diff --git a/README.md b/README.md
index dfc2561..3d8566f 100644
--- a/README.md
+++ b/README.md
@@ -61,6 +61,15 @@ The best MCP server for Ptt. Proudly built by <a href="https://pyptt.cc/">PyPtt<
         *   `ghcr.io/pyptt/ptt_mcp_server:latest`: 指定要運行的 Docker 映像檔。
     *   `"env"`: 將 `PTT_ID` 和 `PTT_PW` 直接設定為環境變數。**請務必替換為您自己的 PTT 帳號和密碼。**
 
+    **多帳號設定（選用）：**
+    若您有多組 PTT 帳號，可改用環境變數 `PTT_ACCOUNTS`（格式：`名稱=帳號:密碼`，多組以逗號分隔）一次設定多組，之後即可用 `switch_account("名稱")` 切換帳號、`list_accounts()` 查詢可用名稱：
+
+    ```
+    PTT_ACCOUNTS=default=acc1:pw1,alt=acc2:pw2
+    ```
+
+    名稱不可含 `=`、帳號不可含 `:`、密碼不可含 `,`（PTT 帳密實務上不會用到這些字元）。使用 Docker 時，請在 `args` 中同時加上 `"-e", "PTT_ACCOUNTS"`。原本的單一 `PTT_ID`/`PTT_PW` 設定仍然相容，會自動成為名為 `default` 的帳號。
+
 3.  **啟動與測試**：
     您的 MCP 客戶端現在應該能自動啟動 PTT MCP 伺服器了。您可以嘗試一個簡單的指令來測試連線，例如要求它登入 PTT。
 
diff --git a/README_ENG.md b/README_ENG.md
index 1b66df1..03fd787 100644
--- a/README_ENG.md
+++ b/README_ENG.md
@@ -58,6 +58,15 @@ Using Docker is the most recommended way to deploy the PTT MCP Server, as it pro
      * `-e PTT_ID` and `-e PTT_PW`: Tells Docker to pass the `PTT_ID` and `PTT_PW` environment variables to the container.  
      * `ghcr.io/PyPtt/ptt_mcp_server:latest`: Specifies the Docker image to run.  
    * `env`: Sets `PTT_ID` and `PTT_PW` directly as environment variables. **Be sure to replace these with your own PTT account ID and password.**  
+
+   **Multiple accounts (optional):**  
+   If you have more than one PTT account, you can configure them all at once with the `PTT_ACCOUNTS` environment variable (format: `name=id:password`, comma-separated), then switch between them with `switch_account("name")` and list the available names with `list_accounts()`:
+
+   ```
+   PTT_ACCOUNTS=default=acc1:pw1,alt=acc2:pw2
+   ```
+
+   Names must not contain `=`, IDs must not contain `:`, and passwords must not contain `,` (PTT credentials never use these characters in practice). When using Docker, also add `"-e", "PTT_ACCOUNTS"` to `args`. The single `PTT_ID`/`PTT_PW` setup remains supported and becomes an account named `default`.
 3. Launch and Test:  
    Your MCP client should now be able to start the PTT MCP server automatically. You can try a simple command, such as asking it to log into PTT, to test the connection.
 
diff --git a/src/api_post.py b/src/api_post.py
index d743353..9e635cd 100644
--- a/src/api_post.py
+++ b/src/api_post.py
@@ -7,6 +7,22 @@
 from utils import _call_ptt_service
 
 
+def parse_date_str(date_str: str) -> datetime:
+    # Add a dummy year to make it a full date for comparison.
+    # Assuming all dates are within the current year for simplicity.
+    # For cross-year comparisons, more complex logic would be needed.
+
+    if date_str.count('/') == 2:
+        return datetime.strptime(date_str, "%Y/%m/%d")
+
+    current_year = datetime.now().year
+    return datetime.strptime(f"{current_year}/{date_str}", "%Y/%m/%d")
+
+
+def _md(d: datetime):
+    return (d.month, d.day)
+
+
 def register_tools(mcp: FastMCP, memory_storage: Dict[str, Any], version: str):
     @mcp.tool()
     def get_board_rules() -> Dict[str, Any]:
@@ -53,24 +69,14 @@ def get_post_index_range(board: str, target_date_str: str) -> Dict[str, Any]:
                             失敗時: {'success': False, 'message': str}
         """
 
