WP-5b: FSEvents ReturnWatcher per SPEC-A1c with review corrections

Sources/ShotdeckCore/Capture/CaptureRegion.swift

@@ -0,0 +1,58 @@
+import Foundation
+import AppKit  // NSScreen, NSDeviceDescriptionKey — macOS-only target, no portability concern
+
+/// A remembered rectangle, in CoreGraphics global display coordinates (origin top-left,
+/// y increasing downward — see the conversion note below).
+public struct CaptureRegion: Codable, Sendable, Equatable {
+    public let displayID: CGDirectDisplayID
+    public let rect: CGRect
+    public let capturedScale: CGFloat
+
+    public init(displayID: CGDirectDisplayID, rect: CGRect, capturedScale: CGFloat) {
+        self.displayID = displayID
+        self.rect = rect
+        self.capturedScale = capturedScale
+    }
+
+    /// Converts an AppKit rect in GLOBAL AppKit coordinates (bottom-left origin, y increasing
+    /// upward, anchored at the bottom-left of the PRIMARY screen — exactly what
+    /// `NSWindow.frame`, `NSEvent.mouseLocation` and `NSScreen.frame` already report; no
+    /// screen-local conversion is needed here) into global CoreGraphics coordinates
+    /// (top-left origin, y increasing downward, same primary-screen anchor). Both coordinate
+    /// systems share the SAME horizontal origin and the SAME anchor rectangle (the primary
+    /// screen's bounds) — only the vertical axis is mirrored around the primary's height.
+    /// That is why the flip below is correct for every attached screen, including one with a
+    /// negative AppKit x (to the left of primary) or a y that places it above the primary
+    /// (whose CG y then comes out negative): x is untouched, and the primary height is the
+    /// one fixed reference both systems agree on regardless of which physical screen the
+    /// rect is actually on.
+    public static func fromAppKit(rect: CGRect, on screen: NSScreen) -> CaptureRegion {
+        let displayID = (screen.deviceDescription[NSDeviceDescriptionKey("NSScreenNumber")]
+            as? NSNumber)?.uint32Value ?? CGMainDisplayID()
+        let primaryHeight = NSScreen.screens.first?.frame.height ?? screen.frame.height
+        return fromAppKit(rect: rect, displayID: displayID,
+                           capturedScale: screen.backingScaleFactor, primaryHeight: primaryHeight)
+    }
+
+    /// Injectable overload for deterministic geometry tests — no dependency on real attached
+    /// displays. The public overload above is a thin adapter over this.
+    static func fromAppKit(rect: CGRect, displayID: CGDirectDisplayID,
+                            capturedScale: CGFloat, primaryHeight: CGFloat) -> CaptureRegion {
+        let cgY = primaryHeight - rect.origin.y - rect.height
+        let cgRect = CGRect(x: rect.origin.x, y: cgY, width: rect.width, height: rect.height)
+        return CaptureRegion(displayID: displayID, rect: cgRect, capturedScale: capturedScale)
+    }
+
+    /// True when `displayID` is still attached AND `rect` still lies inside its current
+    /// bounds. Uses `CGDisplayIsActive` (returns 0 safely for an unknown id, never traps) and
+    /// `CGDisplayBounds` — both real CoreGraphics calls, no injection needed since this is a
+    /// live-state check by design.
+    public var isStillValid: Bool {
+        guard CGDisplayIsActive(displayID) != 0 else { return false }
+        let bounds = CGDisplayBounds(displayID)
+        return bounds.contains(rect)
+    }
+
+    /// Persisted in UserDefaults under this key BY THE APP (WP-4a), never by this type.
+    public static let defaultsKey = "ai.flowmaster.shotdeck.region"
+}

Sources/ShotdeckCore/Capture/HotkeyCenter.swift

@@ -0,0 +1,115 @@
+import Carbon.HIToolbox
+import Foundation
+
+/// Carbon's C event handler cannot capture Swift closures, so live handlers are kept in one
+/// process-wide table keyed by the numeric EventHotKeyID Carbon hands back on fire. Safe
+/// because InstallEventHandler on GetApplicationEventTarget() always delivers on the main
+/// thread, and every access here happens either from a @MainActor HotkeyCenter method or from
+/// the C callback below, which this process only ever invokes on the main run loop.
+private final class HotkeyDispatchTable: @unchecked Sendable {
+    static let shared = HotkeyDispatchTable()
+    private var handlers: [UInt32: @MainActor () -> Void] = [:]
+    private init() {}
+    func set(_ numericID: UInt32, _ handler: @escaping @MainActor () -> Void) {
+        handlers[numericID] = handler
+    }
+    func remove(_ numericID: UInt32) { handlers.removeValue(forKey: numericID) }
+    func fire(_ numericID: UInt32) { MainActor.assumeIsolated { handlers[numericID]?() } }
+}
+
+private func shotdeckCarbonHotkeyHandler(
+    _ nextHandler: EventHandlerCallRef?, _ event: EventRef?, _ userData: UnsafeMutableRawPointer?
+) -> OSStatus {
+    guard let event else { return OSStatus(eventNotHandledErr) }
+    var hotKeyID = EventHotKeyID()
+    let status = GetEventParameter(event, EventParamName(kEventParamDirectObject),
+        EventParamType(typeEventHotKeyID), nil, MemoryLayout<EventHotKeyID>.size, nil, &hotKeyID)
+    guard status == noErr else { return status }
+    HotkeyDispatchTable.shared.fire(hotKeyID.id)
+    return noErr
+}
+
+/// Four-character creator code used for every `EventHotKeyID` this process registers.
+private let shotdeckHotKeySignature: OSType = 0x53484F54 // "SHOT"
+
+@MainActor
+public final class HotkeyCenter {
+    private var bindings: [String: (ref: EventHotKeyRef, numericID: UInt32)] = [:]
+    private var nextNumericID: UInt32 = 1
+
+    private static var didInstallGlobalCarbonHandler = false
+    private static var carbonHandlerRef: EventHandlerRef?
+
+    public init() { HotkeyCenter.installGlobalCarbonHandlerIfNeeded() }
+
+    /// Registers a hotkey. `id` is a caller-chosen stable identifier. Re-registering the same
+    /// `id` first unregisters its previous binding, then attempts the new one (idempotent).
+    /// Returns false when Carbon's `RegisterEventHotKey` reports a non-`noErr` status — the
+    /// most common cause is the same keyCode+modifiers combination already being claimed
+    /// system-wide by this or another process.
+    @discardableResult
+    public func register(
+        id: String,
+        keyCode: UInt32,
+        modifiers: UInt32,
+        handler: @escaping @MainActor () -> Void
+    ) -> Bool {
+        unregister(id: id)
+
+        let hotKeyID = EventHotKeyID(signature: shotdeckHotKeySignature, id: nextNumericID)
+        var ref: EventHotKeyRef?
+        let status = RegisterEventHotKey(
+            keyCode,
+            modifiers,
+            hotKeyID,
+            GetApplicationEventTarget(),
+            0,
+            &ref
+        )
+        guard status == noErr, let ref else {
+            return false
+        }
+        bindings[id] = (ref: ref, numericID: nextNumericID)
+        HotkeyDispatchTable.shared.set(nextNumericID, handler)
+        nextNumericID += 1
+        return true
+    }
+
+    public func unregister(id: String) {
+        guard let binding = bindings.removeValue(forKey: id) else { return }
+        _ = UnregisterEventHotKey(binding.ref)
+        HotkeyDispatchTable.shared.remove(binding.numericID)
+    }
+
+    public func unregisterAll() {
+        let ids = Array(bindings.keys)
+        for id in ids {
+            unregister(id: id)
+        }
+    }
+
+    /// Installs the process-wide Carbon hot-key pressed handler exactly once.
+    private static func installGlobalCarbonHandlerIfNeeded() {
+        guard !didInstallGlobalCarbonHandler else { return }
+        didInstallGlobalCarbonHandler = true
+
+        var handlerRef: EventHandlerRef?
+        var eventTypes = [
+            EventTypeSpec(
+                eventClass: OSType(kEventClassKeyboard),
+                eventKind: OSType(kEventHotKeyPressed)
+            )
+        ]
+        let status = InstallEventHandler(
+            GetApplicationEventTarget(),
+            shotdeckCarbonHotkeyHandler,
+            1,
+            &eventTypes,
+            nil,
+            &handlerRef
+        )
+        if status == noErr {
+            carbonHandlerRef = handlerRef
+        }
+    }
+}

