pov: is this a head-hop?

Assuming that Kid A is your primary POV, yes, you did head hop here. Your use of ‘noted’ indicates an internal action. If you said ‘glanced at’, you would have an external action that is observed by your primary POV. 

Or... Does noted mean he said something that is not written.

Eg "...it's hot." "Really? Can't seem to see any red glow there, oh there it is. Huh..."

It would depend on the reader. I may have gone either way, but too me noted often means pointed out, said. 

Or, kid A saw him rubbing his chin and looking close at the stove and just assumed he noted it. However it's not kid A's actual voice narrating, so probably not, and no description is given.

You mean this isn't a real WotF submission yet...

?

Posted by: @lost_bard

Assuming that Kid A is your primary POV, yes, you did head hop here. Your use of ‘noted’ indicates an internal action. If you said ‘glanced at’, you would have an external action that is observed by your primary POV. 

Yes. This can be subtle. "Noted" might work if there were significant physical action behind it that Kid A could observe. But "glanced at" is a great choice to describe what Kid A observed.

You might get away with it. Writers are more conscious of viewpoint slips than readers are. But editors can be more conscious still.

Yeah, I've done this sort of thing too (just got something to that effect in an excellent recent crit of a story of mine). In that case, I'd commented on a second character's emotional state without really describing how it was externally perceived by the POV character in the scene, so it was conveyed as an emotional POV jump into the second character.

Posted by: @han

Or... Does noted mean he said something that is not written.

Eg "...it's hot." "Really? Can't seem to see any red glow there, oh there it is. Huh..."

It would depend on the reader. I may have gone either way, but too me noted often means pointed out, said. 

Or, kid A saw him rubbing his chin and looking close at the stove and just assumed he noted it. However it's not kid A's actual voice narrating, so probably not, and no description is given.

Both you (@han) and @lost_bard fed my confirmation bias, and @martin-l-shoemaker summed it up well.

Merriam-Webster's definition of "note", 1a: "to notice or observe with care" implies the internal act of noting, thus a "head-hop". Certainly not my intent, nor what I envisioned when writing that line. My writer's mind was in definition 2a: "to make special mention of or remark on." In other words, I wanted to concisely convey that Kid B did something like point at the hot coils, put his hand close and felt the heat, etc.: economy of words, and all.

Lesson learned: stick to the economy of words concept, but also be clear. Read like a reader and be aware that some words can legitimately be interpreted multiple ways. I rewrote as "Kid A noted the barely perceptible red glow on the bottom of the coils while his brother backed away."

Thanks for the insights.