From 456569a51c82f9c5ef960dffe47141cd8077d27d Mon Sep 17 00:00:00 2001
From: Sebastien Stormacq <sebastien.stormacq@gmail.com>
Date: Fri, 14 Mar 2025 13:49:07 +0100
Subject: [PATCH 01/23] make LambdaRuntime a singleton without breaking the API

---
 .../ControlPlaneRequest.swift                 |  8 ++--
 .../FoundationSupport/Lambda+JSON.swift       | 12 +++++-
 Sources/AWSLambdaRuntime/LambdaHandlers.swift | 20 +++++++---
 Sources/AWSLambdaRuntime/LambdaRuntime.swift  | 29 ++++++++++++--
 .../LambdaRuntimeClient.swift                 | 32 ++++++++--------
 ...r.swift => LambdaRuntimeClientError.swift} |  2 +-
 .../LambdaRuntimeTests.swift                  | 38 +++++++++++++++++++
 7 files changed, 110 insertions(+), 31 deletions(-)
 rename Sources/AWSLambdaRuntime/{LambdaRuntimeError.swift => LambdaRuntimeClientError.swift} (96%)
 create mode 100644 Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift

diff --git a/Sources/AWSLambdaRuntime/ControlPlaneRequest.swift b/Sources/AWSLambdaRuntime/ControlPlaneRequest.swift
index 29016b0e..b15e1dbd 100644
--- a/Sources/AWSLambdaRuntime/ControlPlaneRequest.swift
+++ b/Sources/AWSLambdaRuntime/ControlPlaneRequest.swift
@@ -36,19 +36,19 @@ package struct InvocationMetadata: Hashable {
     package let clientContext: String?
     package let cognitoIdentity: String?
 
-    package init(headers: HTTPHeaders) throws(LambdaRuntimeError) {
+    package init(headers: HTTPHeaders) throws(LambdaRuntimeClientError) {
         guard let requestID = headers.first(name: AmazonHeaders.requestID), !requestID.isEmpty else {
-            throw LambdaRuntimeError(code: .nextInvocationMissingHeaderRequestID)
+            throw LambdaRuntimeClientError(code: .nextInvocationMissingHeaderRequestID)
         }
 
         guard let deadline = headers.first(name: AmazonHeaders.deadline),
             let unixTimeInMilliseconds = Int64(deadline)
         else {
-            throw LambdaRuntimeError(code: .nextInvocationMissingHeaderDeadline)
+            throw LambdaRuntimeClientError(code: .nextInvocationMissingHeaderDeadline)
         }
 
         guard let invokedFunctionARN = headers.first(name: AmazonHeaders.invokedFunctionARN) else {
-            throw LambdaRuntimeError(code: .nextInvocationMissingHeaderInvokeFuctionARN)
+            throw LambdaRuntimeClientError(code: .nextInvocationMissingHeaderInvokeFuctionARN)
         }
 
         self.requestID = requestID
diff --git a/Sources/AWSLambdaRuntime/FoundationSupport/Lambda+JSON.swift b/Sources/AWSLambdaRuntime/FoundationSupport/Lambda+JSON.swift
index 9bd4d30f..aedf7782 100644
--- a/Sources/AWSLambdaRuntime/FoundationSupport/Lambda+JSON.swift
+++ b/Sources/AWSLambdaRuntime/FoundationSupport/Lambda+JSON.swift
@@ -108,7 +108,11 @@ extension LambdaRuntime {
             handler: LambdaHandlerAdapter(handler: ClosureHandler(body: body))
         )
 
-        self.init(handler: handler)
+        do {
+            try self.init(handler: handler)
+        } catch {
+            fatalError("Failed to initialize LambdaRuntime: \(error)")
+        }
     }
 
     /// Initialize an instance with a `LambdaHandler` defined in the form of a closure **with a `Void` return type**.
@@ -132,7 +136,11 @@ extension LambdaRuntime {
             handler: LambdaHandlerAdapter(handler: ClosureHandler(body: body))
         )
 
-        self.init(handler: handler)
+        do {
+            try self.init(handler: handler)
+        } catch {
+            fatalError("Failed to initialize LambdaRuntime: \(error)")
+        }
     }
 }
 #endif  // trait: FoundationJSONSupport
diff --git a/Sources/AWSLambdaRuntime/LambdaHandlers.swift b/Sources/AWSLambdaRuntime/LambdaHandlers.swift
index d6e0b373..e8f9dac1 100644
--- a/Sources/AWSLambdaRuntime/LambdaHandlers.swift
+++ b/Sources/AWSLambdaRuntime/LambdaHandlers.swift
@@ -179,7 +179,11 @@ extension LambdaRuntime {
     public convenience init(
         body: @Sendable @escaping (ByteBuffer, LambdaResponseStreamWriter, LambdaContext) async throws -> Void
     ) where Handler == StreamingClosureHandler {
-        self.init(handler: StreamingClosureHandler(body: body))
+        do {
+            try self.init(handler: StreamingClosureHandler(body: body))
+        } catch {
+            fatalError("Failed to initialize LambdaRuntime: \(error)")
+        }
     }
 
     /// Initialize an instance with a ``LambdaHandler`` defined in the form of a closure **with a non-`Void` return type**, an encoder, and a decoder.
@@ -213,8 +217,11 @@ extension LambdaRuntime {
             decoder: decoder,
             handler: streamingAdapter
         )
-
-        self.init(handler: codableWrapper)
+        do {
+            try self.init(handler: codableWrapper)
+        } catch {
+            fatalError("Failed to initialize LambdaRuntime: \(error)")
+        }
     }
 
     /// Initialize an instance with a ``LambdaHandler`` defined in the form of a closure **with a `Void` return type**, an encoder, and a decoder.
@@ -238,7 +245,10 @@ extension LambdaRuntime {
             decoder: decoder,
             handler: LambdaHandlerAdapter(handler: ClosureHandler(body: body))
         )
-
-        self.init(handler: handler)
+        do {
+            try self.init(handler: handler)
+        } catch {
+            fatalError("Failed to initialize LambdaRuntime: \(error)")
+        }
     }
 }
diff --git a/Sources/AWSLambdaRuntime/LambdaRuntime.swift b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
index 6bc2403c..c1aed07d 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntime.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
@@ -15,6 +15,7 @@
 import Logging
 import NIOConcurrencyHelpers
 import NIOCore
+import Synchronization
 
 #if canImport(FoundationEssentials)
 import FoundationEssentials
@@ -22,6 +23,13 @@ import FoundationEssentials
 import Foundation
 #endif
 
+// This is our gardian to ensure only one LambdaRuntime is initialized
+// We use a Mutex here to ensure thread safety
+// We don't use LambdaRuntime<> as the type here, as we don't know the concrete type that will be used
+private let _singleton = Mutex<Bool>(false)
+public enum LambdaRuntimeError: Error {
+    case moreThanOneLambdaRuntimeInstance
+}
 // We need `@unchecked` Sendable here, as `NIOLockedValueBox` does not understand `sending` today.
 // We don't want to use `NIOLockedValueBox` here anyway. We would love to use Mutex here, but this
 // sadly crashes the compiler today.
@@ -35,7 +43,22 @@ public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: St
         handler: sending Handler,
         eventLoop: EventLoop = Lambda.defaultEventLoop,
         logger: Logger = Logger(label: "LambdaRuntime")
-    ) {
+    ) throws(LambdaRuntimeError) {
+
+        do {
+            try _singleton.withLock {
+                let alreadyCreated = $0
+                guard alreadyCreated == false else {
+                    throw LambdaRuntimeError.moreThanOneLambdaRuntimeInstance
+                }
+                $0 = true
+            }
+        } catch _ as LambdaRuntimeError {
+            throw LambdaRuntimeError.moreThanOneLambdaRuntimeInstance
+        } catch {
+            fatalError("An unknown error occurred: \(error)")
+        }
+
         self.handlerMutex = NIOLockedValueBox(handler)
         self.eventLoop = eventLoop
 
@@ -56,7 +79,7 @@ public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: St
         }
 
         guard let handler else {
-            throw LambdaRuntimeError(code: .runtimeCanOnlyBeStartedOnce)
+            throw LambdaRuntimeClientError(code: .runtimeCanOnlyBeStartedOnce)
         }
 