Sources/ShotdeckCore/PDF/PDFComposer.swift

@@ -0,0 +1,209 @@
+import AppKit
+import CoreGraphics
+import CoreText
+import Foundation
+import ImageIO
+import os
+
+private let pdfLog = Logger(subsystem: "ai.flowmaster.shotdeck", category: "PDF")
+
+public struct PDFComposer: Sendable {
+    public init() {}
+
+    @discardableResult
+    public func compose(
+        session: CaptureSession,
+        imageURL: (Capture) -> URL,
+        title: String,
+        to outputURL: URL
+    ) throws -> Int {
+        if session.isEmpty {
+            throw ShotdeckError.pdfCompositionFailed(reason: "session has no captures")
+        }
+
+        var loaded: [(Capture, CGImage)] = []
+        loaded.reserveCapacity(session.captures.count)
+        for capture in session.captures {
+            let url = imageURL(capture)
+            if let image = Self.loadCGImage(from: url) {
+                loaded.append((capture, image))
+            } else {
+                pdfLog.error(
+                    "skipping capture \(capture.id.uuidString, privacy: .public) seq \(capture.sequence, privacy: .public): image unreadable at \(url.path, privacy: .public)"
+                )
+            }
+        }
+
+        guard !loaded.isEmpty else {
+            throw ShotdeckError.pdfCompositionFailed(reason: "no readable images in session")
+        }
+
+        let pageCount = loaded.count
+        let tmpURL = outputURL
+            .deletingLastPathComponent()
+            .appendingPathComponent(".tmp-\(UUID().uuidString)-\(outputURL.lastPathComponent)")
+
+        do {
+            try Self.writePDF(
+                loaded: loaded,
+                pageCount: pageCount,
+                title: title,
+                sessionID: session.id,
+                to: tmpURL
+            )
+
+            let handle = try FileHandle(forWritingTo: tmpURL)
+            try handle.synchronize()
+            try handle.close()
+
+            if FileManager.default.fileExists(atPath: outputURL.path) {
+                try FileManager.default.removeItem(at: outputURL)
+            }
+            try FileManager.default.moveItem(at: tmpURL, to: outputURL)
+            return pageCount
+        } catch {
+            try? FileManager.default.removeItem(at: tmpURL)
+            if let shotdeck = error as? ShotdeckError {
+                throw shotdeck
+            }
+            throw ShotdeckError.pdfCompositionFailed(reason: error.localizedDescription)
+        }
+    }
+
+    public static func fileName(for session: CaptureSession) -> String {
+        "Shotdeck-\(DubaiTime.fileStamp(session.createdAt)).pdf"
+    }
+
+    private static func writePDF(
+        loaded: [(Capture, CGImage)],
+        pageCount: Int,
+        title: String,
+        sessionID: UUID,
+        to tmpURL: URL
+    ) throws {
+        guard let consumer = CGDataConsumer(url: tmpURL as CFURL) else {
+            throw ShotdeckError.pdfCompositionFailed(reason: "cannot open output location")
+        }
+
+        let auxiliaryInfo: [String: Any] = [
+            kCGPDFContextCreator as String: "Shotdeck",
+            kCGPDFContextTitle as String: title,
+            kCGPDFContextSubject as String: sessionID.uuidString.lowercased(),
+        ]
+
+        guard let context = CGContext(
+            consumer: consumer,
+            mediaBox: nil,
+            auxiliaryInfo as CFDictionary
+        ) else {
+            throw ShotdeckError.pdfCompositionFailed(reason: "cannot open output location")
+        }
+
+        let lightGrey = CGColor(gray: 0.75, alpha: 1)
+        let black = CGColor(gray: 0, alpha: 1)
+        let timestampColor = CGColor(gray: 0.45, alpha: 1)
+
+        for pageIndex in 1...pageCount {
+            let (capture, cgImage) = loaded[pageIndex - 1]
+            let layout = PageLayout(capture: capture, pageIndex: pageIndex, pageCount: pageCount)
+
+            context.beginPDFPage(Self.pageInfo(mediaBox: layout.pageRect))
+
+            context.draw(cgImage, in: layout.imageRect)
+
+            context.setStrokeColor(lightGrey)
+            context.setLineWidth(0.5)
+            context.move(to: CGPoint(x: layout.headerRect.minX, y: layout.headerRect.minY))
+            context.addLine(to: CGPoint(x: layout.headerRect.maxX, y: layout.headerRect.minY))
+            context.strokePath()
+
+            drawText(
+                layout.pageNumberText,
+                font: layout.pageNumberFont,
+                color: black,
+                at: layout.pageNumberOrigin,
+                in: context
+            )
+            drawText(
+                layout.timestampText,
+                font: layout.timestampFont,
+                color: timestampColor,
+                at: layout.timestampOrigin,
+                in: context
+            )
+            drawText(
+                "PASS",
+                font: layout.tickLabelFont,
+                color: black,
+                at: layout.passLabelOrigin,
+                in: context
+            )
+            drawText(
+                "FAIL",
+                font: layout.tickLabelFont,
+                color: black,
+                at: layout.failLabelOrigin,
+                in: context
+            )
+
+            strokeTickBox(layout.passTickBox, in: context, color: black)
+            strokeTickBox(layout.failTickBox, in: context, color: black)
+
+            context.endPDFPage()
+        }
+
+        context.closePDF()
+    }
+
+    private static func pageInfo(mediaBox: CGRect) -> CFDictionary {
+        var box = mediaBox
+        let data = Data(bytes: &box, count: MemoryLayout<CGRect>.size)
+        return [kCGPDFContextMediaBox as String: data] as CFDictionary
+    }
+
+    private static func drawText(
+        _ string: String,
+        font: NSFont,
+        color: CGColor,
+        at origin: CGPoint,
+        in context: CGContext
+    ) {
+        let attributes: [CFString: Any] = [
+            kCTFontAttributeName: font,
+            kCTForegroundColorAttributeName: color,
+        ]
+        guard let attributed = CFAttributedStringCreate(
+            nil,
+            string as CFString,
+            attributes as CFDictionary
+        ) else {
+            return
+        }
+        let line = CTLineCreateWithAttributedString(attributed)
+        context.textMatrix = .identity
+        context.textPosition = origin
+        CTLineDraw(line, context)
+    }
+
+    private static func strokeTickBox(_ box: CGRect, in context: CGContext, color: CGColor) {
+        let path = CGPath(
+            roundedRect: box,
+            cornerWidth: 2,
+            cornerHeight: 2,
+            transform: nil
+        )
+        context.addPath(path)
+        context.setStrokeColor(color)
+        context.setLineWidth(1.0)
+        context.strokePath()
+    }
+
+    private static func loadCGImage(from url: URL) -> CGImage? {
+        guard let source = CGImageSourceCreateWithURL(url as CFURL, nil),
+              CGImageSourceGetCount(source) > 0
+        else {
+            return nil
+        }
+        return CGImageSourceCreateImageAtIndex(source, 0, nil)
+    }
+}

