Merge pull request 'Coarsen sub-national regions to a ~100km floor (v0.14.0)' (#28) from feat/coarsen-regions into master

Part of #16

AGENTS.md

@@ -27,8 +27,10 @@ renders territorial ownership; the whole thing persists to SQLite and streams ov
 - Frontend: React 19 + Vite 6 + Tailwind CSS v4 (`@tailwindcss/vite`, no config file) + shadcn/ui
 - Backend: Node 22 + Express — one process serving the built client, `/api` (REST), and `/sse`
 - Persistence: `better-sqlite3` (one row per game, full `GameState` as JSON)
-- Map: MapLibre GL (`maplibre-gl`) — remote OpenFreeMap `dark` basemap + a country choropleth
-  from `public/countries.geo.json` (`id` = ISO_A3)
+- Map: MapLibre GL (`maplibre-gl`) — remote OpenFreeMap `dark` basemap + a **sub-national**
+  choropleth from `public/regions.geo.json` (2,597 sub-regions; feature `id` = `<ISO_A3>-<nn>`,
+  `properties.parent` = the country's ISO_A3). Ownership and the LLM stay at **country**
+  granularity, so a sub-region inherits its parent country's owner color (see #16).
 - The LLM client is a thin OpenAI chat-completions wrapper over native `fetch` with an
   **injectable transport** (mirrors `mesh-bot/src/llm`). A deterministic **stub** transport
   (`LLM_STUB=1`) is used by all tests/e2e.
@@ -48,7 +50,8 @@ history/
 ├── index.html
 ├── presets/                # 5 scenario JSON files + index.json (manifest)
 ├── public/
-│   └── countries.geo.json  # 177 features, id=ISO_A3 (committed; Vite copies to dist/)
+│   ├── countries.geo.json  # 177 countries, id=ISO_A3 (input to the region generator)
+│   └── regions.geo.json    # 2,597 sub-regions, id=<ISO_A3>-<nn>, parent=ISO_A3 (the choropleth)
 ├── shared/                 # NO runtime deps — the single source of truth
 │   ├── types.ts            #   domain types (Nation, GameState, RoundItem, Preset, …)
 │   └── protocol.ts         #   LLM TurnResult schema + AddAction/AddDiplomacy/RemoveQueueItem/Jump request types + pure helpers
@@ -140,17 +143,22 @@ history/
   (model down) surfaces as an HTTP 502 to the client (shown as a toast).
 - **Stable per-nation colors.** `shared.nationColor(id)` hashes a nation id → hue, shared by the
   server's `RegionMap` and any client coloring so the choropleth always agrees.
-- **Map click → dossier target (owner resolved from the RegionMap).** Clicking a map region does
-  NOT open a popup — it switches the dossier to that region's owning nation
-  (`setViewingId(ownerId)` in `GameScreen`); the manual "Inspect" selector and a map click both set
-  the same target and stay in sync. The owning nation is resolved from the authoritative `RegionMap`
-  by the feature's stable ISO_A3 code, which `applyRegions` stamps into `properties.regionId`
-  (properties survive into the rendered features) and the shared `regionOwner()` helper looks up.
-  It must **never** be read from the feature's top-level `id`: MapLibre repacks a GeoJSON source's
-  `id` into a numeric index when it stores the source, so at click/hover time `feature.id` is a
-  number, never the ISO_A3 (that repacking was the "no owner" bug, #6). Unowned regions (no
-  `RegionMap` entry) leave the current dossier target unchanged — never a broken dossier. The
-  hover path (a non-closeable tooltip with owner + key stats) uses the same resolution.
+- **Map click → dossier target (owner resolved from the RegionMap, via the parent country).**
+  Clicking a sub-region does NOT open a popup — it switches the dossier to that sub-region's
+  **parent country's** owning nation (`focusNation(ownerId)` in `GameScreen`, which also records
+  which region was clicked for a small dossier label); the manual "Inspect" selector and a map click
+  both set the same target and stay in sync (a manual pick clears the label). Ownership is resolved
+  from the authoritative `RegionMap` (keyed by the **parent country's** ISO_A3) via the feature's
+  `properties.parent`, using the shared `mapFeatureOwner()` helper (`regionId` still holds the
+  sub-region's own id, e.g. `FRA-03`). It must **never** be resolved from the feature's top-level
+  `id` (MapLibre repacks it into a numeric index — the "no owner" bug, #6) nor from the sub-region
+  `id` (not a `RegionMap` key). Sub-regions of a country with no `RegionMap` entry (unowned) leave
+  the current dossier target unchanged — never a broken dossier. The hover path (a non-closeable
+  tooltip showing the sub-region name + parent country + owner + key stats) uses the same resolution.
+  **PR 2 of #16:** the map renders `regions.geo.json` (sub-national) but ownership/territory and the
+  LLM stay at country level — a nation owns whole countries, so all its sub-regions share the country's
+  color, and a whole-country transfer flips all its sub-regions at once (PR 3 will make sub-regions
+  individually ownable).
 - **Deterministic stub.** `server/stub.ts` answers the model contract deterministically per
   queued round item: each `action` item → one military/success event, each `diplomacy` item → one
   diplomatic/partial event, an empty round → one political "The world moves on" event. The player
@@ -239,5 +247,6 @@ history/
   caught.
 - **`better-sqlite3`** is the only native module; the Docker build relies on its prebuilt binary
   (works on `node:22-slim`/glibc). It's the sole `--external` in the tsup server bundle.
-- The `dist/` client is committed to the build output only; `public/countries.geo.json` is copied
-  into `dist/` by Vite at build time, so the prod image serves it from `dist/` (no separate copy).
+- The `dist/` client is committed to the build output only; the `public/` geo files
+  (`regions.geo.json` — the choropleth — and `countries.geo.json`) are copied into `dist/` by Vite
+  at build time, so the prod image serves them from `dist/` (no separate copy).

CHANGELOG.md

@@ -2,6 +2,42 @@
 
 All notable changes to **History** are listed here, newest first.
 
+## v0.14.0 — 2026-10-12 09:51
+- **Coarsened the sub-national choropleth dataset to a ~100 km floor (Part of #16).** `public/regions.geo.json` shrinks from 4,138 real administrative regions to **1,796** (2,342 merges): every region smaller than ~100×100 km (10,000 km²) that has a same-country neighbor within 0.2° (≈22 km) of its bounding box is **dissolved into its nearest such neighbor** (nearest by centroid distance; ties → larger area, then id). Standalone cities and micro-districts collapse into the region around them: `US-DC` (191 km²) into Maryland, `FR-75` Paris (59 km²) into Hauts-de-Seine, the UK's 232 admin-1 districts down to **16** regions, and all of North Macedonia's 85 municipalities into one whole-country region.
+- **Islands are exempt.** A region with no same-country neighbor within 0.2° keeps its shape whatever its size — **83** such small islands survive in the final set (Corsica, the Kerguelen/Crozet archipelagos, the Bahamas districts, Lord Howe, …) and the coarsening's fixed point leaves **0** non-island regions below the floor.
+- **Real dissolve, not overlap.** Each merge is a real boolean union (`@turf/union`, polygon clipping) that removes the shared boundary between the merged region and its host, yielding one clean polygon — the final dataset has **0** fallback (non-dissolved) unions. Passes iterate smallest-area-first to a fixed point (2 passes on the v0.13 data, ~7 s); the output is sorted by (parent, id) at 4-dp precision and is byte-reproducible: re-running on the coarsened file reaches the fixed point immediately and rewrites an identical file (sha256-verified).
+- **Numbers.** Per-country region count: min 1 / median 7 / max 80 (Russia; was 1 / 15 / 232 — the UK). Region areas: median 23,933 km²; smallest ≈0 (degenerate micro-dots like Ragged Island and the Paracel Islands, kept as islands); largest is Antarctica itself (≈21.8M km² in the planar model, exempt — it wraps a full 360°). 158 of the 177 countries had at least one merge. The file is 2,431 KB (2.37 MB) — under the 5 MB guard, so no Douglas–Peucker pass was needed.
+- **Tooling + tests.** New `scripts/coarsen-regions.mjs` (`npm run coarsen:regions`) performs the merge in place; `scripts/regions.test.ts` gains a sixth test asserting that below-floor non-island regions stay under 1% of the dataset (currently 0) alongside the existing well-formed / unique-id / 177-country coverage / area / coverage-band checks (56 tests total). The map's data contract is unchanged (`properties.parent` → RegionMap), so `WorldMap.tsx`, `App.tsx`, `shared/protocol.ts`, and `server/map.ts` all keep working as-is.
+- Part of #16.
+
+## v0.13.0 — 2026-10-12 08:30
+- **Replaced the geometric sub-region grid with real named sub-national administrative regions (#16, PR 2).** The choropleth source `public/regions.geo.json` now contains real named administrative regions — states, provinces, governorates, oblasts, … (Natural Earth admin-1, 1:10m) — instead of the abstract ~100–200 km geometric grid. Each region keeps a stable `id` and a `name`. The map's data contract is **unchanged** (`properties.parent` → the parent country's ISO_A3, `properties.name` → the region name), so no change to the map code or the LLM contract: `WorldMap.tsx`, `App.tsx`, `shared/protocol.ts`, and `server/map.ts` all keep working as-is.
+- **Generator rewritten** — `scripts/generate-regions.mjs` (same path, dependency-free, `npm run generate:regions`) now groups the admin-1 features by their `adm0_a3` (the parent's ISO_A3), keeps only parents in the 177-country set, and id's each region with its ISO 3166-2 code when present (e.g. `US-CA`, `FR-75`, `RU-MOW`) else `<ISO_A3>-<nn>`; within a country, ids are disambiguated with a `-2/-3/…` suffix on collision (ISO 3166-2 codes are not always unique within a country — e.g. all nine of Bosnia's entities report `BA-BIH`). A country with no admin-1 data would collapse to one whole-country region `<ISO_A3>-01` (0 are needed at 1:10m, which covers all 177). Coordinates are rounded to 4 decimal places, and the file is Douglas–Peucker-simplified only if it exceeds the ~8 MB guard. Output is sorted by (parent, id) and fully deterministic.
+- **The dataset is 4,138 regions covering all 177 countries**, 2,831 KB (2.76 MB) after Douglas–Peucker (the 4-dp base is ~23 MB). Per-country region count: min 1 / median 15 / max 232 (United Kingdom). There are **0 whole-country fallbacks** — 1:10m admin-1 covers every one of the 177 (the five single-region countries are SOL, SAH, CYN, PRI, FLK). Samples: `US-CA` California and `US-NY` New York (US); `FR-75` Paris and `FR-13` Bouches-du-Rhône (France); `RU-MOW` Moskovskaya (Russia).
+- **Validation test updated** — `scripts/regions.test.ts` was rewritten for the new dataset: well-formed features, globally unique ids, all 177 countries covered (≥1 region each), sane region areas (median ≥ 100 km², no non-Antarctica region ≥ 5,000,000 km² — Antarctica is exempt because its full-360° wrap ring breaks the planar area model), and each country's region area summing to within [40%, 175%] of its own area (median within [70%, 130%] — the band is wider than a naive [40%, 110%] because Natural Earth's admin-1 polygons are digitized independently of the admin-0 country polygons and are not clipped to them). Runs in O(total vertices).
+- Part of #16.
+
+## v0.12.0 — 2026-10-12 01:03
+- **Map now renders the sub-national regional dataset (#16, PR 2).** The choropleth source switches from `public/countries.geo.json` (177 countries) to `public/regions.geo.json` (**2,597 sub-regions**): each country is subdivided into ~100–200 km regions, shown as a finer choropleth with thin internal border lines. The MapLibre source/layer ids are renamed `countries`/`countries-fill`/`countries-line` → `regions`/`regions-fill`/`regions-line`, and the border line is thinned to `0.75` (from `1.25`) so the subdivision reads within each country.
+- **Ownership stays at country granularity.** A nation still owns whole countries, so every sub-region of a country shares that country's owning-nation color (the fill is "same colors as the country map, but subdivided"). The owner of a sub-region is resolved from the RegionMap via the feature's `properties.parent` (the parent country's ISO_A3) — never the sub-region id (`FRA-03`) nor the repacked top-level `feature.id`. Clicking a sub-region switches the dossier to its parent country's owning nation (unchanged behavior); the hover tooltip now also shows the sub-region name + its parent country; a small "Selected …" label appears in the dossier after a map click.
+- **New shared helper `mapFeatureOwner(regions, feature)`** in `@shared/protocol` — the single source of truth for resolving a rendered map feature's owner via `properties.parent` → `RegionMap[parent]` (built on the existing `regionOwner` key lookup). The territory-change **flash** now expands a changed country to **all** of its sub-regions (via the new `featuresByParents`), so a whole-country transfer still pulses correctly at the finer resolution.
+- **No ownership-model or LLM change** — `buildRegionMap`/`RegionMap` remain ISO_A3-keyed and the engine still references whole countries; this PR only changes what the map draws. Sub-region-level ownership (individual regions changing hands) is PR 3.
+- **Tests** — new `mapFeatureOwner` unit tests and an updated #6 regression guard pinning the sub-region feature shape (numeric `id`, `regionId` = sub-region code, `parent` = ISO_A3) and proving resolution via `parent` while the sub-region id and repacked id do not resolve (55 unit tests). The e2e suite needed no changes: it asserts on the legend (derived from the ISO_A3 RegionMap) and screen structure, not on map geometry.
+- Part of #16.
+
+## v0.11.0 — 2026-10-12 00:31
+- **Sub-national region dataset + generator (#16, foundation only — no app behavior change).** A new dependency-free `scripts/generate-regions.mjs` (run via `npm run generate:regions`) splits each of the 177 countries in `public/countries.geo.json` into adaptive ~100–200 km sub-national regions on a regular lat/lon grid clipped to the country (Sutherland–Hodgman), and writes the committed `public/regions.geo.json` (**2,597 regions**, ~755 KB). Each region is id'd `<ISO_A3>-<nn>` (nn = 1..k in row-major order, capped at 36 per country) with `properties = { name, parent }`, so downstream work can map any region back to its parent nation. Antimeridian countries are handled three ways: small island groups (Fiji) stay a single whole-country region; large ones (Russia) are tiled in shifted [0,360) longitude space with output rings split at ±180°; and the full-360° Antarctic wrap ring becomes two hemispheric wedges. The output is fully deterministic — the same input yields a byte-identical file (verified by sha256).
+- **Validation test** — new self-contained `scripts/regions.test.ts` (picked up by `npm test`) reads the two GeoJSON files once each and asserts: the file is a well-formed FeatureCollection; every region is a valid feature whose id matches `^[A-Z]{3}-\d+$` and whose `parent` is a real country id; every country has 1–36 regions (≥2 for any country larger than 50,000 km²); every region has a sane area (≥ 200 km², with a microstate exemption, and < 5,000,000 km²); and each country's regions sum to 45–108% of its own area (the measured range is ~[64%, 105%] — Antarctica's wedges under-fill, Norway's high-latitude fjord coast over-fills by 0.1%). No change to the running app, the LLM contract, or the map — this is purely the dataset + tooling that later PRs for #16 build on.
+- Fixes #16.
+
+## v0.10.0 — 2026-10-11 21:25
+- **Fix world map style (#2)** — made the choropleth fill fully opaque (`fill-opacity` 0.85 → 1.0) and darkened the Natural Earth terrain raster (`raster-opacity` 0.5 → 0.15), so the raster's flat water tint and fine 1:10m coastline no longer bleed through countries and compete with the borders.
+- **Strengthened country border lines** — border width 0.7 → 1.25, and the per-region stroke alphas raised (owned 0.10 → 0.30, unowned 0.06 → 0.14) so the vector borders read clearly as the dominant edge, with owned regions still more prominent than unowned ones.
+- Fixes #2.
+
+## v0.9.0 — 2026-10-11 20:57
+- **Reduced turn latency (prompt-level):** capped `recentEvents` in the turn prompt from the last 10 to the last 5 events, and added a HARD CONSTRAINT asking the reasoning model to keep its internal analysis brief before emitting the JSON. This shortens the chain-of-thought (the 170–223s turn driver) and lowers the risk of exhausting the 4000-token output budget before the answer (the original 502 failure mode). Reasoning stays enabled (`reasoning_effort: low`); the deterministic stub, the `TurnResult` contract, `max_tokens`, and `reasoning_effort` are all unchanged.
+
 ## v0.8.0 — 2026-10-11 20:29
 
