diff --git a/src/index.ts b/src/index.ts
index 58ed041..a44c35e 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,7 +1,35 @@
-import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";
+import type { ExtensionAPI, Skill } from "@earendil-works/pi-coding-agent";
+import { detectSlashSkill } from "./detect.js";
+import { findRegisteredSkillByName, resolveRegisteredSkills } from "./skills-registry.js";
+import { createInitialState, trackSkill } from "./state.js";
 
 export default function skillReinject(pi: ExtensionAPI): void {
-	pi.on("session_start", () => {
-		// Phase 0 shell — hooks wired in later phases
+	const state = createInitialState();
+	let registeredSkills: Skill[] = [];
+
+	pi.on("before_agent_start", async (event) => {
+		registeredSkills = event.systemPromptOptions.skills ?? registeredSkills;
+	});
+
+	pi.on("input", async (event, ctx) => {
+		if (event.source === "extension") {
+			return { action: "continue" };
+		}
+
+		const skillName = detectSlashSkill(event.text);
+		if (skillName) {
+			const skills = resolveRegisteredSkills(ctx.cwd, registeredSkills);
+			const skill = findRegisteredSkillByName(skills, skillName);
+			if (skill) {
+				trackSkill(state, {
+					name: skill.name,
+					filePath: skill.filePath,
+					baseDir: skill.baseDir,
+					source: "slash",
+				});
+			}
+		}
+
+		return { action: "continue" };
 	});
 }
diff --git a/src/skills-registry.ts b/src/skills-registry.ts
new file mode 100644
index 0000000..2f2e3dc
--- /dev/null
+++ b/src/skills-registry.ts
@@ -0,0 +1,27 @@
+import { getAgentDir, loadSkills, type Skill } from "@earendil-works/pi-coding-agent";
+
+/** First match on name collision (SPEC §11). */
+export function findRegisteredSkillByName(
+	skills: readonly Skill[],
+	name: string,
+): Skill | undefined {
+	return skills.find((skill) => skill.name === name);
+}
+
+/** Mirror resourceLoader skill list when cache is empty (e.g. first user input). */
+export function loadRegisteredSkills(cwd: string): Skill[] {
+	return loadSkills({
+		cwd,
+		agentDir: getAgentDir(),
+		skillPaths: [],
+		includeDefaults: true,
+	}).skills;
+}
+
+/** Prefer live skills from before_agent_start; fall back to loadSkills (SPEC §6.2). */
+export function resolveRegisteredSkills(cwd: string, cached: readonly Skill[]): Skill[] {
+	if (cached.length > 0) {
+		return [...cached];
+	}
+	return loadRegisteredSkills(cwd);
+}