Can an Artificer use a Veteran's Cane created with Replicate Magic Item as a Focus after it has changed to a Longsword?

Question

Relevant Text:

Artificer:

TOOLS REQUIRED "...After you gain the Infuse Item feature at 2nd level, you can also use any item bearing one of your infusions as a spellcasting focus."

Magic Item:

Veteran's Cane
Wondrous item, common

When you grasp this walking cane and use a bonus action to speak the command word, it transforms into an ordinary longsword and ceases to be magical.

Question: Can this Artificer who used their infusion for a Veteran's cane be able to cast their spells using a non-magical longsword?

For clarification, the scenario is regarding if an Artificer used an infusion to create a Veteran's Cane using the Replicate Magic Item option to use any common magical item in the game.

Answer 1

Ask your DM

The infusion feature says:

Whenever you finish a long rest, you can touch a nonmagical object and imbue it with one of your artificer infusions, turning it into a magic item.

Infusing a veteran's cane

The veteran's cane, as long as it is still a cane, is a magic item and therefore cannot be infused. So if you want to do that, the story ends here: it cannot receive an infusion, and without infusion, you cannot transform it while bearing an infusion into a sword to use as a focus.

Creating a magical sword by infusion

So, what if you first transform it? Once it is transformed, it turns into an ordinary sword, and is no longer magical. A sword is also an object. This nonmagical object can be infused. Let's assume you infuse it with an infusion that works on a longsword. Then (TCoE, p. 11):

After you gain the Infuse Item feature at 2nd level, you can also use any item bearing one of your infu­sions as a spellcasting focus.

Once infused, the sword is bearing one of your infusions and thus can act as your spellcasting focus. That would work, for example, you could use the enhanced weapon infusion to also get a +1 (or higher) bonus to attack and damage rolls, and a magical weapon.

It does not matter that the nonmagical sword used to be a magic item at some point in the past. The Infuse an Item feature checks if the object is a legal target at the time when you try to infuse the item. It does not travel back in time to check what might have been the case before then.

Creating a veteran's cane by infusion

PS. @draconis pointed out there is yet another scenario, you start with a normal cane, and turn that into a veteran's cane (which you can because Replicate Magic Item allows any common item in the game). In that case, once you transform the infused veteran's cane, it turns into a normal, non-magical sword. The rules say that

Your infusion remains in an item indefinitely, but when you die, the infusion vanishes after a number of days equal to your Intelligence modifier (minimum of 1 day). The infusion also vanishes if you replace your knowledge of the infusion.

You neither died nor did you replace your knowledge of the infusion. The transformed staff might still be the same object, just transformed, so the infusion might still be "in" it. At the same time, this now is not a magic item any more, and normally infusions are always magic items.

I think this corner case is sufficiently unclear to better ask your DM how they want to handle it.

To me it wouldn't seem overpowered if you can use a normal sword as your focus and hit people with it too, in exchange of giving up one of your infusions, so I would probably allow it. This would be much worse except in corner cases than just getting a magical sword by infusion.

Conclusion

You can infuse a normal sword (that used to be a magical cane) and then use that magic item as your focus. You can infuse a normal cane to become a veteran's cane, and should ask your DM if it still is infused once you turned that into a normal sword.

Answer 2

No.

Artificer infusions turn nonmagical items into magic items.

Whenever you finish a long rest, you can touch a nonmagical object and imbue it with one of your artificer infusions, turning it into a magic item.

But when a veteran's cane is used, it ceases to be a magic item.

…it transforms into an ordinary longsword and ceases to be magical.

Thus the infusion ends—it's no longer "bearing one of your infusions", and so it's not a viable spellcasting focus.

EDIT: I was assuming you created the veteran's cane using the infusion "Replicate Magic Item", which can create any of the common magic items in the game, including the cane. Apparently this isn't how others have interpreted the question. If you're talking about using an infusion like "Enhanced Weapon" instead, that's a different matter.

Answer 3

Yes you can

Here's why. (TLDR "Infused" is correlated but not the same as "Magical")

First, the Tools Required feature allows you to:

use any item bearing one of your infusions as a spellcasting focus.

Note what this does not say, it does not say that this infused item needs to be magical. If it doesn't say it, it's not part of the rules.

Second, Infusing an item says:

you can touch a nonmagical object and imbue it with one of your artificer infusions, turning it into a magic item.

Notably it does not say that the infused item needs to remain magical in order to be an infused item, only that it turns into a magic item when you touch it. Therefore, if by DM's decree, you're allowed to make a Veteran's Cane, which you then turn into a non-magical sword, you should still be able to use it as a spellcasting focus as it is now technically an infused non-magical longsword.

There are several ways listed that will end your infusion on an object, but the item ceasing to be magical is not on that list. Quotation below:

Your infusion remains in an item indefinitely, but when you die, the infusion vanishes after a number of days equal to your Intelligence modifier (minimum of 1 day). The infusion also vanishes if you replace your knowledge of the infusion.

You can infuse more than one nonmagical object at the end of a long rest; the maximum number of objects appears in the Infused Items column of the Artificer table. You must touch each of the objects, and each of your infusions can be in only one object at a time. Moreover, no object can bear more than one of your infusions at a time. If you try to exceed your maximum number of infusions, the oldest infusion ends, and then the new infusion applies.