diff --git a/Coder Desktop/Coder Desktop.xcodeproj/project.pbxproj b/Coder Desktop/Coder Desktop.xcodeproj/project.pbxproj
index 223b83f..e5ae28b 100644
--- a/Coder Desktop/Coder Desktop.xcodeproj/project.pbxproj	
+++ b/Coder Desktop/Coder Desktop.xcodeproj/project.pbxproj	
@@ -660,7 +660,7 @@
 				PRODUCT_BUNDLE_IDENTIFIER = "com.coder.Coder-Desktop";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SWIFT_EMIT_LOC_STRINGS = YES;
-				SWIFT_VERSION = 5.0;
+				SWIFT_VERSION = 6.0;
 			};
 			name = Debug;
 		};
@@ -690,7 +690,7 @@
 				PRODUCT_BUNDLE_IDENTIFIER = "com.coder.Coder-Desktop";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SWIFT_EMIT_LOC_STRINGS = YES;
-				SWIFT_VERSION = 5.0;
+				SWIFT_VERSION = 6.0;
 			};
 			name = Release;
 		};
@@ -835,7 +835,7 @@
 				PRODUCT_BUNDLE_IDENTIFIER = "com.coder.Coder-Desktop.ProtoTests";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SWIFT_EMIT_LOC_STRINGS = NO;
-				SWIFT_VERSION = 5.0;
+				SWIFT_VERSION = 6.0;
 				TEST_HOST = "$(BUILT_PRODUCTS_DIR)/Coder Desktop.app/$(BUNDLE_EXECUTABLE_FOLDER_PATH)/Coder Desktop";
 			};
 			name = Debug;
@@ -853,7 +853,7 @@
 				PRODUCT_BUNDLE_IDENTIFIER = "com.coder.Coder-Desktop.ProtoTests";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SWIFT_EMIT_LOC_STRINGS = NO;
-				SWIFT_VERSION = 5.0;
+				SWIFT_VERSION = 6.0;
 				TEST_HOST = "$(BUILT_PRODUCTS_DIR)/Coder Desktop.app/$(BUNDLE_EXECUTABLE_FOLDER_PATH)/Coder Desktop";
 			};
 			name = Release;
diff --git a/Coder Desktop/Coder Desktop.xcodeproj/xcshareddata/xcschemes/ProtoTests.xcscheme b/Coder Desktop/Coder Desktop.xcodeproj/xcshareddata/xcschemes/ProtoTests.xcscheme
index 3366121..556492f 100644
--- a/Coder Desktop/Coder Desktop.xcodeproj/xcshareddata/xcschemes/ProtoTests.xcscheme	
+++ b/Coder Desktop/Coder Desktop.xcodeproj/xcshareddata/xcschemes/ProtoTests.xcscheme	
@@ -54,6 +54,15 @@
       savedToolIdentifier = ""
       useCustomWorkingDirectory = "NO"
       debugDocumentVersioning = "YES">
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "961678FB2CFF100D00B2B6DF"
+            BuildableName = "Coder Desktop.app"
+            BlueprintName = "Coder Desktop"
+            ReferencedContainer = "container:Coder Desktop.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
    </ProfileAction>
    <AnalyzeAction
       buildConfiguration = "Debug">
diff --git a/Coder Desktop/Proto/Receiver.swift b/Coder Desktop/Proto/Receiver.swift
index 74a85cb..6a279e6 100644
--- a/Coder Desktop/Proto/Receiver.swift	
+++ b/Coder Desktop/Proto/Receiver.swift	
@@ -22,7 +22,7 @@ actor Receiver<RecvMsg: Message> {
             dispatch.read(offset: 0, length: 4, queue: queue) { done, data, error in
                 guard error == 0 else {
                     let errStrPtr = strerror(error)
-                    let errStr = String(validatingUTF8: errStrPtr!)!
+                    let errStr = String(validatingCString: errStrPtr!)!
                     continuation.resume(throwing: ReceiveError.readError(errStr))
                     return
                 }
@@ -42,7 +42,7 @@ actor Receiver<RecvMsg: Message> {
             dispatch.read(offset: 0, length: Int(length), queue: queue) { done, data, error in
                 guard error == 0 else {
                     let errStrPtr = strerror(error)
-                    let errStr = String(validatingUTF8: errStrPtr!)!
+                    let errStr = String(validatingCString: errStrPtr!)!
                     continuation.resume(throwing: ReceiveError.readError(errStr))
                     return
                 }
diff --git a/Coder Desktop/Proto/Speaker.swift b/Coder Desktop/Proto/Speaker.swift
index fdb334b..ca0740d 100644
--- a/Coder Desktop/Proto/Speaker.swift	
+++ b/Coder Desktop/Proto/Speaker.swift	
@@ -133,20 +133,20 @@ class Speaker<SendMsg: RPCMessage & Message, RecvMsg: RPCMessage & Message> {
     /// Send a unary RPC message and handle the response
     func unaryRPC(_ req: SendMsg) async throws -> RecvMsg {
         return try await withCheckedThrowingContinuation { continuation in
-            Task {
-                let msgID = await self.secretary.record(continuation: continuation)
+            Task { [sender, secretary, logger] in
+                let msgID = await secretary.record(continuation: continuation)
                 var req = req
                 req.rpc = Vpn_RPC()
                 req.rpc.msgID = msgID
                 do {
-                    self.logger.debug("sending RPC with msgID: \(msgID)")
-                    try await self.sender.send(req)
+                    logger.debug("sending RPC with msgID: \(msgID)")
+                    try await sender.send(req)
                 } catch {
-                    self.logger.warning("failed to send RPC with msgID: \(msgID): \(error)")
-                    await self.secretary.erase(id: req.rpc.msgID)
+                    logger.warning("failed to send RPC with msgID: \(msgID): \(error)")
+                    await secretary.erase(id: req.rpc.msgID)
                     continuation.resume(throwing: error)
                 }
-                self.logger.debug("sent RPC with msgID: \(msgID)")
+                logger.debug("sent RPC with msgID: \(msgID)")
             }
         }
     }
@@ -169,7 +169,7 @@ class Speaker<SendMsg: RPCMessage & Message, RecvMsg: RPCMessage & Message> {
 }
 
