BLE Connection Drops on iPhone 17 Series When 2M PHY Update Fails (Does Not Fallback to 1M PHY)

Question

Created Nov ’25

Replies 2

Boosts 0

Participants 1

Hello Apple engineering team,

We are encountering a BLE connection issue on iPhone 17 series devices running iOS 26.x, while using CoreBluetooth to connect to our Bluetooth accessory in our app Aroma-Link. The problem does not occur on previous iPhone models or earlier iOS versions.

Issue Summary

Our BLE device uses a specific chipset batch where the 2M PHY capability is not fully supported. The expected behavior (as observed on iPhone 16 / 15 / older models) is:

Connection starts on 1M PHY

System attempts to upgrade to 2M PHY

If 2M PHY upgrade fails → system should fallback and continue using 1M PHY

Connection remains active

However, on iPhone 17 series:

After the system attempts to switch from 1M to 2M PHY and the upgrade fails

The device disconnects immediately

No fallback to the original 1M PHY occurs

This results in an unintended and user-visible disconnection.

Reproduction Steps

Use an iPhone 17 series device running iOS 26.x

Connect to the target BLE peripheral via CoreBluetooth (centralManager connectPeripheral)

The system Bluetooth stack initiates a PHY upgrade from 1M → 2M

The peripheral rejects / fails the PHY update

The connection is disconnected automatically

Observed Result

centralManager:didDisconnectPeripheral:error: is triggered immediately after the PHY update fails.

Expected Result

The connection should remain active on 1M PHY, consistent with behavior on:

iPhone 16 / 15 / 14 / etc.

Earlier iOS versions

Impact

This causes:

Connection instability specifically on iPhone 17 users

Inconsistent BLE behavior across device models

Unexpected disconnection despite valid 1M PHY link capability

Environment Item Details App Aroma-Link Bluetooth Framework CoreBluetooth Devices Affected iPhone 17 series iOS Versions iOS 26.x Reproducibility 100% BLE Peripheral Chipset Specific batch with known 2M PHY limitation Request

Could Apple confirm whether the PHY fallback behavior has changed on the iPhone 17 BLE stack, and whether this is an intended change or a regression?

We are happy to provide:

iOS sysdiagnose logs

HCI sniffer captures

Peripheral firmware logs

Please advise on the recommended next steps for debugging or mitigation.

Thank you.

Boost

Answer 1

13625642209@163.com OP

Nov ’25

Hi Quinn “The Eskimo!” (Apple DTS),

Thanks for your follow-up.

We’ve submitted the complete diagnostic data and supporting logs through Feedback Assistant.
Feedback ID: FB20868550

📂 Uploaded files include:

Full sysdiagnose from iPhone 17 (iOS 26.0.1)
Device-side BLE log showing PHY update and disconnect
nRF Sniffer trace (2M PHY update failure)
Comparison trace from iPhone 16 (iOS 25) — fallback works correctly
Readme with timestamps and reproduction steps

🧩 Issue summary

When connecting to our BLE device, iPhone 17 (iOS 26.x) first connects using 1M PHY, then attempts to update to 2M PHY.
If the 2M update fails, the phone immediately disconnects instead of falling back to 1M — unlike other iPhones which recover gracefully.
This issue causes immediate disconnection and affects compatibility with over one million deployed devices.

Please confirm if the diagnostic files under FB20868550 are accessible and sufficient for analysis,
or let us know if any additional logs or captures would be helpful.

Thanks again for your time and support.

Best regards,
Steven
Quectel Wireless Solutions

0

Answer 2

13625642209@163.com OP

Nov ’25

Hi Quinn (@eskimo),

We have re-tested this issue on iPhone 17 running iOS 26.2 Beta (latest build), and the Bluetooth connection problem appears to be resolved in this version.

Specifically, the previous behavior — when the phone switched from 1M PHY to 2M PHY, the update failed and caused an immediate disconnection — no longer occurs.
Now, when the 2M PHY update fails, the connection remains stable on 1M PHY, which matches the expected and normal behavior.

Our Feedback Assistant report ID is FB20868550, and we have already uploaded both the iPhone sysdiagnose logs and the device-side connection logs.

Could you please help confirm whether this fix is part of the internal changes in iOS 26.2 (perhaps related to Bluetooth controller firmware or connection handling improvements)?
This confirmation would be very helpful for us to communicate to our partners and customers.

Thank you very much for your support and follow-up!

Best regards,
Steven
Quectel Wireless Solutions

0