diff --git a/src/utils/route-encoding.ts b/src/utils/route-encoding.ts
index 49365b8c1..2f23f64ff 100644
--- a/src/utils/route-encoding.ts
+++ b/src/utils/route-encoding.ts
@@ -11,7 +11,7 @@ export function decodePackageNameSlug(slug: string) {
     try {
       const decoded = decodeURIComponent(next)
       if (decoded === next) {
-        return decoded
+        break
       }
       next = decoded
     } catch {
@@ -19,6 +19,14 @@ export function decodePackageNameSlug(slug: string) {
     }
   }
 
+  // Back-compat: legacy links encoded the scope separator as `__`
+  // (`@scope/name` -> `@scope__name`). Those URLs are still indexed, so
+  // restore the separator instead of failing package-name validation.
+  // Matches the stats route (`src/routes/stats/npm/-utils.ts`).
+  if (next.startsWith('@') && next.includes('__') && !next.includes('/')) {
+    return next.replace('__', '/')
+  }
+
   return next
 }
 
diff --git a/tests/route-encoding.test.ts b/tests/route-encoding.test.ts
index 4ef53eea3..ac42d0f15 100644
--- a/tests/route-encoding.test.ts
+++ b/tests/route-encoding.test.ts
@@ -28,6 +28,34 @@ assert.equal(
   'double-encoded package route slugs decode for router/browser compatibility',
 )
 
+// Legacy `__` scope-separator slugs (still indexed by search engines) must
+// resolve to the real scoped name instead of failing package-name validation.
+assert.equal(
+  decodePackageNameSlug('@firfi__quint-connect'),
+  '@firfi/quint-connect',
+  'legacy __ scoped slug decodes to the scoped package name',
+)
+
+assert.equal(
+  decodePackageNameSlug('%40apollo__client'),
+  '@apollo/client',
+  'legacy __ scoped slug decodes from the percent-encoded form',
+)
+
+// Only the scope separator is restored; a `__` inside the package name stays.
+assert.equal(
+  decodePackageNameSlug('@depup__trpc__server'),
+  '@depup/trpc__server',
+  'only the leading scope-separator __ is restored',
+)
+
+// Unscoped names that contain `__` are not legacy scoped slugs.
+assert.equal(
+  decodePackageNameSlug('tanstack__intent'),
+  'tanstack__intent',
+  'unscoped __ names are left intact',
+)
+
 assert.equal(
   getRowFieldId('moderation-note', '@scope/pkg', 'note'),
   'moderation-note-scope-pkg-note',