import AppKit
import ApplicationServices
import CoreGraphics
import Darwin
import Foundation
import ImageIO
import OrcaComputerUseMacOSCore
import ScreenCaptureKit

private let providerName = "orca-computer-use-macos"
private let providerVersion = "1.0.0"
private let providerProtocolVersion = 1

struct Request: Decodable {
    let id: Int
    let method: String
    let params: [String: JSONValue]?
    let token: String?
}

enum JSONValue: Decodable {
    case string(String)
    case number(Double)
    case bool(Bool)
    case object([String: JSONValue])
    case array([JSONValue])
    case null

    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        if container.decodeNil() {
            self = .null
        } else if let value = try? container.decode(Bool.self) {
            self = .bool(value)
        } else if let value = try? container.decode(Double.self) {
            self = .number(value)
        } else if let value = try? container.decode(String.self) {
            self = .string(value)
        } else if let value = try? container.decode([JSONValue].self) {
            self = .array(value)
        } else {
            self = .object(try container.decode([String: JSONValue].self))
        }
    }

    var string: String? {
        if case let .string(value) = self { return value }
        return nil
    }

    var number: Double? {
        if case let .number(value) = self { return value }
        return nil
    }

    var bool: Bool? {
        if case let .bool(value) = self { return value }
        return nil
    }
}

enum ProviderError: Error {
    case coded(String, String)

    var code: String {
        switch self {
        case let .coded(code, _):
            return code
        }
    }

    var message: String {
        switch self {
        case let .coded(_, message):
            return message
        }
    }
}

struct AppDescriptor {
    let name: String
    let bundleId: String?
    let pid: pid_t
    let app: NSRunningApplication

    var needsManualAccessibilityMode: Bool {
        // Chromium/Electron apps often need this private AX mode, but applying it
        // broadly can corrupt native Cocoa app trees into app-root-only nodes.
        guard let bundleId = bundleId?.lowercased() else {
            return false
        }
        return bundleId.hasPrefix("com.google.chrome") ||
            bundleId.hasPrefix("com.microsoft.edgemac") ||
            bundleId.hasPrefix("com.brave.browser") ||
            bundleId.hasPrefix("com.operasoftware.opera") ||
            bundleId.hasPrefix("com.vivaldi.vivaldi") ||
            bundleId == "com.github.electron" ||
            bundleId == "com.tinyspeck.slackmacgap" ||
            bundleId == "com.spotify.client" ||
            bundleId == "com.hnc.discord" ||
            bundleId == "com.microsoft.teams2" ||
            bundleId == "notion.id"
    }

    var isKnownBrowser: Bool {
        let bundle = bundleId?.lowercased() ?? ""
        let appName = name.lowercased()
        return bundle == "com.apple.safari" ||
            bundle == "org.mozilla.firefox" ||
            bundle == "company.thebrowser.browser" ||
            bundle == "app.zen-browser.zen" ||
            bundle.hasPrefix("com.google.chrome") ||
            bundle.hasPrefix("com.microsoft.edgemac") ||
            bundle.hasPrefix("com.brave.browser") ||
            bundle.hasPrefix("com.operasoftware.opera") ||
            bundle.hasPrefix("com.vivaldi.vivaldi") ||
            appName == "safari" ||
            appName == "firefox" ||
            appName == "arc" ||
            appName == "zen" ||
            appName.contains("chrome") ||
            appName.contains("chromium") ||
            appName.contains("edge") ||
            appName.contains("brave") ||
            appName.contains("opera") ||
            appName.contains("vivaldi")
    }
}

final class ElementRecord {
    let index: Int
    let element: AXUIElement
    let localFrame: CGRect?
    let actions: [String]
    let signature: String

    init(index: Int, element: AXUIElement, localFrame: CGRect?, actions: [String], signature: String) {
        self.index = index
        self.element = element
        self.localFrame = localFrame
        self.actions = actions
        self.signature = signature
    }
}

struct Snapshot {
    let id: String
    let app: AppDescriptor
    let windowTitle: String
    let windowBounds: CGRect
    let windowId: CGWindowID
    let windowLayer: Int
    let treeText: String
    let focusedElementId: Int?
    let screenshot: ScreenshotPayload?
    let screenshotStatus: ScreenshotStatus
    let screenshotScale: CGSize
    let screenshotEngine: String?
    let elements: [Int: ElementRecord]
    let elementOrder: [Int]
    let nextFreshElementIndex: Int
    let truncated: Bool
    let maxDepthReached: Bool
    /// On-screen windows of the app (menus and sheets included), so a new or closed window counts as a change.
    let appWindowIds: [CGWindowID]

    func showsSameState(as other: Snapshot) -> Bool {
        treeText == other.treeText && windowBounds == other.windowBounds && appWindowIds == other.appWindowIds
    }

    func withoutScreenshotPayload() -> Snapshot {
        Snapshot(
            id: id,
            app: app,
            windowTitle: windowTitle,
            windowBounds: windowBounds,
            windowId: windowId,
            windowLayer: windowLayer,
            treeText: treeText,
            focusedElementId: focusedElementId,
            screenshot: nil,
            screenshotStatus: .skipped,
            screenshotScale: CGSize(width: 1, height: 1),
            screenshotEngine: nil,
            elements: elements,
            elementOrder: elementOrder,
            nextFreshElementIndex: nextFreshElementIndex,
            truncated: truncated,
            maxDepthReached: maxDepthReached,
            appWindowIds: appWindowIds
        )
    }
}

struct ScreenshotPayload {
    let data: String
    let width: Int
    let height: Int
    let scale: Double
}

struct CapturedImage {
    let image: CGImage
    let engine: String
}

enum ScreenshotStatus {
    case captured
    case skipped
    case failed(String)
}

private struct CachedSnapshotEntry {
    let snapshotId: String
    let keys: [String]
    let createdAt: Date
}

final class Provider {
    private var snapshots: [String: Snapshot] = [:]
    private var snapshotEntries: [CachedSnapshotEntry] = []

    init() {
        // Why: the system-wide element sets the wait for every AX call in this process, so a hung app costs one bounded timeout whatever the macOS default.
        _ = AXUIElementSetMessagingTimeout(AXUIElementCreateSystemWide(), AccessibilityMessaging.timeoutSeconds)
    }

    func handle(method: String, params: [String: JSONValue]) throws -> Any {
        switch method {
        case "handshake":
            return providerHandshake()
        case "listApps":
            return ["apps": listApps().map(renderListedApp)]
        case "listWindows":
            return try listWindows(params: params)
        case "getAppState":
            return try renderSnapshot(observe(params: params))
        case "click":
            return try actionResult(params: params) { try click(params: params) }
        case "performSecondaryAction":
            return try actionResult(params: params) { try performSecondaryAction(params: params) }
        case "setValue":
            return try actionResult(params: params) { try setValue(params: params) }
        case "typeText":
            return try actionResult(params: params) { try typeText(params: params) }
        case "pressKey":
            return try actionResult(params: params) { try pressKey(params: params) }
        case "hotkey":
            return try actionResult(params: params) { try hotkey(params: params) }
        case "pasteText":
            return try actionResult(params: params) { try pasteText(params: params) }
        case "scroll":
            return try actionResult(params: params) { try scroll(params: params) }
        case "drag":
            return try actionResult(params: params) { try drag(params: params) }
        default:
            throw ProviderError.coded("invalid_argument", "unknown method '\(method)'")
        }
    }

    private func actionResult(params: [String: JSONValue], action runAction: () throws -> [String: Any]) throws -> [String: Any] {
        var action = try runAction()
        // Why: only --restore-window activates the app or posts to the HID tap; every other route leaves the user's desktop alone.
        action["delivery"] = isForegroundRequest(params) ? "foreground" : "background"
        // Why: the action's currentSnapshot just cached this target's tree from before the action.
        let before = action["path"] as? String == "accessibility" && action["verification"] == nil
            ? try? cachedSnapshot(params: params)
            : nil
        do {
            let after = try observe(params: params)
            guard let before, after.showsSameState(as: before) else {
                return renderActionResult(action: action, snapshot: after)
            }
            if let changed = try observeLateChange(before: before, params: params) {
                return renderActionResult(action: action, snapshot: changed)
            }
            // Why: an AX call can succeed and do nothing, as AXPress does on many web controls (#31758).
            action["verification"] = unverifiedAction(reason: "suspected_noop")
            return renderActionResult(action: action, snapshot: after)
        } catch let error as ProviderError where (error.code == "window_not_found" || error.code == "window_stale") && hasRequestedWindowSelector(params) {
            var fallbackParams = params
            fallbackParams.removeValue(forKey: "windowId")
            fallbackParams.removeValue(forKey: "windowIndex")
            if action["verification"] == nil {
                action["verification"] = ["state": "unverified", "reason": "window_changed"]
            }
            return try renderActionResult(action: action, snapshot: observe(params: fallbackParams))
        }
    }

    /// Re-reads the target for about a second, since apps often apply an action on a later run-loop turn.
    /// Returns the observation to report once something changed, or nil if nothing did.
    private func observeLateChange(before: Snapshot, params: [String: JSONValue]) throws -> Snapshot? {
        let settleParams = params.merging(["restoreWindow": .bool(false)]) { _, replacement in replacement }
        let quietParams = settleParams.merging(["noScreenshot": .bool(true)]) { _, replacement in replacement }
        let deadline = Date().addingTimeInterval(1)
        while Date() < deadline {
            Thread.sleep(forTimeInterval: 0.2)
            let polled = try observe(params: quietParams)
            if !polled.showsSameState(as: before) {
                if params["noScreenshot"]?.bool == true { return polled }
                return try observe(params: settleParams)
            }
        }
        return nil
    }

    private func observe(params: [String: JSONValue]) throws -> Snapshot {
        let query = try requiredString(params, "app")
        let windowId = try requestedWindowId(params)
        let windowIndex = try requestedWindowIndex(params)
        let app = try resolveApp(query)
        if params["restoreWindow"]?.bool == true {
            recoverWindow(app)
        }
        let namespace = snapshotNamespace(params)
        pruneSnapshotCache()
        let snapshot = try buildSnapshot(
            app: app,
            includeScreenshot: params["noScreenshot"]?.bool != true,
            windowId: windowId,
            windowIndex: windowIndex,
            restoreWindow: params["restoreWindow"]?.bool == true,
            previousSnapshot: { [snapshots] resolvedWindowId in
                // Why: indexes carry over from this caller's own last view of exactly this window.
                snapshots[namespacedSnapshotKey(namespace, snapshotCanonicalWindowIdKey(resolvedWindowId))]
                    .flatMap { $0.app.pid == app.pid ? $0 : nil }
            }
        )
        // Why: cached snapshots only validate element identity for follow-up
        // actions; retaining MB-scale screenshot base64 in the long-lived agent grows memory.
        rememberSnapshot(
            query: query,
            app: app,
            snapshot: snapshot.withoutScreenshotPayload(),
            params: params,
            windowIndex: windowIndex
        )
        return snapshot
    }

    private func rememberSnapshot(
        query: String,
        app: AppDescriptor,
        snapshot cachedSnapshot: Snapshot,
        params: [String: JSONValue],
        windowIndex: Int?
    ) {
        let keys = [query, app.name, app.bundleId ?? "", "pid:\(app.pid)"]
            .filter { !$0.isEmpty }
            .map { $0.lowercased() }
        let namespace = snapshotNamespace(params)
        var storedKeys: [String] = []
        let canonicalWindowKey = snapshotCanonicalWindowIdKey(cachedSnapshot.windowId)
        if !isExplicitSnapshotNamespace(namespace) {
            snapshots[canonicalWindowKey.lowercased()] = cachedSnapshot
            storedKeys.append(canonicalWindowKey.lowercased())
        }
        snapshots[namespacedSnapshotKey(namespace, canonicalWindowKey)] = cachedSnapshot
        storedKeys.append(namespacedSnapshotKey(namespace, canonicalWindowKey))
        if let windowIndex {
            let canonicalWindowIndexKey = snapshotCanonicalWindowIndexKey(windowIndex)
            if !isExplicitSnapshotNamespace(namespace) {
                snapshots[canonicalWindowIndexKey.lowercased()] = cachedSnapshot
                storedKeys.append(canonicalWindowIndexKey.lowercased())
            }
            snapshots[namespacedSnapshotKey(namespace, canonicalWindowIndexKey)] = cachedSnapshot
            storedKeys.append(namespacedSnapshotKey(namespace, canonicalWindowIndexKey))
        }
        for key in keys {
            if !isExplicitSnapshotNamespace(namespace) {
                snapshots[key] = cachedSnapshot
                storedKeys.append(key)
                snapshots[snapshotWindowKey(key, cachedSnapshot.windowId)] = cachedSnapshot
                storedKeys.append(snapshotWindowKey(key, cachedSnapshot.windowId))
                if let windowIndex {
                    snapshots[snapshotWindowIndexKey(key, windowIndex)] = cachedSnapshot
                    storedKeys.append(snapshotWindowIndexKey(key, windowIndex))
                }
            }
            snapshots[namespacedSnapshotKey(namespace, key)] = cachedSnapshot
            storedKeys.append(namespacedSnapshotKey(namespace, key))
            let namespacedWindowKey = namespacedSnapshotKey(
                namespace,
                snapshotWindowKey(key, cachedSnapshot.windowId)
            )
            snapshots[namespacedWindowKey] = cachedSnapshot
            storedKeys.append(namespacedWindowKey)
            if let windowIndex {
                let namespacedWindowIndexKey = namespacedSnapshotKey(
                    namespace,
                    snapshotWindowIndexKey(key, windowIndex)
                )
                snapshots[namespacedWindowIndexKey] = cachedSnapshot
                storedKeys.append(namespacedWindowIndexKey)
            }
        }
        snapshotEntries.append(
            CachedSnapshotEntry(snapshotId: cachedSnapshot.id, keys: storedKeys, createdAt: Date())
        )
        pruneSnapshotCache()
    }

    private func pruneSnapshotCache() {
        let now = Date()
        while let oldest = snapshotEntries.first,
              ComputerSnapshotCachePolicy.shouldPrune(
                  entryCount: snapshotEntries.count,
                  createdAt: oldest.createdAt,
                  now: now
              ) {
            let expired = snapshotEntries.removeFirst()
            for key in expired.keys where snapshots[key]?.id == expired.snapshotId {
                snapshots.removeValue(forKey: key)
            }
        }
    }

    private func currentSnapshot(params: [String: JSONValue]) throws -> Snapshot {
        pruneSnapshotCache()
        let cached = try cachedSnapshot(params: params)
        // Why: cached AX frames can be stale after a window move or resize, and
        // stale geometry can turn an intended action into a misclick.
        let snapshot = try observe(params: params.merging(["noScreenshot": .bool(true)]) { _, replacement in replacement })
        try validateRequestedElements(cached: cached, current: snapshot, params: params)
        return snapshot
    }

    private func currentKeyboardSnapshot(params: [String: JSONValue]) throws -> Snapshot {
        // Why: keyboard actions need fresh focused-element state, never pixels.
        try currentSnapshot(params: params.merging(["noScreenshot": .bool(true)]) { _, replacement in replacement })
    }

    private func cachedSnapshot(params: [String: JSONValue]) throws -> Snapshot? {
        guard let query = params["app"]?.string, !query.isEmpty else { return nil }
        let namespace = snapshotNamespace(params)
        if let targetWindowId = try requestedWindowId(params) {
            let canonicalKey = snapshotCanonicalWindowIdKey(targetWindowId)
            if let cached = snapshots[namespacedSnapshotKey(namespace, canonicalKey)] {
                return cached
            }
            if !isExplicitSnapshotNamespace(namespace), let cached = snapshots[canonicalKey.lowercased()] {
                return cached
            }
            let windowKey = snapshotWindowKey(query.lowercased(), targetWindowId)
            if let cached = snapshots[namespacedSnapshotKey(namespace, windowKey)] {
                return cached
            }
            if !isExplicitSnapshotNamespace(namespace), let cached = snapshots[windowKey] {
                return cached
            }
            return nil
        }
        if let targetWindowIndex = try requestedWindowIndex(params) {
            let canonicalKey = snapshotCanonicalWindowIndexKey(targetWindowIndex)
            if let cached = snapshots[namespacedSnapshotKey(namespace, canonicalKey)] {
                return cached
            }
            if !isExplicitSnapshotNamespace(namespace), let cached = snapshots[canonicalKey.lowercased()] {
                return cached
            }
            let windowKey = snapshotWindowIndexKey(query.lowercased(), targetWindowIndex)
            if let cached = snapshots[namespacedSnapshotKey(namespace, windowKey)] {
                return cached
            }
            if !isExplicitSnapshotNamespace(namespace), let cached = snapshots[windowKey] {
                return cached
            }
            return nil
        }
        let key = query.lowercased()
        return snapshots[namespacedSnapshotKey(namespace, key)] ??
            (isExplicitSnapshotNamespace(namespace) ? nil : snapshots[key])
    }

    private func validateRequestedElements(cached: Snapshot?, current: Snapshot, params: [String: JSONValue]) throws {
        let requestedIndexes = try ["elementIndex", "fromElementIndex", "toElementIndex"].compactMap { key -> Int? in
            guard params[key]?.number != nil else { return nil }
            return try optionalInteger(params, key)
        }
        guard !requestedIndexes.isEmpty else { return }
        guard let cached else {
            throw ProviderError.coded("element_not_found", "element indexes require a fresh get-app-state snapshot for this app/window")
        }
        for index in requestedIndexes {
            guard let expected = cached.elements[index], let actual = current.elements[index] else {
                throw ProviderError.coded("element_not_found", "element \(index) is stale; run get-app-state again and use a fresh element index")
            }
            guard expected.signature == actual.signature else {
                throw ProviderError.coded("element_not_found", "element \(index) changed since the last snapshot; run get-app-state again and use a fresh element index")
            }
        }
    }

    private func ensureWindowStillAvailable(_ snapshot: Snapshot) throws {
        guard WindowCapture.candidates(pid: snapshot.app.pid).contains(where: { $0.windowId == snapshot.windowId }) else {
            throw ProviderError.coded("window_stale", "window \(Int(snapshot.windowId)) is no longer available; run get-app-state again to refresh the target window")
        }
    }

    private func listApps() -> [AppDescriptor] {
        var seen = Set<String>()
        return NSWorkspace.shared.runningApplications
            .filter { !$0.isTerminated && $0.activationPolicy == .regular }
            .compactMap { app in
                guard let name = app.localizedName, !name.isEmpty else { return nil }
                let pid = app.processIdentifier
                guard pid > 0, pidIsLive(pid) else { return nil }
                let key = (app.bundleIdentifier ?? "pid:\(pid)").lowercased()
                guard seen.insert(key).inserted else { return nil }
                return AppDescriptor(name: name, bundleId: app.bundleIdentifier, pid: pid, app: app)
            }
            .sorted { lhs, rhs in
                if lhs.app.isActive != rhs.app.isActive {
                    return lhs.app.isActive && !rhs.app.isActive
                }
                return lhs.name.localizedCaseInsensitiveCompare(rhs.name) == .orderedAscending
            }
    }

    private func renderListedApp(_ app: AppDescriptor) -> [String: Any] {
        [
            "name": app.name,
            "bundleId": jsonNullable(app.bundleId),
            "pid": Int(app.pid),
            "isRunning": true,
            "lastUsedAt": NSNull(),
            "useCount": NSNull(),
        ]
    }

    private func providerHandshake() -> [String: Any] {
        [
            "platform": "darwin",
            "provider": providerName,
            "providerVersion": providerVersion,
            "protocolVersion": providerProtocolVersion,
            "supports": [
                "apps": [
                    "list": true,
                    "bundleIds": true,
                    "pids": true,
                ],
                "windows": [
                    "list": true,
                    "targetById": true,
                    "targetByIndex": true,
                    "focus": false,
                    "moveResize": false,
                ],
                "observation": [
                    "screenshot": true,
                    "annotatedScreenshot": false,
                    "elementFrames": true,
                    "ocr": false,
                ],
                "actions": [
                    "click": true,
                    "typeText": true,
                    "pressKey": true,
                    "hotkey": true,
                    "pasteText": true,
                    "scroll": true,
                    "drag": true,
                    "setValue": true,
                    "performAction": true,
                ],
                "surfaces": [
                    "menus": false,
                    "dialogs": false,
                    "dock": false,
                    "menubar": false,
                ],
                "input": [
                    "background": BackgroundInputTransport.isAvailable,
                ],
            ],
        ]
    }

    private func resolveApp(_ query: String) throws -> AppDescriptor {
        let trimmed = query.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !trimmed.isEmpty else {
            throw ProviderError.coded("invalid_argument", "app query must not be empty")
        }
        if let pid = parsePid(trimmed) {
            if let app = appByPid(pid) {
                try rejectBlockedApp(app)
                return app
            }
            throw ProviderError.coded("app_not_found", "app '\(trimmed)' not found")
        }
        if blockedBundleIds.contains(trimmed) {
            throw ProviderError.coded("app_blocked", "app '\(trimmed)' is blocked for safety")
        }
        if let app = listApps().first(where: { matches($0, query: trimmed) }) {
            try rejectBlockedApp(app)
            return app
        }
        throw ProviderError.coded("app_not_found", "app '\(trimmed)' not found")
    }