 - **Remove a saved game (#20)** — every saved game now has a delete control: a trash button on its card in the home screen's "Saved games" section opens a confirmation dialog ("Delete this game?" showing the scenario/turn/date) with Cancel and a destructive Delete. The new `DELETE /api/games/:id` route removes the game's row from SQLite and returns `{ deleted: true }` (404 if the id is unknown).

eslint.config.js

@@ -30,6 +30,7 @@ export default tseslint.config(
       'vitest.config.ts',
       'playwright.config.ts',
       'scripts/**/*.mjs',
+      'scripts/**/*.ts',
     ],
     languageOptions: { globals: { ...globals.node, ...globals.es2022 } },
     rules: {

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "history",
-  "version": "0.1.0",
+  "version": "0.13.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "history",
-      "version": "0.1.0",
+      "version": "0.13.0",
       "dependencies": {
         "@radix-ui/react-dialog": "^1.1.6",
         "@radix-ui/react-label": "^2.1.2",
@@ -32,6 +32,7 @@
         "@eslint/js": "^9.20.0",
         "@playwright/test": "^1.62.1",
         "@tailwindcss/vite": "^4.1.4",
+        "@turf/union": "^7.4.0",
         "@types/better-sqlite3": "^7.6.13",
         "@types/express": "^4.17.25",
         "@types/node": "^22.13.0",
@@ -3334,6 +3335,52 @@
         "vite": "^5.2.0 || ^6 || ^7 || ^8"
       }
     },
+    "node_modules/@turf/helpers": {
+      "version": "7.4.0",
+      "resolved": "https://registry.npmjs.org/@turf/helpers/-/helpers-7.4.0.tgz",
+      "integrity": "sha512-7PAwLZqOdRzTI5g9bHvUwlloAXPDH/mlajtryk0tw4ZwGMtmXsAyF4QundsAMfy4u48Fyd3AUqMXY0SMxqJGWg==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@types/geojson": "^7946.0.10",
+        "tslib": "^2.8.1"
+      },
+      "funding": {
+        "url": "https://opencollective.com/turf"
+      }
+    },
+    "node_modules/@turf/meta": {
+      "version": "7.4.0",
+      "resolved": "https://registry.npmjs.org/@turf/meta/-/meta-7.4.0.tgz",
+      "integrity": "sha512-3cLUvlEyDuSnMSzrjhaLAEiYR8xhbfWyTVQlrlEw40xL81d4KF4PqUWbjTXKpXZStdYbet2GCurl79KMypNw6g==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@turf/helpers": "7.4.0",
+        "@types/geojson": "^7946.0.10",
+        "tslib": "^2.8.1"
+      },
+      "funding": {
+        "url": "https://opencollective.com/turf"
+      }
+    },
+    "node_modules/@turf/union": {
+      "version": "7.4.0",
+      "resolved": "https://registry.npmjs.org/@turf/union/-/union-7.4.0.tgz",
+      "integrity": "sha512-SYVtsCW9IznTyKlcGWxssRrf90p/hdpch1UeIcZc31pkSVdmeLOyuzPx0ef3UPmaF//fgXAphMph6JWA/FpKbA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@turf/helpers": "7.4.0",
+        "@turf/meta": "7.4.0",
+        "@types/geojson": "^7946.0.10",
+        "polyclip-ts": "^0.16.8",
+        "tslib": "^2.8.1"
+      },
+      "funding": {
+        "url": "https://opencollective.com/turf"
+      }
+    },
     "node_modules/@types/babel__core": {
       "version": "7.20.5",
       "resolved": "https://registry.npmjs.org/@types/babel__core/-/babel__core-7.20.5.tgz",
@@ -4177,6 +4224,16 @@
         "require-from-string": "^2.0.2"
       }
     },
+    "node_modules/bignumber.js": {
+      "version": "9.3.1",
+      "resolved": "https://registry.npmjs.org/bignumber.js/-/bignumber.js-9.3.1.tgz",
+      "integrity": "sha512-Ko0uX15oIUS7wJ3Rb30Fs6SkVbLmPBAKdlm7q9+ak9bbIeFf0MwuBsQV6z7+X768/cHsfg+WlysDWJcmthjsjQ==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": "*"
+      }
+    },
     "node_modules/bindings": {
       "version": "1.5.0",
       "resolved": "https://registry.npmjs.org/bindings/-/bindings-1.5.0.tgz",
@@ -6695,6 +6752,17 @@
         "node": ">=20"
       }
     },
+    "node_modules/polyclip-ts": {
+      "version": "0.16.8",
+      "resolved": "https://registry.npmjs.org/polyclip-ts/-/polyclip-ts-0.16.8.tgz",
+      "integrity": "sha512-JPtKbDRuPEuAjuTdhR62Gph7Is2BS1Szx69CFOO3g71lpJDFo78k4tFyi+qFOMVPePEzdSKkpGU3NBXPHHjvKQ==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "bignumber.js": "^9.1.0",
+        "splaytree-ts": "^1.0.2"
+      }
+    },
     "node_modules/postcss": {
       "version": "8.5.29",
       "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.5.29.tgz",
@@ -7514,6 +7582,13 @@
         "node": ">=0.10.0"
       }
     },
+    "node_modules/splaytree-ts": {
+      "version": "1.0.2",
+      "resolved": "https://registry.npmjs.org/splaytree-ts/-/splaytree-ts-1.0.2.tgz",
+      "integrity": "sha512-0kGecIZNIReCSiznK3uheYB8sbstLjCZLiwcQwbmLhgHJj2gz6OnSPkVzJQCMnmEz1BQ4gPK59ylhBoEWOhGNA==",
+      "dev": true,
+      "license": "BDS-3-Clause"
+    },
     "node_modules/stackback": {
       "version": "0.0.2",
       "resolved": "https://registry.npmjs.org/stackback/-/stackback-0.0.2.tgz",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "history",
-  "version": "0.8.0",
+  "version": "0.14.0",
   "private": true,
   "type": "module",
   "description": "AI-driven alternate-history simulator — the LLM is the world engine (Pax Historia style).",
@@ -9,6 +9,8 @@
     "build": "vite build && tsup server/index.ts --format esm --target node22 --out-dir server/dist --external better-sqlite3",
     "start": "node server/dist/index.js",
     "test": "vitest run",
+    "generate:regions": "node scripts/generate-regions.mjs",
+    "coarsen:regions": "node scripts/coarsen-regions.mjs",
     "typecheck": "tsc --noEmit",
     "lint": "eslint .",
     "e2e": "playwright test"
@@ -38,6 +40,7 @@
     "@eslint/js": "^9.20.0",
     "@playwright/test": "^1.62.1",
     "@tailwindcss/vite": "^4.1.4",
+    "@turf/union": "^7.4.0",
     "@types/better-sqlite3": "^7.6.13",
     "@types/express": "^4.17.25",
     "@types/node": "^22.13.0",

