cmux/Sources/GhosttyTerminalView.swift

import Foundation
import SwiftUI
import AppKit
import Metal
import QuartzCore
import Combine
import Darwin
import Sentry
import Bonsplit
import IOSurface

#if os(macOS)
func cmuxShouldUseTransparentBackgroundWindow() -> Bool {
    let defaults = UserDefaults.standard
    let sidebarBlendMode = defaults.string(forKey: "sidebarBlendMode") ?? "withinWindow"
    let bgGlassEnabled = defaults.object(forKey: "bgGlassEnabled") as? Bool ?? false
    return sidebarBlendMode == "behindWindow" && bgGlassEnabled && !WindowGlassEffect.isAvailable
}

func cmuxShouldUseClearWindowBackground(for opacity: Double) -> Bool {
    cmuxShouldUseTransparentBackgroundWindow() || opacity < 0.999
}

private func cmuxTransparentWindowBaseColor() -> NSColor {
    // A tiny non-zero alpha matches Ghostty's window compositing behavior on macOS and
    // avoids visual artifacts that can happen with a fully clear window background.
    NSColor.white.withAlphaComponent(0.001)
}
#endif

#if DEBUG
private func cmuxChildExitProbePath() -> String? {
    let env = ProcessInfo.processInfo.environment
    guard env["CMUX_UI_TEST_CHILD_EXIT_KEYBOARD_SETUP"] == "1",
          let path = env["CMUX_UI_TEST_CHILD_EXIT_KEYBOARD_PATH"],
          !path.isEmpty else {
        return nil
    }
    return path
}

private func cmuxLoadChildExitProbe(at path: String) -> [String: String] {
    guard let data = try? Data(contentsOf: URL(fileURLWithPath: path)),
          let object = try? JSONSerialization.jsonObject(with: data) as? [String: String] else {
        return [:]
    }
    return object
}

private func cmuxWriteChildExitProbe(_ updates: [String: String], increments: [String: Int] = [:]) {
    guard let path = cmuxChildExitProbePath() else { return }
    var payload = cmuxLoadChildExitProbe(at: path)
    for (key, by) in increments {
        let current = Int(payload[key] ?? "") ?? 0
        payload[key] = String(current + by)
    }
    for (key, value) in updates {
        payload[key] = value
    }
    guard let out = try? JSONSerialization.data(withJSONObject: payload) else { return }
    try? out.write(to: URL(fileURLWithPath: path), options: .atomic)
}

private func cmuxScalarHex(_ value: String?) -> String {
    guard let value else { return "" }
    return value.unicodeScalars
        .map { String(format: "%04X", $0.value) }
        .joined(separator: ",")
}
#endif

private enum GhosttyPasteboardHelper {
    private static let selectionPasteboard = NSPasteboard(
        name: NSPasteboard.Name("com.mitchellh.ghostty.selection")
    )
    private static let utf8PlainTextType = NSPasteboard.PasteboardType("public.utf8-plain-text")
    private static let shellEscapeCharacters = "\\ ()[]{}<>\"'`!#$&;|*?\t"

    static func pasteboard(for location: ghostty_clipboard_e) -> NSPasteboard? {
        switch location {
        case GHOSTTY_CLIPBOARD_STANDARD:
            return .general
        case GHOSTTY_CLIPBOARD_SELECTION:
            return selectionPasteboard
        default:
            return nil
        }
    }

    static func stringContents(from pasteboard: NSPasteboard) -> String? {
        if let urls = pasteboard.readObjects(forClasses: [NSURL.self]) as? [URL],
           !urls.isEmpty {
            return urls
                .map { $0.isFileURL ? escapeForShell($0.path) : $0.absoluteString }
                .joined(separator: " ")
        }

        if let value = pasteboard.string(forType: .string) {
            return value
        }

        return pasteboard.string(forType: utf8PlainTextType)
    }

    static func hasString(for location: ghostty_clipboard_e) -> Bool {
        guard let pasteboard = pasteboard(for: location) else { return false }
        return (stringContents(from: pasteboard) ?? "").isEmpty == false
    }

    static func writeString(_ string: String, to location: ghostty_clipboard_e) {
        guard let pasteboard = pasteboard(for: location) else { return }
        pasteboard.clearContents()
        pasteboard.setString(string, forType: .string)
    }

    private static func escapeForShell(_ value: String) -> String {
        var result = value
        for char in shellEscapeCharacters {
            result = result.replacingOccurrences(of: String(char), with: "\\\(char)")
        }
        return result
    }
}

enum TerminalOpenURLTarget: Equatable {
    case embeddedBrowser(URL)
    case external(URL)

    var url: URL {
        switch self {
        case let .embeddedBrowser(url), let .external(url):
            return url
        }
    }
}

enum GhosttyDefaultBackgroundUpdateScope: Int {
    case unscoped = 0
    case app = 1
    case surface = 2

    var logLabel: String {
        switch self {
        case .unscoped: return "unscoped"
        case .app: return "app"
        case .surface: return "surface"
        }
    }
}

/// Coalesces Ghostty background notifications so consumers only observe
/// the latest runtime background for a burst of updates.
final class GhosttyDefaultBackgroundNotificationDispatcher {
    private let coalescer: NotificationBurstCoalescer
    private let postNotification: ([AnyHashable: Any]) -> Void
    private var pendingUserInfo: [AnyHashable: Any]?
    private var pendingEventId: UInt64 = 0
    private var pendingSource: String = "unspecified"
    private let logEvent: ((String) -> Void)?

    init(
        delay: TimeInterval = 1.0 / 30.0,
        logEvent: ((String) -> Void)? = nil,
        postNotification: @escaping ([AnyHashable: Any]) -> Void = { userInfo in
            NotificationCenter.default.post(
                name: .ghosttyDefaultBackgroundDidChange,
                object: nil,
                userInfo: userInfo
            )
        }
    ) {
        coalescer = NotificationBurstCoalescer(delay: delay)
        self.logEvent = logEvent
        self.postNotification = postNotification
    }

    func signal(backgroundColor: NSColor, opacity: Double, eventId: UInt64, source: String) {
        let signalOnMain = { [self] in
            pendingEventId = eventId
            pendingSource = source
            pendingUserInfo = [
                GhosttyNotificationKey.backgroundColor: backgroundColor,
                GhosttyNotificationKey.backgroundOpacity: opacity,
                GhosttyNotificationKey.backgroundEventId: NSNumber(value: eventId),
                GhosttyNotificationKey.backgroundSource: source
            ]
            logEvent?(
                "bg notify queued id=\(eventId) source=\(source) color=\(backgroundColor.hexString()) opacity=\(String(format: "%.3f", opacity))"
            )
            coalescer.signal { [self] in
                guard let userInfo = pendingUserInfo else { return }
                let eventId = pendingEventId
                let source = pendingSource
                pendingUserInfo = nil
                logEvent?("bg notify flushed id=\(eventId) source=\(source)")
                logEvent?("bg notify posting id=\(eventId) source=\(source)")
                postNotification(userInfo)
                logEvent?("bg notify posted id=\(eventId) source=\(source)")
            }
        }

        if Thread.isMainThread {
            signalOnMain()
        } else {
            DispatchQueue.main.async(execute: signalOnMain)
        }
    }
}

func resolveTerminalOpenURLTarget(_ rawValue: String) -> TerminalOpenURLTarget? {
    let trimmed = rawValue.trimmingCharacters(in: .whitespacesAndNewlines)
    #if DEBUG
    dlog("link.resolve input=\(trimmed)")
    #endif
    guard !trimmed.isEmpty else {
        #if DEBUG
        dlog("link.resolve result=nil (empty)")
        #endif
        return nil
    }

    if NSString(string: trimmed).isAbsolutePath {
        #if DEBUG
        dlog("link.resolve result=external(absolutePath) url=\(trimmed)")
        #endif
        return .external(URL(fileURLWithPath: trimmed))
    }

    if let parsed = URL(string: trimmed),
       let scheme = parsed.scheme?.lowercased() {
        if scheme == "http" || scheme == "https" {
            guard BrowserInsecureHTTPSettings.normalizeHost(parsed.host ?? "") != nil else {
                #if DEBUG
                dlog("link.resolve result=external(invalidHost) url=\(parsed)")
                #endif
                return .external(parsed)
            }
            #if DEBUG
            dlog("link.resolve result=embeddedBrowser url=\(parsed)")
            #endif
            return .embeddedBrowser(parsed)
        }
        #if DEBUG
        dlog("link.resolve result=external(scheme=\(scheme)) url=\(parsed)")
        #endif
        return .external(parsed)
    }

    if let webURL = resolveBrowserNavigableURL(trimmed) {
        guard BrowserInsecureHTTPSettings.normalizeHost(webURL.host ?? "") != nil else {
            #if DEBUG
            dlog("link.resolve result=external(bareHost-invalidHost) url=\(webURL)")
            #endif
            return .external(webURL)
        }
        #if DEBUG
        dlog("link.resolve result=embeddedBrowser(bareHost) url=\(webURL)")
        #endif
        return .embeddedBrowser(webURL)
    }

    guard let fallback = URL(string: trimmed) else {
        #if DEBUG
        dlog("link.resolve result=nil (unparseable)")
        #endif
        return nil
    }
    #if DEBUG
    dlog("link.resolve result=external(fallback) url=\(fallback)")
    #endif
    return .external(fallback)
}

enum TerminalKeyboardCopyModeSelectionMove: String, Equatable {
    case left
    case right
    case up
    case down
    case pageUp = "page_up"
    case pageDown = "page_down"
    case home
    case end
    case beginningOfLine = "beginning_of_line"
    case endOfLine = "end_of_line"
}

enum TerminalKeyboardCopyModeAction: Equatable {
    case exit
    case startSelection
    case clearSelection
    case copyAndExit
    case copyLineAndExit
    case scrollLines(Int)
    case scrollPage(Int)
    case scrollToTop
    case scrollToBottom
    case jumpToPrompt(Int)
    case startSearch
    case searchNext
    case searchPrevious
    case adjustSelection(TerminalKeyboardCopyModeSelectionMove)
}

struct TerminalKeyboardCopyModeInputState: Equatable {
    var countPrefix: Int?
    var pendingYankLine = false

    mutating func reset() {
        countPrefix = nil
        pendingYankLine = false
    }
}

enum TerminalKeyboardCopyModeResolution: Equatable {
    case perform(TerminalKeyboardCopyModeAction, count: Int)
    case consume
}

private let terminalKeyboardCopyModeMaxCount = 9_999

private func terminalKeyboardCopyModeClampCount(_ value: Int) -> Int {
    min(max(value, 1), terminalKeyboardCopyModeMaxCount)
}

func terminalKeyboardCopyModeInitialViewportRow(
    rows: Int,
    imePointY: Double,
    imeCellHeight: Double,
    topPadding: Double = 0
) -> Int {
    let clampedRows = max(rows, 1)
    guard imeCellHeight > 0 else { return clampedRows - 1 }

    // `ghostty_surface_ime_point` returns a top-origin Y coordinate at the
    // cursor baseline plus one cell-height. Convert that to a zero-based row.
    let estimatedRow = Int(floor(((imePointY - topPadding) / imeCellHeight) - 1))
    return max(0, min(clampedRows - 1, estimatedRow))
}

private func terminalKeyboardCopyModeNormalizedModifiers(
    _ modifierFlags: NSEvent.ModifierFlags
) -> NSEvent.ModifierFlags {
    modifierFlags
        .intersection(.deviceIndependentFlagsMask)
        .subtracting([.numericPad, .function, .capsLock])
}

private func terminalKeyboardCopyModeChars(
    _ charactersIgnoringModifiers: String?
) -> String {
    guard let scalar = charactersIgnoringModifiers?.unicodeScalars.first else {
        return ""
    }
    return String(scalar).lowercased()
}

func terminalKeyboardCopyModeShouldBypassForShortcut(modifierFlags: NSEvent.ModifierFlags) -> Bool {
    let normalized = terminalKeyboardCopyModeNormalizedModifiers(modifierFlags)
    return normalized.contains(.command)
}

func terminalKeyboardCopyModeAction(
    keyCode: UInt16,
    charactersIgnoringModifiers: String?,
    modifierFlags: NSEvent.ModifierFlags,
    hasSelection: Bool
) -> TerminalKeyboardCopyModeAction? {
    let normalized = terminalKeyboardCopyModeNormalizedModifiers(modifierFlags)
    let chars = terminalKeyboardCopyModeChars(charactersIgnoringModifiers)

    if keyCode == 53 { // Escape
        return .exit
    }

    switch keyCode {
    case 126: // Up
        return hasSelection ? .adjustSelection(.up) : .scrollLines(-1)
    case 125: // Down
        return hasSelection ? .adjustSelection(.down) : .scrollLines(1)
    case 123: // Left
        return hasSelection ? .adjustSelection(.left) : nil
    case 124: // Right
        return hasSelection ? .adjustSelection(.right) : nil
    case 116: // Page Up
        return hasSelection ? .adjustSelection(.pageUp) : .scrollPage(-1)
    case 121: // Page Down
        return hasSelection ? .adjustSelection(.pageDown) : .scrollPage(1)
    case 115: // Home
        return hasSelection ? .adjustSelection(.home) : .scrollToTop
    case 119: // End
        return hasSelection ? .adjustSelection(.end) : .scrollToBottom
    default:
        break
    }

    if normalized == [.control] {
        if chars == "u" || chars == "\u{15}" {
            return hasSelection ? .adjustSelection(.pageUp) : .scrollPage(-1)
        }
        if chars == "d" || chars == "\u{04}" {
            return hasSelection ? .adjustSelection(.pageDown) : .scrollPage(1)
        }
        if chars == "b" || chars == "\u{02}" {
            return hasSelection ? .adjustSelection(.pageUp) : .scrollPage(-1)
        }
        if chars == "f" || chars == "\u{06}" {
            return hasSelection ? .adjustSelection(.pageDown) : .scrollPage(1)
        }
        if chars == "y" || chars == "\u{19}" {
            return hasSelection ? .adjustSelection(.up) : .scrollLines(-1)
        }
        if chars == "e" || chars == "\u{05}" {
            return hasSelection ? .adjustSelection(.down) : .scrollLines(1)
        }
        return nil
    }

    guard normalized.isEmpty || normalized == [.shift] else { return nil }

    switch chars {
    case "q":
        return .exit
    case "v":
        return hasSelection ? .clearSelection : .startSelection
    case "y":
        if normalized == [.shift], !hasSelection {
            return .copyLineAndExit
        }
        return hasSelection ? .copyAndExit : nil
    case "j":
        return hasSelection ? .adjustSelection(.down) : .scrollLines(1)
    case "k":
        return hasSelection ? .adjustSelection(.up) : .scrollLines(-1)
    case "h":
        return hasSelection ? .adjustSelection(.left) : nil
    case "l":
        return hasSelection ? .adjustSelection(.right) : nil
    case "g":
        if normalized == [.shift] {
            return hasSelection ? .adjustSelection(.end) : .scrollToBottom
        }
        return hasSelection ? .adjustSelection(.home) : .scrollToTop
    case "0", "^":
        return hasSelection ? .adjustSelection(.beginningOfLine) : nil
    case "$", "4":
        guard chars == "$" || normalized == [.shift] else { return nil }
        return hasSelection ? .adjustSelection(.endOfLine) : nil
    case "{", "[":
        guard chars == "{" || normalized == [.shift] else { return nil }
        return .jumpToPrompt(-1)
    case "}", "]":
        guard chars == "}" || normalized == [.shift] else { return nil }
        return .jumpToPrompt(1)
    case "/":
        return .startSearch
    case "n":
        return normalized == [.shift] ? .searchPrevious : .searchNext
    default:
        return nil
    }
}

func terminalKeyboardCopyModeResolve(
    keyCode: UInt16,
    charactersIgnoringModifiers: String?,
    modifierFlags: NSEvent.ModifierFlags,
    hasSelection: Bool,
    state: inout TerminalKeyboardCopyModeInputState
) -> TerminalKeyboardCopyModeResolution {
    let normalized = terminalKeyboardCopyModeNormalizedModifiers(modifierFlags)
    let chars = terminalKeyboardCopyModeChars(charactersIgnoringModifiers)

    if keyCode == 53 { // Escape
        state.reset()
        return .perform(.exit, count: 1)
    }

    if state.pendingYankLine {
        if chars == "y", normalized.isEmpty || normalized == [.shift] {
            let count = terminalKeyboardCopyModeClampCount(state.countPrefix ?? 1)
            state.reset()
            return .perform(.copyLineAndExit, count: count)
        }
        // Only `yy`/`Y` are supported as line-yank operators, so cancel the
        // pending yank and treat this key as a fresh command.
        state.pendingYankLine = false
    }

    if normalized.isEmpty,
       let scalar = chars.unicodeScalars.first,
       scalar.isASCII,
       scalar.value >= 48,
       scalar.value <= 57 {
        let digit = Int(scalar.value - 48)
        if digit == 0 {
            if let currentCount = state.countPrefix {
                state.countPrefix = terminalKeyboardCopyModeClampCount(currentCount * 10)
                return .consume
            }
        } else {
            let currentCount = state.countPrefix ?? 0
            state.countPrefix = terminalKeyboardCopyModeClampCount((currentCount * 10) + digit)
            return .consume
        }
    }

    if !hasSelection, chars == "y", normalized.isEmpty {
        state.pendingYankLine = true
        return .consume
    }

    guard let action = terminalKeyboardCopyModeAction(
        keyCode: keyCode,
        charactersIgnoringModifiers: charactersIgnoringModifiers,
        modifierFlags: modifierFlags,
        hasSelection: hasSelection
    ) else {
        state.reset()
        return .consume
    }

    let count = terminalKeyboardCopyModeClampCount(state.countPrefix ?? 1)
    state.reset()
    return .perform(action, count: count)
}

private final class GhosttySurfaceCallbackContext {
    weak var surfaceView: GhosttyNSView?
    weak var terminalSurface: TerminalSurface?
    let surfaceId: UUID

    init(surfaceView: GhosttyNSView, terminalSurface: TerminalSurface) {
        self.surfaceView = surfaceView
        self.terminalSurface = terminalSurface
        self.surfaceId = terminalSurface.id
    }

    var tabId: UUID? {
        terminalSurface?.tabId ?? surfaceView?.tabId
    }

    var runtimeSurface: ghostty_surface_t? {
        terminalSurface?.surface ?? surfaceView?.terminalSurface?.surface
    }
}

// Minimal Ghostty wrapper for terminal rendering
// This uses libghostty (GhosttyKit.xcframework) for actual terminal emulation

// MARK: - Ghostty App Singleton

class GhosttyApp {
    static let shared = GhosttyApp()
    private static let releaseBundleIdentifier = "com.cmuxterm.app"
    private static let backgroundLogTimestampFormatter: ISO8601DateFormatter = {
        let formatter = ISO8601DateFormatter()
        formatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
        return formatter
    }()

    private(set) var app: ghostty_app_t?
    private(set) var config: ghostty_config_t?
    private(set) var defaultBackgroundColor: NSColor = .windowBackgroundColor
    private(set) var defaultBackgroundOpacity: Double = 1.0
    private static func resolveBackgroundLogURL(
        environment: [String: String] = ProcessInfo.processInfo.environment
    ) -> URL {
        if let explicitPath = environment["CMUX_DEBUG_BG_LOG"],
           !explicitPath.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty {
            return URL(fileURLWithPath: explicitPath)
        }

        if let debugLogPath = environment["CMUX_DEBUG_LOG"],
           !debugLogPath.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty {
            let baseURL = URL(fileURLWithPath: debugLogPath)
            let extensionSeparatorIndex = baseURL.lastPathComponent.lastIndex(of: ".")
            let stem = extensionSeparatorIndex.map { String(baseURL.lastPathComponent[..<$0]) } ?? baseURL.lastPathComponent
            let bgName = "\(stem)-bg.log"
            return baseURL.deletingLastPathComponent().appendingPathComponent(bgName)
        }

        return URL(fileURLWithPath: "/tmp/cmux-bg.log")
    }

    let backgroundLogEnabled = {
        if ProcessInfo.processInfo.environment["CMUX_DEBUG_BG"] == "1" {
            return true
        }
        if ProcessInfo.processInfo.environment["CMUX_DEBUG_LOG"] != nil {
            return true
        }
        if ProcessInfo.processInfo.environment["GHOSTTYTABS_DEBUG_BG"] == "1" {
            return true
        }
        if UserDefaults.standard.bool(forKey: "cmuxDebugBG") {
            return true
        }
        return UserDefaults.standard.bool(forKey: "GhosttyTabsDebugBG")
    }()
    private let backgroundLogURL = GhosttyApp.resolveBackgroundLogURL()
    private let backgroundLogStartUptime = ProcessInfo.processInfo.systemUptime
    private let backgroundLogLock = NSLock()
    private var backgroundLogSequence: UInt64 = 0
    private var appObservers: [NSObjectProtocol] = []
    private var backgroundEventCounter: UInt64 = 0
    private var defaultBackgroundUpdateScope: GhosttyDefaultBackgroundUpdateScope = .unscoped
    private var defaultBackgroundScopeSource: String = "initialize"
    private var lastAppearanceColorScheme: GhosttyConfig.ColorSchemePreference?
    private lazy var defaultBackgroundNotificationDispatcher: GhosttyDefaultBackgroundNotificationDispatcher =
        // Theme chrome should track terminal theme changes in the same frame.
        // Keep coalescing semantics, but flush in the next main turn instead of waiting ~1 frame.
        GhosttyDefaultBackgroundNotificationDispatcher(delay: 0, logEvent: { [weak self] message in
            guard let self, self.backgroundLogEnabled else { return }
            self.logBackground(message)
        })

    // Scroll lag tracking
    private(set) var isScrolling = false
    private var scrollLagSampleCount = 0
    private var scrollLagTotalMs: Double = 0
    private var scrollLagMaxMs: Double = 0
    private let scrollLagThresholdMs: Double = 40
    private let scrollLagMinimumSamples = 8
    private let scrollLagMinimumAverageMs: Double = 12
    private let scrollLagReportCooldownSeconds: TimeInterval = 300
    private var lastScrollLagReportUptime: TimeInterval?
    private var scrollEndTimer: DispatchWorkItem?

    func markScrollActivity(hasMomentum: Bool, momentumEnded: Bool) {
        // Cancel any pending scroll-end timer
        scrollEndTimer?.cancel()
        scrollEndTimer = nil

        if momentumEnded {
            // Trackpad momentum ended - scrolling is done
            endScrollSession()
        } else if hasMomentum {
            // Trackpad scrolling with momentum - wait for momentum to end
            isScrolling = true
        } else {
            // Mouse wheel or non-momentum scroll - use timeout
            isScrolling = true
            let timer = DispatchWorkItem { [weak self] in
                self?.endScrollSession()
            }
            scrollEndTimer = timer
            DispatchQueue.main.asyncAfter(deadline: .now() + 0.15, execute: timer)
        }
    }

    private func endScrollSession() {
        guard isScrolling else { return }
        isScrolling = false

        // Report accumulated lag stats if any exceeded threshold
        if scrollLagSampleCount > 0 {
            let avgLag = scrollLagTotalMs / Double(scrollLagSampleCount)
            let maxLag = scrollLagMaxMs
            let samples = scrollLagSampleCount
            let threshold = scrollLagThresholdMs
            let nowUptime = ProcessInfo.processInfo.systemUptime
            if Self.shouldCaptureScrollLagEvent(
                samples: samples,
                averageMs: avgLag,
                maxMs: maxLag,
                thresholdMs: threshold,
                minimumSamples: scrollLagMinimumSamples,
                minimumAverageMs: scrollLagMinimumAverageMs,
                nowUptime: nowUptime,
                lastReportedUptime: lastScrollLagReportUptime,
                cooldown: scrollLagReportCooldownSeconds
            ) {
                if TelemetrySettings.enabledForCurrentLaunch {
                    SentrySDK.capture(message: "Scroll lag detected") { scope in
                        scope.setLevel(.warning)
                        scope.setContext(value: [
                            "samples": samples,
                            "avg_ms": String(format: "%.2f", avgLag),
                            "max_ms": String(format: "%.2f", maxLag),
                            "threshold_ms": threshold
                        ], key: "scroll_lag")
                    }
                }
                lastScrollLagReportUptime = nowUptime
            }
            // Reset stats
            scrollLagSampleCount = 0
            scrollLagTotalMs = 0
            scrollLagMaxMs = 0
        }
    }

    private init() {
        initializeGhostty()
    }

    #if DEBUG
    private static let initLogPath = "/tmp/cmux-ghostty-init.log"

    private static func initLog(_ message: String) {
        let timestamp = ISO8601DateFormatter().string(from: Date())
        let line = "[\(timestamp)] \(message)\n"
        if let handle = FileHandle(forWritingAtPath: initLogPath) {
            handle.seekToEndOfFile()
            handle.write(line.data(using: .utf8)!)
            handle.closeFile()
        } else {
            FileManager.default.createFile(atPath: initLogPath, contents: line.data(using: .utf8))
        }
    }

    private static func dumpConfigDiagnostics(_ config: ghostty_config_t, label: String) {
        let count = Int(ghostty_config_diagnostics_count(config))
        guard count > 0 else {
            initLog("ghostty diagnostics (\(label)): none")
            return
        }
        initLog("ghostty diagnostics (\(label)): count=\(count)")
        for i in 0..<count {
            let diag = ghostty_config_get_diagnostic(config, UInt32(i))
            let msg = diag.message.flatMap { String(cString: $0) } ?? "(null)"
            initLog("  [\(i)] \(msg)")
        }
    }
    #endif

    private func initializeGhostty() {
        // Ensure TUI apps can use colors even if NO_COLOR is set in the launcher env.
        if getenv("NO_COLOR") != nil {
            unsetenv("NO_COLOR")
        }

        // Initialize Ghostty library first
        let result = ghostty_init(UInt(CommandLine.argc), CommandLine.unsafeArgv)
        if result != GHOSTTY_SUCCESS {
            print("Failed to initialize ghostty: \(result)")
            return
        }

        // Load config
        guard let primaryConfig = ghostty_config_new() else {
            print("Failed to create ghostty config")
            return
        }

        // Load default config (includes user config). If this fails hard (e.g. due to
        // invalid user config), ghostty_app_new may return nil; we fall back below.
        loadDefaultConfigFilesWithLegacyFallback(primaryConfig)
        updateDefaultBackground(from: primaryConfig, source: "initialize.primaryConfig")

        // Create runtime config with callbacks
        var runtimeConfig = ghostty_runtime_config_s()
        runtimeConfig.userdata = Unmanaged.passUnretained(self).toOpaque()
        runtimeConfig.supports_selection_clipboard = true
        runtimeConfig.wakeup_cb = { userdata in
            DispatchQueue.main.async {
                GhosttyApp.shared.tick()
            }
        }
        runtimeConfig.action_cb = { app, target, action in
            return GhosttyApp.shared.handleAction(target: target, action: action)
        }
        runtimeConfig.read_clipboard_cb = { userdata, location, state in
            // Read clipboard
            guard let callbackContext = GhosttyApp.callbackContext(from: userdata),
                  let surface = callbackContext.runtimeSurface else { return }

            let pasteboard = GhosttyPasteboardHelper.pasteboard(for: location)
            let value = pasteboard.flatMap { GhosttyPasteboardHelper.stringContents(from: $0) } ?? ""

            value.withCString { ptr in
                ghostty_surface_complete_clipboard_request(surface, ptr, state, false)
            }
        }
        runtimeConfig.confirm_read_clipboard_cb = { userdata, content, state, _ in
            guard let content else { return }
            guard let callbackContext = GhosttyApp.callbackContext(from: userdata),
                  let surface = callbackContext.runtimeSurface else { return }

            ghostty_surface_complete_clipboard_request(surface, content, state, true)
        }
        runtimeConfig.write_clipboard_cb = { _, location, content, len, _ in
            // Write clipboard
            guard let content = content, len > 0 else { return }
            let buffer = UnsafeBufferPointer(start: content, count: Int(len))

            var fallback: String?
            for item in buffer {
                guard let dataPtr = item.data else { continue }
                let value = String(cString: dataPtr)

                if let mimePtr = item.mime {
                    let mime = String(cString: mimePtr)
                    if mime.hasPrefix("text/plain") {
                        GhosttyPasteboardHelper.writeString(value, to: location)
                        return
                    }
                }

                if fallback == nil {
                    fallback = value
                }
            }

            if let fallback {
                GhosttyPasteboardHelper.writeString(fallback, to: location)
            }
        }
        runtimeConfig.close_surface_cb = { userdata, needsConfirmClose in
            guard let callbackContext = GhosttyApp.callbackContext(from: userdata) else { return }
            let callbackSurfaceId = callbackContext.surfaceId
            let callbackTabId = callbackContext.tabId

#if DEBUG
            cmuxWriteChildExitProbe(
                [
                    "probeCloseSurfaceNeedsConfirm": needsConfirmClose ? "1" : "0",
                    "probeCloseSurfaceTabId": callbackTabId?.uuidString ?? "",
                    "probeCloseSurfaceSurfaceId": callbackSurfaceId.uuidString,
                ],
                increments: ["probeCloseSurfaceCbCount": 1]
            )
#endif

            DispatchQueue.main.async {
                guard let app = AppDelegate.shared else { return }
                // Close requests must be resolved by the callback's workspace/surface IDs only.
                // If the mapping is already gone (duplicate/stale callback), ignore it.
                if let callbackTabId,
                   let manager = app.tabManagerFor(tabId: callbackTabId) ?? app.tabManager,
                   let workspace = manager.tabs.first(where: { $0.id == callbackTabId }),
                   workspace.panels[callbackSurfaceId] != nil {
                    if needsConfirmClose {
                        manager.closeRuntimeSurfaceWithConfirmation(
                            tabId: callbackTabId,
                            surfaceId: callbackSurfaceId
                        )
                    } else {
                        manager.closeRuntimeSurface(
                            tabId: callbackTabId,
                            surfaceId: callbackSurfaceId
                        )
                    }
                }
            }
        }

        // Create app
        if let created = ghostty_app_new(&runtimeConfig, primaryConfig) {
            self.app = created
            self.config = primaryConfig
        } else {
            #if DEBUG
            Self.initLog("ghostty_app_new(primary) failed; attempting fallback config")
            Self.dumpConfigDiagnostics(primaryConfig, label: "primary")
            #endif

            // If the user config is invalid, prefer a minimal fallback configuration so
            // cmux still launches with working terminals.
            ghostty_config_free(primaryConfig)

            guard let fallbackConfig = ghostty_config_new() else {
                print("Failed to create ghostty fallback config")
                return
            }

            ghostty_config_finalize(fallbackConfig)
            updateDefaultBackground(from: fallbackConfig, source: "initialize.fallbackConfig")

            guard let created = ghostty_app_new(&runtimeConfig, fallbackConfig) else {
                #if DEBUG
                Self.initLog("ghostty_app_new(fallback) failed")
                Self.dumpConfigDiagnostics(fallbackConfig, label: "fallback")
                #endif
                print("Failed to create ghostty app")
                ghostty_config_free(fallbackConfig)
                return
            }

            self.app = created
            self.config = fallbackConfig
        }

        // Notify observers that a usable config is available (initial load).
        lastAppearanceColorScheme = GhosttyConfig.currentColorSchemePreference()
        NotificationCenter.default.post(name: .ghosttyConfigDidReload, object: nil)

        #if os(macOS)
        if let app {
            ghostty_app_set_focus(app, NSApp.isActive)
        }

        appObservers.append(NotificationCenter.default.addObserver(
            forName: NSApplication.didBecomeActiveNotification,
            object: nil,
            queue: .main
        ) { [weak self] _ in
            guard let app = self?.app else { return }
            ghostty_app_set_focus(app, true)
        })

        appObservers.append(NotificationCenter.default.addObserver(
            forName: NSApplication.didResignActiveNotification,
            object: nil,
            queue: .main
        ) { [weak self] _ in
            guard let app = self?.app else { return }
            ghostty_app_set_focus(app, false)
        })

