diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index ae3975d..ff9d095 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -77,6 +77,21 @@ unit-tests:
     # survives, and a suite that stopped running entirely would still be
     # counted, by the very check meant to notice that it had stopped.
     - rm -rf ./*/build/test-results
+    # Keep the build output out of Spotlight.
+    #
+    # The module build directories are rewritten every job on a host that is
+    # also the mac-local runner for both app repos. Indexing them drives the
+    # machine to a load average in the hundreds, with `mds_stores` and
+    # `mdworker_shared` at the top of CPU while no build process is near it.
+    # Measured on the iPhone repo: the same from-scratch build peaks at load
+    # ~12 with its output excluded and well over a hundred without.
+    #
+    # Written here rather than committed, because the directories these belong
+    # in are created by the build.
+    - |
+      for m in app engine client obfs4; do
+        mkdir -p "$m/build" && touch "$m/build/.metadata_never_index"
+      done
     # `:obfs4:test` was missing from this list. The module shipped in !77
     # with ~100 tests, the Elligator2 port, the framing, the handshake, the
     # socket factory, and not one of them ran in CI. A break in the transport