine)
+        if combined.location > 0 {
+            combined = NSUnionRange(
+                source.lineRange(for: NSRange(location: combined.location - 1, length: 0)),
+                combined
+            )
+        }
+        if NSMaxRange(combined) < source.length {
+            combined = NSUnionRange(
+                combined,
+                source.lineRange(for: NSRange(location: NSMaxRange(combined), length: 0))
+            )
+        }
+        return NSIntersectionRange(combined, limit)
+    }
 }
diff --git a/Sources/Lithe/Views/Editor/EditorAreaView.swift b/Sources/Lithe/Views/Editor/EditorAreaView.swift
index 058f86db..f830ded8 100644
--- a/Sources/Lithe/Views/Editor/EditorAreaView.swift
+++ b/Sources/Lithe/Views/Editor/EditorAreaView.swift
@@ -255,11 +255,7 @@ struct EditorAreaView: View {
                     size: 13
                 )
                 editorTabTitle(document)
-                if document.isDirty {
-                    Circle()
-                        .fill(LitheTheme.primaryText)
-                        .frame(width: 6, height: 6)
-                }
+                EditorTabDirtyIndicator(document: document)
             }
             .foregroundStyle(model.activeDocumentID == document.id ? LitheTheme.primaryText : LitheTheme.secondaryText)
             .padding(.leading, 11)
@@ -641,12 +637,7 @@ struct EditorAreaView: View {
     ) -> some View {
         codeEditor(document, markdownScrollPosition: markdownScrollPosition)
             .overlay(alignment: .top) {
-                if model.isFindBarVisible {
-                    FindBarView()
-                        .padding(.top, 10)
-                        .padding(.horizontal, 12)
-                        .transition(.move(edge: .top).combined(with: .opacity))
-                }
+                FindBarOverlay()
             }
     }
 
@@ -751,3 +742,28 @@ private struct EditorTabDropDelegate: DropDelegate {
         )
     }
 }
+
+private struct EditorTabDirtyIndicator: View {
+    @ObservedObject var document: EditorDocument
+
+    var body: some View {
+        if document.isDirty {
+            Circle()
+                .fill(LitheTheme.primaryText)
+                .frame(width: 6, height: 6)
+        }
+    }
+}
+
+private struct FindBarOverlay: View {
+    @EnvironmentObject private var chrome: EditorChromeModel
+
+    var body: some View {
+        if chrome.isFindBarVisible {
+            FindBarView()
+                .padding(.top, 10)
+                .padding(.horizontal, 12)
+                .transition(.move(edge: .top).combined(with: .opacity))
+        }
+    }
+}
diff --git a/Sources/Lithe/Views/Editor/FindBarView.swift b/Sources/Lithe/Views/Editor/FindBarView.swift
index 4302e433..8f03a6ab 100644
--- a/Sources/Lithe/Views/Editor/FindBarView.swift
+++ b/Sources/Lithe/Views/Editor/FindBarView.swift
@@ -3,11 +3,12 @@ import SwiftUI
 /// 编辑器内的单文件查找栏：实时高亮、上/下一个、Esc 关闭。
 struct FindBarView: View {
     @EnvironmentObject private var model: AppModel
+    @EnvironmentObject private var chrome: EditorChromeModel
     @FocusState private var focused: Bool
 
     private var queryBinding: Binding<String> {
         Binding(
-            get: { model.findBarQuery },
+            get: { chrome.findBarQuery },
             set: { model.setFindBarQuery($0) }
         )
     }
@@ -43,7 +44,7 @@ struct FindBarView: View {
             }
             .litheIconButton()
             .foregroundStyle(LitheTheme.secondaryText)
-            .disabled(model.findMatchCount == 0)
+            .disabled(chrome.findMatchCount == 0)
             .help("Previous match (Shift+Return)")
 
             Button {
@@ -53,7 +54,7 @@ struct FindBarView: View {
             }
             .litheIconButton()
             .foregroundStyle(LitheTheme.secondaryText)
-            .disabled(model.findMatchCount == 0)
+            .disabled(chrome.findMatchCount == 0)
             .help("Next match (Return)")
 
             Button {
@@ -76,8 +77,8 @@ struct FindBarView: View {
     }
 
     private var matchLabel: String {
-        guard model.findMatchCount > 0 else { return "" }
-        let current = max(0, model.currentFindMatchIndex + 1)
-        return "\(current)/\(model.findMatchCount)"
+        guard chrome.findMatchCount > 0 else { return "" }
+        let current = max(0, chrome.currentFindMatchIndex + 1)
+        return "\(current)/\(chrome.findMatchCount)"
     }
 }
diff --git a/Sources/Lithe/Views/Language/JavaProblemsView.swift b/Sources/Lithe/Views/Language/JavaProblemsView.swift
index 6a6652c2..11e9d4b7 100644
--- a/Sources/Lithe/Views/Language/JavaProblemsView.swift
+++ b/Sources/Lithe/Views/Language/JavaProblemsView.swift
@@ -2,6 +2,7 @@ import SwiftUI
 
 struct ProblemsView: View {
     @EnvironmentObject private var model: AppModel
+    @EnvironmentObject private var diagnosticsStore: EditorDiagnosticsStore
     @State private var severityFilter = Set(DiagnosticSeverity.allCases)
 
