diff --git a/Sources/Overlays/_Testing_CoreGraphics/Attachments/AttachableAsCGImage.swift b/Sources/Overlays/_Testing_CoreGraphics/Attachments/AttachableAsCGImage.swift
index 8ca2a0ae4..e51742dc3 100644
--- a/Sources/Overlays/_Testing_CoreGraphics/Attachments/AttachableAsCGImage.swift
+++ b/Sources/Overlays/_Testing_CoreGraphics/Attachments/AttachableAsCGImage.swift
@@ -20,22 +20,21 @@ private import ImageIO
 /// initializers on ``Testing/Attachment`` that take instances of such types and
 /// handle converting them to image data when needed.
 ///
-/// The following system-provided image types conform to this protocol and can
-/// be attached to a test:
+/// You can attach instances of the following system-provided image types to a
+/// test:
 ///
-/// - [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage)
-/// - [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage)
-/// - [`NSImage`](https://developer.apple.com/documentation/appkit/nsimage)
-///   (macOS)
-/// - [`UIImage`](https://developer.apple.com/documentation/uikit/uiimage)
-///   (iOS, watchOS, tvOS, visionOS, and Mac Catalyst)
+/// | Platform | Supported Types |
+/// |-|-|
+/// | macOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`NSImage`](https://developer.apple.com/documentation/appkit/nsimage) |
+/// | iOS, watchOS, tvOS, and visionOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`UIImage`](https://developer.apple.com/documentation/uikit/uiimage) |
+/// | Windows | [`HBITMAP`](https://learn.microsoft.com/en-us/windows/win32/gdi/bitmaps), [`HICON`](https://learn.microsoft.com/en-us/windows/win32/menurc/icons), [`IWICBitmapSource`](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapsource) (including its subclasses declared by Windows Imaging Component) |
 ///
 /// You do not generally need to add your own conformances to this protocol. If
 /// you have an image in another format that needs to be attached to a test,
 /// first convert it to an instance of one of the types above.
 @_spi(Experimental)
 @available(_uttypesAPI, *)
-public protocol AttachableAsCGImage {
+public protocol AttachableAsCGImage: SendableMetatype {
   /// An instance of `CGImage` representing this image.
   ///
   /// - Throws: Any error that prevents the creation of an image.
diff --git a/Sources/Overlays/_Testing_CoreGraphics/Attachments/Attachment+AttachableAsCGImage.swift b/Sources/Overlays/_Testing_CoreGraphics/Attachments/Attachment+AttachableAsCGImage.swift
index 866240e64..b3349915b 100644
--- a/Sources/Overlays/_Testing_CoreGraphics/Attachments/Attachment+AttachableAsCGImage.swift
+++ b/Sources/Overlays/_Testing_CoreGraphics/Attachments/Attachment+AttachableAsCGImage.swift
@@ -26,15 +26,14 @@ extension Attachment {
   ///     This value is used when recording issues associated with the
   ///     attachment.
   ///
-  /// The following system-provided image types conform to the
-  /// ``AttachableAsCGImage`` protocol and can be attached to a test:
+  /// You can attach instances of the following system-provided image types to a
+  /// test:
   ///
-  /// - [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage)
-  /// - [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage)
-  /// - [`NSImage`](https://developer.apple.com/documentation/appkit/nsimage)
-  ///   (macOS)
-  /// - [`UIImage`](https://developer.apple.com/documentation/uikit/uiimage)
-  ///   (iOS, watchOS, tvOS, visionOS, and Mac Catalyst)
+  /// | Platform | Supported Types |
+  /// |-|-|
+  /// | macOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`NSImage`](https://developer.apple.com/documentation/appkit/nsimage) |
+  /// | iOS, watchOS, tvOS, and visionOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`UIImage`](https://developer.apple.com/documentation/uikit/uiimage) |
+  /// | Windows | [`HBITMAP`](https://learn.microsoft.com/en-us/windows/win32/gdi/bitmaps), [`HICON`](https://learn.microsoft.com/en-us/windows/win32/menurc/icons), [`IWICBitmapSource`](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapsource) (including its subclasses declared by Windows Imaging Component) |
   ///
   /// The testing library uses the image format specified by `imageFormat`. Pass
   /// `nil` to let the testing library decide which image format to use. If you
@@ -48,8 +47,12 @@ extension Attachment {
     named preferredName: String? = nil,
     as imageFormat: AttachableImageFormat? = nil,
     sourceLocation: SourceLocation = #_sourceLocation
-  ) where AttachableValue == _AttachableImageWrapper<T> {
-    let imageWrapper = _AttachableImageWrapper(image: image, imageFormat: imageFormat)
+  ) where T: AttachableAsCGImage, AttachableValue == _AttachableImageWrapper<T> {
+    let imageWrapper = _AttachableImageWrapper(
+      image: image._copyAttachableValue(),
+      imageFormat: imageFormat,
+      deinitializingWith: { _ in }
+    )
     self.init(imageWrapper, named: preferredName, sourceLocation: sourceLocation)
   }
 
