Our Test Agents are now using Chrome 123 and Lighthouse 11.7.1 to test your Sites. You can find details surrounding the 11.7.1 release in the official Lighthouse changelog.
Starting in Chrome 122, new functionality introduced a regression that caused Lighthouse to misreport Total Blocking Time (TBT) for pages with long main thread tasks. In these cases, we observed an increase to TBT measurements and long task visualisation.
While the issue has not yet been resolved in Chrome 123+, Calibre took action by disabling the responsible functionality using Chrome feature flags. Additionally, Lighthouse 11.7.1 includes a fix that removes overlapping long tasks from browser trace processing.
Calibre helped to identify the issue and pinpoint the offending functionality that caused the regression in tandem with the Lighthouse core team. With these fixes in place, affected pages will now report accurate Total Blocking Time measurements.
In addition to the above changes, Calibre also adjusted First Contentful Paint (FCP) timeout from 45 seconds to 15 (the Lighthouse default). If you've observed NO_FCP errors as a result of this change, you may want to consider adjusting Test Profile settings so that FCP is lower than 15 seconds. Please contact support for assistence or advice, we're always happy to help.