From 39ed0033b79c45addf69cb616dae0373d1cfad40 Mon Sep 17 00:00:00 2001
From: Richard L Zarth III <rlziii@icloud.com>
Date: Thu, 4 Jun 2026 19:00:16 -0400
Subject: [PATCH 1/2] Fix CurrentValueRelay concurrency crash.

---
 Sources/Relays/CurrentValueRelay.swift | 7 ++++++-
 Tests/CurrentValueRelayTests.swift     | 8 ++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/Sources/Relays/CurrentValueRelay.swift b/Sources/Relays/CurrentValueRelay.swift
index 6fa08ec..5d9f448 100644
--- a/Sources/Relays/CurrentValueRelay.swift
+++ b/Sources/Relays/CurrentValueRelay.swift
@@ -19,6 +19,8 @@ import Combine
 public class CurrentValueRelay<Output>: Relay {
     public var value: Output { storage.value }
     private let storage: CurrentValueSubject<Output, Never>
+    private let subscriptionsLock = Lock()
+    // All modifications to `subscriptions` should be protected by `lock` to ensure thread-safety.
     private var subscriptions = [Subscription<
         CurrentValueSubject<Output, Never>,
         AnySubscriber<Output, Never>
@@ -40,7 +42,9 @@ public class CurrentValueRelay<Output>: Relay {
 
     public func receive<S: Subscriber>(subscriber: S) where Output == S.Input, Failure == S.Failure {
         let subscription = Subscription(upstream: storage, downstream: AnySubscriber(subscriber))
+        subscriptionsLock.lock()
         subscriptions.append(subscription)
+        subscriptionsLock.unlock()
         subscriber.receive(subscription: subscription)
     }
 
@@ -53,8 +57,9 @@ public class CurrentValueRelay<Output>: Relay {
     }
 
     deinit {
-        // Send a finished event upon dealloation
+        // Send a finished event upon deallocation
         subscriptions.forEach { $0.forceFinish() }
+        subscriptionsLock.cleanupLock()
     }
 }
 
diff --git a/Tests/CurrentValueRelayTests.swift b/Tests/CurrentValueRelayTests.swift
index fb8035b..d407b43 100644
--- a/Tests/CurrentValueRelayTests.swift
+++ b/Tests/CurrentValueRelayTests.swift
@@ -332,5 +332,13 @@ class CurrentValueRelayTests: XCTestCase {
         XCTAssertTrue(StoredObject2.storedObjectReleased)
         XCTAssertNil(container)
     }
+
+    func testConcurrentAccessToCurrentValueRelaySubscriptions() throws {
+        nonisolated(unsafe) let relay = try XCTUnwrap(relay)
+
+        DispatchQueue.concurrentPerform(iterations: 1_000) { _ in
+            let _ = relay.sink { _ in }
+        }
+    }
 }
 #endif

From 789783ff8508fb0067ba08c86737a66b8d5909a8 Mon Sep 17 00:00:00 2001
From: Richard L Zarth III <rlziii@icloud.com>
Date: Thu, 4 Jun 2026 19:02:17 -0400
Subject: [PATCH 2/2] Formatting.

---
 Tests/CurrentValueRelayTests.swift | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Tests/CurrentValueRelayTests.swift b/Tests/CurrentValueRelayTests.swift
index d407b43..bc9cbd8 100644
--- a/Tests/CurrentValueRelayTests.swift
+++ b/Tests/CurrentValueRelayTests.swift
@@ -336,8 +336,8 @@ class CurrentValueRelayTests: XCTestCase {
     func testConcurrentAccessToCurrentValueRelaySubscriptions() throws {
         nonisolated(unsafe) let relay = try XCTUnwrap(relay)
 
-        DispatchQueue.concurrentPerform(iterations: 1_000) { _ in
-            let _ = relay.sink { _ in }
+        DispatchQueue.concurrentPerform(iterations: 1000) { _ in
+            _ = relay.sink { _ in }
         }
     }
 }