diff --git a/Sources/FoundationEssentials/AttributedString/AttributeScope.swift b/Sources/FoundationEssentials/AttributedString/AttributeScope.swift
index 43ae67bef..c7160cf97 100644
--- a/Sources/FoundationEssentials/AttributedString/AttributeScope.swift
+++ b/Sources/FoundationEssentials/AttributedString/AttributeScope.swift
@@ -22,11 +22,17 @@ public protocol AttributeScope : DecodingConfigurationProviding, EncodingConfigu
     static var encodingConfiguration: AttributeScopeCodableConfiguration { get }
 }
 
-@_nonSendable
 @frozen
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
 public enum AttributeScopes { }
 
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes : Sendable {}
+
 #if FOUNDATION_FRAMEWORK
 
 import Darwin
diff --git a/Sources/FoundationEssentials/AttributedString/AttributedStringAttribute.swift b/Sources/FoundationEssentials/AttributedString/AttributedStringAttribute.swift
index 8c9772fc0..cfd3a28cb 100644
--- a/Sources/FoundationEssentials/AttributedString/AttributedStringAttribute.swift
+++ b/Sources/FoundationEssentials/AttributedString/AttributedStringAttribute.swift
@@ -133,7 +133,6 @@ extension AttributedStringKey {
 
 // MARK: Attribute Scopes
 
-@_nonSendable
 @dynamicMemberLookup @frozen
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
 public enum AttributeDynamicLookup {
@@ -142,6 +141,13 @@ public enum AttributeDynamicLookup {
     }
 }
 
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeDynamicLookup : Sendable {}
+
 @dynamicMemberLookup
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
 public struct ScopedAttributeContainer<S: AttributeScope> : Sendable {
diff --git a/Sources/FoundationEssentials/AttributedString/FoundationAttributes.swift b/Sources/FoundationEssentials/AttributedString/FoundationAttributes.swift
index 59d6269f6..2c0e11440 100644
--- a/Sources/FoundationEssentials/AttributedString/FoundationAttributes.swift
+++ b/Sources/FoundationEssentials/AttributedString/FoundationAttributes.swift
@@ -20,7 +20,6 @@ internal import Foundation_Private.NSAttributedString
 extension AttributeScopes {
     public var foundation: FoundationAttributes.Type { FoundationAttributes.self }
     
-    @_nonSendable
     public struct FoundationAttributes : AttributeScope {
         public let link: LinkAttribute
         public let languageIdentifier: LanguageIdentifierAttribute
@@ -65,6 +64,14 @@ extension AttributeScopes {
     }
 }
 
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes : Sendable {}
+
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
 extension AttributeDynamicLookup {
     public subscript<T: AttributedStringKey>(dynamicMember keyPath: KeyPath<AttributeScopes.FoundationAttributes, T>) -> T {
@@ -92,7 +99,6 @@ extension AttributeDynamicLookup {
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
 extension AttributeScopes.FoundationAttributes {
     @frozen
-    @_nonSendable
     @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
     public enum LinkAttribute : CodableAttributedStringKey {
         public typealias Value = URL
@@ -106,7 +112,7 @@ extension AttributeScopes.FoundationAttributes {
     
 #if FOUNDATION_FRAMEWORK
     
-    @frozen @_nonSendable
+    @frozen
     @available(FoundationPreview 0.1, *)
     public enum ReferentConceptAttribute : CodableAttributedStringKey, MarkdownDecodableAttributedStringKey {
         public typealias Value = Int
@@ -114,7 +120,7 @@ extension AttributeScopes.FoundationAttributes {
         public static let markdownName = "referentConcept"
     }
 
-    @frozen @_nonSendable
+    @frozen
     @available(FoundationPreview 0.1, *)
     public enum AgreementConceptAttribute : CodableAttributedStringKey, MarkdownDecodableAttributedStringKey {
         public typealias Value = Int
@@ -122,7 +128,7 @@ extension AttributeScopes.FoundationAttributes {
         public static let markdownName = "agreeWithConcept"
     }
     
-    @frozen @_nonSendable
+    @frozen
     @available(FoundationPreview 0.1, *)
     public enum AgreementArgumentAttribute : CodableAttributedStringKey, MarkdownDecodableAttributedStringKey {
         public typealias Value = Int
@@ -131,7 +137,6 @@ extension AttributeScopes.FoundationAttributes {
     }
     
