diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3b60651..5e1af74 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -405,3 +405,8 @@
 - `ensure_logged_in()` now automatically obtains a new transit token with the approved local device when the token is missing or expired.
 - Falls back to the normal secret-key login prompt when trusted-device renewal is unavailable.
 - Authorization testing passed; included in the private repository release.
+## 1.5.40 (2026-08-17)
+
+### Trusted-device key location
+- Store the trusted-device key at `~/.oracle-jump-query/device-key.json`, shared by all installations of the Skill for the same Windows user.
+- Never migrate or overwrite another key; the private key is created once and never committed or uploaded.
diff --git a/SKILL.md b/SKILL.md
index 4b5273d..995d25b 100644
--- a/SKILL.md
+++ b/SKILL.md
@@ -57,6 +57,8 @@ python scripts/oracle_skill.py login <secretKey> [clientCode]
 | `clients` | 无感刷新当前用户最新授权的 client 列表（只使用当前登录 token） |
 | `device_register [deviceName]` | 在本机生成 Ed25519 密钥并提交可信设备注册请求；后台审批前状态为 `PENDING` |
 | `device_login [clientCode]` | 使用本机密钥完成 challenge/signature 可信设备登录；仅限后台已审批设备 |
+
+可信设备私钥和 `device_id` 保存在当前 Windows 用户目录的 `~/.oracle-jump-query/device-key.json`，同一用户下的不同 Skill 安装共享该文件。首次执行 `device_register` 时生成设备 ID；之后始终从该文件读取，不会覆盖或重新生成，因此同一台电脑的设备 ID 不会变化。该文件不提交到 Git。
 | `switch <clientCode|clientName>` | 按 code 或名称切换当前 client；找不到时自动刷新 client 列表 |
 | `analyze <schema> <proc>` | 完整分析存储过程 |
 | `source <schema> <proc>` | 获取存储过程源码 |
diff --git a/VERSION b/VERSION
index 9caff18..adecc24 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.5.39
+1.5.40
diff --git a/scripts/oracle_skill.py b/scripts/oracle_skill.py
index 2a1b1d5..aea62a1 100644
--- a/scripts/oracle_skill.py
+++ b/scripts/oracle_skill.py
@@ -2002,7 +2002,7 @@ def cmd_login(secret_key: str, client_code: str = ""):
 
 
 def _device_key_path() -> str:
-    return os.path.join(get_script_dir(), "device-key.json")
+    return os.path.join(os.path.expanduser("~"), ".oracle-jump-query", "device-key.json")
 
 
 def _load_device_key() -> Dict[str, Any]:
@@ -2012,7 +2012,8 @@ def _load_device_key() -> Dict[str, Any]:
 
 def _save_device_key(item: Dict[str, Any]) -> None:
     path = _device_key_path()
-    with open(path, "w", encoding="utf-8") as f:
+    os.makedirs(os.path.dirname(path), mode=0o700, exist_ok=True)
+    with open(path, "x", encoding="utf-8") as f:
         json.dump(item, f, ensure_ascii=False, indent=2)
     try:
         os.chmod(path, 0o600)
@@ -2043,7 +2044,11 @@ def cmd_device_register(device_name: str = ""):
         private = Ed25519PrivateKey.generate()
         public = private.public_key().public_bytes_raw()
         key = {"device_id": "device-" + secrets.token_hex(12), "private_key": base64.b64encode(private.private_bytes_raw()).decode("ascii"), "public_key": base64.b64encode(public).decode("ascii"), "key_fingerprint": hashlib.sha256(public).hexdigest()}
-        _save_device_key(key)
+        try:
+            _save_device_key(key)
+        except FileExistsError:
+            # Another Skill process created the stable key first; never overwrite it.
+            key = _load_device_key()
     mac_hash, mac_masked = _device_identity()
     body = {"device_id": key["device_id"], "device_name": device_name or platform.node() or "Trusted device", "computer_name": platform.node(), "os_name": platform.platform(), "key_algorithm": "ED25519", "public_key": key["public_key"], "key_fingerprint": key["key_fingerprint"], "mac_hash": mac_hash, "mac_masked": mac_masked, "description": "Registered by oracle-jump-query skill"}
     try: