diff --git a/setup b/setup
index 275236cd3..d795d314e 100755
--- a/setup
+++ b/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"
+AGY_SKILLS="$HOME/.gemini/config/skills"
+AGY_GSTACK="$AGY_SKILLS/gstack"
 
 IS_WINDOWS=0
 case "$(uname -s)" in
@@ -85,7 +87,7 @@ NO_TEAM_MODE=0
 PLAN_TUNE_HOOKS_MODE=""   # "" = resolve from env/config/prompt; "yes"/"no" = explicit
 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, openclaw, hermes, gbrain, agy, 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 ;;
@@ -101,7 +103,7 @@ while [ $# -gt 0 ]; do
 done
 
 case "$HOST" in
-  claude|codex|kiro|factory|opencode|auto) ;;
+  claude|codex|kiro|factory|opencode|agy|auto) ;;
   openclaw)
     echo ""
     echo "OpenClaw integration uses a different model — OpenClaw spawns Claude Code"
@@ -136,7 +138,7 @@ case "$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, openclaw, hermes, gbrain, agy, or auto)" >&2; exit 1 ;;
 esac
 
 # ─── Resolve skill prefix preference ─────────────────────────
@@ -200,14 +202,16 @@ INSTALL_CODEX=0
 INSTALL_KIRO=0
 INSTALL_FACTORY=0
 INSTALL_OPENCODE=0
+INSTALL_AGY=0
 if [ "$HOST" = "auto" ]; then
   command -v claude >/dev/null 2>&1 && INSTALL_CLAUDE=1
   command -v codex >/dev/null 2>&1 && INSTALL_CODEX=1
   command -v kiro-cli >/dev/null 2>&1 && INSTALL_KIRO=1
   command -v droid >/dev/null 2>&1 && INSTALL_FACTORY=1
   command -v opencode >/dev/null 2>&1 && INSTALL_OPENCODE=1
+  command -v agy >/dev/null 2>&1 && INSTALL_AGY=1
   # If none found, default to claude
-  if [ "$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_AGY" -eq 0 ]; then
     INSTALL_CLAUDE=1
   fi
 elif [ "$HOST" = "claude" ]; then
@@ -220,6 +224,8 @@ elif [ "$HOST" = "factory" ]; then
   INSTALL_FACTORY=1
 elif [ "$HOST" = "opencode" ]; then
   INSTALL_OPENCODE=1
+elif [ "$HOST" = "agy" ]; then
+  INSTALL_AGY=1
 fi
 
 migrate_direct_codex_install() {
@@ -475,6 +481,16 @@ if [ "$INSTALL_OPENCODE" -eq 1 ] && [ "$NEEDS_BUILD" -eq 0 ]; then
   )
 fi
 
+# 1e. Generate .agy/ Antigravity skill docs
+if [ "$INSTALL_AGY" -eq 1 ] && [ "$NEEDS_BUILD" -eq 0 ]; then
+  log "Generating .agy/ skill docs..."
+  (
+    cd "$SOURCE_GSTACK_DIR"
+    bun_cmd install --frozen-lockfile 2>/dev/null || bun_cmd install
+    bun_cmd run gen:skill-docs --host agy
+  )
+fi
+
 # 2. Ensure Playwright's Chromium is available
 if ! ensure_playwright_browser; then
   echo "Installing Playwright Chromium..."
@@ -972,6 +988,99 @@ link_opencode_skill_dirs() {
   fi
 }
 
