diff --git a/src/expand.ts b/src/expand.ts
index c620a3d..61e48b9 100644
--- a/src/expand.ts
+++ b/src/expand.ts
@@ -18,3 +18,12 @@ export function readSkillBody(filePath: string): string {
 export function formatBlock(meta: SkillBlockMeta, body: string): string {
 	return `<skill name="${meta.name}" location="${meta.filePath}">\nReferences are relative to ${meta.baseDir}.\n\n${body}\n</skill>`;
 }
+
+/** Append optional reinject suffix after skill block (SPEC §5.3). */
+export function appendSuffix(block: string, suffix: string | undefined): string {
+	const trimmed = suffix?.trim();
+	if (!trimmed) {
+		return block;
+	}
+	return `${block}\n\n${trimmed}`;
+}