feat(hosts): add GitHub Copilot CLI as a first-class host

.gitignore

@@ -18,6 +18,7 @@ bin/gstack-global-discover
 .openclaw/
 .hermes/
 .gbrain/
+.copilot/
 .gbrain-source
 .context/
 extension/.auth.json

hosts/copilot.ts

@@ -0,0 +1,103 @@
+import type { HostConfig } from '../scripts/host-config';
+
+/**
+ * GitHub Copilot CLI host.
+ *
+ * Copilot CLI discovers custom agents as flat `.agent.md` files in
+ * `~/.copilot/agents/`. Each file has YAML frontmatter (name, description,
+ * tools, target, etc.) followed by markdown instructions. Invoke with
+ * `copilot --agent <name>`.
+ *
+ * Schema reference:
+ *   https://docs.github.com/en/copilot/reference/custom-agents-configuration
+ *
+ * gstack skills are emitted as `gstack-<skill>.agent.md` (flat with prefix —
+ * Copilot CLI does not recurse into subdirectories under ~/.copilot/agents/).
+ */
+const copilot: HostConfig = {
+  name: 'copilot',
+  displayName: 'GitHub Copilot CLI',
+  cliCommand: 'copilot',
+
+  globalRoot: '.copilot/agents',
+  localSkillRoot: '.copilot/agents',
+  hostSubdir: '.copilot',
+  usesEnvVars: true,
+
+  outputLayout: 'flat-agent-md',
+
+  frontmatter: {
+    mode: 'allowlist',
+    keepFields: ['name', 'description'],
+    descriptionLimit: 1024,
+    descriptionLimitBehavior: 'truncate',
+    extraFields: {
+      // `target` is intentionally omitted — defaults to "both" (Copilot CLI + VS Code
+      // Copilot extension), maximising reach. Set to "github-copilot" or "vscode" to
+      // narrow if a deployment ever needs that.
+      // gstack skills need broad tool access. Emit as YAML array via stringified literal —
+      // transformFrontmatter does string-interpolation, so the value is rendered verbatim.
+      // (If transformFrontmatter ever gains real array support, switch to a JS array.)
+      tools: '["*"]',
+    },
+  },
+
+  generation: {
+    generateMetadata: false,
+    // Skipped because they don't fit Copilot CLI's stateless single-invocation
+    // agent model. They either toggle session state, configure other skills,
+    // or wrap a binary that should not recurse:
+    //   'codex'       — wraps the `codex` CLI binary (every external host skips this)
+    //   'copilot'     — would recurse: this skill wraps the `copilot` CLI itself
+    //   'freeze'      — toggles a session-scoped edit boundary; agents are stateless
+    //   'unfreeze'    — pairs with /freeze; same reason
+    //   'careful'     — installs session-scoped destructive-command guardrails
+    //   'guard'       — combines /careful + /freeze; same reason
+    //   'plan-tune'   — interactive UI for tuning AskUserQuestion sensitivity
+    //                   per-skill; only meaningful inside a persistent skill system
+    // Follow-up worth filing: the rules from freeze/careful/guard could be
+    // injected into a project AGENTS.md template so they're ambient across
+    // every Copilot CLI invocation, recovering the protection we drop here.
+    skipSkills: ['codex', 'copilot', 'freeze', 'unfreeze', 'careful', 'guard', 'plan-tune'],
+  },
+
+  pathRewrites: [
+    // Copilot CLI installs are global-only — agents live in ~/.copilot/agents/
+    // and runtime support files (bin/, browse/) live in ~/.copilot/gstack/ via
+    // $GSTACK_ROOT. Both the `~/.claude/skills/gstack` references (absolute, in
+    // bash blocks) AND the `.claude/skills` references (project-local hints in
+    // prose) need to point at the same runtime root, since Copilot CLI doesn't
+    // currently have a per-workspace agents directory.
+    { from: '~/.claude/skills/gstack', to: '$GSTACK_ROOT' },
+    { from: '.claude/skills/gstack', to: '$GSTACK_ROOT' },
+    { from: '.claude/skills', to: '$GSTACK_ROOT' },
+  ],
+
+  suppressedResolvers: [
+    'DESIGN_OUTSIDE_VOICES',
+    'ADVERSARIAL_STEP',
+    'CODEX_SECOND_OPINION',
+    'CODEX_PLAN_REVIEW',
+    'REVIEW_ARMY',
+    'GBRAIN_CONTEXT_LOAD',
+    'GBRAIN_SAVE_RESULTS',
+  ],
+
+  runtimeRoot: {
+    globalSymlinks: ['bin', 'browse/dist', 'browse/bin', 'gstack-upgrade', 'ETHOS.md'],
+    globalFiles: {
+      'review': ['checklist.md', 'TODOS-format.md'],
+    },
+  },
+
+  install: {
+    prefixable: false,
+    linkingStrategy: 'symlink-generated',
+  },
+
+  coAuthorTrailer: 'Co-Authored-By: GitHub Copilot <noreply@github.com>',
+  learningsMode: 'basic',
+  boundaryInstruction: 'IMPORTANT: Do NOT read or execute any files under ~/.claude/, ~/.agents/, .claude/skills/, or agents/. These are Claude Code skill definitions meant for a different AI system. Ignore them. Stay focused on the repository code only.',
+};
+
+export default copilot;

