Can I switch out my Level 1 any-school spell as an Arcane Trickster or Eldritch Knight?

Question

The Arcane Trickster gains access to Wizard spells, primarily limited to the enchantment and illusion schools of magic. Four of the spells he knows can come from any school, however: one of his initial spells learned at 3rd level, and each of the ones learned at 8th, 14th, and 20th. This gives him the opportunity to have a spell in any school for one spell at each level he can cast. Further, like other casters who have known spells, the Trickster can change out one known spell when he levels up, with the following caveat:

Whenever you gain a level in this class, you can replace one of the wizard spells you know with another spell of your choice from the wizard spell list. The new spell must be of a level for which you have spell slots, and it must be an enchantment or illusion spell, unless you're replacing the spell you learned at 8th, 14th, or 20th level. (PHB pp 98)

This means that you can switch out your "any-school" spell of 2nd, 3rd or 4th level. However, your 1st level spell is not mentioned. Is this a simple oversight, or is there any reason why you might not be able to switch out the spell you learn at 3rd level?

This question applies equally to Eldritch Knight.

Answer 1

You can switch out any of the "any-school" spells

The PHB Errata, has now fully solved this issue.

From the "Rogue" section of the errata:

[New] Spells Known of 1st-Level and Higher (p. 98). In the final sentence of this subsection, the closing phrase has changed to read as follows: “… unless you’re replacing the spell you gained at 3rd, 8th, 14th, or 20th level from any school of magic.”

Similarly, the "Fighter" section of the errata states:

Spells Known of 1st-Level and Higher (p. 75). The final sentence ends as follows: “… unless you’re replacing the spell you gained at 3rd, 8th, 14th, or 20th level from any school of magic”.

This means you can indeed retrain the "any-school" spell and replace it with another "any-school" spell as appropriate, both as an Eldritch Knight and an Arcane Trickster.

As a historical note, the fighter section was added to errata at least as early as 2016 while the rogue section was not fixed until 2020 though this tweet from Jeremy Crawford already stated that the same reasoning should apply:

Like an Eldritch Knight, an Arcane Trickster can retrain their 1st-level spell from any school. (An unintended omission.)

Answer 2

While I could speculate and give 'game world' reasons why an Eldritch Knight or an Arcane Trickster may not be able to have the ability to switch out the non restricted spell he or she learned from any wizarding school of magic upon becoming said class; it's only speculation.

Perhaps when the class in question trained to learn these arts, those 3 spells were FIRMLY embedded in their training, in the rituals and practices and whatever repetitive regiment you went through to learn these 3 spells and become magically adept (where you otherwise had no lick of magical inclination in you as a Fighter or Rogue). Then, upon learning a better grasp of magic, you found you were able to switch them around a bit when new insight came o you; but you just can't let go of that first spell you ever learnt.

Personally, I believe it MAY very well be an oversight. I see absolutely nothing game breaking about allowing your AT or EK to switch out that one no restricted spell gained at 3rd level for another each time they level up if they so choose. Why? Because they could have picked any spell from the list in the first place, so allowing them to switch it up later has no bearing on balance. I would rule that you could add "Unless you are replacing the spell you learned at 3rd, 8th, 14th..." etc.

Answer 3

I believe that it's an oversight of nomenclature. In my opinion, the ~spell gained at 8th/14th/20th level~ language excludes the spells gained at 1st level because the 8th/14th/20th (class) level spells are the only newly learned spells being gained at those levels, whereas at 3rd (class) level, the arcane trickster is learning three new spells. If the 8/14/20 language included 3rd (class) level spells gained as well, then the player could interpret being able to swap out either of those two other 1st (spell) level enchantment/illusion spells for any wizard spell, effectively circumventing the enchantment/illusion restrictions of the arcane trickster archetype.

It would have been easier if the author just referred to them as "non-restricted spells", or as you referred to them, as "any-school spells", instead of identifying them by the level at which they were learned.