"I guess the question is, if it's retroactive, how do you prove it to me?"

"Do you remember me taking pictures on my phone and showing you them?"

"You took some pictures of your handbook but you didn't show them to me, and you explained what you were up to but you were whispering and I didn't hear you well enough to know what you meant."

". . . That might be the memory editing again. How about this: can you write a note to yourself, not in your handbook, that I'm about to change the rules to allow cellphones in class?"

"Sure."

She writes it on... her arm. Takes a picture of it with her phone, under the desk.

Dairine opens her notebook to the technology page and photographs it under her desk.

Cell phones, including smartphones, are permitted on campus but must be kept turned off in a student's bag or locker and may be used during class. Use of a phone in the classroom will result in a warning, followed by confiscation. Confiscated items may be picked up at the end of the school day. Personal computers other than phones are not permitted.

Second photograph, hastily hide the phone and close and reopen the notebook just as the teacher starts walking toward Dairine's desk again.

The teacher stops at a different student's desk to confiscate a paper airplane that they might or might not have been folding two seconds ago.

Kestrel's arm now says Dairine is about to do some magic, which... might be shorter than what Dairine remembers seeing her write? But when she checks the picture on her phone to compare (with no particular caution about hiding it), the picture matches the reality.

"What did you do?" she wonders. "Ban paper airplanes?"

"No, I allowed cell phones, they used to be banned according to my timestream."

Does Dairine's phone have the pictures she remembers it having? If it does, what does Kestrel see when she looks at them?

Dairine's phone lives in the new timeline where the contents of her handbook have always been what they currently are. She has two pictures of a single pristine page, no markings anywhere, no differences except in how she was aiming her camera.

Kestrel, leaning over for a look, makes a thoughtful noise and says, "I can almost imagine where you would've written on it, just from the way the pictures are focused... I dunno, maybe I'm making shit up."

"I guess if your arm got retconned then my phone would also get retconned but what the shiiiiit though. Maybe I should write in the handbook that human brains are exempt from retcons."

"Okay, but will that make it so human brains are exempt from retcons, or will it retcon you into a world where there has to be a school rule that human brains are exempt from retcons because people are going around retconning things and human brains might not otherwise be exempt?"

"I mean, empirically I am already going around doing retcons and if other people were doing it do would I even know?"

"No, but like... so you write in the handbook and then the world is the one where the handbook says what you told it to. But it's a student handbook, not a guide to the laws of magic or whatever. So what you change has to be, like... You have to write the student handbook we would have in the world where no one can retcon brains. I think. It's how I would design it, anyway." She pauses. "Can I try writing in it? I won't make the world terrible. Probably. I'll try really hard not to make the world terrible. I just want, like, better cafeteria food and more art classes."

"Go ahead, I'll watch and if it turns out terrible anyway somehow I'll put I back."

She flips through Dairine's book. "I promise if you get your memories erased I'll tell you what I changed," she adds.

Flip flip flip...

"Aha! Found the cafeteria section!"

She scribbles in tiny letters in the margin next to the chart of meal costs:

LRMA is committed to providing tasty, nutritious, affordable food to all students. All school meals will offer vegan and gluten-free options, as well as options that accommodate disclosed food allergies and other dietary restrictions.

After a moment's thought, she crosses out the chart of meal costs and adds, Cafeteria payment options are available on a sliding scale.

Before closing the book, she shows her work to Dairine for approval.

"Fantastic. Sliding scale might screw up the budget but maybe it'll just delay them on building yet more sports stuff." She tries to hold the memory of the changes actively in her consciousness the whole time Kestrel closes and opens the book again.

"I'm hoping that it'll translate to—"

She closes the book and blinks several times. "—whoa, trippy—uh, hoping it'll translate to them charging richer students more to pay for the better food. Which, I, uh, think it did? I think—I think I might remember both timelines? Trippy. Um. Okay. I don't thiiiink I caused any global catastrophes." She bounces a little in her seat. "Let's do more stuff!!! Hey, what happens if we both work on the book at the same time, like you write part of a change and I write part? —oh, um, before that, did it screw with your memory at all? Tell me what I changed."

It does not appear to have screwed with Dairine's memory at all. She remembers with ordinary human clarity what the handbook looked like before Kestrel wrote in it.

"You made there be more cafeteria options for like vegans and stuff and also made them affordable, so unless you did something else I'm immune. But I only remember the original timeline; there lots of people with dietary restrictions now? It used to be like a few percent."

The bell rings for the end of homeroom and Dairine snags her handbook back. "Oh heck, class, let's meet up at lunch and try editing something together!"

"I don't think I knew the statistics in either timeline—yeah, it's a date, see you then!"

Off she trots.

If Dairine finds the time to look up the statistics in this timeline, she will find that it's still "a few percent" but the actual numbers are a little higher, and the issue just generally seems to get more press.

That's pretty neat! Dairine does look it up but also pays attention in Honors World History and Honors English 9. She doesn't pay attention in Algebra 2 because she already knows Algebra 2; instead she does her history homework until Mrs. Whitney tells her off and then she puts away the history book and brainstorms magic handbook edit ideas because that looks more like taking math notes. Kind of ironic how telling her off got her to switch from school stuff to less-school stuff but whatever. She halfassedly pays attention in freshman bio, which is to say she reads ahead in the textbook while thinking about magic. And then it is Finally lunch time! She gets her lunch out of her locker (PB&J, apple slices, bag of almonds, and and a Snickers bar) and finds Kestrel in the cafeteria.

"Okay," she says once they're ensconced at a quiet corner table, "We were going to try making an edit together. My top two ideas are changing the section about the school nurse to mention healing potions and see if that invents healing potions, and changing the grading section to say that if you get good grades on the tests you don't have to do the homework."

"Oooh, let's invent healing potions!"

"Awesome." She flips to the page that says 'Students who become ill during the school day should see the nurse in the health office.'

"So how do we want to do this, I cross out 'see' and write 'get a' and you add 'healing potion from'? Actually maybe we should test magic edits and two-person edits separately."

"Fair... can I do the health potion edit, then, and we'll think of something else for two-person edits?"

"Fire away!" Healing potions! 

She taps her pen thoughtfully against her lips.

"Okay, I want to make really sure I distinguish magic healing potions from, like, homeopathy..."

Students who become ill during the school day should see the nurse in the health office. The nurse is authorized to excuse students from class for any issue not solved by a healing potion.

"There, what do you think? I almost want to add that students who refuse a potion for personal reasons can also be excused but that might undermine the 'they definitely work' subtext..."