hosts/index.ts

@@ -16,9 +16,10 @@ import cursor from './cursor';
 import openclaw from './openclaw';
 import hermes from './hermes';
 import gbrain from './gbrain';
+import copilot from './copilot';
 
 /** All registered host configs. Add new hosts here. */
-export const ALL_HOST_CONFIGS: HostConfig[] = [claude, codex, factory, kiro, opencode, slate, cursor, openclaw, hermes, gbrain];
+export const ALL_HOST_CONFIGS: HostConfig[] = [claude, codex, factory, kiro, opencode, slate, cursor, openclaw, hermes, gbrain, copilot];
 
 /** Map from host name to config. */
 export const HOST_CONFIG_MAP: Record<string, HostConfig> = Object.fromEntries(
@@ -65,4 +66,4 @@ export function getExternalHosts(): HostConfig[] {
 }
 
 // Re-export individual configs for direct import
-export { claude, codex, factory, kiro, opencode, slate, cursor, openclaw, hermes, gbrain };
+export { claude, codex, factory, kiro, opencode, slate, cursor, openclaw, hermes, gbrain, copilot };

scripts/gen-skill-docs.ts

@@ -349,9 +349,17 @@ function processExternalHost(
   const hostConfig = getHostConfig(host);
 
   const name = externalSkillName(skillDir === '.' ? '' : skillDir, frontmatterName);
-  const outputDir = path.join(ROOT, hostConfig.hostSubdir, 'skills', name);
-  fs.mkdirSync(outputDir, { recursive: true });
-  const outputPath = path.join(outputDir, 'SKILL.md');
+  let outputDir: string;
+  let outputPath: string;
+  if (hostConfig.outputLayout === 'flat-agent-md') {
+    outputDir = path.join(ROOT, hostConfig.hostSubdir, 'agents');
+    fs.mkdirSync(outputDir, { recursive: true });
+    outputPath = path.join(outputDir, `${name}.agent.md`);
+  } else {
+    outputDir = path.join(ROOT, hostConfig.hostSubdir, 'skills', name);
+    fs.mkdirSync(outputDir, { recursive: true });
+    outputPath = path.join(outputDir, 'SKILL.md');
+  }
 
   // Guard against symlink loops
   let symlinkLoop = false;

scripts/host-config.ts

@@ -66,6 +66,15 @@ export interface HostConfig {
     includeSkills?: string[];
   };
 