         // are we running inside an AWS Lambda runtime environment ?
@@ -66,7 +89,7 @@ public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: St
 
             let ipAndPort = runtimeEndpoint.split(separator: ":", maxSplits: 1)
             let ip = String(ipAndPort[0])
-            guard let port = Int(ipAndPort[1]) else { throw LambdaRuntimeError(code: .invalidPort) }
+            guard let port = Int(ipAndPort[1]) else { throw LambdaRuntimeClientError(code: .invalidPort) }
 
             try await LambdaRuntimeClient.withRuntimeClient(
                 configuration: .init(ip: ip, port: port),
diff --git a/Sources/AWSLambdaRuntime/LambdaRuntimeClient.swift b/Sources/AWSLambdaRuntime/LambdaRuntimeClient.swift
index 196cbeb1..98fe0c25 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntimeClient.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntimeClient.swift
@@ -134,7 +134,7 @@ final actor LambdaRuntimeClient: LambdaRuntimeClientProtocol {
 
             case .connecting(let continuations):
                 for continuation in continuations {
-                    continuation.resume(throwing: LambdaRuntimeError(code: .closingRuntimeClient))
+                    continuation.resume(throwing: LambdaRuntimeClientError(code: .closingRuntimeClient))
                 }
                 self.connectionState = .connecting([])
 
@@ -173,7 +173,7 @@ final actor LambdaRuntimeClient: LambdaRuntimeClientProtocol {
     private func write(_ buffer: NIOCore.ByteBuffer) async throws {
         switch self.lambdaState {
         case .idle, .sentResponse:
-            throw LambdaRuntimeError(code: .writeAfterFinishHasBeenSent)
+            throw LambdaRuntimeClientError(code: .writeAfterFinishHasBeenSent)
 
         case .waitingForNextInvocation:
             fatalError("Invalid state: \(self.lambdaState)")
@@ -194,7 +194,7 @@ final actor LambdaRuntimeClient: LambdaRuntimeClientProtocol {
     private func writeAndFinish(_ buffer: NIOCore.ByteBuffer?) async throws {
         switch self.lambdaState {
         case .idle, .sentResponse:
-            throw LambdaRuntimeError(code: .finishAfterFinishHasBeenSent)
+            throw LambdaRuntimeClientError(code: .finishAfterFinishHasBeenSent)
 
         case .waitingForNextInvocation:
             fatalError("Invalid state: \(self.lambdaState)")
@@ -261,7 +261,7 @@ final actor LambdaRuntimeClient: LambdaRuntimeClientProtocol {
         case (.connecting(let array), .notClosing):
             self.connectionState = .disconnected
             for continuation in array {
-                continuation.resume(throwing: LambdaRuntimeError(code: .lostConnectionToControlPlane))
+                continuation.resume(throwing: LambdaRuntimeClientError(code: .lostConnectionToControlPlane))
             }
 
         case (.connecting(let array), .closing(let continuation)):
@@ -394,7 +394,7 @@ extension LambdaRuntimeClient: LambdaChannelHandlerDelegate {
                 }
 
                 for continuation in continuations {
-                    continuation.resume(throwing: LambdaRuntimeError(code: .connectionToControlPlaneLost))
+                    continuation.resume(throwing: LambdaRuntimeClientError(code: .connectionToControlPlaneLost))
                 }
 
             case .connected(let stateChannel, _):
@@ -489,7 +489,7 @@ private final class LambdaChannelHandler<Delegate: LambdaChannelHandlerDelegate>
             fatalError("Invalid state: \(self.state)")
 
         case .disconnected:
-            throw LambdaRuntimeError(code: .connectionToControlPlaneLost)
+            throw LambdaRuntimeClientError(code: .connectionToControlPlaneLost)
         }
     }
 
@@ -528,10 +528,10 @@ private final class LambdaChannelHandler<Delegate: LambdaChannelHandlerDelegate>
             )
 
         case .disconnected:
-            throw LambdaRuntimeError(code: .connectionToControlPlaneLost)
+            throw LambdaRuntimeClientError(code: .connectionToControlPlaneLost)
 
         case .closing:
-            throw LambdaRuntimeError(code: .connectionToControlPlaneGoingAway)
+            throw LambdaRuntimeClientError(code: .connectionToControlPlaneGoingAway)
         }
     }
 
@@ -553,13 +553,13 @@ private final class LambdaChannelHandler<Delegate: LambdaChannelHandlerDelegate>
 
         case .connected(_, .idle),
             .connected(_, .sentResponse):
-            throw LambdaRuntimeError(code: .writeAfterFinishHasBeenSent)
+            throw LambdaRuntimeClientError(code: .writeAfterFinishHasBeenSent)
 
         case .disconnected:
-            throw LambdaRuntimeError(code: .connectionToControlPlaneLost)
+            throw LambdaRuntimeClientError(code: .connectionToControlPlaneLost)
 
         case .closing:
-            throw LambdaRuntimeError(code: .connectionToControlPlaneGoingAway)
+            throw LambdaRuntimeClientError(code: .connectionToControlPlaneGoingAway)
         }
     }
 
@@ -586,13 +586,13 @@ private final class LambdaChannelHandler<Delegate: LambdaChannelHandlerDelegate>
             }
 
         case .connected(_, .sentResponse):
-            throw LambdaRuntimeError(code: .finishAfterFinishHasBeenSent)
+            throw LambdaRuntimeClientError(code: .finishAfterFinishHasBeenSent)
 
         case .disconnected:
-            throw LambdaRuntimeError(code: .connectionToControlPlaneLost)
+            throw LambdaRuntimeClientError(code: .connectionToControlPlaneLost)
 
         case .closing:
-            throw LambdaRuntimeError(code: .connectionToControlPlaneGoingAway)
+            throw LambdaRuntimeClientError(code: .connectionToControlPlaneGoingAway)
         }
     }
 
@@ -759,7 +759,7 @@ extension LambdaChannelHandler: ChannelInboundHandler {
                 self.delegate.connectionWillClose(channel: context.channel)
                 context.close(promise: nil)
                 continuation.resume(
-                    throwing: LambdaRuntimeError(code: .invocationMissingMetadata, underlying: error)
+                    throwing: LambdaRuntimeClientError(code: .invocationMissingMetadata, underlying: error)
                 )
             }
 
@@ -769,7 +769,7 @@ extension LambdaChannelHandler: ChannelInboundHandler {
                 continuation.resume()
             } else {
                 self.state = .connected(context, .idle)
-                continuation.resume(throwing: LambdaRuntimeError(code: .unexpectedStatusCodeForRequest))
+                continuation.resume(throwing: LambdaRuntimeClientError(code: .unexpectedStatusCodeForRequest))
             }
 
         case .disconnected, .closing, .connected(_, _):
diff --git a/Sources/AWSLambdaRuntime/LambdaRuntimeError.swift b/Sources/AWSLambdaRuntime/LambdaRuntimeClientError.swift
similarity index 96%
rename from Sources/AWSLambdaRuntime/LambdaRuntimeError.swift
rename to Sources/AWSLambdaRuntime/LambdaRuntimeClientError.swift
index a6b4ac66..3b7ebff2 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntimeError.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntimeClientError.swift
@@ -12,7 +12,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-package struct LambdaRuntimeError: Error {
+package struct LambdaRuntimeClientError: Error {
     package enum Code {
         case closingRuntimeClient
 
diff --git a/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift b/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
new file mode 100644
index 00000000..bacd1b90
--- /dev/null
+++ b/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
@@ -0,0 +1,38 @@
+import Foundation
+import Logging
+import NIOCore
+import Synchronization
+import Testing
+
+@testable import AWSLambdaRuntime
+
+@Suite("LambdaRuntimeTests")
+final class LambdaRuntimeTests {
+
+    @Test("LambdaRuntime can only be initialized once")
+    func testLambdaRuntimeInitializationFatalError() throws {
+
+        // First initialization should succeed
+        try _ = LambdaRuntime(handler: MockHandler(), eventLoop: Lambda.defaultEventLoop, logger: Logger(label: "Test"))
+
+        // Second initialization should trigger LambdaRuntimeError
+        #expect(throws: LambdaRuntimeError.self) {
+            try _ = LambdaRuntime(
+                handler: MockHandler(),
+                eventLoop: Lambda.defaultEventLoop,
+                logger: Logger(label: "Test")
+            )
+        }
+
+    }
+}
+
+struct MockHandler: StreamingLambdaHandler {
+    mutating func handle(
+        _ event: NIOCore.ByteBuffer,
+        responseWriter: some AWSLambdaRuntime.LambdaResponseStreamWriter,
+        context: AWSLambdaRuntime.LambdaContext
+    ) async throws {
+
+    }
+}

From a63a6394288296db7abf3e7bf123363a5750d678 Mon Sep 17 00:00:00 2001
From: Sebastien Stormacq <sebastien.stormacq@gmail.com>
Date: Fri, 14 Mar 2025 13:57:43 +0100
Subject: [PATCH 02/23] fix license header

---
 .../AWSLambdaRuntimeTests/LambdaRuntimeTests.swift | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift b/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
index bacd1b90..12cf4ae0 100644
--- a/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
+++ b/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
@@ -1,3 +1,17 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftAWSLambdaRuntime open source project
+//
+// Copyright (c) 2025 Apple Inc. and the SwiftAWSLambdaRuntime project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftAWSLambdaRuntime project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
 import Foundation
 import Logging
 import NIOCore

