I wasn't immediately able to reproduce this. Here's what I did:

>>> orbital ~/repos/POEMS $ git tag -fm bloop quack HEAD
Updated tag 'quack' (was ae1456f)

Then:

>>> orbital ~/repos/POEMS $ git push --tags --force
Counting objects: 1, done.
Writing objects: 100% (1/1), 153 bytes | 0 bytes/s, done.
Total 1 (delta 0), reused 0 (delta 0)
To ssh://dweller@localhost/diffusion/POEMS/
 + ae1456f...0254e64 quack -> quack (forced update)

Once parsing completed, the new commit was reflected in the UI:

(Note that the commit is not rPOEMSae1456f.)

Can you browse via that tag now? We see the hash update but then get a "Failed to look up tag" exception.

Yeah, works fine locally:

Maybe I could make a test repo on this server and you could try breaking it by pushing tags/commits? I can play around locally a bit more too but I'm sort of just fishing at this point.

Let's do it with a test repo, I'll execute the commands and see if it gets crazy.

Still seeing this issue on a hosted phabrictor instance (hosted by phoreplay, so I don't know if it's up to date). Phabricator version 64c87770266444ff6e4a7156a97c6236c1ff090b, Arcanist Version 46ce8a5a35f9057b30151b5cb99a80642d913d22, libphutil Version 00e1f2da28291027b369f363e82c12f0b70de374. No exceptions generated, just out of date tag information.

64c877702 is about 3 months out of date (April 29).

Fair enough. I am still seeing this bug at that point. I don't know if it's been fixed later...