     var body: some View {
@@ -80,7 +81,7 @@ struct ProblemsView: View {
     }
 
     private var allDiagnostics: [EditorDiagnostic] {
-        model.editorDiagnostics.values
+        diagnosticsStore.diagnosticsByURL.values
             .flatMap { $0 }
             .sorted {
                 let left = model.relativePath(for: $0.fileURL)
diff --git a/Sources/Lithe/Views/Workbench/WorkbenchStatusViews.swift b/Sources/Lithe/Views/Workbench/WorkbenchStatusViews.swift
new file mode 100644
index 00000000..1dc9a766
--- /dev/null
+++ b/Sources/Lithe/Views/Workbench/WorkbenchStatusViews.swift
@@ -0,0 +1,140 @@
+import SwiftUI
+
+struct EditorCaretPositionLabel: View {
+    @ObservedObject var chrome: EditorChromeModel
+
+    var body: some View {
+        Text(chrome.caret.map { "\($0.line + 1):\($0.utf16Column + 1)" } ?? "1:1")
+            .monospacedDigit()
+    }
+}
+
+struct MemoryUsageStatusView: View {
+    @EnvironmentObject private var memoryUsageMonitor: MemoryUsageMonitor
+    @State private var isMemoryUsagePopoverPresented = false
+
+    var body: some View {
+        Button {
+            isMemoryUsagePopoverPresented.toggle()
+        } label: {
+            Label {
+                HStack(spacing: 4) {
+                    Text("Total \(memoryUsageMonitor.totalText)")
+                    Text("·")
+                    Text("Lithe \(memoryUsageMonitor.litheText)")
+                }
+                .monospacedDigit()
+            } icon: {
+                Image(systemName: "memorychip")
+            }
+        }
+        .buttonStyle(.plain)
+        .lithePointer()
+        .help(
+            Text(
+                "Total managed memory: \(memoryUsageMonitor.totalText)\n" +
+                "Lithe: \(memoryUsageMonitor.litheText) · LSP: \(memoryUsageMonitor.lspText) · Services: \(memoryUsageMonitor.serviceText)"
+            )
+        )
+        .popover(isPresented: $isMemoryUsagePopoverPresented, arrowEdge: .top) {
+            memoryUsagePopover
+        }
+        .onChange(of: isMemoryUsagePopoverPresented) { isPresented in
+            memoryUsageMonitor.setDetailedUsageVisible(isPresented)
+        }
+    }
+
+    private var memoryUsagePopover: some View {
+        VStack(alignment: .leading, spacing: 0) {
+            HStack(spacing: 8) {
+                Image(systemName: "memorychip")
+                    .foregroundStyle(LitheTheme.accent)
+                Text("Managed Memory")
+                    .font(.system(size: 12.5, weight: .semibold))
+                    .foregroundStyle(LitheTheme.primaryText)
+                Spacer(minLength: 8)
+                Button {
+                    isMemoryUsagePopoverPresented = false
+                } label: {
+                    Image(systemName: "xmark")
+                        .font(.system(size: 10, weight: .semibold))
+                }
+                .litheIconButton()
+                .help("Close")
+            }
+            .padding(.horizontal, 12)
+            .padding(.vertical, 10)
+
+            Rectangle()
+                .fill(LitheTheme.divider)
+                .frame(height: 1)
+
+            VStack(spacing: 0) {
+                memoryMetric("Lithe", value: memoryUsageMonitor.litheText)
+                memoryMetric(
+                    "Language servers",
+                    value: memoryUsageMonitor.languageServerProcessCount == 0
+                        ? String(localized: "Not running")
+                        : memoryUsageMonitor.lspText
+                )
+                memoryMetric(
+                    "Running services",
+                    value: memoryUsageMonitor.serviceProcessCount == 0
+                        ? String(localized: "Not running")
+                        : memoryUsageMonitor.serviceText
+                )
+                memoryMetric("Total", value: memoryUsageMonitor.totalText)
+                memoryMetric("Average total", value: memoryUsageMonitor.averageText)
+                memoryMetric("Peak total", value: memoryUsageMonitor.peakText)
+                memoryMetric("Runtime", value: memoryUsageMonitor.runtimeText)
+                memoryMetric("Sample interval", value: memoryUsageMonitor.samplingIntervalText)
+            }
+            .padding(.horizontal, 12)
+            .padding(.vertical, 5)
+
+            Rectangle()
+                .fill(LitheTheme.divider)
+                .frame(height: 1)
+
+            HStack(alignment: .top, spacing: 6) {
+                Image(systemName: "info.circle")
+                Text("Resident memory of Lithe and its managed process trees")
+                    .fixedSize(horizontal: false, vertical: true)
+            }
+            .font(LitheTheme.smallFont)
+            .foregroundStyle(LitheTheme.secondaryText)
+            .padding(12)
+        }
+        .frame(width: 280)
+        .background(LitheTheme.popupBackground)
+        .clipShape(RoundedRectangle(cornerRadius: 8))
+    }
+
+    private func memoryMetric(_ title: String, value: String) -> some View {
+        HStack(spacing: 8) {
+            Text(LocalizedStringKey(title))
+                .foregroundStyle(LitheTheme.secondaryText)
+            Spacer(minLength: 8)
+            Text(value)
+                .font(.system(size: 11.5, design: .monospaced))
+                .foregroundStyle(LitheTheme.primaryText)
+                .monospacedDigit()
+        }
+        .frame(minHeight: 27)
+    }
+}
+
+struct FrameRateStatusView: View {
+    @EnvironmentObject private var frameRateMonitor: FrameRateMonitor
+
+    var body: some View {
+        Label {
+            Text(frameRateMonitor.framesPerSecondText)
+                .monospacedDigit()
+        } icon: {
+            Image(systemName: "speedometer")
+        }
+        .help("Frames rendered per second")
+        .accessibilityLabel(Text("\(frameRateMonitor.framesPerSecond) frames per second"))
+    }
+}
diff --git a/Sources/Lithe/Views/Workbench/WorkbenchView.swift b/Sources/Lithe/Views/Workbench/WorkbenchView.swift
index 048c4dd7..9e5ddab0 100644
--- a/Sources/Lithe/Views/Workbench/WorkbenchView.swift
+++ b/Sources/Lithe/Views/Workbench/WorkbenchView.swift
@@ -15,7 +15,6 @@ struct WorkbenchView: View {
     @EnvironmentObject private var model: AppModel
     @EnvironmentObject private var projectSessions: ProjectSessionManager
     @EnvironmentObject private var settings: AppSettings
-    @EnvironmentObject private var memoryUsageMonitor: MemoryUsageMonitor
     @Environment(\.accessibilityReduceMotion) private var reduceMotion
     @StateObject private var linuxDoWebSession = LinuxDoAnonymousWebSession()
     @State private var sidebarWidth: CGFloat = 320
@@ -29,7 +28,6 @@ struct WorkbenchView: View {
     @State private var isCheckoutRevisionPresented = false
     @State private var pendingTopBarPushReference: GitReference?
     @State private var isProjectSwitcherPresented = false
-    @State private var isMemoryUsagePopoverPresented = false
     @State private var isPluginPanelPresented = false
     @State private var didRestoreLayout = false
     @State private var hoveredProjectTabID: UUID?
@@ -898,7 +896,7 @@ struct WorkbenchView: View {
 
