Feature Request: Updating blog's Profile ID triggers internal follower migration

[craigS89]

What

the web-finger for the last previous profile id/Handle should be preserved, to forward on users to the new profile ID/handle with a 'move' object

Why

Changing the blog profile ID/handle creates a hard break that means followers of the old id no longer see updates.

How

Suggested fix:
the plugin can simulate migrating a profile internally.
the webfinger for the last old blog profile ID/handle remains, but is set to forward/migrate followers on to the new/current profile id. it would probably also need one attached object with the 'Move' activity

BDD
GIVEN my current blog handle is @old@blog.address
WHEN i go to the activitypub plugin settings
AND change the profile ID to @new@blog.address
THEN the webfinger url 'blog.address/@old' still remains, but is now set to migrate/forward followers to new handle.

[faisalahammad]

Thanks for the clear writeup.

The plugin already supports account migration through the ActivityPub Move activity, alsoKnownAs, and movedTo, including a manual path via WP-CLI (wp activitypub move <from> <to>) and the Account Aliases field on the blog profile. There is a user guide in docs/how-to/account-migration.md.

The gap this issue points at is real: today, changing the Blog Profile ID (activitypub_blog_identifier) only fires a profile Update, not a Move, and the previous handle is not stored, so the old @old@domain WebFinger lookup stops resolving.

This is already being worked on. #2766 moves blog and user actor IDs from the handle-based permalink form (/@handle) to a stable query-param form (?author=ID), so changing the handle no longer changes the actor ID and can no longer strand followers. It also migrates existing permalink-ID actors with a Move and keeps the old ID resolving with a movedTo, which matches the behavior described here. It depends on #3585, which fixes the move verification and follower notification ahead of it.

One nuance worth noting: with stable IDs the main pain goes away because followers stay subscribed to the ID, not the handle. But keeping an arbitrary old @old@domain WebFinger alive specifically for a handle-to-handle rename (as opposed to a domain move) may still need a small addition on top of #2766, since handle history isn't stored today. That is best confirmed with the maintainer on #2766.

Suggest tracking this against #2766 / #3585 rather than a separate path, so the migration logic stays in one place.