diff --git a/library/composables/useMapProvider.js b/library/composables/useMapProvider.js
index 26790a2df..c499e1cfe 100644
--- a/library/composables/useMapProvider.js
+++ b/library/composables/useMapProvider.js
@@ -106,6 +106,36 @@ export function isMapboxMap(map) {
  * @param {object} map  the live map instance
  * @returns {object|undefined}  the engine namespace, or undefined when neither is loaded
  */
+/**
+ * The provider NAME that built THIS map: 'mapbox', 'maplibre', or undefined when neither global is
+ * loaded or `map` is not a map at all.
+ *
+ * ★ WHY THIS EXISTS, given engineFor() is right above it. engineFor returns the engine NAMESPACE,
+ * which is what you want for constructing things (Marker, Popup, a second Map). Two call sites want
+ * the opposite: a NAME, to put in a diagnostic field and to choose an attribution string. They were
+ * each doing their own `map instanceof window.maplibregl.Map` sniff, which is the raw-global coupling
+ * C3 exists to remove — and `resolveMapProvider()` cannot serve them because it reads a CONFIG, not a
+ * live map, so on a dual-engine page it answers about the wrong thing.
+ *
+ * ★ THE AMBIGUOUS CASE IS THE WHOLE REASON THIS RETURNS undefined RATHER THAN A DEFAULT. Both call
+ * sites tested for MAPLIBRE and fell through to 'mapbox', so a stub, a destroyed map or a page where
+ * neither global loaded read as 'mapbox'. A rewrite in terms of the existing isMapboxMap() would have
+ * inverted that — falling through to 'maplibre' — and silently changed what a diagnostic reports and
+ * which attribution a poster prints. Returning undefined forces each caller to keep its OWN default
+ * visible at the call site, so the migration cannot quietly move a default. Changing a default is not
+ * a curation migration.
+ *
+ * @param {object} map  the live map instance
+ * @returns {'mapbox'|'maplibre'|undefined}
+ */
+export function providerFor(map) {
+  if (typeof window === 'undefined') return undefined
+  const ml = window.maplibregl, mb = window.mapboxgl
+  if (ml && ml.Map && map instanceof ml.Map) return 'maplibre'
+  if (mb && mb.Map && map instanceof mb.Map) return 'mapbox'
+  return undefined
+}
+
 export function engineFor(map) {
   if (typeof window === 'undefined') return undefined
   const ml = window.maplibregl, mb = window.mapboxgl
diff --git a/plugin-designs/all-people-groups/all-people-groups.vue b/plugin-designs/all-people-groups/all-people-groups.vue
index 805464fd5..42b9c9ca8 100644
--- a/plugin-designs/all-people-groups/all-people-groups.vue
+++ b/plugin-designs/all-people-groups/all-people-groups.vue
@@ -31,7 +31,7 @@
  */
 import { inject, ref, computed, onMounted, onBeforeUnmount } from 'vue'
 import { useI18n } from 'vue-i18n'
-import { useMapInstance }     from '@map/composables/useMapInstance.js'
+import { useMapInstance, engineGlobal } from '@map/composables/useMapInstance.js'
 import { resolveMapProvider, setProjectionOn } from '@map/composables/useMapProvider.js'
 import { useMapData }         from '@map/composables/useMapData.js'
 import { useShadowStyles }    from '@map/composables/useShadowStyles.js'
@@ -295,7 +295,9 @@ function addLayer(fc) {
     const pray = doxaRec && doxaRec.slug
       ? `<a href="https://pray.doxa.life/${encodeURIComponent(doxaRec.slug)}?source=doxalife&utm_source=${utmSource()}" target="_blank" rel="noopener">${esc(tr('pray'))}</a>`
       : ''
-    const NS = mapProvider === 'maplibre' ? window.maplibregl : window.mapboxgl
+    // C3: engineGlobal() resolves a provider NAME to its namespace and already defaults to Mapbox
+    // for anything unrecognised, which is exactly what this ternary's else branch did.
