Does Ethersworn Canonist prevent you from casting artifact spells as your one nonartifact spell per turn?

Ethersworn Canonist reads: 'Each player who has cast a nonartifact spell this turn can't cast additional nonartifact spells.' This restriction applies exclusively to nonartifact spells — artifact spells are completely unaffected by the Canonist's ability and may be cast any number of times in a turn.

The key is understanding what the Canonist tracks and restricts. It watches whether you have cast a nonartifact spell this turn, and if you have, it prevents you from casting more nonartifact spells. Artifact spells never enter into this calculation at all — neither as the trigger condition nor as the restricted category (CR 601.2, CR 112.1).

So in practice, you may cast as many artifact spells as you like in a turn regardless of the Canonist. You are limited to one nonartifact spell per turn (the first one is allowed; subsequent ones are prevented).

Example: You control Ethersworn Canonist. You cast Mox Opal (artifact), then Mox Amber (artifact), then a Lightning Bolt (nonartifact). After the Bolt resolves, you cannot cast another nonartifact spell this turn, but you may still cast more artifact spells freely, such as a third Mox.

Note: The Canonist does not prevent casting the first nonartifact spell — it only prevents casting additional ones after the first. Artifact spells remain unrestricted throughout (CR 601.2).