From 40b612720c2c9df36c9e4329fa24c7d63bdc4f87 Mon Sep 17 00:00:00 2001
From: Sebastien Stormacq <sebastien.stormacq@gmail.com>
Date: Fri, 14 Mar 2025 14:04:16 +0100
Subject: [PATCH 03/23] convert Mutex to NIOLockedValueBox

---
 Sources/AWSLambdaRuntime/LambdaRuntime.swift | 21 +++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/Sources/AWSLambdaRuntime/LambdaRuntime.swift b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
index c1aed07d..17a5beeb 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntime.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
@@ -15,7 +15,9 @@
 import Logging
 import NIOConcurrencyHelpers
 import NIOCore
-import Synchronization
+
+// To be re-enabled when we will be able to use Mutex on Linux
+// import Synchronization
 
 #if canImport(FoundationEssentials)
 import FoundationEssentials
@@ -25,14 +27,16 @@ import Foundation
 
 // This is our gardian to ensure only one LambdaRuntime is initialized
 // We use a Mutex here to ensure thread safety
-// We don't use LambdaRuntime<> as the type here, as we don't know the concrete type that will be used
-private let _singleton = Mutex<Bool>(false)
+// We use Bool instead of LambdaRuntime<Handler> as the type here, as we don't know the concrete type that will be used
+// We would love to use Mutex here, but this sadly crashes the compiler today (on Linux).
+// private let _singleton = Mutex<Bool>(false)
+private let _singleton = NIOLockedValueBox<Bool>(false)
 public enum LambdaRuntimeError: Error {
     case moreThanOneLambdaRuntimeInstance
 }
 // We need `@unchecked` Sendable here, as `NIOLockedValueBox` does not understand `sending` today.
 // We don't want to use `NIOLockedValueBox` here anyway. We would love to use Mutex here, but this
-// sadly crashes the compiler today.
+// sadly crashes the compiler today (on Linux).
 public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: StreamingLambdaHandler {
     // TODO: We want to change this to Mutex as soon as this doesn't crash the Swift compiler on Linux anymore
     let handlerMutex: NIOLockedValueBox<Handler?>
@@ -46,7 +50,14 @@ public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: St
     ) throws(LambdaRuntimeError) {
 
         do {
-            try _singleton.withLock {
+            // try _singleton.withLock {
+            //     let alreadyCreated = $0
+            //     guard alreadyCreated == false else {
+            //         throw LambdaRuntimeError.moreThanOneLambdaRuntimeInstance
+            //     }
+            //     $0 = true
+            // }
+            try _singleton.withLockedValue {
                 let alreadyCreated = $0
                 guard alreadyCreated == false else {
                     throw LambdaRuntimeError.moreThanOneLambdaRuntimeInstance

From d474eba60c2b9a3f724fab7235be26f5c5aa1926 Mon Sep 17 00:00:00 2001
From: Sebastien Stormacq <sebastien.stormacq@gmail.com>
Date: Sat, 15 Mar 2025 09:24:17 +0100
Subject: [PATCH 04/23] Replace NIOLockedValueBox with Mutex

---
 Sources/AWSLambdaRuntime/LambdaRuntime.swift | 29 +++++---------------
 1 file changed, 7 insertions(+), 22 deletions(-)

diff --git a/Sources/AWSLambdaRuntime/LambdaRuntime.swift b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
index 17a5beeb..58ab317a 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntime.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
@@ -15,9 +15,7 @@
 import Logging
 import NIOConcurrencyHelpers
 import NIOCore
-
-// To be re-enabled when we will be able to use Mutex on Linux
-// import Synchronization
+import Synchronization
 
 #if canImport(FoundationEssentials)
 import FoundationEssentials
@@ -28,18 +26,12 @@ import Foundation
 // This is our gardian to ensure only one LambdaRuntime is initialized
 // We use a Mutex here to ensure thread safety
 // We use Bool instead of LambdaRuntime<Handler> as the type here, as we don't know the concrete type that will be used
-// We would love to use Mutex here, but this sadly crashes the compiler today (on Linux).
-// private let _singleton = Mutex<Bool>(false)
-private let _singleton = NIOLockedValueBox<Bool>(false)
+private let _singleton = Mutex<Bool>(false)
 public enum LambdaRuntimeError: Error {
     case moreThanOneLambdaRuntimeInstance
 }
-// We need `@unchecked` Sendable here, as `NIOLockedValueBox` does not understand `sending` today.
-// We don't want to use `NIOLockedValueBox` here anyway. We would love to use Mutex here, but this
-// sadly crashes the compiler today (on Linux).
-public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: StreamingLambdaHandler {
-    // TODO: We want to change this to Mutex as soon as this doesn't crash the Swift compiler on Linux anymore
-    let handlerMutex: NIOLockedValueBox<Handler?>
+public final class LambdaRuntime<Handler>: Sendable where Handler: StreamingLambdaHandler {
+    let handlerMutex: Mutex<Handler?>
     let logger: Logger
     let eventLoop: EventLoop
 
@@ -50,14 +42,7 @@ public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: St
     ) throws(LambdaRuntimeError) {
 
         do {
-            // try _singleton.withLock {
-            //     let alreadyCreated = $0
-            //     guard alreadyCreated == false else {
-            //         throw LambdaRuntimeError.moreThanOneLambdaRuntimeInstance
-            //     }
-            //     $0 = true
-            // }
-            try _singleton.withLockedValue {
+            try _singleton.withLock {
                 let alreadyCreated = $0
                 guard alreadyCreated == false else {
                     throw LambdaRuntimeError.moreThanOneLambdaRuntimeInstance
@@ -70,7 +55,7 @@ public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: St
             fatalError("An unknown error occurred: \(error)")
         }
 
-        self.handlerMutex = NIOLockedValueBox(handler)
+        self.handlerMutex = Mutex(handler)
         self.eventLoop = eventLoop
 
         // by setting the log level here, we understand it can not be changed dynamically at runtime
@@ -83,7 +68,7 @@ public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: St
     }
 
     public func run() async throws {
-        let handler = self.handlerMutex.withLockedValue { handler in
+        let handler = self.handlerMutex.withLock { handler in
             let result = handler
             handler = nil
             return result

From 46e76f354401d3c50c1eb76b6a7e55c738fcbc23 Mon Sep 17 00:00:00 2001
From: Sebastien Stormacq <sebastien.stormacq@gmail.com>
Date: Sat, 15 Mar 2025 09:30:34 +0100
Subject: [PATCH 05/23] revert replacing NIOLockedValueBox by Mutex

---
 Sources/AWSLambdaRuntime/LambdaRuntime.swift | 29 +++++++++++++++-----
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/Sources/AWSLambdaRuntime/LambdaRuntime.swift b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
index 58ab317a..a487d3f9 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntime.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
@@ -15,7 +15,9 @@
 import Logging
 import NIOConcurrencyHelpers
 import NIOCore
-import Synchronization
+
+// To be re-enabled when we will be able to use Mutex on Linux
+// import Synchronization
 
 #if canImport(FoundationEssentials)
 import FoundationEssentials
@@ -26,12 +28,18 @@ import Foundation
 // This is our gardian to ensure only one LambdaRuntime is initialized
 // We use a Mutex here to ensure thread safety
 // We use Bool instead of LambdaRuntime<Handler> as the type here, as we don't know the concrete type that will be used
-private let _singleton = Mutex<Bool>(false)
+// We would love to use Mutex here, but this sadly crashes the compiler today (on Linux).
+// private let _singleton = Mutex<Bool>(false)
+private let _singleton: NIOLockedValueBox<Bool> = NIOLockedValueBox<Bool>(false)
 public enum LambdaRuntimeError: Error {
     case moreThanOneLambdaRuntimeInstance
 }
-public final class LambdaRuntime<Handler>: Sendable where Handler: StreamingLambdaHandler {
-    let handlerMutex: Mutex<Handler?>
+// We need `@unchecked` Sendable here, as `NIOLockedValueBox` does not understand `sending` today.
+// We don't want to use `NIOLockedValueBox` here anyway. We would love to use Mutex here, but this
+// sadly crashes the compiler today (on Linux).
+public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: StreamingLambdaHandler {
+    // TODO: We want to change this to Mutex as soon as this doesn't crash the Swift compiler on Linux anymore
+    let handlerMutex: NIOLockedValueBox<Handler?>
     let logger: Logger
     let eventLoop: EventLoop
 
@@ -42,7 +50,14 @@ public final class LambdaRuntime<Handler>: Sendable where Handler: StreamingLamb
     ) throws(LambdaRuntimeError) {
 
         do {
-            try _singleton.withLock {
+            // try _singleton.withLock {
+            //     let alreadyCreated = $0
+            //     guard alreadyCreated == false else {
+            //         throw LambdaRuntimeError.moreThanOneLambdaRuntimeInstance
+            //     }
+            //     $0 = true
+            // }
+            try _singleton.withLockedValue {
                 let alreadyCreated = $0
                 guard alreadyCreated == false else {
                     throw LambdaRuntimeError.moreThanOneLambdaRuntimeInstance
@@ -55,7 +70,7 @@ public final class LambdaRuntime<Handler>: Sendable where Handler: StreamingLamb
             fatalError("An unknown error occurred: \(error)")
         }
 