 /// A class that performs the initial VPN protocol handshake and version negotiation.
-class Handshaker {
+class Handshaker: @unchecked Sendable {
     private let writeFD: FileHandle
     private let dispatch: DispatchIO
     private var theirData: Data = .init()
@@ -219,7 +219,7 @@ class Handshaker {
     private func handleRead(_: Bool, _ data: DispatchData?, _ error: Int32) {
         guard error == 0 else {
             let errStrPtr = strerror(error)
-            let errStr = String(validatingUTF8: errStrPtr!)!
+            let errStr = String(validatingCString: errStrPtr!)!
             continuation?.resume(throwing: HandshakeError.readError(errStr))
             return
         }
@@ -277,7 +277,7 @@ enum HandshakeError: Error {
     case unsupportedVersion([ProtoVersion])
 }
 
-struct RPCRequest<SendMsg: RPCMessage & Message, RecvMsg: RPCMessage> {
+struct RPCRequest<SendMsg: RPCMessage & Message, RecvMsg: RPCMessage & Sendable>: Sendable {
     let msg: RecvMsg
     private let sender: Sender<SendMsg>
 
@@ -302,7 +302,7 @@ enum RPCError: Error {
 }
 
 /// An actor to record outgoing RPCs and route their replies to the original sender
-actor RPCSecretary<RecvMsg: RPCMessage> {
+actor RPCSecretary<RecvMsg: RPCMessage & Sendable> {
     private var continuations: [UInt64: CheckedContinuation<RecvMsg, Error>] = [:]
     private var nextMsgID: UInt64 = 1
 
diff --git a/Coder Desktop/ProtoTests/SpeakerTests.swift b/Coder Desktop/ProtoTests/SpeakerTests.swift
index 08829ff..82651cb 100644
--- a/Coder Desktop/ProtoTests/SpeakerTests.swift	
+++ b/Coder Desktop/ProtoTests/SpeakerTests.swift	
@@ -4,20 +4,45 @@ import Testing
 
 /// A concrete, test class for the abstract Speaker, which overrides the handlers to send things to
 /// continuations we set in the test.
-class TestTunnel: Speaker<Vpn_TunnelMessage, Vpn_ManagerMessage> {
-    var msgHandler: CheckedContinuation<Vpn_ManagerMessage, Error>?
+class TestTunnel: Speaker<Vpn_TunnelMessage, Vpn_ManagerMessage>, @unchecked Sendable {
+    private var msgHandler: CheckedContinuation<Vpn_ManagerMessage, Error>?
     override func handleMessage(_ msg: Vpn_ManagerMessage) {
         msgHandler?.resume(returning: msg)
     }
 
-    var rpcHandler: CheckedContinuation<RPCRequest<Vpn_TunnelMessage, Vpn_ManagerMessage>, Error>?
+    /// Runs the given closure asynchronously and returns the next non-RPC message received.
+    func expectMessage(with closure:
+        @escaping @Sendable () async -> Void) async throws -> Vpn_ManagerMessage
+    {
+        return try await withCheckedThrowingContinuation { continuation in
+            msgHandler = continuation
+            Task {
+                await closure()
+            }
+        }
+    }
+
+    private var rpcHandler: CheckedContinuation<RPCRequest<Vpn_TunnelMessage, Vpn_ManagerMessage>, Error>?
     override func handleRPC(_ req: RPCRequest<Vpn_TunnelMessage, Vpn_ManagerMessage>) {
         rpcHandler?.resume(returning: req)
     }
+
+    /// Runs the given closure asynchronously and return the next non-RPC message received
+    func expectRPC(with closure:
+        @escaping @Sendable () async -> Void) async throws ->
+        RPCRequest<Vpn_TunnelMessage, Vpn_ManagerMessage>
+    {
+        return try await withCheckedThrowingContinuation { continuation in
+            rpcHandler = continuation
+            Task {
+                await closure()
+            }
+        }
+    }
 }
 
 @Suite(.timeLimit(.minutes(1)))
-struct SpeakerTests {
+struct SpeakerTests: Sendable {
     let pipeMT = Pipe()
     let pipeTM = Pipe()
     let uut: TestTunnel
@@ -56,14 +81,11 @@ struct SpeakerTests {
     @Test func handleSingleMessage() async throws {
         async let readDone: () = try uut.readLoop()
 
-        let got = try await withCheckedThrowingContinuation { continuation in
-            uut.msgHandler = continuation
-            Task {
-                var s = Vpn_ManagerMessage()
-                s.start = Vpn_StartRequest()
-                await #expect(throws: Never.self) {
-                    try await sender.send(s)
-                }
+        let got = try await uut.expectMessage {
+            var s = Vpn_ManagerMessage()
+            s.start = Vpn_StartRequest()
+            await #expect(throws: Never.self) {
+                try await sender.send(s)
             }
         }
         #expect(got.msg == .start(Vpn_StartRequest()))
@@ -74,16 +96,13 @@ struct SpeakerTests {
     @Test func handleRPC() async throws {
         async let readDone: () = try uut.readLoop()
 
-        let got = try await withCheckedThrowingContinuation { continuation in
-            uut.rpcHandler = continuation
-            Task {
-                var s = Vpn_ManagerMessage()
-                s.start = Vpn_StartRequest()
-                s.rpc = Vpn_RPC()
-                s.rpc.msgID = 33
-                await #expect(throws: Never.self) {
-                    try await sender.send(s)
-                }
+        let got = try await uut.expectRPC {
+            var s = Vpn_ManagerMessage()
+            s.start = Vpn_StartRequest()
+            s.rpc = Vpn_RPC()
+            s.rpc.msgID = 33
+            await #expect(throws: Never.self) {
+                try await sender.send(s)
             }
         }
         #expect(got.msg.msg == .start(Vpn_StartRequest()))