Unless I'm really dense, it seems like there's no way to update a bug description from the CLI. It can be done using git bug termui, but I mostly use git-bug from the CLI.

Here's what I tried:

$ git bug bug title b7bdac4  # just establishing the bug I want to edit is real
Google Drive UI "File name" doesn't update
$ git bug bug edit b7bdac4
2e94c63	open	Edit exercises and exercise parameters   Dan Passaro     
$ git bug bug b7bdac4 edit
2e94c63	open	Edit exercises and exercise parameters   Dan Passaro     
$ git bug bug update b7bdac4
b7bdac4	open	Google Drive UI "File name" doesn't… ◼   Dan Passaro     
$ git bug bug b7bdac4 update
b7bdac4	open	Google Drive UI "File name" doesn't… ◼   Dan Passaro     
$ git bug edit b7bdac4
Error: unknown command "edit" for "git-bug"
Run 'git-bug --help' for usage.
$ git bug update b7bdac4
Error: unknown command "update" for "git-bug"
Run 'git-bug --help' for usage.

The bug's "message" is stored as the first comment, so you can list the comments like this:

$ git bug bug comment d76a207
Author: Steve Moyer
Id: dd7766a
Date: Sat Sep 27 10:12:58 2025 -0400

    Include the whole thing, it's meta-data and comments

Author: Steve Moyer
Id: db7d65a
Date: Sat Sep 27 10:17:56 2025 -0400

    This is the first "non-message" comment but the second message in the DAG

and then edit the bug's message (description) using this:

$ git bug bug comment edit dd7766a --message "Include the whole thing, it's meta-data and comments.  It would also be nice syntactic sugar to provide a \"short-cut\" command to change the message"

which results in the bug's message (the first comment) being changed as expected:

$ git bug bug comment d76a207
Author: Steve Moyer
Id: dd7766a
Date: Sat Sep 27 10:12:58 2025 -0400

    Include the whole thing, it's meta-data and comments.  It would also be nice syntactic sugar to provide a "short-cut" command to change the message

Author: Steve Moyer
Id: db7d65a
Date: Sat Sep 27 10:17:56 2025 -0400

    This is the first "non-message" comment but the second message in the DAG

It would be nice to have some syntactic sugar to support this in the CLI. The TermUI accomplishes this as above.