-        self.handlerMutex = Mutex(handler)
+        self.handlerMutex = NIOLockedValueBox(handler)
         self.eventLoop = eventLoop
 
         // by setting the log level here, we understand it can not be changed dynamically at runtime
@@ -68,7 +83,7 @@ public final class LambdaRuntime<Handler>: Sendable where Handler: StreamingLamb
     }
 
     public func run() async throws {
-        let handler = self.handlerMutex.withLock { handler in
+        let handler = self.handlerMutex.withLockedValue { handler in
             let result = handler
             handler = nil
             return result

From 299b9bca5dda44d8c713864b6a47c89daa281ec4 Mon Sep 17 00:00:00 2001
From: Sebastien Stormacq <sebastien.stormacq@gmail.com>
Date: Sat, 15 Mar 2025 10:04:52 +0100
Subject: [PATCH 06/23] remove typed throw (workaround for
 https://github.com/swiftlang/swift/issues/80020)

---
 Sources/AWSLambdaRuntime/LambdaRuntime.swift | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/Sources/AWSLambdaRuntime/LambdaRuntime.swift b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
index a487d3f9..b1034ce8 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntime.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
@@ -47,7 +47,10 @@ public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: St
         handler: sending Handler,
         eventLoop: EventLoop = Lambda.defaultEventLoop,
         logger: Logger = Logger(label: "LambdaRuntime")
-    ) throws(LambdaRuntimeError) {
+    ) throws {
+        // technically, this initializer only throws LambdaRuntime Error but the below line crashes the compiler on Linux
+        // https://github.com/swiftlang/swift/issues/80020
+        //    ) throws(LambdaRuntimeError) {
 
         do {
             // try _singleton.withLock {

From e3a3851d36ef63b5487e04469a9bd5df16879f77 Mon Sep 17 00:00:00 2001
From: Sebastien Stormacq <sebastien.stormacq@gmail.com>
Date: Sat, 15 Mar 2025 10:15:37 +0100
Subject: [PATCH 07/23] fix integration tests

---
 Examples/BackgroundTasks/Sources/main.swift | 2 +-
 Examples/Streaming/Sources/main.swift       | 2 +-
 readme.md                                   | 4 ++--
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/Examples/BackgroundTasks/Sources/main.swift b/Examples/BackgroundTasks/Sources/main.swift
index 1985fc34..3b8cef9e 100644
--- a/Examples/BackgroundTasks/Sources/main.swift
+++ b/Examples/BackgroundTasks/Sources/main.swift
@@ -53,5 +53,5 @@ struct BackgroundProcessingHandler: LambdaWithBackgroundProcessingHandler {
 }
 
 let adapter = LambdaCodableAdapter(handler: BackgroundProcessingHandler())
-let runtime = LambdaRuntime.init(handler: adapter)
+let runtime = try LambdaRuntime.init(handler: adapter)
 try await runtime.run()
diff --git a/Examples/Streaming/Sources/main.swift b/Examples/Streaming/Sources/main.swift
index ce92560c..26866546 100644
--- a/Examples/Streaming/Sources/main.swift
+++ b/Examples/Streaming/Sources/main.swift
@@ -32,5 +32,5 @@ struct SendNumbersWithPause: StreamingLambdaHandler {
     }
 }
 
-let runtime = LambdaRuntime.init(handler: SendNumbersWithPause())
+let runtime = try LambdaRuntime.init(handler: SendNumbersWithPause())
 try await runtime.run()
diff --git a/readme.md b/readme.md
index 37596ed2..3c42cff8 100644
--- a/readme.md
+++ b/readme.md
@@ -248,7 +248,7 @@ struct SendNumbersWithPause: StreamingLambdaHandler {
     }
 }
 
-let runtime = LambdaRuntime.init(handler: SendNumbersWithPause())
+let runtime = try LambdaRuntime.init(handler: SendNumbersWithPause())
 try await runtime.run()
 ```
 
@@ -328,7 +328,7 @@ struct BackgroundProcessingHandler: LambdaWithBackgroundProcessingHandler {
 }
 
 let adapter = LambdaCodableAdapter(handler: BackgroundProcessingHandler())
-let runtime = LambdaRuntime.init(handler: adapter)
+let runtime = try LambdaRuntime.init(handler: adapter)
 try await runtime.run()
 ```
 

From 4ebf24f035f7567e57b416f6685a73b3c071682c Mon Sep 17 00:00:00 2001
From: Sebastien Stormacq <sebastien.stormacq@gmail.com>
Date: Sat, 15 Mar 2025 10:40:24 +0100
Subject: [PATCH 08/23] Replace NIOLockedValueBox with Mutex

---
 Sources/AWSLambdaRuntime/LambdaRuntime.swift | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/Sources/AWSLambdaRuntime/LambdaRuntime.swift b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
index b1034ce8..32f84c47 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntime.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
@@ -15,9 +15,7 @@
 import Logging
 import NIOConcurrencyHelpers
 import NIOCore
-
-// To be re-enabled when we will be able to use Mutex on Linux
-// import Synchronization
+import Synchronization
 
 #if canImport(FoundationEssentials)
 import FoundationEssentials
@@ -28,9 +26,7 @@ import Foundation
 // This is our gardian to ensure only one LambdaRuntime is initialized
 // We use a Mutex here to ensure thread safety
 // We use Bool instead of LambdaRuntime<Handler> as the type here, as we don't know the concrete type that will be used
-// We would love to use Mutex here, but this sadly crashes the compiler today (on Linux).
-// private let _singleton = Mutex<Bool>(false)
-private let _singleton: NIOLockedValueBox<Bool> = NIOLockedValueBox<Bool>(false)
+private let _singleton = Mutex<Bool>(false)
 public enum LambdaRuntimeError: Error {
     case moreThanOneLambdaRuntimeInstance
 }
@@ -53,14 +49,7 @@ public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: St
         //    ) throws(LambdaRuntimeError) {
 
         do {
-            // try _singleton.withLock {
-            //     let alreadyCreated = $0
-            //     guard alreadyCreated == false else {
-            //         throw LambdaRuntimeError.moreThanOneLambdaRuntimeInstance
-            //     }
-            //     $0 = true
-            // }
-            try _singleton.withLockedValue {
+            try _singleton.withLock {
                 let alreadyCreated = $0
                 guard alreadyCreated == false else {
                     throw LambdaRuntimeError.moreThanOneLambdaRuntimeInstance

From 3aee427aa4bdb34d26d201814da26bf2958df1a5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Stormacq?= <sebastien.stormacq@gmail.com>
Date: Wed, 19 Mar 2025 20:38:46 +0100
Subject: [PATCH 09/23] use Atomic instead of Mutex. Make the atomix check on
 run() instead of init()

---
 Examples/BackgroundTasks/Sources/main.swift   |  2 +-
 Examples/Streaming/Sources/main.swift         |  2 +-
 .../ControlPlaneRequest.swift                 | 10 +--
 .../FoundationSupport/Lambda+JSON.swift       | 12 +---
 Sources/AWSLambdaRuntime/LambdaHandlers.swift | 18 +-----
 Sources/AWSLambdaRuntime/LambdaRuntime.swift  | 64 +++++++++++--------
 .../LambdaRuntimeClient.swift                 | 32 +++++-----
 ...ntError.swift => LambdaRuntimeError.swift} | 13 ++--
 .../LambdaRuntimeTests.swift                  | 57 +++++++++++++----
 9 files changed, 117 insertions(+), 93 deletions(-)
 rename Sources/AWSLambdaRuntime/{LambdaRuntimeClientError.swift => LambdaRuntimeError.swift} (81%)

diff --git a/Examples/BackgroundTasks/Sources/main.swift b/Examples/BackgroundTasks/Sources/main.swift
index 3b8cef9e..1985fc34 100644
--- a/Examples/BackgroundTasks/Sources/main.swift
+++ b/Examples/BackgroundTasks/Sources/main.swift
@@ -53,5 +53,5 @@ struct BackgroundProcessingHandler: LambdaWithBackgroundProcessingHandler {
 }
 
 let adapter = LambdaCodableAdapter(handler: BackgroundProcessingHandler())
-let runtime = try LambdaRuntime.init(handler: adapter)
+let runtime = LambdaRuntime.init(handler: adapter)
 try await runtime.run()
diff --git a/Examples/Streaming/Sources/main.swift b/Examples/Streaming/Sources/main.swift
index 26866546..ce92560c 100644
--- a/Examples/Streaming/Sources/main.swift
+++ b/Examples/Streaming/Sources/main.swift
@@ -32,5 +32,5 @@ struct SendNumbersWithPause: StreamingLambdaHandler {
     }
 }
 
-let runtime = try LambdaRuntime.init(handler: SendNumbersWithPause())
+let runtime = LambdaRuntime.init(handler: SendNumbersWithPause())
 try await runtime.run()
diff --git a/Sources/AWSLambdaRuntime/ControlPlaneRequest.swift b/Sources/AWSLambdaRuntime/ControlPlaneRequest.swift
index b15e1dbd..b3ce3d52 100644
--- a/Sources/AWSLambdaRuntime/ControlPlaneRequest.swift
+++ b/Sources/AWSLambdaRuntime/ControlPlaneRequest.swift
@@ -36,19 +36,19 @@ package struct InvocationMetadata: Hashable {
     package let clientContext: String?
     package let cognitoIdentity: String?
 