    private func rejectBlockedApp(_ app: AppDescriptor) throws {
        if let bundle = app.bundleId, blockedBundleIds.contains(bundle) {
            throw ProviderError.coded("app_blocked", "app '\(bundle)' is blocked for safety")
        }
    }

    private func listWindows(params: [String: JSONValue]) throws -> [String: Any] {
        let app = try resolveApp(try requiredString(params, "app"))
        let windows = WindowCapture.candidates(pid: app.pid)
            .filter { $0.layer == 0 }
            .enumerated()
            .map { index, candidate -> [String: Any] in
                [
                    "index": index,
                    "app": [
                        "name": app.name,
                        "bundleId": jsonNullable(app.bundleId),
                        "pid": Int(app.pid),
                    ],
                    "id": Int(candidate.windowId),
                    "title": candidate.title ?? "",
                    "x": Int(candidate.bounds.origin.x.rounded()),
                    "y": Int(candidate.bounds.origin.y.rounded()),
                    "width": Int(candidate.bounds.width.rounded()),
                    "height": Int(candidate.bounds.height.rounded()),
                    "isMinimized": false,
                    "isOffscreen": !candidate.isOnScreen,
                    "screenIndex": jsonNullable(screenIndex(for: candidate.bounds)),
                    "isMain": NSNull(),
                    "platform": [
                        "layer": candidate.layer,
                        "alpha": candidate.alpha,
                    ],
                ]
            }
        return [
            "app": renderListedApp(app),
            "windows": windows,
        ]
    }

    private func appByPid(_ pid: pid_t) -> AppDescriptor? {
        guard let app = NSRunningApplication(processIdentifier: pid),
              !app.isTerminated,
              let name = app.localizedName
        else {
            return nil
        }
        return AppDescriptor(name: name, bundleId: app.bundleIdentifier, pid: pid, app: app)
    }

    private func buildSnapshot(
        app: AppDescriptor,
        includeScreenshot: Bool,
        windowId: CGWindowID?,
        windowIndex: Int?,
        restoreWindow: Bool,
        previousSnapshot: (CGWindowID) -> Snapshot?
    ) throws -> Snapshot {
        guard accessibilityTrustedSettled() else {
            // Why: agents retry failed observations. Only the explicit setup flow
            // should open macOS privacy prompts/settings; runtime calls stay quiet.
            throw ProviderError.coded(
                "permission_denied",
                "Accessibility permission is required for Orca Computer Use. Run `orca computer permissions` or open Settings > Computer Use, grant Accessibility to Orca Computer Use, then retry."
            )
        }
        let appElement = AXUIElementCreateApplication(app.pid)
        var role: CFTypeRef?
        let probeStart = CFAbsoluteTimeGetCurrent()
        // Why: a hung app costs one timeout per AX read; walking it anyway held the request lock for every agent until the 60 s RPC timeout.
        if AccessibilityMessaging.timedOut(AXUIElementCopyAttributeValue(appElement, kAXRoleAttribute as CFString, &role), since: probeStart) {
            throw AccessibilityMessaging.appNotResponding(app.name)
        }
        enableManualAccessibilityIfNeeded(appElement, app: app)
        let windowCandidates = WindowCapture.candidates(pid: app.pid)
        let focused = try focusedWindow(
            appElement: appElement,
            app: app,
            visibleWindowCount: windowCandidates.count,
            allowRecovery: restoreWindow
        )
        let focusedTitle = stringAttribute(focused, kAXTitleAttribute as String) ?? app.name
        let canCaptureScreenshot = includeScreenshot && screenCaptureTrustedSettled()
        guard let capture = WindowCapture.resolve(
            candidates: windowCandidates,
            titleHint: focusedTitle,
            windowId: windowId,
            windowIndex: windowIndex,
            captureImage: canCaptureScreenshot
        ) else {
            throw ProviderError.coded("window_not_found", "app '\(app.name)' has no on-screen window")
        }
        guard let window = matchingWindow(appElement: appElement, capture: capture, focused: focused, explicitTarget: windowId != nil || windowIndex != nil) else {
            throw ProviderError.coded("window_not_found", "could not match accessibility window to requested window; run get-app-state again or retry without a window selector")
        }
        let title = stringAttribute(window, kAXTitleAttribute as String) ?? capture.title ?? app.name
        let renderer = TreeRenderer(
            windowBounds: capture.bounds,
            focused: focusedElement(appElement: appElement),
            compactBrowserTabs: app.isKnownBrowser
        )
        renderer.render(window)
        if renderer.appStoppedResponding {
            throw AccessibilityMessaging.appNotResponding(app.name)
        }
        let indexes = renderer.carryOverIndexes(from: previousSnapshot(capture.windowId))
        let screenshot = includeScreenshot ? capture.screenshotPayload() : nil
        let screenshotStatus: ScreenshotStatus = if screenshot != nil {
            .captured
        } else if includeScreenshot && !canCaptureScreenshot {
            .failed("Screen Recording permission is required for Orca Computer Use; grant permission or pass --no-screenshot to inspect accessibility state only.")
        } else if includeScreenshot {
            .failed("window screenshot capture returned no image; retry with --no-screenshot if accessibility state is sufficient.")
        } else {
            .skipped
        }
        return Snapshot(
            id: UUID().uuidString,
            app: app,
            windowTitle: title,
            windowBounds: capture.bounds,
            windowId: capture.windowId,
            windowLayer: capture.layer,
            treeText: renderTreeText(app: app, title: title, bounds: capture.bounds, lines: renderer.lines, focused: renderer.focusedSummary),
            focusedElementId: renderer.focusedElementId,
            screenshot: screenshot,
            screenshotStatus: screenshotStatus,
            screenshotScale: screenshotScale(screenshot: screenshot, bounds: capture.bounds),
            screenshotEngine: capture.image?.engine,
            elements: renderer.records,
            elementOrder: indexes.order,
            nextFreshElementIndex: indexes.nextFreshIndex,
            truncated: renderer.truncated,
            maxDepthReached: renderer.maxDepthReached,
            appWindowIds: windowCandidates.map(\.windowId).sorted()
        )
    }

    private func renderSnapshot(_ snapshot: Snapshot) -> [String: Any] {
        var screenshot: Any = NSNull()
        if let payload = snapshot.screenshot {
            screenshot = [
                "data": payload.data,
                "format": "png",
                "width": payload.width,
                "height": payload.height,
                "scale": payload.scale,
            ]
        }
        return [
            "snapshot": [
                "id": snapshot.id,
                "app": [
                    "name": snapshot.app.name,
                    "bundleId": jsonNullable(snapshot.app.bundleId),
                    "pid": Int(snapshot.app.pid),
                ],
                "window": [
                    "id": Int(snapshot.windowId),
                    "title": snapshot.windowTitle,
                    "x": Int(snapshot.windowBounds.origin.x.rounded()),
                    "y": Int(snapshot.windowBounds.origin.y.rounded()),
                    "width": Int(snapshot.windowBounds.width.rounded()),
                    "height": Int(snapshot.windowBounds.height.rounded()),
                    "isMinimized": false,
                    "isOffscreen": false,
                    "screenIndex": jsonNullable(screenIndex(for: snapshot.windowBounds)),
                    "platform": [
                        "layer": snapshot.windowLayer,
                    ],
                ],
                "coordinateSpace": "window",
                "treeText": snapshot.treeText,
                "elementCount": snapshot.elements.count,
                "focusedElementId": snapshot.focusedElementId as Any,
                "truncation": [
                    "truncated": snapshot.truncated,
                    "maxNodes": TreeRenderer.maxNodes,
                    "maxDepth": TreeRenderer.maxDepth,
                    "maxDepthReached": snapshot.maxDepthReached,
                ],
            ],
            "screenshot": screenshot,
            "screenshotStatus": renderScreenshotStatus(snapshot.screenshotStatus, snapshot: snapshot),
        ]
    }

    private func renderActionResult(action: [String: Any], snapshot: Snapshot) -> [String: Any] {
        var result = renderSnapshot(snapshot)
        var metadata = action
        metadata["targetWindowId"] = Int(snapshot.windowId)
        result["action"] = metadata
        return result
    }

    private func click(params: [String: JSONValue]) throws -> [String: Any] {
        let snapshot = try currentSnapshot(params: params)
        let button = try mouseButton(params["mouseButton"]?.string)
        let count = try positiveInteger(params["clickCount"]?.number, defaultValue: 1, name: "clickCount")
        guard count <= SyntheticMouseClickDelivery.maxClickCount else {
            throw ProviderError.coded(
                "invalid_argument",
                "clickCount must be at most \(SyntheticMouseClickDelivery.maxClickCount)"
            )
        }
        let modifiers = try KeyMap.parseModifiers(params["modifiers"]?.string)
        let foreground = isForegroundRequest(params)
        if foreground {
            recoverWindow(snapshot.app, windowId: snapshot.windowId, windowBounds: snapshot.windowBounds)
        }
        if let elementIndex = try optionalInteger(params, "elementIndex") {
            let record = try element(snapshot, elementIndex)
            if !foreground {
                try requireBackgroundClickAllowed(backgroundClickHit(record.element, snapshot: snapshot))
            }
            if modifiers.isEmpty,
               count <= 1,
               button.hasAccessibilityAction,
               let actionName = try performClickAction(record: record, mouseButton: button) {
                return actionMetadata(path: "accessibility", actionName: actionName)
            }
            if let point = center(record.localFrame, in: snapshot.windowBounds) {
                try clickPointer(at: point, button: button, count: count, modifiers: modifiers, snapshot: snapshot, foreground: foreground, element: record.element)
                return actionMetadata(
                    path: "synthetic",
                    fallbackReason: "actionUnsupported",
                    verification: unverifiedAction(reason: "synthetic_input")
                )
            }
            throw ProviderError.coded("element_not_clickable", "element \(record.index) has no clickable frame")
        }
        let point = try coordinatePoint(params: params, xKey: "x", yKey: "y", snapshot: snapshot)
        try clickPointer(at: point, button: button, count: count, modifiers: modifiers, snapshot: snapshot, foreground: foreground)
        return actionMetadata(
            path: "synthetic",
            verification: unverifiedAction(reason: "synthetic_input")
        )
    }

    private func performClickAction(record: ElementRecord, mouseButton: MouseButtonSelection) throws -> String? {
        if mouseButton == .right {
            return try performAction(record.element, "AXShowMenu") ? "AXShowMenu" : nil
        }
        for action in ["AXPress", "AXConfirm", "AXOpen"] {
            if try performAction(record.element, action) {
                return action
            }
        }
        return nil
    }

    private func performSecondaryAction(params: [String: JSONValue]) throws -> [String: Any] {
        let snapshot = try currentSnapshot(params: params)
        let record = try element(snapshot, try requiredInteger(params, "elementIndex"))
        let requested = try requiredString(params, "action")
        let action = record.actions.first { SnapshotRenderHeuristics.prettyAction($0).caseInsensitiveCompare(requested) == .orderedSame || $0.caseInsensitiveCompare(requested) == .orderedSame }
        guard let action else {
            throw ProviderError.coded("action_not_supported", "'\(requested)' is not a valid secondary action for element \(record.index)")
        }
        guard try performAction(record.element, action) else {
            throw ProviderError.coded("accessibility_error", "AXUIElementPerformAction(\(action)) failed")
        }
        return actionMetadata(path: "accessibility", actionName: action)
    }

    private func setValue(params: [String: JSONValue]) throws -> [String: Any] {
        let snapshot = try currentSnapshot(params: params)
        let record = try element(snapshot, try requiredInteger(params, "elementIndex"))
        let expected = try requiredStringAllowingEmpty(params, "value")
        guard isSettable(record.element, kAXValueAttribute as String) else {
            throw ProviderError.coded("value_not_settable", "element \(record.index) is not settable")
        }
        let current = rawAttributeValue(record.element, kAXValueAttribute as String)
        let coercion = AttributeValueCoercion(existingValue: current, requested: expected)
        let result: AXError
        let writeStart = CFAbsoluteTimeGetCurrent()
        switch coercion.writeValue {
        case .string:
            result = AXUIElementSetAttributeValue(record.element, kAXValueAttribute as CFString, expected as CFString)
        case let .integer(value):
            result = AXUIElementSetAttributeValue(record.element, kAXValueAttribute as CFString, NSNumber(value: value))
        case let .double(value):
            result = AXUIElementSetAttributeValue(record.element, kAXValueAttribute as CFString, NSNumber(value: value))
        case let .boolean(value):
            result = AXUIElementSetAttributeValue(record.element, kAXValueAttribute as CFString, value ? kCFBooleanTrue : kCFBooleanFalse)
        }
        if AccessibilityMessaging.timedOut(result, since: writeStart) {
            throw AccessibilityMessaging.unanswered("the value write")
        }
        guard result == .success else {
            throw ProviderError.coded("accessibility_error", "AXUIElementSetAttributeValue failed with \(result.rawValue)")
        }
        let verification: [String: Any]
        switch coercion.compare(readback: rawAttributeValue(record.element, kAXValueAttribute as String)) {
        case let .match(actualPreview):
            verification = verifiedAction(property: "value", expected: expected, actualPreview: actualPreview)
        case let .mismatch(actualPreview):
            verification = unverifiedAction(reason: "value_mismatch", expected: expected, actualPreview: actualPreview)
        case .unsupported:
            verification = unverifiedAction(reason: "readback_unsupported", expected: expected)
        }
        return actionMetadata(path: "accessibility", actionName: "AXSetValue", verification: verification)
    }

    private func typeText(params: [String: JSONValue]) throws -> [String: Any] {
        let snapshot = try currentKeyboardSnapshot(params: params)
        let text = try requiredString(params, "text")
        if let focused = focusedRecord(snapshot), let verification = try TextInput.replaceSelection(focused.element, with: text) {
            return actionMetadata(path: "accessibility", actionName: "AXReplaceSelection", verification: verification)
        }
        try deliverKeys(try withTransportErrors { try BackgroundInputTransport.textEvents(text) }, snapshot: snapshot, params: params)
        return actionMetadata(
            path: "synthetic",
            actionName: "typeText",
            verification: unverifiedAction(reason: "synthetic_input")
        )
    }

    private func pressKey(params: [String: JSONValue]) throws -> [String: Any] {
        let snapshot = try currentKeyboardSnapshot(params: params)
        try deliverKeys(try Input.keyEvents(try requiredString(params, "key")), snapshot: snapshot, params: params)
        return actionMetadata(
            path: "synthetic",
            actionName: "pressKey",
            verification: unverifiedAction(reason: "synthetic_input")
        )
    }

    private func hotkey(params: [String: JSONValue]) throws -> [String: Any] {
        let snapshot = try currentKeyboardSnapshot(params: params)
        let key = try requiredString(params, "key")
        if isSelectAllHotkey(key), let focused = focusedRecord(snapshot), TextInput.selectAll(focused.element) {
            return actionMetadata(
                path: "accessibility",
                actionName: "AXSelectAll",
                verification: TextInput.selectionVerification(focused.element)
            )
        }
        try deliverKeys(try Input.keyEvents(key), snapshot: snapshot, params: params)
        return actionMetadata(
            path: "synthetic",
            actionName: "hotkey",
            verification: unverifiedAction(reason: "synthetic_input")
        )
    }

    private func pasteText(params: [String: JSONValue]) throws -> [String: Any] {
        let snapshot = try currentKeyboardSnapshot(params: params)
        let text = try requiredString(params, "text")
        if let focused = focusedRecord(snapshot), let verification = try TextInput.replaceSelection(focused.element, with: text) {
            return actionMetadata(path: "accessibility", actionName: "AXReplaceSelection", verification: verification)
        }
        let pasteKeys = try Input.keyEvents("cmd+v")
        try Input.withPasteboardText(text) {
            try deliverKeys(pasteKeys, snapshot: snapshot, params: params)
        }
        return actionMetadata(
            path: "clipboard",
            actionName: "paste",
            verification: unverifiedAction(reason: "clipboard_paste")
        )
    }

    private func scroll(params: [String: JSONValue]) throws -> [String: Any] {
        let snapshot = try currentSnapshot(params: params)
        let direction = try scrollDirection(try requiredString(params, "direction"))
        let pages = try positiveNumber(params["pages"]?.number, defaultValue: 1, name: "pages")
        if let elementIndex = try optionalInteger(params, "elementIndex") {
            let record = try element(snapshot, elementIndex)
            let action = "AXScroll\(direction.capitalized)ByPage"
            if pages.rounded() == pages, let pageCount = boundedInteger(pages, as: Int.self),
               record.actions.contains(action) {
                for _ in 0..<max(1, pageCount) {
                    _ = try performAction(record.element, action)
                }
                return actionMetadata(path: "accessibility", actionName: action)
            }
            guard let point = center(record.localFrame, in: snapshot.windowBounds) else {
                throw ProviderError.coded("element_not_found", "element \(record.index) has no scrollable frame")
            }
            try scrollPointer(at: point, direction: direction, pages: pages, snapshot: snapshot, params: params)
            return actionMetadata(path: "synthetic", fallbackReason: "actionUnsupported")
        }
        let point = try coordinatePoint(params: params, xKey: "x", yKey: "y", snapshot: snapshot)
        try scrollPointer(at: point, direction: direction, pages: pages, snapshot: snapshot, params: params)
        return actionMetadata(path: "synthetic")
    }

    private func drag(params: [String: JSONValue]) throws -> [String: Any] {
        let snapshot = try currentSnapshot(params: params)
        let start: CGPoint
        let end: CGPoint
        if let fromIndex = try optionalInteger(params, "fromElementIndex"),
           let toIndex = try optionalInteger(params, "toElementIndex") {
            let from = try element(snapshot, fromIndex)
            let to = try element(snapshot, toIndex)
            guard let fromPoint = center(from.localFrame, in: snapshot.windowBounds),
                  let toPoint = center(to.localFrame, in: snapshot.windowBounds)
            else {
                throw ProviderError.coded("element_not_found", "drag element has no frame")
            }
            start = fromPoint
            end = toPoint
        } else {
            start = try coordinatePoint(params: params, xKey: "fromX", yKey: "fromY", snapshot: snapshot)
            end = try coordinatePoint(params: params, xKey: "toX", yKey: "toY", snapshot: snapshot)
        }
        if isForegroundRequest(params) {
            try requireTargetWindowFocused(snapshot, restoreWindowRequested: true)
            try Input.drag(from: start, to: end, targetWindow: snapshot)
        } else {
            try withTransportErrors {
                try BackgroundInputTransport.drag(backgroundTarget(snapshot), from: start, to: end)
            }
        }
        return actionMetadata(path: "synthetic")
    }

    private func element(_ snapshot: Snapshot, _ index: Int) throws -> ElementRecord {
        guard let record = snapshot.elements[index] else {
            throw ProviderError.coded("element_not_found", "element \(index) is not in the current cached snapshot for \(snapshot.app.name); run get-app-state again and use a fresh element index")
        }
        return record
    }

    private func focusedRecord(_ snapshot: Snapshot) -> ElementRecord? {
        guard let focusedElementId = snapshot.focusedElementId else {
            return nil
        }
        return snapshot.elements[focusedElementId]
    }
}

private let blockedBundleIds: Set<String> = [
    "com.1password.1password",
    "com.1password.safari",
    "com.bitwarden.desktop",
    "com.dashlane.dashlanephonefinal",
    "com.lastpass.LastPass",
    "com.nordsec.nordpass",
    "me.proton.pass.electron",
    "me.proton.pass.catalyst",
]

private func requiredString(_ params: [String: JSONValue], _ key: String) throws -> String {
    guard let value = params[key]?.string, !value.isEmpty else {
        throw ProviderError.coded("invalid_argument", "missing \(key)")
    }
    return value
}

private func requiredStringAllowingEmpty(_ params: [String: JSONValue], _ key: String) throws -> String {
    guard let value = params[key]?.string else {
        throw ProviderError.coded("invalid_argument", "missing \(key)")
    }
    return value
}

private func requiredNumber(_ params: [String: JSONValue], _ key: String) throws -> Double {
    guard let value = params[key]?.number, value.isFinite else {
        throw ProviderError.coded("invalid_argument", "missing \(key)")
    }
    return value
}

private func requiredInteger(_ params: [String: JSONValue], _ key: String) throws -> Int {
    guard let value = boundedInteger(try requiredNumber(params, key), as: Int.self) else {
        throw ProviderError.coded("invalid_argument", "\(key) is out of range")
    }
    return value
}

private func optionalInteger(_ params: [String: JSONValue], _ key: String) throws -> Int? {
    guard let raw = params[key]?.number else { return nil }
    guard let value = boundedInteger(raw, as: Int.self) else {
        throw ProviderError.coded("invalid_argument", "\(key) is out of range")
    }
    return value
}

