diff --git a/tools/ecosystem-generate.sh b/tools/ecosystem-generate.sh
index 8c556fd..23f7056 100755
--- a/tools/ecosystem-generate.sh
+++ b/tools/ecosystem-generate.sh
@@ -59,7 +59,7 @@ export CATALOG="$MEOSAPI/output/meos-idl.json"
 # each family pulls its own dependency (RASTER -> GDAL, H3 -> libh3, POINTCLOUD -> pgpointcloud).
 cmake -S "$PINWT" -B "$PINWT/build-allfam" -DMEOS=ON -DALL=ON \
   -DH3_INCLUDE_DIR=/usr/include/h3 -DH3_LIBRARY=/usr/lib/x86_64-linux-gnu/libh3.so >/dev/null
-cmake --build "$PINWT/build-allfam" --target meos -j"$(nproc)"
+cmake --build "$PINWT/build-allfam" --target meos -j"${CMAKE_BUILD_PARALLEL_LEVEL:-$(nproc)}"
 export LIBMEOS="$PINWT/build-allfam/libmeos.so"
 
 # ── PHASE 1 — JMEOS jar + the non-JVM bindings (all consume the catalog) ──
diff --git a/tools/provision-meos.sh b/tools/provision-meos.sh
index cb82b02..e58f6d1 100755
--- a/tools/provision-meos.sh
+++ b/tools/provision-meos.sh
@@ -35,6 +35,10 @@
 #   --catalog-out <path>   Copy the catalog here in addition to <meos-api>/output/meos-idl.json.
 #   -h, --help
 #
+# Environment:
+#   CMAKE_BUILD_PARALLEL_LEVEL  The number of jobs the libmeos build runs, as CMake reads it.
+#                               Default: the processors this process may run on (nproc).
+#
 # Outputs (printed as KEY=value, and appended to $GITHUB_OUTPUT when set):
 #   catalog-path=<abs path to meos-idl.json>
 #   libmeos-prefix=<abs runtime prefix, or empty when --build-libmeos is not given>
@@ -103,7 +107,7 @@ if [ "$BUILD_LIBMEOS" = 1 ]; then
   [ -x "${PG_CONFIG:=/usr/lib/postgresql/17/bin/pg_config}" ] && cfg+=(-DPOSTGRESQL_PG_CONFIG="$PG_CONFIG")
 
   cmake -S "$MDB_SRC" -B "$MDB_SRC/build" "${cfg[@]}"
-  cmake --build "$MDB_SRC/build" -j "$(nproc)"
+  cmake --build "$MDB_SRC/build" -j "${CMAKE_BUILD_PARALLEL_LEVEL:-$(nproc)}"
 
   # The parse prefix holds a clean MEOS-only include/; install there first (writable), then
   # into the runtime prefix if it is a different location (e.g. the shared /usr/local).