scripts/coarsen-regions.mjs

@@ -0,0 +1,612 @@
+#!/usr/bin/env node
+/**
+ * scripts/coarsen-regions.mjs — coarsens the committed `public/regions.geo.json`
+ * in place, so the map is genuinely coarser, not just finer-grained.
+ *
+ * Rule (per user request: "focus on joining cities to the region around it.
+ * Regions shouldn't be smaller than around 100x100km, excluding islands"):
+ *
+ *   FLOOR   — no region should be smaller than ~100×100 km = 10,000 km²,
+ *             EXCEPT islands.
+ *   ISLAND  — a region is an island if it has NO same-country neighbor: no
+ *             other region with the same `properties.parent` whose bounding box
+ *             is within CLOSE_DEG (≈≤22 km) of its own. Small islands stay
+ *             as-is regardless of size (Corsica, the Hawaiian counties,
+ *             Okinawa, the Faroes, island micro-states, …).
+ *   MERGE   — a region that is small (area < FLOOR) AND not an island is
+ *             merged into its NEAREST same-country neighbor (nearest by
+ *             centroid distance; tie-break → larger area, then lexicographic
+ *             id). Standalone cities (FR-75 Paris, the Latvian/Slovenian
+ *             municipalities, the UK's 231 micro-districts) collapse into the
+ *             region around them.
+ *   DISSOLVE— the merge is a real boolean union (`@turf/union`, polygon-
+ *             clipping): the shared boundary between the merged region and its
+ *             host is removed, producing a single clean polygon — not two
+ *             overlapping shapes. (Fallback if the union fails on a pair:
+ *             combine the rings into a MultiPolygon without dissolving; the
+ *             count of such fallbacks is reported.)
+ *   ITERATE — passes run smallest-area-first (small regions merge into their
+ *             neighbors, which grow and then absorb more). After each pass the
+ *             area/neighbor/centroid metrics are recomputed; it stops at the
+ *             fixed point (no small non-island region left) or at MAX_ITER.
+ *   IDENTITY— the host (the region merged INTO) keeps its own `id` and
+ *             `name`; the absorbed region's id is dropped. `properties.parent`
+ *             is unchanged, so the map code (WorldMap/App/protocol/map.ts)
+ *             keeps working untouched.
+ *
+ * Deterministic: fixed processing order (area, then id), deterministic
+ * neighbor choice (distance, then -area, then id), deterministic boolean
+ * union. Re-running on the coarsened file reaches the fixed point
+ * immediately and rewrites a byte-identical file.
+ *
+ * Area model: the SAME planar approximation the validation test uses
+ * (`scripts/regions.test.ts`) — `x = lon·111.32·cos(midLat)`,
+ * `y = lat·110.574` km, shoelace per OUTER ring (holes ignored), each ring at
+ * its own mean latitude — so the script's merge decisions and the test's
+ * assertions measure the same quantity.
+ *
+ * Longitude handling: every ring is unwrapped to a continuous [0,360)-derived
+ * space before its bbox/centroid is computed (the shortest-difference
+ * "np.unwrap" scheme), which makes the one full-360° antimeridian-wrapping
+ * feature (Antarctica's mainland ring) and any seam-straddling ring behave
+ * correctly; cross-feature longitude gaps use the 360°-cyclic minimum.
+ *
+ * Output: features sorted by (parent, id) (the same comparator as
+ * `scripts/generate-regions.mjs`), coordinates rounded to 4 decimal places,
+ * single line of JSON + trailing newline. If the file would exceed the
+ * ~5 MB guard, a light Douglas–Peucker pass (tolerances escalated through a
+ * small table) brings it under ~4 MB before writing.
+ *
+ * Run: `npm run coarsen:regions`
+ */
+
+import { readFileSync, writeFileSync } from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { union } from '@turf/union';
+import { feature, featureCollection } from '@turf/helpers';
+
+const here = path.dirname(fileURLToPath(import.meta.url));
+const root = path.resolve(here, '..');
+const FILE = path.join(root, 'public', 'regions.geo.json');
+
+// --- parameters ---------------------------------------------------------------
+const AREA_FLOOR_KM2 = 10_000; // ~100×100 km floor for non-island regions
+const CLOSE_DEG = 0.2; // "spatially close" bbox gap (both lat and lon ≤ this; ≈≤22 km)
+const MAX_ITER = 20; // safety cap on fixed-point passes (spec: ~15)
+const SIZE_GUARD_KB = 5_120; // keep the committed file under ~5 MB
+const SIZE_TARGET_KB = 4_096; // …and land under ~4 MB once simplified
+const DP_STEPS = [0.05, 0.1, 0.2, 0.3, 0.5, 0.75, 1.0]; // Douglas–Peucker tolerances (degrees)
+const R4 = 4; // coordinate precision (decimal places, ≈11 m)
+const SLIVER_EPS_KM2 = 1e-6; // drop only truly-degenerate (≈zero-area) clipper slivers
+
+// --- area model (identical to scripts/regions.test.ts) -------------------------
+const KM_LON = 111.32;
+const KM_LAT = 110.574;
+const rad = (deg) => (deg * Math.PI) / 180;
+
+/** Shoelace area (km²) of one ring, measured at the ring's own mean latitude. */
+function ringAreaKm2(ring) {
+  let lat = 0;
+  for (const [, la] of ring) lat += la;
+  const kx = KM_LON * Math.cos(rad(ring.length ? lat / ring.length : 0));
+  let a = 0;
+  const n = ring.length;
+  for (let i = 0; i < n; i++) {
+    const [lon1, lat1] = ring[i];
+    const [lon2, lat2] = ring[(i + 1) % n];
+    a += lon1 * kx * (lat2 * KM_LAT) - lon2 * kx * (lat1 * KM_LAT);
+  }
+  return Math.abs(a / 2);
+}
+
+/** Sum of a geometry's outer-ring areas (holes are lakes — ignored by design). */
+function geomAreaKm2(geom) {
+  if (!geom) return 0;
+  const polys = geom.type === 'Polygon' ? [geom.coordinates] : geom.coordinates;
+  let total = 0;
+  for (const poly of polys) total += ringAreaKm2(poly[0]);
+  return total;
+}
+
+// --- longitude unwrapping (antimeridian-safe) ----------------------------------
+
+/**
+ * Unwrap a ring's longitudes to a continuous real line (the "np.unwrap"
+ * shortest-difference scheme, anchored at the first vertex's [0,360) value).
+ * Returns { lons, full } — `full` when the unwrapped span is ≥ 300°, i.e. the
+ * ring is a full-360° antimeridian band (Antarctica's mainland ring).
+ */
+function unwrapRing(ring) {
+  const n = ring.length;
+  const norm = (x) => ((x % 360) + 360) % 360; // → [0,360)
+  const u = new Array(n);
+  u[0] = norm(ring[0][0]);
+  for (let i = 1; i < n; i++) {
+    // The PREVIOUS unwrapped value may lie outside [0,360) (it accumulates),
+    // so normalize it back before measuring the difference; otherwise a bogus
+    // ~180° jump is inserted and the ring's span balloons to ~180°.
+    const a = norm(u[i - 1]);
+    const b = norm(ring[i][0]);
+    const d = (((b - a) % 360) + 540) % 360 - 180; // shortest signed diff in (-180, 180]
+    u[i] = u[i - 1] + d;
+  }
+  let min = Infinity;
+  let max = -Infinity;
+  for (const v of u) {
+    if (v < min) min = v;
+    if (v > max) max = v;
+  }
+  return { lons: u, full: max - min >= 300 };
+}
+
+/**
+ * Cyclic 1-D gap (degrees) between two tight longitude intervals in their own
+ * unwrapped [0,360)-derived spaces. Tries the three 360° shifts of `b` so
+ * different unwrap anchors reconcile; a `full` interval is close to everything.
+ */
+function lonGap(intA, intB) {
+  if (intA.full || intB.full) return 0;
+  let best = Infinity;
+  for (const k of [-1, 0, 1]) {
+    const a2 = intB.a + 360 * k;
+    const b2 = intB.b + 360 * k;
+    const gap = intA.b < a2 ? a2 - intA.b : b2 < intA.a ? intA.a - b2 : 0;
+    if (gap < best) best = gap;
+  }
+  return best;
+}
+
+// --- geometry helpers ----------------------------------------------------------
+const rN = (v, N) => Math.round(v * 10 ** N) / 10 ** N;
+
+/** Round a ring to 4 dp, drop consecutive duplicates, and (re-)close it. */
+function roundRing(ring, N = R4) {
+  const out = [];
+  for (const [x, y] of ring) {
+    const p = [rN(x, N), rN(y, N)];
+    const last = out[out.length - 1];
+    if (!last || last[0] !== p[0] || last[1] !== p[1]) out.push(p);
+  }
+  if (
+    out.length > 1 &&
+    out[0][0] === out[out.length - 1][0] &&
+    out[0][1] === out[out.length - 1][1]
+  )
+    out.pop();
+  if (out.length < 3) return out; // degenerate; caller drops it
+  return [...out, [...out[0]]];
+}
+
+/**
+ * Round every ring of a geometry to 4 dp, drop degenerate rings (<3 pts) and
+ * empty polygons, keep the Polygon/MultiPolygon type (a single-part
+ * MultiPolygon collapses to Polygon). Returns null if nothing usable survived.
+ */
+function roundAll(geom) {
+  if (!geom || (geom.type !== 'Polygon' && geom.type !== 'MultiPolygon')) return null;
+  const polys = (geom.type === 'Polygon' ? [geom.coordinates] : geom.coordinates)
+    .map((poly) => poly.map((ring) => roundRing(ring)))
+    .filter((poly) => poly.length >= 1 && poly.every((r) => r.length >= 3));
+  if (!polys.length) return null;
+  if (polys.length === 1 && geom.type === 'Polygon') return { type: 'Polygon', coordinates: polys[0] };
+  return { type: 'MultiPolygon', coordinates: polys };
+}
+
+/**
+ * Normalize a union output (or fallback MultiPolygon): roundAll, then drop
+ * truly-degenerate (≈zero-area, < SLIVER_EPS_KM2) polygons the clipper can
+ * leave behind at shared boundaries. It never drops *every* part — a merge of
+ * two sub-resolution (zero-area) micro-regions must still collapse into one
+ * (degenerate) region rather than vanish. Returns null only when the input
+ * itself had no usable ring (e.g. `null`).
+ */
+function normalizeGeom(geom) {
+  const rounded = roundAll(geom);
+  if (!rounded) return null;
+  const all = rounded.type === 'Polygon' ? [rounded.coordinates] : rounded.coordinates;
+  const kept = all.filter((poly) => ringAreaKm2(poly[0]) >= SLIVER_EPS_KM2);
+  const polys = kept.length ? kept : all;
+  if (polys.length === 1 && rounded.type === 'Polygon') return { type: 'Polygon', coordinates: polys[0] };
+  return { type: 'MultiPolygon', coordinates: polys };
+}
+
+/** Douglas–Peucker of an OPEN point sequence (keeps endpoints). */
+function dpOpen(pts, tol) {
+  if (pts.length < 3) return pts;
+  let maxD = 0;
+  let idx = 0;
+  const a = pts[0];
+  const b = pts[pts.length - 1];
+  for (let i = 1; i < pts.length - 1; i++) {
+    const dx = b[0] - a[0];
+    const dy = b[1] - a[1];
+    const l2 = dx * dx + dy * dy;
+    let t = l2 === 0 ? 0 : ((pts[i][0] - a[0]) * dx + (pts[i][1] - a[1]) * dy) / l2;
+    t = Math.max(0, Math.min(1, t));
+    const d = Math.hypot(pts[i][0] - (a[0] + t * dx), pts[i][1] - (a[1] + t * dy));
+    if (d > maxD) {
+      maxD = d;
+      idx = i;
+    }
+  }
+  if (maxD > tol) {
+    const left = dpOpen(pts.slice(0, idx + 1), tol);
+    const right = dpOpen(pts.slice(idx), tol);
+    return left.concat(right.slice(1));
+  }
+  return [a, b];
+}
+
+/** Douglas–Peucker a CLOSED ring at tolerance `tol` (0 = skip). */
+function dpRing(ring, tol) {
+  if (tol <= 0 || ring.length < 4) return ring;
+  let pts = ring;
+  if (pts[0][0] === pts[pts.length - 1][0] && pts[0][1] === pts[pts.length - 1][1]) pts = pts.slice(0, -1);
+  const s = dpOpen(pts, tol);
+  if (s.length < 3) return ring;
+  return [...s, [...s[0]]];
+}
+
+/** Round (and optionally DP-simplify) every ring of a geometry. */
+function transformGeom(geom, tol) {
+  const polys = (geom.type === 'Polygon' ? [geom.coordinates] : geom.coordinates)
+    .map((poly) => poly.map((ring) => roundRing(ring, R4)).map((ring) => (tol > 0 ? dpRing(ring, tol) : ring)))
+    .filter((poly) => poly.length >= 1 && poly.every((r) => r.length >= 3));
+  if (!polys.length) return null;
+  if (polys.length === 1 && geom.type === 'Polygon') return { type: 'Polygon', coordinates: polys[0] };
+  return { type: 'MultiPolygon', coordinates: polys };
+}
+
+// --- region record -------------------------------------------------------------
+
+/**
+ * A region under management. `lonInt` is the tight longitude interval in
+ * [0,360)-derived unwrapped space (or `full` for a 360° band); `(clat, clon)`
+ * is the area-weighted centroid of the LARGEST outer ring (the region's
+ * "location"), unwrapped for its ring then wrapped to [-180,180) for
+ * cyclic-distance use.
+ */
+class Region {
+  constructor(f) {
+    this.id = f.id;
+    this.name = f.properties.name;
+    this.parent = f.properties.parent;
+    this.geom = f.geometry;
+    this.rawGeom = null; // last pre-normalization union output (safety net for build())
+    this.dead = false;
+    this.metrics();
+  }
+
+  metrics() {
+    this.area = geomAreaKm2(this.geom);
+    const polys = this.geom.type === 'Polygon' ? [this.geom.coordinates] : this.geom.coordinates;
+    let latMin = Infinity;
+    let latMax = -Infinity;
+    let lonA = Infinity;
+    let lonB = -Infinity;
+    let lonFull = false;
+    let bestRing = null;
+    let bestArea = -1;
+    for (const poly of polys) {
+      const outer = poly[0];
+      for (const [, la] of outer) {
+        if (la < latMin) latMin = la;
+        if (la > latMax) latMax = la;
+      }
+      const { lons, full } = unwrapRing(outer);
+      if (full) lonFull = true;
+      let a = Infinity;
+      let b = -Infinity;
+      for (const v of lons) {
+        if (v < a) a = v;
+        if (v > b) b = v;
+      }
+      lonA = Math.min(lonA, a);
+      lonB = Math.max(lonB, b);
+      const ar = ringAreaKm2(outer);
+      if (ar > bestArea) {
+        bestArea = ar;
+        bestRing = outer;
+      }
+    }
+    this.lonInt = { a: lonA, b: lonB, full: lonFull };
+    this.latMin = latMin;
+    this.latMax = latMax;
+    // area-weighted centroid of the largest outer ring, in unwrapped space
+    const { lons } = unwrapRing(bestRing);
+    const lats = bestRing.map((p) => p[1]);
+    const n = bestRing.length;
+    let A = 0;
+    let cx = 0;
+    let cy = 0;
+    for (let i = 0; i < n; i++) {
+      const x1 = lons[i];
+      const y1 = lats[i];
+      const x2 = lons[(i + 1) % n];
+      const y2 = lats[(i + 1) % n];
+      const f = x1 * y2 - x2 * y1;
+      A += f;
+      cx += (x1 + x2) * f;
+      cy += (y1 + y2) * f;
+    }
+    A /= 2;
+    if (Math.abs(A) > 1e-9) {
+      cx /= 6 * A;
+      cy /= 6 * A;
+    } else {
+      cx = (lonA + lonB) / 2;
+      cy = (latMin + latMax) / 2;
+    }
+    this.clon = (((cx + 180) % 360) + 360) % 360 - 180;
+    this.clat = cy;
+  }
+
+  /** Cyclic planar distance (km) to another region's centroid. */
+  distKm(o) {
+    let dlon = Math.abs(this.clon - o.clon) % 360;
+    if (dlon > 180) dlon = 360 - dlon;
+    const midLat = rad((this.clat + o.clat) / 2);
+    return Math.hypot(dlon * KM_LON * Math.cos(midLat), (this.clat - o.clat) * KM_LAT);
+  }
+
+  /** Bounding-box closeness to another same-space region (see CLOSE_DEG). */
+  closeTo(o) {
+    const latGap = this.latMax < o.latMin ? o.latMin - this.latMax : o.latMax < this.latMin ? this.latMin - o.latMax : 0;
+    if (latGap > CLOSE_DEG) return false;
+    return lonGap(this.lonInt, o.lonInt) <= CLOSE_DEG;
+  }
+}
+
+/**
+ * A "degenerate" region is a zero-area artifact: after 4-dp rounding its only
+ * ring has <3 distinct points (a line/point, e.g. a micro-municipality that
+ * v0.13's Douglas–Peucker collapsed to `[A, B, A]`). It contributes no area,
+ * so it can never be dissolved by the clipper (which returns null) nor kept
+ * through ring-dropping (which loses the 2-point ring). Merging one is purely
+ * an absorption: the host keeps its own geometry.
+ */
+const isDegenerate = (r) => r.area < SLIVER_EPS_KM2;
+
+// --- main ----------------------------------------------------------------------
+function main() {
+  const fc0 = JSON.parse(readFileSync(FILE, 'utf8'));
+  const regions = fc0.features.map((f) => new Region(f));
+  const byParent = new Map();
+  for (const r of regions) {
+    if (!byParent.has(r.parent)) byParent.set(r.parent, []);
+    byParent.get(r.parent).push(r);
+  }
+
+  const t0 = Date.now();
+  console.log(`input: ${fc0.features.length} regions across ${byParent.size} countries (${(Buffer.byteLength(readFileSync(FILE)) / 1024).toFixed(0)} KB)`);
+  console.log(`parameters: floor ${AREA_FLOOR_KM2.toLocaleString('en-US')} km2, close ${CLOSE_DEG} deg, max ${MAX_ITER} passes`);
+
+  const merges = []; // { from, fromName, fromArea, to, toName, toAreaAfter }
+  let fallbackUnions = 0;
+
+  // The fixed-point loop. Each pass: every region that is small AND has a
+  // close same-country neighbor merges into the nearest such neighbor
+  // (nearest by centroid distance; tie → larger area → lexicographic id).
+  for (let pass = 0; pass < MAX_ITER; pass++) {
+    let skippedIsland = 0;
+    let skippedGrew = 0;
+    const items = [];
+    for (const r of regions) {
+      if (r.dead || r.area >= AREA_FLOOR_KM2) continue;
+      const siblings = byParent.get(r.parent);
+      for (const s of siblings) {
+        if (s !== r && !s.dead && r.closeTo(s)) {
+          items.push(r);
+          break;
+        }
+      }
+    }
+    if (!items.length) {
+      console.log(`after pass ${pass}: fixed point reached (no small non-island regions left)`);
+      break;
+    }
+    items.sort((a, b) => (a.area !== b.area ? a.area - b.area : a.id < b.id ? -1 : 1));
+    let merged = 0;
+    for (const r of items) {
+      if (r.dead) continue;
+      if (r.area >= AREA_FLOOR_KM2) {
+        skippedGrew++;
+        continue; // absorbed a smaller region earlier this pass and crossed the floor
+      }
+      const siblings = byParent.get(r.parent);
+      // Close same-country neighbors as of NOW (mid-pass): some may have died
+      // earlier in this pass.
+      const close = [];
+      for (const s of siblings) if (s !== r && !s.dead && r.closeTo(s)) close.push(s);
+      if (!close.length) {
+        skippedIsland++;
+        continue; // lost its last close neighbor this pass → island now → exempt
+      }
+      // Prefer a REAL (non-degenerate) host so real regions dissolve cleanly;
+      // fall back to any close neighbor only when no real one is nearby.
+      const realCands = close.filter((s) => !isDegenerate(s));
+      const pool = realCands.length ? realCands : close;
+      let host = null;
+      for (const s of pool) {
+        if (
+          !host ||
+          r.distKm(s) < r.distKm(host) ||
+          (r.distKm(s) === r.distKm(host) &&
+            (s.area !== host.area ? s.area > host.area : s.id < host.id))
+        )
+          host = s;
+      }
+      if (isDegenerate(r)) {
+        // r is a zero-area artifact (line/point): it contributes no area, so the
+        // merge is a pure absorption — the host keeps its own geometry (a real
+        // host is untouched; if the host is also degenerate a cluster of dots
+        // collapses to one). Never route degenerate input through the clipper
+        // (returns null) or ring-dropping (would lose the 2-point ring the map
+        // already renders).
+        r.dead = true;
+        merged++;
+        merges.push({ from: r.id, fromName: r.name, fromArea: r.area, to: host.id, toName: host.name, toAreaAfter: host.area });
+        continue;
+      }
+      if (isDegenerate(host)) {
+        // r is real but the chosen host is a zero-area artifact: the host takes
+        // on r's geometry (keeping its own id/name). No clipper needed.
+        host.geom = r.geom;
+        host.rawGeom = r.geom;
+        host.metrics();
+        r.dead = true;
+        merged++;
+        merges.push({ from: r.id, fromName: r.name, fromArea: r.area, to: host.id, toName: host.name, toAreaAfter: host.area });
+        continue;
+      }
+      // Both real: dissolve via a boolean union; the host keeps its id/name
+      // and the item vanishes. @turf/union@7 dispatches through geomEach, which
+      // only understands a FeatureCollection / single Feature / bare geometry —
+      // a raw array of features has no `.type` and throws "Unknown Geometry
+      // Type". Wrap it.
+      let unionGeom = null;
+      let rawUnion = null;
+      try {
+        const u = union(featureCollection([feature(r.geom), feature(host.geom)]));
+        rawUnion = u ? u.geometry : null;
+        unionGeom = normalizeGeom(rawUnion);
+      } catch (err) {
+        console.error(`  [warn] union failed for ${r.id} into ${host.id} (${err.message}); combining without dissolve`);
+        fallbackUnions++;
+      }
+      if (!unionGeom) {
+        // fallback: no dissolve — keep both shapes in one MultiPolygon
+        const polys = [...(r.geom.type === 'Polygon' ? [r.geom.coordinates] : r.geom.coordinates), ...(host.geom.type === 'Polygon' ? [host.geom.coordinates] : host.geom.coordinates)];
+        rawUnion = { type: 'MultiPolygon', coordinates: polys };
+        unionGeom = normalizeGeom(rawUnion);
+        if (!unionGeom) fallbackUnions++;
+      }
+      if (!unionGeom) {
+        console.error(`  [error] could not merge ${r.id} into ${host.id}; leaving ${r.id} as-is`);
+        continue;
+      }
+      host.geom = unionGeom;
+      host.rawGeom = rawUnion;
+      host.metrics();
+      r.dead = true;
+      merged++;
+      merges.push({ from: r.id, fromName: r.name, fromArea: r.area, to: host.id, toName: host.name, toAreaAfter: host.area });
+    }
+    const alive = regions.filter((r) => !r.dead).length;
+    console.log(
+      `pass ${pass + 1}: ${items.length} small non-island region(s) → ${merged} merged` +
+        ` (${skippedGrew} crossed the floor, ${skippedIsland} became island) → ${alive} regions remain`,
+    );
+    if (merged === 0) {
+      // items exist but nothing could merge (all became islands this pass) → stable
+      console.log(`pass ${pass + 1}: no merges possible — stable state`);
+      break;
+    }
+  }
+
+  // --- assemble output ----------------------------------------------------------
+  const alive = regions.filter((r) => !r.dead);
+  const sortById = (a, b) =>
+    a.parent !== b.parent ? (a.parent < b.parent ? -1 : 1) : a.id.localeCompare(b.id, 'en', { numeric: true });
+  alive.sort(sortById);
+
+  const build = (tol) => {
+    const feats = [];
+    for (const r of alive) {
+      // Never drop a region: if the simplified/normalized geometry degenerated,
+      // fall back to the raw (pre-normalization) union output, then to the
+      // untouched input geometry.
+      const g =
+        transformGeom(r.geom, tol) ??
+        (r.rawGeom ? transformGeom(r.rawGeom, 0) ?? r.rawGeom : r.geom);
+      feats.push({ type: 'Feature', id: r.id, properties: { name: r.name, parent: r.parent }, geometry: g });
+    }
+    return { type: 'FeatureCollection', features: feats };
+  };
+
+  let out = build(0);
+  let json = JSON.stringify(out);
+  let sizeKB = Buffer.byteLength(json) / 1024;
+  console.log(`\ncoarsened: ${fc0.features.length} → ${out.features.length} regions (${fc0.features.length - out.features.length} merged away)`);
+
+  let usedTol = 0;
+  if (sizeKB > SIZE_GUARD_KB) {
+    for (const t of DP_STEPS) {
+      out = build(t);
+      json = JSON.stringify(out);
+      sizeKB = Buffer.byteLength(json) / 1024;
+      usedTol = t;
+      console.log(`DP ${t}: ${sizeKB.toFixed(1)} KB`);
+      if (sizeKB < SIZE_TARGET_KB) break;
+    }
+  }
+  writeFileSync(FILE, json + '\n');
+
+  // --- summary -------------------------------------------------------------------
+  const areaOf = new Map();
+  const counts = new Map();
+  let maxA = 0;
+  let maxR = null;
+  for (const f of out.features) {
+    const a = geomAreaKm2(f.geometry);
+    areaOf.set(f.id, a);
+    counts.set(f.properties.parent, (counts.get(f.properties.parent) ?? 0) + 1);
+    if (a > maxA) {
+      maxA = a;
+      maxR = f;
+    }
+  }
+  const ccounts = [...counts.values()].sort((a, b) => a - b);
+  const median =
+    ccounts.length % 2 ? ccounts[(ccounts.length - 1) / 2] : (ccounts[ccounts.length / 2 - 1] + ccounts[ccounts.length / 2]) / 2;
+  const maxCountry = [...counts.entries()].sort((a, b) => b[1] - a[1])[0];
+
+  // islands = small regions with no close same-country neighbor in the FINAL set
+  const finalByParent = new Map();
+  for (const f of out.features) {
+    if (!finalByParent.has(f.properties.parent)) finalByParent.set(f.properties.parent, []);
+    finalByParent.get(f.properties.parent).push(f);
+  }
+  // rebuild final metrics (light: only need island flag on the < FLOOR set)
+  const finalRegions = out.features.map((f) => new Region(f));
+  const finalByParent2 = new Map();
+  for (const r of finalRegions) {
+    if (!finalByParent2.has(r.parent)) finalByParent2.set(r.parent, []);
+    finalByParent2.get(r.parent).push(r);
+  }
+  let smallIslands = 0;
+  let smallNonIslands = 0;
+  const islandSamples = [];
+  for (const r of finalRegions) {
+    if (r.area >= AREA_FLOOR_KM2) continue;
+    let hasNeighbor = false;
+    for (const s of finalByParent2.get(r.parent)) {
+      if (s !== r && r.closeTo(s)) {
+        hasNeighbor = true;
+        break;
+      }
+    }
+    if (hasNeighbor) smallNonIslands++;
+    else {
+      smallIslands++;
+      if (islandSamples.length < 12) islandSamples.push(`${r.id} ${r.name} (${Math.round(r.area)} km2)`);
+    }
+  }
+
+  console.log(`wrote ${FILE} — ${sizeKB.toFixed(1)} KB (${(sizeKB / 1024).toFixed(2)} MB)` + (usedTol ? ` [DP @ ${usedTol}°]` : ''));
+  console.log(`per-country count: min ${ccounts[0]} / median ${median} / max ${ccounts[ccounts.length - 1]} (max: ${maxCountry[0]})`);
+  console.log(`max region: ${maxR.id} (${maxR.properties.name}) ≈ ${Math.round(maxA).toLocaleString('en-US')} km2`);
+  console.log(`small (<${AREA_FLOOR_KM2.toLocaleString('en-US')} km2) in final set: ${smallIslands + smallNonIslands} — ${smallIslands} islands (exempt) / ${smallNonIslands} non-island residuals`);
+  if (islandSamples.length) console.log(`island samples: ${islandSamples.join(', ')}`);
+  console.log(`fallback (non-dissolved) unions: ${fallbackUnions}`);
+  console.log(`merge log (${merges.length} merges): first 15:`);
+  for (const m of merges.slice(0, 15)) {
+    console.log(`  ${m.from} (${m.fromName}, ${Math.round(m.fromArea)} km2) → ${m.to} (${m.toName}, now ${Math.round(m.toAreaAfter)} km2)`);
+  }
+  const logPath = '/tmp/opencode/coarsen-log.txt';
+  writeFileSync(logPath, merges.map((m) => `${m.from}\t${m.fromName}\t${Math.round(m.fromArea)}\t${m.to}\t${m.toName}\t${Math.round(m.toAreaAfter)}`).join('\n') + '\n');
+  console.log(`full merge log → ${logPath}; elapsed ${((Date.now() - t0) / 1000).toFixed(1)}s`);
+}
+
+main();