private func positiveInteger(_ value: Double?, defaultValue: Int, name: String) throws -> Int {
    switch ActionArgumentValidation.positiveInteger(value, defaultValue: defaultValue, name: name) {
    case let .success(value):
        return value
    case let .failure(error):
        throw ProviderError.coded("invalid_argument", error.message)
    }
}

private func positiveNumber(_ value: Double?, defaultValue: Double, name: String) throws -> Double {
    switch ActionArgumentValidation.positiveNumber(value, defaultValue: defaultValue, name: name) {
    case let .success(value):
        return value
    case let .failure(error):
        throw ProviderError.coded("invalid_argument", error.message)
    }
}

private func scrollDirection(_ value: String) throws -> String {
    switch ActionArgumentValidation.scrollDirection(value) {
    case let .success(value):
        return value
    case let .failure(error):
        throw ProviderError.coded("invalid_argument", error.message)
    }
}

private func parsePid(_ query: String) -> pid_t? {
    guard query.hasPrefix("pid:") else { return nil }
    guard let pid = Int32(query.dropFirst(4)), pid > 0 else { return nil }
    return pid
}

private func matches(_ app: AppDescriptor, query: String) -> Bool {
    app.name.caseInsensitiveCompare(query) == .orderedSame ||
        app.bundleId?.caseInsensitiveCompare(query) == .orderedSame
}

private func pidIsLive(_ pid: pid_t) -> Bool {
    kill(pid, 0) == 0
}

private func accessibilityTrusted() -> Bool {
    AXIsProcessTrusted()
}

private func accessibilityTrustedSettled() -> Bool {
    // Fresh helper processes can receive transient TCC preflight denials before the real grant settles.
    PermissionTrustSettling.settle(probe: accessibilityTrusted).settled
}

private func screenCaptureTrusted() -> Bool {
    CGPreflightScreenCaptureAccess()
}

private func screenCaptureTrustedSettled() -> Bool {
    PermissionTrustSettling.settle(timeoutMs: 2_000, probe: screenCaptureTrusted).settled
}

private func permissionStatusSnapshotSettled() -> PermissionStatusSnapshot {
    PermissionStatusSnapshotProbe.capture(
        accessibilityProbe: accessibilityTrustedSettled,
        screenshotsProbe: screenCaptureTrustedSettled
    )
}

private func requestScreenCaptureAccess() -> Bool {
    CGRequestScreenCaptureAccess()
}

private func openAccessibilitySettings() {
    openSystemSettings("x-apple.systempreferences:com.apple.preference.security?Privacy_Accessibility")
}

private func openScreenRecordingSettings() {
    openSystemSettings("x-apple.systempreferences:com.apple.preference.security?Privacy_ScreenCapture")
}

private func openSystemSettings(_ value: String) {
    guard let url = URL(string: value) else { return }
    NSWorkspace.shared.open(url)
}

private func enableManualAccessibilityIfNeeded(_ appElement: AXUIElement, app: AppDescriptor) {
    guard app.needsManualAccessibilityMode else {
        return
    }
    _ = AXUIElementSetAttributeValue(appElement, "AXManualAccessibility" as CFString, kCFBooleanTrue)
    _ = AXUIElementSetAttributeValue(appElement, "AXEnhancedUserInterface" as CFString, kCFBooleanTrue)
}

private func focusedWindow(appElement: AXUIElement, app: AppDescriptor, visibleWindowCount: Int, allowRecovery: Bool) throws -> AXUIElement {
    let systemWide = AXUIElementCreateSystemWide()
    if let window = lookupUsableWindow(systemWide: systemWide, appElement: appElement, app: app) {
        return window
    }
    if allowRecovery {
        recoverWindow(app)
        if let window = lookupUsableWindow(systemWide: systemWide, appElement: appElement, app: app) {
            return window
        }
    }
    if visibleWindowCount > 0 {
        var settledWindow: AXUIElement?
        let outcome = PermissionTrustSettling.settle {
            settledWindow = lookupUsableWindow(
                systemWide: systemWide,
                appElement: appElement,
                app: app
            )
            return settledWindow != nil
        }
        if let window = settledWindow, outcome.settled {
            return window
        }
        throw ProviderError.coded("permission_denied", "app '\(app.name)' has visible windows but no accessibility window (AX reads stayed blocked for \(outcome.waitedMs)ms after retries). macOS Accessibility may need Orca Computer Use toggled off and on again in System Settings.")
    }
    throw ProviderError.coded("window_not_found", "app '\(app.name)' has no accessibility window; make sure the app has a visible window, then retry with --restore-window.")
}

private func lookupUsableWindow(
    systemWide: AXUIElement,
    appElement: AXUIElement,
    app: AppDescriptor
) -> AXUIElement? {
    if let window = focusedSystemWindow(systemWide: systemWide, app: app) {
        return window
    }
    if let window = copyElement(appElement, kAXFocusedWindowAttribute as String), usableWindow(window) {
        return window
    }
    if let windows = copyArray(appElement, kAXWindowsAttribute as String) {
        return windows.first(where: usableWindow)
    }
    return nil
}

private func focusedSystemWindow(systemWide: AXUIElement, app: AppDescriptor) -> AXUIElement? {
    guard let focusedApp = copyElement(systemWide, kAXFocusedApplicationAttribute as String),
          pidAttribute(focusedApp) == app.pid
    else {
        return nil
    }
    if let window = copyElement(systemWide, kAXFocusedWindowAttribute as String), usableWindow(window) {
        return window
    }
    if let window = copyElement(focusedApp, kAXFocusedWindowAttribute as String), usableWindow(window) {
        return window
    }
    if let windows = copyArray(focusedApp, kAXWindowsAttribute as String) {
        return windows.first(where: usableWindow)
    }
    return nil
}

private func isTargetWindowFocused(_ snapshot: Snapshot) -> Bool {
    focusedSyntheticClickRecipient(
        targetPID: snapshot.app.pid,
        targetCandidates: { WindowCapture.candidates(pid: snapshot.app.pid) }
    ) == .focused(syntheticClickRecipient(pid: snapshot.app.pid, windowId: snapshot.windowId))
}

private enum AXElementProbe {
    case value(AXUIElement)
    case absent
    case unavailable
}

private func copyElementProbe(_ element: AXUIElement, _ attribute: String) -> AXElementProbe {
    var value: CFTypeRef?
    switch AXUIElementCopyAttributeValue(element, attribute as CFString, &value) {
    case .success:
        guard let value else { return .unavailable }
        return .value(value as! AXUIElement)
    case .noValue:
        return .absent
    default:
        return .unavailable
    }
}

private func currentSyntheticClickRecipient(
    snapshot: Snapshot,
    point: CGPoint
) -> SyntheticMouseClickDelivery.RecipientObservation {
    let target = syntheticClickRecipient(pid: snapshot.app.pid, windowId: snapshot.windowId)
    var cachedTargetCandidates: [WindowCandidate]?
    func targetCandidates() -> [WindowCandidate] {
        if let cachedTargetCandidates { return cachedTargetCandidates }
        let candidates = WindowCapture.candidates(pid: snapshot.app.pid)
        cachedTargetCandidates = candidates
        return candidates
    }
    switch focusedSyntheticClickRecipient(
        targetPID: snapshot.app.pid,
        targetCandidates: targetCandidates
    ) {
    case let .focused(focused):
        guard focused == target else { return .focused(focused) }
        switch hitTestSyntheticClickRecipient(
            at: point,
            targetPID: snapshot.app.pid,
            targetCandidates: targetCandidates
        ) {
        case let .focused(recipient):
            return .focused(recipient)
        case .dismissed, .unavailable:
            return .unavailable
        }
    case .dismissed:
        return .dismissed
    case .unavailable:
        return .unavailable
    }
}

private func focusedSyntheticClickRecipient(
    targetPID: pid_t,
    targetCandidates: () -> [WindowCandidate]
) -> SyntheticMouseClickDelivery.RecipientObservation {
    let systemWide = AXUIElementCreateSystemWide()
    let focusedApp: AXUIElement
    switch copyElementProbe(systemWide, kAXFocusedApplicationAttribute as String) {
    case let .value(value):
        focusedApp = value
    case .absent:
        return .dismissed
    case .unavailable:
        return .unavailable
    }
    guard let ownerPID = pidAttribute(focusedApp) else { return .unavailable }

    let focusedWindow: AXUIElement
    switch copyElementProbe(focusedApp, kAXFocusedWindowAttribute as String) {
    case let .value(value):
        focusedWindow = value
    case .absent:
        guard ownerPID == targetPID else { return .unavailable }
        return .dismissed
    case .unavailable:
        return .unavailable
    }

    guard pidAttribute(focusedWindow) == ownerPID else { return .unavailable }
    return pointerRecipient(of: focusedWindow, targetPID: targetPID, targetCandidates: targetCandidates)
}

private func hitTestSyntheticClickRecipient(
    at point: CGPoint,
    targetPID: pid_t,
    targetCandidates: () -> [WindowCandidate]
) -> SyntheticMouseClickDelivery.RecipientObservation {
    guard Float(point.x).isFinite, Float(point.y).isFinite else { return .unavailable }
    let systemWide = AXUIElementCreateSystemWide()
    var hitElement: AXUIElement?
    switch AXUIElementCopyElementAtPosition(
        systemWide,
        Float(point.x),
        Float(point.y),
        &hitElement
    ) {
    case .success:
        break
    case .noValue:
        return .dismissed
    default:
        return .unavailable
    }
    guard let hitElement else { return .unavailable }
    return pointerRecipient(of: hitElement, targetPID: targetPID, targetCandidates: targetCandidates)
}

private func pointerRecipient(
    of element: AXUIElement,
    targetPID: pid_t,
    targetCandidates: () -> [WindowCandidate]
) -> SyntheticMouseClickDelivery.RecipientObservation {
    guard let ownerPID = pidAttribute(element), let window = containingWindow(element) else {
        return .unavailable
    }
    do {
        if let windowID = try AccessibilityWindowIdentity.windowID(of: window) {
            return .focused(syntheticClickRecipient(pid: ownerPID, windowId: windowID))
        }
    } catch {
        return .unavailable
    }
    guard ownerPID == targetPID, let frame = absoluteFrame(window),
          let windows = copyArray(AXUIElementCreateApplication(ownerPID), kAXWindowsAttribute as String)
    else { return .unavailable }
    var matches: [AXUIElement] = []
    for candidate in windows {
        guard let candidateFrame = absoluteFrame(candidate) else { return .unavailable }
        if windowFramesMatch(candidateFrame, frame) { matches.append(candidate) }
    }
    guard matches.count == 1, CFEqual(matches[0], window),
          let candidate = SyntheticMouseClickDelivery.uniqueWindowCandidate(
            from: targetCandidates(),
            matching: { windowFramesMatch($0.bounds, frame) }
          )
    else { return .unavailable }
    return .focused(syntheticClickRecipient(pid: ownerPID, windowId: candidate.windowId))
}

private func containingWindow(_ element: AXUIElement) -> AXUIElement? {
    var current = element
    for _ in 0..<64 {
        if stringAttribute(current, kAXRoleAttribute as String) == kAXWindowRole as String {
            return current
        }
        if let window = copyElement(current, kAXWindowAttribute as String) {
            return window
        }
        guard let parent = copyElement(current, kAXParentAttribute as String) else {
            return nil
        }
        current = parent
    }
    return nil
}

private func syntheticClickRecipient(
    pid: pid_t,
    windowId: CGWindowID
) -> SyntheticMouseClickDelivery.Recipient {
    SyntheticMouseClickDelivery.Recipient(ownerPID: pid, windowID: windowId)
}

private func requireTargetWindowFocused(_ snapshot: Snapshot, restoreWindowRequested: Bool) throws {
    guard let failure = KeyboardInputSafety.syntheticInputFocusFailure(
        targetWindowFocused: isTargetWindowFocused(snapshot),
        restoreWindowRequested: restoreWindowRequested
    ) else {
        return
    }
    switch failure {
    case .targetNotFocused:
        throw ProviderError.coded("window_not_focused", "keyboard input requires the target \(snapshot.app.name) window to be focused; retry with --restore-window or use set-value for editable elements")
    case .targetNotFocusedAfterRestore:
        throw ProviderError.coded("window_not_focused", "keyboard input requires the target \(snapshot.app.name) window to be focused; --restore-window was requested but the target is still not focused; bring it forward manually or check Accessibility permissions")
    }
}

private func isForegroundRequest(_ params: [String: JSONValue]) -> Bool {
    params["restoreWindow"]?.bool == true
}

private func backgroundTarget(_ snapshot: Snapshot) -> BackgroundInputTransport.Target {
    BackgroundInputTransport.Target(pid: snapshot.app.pid, windowID: snapshot.windowId, windowFrame: snapshot.windowBounds)
}

private func withTransportErrors<T>(_ body: () throws -> T) throws -> T {
    do {
        return try body()
    } catch let failure as BackgroundInputTransport.Failure {
        switch failure {
        case let .unavailable(missingSymbols):
            throw ProviderError.coded("background_unavailable", "background input is unavailable on this macOS version (missing \(missingSymbols.joined(separator: ", "))); retry with --restore-window to bring the app forward and use foreground input")
        case .processNotFound:
            throw ProviderError.coded("app_not_found", "the target app quit before input was delivered")
        case .eventCreationFailed:
            throw ProviderError.coded("accessibility_error", "failed to create input event")
        case .targetWindowNotKey:
            throw ProviderError.coded("background_unavailable", "background input cannot change the key window of the active app; retry with --restore-window to target this window explicitly")
        case let .focusRecordFailed(status):
            throw ProviderError.coded("window_not_focused", "background key-window focus record failed (status \(status)); input may already have been delivered, so inspect current state before retrying")
        }
    }
}

private func clickPointer(
    at point: CGPoint,
    button: MouseButtonSelection,
    count: Int,
    modifiers: [KeyModifier],
    snapshot: Snapshot,
    foreground: Bool,
    element: AXUIElement? = nil
) throws {
    if foreground {
        try Input.click(at: point, button: button, count: count, modifiers: modifiers, targetWindow: snapshot)
        return
    }
    let hitElement: AXUIElement
    if let element {
        hitElement = element
    } else {
        var found: AXUIElement?
        guard Float(point.x).isFinite, Float(point.y).isFinite,
              AXUIElementCopyElementAtPosition(AXUIElementCreateApplication(snapshot.app.pid), Float(point.x), Float(point.y), &found) == .success,
              let found
        else {
            throw ProviderError.coded("background_unavailable", "cannot identify the background click target; run get-app-state again or retry with --restore-window")
        }
        hitElement = found
    }
    let hit = try backgroundClickHit(hitElement, snapshot: snapshot)
    try requireBackgroundClickAllowed(hit)
    try withTransportErrors {
        try BackgroundInputTransport.click(
            backgroundTarget(snapshot),
            at: point,
            button: button,
            clickCount: count,
            flags: eventFlags(modifiers),
            hit: hit
        )
    }
}

private func backgroundClickHit(_ element: AXUIElement, snapshot: Snapshot) throws -> BackgroundInputTransport.PointerHit {
    let recipient = pointerRecipient(of: element, targetPID: snapshot.app.pid) {
        WindowCapture.candidates(pid: snapshot.app.pid)
    }
    guard recipient == .focused(syntheticClickRecipient(pid: snapshot.app.pid, windowId: snapshot.windowId)) else {
        throw ProviderError.coded("background_unavailable", "the background click target does not identify the requested window; run get-app-state again or retry with --restore-window")
    }
    return BackgroundInputTransport.classifyPointerHit(element)
}

private func requireBackgroundClickAllowed(_ hit: BackgroundInputTransport.PointerHit) throws {
    guard hit != .popupMenu else {
        throw ProviderError.coded("background_unavailable", "a background click on a popup menu or web <select> opens the menu off screen or wedges the app's input; set the option with set-value on the popup element, or retry with --restore-window for a foreground click")
    }
}

private func scrollPointer(at point: CGPoint, direction: String, pages: Double, snapshot: Snapshot, params: [String: JSONValue]) throws {
    guard let delta = boundedInteger(max(1, (12 * pages).rounded()), as: Int32.self) else {
        throw ProviderError.coded("invalid_argument", "pages is out of range")
    }
    let wheel1: Int32 = direction == "up" ? delta : direction == "down" ? -delta : 0
    let wheel2: Int32 = direction == "left" ? delta : direction == "right" ? -delta : 0
    if isForegroundRequest(params) {
        try requireTargetWindowFocused(snapshot, restoreWindowRequested: true)
        try Input.scroll(at: point, wheel1: wheel1, wheel2: wheel2, targetWindow: snapshot)
        return
    }
    try withTransportErrors {
        try BackgroundInputTransport.scroll(backgroundTarget(snapshot), at: point, wheel1: wheel1, wheel2: wheel2)
    }
}

private func deliverKeys(_ events: [CGEvent], snapshot: Snapshot, params: [String: JSONValue]) throws {
    if isForegroundRequest(params) {
        try requireTargetWindowFocused(snapshot, restoreWindowRequested: true)
        for event in events {
            event.post(tap: .cghidEventTap)
        }
        return
    }
    try withTransportErrors {
        try BackgroundInputTransport.sendKeys(events, to: backgroundTarget(snapshot))
    }
}

private func eventFlags(_ modifiers: [KeyModifier]) -> CGEventFlags {
    modifiers.reduce(into: CGEventFlags()) { result, modifier in
        result.insert(modifier.flag)
    }
}

private func matchingWindow(appElement: AXUIElement, capture: WindowCapture, focused: AXUIElement, explicitTarget: Bool) -> AXUIElement? {
    guard let windows = copyArray(appElement, kAXWindowsAttribute as String) else {
        return nil
    }
    if let byNumber = windows.first(where: { windowNumber($0) == capture.windowId }) {
        return byNumber
    }
    if let byBounds = windows.first(where: { window in
        guard usableWindow(window), let frame = absoluteFrame(window) else { return false }
        let intersection = frame.intersection(capture.bounds)
        return !intersection.isNull && intersection.area >= min(frame.area, capture.bounds.area) * 0.75
    }) {
        return byBounds
    }
    if explicitTarget {
        return nil
    }
    guard let titleHint = capture.title, !titleHint.isEmpty else {
        return focused
    }
    return windows.first {
        usableWindow($0) && stringAttribute($0, kAXTitleAttribute as String) == titleHint
    } ?? focused
}

private func recoverWindow(
    _ app: AppDescriptor,
    windowId: CGWindowID? = nil,
    windowBounds: CGRect? = nil
) {
    _ = app.app.unhide()
    _ = app.app.activate(options: [.activateAllWindows])
    if let bundleId = app.bundleId {
        openBundle(bundleId)
    }
    let appElement = AXUIElementCreateApplication(app.pid)
    let focusedWindow = copyElement(appElement, kAXFocusedWindowAttribute as String)
    var cachedWindows: [AXUIElement]?
    func windows() -> [AXUIElement] {
        if let cachedWindows { return cachedWindows }
        let value = copyArray(appElement, kAXWindowsAttribute as String) ?? []
        cachedWindows = value
        return value
    }
    let targetWindow: AXUIElement?
    if let focusedWindow,
       (windowId == nil && windowBounds == nil || windowMatchesCapture(
           focusedWindow,
           windowId: windowId,
           windowBounds: windowBounds
       )) {
        targetWindow = focusedWindow
    } else {
        let exactWindow = windowId.flatMap { targetId in
            windows().first { windowNumber($0) == targetId }
        }
        targetWindow = exactWindow ?? windowBounds.flatMap { targetBounds in
            windows().first { window in
                absoluteFrame(window).map { windowFramesMatch($0, targetBounds) } == true
            }
        }
    }
    if let window = targetWindow ?? focusedWindow ?? windows().first {
        _ = AXUIElementSetAttributeValue(window, kAXMinimizedAttribute as CFString, kCFBooleanFalse)
        _ = AXUIElementPerformAction(window, kAXRaiseAction as CFString)
        _ = AXUIElementSetAttributeValue(window, kAXMainAttribute as CFString, kCFBooleanTrue)
        _ = AXUIElementSetAttributeValue(window, kAXFocusedAttribute as CFString, kCFBooleanTrue)
    }
    Thread.sleep(forTimeInterval: 0.4)
}

private func windowMatchesCapture(
    _ window: AXUIElement,
    windowId: CGWindowID?,
    windowBounds: CGRect?
) -> Bool {
    if let windowId, windowNumber(window) == windowId { return true }
    guard let windowBounds, let frame = absoluteFrame(window) else { return false }
    return windowFramesMatch(frame, windowBounds)
}

private func windowFramesMatch(_ lhs: CGRect, _ rhs: CGRect) -> Bool {
    let tolerance: CGFloat = 2
    return abs(lhs.minX - rhs.minX) <= tolerance &&
        abs(lhs.minY - rhs.minY) <= tolerance &&
        abs(lhs.width - rhs.width) <= tolerance &&
        abs(lhs.height - rhs.height) <= tolerance
}