+create_agy_runtime_root() {
+  local gstack_dir="$1"
+  local agy_gstack="$2"
+  local agy_dir="$gstack_dir/.agy/skills"
+
+  if [ -L "$agy_gstack" ]; then
+    rm -f "$agy_gstack"
+  elif [ -d "$agy_gstack" ] && [ "$agy_gstack" != "$gstack_dir" ]; then
+    rm -rf "$agy_gstack"
+  fi
+
+  mkdir -p "$agy_gstack" "$agy_gstack/browse" "$agy_gstack/design" "$agy_gstack/gstack-upgrade" "$agy_gstack/review" "$agy_gstack/qa" "$agy_gstack/plan-devex-review"
+
+  if [ -f "$agy_dir/gstack/SKILL.md" ]; then
+    _link_or_copy "$agy_dir/gstack/SKILL.md" "$agy_gstack/SKILL.md"
+  fi
+  if [ -d "$gstack_dir/bin" ]; then
+    _link_or_copy "$gstack_dir/bin" "$agy_gstack/bin"
+  fi
+  if [ -d "$gstack_dir/browse/dist" ]; then
+    _link_or_copy "$gstack_dir/browse/dist" "$agy_gstack/browse/dist"
+  fi
+  if [ -d "$gstack_dir/browse/bin" ]; then
+    _link_or_copy "$gstack_dir/browse/bin" "$agy_gstack/browse/bin"
+  fi
+  if [ -d "$gstack_dir/design/dist" ]; then
+    _link_or_copy "$gstack_dir/design/dist" "$agy_gstack/design/dist"
+  fi
+  if [ -f "$agy_dir/gstack-upgrade/SKILL.md" ]; then
+    _link_or_copy "$agy_dir/gstack-upgrade/SKILL.md" "$agy_gstack/gstack-upgrade/SKILL.md"
+  fi
+  for f in checklist.md design-checklist.md greptile-triage.md TODOS-format.md; do
+    if [ -f "$gstack_dir/review/$f" ]; then
+      _link_or_copy "$gstack_dir/review/$f" "$agy_gstack/review/$f"
+    fi
+  done
+  if [ -d "$gstack_dir/review/specialists" ]; then
+    _link_or_copy "$gstack_dir/review/specialists" "$agy_gstack/review/specialists"
+  fi
+  if [ -d "$gstack_dir/qa/templates" ]; then
+    _link_or_copy "$gstack_dir/qa/templates" "$agy_gstack/qa/templates"
+  fi
+  if [ -d "$gstack_dir/qa/references" ]; then
+    _link_or_copy "$gstack_dir/qa/references" "$agy_gstack/qa/references"
+  fi
+  if [ -f "$gstack_dir/plan-devex-review/dx-hall-of-fame.md" ]; then
+    _link_or_copy "$gstack_dir/plan-devex-review/dx-hall-of-fame.md" "$agy_gstack/plan-devex-review/dx-hall-of-fame.md"
+  fi
+  if [ -f "$gstack_dir/ETHOS.md" ]; then
+    _link_or_copy "$gstack_dir/ETHOS.md" "$agy_gstack/ETHOS.md"
+  fi
+}
+
+link_agy_skill_dirs() {
+  local gstack_dir="$1"
+  local skills_dir="$2"
+  local agy_dir="$gstack_dir/.agy/skills"
+  local linked=()
+
+  if [ ! -d "$agy_dir" ]; then
+    echo "  Generating .agy/ skill docs..."
+    ( cd "$gstack_dir" && bun run gen:skill-docs --host agy )
+  fi
+
+  if [ ! -d "$agy_dir" ]; then
+    echo "  warning: .agy/skills/ generation failed — run 'bun run gen:skill-docs --host agy' manually" >&2
+    return 1
+  fi
+
+  # Verify at least one SKILL.md exists before reporting success (KiDDarn safeguard)
+  local skill_count
+  skill_count=$(find "$agy_dir" -name "SKILL.md" | wc -l | tr -d ' ')
+  if [ "$skill_count" -eq 0 ]; then
+    echo "  warning: no SKILL.md files found in .agy/skills/ — generation may have failed" >&2
+    return 1
+  fi
+
+  for skill_dir in "$agy_dir"/gstack*/; do
+    if [ -f "$skill_dir/SKILL.md" ]; then
+      skill_name="$(basename "$skill_dir")"
+      [ "$skill_name" = "gstack" ] && continue
+      target="$skills_dir/$skill_name"
+      if [ -L "$target" ] || [ ! -e "$target" ]; then
+        _link_or_copy "$skill_dir" "$target"
+        linked+=("$skill_name")
+      fi
+    fi
+  done
+  if [ ${#linked[@]} -gt 0 ]; then
+    echo "  linked skills: ${linked[*]}"
+  fi
+}
+
 # 4. Install for Claude (default)
 SKILLS_BASENAME="$(basename "$INSTALL_SKILLS_DIR")"
 SKILLS_PARENT_BASENAME="$(basename "$(dirname "$INSTALL_SKILLS_DIR")")"
@@ -1193,6 +1302,16 @@ if [ "$INSTALL_OPENCODE" -eq 1 ]; then
   echo "  opencode skills: $OPENCODE_SKILLS"
 fi
 
+# 6d. Install for Antigravity (agy)
+if [ "$INSTALL_AGY" -eq 1 ]; then
+  mkdir -p "$AGY_SKILLS"
+  create_agy_runtime_root "$SOURCE_GSTACK_DIR" "$AGY_GSTACK"
+  link_agy_skill_dirs "$SOURCE_GSTACK_DIR" "$AGY_SKILLS"
+  echo "gstack ready (agy)."
+  echo "  browse: $BROWSE_BIN"
+  echo "  agy skills: $AGY_SKILLS"
+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.
diff --git a/test/host-config.test.ts b/test/host-config.test.ts
index ab0d2cc88..d09e62190 100644
--- a/test/host-config.test.ts
+++ b/test/host-config.test.ts
@@ -22,6 +22,7 @@ import {
   slate,
   cursor,
   openclaw,
+  agy,
 } from '../hosts/index';
 import { HOST_PATHS } from '../scripts/resolvers/types';
 
@@ -53,6 +54,7 @@ describe('hosts/index.ts', () => {
     expect(slate.name).toBe('slate');
     expect(cursor.name).toBe('cursor');
     expect(openclaw.name).toBe('openclaw');
+    expect(agy.name).toBe('agy');
   });
 
   test('getHostConfig returns correct config', () => {
@@ -536,3 +538,31 @@ describe('host config correctness', () => {
     }
   });
 });
+
+// ─── agy specific tests ─────────────────────────────────────
+
+describe('agy specific config', () => {
+  test('agy has correct global root path', () => {
+    expect(agy.globalRoot).toBe('.gemini/config/skills/gstack');
+  });
+
+  test('agy has correct local skill root', () => {
+    expect(agy.localSkillRoot).toBe('.agents/skills/gstack');
+  });
+
+  test('agy runtime root includes all expected sidecars', () => {
+    expect(agy.runtimeRoot.globalSymlinks).toContain('bin');
+    expect(agy.runtimeRoot.globalSymlinks).toContain('browse/dist');
+    expect(agy.runtimeRoot.globalSymlinks).toContain('ETHOS.md');
+  });
+
+  test('agy skill generation produces at least one SKILL.md', () => {
+    const agySkillDir = path.join(ROOT, '.agy', 'skills');
+    if (fs.existsSync(agySkillDir)) {
+      const skills = fs.readdirSync(agySkillDir, { withFileTypes: true });
+      const hasSkillMd = skills.some(d => d.isDirectory() &&
+        fs.existsSync(path.join(agySkillDir, d.name, 'SKILL.md')));
+      expect(hasSkillMd).toBe(true);
+    }
+  });
+});