diff --git a/package-lock.json b/package-lock.json
index 16891ff..5ccfa4a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -18,7 +18,8 @@
       "devDependencies": {
         "concurrently": "^9.2.1",
         "gray-matter": "^4.0.3",
-        "tsx": "^4.21.0"
+        "tsx": "^4.21.0",
+        "vitest": "^4.1.0"
       }
     },
     "node_modules/@antfu/install-pkg": {
diff --git a/package.json b/package.json
index d316f28..8325382 100644
--- a/package.json
+++ b/package.json
@@ -14,11 +14,12 @@
   "scripts": {
     "build": "tsx scripts/build.ts",
     "build:skills": "tsx scripts/build-skills.ts",
-    "test": "npm run test -w @diffity/git && npm run test -w @diffity/parser && npm run test -w @diffity/ui",
+    "test": "npm run test -w @diffity/git && npm run test -w @diffity/parser && npm run test -w @diffity/ui && npm run test:scripts",
     "link-dev": "tsx scripts/link-dev.ts",
     "dev": "tsx scripts/dev.ts",
     "release:patch": "npm run build && tsx scripts/release.ts patch && npm publish -w packages/cli",
-    "release:minor": "npm run build && tsx scripts/release.ts minor && npm publish -w packages/cli"
+    "release:minor": "npm run build && tsx scripts/release.ts minor && npm publish -w packages/cli",
+    "test:scripts": "vitest run scripts"
   },
   "keywords": [
     "git",
@@ -31,6 +32,7 @@
   "devDependencies": {
     "concurrently": "^9.2.1",
     "gray-matter": "^4.0.3",
-    "tsx": "^4.21.0"
+    "tsx": "^4.21.0",
+    "vitest": "^4.1.0"
   }
 }
diff --git a/scripts/build-skills.ts b/scripts/build-skills.ts
index d730bdc..141ec07 100644
--- a/scripts/build-skills.ts
+++ b/scripts/build-skills.ts
@@ -1,7 +1,7 @@
 import { createHash } from 'crypto';
 import { join, dirname } from 'path';
 import { fileURLToPath } from 'url';
-import { readSkills, renderSkill, writeFile, cleanDir } from './lib/utils.js';
+import { readSkills, renderSkill, writeFile, cleanDir, cleanManagedSkills, DEV_SKILL_PREFIX } from './lib/utils.js';
 import { claudeCode } from './lib/transformers/index.js';
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
@@ -30,8 +30,12 @@ writeFile(
 );
 console.log(`Skills hash: ${skillsHash}`);
 
-cleanDir(globalClaudeSkillsDir);
-for (const skill of skills) {
-  claudeCode(skill, homeDir, { binary: 'diffity-dev', namePrefix: 'diffity-dev', slashPrefix: '/diffity-dev-', installHint: 'run `npm run dev` from the diffity repo root to link the CLI' });
+if (process.env.DIFFITY_SKIP_DEV_SKILLS || !homeDir) {
+  console.log('Skipped dev skills sync');
+} else {
+  cleanManagedSkills(globalClaudeSkillsDir, DEV_SKILL_PREFIX);
+  for (const skill of skills) {
+    claudeCode(skill, homeDir, { binary: DEV_SKILL_PREFIX, namePrefix: DEV_SKILL_PREFIX, slashPrefix: `/${DEV_SKILL_PREFIX}-`, installHint: 'run `npm run dev` from the diffity repo root to link the CLI' });
+  }
+  console.log(`Synced ${skills.length} dev skills to ~/.claude/skills/`);
 }
-console.log(`Synced ${skills.length} dev skills to ~/.claude/skills/`);
diff --git a/scripts/dev.ts b/scripts/dev.ts
index 94b33d7..ac28465 100644
--- a/scripts/dev.ts
+++ b/scripts/dev.ts
@@ -2,9 +2,9 @@
 
 import { execSync } from 'child_process';
 import { dirname, resolve, join } from 'path';
-import { rmSync } from 'fs';
 import { fileURLToPath } from 'url';
 import concurrently from 'concurrently';
+import { cleanManagedSkills, DEV_SKILL_PREFIX } from './lib/utils.js';
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
 const rootDir = resolve(__dirname, '..');
@@ -19,7 +19,7 @@ const globalClaudeSkillsDir = join(homeDir, '.claude', 'skills');
 
