Adding support for Copilot Marketplace plugin (#47)

* Add GitHub Copilot plugin and marketplace manifests for Ponytail

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Add Copilot hook adapters and plugin data runtime precedence

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Document Copilot plugin install flow and instruction fallback mode

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Fix Copilot hooks for native output context and state-only mode tracking

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* docs: add Copilot CLI namespaced command examples

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Collapse Copilot hooks into shared activate/mode-tracker

The Copilot hook files duplicated ponytail-activate.js and
ponytail-mode-tracker.js, differing only in output shape. Move that
difference into writeHookOutput (isCopilot branch) and point
copilot-hooks.json at the shared hooks. Deletes both forks (-73 lines).

Refs #1

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* Align Copilot manifest version to 4.4.0 with cross-manifest parity test

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Make Copilot and Codex host detection exclusive in runtime output routing

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Add Copilot debt command validation with a pull request acceptance checklist

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Removed PR template

* Drop tautological copilot command-form test

The namespaced-form assertion built '/ponytail:ponytail-debt' from two
constants and compared it to itself — it tests string concatenation, not
wiring. The file-exists check above already catches a renamed manifest.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

.github/plugin/marketplace.json

@@ -0,0 +1,20 @@
+{
+  "name": "ponytail",
+  "description": "Lazy senior dev mode for AI agents. The best code is the code you never wrote.",
+  "owner": {
+    "name": "Dietrich Gebert",
+    "url": "https://github.com/DietrichGebert"
+  },
+  "plugins": [
+    {
+      "name": "ponytail",
+      "description": "Forces the laziest solution that works. YAGNI, stdlib first, one line over fifty.",
+      "source": "./",
+      "category": "productivity",
+      "tags": ["yagni", "minimalism", "code-review", "productivity"],
+      "commands": "commands/",
+      "skills": "skills/",
+      "hooks": "hooks/copilot-hooks.json"
+    }
+  ]
+}

.github/plugin/plugin.json

@@ -0,0 +1,16 @@
+{
+  "name": "ponytail",
+  "description": "Lazy senior dev mode. Forces the simplest, shortest solution that actually works: YAGNI, stdlib first, no unrequested abstractions.",
+  "version": "4.4.0",
+  "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"],
+  "commands": "commands/",
+  "skills": "skills/",
+  "hooks": "hooks/copilot-hooks.json"
+}

README.md

@@ -88,6 +88,27 @@ 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.
 
