feat: add pi extension (#1)

The doc landed in #2 but was unlinked. Point to it from the adapters section.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

.agents/plugins/marketplace.json

@@ -0,0 +1,21 @@
+{
+  "name": "ponytail",
+  "interface": {
+    "displayName": "Ponytail"
+  },
+  "plugins": [
+    {
+      "name": "ponytail",
+      "source": {
+        "source": "url",
+        "url": "https://github.com/DietrichGebert/ponytail.git",
+        "ref": "main"
+      },
+      "policy": {
+        "installation": "AVAILABLE",
+        "authentication": "ON_INSTALL"
+      },
+      "category": "Productivity"
+    }
+  ]
+}

.claude-plugin/plugin.json

@@ -1,6 +1,6 @@
 {
   "name": "ponytail",
-  "version": "4.0.0",
+  "version": "4.1.0",
   "description": "Lazy senior dev mode. Forces the simplest, shortest solution that actually works: YAGNI, stdlib first, no unrequested abstractions.",
   "author": {
     "name": "Dietrich Gebert",

.codex-plugin/plugin.json

@@ -0,0 +1,31 @@
+{
+  "name": "ponytail",
+  "version": "4.1.0",
+  "description": "Lazy senior dev mode. Forces the simplest, shortest solution that actually works: YAGNI, stdlib first, no unrequested abstractions.",
+  "author": {
+    "name": "Dietrich Gebert",
+    "url": "https://github.com/DietrichGebert"
+  },
+  "homepage": "https://github.com/DietrichGebert/ponytail",
+  "repository": "https://github.com/DietrichGebert/ponytail",
+  "license": "MIT",
+  "keywords": ["yagni", "minimalism", "code-review", "productivity"],
+  "skills": "./skills/",
+  "interface": {
+    "displayName": "Ponytail",
+    "shortDescription": "Lazy senior developer mode",
+    "longDescription": "Prefer YAGNI, the standard library, native platform features, and the smallest correct implementation.",
+    "developerName": "Dietrich Gebert",
+    "category": "Productivity",
+    "capabilities": ["Instructions", "Lifecycle hooks"],
+    "websiteURL": "https://github.com/DietrichGebert/ponytail",
+    "defaultPrompt": [
+      "Use Ponytail mode for this task.",
+      "Review this diff for over-engineering.",
+      "Find the smallest correct implementation."
+    ],
+    "brandColor": "#111111",
+    "composerIcon": "./assets/logo.png",
+    "logo": "./assets/logo.png"
+  }
+}

.kiro/steering/ponytail.md

@@ -0,0 +1,29 @@
+---
+title: Ponytail — lazy senior dev mode
+inclusion: always
+---
+
+# Ponytail — lazy senior dev mode
+
+You are a lazy senior developer. Lazy means efficient, not careless. The best code is the code never written.
+
+Before writing any code, stop at the first rung that holds:
+
+1. Does this need to be built at all? (YAGNI)
+2. Does the standard library already do this? Use it.
+3. Does a native platform feature cover it? Use it.
+4. Does an already-installed dependency solve it? Use it.
+5. Can this be one line? Make it one line.
+6. Only then: write the minimum code that works.
+
+Rules:
+
+- No abstractions that weren't explicitly requested.
+- No new dependency if it can be avoided.
+- No boilerplate nobody asked for.
+- Deletion over addition. Boring over clever. Fewest files possible.
+- Question complex requests: "Do you actually need X, or does Y cover it?"
+- Pick the edge-case-correct option when two stdlib approaches are the same size — lazy means less code, not the flimsier algorithm.
+- Mark intentional simplifications with a `ponytail:` comment. If the shortcut has a known ceiling (global lock, O(n²) scan, naive heuristic), the comment names the ceiling and the upgrade path.
+
+Not lazy about: input validation at trust boundaries, error handling that prevents data loss, security, accessibility, anything explicitly requested. Non-trivial logic leaves ONE runnable check behind — the smallest thing that fails if the logic breaks (an assert-based demo/self-check or one small test file; no frameworks, no fixtures). Trivial one-liners need no test.

README.md

@@ -56,16 +56,49 @@ Lazy, not negligent: trust-boundary validation, data-loss handling, security, an
 
 The most effort ponytail will ever ask of you:
 
+### Claude Code
+
 ```
 /plugin marketplace add DietrichGebert/ponytail
 /plugin install ponytail@ponytail
 ```
 
+### Codex
+
+```bash
+codex plugin marketplace add DietrichGebert/ponytail
+codex
+```
+
+Open `/plugins`, select the Ponytail marketplace, and install Ponytail. Then
+open `/hooks`, review and trust its two lifecycle hooks, and start a new thread.
+
+### Pi agent harness
+
+```
+pi install git:github.com/DietrichGebert/ponytail
+```
+
 That was it. He'd be proud. He won't say it.
 
 Active every session. `/ponytail-review` finds what to delete in your diff. `/ponytail ultra` exists for when the codebase has wronged you personally. `/ponytail-help` explains the rest.
 
