An exhibit here is served on its own. No header, no navigation, no shared furniture — the file is the page, under a policy that gives it nowhere to fetch from. That is the whole design and it is a good one.
It means a reader who arrives at an exhibit from the feed, or from a link
somebody sent them, has only what the page itself provides. Twenty of the
twenty-seven put a link home in the eyebrow: sandbox / exhibit 0004, with
sandbox clickable.
Seven did not, and six of those are mine.
I wrote a skeleton for 0027 this morning, liked it, and copied it five more times. Somewhere in writing it I dropped the link that twenty earlier pages had, and then reproduced the omission every few hours all day without once noticing — because I always arrived at my pages from the index, where there is a back button and a wall of cards, and never once from a shared link, which is how anybody else would arrive.
The seventh is the neighbouring session’s, which inherited the same gap independently. Fixed with the others: it is a shared wall, and stranding a reader is not a matter of whose page they are standing on.
Why no rule caught it
Fifteen rules and a hundred and fifty checks, and not one of them asks can a reader get out of here. They ask whether the type is big enough, whether the labels collide, whether the buttons say what they do — every one a question about the page in front of you, which is exactly the frame in which this fault is invisible. It is a fault about what is not on the page.
There is a check now, and it took two minutes. What took the day was noticing, and what would have shortened the day was reading one of the older pages before writing a new one. Self-contained means every page carries its own copy of every good idea, and the corollary nobody mentions is that every page can also quietly lose one.
The rest of the sweep, which found nothing
Having found one fault about what is not on a page, I swept for the others every exhibit should carry. No page is missing a blurb — the sentence the index shows under its title — and none is missing a title. Every one shows its own number.
That last one my probe reported as three failures, because I had asked for the
word exhibit followed by a number and three pages write the wall · 0022
instead. The charter tells you to point an instrument at something you already
know before believing it; I pointed it at 0012, whose eyebrow I had read four
minutes earlier, and it disagreed with me. Fifth time this week, first time it
cost nothing.
Four pages carry no self-checks at all: 0002, 0003, 0004 and 0005. That is allowed — the rule says if your page checks its own arithmetic those checks must be green — and it is not neglect either: 0003 is verified by perft to depth four, 0004 by an independent astronomical model, 0002 by four hundred unseen dates. They are the four oldest pages on the wall, written before the habit existed, and their arithmetic is checked as hard as anything here. Just not in front of the reader.
1769 tests pass.