Phase 12: skill name collision warn — SPEC §11.

Duplicate names in resourceLoader resolve to the first skill with a one-time UI warning during re-inject expansion.

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

src/reinject.ts

@@ -18,11 +18,38 @@ import type { ExtensionState } from "./state.js";
 
 export const DEFERRED_REINJECT_CUSTOM_TYPE = "skill-reinject:inject";
 
-function notifySkippedSkill(ctx: ExtensionContext | undefined, skillName: string, reason: string): void {
+function notifyWarning(ctx: ExtensionContext | undefined, message: string): void {
 	if (!ctx?.hasUI) {
 		return;
 	}
-	ctx.ui.notify(`skill-reinject: skipped "${skillName}" — ${reason}`, "warning");
+	ctx.ui.notify(message, "warning");
+}
+
+function notifySkippedSkill(ctx: ExtensionContext | undefined, skillName: string, reason: string): void {
+	notifyWarning(ctx, `skill-reinject: skipped "${skillName}" — ${reason}`);
+}
+
+/** First registered skill per name; warn on resourceLoader collisions (SPEC §11). */
+export function registeredSkillsByName<T extends Pick<Skill, "name">>(
+	registeredSkills: readonly T[],
+	ctx?: ExtensionContext,
+): Map<string, T> {
+	const byName = new Map<string, T>();
+	const warned = new Set<string>();
+	for (const skill of registeredSkills) {
+		if (byName.has(skill.name)) {
+			if (!warned.has(skill.name)) {
+				warned.add(skill.name);
+				notifyWarning(
+					ctx,
+					`skill-reinject: duplicate skill name "${skill.name}" — using first from resourceLoader`,
+				);
+			}
+			continue;
+		}
+		byName.set(skill.name, skill);
+	}
+	return byName;
 }
 
 /** Names still registered in resourceLoader (SPEC §5.2). */
@@ -77,7 +104,7 @@ export function buildReinjectBlocks(
 	registeredSkills: readonly Pick<Skill, "name" | "filePath" | "baseDir">[],
 	ctx?: ExtensionContext,
 ): string[] {
-	const registeredByName = new Map(registeredSkills.map((skill) => [skill.name, skill]));
+	const registeredByName = registeredSkillsByName(registeredSkills, ctx);
 	const blocks: string[] = [];
 	for (const name of skillNames) {
 		const tracked = state.skills.find((skill) => skill.name === name);

test/reinject-collision.test.ts

@@ -0,0 +1,31 @@
+import { describe, expect, it, vi } from "vitest";
+import { registeredSkillsByName } from "../src/reinject";
+
+describe("registeredSkillsByName", () => {
+	it("keeps the first skill when names collide", () => {
+		const first = { name: "alpha", filePath: "/a/SKILL.md", baseDir: "/a" };
+		const second = { name: "alpha", filePath: "/b/SKILL.md", baseDir: "/b" };
+
+		const byName = registeredSkillsByName([first, second]);
+
+		expect(byName.get("alpha")).toBe(first);
+	});
+
+	it("warns once per duplicate name", () => {
+		const notify = vi.fn();
+		const ctx = { hasUI: true, ui: { notify } } as never;
+		const skills = [
+			{ name: "alpha", filePath: "/a/SKILL.md", baseDir: "/a" },
+			{ name: "alpha", filePath: "/b/SKILL.md", baseDir: "/b" },
+			{ name: "alpha", filePath: "/c/SKILL.md", baseDir: "/c" },
+		];
+
+		registeredSkillsByName(skills, ctx);
+
+		expect(notify).toHaveBeenCalledTimes(1);
+		expect(notify).toHaveBeenCalledWith(
+			'skill-reinject: duplicate skill name "alpha" — using first from resourceLoader',
+			"warning",
+		);
+	});
+});