diff --git a/Package.swift b/Package.swift
index 49c8b2099..eb9bd297d 100644
--- a/Package.swift
+++ b/Package.swift
@@ -39,30 +39,41 @@ let package = Package(
         name: "SwiftProtobuf",
         exclude: ["CMakeLists.txt"],
         swiftSettings: [
+          .enableUpcomingFeature("ExistentialAny"),
           .enableExperimentalFeature("StrictConcurrency=complete"),
         ]
     ),
     .target(
         name: "SwiftProtobufPluginLibrary",
         dependencies: ["SwiftProtobuf"],
-        exclude: ["CMakeLists.txt"]
+        exclude: ["CMakeLists.txt"],
+        swiftSettings: [
+          .enableUpcomingFeature("ExistentialAny"),
+        ]
     ),
     .target(
         name: "SwiftProtobufTestHelpers",
         dependencies: ["SwiftProtobuf"],
         swiftSettings: [
+          .enableUpcomingFeature("ExistentialAny"),
           .enableExperimentalFeature("StrictConcurrency=complete"),
         ]
     ),
     .executableTarget(
         name: "protoc-gen-swift",
         dependencies: ["SwiftProtobufPluginLibrary", "SwiftProtobuf"],
-        exclude: ["CMakeLists.txt"]
+        exclude: ["CMakeLists.txt"],
+        swiftSettings: [
+          .enableUpcomingFeature("ExistentialAny")
+        ]
     ),
     .executableTarget(
         name: "Conformance",
         dependencies: ["SwiftProtobuf"],
-        exclude: ["failure_list_swift.txt", "text_format_failure_list_swift.txt"]
+        exclude: ["failure_list_swift.txt", "text_format_failure_list_swift.txt"],
+        swiftSettings: [
+          .enableUpcomingFeature("ExistentialAny"),
+        ]
     ),
     .plugin(
         name: "SwiftProtobufPlugin",
@@ -75,16 +86,25 @@ let package = Package(
         name: "SwiftProtobufTests",
         dependencies: ["SwiftProtobuf"],
         swiftSettings: [
+          .enableUpcomingFeature("ExistentialAny"),
           .enableExperimentalFeature("StrictConcurrency=complete"),
         ]
     ),
     .testTarget(
         name: "SwiftProtobufPluginLibraryTests",
-        dependencies: ["SwiftProtobufPluginLibrary", "SwiftProtobufTestHelpers"]
+        dependencies: ["SwiftProtobufPluginLibrary", "SwiftProtobufTestHelpers"],
+        swiftSettings: [
+          .enableUpcomingFeature("ExistentialAny"),
+          .enableExperimentalFeature("StrictConcurrency=complete"),
+        ]
     ),
     .testTarget(
         name: "protoc-gen-swiftTests",
-        dependencies: ["protoc-gen-swift", "SwiftProtobufTestHelpers"]
+        dependencies: ["protoc-gen-swift", "SwiftProtobufTestHelpers"],
+        swiftSettings: [
+          .enableUpcomingFeature("ExistentialAny"),
+          .enableExperimentalFeature("StrictConcurrency=complete"),
+        ]
     ),
   ],
   swiftLanguageVersions: [.v5]
diff --git a/Sources/Conformance/main.swift b/Sources/Conformance/main.swift
index 9b157c175..45c118a62 100644
--- a/Sources/Conformance/main.swift
+++ b/Sources/Conformance/main.swift
@@ -84,8 +84,8 @@ func buildResponse(serializedBytes: [UInt8]) -> Conformance_ConformanceResponse
         return response
     }
 
-    let msgType: SwiftProtobuf.Message.Type
-    let extensions: SwiftProtobuf.ExtensionMap
+    let msgType: any SwiftProtobuf.Message.Type
+    let extensions: any SwiftProtobuf.ExtensionMap
     switch request.messageType {
     case "":
         // Note: This case is here to cover using a old version of the conformance test
@@ -102,7 +102,7 @@ func buildResponse(serializedBytes: [UInt8]) -> Conformance_ConformanceResponse
         return response
     }
 
-    let testMessage: SwiftProtobuf.Message
+    let testMessage: any SwiftProtobuf.Message
     switch request.payload {
     case .protobufPayload(let data)?:
         do {
diff --git a/Sources/SwiftProtobuf/AnyMessageStorage.swift b/Sources/SwiftProtobuf/AnyMessageStorage.swift
index 0bcc30e49..a0d0586a0 100644
--- a/Sources/SwiftProtobuf/AnyMessageStorage.swift
+++ b/Sources/SwiftProtobuf/AnyMessageStorage.swift
@@ -16,14 +16,14 @@
 import Foundation
 
 fileprivate func serializeAnyJSON(
-  for message: Message,
+  for message: any Message,
   typeURL: String,
   options: JSONEncodingOptions
 ) throws -> String {
   var visitor = try JSONEncodingVisitor(type: type(of: message), options: options)
   visitor.startObject(message: message)
   visitor.encodeField(name: "@type", stringValue: typeURL)
-  if let m = message as? _CustomJSONCodable {
+  if let m = message as? (any _CustomJSONCodable) {
     let value = try m.encodedJSONString(options: options)
     visitor.encodeField(name: "value", jsonText: value)
   } else {
@@ -33,7 +33,7 @@ fileprivate func serializeAnyJSON(
   return visitor.stringResult
 }
 
-fileprivate func emitVerboseTextForm(visitor: inout TextFormatEncodingVisitor, message: Message, typeURL: String) {
+fileprivate func emitVerboseTextForm(visitor: inout TextFormatEncodingVisitor, message: any Message, typeURL: String) {
   let url: String
   if typeURL.isEmpty {
     url = buildTypeURL(forMessage: message, typePrefix: defaultAnyTypeURLPrefix)
@@ -53,10 +53,10 @@ fileprivate func asJSONObject(body: [UInt8]) -> Data {
 }
 
 fileprivate func unpack(contentJSON: [UInt8],
-                        extensions: ExtensionMap,
+                        extensions: any ExtensionMap,
                         options: JSONDecodingOptions,
-                        as messageType: Message.Type) throws -> Message {
-  guard messageType is _CustomJSONCodable.Type else {
+                        as messageType: any Message.Type) throws -> any Message {
+  guard messageType is any _CustomJSONCodable.Type else {
     let contentJSONAsObject = asJSONObject(body: contentJSON)
     return try messageType.init(jsonUTF8Bytes: contentJSONAsObject, extensions: extensions, options: options)
   }
@@ -135,7 +135,7 @@ internal class AnyMessageStorage {
     // unpacking that takes new options when a developer decides to decode it.
     case binary(Data)
     // a message
-    case message(Message)
+    case message(any Message)
     // parsed JSON with the @type removed and the decoding options.
     case contentJSON([UInt8], JSONDecodingOptions)
   }
@@ -162,7 +162,7 @@ internal class AnyMessageStorage {
   // replaced during the unpacking and never as a merge.
   func unpackTo<M: Message>(
     target: inout M,
-    extensions: ExtensionMap?,
+    extensions: (any ExtensionMap)?,
     options: BinaryDecodingOptions
   ) throws {
     guard isA(M.self) else {
diff --git a/Sources/SwiftProtobuf/AsyncMessageSequence.swift b/Sources/SwiftProtobuf/AsyncMessageSequence.swift
index 3c88aae75..cd7a743c1 100644
--- a/Sources/SwiftProtobuf/AsyncMessageSequence.swift
+++ b/Sources/SwiftProtobuf/AsyncMessageSequence.swift
@@ -34,7 +34,7 @@ extension AsyncSequence where Element == UInt8 {
   @inlinable
   public func binaryProtobufDelimitedMessages<M: Message>(
     of messageType: M.Type = M.self,
-    extensions: ExtensionMap? = nil,
+    extensions: (any ExtensionMap)? = nil,
     partial: Bool = false,
     options: BinaryDecodingOptions = BinaryDecodingOptions()
   ) -> AsyncMessageSequence<Self, M> {
@@ -58,7 +58,7 @@ public struct AsyncMessageSequence<
   public typealias Element = M
 
   private let base: Base
-  private let extensions: ExtensionMap?
+  private let extensions: (any ExtensionMap)?
   private let partial: Bool
   private let options: BinaryDecodingOptions
 
@@ -80,7 +80,7 @@ public struct AsyncMessageSequence<
   ///           messages.
   public init(
     base: Base,
-    extensions: ExtensionMap? = nil,
+    extensions: (any ExtensionMap)? = nil,
     partial: Bool = false,
     options: BinaryDecodingOptions = BinaryDecodingOptions()
   ) {
@@ -95,7 +95,7 @@ public struct AsyncMessageSequence<
     @usableFromInline
     var iterator: Base.AsyncIterator?
     @usableFromInline
-    let extensions: ExtensionMap?
+    let extensions: (any ExtensionMap)?
     @usableFromInline
     let partial: Bool
     @usableFromInline
@@ -103,7 +103,7 @@ public struct AsyncMessageSequence<
 
     init(
       iterator: Base.AsyncIterator,
-      extensions: ExtensionMap?,
+      extensions: (any ExtensionMap)?,
       partial: Bool,
       options: BinaryDecodingOptions
     ) {
diff --git a/Sources/SwiftProtobuf/BinaryDecoder.swift b/Sources/SwiftProtobuf/BinaryDecoder.swift
index 5377c00d1..849ad70de 100644
--- a/Sources/SwiftProtobuf/BinaryDecoder.swift
+++ b/Sources/SwiftProtobuf/BinaryDecoder.swift
@@ -33,7 +33,7 @@ internal struct BinaryDecoder: Decoder {
     // Field number for last-parsed field tag
     private var fieldNumber: Int = 0
     // Collection of extension fields for this decode
-    private var extensions: ExtensionMap?
+    private var extensions: (any ExtensionMap)?
     // The current group number. See decodeFullGroup(group:fieldNumber:) for how
     // this is used.
     private var groupFieldNumber: Int?
@@ -54,7 +54,7 @@ internal struct BinaryDecoder: Decoder {
       forReadingFrom pointer: UnsafeRawPointer,
       count: Int,
       options: BinaryDecodingOptions,
-      extensions: ExtensionMap? = nil
+      extensions: (any ExtensionMap)? = nil
     ) {
         // Assuming baseAddress is not nil.
         p = pointer
@@ -1088,7 +1088,7 @@ internal struct BinaryDecoder: Decoder {
 
     internal mutating func decodeExtensionField(
       values: inout ExtensionFieldValueSet,
-      messageType: Message.Type,
+      messageType: any Message.Type,
       fieldNumber: Int
     ) throws {
         if let ext = extensions?[messageType, fieldNumber] {
@@ -1102,9 +1102,9 @@ internal struct BinaryDecoder: Decoder {
     /// Helper to reuse between Extension decoding and MessageSet Extension decoding.
     private mutating func decodeExtensionField(
       values: inout ExtensionFieldValueSet,
-      messageType: Message.Type,
+      messageType: any Message.Type,
       fieldNumber: Int,
-      messageExtension ext: AnyMessageExtension
+      messageExtension ext: any AnyMessageExtension
     ) throws {
         assert(!consumed)
         assert(fieldNumber == ext.fieldNumber)
@@ -1129,7 +1129,7 @@ internal struct BinaryDecoder: Decoder {
 
     internal mutating func decodeExtensionFieldsAsMessageSet(
       values: inout ExtensionFieldValueSet,
-      messageType: Message.Type
+      messageType: any Message.Type
     ) throws {
         // Spin looking for the Item group, everything else will end up in unknown fields.
         while let fieldNumber = try self.nextFieldNumber() {
@@ -1173,14 +1173,14 @@ internal struct BinaryDecoder: Decoder {
 
     private mutating func decodeMessageSetItem(
       values: inout ExtensionFieldValueSet,
-      messageType: Message.Type
+      messageType: any Message.Type
     ) throws -> DecodeMessageSetItemResult {
         // This is loosely based on the C++:
         //   ExtensionSet::ParseMessageSetItem()
         //   WireFormat::ParseAndMergeMessageSetItem()
         // (yes, there have two versions that are almost the same)
 
-        var msgExtension: AnyMessageExtension?
+      var msgExtension: (any AnyMessageExtension)?
         var fieldData: Data?
 
