# U7 re-measured before scoping — sections are dead, filename prefixes are not

_2026-09-22 · booth_

**Pre-work, not the unit.** The standing instruction is "re-count the booths
before scoping U7". Done, on the live set (19 booths). No U7 code, no U7
contract — this exists so the scope call is a thirty-second read.

## The set as it actually is

| booth | items | images | subdirs | shape |
|---|---|---|---|---|
| `miranda-is` | 92 | 0 | 0 | report |
| `sindra-bakeoff` | 81 | 40 | **0** | gallery |
| `sindra-corpus-v1` | 66 | 66 | **0** | gallery |
| `sindra` | 61 | 30 | **0** | gallery |
| `sindra-sfw-pool` | 59 | 59 | **0** | gallery |
| `sindra-nude-pool` | 42 | 42 | **0** | gallery |
| `pewpew-ui-brief` | 34 | 1 | 7 | **report** |
| `dfa-concepts` | 21 | 14 | 1 | **report** |
| …11 more | ≤19 | | 0 | |

## Finding 1 — sections are worth ZERO, and this is now measured twice

**Not one gallery booth has a subdirectory.** Zero of eleven. The only two
booths with subfolders are both **reports**, the job where grid navigation
matters least, and `pewpew-ui-brief`'s seven subdirs hold one image.

The IA doc calls sections "most of the navigation fix". On this set they are
none of it. Cutting `Item.section` rendering from U7 costs nothing measurable.
(`Item.section` already exists from U1 and stays — this is about whether U7
builds a section RAIL, not about deleting a field.)

## Finding 2 — the grouping signal is in the FILENAME, and it pays

Tested two heuristics against every large gallery. Strip a trailing digit-run
from the stem and group on what remains:

| booth | images | groups | verdict |
|---|---|---|---|
| `sindra-corpus-v1` | 66 | **16** | useful |
| `sindra-nude-pool` | 42 | **12** | useful |
| `sindra-sfw-pool` | 59 | **10** | useful |
| `sindra-bakeoff` | 40 | **5** | useful |
| `sindra` | 30 | **1** | **degenerates** |

Specimens: `00-sheet-c1-market-noon.png`, `ac01.png`, `a01.png`,
`flag-rear.png`. The competing heuristic — split on the second hyphen — is
useless everywhere (59 "groups" from 59 files).

So a prefix heuristic pays on **4 of 5** large galleries and collapses to one
group on the fifth. **That is a filter/grouping affordance, not a section
rail**, and it must degrade gracefully to "one group" rather than render a
useless single-section rail.

## What this implies for the scope, stated as a recommendation not a decision

U7 as written is four things: sections, a sticky rail, filters, grid keyboard.
The measurement says **drop sections, keep the other three**, and consider
prefix-grouping as the thing sections were supposed to be — with a stated
degenerate case.

⚠ The sizing case has also changed: the unit was scoped against 270-item
booths and **the largest gallery is now 81 items / 40 images**. Everything
about virtualization stays parked ([[2026-09-21-ia-and-v1-gate-landed]] names
it); at 66 images a lazy grid is fine and measuring it first is the rule.

**The booth set churned again during this session** — `sindra-sfw-pool` (59
images) appeared and the `pancake-*` set went. Re-count again before writing
the contract; do not trust this table either.