-    package init(headers: HTTPHeaders) throws(LambdaRuntimeClientError) {
-        guard let requestID = headers.first(name: AmazonHeaders.requestID), !requestID.isEmpty else {
-            throw LambdaRuntimeClientError(code: .nextInvocationMissingHeaderRequestID)
+    package init(headers: HTTPHeaders) throws(LambdaRuntimeError) {
+        guard let requestID: String = headers.first(name: AmazonHeaders.requestID), !requestID.isEmpty else {
+            throw LambdaRuntimeError(code: .nextInvocationMissingHeaderRequestID)
         }
 
         guard let deadline = headers.first(name: AmazonHeaders.deadline),
             let unixTimeInMilliseconds = Int64(deadline)
         else {
-            throw LambdaRuntimeClientError(code: .nextInvocationMissingHeaderDeadline)
+            throw LambdaRuntimeError(code: .nextInvocationMissingHeaderDeadline)
         }
 
         guard let invokedFunctionARN = headers.first(name: AmazonHeaders.invokedFunctionARN) else {
-            throw LambdaRuntimeClientError(code: .nextInvocationMissingHeaderInvokeFuctionARN)
+            throw LambdaRuntimeError(code: .nextInvocationMissingHeaderInvokeFuctionARN)
         }
 
         self.requestID = requestID
diff --git a/Sources/AWSLambdaRuntime/FoundationSupport/Lambda+JSON.swift b/Sources/AWSLambdaRuntime/FoundationSupport/Lambda+JSON.swift
index aedf7782..9bd4d30f 100644
--- a/Sources/AWSLambdaRuntime/FoundationSupport/Lambda+JSON.swift
+++ b/Sources/AWSLambdaRuntime/FoundationSupport/Lambda+JSON.swift
@@ -108,11 +108,7 @@ extension LambdaRuntime {
             handler: LambdaHandlerAdapter(handler: ClosureHandler(body: body))
         )
 
-        do {
-            try self.init(handler: handler)
-        } catch {
-            fatalError("Failed to initialize LambdaRuntime: \(error)")
-        }
+        self.init(handler: handler)
     }
 
     /// Initialize an instance with a `LambdaHandler` defined in the form of a closure **with a `Void` return type**.
@@ -136,11 +132,7 @@ extension LambdaRuntime {
             handler: LambdaHandlerAdapter(handler: ClosureHandler(body: body))
         )
 
-        do {
-            try self.init(handler: handler)
-        } catch {
-            fatalError("Failed to initialize LambdaRuntime: \(error)")
-        }
+        self.init(handler: handler)
     }
 }
 #endif  // trait: FoundationJSONSupport
diff --git a/Sources/AWSLambdaRuntime/LambdaHandlers.swift b/Sources/AWSLambdaRuntime/LambdaHandlers.swift
index e8f9dac1..2bb78cf3 100644
--- a/Sources/AWSLambdaRuntime/LambdaHandlers.swift
+++ b/Sources/AWSLambdaRuntime/LambdaHandlers.swift
@@ -179,11 +179,7 @@ extension LambdaRuntime {
     public convenience init(
         body: @Sendable @escaping (ByteBuffer, LambdaResponseStreamWriter, LambdaContext) async throws -> Void
     ) where Handler == StreamingClosureHandler {
-        do {
-            try self.init(handler: StreamingClosureHandler(body: body))
-        } catch {
-            fatalError("Failed to initialize LambdaRuntime: \(error)")
-        }
+        self.init(handler: StreamingClosureHandler(body: body))
     }
 
     /// Initialize an instance with a ``LambdaHandler`` defined in the form of a closure **with a non-`Void` return type**, an encoder, and a decoder.
@@ -217,11 +213,7 @@ extension LambdaRuntime {
             decoder: decoder,
             handler: streamingAdapter
         )
-        do {
-            try self.init(handler: codableWrapper)
-        } catch {
-            fatalError("Failed to initialize LambdaRuntime: \(error)")
-        }
+        self.init(handler: codableWrapper)
     }
 
     /// Initialize an instance with a ``LambdaHandler`` defined in the form of a closure **with a `Void` return type**, an encoder, and a decoder.
@@ -245,10 +237,6 @@ extension LambdaRuntime {
             decoder: decoder,
             handler: LambdaHandlerAdapter(handler: ClosureHandler(body: body))
         )
-        do {
-            try self.init(handler: handler)
-        } catch {
-            fatalError("Failed to initialize LambdaRuntime: \(error)")
-        }
+        self.init(handler: handler)
     }
 }
diff --git a/Sources/AWSLambdaRuntime/LambdaRuntime.swift b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
index 32f84c47..c70d28b2 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntime.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
@@ -23,13 +23,10 @@ import FoundationEssentials
 import Foundation
 #endif
 
-// This is our gardian to ensure only one LambdaRuntime is initialized
-// We use a Mutex here to ensure thread safety
-// We use Bool instead of LambdaRuntime<Handler> as the type here, as we don't know the concrete type that will be used
-private let _singleton = Mutex<Bool>(false)
-public enum LambdaRuntimeError: Error {
-    case moreThanOneLambdaRuntimeInstance
-}
+// This is our gardian to ensure only one LambdaRuntime is running at the time
+// We use an Atomic here to ensure thread safety
+private let _isRunning = Atomic<Bool>(false)
+
 // We need `@unchecked` Sendable here, as `NIOLockedValueBox` does not understand `sending` today.
 // We don't want to use `NIOLockedValueBox` here anyway. We would love to use Mutex here, but this
 // sadly crashes the compiler today (on Linux).
@@ -43,25 +40,7 @@ public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: St
         handler: sending Handler,
         eventLoop: EventLoop = Lambda.defaultEventLoop,
         logger: Logger = Logger(label: "LambdaRuntime")
-    ) throws {
-        // technically, this initializer only throws LambdaRuntime Error but the below line crashes the compiler on Linux
-        // https://github.com/swiftlang/swift/issues/80020
-        //    ) throws(LambdaRuntimeError) {
-
-        do {
-            try _singleton.withLock {
-                let alreadyCreated = $0
-                guard alreadyCreated == false else {
-                    throw LambdaRuntimeError.moreThanOneLambdaRuntimeInstance
-                }
-                $0 = true
-            }
-        } catch _ as LambdaRuntimeError {
-            throw LambdaRuntimeError.moreThanOneLambdaRuntimeInstance
-        } catch {
-            fatalError("An unknown error occurred: \(error)")
-        }
-
+    ) {
         self.handlerMutex = NIOLockedValueBox(handler)
         self.eventLoop = eventLoop
 
@@ -74,7 +53,36 @@ public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: St
         self.logger.debug("LambdaRuntime initialized")
     }
 
+    /// Make sure only one run() is called at a time
     public func run() async throws {
+
+        // we use an atomic global variable to ensure only one LambdaRuntime is running at the time
+        let (_, original) = _isRunning.compareExchange(expected: false, desired: true, ordering: .relaxed)
+
+        // if the original value was already true, run() is already running
+        if original {
+            throw LambdaRuntimeError(code: .runtimeCanOnlyBeStartedOnce)
+        }
+
+        try await withTaskCancellationHandler {
+            // call the internal _run() method
+            do {
+                try await self._run()
+            } catch {
+                // when we catch an error, flip back the global variable to false
+                _isRunning.store(false, ordering: .relaxed)
+                throw error
+            }
+        } onCancel: {
+            // when task is cancelled, flip back the global variable to false
+            _isRunning.store(false, ordering: .relaxed)
+        }
+
+        // when we're done without error and without cancellation, flip back the global variable to false
+        _isRunning.store(false, ordering: .relaxed)
+    }
+
+    private func _run() async throws {
         let handler = self.handlerMutex.withLockedValue { handler in
             let result = handler
             handler = nil
@@ -82,7 +90,7 @@ public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: St
         }
 
         guard let handler else {
-            throw LambdaRuntimeClientError(code: .runtimeCanOnlyBeStartedOnce)
+            throw LambdaRuntimeError(code: .runtimeCanOnlyBeStartedOnce)
         }
 