         // In this loop, if wire types are wrong, things don't decode,
diff --git a/Sources/SwiftProtobuf/BinaryDelimited.swift b/Sources/SwiftProtobuf/BinaryDelimited.swift
index c8c83ab21..3edbae447 100644
--- a/Sources/SwiftProtobuf/BinaryDelimited.swift
+++ b/Sources/SwiftProtobuf/BinaryDelimited.swift
@@ -65,7 +65,7 @@ public enum BinaryDelimited {
   ///           `BinaryDelimited.Error` for some writing errors, or the
   ///           underlying `OutputStream.streamError` for a stream error.
   public static func serialize(
-    message: Message,
+    message: any Message,
     to stream: OutputStream,
     partial: Bool = false
   ) throws {
@@ -125,7 +125,7 @@ public enum BinaryDelimited {
   public static func parse<M: Message>(
     messageType: M.Type,
     from stream: InputStream,
-    extensions: ExtensionMap? = nil,
+    extensions: (any ExtensionMap)? = nil,
     partial: Bool = false,
     options: BinaryDecodingOptions = BinaryDecodingOptions()
   ) throws -> M {
@@ -166,7 +166,7 @@ public enum BinaryDelimited {
   public static func merge<M: Message>(
     into message: inout M,
     from stream: InputStream,
-    extensions: ExtensionMap? = nil,
+    extensions: (any ExtensionMap)? = nil,
     partial: Bool = false,
     options: BinaryDecodingOptions = BinaryDecodingOptions()
   ) throws {
diff --git a/Sources/SwiftProtobuf/Decoder.swift b/Sources/SwiftProtobuf/Decoder.swift
index 9291dd4a9..9fee303e0 100644
--- a/Sources/SwiftProtobuf/Decoder.swift
+++ b/Sources/SwiftProtobuf/Decoder.swift
@@ -204,11 +204,11 @@ public protocol Decoder {
   // Decode extension fields
 
   /// Decode an extension field
-  mutating func decodeExtensionField(values: inout ExtensionFieldValueSet, messageType: Message.Type, fieldNumber: Int) throws
+  mutating func decodeExtensionField(values: inout ExtensionFieldValueSet, messageType: any Message.Type, fieldNumber: Int) throws
 
   // Run a decode loop decoding the MessageSet format for Extensions.
   mutating func decodeExtensionFieldsAsMessageSet(values: inout ExtensionFieldValueSet,
-                                                  messageType: Message.Type) throws
+                                                  messageType: any Message.Type) throws
 }
 
 /// Most Decoders won't care about Extension handing as in MessageSet
@@ -217,7 +217,7 @@ public protocol Decoder {
 extension Decoder {
   public mutating func decodeExtensionFieldsAsMessageSet(
     values: inout ExtensionFieldValueSet,
-    messageType: Message.Type
+    messageType: any Message.Type
   ) throws {
     while let fieldNumber = try self.nextFieldNumber() {
       try self.decodeExtensionField(values: &values,
diff --git a/Sources/SwiftProtobuf/Enum.swift b/Sources/SwiftProtobuf/Enum.swift
index e5ed92bd1..fea4a7261 100644
--- a/Sources/SwiftProtobuf/Enum.swift
+++ b/Sources/SwiftProtobuf/Enum.swift
@@ -49,7 +49,7 @@ extension Enum {
   /// Since the text format and JSON names are always identical, we don't need
   /// to distinguish them.
   internal var name: _NameMap.Name? {
-    guard let nameProviding = Self.self as? _ProtoNameProviding.Type else {
+    guard let nameProviding = Self.self as? any _ProtoNameProviding.Type else {
       return nil
     }
     return nameProviding._protobuf_nameMap.names(for: rawValue)?.proto
@@ -63,7 +63,7 @@ extension Enum {
   ///
   /// - Parameter name: The name of the enum case.
   internal init?(name: String) {
-    guard let nameProviding = Self.self as? _ProtoNameProviding.Type,
+    guard let nameProviding = Self.self as? any _ProtoNameProviding.Type,
       let number = nameProviding._protobuf_nameMap.number(forJSONName: name) else {
       return nil
     }
@@ -78,7 +78,7 @@ extension Enum {
   ///
   /// - Parameter name: Buffer holding the UTF-8 bytes of the desired name.
   internal init?(rawUTF8: UnsafeRawBufferPointer) {
-    guard let nameProviding = Self.self as? _ProtoNameProviding.Type,
+    guard let nameProviding = Self.self as? any _ProtoNameProviding.Type,
       let number = nameProviding._protobuf_nameMap.number(forJSONName: rawUTF8) else {
       return nil
     }
diff --git a/Sources/SwiftProtobuf/ExtensionFieldValueSet.swift b/Sources/SwiftProtobuf/ExtensionFieldValueSet.swift
index 7d428416c..f429da4b4 100644
--- a/Sources/SwiftProtobuf/ExtensionFieldValueSet.swift
+++ b/Sources/SwiftProtobuf/ExtensionFieldValueSet.swift
@@ -15,7 +15,7 @@
 // -----------------------------------------------------------------------------
 
 public struct ExtensionFieldValueSet: Hashable, Sendable {
-  fileprivate var values = [Int : AnyExtensionField]()
+  fileprivate var values = [Int : any AnyExtensionField]()
 
   public static func ==(lhs: ExtensionFieldValueSet,
                         rhs: ExtensionFieldValueSet) -> Bool {
@@ -62,12 +62,12 @@ public struct ExtensionFieldValueSet: Hashable, Sendable {
     }
   }
 
-  public subscript(index: Int) -> AnyExtensionField? {
+  public subscript(index: Int) -> (any AnyExtensionField)? {
     get { return values[index] }
     set { values[index] = newValue }
   }
 
-  mutating func modify<ReturnType>(index: Int, _ modifier: (inout AnyExtensionField?) throws -> ReturnType) rethrows -> ReturnType {
+  mutating func modify<ReturnType>(index: Int, _ modifier: (inout (any AnyExtensionField)?) throws -> ReturnType) rethrows -> ReturnType {
     // This internal helper exists to invoke the _modify accessor on Dictionary for the given operation, which can avoid CoWs
     // during the modification operation.
     return try modifier(&values[index])
diff --git a/Sources/SwiftProtobuf/ExtensionFields.swift b/Sources/SwiftProtobuf/ExtensionFields.swift
index 07bddf152..f5c12c03a 100644
--- a/Sources/SwiftProtobuf/ExtensionFields.swift
+++ b/Sources/SwiftProtobuf/ExtensionFields.swift
@@ -24,8 +24,8 @@
 //
 public protocol AnyExtensionField: Sendable {
   func hash(into hasher: inout Hasher)
-  var protobufExtension: AnyMessageExtension { get }
-  func isEqual(other: AnyExtensionField) -> Bool
+  var protobufExtension: any AnyMessageExtension { get }
+  func isEqual(other: any AnyExtensionField) -> Bool
 
   /// Merging field decoding
   mutating func decodeExtensionField<T: Decoder>(decoder: inout T) throws
@@ -49,8 +49,8 @@ extension AnyExtensionField {
 public protocol ExtensionField: AnyExtensionField, Hashable, Sendable {
   associatedtype ValueType
   var value: ValueType { get set }
-  init(protobufExtension: AnyMessageExtension, value: ValueType)
-  init?<D: Decoder>(protobufExtension: AnyMessageExtension, decoder: inout D) throws
+  init(protobufExtension: any AnyMessageExtension, value: ValueType)
+  init?<D: Decoder>(protobufExtension: any AnyMessageExtension, decoder: inout D) throws
 }
 
 ///
@@ -60,14 +60,14 @@ public struct OptionalExtensionField<T: FieldType>: ExtensionField {
   public typealias BaseType = T.BaseType
   public typealias ValueType = BaseType
   public var value: ValueType
-  public var protobufExtension: AnyMessageExtension
+  public var protobufExtension: any AnyMessageExtension
 
   public static func ==(lhs: OptionalExtensionField,
                         rhs: OptionalExtensionField) -> Bool {
     return lhs.value == rhs.value
   }
 
-  public init(protobufExtension: AnyMessageExtension, value: ValueType) {
+  public init(protobufExtension: any AnyMessageExtension, value: ValueType) {
     self.protobufExtension = protobufExtension
     self.value = value
   }
@@ -76,7 +76,7 @@ public struct OptionalExtensionField<T: FieldType>: ExtensionField {
     hasher.combine(value)
   }
 
-  public func isEqual(other: AnyExtensionField) -> Bool {
+  public func isEqual(other: any AnyExtensionField) -> Bool {
     let o = other as! OptionalExtensionField<T>
     return self == o
   }
@@ -89,7 +89,7 @@ public struct OptionalExtensionField<T: FieldType>: ExtensionField {
       }
   }
 
-  public init?<D: Decoder>(protobufExtension: AnyMessageExtension, decoder: inout D) throws {
+  public init?<D: Decoder>(protobufExtension: any AnyMessageExtension, decoder: inout D) throws {
     var v: ValueType?
     try T.decodeSingular(value: &v, from: &decoder)
     if let v = v {
@@ -121,14 +121,14 @@ public struct RepeatedExtensionField<T: FieldType>: ExtensionField {
   public typealias BaseType = T.BaseType
   public typealias ValueType = [BaseType]
   public var value: ValueType
-  public var protobufExtension: AnyMessageExtension
+  public var protobufExtension: any AnyMessageExtension
 
   public static func ==(lhs: RepeatedExtensionField,
                         rhs: RepeatedExtensionField) -> Bool {
     return lhs.value == rhs.value
   }
 
-  public init(protobufExtension: AnyMessageExtension, value: ValueType) {
+  public init(protobufExtension: any AnyMessageExtension, value: ValueType) {
     self.protobufExtension = protobufExtension
     self.value = value
   }
@@ -137,7 +137,7 @@ public struct RepeatedExtensionField<T: FieldType>: ExtensionField {
     hasher.combine(value)
   }
 
-  public func isEqual(other: AnyExtensionField) -> Bool {
+  public func isEqual(other: any AnyExtensionField) -> Bool {
     let o = other as! RepeatedExtensionField<T>
     return self == o
   }
@@ -146,7 +146,7 @@ public struct RepeatedExtensionField<T: FieldType>: ExtensionField {
     try T.decodeRepeated(value: &value, from: &decoder)
   }
 
-  public init?<D: Decoder>(protobufExtension: AnyMessageExtension, decoder: inout D) throws {
+  public init?<D: Decoder>(protobufExtension: any AnyMessageExtension, decoder: inout D) throws {
     var v: ValueType = []
     try T.decodeRepeated(value: &v, from: &decoder)
     self.init(protobufExtension: protobufExtension, value: v)
@@ -177,14 +177,14 @@ public struct PackedExtensionField<T: FieldType>: ExtensionField {
   public typealias BaseType = T.BaseType
   public typealias ValueType = [BaseType]
   public var value: ValueType
-  public var protobufExtension: AnyMessageExtension
+  public var protobufExtension: any AnyMessageExtension
 
   public static func ==(lhs: PackedExtensionField,
                         rhs: PackedExtensionField) -> Bool {
     return lhs.value == rhs.value
   }
 