@@ -64,17 +67,14 @@ extension Attachment {
   ///   - sourceLocation: The source location of the call to this function.
   ///
   /// This function creates a new instance of ``Attachment`` wrapping `image`
-  /// and immediately attaches it to the current test.
+  /// and immediately attaches it to the current test. You can attach instances
+  /// of the following system-provided image types to a test:
   ///
-  /// The following system-provided image types conform to the
-  /// ``AttachableAsCGImage`` protocol and can be attached to a test:
-  ///
-  /// - [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage)
-  /// - [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage)
-  /// - [`NSImage`](https://developer.apple.com/documentation/appkit/nsimage)
-  ///   (macOS)
-  /// - [`UIImage`](https://developer.apple.com/documentation/uikit/uiimage)
-  ///   (iOS, watchOS, tvOS, visionOS, and Mac Catalyst)
+  /// | Platform | Supported Types |
+  /// |-|-|
+  /// | macOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`NSImage`](https://developer.apple.com/documentation/appkit/nsimage) |
+  /// | iOS, watchOS, tvOS, and visionOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`UIImage`](https://developer.apple.com/documentation/uikit/uiimage) |
+  /// | Windows | [`HBITMAP`](https://learn.microsoft.com/en-us/windows/win32/gdi/bitmaps), [`HICON`](https://learn.microsoft.com/en-us/windows/win32/menurc/icons), [`IWICBitmapSource`](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapsource) (including its subclasses declared by Windows Imaging Component) |
   ///
   /// The testing library uses the image format specified by `imageFormat`. Pass
   /// `nil` to let the testing library decide which image format to use. If you
@@ -88,19 +88,20 @@ extension Attachment {
     named preferredName: String? = nil,
     as imageFormat: AttachableImageFormat? = nil,
     sourceLocation: SourceLocation = #_sourceLocation
-  ) where AttachableValue == _AttachableImageWrapper<T> {
+  ) where T: AttachableAsCGImage, AttachableValue == _AttachableImageWrapper<T> {
     let attachment = Self(image, named: preferredName, as: imageFormat, sourceLocation: sourceLocation)
     Self.record(attachment, sourceLocation: sourceLocation)
   }
 }
 
+// MARK: -
+
 @_spi(Experimental) // STOP: not part of ST-0014
 @available(_uttypesAPI, *)
 extension Attachment where AttachableValue: AttachableWrapper, AttachableValue.Wrapped: AttachableAsCGImage {
   /// The image format to use when encoding the represented image.
-  @_disfavoredOverload
-  public var imageFormat: AttachableImageFormat? {
-    // FIXME: no way to express `where AttachableValue == _AttachableImageWrapper<???>` on a property
+  @_disfavoredOverload public var imageFormat: AttachableImageFormat? {
+    // FIXME: no way to express `where AttachableValue == _AttachableImageWrapper<???>` on a property (see rdar://47559973)
     (attachableValue as? _AttachableImageWrapper<AttachableValue.Wrapped>)?.imageFormat
   }
 }
diff --git a/Sources/Overlays/_Testing_CoreGraphics/Attachments/ImageAttachmentError.swift b/Sources/Overlays/_Testing_CoreGraphics/Attachments/ImageAttachmentError.swift
deleted file mode 100644
index f957888b7..000000000
--- a/Sources/Overlays/_Testing_CoreGraphics/Attachments/ImageAttachmentError.swift
+++ /dev/null
@@ -1,34 +0,0 @@
-//
-// This source file is part of the Swift.org open source project
-//
-// Copyright (c) 2024 Apple Inc. and the Swift project authors
-// Licensed under Apache License v2.0 with Runtime Library Exception
-//
-// See https://swift.org/LICENSE.txt for license information
-// See https://swift.org/CONTRIBUTORS.txt for Swift project authors
-//
-
-#if SWT_TARGET_OS_APPLE && canImport(CoreGraphics)
-/// A type representing an error that can occur when attaching an image.
-package enum ImageAttachmentError: Error, CustomStringConvertible {
-  /// The image could not be converted to an instance of `CGImage`.
-  case couldNotCreateCGImage
-
-  /// The image destination could not be created.
-  case couldNotCreateImageDestination
-
-  /// The image could not be converted.
-  case couldNotConvertImage
-
-  public var description: String {
-    switch self {
-    case .couldNotCreateCGImage:
-      "Could not create the corresponding Core Graphics image."
-    case .couldNotCreateImageDestination:
-      "Could not create the Core Graphics image destination to encode this image."
-    case .couldNotConvertImage:
-      "Could not convert the image to the specified format."
-    }
-  }
-}
-#endif
diff --git a/Sources/Overlays/_Testing_CoreGraphics/Attachments/_AttachableImageWrapper.swift b/Sources/Overlays/_Testing_CoreGraphics/Attachments/_AttachableImageWrapper+AttachableWrapper.swift
similarity index 66%
rename from Sources/Overlays/_Testing_CoreGraphics/Attachments/_AttachableImageWrapper.swift
rename to Sources/Overlays/_Testing_CoreGraphics/Attachments/_AttachableImageWrapper+AttachableWrapper.swift
index 61904936f..bb0d42b23 100644
--- a/Sources/Overlays/_Testing_CoreGraphics/Attachments/_AttachableImageWrapper.swift
+++ b/Sources/Overlays/_Testing_CoreGraphics/Attachments/_AttachableImageWrapper+AttachableWrapper.swift
@@ -13,7 +13,7 @@
 private import CoreGraphics
 
