RE: thingy53 board target re-runs cmake twice when nrf5340dk does not

DanielNG — Tue, 23 Sep 2025 11:21:36 GMT

Hi Anthony,

For Thingy:53, sysbuild is always used and enabled by default.
=> it builds and therefore runs the Cmake file for each image
=> once for application image and once for MCUboot (also once for the network core image if you use it but it's set to empty_net_core by default)

Please refer to DevAcademy lesson on sysbuild Sysbuild explained - Nordic Developer Academy
and this documentation Sysbuild (System build)

Also, if this below is what you meant by "the entire build system is rebuilt", these are just minimal checks to see if anything changed.

ubuntu@zephyr:~/zephyr-projects/ncs/zephyr/samples/basic/blinky$ west build
[0/1] Re-running CMake...
Loading Zephyr module(s) (Zephyr base (cached)): sysbuild_default
-- Cache files will be written to: /home/ubuntu/.cache/zephyr
-- Found west (found suitable version "1.3.0", minimum required is "0.14.0")
-- Board: thingy53, qualifiers: nrf5340/cpuapp
Parsing /home/ubuntu/zephyr-projects/ncs/zephyr/share/sysbuild/Kconfig
Loaded configuration '/home/ubuntu/zephyr-projects/ncs/zephyr/samples/basic/blinky/build/zephyr/.config'
No change to configuration in '/home/ubuntu/zephyr-projects/ncs/zephyr/samples/basic/blinky/build/zephyr/.config'
No change to Kconfig header in '/home/ubuntu/zephyr-projects/ncs/zephyr/samples/basic/blinky/build/_sysbuild/autoconf.h'