Xcode 26.2 can detect a paired Apple Watch in Device Hub yet fail before it becomes a usable run destination. Device preparation times out while Xcode establishes its development tunnel. This guide explains how to identify the failure, follow Apple’s supported connection checks, collect the diagnostics requested by Apple DTS, and keep working while no confirmed fixed version is available.
Error message
Previous preparation error: A connection to this device could not be established.
Timed out while attempting to establish tunnel using negotiated network parameters.Device Hub may also show the Watch capacity as “Unknown,” or list the Watch without completing preparation. This is a connection-stage failure between the Mac, companion iPhone, and Apple Watch—not a compiler error in the watchOS app.
Cause
In the relevant Apple Developer Forums thread, an Apple DTS Engineer described the Xcode 26.2 behavior as an apparent regression and requested a Feedback Assistant report with diagnostics. Apple has not publicly confirmed the underlying defect or named a fixed Xcode release. Signing, application code, or DerivedData should therefore not be treated as the confirmed cause.
Important: Apple’s public material does not identify a release that definitively fixes this tunnel timeout. Do not present an upgrade to a particular version as a guaranteed solution unless Apple later documents the fix.
Affected configuration
- Apple silicon Mac running macOS 26.x
- Xcode 26.2
- Apple Watch paired with an iPhone running iOS 26.1
- watchOS 26.2; the reported case used build 23S303
- The Watch is visible in Device Hub, but tunnel negotiation times out
This is the environment documented in the official forum report, not a claim that every matching setup fails. Later posts mention other pairing failures on newer software, but different logs should not automatically be assigned the same root cause.
Recommended troubleshooting
1. Verify Developer Mode on both devices
Apple’s Device Hub documentation says Apple Watch development pairing requires Developer Mode on both the companion iPhone and the Watch. If you enable it, complete the required restart and confirmation prompts before returning to Xcode.
2. Keep the iPhone and Watch unlocked and nearby
Place all devices close together, unlock the iPhone and Watch, ensure adequate charge, and keep Bluetooth and Wi-Fi enabled. An Apple engineer specifically advised keeping the Watch unlocked while Xcode mounts its Developer Disk Image.
3. Restore trust with a wired iPhone connection
Connect the companion iPhone directly to the Mac over USB and accept trust prompts on both sides. Apple engineering guidance says that after unpairing or choosing not to trust a device, physically reconnecting the iPhone may be necessary before the Watch can be discovered again.
4. Rebuild the connection state in Device Hub
- Quit Xcode.
- Restart the iPhone and Apple Watch.
- Connect the unlocked iPhone to the Mac by cable.
- Launch Xcode and open Window > Devices and Simulators (Device Hub).
- Wait for Watch preparation to finish before selecting it as a run destination.
If the timeout remains, avoid repeatedly unpairing the Watch and collect diagnostics instead.
5. Capture diagnostics and file Feedback
Apple DTS requested the CoreDevice logging profile on the Mac, iPhone, and Apple Watch, plus the watchOS sysdiagnose profile, followed by a coordinated sysdiagnose around the reproduction time. Xcode device diagnostics can also be collected with:
xcrun devicectl diagnoseAttach the reproduction time, exact Xcode/macOS/iOS/watchOS versions, Device Hub state, and diagnostic archives to Feedback Assistant. Do not post bundles containing private system information publicly.
Temporary alternatives
- Apple Watch Simulator: Continue UI and application-logic work, but verify sensors, Bluetooth, networking, and performance on hardware later.
- TestFlight: Forum participants reported it as a hardware-testing workaround while direct debugging was unavailable. Apple has not documented it as an official fix.
- A different stable network: Some community reports mention improvement, but Apple has not confirmed networking as the root cause. Treat it only as an isolation step.
Warnings
- Do not make
sudo pkill -9 remotepairingda routine fix. An Apple engineer said there was no known issue that should require killing the daemon and requested diagnostics instead. - Do not casually unpair the Watch in Device Hub. In the reported case it disappeared, and recovery required a wired companion-iPhone connection.
- Deleting DerivedData or recreating signing certificates is not Apple’s documented remedy for this tunnel error.
- Test beta or alternate Xcode versions only after checking compatibility and preserving a rollback path.
Verification
- The Watch remains visible as an Xcode run destination.
- Device Hub retrieves capacity and OS details instead of leaving them “Unknown.”
- Preparation completes without the tunnel timeout.
- A small watchOS app builds, installs, launches, and accepts a debugger connection.
Summary
“Timed out while attempting to establish tunnel using negotiated network parameters.” means Xcode could not establish its development connection to Apple Watch. Apple DTS described the Xcode 26.2 case as an apparent regression, but Apple has not published a confirmed fixed release. Verify Developer Mode, keep the Watch unlocked, restore trust through a wired companion-iPhone connection, and inspect Device Hub. If the issue persists, submit CoreDevice logs, a coordinated sysdiagnose, and devicectl diagnose output instead of repeatedly force-killing services or unpairing the Watch.
Official references