-Cursor, Windsurf, Cline, Copilot, Aider: copy the matching rules file from this repo ([`.cursor/rules/`](.cursor/rules/), [`.windsurf/rules/`](.windsurf/rules/), [`.clinerules/`](.clinerules/), [`.github/copilot-instructions.md`](.github/copilot-instructions.md), [`AGENTS.md`](AGENTS.md)).
+In Codex, invoke the skills as `@ponytail`, `@ponytail-review`, and
+`@ponytail-help`. Startup and mode-change text shows the current mode.
+
+Cursor, Windsurf, Cline, Copilot, Aider, Kiro: copy the matching rules file from this repo ([`.cursor/rules/`](.cursor/rules/), [`.windsurf/rules/`](.windsurf/rules/), [`.clinerules/`](.clinerules/), [`.github/copilot-instructions.md`](.github/copilot-instructions.md), [`AGENTS.md`](AGENTS.md), [`.kiro/steering/`](.kiro/steering/)).
+
+Kiro: copy `.kiro/steering/ponytail.md` to `~/.kiro/steering/` (global) or `.kiro/steering/` in your project.
+
+Which files map to which agent: [Agent portability](docs/agent-portability.md).
+
+## Development
+
+When changing the compact rule text, keep the agent copies aligned:
+
+```bash
+node scripts/check-rule-copies.js
+```
 
 ## FAQ
 

docs/agent-portability.md

@@ -0,0 +1,31 @@
+# Agent Portability
+
+Ponytail is an agent-portable skill distribution. The skills in `skills/` hold
+the core behavior; host-specific files are adapters that make that behavior easy
+to load in a given agent.
+
+## Supported Adapters
+
+| Host | Files | Notes |
+|------|-------|-------|
+| Claude Code | `.claude-plugin/`, `commands/`, `hooks/` | Full plugin install with session activation, mode tracking, commands, and statusline support. |
+| Codex | `.codex-plugin/plugin.json`, `hooks/hooks.json`, `hooks/`, `skills/` | Plugin install with the same skills plus lifecycle hooks for activation and mode tracking. |
+| Cursor | `.cursor/rules/ponytail.mdc` | Always-on project rule. |
+| Windsurf | `.windsurf/rules/ponytail.md` | Project rule. |
+| Cline | `.clinerules/ponytail.md` | Project rule. |
+| GitHub Copilot | `.github/copilot-instructions.md` | Repository instruction file. |
+| Kiro | `.kiro/steering/ponytail.md` | Steering rule; copy globally or into a project. |
+| Generic agents | `AGENTS.md` or `skills/*/SKILL.md` | Copy the compact rule file or load the skill files directly. |
+
+## Adapter Rule
+
+Keep adapters thin. When a host supports skills or hooks, point it at the
+existing `skills/` and `hooks/` files. When a host only supports project
+instructions, keep its copied rule text aligned with `AGENTS.md`.
+
+## Portable Behavior
+
+- `skills/ponytail/SKILL.md`: lazy senior dev mode
+- `skills/ponytail-review/SKILL.md`: over-engineering review
+- `skills/ponytail-help/SKILL.md`: quick reference
+- `AGENTS.md`: compact always-on instruction set for agents without skill support

hooks/hooks.json

@@ -0,0 +1,31 @@
+{
+  "hooks": {
+    "SessionStart": [
+      {
+        "matcher": "startup|resume|clear|compact",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "node \"${PLUGIN_ROOT}/hooks/ponytail-activate.js\"",
+            "commandWindows": "node \"%PLUGIN_ROOT%\\hooks\\ponytail-activate.js\"",
+            "timeout": 5,
+            "statusMessage": "Loading ponytail mode..."
+          }
+        ]
+      }
+    ],
+    "UserPromptSubmit": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "node \"${PLUGIN_ROOT}/hooks/ponytail-mode-tracker.js\"",
+            "commandWindows": "node \"%PLUGIN_ROOT%\\hooks\\ponytail-mode-tracker.js\"",
+            "timeout": 5,
+            "statusMessage": "Tracking ponytail mode..."
+          }
+        ]
+      }
+    ]
+  }
+}

hooks/ponytail-activate.js

@@ -10,121 +10,38 @@ const fs = require('fs');
 const path = require('path');
 const os = require('os');
 const { getDefaultMode } = require('./ponytail-config');
+const { getPonytailInstructions } = require('./ponytail-instructions');
+const {
+  clearMode,
+  isCodex,
+  setMode,
+  writeHookOutput,
+} = require('./ponytail-runtime');
 
 const claudeDir = path.join(os.homedir(), '.claude');
-const flagPath = path.join(claudeDir, '.ponytail-active');
 const settingsPath = path.join(claudeDir, 'settings.json');
 
 const mode = getDefaultMode();
 
 // "off" mode — skip activation entirely, don't write flag or emit rules
 if (mode === 'off') {
-  try { fs.unlinkSync(flagPath); } catch (e) {}
+  clearMode();
-  process.stdout.write('OK');
+  writeHookOutput('SessionStart', 'off', isCodex ? '' : 'OK');
   process.exit(0);
 }
 
 // 1. Write flag file
 try {
-  fs.mkdirSync(path.dirname(flagPath), { recursive: true });
+  setMode(mode);
-  fs.writeFileSync(flagPath, mode);
 } catch (e) {
   // Silent fail -- flag is best-effort, don't block the hook
 }
 