-        # Helper to parse and compare dates
-        def parse_date_str(date_str: str) -> datetime:
-            # Add a dummy year to make it a full date for comparison.
-            # Assuming all dates are within the current year for simplicity.
-            # For cross-year comparisons, more complex logic would be needed.
-
-            if date_str.count('/') == 2:
-                return datetime.strptime(date_str, "%Y/%m/%d")
-
-            current_year = datetime.now().year
-            return datetime.strptime(f"{current_year}/{date_str}", "%Y/%m/%d")
-
         try:
             target_date = parse_date_str(target_date_str)
         except ValueError:
             return {"success": False,
                     "message": f"Invalid target_date_str format: {target_date_str}. Expected 'YYYY/MM/DD'."}
 
+        # ponytail: 只比對 month/day（PTT list_date 無年份）。若目標日期區間跨年（12月→1月），binary search 的單調性會被打破、結果可能不對；需要跨年支援時得改用文章 header 的完整日期。
+
         # 1. Get the newest index for the board
         newest_index_response = _call_ptt_service(
             memory_storage,
@@ -115,9 +121,9 @@ def parse_date_str(date_str: str) -> datetime:
                 low = mid + 1
                 continue
 
-            if post_date < target_date:
+            if _md(post_date) < _md(target_date):
                 low = mid + 1
-            elif post_date == target_date:
+            elif _md(post_date) == _md(target_date):
                 start_index = mid
                 high = mid - 1  # Try to find an earlier one
             else:  # post_date > target_date
@@ -148,9 +154,9 @@ def parse_date_str(date_str: str) -> datetime:
                 low = mid + 1
                 continue
 
-            if post_date > target_date:
+            if _md(post_date) > _md(target_date):
                 high = mid - 1
-            elif post_date == target_date:
+            elif _md(post_date) == _md(target_date):
                 end_index = mid
                 low = mid + 1  # Try to find a later one
             else:  # post_date < target_date
@@ -168,8 +174,8 @@ def parse_date_str(date_str: str) -> datetime:
                 index=start_index,
                 query=True,
             )
-            if not start_post_response.get('success') or not start_post_response.get('data') or parse_date_str(
-                    start_post_response['data'].get('list_date', '')) != target_date:
+            if not start_post_response.get('success') or not start_post_response.get('data') or _md(parse_date_str(
+                    start_post_response['data'].get('list_date', ''))) != _md(target_date):
                 return {"success": False,
                         "message": f"在 {board} 板找不到日期 {target_date} 的任何文章 (start_index verification failed)."}
 
@@ -181,8 +187,8 @@ def parse_date_str(date_str: str) -> datetime:
                 index=end_index,
                 query=True,
             )
-            if not end_post_response.get('success') or not end_post_response.get('data') or parse_date_str(
-                    end_post_response['data'].get('list_date', '')) != target_date:
+            if not end_post_response.get('success') or not end_post_response.get('data') or _md(parse_date_str(
+                    end_post_response['data'].get('list_date', ''))) != _md(target_date):
                 return {"success": False,
                         "message": f"在 {board} 板找不到日期 {target_date} 的任何文章 (end_index verification failed)."}
 
diff --git a/src/api_ptt.py b/src/api_ptt.py
index 6efac73..95291ac 100644
--- a/src/api_ptt.py
+++ b/src/api_ptt.py
@@ -1,3 +1,4 @@
+import threading
 from typing import Dict, Any, Optional, List, Tuple
 