+  /**
+   * Output layout for generated skill docs.
+   * - 'per-skill-dir' (default): <hostSubdir>/skills/<name>/SKILL.md
+   *   Used by Codex, Cursor, Factory, OpenCode, etc.
+   * - 'flat-agent-md': <hostSubdir>/agents/<name>.agent.md
+   *   Used by GitHub Copilot CLI (~/.copilot/agents/<name>.agent.md).
+   */
+  outputLayout?: 'per-skill-dir' | 'flat-agent-md';
+
   // --- Content Rewrites ---
   /** Literal string replacements on generated SKILL.md content. Order matters, replaceAll. */
   pathRewrites: Array<{ from: string; to: string }>;

setup

@@ -24,6 +24,8 @@ FACTORY_SKILLS="$HOME/.factory/skills"
 FACTORY_GSTACK="$FACTORY_SKILLS/gstack"
 OPENCODE_SKILLS="$HOME/.config/opencode/skills"
 OPENCODE_GSTACK="$OPENCODE_SKILLS/gstack"
+COPILOT_AGENTS="$HOME/.copilot/agents"
+COPILOT_GSTACK="$HOME/.copilot/gstack"
 
 IS_WINDOWS=0
 case "$(uname -s)" in
@@ -43,7 +45,7 @@ TEAM_MODE=0
 NO_TEAM_MODE=0
 while [ $# -gt 0 ]; do
   case "$1" in
-    --host) [ -z "$2" ] && echo "Missing value for --host (expected claude, codex, kiro, factory, opencode, openclaw, hermes, gbrain, or auto)" >&2 && exit 1; HOST="$2"; shift 2 ;;
+    --host) [ -z "$2" ] && echo "Missing value for --host (expected claude, codex, kiro, factory, opencode, copilot, openclaw, hermes, gbrain, or auto)" >&2 && exit 1; HOST="$2"; shift 2 ;;
     --host=*) HOST="${1#--host=}"; shift ;;
     --local) LOCAL_INSTALL=1; shift ;;
     --prefix)    SKILL_PREFIX=1; SKILL_PREFIX_FLAG=1; shift ;;
@@ -56,7 +58,7 @@ while [ $# -gt 0 ]; do
 done
 
 case "$HOST" in
-  claude|codex|kiro|factory|opencode|auto) ;;
+  claude|codex|kiro|factory|opencode|copilot|auto) ;;
   openclaw)
     echo ""
     echo "OpenClaw integration uses a different model — OpenClaw spawns Claude Code"
@@ -91,7 +93,7 @@ case "$HOST" in
     echo "GBrain setup and brain skills ship from the GBrain repo."
     echo ""
     exit 0 ;;
-  *) echo "Unknown --host value: $HOST (expected claude, codex, kiro, factory, opencode, openclaw, hermes, gbrain, or auto)" >&2; exit 1 ;;
+  *) echo "Unknown --host value: $HOST (expected claude, codex, kiro, factory, opencode, copilot, openclaw, hermes, gbrain, or auto)" >&2; exit 1 ;;
 esac
 