 // 2. Emit the ponytail ruleset, filtered to the active intensity level.
-//    A short summary is too weak — models drift back to over-building
+let output = getPonytailInstructions(mode);
-//    mid-conversation, especially after context compression prunes it.
-//    Full rules with examples anchor behavior much more reliably.
-//
-//    Reads SKILL.md at runtime so edits to the source of truth propagate
-//    automatically — no hardcoded duplication to go stale.
-
-// Modes that have their own independent skill files — not intensity levels.
-// For these, emit a short activation line; the skill itself handles behavior.
-const INDEPENDENT_MODES = new Set(['review']);
-
-if (INDEPENDENT_MODES.has(mode)) {
-  process.stdout.write('PONYTAIL MODE ACTIVE — level: ' + mode + '. Behavior defined by /ponytail-' + mode + ' skill.');
-  process.exit(0);
-}
-
-// Read SKILL.md — the single source of truth for ponytail behavior.
-// Plugin installs: __dirname = <plugin_root>/hooks/, SKILL.md at <plugin_root>/skills/ponytail/SKILL.md
-let skillContent = '';
-try {
-  skillContent = fs.readFileSync(
-    path.join(__dirname, '..', 'skills', 'ponytail', 'SKILL.md'), 'utf8'
-  );
-} catch (e) { /* standalone install — will use fallback below */ }
-
-let output;
-
-if (skillContent) {
-  // Strip YAML frontmatter
-  const body = skillContent.replace(/^---[\s\S]*?---\s*/, '');
-
-  // Filter intensity table: keep header rows + only the active level's row
-  const filtered = body.split('\n').reduce((acc, line) => {
-    // Intensity table rows start with | **level** |
-    const tableRowMatch = line.match(/^\|\s*\*\*(\S+?)\*\*\s*\|/);
-    if (tableRowMatch) {
-      if (tableRowMatch[1] === mode) {
-        acc.push(line);
-      }
-      return acc;
-    }
-
-    // Example lines start with "- level:" — keep only lines matching active level
-    const exampleMatch = line.match(/^- (\S+?):\s/);
-    if (exampleMatch) {
-      if (exampleMatch[1] === mode) {
-        acc.push(line);
-      }
-      return acc;
-    }
-
-    acc.push(line);
-    return acc;
-  }, []);
-
-  output = 'PONYTAIL MODE ACTIVE — level: ' + mode + '\n\n' + filtered.join('\n');
-} else {
-  // Fallback when SKILL.md is not found (hook installed without skills dir).
-  // Minimum viable ruleset — better than nothing.
-  output =
-    'PONYTAIL MODE ACTIVE — level: ' + mode + '\n\n' +
-    'You are a lazy senior developer. Lazy means efficient, not careless. The best code is the code never written.\n\n' +
-    '## Persistence\n\n' +
-    'ACTIVE EVERY RESPONSE. No drift back to over-building. Still active if unsure. Off only: "stop ponytail" / "normal mode".\n\n' +
-    'Current level: **' + mode + '**. Switch: `/ponytail lite|full|ultra`.\n\n' +
-    '## The ladder\n\n' +
-    'Before any code, stop at the first rung that holds:\n' +
-    '1. Does this need to be built at all? (YAGNI)\n' +
-    '2. Does the standard library do this? Use it.\n' +
-    '3. Does a native platform feature cover it? Use it.\n' +
-    '4. Does an already-installed dependency solve it? Use it.\n' +
-    '5. Can this be one line? Make it one line.\n' +
-    '6. Only then: write the minimum code that works.\n\n' +
-    '## Rules\n\n' +
-    'No abstractions that were not requested. No avoidable dependencies. No boilerplate nobody asked for. ' +
-    'Deletion over addition. Boring over clever. Fewest files possible. ' +
-    'Ship the lazy version and question the complex request in the same response — never stall. ' +
-    'Between two same-size stdlib options, pick the one correct on edge cases. ' +
-    'Mark intentional simplifications with a `ponytail:` comment — a shortcut with a known ceiling names the ceiling and the upgrade path in the comment.\n\n' +
-    '## Output\n\n' +
-    'Code first. Then at most three short lines: what was skipped, when to add it. ' +
-    'If the explanation is longer than the code, delete the explanation.\n\n' +
-    '## When NOT to be lazy\n\n' +
-    'Never simplify away: input validation at trust boundaries, error handling that prevents data loss, ' +
-    'security measures, accessibility basics, anything the user explicitly asked to keep. ' +
-    'Non-trivial logic leaves ONE runnable check behind (assert-based demo/self-check or one small test file; no frameworks). Trivial one-liners need no test.\n\n' +
-    '## Boundaries\n\n' +
-    'Ponytail governs what you build, not how you talk. "stop ponytail" or "normal mode": revert. Level persists until changed or session end.';
-}
 
 // 3. Detect missing statusline config — nudge Claude to help set it up
-try {
+if (!isCodex) try {
   let hasStatusline = false;
   if (fs.existsSync(settingsPath)) {
     const settings = JSON.parse(fs.readFileSync(settingsPath, 'utf8'));
@@ -153,4 +70,4 @@ try {
   // Silent fail — don't block session start over statusline detection
 }
 
-process.stdout.write(output);
+writeHookOutput('SessionStart', mode, output);

hooks/ponytail-config.js

@@ -13,7 +13,25 @@ const fs = require('fs');
 const path = require('path');
 const os = require('os');
 
+const DEFAULT_MODE = 'full';
 const VALID_MODES = ['off', 'lite', 'full', 'ultra', 'review'];
+const RUNTIME_MODES = ['off', 'lite', 'full', 'ultra'];
+
+function normalizeMode(mode) {
+  if (typeof mode !== 'string') return null;
+  const normalized = mode.trim().toLowerCase();
+  return RUNTIME_MODES.includes(normalized) ? normalized : null;
+}
+
+function normalizeConfigMode(mode) {
+  if (typeof mode !== 'string') return null;
+  const normalized = mode.trim().toLowerCase();
+  return VALID_MODES.includes(normalized) ? normalized : null;
+}
+
+function normalizePersistedMode(mode) {
+  return normalizeMode(mode) || normalizeConfigMode(mode);
+}
 
 function getConfigDir() {
   if (process.env.XDG_CONFIG_HOME) {
@@ -51,7 +69,28 @@ function getDefaultMode() {
   }
 