+    const NS = engineGlobal(mapProvider)
     new NS.Popup({ closeButton: true, maxWidth: '290px' })
       .setLngLat(e.lngLat)
       .setHTML(`<div class="apg-pop">
diff --git a/plugin-designs/doxa-research-map/research-map.vue b/plugin-designs/doxa-research-map/research-map.vue
index 330dc6c89..cbcf3a13d 100644
--- a/plugin-designs/doxa-research-map/research-map.vue
+++ b/plugin-designs/doxa-research-map/research-map.vue
@@ -41,7 +41,7 @@ import { retryableAsyncComponent } from '@map/composables/retryableAsyncComponen
 
 // ─── Composables (framework) ─────────────────────────────────────────────────
 import { useMapInstance }  from '@map/composables/useMapInstance.js'
-import { resolveMapProvider, providerLabel, setProjectionOn } from '@map/composables/useMapProvider.js'
+import { resolveMapProvider, providerLabel, providerFor, setProjectionOn } from '@map/composables/useMapProvider.js'
 import { useMapLayers, PIN_STROKE_WIDTH_LIGHT, buildDarkRingWidth } from '@map/composables/useMapLayers.js'
 import { useMapTheme, THEME_TOGGLE, FIXED_BASEMAP } from '@map/composables/useMapTheme.js'
 import { useMapEvents }    from '@map/composables/useMapEvents.js'
@@ -1319,7 +1319,9 @@ async function openPoster() {
     spec.slots.scaleBar = false
     spec.slots.north = false
     // Credit the tiles actually drawn: OpenFreeMap on MapLibre, Mapbox otherwise.
-    const onMaplibre = !!(window.maplibregl && map.value instanceof window.maplibregl.Map)
+    // C3: ask the library, not the globals. The explicit === 'maplibre' keeps the original FALSE for
+    // a map that is neither, so the Mapbox attribution stays the fall-through it always was.
+    const onMaplibre = providerFor(map.value) === 'maplibre'
     spec.slots.footer = { ...spec.slots.footer, left: 'pray.doxa.life', right: new Date().toISOString().slice(0, 10),
       attribution: onMaplibre ? '© OpenFreeMap © OpenMapTiles © OpenStreetMap' : '© Mapbox © OpenStreetMap' }
     const blob = await exporter.render(spec, 'png')
diff --git a/plugin-designs/pplr-data-maps/src/utils/pplrData.js b/plugin-designs/pplr-data-maps/src/utils/pplrData.js
index f19741be7..c65c9a130 100644
--- a/plugin-designs/pplr-data-maps/src/utils/pplrData.js
+++ b/plugin-designs/pplr-data-maps/src/utils/pplrData.js
@@ -8,7 +8,7 @@
  */
 import { CDN, pinElement } from '@map/constants/cdn.js'
 import { loadPinnedUmd } from '@map/utils/loadPinnedUmd.js'
-import { setProjectionOn } from '@map/composables/useMapProvider.js'
+import { providerFor, setProjectionOn } from '@map/composables/useMapProvider.js'
 let base = './assets'
 export function setDataBase(b) { if (b) base = String(b).replace(/\/+$/, '') }
 export function dataUrl(file) { return base + '/pplr/' + file }
@@ -112,7 +112,9 @@ export function exposeMap(map) {
     let layers = []
     try { layers = map.getStyle()?.layers || [] } catch (_) {}
     return {
-      engine: window.maplibregl && window.maplibregl.Map && map instanceof window.maplibregl.Map ? 'maplibre' : 'mapbox',
+      // C3: ask the library, not the globals. `|| 'mapbox'` keeps the ORIGINAL fall-through for a map
+      // that is neither (stub, destroyed, neither global loaded) -- see providerFor's own note.
+      engine: providerFor(map) || 'mapbox',
       // 'load' may already have fired before this listener was attached; a loaded style says so too
       loaded: loaded || !!(map.isStyleLoaded && map.isStyleLoaded()),
       styleLayers: layers.length,