     @frozen
-    @_nonSendable
     @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
     public enum MorphologyAttribute : CodableAttributedStringKey, MarkdownDecodableAttributedStringKey {
         public typealias Value = Morphology
@@ -140,7 +145,6 @@ extension AttributeScopes.FoundationAttributes {
     }
     
     @frozen
-    @_nonSendable
     @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
     public enum InflectionRuleAttribute : CodableAttributedStringKey, MarkdownDecodableAttributedStringKey {
         public typealias Value = InflectionRule
@@ -149,7 +153,6 @@ extension AttributeScopes.FoundationAttributes {
     }
     
     @frozen
-    @_nonSendable
     @available(macOS 13, iOS 16, tvOS 16, watchOS 9, *)
     @_spi(AutomaticGrammaticalAgreement)
     public enum AssumedFallbackInflectionAttribute : CodableAttributedStringKey, MarkdownDecodableAttributedStringKey {
@@ -159,7 +162,6 @@ extension AttributeScopes.FoundationAttributes {
     }
     
     @frozen
-    @_nonSendable
     @available(FoundationPreview 0.4, *)
     public enum LocalizedNumberFormatAttribute : CodableAttributedStringKey, MarkdownDecodableAttributedStringKey {
         public struct Value: Equatable, Hashable, Codable, Sendable {
@@ -194,7 +196,6 @@ extension AttributeScopes.FoundationAttributes {
 #endif // FOUNDATION_FRAMEWORK
     
     @frozen
-    @_nonSendable
     @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
     public enum LanguageIdentifierAttribute : CodableAttributedStringKey {
         public typealias Value = String
@@ -202,7 +203,6 @@ extension AttributeScopes.FoundationAttributes {
     }
     
     @frozen
-    @_nonSendable
     @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
     public enum PersonNameComponentAttribute : CodableAttributedStringKey {
         public typealias Value = Component
@@ -213,14 +213,12 @@ extension AttributeScopes.FoundationAttributes {
         }
     }
     
-    @_nonSendable
     @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
     public struct NumberFormatAttributes: AttributeScope {
         public let numberSymbol: SymbolAttribute
         public let numberPart: NumberPartAttribute
         
         @frozen
-        @_nonSendable
         public enum NumberPartAttribute : CodableAttributedStringKey {
             public enum NumberPart : Int, Codable, Sendable {
                 case integer
@@ -232,7 +230,6 @@ extension AttributeScopes.FoundationAttributes {
         }
         
         @frozen
-        @_nonSendable
         public enum SymbolAttribute : CodableAttributedStringKey {
             public enum Symbol : Int, Codable, Sendable {
                 case groupingSeparator
@@ -248,7 +245,6 @@ extension AttributeScopes.FoundationAttributes {
     }
     
     @frozen
-    @_nonSendable
     @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
     public enum DateFieldAttribute : CodableAttributedStringKey {
         public enum Field : Hashable, Codable, Sendable {
@@ -381,7 +377,6 @@ extension AttributeScopes.FoundationAttributes {
 #if FOUNDATION_FRAMEWORK
     
     @frozen
-    @_nonSendable
     @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
     public enum InflectionAlternativeAttribute : CodableAttributedStringKey, MarkdownDecodableAttributedStringKey, ObjectiveCConvertibleAttributedStringKey {
         public typealias Value = AttributedString
@@ -409,7 +404,6 @@ extension AttributeScopes.FoundationAttributes {
     }
     
 	@frozen
-    @_nonSendable
     @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
     public enum InlinePresentationIntentAttribute : CodableAttributedStringKey, ObjectiveCConvertibleAttributedStringKey {
         public typealias Value = InlinePresentationIntent
@@ -426,7 +420,6 @@ extension AttributeScopes.FoundationAttributes {
     }
     
     @frozen
-    @_nonSendable
     @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
     public enum PresentationIntentAttribute : CodableAttributedStringKey {
         public typealias Value = PresentationIntent
@@ -434,7 +427,6 @@ extension AttributeScopes.FoundationAttributes {
     }
     
