Add opt-in Karpathy guidelines skill (#909)

* Add opt-in Karpathy guidelines skill

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

src/plugins/bundled/index.ts

@@ -10,14 +10,15 @@
  * claude-in-chrome), use src/skills/bundled/ instead.
  *
  * To add a new built-in plugin:
- * 1. Import registerBuiltinPlugin from '../builtinPlugins.js'
- * 2. Call registerBuiltinPlugin() with the plugin definition here
+ * 1. Import its registerXPlugin() helper from the plugin module here
+ * 2. Call that helper from initBuiltinPlugins()
  */
 
+import { registerKarpathyGuidelinesPlugin } from './karpathyGuidelines.js'
+
 /**
  * Initialize built-in plugins. Called during CLI startup.
  */
 export function initBuiltinPlugins(): void {
-  // No built-in plugins registered yet — this is the scaffolding for
-  // migrating bundled skills that should be user-toggleable.
+  registerKarpathyGuidelinesPlugin()
 }

src/plugins/bundled/karpathyGuidelines.test.ts

@@ -0,0 +1,41 @@
+import { afterEach, expect, test } from 'bun:test'
+
+import {
+  clearBuiltinPlugins,
+  getBuiltinPluginDefinition,
+} from '../builtinPlugins.js'
+import { registerKarpathyGuidelinesPlugin } from './karpathyGuidelines.js'
+
+afterEach(() => {
+  clearBuiltinPlugins()
+})
+
+test('karpathy guidelines registers as an opt-in built-in plugin', () => {
+  registerKarpathyGuidelinesPlugin()
+
+  const plugin = getBuiltinPluginDefinition('karpathy-guidelines')
+
+  expect(plugin).toBeDefined()
+  expect(plugin?.defaultEnabled).toBe(false)
+  expect(plugin?.skills?.map(skill => skill.name)).toEqual([
+    'karpathy-guidelines',
+  ])
+})
+
+test('karpathy guidelines skill includes optional user focus', async () => {
+  registerKarpathyGuidelinesPlugin()
+
+  const skill = getBuiltinPluginDefinition('karpathy-guidelines')?.skills?.[0]
+  expect(skill).toBeDefined()
+
+  const blocks = await skill!.getPromptForCommand(
+    'prefer tests over snapshots',
+    {} as never,
+  )
+  const text = (blocks[0] as { text: string }).text
+
+  expect(text).toContain('# CLAUDE.md')
+  expect(text).toContain('These guidelines are working if')
+  expect(text).toContain('## User Focus')
+  expect(text).toContain('prefer tests over snapshots')
+})

src/plugins/bundled/karpathyGuidelines.ts

@@ -0,0 +1,96 @@
+import { registerBuiltinPlugin } from '../builtinPlugins.js'
+
+const KARPATHY_GUIDELINES_PROMPT = `# CLAUDE.md
+
+Behavioral guidelines to reduce common LLM coding mistakes. Merge with project-specific instructions as needed.
+
+**Tradeoff:** These guidelines bias toward caution over speed. For trivial tasks, use judgment.
+
+## 1. Think Before Coding
+
+**Don't assume. Don't hide confusion. Surface tradeoffs.**
+
+Before implementing:
+- State your assumptions explicitly. If uncertain, ask.
+- If multiple interpretations exist, present them - don't pick silently.
+- If a simpler approach exists, say so. Push back when warranted.
+- If something is unclear, stop. Name what's confusing. Ask.
+
+## 2. Simplicity First
+
+**Minimum code that solves the problem. Nothing speculative.**
+
+- No features beyond what was asked.
+- No abstractions for single-use code.
+- No "flexibility" or "configurability" that wasn't requested.
+- No error handling for impossible scenarios.
+- If you write 200 lines and it could be 50, rewrite it.
+
+Ask yourself: "Would a senior engineer say this is overcomplicated?" If yes, simplify.
+
+## 3. Surgical Changes
+
+**Touch only what you must. Clean up only your own mess.**
+
+When editing existing code:
+- Don't "improve" adjacent code, comments, or formatting.
+- Don't refactor things that aren't broken.
+- Match existing style, even if you'd do it differently.
+- If you notice unrelated dead code, mention it - don't delete it.
+
+When your changes create orphans:
+- Remove imports/variables/functions that YOUR changes made unused.
+- Don't remove pre-existing dead code unless asked.
+
+The test: Every changed line should trace directly to the user's request.
+
+## 4. Goal-Driven Execution
+
+**Define success criteria. Loop until verified.**
+
+Transform tasks into verifiable goals:
+- "Add validation" -> "Write tests for invalid inputs, then make them pass"
+- "Fix the bug" -> "Write a test that reproduces it, then make it pass"
+- "Refactor X" -> "Ensure tests pass before and after"
+
+For multi-step tasks, state a brief plan:
+\`\`\`
+1. [Step] -> verify: [check]
+2. [Step] -> verify: [check]
+3. [Step] -> verify: [check]
+\`\`\`
+
+Strong success criteria let you loop independently. Weak criteria ("make it work") require constant clarification.
+
+---
+
+**These guidelines are working if:** fewer unnecessary changes in diffs, fewer rewrites due to overcomplication, and clarifying questions come before implementation rather than after mistakes.
+`
+
+export function registerKarpathyGuidelinesPlugin(): void {
+  registerBuiltinPlugin({
+    name: 'karpathy-guidelines',
+    description:
+      'Optional coding guidelines that favor simple, surgical, verifiable changes.',
+    version: '1.0.0',
+    defaultEnabled: false,
+    skills: [
+      {
+        name: 'karpathy-guidelines',
+        description:
+          'Apply coding guidelines that reduce common LLM implementation mistakes.',
+        whenToUse:
+          'Use when writing, reviewing, or refactoring code, especially when a task could become overcomplicated or needs careful verification.',
+        userInvocable: true,
+        async getPromptForCommand(args) {
+          const focus = args.trim()
+          const prompt = focus
+            ? `${KARPATHY_GUIDELINES_PROMPT}\n\n## User Focus\n\n${focus}\n`
+            : KARPATHY_GUIDELINES_PROMPT
+
+          return [{ type: 'text', text: prompt }]
+        },
+      },
+    ],
+  })
+}