-  public init(protobufExtension: AnyMessageExtension, value: ValueType) {
+  public init(protobufExtension: any AnyMessageExtension, value: ValueType) {
     self.protobufExtension = protobufExtension
     self.value = value
   }
@@ -193,7 +193,7 @@ public struct PackedExtensionField<T: FieldType>: ExtensionField {
     hasher.combine(value)
   }
 
-  public func isEqual(other: AnyExtensionField) -> Bool {
+  public func isEqual(other: any AnyExtensionField) -> Bool {
     let o = other as! PackedExtensionField<T>
     return self == o
   }
@@ -202,7 +202,7 @@ public struct PackedExtensionField<T: FieldType>: ExtensionField {
     try T.decodeRepeated(value: &value, from: &decoder)
   }
 
-  public init?<D: Decoder>(protobufExtension: AnyMessageExtension, decoder: inout D) throws {
+  public init?<D: Decoder>(protobufExtension: any AnyMessageExtension, decoder: inout D) throws {
     var v: ValueType = []
     try T.decodeRepeated(value: &v, from: &decoder)
     self.init(protobufExtension: protobufExtension, value: v)
@@ -230,14 +230,14 @@ public struct OptionalEnumExtensionField<E: Enum>: ExtensionField where E.RawVal
   public typealias BaseType = E
   public typealias ValueType = E
   public var value: ValueType
-  public var protobufExtension: AnyMessageExtension
+  public var protobufExtension: any AnyMessageExtension
 
   public static func ==(lhs: OptionalEnumExtensionField,
                         rhs: OptionalEnumExtensionField) -> Bool {
     return lhs.value == rhs.value
   }
 
-  public init(protobufExtension: AnyMessageExtension, value: ValueType) {
+  public init(protobufExtension: any AnyMessageExtension, value: ValueType) {
     self.protobufExtension = protobufExtension
     self.value = value
   }
@@ -246,7 +246,7 @@ public struct OptionalEnumExtensionField<E: Enum>: ExtensionField where E.RawVal
     hasher.combine(value)
   }
 
-  public func isEqual(other: AnyExtensionField) -> Bool {
+  public func isEqual(other: any AnyExtensionField) -> Bool {
     let o = other as! OptionalEnumExtensionField<E>
     return self == o
   }
@@ -259,7 +259,7 @@ public struct OptionalEnumExtensionField<E: Enum>: ExtensionField where E.RawVal
       }
   }
 
-  public init?<D: Decoder>(protobufExtension: AnyMessageExtension, decoder: inout D) throws {
+  public init?<D: Decoder>(protobufExtension: any AnyMessageExtension, decoder: inout D) throws {
     var v: ValueType?
     try decoder.decodeSingularEnumField(value: &v)
     if let v = v {
@@ -293,14 +293,14 @@ public struct RepeatedEnumExtensionField<E: Enum>: ExtensionField where E.RawVal
   public typealias BaseType = E
   public typealias ValueType = [E]
   public var value: ValueType
-  public var protobufExtension: AnyMessageExtension
+  public var protobufExtension: any AnyMessageExtension
 
   public static func ==(lhs: RepeatedEnumExtensionField,
                         rhs: RepeatedEnumExtensionField) -> Bool {
     return lhs.value == rhs.value
   }
 
-  public init(protobufExtension: AnyMessageExtension, value: ValueType) {
+  public init(protobufExtension: any AnyMessageExtension, value: ValueType) {
     self.protobufExtension = protobufExtension
     self.value = value
   }
@@ -309,7 +309,7 @@ public struct RepeatedEnumExtensionField<E: Enum>: ExtensionField where E.RawVal
     hasher.combine(value)
   }
 
-  public func isEqual(other: AnyExtensionField) -> Bool {
+  public func isEqual(other: any AnyExtensionField) -> Bool {
     let o = other as! RepeatedEnumExtensionField<E>
     return self == o
   }
@@ -318,7 +318,7 @@ public struct RepeatedEnumExtensionField<E: Enum>: ExtensionField where E.RawVal
     try decoder.decodeRepeatedEnumField(value: &value)
   }
 
-  public init?<D: Decoder>(protobufExtension: AnyMessageExtension, decoder: inout D) throws {
+  public init?<D: Decoder>(protobufExtension: any AnyMessageExtension, decoder: inout D) throws {
     var v: ValueType = []
     try decoder.decodeRepeatedEnumField(value: &v)
     self.init(protobufExtension: protobufExtension, value: v)
@@ -351,14 +351,14 @@ public struct PackedEnumExtensionField<E: Enum>: ExtensionField where E.RawValue
   public typealias BaseType = E
   public typealias ValueType = [E]
   public var value: ValueType
-  public var protobufExtension: AnyMessageExtension
+  public var protobufExtension: any AnyMessageExtension
 
   public static func ==(lhs: PackedEnumExtensionField,
                         rhs: PackedEnumExtensionField) -> Bool {
     return lhs.value == rhs.value
   }
 
-  public init(protobufExtension: AnyMessageExtension, value: ValueType) {
+  public init(protobufExtension: any AnyMessageExtension, value: ValueType) {
     self.protobufExtension = protobufExtension
     self.value = value
   }
@@ -367,7 +367,7 @@ public struct PackedEnumExtensionField<E: Enum>: ExtensionField where E.RawValue
     hasher.combine(value)
   }
 
-  public func isEqual(other: AnyExtensionField) -> Bool {
+  public func isEqual(other: any AnyExtensionField) -> Bool {
     let o = other as! PackedEnumExtensionField<E>
     return self == o
   }
@@ -376,7 +376,7 @@ public struct PackedEnumExtensionField<E: Enum>: ExtensionField where E.RawValue
     try decoder.decodeRepeatedEnumField(value: &value)
   }
 
-  public init?<D: Decoder>(protobufExtension: AnyMessageExtension, decoder: inout D) throws {
+  public init?<D: Decoder>(protobufExtension: any AnyMessageExtension, decoder: inout D) throws {
     var v: ValueType = []
     try decoder.decodeRepeatedEnumField(value: &v)
     self.init(protobufExtension: protobufExtension, value: v)
@@ -407,14 +407,14 @@ public struct OptionalMessageExtensionField<M: Message & Equatable>:
   public typealias BaseType = M
   public typealias ValueType = BaseType
   public var value: ValueType
-  public var protobufExtension: AnyMessageExtension
+  public var protobufExtension: any AnyMessageExtension
 
   public static func ==(lhs: OptionalMessageExtensionField,
                         rhs: OptionalMessageExtensionField) -> Bool {
     return lhs.value == rhs.value
   }
 
-  public init(protobufExtension: AnyMessageExtension, value: ValueType) {
+  public init(protobufExtension: any AnyMessageExtension, value: ValueType) {
     self.protobufExtension = protobufExtension
     self.value = value
   }
@@ -423,7 +423,7 @@ public struct OptionalMessageExtensionField<M: Message & Equatable>:
     value.hash(into: &hasher)
   }
 
-  public func isEqual(other: AnyExtensionField) -> Bool {
+  public func isEqual(other: any AnyExtensionField) -> Bool {
     let o = other as! OptionalMessageExtensionField<M>
     return self == o
   }
@@ -436,7 +436,7 @@ public struct OptionalMessageExtensionField<M: Message & Equatable>:
     }
   }
 
-  public init?<D: Decoder>(protobufExtension: AnyMessageExtension, decoder: inout D) throws {
+  public init?<D: Decoder>(protobufExtension: any AnyMessageExtension, decoder: inout D) throws {
     var v: ValueType?
     try decoder.decodeSingularMessageField(value: &v)
     if let v = v {
@@ -471,14 +471,14 @@ public struct RepeatedMessageExtensionField<M: Message & Equatable>:
   public typealias BaseType = M
   public typealias ValueType = [BaseType]
   public var value: ValueType
-  public var protobufExtension: AnyMessageExtension
+  public var protobufExtension: any AnyMessageExtension
 
   public static func ==(lhs: RepeatedMessageExtensionField,
                         rhs: RepeatedMessageExtensionField) -> Bool {
     return lhs.value == rhs.value
   }
 
-  public init(protobufExtension: AnyMessageExtension, value: ValueType) {
+  public init(protobufExtension: any AnyMessageExtension, value: ValueType) {
     self.protobufExtension = protobufExtension
     self.value = value
   }
@@ -489,7 +489,7 @@ public struct RepeatedMessageExtensionField<M: Message & Equatable>:
     }
   }
 
-  public func isEqual(other: AnyExtensionField) -> Bool {
+  public func isEqual(other: any AnyExtensionField) -> Bool {
     let o = other as! RepeatedMessageExtensionField<M>
     return self == o
   }
@@ -498,7 +498,7 @@ public struct RepeatedMessageExtensionField<M: Message & Equatable>:
     try decoder.decodeRepeatedMessageField(value: &value)
   }
 
-  public init?<D: Decoder>(protobufExtension: AnyMessageExtension, decoder: inout D) throws {
+  public init?<D: Decoder>(protobufExtension: any AnyMessageExtension, decoder: inout D) throws {
     var v: ValueType = []
     try decoder.decodeRepeatedMessageField(value: &v)
     self.init(protobufExtension: protobufExtension, value: v)
@@ -535,14 +535,14 @@ public struct OptionalGroupExtensionField<G: Message & Hashable>:
   public typealias BaseType = G
   public typealias ValueType = BaseType
   public var value: G
-  public var protobufExtension: AnyMessageExtension
+  public var protobufExtension: any AnyMessageExtension
 
   public static func ==(lhs: OptionalGroupExtensionField,
                         rhs: OptionalGroupExtensionField) -> Bool {
     return lhs.value == rhs.value
   }
 
-  public init(protobufExtension: AnyMessageExtension, value: ValueType) {
+  public init(protobufExtension: any AnyMessageExtension, value: ValueType) {
     self.protobufExtension = protobufExtension
     self.value = value
   }
@@ -551,7 +551,7 @@ public struct OptionalGroupExtensionField<G: Message & Hashable>:
     hasher.combine(value)
   }
 
-  public func isEqual(other: AnyExtensionField) -> Bool {
+  public func isEqual(other: any AnyExtensionField) -> Bool {
     let o = other as! OptionalGroupExtensionField<G>
     return self == o
   }
@@ -564,7 +564,7 @@ public struct OptionalGroupExtensionField<G: Message & Hashable>:
     }
   }
 
-  public init?<D: Decoder>(protobufExtension: AnyMessageExtension, decoder: inout D) throws {
+  public init?<D: Decoder>(protobufExtension: any AnyMessageExtension, decoder: inout D) throws {
     var v: ValueType?
     try decoder.decodeSingularGroupField(value: &v)
     if let v = v {
@@ -599,14 +599,14 @@ public struct RepeatedGroupExtensionField<G: Message & Hashable>:
   public typealias BaseType = G
   public typealias ValueType = [BaseType]
   public var value: ValueType
-  public var protobufExtension: AnyMessageExtension
+  public var protobufExtension: any AnyMessageExtension
 
   public static func ==(lhs: RepeatedGroupExtensionField,
                         rhs: RepeatedGroupExtensionField) -> Bool {
     return lhs.value == rhs.value
   }
 
-  public init(protobufExtension: AnyMessageExtension, value: ValueType) {
+  public init(protobufExtension: any AnyMessageExtension, value: ValueType) {
     self.protobufExtension = protobufExtension
     self.value = value
   }
@@ -615,7 +615,7 @@ public struct RepeatedGroupExtensionField<G: Message & Hashable>:
     hasher.combine(value)
   }
 