Sources/ShotdeckCore/PDF/PageLayout.swift

@@ -0,0 +1,149 @@
+import AppKit
+import CoreGraphics
+import CoreText
+import Foundation
+
+public struct PageLayout: Sendable, Equatable {
+    public let isLandscape: Bool
+    public let pageRect: CGRect
+    public let headerRect: CGRect
+    public let imageBoxRect: CGRect
+    public let imageRect: CGRect
+
+    public let pageNumberText: String
+    public let pageNumberOrigin: CGPoint
+    public let timestampText: String
+    public let timestampOrigin: CGPoint
+
+    public let passLabelOrigin: CGPoint
+    public let failLabelOrigin: CGPoint
+    public let passTickBox: CGRect
+    public let failTickBox: CGRect
+
+    /// Constructed at access time so `PageLayout` stays Sendable under Swift 6
+    /// (`NSFont` is not Sendable). Same `NSFont.systemFont` values used for measurement.
+    public var pageNumberFont: NSFont { NSFont.systemFont(ofSize: 9, weight: .semibold) }
+    public var timestampFont: NSFont { NSFont.systemFont(ofSize: 9, weight: .regular) }
+    public var tickLabelFont: NSFont { NSFont.systemFont(ofSize: 8, weight: .semibold) }
+
+    private static let marginAll: CGFloat = 18
+    private static let headerHeight: CGFloat = 26
+    private static let headerImageGap: CGFloat = 10
+    private static let tickBoxSize: CGFloat = 13
+    private static let tickGroupGap: CGFloat = 8
+    private static let portraitPage = CGSize(width: 595, height: 842)
+    private static let landscapePage = CGSize(width: 842, height: 595)
+
+    /// `pageIndex` and `pageCount` are 1-based / total, over ACTUALLY-WRITTEN pages
+    /// (see SPEC decision D-D), not `capture.sequence` / `session.captures.count`.
+    public init(capture: Capture, pageIndex: Int, pageCount: Int) {
+        let pageNumberFont = NSFont.systemFont(ofSize: 9, weight: .semibold)
+        let timestampFont = NSFont.systemFont(ofSize: 9, weight: .regular)
+        let tickLabelFont = NSFont.systemFont(ofSize: 8, weight: .semibold)
+
+        isLandscape = capture.isLandscape
+        pageRect = CGRect(origin: .zero, size: isLandscape ? Self.landscapePage : Self.portraitPage)
+        let W = pageRect.width
+        let H = pageRect.height
+
+        let contentMinX = Self.marginAll
+        let contentMaxX = W - Self.marginAll
+        let contentMinY = Self.marginAll
+        let contentMaxY = H - Self.marginAll
+        let contentWidth = contentMaxX - contentMinX
+
+        headerRect = CGRect(
+            x: contentMinX,
+            y: contentMaxY - Self.headerHeight,
+            width: contentWidth,
+            height: Self.headerHeight
+        )
+
+        imageBoxRect = CGRect(
+            x: contentMinX,
+            y: contentMinY,
+            width: contentWidth,
+            height: headerRect.minY - Self.headerImageGap - contentMinY
+        )
+
+        let pointSize = CGSize(
+            width: CGFloat(capture.pixelWidth) / capture.scale,
+            height: CGFloat(capture.pixelHeight) / capture.scale
+        )
+        let fitScale = min(
+            imageBoxRect.width / pointSize.width,
+            imageBoxRect.height / pointSize.height,
+            1.0
+        )
+        let drawnSize = CGSize(
+            width: pointSize.width * fitScale,
+            height: pointSize.height * fitScale
+        )
+        imageRect = CGRect(
+            x: imageBoxRect.midX - drawnSize.width / 2,
+            y: imageBoxRect.midY - drawnSize.height / 2,
+            width: drawnSize.width,
+            height: drawnSize.height
+        )
+
+        let metricsFont = timestampFont as CTFont
+        let ascent = CTFontGetAscent(metricsFont)
+        let descent = CTFontGetDescent(metricsFont)
+        let baselineY = headerRect.minY + (headerRect.height - (ascent + descent)) / 2 + descent
+
+        pageNumberText = "\(pageIndex) / \(pageCount)"
+        pageNumberOrigin = CGPoint(x: headerRect.minX, y: baselineY)
+
+        timestampText = DubaiTime.stamp(capture.capturedAt)
+        let pageNumberWidth = Self.measuredWidth(pageNumberText, font: pageNumberFont)
+        timestampOrigin = CGPoint(x: headerRect.minX + pageNumberWidth + 10, y: baselineY)
+
+        let groupRightX = headerRect.maxX
+        let failBoxMinX = groupRightX - Self.tickBoxSize
+        let tickBoxY = headerRect.midY - Self.tickBoxSize / 2
+        failTickBox = CGRect(
+            x: failBoxMinX,
+            y: tickBoxY,
+            width: Self.tickBoxSize,
+            height: Self.tickBoxSize
+        )
+
+        let failLabelWidth = Self.measuredWidth("FAIL", font: tickLabelFont)
+        let failLabelMaxX = failTickBox.minX - Self.tickGroupGap
+        failLabelOrigin = CGPoint(x: failLabelMaxX - failLabelWidth, y: baselineY)
+
+        let passBoxMaxX = failLabelOrigin.x - Self.tickGroupGap
+        passTickBox = CGRect(
+            x: passBoxMaxX - Self.tickBoxSize,
+            y: tickBoxY,
+            width: Self.tickBoxSize,
+            height: Self.tickBoxSize
+        )
+
+        let passLabelWidth = Self.measuredWidth("PASS", font: tickLabelFont)
+        let passLabelMaxX = passTickBox.minX - Self.tickGroupGap
+        passLabelOrigin = CGPoint(x: passLabelMaxX - passLabelWidth, y: baselineY)
+    }
+
+    public static func == (lhs: PageLayout, rhs: PageLayout) -> Bool {
+        lhs.isLandscape == rhs.isLandscape
+            && lhs.pageRect == rhs.pageRect
+            && lhs.headerRect == rhs.headerRect
+            && lhs.imageBoxRect == rhs.imageBoxRect
+            && lhs.imageRect == rhs.imageRect
+            && lhs.pageNumberText == rhs.pageNumberText
+            && lhs.pageNumberOrigin == rhs.pageNumberOrigin
+            && lhs.timestampText == rhs.timestampText
+            && lhs.timestampOrigin == rhs.timestampOrigin
+            && lhs.passLabelOrigin == rhs.passLabelOrigin
+            && lhs.failLabelOrigin == rhs.failLabelOrigin
+            && lhs.passTickBox == rhs.passTickBox
+            && lhs.failTickBox == rhs.failTickBox
+    }
+
+    private static func measuredWidth(_ text: String, font: NSFont) -> CGFloat {
+        let attributed = NSAttributedString(string: text, attributes: [.font: font])
+        let line = CTLineCreateWithAttributedString(attributed)
+        return CGFloat(CTLineGetTypographicBounds(line, nil, nil, nil))
+    }
+}

Sources/ShotdeckCore/Returns/ReturnWatcher.swift

@@ -0,0 +1,154 @@
+import Foundation
+import PDFKit
+import CoreServices   // FSEventStream* APIs; system framework, no Package.swift change needed
+
+public actor ReturnWatcher {
+    private let ledger: ReturnLedger
+    private var watchFolder: URL
+    private var onChange: (@Sendable ([ReturnedDocument]) -> Void)?
+    private var stream: FSEventStreamRef?
+    private var bridge: FSEventBridge?
+    private var pendingScanTask: Task<Void, Never>?
+    private let eventQueue = DispatchQueue(label: "ai.flowmaster.shotdeck.returns.fsevents")
+
+    /// Watch folder is `paths.watchFolder`, which production constructs from
+    /// `FolderSettings.resolve().watch`. This type never calls FolderSettings;
+    /// `updateWatchFolder` is invoked by the UI layer only.
+    public init(paths: AppSupportPaths, ledger: ReturnLedger) {
+        self.ledger = ledger
+        self.watchFolder = paths.watchFolder   // never a literal "~/Downloads" here
+    }
+
+    /// Starts watching paths.watchFolder for returned PDFs. Performs one immediate
+    /// scanNow() before returning, then calls onChange after every subsequent debounced
+    /// batch (even if that batch's result is empty — the caller decides what to do).
+    public func start(onChange: @escaping @Sendable ([ReturnedDocument]) -> Void) async throws {
+        self.onChange = onChange
+        try startStream(on: watchFolder)
+        let found = try await scanNow()
+        onChange(found)
+    }
+
+    /// Idempotent. Stops and releases the FSEventStream if one is running; safe to call
+    /// when never started or already stopped. Cancels any pending debounced scan.
+    public func stop() {
+        // Idempotent: nil stream / already-stopped is a no-op; never started is the same.
+        pendingScanTask?.cancel()
+        pendingScanTask = nil
+        if let stream {
+            FSEventStreamStop(stream)
+            FSEventStreamInvalidate(stream)
+            FSEventStreamRelease(stream)
+        }
+        stream = nil
+        bridge = nil
+    }
+
+    /// Called by whoever owns the Settings "Choose..." folder action (WP-4c) after the user
+    /// picks a new watch folder. If the watcher was running, stops the old FSEventStream,
+    /// switches to the new folder, restarts, and performs one immediate scanNow (reporting
+    /// through the same onChange callback given to start()). If the watcher was never
+    /// started, only updates the stored folder for the next start() call.
+    public func updateWatchFolder(_ url: URL) async throws {
+        let wasRunning = stream != nil
+        stop()
+        watchFolder = url
+        guard wasRunning else { return }
+        try startStream(on: url)
+        let found = try await scanNow()
+        onChange?(found)
+    }
+
+    /// Scans the watch folder once, immediately, without waiting for an event. Every
+    /// recognized, stable, openable Shotdeck PDF present is (re-)inspected and (re-)recorded
+    /// into the ledger; returns exactly the documents processed in this call.
+    @discardableResult
+    public func scanNow() async throws -> [ReturnedDocument] {
+        let fm = FileManager.default
+        let candidates = (try? fm.contentsOfDirectory(
+            at: watchFolder, includingPropertiesForKeys: nil
+        )) ?? []
+        var results: [ReturnedDocument] = []
+        for url in candidates.sorted(by: { $0.lastPathComponent < $1.lastPathComponent }) {
+            let name = url.lastPathComponent
+            // ".pdf.inprogress" already fails hasSuffix(".pdf") -> naturally skipped.
+            guard name.hasSuffix(".pdf"), !name.hasPrefix(".") else { continue }
+            guard await isStableAndReadable(url) else { continue }   // leave for next event
+            guard let document = PDFDocument(url: url),
+                  AnnotationInspector.isShotdeckDocument(document) else { continue }
+            guard let inspected = try? AnnotationInspector.inspect(fileURL: url) else { continue }
+            try await ledger.record(inspected)
+            results.append(inspected)
+        }
+        return results
+    }
+
+    /// Size-stable: two equal byte counts 250 ms apart AND PDFDocument opens;
+    /// otherwise leave the file for the next event.
+    private func isStableAndReadable(_ url: URL) async -> Bool {
+        let fm = FileManager.default
+        guard let size1 = try? fm.attributesOfItem(atPath: url.path)[.size] as? Int else { return false }
+        try? await Task.sleep(for: .milliseconds(250))
+        guard let size2 = try? fm.attributesOfItem(atPath: url.path)[.size] as? Int else { return false }
+        guard size1 == size2, size1 > 0 else { return false }
+        return PDFDocument(url: url) != nil
+    }
+
+    private func startStream(on folder: URL) throws {
+        let bridge = FSEventBridge { [weak self] in
+            guard let self else { return }
+            Task { await self.scheduleDebouncedScan() }
+        }
+        self.bridge = bridge
+        var context = FSEventStreamContext()
+        context.version = 0
+        context.info = Unmanaged.passUnretained(bridge).toOpaque()
+        context.retain = nil
+        context.release = nil
+        context.copyDescription = nil
+        guard let stream = FSEventStreamCreate(
+            kCFAllocatorDefault, shotdeckFSEventsCallback, &context,
+            [folder.path] as CFArray, FSEventStreamEventId(kFSEventStreamEventIdSinceNow),
+            0.0,
+            FSEventStreamCreateFlags(kFSEventStreamCreateFlagFileEvents | kFSEventStreamCreateFlagNoDefer)
+        ) else {
+            throw ShotdeckError.captureFailed(underlying: "could not create FSEventStream for \(folder.path)")
+        }
+        // Dispatch queue, not a run loop: this actor has no run loop of its own, and
+        // FSEventStreamSetDispatchQueue is the modern replacement for
+        // FSEventStreamScheduleWithRunLoop. One dedicated serial queue per watcher.
+        FSEventStreamSetDispatchQueue(stream, eventQueue)
+        guard FSEventStreamStart(stream) else {
+            FSEventStreamInvalidate(stream)
+            FSEventStreamRelease(stream)
+            throw ShotdeckError.captureFailed(underlying: "FSEventStreamStart failed for \(folder.path)")
+        }
+        self.stream = stream
+    }
+
+    private func scheduleDebouncedScan() async {
+        pendingScanTask?.cancel()
+        pendingScanTask = Task {
+            try? await Task.sleep(for: .milliseconds(400))   // coalesce AirDrop's write+rename burst
+            guard !Task.isCancelled else { return }
+            guard let found = try? await self.scanNow() else { return }
+            // One in-flight debounced callback may land after stop(); it is a
+            // harmless read-only rescan (ledger upsert, no watch-folder mutation).
+            self.onChange?(found)
+        }
+    }
+}
+
+/// Non-actor bridge because FSEventStreamCallback is a @convention(c) function pointer and
+/// cannot capture actor-isolated state directly; it hops back onto the actor via Task.
+private final class FSEventBridge: @unchecked Sendable {
+    // @unchecked is safe: `notify` is a let, set once at init, never mutated after — the
+    // type is immutable for its entire lifetime.
+    let notify: @Sendable () -> Void
+    init(notify: @escaping @Sendable () -> Void) { self.notify = notify }
+}
+
+private let shotdeckFSEventsCallback: FSEventStreamCallback = { _, info, _, _, _, _ in
+    guard let info else { return }
+    Unmanaged<FSEventBridge>.fromOpaque(info).takeUnretainedValue().notify()
+}

