Fenenir's page

I'd say no, not only for verisimilitude (I am not using my mental scores for Impulses, therefore Stupefied shouldn't work on me) but also because Stupefied specifies the "Cast a Spell" activity based on its capitalization.

Stupefied is not an "ability that restricts you from casting spells", thus; it is an effect that potentially hinders the specific Cast a Spell activity.

Well, if we're talking about verisimilitude, then all Impulses having the Concentrate trait baked in should make it be affected by mental stuff.

Sigh, yet another anti-spellcaster Condition the "no slot spellcaster" is immune to.
I swear, the Kineticist needed a few more months of playtesting...

The Stupefied condition says

Your thoughts and instincts are clouded. Stupefied always includes a value. You take a status penalty equal to this value on Intelligence-, Wisdom-, and Charisma-based checks and DCs, including Will saving throws, spell attack modifiers, spell DCs, and skill checks that use these attribute modifiers. Any time you attempt to Cast a Spell while stupefied, the spell is disrupted unless you succeed at a flat check with a DC equal to 5 + your stupefied value.

The first half of the Stupefied Condition gives a penalty to Int, Wis, and Cha in much the same way that Enfeebled and Clumsy give a penalty Str and Dex, respectively. Just a flat penalty to Checks and DCs.

The second half specifies that any attempt to Cast a Spell needs to make a flat check or waste the attempt.

Then under Impulses it states that

Impulses are magical, and though they aren't spells, some things that affect spells also affect impulses. Abilities that restrict you from casting spells [...] also apply to impulses.

So, repeating the title - are Kineticists affected by Stupefied, given that although Impulses are not spells (nor Int-/Wis-/Cha-based, for that matter) they are nonetheless affected by things that prevent spells?

"You can use an impulse only if your kinetic aura is active and channeling that element, and only if you have a hand free to shape the elemental flow."

That free hand is potentially the catch. While they don't have the manipulate trait, impulses will still be stopped if you can't reasonably be said to have a hand free. As a GM, I'd probably consider that "handcuffs or being restrained by someone who knows to focus on the hands specifically". But regardless of interpretation, it's definitely less restrictive than what casters would face, and that's probably intentional.

Yeah, the "free hand" thing is the only plausible hook I was able to find. A "free hand" is basically an "empty hand" and, Restrained or not, it's still empty.

I would imagine that the Manipulate trait was intentionally excluded from the Impulse trait due to Reactive Strike (and similar) and I'm perfectly fine with that part, but to ignore a condition that most others would find crippling does not sit right with me.

Recently I've realized that almost none of the Impulses have the Attack or Manipulate trait, meaning that Restrained is little different from Grabbed, when used against a Kineticist.

For all other classes Restrained is utterly crippling - martials can't even Strike and spellcasters can't cast spells. Until they Escape. And even on a success, the Martials still suffer from MAP and lose an Action whereas spellcasters are rather unlikely to ever Escape at all (assuming it's not a lower-level enemy).

Yet Kineticists don't really care. They can use most of their abilities unchallenged. Is this intentional? Am I missing something obvious?