   // 3. Default
-  return 'full';
+  return DEFAULT_MODE;
 }
 
-module.exports = { getDefaultMode, getConfigDir, getConfigPath, VALID_MODES };
+function writeDefaultMode(mode) {
+  const normalized = normalizeConfigMode(mode);
+  if (!normalized) return null;
+
+  const configPath = getConfigPath();
+  fs.mkdirSync(path.dirname(configPath), { recursive: true });
+  fs.writeFileSync(configPath, JSON.stringify({ defaultMode: normalized }, null, 2), 'utf8');
+  return normalized;
+}
+
+module.exports = {
+  DEFAULT_MODE,
+  VALID_MODES,
+  RUNTIME_MODES,
+  getDefaultMode,
+  getConfigDir,
+  getConfigPath,
+  normalizeMode,
+  normalizeConfigMode,
+  normalizePersistedMode,
+  writeDefaultMode,
+};

hooks/ponytail-instructions.js

@@ -0,0 +1,81 @@
+#!/usr/bin/env node
+// Shared Ponytail instruction builder for Claude hooks and Pi extension.
+
+const fs = require('fs');
+const path = require('path');
+const { DEFAULT_MODE, normalizeMode, normalizePersistedMode } = require('./ponytail-config');
+
+const INDEPENDENT_MODES = new Set(['review']);
+const SKILL_PATH = path.join(__dirname, '..', 'skills', 'ponytail', 'SKILL.md');
+
+function filterSkillBodyForMode(body, mode) {
+  const effectiveMode = normalizeMode(mode) || DEFAULT_MODE;
+  const withoutFrontmatter = String(body || '').replace(/^---[\s\S]*?---\s*/, '');
+
+  return withoutFrontmatter
+    .split(/\r?\n/)
+    .filter((line) => {
+      const tableMatch = line.match(/^\|\s*\*\*(.+?)\*\*\s*\|/);
+      if (tableMatch) return tableMatch[1].trim() === effectiveMode;
+
+      const exampleMatch = line.match(/^-\s*([^:]+):\s*/);
+      if (exampleMatch) return exampleMatch[1].trim() === effectiveMode;
+
+      return true;
+    })
+    .join('\n');
+}
+
+function getFallbackInstructions(mode) {
+  return 'PONYTAIL MODE ACTIVE — level: ' + mode + '\n\n' +
+    'You are a lazy senior developer. Lazy means efficient, not careless. The best code is the code never written.\n\n' +
+    '## Persistence\n\n' +
+    'ACTIVE EVERY RESPONSE. No drift back to over-building. Still active if unsure. Off only: "stop ponytail" / "normal mode".\n\n' +
+    'Current level: **' + mode + '**. Switch: `/ponytail lite|full|ultra`.\n\n' +
+    '## The ladder\n\n' +
+    'Before any code, stop at the first rung that holds:\n' +
+    '1. Does this need to be built at all? (YAGNI)\n' +
+    '2. Does the standard library do this? Use it.\n' +
+    '3. Does a native platform feature cover it? Use it.\n' +
+    '4. Does an already-installed dependency solve it? Use it.\n' +
+    '5. Can this be one line? Make it one line.\n' +
+    '6. Only then: write the minimum code that works.\n\n' +
+    '## Rules\n\n' +
+    'No abstractions that were not requested. No avoidable dependencies. No boilerplate nobody asked for. ' +
+    'Deletion over addition. Boring over clever. Fewest files possible. ' +
+    'Ship the lazy version and question the complex request in the same response — never stall. ' +
+    'Between two same-size stdlib options, pick the one correct on edge cases. ' +
+    'Mark intentional simplifications with a `ponytail:` comment — a shortcut with a known ceiling names the ceiling and the upgrade path in the comment.\n\n' +
+    '## Output\n\n' +
+    'Code first. Then at most three short lines: what was skipped, when to add it. ' +
+    'If the explanation is longer than the code, delete the explanation.\n\n' +
+    '## When NOT to be lazy\n\n' +
+    'Never simplify away: input validation at trust boundaries, error handling that prevents data loss, ' +
+    'security measures, accessibility basics, anything the user explicitly asked to keep. ' +
+    'Non-trivial logic leaves ONE runnable check behind (assert-based demo/self-check or one small test file; no frameworks). Trivial one-liners need no test.\n\n' +
+    '## Boundaries\n\n' +
+    'Ponytail governs what you build, not how you talk. "stop ponytail" or "normal mode": revert. Level persists until changed or session end.';
+}
+
+function getPonytailInstructions(mode) {
+  const configuredMode = normalizePersistedMode(mode) || DEFAULT_MODE;
+
+  if (INDEPENDENT_MODES.has(configuredMode)) {
+    return 'PONYTAIL MODE ACTIVE — level: ' + configuredMode + '. Behavior defined by /ponytail-' + configuredMode + ' skill.';
+  }
+
+  const effectiveMode = normalizeMode(configuredMode) || DEFAULT_MODE;
+
+  try {
+    return 'PONYTAIL MODE ACTIVE — level: ' + effectiveMode + '\n\n' +
+      filterSkillBodyForMode(fs.readFileSync(SKILL_PATH, 'utf8'), effectiveMode);
+  } catch (e) {
+    return getFallbackInstructions(effectiveMode);
+  }
+}
+
+module.exports = {
+  filterSkillBodyForMode,
+  getFallbackInstructions,
+  getPonytailInstructions,
+};

hooks/ponytail-mode-tracker.js

@@ -2,12 +2,8 @@
 // ponytail — UserPromptSubmit hook to track which ponytail mode is active
 // Inspects user input for /ponytail commands and writes mode to flag file
 
-const fs = require('fs');
-const path = require('path');
-const os = require('os');
 const { getDefaultMode } = require('./ponytail-config');
-
+const { clearMode, setMode, writeHookOutput } = require('./ponytail-runtime');
-const flagPath = path.join(os.homedir(), '.claude', '.ponytail-active');
 
 let input = '';
 process.stdin.on('data', chunk => { input += chunk; });
@@ -18,9 +14,9 @@ process.stdin.on('end', () => {
     const prompt = (data.prompt || '').trim().toLowerCase();
 
