Thief Rogue/Artillerist Artificer help

[Trickster]

I'm going to be building a spymaster type build, so far I've decided on:
Artillerist Artificer 3/ Thief Rogue X

V human

I was planning on reflavoring my Eldritch Cannon as a pistol/magic crossbow and all my spells as either gadgets or superhuman agility or something of that nature.

How would you optimize this? Is it reliable in combat?

[stoutstien]

What are you looking for from the rogue levels?

[Hairfish]

I'd probably take 1st level in artificer for the con save and armor proficiencies and go for feats similar to the Arcana cleric frontliner, mostly using the protector version of the cannon. You won't get (or want) Shillelagh, so you'll be dex-focused and attacking w/ a dagger, but can skip taking Magic Initiate, get Shield from artillerist, and should be dealing more damage if you can consistently sneak attack.

Arcane trickster is a more optimal subclass choice, so you can stack spell slots from artificer. Battlesmith is probably a better choice than artillerist (SAD, rapier), but would benefit from more artificer levels so your construct doesn't die all the time

[J-H]

Activating the Eldritch Cannon takes an action.
Firing it takes a bonus action. So does using Cunning Action, which is about 40% of the rogue's kit.

I really don't see any synergy here.

[Kane0]

Id optimize by dropping rogue and going full artificer, using tashas with a race that normally provides weapon proficiencies like elf or dwarf to trade for a bunch more tools that artificer gives you expertise in. If you want skill expertises then theres a feat for that rather than going into rogue, especially since the artillerist kit will largely get in the way of sneak attack and cunning action.

[greenstone]

The Eldritch Cannon cannot trigger sneak attack, so there isn't much synergy between the classes.

[stoutstien]

The Eldritch Cannon cannot trigger sneak attack, so there isn't much synergy between the classes.

There is a few things that work well together but most of it doesn't come online until later on.

Like the spell story item is usable by fast hands as long as you don't put it into a <magical> item which changes the action type. Since it's not casting it's one of the few ways where you can constantly get multiple spells off a turn or combine it with other actions.

Coming action is just generally a good feature even if you have a stacked bonus action but armorer is noticably lacking one.

Battle Masters are really good at generating advantage for themselves and have a "permanent" flanking buddy for sneak attack.

None of these are particularly worth delaying artificer for but they aren't bad either. It's just that it has one of the best class progress to a point any multiclassing is something you doing purely to fulfill a very specific character image.

[Trickster]

So I'm getting I should change Artillerist to Battle Smith?

Hmm.. I was going for a Spymaster/Corvo theme. Eldritch Cannon has more versatility than a clunky behemoth that won't be able to heal considering I'm only planning on taking 3 levels of artificer.

Anyone got any background recommendations? Or possible feats down the road? I was planning on taking poisoner at first level bc of V human.

[Kane0]

Armorer Artificer gives you a INT-based, lightning damage weapon with longbow range that you don't need hands to use and works with sneak attacks, plus an extra 5' movement speed and advantage on your stealth checks. It's pretty good for a rogue.
For feats, some good ones to consider are Fey/Shadow Touched, Alert, Observant, Telekinetic and Telepathic. Poisoner, Skill Expert, Mobile and Skulker are also decent if you have the right game to use them in.