 private import ImageIO
-import UniformTypeIdentifiers
+private import UniformTypeIdentifiers
 
 /// ## Why can't images directly conform to Attachable?
 ///
@@ -38,53 +38,13 @@ import UniformTypeIdentifiers
 ///    (And no, the language does not let us write `where T: Self` anywhere
 ///    useful.)
 
-/// A wrapper type for image types such as `CGImage` and `NSImage` that can be
-/// attached indirectly.
-///
-/// You do not need to use this type directly. Instead, initialize an instance
-/// of ``Attachment`` using an instance of an image type that conforms to
-/// ``AttachableAsCGImage``. The following system-provided image types conform
-/// to the ``AttachableAsCGImage`` protocol and can be attached to a test:
-///
-/// - [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage)
-/// - [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage)
-/// - [`NSImage`](https://developer.apple.com/documentation/appkit/nsimage)
-///   (macOS)
-/// - [`UIImage`](https://developer.apple.com/documentation/uikit/uiimage)
-///   (iOS, watchOS, tvOS, visionOS, and Mac Catalyst)
-@_spi(Experimental)
 @available(_uttypesAPI, *)
-public final class _AttachableImageWrapper<Image>: Sendable where Image: AttachableAsCGImage {
-  /// The underlying image.
-  ///
-  /// `CGImage` and `UIImage` are sendable, but `NSImage` is not. `NSImage`
-  /// instances can be created from closures that are run at rendering time.
-  /// The AppKit cross-import overlay is responsible for ensuring that any
-  /// instances of this type it creates hold "safe" `NSImage` instances.
-  nonisolated(unsafe) let image: Image
-
-  /// The image format to use when encoding the represented image.
-  let imageFormat: AttachableImageFormat?
-
-  init(image: Image, imageFormat: AttachableImageFormat?) {
-    self.image = image._copyAttachableValue()
-    self.imageFormat = imageFormat
-  }
-}
-
-// MARK: -
-
-@available(_uttypesAPI, *)
-extension _AttachableImageWrapper: AttachableWrapper {
-  public var wrappedValue: Image {
-    image
-  }
-
+extension _AttachableImageWrapper: Attachable, AttachableWrapper where Image: AttachableAsCGImage {
   public func withUnsafeBytes<R>(for attachment: borrowing Attachment<_AttachableImageWrapper>, _ body: (UnsafeRawBufferPointer) throws -> R) throws -> R {
     let data = NSMutableData()
 
     // Convert the image to a CGImage.
-    let attachableCGImage = try image.attachableCGImage
+    let attachableCGImage = try wrappedValue.attachableCGImage
 
     // Create the image destination.
     let contentType = AttachableImageFormat.computeContentType(for: imageFormat, withPreferredName: attachment.preferredName)
@@ -93,8 +53,8 @@ extension _AttachableImageWrapper: AttachableWrapper {
     }
 
     // Configure the properties of the image conversion operation.
-    let orientation = image._attachmentOrientation
-    let scaleFactor = image._attachmentScaleFactor
+    let orientation = wrappedValue._attachmentOrientation
+    let scaleFactor = wrappedValue._attachmentScaleFactor
     let properties: [CFString: Any] = [
       kCGImageDestinationLossyCompressionQuality: CGFloat(imageFormat?.encodingQuality ?? 1.0),
       kCGImagePropertyOrientation: orientation,
diff --git a/Sources/Overlays/_Testing_WinSDK/Attachments/AttachableAsIWICBitmapSource.swift b/Sources/Overlays/_Testing_WinSDK/Attachments/AttachableAsIWICBitmapSource.swift
index cf23df63a..fdcad1809 100644
--- a/Sources/Overlays/_Testing_WinSDK/Attachments/AttachableAsIWICBitmapSource.swift
+++ b/Sources/Overlays/_Testing_WinSDK/Attachments/AttachableAsIWICBitmapSource.swift
@@ -9,8 +9,7 @@
 //
 
 #if os(Windows)
-@_spi(Experimental) import Testing
-
+private import Testing
 public import WinSDK
 