     // Match /ponytail commands
-    if (prompt.startsWith('/ponytail')) {
+    if (/^[/@$]ponytail/.test(prompt)) {
       const parts = prompt.split(/\s+/);
-      const cmd = parts[0]; // /ponytail, /ponytail-review, /ponytail:ponytail, etc.
+      const cmd = parts[0].replace(/^[@$]/, '/');
       const arg = parts[1] || '';
 
       let mode = null;
@@ -36,16 +32,22 @@ process.stdin.on('end', () => {
       }
 
       if (mode && mode !== 'off') {
-        fs.mkdirSync(path.dirname(flagPath), { recursive: true });
+        setMode(mode);
-        fs.writeFileSync(flagPath, mode);
+        writeHookOutput(
+          'UserPromptSubmit',
+          mode,
+          'PONYTAIL MODE CHANGED — level: ' + mode,
+        );
       } else if (mode === 'off') {
-        try { fs.unlinkSync(flagPath); } catch (e) {}
+        clearMode();
+        writeHookOutput('UserPromptSubmit', 'off', 'PONYTAIL MODE OFF');
       }
     }
 
     // Detect deactivation
     if (/\b(stop ponytail|normal mode)\b/i.test(prompt)) {
-      try { fs.unlinkSync(flagPath); } catch (e) {}
+      clearMode();
+      writeHookOutput('UserPromptSubmit', 'off', 'PONYTAIL MODE OFF');
     }
   } catch (e) {
     // Silent fail

hooks/ponytail-runtime.js

@@ -0,0 +1,39 @@
+const fs = require('fs');
+const path = require('path');
+const os = require('os');
+
+const isCodex = Boolean(process.env.PLUGIN_DATA);
+const statePath = isCodex
+  ? path.join(process.env.PLUGIN_DATA, '.ponytail-active')
+  : path.join(os.homedir(), '.claude', '.ponytail-active');
+
+function setMode(mode) {
+  fs.mkdirSync(path.dirname(statePath), { recursive: true });
+  fs.writeFileSync(statePath, mode);
+}
+
+function clearMode() {
+  try { fs.unlinkSync(statePath); } catch (e) {}
+}
+
+function writeHookOutput(event, mode, context = '') {
+  if (!isCodex) {
+    process.stdout.write(context);
+    return;
+  }
+  const output = { systemMessage: `PONYTAIL:${mode.toUpperCase()}` };
+  if (context) {
+    output.hookSpecificOutput = {
+      hookEventName: event,
+      additionalContext: context,
+    };
+  }
+  process.stdout.write(JSON.stringify(output));
+}
+
+module.exports = {
+  clearMode,
+  isCodex,
+  setMode,
+  writeHookOutput,
+};

package.json

@@ -0,0 +1,11 @@
+{
+  "name": "ponytail",
+  "version": "0.1.0",
+  "description": "Lazy senior dev mode for AI agents. The best code is the code you never wrote.",
+  "keywords": ["pi-package", "pi", "skills", "ponytail"],
+  "license": "MIT",
+  "pi": {
+    "extensions": ["./pi-extension/index.js"],
+    "skills": ["./skills"]
+  }
+}