     private var detailedStatusItems: some View {
         HStack(spacing: 14) {
-            caretPosition
+            EditorCaretPositionLabel(chrome: model.editorChrome)
             Text("UTF-8")
             Text("\(settings.tabWidth) spaces")
             Button {
@@ -911,24 +909,21 @@ struct WorkbenchView: View {
             .help(LocalizedStringKey(
                 model.activeDocument?.isReadOnly == true ? "Read-only document" : "Save"
             ))
-            memoryStatus
+            MemoryUsageStatusView()
+            FrameRateStatusView()
             gitStatus
         }
     }
 
     private var compactStatusItems: some View {
         HStack(spacing: 10) {
-            caretPosition
-            memoryStatus
+            EditorCaretPositionLabel(chrome: model.editorChrome)
+            MemoryUsageStatusView()
+            FrameRateStatusView()
             gitStatus
         }
     }
 
-    private var caretPosition: some View {
-        Text(model.editorCaret.map { "\($0.line + 1):\($0.utf16Column + 1)" } ?? "1:1")
-            .monospacedDigit()
-    }
-
     private var gitStatus: some View {
         HStack(spacing: 7) {
             if model.isReferencesVisible {
@@ -940,116 +935,6 @@ struct WorkbenchView: View {
         }
     }
 
-    private var memoryStatus: some View {
-        Button {
-            isMemoryUsagePopoverPresented.toggle()
-        } label: {
-            Label {
-                HStack(spacing: 4) {
-                    Text("Total \(memoryUsageMonitor.totalText)")
-                    Text("·")
-                    Text("Lithe \(memoryUsageMonitor.litheText)")
-                }
-                .monospacedDigit()
-            } icon: {
-                Image(systemName: "memorychip")
-            }
-        }
-        .buttonStyle(.plain)
-        .lithePointer()
-        .help(
-            Text(
-                "Total managed memory: \(memoryUsageMonitor.totalText)\n" +
-                "Lithe: \(memoryUsageMonitor.litheText) · LSP: \(memoryUsageMonitor.lspText) · Services: \(memoryUsageMonitor.serviceText)"
-            )
-        )
-        .popover(isPresented: $isMemoryUsagePopoverPresented, arrowEdge: .top) {
-            memoryUsagePopover
-        }
-        .onChange(of: isMemoryUsagePopoverPresented) { isPresented in
-            memoryUsageMonitor.setDetailedUsageVisible(isPresented)
-        }
-    }
-
-    private var memoryUsagePopover: some View {
-        VStack(alignment: .leading, spacing: 0) {
-            HStack(spacing: 8) {
-                Image(systemName: "memorychip")
-                    .foregroundStyle(LitheTheme.accent)
-                Text("Managed Memory")
-                    .font(.system(size: 12.5, weight: .semibold))
-                    .foregroundStyle(LitheTheme.primaryText)
-                Spacer(minLength: 8)
-                Button {
-                    isMemoryUsagePopoverPresented = false
-                } label: {
-                    Image(systemName: "xmark")
-                        .font(.system(size: 10, weight: .semibold))
-                }
-                .litheIconButton()
-                .help("Close")
-            }
-            .padding(.horizontal, 12)
-            .padding(.vertical, 10)
-
-            Rectangle()
-                .fill(LitheTheme.divider)
-                .frame(height: 1)
-
-            VStack(spacing: 0) {
-                memoryMetric("Lithe", value: memoryUsageMonitor.litheText)
-                memoryMetric(
-                    "Language servers",
-                    value: memoryUsageMonitor.languageServerProcessCount == 0
-                        ? String(localized: "Not running")
-                        : memoryUsageMonitor.lspText
-                )
-                memoryMetric(
-                    "Running services",
-                    value: memoryUsageMonitor.serviceProcessCount == 0
-                        ? String(localized: "Not running")
-                        : memoryUsageMonitor.serviceText
-                )
-                memoryMetric("Total", value: memoryUsageMonitor.totalText)
-                memoryMetric("Average total", value: memoryUsageMonitor.averageText)
-                memoryMetric("Peak total", value: memoryUsageMonitor.peakText)
-                memoryMetric("Runtime", value: memoryUsageMonitor.runtimeText)
-                memoryMetric("Sample interval", value: memoryUsageMonitor.samplingIntervalText)
-            }
-            .padding(.horizontal, 12)
-            .padding(.vertical, 5)
-
-            Rectangle()
-                .fill(LitheTheme.divider)
-                .frame(height: 1)
-
-            HStack(alignment: .top, spacing: 6) {
-                Image(systemName: "info.circle")
-                Text("Resident memory of Lithe and its managed process trees")
-                    .fixedSize(horizontal: false, vertical: true)
-            }
-            .font(LitheTheme.smallFont)
-            .foregroundStyle(LitheTheme.secondaryText)
-            .padding(12)
-        }
-        .frame(width: 280)
-        .background(LitheTheme.popupBackground)
-        .clipShape(RoundedRectangle(cornerRadius: 8))
-    }
-
-    private func memoryMetric(_ title: String, value: String) -> some View {
-        HStack(spacing: 8) {
-            Text(LocalizedStringKey(title))
-                .foregroundStyle(LitheTheme.secondaryText)
-            Spacer(minLength: 8)
-            Text(value)
-                .font(.system(size: 11.5, design: .monospaced))
-                .foregroundStyle(LitheTheme.primaryText)
-                .monospacedDigit()
-        }
-        .frame(minHeight: 27)
-    }
-
     private var projectInitials: String {
         let words = model.projectName.split(whereSeparator: { !$0.isLetter && !$0.isNumber })
         let initials = words.prefix(2).compactMap(\.first)
diff --git a/Sources/Lithe/Views/Workspace/ProjectSidebarView.swift b/Sources/Lithe/Views/Workspace/ProjectSidebarView.swift
index 20d8fe0f..5fb7e1e3 100644
--- a/Sources/Lithe/Views/Workspace/ProjectSidebarView.swift
+++ b/Sources/Lithe/Views/Workspace/ProjectSidebarView.swift
@@ -1,3 +1,4 @@
+import LitheGitModule
 import SwiftUI
 
