diff --git a/tools/design_amendment_gate.sh b/tools/design_amendment_gate.sh
index 82d844ca..de1cfd20 100755
--- a/tools/design_amendment_gate.sh
+++ b/tools/design_amendment_gate.sh
@@ -33,7 +33,7 @@ is_binding_page() {
 
   if [ "$mode" = index ]; then
     git cat-file -e ":$path" 2>/dev/null || return 1
-    git show ":$path" | grep -qE '^Type: (law|spec)$'
+    git grep --cached -qE '^Type: (law|spec)$' -- "$path"
   else
     [ -f "$path" ] && grep -qE '^Type: (law|spec)$' "$path"
   fi
diff --git a/tools/test_design_amendment_gate.sh b/tools/test_design_amendment_gate.sh
index 1161bc8b..b5cf2707 100755
--- a/tools/test_design_amendment_gate.sh
+++ b/tools/test_design_amendment_gate.sh
@@ -57,6 +57,18 @@ Type: knowledge
 EOF
 expect_pass "index reads staged binding type" $'crates/game/lib.rs\nwiki/process/law.md' --index
 
+# A large binding page with its Type header near the top must not fail under
+# `set -o pipefail` when the matcher exits before a staged blob finishes
+# streaming. This reproduces the old `git show | grep -q` SIGPIPE boundary.
+{
+  printf '# Large spec\nType: spec\n'
+  for ((i = 0; i < 20000; i++)); do
+    printf 'binding detail %05d\n' "$i"
+  done
+} > "$tmp/wiki/process/large.md"
+git -C "$tmp" add wiki/process/large.md
+expect_pass "large staged binding page" $'crates/game/lib.rs\nwiki/process/large.md' --index
+
 # Conversely, a staged deletion is not an amendment merely because an
 # unstaged file with the same path exists in the worktree.
 git -C "$tmp" rm --cached -fq wiki/process/law.md