Replace platforms: block with per-API @available annotations

Package.swift

@@ -14,7 +14,7 @@ let versionNumbers = ["0.1.0"]
 // Availability Macro Utilities
 
 enum _OSAvailability: String {
-    // This should match the package's deployment target
+    // The OS versions in which `Network 0.1.0` APIs first became available.
     case alwaysAvailable = "macOS 26, iOS 26, tvOS 26, watchOS 26, visionOS 26"
     // Use 10000 for future availability to avoid compiler magic around the 9999 version number but ensure it is greater than 9999
     case future = "macOS 10000, iOS 10000, tvOS 10000, watchOS 10000, visionOS 10000"
@@ -46,6 +46,7 @@ var settings: [SwiftSetting] = [
     .define("SWIFTTLS_CERTIFICATE_VERIFICATION"),
     .unsafeFlags(["-Xfrontend", "-experimental-spi-only-imports"]),
     .enableExperimentalFeature("Lifetimes"),
+    .enableExperimentalFeature("AnyAppleOSAvailability"),
     .enableUpcomingFeature("ExistentialAny"),
 ]
 
@@ -88,9 +89,6 @@ settings.append(.define("SHIM_CRYPTO_SPAN_APIS"))
 
 let package = Package(
     name: "swift-network-evolution",
-    platforms: [
-        .macOS("26.0"), .iOS("26.0"), .tvOS("26.0"), .watchOS("26.0"), .visionOS("26.0"),
-    ],
     products: [
         .library(
             name: "SwiftNetwork",
@@ -143,52 +141,52 @@ let package = Package(
         .target(
             name: "SwiftNetworkBenchmarks",
             dependencies: targetDependencies + ["SwiftNetwork"],
-            swiftSettings: settings
+            swiftSettings: availabilityMacros + settings
         ),
         .testTarget(
             name: "SwiftNetworkTests",
             dependencies: ["SwiftNetwork"],
-            swiftSettings: settings
+            swiftSettings: availabilityMacros + settings
         ),
         .testTarget(
             name: "QUICTests",
             dependencies: ["SwiftNetwork"],
-            swiftSettings: settings
+            swiftSettings: availabilityMacros + settings
         ),
         .executableTarget(
             name: "QUICHandshake",
             dependencies: ["SwiftNetwork", "SwiftNetworkBenchmarks"],
             path: "Sources/Tools/QUICHandshake",
             exclude: ["README.md"],
-            swiftSettings: settings,
+            swiftSettings: availabilityMacros + settings,
         ),
         .executableTarget(
             name: "IPUDPTransfer",
             dependencies: ["SwiftNetwork", "SwiftNetworkBenchmarks"],
             path: "Sources/Tools/IPUDPTransfer",
             exclude: ["README.md"],
-            swiftSettings: settings
+            swiftSettings: availabilityMacros + settings
         ),
         .executableTarget(
             name: "QUICTransfer",
             dependencies: ["SwiftNetwork", "SwiftNetworkBenchmarks"],
             path: "Sources/Tools/QUICTransfer",
             exclude: ["README.md"],
-            swiftSettings: settings
+            swiftSettings: availabilityMacros + settings
         ),
         .executableTarget(
             name: "QUICStreamLoad",
             dependencies: ["SwiftNetwork", "SwiftNetworkBenchmarks"],
             path: "Sources/Tools/QUICStreamLoad",
             exclude: ["README.md"],
-            swiftSettings: settings
+            swiftSettings: availabilityMacros + settings
         ),
         .executableTarget(
             name: "SocketTransfer",
             dependencies: ["SwiftNetwork", "SwiftNetworkBenchmarks"],
             path: "Sources/Tools/SocketTransfer",
             exclude: ["README.md"],
-            swiftSettings: settings
+            swiftSettings: availabilityMacros + settings
         ),
     ]
 )

Sources/SwiftNetwork/Connection/Connection.swift

@@ -92,6 +92,7 @@ public protocol NetworkProtocolOptions {
     func configure(parameters: Parameters)
 }
 
+@available(Network 0.1.0, *)
 extension NetworkProtocolOptions {
     public var belowProtocol: BelowProtocol {
         fatalError("This should not be called")

Sources/SwiftNetwork/Connection/DataTransferSnapshot.swift

@@ -13,6 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 #if !NETWORK_EMBEDDED
+@available(Network 0.1.0, *)
 struct DataTransferSnapshot: Equatable {
     var interfaceIndex: UInt64?
 

