diff --git a/tools-sync/scripts/sync_repos.ps1 b/tools-sync/scripts/sync_repos.ps1
index 19968cc..16f7542 100644
--- a/tools-sync/scripts/sync_repos.ps1
+++ b/tools-sync/scripts/sync_repos.ps1
@@ -376,8 +376,17 @@ if ($MirrorRegistry) {
 
     # A primary entry that is itself a link belongs to whichever host installed it (its real home
     # is a registry the host already exposes to Codex). Mirroring it would register it twice.
-    $primarySkills = Get-ChildItem $ClaudeSkills -Directory -Force |
+    $primaryDirs = Get-ChildItem $ClaudeSkills -Directory -Force |
         Where-Object { $_.Name -notlike ".*" -and -not (Test-IsLink $_) }
+    # A directory without SKILL.md at its top level is not a skill -- e.g. 'synced/', the
+    # runtime cache of account-side skills Claude Code downloads. Mirroring it is worse than
+    # useless: its NESTED directories do carry SKILL.md, so Codex would register that whole
+    # set a second time alongside the ones it already gets from the account.
+    $primarySkills = $primaryDirs | Where-Object { Test-Path (Join-Path $_.FullName "SKILL.md") }
+    $notSkills     = $primaryDirs | Where-Object { -not (Test-Path (Join-Path $_.FullName "SKILL.md")) }
+    if ($notSkills) {
+        Write-Host "  not skills (no SKILL.md), not mirrored: $(($notSkills | ForEach-Object Name) -join ', ')"
+    }
     foreach ($d in $primarySkills) {
         $link = Join-Path $MirrorRegistry $d.Name
         if (Test-Path $link) { continue }