 /// A protocol describing images that can be converted to instances of
@@ -21,13 +20,14 @@ public import WinSDK
 /// initializers on ``Testing/Attachment`` that take instances of such types and
 /// handle converting them to image data when needed.
 ///
-/// The following system-provided image types conform to this protocol and can
-/// be attached to a test:
+/// You can attach instances of the following system-provided image types to a
+/// test:
 ///
-/// - [`HBITMAP`](https://learn.microsoft.com/en-us/windows/win32/gdi/bitmaps)
-/// - [`HICON`](https://learn.microsoft.com/en-us/windows/win32/menurc/icons)
-/// - [`IWICBitmapSource`](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapsource)
-///   (including its subclasses declared by Windows Imaging Component)
+/// | Platform | Supported Types |
+/// |-|-|
+/// | macOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`NSImage`](https://developer.apple.com/documentation/appkit/nsimage) |
+/// | iOS, watchOS, tvOS, and visionOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`UIImage`](https://developer.apple.com/documentation/uikit/uiimage) |
+/// | Windows | [`HBITMAP`](https://learn.microsoft.com/en-us/windows/win32/gdi/bitmaps), [`HICON`](https://learn.microsoft.com/en-us/windows/win32/menurc/icons), [`IWICBitmapSource`](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapsource) (including its subclasses declared by Windows Imaging Component) |
 ///
 /// You do not generally need to add your own conformances to this protocol. If
 /// you have an image in another format that needs to be attached to a test,
@@ -93,26 +93,27 @@ public protocol _AttachableByAddressAsIWICBitmapSource {
 }
 
 /// A protocol describing images that can be converted to instances of
-/// ``Testing/Attachment``.
+/// [`Attachment`](https://developer.apple.com/documentation/testing/attachment).
 ///
 /// Instances of types conforming to this protocol do not themselves conform to
-/// ``Testing/Attachable``. Instead, the testing library provides additional
-/// initializers on ``Testing/Attachment`` that take instances of such types and
-/// handle converting them to image data when needed.
+/// [`Attachable`](https://developer.apple.com/documentation/testing/attachable).
+/// Instead, the testing library provides additional initializers on [`Attachment`](https://developer.apple.com/documentation/testing/attachment)
+/// that take instances of such types and handle converting them to image data when needed.
 ///
-/// The following system-provided image types conform to this protocol and can
-/// be attached to a test:
+/// You can attach instances of the following system-provided image types to a
+/// test:
 ///
-/// - [`HBITMAP`](https://learn.microsoft.com/en-us/windows/win32/gdi/bitmaps)
-/// - [`HICON`](https://learn.microsoft.com/en-us/windows/win32/menurc/icons)
-/// - [`IWICBitmapSource`](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapsource)
-///   (including its subclasses declared by Windows Imaging Component)
+/// | Platform | Supported Types |
+/// |-|-|
+/// | macOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`NSImage`](https://developer.apple.com/documentation/appkit/nsimage) |
+/// | iOS, watchOS, tvOS, and visionOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`UIImage`](https://developer.apple.com/documentation/uikit/uiimage) |
+/// | Windows | [`HBITMAP`](https://learn.microsoft.com/en-us/windows/win32/gdi/bitmaps), [`HICON`](https://learn.microsoft.com/en-us/windows/win32/menurc/icons), [`IWICBitmapSource`](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapsource) (including its subclasses declared by Windows Imaging Component) |
 ///
 /// You do not generally need to add your own conformances to this protocol. If
 /// you have an image in another format that needs to be attached to a test,
 /// first convert it to an instance of one of the types above.
 @_spi(Experimental)
-public protocol AttachableAsIWICBitmapSource {
+public protocol AttachableAsIWICBitmapSource: SendableMetatype {
   /// Create a WIC bitmap source representing an instance of this type.
   ///
   /// - Returns: A pointer to a new WIC bitmap source representing this image.
diff --git a/Sources/Overlays/_Testing_WinSDK/Attachments/AttachableImageFormat+CLSID.swift b/Sources/Overlays/_Testing_WinSDK/Attachments/AttachableImageFormat+CLSID.swift
index 009015e13..1881fa036 100644
--- a/Sources/Overlays/_Testing_WinSDK/Attachments/AttachableImageFormat+CLSID.swift
+++ b/Sources/Overlays/_Testing_WinSDK/Attachments/AttachableImageFormat+CLSID.swift
@@ -9,8 +9,7 @@
 //
 