private func openBundle(_ bundleId: String) {
    let process = Process()
    process.executableURL = URL(fileURLWithPath: "/usr/bin/open")
    process.arguments = ["-b", bundleId]
    process.standardOutput = Pipe()
    process.standardError = Pipe()
    try? process.run()
    process.waitUntilExit()
}

private func hasRequestedWindowSelector(_ params: [String: JSONValue]) -> Bool {
    params["windowId"] != nil || params["windowIndex"] != nil
}

private func requestedWindowId(_ params: [String: JSONValue]) throws -> CGWindowID? {
    guard let raw = params["windowId"] else { return nil }
    guard let value = raw.number, value >= 0, let id = boundedInteger(value, as: UInt32.self) else {
        throw ProviderError.coded("invalid_argument", "windowId is out of range")
    }
    return CGWindowID(id)
}

private func snapshotWindowKey(_ query: String, _ windowId: CGWindowID) -> String {
    "\(query.lowercased())#window:\(Int(windowId))"
}

private func snapshotCanonicalWindowIdKey(_ windowId: CGWindowID) -> String {
    "window-id:\(Int(windowId))"
}

private func snapshotWindowIndexKey(_ query: String, _ windowIndex: Int) -> String {
    "\(query.lowercased())#windowIndex:\(windowIndex)"
}

private func snapshotCanonicalWindowIndexKey(_ windowIndex: Int) -> String {
    "window-index:\(windowIndex)"
}

private func snapshotNamespace(_ params: [String: JSONValue]) -> String {
    if let session = params["session"]?.string, !session.isEmpty {
        return "session:\(session)"
    }
    if let worktree = params["worktree"]?.string, !worktree.isEmpty {
        return "worktree:\(worktree)"
    }
    return "default"
}

private func namespacedSnapshotKey(_ namespace: String, _ key: String) -> String {
    "\(namespace):\(key.lowercased())"
}

private func isExplicitSnapshotNamespace(_ namespace: String) -> Bool {
    namespace != "default"
}

private func requestedWindowIndex(_ params: [String: JSONValue]) throws -> Int? {
    guard let raw = params["windowIndex"] else { return nil }
    guard let value = raw.number, value >= 0, let index = boundedInteger(value, as: Int.self) else {
        throw ProviderError.coded("invalid_argument", "windowIndex is out of range")
    }
    return index
}

private func usableWindow(_ element: AXUIElement) -> Bool {
    stringAttribute(element, kAXRoleAttribute as String) == kAXWindowRole as String &&
        boolAttribute(element, kAXMinimizedAttribute as String) != true
}

private func focusedElement(appElement: AXUIElement) -> AXUIElement? {
    copyElement(appElement, kAXFocusedUIElementAttribute as String)
}

private func copyElement(_ element: AXUIElement, _ attribute: String) -> AXUIElement? {
    var value: CFTypeRef?
    guard AXUIElementCopyAttributeValue(element, attribute as CFString, &value) == .success, let value else {
        return nil
    }
    return (value as! AXUIElement)
}

private func copyArray(_ element: AXUIElement, _ attribute: String) -> [AXUIElement]? {
    var value: CFTypeRef?
    guard AXUIElementCopyAttributeValue(element, attribute as CFString, &value) == .success, let value else {
        return nil
    }
    return value as? [AXUIElement]
}

private func pidAttribute(_ element: AXUIElement) -> pid_t? {
    var pid: pid_t = 0
    guard AXUIElementGetPid(element, &pid) == .success else {
        return nil
    }
    return pid
}

private func stringAttribute(_ element: AXUIElement, _ attribute: String) -> String? {
    var value: CFTypeRef?
    guard AXUIElementCopyAttributeValue(element, attribute as CFString, &value) == .success, let value else {
        return nil
    }
    if CFGetTypeID(value) == CFStringGetTypeID(), let string = value as? String {
        let trimmed = string.trimmingCharacters(in: .whitespacesAndNewlines)
        return trimmed.isEmpty ? nil : trimmed
    }
    if CFGetTypeID(value) == CFURLGetTypeID(), let url = value as? URL {
        return url.absoluteString
    }
    return nil
}

private func rawStringAttribute(_ element: AXUIElement, _ attribute: String) -> String? {
    guard let value = rawAttributeValue(element, attribute), CFGetTypeID(value) == CFStringGetTypeID()
    else {
        return nil
    }
    return value as? String
}

private func rawAttributeValue(_ element: AXUIElement, _ attribute: String) -> CFTypeRef? {
    var value: CFTypeRef?
    guard AXUIElementCopyAttributeValue(element, attribute as CFString, &value) == .success else {
        return nil
    }
    return value
}

private func boolAttribute(_ element: AXUIElement, _ attribute: String) -> Bool? {
    var value: CFTypeRef?
    guard AXUIElementCopyAttributeValue(element, attribute as CFString, &value) == .success else {
        return nil
    }
    return value as? Bool
}

private func numberAttribute(_ element: AXUIElement, _ attribute: String) -> NSNumber? {
    var value: CFTypeRef?
    guard AXUIElementCopyAttributeValue(element, attribute as CFString, &value) == .success else {
        return nil
    }
    return value as? NSNumber
}

private func windowNumber(_ element: AXUIElement) -> CGWindowID? {
    try? AccessibilityWindowIdentity.windowID(of: element)
}

private func absoluteFrame(_ element: AXUIElement) -> CGRect? {
    var positionValue: CFTypeRef?
    var sizeValue: CFTypeRef?
    guard AXUIElementCopyAttributeValue(element, kAXPositionAttribute as CFString, &positionValue) == .success,
          AXUIElementCopyAttributeValue(element, kAXSizeAttribute as CFString, &sizeValue) == .success,
          let positionValue,
          let sizeValue
    else {
        return nil
    }
    var point = CGPoint.zero
    var size = CGSize.zero
    guard AXValueGetValue(positionValue as! AXValue, .cgPoint, &point),
          AXValueGetValue(sizeValue as! AXValue, .cgSize, &size)
    else {
        return nil
    }
    return CGRect(origin: point, size: size)
}

private extension CGRect {
    var area: CGFloat {
        max(width, 0) * max(height, 0)
    }
}

private func actions(_ element: AXUIElement) -> [String] {
    var value: CFArray?
    guard AXUIElementCopyActionNames(element, &value) == .success, let value else {
        return []
    }
    return value as? [String] ?? []
}

private enum AccessibilityMessaging {
    static let timeoutSeconds: Float = 3

    /// Why: AX also returns cannotComplete at once for some attributes; only a call that waited out the timeout means the app is not answering.
    static func timedOut(_ result: AXError, since start: CFAbsoluteTime) -> Bool {
        result == .cannotComplete && CFAbsoluteTimeGetCurrent() - start >= Double(timeoutSeconds) * 0.9
    }

    static func appNotResponding(_ appName: String?) -> ProviderError {
        .coded("action_timeout", "\(appName.map { "'\($0)'" } ?? "The app") is not answering accessibility requests (no reply within \(timeoutSeconds) s); it may be busy or hung. Wait until it responds, then retry.")
    }

    /// The request reached the app, which went quiet while handling it, so the effect may have happened.
    static func unanswered(_ request: String) -> ProviderError {
        .coded("action_timeout", "the app did not answer \(request) within \(timeoutSeconds) s; it may be busy or showing a dialog, and the action may already have taken effect. Run get-app-state to check before retrying.")
    }
}

private func performAction(_ element: AXUIElement, _ action: String) throws -> Bool {
    var names: CFArray?
    let start = CFAbsoluteTimeGetCurrent()
    let namesResult = AXUIElementCopyActionNames(element, &names)
    if AccessibilityMessaging.timedOut(namesResult, since: start) {
        throw AccessibilityMessaging.appNotResponding(nil)
    }
    guard namesResult == .success,
          let names = names as? [String],
          names.contains(where: { $0.caseInsensitiveCompare(action) == .orderedSame })
    else {
        return false
    }
    let pressStart = CFAbsoluteTimeGetCurrent()
    let result = AXUIElementPerformAction(element, action as CFString)
    // Why: falling through to another route after a delivered but unanswered press ran the action twice.
    if AccessibilityMessaging.timedOut(result, since: pressStart) {
        throw AccessibilityMessaging.unanswered(action)
    }
    return result == .success
}

private func isSettable(_ element: AXUIElement, _ attribute: String) -> Bool {
    var settable = DarwinBoolean(false)
    return AXUIElementIsAttributeSettable(element, attribute as CFString, &settable) == .success && settable.boolValue
}

private func frame(_ element: AXUIElement, windowBounds: CGRect) -> CGRect? {
    var positionValue: CFTypeRef?
    var sizeValue: CFTypeRef?
    guard AXUIElementCopyAttributeValue(element, kAXPositionAttribute as CFString, &positionValue) == .success,
          AXUIElementCopyAttributeValue(element, kAXSizeAttribute as CFString, &sizeValue) == .success,
          let positionValue,
          let sizeValue
    else {
        return nil
    }
    var point = CGPoint.zero
    var size = CGSize.zero
    guard AXValueGetValue(positionValue as! AXValue, .cgPoint, &point),
          AXValueGetValue(sizeValue as! AXValue, .cgSize, &size)
    else {
        return nil
    }
    return CGRect(x: point.x - windowBounds.minX, y: point.y - windowBounds.minY, width: size.width, height: size.height)
}

private func elementSignature(_ node: SnapshotRenderNode) -> String {
    // Why: cached element validation should prove identity, not reject text
    // controls because their value/placeholder/summary changed after focus.
    [
        node.role,
        node.roleDescription ?? "",
        node.title ?? "",
        node.label ?? "",
        node.linkText ?? "",
        node.url ?? "",
        SnapshotRenderHeuristics.meaningfulActions(node.rawActions, role: node.role).joined(separator: ","),
    ].joined(separator: "\u{1f}")
}

private func center(_ localFrame: CGRect?, in windowBounds: CGRect) -> CGPoint? {
    guard let localFrame else { return nil }
    return CGPoint(x: windowBounds.minX + localFrame.midX, y: windowBounds.minY + localFrame.midY)
}

private func screenIndex(for bounds: CGRect) -> Int? {
    guard let index = NSScreen.screens.firstIndex(where: { $0.frame.intersects(bounds) }) else {
        return nil
    }
    return index
}

private func coordinatePoint(params: [String: JSONValue], xKey: String, yKey: String, snapshot: Snapshot) throws -> CGPoint {
    let x = try requiredNumber(params, xKey)
    let y = try requiredNumber(params, yKey)
    return CGPoint(
        x: snapshot.windowBounds.minX + x,
        y: snapshot.windowBounds.minY + y
    )
}

private func screenshotScale(screenshot: ScreenshotPayload?, bounds: CGRect) -> CGSize {
    guard let screenshot, bounds.width > 0, bounds.height > 0 else {
        return CGSize(width: 1, height: 1)
    }
    return CGSize(
        width: CGFloat(screenshot.width) / bounds.width,
        height: CGFloat(screenshot.height) / bounds.height
    )
}

private func mouseButton(_ raw: String?) throws -> MouseButtonSelection {
    switch ActionArgumentValidation.mouseButton(raw) {
    case let .success(button):
        return button
    case let .failure(error):
        throw ProviderError.coded("invalid_argument", error.message)
    }
}

private func renderTreeText(app: AppDescriptor, title: String, bounds: CGRect, lines: [String], focused: String?) -> String {
    var output = [
        "App=\(app.bundleId ?? app.name.replacingOccurrences(of: " ", with: "_")) (pid \(app.pid))",
        "Window: \"\(sanitize(title))\", App: \(sanitize(app.name)).",
        "",
    ]
    output.append(contentsOf: lines)
    output.append("")
    output.append(focused.map { "The focused UI element is \($0)." } ?? "No UI element is currently focused.")
    return output.joined(separator: "\n")
}

private func renderScreenshotStatus(_ status: ScreenshotStatus, snapshot: Snapshot) -> [String: Any] {
    let metadata: [String: Any] = [
        "engine": snapshot.screenshotEngine ?? "unknown",
        "windowId": Int(snapshot.windowId),
    ]
    switch status {
    case .captured:
        return ["state": "captured", "metadata": metadata]
    case .skipped:
        return ["state": "skipped", "reason": "no_screenshot_flag"]
    case let .failed(message):
        return ["state": "failed", "code": "screenshot_failed", "message": message, "metadata": metadata]
    }
}

private final class TreeRenderer {
    let windowBounds: CGRect
    let focused: AXUIElement?
    let compactBrowserTabs: Bool
    var lines: [String] = []
    var records: [Int: ElementRecord] = [:]
    var focusedSummary: String?
    var focusedElementId: Int?
    var truncated = false
    var maxDepthReached = false
    private let reader = AXSnapshotReader()
    private var nextIndex = 0
    static let maxNodes = 1200
    static let maxDepth = 64

    var appStoppedResponding: Bool { reader.appStoppedResponding }

    init(windowBounds: CGRect, focused: AXUIElement?, compactBrowserTabs: Bool) {
        self.windowBounds = windowBounds
        self.focused = focused
        self.compactBrowserTabs = compactBrowserTabs
    }

    func render(_ element: AXUIElement, depth: Int = 0, ancestors: [AXUIElement] = []) {
        guard !reader.appStoppedResponding else { return }
        guard nextIndex < Self.maxNodes else {
            truncated = true
            return
        }
        guard depth < Self.maxDepth else {
            truncated = true
            maxDepthReached = true
            return
        }
        guard !ancestors.contains(where: { CFEqual($0, element) }) else { return }

        let role = reader.stringAttribute(element, kAXRoleAttribute as String) ?? "AXUnknown"
        let children = reader.primaryChildren(element, role: role, windowBounds: windowBounds)
        let value = reader.valueString(element, role: role)
        let placeholder = reader.placeholderString(element)
        let rawActions = reader.actions(element)
        let rowSummary = reader.rowTextSummary(element, role: role)
        let roleDescription = reader.stringAttribute(element, kAXRoleDescriptionAttribute as String)
        let title = reader.stringAttribute(element, kAXTitleAttribute as String)
        let label = reader.stringAttribute(element, kAXDescriptionAttribute as String)
        let url = reader.stringAttribute(element, kAXURLAttribute as String)
        let linkText = role == "AXLink" ? reader.descendantTextSnippets(element, limit: 2, maxDepth: 3).first : nil
        let baseNode = SnapshotRenderNode(
            role: role,
            roleDescription: roleDescription,
            title: title,
            label: label,
            linkText: linkText,
            value: value,
            placeholder: placeholder,
            url: url,
            traits: [],
            rawActions: rawActions,
            childCount: children.count,
            rowSummary: rowSummary
        )
        let name = SnapshotRenderHeuristics.displayName(baseNode)
        let meaningful = SnapshotRenderHeuristics.meaningfulActions(rawActions, role: role)
        let localFrame = reader.frame(element, windowBounds: windowBounds)
        let traits = reader.traitsFor(element, role: role)
        let webAreaDepth = reader.webAreaDepth(role: role, ancestors: ancestors)
        let summary = reader.genericTextSummary(element, role: role, name: name, actions: meaningful, traits: traits)
        let node = SnapshotRenderNode(
            role: role,
            roleDescription: roleDescription,
            title: title,
            label: label,
            linkText: linkText,
            value: value,
            placeholder: placeholder,
            url: url,
            traits: traits,
            rawActions: rawActions,
            childCount: children.count,
            summary: summary,
            rowSummary: rowSummary,
            webAreaDepth: webAreaDepth
        )
        if SnapshotRenderHeuristics.shouldElide(node) {
            for child in children {
                render(child, depth: depth, ancestors: ancestors + [element])
            }
            return
        }

        let index = nextIndex
        nextIndex += 1
        let line = SnapshotRenderHeuristics.line(index: index, node: node)
        lines.append(String(repeating: "\t", count: depth) + line)
        records[index] = ElementRecord(
            index: index,
            element: element,
            localFrame: localFrame,
            actions: rawActions,
            signature: elementSignature(node)
        )
        if let focused, CFEqual(focused, element) {
            focusedElementId = index
            focusedSummary = line
        }
        if summary != nil || SnapshotRenderHeuristics.shouldSuppressChildren(node) {
            return
        }
        if compactBrowserTabs, let tabStripCompaction = tabStripCompaction(parent: node, children: children) {
            for (childIndex, child) in children.enumerated() where tabStripCompaction.retainedIndexes.contains(childIndex) {
                render(child, depth: depth + 1, ancestors: ancestors + [element])
            }
            lines.append(
                String(repeating: "\t", count: depth + 1) +
                    "... \(tabStripCompaction.omittedCount) inactive browser tabs omitted"
            )
            return
        }
        let childLineStart = lines.count
        for child in children {
            render(child, depth: depth + 1, ancestors: ancestors + [element])
        }
        if compactBrowserTabs {
            compactRenderedBrowserTabs(parent: node, startLine: childLineStart, depth: depth + 1)
        }
    }

    private func tabStripCompaction(parent: SnapshotRenderNode, children: [AXUIElement]) -> SnapshotTabStripCompaction? {
        let childNodes = children.map { child in
            let role = reader.stringAttribute(child, kAXRoleAttribute as String) ?? "AXUnknown"
            return SnapshotRenderNode(
                role: role,
                roleDescription: reader.stringAttribute(child, kAXRoleDescriptionAttribute as String),
                title: reader.stringAttribute(child, kAXTitleAttribute as String),
                label: reader.stringAttribute(child, kAXDescriptionAttribute as String),
                value: reader.valueString(child, role: role),
                traits: reader.traitsFor(child, role: role)
            )
        }
        // Why: browsers expose every open tab through AX; retaining only the active
        // tab keeps snapshots focused on the current page instead of stale tab titles.
        return SnapshotRenderHeuristics.tabStripCompaction(parent: parent, children: childNodes)
    }

    private func compactRenderedBrowserTabs(parent: SnapshotRenderNode, startLine: Int, depth: Int) {
        guard SnapshotRenderHeuristics.roleText(parent) == "scroll area" else { return }
        let indent = String(repeating: "\t", count: depth)
        let tabLineIndexes = lines.indices.dropFirst(startLine).filter { lineIndex in
            isDirectRenderedBrowserTabLine(lines[lineIndex], indent: indent)
        }
        guard tabLineIndexes.count >= 10 else { return }
        let activeLineIndexes = Set(tabLineIndexes.filter { lineIndex in
            isActiveRenderedBrowserTabLine(lines[lineIndex])
        })
        guard !activeLineIndexes.isEmpty else { return }

        let insertionIndex = tabLineIndexes.first!
        var omittedCount = 0
        for lineIndex in tabLineIndexes.reversed() where !activeLineIndexes.contains(lineIndex) {
            if let recordIndex = renderedElementIndex(lines[lineIndex], indent: indent) {
                records.removeValue(forKey: recordIndex)
                if focusedElementId == recordIndex {
                    focusedElementId = nil
                    focusedSummary = nil
                }
            }
            lines.remove(at: lineIndex)
            omittedCount += 1
        }
        guard omittedCount > 0 else { return }
        lines.insert("\(indent)... \(omittedCount) inactive browser tabs omitted", at: insertionIndex)
    }
}

extension TreeRenderer {
    /// Swaps the walk-order indexes for ones carried over from the previous snapshot of this window.
    func carryOverIndexes(from previous: Snapshot?) -> (order: [Int], nextFreshIndex: Int) {
        let walked = records.values.sorted { $0.index < $1.index }
        let assignment = StableElementIndexes.assign(
            current: walked.map(\.element),
            previous: previous?.elementOrder.compactMap { index in
                previous?.elements[index].map { (key: $0.element, index: index) }
            } ?? [],
            previousNextFreshIndex: previous?.nextFreshElementIndex ?? 0
        )
        let renumbered = Dictionary(uniqueKeysWithValues: zip(walked.map(\.index), assignment.indexes))
        records = Dictionary(uniqueKeysWithValues: zip(walked, assignment.indexes).map { record, index in
            (index, ElementRecord(index: index, element: record.element, localFrame: record.localFrame, actions: record.actions, signature: record.signature))
        })
        lines = lines.map { StableElementIndexes.renumber(line: $0, indexes: renumbered) }
        focusedElementId = focusedElementId.flatMap { renumbered[$0] }
        focusedSummary = focusedSummary.map { StableElementIndexes.renumber(line: $0, indexes: renumbered) }
        return (assignment.indexes, assignment.nextFreshIndex)
    }
}

private final class AXSnapshotReader {
    private enum CachedAttribute {
        case missing
        case found(CFTypeRef)
    }

    private final class ElementCache {
        let element: AXUIElement
        var loadedAttributeNames = false
        var advertisedAttributes: Set<String>?
        var attributes: [String: CachedAttribute] = [:]
        var actions: [String]?
        var settable: [String: Bool] = [:]

        init(element: AXUIElement) {
            self.element = element
        }
    }

    private var elementsByHash: [CFHashCode: [ElementCache]] = [:]

    func stringAttribute(_ element: AXUIElement, _ attribute: String) -> String? {
        guard let value = copyAttribute(element, attribute) else { return nil }
        if CFGetTypeID(value) == CFStringGetTypeID(), let string = value as? String {
            let trimmed = string.trimmingCharacters(in: .whitespacesAndNewlines)
            return trimmed.isEmpty ? nil : trimmed
        }
        if CFGetTypeID(value) == CFURLGetTypeID(), let url = value as? URL {
            return url.absoluteString
        }
        return nil
    }

    func boolAttribute(_ element: AXUIElement, _ attribute: String) -> Bool? {
        copyAttribute(element, attribute) as? Bool
    }

    func numberAttribute(_ element: AXUIElement, _ attribute: String) -> NSNumber? {
        copyAttribute(element, attribute) as? NSNumber
    }

    func copyArray(_ element: AXUIElement, _ attribute: String) -> [AXUIElement]? {
        copyAttribute(element, attribute) as? [AXUIElement]
    }

    func actions(_ element: AXUIElement) -> [String] {
        let cache = cache(for: element)
        if let actions = cache.actions {
            return actions
        }
        var value: CFArray?
        let actions = answered { AXUIElementCopyActionNames(element, &value) } == .success ? value as? [String] ?? [] : []
        cache.actions = actions
        return actions
    }

    func isSettable(_ element: AXUIElement, _ attribute: String) -> Bool {
        let cache = cache(for: element)
        if let cached = cache.settable[attribute] {
            return cached
        }
        var settable = DarwinBoolean(false)
        let value = answered { AXUIElementIsAttributeSettable(element, attribute as CFString, &settable) } == .success && settable.boolValue
        cache.settable[attribute] = value
        return value
    }

