[NghiaTranUIT]

Summary

• iOS 26 and iOS 27 add no new URLSession task APIs (diffed the Xcode 27 SDK). iOS 26 adds enablesEarlyData, iOS 26.1 adds allowsUltraConstrainedNetworkAccess.
• The real change is URLSession's new loader built on Network framework. Apps opt in with usesClassicLoadingMode = false (iOS 18.4+), and enablesEarlyData requires it. Apple's header says the default "may be NO in a future OS update" (it's still the classic loader on iOS 27.0 and macOS 27.0.1).
• On the new loader, tasks are NWURLSessionTask (not a subclass of NSURLSessionTask) and none of Atlantis's hooks fired: HTTP, upload, download, async/await and WebSocket traffic were all missed.

Changes

• New loader (NetworkInjector+NWURLSession.swift):
  • -[NWURLSessionTask resume] and the upload methods of NWURLSession
  • Response, body and completion from -[NWURLSessionResponseConsumer* task:deliverResponse:completionHandler:] and task:deliverData:complete:error:completionHandler:
  • WebSocket send/receive/ping/close on NWURLSessionWebSocketTask; the handshake from loaderConnectedWithHTTPConnectionMetadata:CNAMEChain:unlistedTracker:, failures from completeTaskWithError:retryable:
• Existing gaps, both loaders:
  • The request body of async upload(for:from:) and upload(for:fromFile:) was missing (they use the private _uploadTaskWithRequest:…delegate:completionHandler:)
  • WebSocket messages sent before the handshake were dropped, and queued messages were all sent as the last one
  • The resume hook wasn't installed on watchOS 10/11
• Safety: each method is swizzled once, and the hooks reused on the private classes log instead of calling assertionFailure
• README: "What's New" near the top, and a FAQ about the supported APIs
• The new file is added to Atlantis.xcodeproj (Carthage)

Example app

• Redesigned in SwiftUI with a tab for iOS 18 (classic loader), iOS 26 (new loader, Early Data, Ultra Constrained networks) and iOS 27 (AsyncImage(request:), .asyncImageURLSession(_:))
• Each tab lists the APIs that Atlantis captures, grouped. Each row shows the title and the method that Atlantis swizzles
• Tap an API or Run All: the badge shows the status code, a green ✓ means Atlantis captured the request (via AtlantisDelegate)
• WebSocket section on the iOS 18 and iOS 26 tabs: Connect, Send Text, Send Data, Receive, Ping and Close on one URLSessionWebSocketTask (echo.websocket.org)
• The deployment target stays iOS 16.6, rows that need a newer OS are disabled

Testing

• URLSessionLoaderTests.swift: 23 scenarios run on both loaders (URLSessionCaptureTests, NetworkLoaderCaptureTests), plus URLSessionPrivateAPITests that check the private classes, selectors and type encodings. They use an in-process HTTP/SSE/WebSocket server (LocalTestServer.swift), so no internet or Node.js is needed.
• macOS 27.0.1 (swift test): 60 passed, 1 skipped
• iOS 27 simulator (iPhone 18 Pro): 56 passed, 1 skipped. The new suites ran 10 times with 0 failures.
• iPadOS 27 simulator: the new suites passed except the classic refused-upgrade case, which is now skipped
• build-for-testing succeeds for iOS, tvOS, watchOS (simulator and arm64_32 device), visionOS, macOS and Mac Catalyst
• Example app on the iOS 27 simulator: Run All on each tab, every API shows a green ✓ (captured by Atlantis)
• Fixed: the existing testDownloadRequestCaptured used httpbin.proxyman.app/bytes/32, which fails (502, or a reset HTTP/2 stream with an empty body). It downloads /image/png now (df36b7b).
• Skipped: the classic loader's refused WebSocket upgrade. CFNetwork on iOS 27 sometimes never finishes that response (1 in 20 runs), so Atlantis can't see it.

Notes

• Not run: an iOS 26 runtime (the iOS 26 API tests ran on iOS 27), and the watchOS, tvOS and visionOS runtimes.
• CI runs on macOS 15, so the new loader is tested there too. Every hooked method exists on macOS 15 except -[NWURLSessionWebSocketTask completeTaskWithError:retryable:]. It's optional now: a failed handshake is also reported from the receive hook (6c3daae).
• Atlantis.xcodeproj (Carthage) doesn't build with Xcode 27 because its deployment targets (iOS 13, macOS 10.15, tvOS 13) are below Xcode 27's minimum. That's not changed here.

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