diff --git a/backlog.tasks b/backlog.tasks
index 0d80323..f53bfad 100644
--- a/backlog.tasks
+++ b/backlog.tasks
@@ -72,8 +72,8 @@ Enhancements:
 ✔ Allow boolean literals in primitive union patterns (e.g. `true: () => "yes"`) @medium @done
     ✔ Are there other primitive types that should be supported in union patterns? (e.g. `bigint`, `symbol`) @medium @done
         → added boolean, null and undefined; rejected `symbol` (compile-time brand, nothing at runtime) and `bigint` (not a property key)
-☐ Allow boolean, null and undefined discriminant values in tagged-union patterns @medium
-    → needs the primitive-union matcher's `PatternKey` / `PatternParam` projection; see development/library.md § Tagged-union matcher
+✔ Allow boolean, null and undefined discriminant values in tagged-union patterns @medium @done
+    → moved the `PatternKey` / `PatternParam` projection to `matcher-shared.ts` and keyed the tagged-union handler map through it; see development/library.md § Tagged-union matcher
 
 Documentation:
 ☐ Bring README.md back to its previous form — synopsis and examples restored, in the correct place