 import PyPtt
@@ -5,6 +6,75 @@
 
 from utils import _call_ptt_service, _handle_ptt_exception
 
+# ponytail: module-level 鎖序列化池變動，防 FastMCP 併發呼叫造成 double-login/race。
+_pool_lock = threading.Lock()
+
+
+def _login_new_service(
+    ptt_id: str, ptt_pw: str
+) -> Tuple[Optional[Any], Dict[str, Any]]:
+    """建一個新 Service 並登入。成功回 (svc, 成功dict)；失敗先 close() 掉失敗的 svc
+    再回 (None, 錯誤dict)。此 helper 不碰 active session 或池。"""
+    ptt_service = PyPtt.Service({})
+    try:
+        ptt_service.call(
+            "login",
+            {
+                "ptt_id": ptt_id,
+                "ptt_pw": ptt_pw,
+                "kick_other_session": True,
+            },
+        )
+        return ptt_service, {"success": True, "message": "登入成功"}
+    except Exception as e:
+        # 洩漏防護：登入失敗的 Service 內有 daemon thread + 連線，離開前必須 close。
+        try:
+            ptt_service.close()
+        except Exception:
+            pass
+        return None, _handle_ptt_exception(e, {})
+
+
+def _is_alive(svc: Any) -> bool:
+    """驗活：對池裡的 Service 做一個便宜的 authenticated 呼叫探測，丟例外即視為 dead。"""
+    # ponytail: PTT 會斷閒置連線，光看 _is_login flag 偵測不到 server 端斷線，故主動用 get_time 探測。
+    try:
+        svc.call("get_time")
+        return True
+    except Exception:
+        return False
+
+
+def _activate(memory_storage: Dict[str, Any], name: str) -> Dict[str, Any]:
+    """把帳號 name 設為 active（登入並放進池）。原子性：新登入失敗不動 active session。"""
+    accounts = memory_storage["accounts"]
+    with _pool_lock:
+        pool = memory_storage["pool"]
+        svc = pool.get(name)
+
+        # 池裡有但已死 → close 汰換（離開池的 Service 都要 close 防洩漏）。
+        if svc is not None and not _is_alive(svc):
+            try:
+                svc.close()
+            except Exception:
+                pass
+            pool.pop(name, None)
+            svc = None
+
+        if svc is None:
+            svc, result = _login_new_service(accounts[name]["id"], accounts[name]["pw"])
+            if svc is None:
+                # 原子性關鍵：登入失敗，不動 ptt_bot / current_account / ptt_id / ptt_pw。
+                return result
+            pool[name] = svc
+
+        memory_storage["ptt_bot"] = svc
+        memory_storage["current_account"] = name
+        # 同步憑證，讓 bare login() 等仍與 active 帳號一致。
+        memory_storage["ptt_id"] = accounts[name]["id"]
+        memory_storage["ptt_pw"] = accounts[name]["pw"]
+        return {"success": True, "message": "登入成功"}
+
 
 def register_tools(mcp: FastMCP, memory_storage: Dict[str, Any], version: str):
     @mcp.tool()
@@ -34,8 +104,20 @@ def logout() -> Dict[str, Any]:
         if ptt_service is None:
             return {"success": False, "message": "尚未登入，無需登出"}
 
-        result = _call_ptt_service(memory_storage, "logout", success_message="登出成功")
-        memory_storage["ptt_bot"] = None
+        # 只登出 active 帳號：logout 後 close、從池移除、ptt_bot=None；其他池內帳號不動。
+        with _pool_lock:
+            result = _call_ptt_service(
+                memory_storage, "logout", success_message="登出成功"
+            )
+            try:
+                ptt_service.close()
+            except Exception:
+                pass
+            pool = memory_storage["pool"]
+            for pool_name, pool_svc in list(pool.items()):
+                if pool_svc is ptt_service:
+                    del pool[pool_name]
+            memory_storage["ptt_bot"] = None
         return result
 
     @mcp.tool()
@@ -68,31 +150,83 @@ def login() -> Dict[str, Any]:
                             - 'NEED_MODERATOR_PERMISSION': 需要看板管理員權限。
                             - 'UNKNOWN_ERROR': 操作時發生未知錯誤。
         """
-        # 如果已經有一個 bot 實例，先登出舊的
-        if memory_storage["ptt_bot"] is not None:
-            try:
-                memory_storage["ptt_bot"].call("logout")
-                memory_storage["ptt_bot"] = None  # 清除 session
-            except Exception:
-                pass
+        return _activate(memory_storage, memory_storage["current_account"])
 
-        ptt_service = PyPtt.Service({})
-        try:
-            ptt_service.call(
-                "login",
-                {
-                    "ptt_id": memory_storage["ptt_id"],
-                    "ptt_pw": memory_storage["ptt_pw"],
-                    "kick_other_session": True,
-                },
-            )
-            # 登入成功後，將 bot 實例存起來
-            memory_storage["ptt_bot"] = ptt_service
+    @mcp.tool()
+    def list_accounts() -> Dict[str, Any]:
+        """列出已在環境變數設定的 PTT 帳號名稱（不含密碼），以及目前登入中的帳號名稱。
 
