Do not access NSManagedObject outside of NSManagedObjectContext in IdentifiablePayload (#3908)

Author: laevandus

CHANGELOG.md

@@ -3,7 +3,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 # Upcoming
 
-### 🔄 Changed
+## StreamChat
+### 🐞 Fixed
+- Possible fix for rare `thereIsNoSadnessLikeTheDeathOfOptimism` crash in CoreData [#3908](https://github.com/GetStream/stream-chat-swift/pull/3908)
 
 # [4.95.1](https://github.com/GetStream/stream-chat-swift/releases/tag/4.95.1)
 _December 18, 2025_

Sources/StreamChat/APIClient/Endpoints/Payloads/IdentifiablePayload.swift

@@ -58,16 +58,13 @@ extension IdentifiablePayload {
             guard let modelClass = modelClass, let keyPath = modelClass.idKeyPath else { continue }
 
             let values = Array(identifiableValues)
-            var results: [NSManagedObject]?
+            nonisolated(unsafe) var modelMapping: [DatabaseId: NSManagedObjectID] = [:]
             context.performAndWait {
-                results = modelClass.batchFetch(keyPath: keyPath, equalTo: values, context: context)
-            }
-            guard let results = results else { continue }
-
-            var modelMapping: [DatabaseId: NSManagedObjectID] = [:]
-            results.forEach {
-                if let id = modelClass.id(for: $0) {
-                    modelMapping[id] = $0.objectID
+                let results = modelClass.batchFetch(keyPath: keyPath, equalTo: values, context: context)
+                results.forEach {
+                    if let id = modelClass.id(for: $0) {
+                        modelMapping[id] = $0.objectID
+                    }
                 }
             }
             cache[modelClass.className] = modelMapping

Tests/StreamChatTests/APIClient/Endpoints/Payloads/IdentifiablePayload_Tests.swift

@@ -74,6 +74,37 @@ final class IdentifiablePayload_Tests: XCTestCase {
         XCTAssertEqual(cache["\(UserDTO.self)"]?.count, 50)
         XCTAssertEqual(cache["\(MessageReactionDTO.self)"]?.count, 1000)
     }
+    
+    func test_concurrentPerform_getPayloadToModelIdMappings() {
+        let database = DatabaseContainer_Spy()
+        let channelList = createChannelList(
+            channels: 5,
+            users: 5,
+            otherWatchers: 2,
+            messagesPerChannel: 10,
+            readCountsPerChannel: 2,
+            messageReactionsPerChannel: 2
+        )
+        savePayload(payload: channelList, database: database)
+
+        let contexts = [database.writableContext, database.backgroundReadOnlyContext, database.stateLayerContext]
+        let iterations = 2000
+        var caches: [PreWarmedCache] = (0..<iterations).map { _ in [:] }
+        DispatchQueue.concurrentPerform(iterations: iterations) { index in
+            autoreleasepool {
+                let context = contexts[index % contexts.count]
+                caches[index] = channelList.getPayloadToModelIdMappings(context: context)
+            }
+        }
+        
+        for cache in caches {
+            XCTAssertEqual(cache.keys.count, 4)
+            XCTAssertEqual(cache["\(ChannelDTO.self)"]?.count, 5)
+            XCTAssertEqual(cache["\(MessageDTO.self)"]?.count, 50)
+            XCTAssertEqual(cache["\(UserDTO.self)"]?.count, 7)
+            XCTAssertEqual(cache["\(MessageReactionDTO.self)"]?.count, 200)
+        }
+    }
 
     // Identifiable