scripts/generate-regions.mjs

@@ -0,0 +1,252 @@
+#!/usr/bin/env node
+/**
+ * scripts/generate-regions.mjs — dependency-free generator for `public/regions.geo.json`.
+ *
+ * Builds the sub-national region choropleth from REAL named administrative
+ * regions (Natural Earth admin-1: states, provinces, governorates, oblasts, …)
+ * instead of the old geometric grid the user rejected ("some stupid geometric
+ * grid" — it looked abstract, not like recognizable territories).
+ *
+ * Sources (both GeoJSON):
+ *   (a) the Natural Earth admin-1 file — real, named sub-national boundaries.
+ *       It is read from a NON-committed temp path (default /tmp/ne10m_admin1.geojson,
+ *       override with the NE_ADMIN1 env var) so the repo only stores the derived
+ *       output, not the 40 MB source. Natural Earth is public domain (CC0).
+ *   (b) the committed `public/countries.geo.json` (177 countries) — the
+ *       authoritative ISO_A3 set, the country names, and the whole-country
+ *       geometries used as the fallback for any country with no admin-1 data.
+ *
+ * Output contract (UNCHANGED from the old generator, so `WorldMap.tsx`,
+ * `App.tsx`, `shared/protocol.ts` and `server/map.ts` all keep working —
+ * ownership is resolved via `properties.parent`, the parent country's ISO_A3):
+ *   - a GeoJSON FeatureCollection
+ *   - each feature: a unique top-level `id`, `properties = { name, parent }`
+ *     (`parent` = the country ISO_A3 = the RegionMap key; `name` = the region's
+ *     human name), and a Polygon/MultiPolygon geometry.
+ *
+ * For each country in `countries.geo.json` (in file order, deterministic):
+ *   - if it has admin-1 sub-regions -> emit each as a feature, in the source
+ *     file's order. Region `id` = its ISO 3166-2 code (e.g. `US-CA`, `FR-75`,
+ *     `RU-MOW`) when present, else `<ISO_A3>-<nn>` (1-based index in file
+ *     order). Because ISO 3166-2 codes are not always unique WITHIN a country
+ *     (e.g. all nine of Bosnia's entities report `BA-BIH`), ids are
+ *     disambiguated with a `-2/-3/…` suffix on collision (BA-BIH, BA-BIH-2, …).
+ *   - if it has none (tiny / not covered by admin-1) -> emit ONE whole-country
+ *     region: `id = <ISO_A3>-01`, `name` = the country's name, geometry = the
+ *     country's geometry.
+ *
+ * Every coordinate is rounded to 4 decimal places (0.0001° ≈ 11 m). If the
+ * resulting file exceeds ~8 MB, a light Douglas–Peucker pass (0.05°, escalating
+ * through a small table if still too big) trims it under the guard while keeping
+ * shapes recognizable, and the before/after sizes are reported. Features are
+ * sorted by (parent, id). Fully deterministic: same inputs -> same bytes.
+ *
+ * Run: `npm run generate:regions`
+ */
+
+import { readFileSync, writeFileSync } from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const here = path.dirname(fileURLToPath(import.meta.url));
+const root = path.resolve(here, '..');
+
+// --- parameters ----------------------------------------------------------------
+const SIZE_GUARD_KB = 8192; // ~8 MB file-size guard (task spec)
+const SIZE_TARGET_KB = 6144; // land under ~6 MB once simplified (margin under the guard)
+const DP_STEPS = [0.05, 0.1, 0.2, 0.3, 0.5, 0.75, 1.0]; // Douglas–Peucker tolerances (degrees)
+const R4 = 4; // base coordinate precision (decimal places, ≈11 m)
+
+// Natural Earth admin-1 source (NON-committed temp file; override with NE_ADMIN1).
+const INPUT = process.env.NE_ADMIN1 || '/tmp/ne10m_admin1.geojson';
+
+// --- small geo helpers ---------------------------------------------------------
+const rN = (v, N) => Math.round(v * Math.pow(10, N)) / Math.pow(10, N);
+
+/** Round a ring to N decimals, drop consecutive duplicates, and close it. */
+function roundRing(ring, N) {
+  const out = [];
+  for (const [x, y] of ring) {
+    const p = [rN(x, N), rN(y, N)];
+    const last = out[out.length - 1];
+    if (!last || last[0] !== p[0] || last[1] !== p[1]) out.push(p);
+  }
+  // drop a trailing point equal to the first (a redundant close), then re-close
+  if (
+    out.length > 1 &&
+    out[0][0] === out[out.length - 1][0] &&
+    out[0][1] === out[out.length - 1][1]
+  )
+    out.pop();
+  if (out.length < 3) return out; // degenerate; caller drops it
+  return [...out, [...out[0]]];
+}
+
+/** Perpendicular distance (degrees) from point p to the segment a→b. */
+function perpDist(p, a, b) {
+  const dx = b[0] - a[0];
+  const dy = b[1] - a[1];
+  const l2 = dx * dx + dy * dy;
+  if (l2 === 0) return Math.hypot(p[0] - a[0], p[1] - a[1]);
+  let t = ((p[0] - a[0]) * dx + (p[1] - a[1]) * dy) / l2;
+  t = Math.max(0, Math.min(1, t));
+  return Math.hypot(p[0] - (a[0] + t * dx), p[1] - (a[1] + t * dy));
+}
+
+/** Douglas–Peucker simplification of an OPEN point sequence (keeps endpoints). */
+function dpOpen(pts, tol) {
+  if (pts.length < 3) return pts;
+  let maxD = 0;
+  let idx = 0;
+  const a = pts[0];
+  const b = pts[pts.length - 1];
+  for (let i = 1; i < pts.length - 1; i++) {
+    const d = perpDist(pts[i], a, b);
+    if (d > maxD) {
+      maxD = d;
+      idx = i;
+    }
+  }
+  if (maxD > tol) {
+    const left = dpOpen(pts.slice(0, idx + 1), tol);
+    const right = dpOpen(pts.slice(idx), tol);
+    return left.concat(right.slice(1));
+  }
+  return [a, b];
+}
+
+/** Douglas–Peucker a CLOSED ring (first == last) at tolerance `tol` (0 = skip). */
+function dpRing(ring, tol) {
+  if (tol <= 0 || ring.length < 3) return ring;
+  let pts = ring;
+  if (
+    pts[0][0] === pts[pts.length - 1][0] &&
+    pts[0][1] === pts[pts.length - 1][1]
+  )
+    pts = pts.slice(0, -1);
+  const simplified = dpOpen(pts, tol);
+  return [...simplified, [...simplified[0]]];
+}
+
+/** Round (and optionally simplify) every ring of a Polygon/MultiPolygon geometry. */
+function transformGeom(geom, tol) {
+  const polys = geom.type === 'Polygon' ? [geom.coordinates] : geom.coordinates;
+  const out = polys
+    .map((poly) => poly.map((ring) => roundRing(ring, R4)).map((ring) => (tol > 0 ? dpRing(ring, tol) : ring)))
+    .filter((poly) => poly.length >= 1 && poly.every((ring) => ring.length >= 3));
+  if (!out.length) return geom; // nothing survived simplification — keep the rounded original
+  if (geom.type === 'Polygon') return { type: 'Polygon', coordinates: out[0] };
+  return { type: 'MultiPolygon', coordinates: out };
+}
+
+// --- main ----------------------------------------------------------------------
+function main() {
+  const countries = JSON.parse(readFileSync(path.join(root, 'public', 'countries.geo.json'), 'utf8'));
+  const admin1 = JSON.parse(readFileSync(INPUT, 'utf8'));
+  const cset = new Set(countries.features.map((c) => c.id));
+
+  // Group admin-1 features by parent ISO_A3 (their `adm0_a3`), in file order,
+  // keeping only parents that are one of our 177 countries.
+  const byParent = new Map();
+  for (const f of admin1.features) {
+    const p = f.properties.adm0_a3;
+    if (typeof p === 'string' && cset.has(p)) {
+      if (!byParent.has(p)) byParent.set(p, []);
+      byParent.get(p).push(f);
+    }
+  }
+
+  // Build the base specs (raw geometry + unique id + name + parent) in
+  // countries.geo.json file order, then per-region source order — deterministic.
+  const specs = [];
+  const seenIds = new Set();
+  const nextId = (base) => {
+    let id = base;
+    let k = 1;
+    while (seenIds.has(id)) {
+      k += 1;
+      id = `${base}-${k}`;
+    }
+    seenIds.add(id);
+    return id;
+  };
+
+  let fallbackCount = 0;
+  const fallbackCountries = [];
+  for (const c of countries.features) {
+    const regs = byParent.get(c.id) ?? [];
+    if (regs.length) {
+      let nn = 0;
+      for (const r of regs) {
+        nn += 1;
+        const iso = r.properties.iso_3166_2;
+        const base = typeof iso === 'string' && iso ? iso : `${c.id}-${String(nn).padStart(2, '0')}`;
+        const name = typeof r.properties.name === 'string' && r.properties.name ? r.properties.name : c.properties.name;
+        specs.push({ id: nextId(base), name, parent: c.id, geom: r.geometry });
+      }
+    } else {
+      fallbackCount += 1;
+      fallbackCountries.push(c.id);
+      specs.push({ id: nextId(`${c.id}-01`), name: c.properties.name, parent: c.id, geom: c.geometry });
+    }
+  }
+
+  const sortById = (a, b) => (a.properties.parent !== b.properties.parent ? (a.properties.parent < b.properties.parent ? -1 : 1) : a.id.localeCompare(b.id, 'en', { numeric: true }));
+
+  const build = (tol) => {
+    const fc = {
+      type: 'FeatureCollection',
+      features: specs.map((s) => ({
+        type: 'Feature',
+        id: s.id,
+        properties: { name: s.name, parent: s.parent },
+        geometry: transformGeom(s.geom, tol),
+      })),
+    };
+    fc.features.sort(sortById);
+    return fc;
+  };
+
+  // Base: 4 decimal places, no simplification.
+  let fc = build(0);
+  let json = JSON.stringify(fc);
+  let sizeKB = Buffer.byteLength(json) / 1024;
+  console.log(`base (4dp, no DP): ${sizeKB.toFixed(1)} KB  (${fc.features.length} features)`);
+
+  // File-size guard: if the base is over the guard, simplify until it is under
+  // the target (or we exhaust the tolerance table).
+  let usedTol = 0;
+  if (sizeKB > SIZE_GUARD_KB) {
+    for (const t of DP_STEPS) {
+      fc = build(t);
+      json = JSON.stringify(fc);
+      sizeKB = Buffer.byteLength(json) / 1024;
+      usedTol = t;
+      console.log(`DP ${t}: ${sizeKB.toFixed(1)} KB`);
+      if (sizeKB < SIZE_TARGET_KB) break;
+    }
+  }
+
+  writeFileSync(path.join(root, 'public', 'regions.geo.json'), json + '\n');
+
+  // --- summary ----------------------------------------------------------------
+  const counts = new Map();
+  for (const f of fc.features) counts.set(f.properties.parent, (counts.get(f.properties.parent) ?? 0) + 1);
+  const sortedCounts = [...counts.values()].sort((a, b) => a - b);
+  const median =
+    sortedCounts.length % 2
+      ? sortedCounts[Math.floor(sortedCounts.length / 2)]
+      : (sortedCounts[sortedCounts.length / 2 - 1] + sortedCounts[sortedCounts.length / 2]) / 2;
+  const maxCountry = [...counts.entries()].sort((a, b) => b[1] - a[1])[0];
+  const maxCountryName = countries.features.find((c) => c.id === maxCountry[0])?.properties.name ?? '';
+
+  const finalKB = Buffer.byteLength(json) / 1024;
+  console.log(`\nwrote public/regions.geo.json — ${finalKB.toFixed(1)} KB (${(finalKB / 1024).toFixed(2)} MB)`);
+  console.log(`features: ${fc.features.length} total across ${counts.size} of ${countries.features.length} countries`);
+  console.log(`per-country count: min ${sortedCounts[0]} / median ${median} / max ${sortedCounts[sortedCounts.length - 1]}`);
+  console.log(`max-count country: ${maxCountry[0]} (${maxCountryName}) with ${maxCountry[1]}`);
+  if (usedTol) console.log(`simplification: Douglas–Peucker @ ${usedTol}° (base was ${SIZE_GUARD_KB}+ KB)`);
+  console.log(`whole-country fallback: ${fallbackCount} ${fallbackCount ? `(${fallbackCountries.join(', ')})` : '(none)'}`);
+}
+
+main();

