WebHare 4.28 offers a simpler <filetype> definition syntax which makes prebuilt files obsolete.

A quick guide to switch from prebuilt types to filetypes:

Change

<prebuiltpage type="dynamic" tag="prebuilt:type" library="lib.whlib" webpageobjectname="Page" />

to

<filetype namespace="http://example.net/xmlns/filetype" kind="virtualfile">
  <dynamicexecution webpageobjectname="lib.whlib#Page" />
</filetype>

And set up a conversion script:

<?wh

LOADLIB "mod::system/lib/database.whlib";
LOADLIB "mod::system/lib/migrations.whlib";

OpenPrimary()->BeginWork();
ConvertPrebuiltFiles("prebuilt:type", "http://example.net/xmlns/filetype");
GetPrimary()->CommitWork();