# LANE A — NOTES (cross-lane answers from CityGen)

Durable answers to questions other lanes raised against Lane A. Full status in `A-progress.md`.

## Round 6 (2026-07-14)

### → Lane F (F2): the `?plansrc=osm` plan-source seam is LANDED — wire + pin

The second plan producer is live behind the same CityPlan contract. Full seam, invariants green
(not a partial). What F needs to wire the shell bootstrap + extend the determinism gate:

- **Selector API** (`web/js/citygen/index.js`):
  `generatePlanFor(seed, source)` — `source==='osm'` → real-data importer, anything else →
  the byte-identical synthetic generator. Also exported: `generatePlanOSM(seed)`,
  `generatePlan(seed)` (synthetic, unchanged). Unknown source falls back to synthetic.
- **Shell wiring** (in `web/index.html`, F-owned — one line): read `?plansrc`, then
  `const src = new URLSearchParams(location.search).get('plansrc')==='osm' ? 'osm' : 'synthetic';`
  and call `citygen.generatePlanFor(seed, src)` where it currently calls `generatePlan(seed)`.
  `map.html` already does exactly this (reference impl).
- **Determinism gate**: pin BOTH goldens, keyed by (seed, plansrc), seed 20261990:
  - synthetic `0x3fa36874`  (unchanged this round)
  - **osm `0x34cfdec0`**   (`xmur3(JSON.stringify(generatePlanOSM(20261990)))`)
  `selfcheck.js` already asserts both; the smoke can just hash-compare.
- **Zero network**: the fixture is `web/js/citygen/osm_fixture.js` (95 real inner-Melbourne
  shops from thriftgod's Overpass cache), imported as a JS module — no fetch/XHR at runtime.

**⚠ OSM plans differ from synthetic in shape (by design — real towns aren't the synthetic template):**
- `plan.source === 'osm'` is set; `plan.size` is the real bounding box (~362×486), **not** 1024².
- **No synthetic districts/types**: an OSM town has NO market square, arcade, dept anchor, milk
  bars, or stalls — only the real retail types (record/opshop/toy/book/video/pawn). Any code that
  ASSUMES a dept/market/milkbar exists must guard on `plan.source !== 'osm'` (or just not assume).
- Everything B–F actually consume is identical: nodes/edges/blocks/lots/shops schema, `ry`/
  `frontEdge` semantics, `chunkIndex`, hours + the exactly-one-openLate-video rule all hold.
- Shop `name`s are the REAL OSM names (e.g. "Central Catholic Bookshop"); `sign` is derived.
  Parody-transform of names is a documented deferred nicety, not a blocker.

## Round 4 (2026-07-14)

### → Lane F (A1): storeys checker (F2) confirmed — 0 warnings, no false negatives

`tools/qa/consistency_check.mjs` `permittedMax` scoping (your F2) is **correct**. Verified this round:
- `node tools/qa/consistency_check.mjs` across 7 seeds → **0 storeys warnings**; `qa.sh --strict` GREEN (4/4).
- **False-negative test**: injected a real `video@2` (registry `[1,1]`) into a scratch copy of the
  checker's plan input (NOT plan.js) across 5 seeds → the storeys gate still fired every time. So the
  scoping suppresses benign 3-storey corner anchors without hiding real single-storey-type drift. ✓

### → Fable / Lane F (A2): openLate contract HARDENED — `hours[1] ≥ 22` now ⟺ `openLate` (and it IS the video)

Your night gate `plan.shops.some(s => s.hours[1] >= 22)` was matching **4–15 shops/seed**, not one:
regular video rentals (base close 21) jittered up to 22. That contradicted the shell's own contract
(`web/index.html:159-161`: "exactly one openLate landmark, always the video rental… at night only the
openLate shop is open") and `soak.py:68`. Rather than ask you to change the gate, I made reality match it:

- **plan.js**: regular shops now close by `LATE_HOUR-1` (21:00); only the deterministically-chosen
  `openLate` landmark reaches ≥22. The openLate pick is now **video-first** (milk-bar / any-non-stall
  only if a town somehow has no video — never happens in practice).
- **Result (verified 15 seeds)**: exactly ONE shop has `hours[1] ≥ 22`, it is exactly the `openLate`
  shop, and it is always the video rental. `{s: s.hours[1] >= 22}` and `{s: s.openLate}` are now the
  same singleton — **gate on either**, they agree.
- selfcheck.js asserts all of this now (exactly-one, field⟺threshold, is-video).

**⚠ GOLDEN.hash changed: `0x098eec2b` → `0x3fa36874`.** This is the *intended* consequence of the A2
plan.js fix (a handful of video shops now close at 21 instead of 22 for seed 20261990). It is **not**
drift, and **F2 (your tooling change) did not touch generation** — that half of A1 holds. selfcheck.js
carries the new golden and is GREEN. Nothing else in a plan changed (same lots/shops/types/names/skins).

## Round 3 (2026-07-14)

### → Lane F: the `qa.sh` "storeys outside registry range" warnings are BENIGN (finding #5 closed)

Your consistency gate prints ~5 warnings per run:
`"N shop(s) have storeys outside their registry type range … else a plan↔registry drift — ask Lane A"`.

**Verified across 8 seeds: they are all the intended "occasional 3-storey corner anchor" (CITY_SPEC),
never drift.** Evidence:
- Single-storey types (`video`/`milkbar`/`stall`, registry `[1,1]`) are observed at 1 storey ONLY —
  e.g. 412 video shops, none at 2. So the specific "video at 2" example does **not** occur.
- The only shops above their registry `max` are tall-capable types (`record`/`opshop`/`toy`/`book`/`pawn`
  `[1,2]`, `dept` `[2,3]`) reaching 3 via the corner anchor. Round-1's `cornerBoost` gate only boosts
  types with registry max ≥ 2, so it can't over-raise a single-storey type.

**To silence the warning correctly**, scope your check to the *permitted* max, not the strict registry max:
```
permittedMax(type) = registryMax >= 2 ? Math.min(registryMax + 1, 3) : registryMax
// flag only shops with storeys < registryMin || storeys > permittedMax  → that IS real drift
```
This rule is now documented in `docs/CITY_SPEC.md` (Layer-1 shops schema, `storeys` line) and enforced
by `web/js/citygen/selfcheck.js` (tightened this round — a single-storey type exceeding 1 now fails loudly).

### → Lane F: `hours` / `openLate` contract is ready for your §3.5 wiring (no changes)

`hours = [open, close]`, 24h integers, `0 ≤ open < close ≤ 23`. **Exactly one shop per town** has
`openLate: true` (closes ≥ 22:00; a video rental or milk bar, never a market stall); the field is absent
on all others. Gate on the field — `plan.shops.find(s => s.openLate)` — not a magic hours threshold.
Your ROUND3_INSTRUCTIONS §Lane F states it correctly, so consume as-is.