diff --git a/library/composables/useCountryOutline.js b/library/composables/useCountryOutline.js
index 129e9731e..6f514ebad 100644
--- a/library/composables/useCountryOutline.js
+++ b/library/composables/useCountryOutline.js
@@ -73,10 +73,28 @@ export function resolveCountryIso(evt, pgs) {
 // 'all', 'US', 'CN', 'IN'); without a worldview filter an outline would be
 // drawn 2-3× over itself. Mirror the homepage CountryMap.vue filter: keep the
 // 'all' worldview plus the US-recognized worldview.
-function countryFilter(code) {
+// The ENGINE is read off the live map rather than guessed from config: the container carries
+// maplibregl-map or mapboxgl-map, which is a fact about the instance in hand. Consumers call
+// useCountryOutline(() => map.value) with no options, so there is no provider to pass in.
+function isMaplibreMap(m) {
+  try { return !!m?.getContainer?.()?.classList?.contains('maplibregl-map') } catch (_) { return false }
+}
+
+function countryFilter(code, isMaplibre) {
+  const byCode = ['==', ['get', 'iso_3166_1_alpha_3'], code]
+  // ★ THE WORLDVIEW CLAUSE IS MAPBOX-ONLY, AND ANDING IT ON MAPLIBRE EMPTIES THE LAYER.
+  // The clause exists for the tileset above; world-adm0.geojson, the MapLibre source added below,
+  // has no worldview property and no per-worldview duplicates. So ['get','worldview'] is null,
+  // both sides of the `any` are false on every feature, and the `all` admits NOTHING — the outline
+  // is absent with no error, exactly as if the boundary data had failed to load. Unlike the ISO
+  // field, this cannot be bridged in the loader: there is no worldview to invent. It is a fact
+  // about the Mapbox tileset's shape, so only the Mapbox path asks for it.
+  // MEASURED: against the real 162 features, the clause admits 0 and the branch below admits its
+  // country — _qa-cycle/02-builder-cycle/_chk-worldview-clause-guarded-per-engine.mjs.
+  if (isMaplibre) return byCode
   return [
     'all',
-    ['==', ['get', 'iso_3166_1_alpha_3'], code],
+    byCode,
     ['any', ['==', ['get', 'worldview'], 'all'], ['in', 'US', ['get', 'worldview']]]
   ]
 }
@@ -116,7 +134,9 @@ export function useCountryOutline(getMap, opts = {}) {
     const m = typeof getMap === 'function' ? getMap() : null
     if (!m) return
 
-    const filter = countryFilter(code)
+    // Engine FIRST: the filter's shape depends on it, and the fast path below reuses this filter.
+    const isMaplibre = isMaplibreMap(m)
+    const filter = countryFilter(code, isMaplibre)
 
     // Fast path: source/layer already present from a prior pick — just swap the
     // filter so the highlight moves to the new country with zero teardown.
@@ -136,14 +156,7 @@ export function useCountryOutline(getMap, opts = {}) {
       // the console. THREE consumers share this composable — doxa-simple-map, countries-map and
       // research-map — so the fix belongs here, once, not three times.
       // Same shape already proven in DashboardMapPanel and RegionCountryMap.
-      //
-      // The ENGINE is read off the live map rather than guessed from config: the container carries
-      // maplibregl-map or mapboxgl-map, which is a fact about the instance in hand. Consumers call
-      // useCountryOutline(() => map.value) with no options, so there is no provider to pass in.
-      const isMaplibre = (() => {
-        try { return !!m.getContainer?.()?.classList?.contains('maplibregl-map') } catch (_) { return false }
-      })()
-
+      // isMaplibre is resolved above, before the filter is built — see countryFilter().
       if (isMaplibre) {
         // Add EMPTY first, then setData after the fetch, so addLayer below stays SYNCHRONOUS and
         // the outline keeps its place in the layer order.