Add skills system with Claude Code compatibility (#171)

* Add skills system with Claude Code compatibility

* consolidate skills into single module, merge loaders, add <available_skills> XML tags

* add Codex CLI skills compatibility, skip hidden/symlinks

packages/coding-agent/src/core/skills.ts

@@ -0,0 +1,199 @@
+import { existsSync, readdirSync, readFileSync } from "fs";
+import { homedir } from "os";
+import { basename, dirname, join, resolve } from "path";
+import { CONFIG_DIR_NAME } from "../config.js";
+
+export interface SkillFrontmatter {
+	name?: string;
+	description: string;
+}
+
+export type SkillSource = "user" | "project" | "claude-user" | "claude-project" | "codex-user";
+
+export interface Skill {
+	name: string;
+	description: string;
+	filePath: string;
+	baseDir: string;
+	source: SkillSource;
+}
+
+type SkillFormat = "pi" | "claude" | "codex";
+
+function stripQuotes(value: string): string {
+	if ((value.startsWith('"') && value.endsWith('"')) || (value.startsWith("'") && value.endsWith("'"))) {
+		return value.slice(1, -1);
+	}
+	return value;
+}
+
+function parseFrontmatter(content: string): { frontmatter: SkillFrontmatter; body: string } {
+	const frontmatter: SkillFrontmatter = { description: "" };
+
+	const normalizedContent = content.replace(/\r\n/g, "\n").replace(/\r/g, "\n");
+
+	if (!normalizedContent.startsWith("---")) {
+		return { frontmatter, body: normalizedContent };
+	}
+
+	const endIndex = normalizedContent.indexOf("\n---", 3);
+	if (endIndex === -1) {
+		return { frontmatter, body: normalizedContent };
+	}
+
+	const frontmatterBlock = normalizedContent.slice(4, endIndex);
+	const body = normalizedContent.slice(endIndex + 4).trim();
+
+	for (const line of frontmatterBlock.split("\n")) {
+		const match = line.match(/^(\w+):\s*(.*)$/);
+		if (match) {
+			const key = match[1];
+			const value = stripQuotes(match[2].trim());
+			if (key === "name") {
+				frontmatter.name = value;
+			} else if (key === "description") {
+				frontmatter.description = value;
+			}
+		}
+	}
+
+	return { frontmatter, body };
+}
+
+function loadSkillsFromDir(dir: string, source: SkillSource, format: SkillFormat, subdir: string = ""): Skill[] {
+	const skills: Skill[] = [];
+
+	if (!existsSync(dir)) {
+		return skills;
+	}
+
+	try {
+		const entries = readdirSync(dir, { withFileTypes: true });
+
+		for (const entry of entries) {
+			if (entry.name.startsWith(".")) {
+				continue;
+			}
+
+			if (entry.isSymbolicLink()) {
+				continue;
+			}
+
+			const fullPath = join(dir, entry.name);
+
+			if (format === "pi") {
+				if (entry.isDirectory()) {
+					const newSubdir = subdir ? `${subdir}:${entry.name}` : entry.name;
+					skills.push(...loadSkillsFromDir(fullPath, source, format, newSubdir));
+				} else if (entry.isFile() && entry.name.endsWith(".md")) {
+					try {
+						const rawContent = readFileSync(fullPath, "utf-8");
+						const { frontmatter } = parseFrontmatter(rawContent);
+
+						if (!frontmatter.description) {
+							continue;
+						}
+
+						const nameFromFile = entry.name.slice(0, -3);
+						const name = frontmatter.name || (subdir ? `${subdir}:${nameFromFile}` : nameFromFile);
+
+						skills.push({
+							name,
+							description: frontmatter.description,
+							filePath: fullPath,
+							baseDir: dirname(fullPath),
+							source,
+						});
+					} catch {}
+				}
+			} else if (format === "claude") {
+				if (!entry.isDirectory()) {
+					continue;
+				}
+
+				const skillDir = fullPath;
+				const skillFile = join(skillDir, "SKILL.md");
+
+				if (!existsSync(skillFile)) {
+					continue;
+				}
+
+				try {
+					const rawContent = readFileSync(skillFile, "utf-8");
+					const { frontmatter } = parseFrontmatter(rawContent);
+
+					if (!frontmatter.description) {
+						continue;
+					}
+
+					const name = frontmatter.name || entry.name;
+
+					skills.push({
+						name,
+						description: frontmatter.description,
+						filePath: skillFile,
+						baseDir: skillDir,
+						source,
+					});
+				} catch {}
+			} else if (format === "codex") {
+				if (entry.isDirectory()) {
+					skills.push(...loadSkillsFromDir(fullPath, source, format));
+				} else if (entry.isFile() && entry.name === "SKILL.md") {
+					try {
+						const rawContent = readFileSync(fullPath, "utf-8");
+						const { frontmatter } = parseFrontmatter(rawContent);
+
+						if (!frontmatter.description) {
+							continue;
+						}
+
+						const skillDir = dirname(fullPath);
+						const name = frontmatter.name || basename(skillDir);
+
+						skills.push({
+							name,
+							description: frontmatter.description,
+							filePath: fullPath,
+							baseDir: skillDir,
+							source,
+						});
+					} catch {}
+				}
+			}
+		}
+	} catch {}
+
+	return skills;
+}
+
+export function loadSkills(): Skill[] {
+	const skillMap = new Map<string, Skill>();
+
+	const codexUserDir = join(homedir(), ".codex", "skills");
+	for (const skill of loadSkillsFromDir(codexUserDir, "codex-user", "codex")) {
+		skillMap.set(skill.name, skill);
+	}
+
+	const claudeUserDir = join(homedir(), ".claude", "skills");
+	for (const skill of loadSkillsFromDir(claudeUserDir, "claude-user", "claude")) {
+		skillMap.set(skill.name, skill);
+	}
+
+	const claudeProjectDir = resolve(process.cwd(), ".claude", "skills");
+	for (const skill of loadSkillsFromDir(claudeProjectDir, "claude-project", "claude")) {
+		skillMap.set(skill.name, skill);
+	}
+
+	const globalSkillsDir = join(homedir(), CONFIG_DIR_NAME, "agent", "skills");
+	for (const skill of loadSkillsFromDir(globalSkillsDir, "user", "pi")) {
+		skillMap.set(skill.name, skill);
+	}
+
+	const projectSkillsDir = resolve(process.cwd(), CONFIG_DIR_NAME, "skills");
+	for (const skill of loadSkillsFromDir(projectSkillsDir, "project", "pi")) {
+		skillMap.set(skill.name, skill);
+	}
+
+	return Array.from(skillMap.values());
+}