diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 3c97163..932914d 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -76,6 +76,18 @@ unit-tests:
       # Nothing in that says "your CI file is malformed". `ci/lint` does.
       echo "GATE: protocol vectors match flamenet-e2e@$FLAMENET_E2E_PIN"
     - Scripts/generate.sh
+    # Keep the build output out of Spotlight.
+    #
+    # `ci-build` reaches ~700 MB and is rewritten every job. Indexing it drives
+    # this host, which is the mac-local runner and therefore in the merge path
+    # for both app repos, to a load average in the hundreds: `mds_stores` and
+    # `mdworker_shared` sit at the top of CPU while no `xcodebuild` process is
+    # near it. That makes every job slower and the machine unpleasant to use
+    # while CI runs.
+    #
+    # The marker has to be written HERE rather than committed, because the
+    # directory it belongs in is created by the build and removed between runs.
+    - mkdir -p ci-build && touch ci-build/.metadata_never_index
     - |
       # `|| true`, deliberately: the log is the gate, not this pipeline's
       # exit status, and the checks below need to run so they can print the