Add GitHub Copilot CLI support via Claude-compatible skills

CONTRIBUTING.md

@@ -232,6 +232,11 @@ To add a browse command, add it to `browse/src/commands.ts`. To add a snapshot f
 
 gstack generates SKILL.md files for two hosts: **Claude** (`.claude/skills/`) and **Codex** (`.agents/skills/`). Every template change needs to be generated for both.
 
+**Copilot CLI support intentionally reuses the Claude-compatible `.claude/skills/` output.**
+There is no separate `--host copilot` generator mode to maintain. If you change
+install paths or setup behavior, make sure the Claude-format skill tree still works
+for Copilot's documented `.claude/skills` support.
+
 ### Generating for both hosts
 
 ```bash

README.md

@@ -40,7 +40,7 @@ Fork it. Improve it. Make it yours. And if you want to hate on free open source
 
 ## Install — 30 seconds
 
-**Requirements:** [Claude Code](https://docs.anthropic.com/en/docs/claude-code), [Git](https://git-scm.com/), [Bun](https://bun.sh/) v1.0+, [Node.js](https://nodejs.org/) (Windows only)
+**Requirements:** One supported host ([Claude Code](https://docs.anthropic.com/en/docs/claude-code), [GitHub Copilot CLI](https://docs.github.com/copilot/how-tos/use-copilot-agents/use-copilot-cli), or another SKILL.md-compatible agent), [Git](https://git-scm.com/), [Bun](https://bun.sh/) v1.0+, [Node.js](https://nodejs.org/) (Windows only)
 
 ### Step 1: Install on your machine
 
@@ -54,6 +54,23 @@ Open Claude Code and paste this. Claude does the rest.
 
 Real files get committed to your repo (not a submodule), so `git clone` just works. Everything lives inside `.claude/`. Nothing touches your PATH or runs in the background.
 
+### GitHub Copilot CLI
+
+GitHub Copilot CLI officially supports skills from `.claude/skills` and
+`~/.claude/skills`, so the lowest-friction gstack install reuses the same
+Claude-compatible layout instead of introducing a separate Copilot-only tree.
+
+Install once for your user account:
+
+```bash
+git clone https://github.com/garrytan/gstack.git ~/.claude/skills/gstack
+cd ~/.claude/skills/gstack && ./setup --host copilot
+```
+
+For repo-local installs, vendoring gstack into `.claude/skills/gstack` works with
+Copilot CLI too. Put your guidance in `AGENTS.md` or `.github/copilot-instructions.md`,
+then use `/skills reload` if Copilot is already running.
+
 ### Codex, Gemini CLI, or Cursor
 
 gstack works on any agent that supports the [SKILL.md standard](https://github.com/anthropics/claude-code). Skills live in `.agents/skills/` and are discovered automatically.
@@ -156,7 +173,7 @@ Each skill feeds into the next. `/office-hours` writes a design doc that `/plan-
 | `/canary` | **SRE** | Post-deploy monitoring loop. Watches for console errors, performance regressions, and page failures. |
 | `/benchmark` | **Performance Engineer** | Baseline page load times, Core Web Vitals, and resource sizes. Compare before/after on every PR. |
 | `/document-release` | **Technical Writer** | Update all project docs to match what you just shipped. Catches stale READMEs automatically. |
-| `/retro` | **Eng Manager** | Team-aware weekly retro. Per-person breakdowns, shipping streaks, test health trends, growth opportunities. `/retro global` runs across all your projects and AI tools (Claude Code, Codex, Gemini). |
+| `/retro` | **Eng Manager** | Team-aware weekly retro. Per-person breakdowns, shipping streaks, test health trends, growth opportunities. `/retro global` runs across all your projects and AI tools (Claude Code, Codex, Gemini, Copilot). |
 | `/browse` | **QA Engineer** | Real Chromium browser, real clicks, real screenshots. ~100ms per command. |
 | `/setup-browser-cookies` | **Session Manager** | Import cookies from your real browser (Chrome, Arc, Brave, Edge) into the headless session. Test authenticated pages. |
 | `/autoplan` | **Review Pipeline** | One command, fully reviewed plan. Runs CEO → design → eng review automatically with encoded decision principles. Surfaces only taste decisions for your approval. |
@@ -228,6 +245,8 @@ Data is stored in [Supabase](https://supabase.com) (open source Firebase alterna
 
 **Windows users:** gstack works on Windows 11 via Git Bash or WSL. Node.js is required in addition to Bun — Bun has a known bug with Playwright's pipe transport on Windows ([bun#4253](https://github.com/oven-sh/bun/issues/4253)). The browse server automatically falls back to Node.js. Make sure both `bun` and `node` are on your PATH.
 
+**Copilot CLI doesn't see the skills?** Run `/skills list` or `/skills reload`. If you're using the Claude-compatible install path, rerun: `cd ~/.claude/skills/gstack && ./setup --host copilot`
+
 **Claude says it can't see the skills?** Make sure your project's `CLAUDE.md` has a gstack section. Add this:
 