        #endif
    }

    private func loadDefaultConfigFilesWithLegacyFallback(_ config: ghostty_config_t) {
        ghostty_config_load_default_files(config)
        loadReleaseAppSupportGhosttyConfigIfNeeded(config)
        loadLegacyGhosttyConfigIfNeeded(config)
        ghostty_config_load_recursive_files(config)
        ghostty_config_finalize(config)
    }

    static func shouldLoadLegacyGhosttyConfig(
        newConfigFileSize: Int?,
        legacyConfigFileSize: Int?
    ) -> Bool {
        guard let newConfigFileSize, newConfigFileSize == 0 else { return false }
        guard let legacyConfigFileSize, legacyConfigFileSize > 0 else { return false }
        return true
    }

    static func shouldLoadReleaseAppSupportGhosttyConfig(
        currentBundleIdentifier: String?,
        currentConfigFileSize: Int?,
        currentLegacyConfigFileSize: Int?,
        releaseConfigFileSize: Int?,
        releaseLegacyConfigFileSize: Int?
    ) -> Bool {
        guard SocketControlSettings.isDebugLikeBundleIdentifier(currentBundleIdentifier) else { return false }

        let hasCurrentAppSupportConfig = (currentConfigFileSize ?? 0) > 0 || (currentLegacyConfigFileSize ?? 0) > 0
        guard !hasCurrentAppSupportConfig else { return false }

        let hasReleaseAppSupportConfig = (releaseConfigFileSize ?? 0) > 0 || (releaseLegacyConfigFileSize ?? 0) > 0
        return hasReleaseAppSupportConfig
    }

    static func shouldApplyDefaultBackgroundUpdate(
        currentScope: GhosttyDefaultBackgroundUpdateScope,
        incomingScope: GhosttyDefaultBackgroundUpdateScope
    ) -> Bool {
        incomingScope.rawValue >= currentScope.rawValue
    }

    static func shouldReloadConfigurationForAppearanceChange(
        previousColorScheme: GhosttyConfig.ColorSchemePreference?,
        currentColorScheme: GhosttyConfig.ColorSchemePreference
    ) -> Bool {
        previousColorScheme != currentColorScheme
    }

    static func shouldCaptureScrollLagEvent(
        samples: Int,
        averageMs: Double,
        maxMs: Double,
        thresholdMs: Double,
        minimumSamples: Int = 8,
        minimumAverageMs: Double = 12,
        nowUptime: TimeInterval,
        lastReportedUptime: TimeInterval?,
        cooldown: TimeInterval = 300
    ) -> Bool {
        guard samples >= minimumSamples else { return false }
        guard averageMs.isFinite, maxMs.isFinite, thresholdMs.isFinite, nowUptime.isFinite, cooldown.isFinite else {
            return false
        }
        guard averageMs >= minimumAverageMs else { return false }
        guard maxMs > thresholdMs else { return false }
        if let lastReportedUptime, nowUptime - lastReportedUptime < cooldown {
            return false
        }
        return true
    }

    private func loadReleaseAppSupportGhosttyConfigIfNeeded(_ config: ghostty_config_t) {
        #if os(macOS)
        let fm = FileManager.default
        guard let appSupport = fm.urls(for: .applicationSupportDirectory, in: .userDomainMask).first else { return }
        guard let currentBundleIdentifier = Bundle.main.bundleIdentifier,
              !currentBundleIdentifier.isEmpty else { return }

        let currentAppSupportDir = appSupport.appendingPathComponent(currentBundleIdentifier, isDirectory: true)
        let releaseAppSupportDir = appSupport.appendingPathComponent(Self.releaseBundleIdentifier, isDirectory: true)
        let currentConfig = currentAppSupportDir.appendingPathComponent("config.ghostty", isDirectory: false)
        let currentLegacyConfig = currentAppSupportDir.appendingPathComponent("config", isDirectory: false)
        let releaseConfig = releaseAppSupportDir.appendingPathComponent("config.ghostty", isDirectory: false)
        let releaseLegacyConfig = releaseAppSupportDir.appendingPathComponent("config", isDirectory: false)

        func fileSize(_ url: URL) -> Int? {
            guard let attrs = try? fm.attributesOfItem(atPath: url.path),
                  let size = attrs[.size] as? NSNumber else { return nil }
            return size.intValue
        }

        let releaseConfigSize = fileSize(releaseConfig)
        let releaseLegacyConfigSize = fileSize(releaseLegacyConfig)

        guard Self.shouldLoadReleaseAppSupportGhosttyConfig(
            currentBundleIdentifier: currentBundleIdentifier,
            currentConfigFileSize: fileSize(currentConfig),
            currentLegacyConfigFileSize: fileSize(currentLegacyConfig),
            releaseConfigFileSize: releaseConfigSize,
            releaseLegacyConfigFileSize: releaseLegacyConfigSize
        ) else { return }

        if let releaseLegacyConfigSize, releaseLegacyConfigSize > 0 {
            releaseLegacyConfig.path.withCString { path in
                ghostty_config_load_file(config, path)
            }
        }

        if let releaseConfigSize, releaseConfigSize > 0 {
            releaseConfig.path.withCString { path in
                ghostty_config_load_file(config, path)
            }
        }

        #if DEBUG
        Self.initLog(
            "loaded release app support ghostty config fallback from: \(releaseAppSupportDir.path)"
        )
        #endif
        #endif
    }

    private func loadLegacyGhosttyConfigIfNeeded(_ config: ghostty_config_t) {
        #if os(macOS)
        // Ghostty 1.3+ prefers `config.ghostty`, but some users still have their real
        // settings in the legacy `config` file. If the new file exists but is empty,
        // load the legacy file as a compatibility fallback.
        let fm = FileManager.default
        guard let appSupport = fm.urls(for: .applicationSupportDirectory, in: .userDomainMask).first else { return }
        let ghosttyDir = appSupport.appendingPathComponent("com.mitchellh.ghostty", isDirectory: true)
        let configNew = ghosttyDir.appendingPathComponent("config.ghostty", isDirectory: false)
        let configLegacy = ghosttyDir.appendingPathComponent("config", isDirectory: false)

        func fileSize(_ url: URL) -> Int? {
            guard let attrs = try? fm.attributesOfItem(atPath: url.path),
                  let size = attrs[.size] as? NSNumber else { return nil }
            return size.intValue
        }

        guard Self.shouldLoadLegacyGhosttyConfig(
            newConfigFileSize: fileSize(configNew),
            legacyConfigFileSize: fileSize(configLegacy)
        ) else { return }

        configLegacy.path.withCString { path in
            ghostty_config_load_file(config, path)
        }

        #if DEBUG
        Self.initLog("loaded legacy ghostty config because config.ghostty was empty: \(configLegacy.path)")
        #endif
        #endif
    }

    func tick() {
        guard let app = app else { return }

        let start = CACurrentMediaTime()
        ghostty_app_tick(app)
        let elapsedMs = (CACurrentMediaTime() - start) * 1000

        // Track lag during scrolling
        if isScrolling {
            scrollLagSampleCount += 1
            scrollLagTotalMs += elapsedMs
            scrollLagMaxMs = max(scrollLagMaxMs, elapsedMs)
        }
    }

    func reloadConfiguration(soft: Bool = false, source: String = "unspecified") {
        guard let app else {
            logThemeAction("reload skipped source=\(source) soft=\(soft) reason=no_app")
            return
        }
        logThemeAction("reload begin source=\(source) soft=\(soft)")
        resetDefaultBackgroundUpdateScope(source: "reloadConfiguration(source=\(source))")
        if soft, let config {
            ghostty_app_update_config(app, config)
            lastAppearanceColorScheme = GhosttyConfig.currentColorSchemePreference()
            NotificationCenter.default.post(name: .ghosttyConfigDidReload, object: nil)
            scheduleSurfaceRefreshAfterConfigurationReload(source: source)
            logThemeAction("reload end source=\(source) soft=\(soft) mode=soft")
            return
        }

        guard let newConfig = ghostty_config_new() else {
            logThemeAction("reload skipped source=\(source) soft=\(soft) reason=config_alloc_failed")
            return
        }
        loadDefaultConfigFilesWithLegacyFallback(newConfig)
        ghostty_app_update_config(app, newConfig)
        updateDefaultBackground(
            from: newConfig,
            source: "reloadConfiguration(source=\(source))",
            scope: .unscoped
        )
        DispatchQueue.main.async {
            self.applyBackgroundToKeyWindow()
        }
        if let oldConfig = config {
            ghostty_config_free(oldConfig)
        }
        config = newConfig
        lastAppearanceColorScheme = GhosttyConfig.currentColorSchemePreference()
        NotificationCenter.default.post(name: .ghosttyConfigDidReload, object: nil)
        scheduleSurfaceRefreshAfterConfigurationReload(source: source)
        logThemeAction("reload end source=\(source) soft=\(soft) mode=full")
    }

    private func scheduleSurfaceRefreshAfterConfigurationReload(source: String) {
        DispatchQueue.main.async {
            AppDelegate.shared?.refreshTerminalSurfacesAfterGhosttyConfigReload(source: source)
        }
    }

    func synchronizeThemeWithAppearance(_ appearance: NSAppearance?, source: String) {
        let currentColorScheme = GhosttyConfig.currentColorSchemePreference(
            appAppearance: appearance ?? NSApp?.effectiveAppearance
        )
        let shouldReload = Self.shouldReloadConfigurationForAppearanceChange(
            previousColorScheme: lastAppearanceColorScheme,
            currentColorScheme: currentColorScheme
        )
        if backgroundLogEnabled {
            let previousLabel: String
            switch lastAppearanceColorScheme {
            case .light:
                previousLabel = "light"
            case .dark:
                previousLabel = "dark"
            case nil:
                previousLabel = "nil"
            }
            let currentLabel: String = currentColorScheme == .dark ? "dark" : "light"
            logBackground(
                "appearance sync source=\(source) previous=\(previousLabel) current=\(currentLabel) reload=\(shouldReload)"
            )
        }
        guard shouldReload else { return }
        lastAppearanceColorScheme = currentColorScheme
        reloadConfiguration(source: "appearanceSync:\(source)")
    }

    func openConfigurationInTextEdit() {
        #if os(macOS)
        let path = ghosttyStringValue(ghostty_config_open_path())
        guard !path.isEmpty else { return }
        let fileURL = URL(fileURLWithPath: path)
        let editorURL = URL(fileURLWithPath: "/System/Applications/TextEdit.app")
        let configuration = NSWorkspace.OpenConfiguration()
        NSWorkspace.shared.open([fileURL], withApplicationAt: editorURL, configuration: configuration)
        #endif
    }

    private func ghosttyStringValue(_ value: ghostty_string_s) -> String {
        defer { ghostty_string_free(value) }
        guard let ptr = value.ptr, value.len > 0 else { return "" }
        let rawPtr = UnsafeRawPointer(ptr).assumingMemoryBound(to: UInt8.self)
        let buffer = UnsafeBufferPointer(start: rawPtr, count: Int(value.len))
        return String(decoding: buffer, as: UTF8.self)
    }

    private func resetDefaultBackgroundUpdateScope(source: String) {
        let previousScope = defaultBackgroundUpdateScope
        let previousScopeSource = defaultBackgroundScopeSource
        defaultBackgroundUpdateScope = .unscoped
        defaultBackgroundScopeSource = "reset:\(source)"
        if backgroundLogEnabled {
            logBackground(
                "default background scope reset source=\(source) previousScope=\(previousScope.logLabel) previousSource=\(previousScopeSource)"
            )
        }
    }

    private func updateDefaultBackground(
        from config: ghostty_config_t?,
        source: String,
        scope: GhosttyDefaultBackgroundUpdateScope = .unscoped
    ) {
        guard let config else { return }

        var resolvedColor = defaultBackgroundColor
        var color = ghostty_config_color_s()
        let bgKey = "background"
        if ghostty_config_get(config, &color, bgKey, UInt(bgKey.lengthOfBytes(using: .utf8))) {
            resolvedColor = NSColor(
                red: CGFloat(color.r) / 255,
                green: CGFloat(color.g) / 255,
                blue: CGFloat(color.b) / 255,
                alpha: 1.0
            )
        }

        var opacity = defaultBackgroundOpacity
        let opacityKey = "background-opacity"
        _ = ghostty_config_get(config, &opacity, opacityKey, UInt(opacityKey.lengthOfBytes(using: .utf8)))
        opacity = min(1.0, max(0.0, opacity))
        applyDefaultBackground(
            color: resolvedColor,
            opacity: opacity,
            source: source,
            scope: scope
        )
    }

    func focusFollowsMouseEnabled() -> Bool {
        guard let config else { return false }
        var enabled = false
        let key = "focus-follows-mouse"
        let keyLength = UInt(key.lengthOfBytes(using: .utf8))
        let found = ghostty_config_get(config, &enabled, key, keyLength)
        return found && enabled
    }

    private func applyDefaultBackground(
        color: NSColor,
        opacity: Double,
        source: String,
        scope: GhosttyDefaultBackgroundUpdateScope
    ) {
        let previousScope = defaultBackgroundUpdateScope
        let previousScopeSource = defaultBackgroundScopeSource
        guard Self.shouldApplyDefaultBackgroundUpdate(currentScope: previousScope, incomingScope: scope) else {
            if backgroundLogEnabled {
                logBackground(
                    "default background skipped source=\(source) incomingScope=\(scope.logLabel) currentScope=\(previousScope.logLabel) currentSource=\(previousScopeSource) color=\(color.hexString()) opacity=\(String(format: "%.3f", opacity))"
                )
            }
            return
        }

        defaultBackgroundUpdateScope = scope
        defaultBackgroundScopeSource = source

        let previousHex = defaultBackgroundColor.hexString()
        let previousOpacity = defaultBackgroundOpacity
        defaultBackgroundColor = color
        defaultBackgroundOpacity = opacity
        let hasChanged = previousHex != defaultBackgroundColor.hexString() ||
            abs(previousOpacity - defaultBackgroundOpacity) > 0.0001
        if hasChanged {
            notifyDefaultBackgroundDidChange(source: source)
        }
        if backgroundLogEnabled {
            logBackground(
                "default background updated source=\(source) scope=\(scope.logLabel) previousScope=\(previousScope.logLabel) previousScopeSource=\(previousScopeSource) previousColor=\(previousHex) previousOpacity=\(String(format: "%.3f", previousOpacity)) color=\(defaultBackgroundColor) opacity=\(String(format: "%.3f", defaultBackgroundOpacity)) changed=\(hasChanged)"
            )
        }
    }

    private func nextBackgroundEventId() -> UInt64 {
        precondition(Thread.isMainThread, "Background event IDs must be generated on main thread")
        backgroundEventCounter &+= 1
        return backgroundEventCounter
    }

    private func notifyDefaultBackgroundDidChange(source: String) {
        let signal = { [self] in
            let eventId = nextBackgroundEventId()
            defaultBackgroundNotificationDispatcher.signal(
                backgroundColor: defaultBackgroundColor,
                opacity: defaultBackgroundOpacity,
                eventId: eventId,
                source: source
            )
        }
        if Thread.isMainThread {
            signal()
        } else {
            DispatchQueue.main.async(execute: signal)
        }
    }

    private func logThemeAction(_ message: String) {
        guard backgroundLogEnabled else { return }
        logBackground("theme action \(message)")
    }

    private func actionLabel(for action: ghostty_action_s) -> String {
        switch action.tag {
        case GHOSTTY_ACTION_RELOAD_CONFIG:
            return "reload_config"
        case GHOSTTY_ACTION_CONFIG_CHANGE:
            return "config_change"
        case GHOSTTY_ACTION_COLOR_CHANGE:
            return "color_change"
        default:
            return String(describing: action.tag)
        }
    }

    private func logAction(_ action: ghostty_action_s, target: ghostty_target_s, tabId: UUID?, surfaceId: UUID?) {
        guard backgroundLogEnabled else { return }
        let targetLabel = target.tag == GHOSTTY_TARGET_SURFACE ? "surface" : "app"
        logBackground(
            "action event target=\(targetLabel) action=\(actionLabel(for: action)) tab=\(tabId?.uuidString ?? "nil") surface=\(surfaceId?.uuidString ?? "nil")"
        )
    }

    private func performOnMain<T>(_ work: @MainActor () -> T) -> T {
        if Thread.isMainThread {
            return MainActor.assumeIsolated { work() }
        }
        return DispatchQueue.main.sync {
            MainActor.assumeIsolated { work() }
        }
    }

    private func splitDirection(from direction: ghostty_action_split_direction_e) -> SplitDirection? {
        switch direction {
        case GHOSTTY_SPLIT_DIRECTION_RIGHT: return .right
        case GHOSTTY_SPLIT_DIRECTION_LEFT: return .left
        case GHOSTTY_SPLIT_DIRECTION_DOWN: return .down
        case GHOSTTY_SPLIT_DIRECTION_UP: return .up
        default: return nil
        }
    }

    private func focusDirection(from direction: ghostty_action_goto_split_e) -> NavigationDirection? {
        switch direction {
        // For previous/next, we use left/right as a reasonable default
        // Bonsplit doesn't have cycle-based navigation
        case GHOSTTY_GOTO_SPLIT_PREVIOUS: return .left
        case GHOSTTY_GOTO_SPLIT_NEXT: return .right
        case GHOSTTY_GOTO_SPLIT_UP: return .up
        case GHOSTTY_GOTO_SPLIT_DOWN: return .down
        case GHOSTTY_GOTO_SPLIT_LEFT: return .left
        case GHOSTTY_GOTO_SPLIT_RIGHT: return .right
        default: return nil
        }
    }

    private func resizeDirection(from direction: ghostty_action_resize_split_direction_e) -> ResizeDirection? {
        switch direction {
        case GHOSTTY_RESIZE_SPLIT_UP: return .up
        case GHOSTTY_RESIZE_SPLIT_DOWN: return .down
        case GHOSTTY_RESIZE_SPLIT_LEFT: return .left
        case GHOSTTY_RESIZE_SPLIT_RIGHT: return .right
        default: return nil
        }
    }

    private static func callbackContext(from userdata: UnsafeMutableRawPointer?) -> GhosttySurfaceCallbackContext? {
        guard let userdata else { return nil }
        return Unmanaged<GhosttySurfaceCallbackContext>.fromOpaque(userdata).takeUnretainedValue()
    }

    private func handleAction(target: ghostty_target_s, action: ghostty_action_s) -> Bool {
        if target.tag != GHOSTTY_TARGET_SURFACE {
            if action.tag == GHOSTTY_ACTION_RELOAD_CONFIG ||
                action.tag == GHOSTTY_ACTION_CONFIG_CHANGE ||
                action.tag == GHOSTTY_ACTION_COLOR_CHANGE {
                logAction(action, target: target, tabId: nil, surfaceId: nil)
            }

            if action.tag == GHOSTTY_ACTION_DESKTOP_NOTIFICATION {
                let actionTitle = action.action.desktop_notification.title
                    .flatMap { String(cString: $0) } ?? ""
                let actionBody = action.action.desktop_notification.body
                    .flatMap { String(cString: $0) } ?? ""
                return performOnMain {
                    guard let tabManager = AppDelegate.shared?.tabManager,
                          let tabId = tabManager.selectedTabId else {
                        return false
                    }
                    let tabTitle = tabManager.titleForTab(tabId) ?? "Terminal"
                    let command = actionTitle.isEmpty ? tabTitle : actionTitle
                    let body = actionBody
                    let surfaceId = tabManager.focusedSurfaceId(for: tabId)
                    TerminalNotificationStore.shared.addNotification(
                        tabId: tabId,
                        surfaceId: surfaceId,
                        title: command,
                        subtitle: "",
                        body: body
                    )
                    return true
                }
            }

            if action.tag == GHOSTTY_ACTION_RELOAD_CONFIG {
                let soft = action.action.reload_config.soft
                logThemeAction("reload request target=app soft=\(soft)")
                performOnMain {
                    GhosttyApp.shared.reloadConfiguration(soft: soft, source: "action.reload_config.app")
                }
                return true
            }

            if action.tag == GHOSTTY_ACTION_COLOR_CHANGE,
               action.action.color_change.kind == GHOSTTY_ACTION_COLOR_KIND_BACKGROUND {
                let change = action.action.color_change
                let resolvedColor = NSColor(
                    red: CGFloat(change.r) / 255,
                    green: CGFloat(change.g) / 255,
                    blue: CGFloat(change.b) / 255,
                    alpha: 1.0
                )
                applyDefaultBackground(
                    color: resolvedColor,
                    opacity: defaultBackgroundOpacity,
                    source: "action.color_change.app",
                    scope: .app
                )
                DispatchQueue.main.async {
                    GhosttyApp.shared.applyBackgroundToKeyWindow()
                }
                return true
            }

            if action.tag == GHOSTTY_ACTION_CONFIG_CHANGE {
                updateDefaultBackground(
                    from: action.action.config_change.config,
                    source: "action.config_change.app",
                    scope: .app
                )
                DispatchQueue.main.async {
                    GhosttyApp.shared.applyBackgroundToKeyWindow()
                }
                return true
            }

            return false
        }
        let callbackContext = Self.callbackContext(from: ghostty_surface_userdata(target.target.surface))
        let callbackTabId = callbackContext?.tabId
        let callbackSurfaceId = callbackContext?.surfaceId

        if action.tag == GHOSTTY_ACTION_SHOW_CHILD_EXITED {
            // The child (shell) exited. Ghostty will fall back to printing
            // "Process exited. Press any key..." into the terminal unless the host
            // handles this action. For cmux, the correct behavior is to close
            // the panel immediately (no prompt).
#if DEBUG
            dlog(
                "surface.action.showChildExited tab=\(callbackTabId?.uuidString.prefix(5) ?? "nil") " +
                "surface=\(callbackSurfaceId?.uuidString.prefix(5) ?? "nil")"
            )
#endif
#if DEBUG
            cmuxWriteChildExitProbe(
                [
                    "probeShowChildExitedTabId": callbackTabId?.uuidString ?? "",
                    "probeShowChildExitedSurfaceId": callbackSurfaceId?.uuidString ?? "",
                ],
                increments: ["probeShowChildExitedCount": 1]
            )
#endif
            // Keep host-close async to avoid re-entrant close/deinit while Ghostty is still
            // dispatching this action callback.
            DispatchQueue.main.async {
                guard let app = AppDelegate.shared else { return }
                if let callbackTabId,
                   let callbackSurfaceId,
                   let manager = app.tabManagerFor(tabId: callbackTabId) ?? app.tabManager,
                   let workspace = manager.tabs.first(where: { $0.id == callbackTabId }),
                   workspace.panels[callbackSurfaceId] != nil {
                    manager.closePanelAfterChildExited(tabId: callbackTabId, surfaceId: callbackSurfaceId)
                }
            }
            // Always report handled so Ghostty doesn't print the fallback prompt.
            return true
        }

        guard let surfaceView = callbackContext?.surfaceView else { return false }
        if action.tag == GHOSTTY_ACTION_RELOAD_CONFIG ||
            action.tag == GHOSTTY_ACTION_CONFIG_CHANGE ||
            action.tag == GHOSTTY_ACTION_COLOR_CHANGE {
            logAction(
                action,
                target: target,
                tabId: callbackTabId ?? surfaceView.tabId,
                surfaceId: callbackSurfaceId ?? surfaceView.terminalSurface?.id
            )
        }

        switch action.tag {
        case GHOSTTY_ACTION_NEW_SPLIT:
            guard let tabId = surfaceView.tabId,
                  let surfaceId = surfaceView.terminalSurface?.id,
                  let direction = splitDirection(from: action.action.new_split) else {
                return false
            }
            return performOnMain {
                guard let tabManager = AppDelegate.shared?.tabManager else { return false }
                return tabManager.newSplit(tabId: tabId, surfaceId: surfaceId, direction: direction) != nil
            }
        case GHOSTTY_ACTION_GOTO_SPLIT:
            guard let tabId = surfaceView.tabId,
                  let surfaceId = surfaceView.terminalSurface?.id,
                  let direction = focusDirection(from: action.action.goto_split) else {
                return false
            }
            return performOnMain {
                guard let tabManager = AppDelegate.shared?.tabManager else { return false }
                return tabManager.moveSplitFocus(tabId: tabId, surfaceId: surfaceId, direction: direction)
            }
        case GHOSTTY_ACTION_RESIZE_SPLIT:
            guard let tabId = surfaceView.tabId,
                  let surfaceId = surfaceView.terminalSurface?.id,
                  let direction = resizeDirection(from: action.action.resize_split.direction) else {
                return false
            }
            let amount = action.action.resize_split.amount
            return performOnMain {
                guard let tabManager = AppDelegate.shared?.tabManager else { return false }
                return tabManager.resizeSplit(
                    tabId: tabId,
                    surfaceId: surfaceId,
                    direction: direction,
                    amount: amount
                )
            }
        case GHOSTTY_ACTION_EQUALIZE_SPLITS:
            guard let tabId = surfaceView.tabId else {
                return false
            }
            return performOnMain {
                guard let tabManager = AppDelegate.shared?.tabManager else { return false }
                return tabManager.equalizeSplits(tabId: tabId)
            }
        case GHOSTTY_ACTION_TOGGLE_SPLIT_ZOOM:
            guard let tabId = surfaceView.tabId,
                  let surfaceId = surfaceView.terminalSurface?.id else {
                return false
            }
            return performOnMain {
                guard let tabManager = AppDelegate.shared?.tabManager else { return false }
                return tabManager.toggleSplitZoom(tabId: tabId, surfaceId: surfaceId)
            }
        case GHOSTTY_ACTION_SCROLLBAR:
            let scrollbar = GhosttyScrollbar(c: action.action.scrollbar)
            surfaceView.scrollbar = scrollbar
            NotificationCenter.default.post(
                name: .ghosttyDidUpdateScrollbar,
                object: surfaceView,
                userInfo: [GhosttyNotificationKey.scrollbar: scrollbar]
            )
            return true
        case GHOSTTY_ACTION_CELL_SIZE:
            let cellSize = CGSize(
                width: CGFloat(action.action.cell_size.width),
                height: CGFloat(action.action.cell_size.height)
            )
            surfaceView.cellSize = cellSize
            NotificationCenter.default.post(
                name: .ghosttyDidUpdateCellSize,
                object: surfaceView,
                userInfo: [GhosttyNotificationKey.cellSize: cellSize]
            )
            return true
        case GHOSTTY_ACTION_START_SEARCH:
            guard let terminalSurface = surfaceView.terminalSurface else { return true }
            let needle = action.action.start_search.needle.flatMap { String(cString: $0) }
            DispatchQueue.main.async {
                if let searchState = terminalSurface.searchState {
                    if let needle, !needle.isEmpty {
                        searchState.needle = needle
                    }
                } else {
                    terminalSurface.searchState = TerminalSurface.SearchState(needle: needle ?? "")
                }
                NotificationCenter.default.post(name: .ghosttySearchFocus, object: terminalSurface)
            }
            return true
        case GHOSTTY_ACTION_END_SEARCH:
            guard let terminalSurface = surfaceView.terminalSurface else { return true }
            DispatchQueue.main.async {
                terminalSurface.searchState = nil
            }
            return true
        case GHOSTTY_ACTION_SEARCH_TOTAL:
            guard let terminalSurface = surfaceView.terminalSurface else { return true }
            let rawTotal = action.action.search_total.total
            let total: UInt? = rawTotal >= 0 ? UInt(rawTotal) : nil
            DispatchQueue.main.async {
                terminalSurface.searchState?.total = total
            }
            return true
        case GHOSTTY_ACTION_SEARCH_SELECTED:
            guard let terminalSurface = surfaceView.terminalSurface else { return true }
            let rawSelected = action.action.search_selected.selected
            let selected: UInt? = rawSelected >= 0 ? UInt(rawSelected) : nil
            DispatchQueue.main.async {
                terminalSurface.searchState?.selected = selected
            }
            return true
        case GHOSTTY_ACTION_SET_TITLE:
            let title = action.action.set_title.title
                .flatMap { String(cString: $0) } ?? ""
            if let tabId = surfaceView.tabId,
               let surfaceId = surfaceView.terminalSurface?.id {
                DispatchQueue.main.async {
                    NotificationCenter.default.post(
                        name: .ghosttyDidSetTitle,
                        object: surfaceView,
                        userInfo: [
                            GhosttyNotificationKey.tabId: tabId,
                            GhosttyNotificationKey.surfaceId: surfaceId,
                            GhosttyNotificationKey.title: title,
                        ]
                    )
                }
            }
            return true
        case GHOSTTY_ACTION_PWD:
            guard let tabId = surfaceView.tabId,
                  let surfaceId = surfaceView.terminalSurface?.id else { return true }
            let pwd = action.action.pwd.pwd.flatMap { String(cString: $0) } ?? ""
            DispatchQueue.main.async {
                AppDelegate.shared?.tabManager?.updateSurfaceDirectory(
                    tabId: tabId,
                    surfaceId: surfaceId,
                    directory: pwd
                )
            }
            return true
        case GHOSTTY_ACTION_DESKTOP_NOTIFICATION:
            guard let tabId = surfaceView.tabId else { return true }
            let surfaceId = surfaceView.terminalSurface?.id
            let actionTitle = action.action.desktop_notification.title
                .flatMap { String(cString: $0) } ?? ""
            let actionBody = action.action.desktop_notification.body
                .flatMap { String(cString: $0) } ?? ""
            performOnMain {
                let tabTitle = AppDelegate.shared?.tabManager?.titleForTab(tabId) ?? "Terminal"
                let command = actionTitle.isEmpty ? tabTitle : actionTitle
                let body = actionBody
                TerminalNotificationStore.shared.addNotification(
                    tabId: tabId,
                    surfaceId: surfaceId,
                    title: command,
                    subtitle: "",
                    body: body
                )
            }
            return true
        case GHOSTTY_ACTION_COLOR_CHANGE:
            if action.action.color_change.kind == GHOSTTY_ACTION_COLOR_KIND_BACKGROUND {
                let change = action.action.color_change
                surfaceView.backgroundColor = NSColor(
                    red: CGFloat(change.r) / 255,
                    green: CGFloat(change.g) / 255,
                    blue: CGFloat(change.b) / 255,
                    alpha: 1.0
                )
                if backgroundLogEnabled {
                    logBackground(
                        "surface override set tab=\(surfaceView.tabId?.uuidString ?? "nil") surface=\(surfaceView.terminalSurface?.id.uuidString ?? "nil") override=\(surfaceView.backgroundColor?.hexString() ?? "nil") default=\(defaultBackgroundColor.hexString()) source=action.color_change.surface"
                    )
                }
                surfaceView.applySurfaceBackground()
                if backgroundLogEnabled {
                    logBackground("OSC background change tab=\(surfaceView.tabId?.uuidString ?? "unknown") color=\(surfaceView.backgroundColor?.description ?? "nil")")
                }
                DispatchQueue.main.async {
                    surfaceView.applyWindowBackgroundIfActive()
                }
            }
            return true
        case GHOSTTY_ACTION_CONFIG_CHANGE:
            if let staleOverride = surfaceView.backgroundColor {
                surfaceView.backgroundColor = nil
                if backgroundLogEnabled {
                    logBackground(
                        "surface override cleared tab=\(surfaceView.tabId?.uuidString ?? "nil") surface=\(surfaceView.terminalSurface?.id.uuidString ?? "nil") cleared=\(staleOverride.hexString()) source=action.config_change.surface"
                    )
                }
                surfaceView.applySurfaceBackground()
                DispatchQueue.main.async {
                    surfaceView.applyWindowBackgroundIfActive()
                }
            }
            updateDefaultBackground(
                from: action.action.config_change.config,
                source: "action.config_change.surface tab=\(surfaceView.tabId?.uuidString ?? "nil") surface=\(surfaceView.terminalSurface?.id.uuidString ?? "nil")",
                scope: .surface
            )
            if backgroundLogEnabled {
                logBackground(
                    "surface config change deferred terminal bg apply tab=\(surfaceView.tabId?.uuidString ?? "nil") surface=\(surfaceView.terminalSurface?.id.uuidString ?? "nil") override=\(surfaceView.backgroundColor?.hexString() ?? "nil") default=\(defaultBackgroundColor.hexString())"
                )
            }
            return true
        case GHOSTTY_ACTION_RELOAD_CONFIG:
            let soft = action.action.reload_config.soft
            logThemeAction(
                "reload request target=surface tab=\(surfaceView.tabId?.uuidString ?? "nil") surface=\(surfaceView.terminalSurface?.id.uuidString ?? "nil") soft=\(soft)"
            )
            return performOnMain {
                // Keep all runtime theme/default-background state in the same path.
                GhosttyApp.shared.reloadConfiguration(
                    soft: soft,
                    source: "action.reload_config.surface tab=\(surfaceView.tabId?.uuidString ?? "nil") surface=\(surfaceView.terminalSurface?.id.uuidString ?? "nil")"
                )
                return true
            }
        case GHOSTTY_ACTION_KEY_SEQUENCE:
            return performOnMain {
                surfaceView.updateKeySequence(action.action.key_sequence)
                return true
            }
        case GHOSTTY_ACTION_KEY_TABLE:
            return performOnMain {
                surfaceView.updateKeyTable(action.action.key_table)
                return true
            }
        case GHOSTTY_ACTION_OPEN_URL:
            let openUrl = action.action.open_url
            guard let cstr = openUrl.url else { return false }
            let urlString = String(
                data: Data(bytes: cstr, count: Int(openUrl.len)),
                encoding: .utf8
            ) ?? ""
            #if DEBUG
            dlog("link.openURL raw=\(urlString)")
            #endif
            guard let target = resolveTerminalOpenURLTarget(urlString) else {
                #if DEBUG
                dlog("link.openURL resolve failed, returning false")
                #endif
                return false
            }
            if !BrowserLinkOpenSettings.openTerminalLinksInCmuxBrowser() {
                #if DEBUG
                dlog("link.openURL cmuxBrowser=disabled, opening externally url=\(target.url)")
                #endif
                return performOnMain {
                    NSWorkspace.shared.open(target.url)
                }
            }
            switch target {
            case let .external(url):
                #if DEBUG
                dlog("link.openURL target=external, opening externally url=\(url)")
                #endif
                return performOnMain {
                    NSWorkspace.shared.open(url)
                }
            case let .embeddedBrowser(url):
                if BrowserLinkOpenSettings.shouldOpenExternally(url) {
                    #if DEBUG
                    dlog("link.openURL target=embedded but shouldOpenExternally=true url=\(url)")
                    #endif
                    return performOnMain {
                        NSWorkspace.shared.open(url)
                    }
                }
                guard let host = BrowserInsecureHTTPSettings.normalizeHost(url.host ?? "") else {
                    #if DEBUG
                    dlog("link.openURL target=embedded but normalizeHost=nil host=\(url.host ?? "nil") url=\(url)")
                    #endif
                    return performOnMain {
                        NSWorkspace.shared.open(url)
                    }
                }

