Can an Artificer's Infusions act as a spellcasting focus for spells from another class?

Question

I'm specifically looking at the case of a character that starts as an Armorer Artificer, then multiclasses into Wizard for the majority of their career. As I read it, as long as the Artificer has applied an Infusion to their armor, they have a spellcasting focus for both Wizard and Artificer spells in the same hand they use to enact the somatic component of a spell at all times, since their Arcane Armor has covered their entire body.

I am not counting on or involving the Armorer's Arcane Armor feature in any way here, because that clearly states that the armor can only be used for Artificer spells:

You can use the arcane armor as a spellcasting focus for your artificer spells.

I am instead counting on the specific wording of the "Tools Required" subsection of the Artificer's base Spellcasting feature, which they receive at Artificer level 1:

You produce your artificer spell effects through your tools. You must have a spellcasting focus - specifically thieves' tools or some kind of artisan's tool - in hand when you cast any spell with this Spellcasting feature (meaning the spell has an "M" component when you cast it). You must be proficient with the tool to use it in this way. See the equipment chapter in the Player's Handbook for descriptions of these tools. 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.

Note that it only mentions that you can use it as a spellcasting focus, not as a spellcasting focus for your Artificer spells, or with any other specific prohibitions. For precedent, here is the wording on Ruby of the War Mage, which allows Wizards to use weapons as spellcasting foci for their spells:

Etched with eldritch runes, this 1-inch-diameter ruby allows you to use a simple or martial weapon as a spellcasting focus for your spells.

I'm also thinking that the specific wording of the Spellcasting Focus section of the Wizard's Spellcasting feature gives additional precedent to my reading of the Tools Required feature from the Artificer. Here's what the Wizard Spellcasting Focus section says:

You can use an arcane focus as a spellcasting focus for your wizard spells.

This tells me that there are a few options, but I'm trying to opt for the easiest available. I could get an arcane focus of some kind to cast Wizard spells, and I could use my armor to cast Artificer spells, but all of that sounds like a lot of unnecessary work, and juggling of foci, especially when I want to punch a bad guy with both gauntlets.

Am I missing anything?

Answer 1

No

From Artificer in TCoE:

You produce your artificer spell effects through your tools. ...

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

From Wizard in PH:

You can use an arcane focus as a spellcasting focus for your wizard spells.

Tools or infusion for artificer spells; arcane focus (or component pouch) for wizard spells.

Answer 2

Unless I discover contradictory evidence, I've gone far enough down this rabbit hole, that I believe I have a definitive answer to this question:

I assert that the omission of "for your Artificer spells" from the spellcasting focus description of Infused items in Tools Required is intentional, and does indicate that it is a universal spellcasting focus, allowing spells from any class to be cast with it.

In order to settle this, I've looked into absolutely every mention of "Spellcasting Focus" across all classes and subclasses currently in D&D 5e. In absolutely every mention of a spellcasting focus, which necessarily includes every other mention within the same book (Tasha's Cauldron of Everything) which includes at least 6 other specific rules around Spellcasting Foci, the class is mentioned in relation to the spells that can be cast with it. The only place in any content where this part of the description is omitted is within "Tools Required" for the Artificer, and only after you get access to the Infuse Item feature.

Here is the complete list, for the curious:

Artificer

Tools Required

You produce your artificer spell effects through your tools. You must have a spellcasting focus - specifically thieves' tools or some kind of artisan's tool - in hand when you cast any spell with this Spellcasting feature (meaning the spell has an "M" component when you cast it). You must be proficient with the tool to use it in this way. See the equipment chapter in the Player's Handbook for descriptions of these tools.

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.

Armorer

Arcane Armor

You can use the arcane armor as a spellcasting focus for your artificer spells.

Artillerist

Arcane Firearm

You can use your arcane firearm as a spellcasting focus for your artificer spells.

Specialists with no reference to additional Spellcasting Focus

Battle Smith, Alchemist

Bard

Spellcasting Focus

You can use a musical instrument (found in chapter 5) as a spellcasting focus for your bard spells.

College of Spirits

Spiritual Focus

At 3rd level, you employ tools that aid you in channeling spirits, be they historical figures or fictional archetypes. You can use the following objects as a spellcasting focus for your bard spells: a candle, crystal ball, skull, spirit board, or tarokka deck.

College of Swords

Bonus Proficiencies

If you’re proficient with a simple or martial melee weapon, you can use it as a spellcasting focus for your bard spells.

Colleges with no reference to Spellcasting Focus

Whispers, Valor, Lore, Glamour, Eloquence, Creation

Cleric

Spellcasting Focus

You can use a holy symbol as a spellcasting focus for your cleric spells.

Domains with no reference to Spellcasting Focus

All of them: Arcana, Death, Forge, Grave, Knowledge, Life, Light, Nature, Order, Peace, Tempest, Trickery, Twilight, War.

Druid

Spellcasting Focus

You can use a druidic focus as a spellcasting focus for your druid spells.

Circle of Stars

Star Map

At 2nd level, you've created a star chart as part of your heavenly studies. It is a Tiny object and can serve as a spellcasting focus for your druid spells.

Circles with no reference to Spellcasting Focus

Dreams, Land, Moon, Shepherd, Spores, Wildfire

Paladin

Spellcasting Focus

You can use a holy symbol as a spellcasting focus for your paladin spells.

Oaths with no reference to Spellcasting Focus

All of them: Conquest, Crown, Devotion, Glory, Redemption, Vengeance, Watchers, Oathbreaker.

Ranger

Spellcasting Focus (Optional)

At 2nd level, you can use a druidic focus as a spellcasting focus for your ranger spells.

Conclaves with no reference to Spellcasting Focus

All of them: Beast Master, Fey Wanderer, Gloom Stalker, Horizon Walker, Hunter, Monster Slayer, Swarmkeeper, Drakewarden.

Other melee casters with no reference to Spellcasting Focus

Fighter - Eldritch Knight, Rogue - Arcane Trickster

Sorcerer

Spellcasting Focus

You can use an arcane focus as a spellcasting focus for your sorcerer spells.

Sorcerous Origins with no reference to Spellcasting Focus

All of them: Aberrant Mind, Clockwork Soul, Draconic Bloodline, Divine Soul, Lunar Sorcery, Shadow Magic, Storm Sorcery, Wild Magic

Warlock

Spellcasting Focus

You can use an arcane focus as a spellcasting focus for your warlock spells.

The Genie

Genie's Vessel

The vessel is a Tiny object, and you can use it as a spellcasting focus for your warlock spells.

Otherworldly Patrons with no reference to Spellcasting Focus

The Archfey, The Celestial, The Fathomless, The Fiend, The Great Old One, The Hexblade, The Undead, The Undying

Wizard

Spellcasting Focus

You can use an arcane focus as a spellcasting focus for your wizard spells.

Order of Scribes

Awakened Spellbook

You can use the book as a spellcasting focus for your wizard spells.

Arcane Traditions with no reference to Spellcasting Focus

Abjuration, Bladesinging, Chronurgy, Conjuration, Divination, Enchantment, Evocation, Graviturgy, Illusion, Necromancy, Transmutation, War Magic