diff --git a/test/reinject-mid-turn.test.ts b/test/reinject-mid-turn.test.ts
new file mode 100644
index 0000000..2167f7e
--- /dev/null
+++ b/test/reinject-mid-turn.test.ts
@@ -0,0 +1,116 @@
+import { mkdtempSync, mkdirSync, rmSync, writeFileSync } from "fs";
+import { tmpdir } from "os";
+import { join } from "path";
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { createCompactionRuntime } from "../src/compaction";
+import { DEFERRED_REINJECT_CUSTOM_TYPE, deliverDeferredReinjectSteer, tryConsumeDeferredReinject } from "../src/reinject";
+import { createDefaultSettings } from "../src/settings";
+import { createInitialState, trackSkill } from "../src/state";
+
+const tempDirs: string[] = [];
+
+afterEach(() => {
+	for (const dir of tempDirs.splice(0)) {
+		rmSync(dir, { recursive: true, force: true });
+	}
+});
+
+function tempSkillDir(name: string): { filePath: string; baseDir: string } {
+	const root = mkdtempSync(join(tmpdir(), "pi-skill-reinject-mid-turn-"));
+	tempDirs.push(root);
+	const baseDir = join(root, name);
+	mkdirSync(baseDir, { recursive: true });
+	const filePath = join(baseDir, "SKILL.md");
+	writeFileSync(filePath, `---\nname: ${name}\n---\n# body\n`, "utf8");
+	return { filePath, baseDir };
+}
+
+describe("deliverDeferredReinjectSteer", () => {
+	it("sends steer message and clears pending when skills resolve", () => {
+		const { filePath, baseDir } = tempSkillDir("alpha");
+		const runtime = createCompactionRuntime();
+		const state = createInitialState();
+		trackSkill(state, { name: "alpha", filePath, baseDir, source: "slash" });
+		state.pendingReinject = ["alpha"];
+		const sendMessage = vi.fn();
+		const pi = { sendMessage } as never;
+		const registered = [{ name: "alpha", filePath, baseDir }];
+
+		const delivered = deliverDeferredReinjectSteer(
+			pi,
+			state,
+			createDefaultSettings(),
+			registered,
+			runtime,
+			"compact-1",
+		);
+
+		expect(delivered).toBe(true);
+		expect(state.pendingReinject).toEqual([]);
+		expect(runtime.deferredDeliveredForCompactionId).toBe("compact-1");
+		expect(sendMessage).toHaveBeenCalledOnce();
+		expect(sendMessage).toHaveBeenCalledWith(
+			expect.objectContaining({
+				customType: DEFERRED_REINJECT_CUSTOM_TYPE,
+				display: true,
+				content: expect.stringContaining('<skill name="alpha"'),
+			}),
+			{ deliverAs: "steer" },
+		);
+	});
+
+	it("returns false without sendMessage when pending is empty", () => {
+		const runtime = createCompactionRuntime();
+		const state = createInitialState();
+		const sendMessage = vi.fn();
+		const pi = { sendMessage } as never;
+
+		expect(
+			deliverDeferredReinjectSteer(pi, state, createDefaultSettings(), [], runtime, "compact-1"),
+		).toBe(false);
+		expect(sendMessage).not.toHaveBeenCalled();
+	});
+});
+
+describe("tryConsumeDeferredReinject after mid-turn steer", () => {
+	it("skips before_agent_start inject when steer already delivered for compaction", () => {
+		const { filePath, baseDir } = tempSkillDir("beta");
+		const runtime = createCompactionRuntime();
+		runtime.lastCompactionEntryId = "compact-2";
+		runtime.deferredDeliveredForCompactionId = "compact-2";
+		const state = createInitialState();
+		trackSkill(state, { name: "beta", filePath, baseDir, source: "slash" });
+		state.pendingReinject = ["beta"];
+
+		expect(
+			tryConsumeDeferredReinject(
+				state,
+				createDefaultSettings(),
+				[{ name: "beta", filePath, baseDir }],
+				undefined,
+				runtime,
+			),
+		).toBeUndefined();
+	});
+
+	it("consumes pending on before_agent_start when steer did not run (idle path)", () => {
+		const { filePath, baseDir } = tempSkillDir("gamma");
+		const runtime = createCompactionRuntime();
+		runtime.lastCompactionEntryId = "compact-3";
+		const state = createInitialState();
+		trackSkill(state, { name: "gamma", filePath, baseDir, source: "slash" });
+		state.pendingReinject = ["gamma"];
+
+		const result = tryConsumeDeferredReinject(
+			state,
+			createDefaultSettings(),
+			[{ name: "gamma", filePath, baseDir }],
+			undefined,
+			runtime,
+		);
+
+		expect(result?.message.customType).toBe(DEFERRED_REINJECT_CUSTOM_TYPE);
+		expect(state.pendingReinject).toEqual([]);
+		expect(runtime.deferredDeliveredForCompactionId).toBeNull();
+	});
+});