diff --git a/scripts/install-golem15.sh b/scripts/install-golem15.sh
new file mode 100755
index 000000000..41ad07f82
--- /dev/null
+++ b/scripts/install-golem15.sh
@@ -0,0 +1,135 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+usage() {
+  cat <<'EOF'
+Install the private golem15 GSD build for Claude Code and Codex.
+Grok Build consumes the Claude installation through its compatibility layer.
+
+Usage:
+  scripts/install-golem15.sh [--update] [--skip-deps] [--profile PROFILE]
+
+Options:
+  --update           Pull origin/next with --ff-only before installing.
+  --skip-deps        Do not run npm ci.
+  --profile PROFILE  GSD profile: core, standard, or full (default: full).
+  -h, --help         Show this help.
+EOF
+}
+
+update=false
+install_deps=true
+profile="${GSD_PROFILE:-full}"
+
+while (($#)); do
+  case "$1" in
+    --update) update=true ;;
+    --skip-deps) install_deps=false ;;
+    --profile)
+      shift
+      if (($# == 0)); then
+        echo "ERROR: --profile requires a value." >&2
+        exit 2
+      fi
+      profile="$1"
+      ;;
+    -h|--help)
+      usage
+      exit 0
+      ;;
+    *)
+      echo "ERROR: unknown argument: $1" >&2
+      usage >&2
+      exit 2
+      ;;
+  esac
+  shift
+done
+
+case "$profile" in
+  core|standard|full) ;;
+  *)
+    echo "ERROR: profile must be core, standard, or full; got: $profile" >&2
+    exit 2
+    ;;
+esac
+
+script_dir=$(CDPATH='' cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)
+repo_root=$(CDPATH='' cd -- "$script_dir/.." && pwd)
+cd "$repo_root"
+
+node_version=$(node --version 2>/dev/null || true)
+node_major=${node_version#v}
+node_major=${node_major%%.*}
+if [[ ! "$node_major" =~ ^[0-9]+$ ]] || ((node_major < 24)); then
+  cat >&2 <<EOF
+ERROR: this GSD checkout requires Node.js 24 or newer.
+Active Node: ${node_version:-not found}
+
+Install/activate Node 24, then rerun this script.
+EOF
+  exit 1
+fi
+
+if [[ "$update" == true ]]; then
+  echo "==> Updating private mirror from origin/next"
+  git pull --ff-only origin next
+fi
+
+if [[ "$install_deps" == true ]]; then
+  echo "==> Installing locked dependencies"
+  npm ci
+fi
+
+echo "==> Installing GSD for Claude Code (profile: $profile)"
+node bin/install.js --claude --global "--profile=$profile"
+
+echo "==> Installing GSD for Codex (profile: $profile)"
+node bin/install.js --codex --global "--profile=$profile"
+
+claude_root=${CLAUDE_CONFIG_DIR:-"$HOME/.claude"}
+codex_root=${CODEX_HOME:-"$HOME/.codex"}
+recovery_rel=gsd-core/workflows/plan-phase/steps/agent-recovery-and-timing.md
+
+for install_root in "$claude_root" "$codex_root"; do
+  if [[ ! -f "$install_root/$recovery_rel" ]]; then
+    echo "ERROR: patched recovery workflow missing after install: $install_root/$recovery_rel" >&2
+    exit 1
+  fi
+done
+
+active_codex=$(command -v codex 2>/dev/null || true)
+bun_codex="$HOME/.bun/bin/codex"
+if [[ -x "$bun_codex" && "$active_codex" != "$bun_codex" ]]; then
+  active_version=$(${active_codex:-false} --version 2>/dev/null || echo unknown)
+  bun_version=$($bun_codex --version 2>/dev/null || echo unknown)
+  cat >&2 <<EOF
+WARNING: PATH selects ${active_codex:-no Codex binary} (${active_version}),
+but the newer Bun installation is $bun_codex (${bun_version}).
+Put $HOME/.bun/bin before /usr/bin in PATH before starting Codex.
+EOF
+fi
+
+if command -v grok >/dev/null 2>&1; then
+  grok_report=$(mktemp)
+  trap 'rm -f "$grok_report"' EXIT
+  if grok inspect --json >"$grok_report" 2>/dev/null \
+    && grep -Fq "$claude_root/skills/gsd-plan-phase/SKILL.md" "$grok_report"; then
+    echo "==> Grok verified: Claude-compatible gsd-plan-phase skill discovered"
+  else
+    echo "WARNING: Grok did not report the Claude gsd-plan-phase skill; restart Grok and run 'grok inspect'." >&2
+  fi
+fi
+
+cat <<EOF
+
+Private GSD installation complete.
+  Source:  $repo_root
+  Claude:  $claude_root
+  Codex:   $codex_root
+  Profile: $profile
+
+Restart Claude Code, Codex, and Grok Build before using the updated skills.
+For future updates run:
+  $repo_root/scripts/install-golem15.sh --update
+EOF