 ```

bin/gstack-global-discover.ts

@@ -1,6 +1,6 @@
 #!/usr/bin/env bun
 /**
- * gstack-global-discover — Discover AI coding sessions across Claude Code, Codex CLI, and Gemini CLI.
+ * gstack-global-discover — Discover AI coding sessions across Claude Code, Codex CLI, Gemini CLI, and GitHub Copilot CLI.
  * Resolves each session's working directory to a git repo, deduplicates by normalized remote URL,
  * and outputs structured JSON to stdout.
  *
@@ -17,15 +17,15 @@ import { homedir } from "os";
 // ── Types ──────────────────────────────────────────────────────────────────
 
 interface Session {
-  tool: "claude_code" | "codex" | "gemini";
+  tool: "claude_code" | "codex" | "gemini" | "copilot";
   cwd: string;
 }
 
 interface Repo {
   name: string;
   remote: string;
   paths: string[];
-  sessions: { claude_code: number; codex: number; gemini: number };
+  sessions: { claude_code: number; codex: number; gemini: number; copilot: number };
 }
 
 interface DiscoveryResult {
@@ -36,6 +36,7 @@ interface DiscoveryResult {
     claude_code: { total_sessions: number; repos: number };
     codex: { total_sessions: number; repos: number };
     gemini: { total_sessions: number; repos: number };
+    copilot: { total_sessions: number; repos: number };
   };
   total_sessions: number;
   total_repos: number;
@@ -290,6 +291,42 @@ function extractCwdFromJsonl(filePath: string): string | null {
   return null;
 }
 
+function extractCopilotCwdFromWorkspace(filePath: string): string | null {
+  try {
+    const text = readFileSync(filePath, { encoding: "utf-8" });
+    const match = text.match(/^cwd:\s*(.+)$/m);
+    if (!match) return null;
+    return match[1].trim().replace(/^['"]|['"]$/g, "");
+  } catch {
+    return null;
+  }
+}
+
+function extractCopilotCwdFromEvents(filePath: string): string | null {
+  try {
+    const fd = openSync(filePath, "r");
+    const buf = Buffer.alloc(16384);
+    const bytesRead = readSync(fd, buf, 0, 16384, 0);
+    closeSync(fd);
+    const lines = buf.toString("utf-8", 0, bytesRead).split("\n").slice(0, 25);
+    for (const line of lines) {
+      if (!line.trim()) continue;
+      try {
+        const obj = JSON.parse(line);
+        const cwd = obj.data?.context?.cwd;
+        if (obj.type === "session.start" && typeof cwd === "string") {
+          return cwd;
+        }
+      } catch {
+        continue;
+      }
+    }
+  } catch {
+    // File read error
+  }
+  return null;
+}
+
 function scanCodex(since: Date): Session[] {
   const sessionsDir = join(homedir(), ".codex", "sessions");
   if (!existsSync(sessionsDir)) return [];
@@ -440,6 +477,59 @@ function scanGemini(since: Date): Session[] {
   return sessions;
 }
 
+function scanCopilot(since: Date): Session[] {
+  const sessionsDir = join(homedir(), ".copilot", "session-state");
+  if (!existsSync(sessionsDir)) return [];
+
+  const sessions: Session[] = [];
+
+  let dirs: string[];
+  try {
+    dirs = readdirSync(sessionsDir);
+  } catch {
+    return [];
+  }
+
+  for (const dirName of dirs) {
+    const dirPath = join(sessionsDir, dirName);
+    try {
+      const stat = statSync(dirPath);
+      if (!stat.isDirectory()) continue;
+    } catch {
+      continue;
+    }
+
+    const workspacePath = join(dirPath, "workspace.yaml");
+    const eventsPath = join(dirPath, "events.jsonl");
+
+    const hasRecentWorkspace = existsSync(workspacePath) && (() => {
+      try {
+        return statSync(workspacePath).mtime >= since;
+      } catch {
+        return false;
+      }
+    })();
+    const hasRecentEvents = existsSync(eventsPath) && (() => {
+      try {
+        return statSync(eventsPath).mtime >= since;
+      } catch {
+        return false;
+      }
+    })();
+    if (!hasRecentWorkspace && !hasRecentEvents) continue;
+
+    let cwd = hasRecentWorkspace ? extractCopilotCwdFromWorkspace(workspacePath) : null;
+    if ((!cwd || !existsSync(cwd)) && hasRecentEvents) {
+      cwd = extractCopilotCwdFromEvents(eventsPath);
+    }
+    if (!cwd || !existsSync(cwd)) continue;
+
+    sessions.push({ tool: "copilot", cwd });
+  }
+
+  return sessions;
+}
+
 // ── Deduplication ──────────────────────────────────────────────────────────
 
 async function resolveAndDeduplicate(sessions: Session[]): Promise<Repo[]> {
@@ -496,7 +586,7 @@ async function resolveAndDeduplicate(sessions: Session[]): Promise<Repo[]> {
       }
     }
 
