In Safari Web Extensions on iOS 18, declarativeNetRequest Rulesets and Dynamic Rules take over twice as long to apply -- which causes rulesets to often fail to apply before sites load. In a boilerplate Xcode project you can note the time difference toggling the OISD (https://oisd.nl) ruleset on iOS 17 and iOS 18 simulators. Additionally, if you force quit Safari and reopen to a site with ads blocked by OISD list (e.g. espn.com) the content will be blocked in that initial state on iOS 17, but not in iOS 18 due to the latency.
Based on the boilerplate extension, this bug is impacting all Mobile Safari Extensions using declarativeNetRequest Rulesets and Dynamic Rules. We know several other extension developers dealing with this issue.
Our team wrote detailed reproduction steps in our Feedback Assistant ticket: https://feedbackassistant.apple.com/feedback/15196130 but have received no responses. I would attach a screen recording here but it won't allow me.
EricatPie
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