-            return {"success": True, "message": "登入成功"}
-        except Exception as e:
-            memory_storage["ptt_bot"] = None
-            return _handle_ptt_exception(e, {})
+        Returns:
+            Dict[str, Any]: {'success': True,
+                             'accounts': ['default', 'alt', ...],
+                             'current': 'default' 或 None}
+        """
+        # ponytail: 用 whoami 那套真實狀態判定（讀 PyPtt 私有 _is_login），沒 active 登入才不謊報。
+        api = getattr(memory_storage.get("ptt_bot"), "_api", None)
+        current = (
+            memory_storage.get("current_account")
+            if getattr(api, "_is_login", False)
+            else None
+        )
+        return {
+            "success": True,
+            "accounts": list(memory_storage.get("accounts", {}).keys()),
+            "current": current,
+        }
+
+    @mcp.tool()
+    def switch_account(name: str) -> Dict[str, Any]:
+        """切換到指定名稱的 PTT 帳號並登入。
+
+        帳號需事先透過環境變數 PTT_ACCOUNTS 設定（見 README）。切換後會記住此帳號，
+        後續 login() 也會使用它。可先用 list_accounts() 查詢可用名稱。
+
+        Args:
+            name (str): 帳號名稱。
+
+        Returns:
+            Dict[str, Any]: 成功 {'success': True,
+                                  'message': "已切換到帳號 'xxx' 並登入成功",
+                                  'current': 'xxx'}
+                            找不到名稱 {'success': False,
+                                        'message': "找不到帳號 'xxx'",
+                                        'available': [...]}
+                            登入失敗則回傳 login 相同的錯誤格式。
+        """
+        accounts = memory_storage.get("accounts", {})
+        if name not in accounts:
+            return {
+                "success": False,
+                "message": f"找不到帳號 '{name}'",
+                "available": list(accounts.keys()),
+            }
+        result = _activate(memory_storage, name)
+        if result.get("success"):
+            result["message"] = f"已切換到帳號 '{name}' 並登入成功"
+            result["current"] = name
+        return result
+
+    @mcp.tool()
+    def whoami() -> Dict[str, Any]:
+        """回傳目前登入中的 PTT 帳號資訊，實際登入狀態直接向 PyPtt 查詢。
+
+        Returns:
+            Dict[str, Any]: {'success': True,
+                             'account': 'default',   # 帳號名稱（來自 PTT_ACCOUNTS 標籤）
+                             'ptt_id': 'CodingMan',  # PyPtt 目前登入的實際 PTT ID；未登入為 None
+                             'logged_in': True}      # PyPtt 回報是否已登入
+        """
+        # ponytail: 讀 PyPtt 私有屬性取真實狀態；PyPtt 無公開存取方法，改版壞了再換
+        api = getattr(memory_storage.get("ptt_bot"), "_api", None)
+        logged_in = bool(getattr(api, "_is_login", False))
+        # PyPtt 登出不清 ptt_id，未登入時不回報殘留值
+        ptt_id = (getattr(api, "ptt_id", "") or None) if logged_in else None
+        return {
+            "success": True,
+            "account": memory_storage.get("current_account"),
+            "ptt_id": ptt_id,
+            "logged_in": logged_in,
+        }
 
     @mcp.tool()
     def get_post(
diff --git a/src/auto_version.py b/src/auto_version.py
index 27d27b6..1b83391 100644
--- a/src/auto_version.py
+++ b/src/auto_version.py
@@ -38,6 +38,10 @@ def get_version() -> tuple[Optional[str], Optional[str]]:
     return None, None  # Should not be reached
 
 
+def _version_key(version_str: str) -> tuple:
+    return tuple(int(part) for part in version_str.split('.'))
+
+
 def main():
     remote_version, current_version = get_version()
 
@@ -45,7 +49,7 @@ def main():
         print("Failed to retrieve version information.")
         return
 
-    if int(remote_version.replace('.', '')) <= int(current_version.replace('.', '')):
+    if _version_key(remote_version) <= _version_key(current_version):
         print(current_version)
     else:
         print(remote_version)
diff --git a/src/mcp_server.py b/src/mcp_server.py
index 97fad68..ba5e437 100644
--- a/src/mcp_server.py
+++ b/src/mcp_server.py
@@ -1,3 +1,4 @@
+import atexit
 import os
 from typing import Dict, Any
 