Sources/SwiftNetwork/Context/NetworkContext.swift

@@ -229,6 +229,7 @@ public final class NetworkContext: NetworkContextProtocol, @unchecked Sendable {
 // MARK: - Globals
 
 #if !NETWORK_PRIVATE && !NETWORK_STANDALONE && canImport(Dispatch) && !NETWORK_EMBEDDED
+@available(Network 0.1.0, *)
 extension NetworkContext {
     struct TimerEntry: ~Copyable, NetworkComparable {
         var targetTime: DispatchTime
@@ -369,6 +370,7 @@ extension NetworkContext {
 
 // MARK: - Async
 
+@available(Network 0.1.0, *)
 extension NetworkContext {
 
     var queue: DispatchQueue {
@@ -392,6 +394,7 @@ extension NetworkContext {
 
 // MARK: - Timers
 
+@available(Network 0.1.0, *)
 extension NetworkContext {
 
     enum FutureTime {

Sources/SwiftNetwork/Endpoint/EndpointCommon.swift

@@ -39,6 +39,7 @@ public struct EndpointEqualityFlags: OptionSet, Sendable {
     static public let all: EndpointEqualityFlags = [.interface, .parent, .proxyParent, .alternatives, .publicKeys]
 }
 
+@available(Network 0.1.0, *)
 extension Endpoint.EndpointType {
     enum EndpointRawType: UInt32 {
         case invalid = 0
@@ -81,6 +82,7 @@ extension Endpoint.EndpointType {
     }
 }
 
+@available(Network 0.1.0, *)
 protocol EndpointProtocol: CustomStringConvertible {
     var interface: Interface? { get }
     func isEqual(to other: Self, flags: EndpointEqualityFlags) -> Bool
@@ -132,13 +134,15 @@ public protocol EndpointCommonProtocol: Hashable, Equatable {
 }
 
 #if !NETWORK_PRIVATE
+@available(Network 0.1.0, *)
 extension EndpointCommonProtocol {
     var interface: Interface? {
         get { common.interface }
         set { common = EndpointCommon(interface: newValue) }
     }
 }
 
+@available(Network 0.1.0, *)
 extension EndpointCommon {
     init?(_ data: inout [UInt8]) {
         self.interface = nil

Sources/SwiftNetwork/Endpoint/EthernetAddress.swift

@@ -12,6 +12,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+@available(Network 0.1.0, *)
 public struct EthernetAddress: Hashable, CustomDebugStringConvertible {
 
     public static var broadcast: EthernetAddress {

Sources/SwiftNetwork/Endpoint/IPv6Address.swift

@@ -12,6 +12,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+@available(Network 0.1.0, *)
 public struct IPv6Address: IPAddress, Hashable, CustomDebugStringConvertible {
 
     /// The IPv6 "any" address.

Sources/SwiftNetwork/EndpointFlow/EndpointFlow.swift

@@ -28,6 +28,7 @@ internal import os
 internal import Synchronization
 #endif
 
+@available(Network 0.1.0, *)
 final class EndpointFlow: CustomDebugStringConvertible {
 
     /// State used to emit logs on the data path.