     @frozen
-    @_nonSendable
     @available(macOS 13, iOS 16, tvOS 16, watchOS 9, *)
     public enum MarkdownSourcePositionAttribute: CodableAttributedStringKey {
         public static let name = NSAttributedString.Key.markdownSourcePosition.rawValue
@@ -444,7 +436,6 @@ extension AttributeScopes.FoundationAttributes {
 #endif // FOUNDATION_FRAMEWORK
     
     @frozen
-    @_nonSendable
     @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
     public enum AlternateDescriptionAttribute : CodableAttributedStringKey {
         public typealias Value = String
@@ -452,7 +443,6 @@ extension AttributeScopes.FoundationAttributes {
     }
     
     @frozen
-    @_nonSendable
     @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
     public enum ImageURLAttribute : CodableAttributedStringKey {
         public typealias Value = URL
@@ -460,14 +450,12 @@ extension AttributeScopes.FoundationAttributes {
     }
     
     @frozen
-    @_nonSendable
     @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
     public enum ReplacementIndexAttribute : CodableAttributedStringKey {
         public typealias Value = Int
         public static let name = "NSReplacementIndex"
     }
     
-    @_nonSendable
     @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
     public struct MeasurementAttribute : CodableAttributedStringKey {
         public typealias Value = Component
@@ -479,7 +467,6 @@ extension AttributeScopes.FoundationAttributes {
     }
     
     @frozen
-    @_nonSendable
     @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
     public enum ByteCountAttribute : CodableAttributedStringKey {
         public typealias Value = Component
@@ -505,7 +492,6 @@ extension AttributeScopes.FoundationAttributes {
     }
 
     @frozen
-    @_nonSendable
     @available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
     public enum DurationFieldAttribute : CodableAttributedStringKey {
         public typealias Value = Field
@@ -523,7 +509,6 @@ extension AttributeScopes.FoundationAttributes {
     }
     
 #if FOUNDATION_FRAMEWORK
-    @_nonSendable
     @available(macOS 13, iOS 16, tvOS 16, watchOS 9, *)
     public struct LocalizedStringArgumentAttributes {
     
@@ -535,7 +520,6 @@ extension AttributeScopes.FoundationAttributes {
         public let localizedURLArgument: LocalizedURLArgumentAttribute
         
         @frozen
-        @_nonSendable
         @available(macOS 13, iOS 16, tvOS 16, watchOS 9, *)
         public enum LocalizedNumericArgumentAttribute : CodableAttributedStringKey {
             public static let name = "Foundation.LocalizedNumericArgumentAttribute"
@@ -548,7 +532,6 @@ extension AttributeScopes.FoundationAttributes {
         }
         
         @frozen
-        @_nonSendable
         @available(macOS 13, iOS 16, tvOS 16, watchOS 9, *)
         public enum LocalizedDateArgumentAttribute : CodableAttributedStringKey {
             public typealias Value = Date
@@ -556,7 +539,6 @@ extension AttributeScopes.FoundationAttributes {
         }
         
         @frozen
-        @_nonSendable
         @available(macOS 13, iOS 16, tvOS 16, watchOS 9, *)
         public enum LocalizedDateIntervalArgumentAttribute : CodableAttributedStringKey {
             public typealias Value = Range<Date>
@@ -564,7 +546,6 @@ extension AttributeScopes.FoundationAttributes {
         }
         
         @frozen
-        @_nonSendable
         @available(macOS 13, iOS 16, tvOS 16, watchOS 9, *)
         public enum LocalizedURLArgumentAttribute : CodableAttributedStringKey {
             public typealias Value = URL
@@ -574,8 +555,213 @@ extension AttributeScopes.FoundationAttributes {
 #endif // FOUNDATION_FRAMEWORK
 }
 
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.LinkAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.LanguageIdentifierAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.PersonNameComponentAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.NumberFormatAttributes : Sendable {}
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.NumberFormatAttributes.NumberPartAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.NumberFormatAttributes.SymbolAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.DateFieldAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.AlternateDescriptionAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.ImageURLAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.ReplacementIndexAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.MeasurementAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.ByteCountAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 13.0)
+@available(iOS, unavailable, introduced: 16.0)
+@available(tvOS, unavailable, introduced: 16.0)
+@available(watchOS, unavailable, introduced: 9.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.DurationFieldAttribute : Sendable {}
+
 #if FOUNDATION_FRAMEWORK
 