 struct ProjectSidebarView: View {
@@ -22,13 +23,18 @@ struct ProjectSidebarView: View {
                 GeometryReader { geometry in
                     ScrollView([.vertical, .horizontal]) {
                         LazyVStack(alignment: .leading, spacing: 1) {
-                            FileNodeRow(
-                                node: root,
-                                depth: 0,
+                            ProjectFileTreeContent(
+                                root: root,
                                 availableWidth: geometry.size.width,
                                 activeDocumentURL: model.activeDocument?.url,
+                                gitStatus: ProjectGitStatusSnapshot(
+                                    repositoryRoot: model.gitRepositoryRoot,
+                                    projection: model.gitTreeStatusProjection
+                                ),
+                                actions: ProjectTreeActions(model: model),
                                 expandedDirectoryPaths: $expandedDirectoryPaths
                             )
+                            .equatable()
                         }
                         .padding(.vertical, 5)
                         .frame(
@@ -150,14 +156,119 @@ struct ProjectSidebarView: View {
     }
 }
 
+private struct ProjectGitStatusSnapshot: Equatable {
+    let repositoryRoot: URL?
+    let projection: GitTreeStatusProjection
+
+    func kind(for url: URL, isDirectory: Bool) -> GitChangeKind? {
+        guard let repositoryRoot,
+              let relative = Self.relativePath(for: url, root: repositoryRoot) else { return nil }
+        return projection.kind(relativePath: relative, isDirectory: isDirectory)
+    }
+
+    func change(for url: URL) -> GitChange? {
+        guard let repositoryRoot,
+              let relative = Self.relativePath(for: url, root: repositoryRoot) else { return nil }
+        return projection.change(relativePath: relative)
+    }
+
+    private static func relativePath(for url: URL, root: URL) -> String? {
+        let normalizedRoot = root.standardizedFileURL.path
+        let normalizedPath = url.standardizedFileURL.path
+        guard normalizedPath.hasPrefix(normalizedRoot + "/") else { return nil }
+        return String(normalizedPath.dropFirst(normalizedRoot.count + 1))
+    }
+}
+
+private final class ProjectTreeActions: @unchecked Sendable {
+    private let model: AppModel
+
+    init(model: AppModel) {
+        self.model = model
+    }
+
+    // Button and context-menu closures are not MainActor-isolated under the
+    // Swift 6 test/release check. Keep these methods synchronous and hop.
+    nonisolated func openFile(_ url: URL) {
+        Task { @MainActor in self.model.openFile(url) }
+    }
+    nonisolated func requestCreateFile(_ url: URL) {
+        Task { @MainActor in self.model.requestCreateFile(in: url) }
+    }
+    nonisolated func requestCreateDirectory(_ url: URL) {
+        Task { @MainActor in self.model.requestCreateDirectory(in: url) }
+    }
+    nonisolated func revealInFinder(_ url: URL) {
+        Task { @MainActor in self.model.revealProjectItemInFinder(url) }
+    }
+    nonisolated func copyPath(_ url: URL, relative: Bool) {
+        Task { @MainActor in self.model.copyProjectItemPath(url, relative: relative) }
+    }
+    nonisolated func duplicate(_ url: URL) {
+        Task { await self.model.duplicateProjectItem(at: url) }
+    }
+    nonisolated func requestRename(_ url: URL) {
+        Task { @MainActor in self.model.requestRenameProjectItem(at: url) }
+    }
+    nonisolated func requestDelete(_ url: URL, _ isDirectory: Bool) {
+        Task { @MainActor in
+            self.model.requestDeleteProjectItem(at: url, isDirectory: isDirectory)
+        }
+    }
+    nonisolated func refreshWorkspace() {
+        Task { await self.model.refreshWorkspace() }
+    }
+    nonisolated func showGitDirectoryDiff(_ url: URL) {
+        Task { await self.model.showGitDirectoryDiff(for: url) }
+    }
+    nonisolated func selectChange(_ change: GitChange) {
+        Task { @MainActor in self.model.selectChange(change) }
+    }
+    nonisolated func showLocalHistory(_ url: URL) {
+        Task { @MainActor in self.model.showLocalHistory(for: url) }
+    }
+    func javaIconKind(_ url: URL) async -> LitheIconKind? {
+        await model.javaIconKind(for: url)
+    }
+}
+
+private struct ProjectFileTreeContent: View, Equatable {
+    let root: FileNode
+    let availableWidth: CGFloat
+    let activeDocumentURL: URL?
+    let gitStatus: ProjectGitStatusSnapshot
+    let actions: ProjectTreeActions
+    @Binding var expandedDirectoryPaths: Set<String>
+
+    static func == (lhs: ProjectFileTreeContent, rhs: ProjectFileTreeContent) -> Bool {
+        lhs.root == rhs.root
+            && lhs.availableWidth == rhs.availableWidth
+            && lhs.activeDocumentURL == rhs.activeDocumentURL
+            && lhs.gitStatus == rhs.gitStatus
+    }
+
+    var body: some View {
+        FileNodeRow(
+            node: root,
+            depth: 0,
+            availableWidth: availableWidth,
+            activeDocumentURL: activeDocumentURL,
+            gitStatus: gitStatus,
+            actions: actions,
+            expandedDirectoryPaths: $expandedDirectoryPaths
+        )
+    }
+}
+
 private struct FileNodeRow: View {
     private static let horizontalInset: CGFloat = 10
 
