diff --git a/internal/sync-dropin.mjs b/internal/sync-dropin.mjs
index fb3e384fa..853ef3186 100644
--- a/internal/sync-dropin.mjs
+++ b/internal/sync-dropin.mjs
@@ -62,7 +62,10 @@ const VALUE_FLAGS = new Set(['--from', '--tree', '--protect', '--only'])
 const argOf = (k, d) => { const i = args.indexOf(k); const v = args[i + 1]; return i >= 0 && v !== undefined && !v.startsWith('--') ? v : d }
 // Destination: positional <dest> · else DOXA_DROPIN_DEST · else "dropin.dest" in the build-config
 // (the ONE place the host folder is declared; moving the drop-in = changing that line).
-const configDest = (() => { try { const d = JSON.parse(readFileSync(CONFIG, 'utf8')).dropin?.dest; return typeof d === 'string' && d.trim() ? resolve(ROOT, d.trim()) : null } catch { return null } })()
+// A config that EXISTS but does not parse is recorded, never swallowed: with --if-present a silent null would read
+// as "no destination configured" and a green build would never refresh the site.
+let configBroken = ''
+const configDest = (() => { try { const d = JSON.parse(readFileSync(CONFIG, 'utf8')).dropin?.dest; return typeof d === 'string' && d.trim() ? resolve(ROOT, d.trim()) : null } catch (e) { if (existsSync(CONFIG)) configBroken = e.message; return null } })()
 const DEST = args.find((a, i) => !a.startsWith('--') && !VALUE_FLAGS.has(args[i - 1])) || process.env.DOXA_DROPIN_DEST || configDest
 const FROM = resolve(ROOT, argOf('--from', 'public'))
 const DRY = args.includes('--dry-run')
@@ -86,6 +89,10 @@ const excludedInternal = (f) => EXCLUDE.has(f) || isDoc(f) || isStaging(f)
 const excluded = (f) => excludedInternal(f) || isNotShipped(f)
 
 const usage = 'usage: node internal/sync-dropin.mjs [<dest>] [--from public] [--only a,b | --from-config] [--prune] [--protect a,b] [--dry-run]   (<dest> defaults to $DOXA_DROPIN_DEST, then dropin.dest in vite.doxa-maps-build-config.json)'
+if (configBroken && (args.includes('--if-present') || args.includes('--from-config'))) {
+  console.error(`[sync-dropin] build config unreadable: ${norm(relative(ROOT, CONFIG))}: ${configBroken}`)
+  process.exit(1)
+}
 if (!DEST && args.includes('--if-present')) { console.log('[sync-dropin] skipped: no drop-in destination configured (dropin.dest)'); process.exit(0) }
 if (!DEST) { console.error(`[sync-dropin] ${usage}`); process.exit(1) }
 const dest = resolve(DEST)