+@available(macOS, unavailable, introduced: 14.0)
+@available(iOS, unavailable, introduced: 17.0)
+@available(tvOS, unavailable, introduced: 17.0)
+@available(watchOS, unavailable, introduced: 10.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.ReferentConceptAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 14.0)
+@available(iOS, unavailable, introduced: 17.0)
+@available(tvOS, unavailable, introduced: 17.0)
+@available(watchOS, unavailable, introduced: 10.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.AgreementConceptAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 14.0)
+@available(iOS, unavailable, introduced: 17.0)
+@available(tvOS, unavailable, introduced: 17.0)
+@available(watchOS, unavailable, introduced: 10.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.AgreementArgumentAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.MorphologyAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.InflectionRuleAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 13.0)
+@available(iOS, unavailable, introduced: 16.0)
+@available(tvOS, unavailable, introduced: 16.0)
+@available(watchOS, unavailable, introduced: 9.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.AssumedFallbackInflectionAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 15.0)
+@available(iOS, unavailable, introduced: 18.0)
+@available(tvOS, unavailable, introduced: 18.0)
+@available(watchOS, unavailable, introduced: 11.0)
+@available(visionOS, unavailable, introduced: 2.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.LocalizedNumberFormatAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.InflectionAlternativeAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.InlinePresentationIntentAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.PresentationIntentAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 13.0)
+@available(iOS, unavailable, introduced: 16.0)
+@available(tvOS, unavailable, introduced: 16.0)
+@available(watchOS, unavailable, introduced: 9.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.MarkdownSourcePositionAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 13.0)
+@available(iOS, unavailable, introduced: 16.0)
+@available(tvOS, unavailable, introduced: 16.0)
+@available(watchOS, unavailable, introduced: 9.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.LocalizedStringArgumentAttributes : Sendable {}
+
+@available(macOS, unavailable, introduced: 13.0)
+@available(iOS, unavailable, introduced: 16.0)
+@available(tvOS, unavailable, introduced: 16.0)
+@available(watchOS, unavailable, introduced: 9.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.LocalizedStringArgumentAttributes.LocalizedNumericArgumentAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 13.0)
+@available(iOS, unavailable, introduced: 16.0)
+@available(tvOS, unavailable, introduced: 16.0)
+@available(watchOS, unavailable, introduced: 9.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.LocalizedStringArgumentAttributes.LocalizedURLArgumentAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 13.0)
+@available(iOS, unavailable, introduced: 16.0)
+@available(tvOS, unavailable, introduced: 16.0)
+@available(watchOS, unavailable, introduced: 9.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.LocalizedStringArgumentAttributes.LocalizedDateArgumentAttribute : Sendable {}
+
+@available(macOS, unavailable, introduced: 13.0)
+@available(iOS, unavailable, introduced: 16.0)
+@available(tvOS, unavailable, introduced: 16.0)
+@available(watchOS, unavailable, introduced: 9.0)
+@available(*, unavailable)
+extension AttributeScopes.FoundationAttributes.LocalizedStringArgumentAttributes.LocalizedDateIntervalArgumentAttribute : Sendable {}
+
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
 extension AttributeScopes.FoundationAttributes.LinkAttribute : ObjectiveCConvertibleAttributedStringKey {
     public typealias ObjectiveCValue = NSObject // NSURL or NSString
diff --git a/Sources/FoundationEssentials/Data/Data.swift b/Sources/FoundationEssentials/Data/Data.swift
index cf9c07b0a..70df1e878 100644
--- a/Sources/FoundationEssentials/Data/Data.swift
+++ b/Sources/FoundationEssentials/Data/Data.swift
@@ -1844,7 +1844,6 @@ public struct Data : Equatable, Hashable, RandomAccessCollection, MutableCollect
     // A standard or custom deallocator for `Data`.
     ///
     /// When creating a `Data` with the no-copy initializer, you may specify a `Data.Deallocator` to customize the behavior of how the backing store is deallocated.
-    @_nonSendable
     public enum Deallocator {
         /// Use a virtual memory deallocator.
 #if canImport(Darwin)
@@ -2688,6 +2687,13 @@ public struct Data : Equatable, Hashable, RandomAccessCollection, MutableCollect
     }
 }
 
