diff --git a/content-guards/scripts/validate-markdown.sh b/content-guards/scripts/validate-markdown.sh
index f260bcf..f4f2faf 100755
--- a/content-guards/scripts/validate-markdown.sh
+++ b/content-guards/scripts/validate-markdown.sh
@@ -153,7 +153,20 @@ EOF
     fi
   } 2>&1 ); then
     errors+=("markdownlint-cli2 failed:")
-    errors+=("$markdownlint_output")
+    # Cap validator output so a noisy run can't flood Claude's context window.
+    # Single awk pass counts, caps, and formats the overflow footer.
+    max_lines=20
+    if [[ -n "$markdownlint_output" ]]; then
+      capped=$(awk -v max="$max_lines" '
+        NR <= max { print }
+        END {
+          if (NR > max) {
+            print "…and " (NR - max) " more line(s) (capped at " max "; rerun markdownlint-cli2 manually for the full report)"
+          }
+        }
+      ' <<<"$markdownlint_output")
+      errors+=("$capped")
+    fi
   fi
 fi