    /// Set once the app waits out a messaging timeout; later reads return nothing instead of each waiting it out again.
    private(set) var appStoppedResponding = false

    private func answered(_ call: () -> AXError) -> AXError? {
        guard !appStoppedResponding else { return nil }
        let start = CFAbsoluteTimeGetCurrent()
        let result = call()
        if AccessibilityMessaging.timedOut(result, since: start) {
            appStoppedResponding = true
        }
        return result
    }

    func frame(_ element: AXUIElement, windowBounds: CGRect) -> CGRect? {
        guard let absolute = absoluteFrame(element) else { return nil }
        return CGRect(
            x: absolute.minX - windowBounds.minX,
            y: absolute.minY - windowBounds.minY,
            width: absolute.width,
            height: absolute.height
        )
    }

    func primaryChildren(_ element: AXUIElement, role: String, windowBounds: CGRect) -> [AXUIElement] {
        if usesRowsAsPrimaryChildren(role: role), let rows = copyArray(element, kAXRowsAttribute as String), !rows.isEmpty {
            return visibleRows(rows, parent: element, windowBounds: windowBounds)
        }
        return copyArray(element, kAXChildrenAttribute as String) ?? []
    }

    func valueString(_ element: AXUIElement, role: String) -> String? {
        if isSecureTextElement(element, role: role) {
            return "[redacted]"
        }
        if let string = stringAttribute(element, kAXValueAttribute as String) {
            return string
        }
        if let number = numberAttribute(element, kAXValueAttribute as String) {
            return number.stringValue
        }
        return nil
    }

    func placeholderString(_ element: AXUIElement) -> String? {
        stringAttribute(element, "AXPlaceholderValue") ?? stringAttribute(element, "AXPlaceholder")
    }

    func traitsFor(_ element: AXUIElement, role: String) -> [String] {
        var traits: [String] = []
        if boolAttribute(element, kAXSelectedAttribute as String) == true { traits.append("selected") }
        if boolAttribute(element, kAXExpandedAttribute as String) == true { traits.append("expanded") }
        if boolAttribute(element, kAXEnabledAttribute as String) == false { traits.append("disabled") }
        if valueSettableRoles.contains(role), isSettable(element, kAXValueAttribute as String) { traits.append("settable") }
        return traits
    }

    func genericTextSummary(
        _ element: AXUIElement,
        role: String,
        name: String?,
        actions: [String],
        traits: [String]
    ) -> String? {
        guard (role == kAXGroupRole as String || role == kAXUnknownRole as String),
              name == nil,
              actions.isEmpty,
              traits.isEmpty,
              isPlainTextSubtree(element, maxDepth: 4)
        else {
            return nil
        }
        let texts = descendantTextSnippets(element, limit: 8, maxDepth: 4)
        guard texts.count >= 2 else { return nil }
        let summary = texts.joined(separator: " ")
        guard summary.count <= 220 else { return nil }
        return summary
    }

    func rowTextSummary(_ element: AXUIElement, role: String) -> String? {
        guard ["AXRow", "AXCell", "AXOutlineRow"].contains(role) else { return nil }
        let texts = descendantTextSnippets(element, limit: 6, maxDepth: 3)
        guard !texts.isEmpty else { return nil }
        return texts.joined(separator: " ")
    }

    func descendantTextSnippets(_ element: AXUIElement, limit: Int, maxDepth: Int) -> [String] {
        var values: [String] = []
        var seen = Set<String>()

        func collect(_ node: AXUIElement, depth: Int) {
            guard values.count < limit, depth <= maxDepth else { return }
            let role = stringAttribute(node, kAXRoleAttribute as String) ?? ""
            if role == kAXStaticTextRole as String || role == "AXLink" {
                for candidate in [
                    stringAttribute(node, kAXValueAttribute as String),
                    stringAttribute(node, kAXTitleAttribute as String),
                    stringAttribute(node, kAXDescriptionAttribute as String),
                ] {
                    guard let candidate else { continue }
                    let text = preview(candidate, maxLength: 80)
                    guard !text.isEmpty, seen.insert(text).inserted else { continue }
                    values.append(text)
                    if values.count >= limit { return }
                }
            }
            for child in copyArray(node, kAXChildrenAttribute as String) ?? [] {
                collect(child, depth: depth + 1)
                if values.count >= limit { return }
            }
        }

        collect(element, depth: 0)
        return values
    }

    func webAreaDepth(role: String, ancestors: [AXUIElement]) -> Int? {
        if role == "AXWebArea" { return 0 }
        guard let index = ancestors.firstIndex(where: { stringAttribute($0, kAXRoleAttribute as String) == "AXWebArea" }) else {
            return nil
        }
        return ancestors.count - index
    }

    private func copyAttribute(_ element: AXUIElement, _ attribute: String) -> CFTypeRef? {
        let cache = cache(for: element)
        if let cached = cache.attributes[attribute] {
            switch cached {
            case .missing:
                return nil
            case let .found(value):
                return value
            }
        }
        if let advertisedAttributes = advertisedAttributes(cache),
           !SnapshotRenderHeuristics.supportsAttribute(attribute, advertisedAttributes: advertisedAttributes) {
            cache.attributes[attribute] = .missing
            return nil
        }
        var value: CFTypeRef?
        guard answered({ AXUIElementCopyAttributeValue(element, attribute as CFString, &value) }) == .success, let value else {
            cache.attributes[attribute] = .missing
            return nil
        }
        cache.attributes[attribute] = .found(value)
        return value
    }

    private func advertisedAttributes(_ cache: ElementCache) -> Set<String>? {
        if cache.loadedAttributeNames {
            return cache.advertisedAttributes
        }
        cache.loadedAttributeNames = true
        var value: CFArray?
        guard answered({ AXUIElementCopyAttributeNames(cache.element, &value) }) == .success, let attributes = value as? [String] else {
            return nil
        }
        cache.advertisedAttributes = Set(attributes)
        return cache.advertisedAttributes
    }

    private func absoluteFrame(_ element: AXUIElement) -> CGRect? {
        guard let positionValue = copyAttribute(element, kAXPositionAttribute as String),
              let sizeValue = copyAttribute(element, kAXSizeAttribute as String)
        else {
            return nil
        }
        var point = CGPoint.zero
        var size = CGSize.zero
        guard AXValueGetValue(positionValue as! AXValue, .cgPoint, &point),
              AXValueGetValue(sizeValue as! AXValue, .cgSize, &size)
        else {
            return nil
        }
        return CGRect(origin: point, size: size)
    }

    private func visibleRows(_ rows: [AXUIElement], parent: AXUIElement, windowBounds: CGRect) -> [AXUIElement] {
        guard let parentFrame = frame(parent, windowBounds: windowBounds) else {
            return Array(rows.prefix(20))
        }
        let visible = rows.filter { row in
            guard let rowFrame = frame(row, windowBounds: windowBounds) else { return false }
            return rowFrame.intersects(parentFrame)
        }
        return Array((visible.isEmpty ? rows : visible).prefix(20))
    }

    private func isSecureTextElement(_ element: AXUIElement, role: String) -> Bool {
        guard SnapshotRenderHeuristics.shouldProbeSecureTextMetadata(role: role) else {
            return false
        }
        let haystack = [
            role,
            stringAttribute(element, kAXSubroleAttribute as String) ?? "",
            stringAttribute(element, kAXTitleAttribute as String) ?? "",
            stringAttribute(element, kAXDescriptionAttribute as String) ?? "",
            placeholderString(element) ?? "",
        ].joined(separator: " ").lowercased()
        return haystack.contains("secure") ||
            haystack.contains("password") ||
            haystack.contains("passcode") ||
            haystack.contains("verification code") ||
            haystack.contains("one-time code")
    }

    private func isPlainTextSubtree(_ element: AXUIElement, maxDepth: Int) -> Bool {
        var sawText = false
        let allowedContainerRoles: Set<String> = [
            kAXGroupRole as String,
            kAXUnknownRole as String,
            kAXStaticTextRole as String,
            "AXLink",
            "AXImage",
        ]

        func visit(_ node: AXUIElement, depth: Int) -> Bool {
            guard depth <= maxDepth else { return false }
            let role = stringAttribute(node, kAXRoleAttribute as String) ?? "AXUnknown"
            guard allowedContainerRoles.contains(role) else { return false }
            if role == kAXStaticTextRole as String || role == "AXLink" {
                sawText = true
            }
            guard SnapshotRenderHeuristics.meaningfulActions(actions(node), role: role).isEmpty else { return false }
            for child in copyArray(node, kAXChildrenAttribute as String) ?? [] {
                guard visit(child, depth: depth + 1) else { return false }
            }
            return true
        }

        return visit(element, depth: 0) && sawText
    }

    private func cache(for element: AXUIElement) -> ElementCache {
        let hash = CFHash(element)
        if let cache = elementsByHash[hash]?.first(where: { CFEqual($0.element, element) }) {
            return cache
        }
        let cache = ElementCache(element: element)
        elementsByHash[hash, default: []].append(cache)
        return cache
    }
}

private let valueSettableRoles: Set<String> = [
    kAXCheckBoxRole as String,
    kAXComboBoxRole as String,
    kAXRadioButtonRole as String,
    "AXSearchField",
    kAXSliderRole as String,
    kAXTextAreaRole as String,
    kAXTextFieldRole as String,
]

private func usesRowsAsPrimaryChildren(role: String) -> Bool {
    [
        kAXBrowserRole as String,
        kAXListRole as String,
        kAXOutlineRole as String,
        kAXTableRole as String,
    ].contains(role)
}

private func isDirectRenderedBrowserTabLine(_ line: String, indent: String) -> Bool {
    guard line.hasPrefix(indent), !line.dropFirst(indent.count).hasPrefix("\t") else {
        return false
    }
    let text = String(line.dropFirst(indent.count))
    return text.range(of: #"^\d+ tab($| \(|,)"#, options: .regularExpression) != nil
}

private func isActiveRenderedBrowserTabLine(_ line: String) -> Bool {
    line.contains("(selected") || line.contains("Value: 1")
}

private func renderedElementIndex(_ line: String, indent: String) -> Int? {
    let text = line.dropFirst(indent.count)
    let digits = text.prefix { character in
        character >= "0" && character <= "9"
    }
    return Int(digits)
}

private func sanitize(_ value: String) -> String {
    value.replacingOccurrences(of: "\n", with: " ").replacingOccurrences(of: "\r", with: " ")
}

private func preview(_ value: String, maxLength: Int = 120) -> String {
    let clean = sanitize(value)
    if clean.count <= maxLength {
        return clean
    }
    return String(clean.prefix(maxLength)) + "..."
}

private func actionMetadata(
    path: String,
    actionName: String? = nil,
    fallbackReason: String? = nil,
    verification: [String: Any]? = nil
) -> [String: Any] {
    var metadata: [String: Any] = [
        "path": path,
        "actionName": jsonNullable(actionName),
        "fallbackReason": jsonNullable(fallbackReason),
    ]
    if let verification {
        metadata["verification"] = verification
    }
    return metadata
}

private func verifiedAction(property: String, expected: String? = nil, actualPreview: String? = nil) -> [String: Any] {
    [
        "state": "verified",
        "property": property,
        "expected": jsonNullable(expected),
        "actualPreview": jsonNullable(actualPreview),
    ]
}

private func unverifiedAction(reason: String, expected: String? = nil, actualPreview: String? = nil) -> [String: Any] {
    [
        "state": "unverified",
        "reason": reason,
        "expected": jsonNullable(expected),
        "actualPreview": jsonNullable(actualPreview),
    ]
}

private func jsonNullable<T>(_ value: T?) -> Any {
    value ?? NSNull()
}

private struct WindowCandidate {
    let windowId: CGWindowID
    let layer: Int
    let bounds: CGRect
    let title: String?
    let alpha: CGFloat
    let isOnScreen: Bool
    let sharingState: Int?

    var score: Int {
        var value = Int(bounds.width * bounds.height)
        if layer == 0 { value += 1_000_000_000 }
        if title != nil && title?.isEmpty == false { value += 10_000_000 }
        if isOnScreen { value += 1_000_000 }
        if alpha >= 0.99 { value += 100_000 }
        return value
    }
}

private struct WindowCapture {
    let windowId: CGWindowID
    let layer: Int
    let bounds: CGRect
    let title: String?
    let image: CapturedImage?

    static func resolve(
        pid: pid_t,
        titleHint: String?,
        windowId: CGWindowID?,
        windowIndex: Int?,
        captureImage: Bool
    ) -> WindowCapture? {
        resolve(
            candidates: candidates(pid: pid),
            titleHint: titleHint,
            windowId: windowId,
            windowIndex: windowIndex,
            captureImage: captureImage
        )
    }

    static func resolve(
        candidates: [WindowCandidate],
        titleHint: String?,
        windowId: CGWindowID?,
        windowIndex: Int?,
        captureImage: Bool
    ) -> WindowCapture? {
        if let windowId {
            guard let candidate = candidates.first(where: { $0.windowId == windowId }) else { return nil }
            return WindowCapture(candidate: candidate, captureImage: captureImage)
        }
        if let windowIndex {
            let visibleWindows = candidates.filter { $0.layer == 0 }
            guard visibleWindows.indices.contains(windowIndex) else { return nil }
            return WindowCapture(candidate: visibleWindows[windowIndex], captureImage: captureImage)
        }
        guard let best = candidates.sorted(by: { lhs, rhs in
            if let titleHint, lhs.title == titleHint, rhs.title != titleHint { return true }
            if let titleHint, rhs.title == titleHint, lhs.title != titleHint { return false }
            return lhs.score > rhs.score
        }).first else {
            return nil
        }
        return WindowCapture(candidate: best, captureImage: captureImage)
    }

    private init(candidate: WindowCandidate, captureImage: Bool) {
        self.windowId = candidate.windowId
        self.layer = candidate.layer
        self.bounds = candidate.bounds
        self.title = candidate.title
        // Why: probing image APIs before TCC preflight can raise Screen
        // Recording prompts, even for --no-screenshot calls.
        if captureImage {
            self.image = Self.captureImage(windowId: candidate.windowId, bounds: candidate.bounds)
        } else {
            self.image = nil
        }
    }

    static func candidates(pid: pid_t) -> [WindowCandidate] {
        guard let infos = CGWindowListCopyWindowInfo([.optionOnScreenOnly], kCGNullWindowID) as? [[String: Any]] else {
            return []
        }
        return infos.compactMap { info in
            guard let ownerPid = info[kCGWindowOwnerPID as String] as? pid_t, ownerPid == pid,
                  let number = info[kCGWindowNumber as String] as? NSNumber,
                  let layer = info[kCGWindowLayer as String] as? Int,
                  let boundsDictionary = info[kCGWindowBounds as String] as? NSDictionary,
                  let bounds = CGRect(dictionaryRepresentation: boundsDictionary),
                  bounds.width >= 48,
                  bounds.height >= 48
            else {
                return nil
            }
            let alpha = info[kCGWindowAlpha as String] as? CGFloat ?? 1
            guard alpha > 0.01 else { return nil }
            let sharing = (info[kCGWindowSharingState as String] as? NSNumber).map { $0.intValue }
            if sharing == 0 { return nil }
            let isOnScreen = (info[kCGWindowIsOnscreen as String] as? Bool) ?? true
            return WindowCandidate(
                windowId: CGWindowID(number.uint32Value),
                layer: layer,
                bounds: bounds,
                title: info[kCGWindowName as String] as? String,
                alpha: alpha,
                isOnScreen: isOnScreen,
                sharingState: sharing
            )
        }
        .sorted { lhs, rhs in
            lhs.score > rhs.score
        }
    }

    func screenshotPayload() -> ScreenshotPayload? {
        guard let image, let bounded = boundedPngData(image.image) else { return nil }
        return ScreenshotPayload(
            data: bounded.data.base64EncodedString(),
            width: bounded.width,
            height: bounded.height,
            scale: Double(bounded.width) / max(Double(bounds.width), 1)
        )
    }

    private static func captureImage(windowId: CGWindowID, bounds: CGRect) -> CapturedImage? {
        if ProcessInfo.processInfo.environment["ORCA_COMPUTER_USE_SCK_SCREENSHOTS"] == "1",
           let image = captureImageWithScreenCaptureKit(windowId: windowId, bounds: bounds) {
            return CapturedImage(image: image, engine: "screenCaptureKit")
        }
        if let image = CGWindowListCreateImage(.null, [.optionIncludingWindow], windowId, [.boundsIgnoreFraming, .bestResolution]) {
            return CapturedImage(image: image, engine: "cgWindowList")
        }
        return nil
    }

    private static func captureImageWithScreenCaptureKit(windowId: CGWindowID, bounds: CGRect) -> CGImage? {
        try? BlockingAsync.run(timeout: 3) {
            let content = try await SCShareableContent.current
            guard let window = content.windows.first(where: { $0.windowID == windowId }) else {
                return nil
            }
            let filter = SCContentFilter(desktopIndependentWindow: window)
            let configuration = SCStreamConfiguration()
            let scale = NSScreen.screens.first(where: { $0.frame.intersects(bounds) })?.backingScaleFactor ?? NSScreen.main?.backingScaleFactor ?? 2
            configuration.width = size_t(max(1, Int((bounds.width * scale).rounded(.up))))
            configuration.height = size_t(max(1, Int((bounds.height * scale).rounded(.up))))
            configuration.scalesToFit = true
            configuration.preservesAspectRatio = true
            configuration.showsCursor = false
            configuration.ignoreShadowsSingleWindow = true
            configuration.ignoreGlobalClipSingleWindow = true
            return try await SCScreenshotManager.captureImage(contentFilter: filter, configuration: configuration)
        }
    }
}

private final class AsyncBox<T>: @unchecked Sendable {
    var result: Result<T, Error>?
}

private enum BlockingAsync {
    static func run<T>(timeout: TimeInterval, operation: @escaping @Sendable () async throws -> T) throws -> T {
        let semaphore = DispatchSemaphore(value: 0)
        let box = AsyncBox<T>()
        let task = Task.detached {
            do {
                box.result = .success(try await operation())
            } catch {
                box.result = .failure(error)
            }
            semaphore.signal()
        }
        guard semaphore.wait(timeout: .now() + timeout) == .success else {
            task.cancel()
            throw ProviderError.coded("action_timeout", "screenshot capture timed out")
        }
        return try box.result!.get()
    }
}

private struct BoundedPNG {
    let data: Data
    let width: Int
    let height: Int
}

private func boundedPngData(_ image: CGImage) -> BoundedPNG? {
    let rep = NSBitmapImageRep(cgImage: image)
    guard let data = rep.representation(using: .png, properties: [:]) else { return nil }
    if data.count <= 900_000 {
        return BoundedPNG(data: data, width: image.width, height: image.height)
    }
    var scale = min(1, 1280 / CGFloat(max(image.width, image.height)))
    var best = BoundedPNG(data: data, width: image.width, height: image.height)
    while scale >= 0.25 {
        guard let resized = resizePng(image, scale: scale) else {
            break
        }
        best = resized
        if resized.data.count <= 900_000 {
            return resized
        }
        scale *= 0.85
    }
    return best
}