+@available(macOS, unavailable, introduced: 10.10)
+@available(iOS, unavailable, introduced: 8.0)
+@available(tvOS, unavailable, introduced: 9.0)
+@available(watchOS, unavailable, introduced: 2.0)
+@available(*, unavailable)
+extension Data.Deallocator : Sendable {}
+
 #if !FOUNDATION_FRAMEWORK
 // MARK: Exported Types
 extension Data {
diff --git a/Sources/FoundationEssentials/FileManager/SwiftFileManager.swift b/Sources/FoundationEssentials/FileManager/SwiftFileManager.swift
index 26d07fd07..1dcf05419 100644
--- a/Sources/FoundationEssentials/FileManager/SwiftFileManager.swift
+++ b/Sources/FoundationEssentials/FileManager/SwiftFileManager.swift
@@ -176,7 +176,6 @@ extension FileManager {
     }
 }
 
-@_nonSendable
 open class FileManager : @unchecked Sendable {
     // Sendable note: _impl may only be mutated in `init`
     private var _impl: _FileManagerImpl
diff --git a/Sources/FoundationEssentials/Predicate/Predicate.swift b/Sources/FoundationEssentials/Predicate/Predicate.swift
index 584cd7dae..d68fef5f2 100644
--- a/Sources/FoundationEssentials/Predicate/Predicate.swift
+++ b/Sources/FoundationEssentials/Predicate/Predicate.swift
@@ -50,7 +50,14 @@ extension Predicate {
 
 // Namespace for operator expressions
 @available(FoundationPredicate 0.1, *)
-@frozen @_nonSendable public enum PredicateExpressions {}
+@frozen public enum PredicateExpressions {}
+
+@available(macOS, unavailable, introduced: 14.0)
+@available(iOS, unavailable, introduced: 17.0)
+@available(tvOS, unavailable, introduced: 17.0)
+@available(watchOS, unavailable, introduced: 10.0)
+@available(*, unavailable)
+extension PredicateExpressions : Sendable {}
 
 @available(FoundationPredicate 0.1, *)
 extension Sequence {
diff --git a/Sources/FoundationEssentials/Predicate/PredicateBindings.swift b/Sources/FoundationEssentials/Predicate/PredicateBindings.swift
index ef5290069..08ee68130 100644
--- a/Sources/FoundationEssentials/Predicate/PredicateBindings.swift
+++ b/Sources/FoundationEssentials/Predicate/PredicateBindings.swift
@@ -10,7 +10,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-@_nonSendable
 @available(FoundationPredicate 0.1, *)
 public struct PredicateBindings {
     // Store as a values as an array instead of a dictionary (since it is almost always very few elements, this reduces heap allocation and hashing overhead)
@@ -53,3 +52,10 @@ public struct PredicateBindings {
         return mutable
     }
 }
+
+@available(macOS, unavailable, introduced: 14.0)
+@available(iOS, unavailable, introduced: 17.0)
+@available(tvOS, unavailable, introduced: 17.0)
+@available(watchOS, unavailable, introduced: 10.0)
+@available(*, unavailable)
+extension PredicateBindings : Sendable {}
diff --git a/Sources/FoundationEssentials/URL/URL.swift b/Sources/FoundationEssentials/URL/URL.swift
index 9e2dd5677..efdde5da4 100644
--- a/Sources/FoundationEssentials/URL/URL.swift
+++ b/Sources/FoundationEssentials/URL/URL.swift
@@ -22,7 +22,6 @@ internal import CoreFoundation_Private.CFURL
 /// Note that not all property values will exist for all file system URLs. For example, if a file is located on a volume that does not support creation dates, it is valid to request the creation date property, but the returned value will be nil, and no error will be generated.
 ///
 /// Only the fields requested by the keys you pass into the `URL` function to receive this value will be populated. The others will return `nil` regardless of the underlying property on the file system. As a convenience, volume resource values can be requested from any file system URL. The value returned will reflect the property value for the volume on which the resource is located.
-@_nonSendable
 @available(macOS 10.10, iOS 8.0, watchOS 2.0, tvOS 9.0, *)
 public struct URLResourceValues {
 
@@ -596,6 +595,13 @@ public struct URLResourceValues {
 
 #endif // !NO_FILESYSTEM
 }
+
+@available(macOS, unavailable, introduced: 10.10)
+@available(iOS, unavailable, introduced: 8.0)
+@available(tvOS, unavailable, introduced: 9.0)
+@available(watchOS, unavailable, introduced: 2.0)
+@available(*, unavailable)
+extension URLResourceValues : Sendable {}
 #endif // FOUNDATION_FRAMEWORK
 