                // If a host whitelist is configured and this host isn't in it, open externally.
                if !BrowserLinkOpenSettings.hostMatchesWhitelist(host) {
                    #if DEBUG
                    dlog("link.openURL target=embedded but hostWhitelist miss host=\(host) url=\(url)")
                    #endif
                    return performOnMain {
                        NSWorkspace.shared.open(url)
                    }
                }
                guard let tabId = surfaceView.tabId,
                      let surfaceId = surfaceView.terminalSurface?.id else {
                    #if DEBUG
                    dlog("link.openURL target=embedded but tabId/surfaceId=nil")
                    #endif
                    return false
                }
                #if DEBUG
                dlog("link.openURL target=embedded, opening in browser pane host=\(host) url=\(url) tabId=\(tabId) surfaceId=\(surfaceId)")
                #endif
                return performOnMain {
                    guard let app = AppDelegate.shared,
                          let tabManager = app.tabManagerFor(tabId: tabId) ?? app.tabManager,
                          let workspace = tabManager.tabs.first(where: { $0.id == tabId }) else {
                        #if DEBUG
                        dlog("link.openURL embedded but workspace lookup failed tabId=\(tabId)")
                        #endif
                        return false
                    }
                    if let targetPane = workspace.preferredBrowserTargetPane(fromPanelId: surfaceId) {
                        #if DEBUG
                        dlog("link.openURL opening in existing browser pane=\(targetPane)")
                        #endif
                        return workspace.newBrowserSurface(inPane: targetPane, url: url, focus: true) != nil
                    } else {
                        #if DEBUG
                        dlog("link.openURL opening as new browser split from surface=\(surfaceId)")
                        #endif
                        return workspace.newBrowserSplit(from: surfaceId, orientation: .horizontal, url: url) != nil
                    }
                }
            }
        default:
            return false
        }
    }

    private func applyBackgroundToKeyWindow() {
        guard let window = activeMainWindow() else { return }
        if cmuxShouldUseClearWindowBackground(for: defaultBackgroundOpacity) {
            window.backgroundColor = cmuxTransparentWindowBaseColor()
            window.isOpaque = false
            if backgroundLogEnabled {
                logBackground("applied transparent window background opacity=\(String(format: "%.3f", defaultBackgroundOpacity))")
            }
        } else {
            let color = defaultBackgroundColor.withAlphaComponent(defaultBackgroundOpacity)
            window.backgroundColor = color
            window.isOpaque = color.alphaComponent >= 1.0
            if backgroundLogEnabled {
                logBackground("applied default window background color=\(color) opacity=\(String(format: "%.3f", color.alphaComponent))")
            }
        }
    }

    private func activeMainWindow() -> NSWindow? {
        let keyWindow = NSApp.keyWindow
        if let raw = keyWindow?.identifier?.rawValue,
           raw == "cmux.main" || raw.hasPrefix("cmux.main.") {
            return keyWindow
        }
        return NSApp.windows.first(where: { window in
            guard let raw = window.identifier?.rawValue else { return false }
            return raw == "cmux.main" || raw.hasPrefix("cmux.main.")
        })
    }

    func logBackground(_ message: String) {
        let timestamp = Self.backgroundLogTimestampFormatter.string(from: Date())
        let uptimeMs = (ProcessInfo.processInfo.systemUptime - backgroundLogStartUptime) * 1000
        let frame60 = Int((CACurrentMediaTime() * 60.0).rounded(.down))
        let frame120 = Int((CACurrentMediaTime() * 120.0).rounded(.down))
        let threadLabel = Thread.isMainThread ? "main" : "background"
        backgroundLogLock.lock()
        defer { backgroundLogLock.unlock() }
        backgroundLogSequence &+= 1
        let sequence = backgroundLogSequence
        let line =
            "\(timestamp) seq=\(sequence) t+\(String(format: "%.3f", uptimeMs))ms thread=\(threadLabel) frame60=\(frame60) frame120=\(frame120) cmux bg: \(message)\n"
        if let data = line.data(using: .utf8) {
            if FileManager.default.fileExists(atPath: backgroundLogURL.path) == false {
                FileManager.default.createFile(atPath: backgroundLogURL.path, contents: nil)
            }
            if let handle = try? FileHandle(forWritingTo: backgroundLogURL) {
                defer { try? handle.close() }
                try? handle.seekToEnd()
                try? handle.write(contentsOf: data)
            }
        }
    }
}

// MARK: - Debug Render Instrumentation

/// Lightweight instrumentation to detect whether Ghostty is actually requesting Metal drawables.
/// This helps catch "frozen until refocus" regressions without relying on screenshots (which can
/// mask redraw issues by forcing a window server flush).
final class GhosttyMetalLayer: CAMetalLayer {
    private let lock = NSLock()
    private var drawableCount: Int = 0
    private var lastDrawableTime: CFTimeInterval = 0

    func debugStats() -> (count: Int, last: CFTimeInterval) {
        lock.lock()
        defer { lock.unlock() }
        return (drawableCount, lastDrawableTime)
    }

    override func nextDrawable() -> CAMetalDrawable? {
        lock.lock()
        drawableCount += 1
        lastDrawableTime = CACurrentMediaTime()
        lock.unlock()
        return super.nextDrawable()
    }
}

// MARK: - Terminal Surface (owns the ghostty_surface_t lifecycle)

final class TerminalSurface: Identifiable, ObservableObject {
    final class SearchState: ObservableObject {
        @Published var needle: String
        @Published var selected: UInt?
        @Published var total: UInt?

        init(needle: String = "") {
            self.needle = needle
            self.selected = nil
            self.total = nil
        }
    }

    private(set) var surface: ghostty_surface_t?
    private weak var attachedView: GhosttyNSView?
    /// Whether the terminal surface view is currently attached to a window.
    ///
    /// Use the hosted view rather than the inner surface view, since the surface can be
    /// temporarily unattached (surface not yet created / reparenting) even while the panel
    /// is already in the window.
    var isViewInWindow: Bool { hostedView.window != nil }
    let id: UUID
    private(set) var tabId: UUID
    /// Port ordinal for CMUX_PORT range assignment
    var portOrdinal: Int = 0
    /// Snapshotted once per app session so all workspaces use consistent values
    private static let sessionPortBase: Int = {
        let val = UserDefaults.standard.integer(forKey: "cmuxPortBase")
        return val > 0 ? val : 9100
    }()
    private static let sessionPortRangeSize: Int = {
        let val = UserDefaults.standard.integer(forKey: "cmuxPortRange")
        return val > 0 ? val : 10
    }()
    private let surfaceContext: ghostty_surface_context_e
    private let configTemplate: ghostty_surface_config_s?
    private let workingDirectory: String?
    private let additionalEnvironment: [String: String]
    let hostedView: GhosttySurfaceScrollView
    private let surfaceView: GhosttyNSView
    private var lastPixelWidth: UInt32 = 0
    private var lastPixelHeight: UInt32 = 0
    private var lastXScale: CGFloat = 0
    private var lastYScale: CGFloat = 0
    private var pendingTextQueue: [Data] = []
    private var pendingTextBytes: Int = 0
    private let maxPendingTextBytes = 1_048_576
    private var backgroundSurfaceStartQueued = false
    private var surfaceCallbackContext: Unmanaged<GhosttySurfaceCallbackContext>?
    private enum PortalLifecycleState: String {
        case live
        case closing
        case closed
    }
    private var portalLifecycleState: PortalLifecycleState = .live
    private var portalLifecycleGeneration: UInt64 = 1
    @Published var searchState: SearchState? = nil {
	        didSet {
	            if let searchState {
	                hostedView.cancelFocusRequest()
                NSLog("Find: search state created tab=%@ surface=%@", tabId.uuidString, id.uuidString)
                searchNeedleCancellable = searchState.$needle
                    .removeDuplicates()
                    .map { needle -> AnyPublisher<String, Never> in
                        if needle.isEmpty || needle.count >= 3 {
                            return Just(needle).eraseToAnyPublisher()
                        }

                        return Just(needle)
                            .delay(for: .milliseconds(300), scheduler: DispatchQueue.main)
                            .eraseToAnyPublisher()
                    }
                    .switchToLatest()
                    .sink { [weak self] needle in
                        NSLog("Find: needle updated tab=%@ surface=%@ needle=%@", self?.tabId.uuidString ?? "unknown", self?.id.uuidString ?? "unknown", needle)
                        _ = self?.performBindingAction("search:\(needle)")
                    }
            } else if oldValue != nil {
                searchNeedleCancellable = nil
                NSLog("Find: search state cleared tab=%@ surface=%@", tabId.uuidString, id.uuidString)
                _ = performBindingAction("end_search")
            }
        }
    }
    @Published private(set) var keyboardCopyModeActive: Bool = false
    private var searchNeedleCancellable: AnyCancellable?

    init(
        tabId: UUID,
        context: ghostty_surface_context_e,
        configTemplate: ghostty_surface_config_s?,
        workingDirectory: String? = nil,
        additionalEnvironment: [String: String] = [:]
    ) {
        self.id = UUID()
        self.tabId = tabId
        self.surfaceContext = context
        self.configTemplate = configTemplate
        self.workingDirectory = workingDirectory?.trimmingCharacters(in: .whitespacesAndNewlines)
        self.additionalEnvironment = additionalEnvironment
        // Match Ghostty's own SurfaceView: ensure a non-zero initial frame so the backing layer
        // has non-zero bounds and the renderer can initialize without presenting a blank/stretched
        // intermediate frame on the first real resize.
        let view = GhosttyNSView(frame: NSRect(x: 0, y: 0, width: 800, height: 600))
        self.surfaceView = view
        self.hostedView = GhosttySurfaceScrollView(surfaceView: view)
        // Surface is created when attached to a view
        hostedView.attachSurface(self)
    }


    func updateWorkspaceId(_ newTabId: UUID) {
        tabId = newTabId
        attachedView?.tabId = newTabId
        surfaceView.tabId = newTabId
    }

    func portalBindingGeneration() -> UInt64 {
        portalLifecycleGeneration
    }

    func portalBindingStateLabel() -> String {
        portalLifecycleState.rawValue
    }

    func canAcceptPortalBinding(expectedSurfaceId: UUID?, expectedGeneration: UInt64?) -> Bool {
        guard portalLifecycleState == .live else { return false }
        if let expectedSurfaceId, expectedSurfaceId != id {
            return false
        }
        if let expectedGeneration, expectedGeneration != portalLifecycleGeneration {
            return false
        }
        return true
    }

    func beginPortalCloseLifecycle(reason: String) {
        guard portalLifecycleState != .closed else { return }
        guard portalLifecycleState != .closing else { return }
        portalLifecycleState = .closing
        portalLifecycleGeneration &+= 1
#if DEBUG
        dlog(
            "surface.lifecycle.close.begin surface=\(id.uuidString.prefix(5)) " +
            "workspace=\(tabId.uuidString.prefix(5)) reason=\(reason) " +
            "generation=\(portalLifecycleGeneration)"
        )
#endif
    }

    private func markPortalLifecycleClosed(reason: String) {
        guard portalLifecycleState != .closed else { return }
        portalLifecycleState = .closed
        portalLifecycleGeneration &+= 1
#if DEBUG
        dlog(
            "surface.lifecycle.close.sealed surface=\(id.uuidString.prefix(5)) " +
            "workspace=\(tabId.uuidString.prefix(5)) reason=\(reason) " +
            "generation=\(portalLifecycleGeneration)"
        )
#endif
    }
    #if DEBUG
    private static let surfaceLogPath = "/tmp/cmux-ghostty-surface.log"
    private static let sizeLogPath = "/tmp/cmux-ghostty-size.log"

    private static func surfaceLog(_ message: String) {
        let timestamp = ISO8601DateFormatter().string(from: Date())
        let line = "[\(timestamp)] \(message)\n"
        if let handle = FileHandle(forWritingAtPath: surfaceLogPath) {
            handle.seekToEndOfFile()
            handle.write(line.data(using: .utf8)!)
            handle.closeFile()
        } else {
            FileManager.default.createFile(atPath: surfaceLogPath, contents: line.data(using: .utf8))
        }
    }

    private static func sizeLog(_ message: String) {
        let env = ProcessInfo.processInfo.environment
        guard env["CMUX_UI_TEST_SPLIT_CLOSE_RIGHT_VISUAL"] == "1" else { return }
        let timestamp = ISO8601DateFormatter().string(from: Date())
        let line = "[\(timestamp)] \(message)\n"
        if let handle = FileHandle(forWritingAtPath: sizeLogPath) {
            handle.seekToEndOfFile()
            handle.write(line.data(using: .utf8)!)
            handle.closeFile()
        } else {
            FileManager.default.createFile(atPath: sizeLogPath, contents: line.data(using: .utf8))
        }
    }
    #endif

    /// Match upstream Ghostty AppKit sizing: framebuffer dimensions are derived
    /// from backing-space points and truncated (never rounded up).
    private func pixelDimension(from value: CGFloat) -> UInt32 {
        guard value.isFinite else { return 0 }
        let floored = floor(max(0, value))
        if floored >= CGFloat(UInt32.max) {
            return UInt32.max
        }
        return UInt32(floored)
    }

    private func scaleFactors(for view: GhosttyNSView) -> (x: CGFloat, y: CGFloat, layer: CGFloat) {
        let scale = max(
            1.0,
            view.window?.backingScaleFactor
                ?? view.layer?.contentsScale
                ?? NSScreen.main?.backingScaleFactor
                ?? 1.0
        )
        return (scale, scale, scale)
    }

    private func scaleApproximatelyEqual(_ lhs: CGFloat, _ rhs: CGFloat, epsilon: CGFloat = 0.0001) -> Bool {
        abs(lhs - rhs) <= epsilon
    }

    func attachToView(_ view: GhosttyNSView) {
#if DEBUG
        dlog(
            "surface.attach surface=\(id.uuidString.prefix(5)) view=\(Unmanaged.passUnretained(view).toOpaque()) " +
            "attached=\(attachedView != nil ? 1 : 0) hasSurface=\(surface != nil ? 1 : 0) inWindow=\(view.window != nil ? 1 : 0)"
        )
#endif

        // If already attached to this view, nothing to do.
        // Still re-assert the display id: during split close tree restructuring, the view can be
        // removed/re-added (or briefly have window/screen nil) without recreating the surface.
        // Ghostty's vsync-driven renderer depends on having a valid display id; if it is missing
        // or stale, the surface can appear visually frozen until a focus/visibility change.
        if attachedView === view && surface != nil {
#if DEBUG
            dlog("surface.attach.reuse surface=\(id.uuidString.prefix(5)) view=\(Unmanaged.passUnretained(view).toOpaque())")
#endif
            if let screen = view.window?.screen ?? NSScreen.main,
               let displayID = screen.displayID,
               displayID != 0,
               let s = surface {
                ghostty_surface_set_display_id(s, displayID)
            }
            view.forceRefreshSurface()
            return
        }

        if let attachedView, attachedView !== view {
#if DEBUG
            dlog(
                "surface.attach.skip surface=\(id.uuidString.prefix(5)) reason=alreadyAttachedToDifferentView " +
                "current=\(Unmanaged.passUnretained(attachedView).toOpaque()) new=\(Unmanaged.passUnretained(view).toOpaque())"
            )
#endif
            return
        }

        attachedView = view

        // If surface doesn't exist yet, create it once the view is in a real window so
        // content scale and pixel geometry are derived from the actual backing context.
        if surface == nil {
            guard view.window != nil else {
#if DEBUG
                dlog(
                    "surface.attach.defer surface=\(id.uuidString.prefix(5)) reason=noWindow " +
                    "bounds=\(String(format: "%.1fx%.1f", view.bounds.width, view.bounds.height))"
                )
#endif
                return
            }
#if DEBUG
            dlog("surface.attach.create surface=\(id.uuidString.prefix(5))")
#endif
            createSurface(for: view)
#if DEBUG
            dlog("surface.attach.create.done surface=\(id.uuidString.prefix(5)) hasSurface=\(surface != nil ? 1 : 0)")
#endif
        } else if let screen = view.window?.screen ?? NSScreen.main,
                  let displayID = screen.displayID,
                  displayID != 0,
                  let s = surface {
            // Surface exists but we're (re)attaching after a view hierarchy move; ensure display id.
            ghostty_surface_set_display_id(s, displayID)
#if DEBUG
            dlog("surface.attach.displayId surface=\(id.uuidString.prefix(5)) display=\(displayID)")
#endif
        }
    }

    private func createSurface(for view: GhosttyNSView) {
        #if DEBUG
        let resourcesDir = getenv("GHOSTTY_RESOURCES_DIR").flatMap { String(cString: $0) } ?? "(unset)"
        let terminfo = getenv("TERMINFO").flatMap { String(cString: $0) } ?? "(unset)"
        let xdg = getenv("XDG_DATA_DIRS").flatMap { String(cString: $0) } ?? "(unset)"
        let manpath = getenv("MANPATH").flatMap { String(cString: $0) } ?? "(unset)"
        Self.surfaceLog("createSurface start surface=\(id.uuidString) tab=\(tabId.uuidString) bounds=\(view.bounds) inWindow=\(view.window != nil) resources=\(resourcesDir) terminfo=\(terminfo) xdg=\(xdg) manpath=\(manpath)")
        #endif

        guard let app = GhosttyApp.shared.app else {
            print("Ghostty app not initialized")
            #if DEBUG
            Self.surfaceLog("createSurface FAILED surface=\(id.uuidString): ghostty app not initialized")
            #endif
            return
        }

        let scaleFactors = scaleFactors(for: view)

        var surfaceConfig = configTemplate ?? ghostty_surface_config_new()
        surfaceConfig.platform_tag = GHOSTTY_PLATFORM_MACOS
        surfaceConfig.platform = ghostty_platform_u(macos: ghostty_platform_macos_s(
            nsview: Unmanaged.passUnretained(view).toOpaque()
        ))
        let callbackContext = Unmanaged.passRetained(GhosttySurfaceCallbackContext(surfaceView: view, terminalSurface: self))
        surfaceConfig.userdata = callbackContext.toOpaque()
        surfaceCallbackContext?.release()
        surfaceCallbackContext = callbackContext
        surfaceConfig.scale_factor = scaleFactors.layer
        surfaceConfig.context = surfaceContext
#if DEBUG
        let templateFontText = String(format: "%.2f", surfaceConfig.font_size)
        dlog(
            "zoom.create surface=\(id.uuidString.prefix(5)) context=\(cmuxSurfaceContextName(surfaceContext)) " +
            "templateFont=\(templateFontText)"
        )
#endif
        var envVars: [ghostty_env_var_s] = []
        var envStorage: [(UnsafeMutablePointer<CChar>, UnsafeMutablePointer<CChar>)] = []
        defer {
            for (key, value) in envStorage {
                free(key)
                free(value)
            }
        }

        var env: [String: String] = [:]
        if surfaceConfig.env_var_count > 0, let existingEnv = surfaceConfig.env_vars {
            let count = Int(surfaceConfig.env_var_count)
            if count > 0 {
                for i in 0..<count {
                    let item = existingEnv[i]
                    if let key = String(cString: item.key, encoding: .utf8),
                       let value = String(cString: item.value, encoding: .utf8) {
                        env[key] = value
                    }
                }
            }
        }

        env["CMUX_SURFACE_ID"] = id.uuidString
        env["CMUX_WORKSPACE_ID"] = tabId.uuidString
        // Backward-compatible shell integration keys used by existing scripts/tests.
        env["CMUX_PANEL_ID"] = id.uuidString
        env["CMUX_TAB_ID"] = tabId.uuidString
        env["CMUX_SOCKET_PATH"] = SocketControlSettings.socketPath()
        if let bundleId = Bundle.main.bundleIdentifier, !bundleId.isEmpty {
            env["CMUX_BUNDLE_ID"] = bundleId
        }

        // Port range for this workspace (base/range snapshotted once per app session)
        do {
            let startPort = Self.sessionPortBase + portOrdinal * Self.sessionPortRangeSize
            env["CMUX_PORT"] = String(startPort)
            env["CMUX_PORT_END"] = String(startPort + Self.sessionPortRangeSize - 1)
            env["CMUX_PORT_RANGE"] = String(Self.sessionPortRangeSize)
        }

        let claudeHooksEnabled = ClaudeCodeIntegrationSettings.hooksEnabled()
        if !claudeHooksEnabled {
            env["CMUX_CLAUDE_HOOKS_DISABLED"] = "1"
        }

        if let cliBinPath = Bundle.main.resourceURL?.appendingPathComponent("bin").path {
            let currentPath = env["PATH"]
                ?? getenv("PATH").map { String(cString: $0) }
                ?? ProcessInfo.processInfo.environment["PATH"]
                ?? ""
            if !currentPath.split(separator: ":").contains(Substring(cliBinPath)) {
                let separator = currentPath.isEmpty ? "" : ":"
                env["PATH"] = "\(cliBinPath)\(separator)\(currentPath)"
            }
        }

        // Shell integration: inject ZDOTDIR wrapper for zsh shells.
        let shellIntegrationEnabled = UserDefaults.standard.object(forKey: "sidebarShellIntegration") as? Bool ?? true
        if shellIntegrationEnabled,
           let integrationDir = Bundle.main.resourceURL?.appendingPathComponent("shell-integration").path {
            env["CMUX_SHELL_INTEGRATION"] = "1"
            env["CMUX_SHELL_INTEGRATION_DIR"] = integrationDir

            let shell = (env["SHELL"]?.isEmpty == false ? env["SHELL"] : nil)
                ?? getenv("SHELL").map { String(cString: $0) }
                ?? ProcessInfo.processInfo.environment["SHELL"]
                ?? "/bin/zsh"
            let shellName = URL(fileURLWithPath: shell).lastPathComponent
            if shellName == "zsh" {
                let candidateZdotdir = (env["ZDOTDIR"]?.isEmpty == false ? env["ZDOTDIR"] : nil)
                    ?? getenv("ZDOTDIR").map { String(cString: $0) }
                    ?? (ProcessInfo.processInfo.environment["ZDOTDIR"]?.isEmpty == false ? ProcessInfo.processInfo.environment["ZDOTDIR"] : nil)

                if let candidateZdotdir, !candidateZdotdir.isEmpty {
                    var isGhosttyInjected = false
                    let ghosttyResources = (env["GHOSTTY_RESOURCES_DIR"]?.isEmpty == false ? env["GHOSTTY_RESOURCES_DIR"] : nil)
                        ?? getenv("GHOSTTY_RESOURCES_DIR").map { String(cString: $0) }
                        ?? (ProcessInfo.processInfo.environment["GHOSTTY_RESOURCES_DIR"]?.isEmpty == false ? ProcessInfo.processInfo.environment["GHOSTTY_RESOURCES_DIR"] : nil)
                    if let ghosttyResources {
                        let ghosttyZdotdir = URL(fileURLWithPath: ghosttyResources)
                            .appendingPathComponent("shell-integration/zsh").path
                        isGhosttyInjected = (candidateZdotdir == ghosttyZdotdir)
                    }
                    if !isGhosttyInjected {
                        env["CMUX_ZSH_ZDOTDIR"] = candidateZdotdir
                    }
                }

                env["ZDOTDIR"] = integrationDir
            }
        }

        if !additionalEnvironment.isEmpty {
            for (key, value) in additionalEnvironment where !key.isEmpty && !value.isEmpty {
                env[key] = value
            }
        }

        if !env.isEmpty {
            envVars.reserveCapacity(env.count)
            envStorage.reserveCapacity(env.count)
            for (key, value) in env {
                guard let keyPtr = strdup(key), let valuePtr = strdup(value) else { continue }
                envStorage.append((keyPtr, valuePtr))
                envVars.append(ghostty_env_var_s(key: keyPtr, value: valuePtr))
            }
        }

        let createSurface = { [self] in
            if !envVars.isEmpty {
                let envVarsCount = envVars.count
                envVars.withUnsafeMutableBufferPointer { buffer in
                    surfaceConfig.env_vars = buffer.baseAddress
                    surfaceConfig.env_var_count = envVarsCount
                    self.surface = ghostty_surface_new(app, &surfaceConfig)
                }
            } else {
                self.surface = ghostty_surface_new(app, &surfaceConfig)
            }
        }

        if let workingDirectory, !workingDirectory.isEmpty {
            workingDirectory.withCString { cWorkingDir in
                surfaceConfig.working_directory = cWorkingDir
                createSurface()
            }
        } else {
            createSurface()
        }

        if surface == nil {
            surfaceCallbackContext?.release()
            surfaceCallbackContext = nil
            print("Failed to create ghostty surface")
            #if DEBUG
            Self.surfaceLog("createSurface FAILED surface=\(id.uuidString): ghostty_surface_new returned nil")
            if let cfg = GhosttyApp.shared.config {
                let count = Int(ghostty_config_diagnostics_count(cfg))
                Self.surfaceLog("createSurface diagnostics count=\(count)")
                for i in 0..<count {
                    let diag = ghostty_config_get_diagnostic(cfg, UInt32(i))
                    let msg = diag.message.flatMap { String(cString: $0) } ?? "(null)"
                    Self.surfaceLog("  [\(i)] \(msg)")
                }
            } else {
                Self.surfaceLog("createSurface diagnostics: config=nil")
            }
            #endif
            return
        }
        guard let createdSurface = surface else { return }

        // For vsync-driven rendering, Ghostty needs to know which display we're on so it can
        // start a CVDisplayLink with the right refresh rate. If we don't set this early, the
        // renderer can believe vsync is "running" but never deliver frames, which looks like a
        // frozen terminal until focus/visibility changes force a synchronous draw.
        //
        // `view.window?.screen` can be transiently nil during early attachment; fall back to the
        // primary screen so we always set *some* display ID, then update again on screen changes.
        if let screen = view.window?.screen ?? NSScreen.main,
           let displayID = screen.displayID,
           displayID != 0 {
            ghostty_surface_set_display_id(createdSurface, displayID)
        }

        ghostty_surface_set_content_scale(createdSurface, scaleFactors.x, scaleFactors.y)
        let backingSize = view.convertToBacking(NSRect(origin: .zero, size: view.bounds.size)).size
        let wpx = pixelDimension(from: backingSize.width)
        let hpx = pixelDimension(from: backingSize.height)
        if wpx > 0, hpx > 0 {
            ghostty_surface_set_size(createdSurface, wpx, hpx)
            lastPixelWidth = wpx
            lastPixelHeight = hpx
            lastXScale = scaleFactors.x
            lastYScale = scaleFactors.y
        }

        // Some GhosttyKit builds can drop inherited font_size during post-create
        // config/scale reconciliation. If runtime points don't match the inherited
        // template points, re-apply via binding action so all creation paths
        // (new surface, split, new workspace) preserve zoom from the source terminal.
        if let inheritedFontPoints = configTemplate?.font_size,
           inheritedFontPoints > 0 {
            let currentFontPoints = cmuxCurrentSurfaceFontSizePoints(createdSurface)
            let shouldReapply = {
                guard let currentFontPoints else { return true }
                return abs(currentFontPoints - inheritedFontPoints) > 0.05
            }()
            if shouldReapply {
                let action = String(format: "set_font_size:%.3f", inheritedFontPoints)
                _ = performBindingAction(action)
            }
        }

        flushPendingTextIfNeeded()

        // Kick an initial draw after creation/size setup. On some startup paths Ghostty can
        // miss the first vsync callback and sit on a blank frame until another focus/visibility
        // transition nudges the renderer.
        view.forceRefreshSurface()
        ghostty_surface_refresh(createdSurface)

#if DEBUG
        let runtimeFontText = cmuxCurrentSurfaceFontSizePoints(createdSurface).map {
            String(format: "%.2f", $0)
        } ?? "nil"
        dlog(
            "zoom.create.done surface=\(id.uuidString.prefix(5)) context=\(cmuxSurfaceContextName(surfaceContext)) " +
            "runtimeFont=\(runtimeFontText)"
        )
#endif
    }

    func updateSize(
        width: CGFloat,
        height: CGFloat,
        xScale: CGFloat,
        yScale: CGFloat,
        layerScale: CGFloat,
        backingSize: CGSize? = nil
    ) {
        guard let surface = surface else { return }
        _ = layerScale

        let resolvedBackingWidth = backingSize?.width ?? (width * xScale)
        let resolvedBackingHeight = backingSize?.height ?? (height * yScale)
        let wpx = pixelDimension(from: resolvedBackingWidth)
        let hpx = pixelDimension(from: resolvedBackingHeight)
        guard wpx > 0, hpx > 0 else { return }

        let scaleChanged = !scaleApproximatelyEqual(xScale, lastXScale) || !scaleApproximatelyEqual(yScale, lastYScale)
        let sizeChanged = wpx != lastPixelWidth || hpx != lastPixelHeight

        #if DEBUG
        Self.sizeLog("updateSize-call surface=\(id.uuidString.prefix(8)) size=\(wpx)x\(hpx) prev=\(lastPixelWidth)x\(lastPixelHeight) changed=\((scaleChanged || sizeChanged) ? 1 : 0)")
        #endif

        guard scaleChanged || sizeChanged else { return }

        #if DEBUG
        if sizeChanged {
            let win = attachedView?.window != nil ? "1" : "0"
            Self.sizeLog("updateSize surface=\(id.uuidString.prefix(8)) size=\(wpx)x\(hpx) prev=\(lastPixelWidth)x\(lastPixelHeight) win=\(win)")
        }
        #endif

        if scaleChanged {
            ghostty_surface_set_content_scale(surface, xScale, yScale)
            lastXScale = xScale
            lastYScale = yScale
        }

        if sizeChanged {
            ghostty_surface_set_size(surface, wpx, hpx)
            lastPixelWidth = wpx
            lastPixelHeight = hpx
        }

        // Let Ghostty continue rendering on its own wakeups for steady-state frames.
    }

    /// Force a full size recalculation and surface redraw.
    func forceRefresh() {
        let hasSurface = surface != nil
        let viewState: String
        if let view = attachedView {
            let inWindow = view.window != nil
            let bounds = view.bounds
            let metalOK = (view.layer as? CAMetalLayer) != nil
            viewState = "inWindow=\(inWindow) bounds=\(bounds) metalOK=\(metalOK) hasSurface=\(hasSurface)"
        } else {
            viewState = "NO_ATTACHED_VIEW hasSurface=\(hasSurface)"
        }
        #if DEBUG
        let ts = ISO8601DateFormatter().string(from: Date())
        let line = "[\(ts)] forceRefresh: \(id) \(viewState)\n"
        let logPath = "/tmp/cmux-refresh-debug.log"
        if let handle = FileHandle(forWritingAtPath: logPath) {
            handle.seekToEndOfFile()
            handle.write(line.data(using: .utf8)!)
            handle.closeFile()
        } else {
            FileManager.default.createFile(atPath: logPath, contents: line.data(using: .utf8))
        }
        #endif
        guard let view = attachedView,
              view.window != nil,
              view.bounds.width > 0,
              view.bounds.height > 0 else {
            return
        }
        guard let currentSurface = self.surface else { return }

        // Re-read self.surface before each ghostty call to guard against the surface
        // being freed during wake-from-sleep geometry reconciliation (issue #432).
        // The surface can be invalidated between calls when AppKit layout triggers
        // view lifecycle changes (e.g., forceRefreshSurface → layout → deinit → free).