Tests/ShotdeckCoreTests/CaptureRegionTests.swift

@@ -0,0 +1,171 @@
+import Carbon.HIToolbox
+import Foundation
+import Testing
+@testable import ShotdeckCore
+
+@Test("GEO-1 primary-only 1080-tall screen, AppKit rect (100,100,400,300)")
+func geo1_primaryOnlyAppKitRectConvertsToExpectedCGRect() {
+    let region = CaptureRegion.fromAppKit(
+        rect: CGRect(x: 100, y: 100, width: 400, height: 300),
+        displayID: 1,
+        capturedScale: 2,
+        primaryHeight: 1080
+    )
+    #expect(region.rect == CGRect(x: 100, y: 680, width: 400, height: 300))
+}
+
+@Test("GEO-2 rect flush to AppKit bottom (y=0), h=300, primaryHeight=1080")
+func geo2_flushToAppKitBottomYieldsCGY780() {
+    let region = CaptureRegion.fromAppKit(
+        rect: CGRect(x: 50, y: 0, width: 200, height: 300),
+        displayID: 1,
+        capturedScale: 1,
+        primaryHeight: 1080
+    )
+    #expect(region.rect.origin.y == 780)
+}
+
+@Test("GEO-3 rect flush to AppKit top (y+h=primaryHeight), primaryHeight=1080, h=300")
+func geo3_flushToAppKitTopYieldsCGY0() {
+    let region = CaptureRegion.fromAppKit(
+        rect: CGRect(x: 50, y: 780, width: 200, height: 300),
+        displayID: 1,
+        capturedScale: 1,
+        primaryHeight: 1080
+    )
+    #expect(region.rect.origin.y == 0)
+}
+
+@Test("GEO-4 round-trip AppKit→CG via injectable overload, then invert recovers original")
+func geo4_invertRecoverOriginalAppKitRect() {
+    let original = CGRect(x: 100, y: 100, width: 400, height: 300)
+    let primaryHeight: CGFloat = 1080
+    let region = CaptureRegion.fromAppKit(
+        rect: original,
+        displayID: 1,
+        capturedScale: 2,
+        primaryHeight: primaryHeight
+    )
+    let appKitY = primaryHeight - region.rect.origin.y - region.rect.height
+    let recovered = CGRect(
+        x: region.rect.origin.x,
+        y: appKitY,
+        width: region.rect.width,
+        height: region.rect.height
+    )
+    #expect(recovered == original)
+}
+
+@Test("GEO-5 isStillValid for displayID 999_999 is false and does not trap")
+func geo5_unknownDisplayIsNotStillValid() {
+    let region = CaptureRegion(
+        displayID: 999_999,
+        rect: CGRect(x: 0, y: 0, width: 100, height: 100),
+        capturedScale: 1
+    )
+    #expect(region.isStillValid == false)
+}
+
+@Test("GEO-6 CaptureRegion JSONEncoder→JSONDecoder round-trip equals original")
+func geo6_codableRoundTripEqualsOriginal() throws {
+    let original = CaptureRegion(
+        displayID: 42,
+        rect: CGRect(x: 10, y: 20, width: 300, height: 400),
+        capturedScale: 2
+    )
+    let data = try JSONEncoder().encode(original)
+    let decoded = try JSONDecoder().decode(CaptureRegion.self, from: data)
+    #expect(decoded == original)
+}
+
+@Test("GEO-7 secondary screen negative x: AppKit (−1800,200,500,400) → CG (−1800,480,500,400)")
+func geo7_secondaryNegativeXLeavesXUnchanged() {
+    // Secondary AppKit frame (−1920, 0, 1920, 1080); primaryHeight=1080.
+    let region = CaptureRegion.fromAppKit(
+        rect: CGRect(x: -1800, y: 200, width: 500, height: 400),
+        displayID: 2,
+        capturedScale: 1,
+        primaryHeight: 1080
+    )
+    #expect(region.rect == CGRect(x: -1800, y: 480, width: 500, height: 400))
+}
+
+@Test("GEO-8 secondary screen stacked above primary: AppKit (300,1300,600,350) → CG (300,−570,600,350)")
+func geo8_secondaryPositiveYProducesNegativeCGY() {
+    // Secondary AppKit frame (0, 1080, 1920, 1080); primaryHeight=1080.
+    let region = CaptureRegion.fromAppKit(
+        rect: CGRect(x: 300, y: 1300, width: 600, height: 350),
+        displayID: 2,
+        capturedScale: 1,
+        primaryHeight: 1080
+    )
+    #expect(region.rect == CGRect(x: 300, y: -570, width: 600, height: 350))
+}
+
+/// Carbon registrations are process-wide, so these cases must not run in parallel.
+@Suite(.serialized)
+@MainActor
+struct HotkeyCenterCarbonTests {
+    /// kVK_ANSI_2. The app registers this combo once (WP-4a); tests only exercise the registrar.
+    private let captureKeyCode: UInt32 = 19
+    private let captureModifiers = UInt32(optionKey) | UInt32(shiftKey)
+
+    @Test("HK-1 register id a with Option-Shift-2 returns true")
+    func hk1_registerReturnsTrue() {
+        let center = HotkeyCenter()
+        defer { center.unregisterAll() }
+        let ok = center.register(id: "a", keyCode: captureKeyCode, modifiers: captureModifiers) {}
+        if !ok {
+            Issue.record("HK-1: RegisterEventHotKey returned non-noErr inside swift test (no NSApplication). Carbon registration did not function headlessly.")
+            return
+        }
+        #expect(ok)
+    }
+
+    @Test("HK-2 register same combo under a different id returns false")
+    func hk2_duplicateComboRejected() {
+        let center = HotkeyCenter()
+        defer { center.unregisterAll() }
+        let first = center.register(id: "a", keyCode: captureKeyCode, modifiers: captureModifiers) {}
+        if !first {
+            Issue.record("HK-2: first RegisterEventHotKey failed inside swift test (no NSApplication); cannot evaluate duplicate-combo rejection.")
+            return
+        }
+        let second = center.register(id: "b", keyCode: captureKeyCode, modifiers: captureModifiers) {}
+        #expect(second == false)
+    }
+
+    @Test("HK-3 unregister frees the combination so a later register succeeds")
+    func hk3_unregisterFreesCombination() {
+        let center = HotkeyCenter()
+        defer { center.unregisterAll() }
+        let first = center.register(id: "a", keyCode: captureKeyCode, modifiers: captureModifiers) {}
+        if !first {
+            Issue.record("HK-3: first RegisterEventHotKey failed inside swift test (no NSApplication); cannot evaluate unregister.")
+            return
+        }
+        center.unregister(id: "a")
+        let again = center.register(id: "c", keyCode: captureKeyCode, modifiers: captureModifiers) {}
+        #expect(again)
+    }
+
+    @Test("HK-4 unregisterAll frees combinations so a later register succeeds")
+    func hk4_unregisterAllFreesCombinations() {
+        let center = HotkeyCenter()
+        defer { center.unregisterAll() }
+        let first = center.register(id: "a", keyCode: captureKeyCode, modifiers: captureModifiers) {}
+        let other = center.register(
+            id: "other",
+            keyCode: UInt32(kVK_ANSI_3),
+            modifiers: captureModifiers
+        ) {}
+        if !first {
+            Issue.record("HK-4: RegisterEventHotKey failed inside swift test (no NSApplication); cannot evaluate unregisterAll.")
+            return
+        }
+        _ = other
+        center.unregisterAll()
+        let again = center.register(id: "c", keyCode: captureKeyCode, modifiers: captureModifiers) {}
+        #expect(again)
+    }
+}