-  public func isEqual(other: AnyExtensionField) -> Bool {
+  public func isEqual(other: any AnyExtensionField) -> Bool {
     let o = other as! RepeatedGroupExtensionField<G>
     return self == o
   }
@@ -624,7 +624,7 @@ public struct RepeatedGroupExtensionField<G: Message & Hashable>:
     try decoder.decodeRepeatedGroupField(value: &value)
   }
 
-  public init?<D: Decoder>(protobufExtension: AnyMessageExtension, decoder: inout D) throws {
+  public init?<D: Decoder>(protobufExtension: any AnyMessageExtension, decoder: inout D) throws {
     var v: ValueType = []
     try decoder.decodeRepeatedGroupField(value: &v)
     self.init(protobufExtension: protobufExtension, value: v)
diff --git a/Sources/SwiftProtobuf/ExtensionMap.swift b/Sources/SwiftProtobuf/ExtensionMap.swift
index bb98a5a02..ead2c1e67 100644
--- a/Sources/SwiftProtobuf/ExtensionMap.swift
+++ b/Sources/SwiftProtobuf/ExtensionMap.swift
@@ -24,7 +24,7 @@
 /// standard `SimpleExtensionMap` implementation.
 public protocol ExtensionMap: Sendable {
     /// Returns the extension object describing an extension or nil
-    subscript(messageType: Message.Type, fieldNumber: Int) -> AnyMessageExtension? { get }
+    subscript(messageType: any Message.Type, fieldNumber: Int) -> (any AnyMessageExtension)? { get }
 
     /// Returns the field number for a message with a specific field name
     ///
@@ -34,5 +34,5 @@ public protocol ExtensionMap: Sendable {
     /// for the proto file and `message` is the name of the message in
     /// which the extension was defined. (This is different from the
     /// message that is being extended!)
-    func fieldNumberForProto(messageType: Message.Type, protoFieldName: String) -> Int?
+    func fieldNumberForProto(messageType: any Message.Type, protoFieldName: String) -> Int?
 }
diff --git a/Sources/SwiftProtobuf/Google_Protobuf_Any+Extensions.swift b/Sources/SwiftProtobuf/Google_Protobuf_Any+Extensions.swift
index 2557140dd..7459934b8 100644
--- a/Sources/SwiftProtobuf/Google_Protobuf_Any+Extensions.swift
+++ b/Sources/SwiftProtobuf/Google_Protobuf_Any+Extensions.swift
@@ -38,7 +38,7 @@ extension Google_Protobuf_Any {
   /// - Throws: `BinaryEncodingError.missingRequiredFields` if `partial` is
   ///     false and `message` wasn't fully initialized.
   public init(
-    message: Message,
+    message: any Message,
     partial: Bool = false,
     typePrefix: String = defaultAnyTypeURLPrefix
   ) throws {
@@ -63,7 +63,7 @@ extension Google_Protobuf_Any {
   public init(
     textFormatString: String,
     options: TextFormatDecodingOptions = TextFormatDecodingOptions(),
-    extensions: ExtensionMap? = nil
+    extensions: (any ExtensionMap)? = nil
   ) throws {
     self.init()
     if !textFormatString.isEmpty {
diff --git a/Sources/SwiftProtobuf/Google_Protobuf_Any+Registry.swift b/Sources/SwiftProtobuf/Google_Protobuf_Any+Registry.swift
index 83e38d5f7..32eb1e84e 100644
--- a/Sources/SwiftProtobuf/Google_Protobuf_Any+Registry.swift
+++ b/Sources/SwiftProtobuf/Google_Protobuf_Any+Registry.swift
@@ -26,7 +26,7 @@ fileprivate let knownTypesQueue =
 // TODO: Should these first four be exposed as methods to go with
 // the general registry support?
 
-internal func buildTypeURL(forMessage message: Message, typePrefix: String) -> String {
+internal func buildTypeURL(forMessage message: any Message, typePrefix: String) -> String {
   var url = typePrefix
   let needsSlash = typePrefix.isEmpty || typePrefix.last != "/"
   if needsSlash {
@@ -35,7 +35,7 @@ internal func buildTypeURL(forMessage message: Message, typePrefix: String) -> S
   return url + typeName(fromMessage: message)
 }
 
-internal func typeName(fromMessage message: Message) -> String {
+internal func typeName(fromMessage message: any Message) -> String {
   let messageType = type(of: message)
   return messageType.protoMessageName
 }
@@ -67,7 +67,7 @@ fileprivate final class UnsafeMutableTransferBox<Wrapped> {
 extension UnsafeMutableTransferBox: @unchecked Sendable {}
 
 // All access to this should be done on `knownTypesQueue`.
-fileprivate let knownTypes: UnsafeMutableTransferBox<[String:Message.Type]> = .init([
+fileprivate let knownTypes: UnsafeMutableTransferBox<[String:any Message.Type]> = .init([
   // Seeded with the Well Known Types.
   "google.protobuf.Any": Google_Protobuf_Any.self,
   "google.protobuf.BoolValue": Google_Protobuf_BoolValue.self,
@@ -117,7 +117,7 @@ extension Google_Protobuf_Any {
     ///
     /// Returns: true if the type was registered, false if something
     ///   else was already registered for the messageName.
-    @discardableResult public static func register(messageType: Message.Type) -> Bool {
+    @discardableResult public static func register(messageType: any Message.Type) -> Bool {
         let messageTypeName = messageType.protoMessageName
         var result: Bool = false
         execute(flags: .barrier) {
@@ -136,14 +136,14 @@ extension Google_Protobuf_Any {
     }
 
     /// Returns the Message.Type expected for the given type URL.
-    public static func messageType(forTypeURL url: String) -> Message.Type? {
+    public static func messageType(forTypeURL url: String) -> (any Message.Type)? {
       let messageTypeName = typeName(fromURL: url)
       return messageType(forMessageName: messageTypeName)
     }
 
     /// Returns the Message.Type expected for the given proto message name.
-    public static func messageType(forMessageName name: String) -> Message.Type? {
-        var result: Message.Type?
+    public static func messageType(forMessageName name: String) -> (any Message.Type)? {
+        var result: (any Message.Type)?
         execute(flags: .none) {
             result = knownTypes.wrappedValue[name]
         }
diff --git a/Sources/SwiftProtobuf/Internal.swift b/Sources/SwiftProtobuf/Internal.swift
index 156dc062c..ec1c41c69 100644
--- a/Sources/SwiftProtobuf/Internal.swift
+++ b/Sources/SwiftProtobuf/Internal.swift
@@ -22,7 +22,7 @@ public enum Internal {
 
   /// Helper to loop over a list of Messages to see if they are all
   /// initialized (see Message.isInitialized for what that means).
-  public static func areAllInitialized(_ listOfMessages: [Message]) -> Bool {
+  public static func areAllInitialized(_ listOfMessages: [any Message]) -> Bool {
     for msg in listOfMessages {
       if !msg.isInitialized {
         return false
@@ -33,7 +33,7 @@ public enum Internal {
 
   /// Helper to loop over dictionary with values that are Messages to see if
   /// they are all initialized (see Message.isInitialized for what that means).
-  public static func areAllInitialized<K>(_ mapToMessages: [K: Message]) -> Bool {
+  public static func areAllInitialized<K>(_ mapToMessages: [K: any Message]) -> Bool {
     for (_, msg) in mapToMessages {
       if !msg.isInitialized {
         return false
diff --git a/Sources/SwiftProtobuf/JSONDecoder.swift b/Sources/SwiftProtobuf/JSONDecoder.swift
index 65bf0747a..0cd5274fd 100644
--- a/Sources/SwiftProtobuf/JSONDecoder.swift
+++ b/Sources/SwiftProtobuf/JSONDecoder.swift
@@ -16,7 +16,7 @@ import Foundation
 
 internal struct JSONDecoder: Decoder {
   internal var scanner: JSONScanner
-  internal var messageType: Message.Type
+  internal var messageType: any Message.Type
   private var fieldCount = 0
   private var isMapKey = false
   private var fieldNameMap: _NameMap?
@@ -30,14 +30,14 @@ internal struct JSONDecoder: Decoder {
   }
 
   internal init(source: UnsafeRawBufferPointer, options: JSONDecodingOptions,
-                messageType: Message.Type, extensions: ExtensionMap?) {
+                messageType: any Message.Type, extensions: (any ExtensionMap)?) {
     let scanner = JSONScanner(source: source,
                                options: options,
                                extensions: extensions)
     self.init(scanner: scanner, messageType: messageType)
   }
 
-  private init(scanner: JSONScanner, messageType: Message.Type) {
+  private init(scanner: JSONScanner, messageType: any Message.Type) {
     self.scanner = scanner
     self.messageType = messageType
   }
@@ -469,7 +469,7 @@ internal struct JSONDecoder: Decoder {
   mutating func decodeSingularEnumField<E: Enum>(value: inout E?) throws
   where E.RawValue == Int {
     if scanner.skipOptionalNull() {
-      if let customDecodable = E.self as? _CustomJSONCodable.Type {
+      if let customDecodable = E.self as? any _CustomJSONCodable.Type {
         value = try customDecodable.decodedFromJSONNull() as? E
         return
       }
@@ -485,7 +485,7 @@ internal struct JSONDecoder: Decoder {
   mutating func decodeSingularEnumField<E: Enum>(value: inout E) throws
   where E.RawValue == Int {
     if scanner.skipOptionalNull() {
-      if let customDecodable = E.self as? _CustomJSONCodable.Type {
+      if let customDecodable = E.self as? any _CustomJSONCodable.Type {
         value = try customDecodable.decodedFromJSONNull() as! E
         return
       }
@@ -507,7 +507,7 @@ internal struct JSONDecoder: Decoder {
     if scanner.skipOptionalArrayEnd() {
       return
     }
-    let maybeCustomDecodable = E.self as? _CustomJSONCodable.Type
+    let maybeCustomDecodable = E.self as? any _CustomJSONCodable.Type
     while true {
       if scanner.skipOptionalNull() {
         if let customDecodable = maybeCustomDecodable {
@@ -529,11 +529,11 @@ internal struct JSONDecoder: Decoder {
   }
 
   internal mutating func decodeFullObject<M: Message>(message: inout M) throws {
-    guard let nameProviding = (M.self as? _ProtoNameProviding.Type) else {
+    guard let nameProviding = (M.self as? any _ProtoNameProviding.Type) else {
       throw JSONDecodingError.missingFieldNames
     }
     fieldNameMap = nameProviding._protobuf_nameMap
-    if let m = message as? _CustomJSONCodable {
+    if let m = message as? (any _CustomJSONCodable) {
       var customCodable = m
       try customCodable.decodeJSON(from: &self)
       message = customCodable as! M
@@ -548,9 +548,9 @@ internal struct JSONDecoder: Decoder {
 
   mutating func decodeSingularMessageField<M: Message>(value: inout M?) throws {
     if scanner.skipOptionalNull() {
-      if M.self is _CustomJSONCodable.Type {
+      if M.self is any _CustomJSONCodable.Type {
         value =
-          try (M.self as! _CustomJSONCodable.Type).decodedFromJSONNull() as? M
+        try (M.self as! any _CustomJSONCodable.Type).decodedFromJSONNull() as? M
         return
       }
       // All other message field types treat 'null' as an unset
@@ -579,8 +579,8 @@ internal struct JSONDecoder: Decoder {
     while true {
       if scanner.skipOptionalNull() {
         var appended = false
-        if M.self is _CustomJSONCodable.Type {
-          if let message = try (M.self as! _CustomJSONCodable.Type)
+        if M.self is any _CustomJSONCodable.Type {
+          if let message = try (M.self as! any _CustomJSONCodable.Type)
             .decodedFromJSONNull() as? M {
             value.append(message)
             appended = true
@@ -730,7 +730,7 @@ internal struct JSONDecoder: Decoder {
 
   mutating func decodeExtensionField(
     values: inout ExtensionFieldValueSet,
-    messageType: Message.Type,
+    messageType: any Message.Type,
     fieldNumber: Int
   ) throws {
     // Force-unwrap: we can only get here if the extension exists.
diff --git a/Sources/SwiftProtobuf/JSONEncodingVisitor.swift b/Sources/SwiftProtobuf/JSONEncodingVisitor.swift
index db51d22e7..e1f06d8eb 100644
--- a/Sources/SwiftProtobuf/JSONEncodingVisitor.swift
+++ b/Sources/SwiftProtobuf/JSONEncodingVisitor.swift
@@ -34,8 +34,8 @@ internal struct JSONEncodingVisitor: Visitor {
 
