- scripts/ci/configure_build.sh holds build-linux's (primary) and build-linux-split's (split) configure lines, flag for flag as before
- scripts/ci/build_fingerprint.py compares two configured trees (cache, compile commands, link statements, CTest files, toolchain) with the build path normalised and the benchmarks left out; its guard configures a probe through the script and never counts thin evidence as equal
- pipe-gates runs its self-test; no job uses the guard yet
