diff --git a/docs/sleep/plugin_load_test.md b/docs/sleep/plugin_load_test.md
index e08eab4..c420646 100644
--- a/docs/sleep/plugin_load_test.md
+++ b/docs/sleep/plugin_load_test.md
@@ -23,7 +23,7 @@ from scratch for this test. Two forms were used:
 | Shell | What was run | Result |
 |---|---|---|
 | **Claude Code** (`scripts/sleep.sh`) | `harvest`, full `run`, `adopt` | harvest found 2 sessions → 2 tasks; `run` staged a proposal; `adopt` honored the safety contract (no live change when nothing was accepted) |
-| **Codex** (`install.sh` + shared runner) | `install.sh` into a temp HOME | placed the user-level `~/.agents/skills/skillopt-sleep/SKILL.md` skill correctly and did not install a deprecated custom prompt |
+| **Codex** (`install.sh` + shared runner) | `install.sh` into a temp HOME | placed the user-level `~/.agents/skills/skillopt-sleep/SKILL.md` skill correctly and moved any legacy custom prompt aside instead of installing one |
 | **Copilot** (`mcp_server.py`) | `initialize` → `tools/list` → `tools/call sleep_harvest` | 5 tools listed; `sleep_harvest` returned real engine output (2 sessions → 2 tasks) |
 
 ### Genuine improvement (real model, fresh persona)
diff --git a/plugins/codex/README.md b/plugins/codex/README.md
index 59d9381..376bc46 100644
--- a/plugins/codex/README.md
+++ b/plugins/codex/README.md
@@ -28,6 +28,9 @@ bash plugins/codex/install.sh          # installs the skill
 export SKILLOPT_SLEEP_REPO="$(pwd)"    # so the runner is found from anywhere
 ```
 
+If a previous install created `~/.codex/prompts/sleep.md`, the installer moves
+that deprecated prompt aside with a `.skillopt-legacy*.bak` suffix.
+
 Requires Python ≥ 3.10 and the `codex` CLI on PATH.
 
 ## Use
diff --git a/plugins/codex/install.sh b/plugins/codex/install.sh
index e2d413a..11b0735 100755
--- a/plugins/codex/install.sh
+++ b/plugins/codex/install.sh
@@ -4,7 +4,9 @@
 set -euo pipefail
 
 REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+CODEX_HOME="${CODEX_HOME:-$HOME/.codex}"
 AGENTS_SKILLS="${HOME}/.agents/skills"
+LEGACY_PROMPT="$CODEX_HOME/prompts/sleep.md"
 
 echo "[install] repo: $REPO_ROOT"
 
@@ -13,11 +15,21 @@ mkdir -p "$AGENTS_SKILLS/skillopt-sleep"
 cp "$REPO_ROOT/plugins/codex/skills/skillopt-sleep/SKILL.md" "$AGENTS_SKILLS/skillopt-sleep/SKILL.md"
 echo "[install] skill           -> $AGENTS_SKILLS/skillopt-sleep/SKILL.md"
 
-# 2) record the repo location so the runner is found from anywhere
+# 2) retire the old custom prompt entrypoint from previous installs
+if [ -f "$LEGACY_PROMPT" ]; then
+  backup="${LEGACY_PROMPT}.skillopt-legacy.bak"
+  if [ -e "$backup" ]; then
+    backup="${LEGACY_PROMPT}.skillopt-legacy.$(date +%Y%m%d%H%M%S).bak"
+  fi
+  mv "$LEGACY_PROMPT" "$backup"
+  echo "[install] legacy prompt  -> $backup"
+fi
+
+# 3) record the repo location so the runner is found from anywhere
 echo "[install] add to your shell profile:"
 echo "    export SKILLOPT_SLEEP_REPO=\"$REPO_ROOT\""
 
-# 3) optional: append an AGENTS.md hint (only if the user opts in)
+# 4) optional: append an AGENTS.md hint (only if the user opts in)
 cat <<EOF
 
 [install] Optional — add this to ~/.codex/AGENTS.md so Codex always knows the tool: