Distributed test zips go stale and stray. BT_EXPIRE (CMake option,
DEFAULT ON so a zip can never accidentally ship without it) makes the
exe refuse to start BT_EXPIRE_DAYS (default 14) after its build day:
boot logs the remaining window, an expired build logs + shows a
"test build expired -- ask the operator for the current build" box and
exits. btversion.h now stamps BT_BUILD_UNIX (UTC-midnight-rounded so
the only-on-change header churns once per day, not every build) +
BT_BUILD_DATE. Dev is unaffected: every build re-stamps the day.
-DBT_EXPIRE=OFF builds a non-expiring exe; mkdist reads the cache and
marks such a zip "-noexpire" + prints a warning, and the tester README
expiry note is {EXPIRE}-marker-gated like the steam lines. Second
compile-gate exception after BT_STEAM (convention updated in
glass-cockpit.md). Quality gate, not DRM -- a clock rollback defeats it.
Verified live: default build logs "test build window: 14 day(s) left";
a -DBT_EXPIRE_DAYS=0 build logs TEST BUILD EXPIRED and parks on the
explanation box (window title checked) without starting the game;
restored to 14 and rebuilt clean.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
