Pre-flight

python3 ${CLAUDE_PLUGIN_ROOT}/scripts/preflight.py
python3 ${CLAUDE_PLUGIN_ROOT}/scripts/preflight.py --json

Exits non-zero on failure. Everything it checks is something a machine can check; everything it cannot check, it names.

The principle

Check the artifact, not the signal that stands in for it.

Every failure this script is built to catch produces a successful-looking build. Typst exits 0. The PDF opens. KDP accepts the upload. The problem is discovered in a proof copy, which is the most expensive possible place to discover it.