When you use wish as a contingent or glyph spell, when do you get to specify the effect?

Question

Contingency and glyph of warding allow you to store a spell as part of the casting. Both also state the stored spell does not take effect until it is triggered.

Contingency
... but the contingent spell doesn't come into effect. Instead, it takes effect when a certain circumstance occurs.

Glyph of warding
The spell being stored has no immediate effect when cast in this way. When the glyph is triggered, the stored spell is cast.

When you cast wish as the stored spell, do you decide what the wish does before or after it is triggered?

Answer 1

Note that it is quite hard to do such spellcasting to begin with

Contingency

It states

Choose a spell of 5th level or lower that you can cast

So you can not use it along Wish, which is a 9th level spell.

Glyph of Warding

While Glyph of Warding theoretically allows you to store Wish as it states

At Higher Levels: When you cast this spell using a spell slot of 4th Level or higher, the damage of an explosive runes glyph increases by 1d8 for each slot level above 3rd. If you create a spell glyph, you can store any spell of up to the same level as the slot you use for the glyph of warding.

The problem here is that doing it would require you to spend two spell slots of 9th level at the same time. However, this answer suggests that you can use a Spell Scroll or other magic items to cast Wish and fulfill the requirement. I am not entirely sure about that, but I will go along with it.

If you manage to do it

I would go with the answer up to the DM.

From my reading, it is a question of whether the effect of Wish is decided upon cast or upon "resolve". So, I see two ways this could work out:

• If the effect is decided upon cast, then the person casting Glyph and Wish decides the effect of Wish beforehand.
• If the effect is decided upon resolving, then the person triggering the Glyph is granted a Wish, and he decides the effect.

Wish is, by itself, a spell that requires the DM to adjudicate a lot, thus letting the DM make the call on which interpretation should run seems fine.

Personally, depending on the intention of the player doing this trick, I would let them do the one more convenient for their plan (e.g., if they want to create somewhat of a magic lamp, sure, go for it). Unless you are running an official AL table (in which case I am not sure you can get items that allow casting Wish), the rules are guidelines but having fun is more important.

Answer 2

RAW you can't do it

Contingency can only store spell up to level 5:

Choose a spell of 5th level or lower that you can cast

Glyph of warding specifies that the spell must target a single creature or area and wish has a range of self.

Spell Glyph. You can store a prepared spell of 3rd level or lower in the glyph by casting it as part of creating the glyph. The spell must target a single creature or an area. The spell being stored has no immediate effect when cast in this way. When the glyph is triggered, the stored spell is cast. If the spell has a target, it targets the creature that triggered the glyph. If the spell affects an area, the area is centered on that creature. If the spell summons hostile creatures or creates harmful objects or traps, they appear as close as possible to the intruder and attack it. If the spell requires concentration, it lasts until the end of its full duration.

Emphasis mine.