BLE advertising/scanning communication broken on iPhone 17 — CBPeripheralManager + CBCentralManager workflow

There have been some behavioral changes on N1 chip devices; especially in areas where the BT spec has not had a single way of interpreting things. We have been observing these changes and changing them back if appropriate and are considered regressions. So, the first thing you should do is to test all this in the latest iOS 26.3 and see if anything has changed from your earlier observations.

Also, there would have been some changes on patterns of use that were never meant to work, but just happened to work, and those would have been corrected. For example, scanning without services is not supposed to work, and was never expected to work in the background. If you are scanning in the background without services, and whatever the Flutter library may have been doing to work around that limitation (if anything), and that has stopped working, you can consider that a bug that has been fixed.

Similarly, advertising packets in the background have always been on a best effort basis. Also, it has always been possible that due to resource limitations, advertised data could have been hashed into an overflow area, only readable by other Apple devices. If this is happening more often, that would not be necessarily due to the N1 chip changes, but general resource limitations that happen to occur on those devices.

In any case, these need a closer look, and also you may want to look into whether the Flutter library may have anything to do with the issues.

So, we will need more information on all these issues, with sysdiagnoses (with Bluetooth logging profile installed), and the best way to send those over will be via a Bug Report, or several for the different issues, so each can get routed to the appropriate team for the issue.

For each of these issues, please file a separate bug report, include repro steps, and the sysdiagnose from an N1 device and from an earlier device. Also include your reproducible sample project. And please answer the following questions for each issue.

1. peripheralManagerDidStartAdvertising behaviour change What are the errors you are seeing? When you say the advertising is not reaching, have you seen this with a sniffer? Is this during background advertising? If you have logs from the receiving device add those as well. We need to understand if advertising is not being sent out, or this is an interpretation issue with the receiving device.

2. Background scanning stops immediately If you are scanning without services, this is expected behavior, regardless of what you may have observed earlier. If you are scanning with services, the scanning will not stop but slow down. Unless the peripheral is advertising fairly fast, you may be observing a delay rather than a stop. Also, when in the background, didDiscoverPeripheral() will only get called once per scan per peripheral. If the Flutter library has been doing something to workaround this limitation (we see this often), that may have stopped working. In any case, this will need some more debugging on your end, and if you determine this is an issue not with your implementation (library or otherwise), than you could file bug report on this as well.

3. Aggressive session termination on app backgrounding Have you confirmed that your app is staying in the background and not being terminated while in the background? Again, this would not have anything to do with the N1 chip, but the system might be terminating your app due to general resource constraints, not necessarily having to do with Bluetooth. Have you implemented Bluetooth State Preservation/Restoration in your app to make sure the system scans and advertises on your behalf even after your app is terminated?

So, check that the issues are not due to your code/library/target that happens to be exposed on the new phones, and if you believe these should be looked at by the Bluetooth team, please file the bug reports as I explained above, and share the Feedback IDs here. And @mention me in your response, and I will make sure they are routed to the appropriate teams.

Argun Tekant /  WWDR Engineering / Core Technologies

this is actually happening when we do self.peripheralManager?.startAdvertising(self.uuidData) ? do you have any idea.?

  func startAdvertiser(uuid: CBUUID, timeout: Double) -> Single<AdvertiserErrorCode> {
        return Single.create { emitter in
            Utils.blePrint("@startAdvertiser uuid: \(uuid.uuidString), timeout: \(timeout), state: \(self.peripheralManager?.state.rawValue ?? -1), isAdvertising: \(self.advertising)")
            if (self.peripheralManager?.state == CBManagerState.poweredOn) {
                self.timeout = timeout
                self.uuidData = [
                    CBAdvertisementDataServiceUUIDsKey: [uuid]
                ]
                self.emitter = emitter
                self.restartAdvertising()
            } else {
                Utils.blePrint("@startAdvertiser BT not powered on, state: \(self.peripheralManager?.state.rawValue ?? -1)")
                emitter(.success(AdvertiserErrorCode.BLUETOOTH_NOT_ON))
            }
            return Disposables.create {

            }
        }
    }

What is this you say is happening? And there is no startAdvertising() call in your included snippet.