   /// Creates a new visitor for serializing a message of the given type to JSON
   /// format.
-  init(type: Message.Type, options: JSONEncodingOptions) throws {
-    if let nameProviding = type as? _ProtoNameProviding.Type {
+  init(type: any Message.Type, options: JSONEncodingOptions) throws {
+    if let nameProviding = type as? any _ProtoNameProviding.Type {
       self.nameMap = nameProviding._protobuf_nameMap
     } else {
       throw JSONEncodingError.missingFieldNames
@@ -51,13 +51,13 @@ internal struct JSONEncodingVisitor: Visitor {
     encoder.endArray()
   }
 
-  mutating func startObject(message: Message) {
-    self.extensions = (message as? ExtensibleMessage)?._protobuf_extensionFieldValues
+  mutating func startObject(message: any Message) {
+    self.extensions = (message as? (any ExtensibleMessage))?._protobuf_extensionFieldValues
     encoder.startObject()
   }
 
-  mutating func startArrayObject(message: Message) {
-    self.extensions = (message as? ExtensibleMessage)?._protobuf_extensionFieldValues
+  mutating func startArrayObject(message: any Message) {
+    self.extensions = (message as? (any ExtensibleMessage))?._protobuf_extensionFieldValues
     encoder.startArrayObject()
   }
 
@@ -159,7 +159,7 @@ internal struct JSONEncodingVisitor: Visitor {
 
   mutating func visitSingularEnumField<E: Enum>(value: E, fieldNumber: Int) throws {
     try startField(for: fieldNumber)
-    if let e = value as? _CustomJSONCodable {
+    if let e = value as? (any _CustomJSONCodable) {
       let json = try e.encodedJSONString(options: options)
       encoder.append(text: json)
     } else if !options.alwaysPrintEnumsAsInts, let n = value.name {
@@ -171,10 +171,10 @@ internal struct JSONEncodingVisitor: Visitor {
 
   mutating func visitSingularMessageField<M: Message>(value: M, fieldNumber: Int) throws {
     try startField(for: fieldNumber)
-    if let m = value as? _CustomJSONCodable {
+    if let m = value as? (any _CustomJSONCodable) {
       let json = try m.encodedJSONString(options: options)
       encoder.append(text: json)
-    } else if let newNameMap = (M.self as? _ProtoNameProviding.Type)?._protobuf_nameMap {
+    } else if let newNameMap = (M.self as? any _ProtoNameProviding.Type)?._protobuf_nameMap {
       // Preserve outer object's name and extension maps; restore them before returning
       let oldNameMap = self.nameMap
       let oldExtensions = self.extensions
@@ -296,11 +296,11 @@ internal struct JSONEncodingVisitor: Visitor {
   }
 
   mutating func visitRepeatedEnumField<E: Enum>(value: [E], fieldNumber: Int) throws {
-    if let _ = E.self as? _CustomJSONCodable.Type {
+    if let _ = E.self as? any _CustomJSONCodable.Type {
       let options = self.options
       try _visitRepeated(value: value, fieldNumber: fieldNumber) {
         (encoder: inout JSONEncoder, v: E) throws in
-        let e = v as! _CustomJSONCodable
+        let e = v as! (any _CustomJSONCodable)
         let json = try e.encodedJSONString(options: options)
         encoder.append(text: json)
       }
@@ -322,7 +322,7 @@ internal struct JSONEncodingVisitor: Visitor {
     try startField(for: fieldNumber)
     var comma = false
     encoder.startArray()
-    if let _ = M.self as? _CustomJSONCodable.Type {
+    if let _ = M.self as? any _CustomJSONCodable.Type {
       for v in value {
         if comma {
           encoder.comma()
@@ -331,7 +331,7 @@ internal struct JSONEncodingVisitor: Visitor {
         let json = try v.jsonString(options: options)
         encoder.append(text: json)
       }
-    } else if let newNameMap = (M.self as? _ProtoNameProviding.Type)?._protobuf_nameMap {
+    } else if let newNameMap = (M.self as? any _ProtoNameProviding.Type)?._protobuf_nameMap {
       // Preserve name and extension maps for outer object
       let oldNameMap = self.nameMap
       let oldExtensions = self.extensions
diff --git a/Sources/SwiftProtobuf/JSONScanner.swift b/Sources/SwiftProtobuf/JSONScanner.swift
index 6e444481b..98c8c317b 100644
--- a/Sources/SwiftProtobuf/JSONScanner.swift
+++ b/Sources/SwiftProtobuf/JSONScanner.swift
@@ -374,7 +374,7 @@ internal struct JSONScanner {
   private var index: UnsafeRawBufferPointer.Index
   private var numberParser = DoubleParser()
   internal let options: JSONDecodingOptions
-  internal let extensions: ExtensionMap
+  internal let extensions: any ExtensionMap
   internal var recursionBudget: Int
 
   /// True if the scanner has read all of the data from the source, with the
@@ -400,7 +400,7 @@ internal struct JSONScanner {
   internal init(
     source: UnsafeRawBufferPointer,
     options: JSONDecodingOptions,
-    extensions: ExtensionMap?
+    extensions: (any ExtensionMap)?
   ) {
     self.source = source
     self.index = source.startIndex
@@ -1252,7 +1252,7 @@ internal struct JSONScanner {
   /// it silently skips it.
   internal mutating func nextFieldNumber(
     names: _NameMap,
-    messageType: Message.Type
+    messageType: any Message.Type
   ) throws -> Int? {
     while true {
       var fieldName: String
diff --git a/Sources/SwiftProtobuf/Message+AnyAdditions.swift b/Sources/SwiftProtobuf/Message+AnyAdditions.swift
index 67d317820..e8c31b3d6 100644
--- a/Sources/SwiftProtobuf/Message+AnyAdditions.swift
+++ b/Sources/SwiftProtobuf/Message+AnyAdditions.swift
@@ -36,7 +36,7 @@ extension Message {
   ///   `BinaryDecodingError` on failure.
   public init(
     unpackingAny: Google_Protobuf_Any,
-    extensions: ExtensionMap? = nil,
+    extensions: (any ExtensionMap)? = nil,
     options: BinaryDecodingOptions = BinaryDecodingOptions()
   ) throws {
     self.init()
diff --git a/Sources/SwiftProtobuf/Message+BinaryAdditions.swift b/Sources/SwiftProtobuf/Message+BinaryAdditions.swift
index 0e4128ec9..2580ed450 100644
--- a/Sources/SwiftProtobuf/Message+BinaryAdditions.swift
+++ b/Sources/SwiftProtobuf/Message+BinaryAdditions.swift
@@ -91,7 +91,7 @@ extension Message {
   @inlinable
   public init<Bytes: SwiftProtobufContiguousBytes>(
     serializedBytes bytes: Bytes,
-    extensions: ExtensionMap? = nil,
+    extensions: (any ExtensionMap)? = nil,
     partial: Bool = false,
     options: BinaryDecodingOptions = BinaryDecodingOptions()
   ) throws {
@@ -121,7 +121,7 @@ extension Message {
   @inlinable
   public mutating func merge<Bytes: SwiftProtobufContiguousBytes>(
     serializedBytes bytes: Bytes,
-    extensions: ExtensionMap? = nil,
+    extensions: (any ExtensionMap)? = nil,
     partial: Bool = false,
     options: BinaryDecodingOptions = BinaryDecodingOptions()
   ) throws {
@@ -137,7 +137,7 @@ extension Message {
   @usableFromInline
   internal mutating func _merge(
     rawBuffer body: UnsafeRawBufferPointer,
-    extensions: ExtensionMap?,
+    extensions: (any ExtensionMap)?,
     partial: Bool,
     options: BinaryDecodingOptions
   ) throws {
diff --git a/Sources/SwiftProtobuf/Message+BinaryAdditions_Data.swift b/Sources/SwiftProtobuf/Message+BinaryAdditions_Data.swift
index 247272f44..93cb1f3f2 100644
--- a/Sources/SwiftProtobuf/Message+BinaryAdditions_Data.swift
+++ b/Sources/SwiftProtobuf/Message+BinaryAdditions_Data.swift
@@ -33,7 +33,7 @@ extension Message {
   @inlinable
   public init(
     serializedData data: Data,
-    extensions: ExtensionMap? = nil,
+    extensions: (any ExtensionMap)? = nil,
     partial: Bool = false,
     options: BinaryDecodingOptions = BinaryDecodingOptions()
   ) throws {
@@ -63,7 +63,7 @@ extension Message {
   @inlinable
   public mutating func merge(
     serializedData data: Data,
-    extensions: ExtensionMap? = nil,
+    extensions: (any ExtensionMap)? = nil,
     partial: Bool = false,
     options: BinaryDecodingOptions = BinaryDecodingOptions()
   ) throws {
diff --git a/Sources/SwiftProtobuf/Message+JSONAdditions.swift b/Sources/SwiftProtobuf/Message+JSONAdditions.swift
index dc8127c97..8cc822696 100644
--- a/Sources/SwiftProtobuf/Message+JSONAdditions.swift
+++ b/Sources/SwiftProtobuf/Message+JSONAdditions.swift
@@ -28,7 +28,7 @@ extension Message {
   public func jsonString(
     options: JSONEncodingOptions = JSONEncodingOptions()
   ) throws -> String {
-    if let m = self as? _CustomJSONCodable {
+    if let m = self as? (any _CustomJSONCodable) {
       return try m.encodedJSONString(options: options)
     }
     let data: [UInt8] = try jsonUTF8Bytes(options: options)
@@ -47,7 +47,7 @@ extension Message {
   public func jsonUTF8Bytes<Bytes: SwiftProtobufContiguousBytes>(
     options: JSONEncodingOptions = JSONEncodingOptions()
   ) throws -> Bytes {
-    if let m = self as? _CustomJSONCodable {
+    if let m = self as? (any _CustomJSONCodable) {
       let string = try m.encodedJSONString(options: options)
       return Bytes(string.utf8)
     }
@@ -80,7 +80,7 @@ extension Message {
   /// - Throws: `JSONDecodingError` if decoding fails.
   public init(
     jsonString: String,
-    extensions: ExtensionMap? = nil,
+    extensions: (any ExtensionMap)? = nil,
     options: JSONDecodingOptions = JSONDecodingOptions()
   ) throws {
     if jsonString.isEmpty {
@@ -119,7 +119,7 @@ extension Message {
   /// - Throws: `JSONDecodingError` if decoding fails.
   public init<Bytes: SwiftProtobufContiguousBytes>(
     jsonUTF8Bytes: Bytes,
-    extensions: ExtensionMap? = nil,
+    extensions: (any ExtensionMap)? = nil,
     options: JSONDecodingOptions = JSONDecodingOptions()
   ) throws {
     self.init()
@@ -131,7 +131,7 @@ extension Message {
       var decoder = JSONDecoder(source: body, options: options,
                                 messageType: Self.self, extensions: extensions)
       if decoder.scanner.skipOptionalNull() {
-        if let customCodable = Self.self as? _CustomJSONCodable.Type,
+        if let customCodable = Self.self as? any _CustomJSONCodable.Type,
            let message = try customCodable.decodedFromJSONNull() {
           self = message as! Self
         } else {
diff --git a/Sources/SwiftProtobuf/Message+JSONAdditions_Data.swift b/Sources/SwiftProtobuf/Message+JSONAdditions_Data.swift
index a3d4b3bae..f12ef527b 100644
--- a/Sources/SwiftProtobuf/Message+JSONAdditions_Data.swift
+++ b/Sources/SwiftProtobuf/Message+JSONAdditions_Data.swift
@@ -40,7 +40,7 @@ extension Message {
   /// - Throws: `JSONDecodingError` if decoding fails.
   public init(
     jsonUTF8Data: Data,
-    extensions: ExtensionMap? = nil,
+    extensions: (any ExtensionMap)? = nil,
     options: JSONDecodingOptions = JSONDecodingOptions()
   ) throws {
     try self.init(jsonUTF8Bytes: jsonUTF8Data, extensions: extensions, options: options)
diff --git a/Sources/SwiftProtobuf/Message+JSONArrayAdditions.swift b/Sources/SwiftProtobuf/Message+JSONArrayAdditions.swift
index b18faa3a4..4c858649b 100644
--- a/Sources/SwiftProtobuf/Message+JSONArrayAdditions.swift
+++ b/Sources/SwiftProtobuf/Message+JSONArrayAdditions.swift
@@ -83,7 +83,7 @@ extension Message {
   /// - Throws: `JSONDecodingError` if decoding fails.
   public static func array(
     fromJSONString jsonString: String,
-    extensions: ExtensionMap = SimpleExtensionMap(),
+    extensions: any ExtensionMap = SimpleExtensionMap(),
     options: JSONDecodingOptions = JSONDecodingOptions()
   ) throws -> [Self] {
     if jsonString.isEmpty {
@@ -124,7 +124,7 @@ extension Message {
   /// - Throws: `JSONDecodingError` if decoding fails.
   public static func array<Bytes: SwiftProtobufContiguousBytes>(
     fromJSONUTF8Bytes jsonUTF8Bytes: Bytes,
-    extensions: ExtensionMap = SimpleExtensionMap(),
+    extensions: any ExtensionMap = SimpleExtensionMap(),
     options: JSONDecodingOptions = JSONDecodingOptions()
   ) throws -> [Self] {
     return try jsonUTF8Bytes.withUnsafeBytes { (body: UnsafeRawBufferPointer) in
diff --git a/Sources/SwiftProtobuf/Message+JSONArrayAdditions_Data.swift b/Sources/SwiftProtobuf/Message+JSONArrayAdditions_Data.swift
index f9f1fcfe2..2f770a2cc 100644
--- a/Sources/SwiftProtobuf/Message+JSONArrayAdditions_Data.swift
+++ b/Sources/SwiftProtobuf/Message+JSONArrayAdditions_Data.swift
@@ -44,7 +44,7 @@ extension Message {
   /// - Throws: `JSONDecodingError` if decoding fails.
   public static func array(
     fromJSONUTF8Data jsonUTF8Data: Data,
-    extensions: ExtensionMap = SimpleExtensionMap(),
+    extensions: any ExtensionMap = SimpleExtensionMap(),
     options: JSONDecodingOptions = JSONDecodingOptions()
   ) throws -> [Self] {
     return try array(fromJSONUTF8Bytes: jsonUTF8Data,
diff --git a/Sources/SwiftProtobuf/Message+TextFormatAdditions.swift b/Sources/SwiftProtobuf/Message+TextFormatAdditions.swift
index 926df2fa8..9ec430c85 100644
--- a/Sources/SwiftProtobuf/Message+TextFormatAdditions.swift
+++ b/Sources/SwiftProtobuf/Message+TextFormatAdditions.swift
@@ -67,7 +67,7 @@ extension Message {
   public init(
     textFormatString: String,
     options: TextFormatDecodingOptions = TextFormatDecodingOptions(),
-    extensions: ExtensionMap? = nil
+    extensions: (any ExtensionMap)? = nil
   ) throws {
     self.init()
     if !textFormatString.isEmpty {
diff --git a/Sources/SwiftProtobuf/Message.swift b/Sources/SwiftProtobuf/Message.swift
index b78f5d4bb..b619acfd3 100644
--- a/Sources/SwiftProtobuf/Message.swift
+++ b/Sources/SwiftProtobuf/Message.swift
@@ -109,7 +109,7 @@ public protocol Message: _CommonMessageConformances {
   /// Helper to compare `Message`s when not having a specific type to use
   /// normal `Equatable`. `Equatable` is provided with specific generated
   /// types.
-  func isEqualTo(message: Message) -> Bool
+  func isEqualTo(message: any Message) -> Bool
 }
 