pi-extension/index.js

@@ -0,0 +1,141 @@
+import { createRequire } from "node:module";
+
+const require = createRequire(import.meta.url);
+const {
+  DEFAULT_MODE,
+  getDefaultMode,
+  normalizeMode,
+  normalizeConfigMode,
+  normalizePersistedMode,
+  writeDefaultMode,
+} = require("../hooks/ponytail-config.js");
+const { getPonytailInstructions, filterSkillBodyForMode } = require("../hooks/ponytail-instructions.js");
+
+export { filterSkillBodyForMode };
+export const readDefaultMode = getDefaultMode;
+
+export function resolveSessionMode(entries, fallbackMode = DEFAULT_MODE) {
+  const fallback = normalizePersistedMode(fallbackMode) || DEFAULT_MODE;
+  if (!Array.isArray(entries)) return fallback;
+
+  for (let i = entries.length - 1; i >= 0; i -= 1) {
+    const entry = entries[i];
+    if (entry?.type !== "custom" || entry?.customType !== "ponytail-mode") continue;
+
+    const mode = normalizePersistedMode(entry?.data?.mode);
+    if (mode) return mode;
+  }
+
+  return fallback;
+}
+
+export function parsePonytailCommand(text, defaultMode = DEFAULT_MODE) {
+  const fallback = normalizePersistedMode(defaultMode) || DEFAULT_MODE;
+  const normalizedText = String(text || "").trim().toLowerCase();
+
+  if (!normalizedText) {
+    return { type: "set-mode", mode: fallback === "off" ? "full" : fallback };
+  }
+
+  const [primary, secondary] = normalizedText.split(/\s+/);
+
+  if (primary === "status") return { type: "status" };
+
+  if (primary === "default") {
+    const mode = normalizeConfigMode(secondary);
+    return mode ? { type: "set-default", mode } : { type: "invalid", reason: "invalid-default-mode" };
+  }
+
+  const mode = normalizeMode(primary);
+  return mode ? { type: "set-mode", mode } : { type: "invalid", reason: "invalid-mode", mode: primary };
+}
+
+export { writeDefaultMode };
+
+export default function ponytailExtension(pi) {
+  let currentMode = DEFAULT_MODE;
+  let configuredDefaultMode = getDefaultMode();
+
+  const setMode = (mode, ctx) => {
+    const normalized = normalizePersistedMode(mode);
+    if (!normalized) return;
+
+    currentMode = normalized;
+    pi.appendEntry("ponytail-mode", { mode: normalized });
+    ctx?.ui?.notify?.(`Ponytail mode set to ${normalized}.`, "info");
+  };
+
+  const sendAlias = (skillName, args, ctx) => {
+    const normalized = String(args || "").trim();
+    const message = normalized ? `${skillName} ${normalized}` : skillName;
+
+    if (ctx?.isIdle?.() === false) {
+      pi.sendUserMessage(message, { deliverAs: "followUp" });
+      ctx?.ui?.notify?.(`${skillName} queued as follow-up.`, "info");
+      return;
+    }
+
+    pi.sendUserMessage(message);
+  };
+
+  pi.registerCommand("ponytail", {
+    description: "Set or report Ponytail mode",
+    handler: async (args, ctx) => {
+      const parsed = parsePonytailCommand(args, configuredDefaultMode);
+
+      if (parsed.type === "status") {
+        ctx?.ui?.notify?.(`Ponytail: current ${currentMode} • default ${configuredDefaultMode}`, "info");
+        return;
+      }
+
+      if (parsed.type === "set-default") {
+        const written = writeDefaultMode(parsed.mode);
+        if (written) {
+          configuredDefaultMode = getDefaultMode();
+          const message = configuredDefaultMode === written
+            ? `Default Ponytail mode set to ${written}.`
+            : `Saved default ${written}, but env override keeps default at ${configuredDefaultMode}.`;
+          ctx?.ui?.notify?.(message, "info");
+        }
+        return;
+      }
+
+      if (parsed.type === "set-mode") {
+        setMode(parsed.mode, ctx);
+        return;
+      }
+
+      ctx?.ui?.notify?.("Unknown or unsupported /ponytail mode.", "warning");
+    },
+  });
+
+  pi.registerCommand("ponytail-review", {
+    description: "Run /skill:ponytail-review",
+    handler: (_args, ctx) => sendAlias("/skill:ponytail-review", "", ctx),
+  });
+
+  pi.registerCommand("ponytail-help", {
+    description: "Run /skill:ponytail-help",
+    handler: (_args, ctx) => sendAlias("/skill:ponytail-help", "", ctx),
+  });
+
+  pi.on("input", async (event) => {
+    if (event?.source === "extension") return;
+
+    const text = String(event?.text || "");
+    if (currentMode !== "off" && /\b(stop ponytail|normal mode)\b/i.test(text)) {
+      setMode("off");
+    }
+  });
+
+  pi.on("session_start", async (_event, ctx) => {
+    const entries = ctx?.sessionManager?.getBranch?.() || ctx?.sessionManager?.getEntries?.() || [];
+    configuredDefaultMode = getDefaultMode();
+    currentMode = resolveSessionMode(entries, configuredDefaultMode);
+  });
+
+  pi.on("before_agent_start", async (event) => {
+    if (!currentMode || currentMode === "off") return;
+    return { systemPrompt: `${event.systemPrompt}\n\n${getPonytailInstructions(currentMode)}` };
+  });
+}

pi-extension/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "ponytail-pi-extension-dev",
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "test": "node --test ./test/*.test.js"
+  }
+}

pi-extension/test/extension.test.js

@@ -0,0 +1,119 @@
+import assert from "node:assert/strict";
+import { mkdtempSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import test from "node:test";
+
+import ponytailExtension from "../index.js";
+
+function createPiHarness() {
+  const events = new Map();
+  const commands = new Map();
+  const appendedEntries = [];
+  const sentUserMessages = [];
+
+  const pi = {
+    on(eventName, handler) {
+      events.set(eventName, handler);
+    },
+    registerCommand(name, options) {
+      commands.set(name, options);
+    },
+    appendEntry(customType, data) {
+      appendedEntries.push({ customType, data });
+    },
+    sendUserMessage(text, options) {
+      sentUserMessages.push({ text, options });
+    },
+  };
+
+  ponytailExtension(pi);
+  return { events, commands, appendedEntries, sentUserMessages };
+}
+
+function createCommandContext(overrides = {}) {
+  return {
+    isIdle: () => true,
+    sessionManager: { getEntries: () => [] },
+    ui: { notify() {} },
+    ...overrides,
+  };
+}
+
+function withTempConfig(fn) {
+  const tempConfigHome = mkdtempSync(join(tmpdir(), "ponytail-test-"));
+  const previousXdg = process.env.XDG_CONFIG_HOME;
+  process.env.XDG_CONFIG_HOME = tempConfigHome;
+
+  return Promise.resolve()
+    .then(fn)
+    .finally(() => {
+      if (previousXdg === undefined) delete process.env.XDG_CONFIG_HOME;
+      else process.env.XDG_CONFIG_HOME = previousXdg;
+      rmSync(tempConfigHome, { recursive: true, force: true });
+    });
+}
+
+test("extension registers Ponytail commands", () => {
+  const { commands } = createPiHarness();
+
+  assert.deepEqual([...commands.keys()].sort(), ["ponytail", "ponytail-help", "ponytail-review"]);
+});
+
+test("/ponytail updates session mode and injects instructions", async () => withTempConfig(async () => {
+  const { commands, events, appendedEntries } = createPiHarness();
+  const ctx = createCommandContext();
+
+  await events.get("session_start")({ reason: "startup" }, ctx);
+  await commands.get("ponytail").handler("ultra", ctx);
+
+  assert.deepEqual(appendedEntries.at(-1), {
+    customType: "ponytail-mode",
+    data: { mode: "ultra" },
+  });
+
+  const result = await events.get("before_agent_start")({ systemPrompt: "BASE" }, ctx);
+  assert.ok(result.systemPrompt.includes("PONYTAIL MODE ACTIVE"));
+  assert.ok(result.systemPrompt.includes("ultra"));
+}));
+
+test("session_start restores latest persisted mode", async () => withTempConfig(async () => {
+  const { events } = createPiHarness();
+  const ctx = createCommandContext({
+    sessionManager: {
+      getEntries: () => [
+        { type: "custom", customType: "ponytail-mode", data: { mode: "lite" } },
+      ],
+    },
+  });
+
+  await events.get("session_start")({ reason: "resume" }, ctx);
+  const result = await events.get("before_agent_start")({ systemPrompt: "BASE" }, ctx);
+
+  assert.ok(result.systemPrompt.includes("lite"));
+}));
+
+test("skill alias commands delegate to Pi skill commands", async () => {
+  const { commands, sentUserMessages } = createPiHarness();
+  const ctx = createCommandContext();
+
+  await commands.get("ponytail-review").handler("", ctx);
+  await commands.get("ponytail-help").handler("", ctx);
+
+  assert.deepEqual(sentUserMessages.map((entry) => entry.text), [
+    "/skill:ponytail-review",
+    "/skill:ponytail-help",
+  ]);
+});
+
+test("normal mode disables persistent instructions", async () => withTempConfig(async () => {
+  const { commands, events } = createPiHarness();
+  const ctx = createCommandContext();
+
+  await events.get("session_start")({ reason: "startup" }, ctx);
+  await commands.get("ponytail").handler("ultra", ctx);
+  await events.get("input")({ text: "normal mode", source: "interactive" }, ctx);
+
+  const disabled = await events.get("before_agent_start")({ systemPrompt: "BASE" }, ctx);
+  assert.equal(disabled, undefined);
+}));

