diff --git a/src/kept.ts b/src/kept.ts
index be72a9f..4fc50b5 100644
--- a/src/kept.ts
+++ b/src/kept.ts
@@ -2,6 +2,9 @@ import type { SessionEntry } from "@earendil-works/pi-coding-agent";
 import { parseSkillBlocksFromText } from "./detect.js";
 import type { TrackedSkill } from "./state.js";
 
+/** custom_message type for deferred re-inject delivery (SPEC §6.5.1). */
+const SKILL_REINJECT_INJECT_CUSTOM_TYPE = "skill-reinject:inject";
+
 /** Branch slice from firstKeptEntryId through tail (SPEC §6.4). */
 export function getKeptEntries(branch: SessionEntry[], firstKeptEntryId: string): SessionEntry[] {
 	const startIndex = branch.findIndex((entry) => entry.id === firstKeptEntryId);
@@ -31,7 +34,7 @@ function extractUserMessageText(content: unknown): string {
 	return parts.join("\n");
 }
 
-/** Skill names already present as blocks in kept user messages (SPEC §6.4). */
+/** Skill names already present as blocks in kept user messages and reinject custom messages (SPEC §6.4). */
 export function skillsPresentInKeptWindow(
 	keptEntries: SessionEntry[],
 	skillNames: readonly string[],
@@ -43,10 +46,18 @@ export function skillsPresentInKeptWindow(
 	}
 
 	for (const entry of keptEntries) {
-		if (entry.type !== "message" || entry.message.role !== "user") {
+		let text = "";
+		if (entry.type === "message" && entry.message.role === "user") {
+			text = extractUserMessageText(entry.message.content);
+		} else if (
+			entry.type === "custom_message" &&
+			entry.customType === SKILL_REINJECT_INJECT_CUSTOM_TYPE &&
+			typeof entry.content === "string"
+		) {
+			text = entry.content;
+		} else {
 			continue;
 		}
-		const text = extractUserMessageText(entry.message.content);
 		for (const block of parseSkillBlocksFromText(text)) {
 			if (namesToCheck.has(block.name)) {
 				present.add(block.name);