> **This file is a ready-to-use prompt.** Open this repo and say
> "do dopamine-ux-02-structural-check". It is self-contained -- it needs no context from
> any other session.
>
> Canonical copy: `~/src/utils/dopamine-ux/02-structural-check.md` (source of truth; this is a
> distributed copy). Running order and cross-prompt rules: `~/src/utils/dopamine-ux/00-INDEX.md`.
> Generated 2026-08-16 from a survey of this repo -- line numbers are accurate
> as of that date; **anchor on the symbol names, not the line numbers.**

## ⛔ WHEN YOU FINISH THIS PROMPT

Do **both**, in the same session that completes the work:

1. **Delete this file** and commit that deletion together with the
   implementation:
   ```bash
   git rm prompts/dopamine-ux-02-structural-check.md
   ```
   Do not leave a finished prompt lying in the repo -- a stale prompt is
   indistinguishable from a pending one, and the next session will re-run it.

2. **Log completion in the canonical index**, in `~/src/utils` (a *different* repo,
   so it needs its own commit):
   ```bash
   cd ~/src/utils
   # append to the "Completion log" table in dopamine-ux/00-INDEX.md:
   #   | 02-structural-check.md | DONE <YYYY-MM-DD> | <impl commit sha> | <one-line note> |
   git add dopamine-ux/00-INDEX.md
   git commit -m "dopamine-ux: mark 02-structural-check.md done"
   git push
   ```

If you finish only part of the prompt, do **neither** -- instead edit this file
to strike out what is done and state what remains, so the next session starts
from the true state. Partial completion must never be recorded as DONE.

---

Add a structural-token drift checker to CI

## findings (2, ranked by value over effort)

1. **Spacing, radius and type have never been drift-checked** — `palette_check.py`
   parses hex only, so three whole token categories can diverge across stacks
   while CI stays green. Motion inherits the same hole.
2. **`palette_map.py` points at a "scale check" that does not exist** — a
   comment describing a guarantee nobody wrote.

## what

`palette_check.py` guarantees the colour palette agrees across all stack copies.
It does **not** check anything else — verified 2026-08-16 by reading its four
parsers, every one of which requires a `#RRGGBB` value:

```python
parse_css : r"(--[a-z0-9-]+)\s*:\s*(#[0-9A-Fa-f]{6})\s*;"
parse_dart: r"static const Color (\w+) = Color\(0x[fF]{2}([0-9A-Fa-f]{6})\)"
parse_tk  : r'^\s{4}(\w+):\s*str\s*=\s*"(#[0-9A-Fa-f]{6})"'
parse_md  : r"^\|\s*`([a-z0-9-]+)`\s*\|\s*`(#[0-9A-Fa-f]{6})`"
```

So **spacing, radius and type have been silently unprotected all along**, and the
motion tokens added by prompt 01 inherit the same hole. A `--duration-fast: 120ms`
is invisible to every parser: CI passes while the stacks drift apart.

Worse, `scripts/palette_map.py:159` claims structural values are "checked by the
scale check" — **no such script exists anywhere in `~/src/utils`**. That comment
describes a check that was never written. This prompt writes it.

## where

Repo: `~/src/utils`.

**Create** `~/src/utils/unified-design-system/scripts/structural_check.py`.

**Edit** `~/src/utils/.github/workflows/palette-drift.yml` — add a step invoking it.
The workflow deliberately has no `paths:` filter; keep it that way.

**Fix** the stale comment at `~/src/utils/unified-design-system/scripts/palette_map.py`
(~:159) to name the real script.

Sources to compare (three code stacks + the prose freeze):

| Role | Path |
|---|---|
| prose freeze | `~/src/utils/unified-design-system/tokens.md` (spacing/radius/type) |
| motion freeze | `~/src/utils/unified-design-system/motion.md` (**created by prompt 01** — run it first) |
| web/React | `~/src/utils/web_ui/src/tokens.css` |
| Flutter/Dart | `~/src/utils/design_system/lib/src/tokens.dart` |
| Python/Tkinter | `~/src/utils/gatelock/gatelock/_window.py` (`class LockConfig`) |

