Using Zephyr 10.3.0 build on NXP FRDM-MCXN947 leaves board unresponsive after flash.

[DavePutz]

CircuitPython version and board name

Adafruit CircuitPython 10.3.0-alpha.4 on 2026-07-23; FRDM-MCXN947 with mcxn947

Code/REPL

linkserver flash MCXN947:FRDM-MCXN947 load adafruit-circuitpython-nxp_frdm_mcxn947-en_US-10.3.0.elf

Behavior

Flashing the .elf file from 10.3.0-alpha.4 using linkserver works. Using the file from 10.3.0 fails.

Description

A diff of the linkserver outputs doesn't show any interesting differences until the end:

Nc: Starting execution using system reset with a stall address
Nc: Retask read watchpoint 1 at 0x50000040 to use for boot ROM stall
Nc: state - running or following reset request - re-read of state failed - rc Nn(05). Wire ACK Fault in DAP access
Nc: error closing down debug session - Nn(05). Wire ACK Fault in DAP access

After flashing 10.3.0 I don't see CIRCUITPY drive nor can I see any output on the USB port.
Here is the output from 10.3.0-alpha.4 after flashing:

Nc: Starting execution using system reset with a stall address
Nc: Retask read watchpoint 1 at 0x50000040 to use for boot ROM stall
Nc: Boot ROM stalled accessing address 0x50000040 (restoring watchpoint 1)
Ns: Stopped (Was Reset) [Reset from Unknown]: Watchpoint (Temp) #1 - read watchpoint at 0x50000040 Data watch for bootloader stall

Ns: restart on reset

Additional information

[DavePutz]

I used a binary search on nightly builds to determine that adafruit-circuitpython-nxp_frdm_mcxn947-en_US-20260808-main-PR11175-86da044.elf is OK, and adafruit-circuitpython-nxp_frdm_mcxn947-en_US-20260808-main-PR10440-de81f75.elf fails. I see a lot of zephyr-related changes in the diff between those two commits; but did not spot anything immediately suspicious.