-    @EnvironmentObject private var model: AppModel
     let node: FileNode
     let depth: Int
     let availableWidth: CGFloat
     let activeDocumentURL: URL?
+    let gitStatus: ProjectGitStatusSnapshot
+    let actions: ProjectTreeActions
     @Binding var expandedDirectoryPaths: Set<String>
     @State private var resolvedJavaIconKind: LitheIconKind?
 
@@ -182,6 +293,8 @@ private struct FileNodeRow: View {
                         depth: depth + 1,
                         availableWidth: availableWidth,
                         activeDocumentURL: activeDocumentURL,
+                        gitStatus: gitStatus,
+                        actions: actions,
                         expandedDirectoryPaths: $expandedDirectoryPaths
                     )
                 }
@@ -236,7 +349,7 @@ private struct FileNodeRow: View {
 
     private var fileRow: some View {
         Button {
-            model.openFile(node.url)
+            actions.openFile(node.url)
         } label: {
             HStack(spacing: 6) {
                 Color.clear.frame(width: 10)
@@ -249,7 +362,7 @@ private struct FileNodeRow: View {
                     .truncationMode(.middle)
                     .layoutPriority(1)
                 Spacer(minLength: 4)
-                if let status = model.gitChange(for: node.url) {
+                if let status = gitStatus.change(for: node.url) {
                     Text(status.displayStatus)
                         .font(.system(size: 9, weight: .bold, design: .monospaced))
                         .foregroundStyle(gitStatusColor ?? LitheTheme.secondaryText)
@@ -275,56 +388,56 @@ private struct FileNodeRow: View {
         .contextMenu { fileContextMenu }
         .task(id: node.url.standardizedFileURL.path) {
             guard node.url.pathExtension.lowercased() == "java" else { return }
-            resolvedJavaIconKind = await model.javaIconKind(for: node.url)
+            resolvedJavaIconKind = await actions.javaIconKind(node.url)
         }
     }
 
     @ViewBuilder
     private var directoryContextMenu: some View {
-        if model.gitTreeStatus(for: node.url, isDirectory: true) != nil {
+        if gitStatus.kind(for: node.url, isDirectory: true) != nil {
             Button("Show Git Diff") {
-                Task { await model.showGitDirectoryDiff(for: node.url) }
+                actions.showGitDirectoryDiff(node.url)
             }
             Divider()
         }
 
         Button("New File…") {
-            model.requestCreateFile(in: node.url)
+            actions.requestCreateFile(node.url)
         }
         Button("New Directory…") {
-            model.requestCreateDirectory(in: node.url)
+            actions.requestCreateDirectory(node.url)
         }
 
         Divider()
 
         Button("Show in Finder") {
-            model.revealProjectItemInFinder(node.url)
+            actions.revealInFinder(node.url)
         }
         Button("Copy Path") {
-            model.copyProjectItemPath(node.url, relative: false)
+            actions.copyPath(node.url, relative: false)
         }
         Button("Copy Relative Path") {
-            model.copyProjectItemPath(node.url, relative: true)
+            actions.copyPath(node.url, relative: true)
         }
 
         if depth > 0 {
             Divider()
 
             Button("Duplicate") {
-                Task { await model.duplicateProjectItem(at: node.url) }
+                actions.duplicate(node.url)
             }
             Button("Rename…") {
-                model.requestRenameProjectItem(at: node.url)
+                actions.requestRename(node.url)
             }
             Button("Move to Trash", role: .destructive) {
-                model.requestDeleteProjectItem(at: node.url, isDirectory: true)
+                actions.requestDelete(node.url, true)
             }
         }
 