private func resizePng(_ image: CGImage, scale: CGFloat) -> BoundedPNG? {
    let width = max(1, Int(CGFloat(image.width) * scale))
    let height = max(1, Int(CGFloat(image.height) * scale))
    guard let context = CGContext(data: nil, width: width, height: height, bitsPerComponent: 8, bytesPerRow: 0, space: CGColorSpaceCreateDeviceRGB(), bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue) else {
        return nil
    }
    context.interpolationQuality = .medium
    context.draw(image, in: CGRect(x: 0, y: 0, width: width, height: height))
    guard let resized = context.makeImage() else { return nil }
    guard let data = NSBitmapImageRep(cgImage: resized).representation(using: .png, properties: [:]) else {
        return nil
    }
    return BoundedPNG(data: data, width: width, height: height)
}

private enum Input {
    static func click(
        at point: CGPoint,
        button: MouseButtonSelection,
        count: Int,
        modifiers: [KeyModifier],
        targetWindow: Snapshot
    ) throws {
        guard let source = CGEventSource(stateID: .combinedSessionState) else {
            throw ProviderError.coded("accessibility_error", "failed to create event source")
        }
        let flags = eventFlags(modifiers)
        let target = syntheticClickRecipient(pid: targetWindow.app.pid, windowId: targetWindow.windowId)
        try withRecipientErrors {
            try SyntheticMouseClickDelivery.deliver(
                clickCount: count,
                target: target,
                currentObservation: {
                    currentSyntheticClickRecipient(snapshot: targetWindow, point: point)
                },
                makeEvent: { step in
                    let type: CGEventType
                    switch step {
                    case .move:
                        type = .mouseMoved
                    case .buttonDown:
                        type = button.downEvent
                    case .buttonUp:
                        type = button.upEvent
                    }
                    guard let event = CGEvent(
                        mouseEventSource: source,
                        mouseType: type,
                        mouseCursorPosition: point,
                        mouseButton: button.cgButton
                    ) else {
                        throw ProviderError.coded("accessibility_error", "failed to create mouse event")
                    }
                    event.flags = flags
                    let clickState = SyntheticMouseClickDelivery.clickState(for: step)
                    if clickState > 0 {
                        event.setIntegerValueField(.mouseEventClickState, value: clickState)
                    }
                    return event
                },
                post: { $0.post(tap: .cghidEventTap) },
                pause: { _ = usleep($0) }
            )
        }
    }

    private static func withRecipientErrors(_ body: () throws -> Void) throws {
        do {
            try body()
        } catch let failure as SyntheticMouseClickDelivery.FenceFailure {
            switch failure {
            case let .recipientChanged(expected, actual, deliveredPresses):
                let actualDescription = actual.map {
                    "pid \($0.ownerPID) window \($0.windowID)"
                } ?? "no focused window"
                let recovery = deliveredPresses == 0
                    ? "bring the target window forward, run get-app-state again, and retry"
                    : "\(deliveredPresses) press(es) may already have been delivered; run get-app-state and verify state before retrying"
                throw ProviderError.coded(
                    "window_not_focused",
                    "pointer input aborted because target pid \(expected.ownerPID) window \(expected.windowID) is no longer the focused topmost recipient (current: \(actualDescription)); \(recovery)"
                )
            }
        }
    }

    static func scroll(at point: CGPoint, wheel1: Int32, wheel2: Int32, targetWindow: Snapshot) throws {
        let move = try mouseEvent(.mouseMoved, at: point)
        guard let wheel = CGEvent(scrollWheelEvent2Source: nil, units: .line, wheelCount: 2, wheel1: wheel1, wheel2: wheel2, wheel3: 0) else {
            throw ProviderError.coded("accessibility_error", "failed to create scroll event")
        }
        wheel.location = point
        try withRecipientErrors {
            try SyntheticMouseClickDelivery.deliverScroll(
                move: move, wheel: wheel,
                target: syntheticClickRecipient(pid: targetWindow.app.pid, windowId: targetWindow.windowId),
                currentObservation: { currentSyntheticClickRecipient(snapshot: targetWindow, point: point) },
                post: { $0.post(tap: .cghidEventTap) },
                pause: { _ = usleep($0) }
            )
        }
    }

    static func drag(from start: CGPoint, to end: CGPoint, targetWindow: Snapshot) throws {
        let move = try mouseEvent(.mouseMoved, at: start)
        let down = try mouseEvent(.leftMouseDown, at: start)
        let up = try mouseEvent(.leftMouseUp, at: end)
        let dragged = try (1...10).map { step in
            let progress = CGFloat(step) / 10
            return try mouseEvent(.leftMouseDragged, at: CGPoint(x: start.x + (end.x - start.x) * progress, y: start.y + (end.y - start.y) * progress))
        }
        try withRecipientErrors {
            try SyntheticMouseClickDelivery.deliverDrag(
                move: move, down: down, dragged: dragged, up: up,
                target: syntheticClickRecipient(pid: targetWindow.app.pid, windowId: targetWindow.windowId),
                currentObservation: { currentSyntheticClickRecipient(snapshot: targetWindow, point: start) },
                post: { $0.post(tap: .cghidEventTap) },
                pause: { _ = usleep($0) }
            )
        }
    }

    static func keyEvents(_ key: String) throws -> [CGEvent] {
        let parsed = try KeyMap.parse(key)
        return try withTransportErrors {
            try BackgroundInputTransport.chordEvents(
                keyCode: parsed.keyCode,
                modifiers: parsed.modifiers.map { (keyCode: $0.keyCode, flag: $0.flag) }
            )
        }
    }

    static func withPasteboardText(_ text: String, _ body: () throws -> Void) throws {
        let pasteboard = NSPasteboard.general
        let previousItems: [NSPasteboardItem] = pasteboard.pasteboardItems?.map { item in
            let copy = NSPasteboardItem()
            for type in item.types {
                if let data = item.data(forType: type) {
                    copy.setData(data, forType: type)
                }
            }
            return copy
        } ?? []
        pasteboard.clearContents()
        pasteboard.setString(text, forType: .string)
        let changeCount = pasteboard.changeCount
        defer {
            // Why: posting Cmd+V returns before the receiver reads the pasteboard.
            usleep(200_000)
            if pasteboard.changeCount == changeCount {
                pasteboard.clearContents()
                if !previousItems.isEmpty {
                    pasteboard.writeObjects(previousItems)
                }
            }
        }
        try body()
    }

    private static func mouseEvent(_ type: CGEventType, at point: CGPoint) throws -> CGEvent {
        guard point.x.isFinite, point.y.isFinite else {
            throw ProviderError.coded("invalid_argument", "pointer coordinates are out of range")
        }
        guard let event = CGEvent(mouseEventSource: nil, mouseType: type, mouseCursorPosition: point, mouseButton: .left) else {
            throw ProviderError.coded("accessibility_error", "failed to create mouse event")
        }
        return event
    }
}

private enum TextInput {
    static func replaceSelection(_ element: AXUIElement, with text: String) throws -> [String: Any]? {
        guard isSettable(element, kAXValueAttribute as String),
              let current = rawStringAttribute(element, kAXValueAttribute as String)
        else {
            return nil
        }
        let selectedRange = selectedTextRange(element) ?? CFRange(location: current.utf16.count, length: 0)
        let startOffset = max(0, min(selectedRange.location, current.utf16.count))
        let endOffset = max(startOffset, min(startOffset + selectedRange.length, current.utf16.count))
        let start = String.Index(utf16Offset: startOffset, in: current)
        let end = String.Index(utf16Offset: endOffset, in: current)
        let next = String(current[..<start]) + text + String(current[end...])
        let writeStart = CFAbsoluteTimeGetCurrent()
        let result = AXUIElementSetAttributeValue(element, kAXValueAttribute as CFString, next as CFString)
        // Why: typing the text as keys after an unanswered write could enter it twice.
        if AccessibilityMessaging.timedOut(result, since: writeStart) {
            throw AccessibilityMessaging.unanswered("the text write")
        }
        guard result == .success else {
            return nil
        }
        setSelectedTextRange(element, CFRange(location: startOffset + text.utf16.count, length: 0))
        guard rawStringAttribute(element, kAXValueAttribute as String) == next else {
            return nil
        }
        return verifiedAction(
            property: "focusedText",
            expected: text,
            actualPreview: preview(next)
        )
    }

    static func selectAll(_ element: AXUIElement) -> Bool {
        guard let current = rawStringAttribute(element, kAXValueAttribute as String) else {
            return false
        }
        return setSelectedTextRange(element, CFRange(location: 0, length: current.utf16.count))
    }

    static func selectionVerification(_ element: AXUIElement) -> [String: Any] {
        guard let current = rawStringAttribute(element, kAXValueAttribute as String),
              let selectedRange = selectedTextRange(element),
              selectedRange.location == 0,
              selectedRange.length == current.utf16.count
        else {
            return unverifiedAction(reason: "provider_unavailable")
        }
        return verifiedAction(property: "selection", actualPreview: preview(current))
    }

    private static func selectedTextRange(_ element: AXUIElement) -> CFRange? {
        var value: CFTypeRef?
        guard AXUIElementCopyAttributeValue(element, kAXSelectedTextRangeAttribute as CFString, &value) == .success,
              let value,
              CFGetTypeID(value) == AXValueGetTypeID()
        else {
            return nil
        }
        var range = CFRange(location: 0, length: 0)
        guard AXValueGetValue(value as! AXValue, .cfRange, &range) else {
            return nil
        }
        return range
    }

    @discardableResult
    private static func setSelectedTextRange(_ element: AXUIElement, _ range: CFRange) -> Bool {
        var mutableRange = range
        guard let value = AXValueCreate(.cfRange, &mutableRange) else {
            return false
        }
        return AXUIElementSetAttributeValue(element, kAXSelectedTextRangeAttribute as CFString, value) == .success
    }
}

private func isSelectAllHotkey(_ key: String) -> Bool {
    let parts = key
        .lowercased()
        .replacingOccurrences(of: " ", with: "")
        .replacingOccurrences(of: "-", with: "+")
        .split(separator: "+")
        .map(String.init)
    guard parts.last == "a" else {
        return false
    }
    let modifiers = Set(parts.dropLast())
    return modifiers.contains("cmd") ||
        modifiers.contains("command") ||
        modifiers.contains("meta") ||
        modifiers.contains("cmdorctrl") ||
        modifiers.contains("commandorcontrol")
}

private struct KeyModifier {
    let keyCode: CGKeyCode
    let flag: CGEventFlags
}

private struct ParsedKey {
    let keyCode: CGKeyCode
    let modifiers: [KeyModifier]
}

private enum KeyMap {
    static func parse(_ spec: String) throws -> ParsedKey {
        let parts = spec.split(separator: "+").map { String($0).lowercased() }
        var modifiers: [KeyModifier] = []
        var keyName: String?
        for part in parts {
            if let modifier = modifier(part) {
                modifiers.append(modifier)
            } else {
                keyName = part
            }
        }
        guard let keyName, let keyCode = codes[keyName] else {
            throw ProviderError.coded("invalid_argument", "unsupported key '\(spec)'")
        }
        return ParsedKey(keyCode: keyCode, modifiers: modifiers)
    }

    static func parseModifiers(_ spec: String?) throws -> [KeyModifier] {
        guard let spec else {
            return []
        }
        let parts = spec.split(separator: "+", omittingEmptySubsequences: false)
            .map { String($0).trimmingCharacters(in: .whitespacesAndNewlines).lowercased() }
        guard !parts.isEmpty, !parts.contains(where: \.isEmpty) else {
            throw ProviderError.coded("invalid_argument", "click modifiers require modifier keys only")
        }
        return try parts.map { part in
            guard let modifier = modifier(part) else {
                throw ProviderError.coded("invalid_argument", "unsupported click modifier '\(part)'")
            }
            return modifier
        }
    }

    private static func modifier(_ part: String) -> KeyModifier? {
        switch part {
        case "cmd", "command", "meta", "super", "win", "cmdorctrl", "commandorcontrol":
            return KeyModifier(keyCode: 55, flag: .maskCommand)
        case "ctrl", "control":
            return KeyModifier(keyCode: 59, flag: .maskControl)
        case "alt", "option":
            return KeyModifier(keyCode: 58, flag: .maskAlternate)
        case "shift":
            return KeyModifier(keyCode: 56, flag: .maskShift)
        default:
            return nil
        }
    }

    private static let codes: [String: CGKeyCode] = [
        "a": 0, "s": 1, "d": 2, "f": 3, "h": 4, "g": 5, "z": 6, "x": 7, "c": 8, "v": 9,
        "b": 11, "q": 12, "w": 13, "e": 14, "r": 15, "y": 16, "t": 17, "1": 18, "2": 19,
        "3": 20, "4": 21, "6": 22, "5": 23, "=": 24, "9": 25, "7": 26, "-": 27, "8": 28,
        "0": 29, "]": 30, "o": 31, "u": 32, "[": 33, "i": 34, "p": 35, "return": 36,
        "enter": 36, "l": 37, "j": 38, "'": 39, "k": 40, ";": 41, "\\": 42, ",": 43,
        "/": 44, "n": 45, "m": 46, ".": 47, "tab": 48, "space": 49, "`": 50,
        "backspace": 51, "delete": 51, "escape": 53, "esc": 53, "left": 123, "right": 124,
        "down": 125, "up": 126, "insert": 114, "home": 115, "pageup": 116, "page_up": 116,
        "forwarddelete": 117, "end": 119, "pagedown": 121, "page_down": 121,
    ]
}

private final class AgentRuntime: NSObject, NSApplicationDelegate {
    private static let unclaimedSessionDeadline: TimeInterval = 30

    private let socketPath: String
    private let token: String?
    private var listener: SocketListener?
    private var unclaimedSessionTimeout: DispatchWorkItem?

    init(socketPath: String, token: String?) {
        self.socketPath = socketPath
        self.token = token
    }

    func applicationDidFinishLaunching(_ notification: Notification) {
        do {
            let timeout = DispatchWorkItem {
                fputs("computer-use agent received no authenticated session before its deadline\n", stderr)
                NSApp.terminate(nil)
            }
            unclaimedSessionTimeout = timeout
            let listener = try SocketListener(
                socketPath: socketPath,
                token: token,
                onSessionClaimed: {
                    timeout.cancel()
                },
                onSessionClosed: {
                    DispatchQueue.main.async {
                        NSApp.terminate(nil)
                    }
                }
            )
            self.listener = listener
            listener.start()
            DispatchQueue.main.asyncAfter(
                deadline: .now() + Self.unclaimedSessionDeadline,
                execute: timeout
            )
        } catch {
            fputs("failed to start computer-use socket: \(error)\n", stderr)
            NSApp.terminate(nil)
        }
    }

    func applicationWillTerminate(_ notification: Notification) {
        unclaimedSessionTimeout?.cancel()
        unclaimedSessionTimeout = nil
        listener?.stop()
    }
}

private final class PermissionRuntime: NSObject, NSApplicationDelegate {
    private let initialPermission: PermissionKind?
    private var windowController: PermissionWindowController?

    init(initialPermission: PermissionKind?) {
        self.initialPermission = initialPermission
    }

    func applicationDidFinishLaunching(_ notification: Notification) {
        windowController = PermissionWindowController(
            initialPermission: initialPermission,
            terminateWhenDragAssistantCloses: initialPermission != nil
        )
        if let initialPermission {
            windowController?.openPermission(initialPermission)
        } else {
            windowController?.showWindow(nil)
            windowController?.window?.makeKeyAndOrderFront(nil)
            NSApp.activate(ignoringOtherApps: true)
        }
        windowController?.refreshPermissions()
    }

    func applicationDidBecomeActive(_ notification: Notification) {
        windowController?.refreshPermissions()
    }

    func applicationShouldTerminateAfterLastWindowClosed(_ sender: NSApplication) -> Bool {
        initialPermission == nil
    }
}

private final class PermissionWindowController: NSWindowController {
    private var dragAssistant: PermissionDragAssistantController?
    private var dragAssistantPermission: PermissionKind?
    private let initialPermission: PermissionKind?
    private let terminateWhenDragAssistantCloses: Bool
    private var permissionStatusRefresh: PermissionStatusRefreshCoordinator?

    convenience init(initialPermission: PermissionKind? = nil, terminateWhenDragAssistantCloses: Bool = false) {
        let window = NSWindow(
            contentRect: NSRect(x: 0, y: 0, width: 300, height: 315),
            styleMask: [.titled, .closable, .miniaturizable, .fullSizeContentView],
            backing: .buffered,
            defer: false
        )
        window.title = "Enable Orca Computer Use"
        window.titleVisibility = .hidden
        window.titlebarAppearsTransparent = true
        window.backgroundColor = PermissionPalette.background
        window.center()
        window.isReleasedWhenClosed = false
        self.init(window: window, initialPermission: initialPermission, terminateWhenDragAssistantCloses: terminateWhenDragAssistantCloses)
        window.contentView = PermissionView(
            frame: window.contentView?.bounds ?? .zero,
            showDragAssistant: { [weak self] permission in
                self?.showDragAssistant(for: permission)
            },
            close: { [weak self] in
                self?.closePermissionWindow()
            }
        )
    }

    init(window: NSWindow?, initialPermission: PermissionKind?, terminateWhenDragAssistantCloses: Bool) {
        self.initialPermission = initialPermission
        self.terminateWhenDragAssistantCloses = terminateWhenDragAssistantCloses
        super.init(window: window)
        permissionStatusRefresh = PermissionStatusRefreshCoordinator(
            probe: permissionStatusSnapshotSettled,
            handler: { [weak self] snapshot in
                Task { @MainActor in
                    self?.applyPermissionStatus(snapshot)
                }
            }
        )
    }

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

    private func showDragAssistant(for permission: PermissionKind) {
        dragAssistant?.close()
        dragAssistantPermission = permission
        dragAssistant = PermissionDragAssistantController(
            permission: permission,
            fallbackVisibleFrame: window?.screen?.visibleFrame,
            onRefreshPermissions: { [weak self] in
                self?.refreshPermissions()
            },
            onClose: { [weak self] in
                if self?.terminateWhenDragAssistantCloses == true {
                    NSApp.terminate(nil)
                }
            }
        )
        dragAssistant?.showWhenReady()
    }

    private func closeDragAssistant() {
        dragAssistant?.close()
        dragAssistant = nil
        dragAssistantPermission = nil
    }

    private func completeDragAssistant() {
        guard let dragAssistant else {
            dragAssistantPermission = nil
            if terminateWhenDragAssistantCloses {
                NSApp.terminate(nil)
            }
            return
        }
        self.dragAssistant = nil
        dragAssistantPermission = nil
        dragAssistant.complete()
    }

    private func closePermissionWindow() {
        // Why: the floating assistant is a separate retained window controller and
        // can keep the helper app alive after the main permission window closes.
        closeDragAssistant()
        window?.close()
    }

    func openPermission(_ permission: PermissionKind) {
        permission.requestAndOpenSettings()
        showDragAssistant(for: permission)
    }

    func refreshPermissions() {
        permissionStatusRefresh?.refresh()
    }

    private func applyPermissionStatus(_ snapshot: PermissionStatusSnapshot) {
        if let initialPermission, initialPermission.isGranted(in: snapshot) {
            // Why: targeted permission helpers should finish once the requested
            // grant lands, even if other Computer Use permissions remain unset.
            completeDragAssistant()
            return
        }
        if dragAssistantPermission?.isGranted(in: snapshot) == true {
            // Why: after one grant in full setup, the remaining missing permission
            // needs fresh guidance instead of the old assistant's instructions.
            closeDragAssistant()
        }
        if PermissionKind.allCases.allSatisfy({ $0.isGranted(in: snapshot) }) {
            closeDragAssistant()
        }
        (window?.contentView as? PermissionView)?.refreshPermissions(snapshot)
    }
}

private enum PermissionKind: CaseIterable {
    case accessibility
    case screenshots

    static func parse(_ value: String?) -> PermissionKind? {
        switch value {
        case "accessibility":
            .accessibility
        case "screenshots", "screen", "screen-recording":
            .screenshots
        default:
            nil
        }
    }

    var dragInstruction: String {
        switch self {
        case .accessibility:
            "Drag Orca Computer Use into the list above to allow Accessibility."
        case .screenshots:
            "Drag Orca Computer Use into the list above to allow Screenshots."
        }
    }

    var title: String {
        switch self {
        case .accessibility:
            "Accessibility"
        case .screenshots:
            "Screenshots"
        }
    }

    var detail: String {
        switch self {
        case .accessibility:
            "Read and control app interfaces"
        case .screenshots:
            "Capture windows for visual state"
        }
    }

    var icon: NSImage {
        switch self {
        case .accessibility:
            NSImage(systemSymbolName: "figure", accessibilityDescription: "Accessibility") ?? NSImage()
        case .screenshots:
            NSImage(systemSymbolName: "camera.viewfinder", accessibilityDescription: "Screen Recording") ?? NSImage()
        }
    }

    func isGranted(in snapshot: PermissionStatusSnapshot) -> Bool {
        switch self {
        case .accessibility:
            snapshot.accessibilityGranted
        case .screenshots:
            snapshot.screenshotsGranted
        }
    }

    func requestAndOpenSettings() {
        switch self {
        case .accessibility:
            openAccessibilitySettings()
        case .screenshots:
            _ = requestScreenCaptureAccess()
            openScreenRecordingSettings()
        }
    }
}

private final class PermissionView: NSView {
    private let appURL = Bundle.main.bundleURL
    private let showDragAssistant: (PermissionKind) -> Void
    private let close: () -> Void
    private var contentStack: NSStackView?
    private var contentConstraints: [NSLayoutConstraint] = []
    private var permissionStatus: PermissionStatusSnapshot?