@@ -7,21 +8,75 @@
 import api_ptt
 from _version import __version__
 
+
+def parse_accounts(raw: str) -> Dict[str, Dict[str, str]]:
+    """解析 PTT_ACCOUNTS 字串：'名稱=帳號:密碼,名稱2=帳號2:密碼2'。"""
+    accounts: Dict[str, Dict[str, str]] = {}
+    # ponytail: 逗號分隔項目、= 分名稱、: 分帳密；名稱不可含 =、帳號不可含 :、密碼不可含 ,。
+    # PTT 帳號為英數、密碼 ≤8 碼，實務上不會撞到這些分隔字元；若未來要支援特殊字元再換 JSON/檔案。
+    for entry in raw.split(","):
+        entry = entry.strip()
+        if not entry:
+            continue
+        if "=" not in entry:
+            raise ValueError(
+                f"PTT_ACCOUNTS 項目格式錯誤（需 名稱=帳號:密碼）: {entry!r}"
+            )
+        name, cred = entry.split("=", 1)
+        name = name.strip()
+        if ":" not in cred:
+            raise ValueError(f"PTT_ACCOUNTS['{name}'] 需為 帳號:密碼 格式")
+        acc_id, acc_pw = cred.split(":", 1)
+        acc_id, acc_pw = acc_id.strip(), acc_pw.strip()
+        if not name or not acc_id or not acc_pw:
+            raise ValueError(f"PTT_ACCOUNTS 項目名稱/帳號/密碼不可為空: {entry!r}")
+        accounts[name] = {"id": acc_id, "pw": acc_pw}
+    return accounts
+
+
 PTT_ID = os.getenv("PTT_ID")
 PTT_PW = os.getenv("PTT_PW")
+PTT_ACCOUNTS_RAW = os.getenv("PTT_ACCOUNTS")
+
+accounts: Dict[str, Dict[str, str]] = (
+    parse_accounts(PTT_ACCOUNTS_RAW) if PTT_ACCOUNTS_RAW else {}
+)
 
-if not PTT_ID or not PTT_PW:
-    raise ValueError("PTT_ID and PTT_PW environment variables must be set.")
+# 相容舊設定：PTT_ID/PTT_PW 視為名為 default 的帳號
+if PTT_ID and PTT_PW:
+    accounts.setdefault("default", {"id": PTT_ID, "pw": PTT_PW})
+
+if not accounts:
+    raise ValueError("請設定 PTT_ACCOUNTS，或 PTT_ID 與 PTT_PW 環境變數。")
+
+initial = "default" if "default" in accounts else next(iter(accounts))
 
 mcp: FastMCP = FastMCP(f"Ptt MCP Server v{__version__}")
 
-MEMORY_STORAGE: Dict[str, Any] = {"ptt_bot": None, "ptt_id": PTT_ID, "ptt_pw": PTT_PW}
+MEMORY_STORAGE: Dict[str, Any] = {
+    "ptt_bot": None,
+    "pool": {},
+    "ptt_id": accounts[initial]["id"],
+    "ptt_pw": accounts[initial]["pw"],
+    "accounts": accounts,
+    "current_account": initial,
+}
+
+
+def _close_pool() -> None:
+    # 關站時關掉池內所有 Service（各有 daemon thread + 連線），避免洩漏。
+    for svc in MEMORY_STORAGE["pool"].values():
+        try:
+            svc.close()
+        except Exception:
+            pass
 
 
 def main():
     api_ptt.register_tools(mcp, MEMORY_STORAGE, __version__)
     api_post.register_tools(mcp, MEMORY_STORAGE, __version__)
 
+    atexit.register(_close_pool)
     mcp.run()
 
