Phase 14: add debug reinject diag logging — B-002 filter visibility

Expose settings.debug snapshots on session_compact and before_agent_start
so Phase 14 can see which filter stage drops --skill paths.

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

test/diag.test.ts

@@ -0,0 +1,81 @@
+import { describe, expect, it, vi } from "vitest";
+import { buildReinjectDiagSnapshot, notifyReinjectDiag } from "../src/diag.js";
+import { createDefaultSettings } from "../src/settings.js";
+import { createInitialState } from "../src/state.js";
+
+describe("buildReinjectDiagSnapshot", () => {
+	it("collects tracked, kept, registered, planned, and pending", () => {
+		const state = createInitialState();
+		state.skills.push({
+			name: "alpha",
+			filePath: "/skills/alpha/SKILL.md",
+			baseDir: "/skills/alpha",
+			firstSeenAt: 1,
+			lastSeenAt: 1,
+			sources: ["slash"],
+		});
+		state.pendingReinject = ["alpha"];
+
+		expect(
+			buildReinjectDiagSnapshot(
+				state,
+				[{ name: "beta" }],
+				new Set(["gamma"]),
+				["alpha"],
+			),
+		).toEqual({
+			tracked: ["alpha"],
+			kept: ["gamma"],
+			registered: ["beta"],
+			planned: ["alpha"],
+			pending: ["alpha"],
+		});
+	});
+});
+
+describe("notifyReinjectDiag", () => {
+	it("no-ops when debug is off", () => {
+		const notify = vi.fn();
+		notifyReinjectDiag(
+			{
+				hasUI: true,
+				ui: { notify },
+			} as never,
+			createDefaultSettings(),
+			"session_compact",
+			{
+				tracked: [],
+				kept: [],
+				registered: [],
+				planned: [],
+				pending: [],
+			},
+		);
+		expect(notify).not.toHaveBeenCalled();
+	});
+
+	it("notifies with JSON snapshot when debug is on", () => {
+		const notify = vi.fn();
+		const settings = { ...createDefaultSettings(), debug: true };
+		const snapshot = {
+			tracked: ["a"],
+			kept: [],
+			registered: [],
+			planned: ["a"],
+			pending: ["a"],
+		};
+		notifyReinjectDiag(
+			{
+				hasUI: true,
+				ui: { notify },
+			} as never,
+			settings,
+			"before_agent_start",
+			snapshot,
+		);
+		expect(notify).toHaveBeenCalledWith(
+			`skill-reinject [before_agent_start]: ${JSON.stringify(snapshot)}`,
+			"info",
+		);
+	});
+});

test/settings.test.ts

@@ -54,6 +54,10 @@ describe("parseSkillReinjectPartial", () => {
 			}),
 		).toEqual({ enabled: true, suffix: "custom" });
 	});
+
+	it("parses debug flag", () => {
+		expect(parseSkillReinjectPartial({ debug: true })).toEqual({ debug: true });
+	});
 });
 
 describe("mergeSkillReinjectSettings", () => {