I want to know why Hydration Error issues still appear after I set ignoreErrors (see Why aren't some hydration errors being dropped by the SDK?) and enabled the hydration error inbound filter.

These issues are often Replay Issues created from Session Replay data through Project Settings → Replay → Create Hydration Error Issues.

Because they are generated from Replay data rather than from the filtered error event itself, inbound filters and ignoreErrors do not prevent them from being created. Replay Issues also do not count toward your error quota.

If you don't want Sentry to create these issues, turn off Create Hydration Error Issues in your project's Replay settings.

If you want to keep the Replay Issues but exclude them from the main Issues stream when searching, you can use issue.category:error. To show only Replay Issues, use issue.category:replay.