 # ─── Resolve skill prefix preference ─────────────────────────
@@ -155,14 +157,16 @@ INSTALL_CODEX=0
 INSTALL_KIRO=0
 INSTALL_FACTORY=0
 INSTALL_OPENCODE=0
+INSTALL_COPILOT=0
 if [ "$HOST" = "auto" ]; then
   command -v claude >/dev/null 2>&1 && INSTALL_CLAUDE=1
   command -v codex >/dev/null 2>&1 && INSTALL_CODEX=1
   command -v kiro-cli >/dev/null 2>&1 && INSTALL_KIRO=1
   command -v droid >/dev/null 2>&1 && INSTALL_FACTORY=1
   command -v opencode >/dev/null 2>&1 && INSTALL_OPENCODE=1
+  command -v copilot >/dev/null 2>&1 && INSTALL_COPILOT=1
   # If none found, default to claude
-  if [ "$INSTALL_CLAUDE" -eq 0 ] && [ "$INSTALL_CODEX" -eq 0 ] && [ "$INSTALL_KIRO" -eq 0 ] && [ "$INSTALL_FACTORY" -eq 0 ] && [ "$INSTALL_OPENCODE" -eq 0 ]; then
+  if [ "$INSTALL_CLAUDE" -eq 0 ] && [ "$INSTALL_CODEX" -eq 0 ] && [ "$INSTALL_KIRO" -eq 0 ] && [ "$INSTALL_FACTORY" -eq 0 ] && [ "$INSTALL_OPENCODE" -eq 0 ] && [ "$INSTALL_COPILOT" -eq 0 ]; then
     INSTALL_CLAUDE=1
   fi
 elif [ "$HOST" = "claude" ]; then
@@ -175,6 +179,8 @@ elif [ "$HOST" = "factory" ]; then
   INSTALL_FACTORY=1
 elif [ "$HOST" = "opencode" ]; then
   INSTALL_OPENCODE=1
+elif [ "$HOST" = "copilot" ]; then
+  INSTALL_COPILOT=1
 fi
 
 migrate_direct_codex_install() {
@@ -321,6 +327,16 @@ if [ "$INSTALL_OPENCODE" -eq 1 ] && [ "$NEEDS_BUILD" -eq 0 ]; then
   )
 fi
 
+# 1e. Generate .copilot/ GitHub Copilot CLI agent files
+if [ "$INSTALL_COPILOT" -eq 1 ] && [ "$NEEDS_BUILD" -eq 0 ]; then
+  log "Generating .copilot/ agent files..."
+  (
+    cd "$SOURCE_GSTACK_DIR"
+    bun install --frozen-lockfile 2>/dev/null || bun install
+    bun run gen:skill-docs --host copilot
+  )
+fi
+
 # 2. Ensure Playwright's Chromium is available
 if ! ensure_playwright_browser; then
   echo "Installing Playwright Chromium..."
@@ -935,6 +951,40 @@ if [ "$INSTALL_OPENCODE" -eq 1 ]; then
   echo "  opencode skills: $OPENCODE_SKILLS"
 fi
 
+# 6d. Install for GitHub Copilot CLI
+# Copilot discovers agents as flat `.agent.md` files under ~/.copilot/agents/.
+# We symlink each generated `gstack-<skill>.agent.md` from the repo's
+# .copilot/agents/ dir, and create ~/.copilot/gstack/ with bin/browse symlinks
+# so agents can resolve $GSTACK_ROOT-relative tooling.
+if [ "$INSTALL_COPILOT" -eq 1 ]; then
+  mkdir -p "$COPILOT_AGENTS"
+  mkdir -p "$COPILOT_GSTACK"
+  # Clean stale gstack symlinks first so renamed/removed skills don't leave
+  # orphan entries pointing at non-existent source files.
+  find "$COPILOT_AGENTS" -maxdepth 1 -name "gstack-*.agent.md" -type l -delete 2>/dev/null || true
+  # Symlink each agent file (flat layout — Copilot CLI does not recurse)
+  for f in "$SOURCE_GSTACK_DIR"/.copilot/agents/*.agent.md; do
+    [ -e "$f" ] || continue  # tolerate no matches
+    ln -sf "$f" "$COPILOT_AGENTS/$(basename "$f")"
+  done
+  # Runtime support files referenced by agent prompts via $GSTACK_ROOT
+  ln -sfn "$SOURCE_GSTACK_DIR/bin" "$COPILOT_GSTACK/bin"
+  ln -sfn "$SOURCE_GSTACK_DIR/browse/dist" "$COPILOT_GSTACK/browse-dist"
+  ln -sfn "$SOURCE_GSTACK_DIR/gstack-upgrade" "$COPILOT_GSTACK/gstack-upgrade"
+  [ -f "$SOURCE_GSTACK_DIR/ETHOS.md" ] && ln -sfn "$SOURCE_GSTACK_DIR/ETHOS.md" "$COPILOT_GSTACK/ETHOS.md"
+  AGENT_COUNT=$(ls "$COPILOT_AGENTS"/gstack-*.agent.md 2>/dev/null | wc -l | tr -d ' ')
+  echo "gstack ready (copilot)."
+  echo "  browse: $BROWSE_BIN"
+  echo "  copilot agents: $COPILOT_AGENTS ($AGENT_COUNT gstack-*.agent.md files)"
+  echo "  runtime root: $COPILOT_GSTACK"
+  echo ""
+  echo "  IMPORTANT: agents reference \$GSTACK_ROOT — set it before launching copilot:"
+  echo "    export GSTACK_ROOT=$COPILOT_GSTACK"
+  echo "  Or persist in ~/.copilot/settings.json under secret-env-vars."
+  echo ""
+  echo "  Invoke any gstack agent: copilot --agent gstack-<skill> \"<prompt>\""
+fi
+
 # 7. Create .agents/ sidecar symlinks for the real Codex skill target.
 # The root Codex skill ends up pointing at $SOURCE_GSTACK_DIR/.agents/skills/gstack,
 # so the runtime assets must live there for both global and repo-local installs.