        // Reassert display id on topology churn (split close/reparent) before forcing a refresh.
        // This avoids a first-run stuck-vsync state where Ghostty believes vsync is active
        // but callbacks have not resumed for the current display.
        if let displayID = (view.window?.screen ?? NSScreen.main)?.displayID,
           displayID != 0 {
            ghostty_surface_set_display_id(currentSurface, displayID)
        }

        view.forceRefreshSurface()
        guard let surface = self.surface else { return }
        ghostty_surface_refresh(surface)
    }

    func applyWindowBackgroundIfActive() {
        surfaceView.applyWindowBackgroundIfActive()
    }

    func setFocus(_ focused: Bool) {
        guard let surface = surface else { return }
        ghostty_surface_set_focus(surface, focused)

        // If we focus a surface while it is being rapidly reparented (closing splits, etc),
        // Ghostty's CVDisplayLink can end up started before the display id is valid, leaving
        // hasVsync() true but with no callbacks ("stuck-vsync-no-frames"). Reasserting the
        // display id *after* focusing lets Ghostty restart the display link when needed.
        if focused {
            if let view = attachedView,
               let displayID = (view.window?.screen ?? NSScreen.main)?.displayID,
               displayID != 0 {
                ghostty_surface_set_display_id(surface, displayID)
            }
        }
    }

    func setOcclusion(_ visible: Bool) {
        guard let surface = surface else { return }
        ghostty_surface_set_occlusion(surface, visible)
    }

    func needsConfirmClose() -> Bool {
        guard let surface = surface else { return false }
        return ghostty_surface_needs_confirm_quit(surface)
    }

    func sendText(_ text: String) {
        guard let data = text.data(using: .utf8), !data.isEmpty else { return }
        guard let surface = surface else {
            enqueuePendingText(data)
            return
        }
        writeTextData(data, to: surface)
    }

    func requestBackgroundSurfaceStartIfNeeded() {
        if !Thread.isMainThread {
            DispatchQueue.main.async { [weak self] in
                self?.requestBackgroundSurfaceStartIfNeeded()
            }
            return
        }

        guard surface == nil, attachedView != nil else { return }
        guard !backgroundSurfaceStartQueued else { return }
        backgroundSurfaceStartQueued = true

        DispatchQueue.main.async { [weak self] in
            guard let self else { return }
            self.backgroundSurfaceStartQueued = false
            guard self.surface == nil, let view = self.attachedView else { return }
            #if DEBUG
            let startedAt = ProcessInfo.processInfo.systemUptime
            #endif
            self.createSurface(for: view)
            #if DEBUG
            let elapsedMs = (ProcessInfo.processInfo.systemUptime - startedAt) * 1000.0
            dlog(
                "surface.background_start surface=\(self.id.uuidString.prefix(8)) inWindow=\(view.window != nil ? 1 : 0) ready=\(self.surface != nil ? 1 : 0) ms=\(String(format: "%.2f", elapsedMs))"
            )
            #endif
        }
    }

    private func writeTextData(_ data: Data, to surface: ghostty_surface_t) {
        data.withUnsafeBytes { rawBuffer in
            guard let baseAddress = rawBuffer.baseAddress?.assumingMemoryBound(to: CChar.self) else { return }
            ghostty_surface_text(surface, baseAddress, UInt(rawBuffer.count))
        }
    }

    private func enqueuePendingText(_ data: Data) {
        let incomingBytes = data.count
        while !pendingTextQueue.isEmpty && pendingTextBytes + incomingBytes > maxPendingTextBytes {
            let dropped = pendingTextQueue.removeFirst()
            pendingTextBytes -= dropped.count
        }

        pendingTextQueue.append(data)
        pendingTextBytes += incomingBytes
        #if DEBUG
        dlog(
            "surface.send_text.queue surface=\(id.uuidString.prefix(8)) chunks=\(pendingTextQueue.count) bytes=\(pendingTextBytes)"
        )
        #endif
    }

    private func flushPendingTextIfNeeded() {
        guard let surface = surface, !pendingTextQueue.isEmpty else { return }
        let queued = pendingTextQueue
        let queuedBytes = pendingTextBytes
        pendingTextQueue.removeAll(keepingCapacity: false)
        pendingTextBytes = 0

        for chunk in queued {
            writeTextData(chunk, to: surface)
        }
        #if DEBUG
        dlog(
            "surface.send_text.flush surface=\(id.uuidString.prefix(8)) chunks=\(queued.count) bytes=\(queuedBytes)"
        )
        #endif
    }

    func performBindingAction(_ action: String) -> Bool {
        guard let surface = surface else { return false }
        return action.withCString { cString in
            ghostty_surface_binding_action(surface, cString, UInt(strlen(cString)))
        }
    }

    @discardableResult
    func toggleKeyboardCopyMode() -> Bool {
        let handled = surfaceView.toggleKeyboardCopyMode()
        if handled {
            setKeyboardCopyModeActive(surfaceView.isKeyboardCopyModeActive)
        }
        return handled
    }

    func setKeyboardCopyModeActive(_ active: Bool) {
        if !Thread.isMainThread {
            DispatchQueue.main.async { [weak self] in
                self?.setKeyboardCopyModeActive(active)
            }
            return
        }

        if keyboardCopyModeActive != active {
            keyboardCopyModeActive = active
        }
        hostedView.setKeyboardCopyModeIndicator(visible: active)
    }

    func hasSelection() -> Bool {
        guard let surface = surface else { return false }
        return ghostty_surface_has_selection(surface)
    }

#if DEBUG
    /// Test-only helper to deterministically simulate a released runtime surface.
    @MainActor
    func releaseSurfaceForTesting() {
        let callbackContext = surfaceCallbackContext
        surfaceCallbackContext = nil

        guard let surfaceToFree = surface else {
            callbackContext?.release()
            return
        }

        surface = nil
        ghostty_surface_free(surfaceToFree)
        callbackContext?.release()
    }
#endif

    deinit {
        markPortalLifecycleClosed(reason: "deinit")

        let callbackContext = surfaceCallbackContext
        surfaceCallbackContext = nil

        // Nil out the surface pointer so any in-flight closures (e.g. geometry
        // reconcile dispatched via DispatchQueue.main.async) that read self.surface
        // before this object is fully deallocated will see nil and bail out,
        // rather than passing a freed pointer to ghostty_surface_refresh (#432).
        let surfaceToFree = surface
        surface = nil

        guard let surfaceToFree else {
#if DEBUG
            dlog(
                "surface.lifecycle.deinit.skip surface=\(id.uuidString.prefix(5)) " +
                "workspace=\(tabId.uuidString.prefix(5)) reason=noRuntimeSurface"
            )
#endif
            callbackContext?.release()
            return
        }

#if DEBUG
        let surfaceToken = String(id.uuidString.prefix(5))
        let workspaceToken = String(tabId.uuidString.prefix(5))
        dlog(
            "surface.lifecycle.deinit.begin surface=\(surfaceToken) " +
            "workspace=\(workspaceToken) hasAttachedView=\(attachedView != nil ? 1 : 0) " +
            "hostedInWindow=\(hostedView.window != nil ? 1 : 0)"
        )
#endif

        // Keep teardown asynchronous to avoid re-entrant close/deinit loops, but retain
        // callback userdata until surface free completes so callbacks never dereference
        // a deallocated view pointer.
        Task { @MainActor in
            ghostty_surface_free(surfaceToFree)
            callbackContext?.release()
#if DEBUG
            dlog(
                "surface.lifecycle.deinit.end surface=\(surfaceToken) " +
                "workspace=\(workspaceToken) freed=1"
            )
#endif
        }
    }
}

// MARK: - Ghostty Surface View

class GhosttyNSView: NSView, NSUserInterfaceValidations {
    private static let focusDebugEnabled: Bool = {
        if ProcessInfo.processInfo.environment["CMUX_FOCUS_DEBUG"] == "1" {
            return true
        }
        return UserDefaults.standard.bool(forKey: "cmuxFocusDebug")
    }()
    private static let dropTypes: Set<NSPasteboard.PasteboardType> = [
        .string,
        .fileURL,
        .URL
    ]
    private static let shellEscapeCharacters = "\\ ()[]{}<>\"'`!#$&;|*?\t"

    fileprivate static func focusLog(_ message: String) {
        guard focusDebugEnabled else { return }
        FocusLogStore.shared.append(message)
        NSLog("[FOCUSDBG] %@", message)
    }

    weak var terminalSurface: TerminalSurface?
    var scrollbar: GhosttyScrollbar?
    var cellSize: CGSize = .zero
    var desiredFocus: Bool = false
    var suppressingReparentFocus: Bool = false
    var tabId: UUID?
    var onFocus: (() -> Void)?
    var onTriggerFlash: (() -> Void)?
    var backgroundColor: NSColor?
    private var appliedColorScheme: ghostty_color_scheme_e?
    private var lastLoggedSurfaceBackgroundSignature: String?
    private var lastLoggedWindowBackgroundSignature: String?
    private var keySequence: [ghostty_input_trigger_s] = []
    private var keyTables: [String] = []
    fileprivate private(set) var keyboardCopyModeActive = false
    private var keyboardCopyModeConsumedKeyUps: Set<UInt16> = []
    private var keyboardCopyModeInputState = TerminalKeyboardCopyModeInputState()
    private var keyboardCopyModeViewportRow: Int?
    fileprivate var isKeyboardCopyModeActive: Bool { keyboardCopyModeActive }
#if DEBUG
    private static let keyLatencyProbeEnabled: Bool = {
        if ProcessInfo.processInfo.environment["CMUX_KEY_LATENCY_PROBE"] == "1" {
            return true
        }
        return UserDefaults.standard.bool(forKey: "cmuxKeyLatencyProbe")
    }()
    static var debugGhosttySurfaceKeyEventObserver: ((ghostty_input_key_s) -> Void)?
#endif
    private var eventMonitor: Any?
    private var trackingArea: NSTrackingArea?
    private var windowObserver: NSObjectProtocol?
	    private var lastScrollEventTime: CFTimeInterval = 0
    private var visibleInUI: Bool = true
    private var pendingSurfaceSize: CGSize?
#if DEBUG
    private var lastSizeSkipSignature: String?
#endif

    private var hasUsableFocusGeometry: Bool {
        bounds.width > 1 && bounds.height > 1
    }

    static func shouldRequestFirstResponderForMouseFocus(
        focusFollowsMouseEnabled: Bool,
        pressedMouseButtons: Int,
        appIsActive: Bool,
        windowIsKey: Bool,
        alreadyFirstResponder: Bool,
        visibleInUI: Bool,
        hasUsableGeometry: Bool,
        hiddenInHierarchy: Bool
    ) -> Bool {
        guard focusFollowsMouseEnabled else { return false }
        guard pressedMouseButtons == 0 else { return false }
        guard appIsActive, windowIsKey else { return false }
        guard !alreadyFirstResponder else { return false }
        guard visibleInUI, hasUsableGeometry, !hiddenInHierarchy else { return false }
        return true
    }

        // Visibility is used for focus gating, not for libghostty occlusion.
        fileprivate var isVisibleInUI: Bool { visibleInUI }
        fileprivate func setVisibleInUI(_ visible: Bool) {
            visibleInUI = visible
        }

    override init(frame frameRect: NSRect) {
        super.init(frame: frameRect)
        setup()
    }

    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setup()
    }

    private func setup() {
        // Only enable our instrumented CAMetalLayer in targeted debug/test scenarios.
        // The lock in GhosttyMetalLayer.nextDrawable() adds overhead we don't want in normal runs.
        wantsLayer = true
        layer?.masksToBounds = true
        installEventMonitor()
        updateTrackingAreas()
        registerForDraggedTypes(Array(Self.dropTypes))
    }

    private func effectiveBackgroundColor() -> NSColor {
        let base = backgroundColor ?? GhosttyApp.shared.defaultBackgroundColor
        let opacity = GhosttyApp.shared.defaultBackgroundOpacity
        return base.withAlphaComponent(opacity)
    }

    func applySurfaceBackground() {
        let color = effectiveBackgroundColor()
        if let layer {
            CATransaction.begin()
            CATransaction.setDisableActions(true)
            // GhosttySurfaceScrollView owns the panel background fill. Keeping this layer clear
            // avoids stacking multiple identical translucent backgrounds (which looks opaque).
            layer.backgroundColor = NSColor.clear.cgColor
            layer.isOpaque = false
            CATransaction.commit()
        }
        terminalSurface?.hostedView.setBackgroundColor(color)
        if GhosttyApp.shared.backgroundLogEnabled {
            let signature = "\(color.hexString()):\(String(format: "%.3f", color.alphaComponent))"
            if signature != lastLoggedSurfaceBackgroundSignature {
                lastLoggedSurfaceBackgroundSignature = signature
                let hasOverride = backgroundColor != nil
                let overrideHex = backgroundColor?.hexString() ?? "nil"
                let defaultHex = GhosttyApp.shared.defaultBackgroundColor.hexString()
                let source = hasOverride ? "surfaceOverride" : "defaultBackground"
                GhosttyApp.shared.logBackground(
                    "surface background applied tab=\(tabId?.uuidString ?? "unknown") surface=\(terminalSurface?.id.uuidString ?? "unknown") source=\(source) override=\(overrideHex) default=\(defaultHex) color=\(color.hexString()) opacity=\(String(format: "%.3f", color.alphaComponent))"
                )
            }
        }
    }

    func applyWindowBackgroundIfActive() {
        guard let window else { return }
        if let tabId, let selectedId = AppDelegate.shared?.tabManager?.selectedTabId, tabId != selectedId {
            return
        }
        applySurfaceBackground()
        let color = effectiveBackgroundColor()
        if cmuxShouldUseClearWindowBackground(for: color.alphaComponent) {
            window.backgroundColor = cmuxTransparentWindowBaseColor()
            window.isOpaque = false
        } else {
            window.backgroundColor = color
            window.isOpaque = color.alphaComponent >= 1.0
        }
        if GhosttyApp.shared.backgroundLogEnabled {
            let signature = "\(cmuxShouldUseClearWindowBackground(for: color.alphaComponent) ? "transparent" : color.hexString()):\(String(format: "%.3f", color.alphaComponent))"
            if signature != lastLoggedWindowBackgroundSignature {
                lastLoggedWindowBackgroundSignature = signature
                let hasOverride = backgroundColor != nil
                let overrideHex = backgroundColor?.hexString() ?? "nil"
                let defaultHex = GhosttyApp.shared.defaultBackgroundColor.hexString()
                let source = hasOverride ? "surfaceOverride" : "defaultBackground"
                GhosttyApp.shared.logBackground(
                    "window background applied tab=\(tabId?.uuidString ?? "unknown") surface=\(terminalSurface?.id.uuidString ?? "unknown") source=\(source) override=\(overrideHex) default=\(defaultHex) transparent=\(cmuxShouldUseClearWindowBackground(for: color.alphaComponent)) color=\(color.hexString()) opacity=\(String(format: "%.3f", color.alphaComponent))"
                )
            }
        }
    }

    private func installEventMonitor() {
        guard eventMonitor == nil else { return }
        eventMonitor = NSEvent.addLocalMonitorForEvents(matching: [.scrollWheel]) { [weak self] event in
            return self?.localEventHandler(event) ?? event
        }
    }

    private func localEventHandler(_ event: NSEvent) -> NSEvent? {
        switch event.type {
        case .scrollWheel:
            return localEventScrollWheel(event)
        default:
            return event
        }
    }

    private func localEventScrollWheel(_ event: NSEvent) -> NSEvent? {
        guard let window,
              let eventWindow = event.window,
              window == eventWindow else { return event }

        let location = convert(event.locationInWindow, from: nil)
        guard hitTest(location) == self else { return event }

        Self.focusLog("localEventScrollWheel: window=\(ObjectIdentifier(window)) firstResponder=\(String(describing: window.firstResponder))")
        return event
    }

    func attachSurface(_ surface: TerminalSurface) {
        appliedColorScheme = nil
        terminalSurface = surface
        tabId = surface.tabId
        surface.attachToView(self)
        surface.setKeyboardCopyModeActive(keyboardCopyModeActive)
        updateSurfaceSize()
        applySurfaceBackground()
        applySurfaceColorScheme(force: true)
    }

    override func viewDidMoveToWindow() {
        super.viewDidMoveToWindow()
        if let windowObserver {
            NotificationCenter.default.removeObserver(windowObserver)
            self.windowObserver = nil
        }
#if DEBUG
        dlog(
            "surface.view.windowMove surface=\(terminalSurface?.id.uuidString.prefix(5) ?? "nil") " +
            "inWindow=\(window != nil ? 1 : 0) bounds=\(String(format: "%.1fx%.1f", bounds.width, bounds.height)) " +
            "pending=\(String(format: "%.1fx%.1f", pendingSurfaceSize?.width ?? 0, pendingSurfaceSize?.height ?? 0))"
        )
#endif
        guard let window else { return }

        // If the surface creation was deferred while detached, create/attach it now.
        terminalSurface?.attachToView(self)

        windowObserver = NotificationCenter.default.addObserver(
            forName: NSWindow.didChangeScreenNotification,
            object: window,
            queue: .main
        ) { [weak self] notification in
            self?.windowDidChangeScreen(notification)
        }

        if let surface = terminalSurface?.surface,
           let displayID = window.screen?.displayID,
           displayID != 0 {
            ghostty_surface_set_display_id(surface, displayID)
        }

        // Recompute from current bounds after layout. Pending size is only a fallback
        // when we don't have usable bounds (e.g. detached/off-window transitions).
        superview?.layoutSubtreeIfNeeded()
        layoutSubtreeIfNeeded()
        updateSurfaceSize()
        applySurfaceBackground()
        applySurfaceColorScheme(force: true)
        GhosttyApp.shared.synchronizeThemeWithAppearance(
            effectiveAppearance,
            source: "surface.viewDidMoveToWindow"
        )
        applyWindowBackgroundIfActive()
    }

    override func viewDidChangeEffectiveAppearance() {
        super.viewDidChangeEffectiveAppearance()
        if GhosttyApp.shared.backgroundLogEnabled {
            let bestMatch = effectiveAppearance.bestMatch(from: [.darkAqua, .aqua])
            GhosttyApp.shared.logBackground(
                "surface appearance changed tab=\(tabId?.uuidString ?? "nil") surface=\(terminalSurface?.id.uuidString ?? "nil") bestMatch=\(bestMatch?.rawValue ?? "nil")"
            )
        }
        applySurfaceColorScheme()
        GhosttyApp.shared.synchronizeThemeWithAppearance(
            effectiveAppearance,
            source: "surface.viewDidChangeEffectiveAppearance"
        )
    }

    fileprivate func updateOcclusionState() {
        // Intentionally no-op: we don't drive libghostty occlusion from AppKit occlusion state.
        // This avoids transient clears during reparenting and keeps rendering logic minimal.
    }

    override func viewDidChangeBackingProperties() {
        super.viewDidChangeBackingProperties()
        if let window {
            CATransaction.begin()
            CATransaction.setDisableActions(true)
            layer?.contentsScale = window.backingScaleFactor
            CATransaction.commit()
        }
        updateSurfaceSize()
    }

    override func layout() {
        super.layout()
        updateSurfaceSize()
    }

    override var isOpaque: Bool { false }

    private func resolvedSurfaceSize(preferred size: CGSize?) -> CGSize {
        if let size,
           size.width > 0,
           size.height > 0 {
            return size
        }

        let currentBounds = bounds.size
        if currentBounds.width > 0, currentBounds.height > 0 {
            return currentBounds
        }

        if let pending = pendingSurfaceSize,
           pending.width > 0,
           pending.height > 0 {
            return pending
        }

        return currentBounds
    }

    private func updateSurfaceSize(size: CGSize? = nil) {
        guard let terminalSurface = terminalSurface else { return }
        let size = resolvedSurfaceSize(preferred: size)
        guard size.width > 0 && size.height > 0 else {
#if DEBUG
            let signature = "nonPositive-\(Int(size.width))x\(Int(size.height))"
            if lastSizeSkipSignature != signature {
                dlog(
                    "surface.size.defer surface=\(terminalSurface.id.uuidString.prefix(5)) " +
                    "reason=nonPositive size=\(String(format: "%.1fx%.1f", size.width, size.height)) " +
                    "inWindow=\(window != nil ? 1 : 0)"
                )
                lastSizeSkipSignature = signature
            }
#endif
            return
        }
        pendingSurfaceSize = size
        guard let window else {
#if DEBUG
            let signature = "noWindow-\(Int(size.width))x\(Int(size.height))"
            if lastSizeSkipSignature != signature {
                dlog(
                    "surface.size.defer surface=\(terminalSurface.id.uuidString.prefix(5)) reason=noWindow " +
                    "size=\(String(format: "%.1fx%.1f", size.width, size.height))"
                )
                lastSizeSkipSignature = signature
            }
#endif
            return
        }

        // First principles: derive pixel size from AppKit's backing conversion for the current
        // window/screen. Avoid updating Ghostty while detached from a window.
        let backingSize = convertToBacking(NSRect(origin: .zero, size: size)).size
        guard backingSize.width > 0, backingSize.height > 0 else {
#if DEBUG
            let signature = "zeroBacking-\(Int(backingSize.width))x\(Int(backingSize.height))"
            if lastSizeSkipSignature != signature {
                dlog(
                    "surface.size.defer surface=\(terminalSurface.id.uuidString.prefix(5)) reason=zeroBacking " +
                    "size=\(String(format: "%.1fx%.1f", size.width, size.height)) " +
                    "backing=\(String(format: "%.1fx%.1f", backingSize.width, backingSize.height))"
                )
                lastSizeSkipSignature = signature
            }
#endif
            return
        }
#if DEBUG
        if lastSizeSkipSignature != nil {
            dlog(
                "surface.size.resume surface=\(terminalSurface.id.uuidString.prefix(5)) " +
                "size=\(String(format: "%.1fx%.1f", size.width, size.height)) " +
                "backing=\(String(format: "%.1fx%.1f", backingSize.width, backingSize.height))"
            )
            lastSizeSkipSignature = nil
        }
#endif
        let xScale = backingSize.width / size.width
        let yScale = backingSize.height / size.height
        let layerScale = max(1.0, window.backingScaleFactor)
        let drawablePixelSize = CGSize(
            width: floor(max(0, backingSize.width)),
            height: floor(max(0, backingSize.height))
        )

        CATransaction.begin()
        CATransaction.setDisableActions(true)
        layer?.contentsScale = layerScale
        layer?.masksToBounds = true
        if let metalLayer = layer as? CAMetalLayer {
            metalLayer.drawableSize = drawablePixelSize
        }
        CATransaction.commit()

        terminalSurface.updateSize(
            width: size.width,
            height: size.height,
            xScale: xScale,
            yScale: yScale,
            layerScale: layerScale,
            backingSize: backingSize
        )
    }

    fileprivate func pushTargetSurfaceSize(_ size: CGSize) {
        updateSurfaceSize(size: size)
    }

    /// Force a full size recalculation and Metal layer refresh.
    /// Resets cached metrics so updateSurfaceSize() re-runs unconditionally.
    func forceRefreshSurface() {
        updateSurfaceSize()
    }

    private func nearlyEqual(_ lhs: CGFloat, _ rhs: CGFloat, epsilon: CGFloat = 0.0001) -> Bool {
        abs(lhs - rhs) <= epsilon
    }

    func expectedPixelSize(for pointsSize: CGSize) -> CGSize {
        let backing = convertToBacking(NSRect(origin: .zero, size: pointsSize)).size
        if backing.width > 0, backing.height > 0 {
            return backing
        }
        let scale = max(1.0, window?.backingScaleFactor ?? layer?.contentsScale ?? 1.0)
        return CGSize(width: pointsSize.width * scale, height: pointsSize.height * scale)
    }

    // Convenience accessor for the ghostty surface
    private var surface: ghostty_surface_t? {
        terminalSurface?.surface
    }

    private func applySurfaceColorScheme(force: Bool = false) {
        guard let surface else { return }
        let bestMatch = effectiveAppearance.bestMatch(from: [.darkAqua, .aqua])
        let scheme: ghostty_color_scheme_e = bestMatch == .darkAqua
            ? GHOSTTY_COLOR_SCHEME_DARK
            : GHOSTTY_COLOR_SCHEME_LIGHT
        if !force, appliedColorScheme == scheme {
            if GhosttyApp.shared.backgroundLogEnabled {
                let schemeLabel = scheme == GHOSTTY_COLOR_SCHEME_DARK ? "dark" : "light"
                GhosttyApp.shared.logBackground(
                    "surface color scheme tab=\(tabId?.uuidString ?? "nil") surface=\(terminalSurface?.id.uuidString ?? "nil") bestMatch=\(bestMatch?.rawValue ?? "nil") scheme=\(schemeLabel) force=\(force) applied=false"
                )
            }
            return
        }
        ghostty_surface_set_color_scheme(surface, scheme)
        appliedColorScheme = scheme
        if GhosttyApp.shared.backgroundLogEnabled {
            let schemeLabel = scheme == GHOSTTY_COLOR_SCHEME_DARK ? "dark" : "light"
            GhosttyApp.shared.logBackground(
                "surface color scheme tab=\(tabId?.uuidString ?? "nil") surface=\(terminalSurface?.id.uuidString ?? "nil") bestMatch=\(bestMatch?.rawValue ?? "nil") scheme=\(schemeLabel) force=\(force) applied=true"
            )
        }
    }

    @discardableResult
    private func ensureSurfaceReadyForInput() -> ghostty_surface_t? {
        if let surface = surface {
            return surface
        }
        guard window != nil else { return nil }
        terminalSurface?.attachToView(self)
        updateSurfaceSize(size: bounds.size)
        applySurfaceColorScheme(force: true)
        return surface
    }

    func performBindingAction(_ action: String) -> Bool {
        guard let surface = surface else { return false }
        return action.withCString { cString in
            ghostty_surface_binding_action(surface, cString, UInt(strlen(cString)))
        }
    }

    @discardableResult
    func toggleKeyboardCopyMode() -> Bool {
        guard surface != nil else { return false }
        setKeyboardCopyModeActive(!keyboardCopyModeActive)
        if !keyboardCopyModeActive, let surface {
            _ = ghostty_surface_clear_selection(surface)
        }
        return true
    }

    private func setKeyboardCopyModeActive(_ active: Bool) {
        keyboardCopyModeInputState.reset()
        keyboardCopyModeActive = active
        if active, let surface {
            keyboardCopyModeViewportRow = keyboardCopyModeSelectionAnchor(surface: surface)?.row
            _ = ghostty_surface_clear_selection(surface)
            if keyboardCopyModeViewportRow == nil {
                keyboardCopyModeViewportRow = keyboardCopyModeImeViewportRow(surface: surface)
            }
        } else {
            keyboardCopyModeViewportRow = nil
        }
        terminalSurface?.setKeyboardCopyModeActive(active)
    }

    private func performBindingAction(_ action: String, repeatCount: Int) {
        let count = terminalKeyboardCopyModeClampCount(repeatCount)
        for _ in 0 ..< count {
            _ = performBindingAction(action)
        }
    }

    private func currentKeyboardCopyModeViewportRow(surface: ghostty_surface_t) -> Int {
        let rows = max(Int(ghostty_surface_size(surface).rows), 1)
        let fallback = rows - 1
        return max(0, min(rows - 1, keyboardCopyModeViewportRow ?? fallback))
    }

    private func keyboardCopyModeImeViewportRow(surface: ghostty_surface_t) -> Int {
        let rows = max(Int(ghostty_surface_size(surface).rows), 1)
        var x: Double = 0
        var y: Double = 0
        var width: Double = 0
        var height: Double = 0
        ghostty_surface_ime_point(surface, &x, &y, &width, &height)
        return terminalKeyboardCopyModeInitialViewportRow(
            rows: rows,
            imePointY: y,
            imeCellHeight: height
        )
    }

    private func keyboardCopyModeSelectionAnchor(surface: ghostty_surface_t) -> (row: Int, y: Double)? {
        let size = ghostty_surface_size(surface)
        guard size.rows > 0, size.columns > 0 else { return nil }
        guard ghostty_surface_select_cursor_cell(surface) else { return nil }

        var text = ghostty_text_s()
        guard ghostty_surface_read_selection(surface, &text) else { return nil }
        defer { ghostty_surface_free_text(surface, &text) }

        let rows = max(Int(size.rows), 1)
        let cols = max(Int(size.columns), 1)
        let rawRow = Int(text.offset_start) / cols
        let clampedRow = max(0, min(rows - 1, rawRow))
        return (row: clampedRow, y: text.tl_px_y)
    }

    private func refreshKeyboardCopyModeViewportRowFromVisibleAnchor(surface: ghostty_surface_t) {
        guard !ghostty_surface_has_selection(surface) else { return }
        guard let anchor = keyboardCopyModeSelectionAnchor(surface: surface) else { return }
        keyboardCopyModeViewportRow = anchor.row
        _ = ghostty_surface_clear_selection(surface)
    }

    private func copyCurrentViewportLinesToClipboard(
        surface: ghostty_surface_t,
        startRow: Int,
        lineCount: Int
    ) -> Bool {
        let clampedCount = terminalKeyboardCopyModeClampCount(lineCount)
        let rows = max(Int(ghostty_surface_size(surface).rows), 1)
        let targetRow = max(0, min(rows - 1, startRow))
        let endRow = min(rows - 1, targetRow + clampedCount - 1)
        guard let anchor = keyboardCopyModeSelectionAnchor(surface: surface) else {
            return false
        }
        _ = ghostty_surface_clear_selection(surface)

        var imeX: Double = 0
        var imeY: Double = 0
        var imeWidth: Double = 0
        var imeHeight: Double = 0
        ghostty_surface_ime_point(surface, &imeX, &imeY, &imeWidth, &imeHeight)
        let cellHeight = imeHeight > 0 ? imeHeight : max(bounds.height / Double(rows), 1)
        let yMax = max(bounds.height - 1, 0)

        let startRawY = anchor.y + (Double(targetRow - anchor.row) * cellHeight)
        let endRawY = anchor.y + (Double(endRow - anchor.row) * cellHeight)
        let startY = max(0, min(startRawY, yMax))
        let endY = max(0, min(endRawY, yMax))
        let xMax = max(bounds.width - 1, 0)
        let startX = min(1, xMax)
        let endX = xMax

        let mods = ghostty_input_mods_e(rawValue: GHOSTTY_MODS_NONE.rawValue) ?? GHOSTTY_MODS_NONE
        ghostty_surface_mouse_pos(surface, startX, startY, mods)
        guard ghostty_surface_mouse_button(surface, GHOSTTY_MOUSE_PRESS, GHOSTTY_MOUSE_LEFT, mods) else {
            return false
        }
        defer {
            _ = ghostty_surface_mouse_button(surface, GHOSTTY_MOUSE_RELEASE, GHOSTTY_MOUSE_LEFT, mods)
        }
        ghostty_surface_mouse_pos(surface, endX, endY, mods)
        guard ghostty_surface_has_selection(surface) else { return false }

        return performBindingAction("copy_to_clipboard")
    }

    private func handleKeyboardCopyModeIfNeeded(_ event: NSEvent, surface: ghostty_surface_t) -> Bool {
        guard keyboardCopyModeActive else { return false }

        if terminalKeyboardCopyModeShouldBypassForShortcut(modifierFlags: event.modifierFlags) {
            keyboardCopyModeInputState.reset()
            return false
        }

        let hasSelection = ghostty_surface_has_selection(surface)
        let resolution = terminalKeyboardCopyModeResolve(
            keyCode: event.keyCode,
            charactersIgnoringModifiers: event.charactersIgnoringModifiers,
            modifierFlags: event.modifierFlags,
            hasSelection: hasSelection,
            state: &keyboardCopyModeInputState
        )
        guard case let .perform(action, count) = resolution else {
            return true
        }

        switch action {
        case .exit:
            _ = ghostty_surface_clear_selection(surface)
            setKeyboardCopyModeActive(false)
        case .startSelection:
            _ = ghostty_surface_select_cursor_cell(surface)
        case .clearSelection:
            _ = ghostty_surface_clear_selection(surface)
        case .copyAndExit:
            _ = performBindingAction("copy_to_clipboard")
            _ = ghostty_surface_clear_selection(surface)
            setKeyboardCopyModeActive(false)
        case .copyLineAndExit:
            let startRow = currentKeyboardCopyModeViewportRow(surface: surface)
            _ = copyCurrentViewportLinesToClipboard(
                surface: surface,
                startRow: startRow,
                lineCount: count
            )
            _ = ghostty_surface_clear_selection(surface)
            setKeyboardCopyModeActive(false)
        case let .scrollLines(delta):
            _ = performBindingAction("scroll_page_lines:\(delta * count)")
            refreshKeyboardCopyModeViewportRowFromVisibleAnchor(surface: surface)
        case let .scrollPage(delta):
            performBindingAction(delta > 0 ? "scroll_page_down" : "scroll_page_up", repeatCount: count)
            refreshKeyboardCopyModeViewportRowFromVisibleAnchor(surface: surface)
        case .scrollToTop:
            keyboardCopyModeViewportRow = 0
            _ = performBindingAction("scroll_to_top")
        case .scrollToBottom:
            keyboardCopyModeViewportRow = max(Int(ghostty_surface_size(surface).rows) - 1, 0)
            _ = performBindingAction("scroll_to_bottom")
        case let .jumpToPrompt(delta):
            _ = performBindingAction("jump_to_prompt:\(delta * count)")
            refreshKeyboardCopyModeViewportRowFromVisibleAnchor(surface: surface)
        case .startSearch:
            _ = performBindingAction("start_search")
        case .searchNext:
            performBindingAction("navigate_search:next", repeatCount: count)
            refreshKeyboardCopyModeViewportRowFromVisibleAnchor(surface: surface)
        case .searchPrevious:
            performBindingAction("navigate_search:previous", repeatCount: count)
            refreshKeyboardCopyModeViewportRowFromVisibleAnchor(surface: surface)
        case let .adjustSelection(direction):
            performBindingAction("adjust_selection:\(direction.rawValue)", repeatCount: count)
        }
        return true
    }

