I added one tiny thing to paper:
.paper/latest.json
Now you don't even have to touch CLI. Agent runs paper run <cmd>. Paper traps the exit code, dumps structured execution JSON to disk, prints COMMAND FAILED, and exits 0.
got a bit addicted to making CAD rendering lol. i used argon again to make a mini cheetah leg. but then turns out it hallucinated some of the system details so i got sonnet 5.5 to fix it up a bit.