diff --git a/test/filters/browser_tests.filter b/test/filters/browser_tests.filter
index 49a9004a439..2d809b7a4e1 100644
--- a/test/filters/browser_tests.filter
+++ b/test/filters/browser_tests.filter
@@ -3586,6 +3586,15 @@
 # https://github.com/brave/brave-browser/issues/54039
 -ChromeDataUseMeasurementBrowserTest.DataUseRecorded
 
+# This Chromium test times out because RunUntilIdle() at
+# browser_test_base.cc:966 never completes — Brave's additional startup
+# services (stats updater, referrals, P3A, NTP background images, etc.) keep
+# the UI thread task queue non-idle, exceeding the 30-second
+# action_max_timeout. Upstream flake rate: 0.2% (stable). No Brave
+# modifications to the extension module API code under test.
+# https://github.com/brave/brave-browser/issues/54187
+-PersistentBackground/ExtensionModuleApiTest.CognitoFile/0
+
 # Chromium test: known upstream flake (3.4% flake rate over 30 days,
 # 112k+ verdicts). No Brave modifications in chrome/browser/save_to_drive/.
 # Test times out during PDF extension host loading in SetUpOnMainThread.