With gerrit 151806, the Echo notifications.feature browser tests have a step "another user writes on my talk page" that uses MediawikiApi::Client.create_page.
This silently fails if the user's talk page is a Flow board, which is the default on the Flow team's test servers.
The action=edit API call returns successfully, but if you ask for the content of the page, e.g. Special:Export, you'll see that the revision ID is updated but the text content is an empty array. The moment someone visits the Flow board its content changes back to being {"flow-workflow":"<UUID>"}.
The Flow team needs to figure out what should happen when someone uses the action=edit API on a Flow board. It seems either it should fail, or it could succeed and modify the Flow board's header area.
Version: unspecified
Severity: normal