305671 2026-01-16 15:29:11 -0800 [Tahoe Release] fast/animation/css-animation-throttling.html is a flakey text failure. 2026-04-18 01:38:00 -0700 1 1 1 Unclassified WebKit Animations WebKit Nightly Build Unspecified Unspecified REOPENED InRadar P2 Normal --- 1 d_delatoba graouts graouts webkit-bot-watchers-bugzilla webkit-bug-importer oldest_to_newest 2172629 0 d_delatoba 2026-01-16 15:29:11 -0800 fast/animation/css-animation-throttling.html is a flakey text failure on Tahoe MacOS release. HISTORY: https://results.webkit.org/?suite=layout-tests&test=fast%2Fanimation%2Fcss-animation-throttling.html&version_name=Tahoe&architecture=arm64&recent=false TEXT DIFF: --- /Volumes/Data/worker/Apple-Tahoe-Release-AppleSilicon-WK2-Tests/build/layout-test-results/fast/animation/css-animation-throttling-expected.txt +++ /Volumes/Data/worker/Apple-Tahoe-Release-AppleSilicon-WK2-Tests/build/layout-test-results/fast/animation/css-animation-throttling-actual.txt @@ -4,11 +4,11 @@ internals.setLowPowerModeEnabled(true) -PASS internals.animationsInterval is throttled +FAIL internals.animationsInterval should be 0.05333333333333334. Was 0.02666666666666667. internals.setLowPowerModeEnabled(false) PASS internals.animationsInterval is unthrottled internals.setAggressiveThermalMitigationEnabled(true) -PASS internals.animationsInterval is throttled +FAIL internals.animationsInterval should be 0.05333333333333334. Was 0.02666666666666667. internals.setAggressiveThermalMitigationEnabled(false) PASS internals.animationsInterval is unthrottled PASS successfullyParsed is true TEXT URL: https://build.webkit.org/results/Apple-Tahoe-Release-AppleSilicon-WK2-Tests/305729@main%20(1157)/fast/animation/css-animation-throttling-pretty-diff.html STEPS TO REPRODUCE: I was NOT able to reproduce this failure at macOS Tahoe ToT running the test as follows: run-webkit-tests fast/animation/css-animation-throttling.html --iterations 5000 I am going to mark expectations for this test as a pass failure while it is under investigation. 2172630 1 webkit-bug-importer 2026-01-16 15:29:17 -0800 <rdar://problem/168329911> 2172632 2 d_delatoba 2026-01-16 15:34:04 -0800 Pull request: https://github.com/WebKit/WebKit/pull/56742 2172633 3 ews-feeder 2026-01-16 15:37:28 -0800 Test gardening commit 305739@main (f13ad2306836): <https://commits.webkit.org/305739@main> Reviewed commits have been landed. Closing PR #56742 and removing active labels. 2201548 4 graouts 2026-04-17 09:12:26 -0700 I can't reproduce this flakiness locally but inspecting the code I don't see any code that guarantees that neither low-power mode nor aggressive thermal mitigation mode are disabled prior to the test starting. Something else that appears to be unexpected (to me anyway) is that the intervals in question do not match either `FullSpeedAnimationInterval` (15ms) nor `HalfSpeedThrottlingAnimationInterval` (30ms), which would indicate that `nominalFramesPerSecond` passed to `Seconds preferredFrameInterval(OptionSet<ThrottlingReason>, std::optional<FramesPerSecond>, bool)` is set to something other than `FullSpeedFramesPerSecond`. I'll add assertions that check that we're in the expected throttling state prior to the test starting to determine whether that is the issue. 2201553 5 graouts 2026-04-17 09:23:51 -0700 We don't have existing APIs to query the throttling state, so let's just ensure it's set to be what we expect the default to be. 2201554 6 graouts 2026-04-17 09:27:40 -0700 Pull request: https://github.com/WebKit/WebKit/pull/62983 2201655 7 ews-feeder 2026-04-17 14:36:57 -0700 Committed 311474@main (cb5bd2d7b52c): <https://commits.webkit.org/311474@main> Reviewed commits have been landed. Closing PR #62983 and removing active labels. 2201804 8 graouts 2026-04-17 23:38:04 -0700 Bots indicate this is still an issue, reopening as such. 2201818 9 graouts 2026-04-18 01:17:26 -0700 Interesting to see that the last failed run (https://build.webkit.org/#/builders/1716/builds/3268) shows other throttling-related tests failing: fast/animation/request-animation-frame-throttle-inside-overflow-scroll.html [ Failure ] fast/animation/request-animation-frame-throttle-subframe-display-none.html [ Failure ] fast/animation/request-animation-frame-throttle-subframe.html [ Timeout ] I wonder if we get in a situation where the bot is actually legitimately entering one of those throttling reasons. 2201821 10 graouts 2026-04-18 01:38:00 -0700 Hmm, looking at the other test failures (https://build.webkit.org/results/Apple-Tahoe-Release-AppleSilicon-WK2-Tests/311205@main%20(3268)/results.html) it would appear that throttling is unexpectedly set to `VisuallyIdle`. I expect this is the core issue, that throttling is set in this test due to other reasons.