Tests/ShotdeckCoreTests/PDFComposerTests.swift

@@ -0,0 +1,579 @@
+import CoreGraphics
+import Foundation
+import ImageIO
+import PDFKit
+import ShotdeckCore
+import Testing
+import UniformTypeIdentifiers
+
+enum TestFixtureError: Error { case cannotCreateBitmap, cannotCreatePNG, cannotFinalizePNG }
+
+func writeSolidPNG(
+    pixelWidth: Int,
+    pixelHeight: Int,
+    red: UInt8,
+    green: UInt8,
+    blue: UInt8,
+    to url: URL
+) throws {
+    let colorSpace = CGColorSpaceCreateDeviceRGB()
+    guard let context = CGContext(
+        data: nil,
+        width: pixelWidth,
+        height: pixelHeight,
+        bitsPerComponent: 8,
+        bytesPerRow: pixelWidth * 4,
+        space: colorSpace,
+        bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue
+    ) else { throw TestFixtureError.cannotCreateBitmap }
+    context.setFillColor(CGColor(
+        red: CGFloat(red) / 255,
+        green: CGFloat(green) / 255,
+        blue: CGFloat(blue) / 255,
+        alpha: 1
+    ))
+    context.fill(CGRect(x: 0, y: 0, width: pixelWidth, height: pixelHeight))
+    guard let image = context.makeImage(),
+          let destination = CGImageDestinationCreateWithURL(
+              url as CFURL,
+              UTType.png.identifier as CFString,
+              1,
+              nil
+          )
+    else { throw TestFixtureError.cannotCreatePNG }
+    CGImageDestinationAddImage(destination, image, nil)
+    guard CGImageDestinationFinalize(destination) else { throw TestFixtureError.cannotFinalizePNG }
+}
+
+private let fixtureDate = Date(timeIntervalSince1970: 1_777_482_180)
+
+private func makeCapture(
+    sequence: Int,
+    pixelWidth: Int,
+    pixelHeight: Int,
+    scale: CGFloat = 1,
+    capturedAt: Date = fixtureDate,
+    id: UUID = UUID(),
+    fileName: String? = nil
+) -> Capture {
+    Capture(
+        id: id,
+        sequence: sequence,
+        fileName: fileName ?? String(format: "%03d.png", sequence),
+        pixelWidth: pixelWidth,
+        pixelHeight: pixelHeight,
+        scale: scale,
+        capturedAt: capturedAt
+    )
+}
+
+private func makeSession(
+    captures: [Capture],
+    id: UUID = UUID(),
+    createdAt: Date = fixtureDate
+) -> CaptureSession {
+    CaptureSession(
+        id: id,
+        createdAt: createdAt,
+        state: .open,
+        captures: captures,
+        pdfFileName: nil
+    )
+}
+
+private func makeScratchDirectory() throws -> URL {
+    let url = FileManager.default.temporaryDirectory
+        .appendingPathComponent("shotdeck-pdf-\(UUID().uuidString)", isDirectory: true)
+    try FileManager.default.createDirectory(at: url, withIntermediateDirectories: true)
+    return url
+}
+
+private func writePNG(
+    for capture: Capture,
+    red: UInt8,
+    green: UInt8,
+    blue: UInt8,
+    in directory: URL
+) throws -> URL {
+    let url = directory.appendingPathComponent(capture.fileName)
+    try writeSolidPNG(
+        pixelWidth: capture.pixelWidth,
+        pixelHeight: capture.pixelHeight,
+        red: red,
+        green: green,
+        blue: blue,
+        to: url
+    )
+    return url
+}
+
+private func imageURLMap(_ urls: [UUID: URL]) -> (Capture) -> URL {
+    { capture in
+        urls[capture.id] ?? URL(fileURLWithPath: "/nonexistent/\(capture.id.uuidString).png")
+    }
+}
+
+private func openDocument(_ url: URL) throws -> PDFDocument {
+    let document = try #require(PDFDocument(url: url))
+    return document
+}
+
+private func pdftoppm(pdf: URL, prefix: URL) throws {
+    let process = Process()
+    process.executableURL = URL(fileURLWithPath: "/opt/homebrew/bin/pdftoppm")
+    process.arguments = ["-png", "-r", "110", pdf.path, prefix.path]
+    let err = Pipe()
+    process.standardError = err
+    try process.run()
+    process.waitUntilExit()
+    guard process.terminationStatus == 0 else {
+        let message = String(data: err.fileHandleForReading.readDataToEndOfFile(), encoding: .utf8) ?? ""
+        throw ShotdeckError.pdfCompositionFailed(reason: "pdftoppm failed: \(message)")
+    }
+}
+
+private struct RGBABitmap {
+    let width: Int
+    let height: Int
+    let bytesPerRow: Int
+    let data: Data
+
+    func pixel(x: Int, y: Int) -> (UInt8, UInt8, UInt8)? {
+        guard x >= 0, y >= 0, x < width, y < height else { return nil }
+        let offset = y * bytesPerRow + x * 4
+        guard offset + 2 < data.count else { return nil }
+        return (data[offset], data[offset + 1], data[offset + 2])
+    }
+
+    func containsNonWhite(x0: Int, y0: Int, x1: Int, y1: Int) -> Bool {
+        let xStart = max(0, x0)
+        let yStart = max(0, y0)
+        let xEnd = min(width, x1)
+        let yEnd = min(height, y1)
+        guard xStart < xEnd, yStart < yEnd else { return false }
+        for y in yStart..<yEnd {
+            for x in xStart..<xEnd {
+                if let (r, g, b) = pixel(x: x, y: y), r != 255 || g != 255 || b != 255 {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+
+    static func loadPNG(at url: URL) throws -> RGBABitmap {
+        let colorSpace = CGColorSpaceCreateDeviceRGB()
+        let source = try #require(CGImageSourceCreateWithURL(url as CFURL, nil))
+        let image = try #require(CGImageSourceCreateImageAtIndex(source, 0, nil))
+        let width = image.width
+        let height = image.height
+        let bytesPerRow = width * 4
+        var data = Data(count: bytesPerRow * height)
+        try data.withUnsafeMutableBytes { raw in
+            guard let base = raw.baseAddress else {
+                throw TestFixtureError.cannotCreateBitmap
+            }
+            guard let context = CGContext(
+                data: base,
+                width: width,
+                height: height,
+                bitsPerComponent: 8,
+                bytesPerRow: bytesPerRow,
+                space: colorSpace,
+                bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue
+            ) else {
+                throw TestFixtureError.cannotCreateBitmap
+            }
+            context.interpolationQuality = .none
+            context.draw(image, in: CGRect(x: 0, y: 0, width: width, height: height))
+        }
+        return RGBABitmap(width: width, height: height, bytesPerRow: bytesPerRow, data: data)
+    }
+}
+
+private func pixelWindow(
+    for rect: CGRect,
+    pageHeightPt: CGFloat,
+    scale k: CGFloat
+) -> (x0: Int, y0: Int, x1: Int, y1: Int) {
+    let pixelX0 = Int(floor(rect.minX * k))
+    let pixelX1 = Int(ceil(rect.maxX * k))
+    let pixelY0 = Int(floor((pageHeightPt - rect.maxY) * k))
+    let pixelY1 = Int(ceil((pageHeightPt - rect.minY) * k))
+    return (pixelX0, pixelY0, pixelX1, pixelY1)
+}
+
+@Test("Three-page basic compose")
+func threePageBasicCompose() throws {
+    let directory = try makeScratchDirectory()
+    defer { try? FileManager.default.removeItem(at: directory) }
+
+    let c1 = makeCapture(sequence: 1, pixelWidth: 1600, pixelHeight: 900)
+    let c2 = makeCapture(sequence: 2, pixelWidth: 900, pixelHeight: 1600)
+    let c3 = makeCapture(sequence: 3, pixelWidth: 1200, pixelHeight: 800)
+    let urls: [UUID: URL] = [
+        c1.id: try writePNG(for: c1, red: 200, green: 20, blue: 20, in: directory),
+        c2.id: try writePNG(for: c2, red: 20, green: 200, blue: 20, in: directory),
+        c3.id: try writePNG(for: c3, red: 20, green: 20, blue: 200, in: directory),
+    ]
+    let session = makeSession(captures: [c1, c2, c3])
+    let output = directory.appendingPathComponent("three.pdf")
+    let pageCount = try PDFComposer().compose(
+        session: session,
+        imageURL: imageURLMap(urls),
+        title: "Three page",
+        to: output
+    )
+    #expect(pageCount == 3)
+    let document = try openDocument(output)
+    #expect(document.pageCount == 3)
+    let p0 = try #require(document.page(at: 0))
+    let p1 = try #require(document.page(at: 1))
+    let p2 = try #require(document.page(at: 2))
+    #expect(p0.bounds(for: .mediaBox) == CGRect(x: 0, y: 0, width: 842, height: 595))
+    #expect(p1.bounds(for: .mediaBox) == CGRect(x: 0, y: 0, width: 595, height: 842))
+    #expect(p2.bounds(for: .mediaBox) == CGRect(x: 0, y: 0, width: 842, height: 595))
+}
+
+@Test("Wide/tall page geometry exact")