 function cleanupDevSkills() {
   try {
-    rmSync(globalClaudeSkillsDir, { recursive: true, force: true });
+    cleanManagedSkills(globalClaudeSkillsDir, DEV_SKILL_PREFIX);
     console.log('Cleaned up dev skills');
   } catch {}
 }
diff --git a/scripts/lib/utils.test.ts b/scripts/lib/utils.test.ts
new file mode 100644
index 0000000..dc32f60
--- /dev/null
+++ b/scripts/lib/utils.test.ts
@@ -0,0 +1,59 @@
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import { mkdtempSync, mkdirSync, writeFileSync, existsSync, readdirSync, rmSync } from 'fs';
+import { join } from 'path';
+import { tmpdir } from 'os';
+import { cleanManagedSkills, DEV_SKILL_PREFIX } from './utils.js';
+
+describe('cleanManagedSkills', () => {
+  let dir: string;
+
+  beforeEach(() => {
+    dir = mkdtempSync(join(tmpdir(), 'diffity-skills-'));
+  });
+
+  afterEach(() => {
+    rmSync(dir, { recursive: true, force: true });
+  });
+
+  function seed(): void {
+    mkdirSync(join(dir, `${DEV_SKILL_PREFIX}-review`), { recursive: true });
+    writeFileSync(join(dir, `${DEV_SKILL_PREFIX}-review`, 'SKILL.md'), 'dev skill');
+    mkdirSync(join(dir, 'slack-canvas', 'scripts'), { recursive: true });
+    writeFileSync(join(dir, 'slack-canvas', 'scripts', 'slack-canvas.sh'), '#!/bin/sh');
+    mkdirSync(join(dir, 'standup'), { recursive: true });
+    writeFileSync(join(dir, 'loose-file.md'), 'not a skill');
+  }
+
+  it('removes only the directories it manages', () => {
+    seed();
+
+    cleanManagedSkills(dir, DEV_SKILL_PREFIX);
+
+    expect(readdirSync(dir).sort()).toEqual(['loose-file.md', 'slack-canvas', 'standup']);
+    expect(existsSync(join(dir, 'slack-canvas', 'scripts', 'slack-canvas.sh'))).toBe(true);
+  });
+
+  it('leaves the containing directory in place', () => {
+    seed();
+
+    cleanManagedSkills(dir, DEV_SKILL_PREFIX);
+
+    expect(existsSync(dir)).toBe(true);
+  });
+
+  it('creates the directory when it does not exist yet', () => {
+    const missing = join(dir, 'nested', 'skills');
+
+    cleanManagedSkills(missing, DEV_SKILL_PREFIX);
+
+    expect(existsSync(missing)).toBe(true);
+  });
+
+  it('does not treat an empty prefix as "everything"', () => {
+    seed();
+
+    cleanManagedSkills(dir, '');
+
+    expect(readdirSync(dir)).toHaveLength(4);
+  });
+});
diff --git a/scripts/lib/utils.ts b/scripts/lib/utils.ts
index fdfd988..d0962f6 100644
--- a/scripts/lib/utils.ts
+++ b/scripts/lib/utils.ts
@@ -68,3 +68,18 @@ export function cleanDir(dir: string): void {
   }
   mkdirSync(dir, { recursive: true });
 }
+
+export const DEV_SKILL_PREFIX = 'diffity-dev';
+
+// Remove only the skill directories diffity manages (those named `${prefix}-*`),
+// leaving any other skills in the directory untouched. Unlike cleanDir, this is
+// safe to run against a shared location like ~/.claude/skills, which may hold
+// the user's own skills or skills installed by other tools.
+export function cleanManagedSkills(dir: string, prefix: string): void {
+  mkdirSync(dir, { recursive: true });
+  for (const entry of readdirSync(dir, { withFileTypes: true })) {
+    if (entry.isDirectory() && entry.name.startsWith(`${prefix}-`)) {
+      rmSync(join(dir, entry.name), { recursive: true, force: true });
+    }
+  }
+}