diff --git a/src/compaction.ts b/src/compaction.ts
index 6bf2ff4..a49cf72 100644
--- a/src/compaction.ts
+++ b/src/compaction.ts
@@ -10,3 +10,10 @@ export function createCompactionRuntime(): CompactionRuntime {
 		pendingCompactionSource: null,
 	};
 }
+
+/** Input hook before expansion: user `/compact` marks manual source (SPEC §8). */
+export function markManualCompactionFromInput(text: string, runtime: CompactionRuntime): void {
+	if (text.startsWith("/compact")) {
+		runtime.pendingCompactionSource = "manual";
+	}
+}