         Divider()
 
         Button("Refresh") {
-            Task { await model.refreshWorkspace() }
+            actions.refreshWorkspace()
         }
     }
 
@@ -332,12 +445,12 @@ private struct FileNodeRow: View {
     private var fileContextMenu: some View {
         Group {
             Button("Open") {
-                model.openFile(node.url)
+                actions.openFile(node.url)
             }
 
-            if let change = model.gitChange(for: node.url) {
+            if let change = gitStatus.change(for: node.url) {
                 Button("Show Git Diff") {
-                    model.selectChange(change)
+                    actions.selectChange(change)
                 }
             }
         }
@@ -346,16 +459,16 @@ private struct FileNodeRow: View {
 
         Group {
             Button("Duplicate") {
-                Task { await model.duplicateProjectItem(at: node.url) }
+                actions.duplicate(node.url)
             }
             Button("Rename…") {
-                model.requestRenameProjectItem(at: node.url)
+                actions.requestRename(node.url)
             }
             Button("Local History…") {
-                model.showLocalHistory(for: node.url)
+                actions.showLocalHistory(node.url)
             }
             Button("Move to Trash", role: .destructive) {
-                model.requestDeleteProjectItem(at: node.url, isDirectory: false)
+                actions.requestDelete(node.url, false)
             }
         }
 
@@ -363,19 +476,19 @@ private struct FileNodeRow: View {
 
         Group {
             Button("Show in Finder") {
-                model.revealProjectItemInFinder(node.url)
+                actions.revealInFinder(node.url)
             }
             Button("Copy Path") {
-                model.copyProjectItemPath(node.url, relative: false)
+                actions.copyPath(node.url, relative: false)
             }
             Button("Copy Relative Path") {
-                model.copyProjectItemPath(node.url, relative: true)
+                actions.copyPath(node.url, relative: true)
             }
         }
     }
 
     private var gitStatusColor: Color? {
-        guard let kind = model.gitTreeStatus(for: node.url, isDirectory: node.isDirectory) else {
+        guard let kind = gitStatus.kind(for: node.url, isDirectory: node.isDirectory) else {
             return nil
         }
         switch kind {
diff --git a/Sources/LitheGitModule/Application/GitFeatureModel.swift b/Sources/LitheGitModule/Application/GitFeatureModel.swift
index 0b200a1d..7d75b0b7 100644
--- a/Sources/LitheGitModule/Application/GitFeatureModel.swift
+++ b/Sources/LitheGitModule/Application/GitFeatureModel.swift
@@ -7,7 +7,10 @@ import LitheModuleAPI
 /// in AppModel. Git command construction and parsing remain in GitService/Core.
 @MainActor
 package final class GitFeatureModel: ObservableObject {
-    @Published package private(set) var gitChanges: [GitChange] = []
+    @Published package private(set) var gitChanges: [GitChange] = [] {
+        didSet { gitTreeStatus = GitTreeStatusProjection(changes: gitChanges) }
+    }
+    package private(set) var gitTreeStatus = GitTreeStatusProjection(changes: [])
     @Published private var pendingStagingStates: [GitChange.ID: Bool] = [:]
     @Published package private(set) var gitStashes: [GitStash] = []
     @Published package private(set) var gitShelves: [GitShelfEntry] = []
diff --git a/Sources/LitheGitModule/Models/GitModels.swift b/Sources/LitheGitModule/Models/GitModels.swift
index 333edd1d..0c891521 100644
--- a/Sources/LitheGitModule/Models/GitModels.swift
+++ b/Sources/LitheGitModule/Models/GitModels.swift
@@ -431,31 +431,56 @@ package enum GitChangeKind: String, Sendable {
 /// Projects repository-relative Git changes onto file and directory rows.
 /// Directory status uses the most urgent descendant state so conflicts and
 /// deletions are never hidden behind a lower-priority modification.
-package struct GitTreeStatusProjection: Sendable {
-    private let changes: [GitChange]
+package struct GitTreeStatusProjection: Equatable, Sendable {
+    private let changesByPath: [String: GitChange]
+    private let directoryKinds: [String: GitChangeKind]
 
     package init(changes: [GitChange]) {
-        self.changes = changes
+        var changesByPath: [String: GitChange] = [:]
+        var directoryKinds: [String: GitChangeKind] = [:]
+        for change in changes {
+            let path = Self.normalized(change.path)
+            if changesByPath[path] == nil {
+                changesByPath[path] = change
+            }
+            var remainder = path
+            while let slash = remainder.lastIndex(of: "/") {
+                remainder = String(remainder[..<slash])
+                if let current = directoryKinds[remainder] {
+                    if Self.priority(change.kind) > Self.priority(current) {
+                        directoryKinds[remainder] = change.kind
+                    }
+                } else {
+                    directoryKinds[remainder] = change.kind
+                }
+            }
+            if !path.isEmpty {
+                if let current = directoryKinds[""] {
+                    if Self.priority(change.kind) > Self.priority(current) {
+                        directoryKinds[""] = change.kind
+                    }
+                } else {
+                    directoryKinds[""] = change.kind
+                }
+            }
+        }
+        self.changesByPath = changesByPath
+        self.directoryKinds = directoryKinds
     }
 
     package func change(relativePath: String) -> GitChange? {
-        let normalized = Self.normalized(relativePath)
-        return changes.first { Self.normalized($0.path) == normalized }
+        changesByPath[Self.normalized(relativePath)]
     }
 
     package func kind(relativePath: String, isDirectory: Bool) -> GitChangeKind? {
         let normalized = Self.normalized(relativePath)
         if !isDirectory {
-            return change(relativePath: normalized)?.kind
+            return changesByPath[normalized]?.kind
         }
-        let prefix = normalized.isEmpty ? "" : normalized + "/"
-        return changes
-            .filter { normalized.isEmpty || Self.normalized($0.path).hasPrefix(prefix) }
-            .map(\.kind)
-            .max { priority($0) < priority($1) }
+        return directoryKinds[normalized]
     }
 