         // are we running inside an AWS Lambda runtime environment ?
@@ -92,7 +100,7 @@ public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: St
 
             let ipAndPort = runtimeEndpoint.split(separator: ":", maxSplits: 1)
             let ip = String(ipAndPort[0])
-            guard let port = Int(ipAndPort[1]) else { throw LambdaRuntimeClientError(code: .invalidPort) }
+            guard let port = Int(ipAndPort[1]) else { throw LambdaRuntimeError(code: .invalidPort) }
 
             try await LambdaRuntimeClient.withRuntimeClient(
                 configuration: .init(ip: ip, port: port),
diff --git a/Sources/AWSLambdaRuntime/LambdaRuntimeClient.swift b/Sources/AWSLambdaRuntime/LambdaRuntimeClient.swift
index 98fe0c25..196cbeb1 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntimeClient.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntimeClient.swift
@@ -134,7 +134,7 @@ final actor LambdaRuntimeClient: LambdaRuntimeClientProtocol {
 
             case .connecting(let continuations):
                 for continuation in continuations {
-                    continuation.resume(throwing: LambdaRuntimeClientError(code: .closingRuntimeClient))
+                    continuation.resume(throwing: LambdaRuntimeError(code: .closingRuntimeClient))
                 }
                 self.connectionState = .connecting([])
 
@@ -173,7 +173,7 @@ final actor LambdaRuntimeClient: LambdaRuntimeClientProtocol {
     private func write(_ buffer: NIOCore.ByteBuffer) async throws {
         switch self.lambdaState {
         case .idle, .sentResponse:
-            throw LambdaRuntimeClientError(code: .writeAfterFinishHasBeenSent)
+            throw LambdaRuntimeError(code: .writeAfterFinishHasBeenSent)
 
         case .waitingForNextInvocation:
             fatalError("Invalid state: \(self.lambdaState)")
@@ -194,7 +194,7 @@ final actor LambdaRuntimeClient: LambdaRuntimeClientProtocol {
     private func writeAndFinish(_ buffer: NIOCore.ByteBuffer?) async throws {
         switch self.lambdaState {
         case .idle, .sentResponse:
-            throw LambdaRuntimeClientError(code: .finishAfterFinishHasBeenSent)
+            throw LambdaRuntimeError(code: .finishAfterFinishHasBeenSent)
 
         case .waitingForNextInvocation:
             fatalError("Invalid state: \(self.lambdaState)")
@@ -261,7 +261,7 @@ final actor LambdaRuntimeClient: LambdaRuntimeClientProtocol {
         case (.connecting(let array), .notClosing):
             self.connectionState = .disconnected
             for continuation in array {
-                continuation.resume(throwing: LambdaRuntimeClientError(code: .lostConnectionToControlPlane))
+                continuation.resume(throwing: LambdaRuntimeError(code: .lostConnectionToControlPlane))
             }
 
         case (.connecting(let array), .closing(let continuation)):
@@ -394,7 +394,7 @@ extension LambdaRuntimeClient: LambdaChannelHandlerDelegate {
                 }
 
                 for continuation in continuations {
-                    continuation.resume(throwing: LambdaRuntimeClientError(code: .connectionToControlPlaneLost))
+                    continuation.resume(throwing: LambdaRuntimeError(code: .connectionToControlPlaneLost))
                 }
 
             case .connected(let stateChannel, _):
@@ -489,7 +489,7 @@ private final class LambdaChannelHandler<Delegate: LambdaChannelHandlerDelegate>
             fatalError("Invalid state: \(self.state)")
 
         case .disconnected:
-            throw LambdaRuntimeClientError(code: .connectionToControlPlaneLost)
+            throw LambdaRuntimeError(code: .connectionToControlPlaneLost)
         }
     }
 
@@ -528,10 +528,10 @@ private final class LambdaChannelHandler<Delegate: LambdaChannelHandlerDelegate>
             )
 
         case .disconnected:
-            throw LambdaRuntimeClientError(code: .connectionToControlPlaneLost)
+            throw LambdaRuntimeError(code: .connectionToControlPlaneLost)
 
         case .closing:
-            throw LambdaRuntimeClientError(code: .connectionToControlPlaneGoingAway)
+            throw LambdaRuntimeError(code: .connectionToControlPlaneGoingAway)
         }
     }
 
@@ -553,13 +553,13 @@ private final class LambdaChannelHandler<Delegate: LambdaChannelHandlerDelegate>
 
         case .connected(_, .idle),
             .connected(_, .sentResponse):
-            throw LambdaRuntimeClientError(code: .writeAfterFinishHasBeenSent)
+            throw LambdaRuntimeError(code: .writeAfterFinishHasBeenSent)
 
         case .disconnected:
-            throw LambdaRuntimeClientError(code: .connectionToControlPlaneLost)
+            throw LambdaRuntimeError(code: .connectionToControlPlaneLost)
 
         case .closing:
-            throw LambdaRuntimeClientError(code: .connectionToControlPlaneGoingAway)
+            throw LambdaRuntimeError(code: .connectionToControlPlaneGoingAway)
         }
     }
 
@@ -586,13 +586,13 @@ private final class LambdaChannelHandler<Delegate: LambdaChannelHandlerDelegate>
             }
 
         case .connected(_, .sentResponse):
-            throw LambdaRuntimeClientError(code: .finishAfterFinishHasBeenSent)
+            throw LambdaRuntimeError(code: .finishAfterFinishHasBeenSent)
 
         case .disconnected:
-            throw LambdaRuntimeClientError(code: .connectionToControlPlaneLost)
+            throw LambdaRuntimeError(code: .connectionToControlPlaneLost)
 
         case .closing:
-            throw LambdaRuntimeClientError(code: .connectionToControlPlaneGoingAway)
+            throw LambdaRuntimeError(code: .connectionToControlPlaneGoingAway)
         }
     }
 
@@ -759,7 +759,7 @@ extension LambdaChannelHandler: ChannelInboundHandler {
                 self.delegate.connectionWillClose(channel: context.channel)
                 context.close(promise: nil)
                 continuation.resume(
-                    throwing: LambdaRuntimeClientError(code: .invocationMissingMetadata, underlying: error)
+                    throwing: LambdaRuntimeError(code: .invocationMissingMetadata, underlying: error)
                 )
             }
 
@@ -769,7 +769,7 @@ extension LambdaChannelHandler: ChannelInboundHandler {
                 continuation.resume()
             } else {
                 self.state = .connected(context, .idle)
-                continuation.resume(throwing: LambdaRuntimeClientError(code: .unexpectedStatusCodeForRequest))
+                continuation.resume(throwing: LambdaRuntimeError(code: .unexpectedStatusCodeForRequest))
             }
 
         case .disconnected, .closing, .connected(_, _):
diff --git a/Sources/AWSLambdaRuntime/LambdaRuntimeClientError.swift b/Sources/AWSLambdaRuntime/LambdaRuntimeError.swift
similarity index 81%
rename from Sources/AWSLambdaRuntime/LambdaRuntimeClientError.swift
rename to Sources/AWSLambdaRuntime/LambdaRuntimeError.swift
index 3b7ebff2..1b9cfe02 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntimeClientError.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntimeError.swift
@@ -12,8 +12,10 @@
 //
 //===----------------------------------------------------------------------===//
 
-package struct LambdaRuntimeClientError: Error {
-    package enum Code {
+public struct LambdaRuntimeError: Error {
+    public enum Code: Sendable {
+
+        /// internal error codes for LambdaRuntimeClient
         case closingRuntimeClient
 
         case connectionToControlPlaneLost
@@ -32,6 +34,9 @@ package struct LambdaRuntimeClientError: Error {
         case missingLambdaRuntimeAPIEnvironmentVariable
         case runtimeCanOnlyBeStartedOnce
         case invalidPort
+
+        /// public error codes for LambdaRuntime
+        case moreThanOneLambdaRuntimeInstance
     }
 
     package init(code: Code, underlying: (any Error)? = nil) {
@@ -39,7 +44,7 @@ package struct LambdaRuntimeClientError: Error {
         self.underlying = underlying
     }
 
-    package var code: Code
-    package var underlying: (any Error)?
+    public var code: Code
+    public var underlying: (any Error)?
 