+func wideTallPageGeometryExact() throws {
+    let directory = try makeScratchDirectory()
+    defer { try? FileManager.default.removeItem(at: directory) }
+
+    let wide = makeCapture(sequence: 1, pixelWidth: 1600, pixelHeight: 900)
+    let tall = makeCapture(sequence: 1, pixelWidth: 900, pixelHeight: 1600)
+    let wideURL = try writePNG(for: wide, red: 10, green: 10, blue: 10, in: directory)
+    let tallURL = try writePNG(for: tall, red: 10, green: 10, blue: 10, in: directory)
+
+    let wideOut = directory.appendingPathComponent("wide.pdf")
+    _ = try PDFComposer().compose(
+        session: makeSession(captures: [wide]),
+        imageURL: { _ in wideURL },
+        title: "Wide",
+        to: wideOut
+    )
+    let tallOut = directory.appendingPathComponent("tall.pdf")
+    _ = try PDFComposer().compose(
+        session: makeSession(captures: [tall]),
+        imageURL: { _ in tallURL },
+        title: "Tall",
+        to: tallOut
+    )
+
+    let widePage = try #require(openDocument(wideOut).page(at: 0))
+    let tallPage = try #require(openDocument(tallOut).page(at: 0))
+    #expect(widePage.bounds(for: .mediaBox) == CGRect(x: 0, y: 0, width: 842, height: 595))
+    #expect(tallPage.bounds(for: .mediaBox) == CGRect(x: 0, y: 0, width: 595, height: 842))
+}
+
+@Test("Square resolves to portrait (Capture.swift:39-42 isLandscape strict >)")
+func squareResolvesToPortrait() throws {
+    let directory = try makeScratchDirectory()
+    defer { try? FileManager.default.removeItem(at: directory) }
+
+    let square = makeCapture(sequence: 1, pixelWidth: 1000, pixelHeight: 1000)
+    let png = try writePNG(for: square, red: 80, green: 80, blue: 80, in: directory)
+    let output = directory.appendingPathComponent("square.pdf")
+    _ = try PDFComposer().compose(
+        session: makeSession(captures: [square]),
+        imageURL: { _ in png },
+        title: "Square",
+        to: output
+    )
+    let page = try #require(openDocument(output).page(at: 0))
+    #expect(page.bounds(for: .mediaBox) == CGRect(x: 0, y: 0, width: 595, height: 842))
+}
+
+@Test("Retina capture uses point size, not pixel size")
+func retinaCaptureUsesPointSize() throws {
+    let capture = makeCapture(sequence: 1, pixelWidth: 2880, pixelHeight: 1620, scale: 2.0)
+    let layout = PageLayout(capture: capture, pageIndex: 1, pageCount: 1)
+    let expectedScale = min(806.0 / 1440.0, 523.0 / 810.0, 1.0)
+    let expected = CGSize(width: 1440.0 * expectedScale, height: 810.0 * expectedScale)
+    #expect(abs(layout.imageRect.width - expected.width) < 0.01)
+    #expect(abs(layout.imageRect.height - expected.height) < 0.01)
+    #expect(layout.imageRect.width < 2000)
+    #expect(layout.isLandscape)
+}
+
+@Test("Zero PDFAnnotation objects on every page")
+func zeroPDFAnnotationObjects() throws {
+    let directory = try makeScratchDirectory()
+    defer { try? FileManager.default.removeItem(at: directory) }
+
+    let c1 = makeCapture(sequence: 1, pixelWidth: 800, pixelHeight: 600)
+    let c2 = makeCapture(sequence: 2, pixelWidth: 600, pixelHeight: 800)
+    let c3 = makeCapture(sequence: 3, pixelWidth: 1000, pixelHeight: 1000)
+    let urls: [UUID: URL] = [
+        c1.id: try writePNG(for: c1, red: 30, green: 30, blue: 30, in: directory),
+        c2.id: try writePNG(for: c2, red: 40, green: 40, blue: 40, in: directory),
+        c3.id: try writePNG(for: c3, red: 50, green: 50, blue: 50, in: directory),
+    ]
+    let output = directory.appendingPathComponent("no-annots.pdf")
+    _ = try PDFComposer().compose(
+        session: makeSession(captures: [c1, c2, c3]),
+        imageURL: imageURLMap(urls),
+        title: "No annotations",
+        to: output
+    )
+    let document = try openDocument(output)
+    #expect(document.pageCount == 3)
+    for index in 0..<document.pageCount {
+        let page = try #require(document.page(at: index))
+        #expect(page.annotations.isEmpty)
+    }
+}
+
+@Test("Mixed orientations coexist, unnormalised")
+func mixedOrientationsCoexist() throws {
+    let directory = try makeScratchDirectory()
+    defer { try? FileManager.default.removeItem(at: directory) }
+
+    let wide = makeCapture(sequence: 1, pixelWidth: 1600, pixelHeight: 900)
+    let tall = makeCapture(sequence: 2, pixelWidth: 900, pixelHeight: 1600)
+    let square = makeCapture(sequence: 3, pixelWidth: 1000, pixelHeight: 1000)
+    let urls: [UUID: URL] = [
+        wide.id: try writePNG(for: wide, red: 90, green: 10, blue: 10, in: directory),
+        tall.id: try writePNG(for: tall, red: 10, green: 90, blue: 10, in: directory),
+        square.id: try writePNG(for: square, red: 10, green: 10, blue: 90, in: directory),
+    ]
+    let output = directory.appendingPathComponent("mixed.pdf")
+    _ = try PDFComposer().compose(
+        session: makeSession(captures: [wide, tall, square]),
+        imageURL: imageURLMap(urls),
+        title: "Mixed",
+        to: output
+    )
+    let document = try openDocument(output)
+    #expect(document.pageCount == 3)
+    let p0 = try #require(document.page(at: 0))
+    let p1 = try #require(document.page(at: 1))
+    let p2 = try #require(document.page(at: 2))
+    #expect(p0.bounds(for: .mediaBox) == CGRect(x: 0, y: 0, width: 842, height: 595))
+    #expect(p1.bounds(for: .mediaBox) == CGRect(x: 0, y: 0, width: 595, height: 842))
+    #expect(p2.bounds(for: .mediaBox) == CGRect(x: 0, y: 0, width: 595, height: 842))
+}
+
+@Test("No cover page, no before/after, exactly one page per capture")
+func noCoverPageExactlyOnePagePerCapture() throws {
+    let directory = try makeScratchDirectory()
+    defer { try? FileManager.default.removeItem(at: directory) }
+
+    let c1 = makeCapture(sequence: 1, pixelWidth: 800, pixelHeight: 500)
+    let c2 = makeCapture(sequence: 2, pixelWidth: 500, pixelHeight: 800)
+    let urls: [UUID: URL] = [
+        c1.id: try writePNG(for: c1, red: 12, green: 12, blue: 12, in: directory),
+        c2.id: try writePNG(for: c2, red: 22, green: 22, blue: 22, in: directory),
+    ]
+    let output = directory.appendingPathComponent("two.pdf")
+    let pageCount = try PDFComposer().compose(
+        session: makeSession(captures: [c1, c2]),
+        imageURL: imageURLMap(urls),
+        title: "Two",
+        to: output
+    )
+    #expect(pageCount == 2)
+    #expect(try openDocument(output).pageCount == 2)
+}
+
+@Test("Small image is never upscaled")
+func smallImageIsNeverUpscaled() throws {
+    let capture = makeCapture(sequence: 1, pixelWidth: 200, pixelHeight: 150)
+    let layout = PageLayout(capture: capture, pageIndex: 1, pageCount: 1)
+    #expect(layout.imageRect.size == CGSize(width: 200, height: 150))
+}
+
+@Test("Empty session throws, produces nothing on disk")
+func emptySessionThrowsProducesNothing() throws {
+    let directory = try makeScratchDirectory()
+    defer { try? FileManager.default.removeItem(at: directory) }
+
+    let output = directory.appendingPathComponent("empty.pdf")
+    var threwCompositionFailed = false
+    do {
+        _ = try PDFComposer().compose(
+            session: makeSession(captures: []),
+            imageURL: { _ in directory.appendingPathComponent("missing.png") },
+            title: "Empty",
+            to: output
+        )
+    } catch ShotdeckError.pdfCompositionFailed {
+        threwCompositionFailed = true
+    }
+    #expect(threwCompositionFailed)
+    #expect(!FileManager.default.fileExists(atPath: output.path))
+    let leftover = try FileManager.default.contentsOfDirectory(atPath: directory.path)
+    #expect(leftover.isEmpty)
+}
+
+@Test("A missing PNG is skipped, page count drops, document still opens")
+func missingPNGIsSkipped() throws {
+    let directory = try makeScratchDirectory()
+    defer { try? FileManager.default.removeItem(at: directory) }
+
+    let first = makeCapture(sequence: 1, pixelWidth: 1600, pixelHeight: 900)
+    let missing = makeCapture(sequence: 2, pixelWidth: 800, pixelHeight: 600)
+    let third = makeCapture(sequence: 3, pixelWidth: 900, pixelHeight: 1600)
+    let firstURL = try writePNG(for: first, red: 220, green: 10, blue: 10, in: directory)
+    let thirdURL = try writePNG(for: third, red: 10, green: 10, blue: 220, in: directory)