 #if DEBUG
@@ -189,7 +189,7 @@ public protocol _MessageImplementationBase: Message, Hashable {
 }
 
 extension _MessageImplementationBase {
-  public func isEqualTo(message: Message) -> Bool {
+  public func isEqualTo(message: any Message) -> Bool {
     guard let other = message as? Self else {
       return false
     }
diff --git a/Sources/SwiftProtobuf/MessageExtension.swift b/Sources/SwiftProtobuf/MessageExtension.swift
index 300765414..80b5ac383 100644
--- a/Sources/SwiftProtobuf/MessageExtension.swift
+++ b/Sources/SwiftProtobuf/MessageExtension.swift
@@ -19,8 +19,8 @@
 public protocol AnyMessageExtension: Sendable {
     var fieldNumber: Int { get }
     var fieldName: String { get }
-    var messageType: Message.Type { get }
-    func _protobuf_newField<D: Decoder>(decoder: inout D) throws -> AnyExtensionField?
+    var messageType: any Message.Type { get }
+    func _protobuf_newField<D: Decoder>(decoder: inout D) throws -> (any AnyExtensionField)?
 }
 
 /// A "Message Extension" relates a particular extension field to
@@ -29,13 +29,13 @@ public protocol AnyMessageExtension: Sendable {
 public final class MessageExtension<FieldType: ExtensionField, MessageType: Message>: AnyMessageExtension {
     public let fieldNumber: Int
     public let fieldName: String
-    public let messageType: Message.Type
+    public let messageType: any Message.Type
     public init(_protobuf_fieldNumber: Int, fieldName: String) {
         self.fieldNumber = _protobuf_fieldNumber
         self.fieldName = fieldName
         self.messageType = MessageType.self
     }
-    public func _protobuf_newField<D: Decoder>(decoder: inout D) throws -> AnyExtensionField? {
+    public func _protobuf_newField<D: Decoder>(decoder: inout D) throws -> (any AnyExtensionField)? {
         return try FieldType(protobufExtension: self, decoder: &decoder)
     }
 }
diff --git a/Sources/SwiftProtobuf/SimpleExtensionMap.swift b/Sources/SwiftProtobuf/SimpleExtensionMap.swift
index c41bee8fd..5c7da6015 100644
--- a/Sources/SwiftProtobuf/SimpleExtensionMap.swift
+++ b/Sources/SwiftProtobuf/SimpleExtensionMap.swift
@@ -18,11 +18,11 @@ public struct SimpleExtensionMap: ExtensionMap, ExpressibleByArrayLiteral {
     public typealias Element = AnyMessageExtension
 
     // Since type objects aren't Hashable, we can't do much better than this...
-    internal var fields = [Int: Array<AnyMessageExtension>]()
+    internal var fields = [Int: Array<any AnyMessageExtension>]()
 
     public init() {}
 
-    public init(arrayLiteral: Element...) {
+    public init(arrayLiteral: any Element...) {
         insert(contentsOf: arrayLiteral)
     }
 
@@ -32,7 +32,7 @@ public struct SimpleExtensionMap: ExtensionMap, ExpressibleByArrayLiteral {
       }
     }
 
-    public subscript(messageType: Message.Type, fieldNumber: Int) -> AnyMessageExtension? {
+    public subscript(messageType: any Message.Type, fieldNumber: Int) -> (any AnyMessageExtension)? {
         get {
             if let l = fields[fieldNumber] {
                 for e in l {
@@ -45,7 +45,7 @@ public struct SimpleExtensionMap: ExtensionMap, ExpressibleByArrayLiteral {
         }
     }
 
-    public func fieldNumberForProto(messageType: Message.Type, protoFieldName: String) -> Int? {
+    public func fieldNumberForProto(messageType: any Message.Type, protoFieldName: String) -> Int? {
         // TODO: Make this faster...
         for (_, list) in fields {
             for e in list {
@@ -57,7 +57,7 @@ public struct SimpleExtensionMap: ExtensionMap, ExpressibleByArrayLiteral {
         return nil
     }
 
-    public mutating func insert(_ newValue: Element) {
+    public mutating func insert(_ newValue: any Element) {
         let fieldNumber = newValue.fieldNumber
         if let l = fields[fieldNumber] {
             let messageType = newValue.messageType
@@ -69,7 +69,7 @@ public struct SimpleExtensionMap: ExtensionMap, ExpressibleByArrayLiteral {
         }
     }
 
-    public mutating func insert(contentsOf: [Element]) {
+    public mutating func insert(contentsOf: [any Element]) {
         for e in contentsOf {
             insert(e)
         }
diff --git a/Sources/SwiftProtobuf/TextFormatDecoder.swift b/Sources/SwiftProtobuf/TextFormatDecoder.swift
index 1c99cf4e7..a51c95581 100644
--- a/Sources/SwiftProtobuf/TextFormatDecoder.swift
+++ b/Sources/SwiftProtobuf/TextFormatDecoder.swift
@@ -25,7 +25,7 @@ internal struct TextFormatDecoder: Decoder {
     private var fieldCount = 0
     private var terminator: UInt8?
     private var fieldNameMap: _NameMap?
-    private var messageType: Message.Type?
+    private var messageType: (any Message.Type)?
 
     internal var complete: Bool {
         mutating get {
@@ -34,24 +34,24 @@ internal struct TextFormatDecoder: Decoder {
     }
 
     internal init(
-      messageType: Message.Type,
+      messageType: any Message.Type,
       utf8Pointer: UnsafeRawPointer,
       count: Int,
       options: TextFormatDecodingOptions,
-      extensions: ExtensionMap?
+      extensions: (any ExtensionMap)?
     ) throws {
         scanner = TextFormatScanner(utf8Pointer: utf8Pointer, count: count, options: options, extensions: extensions)
-        guard let nameProviding = (messageType as? _ProtoNameProviding.Type) else {
+        guard let nameProviding = (messageType as? any _ProtoNameProviding.Type) else {
             throw TextFormatDecodingError.missingFieldNames
         }
         fieldNameMap = nameProviding._protobuf_nameMap
         self.messageType = messageType
     }
 
-    internal init(messageType: Message.Type, scanner: TextFormatScanner, terminator: UInt8?) throws {
+    internal init(messageType: any Message.Type, scanner: TextFormatScanner, terminator: UInt8?) throws {
         self.scanner = scanner
         self.terminator = terminator
-        guard let nameProviding = (messageType as? _ProtoNameProviding.Type) else {
+        guard let nameProviding = (messageType as? any _ProtoNameProviding.Type) else {
             throw TextFormatDecodingError.missingFieldNames
         }
         fieldNameMap = nameProviding._protobuf_nameMap
@@ -706,7 +706,7 @@ internal struct TextFormatDecoder: Decoder {
         }
     }
 