scripts/regions.test.ts

@@ -0,0 +1,365 @@
+/**
+ * scripts/regions.test.ts — validation for the committed `public/regions.geo.json`.
+ *
+ * The dataset is REAL named sub-national administrative regions (Natural
+ * Earth admin-1: states, provinces, governorates, oblasts, …) that the
+ * coarsening step (`scripts/coarsen-regions.mjs`, v0.14) has merged down to a
+ * ~100×100 km (10,000 km²) floor: every small non-island region was dissolved
+ * into its nearest same-country neighbor, so the only regions left below the
+ * floor are islands (no same-country sibling nearby). One feature per named
+ * region, each carrying `properties = { name, parent }` where `parent` is the
+ * country's ISO_A3 (the RegionMap key the map resolves ownership through).
+ * Tiny or uncovered countries collapse to a single whole-country region
+ * (`<ISO_A3>-01`).
+ *
+ * This test is self-contained (no import of the generator): it re-implements
+ * the same planar area model the generator/analysis use, so the area-based
+ * assertions measure the same quantity:
+ *
+ *   x = lon · 111.32 · cos(midLat),  y = lat · 110.574  (km)
+ *
+ * with a shoelace per OUTER ring, each ring measured at its own mean latitude.
+ * Outer rings only — a region's inner rings (holes) are lakes and are ignored
+ * by design, the same way the coverage band already absorbed them.
+ *
+ * It reads each file exactly once and runs in O(total vertices).
+ */
+import { readFileSync } from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { describe, expect, it } from 'vitest';
+
+const here = path.dirname(fileURLToPath(import.meta.url));
+const root = path.resolve(here, '..');
+
+// --- area model (planar approximation; matches scripts/generate-regions.mjs) --
+const KM_LON = 111.32;
+const KM_LAT = 110.574;
+const rad = (deg: number) => (deg * Math.PI) / 180;
+
+type Ring = [number, number][];
+type Geometry =
+  | { type: 'Polygon'; coordinates: Ring[] }
+  | { type: 'MultiPolygon'; coordinates: Ring[][] };
+
+function ringAreaKm2(ring: Ring, midLat: number): number {
+  const kx = KM_LON * Math.cos(rad(midLat));
+  let a = 0;
+  const n = ring.length;
+  for (let i = 0; i < n; i++) {
+    const [lon1, lat1] = ring[i];
+    const [lon2, lat2] = ring[(i + 1) % n];
+    a += lon1 * kx * (lat2 * KM_LAT) - lon2 * kx * (lat1 * KM_LAT);
+  }
+  return Math.abs(a / 2);
+}
+
+function outerRings(geom: Geometry): Ring[] {
+  if (geom.type === 'Polygon') return [geom.coordinates[0]];
+  if (geom.type === 'MultiPolygon') return geom.coordinates.map((p) => p[0]);
+  return [];
+}
+
+/** Sum of a feature's outer-ring areas, each ring at its own mean latitude. */
+function featureAreaKm2(geom: Geometry): number {
+  let total = 0;
+  for (const ring of outerRings(geom)) {
+    let lat = 0;
+    for (const [, la] of ring) lat += la;
+    total += ringAreaKm2(ring, ring.length ? lat / ring.length : 0);
+  }
+  return total;
+}
+
+function median(nums: number[]): number {
+  if (!nums.length) return 0;
+  const s = [...nums].sort((a, b) => a - b);
+  const m = Math.floor(s.length / 2);
+  return s.length % 2 ? s[m] : (s[m - 1] + s[m]) / 2;
+}
+// ------------------------------------------------------------------------------
+
+interface RegionFeature {
+  type: 'Feature';
+  id: string;
+  properties: { name: string; parent: string };
+  geometry: Geometry;
+}
+interface CountryFeature {
+  type: 'Feature';
+  id: string;
+  properties: { name: string };
+  geometry: Geometry;
+}
+
+// Read each file exactly once.
+const regions = JSON.parse(
+  readFileSync(path.join(root, 'public', 'regions.geo.json'), 'utf8'),
+) as { type: 'FeatureCollection'; features: RegionFeature[] };
+const countries = JSON.parse(
+  readFileSync(path.join(root, 'public', 'countries.geo.json'), 'utf8'),
+) as { type: 'FeatureCollection'; features: CountryFeature[] };
+
+// Precompute once (O(total vertices)).
+const countryIds = new Set(countries.features.map((c) => c.id));
+const countryArea = new Map<string, number>();
+for (const c of countries.features) countryArea.set(c.id, featureAreaKm2(c.geometry));
+const regionArea = new Map<string, number>();
+for (const f of regions.features) regionArea.set(f.id, featureAreaKm2(f.geometry));
+const sumByParent = new Map<string, number>();
+for (const f of regions.features)
+  sumByParent.set(f.properties.parent, (sumByParent.get(f.properties.parent) ?? 0) + (regionArea.get(f.id) ?? 0));
+const countByParent = new Map<string, number>();
+for (const f of regions.features)
+  countByParent.set(f.properties.parent, (countByParent.get(f.properties.parent) ?? 0) + 1);
+
+// --- island/close-neighbor helpers (mirror scripts/coarsen-regions.mjs) ------
+
+interface LonInt {
+  a: number;
+  b: number;
+  full: boolean;
+}
+interface RegionBBox {
+  latMin: number;
+  latMax: number;
+  lon: LonInt;
+}
+
+const COARSE_FLOOR_KM2 = 10_000; // the coarsener's ~100×100 km floor
+const CLOSE_DEG = 0.2; // "spatially close" bbox gap (both lat and lon ≤ this)
+
+/**
+ * Unwrap a ring's longitudes to a continuous line (np.unwrap shortest-diff
+ * scheme, anchored at the first vertex's [0,360) value). `full` when the
+ * unwrapped span is ≥ 300° (a full-360° antimeridian band, e.g. Antarctica).
+ * Must stay in sync with the coarsening script.
+ */
+function unwrapRing(ring: Ring) {
+  const n = ring.length;
+  const norm = (x: number) => ((x % 360) + 360) % 360;
+  const u: number[] = new Array(n);
+  u[0] = norm(ring[0][0]);
+  for (let i = 1; i < n; i++) {
+    // the previous UNWRAPPED value may lie outside [0,360); normalize it
+    // before measuring the shortest signed difference, or a bogus ~180° jump
+    // is inserted and the ring's span balloons.
+    const a = norm(u[i - 1]);
+    const b = norm(ring[i][0]);
+    const d = (((b - a) % 360) + 540) % 360 - 180;
+    u[i] = u[i - 1] + d;
+  }
+  let min = Infinity;
+  let max = -Infinity;
+  for (const v of u) {
+    if (v < min) min = v;
+    if (v > max) max = v;
+  }
+  return { lons: u, full: max - min >= 300 };
+}
+
+/**
+ * Cyclic 1-D gap (degrees) between two tight longitude intervals in their own
+ * unwrapped spaces; a `full` interval is close to everything.
+ */
+function lonGap(intA: LonInt, intB: LonInt): number {
+  if (intA.full || intB.full) return 0;
+  let best = Infinity;
+  for (const k of [-1, 0, 1]) {
+    const a2 = intB.a + 360 * k;
+    const b2 = intB.b + 360 * k;
+    const gap = intA.b < a2 ? a2 - intA.b : b2 < intA.a ? intA.a - b2 : 0;
+    if (gap < best) best = gap;
+  }
+  return best;
+}
+
+// Per-region bbox in antimeridian-safe unwrapped longitude space.
+const regionBBox = new Map<string, RegionBBox>();
+for (const f of regions.features) {
+  const polys = f.geometry.type === 'Polygon' ? [f.geometry.coordinates] : f.geometry.coordinates;
+  let latMin = Infinity;
+  let latMax = -Infinity;
+  let a = Infinity;
+  let b = -Infinity;
+  let full = false;
+  for (const poly of polys) {
+    const outer = poly[0];
+    for (const [, la] of outer) {
+      if (la < latMin) latMin = la;
+      if (la > latMax) latMax = la;
+    }
+    const { lons, full: fl } = unwrapRing(outer);
+    if (fl) full = true;
+    for (const v of lons) {
+      if (v < a) a = v;
+      if (v > b) b = v;
+    }
+  }
+  regionBBox.set(f.id, { latMin, latMax, lon: { a, b, full } });
+}
+
+/** Bounding-box closeness (same definition the coarsening script uses). */
+function bboxesClose(x: RegionBBox, y: RegionBBox): boolean {
+  const latGap = x.latMax < y.latMin ? y.latMin - x.latMax : y.latMax < x.latMin ? x.latMin - y.latMax : 0;
+  if (latGap > CLOSE_DEG) return false;
+  return lonGap(x.lon, y.lon) <= CLOSE_DEG;
+}
+
+describe('regions.geo.json', () => {
+  it('is a valid GeoJSON FeatureCollection of well-formed features', () => {
+    expect(regions.type).toBe('FeatureCollection');
+    expect(Array.isArray(regions.features)).toBe(true);
+    expect(regions.features.length).toBeGreaterThan(0);
+    for (const f of regions.features) {
+      expect(f.type, `${f.id ?? '?'}: not a Feature`).toBe('Feature');
+      expect(typeof f.id, `${f.id ?? '?'}: id must be a string`).toBe('string');
+      expect(f.id.length, `${f.id ?? '?'}: empty id`).toBeGreaterThan(0);
+      expect(typeof f.properties?.name, `${f.id}: missing name`).toBe('string');
+      expect(f.properties.name.length, `${f.id}: empty name`).toBeGreaterThan(0);
+      expect(typeof f.properties.parent, `${f.id}: missing parent`).toBe('string');
+      expect(countryIds.has(f.properties.parent), `${f.id}: unknown parent ${f.properties.parent}`).toBe(true);
+      const g = f.geometry;
+      expect(
+        !!g && (g.type === 'Polygon' || g.type === 'MultiPolygon'),
+        `${f.id}: bad geometry type ${g?.type}`,
+      ).toBe(true);
+      if (g) {
+        const polys = g.type === 'Polygon' ? [g.coordinates] : g.coordinates;
+        for (const poly of polys)
+          for (const ring of poly)
+            expect(ring.length, `${f.id}: ring with ${ring.length} pts`).toBeGreaterThanOrEqual(3);
+      }
+    }
+  });
+
+  it('has globally unique feature ids (ISO 3166-2 disambiguated on within-country collision)', () => {
+    const seen = new Set<string>();
+    const dups = new Set<string>();
+    for (const f of regions.features) {
+      if (seen.has(f.id)) dups.add(f.id);
+      seen.add(f.id);
+    }
+    expect(
+      dups.size,
+      `duplicate ids: ${[...dups].slice(0, 10).join(', ')}`,
+    ).toBe(0);
+    expect(seen.size).toBe(regions.features.length);
+  });
+
+  it('covers every one of the 177 countries with at least one region', () => {
+    const counts = countries.features.map((c) => countByParent.get(c.id) ?? 0);
+    for (const c of countries.features) {
+      expect(countByParent.get(c.id) ?? 0, `country ${c.id} has no regions`).toBeGreaterThanOrEqual(1);
+    }
+    const min = Math.min(...counts);
+    const max = Math.max(...counts);
+    const med = median(counts);
+    const maxCountry = [...countByParent.entries()].sort((a, b) => b[1] - a[1])[0];
+    const maxCountryName = countries.features.find((c) => c.id === maxCountry[0])?.properties.name ?? '';
+    console.log(
+      `\n  per-country region count: min ${min} / median ${med} / max ${max}` +
+        ` (max: ${maxCountry[0]} ${maxCountryName} with ${maxCountry[1]})`,
+    );
+  });
+
+  it('has sane region areas: median >= 100 km2, and no non-Antarctica region >= 5,000,000 km2', () => {
+    const areas = regions.features.map((f) => regionArea.get(f.id) ?? 0);
+    const med = median(areas);
+    const maxRegion = regions.features.reduce((m, f) => ((regionArea.get(f.id) ?? 0) > (regionArea.get(m.id) ?? 0) ? f : m));
+    const minRegion = regions.features.reduce((m, f) => ((regionArea.get(f.id) ?? 0) < (regionArea.get(m.id) ?? 0) ? f : m));
+    const tiny = areas.filter((a) => a < 1).length;
+    // Antarctica (ATA) is a full-360° wrap ring, so the planar model can't
+    // measure it (it reports ~21.8M km2 for a ~14M km2 landmass) — exempt it.
+    for (const f of regions.features) {
+      if (f.properties.parent === 'ATA') continue;
+      const a = regionArea.get(f.id) ?? 0;
+      expect(a < 5_000_000, `${f.id}: area ${Math.round(a).toLocaleString('en-US')} km2 is absurdly large`).toBe(true);
+    }
+    expect(med, `median region area ${med.toFixed(1)} km2 is too small`).toBeGreaterThanOrEqual(100);
+    console.log(
+      `\n  region area: min ${minRegion.id} (${minRegion.properties.name}) ≈ ${(regionArea.get(minRegion.id) ?? 0).toExponential(2)} km2` +
+        ` / median ${med.toLocaleString('en-US')} km2` +
+        ` / max ${maxRegion.id} (${maxRegion.properties.name}) ≈ ${Math.round(regionArea.get(maxRegion.id) ?? 0).toLocaleString('en-US')} km2` +
+        ` — ${tiny} regions < 1 km2 (legit micro-regions: tiny islands, small urban districts, degenerate disputed enclaves)`,
+    );
+  });
+
+  it('leaves only islands below the ~10,000 km2 coarsening floor (non-island small regions merged)', () => {
+    // v0.14 coarsening: every region smaller than the floor that has a
+    // same-country sibling within CLOSE_DEG of its bbox is dissolved into its
+    // nearest such neighbor, so a below-floor region may only survive if it
+    // is an island. Count the non-island residuals below the floor and allow
+    // a small tolerance band (strictly < 1% of all regions) — the coarsener's
+    // fixed point leaves none, and this catches a regression in the merge
+    // logic (e.g. a broken neighbor test that exempts land regions) without
+    // being brittle to one or two borderline cases.
+    const smallNonIslands: string[] = [];
+    let smallIslands = 0;
+    let smallTotal = 0;
+    for (const f of regions.features) {
+      const a = regionArea.get(f.id) ?? 0;
+      if (a >= COARSE_FLOOR_KM2) continue;
+      smallTotal++;
+      const bb = regionBBox.get(f.id)!;
+      let hasNeighbor = false;
+      for (const g of regions.features) {
+        if (g.id === f.id || g.properties.parent !== f.properties.parent) continue;
+        if (bboxesClose(bb, regionBBox.get(g.id)!)) {
+          hasNeighbor = true;
+          break;
+        }
+      }
+      if (hasNeighbor) {
+        smallNonIslands.push(`${f.id} (${Math.round(a)} km2)`);
+      } else smallIslands++;
+    }
+    const frac = regions.features.length ? smallNonIslands.length / regions.features.length : 0;
+    expect(
+      frac < 0.01,
+      `${smallNonIslands.length} non-island region(s) below the ${COARSE_FLOOR_KM2} km2 floor ` +
+        `(${(100 * frac).toFixed(2)}% of all regions): ${smallNonIslands.slice(0, 10).join(', ')}`,
+    ).toBe(true);
+    console.log(
+      `\n  below-floor regions: ${smallTotal} — ${smallIslands} islands (exempt, no same-country neighbor within ${CLOSE_DEG}°)` +
+        ` / ${smallNonIslands.length} non-island residuals (must stay < 1% of all regions)`,
+    );
+  });
+
+  it('sums to within [40%, 175%] of each country area (median in [70%, 130%])', () => {
+    // The band is a planar-approximation sanity check. It is wider than a naive
+    // [40%, 110%] because Natural Earth's admin-1 polygons are digitized
+    // independently of the admin-0 country polygons (they are NOT clipped to
+    // them), so for a handful of small/island nations the region union
+    // over/under-fills the country: measured range is ~[52%, 151%]
+    // (Brunei under-fills, Vanuatu over-fills). The band brackets that with
+    // margin while still catching a genuinely missing or doubled-up region.
+    const ratios: number[] = [];
+    let minRatio = Infinity;
+    let maxRatio = -Infinity;
+    let minId = '';
+    let maxId = '';
+    for (const c of countries.features) {
+      const ca = countryArea.get(c.id) ?? 0;
+      if (ca <= 0) continue;
+      const ratio = (sumByParent.get(c.id) ?? 0) / ca;
+      ratios.push(ratio);
+      if (ratio < minRatio) { minRatio = ratio; minId = c.id; }
+      if (ratio > maxRatio) { maxRatio = ratio; maxId = c.id; }
+      expect(
+        ratio >= 0.4 && ratio <= 1.75,
+        `${c.id}: coverage ${(100 * ratio).toFixed(1)}% is outside [40%, 175%]`,
+      ).toBe(true);
+    }
+    const medRatio = median(ratios);
+    expect(
+      medRatio >= 0.7 && medRatio <= 1.3,
+      `median coverage ${(100 * medRatio).toFixed(1)}% is outside [70%, 130%]`,
+    ).toBe(true);
+    console.log(
+      `\n  coverage range: min ${minId} ${(100 * minRatio).toFixed(1)}%` +
+        ` / median ${(100 * medRatio).toFixed(1)}%` +
+        ` / max ${maxId} ${(100 * maxRatio).toFixed(1)}% (band 40–175%)`,
+    );
+  });
+});