    // MARK: - Input Handling

    @IBAction func copy(_ sender: Any?) {
        _ = performBindingAction("copy_to_clipboard")
    }

    // MARK: - Clipboard image paste

    private static let maxClipboardImageSize = 10 * 1024 * 1024  // 10 MB

    /// Quick check: does the clipboard have image data and no text?
    private static func clipboardHasImageOnly() -> Bool {
        let pb = NSPasteboard.general
        let types = pb.types ?? []
        let hasText = types.contains(.string) || types.contains(.html)
            || types.contains(.rtf) || types.contains(.rtfd)
        if hasText { return false }
        return types.contains(.tiff) || types.contains(.png)
    }

    /// When the clipboard contains only image data (no text/HTML), saves it as
    /// a temporary PNG file and returns the file path. Returns nil if the
    /// clipboard contains text or no image.
    private static func saveClipboardImageIfNeeded() -> String? {
        let pb = NSPasteboard.general
        let types = pb.types ?? []

        // If pasteboard has text/HTML, this is a normal copy — let Ghostty handle it.
        let hasText = types.contains(.string) || types.contains(.html)
            || types.contains(.rtf) || types.contains(.rtfd)
        if hasText { return nil }

        // Check for image types (TIFF from screenshots, PNG from some tools).
        guard types.contains(.tiff) || types.contains(.png) else { return nil }
        guard let image = NSImage(pasteboard: pb),
              let tiffData = image.tiffRepresentation,
              let bitmap = NSBitmapImageRep(data: tiffData),
              let pngData = bitmap.representation(using: .png, properties: [:]) else { return nil }

        guard pngData.count <= maxClipboardImageSize else {
#if DEBUG
            dlog("terminal.paste.image.rejected reason=tooLarge bytes=\(pngData.count)")
#endif
            return nil
        }

        let formatter = DateFormatter()
        formatter.dateFormat = "yyyy-MM-dd-HHmmss"
        formatter.locale = Locale(identifier: "en_US_POSIX")
        let timestamp = formatter.string(from: Date())
        let filename = "clipboard-\(timestamp)-\(UUID().uuidString.prefix(8)).png"
        let path = (NSTemporaryDirectory() as NSString).appendingPathComponent(filename)

        do {
            try pngData.write(to: URL(fileURLWithPath: path))
        } catch {
#if DEBUG
            dlog("terminal.paste.image.writeFailed error=\(error.localizedDescription)")
#endif
            return nil
        }

        return path
    }

    /// Pastes clipboard content into the terminal. If the clipboard contains only
    /// image data, saves it as a temporary PNG and pastes the shell-escaped file path.
    @IBAction func paste(_ sender: Any?) {
        // When the clipboard contains only image data (e.g. from Cmd+Ctrl+Shift+4
        // screenshot), save it as a temporary PNG and paste the file path so that
        // CLI tools like Claude Code can accept the image.
        if let path = Self.saveClipboardImageIfNeeded() {
#if DEBUG
            dlog("terminal.paste.image path=\(path)")
#endif
            terminalSurface?.sendText(Self.escapeDropForShell(path))
            return
        }
        _ = performBindingAction("paste_from_clipboard")
    }

    /// Pastes clipboard text as plain text, stripping any rich formatting.
    @IBAction func pasteAsPlainText(_ sender: Any?) {
        _ = performBindingAction("paste_from_clipboard")
    }

    /// Validates whether edit menu items (copy, paste, split) should be enabled.
    func validateUserInterfaceItem(_ item: NSValidatedUserInterfaceItem) -> Bool {
        switch item.action {
        case #selector(copy(_:)):
            guard let surface = surface else { return false }
            return ghostty_surface_has_selection(surface)
        case #selector(paste(_:)):
            return GhosttyPasteboardHelper.hasString(for: GHOSTTY_CLIPBOARD_STANDARD)
                || Self.clipboardHasImageOnly()
        case #selector(pasteAsPlainText(_:)):
            return GhosttyPasteboardHelper.hasString(for: GHOSTTY_CLIPBOARD_STANDARD)
        case #selector(splitHorizontally(_:)), #selector(splitVertically(_:)):
            return canSplitCurrentSurface()
        default:
            return true
        }
    }

    override var acceptsFirstResponder: Bool { true }

    override func becomeFirstResponder() -> Bool {
        let result = super.becomeFirstResponder()
        var shouldApplySurfaceFocus = false
        if result {
            // If we become first responder before the ghostty surface exists (e.g. during
            // split/tab creation while the surface is still being created), record the desired focus.
            desiredFocus = true

            // During programmatic splits, SwiftUI reparents the old NSView which triggers
            // becomeFirstResponder. Suppress onFocus + ghostty_surface_set_focus to prevent
            // the old view from stealing focus and creating model/surface divergence.
            if suppressingReparentFocus {
#if DEBUG
                dlog("focus.firstResponder SUPPRESSED (reparent) surface=\(terminalSurface?.id.uuidString.prefix(5) ?? "nil")")
#endif
                return result
            }

            // Always notify the host app that this pane became the first responder so bonsplit
            // focus/selection can converge. Previously this was gated on `surface != nil`, which
            // allowed a mismatch where AppKit focus moved but the UI focus indicator (bonsplit)
            // stayed behind.
            let hiddenInHierarchy = isHiddenOrHasHiddenAncestor
            if isVisibleInUI && hasUsableFocusGeometry && !hiddenInHierarchy {
                shouldApplySurfaceFocus = true
                onFocus?()
            } else if isVisibleInUI && (!hasUsableFocusGeometry || hiddenInHierarchy) {
#if DEBUG
                dlog(
                    "focus.firstResponder SUPPRESSED (hidden_or_tiny) surface=\(terminalSurface?.id.uuidString.prefix(5) ?? "nil") " +
                    "frame=\(String(format: "%.1fx%.1f", bounds.width, bounds.height)) hidden=\(hiddenInHierarchy ? 1 : 0)"
                )
#endif
            }
        }
        if result, shouldApplySurfaceFocus, let surface = ensureSurfaceReadyForInput() {
            let now = CACurrentMediaTime()
            let deltaMs = (now - lastScrollEventTime) * 1000
            Self.focusLog("becomeFirstResponder: surface=\(terminalSurface?.id.uuidString ?? "nil") deltaSinceScrollMs=\(String(format: "%.2f", deltaMs))")
#if DEBUG
            dlog("focus.firstResponder surface=\(terminalSurface?.id.uuidString.prefix(5) ?? "nil")")
            if let terminalSurface {
                AppDelegate.shared?.recordJumpUnreadFocusIfExpected(
                    tabId: terminalSurface.tabId,
                    surfaceId: terminalSurface.id
                )
            }
#endif
            if let terminalSurface {
                NotificationCenter.default.post(
                    name: .ghosttyDidBecomeFirstResponderSurface,
                    object: nil,
                    userInfo: [
                        GhosttyNotificationKey.tabId: terminalSurface.tabId,
                        GhosttyNotificationKey.surfaceId: terminalSurface.id,
                    ]
                )
            }
            ghostty_surface_set_focus(surface, true)

            // Ghostty only restarts its vsync display link on display-id changes while focused.
            // During rapid split close / SwiftUI reparenting, the view can reattach to a window
            // and get its display id set *before* it becomes first responder; in that case, the
            // renderer can remain stuck until some later screen/focus transition. Reassert the
            // display id now that we're focused to ensure the renderer is running.
            if let displayID = window?.screen?.displayID, displayID != 0 {
                ghostty_surface_set_display_id(surface, displayID)
            }
        }
        return result
    }

    override func resignFirstResponder() -> Bool {
        let result = super.resignFirstResponder()
        if result {
            desiredFocus = false
        }
        if result, let surface = surface {
            let now = CACurrentMediaTime()
            let deltaMs = (now - lastScrollEventTime) * 1000
            Self.focusLog("resignFirstResponder: surface=\(terminalSurface?.id.uuidString ?? "nil") deltaSinceScrollMs=\(String(format: "%.2f", deltaMs))")
            ghostty_surface_set_focus(surface, false)
        }
        return result
    }

    // For NSTextInputClient - accumulates text during key events
    private var keyTextAccumulator: [String]? = nil
    private var markedText = NSMutableAttributedString()
    private var lastPerformKeyEvent: TimeInterval?

#if DEBUG
    // Test-only accessors for keyTextAccumulator to verify CJK IME composition behavior.
    func setKeyTextAccumulatorForTesting(_ value: [String]?) {
        keyTextAccumulator = value
    }
    var keyTextAccumulatorForTesting: [String]? {
        keyTextAccumulator
    }
    func shouldSuppressShiftSpaceFallbackTextForTesting(event: NSEvent, markedTextBefore: Bool) -> Bool {
        shouldSuppressShiftSpaceFallbackText(event: event, markedTextBefore: markedTextBefore)
    }

    // Test-only IME point override so firstRect behavior can be regression tested.
    private var imePointOverrideForTesting: (x: Double, y: Double, width: Double, height: Double)?

    func setIMEPointForTesting(x: Double, y: Double, width: Double, height: Double) {
        imePointOverrideForTesting = (x, y, width, height)
    }

    func clearIMEPointForTesting() {
        imePointOverrideForTesting = nil
    }
#endif

#if DEBUG
    private func recordKeyLatency(path: String, event: NSEvent) {
        guard Self.keyLatencyProbeEnabled else { return }
        guard event.timestamp > 0 else { return }
        let delayMs = max(0, (CACurrentMediaTime() - event.timestamp) * 1000)
        let delayText = String(format: "%.2f", delayMs)
        dlog("key.latency path=\(path) ms=\(delayText) keyCode=\(event.keyCode) mods=\(event.modifierFlags.rawValue) repeat=\(event.isARepeat ? 1 : 0)")
    }
#endif

    // Prevents NSBeep for unimplemented actions from interpretKeyEvents
    override func doCommand(by selector: Selector) {
        // Intentionally empty - prevents system beep on unhandled key commands
    }

    override func performKeyEquivalent(with event: NSEvent) -> Bool {
        guard event.type == .keyDown else { return false }
        guard let fr = window?.firstResponder as? NSView,
              fr === self || fr.isDescendant(of: self) else { return false }
        guard let surface = ensureSurfaceReadyForInput() else { return false }

        // If the IME is composing (marked text present) and the key has no Cmd
        // modifier, don't intercept — let it flow through to keyDown so the input
        // method can process it normally. Cmd-based shortcuts should still work
        // during composition since Cmd is never part of IME input sequences.
        if hasMarkedText(), !event.modifierFlags.intersection(.deviceIndependentFlagsMask).contains(.command) {
            return false
        }

#if DEBUG
        recordKeyLatency(path: "performKeyEquivalent", event: event)
#endif

#if DEBUG
        cmuxWriteChildExitProbe(
            [
                "probePerformCharsHex": cmuxScalarHex(event.characters),
                "probePerformCharsIgnoringHex": cmuxScalarHex(event.charactersIgnoringModifiers),
                "probePerformKeyCode": String(event.keyCode),
                "probePerformModsRaw": String(event.modifierFlags.rawValue),
                "probePerformSurfaceId": terminalSurface?.id.uuidString ?? "",
            ],
            increments: ["probePerformKeyEquivalentCount": 1]
        )
#endif

        // Check if this event matches a Ghostty keybinding.
        let bindingFlags: ghostty_binding_flags_e? = {
            var keyEvent = ghosttyKeyEvent(for: event, surface: surface)
            let text = event.characters ?? ""
            var flags = ghostty_binding_flags_e(0)
            let isBinding = text.withCString { ptr in
                keyEvent.text = ptr
                return ghostty_surface_key_is_binding(surface, keyEvent, &flags)
            }
            return isBinding ? flags : nil
        }()

        if let bindingFlags {
            let isConsumed = (bindingFlags.rawValue & GHOSTTY_BINDING_FLAGS_CONSUMED.rawValue) != 0
            let isAll = (bindingFlags.rawValue & GHOSTTY_BINDING_FLAGS_ALL.rawValue) != 0
            let isPerformable = (bindingFlags.rawValue & GHOSTTY_BINDING_FLAGS_PERFORMABLE.rawValue) != 0

            // If the binding is consumed and not meant for the menu, allow menu first.
            if isConsumed && !isAll && !isPerformable && keySequence.isEmpty && keyTables.isEmpty {
                if let menu = NSApp.mainMenu, menu.performKeyEquivalent(with: event) {
                    return true
                }
            }

            keyDown(with: event)
            return true
        }

        let equivalent: String
        switch event.charactersIgnoringModifiers {
        case "\r":
            // Pass Ctrl+Return through verbatim (prevent context menu equivalent).
            guard event.modifierFlags.contains(.control) else { return false }
            equivalent = "\r"

        case "/":
            // Treat Ctrl+/ as Ctrl+_ to avoid the system beep.
            guard event.modifierFlags.contains(.control),
                  event.modifierFlags.isDisjoint(with: [.shift, .command, .option]) else {
                return false
            }
            equivalent = "_"

        default:
            // Ignore synthetic events.
            if event.timestamp == 0 {
                return false
            }

            // Match AppKit key-equivalent routing for menu-style shortcuts (Command-modified).
            // Control-only terminal input (e.g. Ctrl+D) should not participate in redispatch;
            // it must flow through the normal keyDown path exactly once.
            if !event.modifierFlags.contains(.command) {
                lastPerformKeyEvent = nil
                return false
            }

            if let lastPerformKeyEvent {
                self.lastPerformKeyEvent = nil
                if lastPerformKeyEvent == event.timestamp {
                    equivalent = event.characters ?? ""
                    break
                }
            }

            lastPerformKeyEvent = event.timestamp
            return false
        }

        let finalEvent = NSEvent.keyEvent(
            with: .keyDown,
            location: event.locationInWindow,
            modifierFlags: event.modifierFlags,
            timestamp: event.timestamp,
            windowNumber: event.windowNumber,
            context: nil,
            characters: equivalent,
            charactersIgnoringModifiers: equivalent,
            isARepeat: event.isARepeat,
            keyCode: event.keyCode
        )

        if let finalEvent {
            keyDown(with: finalEvent)
            return true
        }

        return false
    }

    override func keyDown(with event: NSEvent) {
        guard let surface = ensureSurfaceReadyForInput() else {
            super.keyDown(with: event)
            return
        }
        if handleKeyboardCopyModeIfNeeded(event, surface: surface) {
            keyboardCopyModeConsumedKeyUps.insert(event.keyCode)
            return
        }
#if DEBUG
        recordKeyLatency(path: "keyDown", event: event)
#endif

#if DEBUG
        cmuxWriteChildExitProbe(
            [
                "probeKeyDownCharsHex": cmuxScalarHex(event.characters),
                "probeKeyDownCharsIgnoringHex": cmuxScalarHex(event.charactersIgnoringModifiers),
                "probeKeyDownKeyCode": String(event.keyCode),
                "probeKeyDownModsRaw": String(event.modifierFlags.rawValue),
                "probeKeyDownSurfaceId": terminalSurface?.id.uuidString ?? "",
            ],
            increments: ["probeKeyDownCount": 1]
        )
#endif

        // Fast path for control-modified terminal input (for example Ctrl+D).
        //
        // These keys are terminal control input, not text composition, so we bypass
        // AppKit text interpretation and send a single deterministic Ghostty key event.
        // This avoids intermittent drops after rapid split close/reparent transitions.
        let flags = event.modifierFlags.intersection(.deviceIndependentFlagsMask)
        if flags.contains(.control) && !flags.contains(.command) && !flags.contains(.option) {
            ghostty_surface_set_focus(surface, true)
            var keyEvent = ghostty_input_key_s()
            keyEvent.action = event.isARepeat ? GHOSTTY_ACTION_REPEAT : GHOSTTY_ACTION_PRESS
            keyEvent.keycode = UInt32(event.keyCode)
            keyEvent.mods = modsFromEvent(event)
            keyEvent.consumed_mods = GHOSTTY_MODS_NONE
            keyEvent.composing = false
            keyEvent.unshifted_codepoint = unshiftedCodepointFromEvent(event)

            let text = (event.charactersIgnoringModifiers ?? event.characters ?? "")
            let handled: Bool
            if text.isEmpty {
                keyEvent.text = nil
                handled = ghostty_surface_key(surface, keyEvent)
            } else {
                handled = text.withCString { ptr in
                    keyEvent.text = ptr
                    return ghostty_surface_key(surface, keyEvent)
                }
            }
#if DEBUG
            dlog(
                "key.ctrl path=ghostty surface=\(terminalSurface?.id.uuidString.prefix(5) ?? "nil") " +
                "handled=\(handled ? 1 : 0) keyCode=\(event.keyCode) chars=\(cmuxScalarHex(event.characters)) " +
                "ign=\(cmuxScalarHex(event.charactersIgnoringModifiers)) mods=\(event.modifierFlags.rawValue)"
            )
#endif
            // If Ghostty handled the key (action/encoding), we're done.
            // If not (e.g. `ignore` keybind), fall through to interpretKeyEvents
            // so the IME gets a chance to process this event.
            if handled { return }
        }

        let action = event.isARepeat ? GHOSTTY_ACTION_REPEAT : GHOSTTY_ACTION_PRESS

        // Translate mods to respect Ghostty config (e.g., macos-option-as-alt)
        let translationModsGhostty = ghostty_surface_key_translation_mods(surface, modsFromEvent(event))
        var translationMods = event.modifierFlags
        for flag in [NSEvent.ModifierFlags.shift, .control, .option, .command] {
            let hasFlag: Bool
            switch flag {
            case .shift:
                hasFlag = (translationModsGhostty.rawValue & GHOSTTY_MODS_SHIFT.rawValue) != 0
            case .control:
                hasFlag = (translationModsGhostty.rawValue & GHOSTTY_MODS_CTRL.rawValue) != 0
            case .option:
                hasFlag = (translationModsGhostty.rawValue & GHOSTTY_MODS_ALT.rawValue) != 0
            case .command:
                hasFlag = (translationModsGhostty.rawValue & GHOSTTY_MODS_SUPER.rawValue) != 0
            default:
                hasFlag = translationMods.contains(flag)
            }
            if hasFlag {
                translationMods.insert(flag)
            } else {
                translationMods.remove(flag)
            }
        }

        let translationEvent: NSEvent
        if translationMods == event.modifierFlags {
            translationEvent = event
        } else {
            translationEvent = NSEvent.keyEvent(
                with: event.type,
                location: event.locationInWindow,
                modifierFlags: translationMods,
                timestamp: event.timestamp,
                windowNumber: event.windowNumber,
                context: nil,
                characters: event.characters(byApplyingModifiers: translationMods) ?? "",
                charactersIgnoringModifiers: event.charactersIgnoringModifiers ?? "",
                isARepeat: event.isARepeat,
                keyCode: event.keyCode
            ) ?? event
        }

        // Set up text accumulator for interpretKeyEvents
        keyTextAccumulator = []
        defer { keyTextAccumulator = nil }

        // Track whether we had marked text (IME preedit) before this event,
        // so we can detect when composition ends.
        let markedTextBefore = markedText.length > 0

        // Capture the keyboard layout ID before interpretation so we can
        // detect if an IME changed it (e.g. toggling input methods).
        // We only check when not already in a preedit state.
        let keyboardIdBefore: String? = if (!markedTextBefore) {
            KeyboardLayout.id
        } else {
            nil
        }

        // Let the input system handle the event (for IME, dead keys, etc.)
        interpretKeyEvents([translationEvent])

        // If the keyboard layout changed, an input method grabbed the event.
        // Sync preedit and return without sending the key to Ghostty.
        if !markedTextBefore, let kbBefore = keyboardIdBefore, kbBefore != KeyboardLayout.id {
            syncPreedit(clearIfNeeded: markedTextBefore)
            return
        }

        // Sync the preedit state with Ghostty so it can render the IME
        // composition overlay (e.g. for Korean, Japanese, Chinese input).
        syncPreedit(clearIfNeeded: markedTextBefore)

        // Build the key event
        var keyEvent = ghostty_input_key_s()
        keyEvent.action = action
        keyEvent.keycode = UInt32(event.keyCode)
        keyEvent.mods = modsFromEvent(event)
        // Control and Command never contribute to text translation
        keyEvent.consumed_mods = consumedModsFromFlags(translationMods)
        keyEvent.unshifted_codepoint = unshiftedCodepointFromEvent(event)

        // We're composing if we have preedit (the obvious case). But we're also
        // composing if we don't have preedit and we had marked text before,
        // because this input probably just reset the preedit state. It shouldn't
        // be encoded. Example: Japanese begin composing, then press backspace.
        // This should only cancel the composing state but not actually delete
        // the prior input characters (prior to the composing).
        keyEvent.composing = markedText.length > 0 || markedTextBefore

        // Use accumulated text from insertText (for IME), or compute text for key
        let accumulatedText = keyTextAccumulator ?? []
        if !accumulatedText.isEmpty {
            // Accumulated text comes from insertText (IME composition result).
            // These never have "composing" set to true because these are the
            // result of a composition.
            keyEvent.composing = false
            for text in accumulatedText {
                if shouldSendText(text) {
                    text.withCString { ptr in
                        keyEvent.text = ptr
                        _ = ghostty_surface_key(surface, keyEvent)
                    }
                } else {
                    keyEvent.text = nil
                    _ = ghostty_surface_key(surface, keyEvent)
                }
            }
        } else {
            // Get the appropriate text for this key event
            // For control characters, this returns the unmodified character
            // so Ghostty's KeyEncoder can handle ctrl encoding
            let suppressShiftSpaceFallbackText =
                shouldSuppressShiftSpaceFallbackText(
                    event: translationEvent,
                    markedTextBefore: markedTextBefore
                )
            if let text = textForKeyEvent(translationEvent) {
                if shouldSendText(text), !suppressShiftSpaceFallbackText {
                    text.withCString { ptr in
                        keyEvent.text = ptr
                        _ = ghostty_surface_key(surface, keyEvent)
                    }
                } else {
                    keyEvent.text = nil
                    _ = ghostty_surface_key(surface, keyEvent)
                }
            } else {
                keyEvent.text = nil
                _ = ghostty_surface_key(surface, keyEvent)
            }
        }

        // Rendering is driven by Ghostty's wakeups/renderer.
    }

    @discardableResult
    private func sendGhosttyKey(_ surface: ghostty_surface_t, _ keyEvent: ghostty_input_key_s) -> Bool {
#if DEBUG
        Self.debugGhosttySurfaceKeyEventObserver?(keyEvent)
#endif
        return ghostty_surface_key(surface, keyEvent)
    }

    override func keyUp(with event: NSEvent) {
        guard let surface = ensureSurfaceReadyForInput() else {
            super.keyUp(with: event)
            return
        }

        if keyboardCopyModeConsumedKeyUps.remove(event.keyCode) != nil {
            return
        }

        // Build release events from the same translation path as keyDown so
        // consumers that depend on precise key identity (for example Space
        // hold/release flows) receive consistent metadata.
        var keyEvent = ghosttyKeyEvent(for: event, surface: surface)
        keyEvent.action = GHOSTTY_ACTION_RELEASE
        keyEvent.text = nil
        keyEvent.composing = false
        _ = sendGhosttyKey(surface, keyEvent)
    }

    override func flagsChanged(with event: NSEvent) {
        guard let surface = surface else {
            super.flagsChanged(with: event)
            return
        }

        var keyEvent = ghostty_input_key_s()
        keyEvent.action = GHOSTTY_ACTION_PRESS
        keyEvent.keycode = UInt32(event.keyCode)
        keyEvent.mods = modsFromEvent(event)
        keyEvent.consumed_mods = GHOSTTY_MODS_NONE
        keyEvent.text = nil
        keyEvent.composing = false
        _ = ghostty_surface_key(surface, keyEvent)
    }

    private func modsFromEvent(_ event: NSEvent) -> ghostty_input_mods_e {
        var mods = GHOSTTY_MODS_NONE.rawValue
        if event.modifierFlags.contains(.shift) { mods |= GHOSTTY_MODS_SHIFT.rawValue }
        if event.modifierFlags.contains(.control) { mods |= GHOSTTY_MODS_CTRL.rawValue }
        if event.modifierFlags.contains(.option) { mods |= GHOSTTY_MODS_ALT.rawValue }
        if event.modifierFlags.contains(.command) { mods |= GHOSTTY_MODS_SUPER.rawValue }
        return ghostty_input_mods_e(rawValue: mods)
    }

    /// Consumed mods are modifiers that were used for text translation.
    /// Control and Command never contribute to text translation, so they
    /// should be excluded from consumed_mods.
    private func consumedModsFromFlags(_ flags: NSEvent.ModifierFlags) -> ghostty_input_mods_e {
        var mods = GHOSTTY_MODS_NONE.rawValue
        // Only include Shift and Option as potentially consumed
        // Control and Command are never consumed for text translation
        if flags.contains(.shift) { mods |= GHOSTTY_MODS_SHIFT.rawValue }
        if flags.contains(.option) { mods |= GHOSTTY_MODS_ALT.rawValue }
        return ghostty_input_mods_e(rawValue: mods)
    }

    /// Get the characters for a key event with control character handling.
    /// When control is pressed, we get the character without the control modifier
    /// so Ghostty's KeyEncoder can apply its own control character encoding.
    private func textForKeyEvent(_ event: NSEvent) -> String? {
        guard let chars = event.characters, !chars.isEmpty else { return nil }

        if chars.count == 1, let scalar = chars.unicodeScalars.first {
            let flags = event.modifierFlags.intersection(.deviceIndependentFlagsMask)

            // If we have a single control character, return the character without
            // the control modifier so Ghostty's KeyEncoder can handle it.
            if scalar.value < 0x20 {
                if flags.contains(.control) {
                    return event.characters(byApplyingModifiers: event.modifierFlags.subtracting(.control))
                }

                // Some AppKit key paths can report Shift+` as a bare ESC control
                // character even though the physical key should produce "~".
                if scalar.value == 0x1B,
                   flags == [.shift],
                   event.charactersIgnoringModifiers == "`" {
                    return "~"
                }
            }
            // Private Use Area characters (function keys) should not be sent
            if scalar.value >= 0xF700 && scalar.value <= 0xF8FF {
                return nil
            }
        }

        return chars
    }

    /// Get the unshifted codepoint for the key event
    private func unshiftedCodepointFromEvent(_ event: NSEvent) -> UInt32 {
        if let layoutChars = KeyboardLayout.character(forKeyCode: event.keyCode),
           layoutChars.count == 1,
           let layoutScalar = layoutChars.unicodeScalars.first,
           layoutScalar.value >= 0x20,
           !(layoutScalar.value >= 0xF700 && layoutScalar.value <= 0xF8FF) {
            return layoutScalar.value
        }

        guard let chars = (event.characters(byApplyingModifiers: []) ?? event.charactersIgnoringModifiers ?? event.characters),
              let scalar = chars.unicodeScalars.first else { return 0 }
        return scalar.value
    }

    private func shouldSendText(_ text: String) -> Bool {
        guard let first = text.utf8.first else { return false }
        return first >= 0x20
    }

    /// If AppKit consumed Shift+Space for IME/input-source switching, interpretKeyEvents
    /// can return without insertText and without a detectable layout ID change.
    /// In that case we must not synthesize a literal space fallback.
    private func shouldSuppressShiftSpaceFallbackText(event: NSEvent, markedTextBefore: Bool) -> Bool {
        guard event.keyCode == 49 else { return false }
        let flags = event.modifierFlags.intersection(.deviceIndependentFlagsMask)
        guard flags == [.shift] else { return false }
        guard !markedTextBefore, markedText.length == 0 else { return false }
        return true
    }

    private func ghosttyKeyEvent(for event: NSEvent, surface: ghostty_surface_t) -> ghostty_input_key_s {
        var keyEvent = ghostty_input_key_s()
        keyEvent.action = GHOSTTY_ACTION_PRESS
        keyEvent.keycode = UInt32(event.keyCode)
        keyEvent.mods = modsFromEvent(event)

        // Translate mods to respect Ghostty config (e.g., macos-option-as-alt).
        let translationModsGhostty = ghostty_surface_key_translation_mods(surface, modsFromEvent(event))
        var translationMods = event.modifierFlags
        for flag in [NSEvent.ModifierFlags.shift, .control, .option, .command] {
            let hasFlag: Bool
            switch flag {
            case .shift:
                hasFlag = (translationModsGhostty.rawValue & GHOSTTY_MODS_SHIFT.rawValue) != 0
            case .control:
                hasFlag = (translationModsGhostty.rawValue & GHOSTTY_MODS_CTRL.rawValue) != 0
            case .option:
                hasFlag = (translationModsGhostty.rawValue & GHOSTTY_MODS_ALT.rawValue) != 0
            case .command:
                hasFlag = (translationModsGhostty.rawValue & GHOSTTY_MODS_SUPER.rawValue) != 0
            default:
                hasFlag = translationMods.contains(flag)
            }
            if hasFlag {
                translationMods.insert(flag)
            } else {
                translationMods.remove(flag)
            }
        }

        keyEvent.consumed_mods = consumedModsFromFlags(translationMods)
        keyEvent.text = nil
        keyEvent.composing = false
        keyEvent.unshifted_codepoint = unshiftedCodepointFromEvent(event)
        return keyEvent
    }

    func updateKeySequence(_ action: ghostty_action_key_sequence_s) {
        if action.active {
            keySequence.append(action.trigger)
        } else {
            keySequence.removeAll()
        }
    }

    func updateKeyTable(_ action: ghostty_action_key_table_s) {
        switch action.tag {
        case GHOSTTY_KEY_TABLE_ACTIVATE:
            let namePtr = action.value.activate.name
            let nameLen = Int(action.value.activate.len)
            if let namePtr, nameLen > 0 {
                let data = Data(bytes: namePtr, count: nameLen)
                if let name = String(data: data, encoding: .utf8) {
                    keyTables.append(name)
                }
            }
        case GHOSTTY_KEY_TABLE_DEACTIVATE:
            _ = keyTables.popLast()
        case GHOSTTY_KEY_TABLE_DEACTIVATE_ALL:
            keyTables.removeAll()
        default:
            break
        }
    }

