diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c5a17e6..978bd38 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -40,8 +40,10 @@ jobs:
     steps:
       - uses: actions/checkout@v7
 
-      # shipyard installs itself via its own action (HTTPS via the runner token). It self-registers
-      # in the user package registry, so find_package resolves it downstream with no CMAKE_PREFIX_PATH.
+      # shipyard installs itself via its own action (HTTPS via the runner token). The action puts
+      # shipyard-cmake on PATH and exports SHIPYARD_SCRIPTS; shipyard-cmake is the only cmake that
+      # configures against shipyard, and it supplies the prefix find_package(MavericksShipyard)
+      # resolves from, so there is nothing to register and no CMAKE_PREFIX_PATH to set.
       - name: Install mavericks-shipyard
         uses: ModernMavericks/shipyard/.github/actions/install@v1
 
@@ -53,9 +55,9 @@ jobs:
       # guard runs as a build-time POST_BUILD (static otool check; no Rosetta).
       - name: Configure + build (x86_64 @ 10.9) — compat guard gates Porthole
         run: |
-          cmake --preset cross
-          cmake --build build-cross
+          shipyard-cmake --preset cross
+          shipyard-cmake --build build-cross
           echo "Porthole slice:"; lipo -info build-cross/porthole/viewer/Porthole.app/Contents/MacOS/Porthole
 
       - name: Off-device codec test (Rosetta)
-        run: ctest --preset cross -R '^protocol$' --output-on-failure
+        run: shipyard-ctest --preset cross -R '^protocol$' --output-on-failure
diff --git a/build/msc.sh b/build/msc.sh
index 605ee1e..43c2af0 100644
--- a/build/msc.sh
+++ b/build/msc.sh
@@ -1,6 +1,25 @@
-# build/msc.sh -- sourced: locate the installed mavericks-shipyard scripts dir as $SHIPYARD.
+#   usage: . build/msc.sh
+#          Sourced by a ModernMavericks product's build scripts: locates shipyard's scripts as
+#          $SHIPYARD and exports SHIPYARD_SCRIPTS. In CI, install@v1 has already exported
+#          SHIPYARD_SCRIPTS; anywhere else this asks shipyard-cmake -- the only cmake that configures
+#          against shipyard -- where find_package(MavericksShipyard) lands, so a CMAKE_PREFIX_PATH
+#          dev override moves the scripts together with the modules. About 2 s, exported so children
+#          skip it. CANONICAL COPY: shipyard's scripts/templates/msc.sh; conventions check 17
+#          requires every product's copy to match it byte for byte, so change it there, not here.
 SHIPYARD="${SHIPYARD_SCRIPTS:-}"
-[ -d "$SHIPYARD" ] || SHIPYARD="$(cat "$HOME/.cmake/packages/MavericksShipyard/"* 2>/dev/null | head -1)/scripts"
-[ -d "$SHIPYARD" ] || SHIPYARD="$(cd "$(dirname "$0")/.." && pwd)/../mavericks-shipyard/scripts"
-[ -d "$SHIPYARD" ] || { echo "cannot locate mavericks-shipyard scripts (install it, or set SHIPYARD_SCRIPTS)" >&2; return 1 2>/dev/null || exit 1; }
-export SHIPYARD
+if [ ! -d "$SHIPYARD" ]; then
+  _msc_probe="$(mktemp -d "${TMPDIR:-/tmp}/shipyard-probe.XXXXXX")"
+  printf '%s\n' 'cmake_minimum_required(VERSION 3.16)' 'project(shipyard_probe NONE)' \
+    'find_package(MavericksShipyard REQUIRED)' 'message(STATUS "SHIPYARD_DIR=${MavericksShipyard_DIR}")' \
+    > "$_msc_probe/CMakeLists.txt"
+  # platform: appending /scripts to the substitution directly made a failed probe (no
+  #           shipyard-cmake, a refused configure) yield the literal "/scripts" -- an absolute path,
+  #           plausible-looking, and the error below would then complain about the wrong thing. So
+  #           assign the probe's answer first and append only if there was one.
+  _msc_dir="$(shipyard-cmake -S "$_msc_probe" -B "$_msc_probe/b" 2>/dev/null | sed -n 's/^-- SHIPYARD_DIR=//p')"
+  if [ -n "$_msc_dir" ]; then SHIPYARD="$_msc_dir/scripts"; fi
+  rm -rf "$_msc_probe"; unset _msc_probe _msc_dir
+fi
+[ -d "$SHIPYARD" ] || { echo "msc.sh: cannot locate shipyard -- install the shipyard pkg (it provides shipyard-cmake), or set SHIPYARD_SCRIPTS" >&2; return 1 2>/dev/null || exit 1; }
+SHIPYARD_SCRIPTS="$SHIPYARD"
+export SHIPYARD SHIPYARD_SCRIPTS