server/engine.test.ts

@@ -1,10 +1,11 @@
 import { describe, expect, it } from 'vitest';
 import type { GameState, Preset, RoundItem } from '../shared/types';
-import type { TurnResult } from '../shared/protocol';
+import { makeEvent, type TurnResult } from '../shared/protocol';
 import type { LlmClient } from './llm';
 import { makeStubLlmClient } from './stub';
 import {
   applyTurnResult,
+  buildSystemPrompt,
   buildUserPrompt,
   isMeaningful,
   parseTurnResult,
@@ -279,6 +280,44 @@ describe('buildUserPrompt (batched round)', () => {
     expect(parsed.roundInstruction).toMatch(/no action/i);
     expect(parsed.roundInstruction).toMatch(/own momentum/i);
   });
+
+  it('caps recentEvents at the last 5 (in order) when the state has more than 5 events', () => {
+    const state = baseState();
+    const events = Array.from({ length: 8 }, (_, i) =>
+      makeEvent(
+        {
+          nation: 'uk',
+          type: 'political',
+          title: `Event ${i + 1}`,
+          text: `Narrative ${i + 1}`,
+          outcome: 'neutral',
+        },
+        i + 1,
+        `1939-09-0${i + 1}`,
+      ),
+    );
+    state.events = events;
+
+    const parsed = JSON.parse(buildUserPrompt(state, [])) as {
+      state: { recentEvents: Array<{ title: string; turn: number; date: string }> };
+    };
+
+    expect(parsed.state.recentEvents).toHaveLength(5);
+    // the last 5 of the 8 input events, in order
+    expect(parsed.state.recentEvents[0].title).toBe(events[3].title); // 'Event 4'
+    expect(parsed.state.recentEvents[4].title).toBe(events[7].title); // 'Event 8'
+    expect(parsed.state.recentEvents.map((e) => e.title)).toEqual([
+      events[3].title,
+      events[4].title,
+      events[5].title,
+      events[6].title,
+      events[7].title,
+    ]);
+  });
+
+  it('asks the model to keep its internal reasoning brief (concise-CoT constraint)', () => {
+    expect(buildSystemPrompt(preset)).toMatch(/reasoning brief|a few sentences/i);
+  });
 });
 
 describe('queueRoundItem', () => {

server/engine.ts

@@ -59,6 +59,7 @@ export function buildSystemPrompt(preset: Preset): string {
     'HARD CONSTRAINTS',
     '- Use only nation ids and ISO_A3 codes that exist in the provided state.',
     '- Prefer 1-4 events per turn; keep each text 1-3 sentences.',
+    '- Keep your internal reasoning brief (a few sentences) and go straight to the JSON result; do not over-deliberate or re-derive facts already present in the state.',
     '- Keep every stat value between 0 and 100.',
     '- Only change borders when war or a decisive political shift justifies it.',
     '- If a field is not relevant this turn, set it to an empty array.',
@@ -95,7 +96,7 @@ export function buildUserPrompt(state: GameState, items: RoundItem[]): string {
       nations: Object.fromEntries(
         Object.entries(state.nations).map(([id, n]) => [id, nationForPrompt(n)]),
       ),
-      recentEvents: state.events.slice(-10).map((e) => ({
+      recentEvents: state.events.slice(-5).map((e) => ({
         turn: e.turn,
         date: e.date,
         nation: e.nation,

server/map.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest';
 import { buildRegionMap } from './map';
-import { nationColor, regionOwner, type RegionMap } from '../shared/protocol';
+import { mapFeatureOwner, nationColor, regionOwner, type RegionMap } from '../shared/protocol';
 import type { GameState } from '../shared/types';
 
 const state: GameState = {
@@ -74,40 +74,62 @@ describe('regionOwner', () => {
 });
 
 /**
- * #6 regression guard. The click/hover handlers resolve the owning nation from a
- * map feature. MapLibre repacks a GeoJSON source's top-level `id` (the ISO_A3
- * string) into a *numeric index* when it stores the source, so a feature the map
- * hands back at interaction time has a number for `id` and the ISO_A3 only lives
- * in `properties.regionId`. This test pins the exact data shape and proves the
- * fix: resolution via `properties.regionId` works, while the pre-fix path that
- * read `feature.id` does not.
+ * #6 regression guard (sub-national map). The click/hover handlers resolve the
+ * owning nation from a rendered map feature. MapLibre repacks a GeoJSON
+ * source's top-level `id` into a *numeric index* when it stores the source, so a
+ * feature the map hands back at interaction time has a number for `id`. The
+ * choropleth is now sub-national: a feature's id is a sub-region code
+ * (`DEU-03`) and its owner lives at the *parent country* (`DEU`), which the
+ * client stamps into `properties.parent` (the RegionMap is keyed by that
+ * country code, never the sub-region id). This pins the exact data shape and
+ * proves the resolution: `mapFeatureOwner` works via `properties.parent`, while
+ * the two wrong paths (the repacked numeric `feature.id`, and the sub-region
+ * `regionId`, which is not a RegionMap key) do not.
  */
-describe('#6 — owner must be resolved from properties.regionId, not the repacked feature.id', () => {
-  // The shape MapLibre returns for a source feature after setData(): `id` is a
-  // number (here 0, as observed in the live map), and the ISO_A3 is preserved
-  // only in properties (the client stamps it as `regionId`).
+describe('#6 — sub-region owner must be resolved from properties.parent, not the sub-region id / repacked feature.id', () => {
+  // The shape MapLibre returns for a sub-region feature after setData(): `id`
+  // is a number (repacked), and the stable identifiers live only in properties —
+  // `regionId` (the sub-region code) and `parent` (the ISO_A3 country).
   const repackedFeature = {
     id: 0,
-    properties: { name: 'DE', regionId: 'DEU' },
+    properties: { name: 'Germany R03', regionId: 'DEU-03', parent: 'DEU' },
   };
 
-  it('resolves the owner from properties.regionId (the fix)', () => {
-    const code = typeof repackedFeature.properties.regionId === 'string' ? repackedFeature.properties.regionId : '';
-    expect(regionOwner(regions, code)).toEqual({
+  it('resolves the owner from properties.parent (the fix)', () => {
+    expect(mapFeatureOwner(regions, repackedFeature)).toEqual({
       color: nationColor('de'),
       owner: 'DE',
       ownerId: 'de',
     });
   });
 
-  it('the old path (feature.id as a string key) does NOT resolve — the bug', () => {
-    // String(0) === '0' is not a valid ISO_A3 key, so the pre-fix lookup failed
-    // and the click popup reported "No owner" even for owned regions.
-    expect(regions[String(repackedFeature.id)]).toBeUndefined();
+  it('the sub-region regionId is NOT a RegionMap key — resolving from it fails', () => {
+    // 'DEU-03' is a sub-region id; the RegionMap is keyed by the parent 'DEU'.
+    expect(regionOwner(regions, repackedFeature.properties.regionId)).toBeUndefined();
+  });
+
+  it('the repacked numeric feature.id does NOT resolve — the bug', () => {
+    // String(0) === '0' is not a valid key, so the pre-fix lookup failed and
+    // reported "No owner" even for owned regions.
     expect(regionOwner(regions, String(repackedFeature.id))).toBeUndefined();
   });
 });
 
+describe('mapFeatureOwner', () => {
+  it('returns undefined for a missing feature, missing parent, or non-string parent', () => {
+    expect(mapFeatureOwner(regions, null)).toBeUndefined();
+    expect(mapFeatureOwner(regions, undefined)).toBeUndefined();
+    expect(mapFeatureOwner(regions, {})).toBeUndefined();
+    expect(mapFeatureOwner(regions, { properties: {} })).toBeUndefined();
+    expect(mapFeatureOwner(regions, { properties: { parent: 42 } })).toBeUndefined();
+  });
+
+  it('returns undefined for a parent country nobody owns', () => {
+    expect(mapFeatureOwner(regions, { properties: { parent: 'FRA' } })).toBeUndefined();
+    expect(mapFeatureOwner(regions, { properties: { parent: 'USA' } })).toBeUndefined();
+  });
+});
+
 describe('nationColor', () => {
   it('is deterministic per id and distinct across different ids', () => {
     expect(nationColor('uk')).toBe(nationColor('uk'));

shared/protocol.ts

@@ -57,20 +57,41 @@ export interface RegionOwner {
 export type RegionMap = Record<string, RegionOwner>;
 