-    const sessionCounts = { claude_code: 0, codex: 0, gemini: 0 };
+    const sessionCounts = { claude_code: 0, codex: 0, gemini: 0, copilot: 0 };
     for (const s of data.sessions) {
       sessionCounts[s.tool]++;
     }
@@ -512,8 +602,8 @@ async function resolveAndDeduplicate(sessions: Session[]): Promise<Repo[]> {
   // Sort by total sessions descending
   repos.sort(
     (a, b) =>
-      b.sessions.claude_code + b.sessions.codex + b.sessions.gemini -
-      (a.sessions.claude_code + a.sessions.codex + a.sessions.gemini)
+      b.sessions.claude_code + b.sessions.codex + b.sessions.gemini + b.sessions.copilot -
+      (a.sessions.claude_code + a.sessions.codex + a.sessions.gemini + a.sessions.copilot)
   );
 
   return repos;
@@ -530,12 +620,13 @@ async function main() {
   const ccSessions = scanClaudeCode(sinceDate);
   const codexSessions = scanCodex(sinceDate);
   const geminiSessions = scanGemini(sinceDate);
+  const copilotSessions = scanCopilot(sinceDate);
 
-  const allSessions = [...ccSessions, ...codexSessions, ...geminiSessions];
+  const allSessions = [...ccSessions, ...codexSessions, ...geminiSessions, ...copilotSessions];
 
   // Summary to stderr
   console.error(
-    `Discovered: ${ccSessions.length} CC sessions, ${codexSessions.length} Codex sessions, ${geminiSessions.length} Gemini sessions`
+    `Discovered: ${ccSessions.length} CC sessions, ${codexSessions.length} Codex sessions, ${geminiSessions.length} Gemini sessions, ${copilotSessions.length} Copilot sessions`
   );
 
   // Deduplicate
@@ -547,6 +638,7 @@ async function main() {
   const ccRepos = new Set(repos.filter((r) => r.sessions.claude_code > 0).map((r) => r.remote)).size;
   const codexRepos = new Set(repos.filter((r) => r.sessions.codex > 0).map((r) => r.remote)).size;
   const geminiRepos = new Set(repos.filter((r) => r.sessions.gemini > 0).map((r) => r.remote)).size;
+  const copilotRepos = new Set(repos.filter((r) => r.sessions.copilot > 0).map((r) => r.remote)).size;
 
   const result: DiscoveryResult = {
     window: since,
@@ -556,6 +648,7 @@ async function main() {
       claude_code: { total_sessions: ccSessions.length, repos: ccRepos },
       codex: { total_sessions: codexSessions.length, repos: codexRepos },
       gemini: { total_sessions: geminiSessions.length, repos: geminiRepos },
+      copilot: { total_sessions: copilotSessions.length, repos: copilotRepos },
     },
     total_sessions: allSessions.length,
     total_repos: repos.length,
@@ -566,15 +659,20 @@ async function main() {
   } else {
     // Summary format
     console.log(`Window: ${since} (since ${startDate})`);
-    console.log(`Sessions: ${allSessions.length} total (CC: ${ccSessions.length}, Codex: ${codexSessions.length}, Gemini: ${geminiSessions.length})`);
+    console.log(`Sessions: ${allSessions.length} total (CC: ${ccSessions.length}, Codex: ${codexSessions.length}, Gemini: ${geminiSessions.length}, Copilot: ${copilotSessions.length})`);
     console.log(`Repos: ${repos.length} unique`);
     console.log("");
     for (const repo of repos) {
-      const total = repo.sessions.claude_code + repo.sessions.codex + repo.sessions.gemini;
+      const total =
+        repo.sessions.claude_code +
+        repo.sessions.codex +
+        repo.sessions.gemini +
+        repo.sessions.copilot;
       const tools = [];
       if (repo.sessions.claude_code > 0) tools.push(`CC:${repo.sessions.claude_code}`);
       if (repo.sessions.codex > 0) tools.push(`Codex:${repo.sessions.codex}`);
       if (repo.sessions.gemini > 0) tools.push(`Gemini:${repo.sessions.gemini}`);
+      if (repo.sessions.copilot > 0) tools.push(`Copilot:${repo.sessions.copilot}`);
       console.log(`  ${repo.name} (${total} sessions) — ${tools.join(", ")}`);
       console.log(`    Remote: ${repo.remote}`);
       console.log(`    Paths: ${repo.paths.join(", ")}`);