+    let missingURL = directory.appendingPathComponent("does-not-exist.png")
+    let urls: [UUID: URL] = [
+        first.id: firstURL,
+        missing.id: missingURL,
+        third.id: thirdURL,
+    ]
+    let output = directory.appendingPathComponent("skip-missing.pdf")
+    let pageCount = try PDFComposer().compose(
+        session: makeSession(captures: [first, missing, third]),
+        imageURL: imageURLMap(urls),
+        title: "Skip missing",
+        to: output
+    )
+    #expect(pageCount == 2)
+    let document = try openDocument(output)
+    #expect(document.pageCount == 2)
+    let p0 = try #require(document.page(at: 0))
+    let p1 = try #require(document.page(at: 1))
+    #expect(p0.bounds(for: .mediaBox) == CGRect(x: 0, y: 0, width: 842, height: 595))
+    #expect(p1.bounds(for: .mediaBox) == CGRect(x: 0, y: 0, width: 595, height: 842))
+
+    // Distinct fill colors sampled from pdftoppm at each imageRect center.
+    let prefix = directory.appendingPathComponent("skip-missing")
+    try pdftoppm(pdf: output, prefix: prefix)
+    let page1PNG = directory.appendingPathComponent("skip-missing-1.png")
+    let page2PNG = directory.appendingPathComponent("skip-missing-2.png")
+    let bitmap1 = try RGBABitmap.loadPNG(at: page1PNG)
+    let bitmap2 = try RGBABitmap.loadPNG(at: page2PNG)
+    let k = 110.0 / 72.0
+    let layout1 = PageLayout(capture: first, pageIndex: 1, pageCount: 2)
+    let layout2 = PageLayout(capture: third, pageIndex: 2, pageCount: 2)
+    let c1 = try #require(bitmap1.pixel(
+        x: Int((layout1.imageRect.midX * k).rounded()),
+        y: Int(((layout1.pageRect.height - layout1.imageRect.midY) * k).rounded())
+    ))
+    let c2 = try #require(bitmap2.pixel(
+        x: Int((layout2.imageRect.midX * k).rounded()),
+        y: Int(((layout2.pageRect.height - layout2.imageRect.midY) * k).rounded())
+    ))
+    #expect(c1.0 > 150 && c1.1 < 80 && c1.2 < 80)
+    #expect(c2.2 > 150 && c2.0 < 80 && c2.1 < 80)
+}
+
+@Test("An unreadable (corrupt) PNG is treated exactly like a missing one (D-A)")
+func unreadablePNGIsSkippedLikeMissing() throws {
+    let directory = try makeScratchDirectory()
+    defer { try? FileManager.default.removeItem(at: directory) }
+
+    let good = makeCapture(sequence: 1, pixelWidth: 800, pixelHeight: 500)
+    let bad = makeCapture(sequence: 2, pixelWidth: 800, pixelHeight: 500)
+    let goodURL = try writePNG(for: good, red: 30, green: 140, blue: 30, in: directory)
+    let badURL = directory.appendingPathComponent("corrupt.png")
+    try Data([0x00, 0x01, 0x02, 0xFF, 0xD8, 0x00]).write(to: badURL)
+    let urls: [UUID: URL] = [good.id: goodURL, bad.id: badURL]
+    let output = directory.appendingPathComponent("skip-corrupt.pdf")
+    let pageCount = try PDFComposer().compose(
+        session: makeSession(captures: [good, bad]),
+        imageURL: imageURLMap(urls),
+        title: "Skip corrupt",
+        to: output
+    )
+    #expect(pageCount == 1)
+    let document = try openDocument(output)
+    #expect(document.pageCount == 1)
+}
+
+@Test("Document attributes round-trip exactly")
+func documentAttributesRoundTrip() throws {
+    let directory = try makeScratchDirectory()
+    defer { try? FileManager.default.removeItem(at: directory) }
+
+    let sessionID = try #require(UUID(uuidString: "deadbeef-dead-4eef-8ead-deadbeef0001"))
+    let capture = makeCapture(sequence: 1, pixelWidth: 640, pixelHeight: 480)
+    let png = try writePNG(for: capture, red: 40, green: 40, blue: 40, in: directory)
+    let output = directory.appendingPathComponent("attrs.pdf")
+    _ = try PDFComposer().compose(
+        session: makeSession(captures: [capture], id: sessionID),
+        imageURL: { _ in png },
+        title: "Ben review — 2026-08-30",
+        to: output
+    )
+    let document = try openDocument(output)
+    let attributes = try #require(document.documentAttributes)
+    #expect(attributes[PDFDocumentAttribute.creatorAttribute] as? String == "Shotdeck")
+    #expect(attributes[PDFDocumentAttribute.titleAttribute] as? String == "Ben review — 2026-08-30")
+    #expect(attributes[PDFDocumentAttribute.subjectAttribute] as? String == "deadbeef-dead-4eef-8ead-deadbeef0001")
+    #expect(document.pageCount == 1)
+    #expect(try #require(document.page(at: 0)).annotations.isEmpty)
+}
+
+@Test("Rendered page is not blank (pdftoppm, pinned renderer + rounding)")
+func renderedPageIsNotBlank() throws {
+    let directory = try makeScratchDirectory()
+    defer { try? FileManager.default.removeItem(at: directory) }
+
+    let capture = makeCapture(sequence: 1, pixelWidth: 1600, pixelHeight: 900)
+    let png = try writePNG(for: capture, red: 128, green: 128, blue: 128, in: directory)
+    let output = directory.appendingPathComponent("not-blank.pdf")
+    _ = try PDFComposer().compose(
+        session: makeSession(captures: [capture]),
+        imageURL: { _ in png },
+        title: "Not blank",
+        to: output
+    )
+    let prefix = directory.appendingPathComponent("not-blank")
+    try pdftoppm(pdf: output, prefix: prefix)
+    let rendered = directory.appendingPathComponent("not-blank-1.png")
+    let bitmap = try RGBABitmap.loadPNG(at: rendered)
+    let layout = PageLayout(capture: capture, pageIndex: 1, pageCount: 1)
+    let k: CGFloat = 110.0 / 72.0
+    let imageWin = pixelWindow(for: layout.imageRect, pageHeightPt: layout.pageRect.height, scale: k)
+    let headerWin = pixelWindow(for: layout.headerRect, pageHeightPt: layout.pageRect.height, scale: k)
+    #expect(bitmap.containsNonWhite(x0: imageWin.x0, y0: imageWin.y0, x1: imageWin.x1, y1: imageWin.y1))
+    #expect(bitmap.containsNonWhite(x0: headerWin.x0, y0: headerWin.y0, x1: headerWin.x1, y1: headerWin.y1))
+}
+
+@Test("Right-edge tick group geometry matches D-12 exactly, both orientations")
+func rightEdgeTickGroupGeometry() throws {
+    let landscape = makeCapture(sequence: 1, pixelWidth: 1600, pixelHeight: 900)
+    let portrait = makeCapture(sequence: 1, pixelWidth: 900, pixelHeight: 1600)
+    let landscapeLayout = PageLayout(capture: landscape, pageIndex: 1, pageCount: 1)
+    let portraitLayout = PageLayout(capture: portrait, pageIndex: 1, pageCount: 1)
+
+    #expect(landscapeLayout.failTickBox.maxX == 824)
+    #expect(landscapeLayout.headerRect.maxX == 824)
+    #expect(portraitLayout.failTickBox.maxX == 577)
+    #expect(portraitLayout.headerRect.maxX == 577)
+    #expect(landscapeLayout.failTickBox.width == 13)
+    #expect(landscapeLayout.failTickBox.height == 13)
+    #expect(portraitLayout.failTickBox.width == 13)
+    #expect(portraitLayout.failTickBox.height == 13)
+    #expect(landscapeLayout.passTickBox.maxX == landscapeLayout.failLabelOrigin.x - 8)
+    #expect(portraitLayout.passTickBox.maxX == portraitLayout.failLabelOrigin.x - 8)
+}
+
+@Test("Writes visual sample for review")
+func writesVisualSampleForReview() throws {
+    let verifyDir = URL(fileURLWithPath: "/Users/benjaminhippler/mmd-projects/multi-agent-runs/shotdeck-20260830/verify")
+    try FileManager.default.createDirectory(at: verifyDir, withIntermediateDirectories: true)
+    let scratch = try makeScratchDirectory()
+    defer { try? FileManager.default.removeItem(at: scratch) }
+
+    let wide = makeCapture(sequence: 1, pixelWidth: 1600, pixelHeight: 900)
+    let tall = makeCapture(sequence: 2, pixelWidth: 900, pixelHeight: 1600)
+    let retina = makeCapture(sequence: 3, pixelWidth: 2880, pixelHeight: 1620, scale: 2.0)
+    let urls: [UUID: URL] = [
+        wide.id: try writePNG(for: wide, red: 196, green: 42, blue: 42, in: scratch),
+        tall.id: try writePNG(for: tall, red: 32, green: 96, blue: 176, in: scratch),
+        retina.id: try writePNG(for: retina, red: 36, green: 148, blue: 84, in: scratch),
+    ]
+    let output = verifyDir.appendingPathComponent("wp2-sample.pdf")
+    let pageCount = try PDFComposer().compose(
+        session: makeSession(captures: [wide, tall, retina]),
+        imageURL: imageURLMap(urls),
+        title: "WP-2 visual sample",
+        to: output
+    )
+    #expect(pageCount == 3)
+    let prefix = verifyDir.appendingPathComponent("wp2-sample")
+    try pdftoppm(pdf: output, prefix: prefix)
+}

