Phase 12: recalculate pending on each compact — SPEC §16.6.

Every session_compact replans pendingReinject in defer mode; skipped reinject clears the queue unless manual compaction is waiting for the next user prompt.

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

test/reinject-double-compact.test.ts

@@ -0,0 +1,37 @@
+import { describe, expect, it } from "vitest";
+import { createCompactionRuntime } from "../src/compaction";
+import { applyPendingReinjectAfterCompact } from "../src/reinject";
+import { createInitialState } from "../src/state";
+
+describe("applyPendingReinjectAfterCompact", () => {
+	it("replaces pending with a new plan on each compact", () => {
+		const runtime = createCompactionRuntime();
+		const state = createInitialState();
+		state.pendingReinject = ["alpha"];
+
+		applyPendingReinjectAfterCompact(state, runtime, true, ["beta", "gamma"]);
+
+		expect(state.pendingReinject).toEqual(["beta", "gamma"]);
+	});
+
+	it("clears pending when reinject is skipped", () => {
+		const runtime = createCompactionRuntime();
+		const state = createInitialState();
+		state.pendingReinject = ["alpha"];
+
+		applyPendingReinjectAfterCompact(state, runtime, false, ["beta"]);
+
+		expect(state.pendingReinject).toEqual([]);
+	});
+
+	it("keeps stale pending when manual compaction scheduled a user-prompt clear", () => {
+		const runtime = createCompactionRuntime();
+		runtime.clearPendingReinjectOnNextUserInput = true;
+		const state = createInitialState();
+		state.pendingReinject = ["alpha"];
+
+		applyPendingReinjectAfterCompact(state, runtime, false, ["beta"]);
+
+		expect(state.pendingReinject).toEqual(["alpha"]);
+	});
+});