Sources/SwiftNetwork/EndpointFlow/EndpointFlowExtension.swift

@@ -19,11 +19,13 @@ internal import Logging
 internal import os
 #endif
 
+@available(Network 0.1.0, *)
 struct EndpointFlowPrivateStorage {
     func handleStateChange(_ state: EndpointFlow.State) {}
     mutating func initForReuse(_ flow: EndpointFlow) {}
 }
 
+@available(Network 0.1.0, *)
 extension EndpointFlow {
 
     internal func startOnQueue() throws(NetworkError) {

Sources/SwiftNetwork/EndpointFlow/EndpointFlowProtocols.swift

@@ -19,10 +19,12 @@ internal import Logging
 internal import os
 #endif
 
+@available(Network 0.1.0, *)
 protocol AbstractEndpointFlowProtocol: InboundDataHandler, LoggableProtocol {
     func teardown()
 }
 
+@available(Network 0.1.0, *)
 class EndpointFlowProtocol<LinkageType: InboundDataLinkage>: ProtocolInstanceContainer, AbstractEndpointFlowProtocol {
     typealias LowerProtocol = LinkageType.PairedLinkage
 
@@ -247,6 +249,7 @@ class EndpointFlowProtocol<LinkageType: InboundDataLinkage>: ProtocolInstanceCon
     }
 }
 
+@available(Network 0.1.0, *)
 final class DatagramEndpointFlowProtocol: EndpointFlowProtocol<InboundDatagramLinkage>, InboundDatagramHandler {
 
     override var reference: ProtocolInstanceReference { ProtocolInstanceReference(datagramEndpointFlow: self) }
@@ -375,6 +378,7 @@ final class DatagramEndpointFlowProtocol: EndpointFlowProtocol<InboundDatagramLi
     }
 }
 
+@available(Network 0.1.0, *)
 final class StreamEndpointFlowProtocol: EndpointFlowProtocol<InboundStreamLinkage>, InboundStreamHandler {
 
     override var reference: ProtocolInstanceReference { ProtocolInstanceReference(streamEndpointFlow: self) }

Sources/SwiftNetwork/EndpointFlow/ReadRequest.swift

@@ -12,6 +12,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+@available(Network 0.1.0, *)
 struct ReadRequest {
     let minimumBytes: Int
     let maximumBytes: Int

Sources/SwiftNetwork/EndpointFlow/WriteRequest.swift

@@ -23,6 +23,7 @@ internal import Logging
 internal import os
 #endif
 
+@available(Network 0.1.0, *)
 struct WriteRequest: ~Copyable {
     var frame: Frame
     let completion: (@Sendable (Result<Void, NetworkError>) -> Void)?

Sources/SwiftNetwork/Parameters/Parameters.swift

@@ -777,6 +777,7 @@ public struct Parameters: Hashable, CustomStringConvertible {
 
 // MARK: - Description
 
+@available(Network 0.1.0, *)
 extension Parameters {
     public var description: String {
         #if !NETWORK_EMBEDDED
@@ -880,6 +881,7 @@ extension Parameters {
 
 // MARK: - Accessors
 
+@available(Network 0.1.0, *)
 extension Parameters {
     var processUUID: SystemUUID {
         get { pathParameters.processPathValue.processUUID }

Sources/SwiftNetwork/Parameters/PathParameters.swift

@@ -24,6 +24,7 @@ internal import Logging
 internal import os
 #endif
 
+@available(Network 0.1.0, *)
 struct PathParameters: Hashable, CustomStringConvertible {
     struct ProcessPathValue: Hashable {
         // Parameters that influence path selection for process delegation, by value, that
@@ -364,6 +365,7 @@ struct PathParameters: Hashable, CustomStringConvertible {
 }
 
 // MARK: - Copying and comparing
+@available(Network 0.1.0, *)
 extension PathParameters {
     init(deepCopy other: PathParameters) {
         self = other
@@ -451,6 +453,7 @@ extension PathParameters {
 }
 
 // MARK: - Description and logging
+@available(Network 0.1.0, *)
 extension PathParameters {
     var description: String {
         #if !NETWORK_EMBEDDED

Sources/SwiftNetwork/Parameters/ProtocolTransform.swift

@@ -17,6 +17,7 @@ import BasicContainers
 internal import DequeModule
 #endif
 
+@available(Network 0.1.0, *)
 struct ProtocolTransform: Hashable {
     var transformStack: ProtocolStack?
     var trafficClass: UInt32?