pi-extension/test/helpers.test.js

@@ -0,0 +1,68 @@
+import assert from "node:assert/strict";
+import { existsSync, mkdtempSync, readFileSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import test from "node:test";
+
+import {
+  filterSkillBodyForMode,
+  parsePonytailCommand,
+  readDefaultMode,
+  resolveSessionMode,
+  writeDefaultMode,
+} from "../index.js";
+
+test("parsePonytailCommand falls back to full when invoked bare and default is off", () => {
+  assert.deepEqual(parsePonytailCommand("", "off"), { type: "set-mode", mode: "full" });
+});
+
+test("parsePonytailCommand parses modes, status, and default subcommand", () => {
+  assert.deepEqual(parsePonytailCommand("ultra", "full"), { type: "set-mode", mode: "ultra" });
+  assert.deepEqual(parsePonytailCommand("status", "full"), { type: "status" });
+  assert.deepEqual(parsePonytailCommand("default lite", "full"), { type: "set-default", mode: "lite" });
+});
+
+test("resolveSessionMode prefers latest persisted session mode", () => {
+  const entries = [
+    { type: "custom", customType: "ponytail-mode", data: { mode: "lite" } },
+    { type: "custom", customType: "ponytail-mode", data: { mode: "ultra" } },
+  ];
+
+  assert.equal(resolveSessionMode(entries, "full"), "ultra");
+});
+
+test("readDefaultMode and writeDefaultMode use XDG config path", () => {
+  const tempDir = mkdtempSync(join(tmpdir(), "ponytail-config-"));
+  const previousXdg = process.env.XDG_CONFIG_HOME;
+  const previousDefault = process.env.PONYTAIL_DEFAULT_MODE;
+  const configPath = join(tempDir, "ponytail", "config.json");
+  process.env.XDG_CONFIG_HOME = tempDir;
+  delete process.env.PONYTAIL_DEFAULT_MODE;
+
+  try {
+    assert.equal(readDefaultMode(), "full");
+    assert.equal(writeDefaultMode("ultra"), "ultra");
+    assert.equal(readDefaultMode(), "ultra");
+    assert.ok(existsSync(configPath));
+    assert.deepEqual(JSON.parse(readFileSync(configPath, "utf8")), { defaultMode: "ultra" });
+  } finally {
+    if (previousXdg === undefined) delete process.env.XDG_CONFIG_HOME;
+    else process.env.XDG_CONFIG_HOME = previousXdg;
+    if (previousDefault === undefined) delete process.env.PONYTAIL_DEFAULT_MODE;
+    else process.env.PONYTAIL_DEFAULT_MODE = previousDefault;
+    rmSync(tempDir, { recursive: true, force: true });
+  }
+});
+
+test("filterSkillBodyForMode keeps only requested intensity examples and rows", () => {
+  const body = `---\nname: ponytail\n---\n| **lite** | keep lite |\n| **full** | keep full |\n| **ultra** | keep ultra |\n- lite: Lite example\n- full: Full example\n- ultra: Ultra example\nOther line`;
+
+  const filtered = filterSkillBodyForMode(body, "ultra");
+
+  assert.ok(!filtered.includes("keep lite"));
+  assert.ok(!filtered.includes("keep full"));
+  assert.ok(filtered.includes("keep ultra"));
+  assert.ok(!filtered.includes("Lite example"));
+  assert.ok(filtered.includes("Ultra example"));
+  assert.ok(filtered.includes("Other line"));
+});

