diff --git a/infra/config/generated/cq-builders.md b/infra/config/generated/cq-builders.md
index dcb1778..d933fe24 100644
--- a/infra/config/generated/cq-builders.md
+++ b/infra/config/generated/cq-builders.md
@@ -898,7 +898,7 @@
* Experiment percentage: 10.0
* [mac15-arm64-rel](https://ci.chromium.org/p/chromium/builders/try/mac15-arm64-rel) ([definition](https://cs.chromium.org/search?q=+file:/try/.*\.star$+""mac15-arm64-rel""))
- * Experiment percentage: 100.0
+ * Experiment percentage: 66.0
* [tricium-clang-tidy](https://ci.chromium.org/p/chromium/builders/try/tricium-clang-tidy) ([definition](https://cs.chromium.org/search?q=+file:/try/.*\.star$+""tricium-clang-tidy""))
* Experiment percentage: 100.0
diff --git a/infra/config/generated/luci/commit-queue.cfg b/infra/config/generated/luci/commit-queue.cfg
index 06b5d8b..35e045c 100644
--- a/infra/config/generated/luci/commit-queue.cfg
+++ b/infra/config/generated/luci/commit-queue.cfg
@@ -6936,7 +6936,7 @@
builders {
name: "chromium/try/mac15-arm64-rel"
disable_reuse_footers: "Include-Ci-Only-Tests"
- experiment_percentage: 100
+ experiment_percentage: 66
location_filters {
gerrit_host_regexp: ".*"
gerrit_project_regexp: ".*"
diff --git a/infra/config/subprojects/chromium/try/tryserver.chromium.mac.star b/infra/config/subprojects/chromium/try/tryserver.chromium.mac.star
index 137006e..630dffb1 100644
--- a/infra/config/subprojects/chromium/try/tryserver.chromium.mac.star
+++ b/infra/config/subprojects/chromium/try/tryserver.chromium.mac.star
@@ -340,7 +340,7 @@
# TODO (crbug.com/415099984): change to 100,
# then move out of experimental CQ after,
# mac15-arm64-rel replaces mac14-arm64-rel on CQ.
- experiment_percentage = 100,
+ experiment_percentage = 66,
),
)