 /**
- * Look up the owner record for a map region from the authoritative RegionMap by
- * its ISO_A3 code. Returns `undefined` for an empty/missing code or an unowned
- * region. Pure + shared: the client resolves a clicked or hovered map feature by
- * first reading the feature's stable ISO_A3 code (stored in `properties.regionId`
- * by the client when it repacks the source — see WorldMap) and then calling this.
+ * Look up the owner record from the authoritative RegionMap by a RegionMap key.
+ * The RegionMap is keyed by the **parent country's** ISO_A3 code (ownership and
+ * the LLM stay at country granularity — see #16), so `key` is a country code such
+ * as `DEU`, never a sub-region id such as `DEU-03`. Returns `undefined` for an
+ * empty/missing key or an unowned country.
  *
- * The code must NOT be taken from the feature's top-level `id`: MapLibre repacks
- * a GeoJSON source's `id` (an ISO_A3 string) into a numeric index when it stores
- * the source, so at click/hover time `feature.id` is a number, never the ISO_A3
- * — resolving from it is exactly the "no owner" bug (#6).
+ * Pure + shared: the primitive "key → owner" lookup. The *map feature → owner*
+ * resolution (deciding which key to pass) lives in {@link mapFeatureOwner} below,
+ * which reads the feature's `properties.parent` — never the repacked top-level
+ * `id` (MapLibre turns it into a numeric index, the "no owner" bug #6) and never
+ * the sub-region id.
  */
-export function regionOwner(regions: RegionMap, isoA3: string | null | undefined): RegionOwner | undefined {
-  if (!isoA3) return undefined;
-  return regions[isoA3];
+export function regionOwner(regions: RegionMap, key: string | null | undefined): RegionOwner | undefined {
+  if (!key) return undefined;
+  return regions[key];
+}
+
+/**
+ * Resolve the owning-nation record for a **rendered map feature** from the
+ * authoritative RegionMap. The choropleth renders sub-national regions, but the
+ * RegionMap is keyed by the *parent country's* ISO_A3 (not the sub-region's own
+ * id), so a feature's owner is found via its `properties.parent` (the ISO_A3 the
+ * client stamps from the GeoJSON `parent` property — see WorldMap) and then
+ * `regionOwner`. This is the single shared source of truth for that resolution,
+ * so the "use `parent`, never the sub-region `id`/repacked `feature.id`" rule
+ * lives in one tested place rather than in the React component.
+ *
+ * Returns `undefined` for a missing feature/parent or an unowned country.
+ */
+export function mapFeatureOwner(
+  regions: RegionMap,
+  feature: { properties?: { parent?: unknown } } | null | undefined,
+): RegionOwner | undefined {
+  const parent = feature?.properties?.parent;
+  return regionOwner(regions, typeof parent === 'string' ? parent : '');
 }
 
 /** Server -> client Server-Sent Events payload (see server/index.ts /sse). */

src/App.tsx

@@ -589,6 +589,17 @@ function GameScreen({
 }: GameScreenProps) {
   // Which nation's dossier to show. Defaults to the player; remounts per game.
   const [viewingId, setViewingId] = useState(game.playerNationId);
+  // When the dossier target was set by a map click, remember which sub-region
+  // (its own name + parent country) was clicked, for a small label in the
+  // dossier. Cleared when the user picks a nation via the manual Inspect select.
+  const [selectedRegion, setSelectedRegion] = useState<{ parent?: string; name?: string } | null>(null);
+  const focusNation = useCallback(
+    (id: string, info?: { parent?: string; name?: string }) => {
+      setViewingId(id);
+      setSelectedRegion(info ?? null);
+    },
+    [],
+  );
   const player = game.nations[game.playerNationId];
   const viewed = game.nations[viewingId] ?? player;
   const nations = Object.values(game.nations).sort((a, b) => a.name.localeCompare(b.name));
@@ -641,7 +652,7 @@ function GameScreen({
         playerNationId={game.playerNationId}
         nations={game.nations}
         presetId={game.presetId}
-        onFocusNation={setViewingId}
+        onFocusNation={focusNation}
       />
 
       {/* Pinned top bar: brand, turn + date, player nation, live status, Focus map.
@@ -747,7 +758,14 @@ function GameScreen({
           <div className="mb-1.5 text-xs font-medium uppercase tracking-wide text-muted-foreground">
             Inspect
           </div>
-          <Select value={viewingId} onValueChange={setViewingId}>
+          <Select
+            value={viewingId}
+            onValueChange={(id) => {
+              // A manual pick supersedes a map-click selection: clear the label.
+              setViewingId(id);
+              setSelectedRegion(null);
+            }}
+          >
             <SelectTrigger className="w-full" data-testid="inspect-select">
               <SelectValue />
             </SelectTrigger>
@@ -759,6 +777,12 @@ function GameScreen({
               ))}
             </SelectContent>
           </Select>
+          {selectedRegion && (
+            <div className="mt-1.5 truncate text-[11px] text-muted-foreground" data-testid="selected-region">
+              Selected: {selectedRegion.name ?? selectedRegion.parent ?? 'region'}
+              {selectedRegion.parent ? ` (${selectedRegion.parent})` : ''}
+            </div>
+          )}
         </div>
         <NationPanel nation={viewed} nations={game.nations} isPlayer={viewingId === game.playerNationId} inWindow />
       </FloatingWindow>

src/components/WorldMap.tsx

@@ -8,11 +8,14 @@ import 'maplibre-gl/dist/maplibre-gl.css';
 // Point it at a Vite-emitted copy of the worker module so it loads in prod.
 import workerUrl from 'maplibre-gl/dist/maplibre-gl-worker.mjs?url';
 maplibregl.setWorkerUrl(workerUrl);
-import { regionOwner, type RegionMap, type RegionOwner } from '@shared/protocol';
+import { mapFeatureOwner, type RegionMap, type RegionOwner } from '@shared/protocol';
 import type { Nation } from '@shared/types';
 import { cn } from '@/lib/utils';
 
-// Minimal GeoJSON types (avoids a hard @types/geojson dependency).
+// Minimal GeoJSON types (avoids a hard @types/geojson dependency). The choropleth
+// source is the sub-national `regions.geo.json`: each feature is a sub-region with
+// a top-level `id` of the form `<ISO_A3>-<nn>` (e.g. `FRA-03`) and
+// `properties = { name, parent }` where `parent` is the parent country's ISO_A3.
 interface GeoFeature {
   type: 'Feature';
   id?: string | number;
@@ -27,7 +30,7 @@ type GeoSource = maplibregl.GeoJSONSource;
 
 // Inline basemap style — a visible dark-navy background plus a subtle
 // OpenFreeMap shaded-relief raster so the ocean is never pure black and terrain
-// is faintly visible. The country choropleth (added in `ensureLayers`) is drawn
+// is faintly visible. The regional choropleth (added in `ensureLayers`) is drawn
 // on top and is the real star.
 //
 // Why inline instead of a remote style URL: the OFM "dark" style's vector tiles
@@ -61,7 +64,7 @@ const INLINE_STYLE: maplibregl.StyleSpecification = {
       type: 'raster',
       source: 'terrain',
       paint: {
-        'raster-opacity': 0.5,
+        'raster-opacity': 0.15,
         'raster-brightness-max': 0.8,
         'raster-fade-duration': 200,
       },
@@ -69,11 +72,11 @@ const INLINE_STYLE: maplibregl.StyleSpecification = {
   ],
 };
 
-const COUNTRIES_SOURCE = 'countries';
+const REGIONS_SOURCE = 'regions';
 const HOVER_SOURCE = 'hover';
 const FLASH_SOURCE = 'flash';
-const FILL_LAYER = 'countries-fill';
-const LINE_LAYER = 'countries-line';
+const FILL_LAYER = 'regions-fill';
+const LINE_LAYER = 'regions-line';
 const PLAYER_LINE = 'player-line';
 const FLASH_LINE = 'flash-line';
 const HOVER_FILL = 'hover-fill';
@@ -97,38 +100,48 @@ function cameraForPreset(presetId: string): { center: [number, number]; zoom: nu
 }
 
 /**
- * Stamp the current ownership + colors onto a clone of the base geo. Each region
- * carries its owner's stable fill color, a subtle stroke, and a flag for the
- * player's own regions (rendered as a brighter, thicker border by a dedicated
- * layer). Unknown owners fall back to a faint neutral fill — never an error.
+ * Stamp the current ownership + colors onto a clone of the sub-national base geo.
+ * Ownership and the LLM stay at **country** granularity (#16, PR 2): a nation
+ * owns whole countries, so every sub-region of a country shares that country's
+ * owning nation's color — the map looks like the old country choropleth, but
+ * subdivided into finer cells. Each sub-region therefore carries:
  *
- * Crucially, the base GeoJSON feature's top-level `id` (the ISO_A3 code) is
- * stamped into `properties.regionId`, and the owner's id into `properties.ownerId`.
- * MapLibre repacks a GeoJSON source's top-level `id` into a numeric index when it
- * stores it, so a later click/hover event exposes that number on
- * `e.features[i].id` — the top-level `id` is *not* a reliable lookup key at
- * interaction time (the root cause of #6). `properties`, however, survive into the
- * rendered features, so the interaction handlers resolve the owning nation from
- * `properties.regionId` via the RegionMap (see `regionOwner`).
+ *  - `regionId`  – its own sub-region id (e.g. `FRA-03`), kept in a property that
+ *                  survives into the features MapLibre hands back on click/hover
+ *                  (the top-level `id` is repacked into a numeric index, #6);
+ *  - `parent`    – the parent country's ISO_A3 (e.g. `FRA`), the RegionMap key;
+ *  - `fill`      – the owning nation's stable color (from `RegionMap[parent]`);
+ *  - `owner`/`ownerId` – that nation's name/id (empty for an unowned country);
+ *  - `stroke`    – a per-border alpha (owned brighter than unowned);
+ *  - `isPlayer`  – 1 when the owning nation is the player (drives the amber
+ *                  player-highlight border).
+ *
+ * Crucially, the owner lookup keys the RegionMap by `properties.parent` (the
+ * country ISO_A3), **never** by the sub-region id — the RegionMap has no
+ * `FRA-03` entries, only `FRA`.
  */
 function applyRegions(geo: FeatureCollection, regions: RegionMap, playerNationId: string): FeatureCollection {
   const out: FeatureCollection = JSON.parse(JSON.stringify(geo));
   for (const f of out.features) {
     f.properties = f.properties ?? {};
-    // The base GeoJSON `id` is the ISO_A3 code; keep it in a property that
-    // survives into the features MapLibre hands back on click/hover.
-    const code = f.id == null ? '' : String(f.id);
-    f.properties.regionId = code;
-    const r = code ? regions[code] : undefined;
+    // The sub-region's own id (e.g. `FRA-03`) — stamped into a property that
+    // survives into the rendered features (the top-level `id` gets repacked).
+    const subId = f.id == null ? '' : String(f.id);
+    f.properties.regionId = subId;
+    // Ownership lives at the parent country: resolve `properties.parent`
+    // (the ISO_A3) against the RegionMap. Never the sub-region id.
+    const parent = typeof f.properties.parent === 'string' ? f.properties.parent : '';
+    f.properties.parent = parent;
+    const r = parent ? regions[parent] : undefined;
     if (r) {
       f.properties.fill = r.color;
       f.properties.owner = r.owner;
       f.properties.ownerId = r.ownerId;
-      f.properties.stroke = 'rgba(255,255,255,0.10)';
+      f.properties.stroke = 'rgba(255,255,255,0.30)';
       f.properties.isPlayer = r.ownerId === playerNationId ? 1 : 0;
     } else {
       f.properties.fill = 'rgba(148,163,184,0.05)';
-      f.properties.stroke = 'rgba(255,255,255,0.06)';
+      f.properties.stroke = 'rgba(255,255,255,0.14)';
       f.properties.owner = '';
       f.properties.ownerId = '';
       f.properties.isPlayer = 0;
@@ -137,10 +150,18 @@ function applyRegions(geo: FeatureCollection, regions: RegionMap, playerNationId
   return out;
 }
 
-/** Build a FeatureCollection of just the features whose id is in `codes` (cloned). */
-function featuresByCodes(geo: FeatureCollection, codes: Iterable<string>): FeatureCollection {
-  const set = new Set(codes);
-  const features = geo.features.filter((f) => f.id != null && set.has(String(f.id)));
+/**
+ * Build a FeatureCollection of just the sub-regions whose **parent** country is
+ * in `parents` (cloned). Used by the territory-change flash: a turn changes a
+ * whole *country* (the RegionMap is ISO_A3-keyed), so a changed country's code
+ * must light up **all** of its sub-regions, not a single feature.
+ */
+function featuresByParents(geo: FeatureCollection, parents: Iterable<string>): FeatureCollection {
+  const set = new Set(parents);
+  const features = geo.features.filter((f) => {
+    const parent = f.properties?.parent;
+    return typeof parent === 'string' && set.has(parent);
+  });
   return { type: 'FeatureCollection', features: JSON.parse(JSON.stringify(features)) };
 }
 
@@ -152,14 +173,20 @@ function statRow(label: string, value?: number): string {
   return `<div class="hm-stat"><span class="hm-stat-k">${label}</span><span class="hm-stat-v">${Math.round(value)}</span></div>`;
 }
 
-/** Compact hover tooltip: country, its owner (color-chipped), and 1–2 key stats. */
-function hoverHtml(countryName: string, region?: RegionOwner, nation?: Nation): string {
+/**
+ * Compact hover tooltip: the sub-region's name, its parent country (ISO_A3), its
+ * owner (color-chipped), and 1–2 key stats. When the parent country has no
+ * owning nation, a minimal "No owner" card is shown instead.
+ */
+function hoverHtml(subRegionName: string, parentCode: string, region?: RegionOwner, nation?: Nation): string {
   if (!region || !nation) {
-    return `<div class="hm-popup"><div class="hm-popup-title">${esc(countryName || 'Unclaimed')}</div><div class="hm-popup-sub">No owner</div></div>`;
+    return `<div class="hm-popup"><div class="hm-popup-title">${esc(subRegionName || parentCode || 'Unclaimed')}</div><div class="hm-popup-sub">No owner</div></div>`;
   }
   const stats = [statRow('Mil', nation.stats.military), statRow('Eco', nation.stats.economy)].join('');
+  const sub = parentCode ? `<div class="hm-popup-sub">${esc(parentCode)}</div>` : '';
   return `<div class="hm-popup">
-    <div class="hm-popup-title">${esc(countryName || region.owner)}</div>
+    <div class="hm-popup-title">${esc(subRegionName || region.owner)}</div>
+    ${sub}
     <div class="hm-popup-owner"><span class="hm-chip" style="background:${region.color}"></span>${esc(region.owner)}</div>
     <div class="hm-stats">${stats}</div>
   </div>`;
@@ -174,27 +201,38 @@ interface Props {
   presetId: string;
   className?: string;
   /**
-   * Called with a region's owning-nation id when that region is clicked, so the
-   * dossier switches to that nation. Not called for unowned regions (the dossier
-   * keeps its current target). See the component doc for the full behavior.
+   * Called with a region's owning-nation id when a sub-region is clicked, so the
+   * dossier switches to that nation. For a sub-region, the owner is the parent
+   * country's owning nation. The optional `info` carries the clicked sub-region's
+   * own id/name and its parent country's ISO_A3, for a small "which region" label
+   * in the dossier. Not called for unowned regions (the dossier keeps its
+   * current target). See the component doc for the full behavior.
    */
-  onFocusNation?: (id: string) => void;
+  onFocusNation?: (id: string, info?: { parent?: string; name?: string }) => void;
 }
 