-    mutating func decodeExtensionField(values: inout ExtensionFieldValueSet, messageType: Message.Type, fieldNumber: Int) throws {
+    mutating func decodeExtensionField(values: inout ExtensionFieldValueSet, messageType: any Message.Type, fieldNumber: Int) throws {
         if let ext = scanner.extensions?[messageType, fieldNumber] {
             try values.modify(index: fieldNumber) { fieldValue in
                 if fieldValue != nil {
diff --git a/Sources/SwiftProtobuf/TextFormatEncodingVisitor.swift b/Sources/SwiftProtobuf/TextFormatEncodingVisitor.swift
index a82580727..a67953522 100644
--- a/Sources/SwiftProtobuf/TextFormatEncodingVisitor.swift
+++ b/Sources/SwiftProtobuf/TextFormatEncodingVisitor.swift
@@ -32,14 +32,14 @@ internal struct TextFormatEncodingVisitor: Visitor {
 
   /// Creates a new visitor that serializes the given message to protobuf text
   /// format.
-  init(message: Message, options: TextFormatEncodingOptions) {
+  init(message: any Message, options: TextFormatEncodingOptions) {
     let nameMap: _NameMap?
-    if let nameProviding = message as? _ProtoNameProviding {
+    if let nameProviding = message as? (any _ProtoNameProviding) {
         nameMap = type(of: nameProviding)._protobuf_nameMap
     } else {
         nameMap = nil
     }
-    let extensions = (message as? ExtensibleMessage)?._protobuf_extensionFieldValues
+    let extensions = (message as? (any ExtensibleMessage))?._protobuf_extensionFieldValues
 
     self.nameMap = nameMap
     self.nameResolver = [:]
@@ -270,9 +270,9 @@ internal struct TextFormatEncodingVisitor: Visitor {
       let oldNameResolver = self.nameResolver
       let oldExtensions = self.extensions
       // Update configuration for new message
-      self.nameMap = (M.self as? _ProtoNameProviding.Type)?._protobuf_nameMap
+    self.nameMap = (M.self as? any _ProtoNameProviding.Type)?._protobuf_nameMap
       self.nameResolver = [:]
-      self.extensions = (value as? ExtensibleMessage)?._protobuf_extensionFieldValues
+    self.extensions = (value as? (any ExtensibleMessage))?._protobuf_extensionFieldValues
       // Encode submessage
       encoder.startMessageField()
       if let any = value as? Google_Protobuf_Any {
@@ -290,7 +290,7 @@ internal struct TextFormatEncodingVisitor: Visitor {
   // Emit the full "verbose" form of an Any.  This writes the typeURL
   // as a field name in `[...]` followed by the fields of the
   // contained message.
-  internal mutating func visitAnyVerbose(value: Message, typeURL: String) {
+  internal mutating func visitAnyVerbose(value: any Message, typeURL: String) {
       encoder.emitExtensionFieldName(name: typeURL)
       encoder.startMessageField()
 
@@ -299,9 +299,9 @@ internal struct TextFormatEncodingVisitor: Visitor {
       let oldNameResolver = self.nameResolver
       let oldExtensions = self.extensions
       // Update configuration for new message
-      self.nameMap = (type(of: value) as? _ProtoNameProviding.Type)?._protobuf_nameMap
+    self.nameMap = (type(of: value) as? any _ProtoNameProviding.Type)?._protobuf_nameMap
       self.nameResolver = [:]
-      self.extensions = (value as? ExtensibleMessage)?._protobuf_extensionFieldValues
+    self.extensions = (value as? (any ExtensibleMessage))?._protobuf_extensionFieldValues
 
       if let any = value as? Google_Protobuf_Any {
           any.textTraverse(visitor: &self)
@@ -470,9 +470,9 @@ internal struct TextFormatEncodingVisitor: Visitor {
       let oldNameResolver = self.nameResolver
       let oldExtensions = self.extensions
       // Update encoding state for new message type
-      self.nameMap = (M.self as? _ProtoNameProviding.Type)?._protobuf_nameMap
+    self.nameMap = (M.self as? any _ProtoNameProviding.Type)?._protobuf_nameMap
       self.nameResolver = [:]
-      self.extensions = (value as? ExtensibleMessage)?._protobuf_extensionFieldValues
+    self.extensions = (value as? (any ExtensibleMessage))?._protobuf_extensionFieldValues
       // Iterate and encode each message
       for v in value {
           encoder.emitFieldName(name: fieldName)
diff --git a/Sources/SwiftProtobuf/TextFormatScanner.swift b/Sources/SwiftProtobuf/TextFormatScanner.swift
index e2bbbf6e8..f635087e3 100644
--- a/Sources/SwiftProtobuf/TextFormatScanner.swift
+++ b/Sources/SwiftProtobuf/TextFormatScanner.swift
@@ -232,7 +232,7 @@ private func decodeString(_ s: String) -> String? {
 /// TextFormatScanner has no public members.
 ///
 internal struct TextFormatScanner {
-    internal var extensions: ExtensionMap?
+    internal var extensions: (any ExtensionMap)?
     private var p: UnsafeRawPointer
     private var end: UnsafeRawPointer
     private var doubleParser = DoubleParser()
@@ -250,7 +250,7 @@ internal struct TextFormatScanner {
       utf8Pointer: UnsafeRawPointer,
       count: Int,
       options: TextFormatDecodingOptions,
-      extensions: ExtensionMap? = nil
+      extensions: (any ExtensionMap)? = nil
     ) {
         p = utf8Pointer
         end = p + count
diff --git a/Sources/SwiftProtobufPluginLibrary/CodeGenerator.swift b/Sources/SwiftProtobufPluginLibrary/CodeGenerator.swift
index c6fd4a00e..540bed519 100644
--- a/Sources/SwiftProtobufPluginLibrary/CodeGenerator.swift
+++ b/Sources/SwiftProtobufPluginLibrary/CodeGenerator.swift
@@ -37,9 +37,9 @@ public protocol CodeGenerator {
   ///       to the user attempting to generate sources.
   func generate(
     files: [FileDescriptor],
-    parameter: CodeGeneratorParameter,
-    protoCompilerContext: ProtoCompilerContext,
-    generatorOutputs: GeneratorOutputs) throws
+    parameter: any CodeGeneratorParameter,
+    protoCompilerContext: any ProtoCompilerContext,
+    generatorOutputs: any GeneratorOutputs) throws
 
   /// The list of features this CodeGenerator support to be reported back to
   /// the protocol buffer compiler.
@@ -161,7 +161,7 @@ extension CodeGenerator {
 ///    generation.
 public func generateCode(
   request: Google_Protobuf_Compiler_CodeGeneratorRequest,
-  generator: CodeGenerator
+  generator: any CodeGenerator
 ) -> Google_Protobuf_Compiler_CodeGeneratorResponse {
   // TODO: This will need update to support editions and language specific features.
 
diff --git a/Sources/protoc-gen-swift/GenerationError.swift b/Sources/protoc-gen-swift/GenerationError.swift
index eb67bf1a5..fbfedfcc0 100644
--- a/Sources/protoc-gen-swift/GenerationError.swift
+++ b/Sources/protoc-gen-swift/GenerationError.swift
@@ -14,7 +14,7 @@ enum GenerationError: Error {
   /// Raised when a parameter was given an invalid value.
   case invalidParameterValue(name: String, value: String)
   /// Raised to wrap another error but provide a context message.
-  case wrappedError(message: String, error: Error)
+  case wrappedError(message: String, error: any Error)
   /// Raised with an specific message
   case message(message: String)
 
diff --git a/Sources/protoc-gen-swift/GeneratorOptions.swift b/Sources/protoc-gen-swift/GeneratorOptions.swift
index 7b7b4bad7..6d875e2a6 100644
--- a/Sources/protoc-gen-swift/GeneratorOptions.swift
+++ b/Sources/protoc-gen-swift/GeneratorOptions.swift
@@ -57,7 +57,7 @@ class GeneratorOptions {
   /// A string snippet to insert for the visibility
   let visibilitySourceSnippet: String
 
-  init(parameter: CodeGeneratorParameter) throws {
+  init(parameter: any CodeGeneratorParameter) throws {
     var outputNaming: OutputNaming = .fullPath
     var moduleMapPath: String?
     var visibility: Visibility = .internal
diff --git a/Sources/protoc-gen-swift/MessageGenerator.swift b/Sources/protoc-gen-swift/MessageGenerator.swift
index f2dd6f0bf..9ef1a9729 100644
--- a/Sources/protoc-gen-swift/MessageGenerator.swift
+++ b/Sources/protoc-gen-swift/MessageGenerator.swift
@@ -25,8 +25,8 @@ class MessageGenerator {
   private let visibility: String
   private let swiftFullName: String
   private let swiftRelativeName: String
-  private let fields: [FieldGenerator]
-  private let fieldsSortedByNumber: [FieldGenerator]
+  private let fields: [any FieldGenerator]
+  private let fieldsSortedByNumber: [any FieldGenerator]
   private let oneofs: [OneofGenerator]
   private let storage: MessageStorageClassGenerator?
   private let enums: [EnumGenerator]
@@ -529,7 +529,7 @@ fileprivate struct MessageFieldFactory {
     oneofs = oneofGenerators
   }
 
-  func make(forFieldDescriptor field: FieldDescriptor) -> FieldGenerator {
+  func make(forFieldDescriptor field: FieldDescriptor) -> any FieldGenerator {
     guard field.realContainingOneof == nil else {
       return oneofs[Int(field.oneofIndex!)].fieldGenerator(forFieldNumber: Int(field.number))
     }
diff --git a/Sources/protoc-gen-swift/MessageStorageClassGenerator.swift b/Sources/protoc-gen-swift/MessageStorageClassGenerator.swift
index 5b3d22715..4a2e9cece 100644
--- a/Sources/protoc-gen-swift/MessageStorageClassGenerator.swift
+++ b/Sources/protoc-gen-swift/MessageStorageClassGenerator.swift
@@ -20,10 +20,10 @@ import SwiftProtobuf
 /// Generates the `_StorageClass` used for messages that employ copy-on-write
 /// logic for some of their fields.
 class MessageStorageClassGenerator {
-  private let fields: [FieldGenerator]
+  private let fields: [any FieldGenerator]
 
   /// Creates a new `MessageStorageClassGenerator`.
-  init(fields: [FieldGenerator]) {
+  init(fields: [any FieldGenerator]) {
     self.fields = fields
   }
 
diff --git a/Sources/protoc-gen-swift/OneofGenerator.swift b/Sources/protoc-gen-swift/OneofGenerator.swift
index da9db37aa..5c78b5bcd 100644
--- a/Sources/protoc-gen-swift/OneofGenerator.swift
+++ b/Sources/protoc-gen-swift/OneofGenerator.swift
@@ -188,7 +188,7 @@ class OneofGenerator {
         }
     }
 
-    func fieldGenerator(forFieldNumber fieldNumber: Int) -> FieldGenerator {
+    func fieldGenerator(forFieldNumber fieldNumber: Int) -> any FieldGenerator {
         for f in fields {
             if f.number == fieldNumber {
                 return f
diff --git a/Sources/protoc-gen-swift/SwiftGeneratorPlugin.swift b/Sources/protoc-gen-swift/SwiftGeneratorPlugin.swift
index c0f4e268e..942f1043e 100644
--- a/Sources/protoc-gen-swift/SwiftGeneratorPlugin.swift
+++ b/Sources/protoc-gen-swift/SwiftGeneratorPlugin.swift
@@ -25,9 +25,9 @@ struct SwiftGeneratorPlugin: CodeGenerator {
 
   func generate(
     files: [SwiftProtobufPluginLibrary.FileDescriptor],
-    parameter: CodeGeneratorParameter,
-    protoCompilerContext: SwiftProtobufPluginLibrary.ProtoCompilerContext,
-    generatorOutputs: SwiftProtobufPluginLibrary.GeneratorOutputs
+    parameter: any CodeGeneratorParameter,
+    protoCompilerContext: any SwiftProtobufPluginLibrary.ProtoCompilerContext,
+    generatorOutputs: any SwiftProtobufPluginLibrary.GeneratorOutputs
   ) throws {
     let options = try GeneratorOptions(parameter: parameter)
 
