diff --git a/.gitattributes b/.gitattributes
index 7b5c50b08..218fe3730 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -63,3 +63,14 @@
 # conclusions and should remain reviewable in PRs.
 docs/lost-substrate/artifacts/**/*.txt linguist-generated=true -diff
 docs/lost-substrate/artifacts/**/*.log linguist-generated=true -diff
+
+# memory/MEMORY.md is an unordered append-only index. Multiple
+# in-flight PRs each adding a row produced recurring rebase conflicts
+# (always trivial — keep both entries — but a token-tax recurring
+# friction). The `union` merge driver auto-appends both sides on
+# conflict, eliminating manual resolution. Multi-AI flagged: Claude.ai,
+# Gemini, Ani, Deepseek (4 reviewers in the 2026-04-30 session), Gemini
+# named the mechanism. Composes with Otto-363 substrate-or-it-didn't-
+# happen — index-row landings are substrate; the merge driver makes
+# their landing structurally robust.
+memory/MEMORY.md merge=union