 #if os(Windows)
-@_spi(Experimental) import Testing
-
+@_spi(Experimental) public import Testing
 public import WinSDK
 
 extension AttachableImageFormat {
@@ -258,7 +257,7 @@ extension AttachableImageFormat {
   ///
   /// If `clsid` does not represent an image encoder type supported by WIC, the
   /// result is undefined. For a list of image encoders supported by WIC, see
-  /// the documentation for the [IWICBitmapEncoder](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapencoder)
+  /// the documentation for the [`IWICBitmapEncoder`](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapencoder)
   /// class.
   public init(_ clsid: CLSID, encodingQuality: Float = 1.0) {
     self.init(kind: .systemValue(clsid), encodingQuality: encodingQuality)
diff --git a/Sources/Overlays/_Testing_WinSDK/Attachments/Attachment+AttachableAsIWICBitmapSource.swift b/Sources/Overlays/_Testing_WinSDK/Attachments/Attachment+AttachableAsIWICBitmapSource.swift
index ec0bb016b..8068e7a8e 100644
--- a/Sources/Overlays/_Testing_WinSDK/Attachments/Attachment+AttachableAsIWICBitmapSource.swift
+++ b/Sources/Overlays/_Testing_WinSDK/Attachments/Attachment+AttachableAsIWICBitmapSource.swift
@@ -26,13 +26,14 @@ extension Attachment {
   ///     This value is used when recording issues associated with the
   ///     attachment.
   ///
-  /// The following system-provided image types conform to the
-  /// ``AttachableAsIWICBitmapSource`` protocol and can be attached to a test:
+  /// You can attach instances of the following system-provided image types to a
+  /// test:
   ///
-  /// - [`HBITMAP`](https://learn.microsoft.com/en-us/windows/win32/gdi/bitmaps)
-  /// - [`HICON`](https://learn.microsoft.com/en-us/windows/win32/menurc/icons)
-  /// - [`IWICBitmapSource`](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapsource)
-  ///   (including its subclasses declared by Windows Imaging Component)
+  /// | Platform | Supported Types |
+  /// |-|-|
+  /// | macOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`NSImage`](https://developer.apple.com/documentation/appkit/nsimage) |
+  /// | iOS, watchOS, tvOS, and visionOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`UIImage`](https://developer.apple.com/documentation/uikit/uiimage) |
+  /// | Windows | [`HBITMAP`](https://learn.microsoft.com/en-us/windows/win32/gdi/bitmaps), [`HICON`](https://learn.microsoft.com/en-us/windows/win32/menurc/icons), [`IWICBitmapSource`](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapsource) (including its subclasses declared by Windows Imaging Component) |
   ///
   /// The testing library uses the image format specified by `imageFormat`. Pass
   /// `nil` to let the testing library decide which image format to use. If you
@@ -46,8 +47,12 @@ extension Attachment {
     named preferredName: String? = nil,
     as imageFormat: AttachableImageFormat? = nil,
     sourceLocation: SourceLocation = #_sourceLocation
-  ) where AttachableValue == _AttachableImageWrapper<T> {
-    let imageWrapper = _AttachableImageWrapper(image: image, imageFormat: imageFormat)
+  ) where T: AttachableAsIWICBitmapSource, AttachableValue == _AttachableImageWrapper<T> {
+    let imageWrapper = _AttachableImageWrapper(
+      image: image._copyAttachableValue(),
+      imageFormat: imageFormat,
+      deinitializingWith: { $0._deinitializeAttachableValue() }
+    )
     self.init(imageWrapper, named: preferredName, sourceLocation: sourceLocation)
   }
 
