Phase 14: defer reinject plan without registry at compaction — B-002 stage 1

planDeferredReinject locks pending by kept-window only; defer path in index uses it while immediate keeps registered filter at compact time.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/index.ts

@@ -23,6 +23,7 @@ import {
 import {
 	applyPendingReinjectAfterCompact,
 	clearPendingReinjectOnUserPrompt,
+	planDeferredReinject,
 	planReinject,
 	sendImmediateReinjectAllFollowUp,
 	sendImmediateReinjectIdle,
@@ -102,7 +103,6 @@ export default function skillReinject(pi: ExtensionAPI): void {
 		const trackedNames = state.skills.map((skill) => skill.name);
 		const keptEntries = getKeptEntries(branch, event.compactionEntry.firstKeptEntryId);
 		const keptPresent = skillsPresentInKeptWindow(keptEntries, trackedNames);
-		const planned = planReinject(state, settings, ctx, event, skills);
 		const shouldReinject = consumeCompactionOnSessionCompact(
 			compactionRuntime,
 			state,
@@ -110,6 +110,10 @@ export default function skillReinject(pi: ExtensionAPI): void {
 			settings,
 		);
 		const deliveryMode = resolveDeliveryMode(settings, runtime, state.sessionIntegrationOverride);
+		const planned =
+			deliveryMode === "defer"
+				? planDeferredReinject(state, ctx, event)
+				: planReinject(state, settings, ctx, event, skills);
 
 		applyPendingReinjectAfterCompact(state, compactionRuntime, shouldReinject, planned);
 		notifyReinjectDiag(

src/reinject.ts

@@ -9,6 +9,7 @@ import { existsSync } from "node:fs";
 import { expandSkill } from "./expand.js";
 import {
 	filterSkillsNeedingReinject,
+	filterSkillsNeedingReinjectByKept,
 	getKeptEntries,
 	skillsPresentInKeptWindow,
 } from "./kept.js";
@@ -57,6 +58,31 @@ export function registeredSkillNames(skills: readonly Pick<Skill, "name">[]): Re
 	return new Set(skills.map((skill) => skill.name));
 }
 
+/** Kept-window skill names present after compaction (shared by plan helpers). */
+function keptPresentAfterCompaction(
+	state: ExtensionState,
+	ctx: ExtensionContext,
+	compactionEvent: SessionCompactEvent,
+): Set<string> {
+	const branch = ctx.sessionManager.getBranch();
+	const keptEntries = getKeptEntries(branch, compactionEvent.compactionEntry.firstKeptEntryId);
+	const trackedNames = state.skills.map((skill) => skill.name);
+	return skillsPresentInKeptWindow(keptEntries, trackedNames);
+}
+
+/**
+ * Defer planning at compaction: tracked skills absent from kept window only (SPEC §6.5.1).
+ * Registry filter runs later on before_agent_start (Phase 14 / B-002).
+ */
+export function planDeferredReinject(
+	state: ExtensionState,
+	ctx: ExtensionContext,
+	compactionEvent: SessionCompactEvent,
+): string[] {
+	const keptPresent = keptPresentAfterCompaction(state, ctx, compactionEvent);
+	return filterSkillsNeedingReinjectByKept(state.skills, keptPresent);
+}
+
 /**
  * Skill names to re-inject after compaction: tracked, absent from kept window, still registered (SPEC §5.2).
  * `registeredSkills` comes from resourceLoader — ExtensionContext has no getSkills(); wired in index.ts.
@@ -68,10 +94,7 @@ export function planReinject(
 	compactionEvent: SessionCompactEvent,
 	registeredSkills: readonly Pick<Skill, "name">[],
 ): string[] {
-	const branch = ctx.sessionManager.getBranch();
-	const keptEntries = getKeptEntries(branch, compactionEvent.compactionEntry.firstKeptEntryId);
-	const trackedNames = state.skills.map((skill) => skill.name);
-	const keptPresent = skillsPresentInKeptWindow(keptEntries, trackedNames);
+	const keptPresent = keptPresentAfterCompaction(state, ctx, compactionEvent);
 	return filterSkillsNeedingReinject(
 		state.skills,
 		keptPresent,
@@ -82,18 +105,12 @@ export function planReinject(
 /** Defer path on session_compact: queue planned skills without sendUserMessage (SPEC §6.5.1, §16.2). */
 export function enqueueDeferredReinjectFromCompact(
 	state: ExtensionState,
-	settings: SkillReinjectSettings,
+	_settings: SkillReinjectSettings,
 	ctx: ExtensionContext,
 	compactionEvent: SessionCompactEvent,
-	registeredSkills: readonly Pick<Skill, "name">[],
+	_registeredSkills: readonly Pick<Skill, "name">[],
 ): void {
-	state.pendingReinject = planReinject(
-		state,
-		settings,
-		ctx,
-		compactionEvent,
-		registeredSkills,
-	);
+	state.pendingReinject = planDeferredReinject(state, ctx, compactionEvent);
 }
 
 /**

test/b002-repro-pre-fix.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from "vitest";
-import { planReinject } from "../src/reinject.js";
+import { planDeferredReinject, planReinject } from "../src/reinject.js";
 import { createDefaultSettings } from "../src/settings.js";
 import { createInitialState, trackSkill } from "../src/state.js";
 
@@ -67,4 +67,32 @@ describe("B-002 pre-fix filter hypothesis", () => {
 
 		expect(planned).toEqual([]);
 	});
+
+	it("defer plan includes skill absent from kept even when registered is empty", () => {
+		const state = createInitialState();
+		trackSkill(state, {
+			name: "fup-blame-commits",
+			filePath: "/home/user/.cursor/skills/fup-blame-commits/SKILL.md",
+			baseDir: "/home/user/.cursor/skills/fup-blame-commits",
+			source: "skill-block",
+		});
+
+		const branch = [
+			{
+				id: "keep-1",
+				type: "message",
+				message: { role: "user", content: "plain text after compact" },
+			},
+		] as never;
+
+		const planned = planDeferredReinject(
+			state,
+			{
+				sessionManager: { getBranch: () => branch },
+			} as never,
+			{ compactionEntry: { firstKeptEntryId: "keep-1" } } as never,
+		);
+
+		expect(planned).toEqual(["fup-blame-commits"]);
+	});
 });