For some reason, the infusion "enhanced arcane focus", which grants a +1 to spell attack rolls, does not affect the Eldritch Cannon, which utilizes the PC's spell attack modifier (e.g. a level 4 artillerist with 18 int and enhanced arcane focus has a +7 to spell attacks, but the Eldritch Cannon is listed as having +6 to hit)
Is this a bug or am I misinterpreting the rules of these class features?
After scouring the rules and the reddits for discussion of this issue, the consensus seems to be... while you hold it, the enhanced arcane focus adds +1 to your spell attack rolls, and the attack ignores half cover. With Eldritch Cannon's Force Ballista, you use your bonus action to make a ranged spell attack from the cannon, using your To-Hit for spell attacks, therefore the +1 should apply to the attack roll.
(But apparently any damage bonus from using the enhanced focus as your Arcane Firearm won't apply to cannon damage, only to attacks you make by casting artificer spells through the focus.)
So yes, I would say it is a bug, but it may not be a quick fix. In the meantime, you can customize the Force Ballista to add a bonus +1 to the attack, assuming you have the enhanced arcane focus equipped. Not ideal but you get the numbers you need.
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Helpful rewriter of Japanese->English translation and delver into software codebases (she/e/they)
For some reason, the infusion "enhanced arcane focus", which grants a +1 to spell attack rolls, does not affect the Eldritch Cannon, which utilizes the PC's spell attack modifier (e.g. a level 4 artillerist with 18 int and enhanced arcane focus has a +7 to spell attacks, but the Eldritch Cannon is listed as having +6 to hit)
Is this a bug or am I misinterpreting the rules of these class features?
After scouring the rules and the reddits for discussion of this issue, the consensus seems to be... while you hold it, the enhanced arcane focus adds +1 to your spell attack rolls, and the attack ignores half cover. With Eldritch Cannon's Force Ballista, you use your bonus action to make a ranged spell attack from the cannon, using your To-Hit for spell attacks, therefore the +1 should apply to the attack roll.
(But apparently any damage bonus from using the enhanced focus as your Arcane Firearm won't apply to cannon damage, only to attacks you make by casting artificer spells through the focus.)
So yes, I would say it is a bug, but it may not be a quick fix. In the meantime, you can customize the Force Ballista to add a bonus +1 to the attack, assuming you have the enhanced arcane focus equipped. Not ideal but you get the numbers you need.
Helpful rewriter of Japanese->English translation and delver into software codebases (she/e/they)
I talked to my DM and they agree with this interpretation too. Thank you very much for the advice!