Make font-holding config structs Sendable via SendableFont wrapper

Sources/MarkdownText/Models/MarkdownRenderConfig.swift

@@ -111,24 +111,27 @@ public struct MarkdownRenderConfig: Hashable, Sendable {
     /// Foreground color applied to bold-emphasis runs.
     public let boldTextColor: Color
     /// Font used for link runs.
-    public let linkTextFont: MDFont
+    public var linkTextFont: MDFont { internalLinkTextFont.font }
     /// Foreground color applied to link runs.
     public let linkTextColor: Color
     /// Font used for inline code spans.
-    public let codeTextFont: MDFont
+    public var codeTextFont: MDFont { internalCodeTextFont.font }
     /// Foreground color applied to inline code spans.
     public let codeTextColor: Color
     /// Background fill behind inline code spans.
     public let codeBackgroundColor: Color
     /// Underline color drawn beneath inline code spans.
     public let codeUnderlineColor: Color
 
+    private let internalLinkTextFont: SendableFont
+    private let internalCodeTextFont: SendableFont
+
     /// Create an inline text style with the supplied fonts and color palette.
     public init(boldTextColor: Color, linkTextFont: MDFont, linkTextColor: Color, codeTextFont: MDFont, codeTextColor: Color, codeBackgroundColor: Color, codeUnderlineColor: Color) {
       self.boldTextColor = boldTextColor
-      self.linkTextFont = linkTextFont
+      self.internalLinkTextFont = SendableFont(linkTextFont)
       self.linkTextColor = linkTextColor
-      self.codeTextFont = codeTextFont
+      self.internalCodeTextFont = SendableFont(codeTextFont)
       self.codeTextColor = codeTextColor
       self.codeBackgroundColor = codeBackgroundColor
       self.codeUnderlineColor = codeUnderlineColor
@@ -142,12 +145,14 @@ public struct MarkdownRenderConfig: Hashable, Sendable {
     /// Encoder/decoder used to embed citation payloads into the markdown.
     public let coder: CitationCoder
     /// Font applied to the rendered citation chip.
-    public let font: MDFont
+    public var font: MDFont { internalFont.font }
     /// Foreground color of the citation chip text.
     public let textColor: Color
     /// Background fill of the citation chip.
     public let backgroundColor: Color
 
+    private let internalFont: SendableFont
+
     /// Create a citation configuration.
     /// - Parameters:
     ///   - isEnabled: See `isEnabled`. Defaults to `true`.
@@ -164,7 +169,7 @@ public struct MarkdownRenderConfig: Hashable, Sendable {
     ) {
       self.isEnabled = isEnabled
       self.coder = coder
-      self.font = font
+      self.internalFont = SendableFont(font)
       self.textColor = textColor
       self.backgroundColor = backgroundColor
     }

Sources/MarkdownText/Style/TextFonts.swift

@@ -10,25 +10,30 @@ import SwiftUI
 /// to style a run of text.
 public struct TextFonts: Hashable, Sendable {
   /// Regular variant. Always required.
-  public let normal: MDFont
+  public var normal: MDFont { internalNormal.font }
   /// Italic variant, or `nil` to fall back to `normal` for emphasis.
-  public let italic: MDFont?
+  public var italic: MDFont? { internalItalic?.font }
   /// Bold variant, or `nil` to fall back to `normal` for strong runs.
-  public let bold: MDFont?
+  public var bold: MDFont? { internalBold?.font }
   /// Bold-italic variant, or `nil` to fall back to `bold` then `italic`.
-  public let boldItalic: MDFont?
+  public var boldItalic: MDFont? { internalBoldItalic?.font }
   /// Optional kerning override applied via `NSAttributedString.Key.kern`.
   public let preferredLetterSpacing: CGFloat?
   /// Optional preferred line height in points. When greater than the font's
   /// natural line height, the renderer adds the difference as line spacing.
   public let preferredLineHeight: CGFloat?
 
+  private let internalNormal: SendableFont
+  private let internalItalic: SendableFont?
+  private let internalBold: SendableFont?
+  private let internalBoldItalic: SendableFont?
+
   /// Create a font set with explicit variants and optional spacing overrides.
   public init(normal: MDFont, italic: MDFont?, bold: MDFont?, boldItalic: MDFont?, preferredLetterSpacing: CGFloat?, preferredLineHeight: CGFloat?) {
-    self.normal = normal
-    self.italic = italic
-    self.bold = bold
-    self.boldItalic = boldItalic
+    self.internalNormal = SendableFont(normal)
+    self.internalItalic = italic.map(SendableFont.init)
+    self.internalBold = bold.map(SendableFont.init)
+    self.internalBoldItalic = boldItalic.map(SendableFont.init)
     self.preferredLetterSpacing = preferredLetterSpacing
     self.preferredLineHeight = preferredLineHeight
   }

Sources/MarkdownText/Utilities/SendableFont.swift

@@ -0,0 +1,26 @@
+//
+//  Copyright (c) Microsoft Corporation. All rights reserved.
+//  Licensed under the MIT License. See LICENSE in the project root for license information.
+//
+
+#if canImport(UIKit)
+import UIKit
+#elseif canImport(AppKit)
+import AppKit
+#endif
+
+/// A `Sendable` wrapper around `MDFont` (`UIFont`/`NSFont`).
+///
+/// `UIFont`/`NSFont` are effectively immutable and safe to share across
+/// concurrency domains, but the SDK does not mark them as `Sendable`. Storing a
+/// font in this value type keeps the unchecked assertion in a single, auditable
+/// place so font-holding configuration types can be plainly `Sendable` without
+/// leaking a retroactive `Sendable` conformance onto the platform font types.
+struct SendableFont: Hashable, @unchecked Sendable {
+  /// The wrapped platform font.
+  let font: MDFont
+
+  init(_ font: MDFont) {
+    self.font = font
+  }
+}