@@ -64,15 +69,14 @@ extension Attachment {
   ///     attachment.
   ///
   /// This function creates a new instance of ``Attachment`` wrapping `image`
-  /// and immediately attaches it to the current test.
+  /// and immediately attaches it to the current test. You can attach instances
+  /// of the following system-provided image types to a test:
   ///
-  /// The following system-provided image types conform to the
-  /// ``AttachableAsIWICBitmapSource`` protocol and can be attached to a test:
-  ///
-  /// - [`HBITMAP`](https://learn.microsoft.com/en-us/windows/win32/gdi/bitmaps)
-  /// - [`HICON`](https://learn.microsoft.com/en-us/windows/win32/menurc/icons)
-  /// - [`IWICBitmapSource`](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapsource)
-  ///   (including its subclasses declared by Windows Imaging Component)
+  /// | Platform | Supported Types |
+  /// |-|-|
+  /// | macOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`NSImage`](https://developer.apple.com/documentation/appkit/nsimage) |
+  /// | iOS, watchOS, tvOS, and visionOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`UIImage`](https://developer.apple.com/documentation/uikit/uiimage) |
+  /// | Windows | [`HBITMAP`](https://learn.microsoft.com/en-us/windows/win32/gdi/bitmaps), [`HICON`](https://learn.microsoft.com/en-us/windows/win32/menurc/icons), [`IWICBitmapSource`](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapsource) (including its subclasses declared by Windows Imaging Component) |
   ///
   /// The testing library uses the image format specified by `imageFormat`. Pass
   /// `nil` to let the testing library decide which image format to use. If you
@@ -86,9 +90,8 @@ extension Attachment {
     named preferredName: String? = nil,
     as imageFormat: AttachableImageFormat? = nil,
     sourceLocation: SourceLocation = #_sourceLocation
-  ) where AttachableValue == _AttachableImageWrapper<T> {
-    let imageWrapper = _AttachableImageWrapper(image: image, imageFormat: imageFormat)
-    let attachment = Self(imageWrapper, named: preferredName, sourceLocation: sourceLocation)
+  ) where T: AttachableAsIWICBitmapSource, AttachableValue == _AttachableImageWrapper<T> {
+    let attachment = Self(image, named: preferredName, as: imageFormat, sourceLocation: sourceLocation)
     Self.record(attachment, sourceLocation: sourceLocation)
   }
 }
@@ -96,9 +99,8 @@ extension Attachment {
 @_spi(Experimental)
 extension Attachment where AttachableValue: AttachableWrapper, AttachableValue.Wrapped: AttachableAsIWICBitmapSource {
   /// The image format to use when encoding the represented image.
-  @_disfavoredOverload
-  public var imageFormat: AttachableImageFormat? {
-    // FIXME: no way to express `where AttachableValue == _AttachableImageWrapper<???>` on a property
+  @_disfavoredOverload public var imageFormat: AttachableImageFormat? {
+    // FIXME: no way to express `where AttachableValue == _AttachableImageWrapper<???>` on a property (see rdar://47559973)
     (attachableValue as? _AttachableImageWrapper<AttachableValue.Wrapped>)?.imageFormat
   }
 }
diff --git a/Sources/Overlays/_Testing_WinSDK/Attachments/HBITMAP+AttachableAsIWICBitmapSource.swift b/Sources/Overlays/_Testing_WinSDK/Attachments/HBITMAP+AttachableAsIWICBitmapSource.swift
index 0d11fd0bc..4baef8d36 100644
--- a/Sources/Overlays/_Testing_WinSDK/Attachments/HBITMAP+AttachableAsIWICBitmapSource.swift
+++ b/Sources/Overlays/_Testing_WinSDK/Attachments/HBITMAP+AttachableAsIWICBitmapSource.swift
@@ -9,8 +9,7 @@
 //
 
 #if os(Windows)
-import Testing
-
+private import Testing
 public import WinSDK
 
 @_spi(Experimental)
diff --git a/Sources/Overlays/_Testing_WinSDK/Attachments/HICON+AttachableAsIWICBitmapSource.swift b/Sources/Overlays/_Testing_WinSDK/Attachments/HICON+AttachableAsIWICBitmapSource.swift
index a25e8f371..36f4fcc9e 100644
--- a/Sources/Overlays/_Testing_WinSDK/Attachments/HICON+AttachableAsIWICBitmapSource.swift
+++ b/Sources/Overlays/_Testing_WinSDK/Attachments/HICON+AttachableAsIWICBitmapSource.swift
@@ -9,8 +9,7 @@
 //
 
 #if os(Windows)
-import Testing
-
+private import Testing
 public import WinSDK
 
 @_spi(Experimental)
diff --git a/Sources/Overlays/_Testing_WinSDK/Attachments/IWICBitmapSource+AttachableAsIWICBitmapSource.swift b/Sources/Overlays/_Testing_WinSDK/Attachments/IWICBitmapSource+AttachableAsIWICBitmapSource.swift
index 401e6f480..8ff6d5430 100644
--- a/Sources/Overlays/_Testing_WinSDK/Attachments/IWICBitmapSource+AttachableAsIWICBitmapSource.swift
+++ b/Sources/Overlays/_Testing_WinSDK/Attachments/IWICBitmapSource+AttachableAsIWICBitmapSource.swift
@@ -9,8 +9,7 @@
 //
 
 #if os(Windows)
-import Testing
-
+private import Testing
 public import WinSDK
 
 /// - Important: The casts in this file to `IUnknown` are safe insofar as we use
diff --git a/Sources/Overlays/_Testing_WinSDK/Attachments/UnsafeMutablePointer+AttachableAsIWICBitmapSource.swift b/Sources/Overlays/_Testing_WinSDK/Attachments/UnsafeMutablePointer+AttachableAsIWICBitmapSource.swift
index 6d34a6e90..297e1f25a 100644
--- a/Sources/Overlays/_Testing_WinSDK/Attachments/UnsafeMutablePointer+AttachableAsIWICBitmapSource.swift
+++ b/Sources/Overlays/_Testing_WinSDK/Attachments/UnsafeMutablePointer+AttachableAsIWICBitmapSource.swift
@@ -9,8 +9,7 @@
 //
 
