Unsure Pursuit happens before Terastallization

[Suuicunee]

What type of bug are you reporting? Unsure

What is the bug?
Terastallising at the end of turn during pursuit in trick room

Are you able to replicate it? If so, how?
Yes, by starting trick room, I was playing national dex and set trick room and switch out while the opponent terastallises and clicks pursuit on the switch

https://replay.pokemonshowdown.com/gen9nationaldex-2139599990 - original - turn 9

https://replay.pokemonshowdown.com/gen9nationaldex-2139603084 - replication - turn 2

 

[Mathy]

This behavior is obviously undefined in the real game, so it's up to the NatDex council to decide. The closest comparison would be Mega Evolution, which is promoted to happen before a boosted Pursuit.

 

[PizzaTimeJoshua]

What type of bug are you reporting? Mechanics

What is the bug?
Pursuit does not gain a boost from Terastallization when it is used against an opposing Pokemon switching out, instead activating after the opposing Pokemon switches. Additionally, if the Pokemon that used Pursuit faints before due to recoil damage (Rocky Helmet, Life Orb, Iron Barb...), the Pokemon that used Pursuit will Terastallize after it fainted. The team would then be unable to a different Pokemon Terastallize afterward.

Are you able to replicate it? If so, how?
Due to Terastallizing and Pursuit only being available in the National Dex format, it is only possible to do it there.
Here is a battle where Pursuit will always miss the OHKO on Sigilyph unless the user is Terastallized.

252+ Atk Scizor switching boosted Pursuit (80 BP) vs. 0 HP / 0 Def Sigilyph: 232-274 (81.4 - 96.1%) -- guaranteed 2HKO

252+ Atk Tera Dark Scizor switching boosted Pursuit (80 BP) vs. 0 HP / 0 Def Sigilyph: 348-410 (122.1 - 143.8%) -- guaranteed OHKO

https://replay.pokemonshowdown.com/gen9nationaldexag-2190614867

Here's a rated battle in which this particular bug occurred at the start of Turn 5:

https://replay.pokemonshowdown.com/gen9nationaldex-2184131811