fix(sync): parse skill descriptions with yaml

.changeset/sync-skill-descriptions.md

@@ -0,0 +1,5 @@
+---
+'@bomb.sh/tools': patch
+---
+
+Fixes `bsh sync` writing garbled or truncated skill descriptions to `AGENTS.md`

package.json

@@ -70,9 +70,9 @@
     "publint": "^0.3.18",
     "tinyexec": "^1.1.1",
     "tsdown": "^0.22.3",
-    "ultramatter": "^0.0.4",
     "vitest": "^4.1.2",
-    "vitest-ansi-serializer": "^0.2.1"
+    "vitest-ansi-serializer": "^0.2.1",
+    "yaml": "^2.9.1"
   },
   "devDependencies": {
     "@changesets/cli": "^2.30.0",

src/commands/sync.test.ts

@@ -2,7 +2,7 @@ import { lstat, readlink } from 'node:fs/promises';
 import { fileURLToPath } from 'node:url';
 import { describe, it, expect } from 'vitest';
 import { createFixture, createMocks } from '../test-utils/index.ts';
-import { copySkills, findParentPackage } from './sync.ts';
+import { copySkills, findParentPackage, updateAgentsMd } from './sync.ts';
 
 describe('copySkills', () => {
 	it('symlinks each skill into the destination', async () => {
@@ -53,6 +53,55 @@ describe('copySkills', () => {
 		expect(await fixture.text('source-skills/build/SKILL.md')).toContain('name: build');
 		expect(await fixture.text('project/skills/build/SKILL.md')).toContain('name: build');
 	});
+
+	it('reads block scalar descriptions without the indicator', async () => {
+		const fixture = await createFixture({
+			'source-skills': {
+				test: {
+					'SKILL.md':
+						'---\nname: test\ndescription: >\n  Vitest test runner with colocated .test.ts files.\n  Use when writing tests.\nmetadata:\n  type: core\n---\nbody',
+				},
+				lint: {
+					'SKILL.md': '---\nname: lint\ndescription: |-\n  Lint the project.\n---\nbody',
+				},
+			},
+		});
+
+		const skills = await copySkills({
+			source: new URL('source-skills/', fixture.root),
+			dest: new URL('project/skills/', fixture.root),
+		});
+
+		expect(skills).toEqual(
+			expect.arrayContaining([
+				{
+					name: 'test',
+					description: 'Vitest test runner with colocated .test.ts files. Use when writing tests.',
+				},
+				{ name: 'lint', description: 'Lint the project.' },
+			]),
+		);
+	});
+});
+
+describe('updateAgentsMd', () => {
+	it('summarizes each skill with its first full sentence', async () => {
+		const fixture = await createFixture({ 'AGENTS.md': '# Project\n' });
+
+		await updateAgentsMd({
+			root: fixture.root,
+			skills: [
+				{
+					name: 'test',
+					description: 'Vitest test runner with colocated .test.ts files. Use when writing tests.',
+				},
+			],
+		});
+
+		expect(await fixture.text('AGENTS.md')).toContain(
+			'- **test** — [skills/test/SKILL.md](skills/test/SKILL.md) - Vitest test runner with colocated .test.ts files\n',
+		);
+	});
 });
 
 describe('findParentPackage', () => {

src/commands/sync.ts

@@ -3,7 +3,7 @@ import { findPackageJSON } from 'node:module';
 import { cwd, env, platform } from 'node:process';
 import { fileURLToPath, pathToFileURL } from 'node:url';
 import { NodeHfs } from '@humanfs/node';
-import { parse } from 'ultramatter';
+import { parse } from 'yaml';
 import type { CommandContext } from '../context.ts';
 import { relativeUrlPath, resolveLinkTarget } from '../utils.ts';
 
@@ -126,13 +126,13 @@ async function updateGitignore(options: { root: URL; skills: SkillInfo[] }): Pro
 	await hfs.write(gitignorePath, content);
 }
 
-async function updateAgentsMd(options: { root: URL; skills: SkillInfo[] }): Promise<void> {
+export async function updateAgentsMd(options: { root: URL; skills: SkillInfo[] }): Promise<void> {
 	const { root, skills } = options;
 	const agentsPath = new URL('AGENTS.md', root);
 	let content = (await hfs.text(agentsPath)) ?? '';
 
 	const lines = skills.map((s) => {
-		const desc = s.description.split('.')[0]?.trim();
+		const desc = s.description.split(/\.(?:\s|$)/)[0]?.trim();
 		return `- **${s.name}** — [skills/${s.name}/SKILL.md](skills/${s.name}/SKILL.md)${desc ? ` - ${desc}` : ''}`;
 	});
 
@@ -160,7 +160,9 @@ async function updateAgentsMd(options: { root: URL; skills: SkillInfo[] }): Prom
 }
 
 function parseFrontmatter(content: string): SkillInfo | undefined {
-	const { frontmatter } = parse(content);
+	const match = /^---\r?\n([\s\S]*?)\r?\n---/.exec(content);
+	if (!match) return undefined;
+	const frontmatter = parse(match[1]!) as Record<string, unknown> | null;
 	if (!frontmatter) return undefined;
 	const name = frontmatter.name as string | undefined;
 	const description =