 #if os(Windows)
-import Testing
-
+private import Testing
 public import WinSDK
 
 @_spi(Experimental)
diff --git a/Sources/Overlays/_Testing_WinSDK/Attachments/_AttachableImageWrapper.swift b/Sources/Overlays/_Testing_WinSDK/Attachments/_AttachableImageWrapper+AttachableWrapper.swift
similarity index 76%
rename from Sources/Overlays/_Testing_WinSDK/Attachments/_AttachableImageWrapper.swift
rename to Sources/Overlays/_Testing_WinSDK/Attachments/_AttachableImageWrapper+AttachableWrapper.swift
index 63931c378..7cfe181b8 100644
--- a/Sources/Overlays/_Testing_WinSDK/Attachments/_AttachableImageWrapper.swift
+++ b/Sources/Overlays/_Testing_WinSDK/Attachments/_AttachableImageWrapper+AttachableWrapper.swift
@@ -10,47 +10,9 @@
 
 #if os(Windows)
 @_spi(Experimental) public import Testing
+private import WinSDK
 
-internal import WinSDK
-
-/// A wrapper type for image types such as `HBITMAP` and `HICON` that can be
-/// attached indirectly.
-///
-/// You do not need to use this type directly. Instead, initialize an instance
-/// of ``Attachment`` using an instance of an image type that conforms to
-/// ``AttachableAsIWICBitmapSource``. The following system-provided image types
-/// conform to the ``AttachableAsIWICBitmapSource`` protocol and can be attached
-/// to a test:
-///
-/// - [`HBITMAP`](https://learn.microsoft.com/en-us/windows/win32/gdi/bitmaps)
-/// - [`HICON`](https://learn.microsoft.com/en-us/windows/win32/menurc/icons)
-/// - [`IWICBitmapSource`](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapsource)
-///   (including its subclasses declared by Windows Imaging Component)
-@_spi(Experimental)
-public final class _AttachableImageWrapper<Image>: Sendable where Image: AttachableAsIWICBitmapSource {
-  /// The underlying image.
-  nonisolated(unsafe) let image: Image
-
-  /// The image format to use when encoding the represented image.
-  let imageFormat: AttachableImageFormat?
-
-  init(image: borrowing Image, imageFormat: AttachableImageFormat?) {
-    self.image = image._copyAttachableValue()
-    self.imageFormat = imageFormat
-  }
-
-  deinit {
-    image._deinitializeAttachableValue()
-  }
-}
-
-// MARK: -
-
-extension _AttachableImageWrapper: AttachableWrapper {
-  public var wrappedValue: Image {
-    image
-  }
-
+extension _AttachableImageWrapper: Attachable, AttachableWrapper where Image: AttachableAsIWICBitmapSource {
   public func withUnsafeBytes<R>(for attachment: borrowing Attachment<_AttachableImageWrapper>, _ body: (UnsafeRawBufferPointer) throws -> R) throws -> R {
     // Create an in-memory stream to write the image data to. Note that Windows
     // documentation recommends SHCreateMemStream() instead, but that function
@@ -71,7 +33,7 @@ extension _AttachableImageWrapper: AttachableWrapper {
     }
 
     // Create the bitmap and downcast it to an IWICBitmapSource for later use.
-    let bitmap = try image._copyAttachableIWICBitmapSource(using: factory)
+    let bitmap = try wrappedValue._copyAttachableIWICBitmapSource(using: factory)
     defer {
       _ = bitmap.pointee.lpVtbl.pointee.Release(bitmap)
     }
diff --git a/Sources/Testing/Attachments/AttachableImageFormat.swift b/Sources/Testing/Attachments/Images/AttachableImageFormat.swift
similarity index 100%
rename from Sources/Testing/Attachments/AttachableImageFormat.swift
rename to Sources/Testing/Attachments/Images/AttachableImageFormat.swift
diff --git a/Sources/Overlays/_Testing_WinSDK/Attachments/ImageAttachmentError.swift b/Sources/Testing/Attachments/Images/ImageAttachmentError.swift
similarity index 54%
rename from Sources/Overlays/_Testing_WinSDK/Attachments/ImageAttachmentError.swift
rename to Sources/Testing/Attachments/Images/ImageAttachmentError.swift
index 1b37df4a9..7cd6f8180 100644
--- a/Sources/Overlays/_Testing_WinSDK/Attachments/ImageAttachmentError.swift
+++ b/Sources/Testing/Attachments/Images/ImageAttachmentError.swift
@@ -1,38 +1,56 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2025 Apple Inc. and the Swift project authors
+// Copyright (c) 2024 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
 // See https://swift.org/CONTRIBUTORS.txt for Swift project authors
 //
 
-#if os(Windows)
-@_spi(Experimental) import Testing
-
-internal import WinSDK
+private import _TestingInternals
 