 #if FOUNDATION_FRAMEWORK_NSURL
diff --git a/Sources/FoundationInternationalization/Formatting/Number/NumberFormatStyleConfiguration.swift b/Sources/FoundationInternationalization/Formatting/Number/NumberFormatStyleConfiguration.swift
index 4177b6eed..5898bf071 100644
--- a/Sources/FoundationInternationalization/Formatting/Number/NumberFormatStyleConfiguration.swift
+++ b/Sources/FoundationInternationalization/Formatting/Number/NumberFormatStyleConfiguration.swift
@@ -88,7 +88,6 @@ public struct FormatStyleCapitalizationContext : Codable, Hashable, Sendable {
     }
 }
 
-@_nonSendable
 @available(macOS 12.0, iOS 15.0, tvOS 15.0, watchOS 8.0, *)
 public enum NumberFormatStyleConfiguration {
     internal struct Collection : Codable, Hashable, Sendable {
@@ -305,7 +304,13 @@ public enum NumberFormatStyleConfiguration {
     }
 }
 
-@_nonSendable
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension NumberFormatStyleConfiguration : Sendable {}
+
 @available(macOS 12.0, iOS 15.0, tvOS 15.0, watchOS 8.0, *)
 public enum CurrencyFormatStyleConfiguration {
     public typealias Grouping = NumberFormatStyleConfiguration.Grouping
@@ -377,7 +382,13 @@ public enum CurrencyFormatStyleConfiguration {
     }
 }
 
-@_nonSendable
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension CurrencyFormatStyleConfiguration : Sendable {}
+
 @available(macOS 12.0, iOS 15.0, tvOS 15.0, watchOS 8.0, *)
 public enum DescriptiveNumberFormatConfiguration {
     public typealias CapitalizationContext = FormatStyleCapitalizationContext
@@ -428,6 +439,13 @@ public enum DescriptiveNumberFormatConfiguration {
     }
 }
 
+@available(macOS, unavailable, introduced: 12.0)
+@available(iOS, unavailable, introduced: 15.0)
+@available(tvOS, unavailable, introduced: 15.0)
+@available(watchOS, unavailable, introduced: 8.0)
+@available(*, unavailable)
+extension DescriptiveNumberFormatConfiguration : Sendable {}
+
 // MARK: - Codable
 
 @available(macOS 12.0, iOS 15.0, tvOS 15.0, watchOS 8.0, *)
diff --git a/Sources/FoundationInternationalization/String/KeyPathComparator.swift b/Sources/FoundationInternationalization/String/KeyPathComparator.swift
index 38ec3bbc3..d3513ed2d 100644
--- a/Sources/FoundationInternationalization/String/KeyPathComparator.swift
+++ b/Sources/FoundationInternationalization/String/KeyPathComparator.swift
@@ -16,7 +16,6 @@ import FoundationEssentials
 
 /// Compares elements using a `KeyPath`, and a `SortComparator` which compares
 /// elements of the `KeyPath`s `Value` type.
-@_nonSendable
 @available(iOS 15.0, macOS 12.0, tvOS 15.0, watchOS 8.0, *)
 public struct KeyPathComparator<Compared>: SortComparator {
     /// The key path to the property to be used for comparisons.
diff --git a/Tests/FoundationInternationalizationTests/SortDescriptorTests.swift b/Tests/FoundationInternationalizationTests/SortDescriptorTests.swift
index 96d190599..0e68facdc 100644
--- a/Tests/FoundationInternationalizationTests/SortDescriptorTests.swift
+++ b/Tests/FoundationInternationalizationTests/SortDescriptorTests.swift
@@ -21,11 +21,13 @@ import TestSupport
 @testable import FoundationInternationalization
 #endif // FOUNDATION_FRAMEWORK
 
-@_nonSendable
 class Hello {
     var str: NSMutableString = "hi"
 }
 
+@available(*, unavailable)
+extension Hello : Sendable {}
+
 @available(FoundationPreview 0.1, *)
 final class SortDescriptorTests: XCTestCase {
     struct NonNSObjectRoot {