diff --git a/internal/check-shared-component-reached-bundles.mjs b/internal/check-shared-component-reached-bundles.mjs
index afa5c211b..a81bce70c 100644
--- a/internal/check-shared-component-reached-bundles.mjs
+++ b/internal/check-shared-component-reached-bundles.mjs
@@ -72,6 +72,13 @@ const MARKERS = [
     component: 'library/composables/useMapInstance.js',
     sourceRe: /if \(!element\) return\n\s*const root = element\.getRootNode\(\)/,
     builtRe: /if\(!([\w$]+)\)return;const ([\w$]+)=\1\.getRootNode\(\);if\(!\(\2 instanceof ShadowRoot\)\)return/,
+    // ★ NOT EVERY CONSUMER COMPILES THE GUARDED FUNCTION. ensureEngineCSS is only called by
+    // initializeMap; a bundle that imports pieces of useMapInstance (ensureEngineScript, engineGlobal…)
+    // but never initializeMap gets it TREE-SHAKEN AWAY, so the guard can never appear there — and the
+    // race cannot happen there either. Reported by upg100 (my-upg-100-list) 2026-09-25: 3 of 12
+    // bundles were false negatives. `staleRe` is the UNGUARDED shape: a bundle is MISSING the fix only
+    // if it still compiles ensureEngineCSS without the guard; with neither shape it is NOT AFFECTED.
+    staleRe: /const ([\w$]+)=([\w$]+)\.getRootNode\(\);if\(!\(\1 instanceof ShadowRoot\)\)return/g,
     marker: 'if (!element) return (ensureEngineCSS)',
     landed: 'studio, 2026-09-25',
     why: 'a map whose pane unmounts mid-initialise no longer throws "reading getRootNode" (check-map-unmount-mid-init)',
@@ -80,6 +87,13 @@ const MARKERS = [
 // A marker is a literal (`marker`, matched with includes) unless the entry supplies regexes.
 const inSource = (m, src) => (m.sourceRe ? m.sourceRe.test(src) : src.includes(m.marker))
 const inBuilt = (m, js) => (m.builtRe ? m.builtRe.test(js) : js.includes(m.marker))
+// With a staleRe: does the bundle compile the OLD shape — an occurrence NOT immediately preceded by
+// the guard? (The guarded form contains the old shape as a substring, hence the look-behind.)
+const hasStale = (m, js) => {
+  if (!m.staleRe) return true
+  for (const x of js.matchAll(new RegExp(m.staleRe.source, 'g'))) if (!/return;$/.test(js.slice(Math.max(0, x.index - 24), x.index))) return true
+  return false
+}
 
 if (!existsSync(TREE)) {
   console.log(`SHARED-REACHED-BUNDLES: SKIP — no built tree at ${TREE}.`)
@@ -158,19 +172,23 @@ for (const m of MARKERS) {
   const have = []
   const missing = []
   const unbuilt = []
+  const unaffected = []
   for (const bundle of consumers) {
     const built = join(TREE, bundle, `${bundle}.js`)
     if (!existsSync(built)) { unbuilt.push(bundle); continue }
     const js = readFileSync(built, 'utf8')
-    ;(inBuilt(m, js) ? have : missing).push(bundle)
+    if (inBuilt(m, js)) have.push(bundle)
+    else if (hasStale(m, js)) missing.push(bundle)
+    else unaffected.push(bundle)
   }
 
   console.log(`  ${m.id} — ${m.why}`)
   console.log(`    landed ${m.landed}; ${have.length} of ${have.length + missing.length} built `
-    + `consumer(s) carry it${unbuilt.length ? `, ${unbuilt.length} not built` : ''}`)
+    + `consumer(s) carry it${unaffected.length ? ` (${unaffected.length} not affected)` : ''}${unbuilt.length ? `, ${unbuilt.length} not built` : ''}`)
   if (have.length) console.log(`    ✓ ${have.join(', ')}`)
   if (missing.length) console.log(`    ✗ ${missing.join(', ')}`)
   if (unbuilt.length) console.log(`    · not built: ${unbuilt.join(', ')}`)
+  if (unaffected.length) console.log(`    – not affected (the changed code is not compiled in): ${unaffected.join(', ')}`)
 
   if (missing.length) {
     fails.push(`${m.id}: ${missing.length} bundle(s) do NOT carry "${m.why}" — ${missing.join(', ')}`)