Tests/ShotdeckCoreTests/ReturnWatcherTests.swift

@@ -0,0 +1,173 @@
+import AppKit
+import Foundation
+import PDFKit
+import Testing
+import ShotdeckCore
+
+private let pageBounds = CGRect(x: 0, y: 0, width: 600, height: 800)
+
+private func makeAnnotation(
+    _ subtype: PDFAnnotationSubtype,
+    bounds: CGRect = CGRect(x: 100, y: 100, width: 80, height: 40),
+    contents: String? = nil
+) -> PDFAnnotation {
+    let annotation = PDFAnnotation(
+        bounds: bounds,
+        forType: subtype,
+        withProperties: nil
+    )
+    annotation.contents = contents
+    return annotation
+}
+
+private func makePDF(
+    at url: URL,
+    pageCount: Int,
+    creator: String? = "Shotdeck",
+    subject: String? = nil,
+    annotations: [(page: Int, annotation: PDFAnnotation)] = []
+) throws {
+    let document = PDFDocument()
+    for index in 0..<pageCount {
+        let page = PDFPage()
+        page.setBounds(pageBounds, for: .mediaBox)
+        document.insert(page, at: index)
+    }
+
+    var attributes = [PDFDocumentAttribute: Any]()
+    if let creator { attributes[.creatorAttribute] = creator }
+    if let subject { attributes[.subjectAttribute] = subject }
+    document.documentAttributes = attributes
+
+    for item in annotations {
+        guard let page = document.page(at: item.page) else {
+            throw NSError(domain: "WP5Test", code: 1)
+        }
+        page.addAnnotation(item.annotation)
+    }
+
+    guard document.write(to: url) else {
+        throw NSError(domain: "WP5Test", code: 2)
+    }
+}
+
+private func makeCasePaths() throws -> (paths: AppSupportPaths, cleanup: URL) {
+    let cleanup = FileManager.default.temporaryDirectory
+        .appendingPathComponent("shotdeck-wp5b-\(UUID().uuidString)", isDirectory: true)
+    let paths = try AppSupportPaths(
+        root: cleanup.appendingPathComponent("root", isDirectory: true),
+        outbox: cleanup.appendingPathComponent("outbox", isDirectory: true),
+        watchFolder: cleanup.appendingPathComponent("watch", isDirectory: true)
+    )
+    return (paths, cleanup)
+}
+
+/// Guards `confirmation(expectedCount: 1)` against a create+rename double-event.
+private final class ConfirmOnce: @unchecked Sendable {
+    private let lock = NSLock()
+    private var fired = false
+    func run(_ body: () -> Void) {
+        lock.lock()
+        defer { lock.unlock() }
+        guard !fired else { return }
+        fired = true
+        body()
+    }
+}
+
+@Test("W-25 Duplicate-name suffix is the normal AirDrop return (scanNow)")
+func w25_duplicateNameSuffixIsRecognizedByScanNow() async throws {
+    let (paths, cleanup) = try makeCasePaths()
+    defer { try? FileManager.default.removeItem(at: cleanup) }
+
+    let ledger = try ReturnLedger(paths: paths)
+    let watcher = ReturnWatcher(paths: paths, ledger: ledger)
+    let pdfURL = paths.watchFolder.appendingPathComponent("Shotdeck-20260830-134205 2.pdf")
+
+    try makePDF(
+        at: pdfURL,
+        pageCount: 1,
+        creator: nil,
+        subject: "33333333-3333-3333-3333-333333333333",
+        annotations: [(page: 0, annotation: makeAnnotation(
+            .ink, bounds: CGRect(x: 100, y: 100, width: 120, height: 50)
+        ))]
+    )
+
+    let found = try await watcher.scanNow()
+    #expect(found.count == 1)
+    let doc = try #require(found.first)
+    #expect(doc.fileURL.lastPathComponent == "Shotdeck-20260830-134205 2.pdf")
+    #expect(doc.fileURL.resolvingSymlinksInPath().path == pdfURL.resolvingSymlinksInPath().path)
+    #expect(doc.pageCount == 1)
+    #expect(doc.annotatedPages == [1])
+    #expect(doc.isCommented == true)
+
+    let commented = try await ledger.commented()
+    #expect(commented.count == 1)
+    #expect(commented[0].fileURL.lastPathComponent == pdfURL.lastPathComponent)
+    #expect(commented[0].fileURL.resolvingSymlinksInPath().path == pdfURL.resolvingSymlinksInPath().path)
+}
+
+@Test("W-26 Creator provenance negative at the scan level")
+func w26_presentNonShotdeckCreatorIsIgnoredByScanNow() async throws {
+    let (paths, cleanup) = try makeCasePaths()
+    defer { try? FileManager.default.removeItem(at: cleanup) }
+
+    let ledger = try ReturnLedger(paths: paths)
+    let watcher = ReturnWatcher(paths: paths, ledger: ledger)
+    let pdfURL = paths.watchFolder.appendingPathComponent("Shotdeck-20260830-134218.pdf")
+
+    try makePDF(
+        at: pdfURL,
+        pageCount: 1,
+        creator: "Preview",
+        annotations: [(page: 0, annotation: makeAnnotation(
+            .ink, bounds: CGRect(x: 100, y: 100, width: 120, height: 50)
+        ))]
+    )
+
+    let found = try await watcher.scanNow()
+    #expect(found.isEmpty)
+    let all = try await ledger.all()
+    #expect(all.isEmpty)
+}
+
+@Test("W-27 FSEvents live callback fires on a real file arrival")
+func w27_fsEventsCallbackFiresOnRealArrival() async throws {
+    let (paths, cleanup) = try makeCasePaths()
+    defer { try? FileManager.default.removeItem(at: cleanup) }
+
+    let ledger = try ReturnLedger(paths: paths)
+    let watcher = ReturnWatcher(paths: paths, ledger: ledger)
+    let pdfURL = paths.watchFolder.appendingPathComponent("Shotdeck-20260830-140000.pdf")
+    let once = ConfirmOnce()
+
+    try await confirmation("watcher reports the arrived PDF", expectedCount: 1) { confirm in
+        do {
+            try await watcher.start { docs in
+                if docs.contains(where: { $0.fileURL.lastPathComponent == pdfURL.lastPathComponent }) {
+                    once.run { confirm() }
+                }
+            }
+            // Simulate AirDrop's own write-then-rename so the watcher must survive that pattern.
+            let tmpURL = pdfURL.appendingPathExtension("inprogress")
+            try makePDF(
+                at: tmpURL, pageCount: 1, creator: "Shotdeck",
+                annotations: [(page: 0, annotation: makeAnnotation(
+                    .ink, bounds: CGRect(x: 100, y: 100, width: 120, height: 50)
+                ))]
+            )
+            try FileManager.default.moveItem(at: tmpURL, to: pdfURL)
+        } catch {
+            print("fsEventsCallbackFiresOnRealArrival error: \(error)")
+            await watcher.stop()
+            throw error
+        }
+        // Budget: 400ms debounce + FS latency + the 250ms stability re-read + PDFKit open.
+        // 5s is a generous, fixed ceiling — never a "some time" wait.
+        try await Task.sleep(for: .seconds(5))
+        await watcher.stop()
+        await watcher.stop()
+    }
+}