 }
diff --git a/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift b/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
index 12cf4ae0..c5647e7e 100644
--- a/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
+++ b/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
@@ -23,21 +23,52 @@ import Testing
 @Suite("LambdaRuntimeTests")
 final class LambdaRuntimeTests {
 
-    @Test("LambdaRuntime can only be initialized once")
-    func testLambdaRuntimeInitializationFatalError() throws {
-
-        // First initialization should succeed
-        try _ = LambdaRuntime(handler: MockHandler(), eventLoop: Lambda.defaultEventLoop, logger: Logger(label: "Test"))
-
-        // Second initialization should trigger LambdaRuntimeError
-        #expect(throws: LambdaRuntimeError.self) {
-            try _ = LambdaRuntime(
-                handler: MockHandler(),
-                eventLoop: Lambda.defaultEventLoop,
-                logger: Logger(label: "Test")
-            )
+    @Test("LambdaRuntime can only be run once")
+    func testLambdaRuntimerunOnce() async throws {
+
+        // First runtime
+        let runtime1 = LambdaRuntime(
+            handler: MockHandler(),
+            eventLoop: Lambda.defaultEventLoop,
+            logger: Logger(label: "Runtime1")
+        )
+
+        // Second runtime
+        let runtime2 = LambdaRuntime(
+            handler: MockHandler(),
+            eventLoop: Lambda.defaultEventLoop,
+            logger: Logger(label: "Runtime1")
+        )
+
+        // start the first runtime
+        let task1 = Task {
+            try await runtime1.run()
+        }
+
+        // wait a small amount to ensure runtime1 task is started
+        try await Task.sleep(for: .seconds(1))
+
+        // Running the second runtime should trigger LambdaRuntimeError
+        await #expect(throws: LambdaRuntimeError.self) {
+            try await runtime2.run()
         }
 
+        // cancel runtime 1 / task 1
+        print("--- cancelling ---")
+        task1.cancel()
+
+        // Running the second runtime should work now
+        await #expect(throws: Never.self) {
+
+            let nonReturningTask = Task.detached(priority: .userInitiated) {
+                try await runtime2.run()
+            }
+
+            // Set timeout and cancel the runtime 2
+            try await Task.sleep(for: .seconds(2))
+            nonReturningTask.cancel()
+
+        }
     }
 }
 

From 0509eaa1920cc77ecfd258d845d1cf11e28c1b65 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Stormacq?= <sebastien.stormacq@gmail.com>
Date: Wed, 19 Mar 2025 20:43:04 +0100
Subject: [PATCH 10/23] revert `try` on `runtime.init()` in doc

---
 readme.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/readme.md b/readme.md
index 3c42cff8..37596ed2 100644
--- a/readme.md
+++ b/readme.md
@@ -248,7 +248,7 @@ struct SendNumbersWithPause: StreamingLambdaHandler {
     }
 }
 
-let runtime = try LambdaRuntime.init(handler: SendNumbersWithPause())
+let runtime = LambdaRuntime.init(handler: SendNumbersWithPause())
 try await runtime.run()
 ```
 
@@ -328,7 +328,7 @@ struct BackgroundProcessingHandler: LambdaWithBackgroundProcessingHandler {
 }
 
 let adapter = LambdaCodableAdapter(handler: BackgroundProcessingHandler())
-let runtime = try LambdaRuntime.init(handler: adapter)
+let runtime = LambdaRuntime.init(handler: adapter)
 try await runtime.run()
 ```
 

From aa6395fd1eaa98591c87ccd704aba74bd2861170 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Stormacq?= <sebastien.stormacq@gmail.com>
Date: Wed, 19 Mar 2025 20:43:54 +0100
Subject: [PATCH 11/23] revert unwanted change

---
 Sources/AWSLambdaRuntime/ControlPlaneRequest.swift | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Sources/AWSLambdaRuntime/ControlPlaneRequest.swift b/Sources/AWSLambdaRuntime/ControlPlaneRequest.swift
index b3ce3d52..29016b0e 100644
--- a/Sources/AWSLambdaRuntime/ControlPlaneRequest.swift
+++ b/Sources/AWSLambdaRuntime/ControlPlaneRequest.swift
@@ -37,7 +37,7 @@ package struct InvocationMetadata: Hashable {
     package let cognitoIdentity: String?
 
     package init(headers: HTTPHeaders) throws(LambdaRuntimeError) {
-        guard let requestID: String = headers.first(name: AmazonHeaders.requestID), !requestID.isEmpty else {
+        guard let requestID = headers.first(name: AmazonHeaders.requestID), !requestID.isEmpty else {
             throw LambdaRuntimeError(code: .nextInvocationMissingHeaderRequestID)
         }
 

From 066ab76f3c8a0d8e81c2389660aafb8cc82f20e1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Stormacq?= <sebastien.stormacq@gmail.com>
Date: Wed, 19 Mar 2025 20:44:30 +0100
Subject: [PATCH 12/23] revert unwanted change

---
 Sources/AWSLambdaRuntime/LambdaHandlers.swift | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Sources/AWSLambdaRuntime/LambdaHandlers.swift b/Sources/AWSLambdaRuntime/LambdaHandlers.swift
index 2bb78cf3..89edad2b 100644
--- a/Sources/AWSLambdaRuntime/LambdaHandlers.swift
+++ b/Sources/AWSLambdaRuntime/LambdaHandlers.swift
@@ -213,6 +213,7 @@ extension LambdaRuntime {
             decoder: decoder,
             handler: streamingAdapter
         )
+
         self.init(handler: codableWrapper)
     }
 
@@ -237,6 +238,7 @@ extension LambdaRuntime {
             decoder: decoder,
             handler: LambdaHandlerAdapter(handler: ClosureHandler(body: body))
         )
+        
         self.init(handler: handler)
     }
 }

From e01b25d03b2538149493854f56e09df1cecd86fe Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Stormacq?= <sebastien.stormacq@gmail.com>
Date: Wed, 19 Mar 2025 20:45:11 +0100
Subject: [PATCH 13/23] swift-format

---
 Sources/AWSLambdaRuntime/LambdaHandlers.swift | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Sources/AWSLambdaRuntime/LambdaHandlers.swift b/Sources/AWSLambdaRuntime/LambdaHandlers.swift
index 89edad2b..d6e0b373 100644
--- a/Sources/AWSLambdaRuntime/LambdaHandlers.swift
+++ b/Sources/AWSLambdaRuntime/LambdaHandlers.swift
@@ -238,7 +238,7 @@ extension LambdaRuntime {
             decoder: decoder,
             handler: LambdaHandlerAdapter(handler: ClosureHandler(body: body))
         )
-        
+
         self.init(handler: handler)
     }
 }

From 57e23961df69958e96d63df99fe46c74ae84bd2f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Stormacq?= <sebastien.stormacq@gmail.com>
Date: Fri, 21 Mar 2025 07:54:13 +0100
Subject: [PATCH 14/23] Update Sources/AWSLambdaRuntime/LambdaRuntime.swift

Co-authored-by: Fabian Fett <fabianfett@apple.com>
---
 Sources/AWSLambdaRuntime/LambdaRuntime.swift | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Sources/AWSLambdaRuntime/LambdaRuntime.swift b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
index c70d28b2..59b3fefd 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntime.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
@@ -57,7 +57,7 @@ public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: St
     public func run() async throws {
 
         // we use an atomic global variable to ensure only one LambdaRuntime is running at the time
-        let (_, original) = _isRunning.compareExchange(expected: false, desired: true, ordering: .relaxed)
+        let (_, original) = _isRunning.compareExchange(expected: false, desired: true, ordering: .acquiringAndReleasing)
 
         // if the original value was already true, run() is already running
         if original {

From 85c988db592b3da3c93f3f8eb9332a9cff2aa926 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Stormacq?= <sebastien.stormacq@gmail.com>
Date: Fri, 21 Mar 2025 07:54:37 +0100
Subject: [PATCH 15/23] Update Sources/AWSLambdaRuntime/LambdaRuntime.swift

Co-authored-by: Fabian Fett <fabianfett@apple.com>
---
 Sources/AWSLambdaRuntime/LambdaRuntime.swift | 23 +++++---------------
 1 file changed, 6 insertions(+), 17 deletions(-)

diff --git a/Sources/AWSLambdaRuntime/LambdaRuntime.swift b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
index 59b3fefd..8d11e6d4 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntime.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
@@ -61,25 +61,14 @@ public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: St
 
         // if the original value was already true, run() is already running
         if original {
-            throw LambdaRuntimeError(code: .runtimeCanOnlyBeStartedOnce)
+            throw LambdaRuntimeError(code: .moreThanOneLambdaRuntimeInstance)
         }
-
-        try await withTaskCancellationHandler {
-            // call the internal _run() method
-            do {
-                try await self._run()
-            } catch {
-                // when we catch an error, flip back the global variable to false
-                _isRunning.store(false, ordering: .relaxed)
-                throw error
-            }
-        } onCancel: {
-            // when task is cancelled, flip back the global variable to false
-            _isRunning.store(false, ordering: .relaxed)
+        
+        defer {
+            _isRunning.store(false, ordering: . releasing)
         }
-
-        // when we're done without error and without cancellation, flip back the global variable to false
-        _isRunning.store(false, ordering: .relaxed)
+        
+        try await self._run()
     }
 
     private func _run() async throws {

From ab80580af6a80ba5b8257fb28aa23d38dfa3c06f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Stormacq?= <sebastien.stormacq@gmail.com>
Date: Fri, 21 Mar 2025 07:54:59 +0100
Subject: [PATCH 16/23] Update
 Sources/AWSLambdaRuntime/LambdaRuntimeError.swift