    init(frame frameRect: NSRect, showDragAssistant: @escaping (PermissionKind) -> Void, close: @escaping () -> Void) {
        self.showDragAssistant = showDragAssistant
        self.close = close
        super.init(frame: frameRect)
        wantsLayer = true
        layer?.backgroundColor = PermissionPalette.background.cgColor
        build()
    }

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

    private func build() {
        NSLayoutConstraint.deactivate(contentConstraints)
        contentStack?.removeFromSuperview()
        contentConstraints = []

        let stack = NSStackView()
        stack.orientation = .vertical
        stack.alignment = .leading
        stack.spacing = 10
        stack.distribution = .gravityAreas
        stack.translatesAutoresizingMaskIntoConstraints = false
        addSubview(stack)
        contentStack = stack

        let icon = NSImageView(image: NSWorkspace.shared.icon(forFile: appURL.path))
        icon.imageScaling = .scaleProportionallyUpOrDown
        icon.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            icon.widthAnchor.constraint(equalToConstant: 58),
            icon.heightAnchor.constraint(equalToConstant: 58)
        ])

        let missingPermissions = permissionStatus.map { snapshot in
            PermissionKind.allCases.filter { !$0.isGranted(in: snapshot) }
        } ?? []
        let checking = permissionStatus == nil
        let ready = !checking && missingPermissions.isEmpty

        let titleText = checking
            ? "Checking Computer Use"
            : (ready ? "Computer Use is Ready" : "Enable Orca Computer Use")
        let title = label(titleText, size: 22, weight: .bold)
        let subtitle = label(
            checking
                ? "Checking Accessibility and Screenshots."
                : (ready
                    ? "Orca can use local apps when you ask."
                    : "Grant permissions so Orca can use apps when you ask."),
            size: 12,
            weight: .regular
        )
        subtitle.textColor = PermissionPalette.secondaryText
        subtitle.alignment = .center
        subtitle.maximumNumberOfLines = 3

        let header = NSStackView(views: [icon, title, subtitle])
        header.orientation = .vertical
        header.alignment = .centerX
        header.spacing = 6
        header.translatesAutoresizingMaskIntoConstraints = false
        stack.addArrangedSubview(header)
        header.widthAnchor.constraint(equalTo: stack.widthAnchor).isActive = true
        subtitle.widthAnchor.constraint(equalTo: stack.widthAnchor, constant: -10).isActive = true

        if checking {
            let progress = NSProgressIndicator()
            progress.style = .spinning
            progress.controlSize = .small
            progress.translatesAutoresizingMaskIntoConstraints = false
            progress.startAnimation(nil)
            stack.addArrangedSubview(progress)
            progress.setContentHuggingPriority(.required, for: .horizontal)
            progress.centerXAnchor.constraint(equalTo: stack.centerXAnchor).isActive = true
        } else if ready {
            stack.addArrangedSubview(doneButton())
        } else {
            for permission in missingPermissions {
                stack.addArrangedSubview(permissionRow(permission: permission) { [weak self] in
                    permission.requestAndOpenSettings()
                    self?.showDragAssistant(permission)
                })
            }
        }

        contentConstraints = [
            stack.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 18),
            stack.trailingAnchor.constraint(equalTo: trailingAnchor, constant: -18),
            stack.topAnchor.constraint(equalTo: topAnchor, constant: 22),
            stack.bottomAnchor.constraint(lessThanOrEqualTo: bottomAnchor, constant: -20)
        ]
        NSLayoutConstraint.activate(contentConstraints)
    }

    func refreshPermissions(_ snapshot: PermissionStatusSnapshot) {
        guard permissionStatus != snapshot else { return }
        permissionStatus = snapshot
        build()
    }

    private func permissionRow(permission: PermissionKind, action: @escaping () -> Void) -> NSView {
        let row = NSView()
        row.wantsLayer = true
        row.layer?.cornerRadius = 14
        row.layer?.borderWidth = 1
        row.layer?.borderColor = PermissionPalette.border.cgColor
        row.layer?.backgroundColor = PermissionPalette.card.cgColor
        row.translatesAutoresizingMaskIntoConstraints = false

        let iconView = NSImageView(image: permission.icon)
        iconView.symbolConfiguration = NSImage.SymbolConfiguration(pointSize: 30, weight: .regular)
        iconView.contentTintColor = .controlAccentColor
        iconView.translatesAutoresizingMaskIntoConstraints = false

        let titleLabel = label(permission.title, size: 13, weight: .bold)
        let detailLabel = label(permission.detail, size: 11, weight: .regular)
        detailLabel.textColor = PermissionPalette.secondaryText
        let textStack = NSStackView(views: [titleLabel, detailLabel])
        textStack.orientation = .vertical
        textStack.alignment = .leading
        textStack.spacing = 4
        textStack.translatesAutoresizingMaskIntoConstraints = false

        let button = NSButton(title: "Allow", target: nil, action: nil)
        button.bezelStyle = .rounded
        button.controlSize = .regular
        button.font = NSFont.systemFont(ofSize: 13, weight: .semibold)
        button.contentTintColor = .white
        button.bezelColor = .controlAccentColor
        let buttonTitleAttributes: [NSAttributedString.Key: Any] = [
            .foregroundColor: NSColor.white,
            .font: NSFont.systemFont(ofSize: 13, weight: .semibold)
        ]
        button.attributedTitle = NSAttributedString(string: "Allow", attributes: buttonTitleAttributes)
        button.attributedAlternateTitle = NSAttributedString(string: "Allow", attributes: buttonTitleAttributes)
        let target = ButtonTarget(action)
        button.target = target
        button.action = #selector(ButtonTarget.run)
        objc_setAssociatedObject(button, "orca-action", target, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        button.translatesAutoresizingMaskIntoConstraints = false

        row.addSubview(iconView)
        row.addSubview(textStack)
        row.addSubview(button)
        NSLayoutConstraint.activate([
            row.heightAnchor.constraint(equalToConstant: 62),
            iconView.leadingAnchor.constraint(equalTo: row.leadingAnchor, constant: 12),
            iconView.centerYAnchor.constraint(equalTo: row.centerYAnchor),
            iconView.widthAnchor.constraint(equalToConstant: 34),
            iconView.heightAnchor.constraint(equalToConstant: 34),
            textStack.leadingAnchor.constraint(equalTo: iconView.trailingAnchor, constant: 10),
            textStack.centerYAnchor.constraint(equalTo: row.centerYAnchor),
            button.widthAnchor.constraint(greaterThanOrEqualToConstant: 52),
            button.heightAnchor.constraint(equalToConstant: 30),
            button.trailingAnchor.constraint(equalTo: row.trailingAnchor, constant: -12),
            button.centerYAnchor.constraint(equalTo: row.centerYAnchor),
            textStack.trailingAnchor.constraint(lessThanOrEqualTo: button.leadingAnchor, constant: -12)
        ])
        return row
    }

    private func doneButton() -> NSView {
        let button = NSButton(title: "Done", target: nil, action: nil)
        button.bezelStyle = .rounded
        button.controlSize = .regular
        button.font = NSFont.systemFont(ofSize: 13, weight: .semibold)
        button.contentTintColor = .white
        button.bezelColor = .controlAccentColor
        let buttonTitleAttributes: [NSAttributedString.Key: Any] = [
            .foregroundColor: NSColor.white,
            .font: NSFont.systemFont(ofSize: 13, weight: .semibold)
        ]
        button.attributedTitle = NSAttributedString(string: "Done", attributes: buttonTitleAttributes)
        button.attributedAlternateTitle = NSAttributedString(string: "Done", attributes: buttonTitleAttributes)
        let target = ButtonTarget(close)
        button.target = target
        button.action = #selector(ButtonTarget.run)
        objc_setAssociatedObject(button, "orca-action", target, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        button.translatesAutoresizingMaskIntoConstraints = false
        button.widthAnchor.constraint(greaterThanOrEqualToConstant: 82).isActive = true
        button.heightAnchor.constraint(equalToConstant: 32).isActive = true
        return button
    }

    private func label(_ text: String, size: CGFloat, weight: NSFont.Weight) -> NSTextField {
        let label = NSTextField(labelWithString: text)
        label.font = NSFont.systemFont(ofSize: size, weight: weight)
        label.lineBreakMode = .byWordWrapping
        label.textColor = PermissionPalette.primaryText
        label.translatesAutoresizingMaskIntoConstraints = false
        return label
    }
}

private final class PermissionDragAssistantController: NSWindowController {
    private struct SettingsWindowState {
        let frame: NSRect
        let isVisible: Bool
    }

    private let fallbackVisibleFrame: NSRect?
    private let onRefreshPermissions: () -> Void
    private let onClose: () -> Void
    private var hasSeenSettingsWindow = false
    private var followTimer: Timer?
    private var isDismissed = false
    private var scheduledShowWorkItems: [DispatchWorkItem] = []

    convenience init(
        permission: PermissionKind,
        fallbackVisibleFrame: NSRect?,
        onRefreshPermissions: @escaping () -> Void,
        onClose: @escaping () -> Void
    ) {
        let window = NSPanel(
            contentRect: NSRect(x: 0, y: 0, width: 390, height: 92),
            styleMask: [.borderless, .nonactivatingPanel],
            backing: .buffered,
            defer: false
        )
        window.title = "Drag Orca Computer Use"
        window.backgroundColor = .clear
        window.isOpaque = false
        window.isReleasedWhenClosed = false
        window.level = .floating
        window.hidesOnDeactivate = false
        window.isFloatingPanel = true
        window.becomesKeyOnlyIfNeeded = true
        // Why: the assistant belongs to System Settings' position; user drags
        // should either start the app-file drag or do nothing, not move the panel.
        window.isMovable = false
        window.isMovableByWindowBackground = false
        window.hasShadow = true
        self.init(
            window: window,
            fallbackVisibleFrame: fallbackVisibleFrame,
            onRefreshPermissions: onRefreshPermissions,
            onClose: onClose
        )
        window.contentView = PermissionDragAssistantView(permission: permission, appURL: Bundle.main.bundleURL) { [weak self] in
            self?.dismissFromCloseButton()
        }
    }

    init(
        window: NSWindow?,
        fallbackVisibleFrame: NSRect?,
        onRefreshPermissions: @escaping () -> Void,
        onClose: @escaping () -> Void
    ) {
        self.fallbackVisibleFrame = fallbackVisibleFrame
        self.onRefreshPermissions = onRefreshPermissions
        self.onClose = onClose
        super.init(window: window)
    }

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

    func showWhenReady() {
        guard !isDismissed else { return }
        startFollowingSettingsWindow()
        schedulePositionAndShow()
    }

    override func close() {
        isDismissed = true
        scheduledShowWorkItems.forEach { $0.cancel() }
        scheduledShowWorkItems.removeAll()
        followTimer?.invalidate()
        followTimer = nil
        super.close()
    }

    private func dismissFromCloseButton() {
        // Why: closing the NSWindow directly skips this controller's timer cleanup,
        // letting the assistant reappear while System Settings remains visible.
        complete()
    }

    func complete() {
        close()
        onClose()
    }

    private func schedulePositionAndShow() {
        scheduledShowWorkItems.forEach { $0.cancel() }
        scheduledShowWorkItems.removeAll()
        let delays = [0.12, 0.25, 0.4, 0.65, 0.95, 1.35, 1.8, 2.5]
        for (index, delay) in delays.enumerated() {
            let workItem = DispatchWorkItem { [weak self] in
                guard let self, !self.isDismissed, self.window?.isVisible != true else { return }
                if let settingsWindow = self.systemSettingsWindowState(), settingsWindow.isVisible {
                    self.positionNearSettingsWindow(settingsWindow.frame)
                    guard !self.isDismissed else { return }
                    self.showWindow(nil)
                    self.window?.orderFrontRegardless()
                } else if index == delays.count - 1 && self.systemSettingsIsFrontmost() {
                    self.positionFallback()
                    guard !self.isDismissed else { return }
                    self.showWindow(nil)
                    self.window?.orderFrontRegardless()
                }
            }
            scheduledShowWorkItems.append(workItem)
            DispatchQueue.main.asyncAfter(deadline: .now() + delay, execute: workItem)
        }
    }

    private func startFollowingSettingsWindow() {
        followTimer?.invalidate()
        followTimer = Timer.scheduledTimer(withTimeInterval: 0.35, repeats: true) { [weak self] _ in
            Task { @MainActor in
                guard let self, !self.isDismissed else { return }
                self.syncVisibilityWithSettingsWindow()
            }
        }
    }

    private func syncVisibilityWithSettingsWindow() {
        guard !isDismissed else {
            followTimer?.invalidate()
            followTimer = nil
            return
        }
        guard let window else {
            followTimer?.invalidate()
            followTimer = nil
            return
        }
        let settingsWindow = systemSettingsWindowState()
        if settingsWindow != nil {
            hasSeenSettingsWindow = true
        } else if hasSeenSettingsWindow {
            NSApp.terminate(nil)
            return
        }
        // Why: System Settings can stay visible on one display while the user
        // works on another; follow actual occlusion instead of app focus.
        if let settingsWindow, settingsWindow.isVisible {
            onRefreshPermissions()
            guard !isDismissed else { return }
            positionNearSettingsWindow(settingsWindow.frame)
            guard !isDismissed else { return }
            if !window.isVisible {
                showWindow(nil)
            }
            guard !isDismissed else { return }
            window.orderFrontRegardless()
        } else if window.isVisible {
            window.orderOut(nil)
        }
    }

    private func systemSettingsIsFrontmost() -> Bool {
        let bundleId = NSWorkspace.shared.frontmostApplication?.bundleIdentifier
        return bundleId == "com.apple.systempreferences" || bundleId == "com.apple.SystemSettings"
    }

    private func positionNearSettingsWindow(_ settingsFrame: NSRect) {
        guard let window else { return }
        let visibleFrame = visibleFrameContaining(settingsFrame)
        let x = settingsFrame.maxX - window.frame.width - 18
        let y = settingsFrame.minY + 18
        window.setFrameOrigin(clampedOrigin(x: x, y: y, window: window, visibleFrame: visibleFrame))
    }

    private func positionFallback() {
        guard let window else { return }
        let visibleFrame = fallbackVisibleFrame ?? NSScreen.main?.visibleFrame ?? NSRect(x: 0, y: 0, width: 900, height: 700)
        let origin = NSPoint(
            x: visibleFrame.midX - window.frame.width / 2,
            y: visibleFrame.minY + 24
        )
        window.setFrameOrigin(clampedOrigin(x: origin.x, y: origin.y, window: window, visibleFrame: visibleFrame))
    }

    private func clampedOrigin(x: CGFloat, y: CGFloat, window: NSWindow, visibleFrame: NSRect) -> NSPoint {
        let inset: CGFloat = 10
        let minX = visibleFrame.minX + inset
        let maxX = visibleFrame.maxX - window.frame.width - inset
        let minY = visibleFrame.minY + inset
        let maxY = visibleFrame.maxY - window.frame.height - inset
        return NSPoint(
            x: min(max(x, minX), maxX),
            y: min(max(y, minY), maxY)
        )
    }

    private func systemSettingsWindowState() -> SettingsWindowState? {
        guard let windows = CGWindowListCopyWindowInfo([.optionOnScreenOnly, .excludeDesktopElements], kCGNullWindowID) as? [[String: Any]] else {
            return nil
        }
        var occludingFrames: [NSRect] = []
        for windowInfo in windows {
            guard let frame = cgWindowFrame(windowInfo), isNormalWindow(windowInfo), frame.width > 0, frame.height > 0 else {
                continue
            }
            if isSystemSettingsWindow(windowInfo), frame.width > 520, frame.height > 360 {
                return SettingsWindowState(
                    frame: appKitFrameForCGWindowFrame(frame),
                    isVisible: !isWindowFullyCovered(frame, by: occludingFrames)
                )
            }
            occludingFrames.append(frame)
        }
        return nil
    }

    private func isSystemSettingsWindow(_ windowInfo: [String: Any]) -> Bool {
        guard let ownerName = windowInfo[kCGWindowOwnerName as String] as? String else {
            return false
        }
        return ownerName == "System Settings" || ownerName == "System Preferences"
    }

    private func isNormalWindow(_ windowInfo: [String: Any]) -> Bool {
        guard (windowInfo[kCGWindowLayer as String] as? Int) == 0 else {
            return false
        }
        if let alpha = windowInfo[kCGWindowAlpha as String] as? CGFloat, alpha <= 0 {
            return false
        }
        return true
    }

    private func cgWindowFrame(_ windowInfo: [String: Any]) -> NSRect? {
        guard
            let bounds = windowInfo[kCGWindowBounds as String] as? [String: CGFloat],
            let x = bounds["X"],
            let y = bounds["Y"],
            let width = bounds["Width"],
            let height = bounds["Height"]
        else {
            return nil
        }
        return NSRect(x: x, y: y, width: width, height: height)
    }

    private func isWindowFullyCovered(_ frame: NSRect, by occludingFrames: [NSRect]) -> Bool {
        var uncoveredFrames = [frame]
        for occludingFrame in occludingFrames {
            uncoveredFrames = uncoveredFrames.flatMap { subtract(occludingFrame, from: $0) }
            if uncoveredFrames.isEmpty {
                return true
            }
        }
        return false
    }

    private func subtract(_ coveringFrame: NSRect, from frame: NSRect) -> [NSRect] {
        let overlap = frame.intersection(coveringFrame)
        guard !overlap.isNull, overlap.width > 0, overlap.height > 0 else {
            return [frame]
        }

        var remaining: [NSRect] = []
        if overlap.minY > frame.minY {
            remaining.append(NSRect(x: frame.minX, y: frame.minY, width: frame.width, height: overlap.minY - frame.minY))
        }
        if overlap.maxY < frame.maxY {
            remaining.append(NSRect(x: frame.minX, y: overlap.maxY, width: frame.width, height: frame.maxY - overlap.maxY))
        }
        if overlap.minX > frame.minX {
            remaining.append(NSRect(x: frame.minX, y: overlap.minY, width: overlap.minX - frame.minX, height: overlap.height))
        }
        if overlap.maxX < frame.maxX {
            remaining.append(NSRect(x: overlap.maxX, y: overlap.minY, width: frame.maxX - overlap.maxX, height: overlap.height))
        }
        return remaining.filter { $0.width > 0 && $0.height > 0 }
    }

    private func appKitFrameForCGWindowFrame(_ cgFrame: NSRect) -> NSRect {
        guard let screen = screenContainingCGFrame(cgFrame),
              let screenNumber = screen.deviceDescription[NSDeviceDescriptionKey("NSScreenNumber")] as? NSNumber
        else {
            return cgFrame
        }

        let displayBounds = CGDisplayBounds(CGDirectDisplayID(screenNumber.uint32Value))
        return NSRect(
            x: cgFrame.minX,
            y: screen.frame.maxY - (cgFrame.minY - displayBounds.minY) - cgFrame.height,
            width: cgFrame.width,
            height: cgFrame.height
        )
    }

    private func screenContainingCGFrame(_ frame: NSRect) -> NSScreen? {
        NSScreen.screens.max { lhs, rhs in
            cgDisplayBounds(for: lhs).intersection(frame).width * cgDisplayBounds(for: lhs).intersection(frame).height <
                cgDisplayBounds(for: rhs).intersection(frame).width * cgDisplayBounds(for: rhs).intersection(frame).height
        }
    }

    private func cgDisplayBounds(for screen: NSScreen) -> NSRect {
        guard let screenNumber = screen.deviceDescription[NSDeviceDescriptionKey("NSScreenNumber")] as? NSNumber else {
            return screen.frame
        }
        return CGDisplayBounds(CGDirectDisplayID(screenNumber.uint32Value))
    }

    private func visibleFrameContaining(_ frame: NSRect) -> NSRect {
        let screen = NSScreen.screens.max { lhs, rhs in
            lhs.frame.intersection(frame).width * lhs.frame.intersection(frame).height <
                rhs.frame.intersection(frame).width * rhs.frame.intersection(frame).height
        }
        return screen?.visibleFrame ?? NSScreen.main?.visibleFrame ?? NSRect(x: 0, y: 0, width: 900, height: 700)
    }
}

private final class PermissionDragAssistantView: NSView {
    private let permission: PermissionKind
    private let appURL: URL
    private let close: () -> Void

    init(permission: PermissionKind, appURL: URL, close: @escaping () -> Void) {
        self.permission = permission
        self.appURL = appURL
        self.close = close
        super.init(frame: .zero)
        wantsLayer = true
        layer?.backgroundColor = PermissionPalette.background.cgColor
        layer?.cornerRadius = 14
        layer?.borderWidth = 1
        layer?.borderColor = PermissionPalette.border.cgColor
        layer?.masksToBounds = true
        build()
    }