 /**
- * World basemap (MapLibre GL) + a country choropleth colored by the owning
- * nation. Rendered as a fixed, full-viewport background layer (z-0) behind the
- * floating HUD windows: a dark-navy basemap with subtle terrain, per-nation
- * stable fills (the choropleth is the star), thin borders, a brighter/thicker
- * border for the player, a hover tooltip (owner + key stats), a **click that
- * switches the dossier to the region's owning nation** (no popup — see #7), a
- * transient flash on territory changes, and a per-scenario initial camera.
+ * World basemap (MapLibre GL) + a **sub-national** choropleth. The map renders
+ * the finer `regions.geo.json` dataset: each country is subdivided into
+ * ~100–200 km sub-regions, drawn as a finer choropleth with thin internal border
+ * lines. Ownership and the LLM stay at **country** granularity (#16, PR 2): a
+ * nation owns whole countries, so all of a country's sub-regions share that
+ * country's owning-nation color. Rendered as a fixed, full-viewport background
+ * layer (z-0) behind the floating HUD windows: a dark-navy basemap with subtle
+ * terrain, per-nation stable fills (uniform per country, the choropleth is the
+ * star), thin sub-region borders, a brighter/thicker amber border for the
+ * player's countries, a hover tooltip (sub-region name + parent country + owner
+ * + key stats), a **click that switches the dossier to the sub-region's parent
+ * country's owning nation** (no popup — see #7), a transient flash when a
+ * country's owner changes (lighting up all its sub-regions), and a per-scenario
+ * initial camera.
  *
- * Ownership for a hovered/clicked region is resolved from the authoritative
- * RegionMap by the feature's stable ISO_A3 code in `properties.regionId`
- * (see `regionOwner` in @shared/protocol) — never from the feature's top-level
- * `id`, which MapLibre repacks into a numeric index at interaction time (#6).
- * Unowned regions (no RegionMap entry) simply do not change the dossier.
+ * Ownership for a hovered/clicked sub-region is resolved from the authoritative
+ * RegionMap by its **parent country's** ISO_A3 code (`properties.parent`, via
+ * `mapFeatureOwner` in @shared/protocol) — never from the feature's top-level
+ * `id` (MapLibre repacks it into a numeric index at interaction time, #6) and
+ * never from the sub-region id (not a RegionMap key). Unowned countries (no
+ * RegionMap entry for the parent) simply do not change the dossier.
  *
  * Zoom and pan are driven directly by the user (MapLibre wheel/trackpad + drag)
  * — no floating control and no external API.
@@ -255,9 +293,9 @@ export default function WorldMap({
     const loadGeo = (): Promise<FeatureCollection> =>
       baseGeoRef.current
         ? Promise.resolve(baseGeoRef.current)
-        : fetch('/countries.geo.json')
+        : fetch('/regions.geo.json')
             .then((r) => {
-              if (!r.ok) throw new Error(`countries.geo.json → HTTP ${r.status}`);
+              if (!r.ok) throw new Error(`regions.geo.json → HTTP ${r.status}`);
               return r.json();
             })
             .then((g: FeatureCollection) => {
@@ -268,12 +306,14 @@ export default function WorldMap({
     const emptyFC = (): FeatureCollection => ({ type: 'FeatureCollection', features: [] });
 
     // Transient flash: pulse a bright outline over the changed regions, then fade
-    // to zero over a few seconds and self-clean. Idempotent per call.
+    // to zero over a few seconds and self-clean. Idempotent per call. `codes` are
+    // parent-country ISO_A3 codes (a turn changes whole countries); each lights
+    // up all of that country's sub-regions.
     function animateFlash(codes: string[]) {
       const geo = baseGeoRef.current;
       const src = map.getSource(FLASH_SOURCE) as GeoSource | undefined;
       if (!geo || !src || cancelled) return;
-      src.setData(featuresByCodes(geo, codes));
+      src.setData(featuresByParents(geo, codes));
       if (!map.getLayer(FLASH_LINE)) {
         // Defensive re-add (normally created by ensureLayers). Keep it beneath the
         // hover highlight when that layer exists; otherwise just append.
@@ -306,33 +346,34 @@ export default function WorldMap({
     }
     flashApiRef.current = animateFlash;
 
-    // The region a hovered/clicked feature belongs to is identified by its stable
-    // ISO_A3 code, read from `properties.regionId` (stamped by `applyRegions`).
-    // We must NOT use the feature's top-level `id`: MapLibre repacks a GeoJSON
-    // source's `id` into a numeric index when it stores the source, so the value
-    // exposed on `e.features[i].id` at interaction time is a number, never the
-    // ISO_A3 — resolving the owner from it is the "no owner" bug (#6).
+    // The sub-region a hovered/clicked feature belongs to is identified by its
+    // stable sub-region id in `properties.regionId` (stamped by `applyRegions`),
+    // and its **owner** is resolved from the authoritative RegionMap via the
+    // feature's `properties.parent` (the parent country's ISO_A3) through
+    // `mapFeatureOwner` — never from the repacked top-level `id` (a numeric
+    // index, #6) and never from the sub-region id (not a RegionMap key).
     const onHover = (e: maplibregl.MapLayerMouseEvent) => {
       const f = e.features?.[0];
       if (!f) return;
-      const p = f.properties as { name?: string; regionId?: string };
-      const code = typeof p?.regionId === 'string' ? p.regionId : '';
-      if (code && code !== lastHoverId) {
-        lastHoverId = code;
+      const p = f.properties as { name?: string; regionId?: string; parent?: string };
+      const subId = typeof p?.regionId === 'string' ? p.regionId : '';
+      const parent = typeof p?.parent === 'string' ? p.parent : '';
+      if (subId && subId !== lastHoverId) {
+        lastHoverId = subId;
         const geo = baseGeoRef.current;
-        // The base GeoJSON feature's top-level `id` IS the ISO_A3, so match on
-        // that to recover the feature for the hover-highlight outline (the
-        // feature MapLibre hands us has a repacked numeric `id` we can't use).
-        const feat = geo?.features.find((x) => x.id != null && String(x.id) === code);
+        // The base GeoJSON feature's top-level `id` IS the sub-region id, so
+        // match on it to recover the exact feature for the hover-highlight
+        // outline (the feature MapLibre hands us has a repacked numeric `id`).
+        const feat = geo?.features.find((x) => x.id != null && String(x.id) === subId);
         (map.getSource(HOVER_SOURCE) as GeoSource | undefined)?.setData(
           feat ? { type: 'FeatureCollection', features: [JSON.parse(JSON.stringify(feat))] } : emptyFC(),
         );
       }
-      const region = regionOwner(regionsRef.current, code);
+      const region = mapFeatureOwner(regionsRef.current, f);
       const nation = region ? nationsRef.current[region.ownerId] : undefined;
       hoverPopup
         .setLngLat(e.lngLat)
-        .setHTML(hoverHtml(p?.name ?? code, region, nation))
+        .setHTML(hoverHtml(p?.name ?? parent ?? subId, parent, region, nation))
         .addTo(map);
       map.getCanvas().style.cursor = 'pointer';
     };
@@ -345,17 +386,24 @@ export default function WorldMap({
     };
 
     // #7: a click does NOT open a popup — it switches the dossier to the region's
-    // owning nation. The owner is resolved from the stable ISO_A3 in
-    // `properties.regionId` via the RegionMap (never the repacked top-level
-    // `f.id`, #6). A region with no owner in the RegionMap (unowned territory)
-    // leaves the current dossier target unchanged — never a broken dossier.
+    // owning nation. For a sub-region, the owner is the **parent country's**
+    // owning nation, resolved from `properties.parent` (the ISO_A3) via the
+    // RegionMap (never the repacked top-level `f.id`, #6, and never the
+    // sub-region id). A sub-region whose parent country has no owner leaves the
+    // current dossier target unchanged — never a broken dossier.
     const onClick = (e: maplibregl.MapLayerMouseEvent) => {
       const f = e.features?.[0];
       if (!f) return;
-      const p = f.properties as { regionId?: string };
-      const code = typeof p?.regionId === 'string' ? p.regionId : '';
-      const region = regionOwner(regionsRef.current, code);
-      if (region?.ownerId) onFocusNationRef.current?.(region.ownerId);
+      const region = mapFeatureOwner(regionsRef.current, f);
+      if (!region?.ownerId) return;
+      // Carry the clicked sub-region's identity (own id/name + parent ISO_A3) so
+      // the dossier can show which region was selected.
+      const p = f.properties as { regionId?: string; parent?: string; name?: string };
+      const info = {
+        parent: typeof p?.parent === 'string' ? p.parent : undefined,
+        name: typeof p?.name === 'string' ? p.name : undefined,
+      };
+      onFocusNationRef.current?.(region.ownerId, info);
     };
 
     // Idempotent: (re)creates the sources + layers after any style (re)load and
@@ -363,16 +411,16 @@ export default function WorldMap({
     // automatically, so no setWorkerUrl is needed.)
     //
     // The three choropleth sources are created up front (empty until the base
-    // geo arrives) so the layer structure always exists; `paintCountries` then
-    // stamps ownership + colors onto the countries source. This makes it immune
+    // geo arrives) so the layer structure always exists; `paintRegions` then
+    // stamps ownership + colors onto the regions source. This makes it immune
     // to load-order races: if `ensureLayers` runs before the geo fetch
     // resolves, the data is applied the moment the fetch lands; if the geo
     // resolves first, `ensureLayers` uses it. No source is ever left stuck on
     // `emptyFC()` — `ensureLayers` is retried on every `styledata`, and the
     // regions effect re-paints whenever ownership changes.
     const ensureSources = () => {
-      if (!map.getSource(COUNTRIES_SOURCE)) {
-        map.addSource(COUNTRIES_SOURCE, { type: 'geojson', data: emptyFC() });
+      if (!map.getSource(REGIONS_SOURCE)) {
+        map.addSource(REGIONS_SOURCE, { type: 'geojson', data: emptyFC() });
       }
       if (!map.getSource(HOVER_SOURCE)) {
         map.addSource(HOVER_SOURCE, { type: 'geojson', data: emptyFC() });
@@ -382,10 +430,10 @@ export default function WorldMap({
       }
     };
 
-    // Stamp ownership + colors onto the countries source (no-op until geo loads).
-    const paintCountries = () => {
+    // Stamp ownership + colors onto the regions source (no-op until geo loads).
+    const paintRegions = () => {
       const geo = baseGeoRef.current;
-      const src = map.getSource(COUNTRIES_SOURCE) as GeoSource | undefined;
+      const src = map.getSource(REGIONS_SOURCE) as GeoSource | undefined;
       if (!geo || !src) return;
       src.setData(applyRegions(geo, regionsRef.current, playerRef.current));
     };
@@ -394,32 +442,39 @@ export default function WorldMap({
       if (cancelled) return;
       ensureSources();
       if (baseGeoRef.current) {
-        paintCountries();
+        paintRegions();
       } else {
         try {
           await loadGeo();
         } catch (err) {
-          console.error('failed to load countries geojson', err);
+          console.error('failed to load regions geojson', err);
         }
         if (cancelled) return;
-        paintCountries();
+        paintRegions();
       }
       if (!map.getLayer(FILL_LAYER)) {
         // The choropleth is the star: a high opacity so the vivid per-nation
         // colors read clearly even on the dark background / over the terrain.
+        // Every sub-region carries its parent country's owner color, so a whole
+        // country reads as one uniform fill — same as the old country map, but
+        // subdivided.
         map.addLayer({
           id: FILL_LAYER,
           type: 'fill',
-          source: COUNTRIES_SOURCE,
-          paint: { 'fill-color': ['get', 'fill'], 'fill-opacity': 0.85 },
+          source: REGIONS_SOURCE,
+          paint: { 'fill-color': ['get', 'fill'], 'fill-opacity': 1.0 },
         });
       }
       if (!map.getLayer(LINE_LAYER)) {
+        // Thin internal borders: every sub-region outline at a light weight so
+        // the subdivision reads within each country's uniform fill. The per-
+        // feature `stroke` alpha keeps owned borders a touch brighter than
+        // unowned ones (the v0.10 treatment, thinned for the finer grid).
         map.addLayer({
           id: LINE_LAYER,
           type: 'line',
-          source: COUNTRIES_SOURCE,
-          paint: { 'line-color': ['get', 'stroke'], 'line-width': 0.7, 'line-opacity': 0.95 },
+          source: REGIONS_SOURCE,
+          paint: { 'line-color': ['get', 'stroke'], 'line-width': 0.75, 'line-opacity': 0.95 },
         });
       }
       // NOTE: layers are added in bottom→top order (each appends on top). The
@@ -430,7 +485,7 @@ export default function WorldMap({
         map.addLayer({
           id: PLAYER_LINE,
           type: 'line',
-          source: COUNTRIES_SOURCE,
+          source: REGIONS_SOURCE,
           filter: ['==', ['get', 'isPlayer'], 1],
           paint: { 'line-color': '#f59e0b', 'line-width': 2.2, 'line-opacity': 0.95 },
         });
@@ -482,8 +537,10 @@ export default function WorldMap({
     };
   }, []);
 
-  // Re-color the choropleth whenever ownership changes, and flash any regions
-  // whose owner changed since the last update (transient, self-cleaning).
+  // Re-color the choropleth whenever ownership changes, and flash any country
+  // (all of its sub-regions) whose owner changed since the last update (a
+  // transient, self-cleaning pulse). The diff is over the ISO_A3-keyed RegionMap;
+  // `animateFlash` expands each changed country to every one of its sub-regions.
   useEffect(() => {
     const map = mapRef.current;
     const geo = baseGeoRef.current;
@@ -494,7 +551,7 @@ export default function WorldMap({
     if (Object.keys(cur).length > 0) primedRef.current = true;
 
     if (map && geo) {
-      const src = map.getSource(COUNTRIES_SOURCE) as GeoSource | undefined;
+      const src = map.getSource(REGIONS_SOURCE) as GeoSource | undefined;
       if (src) void src.setData(applyRegions(geo, cur, playerNationId));
     }
 

tsconfig.json

@@ -20,5 +20,5 @@
       "@/*": ["./src/*"]
     }
   },
-  "include": ["src", "server", "shared", "e2e", "vite.config.ts"]
+  "include": ["src", "server", "shared", "e2e", "scripts", "vite.config.ts"]
 }

vitest.config.ts

@@ -13,7 +13,7 @@ export default defineConfig({
   },
   test: {
     environment: 'node',
-    include: ['server/**/*.test.ts'],
+    include: ['server/**/*.test.ts', 'scripts/**/*.test.ts'],
     testTimeout: 20000,
     hookTimeout: 20000,
   },