    // MARK: - Mouse Handling

    #if DEBUG
    private func debugModifierString(_ flags: NSEvent.ModifierFlags) -> String {
        [
            flags.contains(.command) ? "cmd" : nil,
            flags.contains(.shift) ? "shift" : nil,
            flags.contains(.control) ? "ctrl" : nil,
            flags.contains(.option) ? "opt" : nil,
        ].compactMap { $0 }.joined(separator: "+")
    }
    #endif

    override func mouseDown(with event: NSEvent) {
        #if DEBUG
        let debugPoint = convert(event.locationInWindow, from: nil)
        dlog("terminal.mouseDown surface=\(terminalSurface?.id.uuidString.prefix(5) ?? "nil") mods=[\(debugModifierString(event.modifierFlags))] clickCount=\(event.clickCount) point=(\(String(format: "%.0f", debugPoint.x)),\(String(format: "%.0f", debugPoint.y)))")
        #endif
        window?.makeFirstResponder(self)
        guard let surface = surface else { return }
        let point = convert(event.locationInWindow, from: nil)
        ghostty_surface_mouse_pos(surface, point.x, bounds.height - point.y, modsFromEvent(event))
        _ = ghostty_surface_mouse_button(surface, GHOSTTY_MOUSE_PRESS, GHOSTTY_MOUSE_LEFT, modsFromEvent(event))
    }

    override func mouseUp(with event: NSEvent) {
        #if DEBUG
        dlog("terminal.mouseUp surface=\(terminalSurface?.id.uuidString.prefix(5) ?? "nil") mods=[\(debugModifierString(event.modifierFlags))]")
        #endif
        guard let surface = surface else { return }
        _ = ghostty_surface_mouse_button(surface, GHOSTTY_MOUSE_RELEASE, GHOSTTY_MOUSE_LEFT, modsFromEvent(event))
    }

    override func rightMouseDown(with event: NSEvent) {
        guard let surface = surface else { return }
        if !ghostty_surface_mouse_captured(surface) {
            super.rightMouseDown(with: event)
            return
        }

        window?.makeFirstResponder(self)
        let point = convert(event.locationInWindow, from: nil)
        ghostty_surface_mouse_pos(surface, point.x, bounds.height - point.y, modsFromEvent(event))
        _ = ghostty_surface_mouse_button(surface, GHOSTTY_MOUSE_PRESS, GHOSTTY_MOUSE_RIGHT, modsFromEvent(event))
    }

    override func rightMouseUp(with event: NSEvent) {
        guard let surface = surface else { return }
        if !ghostty_surface_mouse_captured(surface) {
            super.rightMouseUp(with: event)
            return
        }

        _ = ghostty_surface_mouse_button(surface, GHOSTTY_MOUSE_RELEASE, GHOSTTY_MOUSE_RIGHT, modsFromEvent(event))
    }

    override func otherMouseDown(with event: NSEvent) {
        guard event.buttonNumber == 2 else {
            super.otherMouseDown(with: event)
            return
        }
        window?.makeFirstResponder(self)
        guard let surface = surface else { return }
        let point = convert(event.locationInWindow, from: nil)
        ghostty_surface_mouse_pos(surface, point.x, bounds.height - point.y, modsFromEvent(event))
        _ = ghostty_surface_mouse_button(surface, GHOSTTY_MOUSE_PRESS, GHOSTTY_MOUSE_MIDDLE, modsFromEvent(event))
    }

    override func otherMouseUp(with event: NSEvent) {
        guard event.buttonNumber == 2 else {
            super.otherMouseUp(with: event)
            return
        }
        guard let surface = surface else { return }
        _ = ghostty_surface_mouse_button(surface, GHOSTTY_MOUSE_RELEASE, GHOSTTY_MOUSE_MIDDLE, modsFromEvent(event))
    }

    override func menu(for event: NSEvent) -> NSMenu? {
        guard let surface = surface else { return nil }
        if ghostty_surface_mouse_captured(surface) {
            return nil
        }

        window?.makeFirstResponder(self)
        let point = convert(event.locationInWindow, from: nil)
        ghostty_surface_mouse_pos(surface, point.x, bounds.height - point.y, modsFromEvent(event))
        _ = ghostty_surface_mouse_button(surface, GHOSTTY_MOUSE_PRESS, GHOSTTY_MOUSE_RIGHT, modsFromEvent(event))

        let menu = NSMenu()
        if onTriggerFlash != nil {
            let flashItem = menu.addItem(withTitle: "Trigger Flash", action: #selector(triggerFlash(_:)), keyEquivalent: "")
            flashItem.target = self
            menu.addItem(.separator())
        }
        if ghostty_surface_has_selection(surface) {
            let item = menu.addItem(withTitle: "Copy", action: #selector(copy(_:)), keyEquivalent: "")
            item.target = self
        }
        let pasteItem = menu.addItem(withTitle: "Paste", action: #selector(paste(_:)), keyEquivalent: "")
        pasteItem.target = self
        menu.addItem(.separator())
        let splitHorizontallyItem = menu.addItem(
            withTitle: "Split Horizontally",
            action: #selector(splitHorizontally(_:)),
            keyEquivalent: "d"
        )
        splitHorizontallyItem.target = self
        splitHorizontallyItem.keyEquivalentModifierMask = [.command, .shift]
        splitHorizontallyItem.image = NSImage(
            systemSymbolName: "rectangle.bottomhalf.inset.filled",
            accessibilityDescription: nil
        )

        let splitVerticallyItem = menu.addItem(
            withTitle: "Split Vertically",
            action: #selector(splitVertically(_:)),
            keyEquivalent: "d"
        )
        splitVerticallyItem.target = self
        splitVerticallyItem.keyEquivalentModifierMask = [.command]
        splitVerticallyItem.image = NSImage(
            systemSymbolName: "rectangle.righthalf.inset.filled",
            accessibilityDescription: nil
        )
        return menu
    }

    private func canSplitCurrentSurface() -> Bool {
        guard let tabId,
              let surfaceId = terminalSurface?.id,
              let app = AppDelegate.shared,
              let manager = app.tabManagerFor(tabId: tabId) ?? app.tabManager,
              let workspace = manager.tabs.first(where: { $0.id == tabId }) else {
            return false
        }
        return workspace.panels[surfaceId] != nil
    }

    @objc private func splitHorizontally(_ sender: Any?) {
        _ = splitCurrentSurface(direction: .down)
    }

    @objc private func splitVertically(_ sender: Any?) {
        _ = splitCurrentSurface(direction: .right)
    }

    @discardableResult
    private func splitCurrentSurface(direction: SplitDirection) -> Bool {
        guard let tabId,
              let surfaceId = terminalSurface?.id,
              let app = AppDelegate.shared,
              let manager = app.tabManagerFor(tabId: tabId) ?? app.tabManager else {
            return false
        }
        return manager.newSplit(tabId: tabId, surfaceId: surfaceId, direction: direction) != nil
    }

    @objc private func triggerFlash(_ sender: Any?) {
        onTriggerFlash?()
    }

    override func mouseMoved(with event: NSEvent) {
        maybeRequestFirstResponderForMouseFocus()
        guard let surface = surface else { return }
        let point = convert(event.locationInWindow, from: nil)
        ghostty_surface_mouse_pos(surface, point.x, bounds.height - point.y, modsFromEvent(event))
    }

    override func mouseEntered(with event: NSEvent) {
        super.mouseEntered(with: event)
        maybeRequestFirstResponderForMouseFocus()
        guard let surface = surface else { return }
        let point = convert(event.locationInWindow, from: nil)
        ghostty_surface_mouse_pos(surface, point.x, bounds.height - point.y, modsFromEvent(event))
    }

    private func maybeRequestFirstResponderForMouseFocus() {
        guard let window else { return }
        let alreadyFirstResponder = window.firstResponder === self
        let shouldRequest = Self.shouldRequestFirstResponderForMouseFocus(
            focusFollowsMouseEnabled: GhosttyApp.shared.focusFollowsMouseEnabled(),
            pressedMouseButtons: NSEvent.pressedMouseButtons,
            appIsActive: NSApp.isActive,
            windowIsKey: window.isKeyWindow,
            alreadyFirstResponder: alreadyFirstResponder,
            visibleInUI: isVisibleInUI,
            hasUsableGeometry: hasUsableFocusGeometry,
            hiddenInHierarchy: isHiddenOrHasHiddenAncestor
        )
        guard shouldRequest else { return }
        window.makeFirstResponder(self)
    }

    override func mouseExited(with event: NSEvent) {
        guard let surface = surface else { return }
        if NSEvent.pressedMouseButtons != 0 {
            return
        }
        ghostty_surface_mouse_pos(surface, -1, -1, modsFromEvent(event))
    }

    override func mouseDragged(with event: NSEvent) {
        guard let surface = surface else { return }
        let point = convert(event.locationInWindow, from: nil)
        ghostty_surface_mouse_pos(surface, point.x, bounds.height - point.y, modsFromEvent(event))
    }

    override func scrollWheel(with event: NSEvent) {
        guard let surface = surface else { return }
        lastScrollEventTime = CACurrentMediaTime()
        Self.focusLog("scrollWheel: surface=\(terminalSurface?.id.uuidString ?? "nil") firstResponder=\(String(describing: window?.firstResponder))")
        var x = event.scrollingDeltaX
        var y = event.scrollingDeltaY
        let precision = event.hasPreciseScrollingDeltas
        if precision {
            x *= 2
            y *= 2
        }

        var mods: Int32 = 0
        if precision {
            mods |= 0b0000_0001
        }

        let momentum: Int32
        switch event.momentumPhase {
        case .began:
            momentum = Int32(GHOSTTY_MOUSE_MOMENTUM_BEGAN.rawValue)
        case .stationary:
            momentum = Int32(GHOSTTY_MOUSE_MOMENTUM_STATIONARY.rawValue)
        case .changed:
            momentum = Int32(GHOSTTY_MOUSE_MOMENTUM_CHANGED.rawValue)
        case .ended:
            momentum = Int32(GHOSTTY_MOUSE_MOMENTUM_ENDED.rawValue)
        case .cancelled:
            momentum = Int32(GHOSTTY_MOUSE_MOMENTUM_CANCELLED.rawValue)
        case .mayBegin:
            momentum = Int32(GHOSTTY_MOUSE_MOMENTUM_MAY_BEGIN.rawValue)
        default:
            momentum = Int32(GHOSTTY_MOUSE_MOMENTUM_NONE.rawValue)
        }
        mods |= momentum << 1

        // Track scroll state for lag detection
        let hasMomentum = event.momentumPhase != [] && event.momentumPhase != .mayBegin
        let momentumEnded = event.momentumPhase == .ended || event.momentumPhase == .cancelled
        GhosttyApp.shared.markScrollActivity(hasMomentum: hasMomentum, momentumEnded: momentumEnded)

        ghostty_surface_mouse_scroll(
            surface,
            x,
            y,
            ghostty_input_scroll_mods_t(mods)
        )
    }

    deinit {
        // Surface lifecycle is managed by TerminalSurface, not the view
#if DEBUG
        dlog(
            "surface.view.deinit view=\(Unmanaged.passUnretained(self).toOpaque()) " +
            "surface=\(terminalSurface?.id.uuidString.prefix(5) ?? "nil") " +
            "inWindow=\(window != nil ? 1 : 0) hasSuperview=\(superview != nil ? 1 : 0)"
        )
#endif
        if let eventMonitor {
            NSEvent.removeMonitor(eventMonitor)
        }
        if let windowObserver {
            NotificationCenter.default.removeObserver(windowObserver)
        }
        terminalSurface = nil
    }

    override func updateTrackingAreas() {
        super.updateTrackingAreas()

        if let trackingArea {
            removeTrackingArea(trackingArea)
        }

        trackingArea = NSTrackingArea(
            rect: bounds,
            options: [
                .mouseEnteredAndExited,
                .mouseMoved,
                .inVisibleRect,
                .activeAlways,
            ],
            owner: self,
            userInfo: nil
        )

        if let trackingArea {
            addTrackingArea(trackingArea)
        }
    }

    private func windowDidChangeScreen(_ notification: Notification) {
        guard let window else { return }
        guard let object = notification.object as? NSWindow, window == object else { return }
        guard let screen = window.screen else { return }
        guard let surface = terminalSurface?.surface else { return }

        if let displayID = screen.displayID,
           displayID != 0 {
            ghostty_surface_set_display_id(surface, displayID)
        }

        DispatchQueue.main.async { [weak self] in
            self?.viewDidChangeBackingProperties()
        }
    }

    fileprivate static func escapeDropForShell(_ value: String) -> String {
        var result = value
        for char in shellEscapeCharacters {
            result = result.replacingOccurrences(of: String(char), with: "\\\(char)")
        }
        return result
    }

    private func droppedContent(from pasteboard: NSPasteboard) -> String? {
        if let urls = pasteboard.readObjects(forClasses: [NSURL.self]) as? [URL], !urls.isEmpty {
            return urls
                .map { Self.escapeDropForShell($0.path) }
                .joined(separator: " ")
        }

        if let rawURL = pasteboard.string(forType: .URL), !rawURL.isEmpty {
            return Self.escapeDropForShell(rawURL)
        }

        if let str = pasteboard.string(forType: .string), !str.isEmpty {
            return str
        }

        return nil
    }

    @discardableResult
    fileprivate func insertDroppedPasteboard(_ pasteboard: NSPasteboard) -> Bool {
        guard let content = droppedContent(from: pasteboard) else { return false }
        // Use the text/paste path (ghostty_surface_text) instead of the key event
        // path (ghostty_surface_key) so bracketed paste mode is triggered and the
        // insertion is instant, matching upstream Ghostty behaviour.
        terminalSurface?.sendText(content)
        return true
    }

#if DEBUG
    @discardableResult
    fileprivate func debugSimulateFileDrop(paths: [String]) -> Bool {
        guard !paths.isEmpty else { return false }
        let urls = paths.map { URL(fileURLWithPath: $0) as NSURL }
        let pbName = NSPasteboard.Name("cmux.debug.drop.\(UUID().uuidString)")
        let pasteboard = NSPasteboard(name: pbName)
        pasteboard.clearContents()
        pasteboard.writeObjects(urls)
        return insertDroppedPasteboard(pasteboard)
    }

    fileprivate func debugRegisteredDropTypes() -> [String] {
        (registeredDraggedTypes ?? []).map(\.rawValue)
    }
#endif

    // MARK: NSDraggingDestination

    override func draggingEntered(_ sender: any NSDraggingInfo) -> NSDragOperation {
        #if DEBUG
        let types = sender.draggingPasteboard.types ?? []
        dlog("terminal.draggingEntered surface=\(terminalSurface?.id.uuidString.prefix(5) ?? "nil") types=\(types.map(\.rawValue))")
        #endif
        guard let types = sender.draggingPasteboard.types else { return [] }
        if Set(types).isDisjoint(with: Self.dropTypes) {
            return []
        }
        return .copy
    }

    override func draggingUpdated(_ sender: any NSDraggingInfo) -> NSDragOperation {
        #if DEBUG
        let types = sender.draggingPasteboard.types ?? []
        dlog("terminal.draggingUpdated surface=\(terminalSurface?.id.uuidString.prefix(5) ?? "nil") types=\(types.map(\.rawValue))")
        #endif
        guard let types = sender.draggingPasteboard.types else { return [] }
        if Set(types).isDisjoint(with: Self.dropTypes) {
            return []
        }
        return .copy
    }

    override func performDragOperation(_ sender: any NSDraggingInfo) -> Bool {
        #if DEBUG
        dlog("terminal.fileDrop surface=\(terminalSurface?.id.uuidString.prefix(5) ?? "nil")")
        #endif
        return insertDroppedPasteboard(sender.draggingPasteboard)
    }
}

private extension NSScreen {
    var displayID: UInt32? {
        let key = NSDeviceDescriptionKey("NSScreenNumber")
        if let v = deviceDescription[key] as? UInt32 { return v }
        if let v = deviceDescription[key] as? Int { return UInt32(v) }
        if let v = deviceDescription[key] as? NSNumber { return v.uint32Value }
        return nil
    }
}

struct GhosttyScrollbar {
    let total: UInt64
    let offset: UInt64
    let len: UInt64

    init(c: ghostty_action_scrollbar_s) {
        total = c.total
        offset = c.offset
        len = c.len
    }
}

enum GhosttyNotificationKey {
    static let scrollbar = "ghostty.scrollbar"
    static let cellSize = "ghostty.cellSize"
    static let tabId = "ghostty.tabId"
    static let surfaceId = "ghostty.surfaceId"
    static let title = "ghostty.title"
    static let backgroundColor = "ghostty.backgroundColor"
    static let backgroundOpacity = "ghostty.backgroundOpacity"
    static let backgroundEventId = "ghostty.backgroundEventId"
    static let backgroundSource = "ghostty.backgroundSource"
}

extension Notification.Name {
    static let ghosttyDidUpdateScrollbar = Notification.Name("ghosttyDidUpdateScrollbar")
    static let ghosttyDidUpdateCellSize = Notification.Name("ghosttyDidUpdateCellSize")
    static let ghosttySearchFocus = Notification.Name("ghosttySearchFocus")
    static let ghosttyConfigDidReload = Notification.Name("ghosttyConfigDidReload")
    static let ghosttyDefaultBackgroundDidChange = Notification.Name("ghosttyDefaultBackgroundDidChange")
}

// MARK: - Scroll View Wrapper (Ghostty-style scrollbar)

private final class GhosttyScrollView: NSScrollView {
    weak var surfaceView: GhosttyNSView?

    // Keep keyboard routing on the terminal surface; this wrapper is viewport plumbing.
    override var acceptsFirstResponder: Bool { false }

    override func scrollWheel(with event: NSEvent) {
        guard let surfaceView else {
            super.scrollWheel(with: event)
            return
        }

        // Route wheel gestures to the terminal surface so Ghostty handles scrollback.
        // Letting NSScrollView consume these events moves the wrapper viewport itself,
        // which causes pane-content drift instead of terminal scrollback movement.
        GhosttyNSView.focusLog("GhosttyScrollView.scrollWheel: surface scroll")
        if window?.firstResponder !== surfaceView {
            window?.makeFirstResponder(surfaceView)
        }
        surfaceView.scrollWheel(with: event)
    }
}

private final class GhosttyFlashOverlayView: NSView {
    override var acceptsFirstResponder: Bool { false }

    override func hitTest(_ point: NSPoint) -> NSView? {
        nil
    }
}

private final class GhosttyPassthroughVisualEffectView: NSVisualEffectView {
    override var acceptsFirstResponder: Bool { false }

    override func hitTest(_ point: NSPoint) -> NSView? {
        nil
    }
}

final class GhosttySurfaceScrollView: NSView {
    private let backgroundView: NSView
    private let scrollView: GhosttyScrollView
    private let documentView: NSView
    private let surfaceView: GhosttyNSView
    private let inactiveOverlayView: GhosttyFlashOverlayView
    private let dropZoneOverlayView: GhosttyFlashOverlayView
    private let notificationRingOverlayView: GhosttyFlashOverlayView
    private let notificationRingLayer: CAShapeLayer
    private let flashOverlayView: GhosttyFlashOverlayView
    private let flashLayer: CAShapeLayer
    private let keyboardCopyModeBadgeView: GhosttyPassthroughVisualEffectView
    private let keyboardCopyModeBadgeLabel: NSTextField
    private var searchOverlayHostingView: NSHostingView<SurfaceSearchOverlay>?
    private var observers: [NSObjectProtocol] = []
	    private var windowObservers: [NSObjectProtocol] = []
	    private var isLiveScrolling = false
    private var lastSentRow: Int?
    private var isActive = true
    private var activeDropZone: DropZone?
    private var pendingDropZone: DropZone?
    private var dropZoneOverlayAnimationGeneration: UInt64 = 0
    // Intentionally no focus retry loops: rely on AppKit first-responder and bonsplit selection.

    private static func panelBackgroundFillColor(for terminalBackgroundColor: NSColor) -> NSColor {
        // The Ghostty renderer already draws translucent terminal backgrounds. If we paint an
        // additional translucent layer here, alpha stacks and appears effectively opaque.
        terminalBackgroundColor.alphaComponent < 0.999 ? .clear : terminalBackgroundColor
    }

#if DEBUG
    private var lastDropZoneOverlayLogSignature: String?
	    private static var flashCounts: [UUID: Int] = [:]
	    private static var drawCounts: [UUID: Int] = [:]
	    private static var lastDrawTimes: [UUID: CFTimeInterval] = [:]
	    private static var presentCounts: [UUID: Int] = [:]
    private static var dropOverlayShowCounts: [UUID: Int] = [:]
    private static var lastPresentTimes: [UUID: CFTimeInterval] = [:]
    private static var lastContentsKeys: [UUID: String] = [:]

    static func flashCount(for surfaceId: UUID) -> Int {
        flashCounts[surfaceId, default: 0]
    }

    static func resetFlashCounts() {
        flashCounts.removeAll()
    }

    private static func recordFlash(for surfaceId: UUID) {
        flashCounts[surfaceId, default: 0] += 1
    }

    static func drawStats(for surfaceId: UUID) -> (count: Int, last: CFTimeInterval) {
        (drawCounts[surfaceId, default: 0], lastDrawTimes[surfaceId, default: 0])
    }

    static func resetDrawStats() {
        drawCounts.removeAll()
        lastDrawTimes.removeAll()
    }

    static func recordSurfaceDraw(_ surfaceId: UUID) {
        drawCounts[surfaceId, default: 0] += 1
        lastDrawTimes[surfaceId] = CACurrentMediaTime()
    }

    private static func contentsKey(for layer: CALayer?) -> String {
        guard let modelLayer = layer else { return "nil" }
        // Prefer the presentation layer to better reflect what the user sees on screen.
        let layer = modelLayer.presentation() ?? modelLayer
        guard let contents = layer.contents else { return "nil" }
        // Prefer pointer identity for object/CFType contents.
        if let obj = contents as AnyObject? {
            let ptr = Unmanaged.passUnretained(obj).toOpaque()
            var key = "0x" + String(UInt(bitPattern: ptr), radix: 16)

            // For IOSurface-backed terminal layers, the IOSurface object can remain stable while
            // its contents change. Include the IOSurface seed so "new frame rendered" is visible
            // to debug/test tooling even when the pointer identity doesn't change.
            let cf = contents as CFTypeRef
            if CFGetTypeID(cf) == IOSurfaceGetTypeID() {
                let surfaceRef = (contents as! IOSurfaceRef)
                let seed = IOSurfaceGetSeed(surfaceRef)
                key += ":seed=\(seed)"
            }

            return key
        }
        return String(describing: contents)
    }

    private static func updatePresentStats(surfaceId: UUID, layer: CALayer?) -> (count: Int, last: CFTimeInterval, key: String) {
        let key = contentsKey(for: layer)
        if lastContentsKeys[surfaceId] != key {
            presentCounts[surfaceId, default: 0] += 1
            lastPresentTimes[surfaceId] = CACurrentMediaTime()
            lastContentsKeys[surfaceId] = key
        }
        return (presentCounts[surfaceId, default: 0], lastPresentTimes[surfaceId, default: 0], key)
    }

    private func recordDropOverlayShowAnimation() {
        guard let surfaceId = surfaceView.terminalSurface?.id else { return }
        Self.dropOverlayShowCounts[surfaceId, default: 0] += 1
    }

    func debugProbeDropOverlayAnimation(useDeferredPath: Bool) -> (before: Int, after: Int, bounds: CGSize) {
        guard let surfaceId = surfaceView.terminalSurface?.id else {
            return (0, 0, bounds.size)
        }

        let before = Self.dropOverlayShowCounts[surfaceId, default: 0]

        // Reset to a hidden baseline so each probe exercises an initial-show transition.
        dropZoneOverlayAnimationGeneration &+= 1
        activeDropZone = nil
        pendingDropZone = nil
        dropZoneOverlayView.layer?.removeAllAnimations()
        dropZoneOverlayView.isHidden = true
        dropZoneOverlayView.alphaValue = 1

        if useDeferredPath {
            pendingDropZone = .left
            synchronizeGeometryAndContent()
        } else {
            setDropZoneOverlay(zone: .left)
        }

        let after = Self.dropOverlayShowCounts[surfaceId, default: 0]
        setDropZoneOverlay(zone: nil)
        return (before, after, bounds.size)
    }

    var debugSurfaceId: UUID? {
        surfaceView.terminalSurface?.id
    }
#endif

    func portalBindingGuardState() -> (surfaceId: UUID?, generation: UInt64?, state: String) {
        guard let terminalSurface = surfaceView.terminalSurface else {
            return (surfaceId: nil, generation: nil, state: "missingSurface")
        }
        return (
            surfaceId: terminalSurface.id,
            generation: terminalSurface.portalBindingGeneration(),
            state: terminalSurface.portalBindingStateLabel()
        )
    }

    func canAcceptPortalBinding(expectedSurfaceId: UUID?, expectedGeneration: UInt64?) -> Bool {
        guard let terminalSurface = surfaceView.terminalSurface else { return false }
        return terminalSurface.canAcceptPortalBinding(
            expectedSurfaceId: expectedSurfaceId,
            expectedGeneration: expectedGeneration
        )
    }

    init(surfaceView: GhosttyNSView) {
        self.surfaceView = surfaceView
        backgroundView = NSView(frame: .zero)
        scrollView = GhosttyScrollView()
        inactiveOverlayView = GhosttyFlashOverlayView(frame: .zero)
        dropZoneOverlayView = GhosttyFlashOverlayView(frame: .zero)
        notificationRingOverlayView = GhosttyFlashOverlayView(frame: .zero)
        notificationRingLayer = CAShapeLayer()
        flashOverlayView = GhosttyFlashOverlayView(frame: .zero)
        flashLayer = CAShapeLayer()
        keyboardCopyModeBadgeView = GhosttyPassthroughVisualEffectView(frame: .zero)
        keyboardCopyModeBadgeLabel = NSTextField(labelWithString: "VI MODE")
        scrollView.hasVerticalScroller = true
        scrollView.hasHorizontalScroller = false
        scrollView.autohidesScrollers = false
        scrollView.usesPredominantAxisScrolling = true
        scrollView.scrollerStyle = .overlay
        scrollView.drawsBackground = false
        scrollView.backgroundColor = .clear
        scrollView.contentView.clipsToBounds = true
        scrollView.contentView.drawsBackground = false
        scrollView.contentView.backgroundColor = .clear
        scrollView.surfaceView = surfaceView

        documentView = NSView(frame: .zero)
        scrollView.documentView = documentView
        documentView.addSubview(surfaceView)

        super.init(frame: .zero)
        wantsLayer = true
        layer?.masksToBounds = true

        backgroundView.wantsLayer = true
        let initialTerminalBackground = GhosttyApp.shared.defaultBackgroundColor
            .withAlphaComponent(GhosttyApp.shared.defaultBackgroundOpacity)
        let initialPanelFill = Self.panelBackgroundFillColor(for: initialTerminalBackground)
        backgroundView.layer?.backgroundColor = initialPanelFill.cgColor
        backgroundView.layer?.isOpaque = initialPanelFill.alphaComponent >= 1.0
        addSubview(backgroundView)
        addSubview(scrollView)
        inactiveOverlayView.wantsLayer = true
        inactiveOverlayView.layer?.backgroundColor = NSColor.clear.cgColor
        inactiveOverlayView.isHidden = true
        addSubview(inactiveOverlayView)
        dropZoneOverlayView.wantsLayer = true
        dropZoneOverlayView.layer?.backgroundColor = cmuxAccentNSColor().withAlphaComponent(0.25).cgColor
        dropZoneOverlayView.layer?.borderColor = cmuxAccentNSColor().cgColor
        dropZoneOverlayView.layer?.borderWidth = 2
        dropZoneOverlayView.layer?.cornerRadius = 8
        dropZoneOverlayView.isHidden = true
        addSubview(dropZoneOverlayView)
        notificationRingOverlayView.wantsLayer = true
        notificationRingOverlayView.layer?.backgroundColor = NSColor.clear.cgColor
        notificationRingOverlayView.layer?.masksToBounds = false
        notificationRingOverlayView.autoresizingMask = [.width, .height]
        notificationRingLayer.fillColor = NSColor.clear.cgColor
        notificationRingLayer.strokeColor = NSColor.systemBlue.cgColor
        notificationRingLayer.lineWidth = 2.5
        notificationRingLayer.lineJoin = .round
        notificationRingLayer.lineCap = .round
        notificationRingLayer.shadowColor = NSColor.systemBlue.cgColor
        notificationRingLayer.shadowOpacity = 0.35
        notificationRingLayer.shadowRadius = 3
        notificationRingLayer.shadowOffset = .zero
        notificationRingLayer.opacity = 0
        notificationRingOverlayView.layer?.addSublayer(notificationRingLayer)
        notificationRingOverlayView.isHidden = true
        addSubview(notificationRingOverlayView)
        flashOverlayView.wantsLayer = true
        flashOverlayView.layer?.backgroundColor = NSColor.clear.cgColor
        flashOverlayView.layer?.masksToBounds = false
        flashOverlayView.autoresizingMask = [.width, .height]
        flashLayer.fillColor = NSColor.clear.cgColor
        flashLayer.strokeColor = NSColor.systemBlue.cgColor
        flashLayer.lineWidth = 3
        flashLayer.lineJoin = .round
        flashLayer.lineCap = .round
        flashLayer.shadowColor = NSColor.systemBlue.cgColor
        flashLayer.shadowOpacity = 0.6
        flashLayer.shadowRadius = 6
        flashLayer.shadowOffset = .zero
        flashLayer.opacity = 0
        flashOverlayView.layer?.addSublayer(flashLayer)
        addSubview(flashOverlayView)
        keyboardCopyModeBadgeView.translatesAutoresizingMaskIntoConstraints = false
        keyboardCopyModeBadgeView.wantsLayer = true
        keyboardCopyModeBadgeView.material = .hudWindow
        keyboardCopyModeBadgeView.blendingMode = .withinWindow
        keyboardCopyModeBadgeView.state = .active
        keyboardCopyModeBadgeView.layer?.cornerRadius = 7
        keyboardCopyModeBadgeView.layer?.masksToBounds = true
        keyboardCopyModeBadgeView.layer?.borderWidth = 1
        keyboardCopyModeBadgeView.layer?.borderColor = cmuxAccentNSColor().withAlphaComponent(0.45).cgColor
        keyboardCopyModeBadgeView.alphaValue = 0.97
        keyboardCopyModeBadgeLabel.translatesAutoresizingMaskIntoConstraints = false
        keyboardCopyModeBadgeLabel.textColor = NSColor.labelColor
        keyboardCopyModeBadgeLabel.lineBreakMode = .byClipping
        keyboardCopyModeBadgeView.addSubview(keyboardCopyModeBadgeLabel)
        NSLayoutConstraint.activate([
            keyboardCopyModeBadgeLabel.leadingAnchor.constraint(equalTo: keyboardCopyModeBadgeView.leadingAnchor, constant: 8),
            keyboardCopyModeBadgeLabel.trailingAnchor.constraint(equalTo: keyboardCopyModeBadgeView.trailingAnchor, constant: -8),
            keyboardCopyModeBadgeLabel.topAnchor.constraint(equalTo: keyboardCopyModeBadgeView.topAnchor, constant: 4),
            keyboardCopyModeBadgeLabel.bottomAnchor.constraint(equalTo: keyboardCopyModeBadgeView.bottomAnchor, constant: -4),
        ])
        keyboardCopyModeBadgeView.isHidden = true
        addSubview(keyboardCopyModeBadgeView)
        NSLayoutConstraint.activate([
            keyboardCopyModeBadgeView.topAnchor.constraint(equalTo: topAnchor, constant: 8),
            keyboardCopyModeBadgeView.trailingAnchor.constraint(equalTo: trailingAnchor, constant: -8),
        ])

        scrollView.contentView.postsBoundsChangedNotifications = true
        observers.append(NotificationCenter.default.addObserver(
            forName: NSView.boundsDidChangeNotification,
            object: scrollView.contentView,
            queue: .main
        ) { [weak self] _ in
            self?.handleScrollChange()
        })

        observers.append(NotificationCenter.default.addObserver(
            forName: NSScrollView.willStartLiveScrollNotification,
            object: scrollView,
            queue: .main
        ) { [weak self] _ in
            self?.isLiveScrolling = true
        })

        observers.append(NotificationCenter.default.addObserver(
            forName: NSScrollView.didEndLiveScrollNotification,
            object: scrollView,
            queue: .main
        ) { [weak self] _ in
            self?.isLiveScrolling = false
        })

        observers.append(NotificationCenter.default.addObserver(
            forName: NSScrollView.didLiveScrollNotification,
            object: scrollView,
            queue: .main
        ) { [weak self] _ in
            self?.handleLiveScroll()
        })

        observers.append(NotificationCenter.default.addObserver(
            forName: .ghosttyDidUpdateScrollbar,
            object: surfaceView,
            queue: .main
        ) { [weak self] notification in
            self?.handleScrollbarUpdate(notification)
        })

        observers.append(NotificationCenter.default.addObserver(
            forName: .ghosttyDidUpdateCellSize,
            object: surfaceView,
            queue: .main
        ) { [weak self] _ in
            self?.synchronizeScrollView()
        })
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) not implemented")
    }

    deinit {
#if DEBUG
        dlog(
            "surface.hosted.deinit surface=\(debugSurfaceId?.uuidString.prefix(5) ?? "nil") " +
            "inWindow=\(window != nil ? 1 : 0) hasSuperview=\(superview != nil ? 1 : 0) " +
            "hidden=\(isHidden ? 1 : 0) frame=\(String(format: "%.1fx%.1f", frame.width, frame.height))"
        )
#endif
        observers.forEach { NotificationCenter.default.removeObserver($0) }
        windowObservers.forEach { NotificationCenter.default.removeObserver($0) }
        cancelFocusRequest()
    }

    override var safeAreaInsets: NSEdgeInsets { NSEdgeInsetsZero }

    // Avoid stealing focus on scroll; focus is managed explicitly by the surface view.
    override var acceptsFirstResponder: Bool { false }

    override func layout() {
        super.layout()
        synchronizeGeometryAndContent()
    }