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

    private func build() {
        let closeButton = NSButton(title: "", target: nil, action: nil)
        closeButton.bezelStyle = .shadowlessSquare
        closeButton.isBordered = false
        closeButton.image = NSImage(systemSymbolName: "xmark", accessibilityDescription: "Close")
        closeButton.imagePosition = .imageOnly
        closeButton.contentTintColor = PermissionPalette.secondaryText
        closeButton.controlSize = .small
        closeButton.translatesAutoresizingMaskIntoConstraints = false
        let target = ButtonTarget(close)
        closeButton.target = target
        closeButton.action = #selector(ButtonTarget.run)
        objc_setAssociatedObject(closeButton, "orca-action", target, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)

        let instruction = label(permission.dragInstruction, size: 12, weight: .semibold)
        instruction.textColor = PermissionPalette.primaryText
        instruction.maximumNumberOfLines = 2

        let dragTile = DraggableAppTile(appURL: appURL)
        dragTile.translatesAutoresizingMaskIntoConstraints = false

        addSubview(closeButton)
        addSubview(instruction)
        addSubview(dragTile)

        NSLayoutConstraint.activate([
            closeButton.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 10),
            closeButton.topAnchor.constraint(equalTo: topAnchor, constant: 10),
            closeButton.widthAnchor.constraint(equalToConstant: 18),
            closeButton.heightAnchor.constraint(equalToConstant: 18),
            instruction.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 36),
            instruction.trailingAnchor.constraint(equalTo: trailingAnchor, constant: -16),
            instruction.centerYAnchor.constraint(equalTo: closeButton.centerYAnchor),
            dragTile.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 16),
            dragTile.trailingAnchor.constraint(equalTo: trailingAnchor, constant: -16),
            dragTile.topAnchor.constraint(equalTo: instruction.bottomAnchor, constant: 8),
            dragTile.heightAnchor.constraint(equalToConstant: 42)
        ])
    }

    private func label(_ text: String, size: CGFloat, weight: NSFont.Weight) -> NSTextField {
        let label = NSTextField(labelWithString: text)
        label.font = NSFont.systemFont(ofSize: size, weight: weight)
        label.lineBreakMode = .byWordWrapping
        label.textColor = PermissionPalette.primaryText
        label.translatesAutoresizingMaskIntoConstraints = false
        return label
    }
}

private final class DraggableAppTile: NSView, NSDraggingSource {
    private let appURL: URL

    override var mouseDownCanMoveWindow: Bool { false }

    init(appURL: URL) {
        self.appURL = appURL
        super.init(frame: .zero)
        wantsLayer = true
        layer?.cornerRadius = 12
        layer?.borderWidth = 1
        layer?.borderColor = PermissionPalette.border.cgColor
        layer?.backgroundColor = PermissionPalette.card.cgColor
        build()
    }

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

    override func mouseDragged(with event: NSEvent) {
        let item = NSPasteboardItem()
        item.setString(appURL.absoluteString, forType: .fileURL)
        item.setString(appURL.path, forType: .string)

        let draggingItem = NSDraggingItem(pasteboardWriter: item)
        let iconSize: CGFloat = 64
        let location = convert(event.locationInWindow, from: nil)
        let dragFrame = NSRect(
            x: location.x - iconSize / 2,
            y: location.y - iconSize / 2,
            width: iconSize,
            height: iconSize
        )
        draggingItem.setDraggingFrame(dragFrame, contents: appIcon(size: iconSize))
        beginDraggingSession(with: [draggingItem], event: event, source: self)
    }

    func draggingSession(_ session: NSDraggingSession, sourceOperationMaskFor context: NSDraggingContext) -> NSDragOperation {
        .copy
    }

    private func build() {
        let icon = NSImageView(image: appIcon(size: 34))
        icon.imageScaling = .scaleProportionallyUpOrDown
        icon.translatesAutoresizingMaskIntoConstraints = false

        let title = NSTextField(labelWithString: "Orca Computer Use")
        title.font = NSFont.systemFont(ofSize: 15, weight: .semibold)
        title.textColor = PermissionPalette.primaryText
        title.translatesAutoresizingMaskIntoConstraints = false

        addSubview(icon)
        addSubview(title)
        NSLayoutConstraint.activate([
            icon.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 16),
            icon.centerYAnchor.constraint(equalTo: centerYAnchor),
            icon.widthAnchor.constraint(equalToConstant: 34),
            icon.heightAnchor.constraint(equalToConstant: 34),
            title.leadingAnchor.constraint(equalTo: icon.trailingAnchor, constant: 14),
            title.centerYAnchor.constraint(equalTo: centerYAnchor),
            title.trailingAnchor.constraint(lessThanOrEqualTo: trailingAnchor, constant: -20)
        ])
    }

    private func appIcon(size: CGFloat) -> NSImage {
        let icon = NSWorkspace.shared.icon(forFile: appURL.path)
        icon.size = NSSize(width: size, height: size)
        return icon
    }
}

private enum PermissionPalette {
    static let background = adaptiveColor(
        light: NSColor(calibratedWhite: 0.94, alpha: 0.98),
        dark: NSColor(calibratedWhite: 0.20, alpha: 0.98)
    )
    static let card = adaptiveColor(
        light: NSColor(calibratedWhite: 0.99, alpha: 0.98),
        dark: NSColor(calibratedWhite: 0.25, alpha: 0.98)
    )
    static let border = adaptiveColor(
        light: NSColor(calibratedWhite: 0.0, alpha: 0.14),
        dark: NSColor(calibratedWhite: 1.0, alpha: 0.22)
    )
    static let primaryText = NSColor.labelColor
    static let secondaryText = NSColor.secondaryLabelColor

    private static func adaptiveColor(light: NSColor, dark: NSColor) -> NSColor {
        NSColor(name: nil) { appearance in
            let bestMatch = appearance.bestMatch(from: [
                .aqua,
                .darkAqua,
                .accessibilityHighContrastAqua,
                .accessibilityHighContrastDarkAqua
            ])
            return bestMatch == .darkAqua || bestMatch == .accessibilityHighContrastDarkAqua ? dark : light
        }
    }
}

private final class ButtonTarget: NSObject {
    private let actionBlock: () -> Void

    init(_ actionBlock: @escaping () -> Void) {
        self.actionBlock = actionBlock
    }

    @objc func run() {
        actionBlock()
    }
}

private final class SocketListener: @unchecked Sendable {
    private let socketPath: String
    private let token: String?
    private let onSessionClaimed: () -> Void
    private let onSessionClosed: () -> Void
    private let provider = Provider()
    private let providerLock = NSLock()
    private let sessionLock = NSLock()
    private var sessionOwnership = AgentSessionOwnership()
    private var lastConnectionID: UInt64 = 0
    private var socketFd: Int32 = -1
    private var isStopped = false

    init(
        socketPath: String,
        token: String?,
        onSessionClaimed: @escaping () -> Void,
        onSessionClosed: @escaping () -> Void
    ) throws {
        self.socketPath = socketPath
        self.token = token
        self.onSessionClaimed = onSessionClaimed
        self.onSessionClosed = onSessionClosed
        try bindSocket()
    }

    func start() {
        Thread.detachNewThread { [weak self] in
            self?.acceptLoop()
        }
    }

    func stop() {
        isStopped = true
        if socketFd >= 0 {
            close(socketFd)
            socketFd = -1
        }
        // Why: the parent owns the private temp directory cleanup; the helper
        // must not unlink arbitrary caller-supplied paths on shutdown.
    }

    private func bindSocket() throws {
        socketFd = socket(AF_UNIX, SOCK_STREAM, 0)
        guard socketFd >= 0 else {
            throw ProviderError.coded("accessibility_error", "failed to create computer-use socket")
        }

        var address = sockaddr_un()
        address.sun_family = sa_family_t(AF_UNIX)
        let maxPathLength = MemoryLayout.size(ofValue: address.sun_path)
        guard socketPath.utf8.count < maxPathLength else {
            throw ProviderError.coded("invalid_argument", "computer-use socket path is too long")
        }
        _ = withUnsafeMutablePointer(to: &address.sun_path) { pointer in
            socketPath.withCString { source in
                strncpy(UnsafeMutableRawPointer(pointer).assumingMemoryBound(to: CChar.self), source, maxPathLength)
            }
        }

        let result = withUnsafePointer(to: &address) { pointer -> Int32 in
            pointer.withMemoryRebound(to: sockaddr.self, capacity: 1) { sockaddrPointer in
                bind(socketFd, sockaddrPointer, socklen_t(MemoryLayout<sockaddr_un>.size))
            }
        }
        guard result == 0 else {
            let bindErrno = errno
            let message = String(cString: strerror(bindErrno))
            close(socketFd)
            socketFd = -1
            if UnixSocketPathSafety.shouldRejectExistingPathAfterBindFailure(
                bindErrno: bindErrno,
                existingMode: existingPathMode(socketPath)
            ) {
                throw ProviderError.coded("invalid_argument", "refusing to replace non-socket file at computer-use socket path")
            }
            throw ProviderError.coded("accessibility_error", "failed to bind computer-use socket: \(message)")
        }
        chmod(socketPath, 0o600)

        guard listen(socketFd, 8) == 0 else {
            let message = String(cString: strerror(errno))
            close(socketFd)
            socketFd = -1
            throw ProviderError.coded("accessibility_error", "failed to listen on computer-use socket: \(message)")
        }
    }

    private func acceptLoop() {
        while !isStopped {
            let fd = accept(socketFd, nil, nil)
            if fd < 0 {
                if !isStopped {
                    fputs("computer-use socket accept failed: \(String(cString: strerror(errno)))\n", stderr)
                }
                continue
            }
            guard let connectionID = allocateConnectionID() else {
                fputs("computer-use socket exhausted connection identities\n", stderr)
                close(fd)
                continue
            }
            Thread.detachNewThread { [weak self] in
                self?.handleConnection(fd, connectionID: connectionID)
            }
        }
    }

    private func allocateConnectionID() -> AgentSessionConnectionID? {
        sessionLock.lock()
        defer { sessionLock.unlock() }
        guard lastConnectionID < UInt64.max else { return nil }
        lastConnectionID += 1
        return AgentSessionConnectionID(rawValue: lastConnectionID)
    }

    private func handleConnection(_ fd: Int32, connectionID: AgentSessionConnectionID) {
        var registeredSession = false
        var hangupMonitor: AuthenticatedConnectionHangupMonitor?
        defer {
            hangupMonitor?.cancel()
            if registeredSession {
                disconnectSession(connectionID)
            }
            close(fd)
        }
        let authorizedPeer = peerProcessId(fd).map(isAuthorizedAgentPeer) == true
        let decoder = JSONDecoder()
        AgentConnectionRequestLoop.run(readLine: { readLine(from: fd) }) { line in
            guard let data = line.data(using: .utf8),
                  let request = try? decoder.decode(Request.self, from: data)
            else {
                return true
            }
            if !registeredSession && isAuthenticatedAgentSession(
                expectedToken: token,
                requestToken: request.token,
                authorizedPeer: authorizedPeer
            ) {
                let monitor: AuthenticatedConnectionHangupMonitor
                do {
                    monitor = try AuthenticatedConnectionHangupMonitor(
                        fileDescriptor: fd,
                        onHangup: { [weak self] in
                            self?.disconnectSession(connectionID)
                        }
                    )
                } catch {
                    fputs("computer-use owner monitor failed: \(error)\n", stderr)
                    return false
                }
                sessionLock.lock()
                let registration = sessionOwnership.registerConnection(
                    connectionID,
                    authenticated: true
                )
                sessionLock.unlock()
                guard registration != .rejected else {
                    monitor.cancel()
                    return false
                }
                registeredSession = true
                hangupMonitor = monitor
                monitor.start()
                if registration == .claimed {
                    onSessionClaimed()
                }
            }
            let response = handleRequest(
                provider: provider,
                lock: providerLock,
                request: request,
                expectedToken: token,
                authorizedPeer: authorizedPeer
            )
            writeJSON(response, to: fd)
            return true
        }
    }

    private func disconnectSession(_ connectionID: AgentSessionConnectionID) {
        sessionLock.lock()
        let shouldTerminate = sessionOwnership.disconnect(connectionID)
        sessionLock.unlock()
        if shouldTerminate {
            onSessionClosed()
        }
    }
}

private func existingPathMode(_ path: String) -> mode_t? {
    var statInfo = stat()
    guard lstat(path, &statInfo) == 0 else {
        return nil
    }
    return statInfo.st_mode
}

private func peerProcessId(_ fd: Int32) -> pid_t? {
    var pid = pid_t(0)
    var length = socklen_t(MemoryLayout<pid_t>.size)
    let result = withUnsafeMutablePointer(to: &pid) { pointer in
        getsockopt(fd, 0, 2, pointer, &length)
    }
    return result == 0 && pid > 0 ? pid : nil
}

private func isAuthorizedAgentPeer(_ pid: pid_t) -> Bool {
    guard let command = processCommand(pid),
          command.contains("/out/main/computer-sidecar.js")
              || command.contains("/Contents/Resources/app.asar.unpacked/out/main/computer-sidecar.js")
    else {
        return false
    }
    if isTrustedOrcaApplication(pid) {
        return true
    }
    guard let parentPid = parentProcessId(pid) else { return false }
    return isTrustedOrcaApplication(parentPid)
}

private func isTrustedOrcaApplication(_ pid: pid_t) -> Bool {
    guard let app = NSRunningApplication(processIdentifier: pid),
          let bundleId = app.bundleIdentifier
    else {
        return false
    }
    return TrustedOrcaApplication.isTrusted(bundleId: bundleId)
}

private func parentProcessId(_ pid: pid_t) -> pid_t? {
    guard let output = processField(pid: pid, field: "ppid=") else {
        return nil
    }
    let trimmed = output.trimmingCharacters(in: .whitespacesAndNewlines)
    guard let parentPid = pid_t(trimmed), parentPid > 1 else {
        return nil
    }
    return parentPid
}

private func processCommand(_ pid: pid_t) -> String? {
    return processField(pid: pid, field: "command=")
}

private func processField(pid: pid_t, field: String) -> String? {
    let process = Process()
    let pipe = Pipe()
    process.executableURL = URL(fileURLWithPath: "/bin/ps")
    process.arguments = ["-p", "\(pid)", "-o", field]
    process.standardOutput = pipe
    process.standardError = Pipe()
    do {
        try process.run()
        process.waitUntilExit()
        guard process.terminationStatus == 0 else { return nil }
        let data = pipe.fileHandleForReading.readDataToEndOfFile()
        return String(data: data, encoding: .utf8)
    } catch {
        return nil
    }
}

@MainActor
private func runAgent(socketPath: String, token: String?) {
    let app = NSApplication.shared
    let delegate = AgentRuntime(socketPath: socketPath, token: token)
    app.delegate = delegate
    // Why: SCK is reliable once this code runs as a signed app with a real TCC identity.
    setenv("ORCA_COMPUTER_USE_SCK_SCREENSHOTS", "1", 1)
    app.run()
}

@MainActor
private func runPermissionCheck(initialPermission: PermissionKind? = nil) {
    let app = NSApplication.shared
    let delegate = PermissionRuntime(initialPermission: initialPermission)
    app.delegate = delegate
    // Why: setup must foreground reliably; the long-running agent path stays accessory-only.
    app.setActivationPolicy(.regular)
    app.run()
}

private func printPermissionStatus() {
    let snapshot = permissionStatusSnapshotSettled()
    let accessibility = snapshot.accessibilityGranted ? "granted" : "not-granted"
    let screenshots = snapshot.screenshotsGranted ? "granted" : "not-granted"
    print(#"{"accessibility":"\#(accessibility)","screenshots":"\#(screenshots)"}"#)
}

private func writePermissionStatus(to path: String) {
    let snapshot = permissionStatusSnapshotSettled()
    let accessibility = snapshot.accessibilityGranted ? "granted" : "not-granted"
    let screenshots = snapshot.screenshotsGranted ? "granted" : "not-granted"
    let text = #"{"accessibility":"\#(accessibility)","screenshots":"\#(screenshots)"}"#
    do {
        try text.write(toFile: path, atomically: true, encoding: .utf8)
    } catch {
        fputs("failed to write permission status: \(error)\n", stderr)
        exit(1)
    }
}

private func runStdio() {
    fputs("Orca Computer Use provider must be launched by Orca in app-agent mode.\n", stderr)
    exit(13)
}

private func handleRequest(
    provider: Provider,
    lock: NSLock,
    request: Request,
    expectedToken: String?,
    authorizedPeer: Bool
) -> Any {
    if let expectedToken, request.token != expectedToken {
        return ["id": request.id, "ok": false, "error": ["code": "permission_denied", "message": "invalid computer-use agent token"]]
    }
    if expectedToken != nil && !authorizedPeer {
        return ["id": request.id, "ok": false, "error": ["code": "permission_denied", "message": "computer-use agent peer is not authorized"]]
    }
    if request.method == "terminate" {
        DispatchQueue.main.async {
            NSApp.terminate(nil)
        }
        return ["id": request.id, "ok": true, "result": ["ok": true]]
    }

    do {
        lock.lock()
        defer { lock.unlock() }
        let result = try provider.handle(method: request.method, params: request.params ?? [:])
        return ["id": request.id, "ok": true, "result": result]
    } catch let error as ProviderError {
        return ["id": request.id, "ok": false, "error": ["code": error.code, "message": error.message]]
    } catch {
        return ["id": request.id, "ok": false, "error": ["code": "accessibility_error", "message": String(describing: error)]]
    }
}

private func readLine(from fd: Int32) -> String? {
    var bytes: [UInt8] = []
    var byte: UInt8 = 0
    while true {
        let count = read(fd, &byte, 1)
        if count == 0 {
            return bytes.isEmpty ? nil : String(bytes: bytes, encoding: .utf8)
        }
        if count < 0 {
            return nil
        }
        if byte == 10 {
            return String(bytes: bytes, encoding: .utf8)
        }
        bytes.append(byte)
    }
}

private func writeJSON(_ object: Any, to fd: Int32?) {
    guard JSONSerialization.isValidJSONObject(object),
          let data = try? JSONSerialization.data(withJSONObject: object, options: [.withoutEscapingSlashes])
    else {
        return
    }
    if let fd {
        _ = writeAll(data, to: fd)
        _ = writeAll(Data([10]), to: fd)
    } else {
        guard let text = String(data: data, encoding: .utf8) else {
            return
        }
        print(text)
        fflush(stdout)
    }
}

private func writeAll(_ data: Data, to fd: Int32) -> Bool {
    data.withUnsafeBytes { rawBuffer in
        guard let baseAddress = rawBuffer.baseAddress else {
            return true
        }
        var offset = 0
        while offset < rawBuffer.count {
            let written = write(fd, baseAddress.advanced(by: offset), rawBuffer.count - offset)
            if written < 0 {
                if errno == EINTR {
                    continue
                }
                return false
            }
            if written == 0 {
                return false
            }
            offset += written
        }
        return true
    }
}

let arguments = Array(CommandLine.arguments.dropFirst())
if arguments.first == "--agent" {
    guard arguments.count >= 2 else {
        fputs("usage: orca-computer-use-macos --agent <socket-path> --token-file <token-path>\n", stderr)
        exit(2)
    }
    let tokenFileIndex = arguments.firstIndex(of: "--token-file")
    let token = tokenFileIndex.flatMap { index -> String? in
        let valueIndex = index + 1
        guard valueIndex < arguments.count else { return nil }
        let tokenPath = arguments[valueIndex]
        return try? String(contentsOfFile: tokenPath, encoding: .utf8)
            .trimmingCharacters(in: .whitespacesAndNewlines)
    }
    guard let token, !token.isEmpty else {
        fputs("orca-computer-use-macos --agent requires a non-empty --token-file\n", stderr)
        exit(2)
    }
    runAgent(socketPath: arguments[1], token: token)
} else if arguments.first == "--permissions" {
    runPermissionCheck()
} else if arguments.first == "--permission" {
    runPermissionCheck(initialPermission: PermissionKind.parse(arguments.dropFirst().first))
} else if arguments.first == "--permission-status" {
    printPermissionStatus()
} else if arguments.first == "--permission-status-file" {
    guard arguments.count >= 2 else {
        fputs("usage: orca-computer-use-macos --permission-status-file <path>\n", stderr)
        exit(2)
    }
    writePermissionStatus(to: arguments[1])
} else {
    runStdio()
}