diff --git a/.gitignore b/.gitignore
index f309198e..6fad3718 100644
--- a/.gitignore
+++ b/.gitignore
@@ -47,3 +47,6 @@ firestore-tests/node_modules/
 firebase-debug.log
 firestore-debug.log
 UI-PLAN.md
+
+# Build plans (agent-only, never commit)
+*_build_plan.md