    /// Reconcile AppKit geometry with ghostty surface geometry synchronously.
    /// Used after split topology mutations (close/split) to prevent a stale one-frame
    /// IOSurface size from being presented after pane expansion.
    func reconcileGeometryNow() {
        guard Thread.isMainThread else {
            DispatchQueue.main.async { [weak self] in
                self?.reconcileGeometryNow()
            }
            return
        }

        synchronizeGeometryAndContent()
    }

    /// Request an immediate terminal redraw after geometry updates so stale IOSurface
    /// contents do not remain stretched during live resize churn.
    func refreshSurfaceNow() {
        surfaceView.terminalSurface?.forceRefresh()
    }

    private func synchronizeGeometryAndContent() {
        CATransaction.begin()
        CATransaction.setDisableActions(true)
        defer { CATransaction.commit() }

        backgroundView.frame = bounds
        scrollView.frame = bounds
        let targetSize = scrollView.bounds.size
        surfaceView.frame.size = targetSize
        documentView.frame.size.width = scrollView.bounds.width
        inactiveOverlayView.frame = bounds
        if let zone = activeDropZone {
            dropZoneOverlayView.frame = dropZoneOverlayFrame(for: zone, in: bounds.size)
        }
        if let pending = pendingDropZone,
           bounds.width > 2,
           bounds.height > 2 {
            pendingDropZone = nil
#if DEBUG
            let frame = dropZoneOverlayFrame(for: pending, in: bounds.size)
            logDropZoneOverlay(event: "flushPending", zone: pending, frame: frame)
#endif
            // Reuse the normal show/update path so deferred overlays get the
            // same initial animation as direct drop-zone activation.
            setDropZoneOverlay(zone: pending)
        }
        notificationRingOverlayView.frame = bounds
        flashOverlayView.frame = bounds
        updateNotificationRingPath()
        updateFlashPath()
        synchronizeScrollView()
        synchronizeSurfaceView()
        synchronizeCoreSurface()
    }

    override func viewDidMoveToWindow() {
        super.viewDidMoveToWindow()
        windowObservers.forEach { NotificationCenter.default.removeObserver($0) }
        windowObservers.removeAll()
        guard let window else { return }
        windowObservers.append(NotificationCenter.default.addObserver(
            forName: NSWindow.didBecomeKeyNotification,
            object: window,
            queue: .main
        ) { [weak self] _ in
            self?.applyFirstResponderIfNeeded()
        })
        windowObservers.append(NotificationCenter.default.addObserver(
            forName: NSWindow.didResignKeyNotification,
            object: window,
            queue: .main
        ) { [weak self] _ in
            guard let self, let window = self.window else { return }
            // Losing key window does not always trigger first-responder resignation, so force
            // the focused terminal view to yield responder to keep Ghostty cursor/focus state in sync.
            if let fr = window.firstResponder as? NSView,
               fr === self.surfaceView || fr.isDescendant(of: self.surfaceView) {
                window.makeFirstResponder(nil)
            }
        })
        if window.isKeyWindow { applyFirstResponderIfNeeded() }
    }

    func attachSurface(_ terminalSurface: TerminalSurface) {
        surfaceView.attachSurface(terminalSurface)
    }

    func setFocusHandler(_ handler: (() -> Void)?) {
        surfaceView.onFocus = handler
    }

    func setTriggerFlashHandler(_ handler: (() -> Void)?) {
        surfaceView.onTriggerFlash = handler
    }

    func setBackgroundColor(_ color: NSColor) {
        guard let layer = backgroundView.layer else { return }
        let fillColor = Self.panelBackgroundFillColor(for: color)
        CATransaction.begin()
        CATransaction.setDisableActions(true)
        layer.backgroundColor = fillColor.cgColor
        layer.isOpaque = fillColor.alphaComponent >= 1.0
        CATransaction.commit()
    }

    func setInactiveOverlay(color: NSColor, opacity: CGFloat, visible: Bool) {
        let clampedOpacity = max(0, min(1, opacity))
        CATransaction.begin()
        CATransaction.setDisableActions(true)
        inactiveOverlayView.layer?.backgroundColor = color.withAlphaComponent(clampedOpacity).cgColor
        inactiveOverlayView.isHidden = !(visible && clampedOpacity > 0.0001)
        CATransaction.commit()
    }

    func setNotificationRing(visible: Bool) {
        if !Thread.isMainThread {
            DispatchQueue.main.async { [weak self] in
                self?.setNotificationRing(visible: visible)
            }
            return
        }

        CATransaction.begin()
        CATransaction.setDisableActions(true)
        notificationRingOverlayView.isHidden = !visible
        notificationRingLayer.opacity = visible ? 1 : 0
        CATransaction.commit()
    }

    func setSearchOverlay(searchState: TerminalSurface.SearchState?) {
        if !Thread.isMainThread {
            DispatchQueue.main.async { [weak self] in
                self?.setSearchOverlay(searchState: searchState)
            }
            return
        }

        // Layering contract: keep terminal Cmd+F UI inside this portal-hosted AppKit view.
        // SwiftUI panel-level overlays can fall behind portal-hosted terminal surfaces.
        guard let terminalSurface = surfaceView.terminalSurface,
              let searchState else {
            searchOverlayHostingView?.removeFromSuperview()
            searchOverlayHostingView = nil
            return
        }

        let tabId = terminalSurface.tabId
        let surfaceId = terminalSurface.id
        let rootView = SurfaceSearchOverlay(
            tabId: tabId,
            surfaceId: surfaceId,
            searchState: searchState,
            onMoveFocusToTerminal: { [weak self] in
                self?.moveFocus()
            },
            onNavigateSearch: { [weak terminalSurface] action in
                _ = terminalSurface?.performBindingAction(action)
            },
            onClose: { [weak self, weak terminalSurface] in
                terminalSurface?.searchState = nil
                self?.moveFocus()
            }
        )

        if let overlay = searchOverlayHostingView {
            overlay.rootView = rootView
            if overlay.superview !== self {
                overlay.removeFromSuperview()
                addSubview(overlay)
                NSLayoutConstraint.activate([
                    overlay.topAnchor.constraint(equalTo: topAnchor),
                    overlay.bottomAnchor.constraint(equalTo: bottomAnchor),
                    overlay.leadingAnchor.constraint(equalTo: leadingAnchor),
                    overlay.trailingAnchor.constraint(equalTo: trailingAnchor),
                ])
            }
            if !keyboardCopyModeBadgeView.isHidden {
                addSubview(keyboardCopyModeBadgeView, positioned: .above, relativeTo: overlay)
            }
            return
        }

        let overlay = NSHostingView(rootView: rootView)
        overlay.translatesAutoresizingMaskIntoConstraints = false
        addSubview(overlay)
        NSLayoutConstraint.activate([
            overlay.topAnchor.constraint(equalTo: topAnchor),
            overlay.bottomAnchor.constraint(equalTo: bottomAnchor),
            overlay.leadingAnchor.constraint(equalTo: leadingAnchor),
            overlay.trailingAnchor.constraint(equalTo: trailingAnchor),
        ])
        if !keyboardCopyModeBadgeView.isHidden {
            addSubview(keyboardCopyModeBadgeView, positioned: .above, relativeTo: overlay)
        }
        searchOverlayHostingView = overlay
    }

    func setKeyboardCopyModeIndicator(visible: Bool) {
        if !Thread.isMainThread {
            DispatchQueue.main.async { [weak self] in
                self?.setKeyboardCopyModeIndicator(visible: visible)
            }
            return
        }

        keyboardCopyModeBadgeView.isHidden = !visible
        if visible {
            if let overlay = searchOverlayHostingView {
                addSubview(keyboardCopyModeBadgeView, positioned: .above, relativeTo: overlay)
            } else {
                addSubview(keyboardCopyModeBadgeView, positioned: .above, relativeTo: nil)
            }
        }
    }

    private func dropZoneOverlayFrame(for zone: DropZone, in size: CGSize) -> CGRect {
        let padding: CGFloat = 4
        switch zone {
        case .center:
            return CGRect(x: padding, y: padding, width: size.width - padding * 2, height: size.height - padding * 2)
        case .left:
            return CGRect(x: padding, y: padding, width: size.width / 2 - padding, height: size.height - padding * 2)
        case .right:
            return CGRect(x: size.width / 2, y: padding, width: size.width / 2 - padding, height: size.height - padding * 2)
        case .top:
            return CGRect(x: padding, y: size.height / 2, width: size.width - padding * 2, height: size.height / 2 - padding)
        case .bottom:
            return CGRect(x: padding, y: padding, width: size.width - padding * 2, height: size.height / 2 - padding)
        }
    }

    private static func rectApproximatelyEqual(_ lhs: CGRect, _ rhs: CGRect, epsilon: CGFloat = 0.5) -> Bool {
        abs(lhs.origin.x - rhs.origin.x) <= epsilon &&
            abs(lhs.origin.y - rhs.origin.y) <= epsilon &&
            abs(lhs.size.width - rhs.size.width) <= epsilon &&
            abs(lhs.size.height - rhs.size.height) <= epsilon
    }

    func setDropZoneOverlay(zone: DropZone?) {
        if !Thread.isMainThread {
            DispatchQueue.main.async { [weak self] in
                self?.setDropZoneOverlay(zone: zone)
            }
            return
        }

        if let zone, (bounds.width <= 2 || bounds.height <= 2) {
            pendingDropZone = zone
#if DEBUG
            logDropZoneOverlay(event: "deferZeroBounds", zone: zone, frame: nil)
#endif
            return
        }

        let previousZone = activeDropZone
        activeDropZone = zone
        pendingDropZone = nil

        let previousFrame = dropZoneOverlayView.frame

        if let zone {
#if DEBUG
            if window == nil {
                logDropZoneOverlay(event: "showNoWindow", zone: zone, frame: nil)
            }
#endif
            let targetFrame = dropZoneOverlayFrame(for: zone, in: bounds.size)
            let isSameFrame = Self.rectApproximatelyEqual(previousFrame, targetFrame)
            let needsFrameUpdate = !isSameFrame
            let zoneChanged = previousZone != zone

            if !dropZoneOverlayView.isHidden && !needsFrameUpdate && !zoneChanged {
                return
            }

            dropZoneOverlayAnimationGeneration &+= 1
            dropZoneOverlayView.layer?.removeAllAnimations()

            if dropZoneOverlayView.isHidden {
                dropZoneOverlayView.frame = targetFrame
                dropZoneOverlayView.alphaValue = 0
                dropZoneOverlayView.isHidden = false
#if DEBUG
                recordDropOverlayShowAnimation()
#endif
#if DEBUG
                logDropZoneOverlay(event: "show", zone: zone, frame: targetFrame)
#endif

                NSAnimationContext.runAnimationGroup { context in
                    context.duration = 0.18
                    context.timingFunction = CAMediaTimingFunction(name: .easeInEaseOut)
                    dropZoneOverlayView.animator().alphaValue = 1
                } completionHandler: { [weak self] in
#if DEBUG
                    guard let self else { return }
                    guard self.activeDropZone == zone else { return }
                    self.logDropZoneOverlay(event: "showComplete", zone: zone, frame: targetFrame)
#endif
                }
                return
            }

#if DEBUG
            if needsFrameUpdate || zoneChanged {
                logDropZoneOverlay(event: "update", zone: zone, frame: targetFrame)
            }
#endif
            NSAnimationContext.runAnimationGroup { context in
                context.duration = 0.18
                context.timingFunction = CAMediaTimingFunction(name: .easeInEaseOut)
                if needsFrameUpdate {
                    dropZoneOverlayView.animator().frame = targetFrame
                }
                if dropZoneOverlayView.alphaValue < 1 {
                    dropZoneOverlayView.animator().alphaValue = 1
                }
            }
        } else {
            guard !dropZoneOverlayView.isHidden else { return }
            dropZoneOverlayAnimationGeneration &+= 1
            let animationGeneration = dropZoneOverlayAnimationGeneration
            dropZoneOverlayView.layer?.removeAllAnimations()
#if DEBUG
            logDropZoneOverlay(event: "hide", zone: nil, frame: nil)
#endif

            NSAnimationContext.runAnimationGroup { context in
                context.duration = 0.14
                context.timingFunction = CAMediaTimingFunction(name: .easeOut)
                dropZoneOverlayView.animator().alphaValue = 0
            } completionHandler: { [weak self] in
                guard let self else { return }
                guard self.dropZoneOverlayAnimationGeneration == animationGeneration else { return }
                guard self.activeDropZone == nil else { return }
                self.dropZoneOverlayView.isHidden = true
                self.dropZoneOverlayView.alphaValue = 1
#if DEBUG
                self.logDropZoneOverlay(event: "hideComplete", zone: nil, frame: nil)
#endif
            }
        }
    }

#if DEBUG
    private func logDropZoneOverlay(event: String, zone: DropZone?, frame: CGRect?) {
        let surface = surfaceView.terminalSurface?.id.uuidString.prefix(5) ?? "nil"
        let zoneText = zone.map { String(describing: $0) } ?? "none"
        let boundsText = String(format: "%.1fx%.1f", bounds.width, bounds.height)
        let frameText: String
        if let frame {
            frameText = String(
                format: "%.1f,%.1f %.1fx%.1f",
                frame.origin.x, frame.origin.y, frame.width, frame.height
            )
        } else {
            frameText = "-"
        }
        let signature = "\(event)|\(surface)|\(zoneText)|\(boundsText)|\(frameText)|\(dropZoneOverlayView.isHidden ? 1 : 0)"
        guard lastDropZoneOverlayLogSignature != signature else { return }
        lastDropZoneOverlayLogSignature = signature
        dlog(
            "terminal.dropOverlay event=\(event) surface=\(surface) zone=\(zoneText) " +
            "hidden=\(dropZoneOverlayView.isHidden ? 1 : 0) bounds=\(boundsText) frame=\(frameText)"
        )
    }
#endif

    func triggerFlash() {
        DispatchQueue.main.async { [weak self] in
            guard let self else { return }
#if DEBUG
            if let surfaceId = self.surfaceView.terminalSurface?.id {
                Self.recordFlash(for: surfaceId)
            }
#endif
            self.updateFlashPath()
            self.flashLayer.removeAllAnimations()
            self.flashLayer.opacity = 0
            let animation = CAKeyframeAnimation(keyPath: "opacity")
            animation.values = FocusFlashPattern.values.map { NSNumber(value: $0) }
            animation.keyTimes = FocusFlashPattern.keyTimes.map { NSNumber(value: $0) }
            animation.duration = FocusFlashPattern.duration
            animation.timingFunctions = FocusFlashPattern.curves.map { curve in
                switch curve {
                case .easeIn:
                    return CAMediaTimingFunction(name: .easeIn)
                case .easeOut:
                    return CAMediaTimingFunction(name: .easeOut)
                }
            }
            self.flashLayer.add(animation, forKey: "cmux.flash")
        }
    }

    func setVisibleInUI(_ visible: Bool) {
        let wasVisible = surfaceView.isVisibleInUI
        surfaceView.setVisibleInUI(visible)
        isHidden = !visible
#if DEBUG
        if wasVisible != visible {
            let transition = "\(wasVisible ? 1 : 0)->\(visible ? 1 : 0)"
            let suffix = debugVisibilityStateSuffix(transition: transition)
            debugLogWorkspaceSwitchTiming(
                event: "ws.term.visible",
                suffix: suffix
            )
        }
#endif
        if !visible {
            // If we were focused, yield first responder.
            if let window, let fr = window.firstResponder as? NSView,
               fr === surfaceView || fr.isDescendant(of: surfaceView) {
                window.makeFirstResponder(nil)
            }
        } else {
            applyFirstResponderIfNeeded()
        }
    }

    func setActive(_ active: Bool) {
        let wasActive = isActive
        isActive = active
#if DEBUG
        if wasActive != active {
            let transition = "\(wasActive ? 1 : 0)->\(active ? 1 : 0)"
            let suffix = debugVisibilityStateSuffix(transition: transition)
            debugLogWorkspaceSwitchTiming(
                event: "ws.term.active",
                suffix: suffix
            )
        }
#endif
        if active {
            applyFirstResponderIfNeeded()
        } else if let window,
                  let fr = window.firstResponder as? NSView,
                  fr === surfaceView || fr.isDescendant(of: surfaceView) {
            window.makeFirstResponder(nil)
        }
    }

#if DEBUG
    private func debugLogWorkspaceSwitchTiming(event: String, suffix: String) {
        guard let snapshot = AppDelegate.shared?.tabManager?.debugCurrentWorkspaceSwitchSnapshot() else {
            dlog("\(event) id=none \(suffix)")
            return
        }
        let dtMs = (CACurrentMediaTime() - snapshot.startedAt) * 1000
        dlog("\(event) id=\(snapshot.id) dt=\(String(format: "%.2fms", dtMs)) \(suffix)")
    }

    private func debugFirstResponderLabel() -> String {
        guard let window, let firstResponder = window.firstResponder else { return "nil" }
        if let view = firstResponder as? NSView {
            if view === surfaceView {
                return "surfaceView"
            }
            if view.isDescendant(of: surfaceView) {
                return "surfaceDescendant"
            }
            return String(describing: type(of: view))
        }
        return String(describing: type(of: firstResponder))
    }

    private func debugVisibilityStateSuffix(transition: String) -> String {
        let surface = surfaceView.terminalSurface?.id.uuidString.prefix(5) ?? "nil"
        let hiddenInHierarchy = (isHiddenOrHasHiddenAncestor || surfaceView.isHiddenOrHasHiddenAncestor) ? 1 : 0
        let inWindow = window != nil ? 1 : 0
        let hasSuperview = superview != nil ? 1 : 0
        let hostHidden = isHidden ? 1 : 0
        let surfaceHidden = surfaceView.isHidden ? 1 : 0
        let boundsText = String(format: "%.1fx%.1f", bounds.width, bounds.height)
        let frameText = String(format: "%.1fx%.1f", frame.width, frame.height)
        let responder = debugFirstResponderLabel()
        return
            "surface=\(surface) transition=\(transition) active=\(isActive ? 1 : 0) " +
            "visibleFlag=\(surfaceView.isVisibleInUI ? 1 : 0) hostHidden=\(hostHidden) surfaceHidden=\(surfaceHidden) " +
            "hiddenHierarchy=\(hiddenInHierarchy) inWindow=\(inWindow) hasSuperview=\(hasSuperview) " +
            "bounds=\(boundsText) frame=\(frameText) firstResponder=\(responder)"
    }
#endif

    func moveFocus(from previous: GhosttySurfaceScrollView? = nil, delay: TimeInterval? = nil) {
#if DEBUG
        dlog("focus.moveFocus to=\(self.surfaceView.terminalSurface?.id.uuidString.prefix(5) ?? "nil")")
#endif
        let work = { [weak self] in
            guard let self else { return }
            guard let window = self.window else { return }
            if let previous, previous !== self {
                _ = previous.surfaceView.resignFirstResponder()
            }
            window.makeFirstResponder(self.surfaceView)
        }

        if let delay, delay > 0 {
            DispatchQueue.main.asyncAfter(deadline: .now() + delay) { work() }
        } else {
            if Thread.isMainThread {
                work()
            } else {
                DispatchQueue.main.async { work() }
            }
        }
    }

#if DEBUG
    @discardableResult
    func debugSimulateFileDrop(paths: [String]) -> Bool {
        surfaceView.debugSimulateFileDrop(paths: paths)
    }

    func debugRegisteredDropTypes() -> [String] {
        surfaceView.debugRegisteredDropTypes()
    }

    func debugInactiveOverlayState() -> (isHidden: Bool, alpha: CGFloat) {
        (
            inactiveOverlayView.isHidden,
            inactiveOverlayView.layer?.backgroundColor.flatMap { NSColor(cgColor: $0)?.alphaComponent } ?? 0
        )
    }

    func debugNotificationRingState() -> (isHidden: Bool, opacity: Float) {
        (
            notificationRingOverlayView.isHidden,
            notificationRingLayer.opacity
        )
    }

    func debugHasSearchOverlay() -> Bool {
        guard let overlay = searchOverlayHostingView else { return false }
        return overlay.superview === self && !overlay.isHidden
    }

    func debugHasKeyboardCopyModeIndicator() -> Bool {
        keyboardCopyModeBadgeView.superview === self && !keyboardCopyModeBadgeView.isHidden
    }

#endif

    /// Handle file/URL drops, forwarding to the terminal as shell-escaped paths.
    func handleDroppedURLs(_ urls: [URL]) -> Bool {
        guard !urls.isEmpty else { return false }
        let content = urls
            .map { GhosttyNSView.escapeDropForShell($0.path) }
            .joined(separator: " ")
        #if DEBUG
        dlog("terminal.swiftUIDrop surface=\(surfaceView.terminalSurface?.id.uuidString.prefix(5) ?? "nil") urls=\(urls.map(\.lastPathComponent))")
        #endif
        surfaceView.terminalSurface?.sendText(content)
        return true
    }

    func terminalViewForDrop(at point: NSPoint) -> GhosttyNSView? {
        guard bounds.contains(point), !isHidden else { return nil }
        return surfaceView
    }

#if DEBUG
    /// Sends a synthetic key press/release pair directly to the surface view.
    /// This exercises the same key path as real keyboard input (ghostty_surface_key),
    /// unlike sendText, which bypasses key translation.
    @discardableResult
    func debugSendSyntheticKeyPressAndReleaseForUITest(
        characters: String,
        charactersIgnoringModifiers: String,
        keyCode: UInt16,
        modifierFlags: NSEvent.ModifierFlags = []
    ) -> Bool {
        guard let window else { return false }
        window.makeFirstResponder(surfaceView)

        let timestamp = ProcessInfo.processInfo.systemUptime
        guard let keyDown = NSEvent.keyEvent(
            with: .keyDown,
            location: .zero,
            modifierFlags: modifierFlags,
            timestamp: timestamp,
            windowNumber: window.windowNumber,
            context: nil,
            characters: characters,
            charactersIgnoringModifiers: charactersIgnoringModifiers,
            isARepeat: false,
            keyCode: keyCode
        ) else { return false }

        guard let keyUp = NSEvent.keyEvent(
            with: .keyUp,
            location: .zero,
            modifierFlags: modifierFlags,
            timestamp: timestamp + 0.001,
            windowNumber: window.windowNumber,
            context: nil,
            characters: characters,
            charactersIgnoringModifiers: charactersIgnoringModifiers,
            isARepeat: false,
            keyCode: keyCode
        ) else { return false }

        surfaceView.keyDown(with: keyDown)
        surfaceView.keyUp(with: keyUp)
        return true
    }

    /// Sends a synthetic Ctrl+D key press directly to the surface view.
    /// This exercises the same key path as real keyboard input (ghostty_surface_key),
    /// unlike `sendText`, which bypasses key translation.
    @discardableResult
    func sendSyntheticCtrlDForUITest(modifierFlags: NSEvent.ModifierFlags = [.control]) -> Bool {
        debugSendSyntheticKeyPressAndReleaseForUITest(
            characters: "\u{04}",
            charactersIgnoringModifiers: "d",
            keyCode: 2,
            modifierFlags: modifierFlags
        )
    }
    #endif

    func ensureFocus(for tabId: UUID, surfaceId: UUID, attemptsRemaining: Int = 3) {
        func retry() {
            guard attemptsRemaining > 0 else { return }
            DispatchQueue.main.asyncAfter(deadline: .now() + 0.03) { [weak self] in
                self?.ensureFocus(for: tabId, surfaceId: surfaceId, attemptsRemaining: attemptsRemaining - 1)
            }
        }

        let hasUsablePortalGeometry: Bool = {
            let size = bounds.size
            return size.width > 1 && size.height > 1
        }()
        let isHiddenForFocus = isHiddenOrHasHiddenAncestor || surfaceView.isHiddenOrHasHiddenAncestor

        guard isActive else { return }
        guard surfaceView.terminalSurface?.searchState == nil else { return }
        guard let window else { return }
        guard surfaceView.isVisibleInUI else {
            retry()
            return
        }
        guard !isHiddenForFocus, hasUsablePortalGeometry else {
#if DEBUG
            dlog(
                "focus.ensure.defer surface=\(surfaceView.terminalSurface?.id.uuidString.prefix(5) ?? "nil") " +
                "reason=hidden_or_tiny hidden=\(isHiddenForFocus ? 1 : 0) " +
                "frame=\(String(format: "%.1fx%.1f", bounds.width, bounds.height)) attempts=\(attemptsRemaining)"
            )
#endif
            retry()
            return
        }

        guard let delegate = AppDelegate.shared,
              let tabManager = delegate.tabManagerFor(tabId: tabId) ?? delegate.tabManager,
              tabManager.selectedTabId == tabId else {
            retry()
            return
        }

        guard let tab = tabManager.tabs.first(where: { $0.id == tabId }),
              let tabIdForSurface = tab.surfaceIdFromPanelId(surfaceId),
              let paneId = tab.bonsplitController.allPaneIds.first(where: { paneId in
                  tab.bonsplitController.tabs(inPane: paneId).contains(where: { $0.id == tabIdForSurface })
              }) else {
            retry()
            return
        }

        guard tab.bonsplitController.selectedTab(inPane: paneId)?.id == tabIdForSurface,
              tab.bonsplitController.focusedPaneId == paneId else {
            retry()
            return
        }

        if let fr = window.firstResponder as? NSView,
           fr === surfaceView || fr.isDescendant(of: surfaceView) {
            return
        }

        if !window.isKeyWindow {
            window.makeKeyAndOrderFront(nil)
        }
        _ = window.makeFirstResponder(surfaceView)

        if !isSurfaceViewFirstResponder() {
            retry()
        }
    }

    /// Suppress the surface view's onFocus callback and ghostty_surface_set_focus during
    /// SwiftUI reparenting (programmatic splits). Call clearSuppressReparentFocus() after layout settles.
    func suppressReparentFocus() {
        surfaceView.suppressingReparentFocus = true
    }

    func clearSuppressReparentFocus() {
        surfaceView.suppressingReparentFocus = false
    }

    /// Returns true if the terminal's actual Ghostty surface view is (or contains) the window first responder.
    /// This is stricter than checking `hostedView` descendants, since the scroll view can sometimes become
    /// first responder transiently while focus is being applied.
    func isSurfaceViewFirstResponder() -> Bool {
        guard let window, let fr = window.firstResponder as? NSView else { return false }
        return fr === surfaceView || fr.isDescendant(of: surfaceView)
    }

    private func applyFirstResponderIfNeeded() {
        let hasUsablePortalGeometry: Bool = {
            let size = bounds.size
            return size.width > 1 && size.height > 1
        }()
        let isHiddenForFocus = isHiddenOrHasHiddenAncestor || surfaceView.isHiddenOrHasHiddenAncestor

        guard isActive else { return }
        guard surfaceView.isVisibleInUI else { return }
        guard !isHiddenForFocus, hasUsablePortalGeometry else {
#if DEBUG
            dlog(
                "focus.apply.skip surface=\(surfaceView.terminalSurface?.id.uuidString.prefix(5) ?? "nil") " +
                "reason=hidden_or_tiny hidden=\(isHiddenForFocus ? 1 : 0) frame=\(String(format: "%.1fx%.1f", bounds.width, bounds.height))"
            )
#endif
            return
        }
        guard surfaceView.terminalSurface?.searchState == nil else { return }
        guard let window, window.isKeyWindow else { return }
        if let fr = window.firstResponder as? NSView,
           fr === surfaceView || fr.isDescendant(of: surfaceView) {
            return
        }
        window.makeFirstResponder(surfaceView)
    }

#if DEBUG
    struct DebugRenderStats {
        let drawCount: Int
        let lastDrawTime: CFTimeInterval
        let metalDrawableCount: Int
        let metalLastDrawableTime: CFTimeInterval
        let presentCount: Int
        let lastPresentTime: CFTimeInterval
        let layerClass: String
        let layerContentsKey: String
        let inWindow: Bool
        let windowIsKey: Bool
        let windowOcclusionVisible: Bool
        let appIsActive: Bool
        let isActive: Bool
        let desiredFocus: Bool
        let isFirstResponder: Bool
    }

    func debugRenderStats() -> DebugRenderStats {
        let layerClass = surfaceView.layer.map { String(describing: type(of: $0)) } ?? "nil"
        let (metalCount, metalLast) = (surfaceView.layer as? GhosttyMetalLayer)?.debugStats() ?? (0, 0)
        let (drawCount, lastDraw): (Int, CFTimeInterval) = surfaceView.terminalSurface.map { terminalSurface in
            Self.drawStats(for: terminalSurface.id)
        } ?? (0, 0)
        let (presentCount, lastPresent, contentsKey): (Int, CFTimeInterval, String) = surfaceView.terminalSurface.map { terminalSurface in
            let stats = Self.updatePresentStats(surfaceId: terminalSurface.id, layer: surfaceView.layer)
            return (stats.count, stats.last, stats.key)
        } ?? (0, 0, Self.contentsKey(for: surfaceView.layer))
        let inWindow = (window != nil)
        let windowIsKey = window?.isKeyWindow ?? false
        let windowOcclusionVisible = (window?.occlusionState.contains(.visible) ?? false) || (window?.isKeyWindow ?? false)
        let appIsActive = NSApp.isActive
        let fr = window?.firstResponder as? NSView
        let isFirstResponder = fr == surfaceView || (fr?.isDescendant(of: surfaceView) ?? false)
        return DebugRenderStats(
            drawCount: drawCount,
            lastDrawTime: lastDraw,
            metalDrawableCount: metalCount,
            metalLastDrawableTime: metalLast,
            presentCount: presentCount,
            lastPresentTime: lastPresent,
            layerClass: layerClass,
            layerContentsKey: contentsKey,
            inWindow: inWindow,
            windowIsKey: windowIsKey,
            windowOcclusionVisible: windowOcclusionVisible,
            appIsActive: appIsActive,
            isActive: isActive,
            desiredFocus: surfaceView.desiredFocus,
            isFirstResponder: isFirstResponder
        )
    }
#endif