 /// A type representing an error that can occur when attaching an image.
-enum ImageAttachmentError: Error {
+package enum ImageAttachmentError: Error {
+#if SWT_TARGET_OS_APPLE
+  /// The image could not be converted to an instance of `CGImage`.
+  case couldNotCreateCGImage
+
+  /// The image destination could not be created.
+  case couldNotCreateImageDestination
+
+  /// The image could not be converted.
+  case couldNotConvertImage
+#elseif os(Windows)
   /// A call to `QueryInterface()` failed.
-  case queryInterfaceFailed(Any.Type, HRESULT)
+  case queryInterfaceFailed(Any.Type, Int32)
 
   /// The testing library failed to create a COM object.
-  case comObjectCreationFailed(Any.Type, HRESULT)
+  case comObjectCreationFailed(Any.Type, Int32)
 
   /// An image could not be written.
-  case imageWritingFailed(HRESULT)
+  case imageWritingFailed(Int32)
 
   /// The testing library failed to get an in-memory stream's underlying buffer.
-  case globalFromStreamFailed(HRESULT)
+  case globalFromStreamFailed(Int32)
 
   /// A property could not be written to a property bag.
-  case propertyBagWritingFailed(String, HRESULT)
+  case propertyBagWritingFailed(String, Int32)
+#endif
 }
 
 extension ImageAttachmentError: CustomStringConvertible {
-  var description: String {
+  package var description: String {
+#if SWT_TARGET_OS_APPLE
+    switch self {
+    case .couldNotCreateCGImage:
+      "Could not create the corresponding Core Graphics image."
+    case .couldNotCreateImageDestination:
+      "Could not create the Core Graphics image destination to encode this image."
+    case .couldNotConvertImage:
+      "Could not convert the image to the specified format."
+    }
+#elseif os(Windows)
     switch self {
     case let .queryInterfaceFailed(type, result):
       "Could not cast a COM object to type '\(type)' (HRESULT \(result))."
@@ -45,6 +63,8 @@ extension ImageAttachmentError: CustomStringConvertible {
     case let .propertyBagWritingFailed(name, result):
       "Could not set the property '\(name)' (HRESULT \(result))."
     }
+#else
+    swt_unreachable()
+#endif
   }
 }
-#endif
diff --git a/Sources/Testing/Attachments/Images/_AttachableImageWrapper.swift b/Sources/Testing/Attachments/Images/_AttachableImageWrapper.swift
new file mode 100644
index 000000000..71623538a
--- /dev/null
+++ b/Sources/Testing/Attachments/Images/_AttachableImageWrapper.swift
@@ -0,0 +1,49 @@
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for Swift project authors
+//
+
+/// A wrapper type for images that can be indirectly attached to a test.
+///
+/// You can attach instances of the following system-provided image types to a
+/// test:
+///
+/// | Platform | Supported Types |
+/// |-|-|
+/// | macOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`NSImage`](https://developer.apple.com/documentation/appkit/nsimage) |
+/// | iOS, watchOS, tvOS, and visionOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`UIImage`](https://developer.apple.com/documentation/uikit/uiimage) |
+/// | Windows | [`HBITMAP`](https://learn.microsoft.com/en-us/windows/win32/gdi/bitmaps), [`HICON`](https://learn.microsoft.com/en-us/windows/win32/menurc/icons), [`IWICBitmapSource`](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapsource) (including its subclasses declared by Windows Imaging Component) |
+@_spi(Experimental)
+@available(_uttypesAPI, *)
+public final class _AttachableImageWrapper<Image>: Sendable {
+  /// The underlying image.
+  private nonisolated(unsafe) let _image: Image
+
+  /// The image format to use when encoding the represented image.
+  package let imageFormat: AttachableImageFormat?
+
+  /// A deinitializer function to call to clean up `image`.
+  private let _deinit: @Sendable (consuming Image) -> Void
+
+  package init(image: Image, imageFormat: AttachableImageFormat?, deinitializingWith `deinit`: @escaping @Sendable (consuming Image) -> Void) {
+    self._image = image
+    self.imageFormat = imageFormat
+    self._deinit = `deinit`
+  }
+
+  deinit {
+    _deinit(_image)
+  }
+}
+
+@available(_uttypesAPI, *)
+extension _AttachableImageWrapper {
+  public var wrappedValue: Image {
+    _image
+  }
+}
diff --git a/Sources/Testing/CMakeLists.txt b/Sources/Testing/CMakeLists.txt
index 36437e167..531d27cfc 100644
--- a/Sources/Testing/CMakeLists.txt
+++ b/Sources/Testing/CMakeLists.txt
@@ -21,6 +21,9 @@ add_library(Testing
   ABI/Encoded/ABI.EncodedIssue.swift
   ABI/Encoded/ABI.EncodedMessage.swift
   ABI/Encoded/ABI.EncodedTest.swift
+  Attachments/Images/_AttachableImageWrapper.swift
+  Attachments/Images/AttachableImageFormat.swift
+  Attachments/Images/ImageAttachmentError.swift
   Attachments/Attachable.swift
   Attachments/AttachableWrapper.swift
   Attachments/Attachment.swift