I wonder if it would be a good idea to move the option to change the topic author to the ones shown when clicking the gear icon.
Currently, one must select the option from the first post of the topic, even though it is a function that applies to the topic as a whole, not to its first message.
It’s a simple change that would facilitate editing tasks, especially when using conversations from the AI Bot, where moderation handles moving them, adding tags, and/or changing their authorship.
well kinda, but each Post usually has a different author?
I think for brevity it re-uses the same control for each Post.
That keeps the interface more consistent and compact.
Honestly, after having moderated and/or administered several discussion forums, I find it very unlikely that someone would change the authorship of posts, whereas changing topics is much more common.
Both could coexist, and in that way, the shortcut for topics would be within reach of the tools and the dedicated icon for it.
btw, what do you mean about “gear icon”? - I only see a topic admin wrench aside from the post controls.
To edit the first post you use a control on the first post, so changing the author there too feels logical.
And if you were reviewing this further - why wouldn’t you put changing the author control as part of the topic’s meta like title and category in precedence over moving it to the admin wrench?
I disagree with the statement that the author of the first post is more than that. You don’t really own a topic. Staff can move the post into another topic, and right at that moment, the author is nothing more than the author of the post they have written.
I think the topic wrench and the post wrench have caused confusion before. Mixing the functionality between them wouldn’t clear this confusion but make things even more complicated.
Actions that affect the topic, like closing, pinning, and topic timers, are in the topic menu. Actions that affect the post, like staff notices, post ownership, and locking edits, are in the post menu.
With the argument that the author of the currently first post also being the topic author and thus the option to change it should be in the topic menu, you could also argue that pinning shows the excerpt of the first post in the topic list or as a banner, and therefore this option should be in the post menu. And we can probably find arguments for the other options too. But I think duplicating the content of these already quite feature-rich menus won’t make it easier to find what you are looking for, and keeping topic and post actions separate seems a helpful concept.
Boom 
nailed it.
That for me settles it. Keep it in the Post menu. (imho)
The most common and valuable usecase is when a post was created by an agent and then it would be authored by system.
Is a topic from a post. The wrench is about the topic, formerly, first post.
It is okay if you are not agree. From this usage experience I described clicking three dots, a new wrench and then look into ‘change author’ in the post (it is actually the topic) makes no sense at all 
The Topic wrench is about Topic Admin.
That’s not exactly the same thing as Topic meta data (which includes title, category, tags etc.) as well as author by virtue of the first post.