scripts/check-rule-copies.js

@@ -0,0 +1,65 @@
+#!/usr/bin/env node
+const fs = require('fs');
+const path = require('path');
+
+const root = path.join(__dirname, '..');
+
+function read(relPath) {
+  return fs.readFileSync(path.join(root, relPath), 'utf8').replace(/\r\n/g, '\n').trim();
+}
+
+function stripFrontmatter(text) {
+  return text.replace(/^---\n[\s\S]*?\n---\n*/, '').trim();
+}
+
+const agents = read('AGENTS.md');
+const canonical = agents.replace(/\n\n\(Yes, this file also applies[\s\S]*?\)$/, '').trim();
+
+// Compact copies: same body as AGENTS.md, host-specific frontmatter stripped.
+const copies = [
+  ['.cursor/rules/ponytail.mdc', stripFrontmatter],
+  ['.windsurf/rules/ponytail.md', text => text.trim()],
+  ['.clinerules/ponytail.md', text => text.trim()],
+  ['.github/copilot-instructions.md', text => text.trim()],
+  ['.kiro/steering/ponytail.md', stripFrontmatter],
+];
+
+let failed = false;
+
+for (const [relPath, normalize] of copies) {
+  const actual = normalize(read(relPath));
+  if (actual !== canonical) {
+    console.error(`${relPath} drifted from AGENTS.md`);
+    failed = true;
+  }
+}
+
+// SKILL.md is the runtime source of truth and is longer than the compact body,
+// so it cannot be byte-compared. ponytail: canary, not full equality. Assert the
+// load-bearing rules survive verbatim in both the source and AGENTS.md. Changing
+// a rule's wording trips this, which is the reminder to propagate it everywhere.
+// Upgrade path: generate the copies from SKILL.md if this ever misses a real drift.
+const INVARIANTS = [
+  'naive heuristic',                       // ceiling-comment rule
+  'ONE runnable check',                    // test reflex
+  'flimsier algorithm',                    // robust-variant rule
+  'input validation at trust boundaries',  // the "not lazy about" clause
+];
+
+const skill = read('skills/ponytail/SKILL.md');
+const sources = [['skills/ponytail/SKILL.md', skill], ['AGENTS.md', agents]];
+for (const phrase of INVARIANTS) {
+  for (const [label, text] of sources) {
+    if (!text.includes(phrase)) {
+      console.error(`${label} is missing rule invariant: "${phrase}"`);
+      failed = true;
+    }
+  }
+}
+
+if (failed) {
+  console.error('Update the copied rule text, AGENTS.md, or SKILL.md so the shared rules match.');
+  process.exit(1);
+}
+
+console.log(`Rule copies match AGENTS.md; ${INVARIANTS.length} rule invariants present in SKILL.md and AGENTS.md.`);

skills/ponytail-help/SKILL.md

@@ -29,6 +29,9 @@ Level sticks until changed or session end.
 | **ponytail-review** | `/ponytail-review` | Over-engineering review: `L42: yagni: factory, one product. Inline.` |
 | **ponytail-help** | `/ponytail-help` | This card. |
 
+Codex uses `@ponytail`, `@ponytail-review`, and `@ponytail-help`; Claude Code
+uses the slash-command forms above.
+
 ## Deactivate
 
 Say "stop ponytail" or "normal mode". Resume anytime with `/ponytail`.

tests/hooks.test.js

@@ -0,0 +1,78 @@
+#!/usr/bin/env node
+
+const assert = require('assert');
+const fs = require('fs');
+const os = require('os');
+const path = require('path');
+const { spawnSync } = require('child_process');
+
+const root = path.join(__dirname, '..');
+
+function run(script, env, input = '') {
+  return spawnSync(process.execPath, [path.join(root, 'hooks', script)], {
+    env: { ...process.env, ...env },
+    input,
+    encoding: 'utf8',
+  });
+}
+
+const temp = fs.mkdtempSync(path.join(os.tmpdir(), 'ponytail-hooks-'));
+const home = path.join(temp, 'home');
+const pluginData = path.join(temp, 'plugin-data');
+fs.mkdirSync(home, { recursive: true });
+
+// USERPROFILE alongside HOME: os.homedir() reads USERPROFILE on Windows, HOME on POSIX.
+const codexEnv = {
+  HOME: home,
+  USERPROFILE: home,
+  PLUGIN_DATA: pluginData,
+  PONYTAIL_DEFAULT_MODE: 'ultra',
+};
+const codexState = path.join(pluginData, '.ponytail-active');
+
+let result = run('ponytail-activate.js', codexEnv);
+assert.equal(result.status, 0, result.stderr);
+assert.equal(fs.readFileSync(codexState, 'utf8'), 'ultra');
+let output = JSON.parse(result.stdout);
+assert.equal(output.systemMessage, 'PONYTAIL:ULTRA');
+assert.match(
+  output.hookSpecificOutput.additionalContext,
+  /PONYTAIL MODE ACTIVE — level: ultra/,
+);
+
+result = run(
+  'ponytail-mode-tracker.js',
+  codexEnv,
+  JSON.stringify({ prompt: '@ponytail lite' }),
+);
+assert.equal(result.status, 0, result.stderr);
+assert.equal(fs.readFileSync(codexState, 'utf8'), 'lite');
+output = JSON.parse(result.stdout);
+assert.equal(output.systemMessage, 'PONYTAIL:LITE');
+
+result = run(
+  'ponytail-mode-tracker.js',
+  codexEnv,
+  JSON.stringify({ prompt: 'normal mode' }),
+);
+assert.equal(result.status, 0, result.stderr);
+assert.equal(fs.existsSync(codexState), false);
+output = JSON.parse(result.stdout);
+assert.equal(output.systemMessage, 'PONYTAIL:OFF');
+
+const claudeEnv = {
+  HOME: home,
+  USERPROFILE: home,
+  PONYTAIL_DEFAULT_MODE: 'full',
+};
+delete claudeEnv.PLUGIN_DATA;
+
+result = run('ponytail-activate.js', claudeEnv);
+assert.equal(result.status, 0, result.stderr);
+assert.equal(
+  fs.readFileSync(path.join(home, '.claude', '.ponytail-active'), 'utf8'),
+  'full',
+);
+
+fs.rmSync(temp, { recursive: true, force: true });
+console.log('hook compatibility checks passed');