@@ -54,7 +54,7 @@ struct SwiftGeneratorPlugin: CodeGenerator {
   var copyrightLine: String? { return "\(Version.copyright)" }
   var projectURL: String? { return "https://github.com/apple/swift-protobuf" }
 
-  private func auditProtoCVersion(context: SwiftProtobufPluginLibrary.ProtoCompilerContext) {
+  private func auditProtoCVersion(context: any SwiftProtobufPluginLibrary.ProtoCompilerContext) {
     guard context.version != nil else {
       Stderr.print("WARNING: unknown version of protoc, use 3.2.x or later to ensure JSON support is correct.")
       return
diff --git a/Tests/SwiftProtobufTests/TestHelpers.swift b/Tests/SwiftProtobufTests/TestHelpers.swift
index 4eedd1027..12f795ff6 100644
--- a/Tests/SwiftProtobufTests/TestHelpers.swift
+++ b/Tests/SwiftProtobufTests/TestHelpers.swift
@@ -134,7 +134,7 @@ extension PBTestHelpers where MessageTestType: SwiftProtobuf.Message & Equatable
 
     }
 
-    func assertJSONEncode(_ expected: String, extensions: ExtensionMap = SimpleExtensionMap(), encodingOptions: JSONEncodingOptions = .init(), file: XCTestFileArgType = #file, line: UInt = #line, configure: (inout MessageTestType) -> Void) {
+    func assertJSONEncode(_ expected: String, extensions: any ExtensionMap = SimpleExtensionMap(), encodingOptions: JSONEncodingOptions = .init(), file: XCTestFileArgType = #file, line: UInt = #line, configure: (inout MessageTestType) -> Void) {
         let empty = MessageTestType()
         var configured = empty
         configure(&configured)
@@ -173,7 +173,7 @@ extension PBTestHelpers where MessageTestType: SwiftProtobuf.Message & Equatable
     /// This uses the provided block to initialize the object, then:
     /// * Encodes the object and checks that the result is the expected result
     /// * Decodes it again and verifies that the round-trip gives an equal object
-    func assertTextFormatEncode(_ expected: String, extensions: ExtensionMap? = nil, file: XCTestFileArgType = #file, line: UInt = #line, configure: (inout MessageTestType) -> Void) {
+    func assertTextFormatEncode(_ expected: String, extensions: (any ExtensionMap)? = nil, file: XCTestFileArgType = #file, line: UInt = #line, configure: (inout MessageTestType) -> Void) {
         let empty = MessageTestType()
         var configured = empty
         configure(&configured)
@@ -191,7 +191,7 @@ extension PBTestHelpers where MessageTestType: SwiftProtobuf.Message & Equatable
 
     func assertJSONArrayEncode(
         _ expected: String,
-        extensions: ExtensionMap = SimpleExtensionMap(),
+        extensions: any ExtensionMap = SimpleExtensionMap(),
         file: XCTestFileArgType = #file,
         line: UInt = #line,
         configure: (inout [MessageTestType]) -> Void
@@ -218,7 +218,7 @@ extension PBTestHelpers where MessageTestType: SwiftProtobuf.Message & Equatable
     func assertJSONDecodeSucceeds(
         _ json: String,
         options: JSONDecodingOptions = JSONDecodingOptions(),
-        extensions: ExtensionMap = SimpleExtensionMap(),
+        extensions: any ExtensionMap = SimpleExtensionMap(),
         file: XCTestFileArgType = #file,
         line: UInt = #line,
         check: (MessageTestType) -> Bool
@@ -326,7 +326,7 @@ extension PBTestHelpers where MessageTestType: SwiftProtobuf.Message & Equatable
 
     func assertJSONDecodeFails(
         _ json: String,
-        extensions: ExtensionMap = SimpleExtensionMap(),
+        extensions: any ExtensionMap = SimpleExtensionMap(),
         options: JSONDecodingOptions = JSONDecodingOptions(),
         file: XCTestFileArgType = #file,
         line: UInt = #line
@@ -358,7 +358,7 @@ extension PBTestHelpers where MessageTestType: SwiftProtobuf.Message & Equatable
 
     func assertJSONArrayDecodeFails(
         _ json: String,
-        extensions: ExtensionMap = SimpleExtensionMap(),
+        extensions: any ExtensionMap = SimpleExtensionMap(),
         file: XCTestFileArgType = #file,
         line: UInt = #line
     ) {
@@ -382,7 +382,7 @@ extension PBTestHelpers where MessageTestType: SwiftProtobuf.Message & Equatable
 }
 
 extension XCTestCase {
-    func assertDebugDescription(_ expected: String, _ m: SwiftProtobuf.Message, fmt: String? = nil, file: XCTestFileArgType = #file, line: UInt = #line) {
+    func assertDebugDescription(_ expected: String, _ m: any SwiftProtobuf.Message, fmt: String? = nil, file: XCTestFileArgType = #file, line: UInt = #line) {
         // `assertDebugDescription` is a no-op in release as `debugDescription` is unavailable.
         #if DEBUG
         let actual = m.debugDescription
@@ -392,7 +392,7 @@ extension XCTestCase {
     /// Like ``assertDebugDescription``, but only checks the the ``debugDescription`` ends with
     /// ``expectedSuffix``, mainly useful where you want to be agnotics to some preable like
     /// the module name.
-    func assertDebugDescriptionSuffix(_ expectedSuffix: String, _ m: SwiftProtobuf.Message, fmt: String? = nil, file: XCTestFileArgType = #file, line: UInt = #line) {
+    func assertDebugDescriptionSuffix(_ expectedSuffix: String, _ m: any SwiftProtobuf.Message, fmt: String? = nil, file: XCTestFileArgType = #file, line: UInt = #line) {
         // `assertDebugDescriptionSuffix` is a no-op in release as `debugDescription` is unavailable.
 #if DEBUG
         let actual = m.debugDescription
diff --git a/Tests/SwiftProtobufTests/Test_Any.swift b/Tests/SwiftProtobufTests/Test_Any.swift
index bd1bdda6f..602c81ac5 100644
--- a/Tests/SwiftProtobufTests/Test_Any.swift
+++ b/Tests/SwiftProtobufTests/Test_Any.swift
@@ -795,7 +795,7 @@ final class Test_Any: XCTestCase {
       XCTAssertNil(Google_Protobuf_Any.messageType(forMessageName: SwiftProtoTesting_TestMap.protoMessageName))
 
       // All the WKTs should be registered.
-      let wkts: [Message.Type] = [
+      let wkts: [any Message.Type] = [
         Google_Protobuf_Any.self,
         Google_Protobuf_BoolValue.self,
         Google_Protobuf_BytesValue.self,
diff --git a/Tests/SwiftProtobufTests/Test_AsyncMessageSequence.swift b/Tests/SwiftProtobufTests/Test_AsyncMessageSequence.swift
index 9304ab310..4c86dc22a 100644
--- a/Tests/SwiftProtobufTests/Test_AsyncMessageSequence.swift
+++ b/Tests/SwiftProtobufTests/Test_AsyncMessageSequence.swift
@@ -229,7 +229,7 @@ final class Test_AsyncMessageSequence: XCTestCase {
       }
   }
 
-  fileprivate func serializedMessageData(messages: [Message]) throws -> [UInt8] {
+  fileprivate func serializedMessageData(messages: [any Message]) throws -> [UInt8] {
     let memoryOutputStream = OutputStream.toMemory()
     memoryOutputStream.open()
     for message in messages {
diff --git a/Tests/SwiftProtobufTests/Test_BinaryDecodingOptions.swift b/Tests/SwiftProtobufTests/Test_BinaryDecodingOptions.swift
index 207cd4522..cebfbb8a3 100644
--- a/Tests/SwiftProtobufTests/Test_BinaryDecodingOptions.swift
+++ b/Tests/SwiftProtobufTests/Test_BinaryDecodingOptions.swift
@@ -20,7 +20,7 @@ final class Test_BinaryDecodingOptions: XCTestCase {
 
     func testMessageDepthLimit() throws {
 
-        let tests: [([UInt8], Message.Type, ExtensionMap?, [(Int, Bool)])] = [
+        let tests: [([UInt8], any Message.Type, (any ExtensionMap)?, [(Int, Bool)])] = [
             // Input, (Limit, success/failure)
 
             // Messages within messages:     // outer is msg 1
diff --git a/Tests/SwiftProtobufTests/Test_SimpleExtensionMap.swift b/Tests/SwiftProtobufTests/Test_SimpleExtensionMap.swift
index 606ce1663..50f2c2650 100644
--- a/Tests/SwiftProtobufTests/Test_SimpleExtensionMap.swift
+++ b/Tests/SwiftProtobufTests/Test_SimpleExtensionMap.swift
@@ -18,7 +18,7 @@ import XCTest
 
 extension AnyMessageExtension {
   // Support equality to simplify testing of getting the correct errors.
-  func isEqual(_ other: AnyMessageExtension) -> Bool {
+  func isEqual(_ other: any AnyMessageExtension) -> Bool {
     return (fieldNumber == other.fieldNumber &&
       fieldName == other.fieldName &&
       messageType == other.messageType)
@@ -51,9 +51,9 @@ let ext4 = MessageExtension<OptionalExtensionField<ProtobufBool>, SwiftProtoTest
 
 
 final class Test_SimpleExtensionMap: XCTestCase {
-  func assert(map: SimpleExtensionMap, contains: [AnyMessageExtension], line: UInt = #line) {
+  func assert(map: SimpleExtensionMap, contains: [any AnyMessageExtension], line: UInt = #line) {
     // Extact what it constaings.
-    var includes = [AnyMessageExtension]()
+    var includes = [any AnyMessageExtension]()
     for (_, l) in map.fields {
       for e in l {
         includes.append(e)
diff --git a/Tests/SwiftProtobufTests/Test_Unknown_proto2.swift b/Tests/SwiftProtobufTests/Test_Unknown_proto2.swift
index dab869df7..23c1f3b2b 100644
--- a/Tests/SwiftProtobufTests/Test_Unknown_proto2.swift
+++ b/Tests/SwiftProtobufTests/Test_Unknown_proto2.swift
@@ -159,7 +159,7 @@ final class Test_Unknown_proto2: XCTestCase, PBTestHelpers {
     }
 
 
-    func assertUnknownFields(_ message: Message, _ bytes: [UInt8], line: UInt = #line) {
+    func assertUnknownFields(_ message: any Message, _ bytes: [UInt8], line: UInt = #line) {
         XCTAssertEqual(message.unknownFields.data, Data(bytes), line: line)
     }
 
diff --git a/Tests/SwiftProtobufTests/Test_Unknown_proto3.swift b/Tests/SwiftProtobufTests/Test_Unknown_proto3.swift
index e086cc5bc..47f6ac1d5 100644
--- a/Tests/SwiftProtobufTests/Test_Unknown_proto3.swift
+++ b/Tests/SwiftProtobufTests/Test_Unknown_proto3.swift
@@ -161,7 +161,7 @@ final class Test_Unknown_proto3: XCTestCase, PBTestHelpers {
     }
 
 
-    func assertUnknownFields(_ message: Message, _ bytes: [UInt8], line: UInt = #line) {
+    func assertUnknownFields(_ message: any Message, _ bytes: [UInt8], line: UInt = #line) {
         XCTAssertEqual(message.unknownFields.data, Data(bytes), line: line)
     }