Sources/SwiftNetwork/Path/Interface.swift

@@ -489,6 +489,7 @@ public struct Interface: Sendable, Hashable, CustomStringConvertible {
 }
 
 #if !NETWORK_EMBEDDED
+@available(Network 0.1.0, *)
 extension Interface: Codable {
     enum CodingKeys: String, CodingKey {
         case name
@@ -518,6 +519,7 @@ extension Interface: Codable {
     }
 }
 
+@available(Network 0.1.0, *)
 extension InterfaceType: Codable {
     enum CodingKeys: String, CodingKey {
         case value
@@ -535,6 +537,7 @@ extension InterfaceType: Codable {
     }
 }
 
+@available(Network 0.1.0, *)
 extension InterfaceSubtype: Codable {
     enum CodingKeys: String, CodingKey {
         case value

Sources/SwiftNetwork/Protocols/BottomProtocol.swift

@@ -168,6 +168,7 @@ where UpperProtocol == InboundDatagramLinkage {
 
 // MARK: - Bottom Protocol Implementation Details
 
+@available(Network 0.1.0, *)
 extension BottomProtocolHandler where Self: ~Copyable {
     var asLower: UpperProtocol.PairedLinkage { .init(reference: reference) }
 
@@ -256,6 +257,7 @@ extension BottomProtocolHandler where Self: ~Copyable {
 }
 
 // Default implementations, to be overridden as necessary
+@available(Network 0.1.0, *)
 extension BottomProtocolHandler where Self: ~Copyable {
     public func setup(
         remote: Endpoint?,
@@ -281,6 +283,7 @@ extension BottomProtocolHandler where Self: ~Copyable {
     #endif
 }
 
+@available(Network 0.1.0, *)
 extension BottomProtocolHandler where Self: ~Copyable, UpperProtocol == InboundDatagramLinkage {
     public mutating func attachUpperDatagramProtocol(
         _ from: ProtocolInstanceReference,
@@ -305,6 +308,7 @@ extension BottomProtocolHandler where Self: ~Copyable, UpperProtocol == InboundD
     }
 }
 
+@available(Network 0.1.0, *)
 extension BottomProtocolHandler where Self: ~Copyable, UpperProtocol == InboundStreamLinkage {
     public mutating func attachUpperStreamProtocol(
         _ from: ProtocolInstanceReference,
@@ -329,6 +333,7 @@ extension BottomProtocolHandler where Self: ~Copyable, UpperProtocol == InboundS
     }
 }
 
+@available(Network 0.1.0, *)
 extension BottomDatagramProtocol where Self: ~Copyable {
     public mutating func receiveDatagrams(
         _ from: ProtocolInstanceReference,
@@ -366,6 +371,7 @@ extension BottomDatagramProtocol where Self: ~Copyable {
     }
 }
 
+@available(Network 0.1.0, *)
 extension BottomStreamProtocol where Self: ~Copyable {
     public mutating func receiveStreamData(
         _ from: ProtocolInstanceReference,

Sources/SwiftNetwork/Protocols/Checksum.swift

@@ -54,6 +54,7 @@ enum ChecksumError: Error {
     case invalidBuffer
 }
 
+@available(Network 0.1.0, *)
 extension IPv6Address {
     func checksum() -> UInt32 {
         let address = self.addressValue
@@ -66,6 +67,7 @@ extension IPv6Address {
     }
 }
 
+@available(Network 0.1.0, *)
 struct Checksum: ~Copyable {
 
     // Compute IPv6 pseudo-header checksum
@@ -104,6 +106,7 @@ struct Checksum: ~Copyable {
     }
 }
 
+@available(Network 0.1.0, *)
 extension Frame {
     func checksum16(offset: Int, length: Int) throws(ChecksumError) -> UInt16 {
         let frameLength = self.unclaimedLength

Sources/SwiftNetwork/Protocols/CustomIPProtocol.swift

@@ -118,6 +118,7 @@ public struct CustomIPProtocol: NetworkProtocol {
     }
 }
 
+@available(Network 0.1.0, *)
 extension ProtocolOptions<CustomIPProtocol> {
     var ipProtocolNumber: UInt8 {
         get { perProtocolOptions!.ipProtocolNumber }