diff --git a/README.md b/README.md
index 253d5425..c7fbc093 100644
--- a/README.md
+++ b/README.md
@@ -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.
 
+### Optional: enforce plan decisions
+
+gstack's plan skills (`/plan-eng-review`, `/plan-ceo-review`, `/plan-design-review`) produce real decisions, scope constraints, architecture choices, deferred items. By default those decisions live in the conversation and are gone when the session ends. Nothing stops the agent from drifting.
+
+Pass `--enforcement` to setup and gstack will install [Rippletide](https://www.rippletide.com/dev) (open source) automatically:
+
+```sh
+./setup --enforcement
+```
+
+Rippletide adds enforcement via Claude Code hooks:
+
+- **Before the next plan session** — a `UserPromptSubmit` hook injects decisions from prior reviews before Claude produces any output, so each plan review builds on the last.
+- **Before every file write** — a `PreToolUse` hook validates the change against those decisions and blocks violations before they land.
+
+Without `--enforcement`, gstack works exactly as before, no enforcement, no dependency. If you do run it, check `CLAUDE.md` afterward and preserve or re-add the `## gstack` section if it was overwritten.
+
 ### 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.
diff --git a/setup b/setup
index bfae8785..97d2b334 100755
--- a/setup
+++ b/setup
@@ -27,6 +27,7 @@ while [ $# -gt 0 ]; do
   case "$1" in
     --host) [ -z "$2" ] && echo "Missing value for --host (expected claude, codex, kiro, or auto)" >&2 && exit 1; HOST="$2"; shift 2 ;;
     --host=*) HOST="${1#--host=}"; shift ;;
+    --enforcement) INSTALL_ENFORCEMENT=1; shift ;;
     --local) LOCAL_INSTALL=1; shift ;;
     *) shift ;;
   esac
@@ -51,6 +52,7 @@ fi
 
 # For auto: detect which agents are installed
 INSTALL_CLAUDE=0
+INSTALL_ENFORCEMENT=0
 INSTALL_CODEX=0
 INSTALL_KIRO=0
 if [ "$HOST" = "auto" ]; then
@@ -447,7 +449,19 @@ if [ "$INSTALL_CODEX" -eq 1 ]; then
   create_agents_sidecar "$SOURCE_GSTACK_DIR"
 fi
 
-# 8. First-time welcome + legacy cleanup
+# 8. Optional: install Rippletide for plan decision enforcement
+if [ "$INSTALL_ENFORCEMENT" -eq 1 ]; then
+  echo ""
+  echo "Installing Rippletide enforcement..."
+  npx rippletide-code@latest connect
+  echo ""
+  echo "Rippletide connected. Plan decisions from /plan-eng-review, /plan-ceo-review,"
+  echo "and /plan-design-review will now be enforced via Claude Code hooks."
+  echo ""
+  echo "Note: check CLAUDE.md and re-add the '## gstack' section if it was overwritten."
+fi
+
+# 9. First-time welcome + legacy cleanup
 if [ ! -d "$HOME/.gstack" ]; then
   mkdir -p "$HOME/.gstack"
   echo "  Welcome! Run /gstack-upgrade anytime to stay current."