test/gen-skill-docs.test.ts

@@ -2069,7 +2069,25 @@ import { ALL_HOST_CONFIGS, getExternalHosts } from '../hosts/index';
 describe('Parameterized host smoke tests', () => {
   for (const hostConfig of getExternalHosts()) {
     describe(`${hostConfig.displayName} (--host ${hostConfig.name})`, () => {
-      const hostDir = path.join(ROOT, hostConfig.hostSubdir, 'skills');
+      // Layout-aware helpers — `flat-agent-md` hosts (Copilot CLI) emit
+      // <hostSubdir>/agents/<name>.agent.md; default hosts emit
+      // <hostSubdir>/skills/<name>/SKILL.md.
+      const isFlat = hostConfig.outputLayout === 'flat-agent-md';
+      const hostDir = path.join(ROOT, hostConfig.hostSubdir, isFlat ? 'agents' : 'skills');
+      const skillFilePath = (name: string) => isFlat
+        ? path.join(hostDir, `${name}.agent.md`)
+        : path.join(hostDir, name, 'SKILL.md');
+      const listSkillFiles = (): Array<{ name: string; path: string }> => {
+        if (!fs.existsSync(hostDir)) return [];
+        if (isFlat) {
+          return fs.readdirSync(hostDir)
+            .filter(f => f.endsWith('.agent.md'))
+            .map(f => ({ name: f.replace(/\.agent\.md$/, ''), path: path.join(hostDir, f) }));
+        }
+        return fs.readdirSync(hostDir)
+          .filter(d => fs.existsSync(path.join(hostDir, d, 'SKILL.md')))
+          .map(d => ({ name: d, path: path.join(hostDir, d, 'SKILL.md') }));
+      };
 
       test('generates output that exists on disk', () => {
         // Generated dir should exist (created by earlier bun run gen:skill-docs --host all)
@@ -2080,37 +2098,27 @@ describe('Parameterized host smoke tests', () => {
           });
         }
         expect(fs.existsSync(hostDir)).toBe(true);
-        const skills = fs.readdirSync(hostDir).filter(d =>
-          fs.existsSync(path.join(hostDir, d, 'SKILL.md'))
-        );
-        expect(skills.length).toBeGreaterThan(0);
+        expect(listSkillFiles().length).toBeGreaterThan(0);
       });
 