+### GitHub Copilot CLI
+
+```bash
+copilot plugin marketplace add DietrichGebert/ponytail
+copilot plugin install ponytail@ponytail
+```
+
+In an interactive Copilot CLI session, use the slash equivalents:
+
+```
+/plugin marketplace add DietrichGebert/ponytail
+/plugin install ponytail@ponytail
+```
+
+Copilot CLI namespaces plugin commands by plugin name. For example:
+
+```text
+/ponytail:ponytail ultra
+/ponytail:ponytail-review
+```
+
 ### Pi agent harness
 
 ```
@@ -116,11 +137,11 @@ That was it. He'd be proud. He won't say it.
 
 Active every session, with a handful of commands (see [Commands](#commands)). `/ponytail ultra` exists for when the codebase has wronged you personally. 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/)).
+Cursor, Windsurf, Cline, GitHub Copilot (editor), 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.
 
-GitHub Copilot CLI: it already reads `AGENTS.md` and `.github/copilot-instructions.md` in a project, or copy the rules into `~/.copilot/copilot-instructions.md` to run ponytail in every project.
+GitHub Copilot CLI fallback (instruction-only mode): it reads `AGENTS.md` and `.github/copilot-instructions.md` in a project, or copy the rules into `~/.copilot/copilot-instructions.md` to run ponytail in every project. This path keeps always-on guidance, but does not add plugin mode switches or hooks.
 
 Antigravity and VS Code with the Codex extension: both read `AGENTS.md`, which this repo ships, so it works from the repo root with no setup (`~/.codex/AGENTS.md` makes Codex global, `.agents/rules/` makes it an always-on rule in Antigravity).
 

docs/agent-portability.md

@@ -17,7 +17,7 @@ to load in a given agent.
 | Windsurf | `.windsurf/rules/ponytail.md` | Project rule. |
 | Cline | `.clinerules/ponytail.md` | Project rule. |
 | GitHub Copilot | `.github/copilot-instructions.md` | Repository instruction file. |
-| GitHub Copilot CLI | `AGENTS.md`, `.github/copilot-instructions.md`, `~/.copilot/copilot-instructions.md` | Reads custom instructions: per-project from `AGENTS.md` or `.github/copilot-instructions.md`, or globally from `~/.copilot/copilot-instructions.md`. Instruction-tier (no `/ponytail` levels or hooks). |
+| GitHub Copilot CLI | `.github/plugin/`, `AGENTS.md`, `.github/copilot-instructions.md`, `~/.copilot/copilot-instructions.md` | Plugin-supported (`copilot plugin marketplace add DietrichGebert/ponytail` + `copilot plugin install ponytail@ponytail`). Fallback instruction mode remains: per-project from `AGENTS.md` or `.github/copilot-instructions.md`, or globally from `~/.copilot/copilot-instructions.md` (instruction-tier, no `/ponytail` levels or hooks). |
 | Antigravity | `AGENTS.md` | Reads `AGENTS.md` at the repo root as always-on rules (like `.cursorrules`/`CLAUDE.md`); `.agents/rules/` also works for workspace rules. Instruction-tier. |
 | VS Code + Codex extension | `AGENTS.md` | The Codex extension reads `AGENTS.md` (repo root, or `~/.codex/AGENTS.md` globally). Instruction-tier; the full Codex plugin row above adds `/ponytail` levels and hooks. |
 | Kiro | `.kiro/steering/ponytail.md` | Steering rule; copy globally or into a project. |

hooks/copilot-hooks.json

@@ -0,0 +1,21 @@
+{
+  "version": 1,
+  "hooks": {
+    "sessionStart": [
+      {
+        "type": "command",
+        "bash": "node \"${PLUGIN_ROOT}/hooks/ponytail-activate.js\"",
+        "powershell": "node \"${PLUGIN_ROOT}\\hooks\\ponytail-activate.js\"",
+        "timeoutSec": 5
+      }
+    ],
+    "userPromptSubmitted": [
+      {
+        "type": "command",
+        "bash": "node \"${PLUGIN_ROOT}/hooks/ponytail-mode-tracker.js\"",
+        "powershell": "node \"${PLUGIN_ROOT}\\hooks\\ponytail-mode-tracker.js\"",
+        "timeoutSec": 5
+      }
+    ]
+  }
+}

hooks/ponytail-runtime.js

@@ -2,10 +2,15 @@ const fs = require('fs');
 const path = require('path');
 const { getClaudeDir } = require('./ponytail-config');
 
-const isCodex = Boolean(process.env.PLUGIN_DATA);
+const STATE_FILE = '.ponytail-active';
-const statePath = isCodex
+const isCopilot = Boolean(process.env.COPILOT_PLUGIN_DATA);
-  ? path.join(process.env.PLUGIN_DATA, '.ponytail-active')
+const isCodex = !isCopilot && Boolean(process.env.PLUGIN_DATA);
-  : path.join(getClaudeDir(), '.ponytail-active');
+
+let stateDir = getClaudeDir();
+if (isCodex) stateDir = process.env.PLUGIN_DATA;
+if (isCopilot) stateDir = process.env.COPILOT_PLUGIN_DATA;
+
+const statePath = path.join(stateDir, STATE_FILE);
 
 function setMode(mode) {
   fs.mkdirSync(path.dirname(statePath), { recursive: true });
@@ -17,10 +22,13 @@ function clearMode() {
 }
 
 function writeHookOutput(event, mode, context = '') {
-  if (!isCodex) {