-    private func priority(_ kind: GitChangeKind) -> Int {
+    private static func priority(_ kind: GitChangeKind) -> Int {
         switch kind {
         case .modified: 0
         case .copied: 1
diff --git a/Tests/LitheGitModuleTests/GitModuleTests.swift b/Tests/LitheGitModuleTests/GitModuleTests.swift
index a4596bf5..04766a71 100644
--- a/Tests/LitheGitModuleTests/GitModuleTests.swift
+++ b/Tests/LitheGitModuleTests/GitModuleTests.swift
@@ -37,6 +37,7 @@ struct GitModuleTests {
         #expect(projection.kind(relativePath: "Sources/Feature", isDirectory: true) == .conflicted)
         #expect(projection.kind(relativePath: "Sources", isDirectory: true) == .conflicted)
         #expect(projection.kind(relativePath: "Tests", isDirectory: true) == nil)
+        #expect(projection.kind(relativePath: "", isDirectory: true) == .conflicted)
     }
 
     @Test
diff --git a/Tests/LitheTests/EditorChromeModelTests.swift b/Tests/LitheTests/EditorChromeModelTests.swift
new file mode 100644
index 00000000..797e17d9
--- /dev/null
+++ b/Tests/LitheTests/EditorChromeModelTests.swift
@@ -0,0 +1,75 @@
+import Combine
+import Foundation
+import Testing
+@testable import Lithe
+
+@MainActor
+struct EditorChromeModelTests {
+    @Test
+    func unchangedCaretAndSelectionDoNotPublish() {
+        let chrome = EditorChromeModel()
+        let caret = EditorCaret(
+            url: URL(fileURLWithPath: "/workspace/App.java"),
+            line: 3,
+            utf16Column: 8
+        )
+        chrome.update(caret: caret)
+        chrome.update(selectedText: "name")
+
+        var publishCount = 0
+        let observation = chrome.objectWillChange.sink { _ in publishCount += 1 }
+        defer { observation.cancel() }
+
+        chrome.update(caret: caret)
+        chrome.update(selectedText: "name")
+        #expect(publishCount == 0)
+
+        chrome.update(caret: EditorCaret(url: caret.url, line: 4, utf16Column: 0))
+        #expect(publishCount == 1)
+        chrome.update(selectedText: "")
+        #expect(publishCount == 2)
+    }
+
+    @Test
+    func resetClearsCaretAndSelectionOnceEach() {
+        let chrome = EditorChromeModel()
+        chrome.update(
+            caret: EditorCaret(url: URL(fileURLWithPath: "/workspace/App.java"), line: 0, utf16Column: 0)
+        )
+        chrome.update(selectedText: "foo")
+
+        var publishCount = 0
+        let observation = chrome.objectWillChange.sink { _ in publishCount += 1 }
+        defer { observation.cancel() }
+
+        chrome.reset()
+        #expect(chrome.caret == nil)
+        #expect(chrome.selectedText.isEmpty)
+        #expect(publishCount == 2)
+
+        chrome.reset()
+        #expect(publishCount == 2)
+    }
+
+    @Test
+    func findBarUpdatesDoNotPublishUnchangedValues() {
+        let chrome = EditorChromeModel()
+        chrome.setFindBarVisible(true)
+        chrome.setFindBarQuery("foo")
+        chrome.updateFindState(currentIndex: 1, count: 3)
+
+        var publishCount = 0
+        let observation = chrome.objectWillChange.sink { _ in publishCount += 1 }
+        defer { observation.cancel() }
+
+        chrome.setFindBarVisible(true)
+        chrome.setFindBarQuery("foo")
+        chrome.updateFindState(currentIndex: 1, count: 3)
+        #expect(publishCount == 0)
+
+        chrome.setFindBarQuery("bar")
+        #expect(publishCount == 1)
+        chrome.updateFindState(currentIndex: 0, count: 2)
+        #expect(publishCount == 2)
+    }
+}
diff --git a/Tests/LitheTests/EditorDiagnosticsStoreTests.swift b/Tests/LitheTests/EditorDiagnosticsStoreTests.swift
new file mode 100644
index 00000000..18dc5903
--- /dev/null
+++ b/Tests/LitheTests/EditorDiagnosticsStoreTests.swift
@@ -0,0 +1,39 @@
+import Combine
+import Foundation
+import Testing
+@testable import Lithe
+
+@MainActor
+struct EditorDiagnosticsStoreTests {
+    @Test
+    func unchangedDiagnosticsDoNotPublish() {
+        let store = EditorDiagnosticsStore()
+        let url = URL(fileURLWithPath: "/workspace/App.java")
+        let diagnostic = EditorDiagnostic(
+            id: "d1",
+            fileURL: url,
+            line: 1,
+            utf16Column: 0,
+            endLine: 1,
+            endUTF16Column: 4,
+            severity: .warning,
+            message: "unused",
+            source: nil,
+            code: nil,
+            tags: [],
+            relatedInformation: []
+        )
+        store.replace([url: [diagnostic]])
+
+        var publishCount = 0
+        let observation = store.objectWillChange.sink { _ in publishCount += 1 }
+        defer { observation.cancel() }
+
+        store.replace([url: [diagnostic]])
+        #expect(publishCount == 0)
+
+        store.replace([:])
+        #expect(publishCount == 1)
+        #expect(store.diagnostics(for: url).isEmpty)
+    }
+}
diff --git a/Tests/LitheTests/FrameRateMonitorTests.swift b/Tests/LitheTests/FrameRateMonitorTests.swift
new file mode 100644
index 00000000..3c056a5d
--- /dev/null
+++ b/Tests/LitheTests/FrameRateMonitorTests.swift
@@ -0,0 +1,37 @@
+import Combine
+import Testing
+@testable import Lithe
+
+@MainActor
+struct FrameRateMonitorTests {
+    @Test
+    func publishesWhenDisplayedIntegerChangesAndIgnoresRepeats() {
+        let monitor = FrameRateMonitor(sampleWindow: 0.5)
+        monitor.recordFrameForTesting(at: 0)
+        monitor.recordFrameForTesting(at: 0.5)
+        #expect(monitor.framesPerSecond == 4)
+        #expect(monitor.framesPerSecondText == "4 FPS")
+
+        var publishCount = 0
+        let observation = monitor.objectWillChange.sink { _ in publishCount += 1 }
+        defer { observation.cancel() }
+
+        monitor.recordFrameForTesting(at: 1.0)
+        #expect(monitor.framesPerSecond == 2)
+        #expect(publishCount == 1)
+
+        monitor.recordFrameForTesting(at: 1.5)
+        #expect(monitor.framesPerSecond == 2)
+        #expect(publishCount == 1)
+    }
+
+    @Test
+    func coalescesBurstsAfterAHitch() {
+        let monitor = FrameRateMonitor(sampleWindow: 0.5)
+        monitor.recordFrameForTesting(at: 0)
+        monitor.recordFrameForTesting(at: 0.001)
+        monitor.recordFrameForTesting(at: 0.002)
+        monitor.recordFrameForTesting(at: 0.5)
+        #expect(monitor.framesPerSecond == 4)
+    }
+}
diff --git a/Tests/LitheTests/LitheCoreLogicTests.swift b/Tests/LitheTests/LitheCoreLogicTests.swift
index 3434c789..36764438 100644
--- a/Tests/LitheTests/LitheCoreLogicTests.swift
+++ b/Tests/LitheTests/LitheCoreLogicTests.swift
@@ -1,4 +1,5 @@
 import AppKit
+import Combine
 import CoreServices
 import Foundation
 @testable import LitheDatabaseModule
@@ -2119,6 +2120,38 @@ struct LitheCoreLogicTests {
         #expect(updates.first?.count == 0)
     }
 