#if DEBUG
    struct DebugFrameSample {
        let sampleCount: Int
        let uniqueQuantized: Int
        let lumaStdDev: Double
        let modeFraction: Double
        let fingerprint: UInt64
        let iosurfaceWidthPx: Int
        let iosurfaceHeightPx: Int
        let expectedWidthPx: Int
        let expectedHeightPx: Int
        let layerClass: String
        let layerContentsGravity: String
        let layerContentsKey: String

        var isProbablyBlank: Bool {
            (lumaStdDev < 3.5 && modeFraction > 0.985) ||
            (uniqueQuantized <= 6 && modeFraction > 0.95)
        }
    }

    /// Create a CGImage from the terminal's IOSurface-backed layer contents.
    ///
    /// This avoids Screen Recording permissions (unlike CGWindowListCreateImage) and is therefore
    /// suitable for debug socket tests running in headless/VM contexts.
    func debugCopyIOSurfaceCGImage() -> CGImage? {
        guard let modelLayer = surfaceView.layer else { return nil }
        let layer = modelLayer.presentation() ?? modelLayer
        guard let contents = layer.contents else { return nil }

        let cf = contents as CFTypeRef
        guard CFGetTypeID(cf) == IOSurfaceGetTypeID() else { return nil }
        let surfaceRef = (contents as! IOSurfaceRef)

        let width = Int(IOSurfaceGetWidth(surfaceRef))
        let height = Int(IOSurfaceGetHeight(surfaceRef))
        let bytesPerRow = Int(IOSurfaceGetBytesPerRow(surfaceRef))
        guard width > 0, height > 0, bytesPerRow > 0 else { return nil }

        IOSurfaceLock(surfaceRef, [], nil)
        defer { IOSurfaceUnlock(surfaceRef, [], nil) }

        let base = IOSurfaceGetBaseAddress(surfaceRef)
        let size = bytesPerRow * height
        let data = Data(bytes: base, count: size)

        guard let provider = CGDataProvider(data: data as CFData) else { return nil }
        let colorSpace = CGColorSpaceCreateDeviceRGB()
        let bitmapInfo = CGBitmapInfo.byteOrder32Little.union(
            CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedFirst.rawValue)
        )

        return CGImage(
            width: width,
            height: height,
            bitsPerComponent: 8,
            bitsPerPixel: 32,
            bytesPerRow: bytesPerRow,
            space: colorSpace,
            bitmapInfo: bitmapInfo,
            provider: provider,
            decode: nil,
            shouldInterpolate: false,
            intent: .defaultIntent
        )
    }

    /// Sample the IOSurface backing the terminal layer (if any) to detect a transient blank frame
    /// without using screenshots/screen recording permissions.
    func debugSampleIOSurface(normalizedCrop: CGRect) -> DebugFrameSample? {
        guard let modelLayer = surfaceView.layer else { return nil }
        // Prefer the presentation layer to better match what the user sees on screen.
        let layer = modelLayer.presentation() ?? modelLayer
        let layerClass = String(describing: type(of: layer))
        let layerContentsGravity = layer.contentsGravity.rawValue
        let contentsKey = Self.contentsKey(for: layer)
        let presentationScale = max(1.0, layer.contentsScale)
        let expectedWidthPx = Int((layer.bounds.width * presentationScale).rounded(.toNearestOrAwayFromZero))
        let expectedHeightPx = Int((layer.bounds.height * presentationScale).rounded(.toNearestOrAwayFromZero))

        // Ghostty uses a CoreAnimation layer whose `contents` is an IOSurface-backed object.
        // The concrete layer class is often `IOSurfaceLayer` (private), so avoid referencing it directly.
        guard let anySurface = layer.contents else {
            // Treat "no contents" as a blank frame: this is the visual regression we're guarding.
            return DebugFrameSample(
                sampleCount: 0,
                uniqueQuantized: 0,
                lumaStdDev: 0,
                modeFraction: 1,
                fingerprint: 0,
                iosurfaceWidthPx: 0,
                iosurfaceHeightPx: 0,
                expectedWidthPx: expectedWidthPx,
                expectedHeightPx: expectedHeightPx,
                layerClass: layerClass,
                layerContentsGravity: layerContentsGravity,
                layerContentsKey: contentsKey
            )
        }

        // IOSurfaceLayer.contents is usually an IOSurface, but during mitigation we may
        // temporarily replace contents with a CGImage snapshot to avoid blank flashes.
        // Treat non-IOSurface contents as "non-blank" and avoid unsafe casts.
        let cf = anySurface as CFTypeRef
        guard CFGetTypeID(cf) == IOSurfaceGetTypeID() else {
            var fnv: UInt64 = 1469598103934665603
            for b in contentsKey.utf8 {
                fnv ^= UInt64(b)
                fnv &*= 1099511628211
            }
            return DebugFrameSample(
                sampleCount: 1,
                uniqueQuantized: 1,
                lumaStdDev: 999,
                modeFraction: 0,
                fingerprint: fnv,
                iosurfaceWidthPx: 0,
                iosurfaceHeightPx: 0,
                expectedWidthPx: expectedWidthPx,
                expectedHeightPx: expectedHeightPx,
                layerClass: layerClass,
                layerContentsGravity: layerContentsGravity,
                layerContentsKey: contentsKey
            )
        }

        let surfaceRef = (anySurface as! IOSurfaceRef)

        let width = Int(IOSurfaceGetWidth(surfaceRef))
        let height = Int(IOSurfaceGetHeight(surfaceRef))
        if width <= 0 || height <= 0 { return nil }

        let cropPx = CGRect(
            x: max(0, min(CGFloat(width - 1), normalizedCrop.origin.x * CGFloat(width))),
            y: max(0, min(CGFloat(height - 1), normalizedCrop.origin.y * CGFloat(height))),
            width: max(1, min(CGFloat(width), normalizedCrop.width * CGFloat(width))),
            height: max(1, min(CGFloat(height), normalizedCrop.height * CGFloat(height)))
        ).integral

        let x0 = Int(cropPx.minX)
        let y0 = Int(cropPx.minY)
        let x1 = Int(min(CGFloat(width), cropPx.maxX))
        let y1 = Int(min(CGFloat(height), cropPx.maxY))
        if x1 <= x0 || y1 <= y0 { return nil }

        IOSurfaceLock(surfaceRef, [], nil)
        defer { IOSurfaceUnlock(surfaceRef, [], nil) }

        let base = IOSurfaceGetBaseAddress(surfaceRef)
        let bytesPerRow = IOSurfaceGetBytesPerRow(surfaceRef)
        if bytesPerRow <= 0 { return nil }

        // Assume 4 bytes/pixel BGRA (common for IOSurfaceLayer contents).
        let bytesPerPixel = 4
        let step = 6

        var hist = [UInt16: Int]()
        hist.reserveCapacity(256)

        var lumas = [Double]()
        lumas.reserveCapacity(((x1 - x0) / step) * ((y1 - y0) / step))

        var count = 0
        var fnv: UInt64 = 1469598103934665603

        for y in stride(from: y0, to: y1, by: step) {
            let row = base.advanced(by: y * bytesPerRow)
            for x in stride(from: x0, to: x1, by: step) {
                let p = row.advanced(by: x * bytesPerPixel)
                let b = Double(p.load(fromByteOffset: 0, as: UInt8.self))
                let g = Double(p.load(fromByteOffset: 1, as: UInt8.self))
                let r = Double(p.load(fromByteOffset: 2, as: UInt8.self))
                let luma = 0.2126 * r + 0.7152 * g + 0.0722 * b
                lumas.append(luma)

                let rq = UInt16(UInt8(r) >> 4)
                let gq = UInt16(UInt8(g) >> 4)
                let bq = UInt16(UInt8(b) >> 4)
                let key = (rq << 8) | (gq << 4) | bq
                hist[key, default: 0] += 1
                count += 1

                let lq = UInt8(max(0, min(63, Int(luma / 4.0))))
                fnv ^= UInt64(lq)
                fnv &*= 1099511628211
            }
        }

        guard count > 0 else { return nil }
        let mean = lumas.reduce(0.0, +) / Double(lumas.count)
        let variance = lumas.reduce(0.0) { $0 + ($1 - mean) * ($1 - mean) } / Double(lumas.count)
        let stddev = sqrt(variance)

        let modeCount = hist.values.max() ?? 0
        let modeFrac = Double(modeCount) / Double(count)

        return DebugFrameSample(
            sampleCount: count,
            uniqueQuantized: hist.count,
            lumaStdDev: stddev,
            modeFraction: modeFrac,
            fingerprint: fnv,
            iosurfaceWidthPx: width,
            iosurfaceHeightPx: height,
            expectedWidthPx: expectedWidthPx,
            expectedHeightPx: expectedHeightPx,
            layerClass: layerClass,
            layerContentsGravity: layerContentsGravity,
            layerContentsKey: contentsKey
        )
    }
#endif

    func cancelFocusRequest() {
        // Intentionally no-op (no retry loops).
    }

    private func synchronizeSurfaceView() {
        let visibleRect = scrollView.contentView.documentVisibleRect
        surfaceView.frame.origin = visibleRect.origin
    }

    /// Match upstream Ghostty behavior: use content area width (excluding non-content
    /// regions such as scrollbar space) when telling libghostty the terminal size.
    private func synchronizeCoreSurface() {
        let width = max(0, scrollView.contentSize.width - overlayScrollbarInsetWidth())
        let height = surfaceView.frame.height
        guard width > 0, height > 0 else { return }
        surfaceView.pushTargetSurfaceSize(CGSize(width: width, height: height))
    }

    /// Reserve overlay scrollbar gutter so wrapped text never sits underneath a visible scroller.
    private func overlayScrollbarInsetWidth() -> CGFloat {
        guard scrollView.hasVerticalScroller, scrollView.scrollerStyle == .overlay else { return 0 }

        // If AppKit already reserved non-content width in `contentSize`, avoid double-subtraction.
        let alreadyReserved = max(0, scrollView.bounds.width - scrollView.contentSize.width)
        if alreadyReserved > 0.5 { return 0 }

        let fallback = NSScroller.scrollerWidth(for: .regular, scrollerStyle: .overlay)
        guard let verticalScroller = scrollView.verticalScroller else { return fallback }

        let measuredWidth = verticalScroller.frame.width
        if measuredWidth > 0 {
            return max(measuredWidth, fallback)
        }

        let controlSizeWidth = NSScroller.scrollerWidth(
            for: verticalScroller.controlSize,
            scrollerStyle: .overlay
        )
        return max(controlSizeWidth, fallback)
    }

    private func updateNotificationRingPath() {
        updateOverlayRingPath(
            layer: notificationRingLayer,
            bounds: notificationRingOverlayView.bounds,
            inset: 2,
            radius: 6
        )
    }

    private func updateFlashPath() {
        updateOverlayRingPath(
            layer: flashLayer,
            bounds: flashOverlayView.bounds,
            inset: CGFloat(FocusFlashPattern.ringInset),
            radius: CGFloat(FocusFlashPattern.ringCornerRadius)
        )
    }

    private func updateOverlayRingPath(
        layer: CAShapeLayer,
        bounds: CGRect,
        inset: CGFloat,
        radius: CGFloat
    ) {
        layer.frame = bounds
        guard bounds.width > inset * 2, bounds.height > inset * 2 else {
            layer.path = nil
            return
        }
        let rect = bounds.insetBy(dx: inset, dy: inset)
        layer.path = CGPath(roundedRect: rect, cornerWidth: radius, cornerHeight: radius, transform: nil)
    }

    private func synchronizeScrollView() {
        documentView.frame.size.height = documentHeight()

        if !isLiveScrolling {
            let cellHeight = surfaceView.cellSize.height
            if cellHeight > 0, let scrollbar = surfaceView.scrollbar {
                let offsetY =
                    CGFloat(scrollbar.total - scrollbar.offset - scrollbar.len) * cellHeight
                scrollView.contentView.scroll(to: CGPoint(x: 0, y: offsetY))
                lastSentRow = Int(scrollbar.offset)
            }
        }

        scrollView.reflectScrolledClipView(scrollView.contentView)
    }

    private func handleScrollChange() {
        synchronizeSurfaceView()
    }

    private func handleLiveScroll() {
        let cellHeight = surfaceView.cellSize.height
        guard cellHeight > 0 else { return }

        let visibleRect = scrollView.contentView.documentVisibleRect
        let documentHeight = documentView.frame.height
        let scrollOffset = documentHeight - visibleRect.origin.y - visibleRect.height
        let row = Int(scrollOffset / cellHeight)

        guard row != lastSentRow else { return }
        lastSentRow = row
        _ = surfaceView.performBindingAction("scroll_to_row:\(row)")
    }

    private func handleScrollbarUpdate(_ notification: Notification) {
        guard let scrollbar = notification.userInfo?[GhosttyNotificationKey.scrollbar] as? GhosttyScrollbar else {
            return
        }
        surfaceView.scrollbar = scrollbar
        synchronizeScrollView()
    }

    private func documentHeight() -> CGFloat {
        let contentHeight = scrollView.contentSize.height
        let cellHeight = surfaceView.cellSize.height
        if cellHeight > 0, let scrollbar = surfaceView.scrollbar {
            let documentGridHeight = CGFloat(scrollbar.total) * cellHeight
            let padding = contentHeight - (CGFloat(scrollbar.len) * cellHeight)
            return documentGridHeight + padding
        }
        return contentHeight
    }
}

// MARK: - NSTextInputClient

extension GhosttyNSView: NSTextInputClient {
    fileprivate func sendTextToSurface(_ chars: String) {
        guard let surface = surface else { return }
#if DEBUG
        cmuxWriteChildExitProbe(
            [
                "probeInsertTextCharsHex": cmuxScalarHex(chars),
                "probeInsertTextSurfaceId": terminalSurface?.id.uuidString ?? "",
            ],
            increments: ["probeInsertTextCount": 1]
        )
#endif
        chars.withCString { ptr in
            var keyEvent = ghostty_input_key_s()
            keyEvent.action = GHOSTTY_ACTION_PRESS
            keyEvent.keycode = 0
            keyEvent.mods = GHOSTTY_MODS_NONE
            keyEvent.consumed_mods = GHOSTTY_MODS_NONE
            keyEvent.text = ptr
            keyEvent.composing = false
            _ = ghostty_surface_key(surface, keyEvent)
        }
    }

    func hasMarkedText() -> Bool {
        return markedText.length > 0
    }

    func markedRange() -> NSRange {
        guard markedText.length > 0 else { return NSRange(location: NSNotFound, length: 0) }
        return NSRange(location: 0, length: markedText.length)
    }

    func selectedRange() -> NSRange {
        return NSRange(location: NSNotFound, length: 0)
    }

    func setMarkedText(_ string: Any, selectedRange: NSRange, replacementRange: NSRange) {
        switch string {
        case let v as NSAttributedString:
            markedText = NSMutableAttributedString(attributedString: v)
        case let v as String:
            markedText = NSMutableAttributedString(string: v)
        default:
            break
        }

        // If we're not in a keyDown event, sync preedit immediately.
        // This can happen due to external events like changing keyboard layouts
        // while composing.
        if keyTextAccumulator == nil {
            syncPreedit()
        }
    }

    func unmarkText() {
        if markedText.length > 0 {
            markedText.mutableString.setString("")
            syncPreedit()
        }
    }

    /// Sync the preedit state based on the markedText value to libghostty.
    /// This tells Ghostty about IME composition text so it can render the
    /// preedit overlay (e.g. for Korean, Japanese, Chinese input).
    private func syncPreedit(clearIfNeeded: Bool = true) {
        guard let surface = surface else { return }

        if markedText.length > 0 {
            let str = markedText.string
            let len = str.utf8CString.count
            if len > 0 {
                str.withCString { ptr in
                    // Subtract 1 for the null terminator
                    ghostty_surface_preedit(surface, ptr, UInt(len - 1))
                }
            }
        } else if clearIfNeeded {
            // If we had marked text before but don't now, we're no longer
            // in a preedit state so we can clear it.
            ghostty_surface_preedit(surface, nil, 0)
        }
    }

    func validAttributesForMarkedText() -> [NSAttributedString.Key] {
        return []
    }

    func attributedSubstring(forProposedRange range: NSRange, actualRange: NSRangePointer?) -> NSAttributedString? {
        return nil
    }

    func characterIndex(for point: NSPoint) -> Int {
        return 0
    }

    func firstRect(forCharacterRange range: NSRange, actualRange: NSRangePointer?) -> NSRect {
        guard let window = self.window else {
            return NSRect(x: frame.origin.x, y: frame.origin.y, width: 0, height: 0)
        }

        // Use Ghostty's IME point API for accurate cursor position if available.
        var x: Double = 0
        var y: Double = 0
        var w: Double = cellSize.width
        var h: Double = cellSize.height
#if DEBUG
        if let override = imePointOverrideForTesting {
            x = override.x
            y = override.y
            w = override.width
            h = override.height
        } else if let surface = surface {
            ghostty_surface_ime_point(surface, &x, &y, &w, &h)
        }
#else
        if let surface = surface {
            ghostty_surface_ime_point(surface, &x, &y, &w, &h)
        }
#endif

        // Ghostty coordinates are top-left origin; AppKit expects bottom-left.
        let viewRect = NSRect(
            x: x,
            y: frame.size.height - y,
            width: w,
            height: max(h, cellSize.height)
        )
        let winRect = convert(viewRect, to: nil)
        return window.convertToScreen(winRect)
    }

    func insertText(_ string: Any, replacementRange: NSRange) {
        guard NSApp.currentEvent != nil else { return }

        // Get the string value
        var chars = ""
        switch string {
        case let v as NSAttributedString:
            chars = v.string
        case let v as String:
            chars = v
        default:
            return
        }

        // Clear marked text since we're inserting
        unmarkText()

        // If we have an accumulator, we're in a keyDown event - accumulate the text
        if keyTextAccumulator != nil {
            keyTextAccumulator?.append(chars)
            return
        }

        // Otherwise send directly to the terminal
        sendTextToSurface(chars)
    }
}

// MARK: - SwiftUI Wrapper

struct GhosttyTerminalView: NSViewRepresentable {
    @Environment(\.paneDropZone) var paneDropZone

    let terminalSurface: TerminalSurface
    var isActive: Bool = true
    var isVisibleInUI: Bool = true
    var portalZPriority: Int = 0
    var showsInactiveOverlay: Bool = false
    var showsUnreadNotificationRing: Bool = false
    var inactiveOverlayColor: NSColor = .clear
    var inactiveOverlayOpacity: Double = 0
    var searchState: TerminalSurface.SearchState? = nil
    var reattachToken: UInt64 = 0
    var onFocus: ((UUID) -> Void)? = nil
    var onTriggerFlash: (() -> Void)? = nil

    private final class HostContainerView: NSView {
        var onDidMoveToWindow: (() -> Void)?
        var onGeometryChanged: (() -> Void)?

        override func viewDidMoveToWindow() {
            super.viewDidMoveToWindow()
            onDidMoveToWindow?()
            onGeometryChanged?()
        }

        override func viewDidMoveToSuperview() {
            super.viewDidMoveToSuperview()
            onGeometryChanged?()
        }

        override func layout() {
            super.layout()
            onGeometryChanged?()
        }

        override func setFrameOrigin(_ newOrigin: NSPoint) {
            super.setFrameOrigin(newOrigin)
            onGeometryChanged?()
        }

        override func setFrameSize(_ newSize: NSSize) {
            super.setFrameSize(newSize)
            onGeometryChanged?()
        }
    }

    final class Coordinator {
        var attachGeneration: Int = 0
        // Track the latest desired state so attach retries can re-apply focus after re-parenting.
        var desiredIsActive: Bool = true
        var desiredIsVisibleInUI: Bool = true
        var desiredShowsUnreadNotificationRing: Bool = false
        var desiredPortalZPriority: Int = 0
        var lastBoundHostId: ObjectIdentifier?
        var lastPaneDropZone: DropZone?
        weak var hostedView: GhosttySurfaceScrollView?
    }

    func makeCoordinator() -> Coordinator {
        Coordinator()
    }

    static func shouldApplyImmediateHostedStateUpdate(
        hostedViewHasSuperview: Bool,
        isBoundToCurrentHost: Bool
    ) -> Bool {
        // If this update originates from a stale/replaced host while the hosted view is
        // already attached elsewhere, do not mutate visibility/active state here.
        if isBoundToCurrentHost { return true }
        return !hostedViewHasSuperview
    }

    func makeNSView(context: Context) -> NSView {
        let container = HostContainerView()
        container.wantsLayer = false
        return container
    }

    func updateNSView(_ nsView: NSView, context: Context) {
        let hostedView = terminalSurface.hostedView
        let coordinator = context.coordinator
        let previousDesiredIsActive = coordinator.desiredIsActive
        let previousDesiredIsVisibleInUI = coordinator.desiredIsVisibleInUI
        let previousDesiredShowsUnreadNotificationRing = coordinator.desiredShowsUnreadNotificationRing
        let previousDesiredPortalZPriority = coordinator.desiredPortalZPriority
        let desiredStateChanged =
            previousDesiredIsActive != isActive ||
            previousDesiredIsVisibleInUI != isVisibleInUI ||
            previousDesiredPortalZPriority != portalZPriority
        coordinator.desiredIsActive = isActive
        coordinator.desiredIsVisibleInUI = isVisibleInUI
        coordinator.desiredShowsUnreadNotificationRing = showsUnreadNotificationRing
        coordinator.desiredPortalZPriority = portalZPriority
        coordinator.hostedView = hostedView
#if DEBUG
        if desiredStateChanged {
            if let snapshot = AppDelegate.shared?.tabManager?.debugCurrentWorkspaceSwitchSnapshot() {
                let dtMs = (CACurrentMediaTime() - snapshot.startedAt) * 1000
                dlog(
                    "ws.swiftui.update id=\(snapshot.id) dt=\(String(format: "%.2fms", dtMs)) " +
                    "surface=\(terminalSurface.id.uuidString.prefix(5)) visible=\(isVisibleInUI ? 1 : 0) " +
                    "active=\(isActive ? 1 : 0) z=\(portalZPriority) " +
                    "hostWindow=\(nsView.window != nil ? 1 : 0) hostedWindow=\(hostedView.window != nil ? 1 : 0) " +
                    "hostedSuperview=\(hostedView.superview != nil ? 1 : 0)"
                )
            } else {
                dlog(
                    "ws.swiftui.update id=none surface=\(terminalSurface.id.uuidString.prefix(5)) " +
                    "visible=\(isVisibleInUI ? 1 : 0) active=\(isActive ? 1 : 0) z=\(portalZPriority) " +
                    "hostWindow=\(nsView.window != nil ? 1 : 0) hostedWindow=\(hostedView.window != nil ? 1 : 0) " +
                    "hostedSuperview=\(hostedView.superview != nil ? 1 : 0)"
                )
            }
        }
#endif

        // Keep the surface lifecycle and handlers updated even if we defer re-parenting.
        hostedView.attachSurface(terminalSurface)
        hostedView.setInactiveOverlay(
            color: inactiveOverlayColor,
            opacity: CGFloat(inactiveOverlayOpacity),
            visible: showsInactiveOverlay
        )
        hostedView.setNotificationRing(visible: showsUnreadNotificationRing)
        hostedView.setSearchOverlay(searchState: searchState)
        hostedView.setKeyboardCopyModeIndicator(visible: terminalSurface.keyboardCopyModeActive)
        hostedView.setFocusHandler { onFocus?(terminalSurface.id) }
        hostedView.setTriggerFlashHandler(onTriggerFlash)
        let portalExpectedSurfaceId = terminalSurface.id
        let portalExpectedGeneration = terminalSurface.portalBindingGeneration()
        let forwardedDropZone = isVisibleInUI ? paneDropZone : nil
#if DEBUG
        if coordinator.lastPaneDropZone != paneDropZone {
            let oldZone = coordinator.lastPaneDropZone.map { String(describing: $0) } ?? "none"
            let newZone = paneDropZone.map { String(describing: $0) } ?? "none"
            dlog(
                "terminal.paneDropZone surface=\(terminalSurface.id.uuidString.prefix(5)) " +
                "old=\(oldZone) new=\(newZone) " +
                "active=\(isActive ? 1 : 0) visible=\(isVisibleInUI ? 1 : 0) " +
                "inWindow=\(hostedView.window != nil ? 1 : 0)"
            )
            coordinator.lastPaneDropZone = paneDropZone
        }
        if paneDropZone != nil, !isVisibleInUI {
            dlog(
                "terminal.paneDropZone.suppress surface=\(terminalSurface.id.uuidString.prefix(5)) " +
                "requested=\(String(describing: paneDropZone!)) visible=0 active=\(isActive ? 1 : 0)"
            )
        }
#endif
        hostedView.setDropZoneOverlay(zone: forwardedDropZone)

        coordinator.attachGeneration += 1
        let generation = coordinator.attachGeneration

        let hostContainer = nsView as? HostContainerView
        if let host = hostContainer {
            host.onDidMoveToWindow = { [weak host, weak hostedView, weak coordinator] in
                guard let host, let hostedView, let coordinator else { return }
                guard coordinator.attachGeneration == generation else { return }
                guard host.window != nil else { return }
                TerminalWindowPortalRegistry.bind(
                    hostedView: hostedView,
                    to: host,
                    visibleInUI: coordinator.desiredIsVisibleInUI,
                    zPriority: coordinator.desiredPortalZPriority,
                    expectedSurfaceId: portalExpectedSurfaceId,
                    expectedGeneration: portalExpectedGeneration
                )
                coordinator.lastBoundHostId = ObjectIdentifier(host)
                hostedView.setVisibleInUI(coordinator.desiredIsVisibleInUI)
                hostedView.setActive(coordinator.desiredIsActive)
                hostedView.setNotificationRing(visible: coordinator.desiredShowsUnreadNotificationRing)
            }
            host.onGeometryChanged = { [weak host, weak hostedView, weak coordinator] in
                guard let host, let hostedView, let coordinator else { return }
                guard coordinator.attachGeneration == generation else { return }
                guard coordinator.lastBoundHostId == ObjectIdentifier(host) else { return }
                if host.window != nil,
                   !TerminalWindowPortalRegistry.isHostedView(hostedView, boundTo: host) {
#if DEBUG
                    dlog(
                        "ws.hostState.rebindOnGeometry surface=\(terminalSurface.id.uuidString.prefix(5)) " +
                        "reason=portalEntryMissing visible=\(coordinator.desiredIsVisibleInUI ? 1 : 0) " +
                        "active=\(coordinator.desiredIsActive ? 1 : 0) z=\(coordinator.desiredPortalZPriority)"
                    )
#endif
                    TerminalWindowPortalRegistry.bind(
                        hostedView: hostedView,
                        to: host,
                        visibleInUI: coordinator.desiredIsVisibleInUI,
                        zPriority: coordinator.desiredPortalZPriority,
                        expectedSurfaceId: portalExpectedSurfaceId,
                        expectedGeneration: portalExpectedGeneration
                    )
                    coordinator.lastBoundHostId = ObjectIdentifier(host)
                    hostedView.setVisibleInUI(coordinator.desiredIsVisibleInUI)
                    hostedView.setActive(coordinator.desiredIsActive)
                    hostedView.setNotificationRing(visible: coordinator.desiredShowsUnreadNotificationRing)
                }
                TerminalWindowPortalRegistry.synchronizeForAnchor(host)
            }

            if host.window != nil {
                let hostId = ObjectIdentifier(host)
                let shouldBindNow =
                    coordinator.lastBoundHostId != hostId ||
                    hostedView.superview == nil ||
                    previousDesiredIsVisibleInUI != isVisibleInUI ||
                    previousDesiredShowsUnreadNotificationRing != showsUnreadNotificationRing ||
                    previousDesiredPortalZPriority != portalZPriority
                if shouldBindNow {
                    TerminalWindowPortalRegistry.bind(
                        hostedView: hostedView,
                        to: host,
                        visibleInUI: coordinator.desiredIsVisibleInUI,
                        zPriority: coordinator.desiredPortalZPriority,
                        expectedSurfaceId: portalExpectedSurfaceId,
                        expectedGeneration: portalExpectedGeneration
                    )
                    coordinator.lastBoundHostId = hostId
                }
                TerminalWindowPortalRegistry.synchronizeForAnchor(host)
            } else {
                // Bind is deferred until host moves into a window. Update the
                // existing portal entry's visibleInUI now so that any portal sync
                // that runs before the deferred bind completes won't hide the view.
#if DEBUG
                if desiredStateChanged {
                    dlog(
                        "ws.hostState.deferBind surface=\(terminalSurface.id.uuidString.prefix(5)) " +
                        "reason=hostNoWindow visible=\(coordinator.desiredIsVisibleInUI ? 1 : 0) " +
                        "active=\(coordinator.desiredIsActive ? 1 : 0) z=\(coordinator.desiredPortalZPriority) " +
                        "hostedWindow=\(hostedView.window != nil ? 1 : 0) hostedSuperview=\(hostedView.superview != nil ? 1 : 0)"
                    )
                }
#endif
                TerminalWindowPortalRegistry.updateEntryVisibility(
                    for: hostedView,
                    visibleInUI: coordinator.desiredIsVisibleInUI
                )
            }
        }

        let hostWindowAttached = hostContainer?.window != nil
        let isBoundToCurrentHost = hostContainer.map { host in
            TerminalWindowPortalRegistry.isHostedView(hostedView, boundTo: host)
        } ?? true
        let shouldApplyImmediateHostedState = Self.shouldApplyImmediateHostedStateUpdate(
            hostedViewHasSuperview: hostedView.superview != nil,
            isBoundToCurrentHost: isBoundToCurrentHost
        )

        if shouldApplyImmediateHostedState {
            hostedView.setVisibleInUI(isVisibleInUI)
            hostedView.setActive(isActive)
        } else {
            // Preserve portal entry visibility while a stale host is still receiving SwiftUI updates.
            // The currently bound host remains authoritative for immediate visible/active state.
#if DEBUG
            if desiredStateChanged {
                dlog(
                    "ws.hostState.deferApply surface=\(terminalSurface.id.uuidString.prefix(5)) " +
                    "reason=staleHostBinding hostWindow=\(hostWindowAttached ? 1 : 0) " +
                    "boundToCurrent=\(isBoundToCurrentHost ? 1 : 0) hostedSuperview=\(hostedView.superview != nil ? 1 : 0) " +
                    "visible=\(isVisibleInUI ? 1 : 0) active=\(isActive ? 1 : 0)"
                )
            }
#endif
        }
    }

    static func dismantleNSView(_ nsView: NSView, coordinator: Coordinator) {
        coordinator.attachGeneration += 1
        coordinator.desiredIsActive = false
        coordinator.desiredIsVisibleInUI = false
        coordinator.desiredShowsUnreadNotificationRing = false
        coordinator.desiredPortalZPriority = 0
        coordinator.lastBoundHostId = nil
        let hostedView = coordinator.hostedView
#if DEBUG
        if let hostedView {
            if let snapshot = AppDelegate.shared?.tabManager?.debugCurrentWorkspaceSwitchSnapshot() {
                let dtMs = (CACurrentMediaTime() - snapshot.startedAt) * 1000
                dlog(
                    "ws.swiftui.dismantle id=\(snapshot.id) dt=\(String(format: "%.2fms", dtMs)) " +
                    "surface=\(hostedView.debugSurfaceId?.uuidString.prefix(5) ?? "nil") " +
                    "inWindow=\(hostedView.window != nil ? 1 : 0)"
                )
            } else {
                dlog(
                    "ws.swiftui.dismantle id=none surface=\(hostedView.debugSurfaceId?.uuidString.prefix(5) ?? "nil") " +
                    "inWindow=\(hostedView.window != nil ? 1 : 0)"
                )
            }
        }
#endif

        if let host = nsView as? HostContainerView {
            host.onDidMoveToWindow = nil
            host.onGeometryChanged = nil
        }

        // SwiftUI can transiently dismantle/rebuild NSViewRepresentable instances during split
        // tree updates. Do not force visible/active false here; that causes avoidable blackouts
        // when the same hosted view is rebound moments later.
        hostedView?.setFocusHandler(nil)
        hostedView?.setTriggerFlashHandler(nil)
        hostedView?.setDropZoneOverlay(zone: nil)
        coordinator.hostedView = nil

        nsView.subviews.forEach { $0.removeFromSuperview() }
    }
}