       test('no .claude/skills path leakage outside repo-root sidecar symlinks', () => {
         if (!fs.existsSync(hostDir)) return; // skip if not generated
-        const skills = fs.readdirSync(hostDir);
-        for (const skill of skills) {
+        for (const { name, path: skillMd } of listSkillFiles()) {
           // Dev installs may mount the repo root at host/skills/gstack as a runtime
           // sidecar. The generator skips that symlink loop, so leakage checks should too.
-          if (isRepoRootSymlink(path.join(hostDir, skill))) continue;
-          const skillMd = path.join(hostDir, skill, 'SKILL.md');
-          if (!fs.existsSync(skillMd)) continue;
+          if (!isFlat && isRepoRootSymlink(path.join(hostDir, name))) continue;
           const content = fs.readFileSync(skillMd, 'utf-8');
           // Strip bash blocks (which have legitimate fallback paths)
           const noBash = content.replace(/```bash\n[\s\S]*?```/g, '');
           const leaks = noBash.split('\n').filter(l => l.includes('.claude/skills'));
           if (leaks.length > 0) {
-            throw new Error(`${skill}: .claude/skills leakage:\n${leaks.slice(0, 3).join('\n')}`);
+            throw new Error(`${name}: .claude/skills leakage:\n${leaks.slice(0, 3).join('\n')}`);
           }
         }
       });
 
       test('frontmatter has name and description', () => {
-        if (!fs.existsSync(hostDir)) return;
-        const skills = fs.readdirSync(hostDir);
-        for (const skill of skills) {
-          const skillMd = path.join(hostDir, skill, 'SKILL.md');
-          if (!fs.existsSync(skillMd)) continue;
+        for (const { path: skillMd } of listSkillFiles()) {
           const content = fs.readFileSync(skillMd, 'utf-8');
           expect(content).toMatch(/^---\n/);
           expect(content).toMatch(/^name:\s/m);
@@ -2119,7 +2127,7 @@ describe('Parameterized host smoke tests', () => {
       });
 
       test('generates Claude outside-voice skill for external hosts', () => {
-        const skillMd = path.join(hostDir, 'gstack-claude', 'SKILL.md');
+        const skillMd = skillFilePath('gstack-claude');
         expect(fs.existsSync(skillMd)).toBe(true);
         const content = fs.readFileSync(skillMd, 'utf-8');
         expect(content).toContain('claude -p');
@@ -2140,7 +2148,7 @@ describe('Parameterized host smoke tests', () => {
 
       if (hostConfig.generation.skipSkills?.includes('codex')) {
         test('/codex skill excluded', () => {
-          expect(fs.existsSync(path.join(hostDir, 'gstack-codex', 'SKILL.md'))).toBe(false);
+          expect(fs.existsSync(skillFilePath('gstack-codex'))).toBe(false);
         });
       }
     });
@@ -2159,7 +2167,8 @@ describe('--host all', () => {
     // All hosts should appear in output
     expect(output).toContain('FRESH: SKILL.md');           // claude
     for (const hostConfig of getExternalHosts()) {
-      expect(output).toContain(`FRESH: ${hostConfig.hostSubdir}/skills/`);
+      const subdir = hostConfig.outputLayout === 'flat-agent-md' ? 'agents' : 'skills';
+      expect(output).toContain(`FRESH: ${hostConfig.hostSubdir}/${subdir}/`);
     }
   });
 });
@@ -2270,9 +2279,9 @@ describe('setup script validation', () => {
     expect(fnBody).toContain('rm -f "$target"');
   });
 
-  test('setup supports --host auto|claude|codex|kiro|opencode', () => {
+  test('setup supports --host auto|claude|codex|kiro|opencode|copilot', () => {
     expect(setupContent).toContain('--host');
-    expect(setupContent).toContain('claude|codex|kiro|factory|opencode|auto');
+    expect(setupContent).toContain('claude|codex|kiro|factory|opencode|copilot|auto');
   });
 
   test('auto mode detects claude, codex, kiro, and opencode binaries', () => {