+    @Test
+    @MainActor
+    func codeEditorLineIndexKeepsLineNumbersAfterSingleLineEdit() {
+        let textView = CodeTextView(frame: .zero)
+        textView.string = "one\ntwo\nthree"
+        textView.rebuildLineIndex()
+        #expect(textView.lineNumber(at: 4, in: textView.string as NSString) == 1)
+
+        textView.string = "oneX\ntwo\nthree"
+        textView.applyLineIndexEdit(replacedRange: NSRange(location: 3, length: 0), replacement: "X")
+        let source = textView.string as NSString
+        #expect(textView.lineNumber(at: 0, in: source) == 0)
+        #expect(textView.lineNumber(at: 5, in: source) == 1)
+        #expect(textView.lineNumber(at: 9, in: source) == 2)
+        #expect(textView.characterOffset(forLine: 2, in: source) == 9)
+    }
+
+    @Test
+    @MainActor
+    func codeEditorShiftsFindMatchesAcrossASingleLineEdit() {
+        let textView = CodeTextView(frame: .zero)
+        textView.string = "alpha beta alpha"
+        textView.rebuildLineIndex()
+        textView.updateFindMatches(query: "alpha")
+        #expect(textView.currentFindMatchCountForTesting == 2)
+
+        textView.string = "Xalpha beta alpha"
+        textView.applyFindEdit(replacedRange: NSRange(location: 0, length: 0), insertedLength: 1, query: "alpha")
+        #expect(textView.currentFindMatchCountForTesting == 2)
+        #expect(textView.findMatchLocationsForTesting == [1, 12])
+    }
+
     @Test
     @MainActor
     func codeEditorReportsEachFindStateOnlyOnce() {
@@ -2592,6 +2625,34 @@ struct EditorDocumentTests {
         #expect(try String(contentsOf: url, encoding: .utf8) == "after")
     }
 
+    @Test
+    @MainActor
+    func liveEditorTextPublishesOnlyWhenDirtyStateChanges() {
+        let document = EditorDocument(
+            url: URL(fileURLWithPath: "/tmp/live-editor.txt"),
+            text: "before",
+            modificationDate: nil
+        )
+        var publishCount = 0
+        let observation = document.objectWillChange.sink { _ in publishCount += 1 }
+        defer { observation.cancel() }
+
+        document.applyLiveEditorText("before")
+        #expect(publishCount == 0)
+
+        document.applyLiveEditorText("after")
+        #expect(document.isDirty)
+        #expect(publishCount == 1)
+
+        document.applyLiveEditorText("after more")
+        #expect(document.isDirty)
+        #expect(publishCount == 1)
+
+        document.applyLiveEditorText("before")
+        #expect(!document.isDirty)
+        #expect(publishCount == 2)
+    }
+
     @Test
     func readOnlyDocumentRejectsSave() {
         let url = FileManager.default.temporaryDirectory