+  if (isCopilot) {
-    process.stdout.write(context);
+    // Copilot reads additionalContext on SessionStart; ignores output elsewhere.
+    process.stdout.write(JSON.stringify(
+      event === 'SessionStart' && context ? { additionalContext: context } : {}));
     return;
   }
+  if (isCodex) {
     const output = { systemMessage: `PONYTAIL:${mode.toUpperCase()}` };
     if (context) {
       output.hookSpecificOutput = {
@@ -29,11 +37,15 @@ function writeHookOutput(event, mode, context = '') {
       };
     }
     process.stdout.write(JSON.stringify(output));
+    return;
+  }
+  process.stdout.write(context);
 }
 
 module.exports = {
   clearMode,
   isCodex,
+  isCopilot,
   setMode,
   writeHookOutput,
 };

tests/copilot-plugin.test.js

@@ -0,0 +1,33 @@
+#!/usr/bin/env node
+// Smoke test for the Copilot plugin adapter: keep command wiring minimal and
+// ensure the debt command is part of the shared command surface.
+
+const test = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('fs');
+const path = require('path');
+
+const root = path.join(__dirname, '..');
+const REQUIRED_COMMAND_FILES = [
+  'ponytail.toml',
+  'ponytail-review.toml',
+  'ponytail-audit.toml',
+  'ponytail-debt.toml',
+];
+
+function readJSON(relPath) {
+  return JSON.parse(fs.readFileSync(path.join(root, relPath), 'utf8'));
+}
+
+test('copilot plugin command directory includes ponytail-debt', () => {
+  const manifest = readJSON('.github/plugin/plugin.json');
+  assert.equal(manifest.name, 'ponytail');
+  assert.equal(manifest.commands, 'commands/');
+
+  for (const file of REQUIRED_COMMAND_FILES) {
+    assert.ok(
+      fs.existsSync(path.join(root, manifest.commands, file)),
+      `missing command file: ${manifest.commands}${file}`,
+    );
+  }
+});

tests/gemini-extension.test.js

@@ -16,6 +16,12 @@ const MANIFEST = 'gemini-extension.json';
 const EXTENSION_NAME = 'ponytail';
 // Floating refs are a supply-chain footgun; the manifest version must be pinned.
 const PINNED_SEMVER = /^\d+\.\d+\.\d+$/;
+const VERSIONED_MANIFESTS = [
+  'gemini-extension.json',
+  '.claude-plugin/plugin.json',
+  '.codex-plugin/plugin.json',
+  '.github/plugin/plugin.json',
+];
 // Gemini auto-discovers these by directory; the manifest is only useful if they exist.
 const REUSED_COMMANDS = ['commands/ponytail.toml', 'commands/ponytail-review.toml'];
 const REUSED_SKILLS = ['skills/ponytail/SKILL.md'];
@@ -46,9 +52,15 @@ test('manifest names the ponytail extension with a pinned version', () => {
 });
 
 test('version stays aligned with the other plugin manifests', () => {
-  const manifest = loadManifest();
+  const versions = VERSIONED_MANIFESTS.map((rel) => {
-  const claude = JSON.parse(read('.claude-plugin/plugin.json'));
+    const manifest = JSON.parse(read(rel));
-  assert.equal(manifest.version, claude.version);
+    assert.match(manifest.version, PINNED_SEMVER, `${rel} version must be pinned semver`);
+    return manifest.version;
+  });
+  const [sharedVersion, ...rest] = versions;
+  for (const version of rest) {
+    assert.equal(version, sharedVersion);
+  }
 });
 
 test('contextFileName resolves to a file carrying the ponytail rules', () => {

tests/hooks.test.js

@@ -99,5 +99,44 @@ assert.equal(
   'flag must not land in ~/.claude when CLAUDE_CONFIG_DIR is set',
 );
 
+const copilotData = path.join(temp, 'copilot-data');
+const codexData = path.join(temp, 'codex-data-shadow');
+result = run('ponytail-activate.js', {
+  HOME: home,
+  USERPROFILE: home,
+  COPILOT_PLUGIN_DATA: copilotData,
+  PLUGIN_DATA: codexData,
+  PONYTAIL_DEFAULT_MODE: 'full',
+});
+assert.equal(result.status, 0, result.stderr);
+assert.equal(fs.readFileSync(path.join(copilotData, '.ponytail-active'), 'utf8'), 'full');
+assert.equal(
+  fs.existsSync(path.join(codexData, '.ponytail-active')),
+  false,
+  'copilot hooks must not write mode state to codex PLUGIN_DATA',
+);
+output = JSON.parse(result.stdout);
+assert.match(output.additionalContext, /PONYTAIL MODE ACTIVE — level: full/);
+
+result = run(
+  'ponytail-mode-tracker.js',
+  {
+    HOME: home,
+    USERPROFILE: home,
+    COPILOT_PLUGIN_DATA: copilotData,
+    PLUGIN_DATA: codexData,
+  },
+  JSON.stringify({ prompt: '/ponytail ultra' }),
+);
+assert.equal(result.status, 0, result.stderr);
+assert.equal(fs.readFileSync(path.join(copilotData, '.ponytail-active'), 'utf8'), 'ultra');
+assert.equal(
+  fs.existsSync(path.join(codexData, '.ponytail-active')),
+  false,
+  'copilot mode tracker must keep codex PLUGIN_DATA untouched',
+);
+output = JSON.parse(result.stdout);
+assert.deepEqual(output, {});
+
 fs.rmSync(temp, { recursive: true, force: true });
 console.log('hook compatibility checks passed');