## must

- Cover **motion** (durations, easing) **and** the already-unprotected
  **spacing, radius and type** scales, in one checker.
- Mirror `palette_check.py`'s two-halves design, because it is the part that
  actually works:
  1. **Agreement** — for each mapped token, resolve it in every non-`n/a` stack
     and fail if values disagree.
  2. **Completeness, bidirectional** — every structural value parsed out of any
     source must be mapped, or explicitly exempted. This is what catches
     "added it to one stack, forgot the others".
- Support an explicit **`n/a` per stack**, and require a reason string. Tkinter
  has no animation framework; a duration legitimately does not exist there. An
  honest `n/a` with a reason is correct — a fabricated constant is not.
- **Adjudicate with exit codes.** Exit non-zero on drift with a message naming
  the token and the disagreeing files. No warnings-only mode.
- Keep every file ≤ **250 lines** (`~/src/utils/file_length/config.py`). Note
  `palette_check.py` is 231 and `palette_map.py` is 162 — that pair was split
  precisely to stay under the cap. **Split yours the same way from the start**
  (`structural_check.py` + `structural_map.py`) rather than discovering the
  problem at 251 lines.
- Ruff-clean under the repo's config. No `# noqa`, no `type: ignore`.

- **Expect it to fail on first run.** Spacing/radius/type have never been
  compared; there may be real pre-existing drift. That is the point of writing
  it. Fix whatever it surfaces, in the stack copy that is wrong, and say in the
  session summary what drifted.
- must not: weaken the checker, add an exemption, or narrow its scope to make it
  green. If a token genuinely differs per stack for a good reason, encode it as
  an `n/a`/variant **with the reason recorded**, not as a silent skip.
- must not: modify `palette_check.py`. It works; it is simply colour-only. The
  two scripts run side by side.
- must not: change any token *value* to resolve a disagreement without saying so
  explicitly — that is a design change, and `tokens.md` is a freeze. Surface it
  and let kuhy decide which value is canonical.

- optional: teach it the shadow tier too, if that falls out cheaply.

## done

1. `python3 ~/src/utils/unified-design-system/scripts/structural_check.py` exits 0,
   and exits non-zero when you deliberately break one stack copy (**test both
   directions** — a checker that never fails is not a checker).
2. It is wired into `~/src/utils/.github/workflows/palette-drift.yml` and the
   workflow passes.
3. `palette_map.py`'s "scale check" comment names the real script.
4. `~/src/utils/scripts/check_file_length.sh --all` reports no new violations.
5. The session summary states what drift, if any, the first run found.

## verify

Desktop. Run the script, paste the output. Then prove it fails: change one
spacing or duration value in **one** stack copy, re-run, paste the non-zero exit
and the message, and revert. Both halves of that demonstration are required —
the passing run alone proves nothing.

## read first

- `~/src/utils/unified-design-system/scripts/palette_check.py` — the design to
  mirror. Read `NON_COLOUR_CSS`: it is the regex that currently *excludes*
  spacing/radius/type/shadow from the colour check, and therefore the precise
  list of what you are now covering.
- `~/src/utils/unified-design-system/scripts/palette_map.py` — the `PALETTE` tuple of
  `Token(canonical, md, css, dart, tk, why)` rows. Your map wants the same shape,
  including the `why` field.
- `~/src/utils/.github/workflows/palette-drift.yml` — how `palette_check.py` and
  `ramp_check.py` are invoked; add your step alongside.
- `~/src/utils/unified-design-system/motion.md` — what prompt 01 created.
- `~/src/utils/unified-design-system/tokens.md` — the spacing/radius/type tables.
  **Do not edit it**; it is 260 lines and already over the cap.

## context you would otherwise rediscover

- The four "stack copies" are really **three code stacks plus a prose freeze**.
  There is no fourth code stack; do not hunt for one.
- `~/src/dufs-cloud/app/lib/ui/theme.dart` is a **fifth, uncompared copy** of the
  palette (the Flutter app has no `design_system` dependency and hand-restates
  every hex). It is out of scope here — prompt 07 wires it up properly. Do not
  add it as a source to this checker; wait until 07 has removed it.
- Three Flutter apps (diet-guard, workout_app, wake_alarm) similarly
  hand-transcribe tokens into local `lib/ui/theme.dart` files. Those are
  deliberately outside the checker's scope for now — bringing them in is a much
  larger job than this prompt.
- `~/src/utils/gatelock/` is a package inside this monorepo, not a separate repo.

REMOVE ME AFTER FINISH