diff --git a/hooks/hooks.json b/hooks/hooks.json
index 729bf36..11cc543 100644
--- a/hooks/hooks.json
+++ b/hooks/hooks.json
@@ -4,7 +4,10 @@
       { "hooks": [ { "type": "command", "command": "sh \"${CLAUDE_PLUGIN_ROOT}/hooks/session-timer.sh\" start" } ] }
     ],
     "UserPromptSubmit": [
-      { "hooks": [ { "type": "command", "command": "sh \"${CLAUDE_PLUGIN_ROOT}/hooks/ste100-guard.sh\"" } ] }
+      { "hooks": [
+        { "type": "command", "command": "sh \"${CLAUDE_PLUGIN_ROOT}/hooks/ste100-guard.sh\"" },
+        { "type": "command", "command": "sh \"${CLAUDE_PLUGIN_ROOT}/hooks/sdlc-gate.sh\" check" }
+      ] }
     ],
     "Stop": [
       { "hooks": [ { "type": "command", "command": "sh \"${CLAUDE_PLUGIN_ROOT}/hooks/session-timer.sh\" mark" } ] }
diff --git a/hooks/sdlc-gate.sh b/hooks/sdlc-gate.sh
new file mode 100755
index 0000000..cb1860f
--- /dev/null
+++ b/hooks/sdlc-gate.sh
@@ -0,0 +1,46 @@
+#!/usr/bin/env sh
+# sdlc-gate.sh — SDLC 每 session 模型鎖（stage ∈ plan/analyze/implement/maintain）。
+# 狀態檔: $JSC_HOME/sessions/{sid}.stage，單行「{stage} {model}」。
+# 用法:
+#   sdlc-gate.sh lock {stage} {model}  # 階段閘門通過時上鎖（覆寫既有鎖）
+#   sdlc-gate.sh unlock                # 移除狀態檔
+#   sdlc-gate.sh check                 # hook 模式（UserPromptSubmit）：模型不符時注入繁中提醒
+#   sdlc-gate.sh report                # 印出 {sid} {stage} {model}；無鎖不印
+# 缺資料時安靜降級，永遠 exit 0，不可中斷宿主 CLI。
+HERE=$(dirname "$0"); . "$HERE/lib.sh"
+read_stdin
+sid=$(session_id)
+state="$JSC_HOME/sessions/$sid.stage"
+
+case "${1:-check}" in
+  lock)
+    # 需要 stage 與 model 兩個參數，缺一就安靜降級
+    if [ -n "${2:-}" ] && [ -n "${3:-}" ]; then
+      printf '%s %s\n' "$2" "$3" > "$state" 2>/dev/null || true
+    fi ;;
+  unlock)
+    rm -f "$state" 2>/dev/null || true ;;
+  check)
+    [ -f "$state" ] || exit 0
+    stage=$(sed -n '1s/ .*//p' "$state" 2>/dev/null)
+    locked=$(sed -n '1s/^[^ ]* //p' "$state" 2>/dev/null)
+    [ -n "$stage" ] && [ -n "$locked" ] || exit 0
+    # 目前模型判定順序：stdin JSON model > JSC_MODEL > ~/.claude/settings.json（僅 JSC_CLI 為 claude 或未設定時）
+    cur=$(json_str model)
+    [ -n "$cur" ] || cur="${JSC_MODEL:-}"
+    if [ -z "$cur" ] && { [ -z "${JSC_CLI:-}" ] || [ "${JSC_CLI:-}" = "claude" ]; }; then
+      cur=$(tr -d '\n' < "$HOME/.claude/settings.json" 2>/dev/null \
+        | sed -n 's/.*"model"[[:space:]]*:[[:space:]]*"\([^"]*\)".*/\1/p' | head -n1)
+    fi
+    [ -n "$cur" ] || exit 0
+    # 別名相容：一方包含另一方就視為同一模型（例：opus 對 claude-opus-4-6）
+    case "$cur" in *"$locked"*) exit 0 ;; esac
+    case "$locked" in *"$cur"*) exit 0 ;; esac
+    echo "[jsc] SDLC 模型鎖：階段「${stage}」已鎖定模型「${locked}」，目前模型「${cur}」不符。請拒絕執行任何 SDLC 工作，並請使用者切回模型「${locked}」後再繼續。此鎖會在下一個 SDLC 階段閘門執行時解除。" ;;
+  report)
+    if [ -f "$state" ]; then
+      line=$(sed -n '1p' "$state" 2>/dev/null)
+      [ -n "$line" ] && echo "$sid $line"
+    fi ;;
+esac
+exit 0