Co-authored-by: Fabian Fett <fabianfett@apple.com>
---
 Sources/AWSLambdaRuntime/LambdaRuntimeError.swift | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Sources/AWSLambdaRuntime/LambdaRuntimeError.swift b/Sources/AWSLambdaRuntime/LambdaRuntimeError.swift
index 1b9cfe02..0d2d194d 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntimeError.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntimeError.swift
@@ -13,7 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 public struct LambdaRuntimeError: Error {
-    public enum Code: Sendable {
+    enum Code: Sendable {
 
         /// internal error codes for LambdaRuntimeClient
         case closingRuntimeClient

From 10304cec2d3dfaeea5a261e713c87612ea176d74 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Stormacq?= <sebastien.stormacq@gmail.com>
Date: Fri, 21 Mar 2025 07:55:09 +0100
Subject: [PATCH 17/23] Update
 Sources/AWSLambdaRuntime/LambdaRuntimeError.swift

Co-authored-by: Fabian Fett <fabianfett@apple.com>
---
 Sources/AWSLambdaRuntime/LambdaRuntimeError.swift | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Sources/AWSLambdaRuntime/LambdaRuntimeError.swift b/Sources/AWSLambdaRuntime/LambdaRuntimeError.swift
index 0d2d194d..bca1eed2 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntimeError.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntimeError.swift
@@ -44,7 +44,7 @@ public struct LambdaRuntimeError: Error {
         self.underlying = underlying
     }
 
-    public var code: Code
+    var code: Code
     public var underlying: (any Error)?
 
 }

From c1e68fca423a08fef725b49a5e0fa302df9fcc24 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Stormacq?= <sebastien.stormacq@gmail.com>
Date: Fri, 21 Mar 2025 07:55:21 +0100
Subject: [PATCH 18/23] Update
 Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift

Co-authored-by: Fabian Fett <fabianfett@apple.com>
---
 Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift b/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
index c5647e7e..662a0a19 100644
--- a/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
+++ b/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
@@ -21,7 +21,7 @@ import Testing
 @testable import AWSLambdaRuntime
 
 @Suite("LambdaRuntimeTests")
-final class LambdaRuntimeTests {
+struct LambdaRuntimeTests {
 
     @Test("LambdaRuntime can only be run once")
     func testLambdaRuntimerunOnce() async throws {

From 918492a9910cd8be6bdc93c51e8a2a7530ba93f4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Stormacq?= <sebastien.stormacq@gmail.com>
Date: Fri, 21 Mar 2025 07:56:09 +0100
Subject: [PATCH 19/23] Update
 Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift

Co-authored-by: Fabian Fett <fabianfett@apple.com>
---
 .../LambdaRuntimeTests.swift                  | 32 +++++++++++--------
 1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift b/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
index 662a0a19..b9dd3288 100644
--- a/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
+++ b/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
@@ -40,23 +40,27 @@ struct LambdaRuntimeTests {
             logger: Logger(label: "Runtime1")
         )
 
-        // start the first runtime
-        let task1 = Task {
-            try await runtime1.run()
-        }
-
-        // wait a small amount to ensure runtime1 task is started
-        try await Task.sleep(for: .seconds(1))
+        try await withThrowingTaskGroup(of: Void.self) { taskGroup in
+            // start the first runtime
+            taskGroup.addTask {
+                await #expect(throws: Never.self) {
+                    try await runtime1.run()
+                }
+            }
+            
+            // wait a small amount to ensure runtime1 task is started
+            try await Task.sleep(for: .seconds(1))
 
-        // Running the second runtime should trigger LambdaRuntimeError
-        await #expect(throws: LambdaRuntimeError.self) {
-            try await runtime2.run()
+            // Running the second runtime should trigger LambdaRuntimeError
+            await #expect(throws: LambdaRuntimeError.self) {
+                try await runtime2.run()
+            }
+            
+            // cancel runtime 1 / task 1
+            print("--- cancelling ---")
+            taskGroup.cancelAll()
         }
 
-        // cancel runtime 1 / task 1
-        print("--- cancelling ---")
-        task1.cancel()
-
         // Running the second runtime should work now
         await #expect(throws: Never.self) {
 

From 6ada0414b92b11b0f13b79d7fa577d610b7510f7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Stormacq?= <sebastien.stormacq@gmail.com>
Date: Fri, 21 Mar 2025 07:56:44 +0100
Subject: [PATCH 20/23] Update
 Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift

Co-authored-by: Fabian Fett <fabianfett@apple.com>
---
 Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift b/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
index b9dd3288..b7a3f6cb 100644
--- a/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
+++ b/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
@@ -62,16 +62,14 @@ struct LambdaRuntimeTests {
         }
 
         // Running the second runtime should work now
-        await #expect(throws: Never.self) {
-
-            let nonReturningTask = Task.detached(priority: .userInitiated) {
-                try await runtime2.run()
+        try await withThrowingTaskGroup(of: Void.self) { taskGroup in
+            taskGroup.addTask {
+                await #expect(throws: Never.self) { try await runtime2.run() }
             }
 
             // Set timeout and cancel the runtime 2
             try await Task.sleep(for: .seconds(2))
-            nonReturningTask.cancel()
-
+            taskGroup.cancelAll()
         }
     }
 }

From 06df8316a7176d56da17748f18cd44b0e9de693d Mon Sep 17 00:00:00 2001
From: Sebastien Stormacq <sebastien.stormacq@gmail.com>
Date: Fri, 21 Mar 2025 08:09:43 +0100
Subject: [PATCH 21/23] add package visibility to Code

---
 Sources/AWSLambdaRuntime/LambdaRuntimeError.swift | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Sources/AWSLambdaRuntime/LambdaRuntimeError.swift b/Sources/AWSLambdaRuntime/LambdaRuntimeError.swift
index bca1eed2..c4166731 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntimeError.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntimeError.swift
@@ -13,7 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 public struct LambdaRuntimeError: Error {
-    enum Code: Sendable {
+    package enum Code: Sendable {
 
         /// internal error codes for LambdaRuntimeClient
         case closingRuntimeClient

From 50b9df8a73d0f6df8f23053111d6ea87e1323ac7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Stormacq?= <sebastien.stormacq@gmail.com>
Date: Mon, 24 Mar 2025 09:11:20 +0100
Subject: [PATCH 22/23] swift format

---
 Sources/AWSLambdaRuntime/LambdaRuntime.swift         | 6 +++---
 Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/Sources/AWSLambdaRuntime/LambdaRuntime.swift b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
index 8d11e6d4..b0ebe0ca 100644
--- a/Sources/AWSLambdaRuntime/LambdaRuntime.swift
+++ b/Sources/AWSLambdaRuntime/LambdaRuntime.swift
@@ -63,11 +63,11 @@ public final class LambdaRuntime<Handler>: @unchecked Sendable where Handler: St
         if original {
             throw LambdaRuntimeError(code: .moreThanOneLambdaRuntimeInstance)
         }
-        
+
         defer {
-            _isRunning.store(false, ordering: . releasing)
+            _isRunning.store(false, ordering: .releasing)
         }
-        
+
         try await self._run()
     }
 
diff --git a/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift b/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
index b7a3f6cb..d5a5bec9 100644
--- a/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
+++ b/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
@@ -47,7 +47,7 @@ struct LambdaRuntimeTests {
                     try await runtime1.run()
                 }
             }
-            
+
             // wait a small amount to ensure runtime1 task is started
             try await Task.sleep(for: .seconds(1))
 
@@ -55,7 +55,7 @@ struct LambdaRuntimeTests {
             await #expect(throws: LambdaRuntimeError.self) {
                 try await runtime2.run()
             }
-            
+
             // cancel runtime 1 / task 1
             print("--- cancelling ---")
             taskGroup.cancelAll()

From fa0fd88315e216d830586165a29ed754d08211b3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Stormacq?= <sebastien.stormacq@gmail.com>
Date: Mon, 24 Mar 2025 09:12:59 +0100
Subject: [PATCH 23/23] remove print statement

---
 Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift | 1 -
 1 file changed, 1 deletion(-)

diff --git a/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift b/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
index d5a5bec9..bd3ca6d3 100644
--- a/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
+++ b/Tests/AWSLambdaRuntimeTests/LambdaRuntimeTests.swift
@@ -57,7 +57,6 @@ struct LambdaRuntimeTests {
             }
 
             // cancel runtime 1 / task 1
-            print("--- cancelling ---")
             taskGroup.cancelAll()
         }