 
diff --git a/src/test_api_post.py b/src/test_api_post.py
new file mode 100644
index 0000000..e0dd9a2
--- /dev/null
+++ b/src/test_api_post.py
@@ -0,0 +1,38 @@
+import os
+import sys
+import types
+
+
+def _load_helpers():
+    # Allow running from the repo root: `python src/test_api_post.py`.
+    src_dir = os.path.dirname(os.path.abspath(__file__))
+    if src_dir not in sys.path:
+        sys.path.insert(0, src_dir)
+
+    # api_post (via utils) imports PyPtt and fastmcp at module load time. Those
+    # are heavy runtime deps that may not be installed in a test environment, so
+    # stub them out before importing the pure date helpers we want to test.
+    sys.modules.setdefault("PyPtt", types.ModuleType("PyPtt"))
+    if "fastmcp" not in sys.modules:
+        fastmcp_stub = types.ModuleType("fastmcp")
+        setattr(fastmcp_stub, "FastMCP", object)
+        sys.modules["fastmcp"] = fastmcp_stub
+
+    from api_post import _md, parse_date_str
+
+    return _md, parse_date_str
+
+
+def test_md_compare():
+    _md, parse_date_str = _load_helpers()
+
+    # A target date carrying a year (e.g. "1987/09/06") must match a yearless
+    # PTT list_date ("9/06") once compared via _md(). The original broken case.
+    assert _md(parse_date_str("1987/09/06")) == _md(parse_date_str("9/06"))
+    assert _md(parse_date_str("6/29")) == (6, 29)
+    assert _md(parse_date_str("6/29")) != _md(parse_date_str("6/30"))
+
+
+if __name__ == "__main__":
+    test_md_compare()
+    print("OK")
diff --git a/src/test_auto_version.py b/src/test_auto_version.py
new file mode 100644
index 0000000..a4db103
--- /dev/null
+++ b/src/test_auto_version.py
@@ -0,0 +1,13 @@
+from auto_version import _version_key
+
+
+def test_version_key():
+    assert _version_key("0.3.0") > _version_key("0.2.15")
+    assert _version_key("1.0.0") > _version_key("0.20.0")
+    assert _version_key("0.10.0") > _version_key("0.9.0")
+    assert _version_key("0.3.0") == _version_key("0.3.0")
+
+
+if __name__ == "__main__":
+    test_version_key()
+    print("OK")
diff --git a/src/test_parse_accounts.py b/src/test_parse_accounts.py
new file mode 100644
index 0000000..2085e76
--- /dev/null
+++ b/src/test_parse_accounts.py
@@ -0,0 +1,77 @@
+import os
+import sys
+import types
+
+
+class _FakeFastMCP:
+    # mcp_server 會在模組載入時執行 FastMCP(name)，stub 需可帶參數實例化。
+    def __init__(self, *args, **kwargs):
+        pass
+
+
+def _load_parse_accounts():
+    # Allow running from the repo root: `python src/test_parse_accounts.py`.
+    src_dir = os.path.dirname(os.path.abspath(__file__))
+    if src_dir not in sys.path:
+        sys.path.insert(0, src_dir)
+
+    # mcp_server (via api_ptt/api_post/utils) imports PyPtt and fastmcp at
+    # module load time. Those are heavy runtime deps that may not be installed
+    # in a test environment, so stub them out before importing.
+    sys.modules.setdefault("PyPtt", types.ModuleType("PyPtt"))
+    fastmcp_mod = sys.modules.get("fastmcp")
+    if fastmcp_mod is None:
+        fastmcp_mod = types.ModuleType("fastmcp")
+        sys.modules["fastmcp"] = fastmcp_mod
+    # 其他測試檔的 stub 以 object 佔位，無法帶參數實例化，這裡一併升級。
+    if getattr(fastmcp_mod, "FastMCP", None) in (None, object):
+        setattr(fastmcp_mod, "FastMCP", _FakeFastMCP)
+
+    # mcp_server 載入時會讀取環境變數並驗證至少有一組帳號。
+    os.environ.pop("PTT_ACCOUNTS", None)
+    os.environ.setdefault("PTT_ID", "testid")
+    os.environ.setdefault("PTT_PW", "testpw")
+
+    from mcp_server import parse_accounts
+
+    return parse_accounts
+
+
+def test_parse_accounts_basic():
+    parse_accounts = _load_parse_accounts()
+
+    assert parse_accounts("default=a:b,alt=c:d") == {
+        "default": {"id": "a", "pw": "b"},
+        "alt": {"id": "c", "pw": "d"},
+    }
+
+
+def test_parse_accounts_strips_whitespace():
+    parse_accounts = _load_parse_accounts()
+
+    assert parse_accounts(" default = a:b ") == {"default": {"id": "a", "pw": "b"}}
+
+
+def test_parse_accounts_invalid():
+    parse_accounts = _load_parse_accounts()
+
+    for raw in [
+        "noequal",  # 缺 =
+        "name=nocolon",  # 缺 :
+        "=a:b",  # 空名稱
+        "name=:pw",  # 空帳號
+        "name=a:",  # 空密碼
+    ]:
+        try:
+            parse_accounts(raw)
+        except ValueError:
+            pass
+        else:
+            raise AssertionError(f"expected ValueError for {raw!r}")
+
+
+if __name__ == "__main__":
+    test_parse_accounts_basic()
+    test_parse_accounts_strips_whitespace()
+    test_parse_accounts_invalid()
+    print("OK")
diff --git a/src/test_switch_account.py b/src/test_switch_account.py
new file mode 100644
index 0000000..2da3c6f
--- /dev/null
+++ b/src/test_switch_account.py
@@ -0,0 +1,148 @@
+import os
+import sys
+import types
+
+
+class _FakeService:
+    # 記錄 login/close 呼叫、支援 get_time 驗活與 logout 的假 Service。
+    def __init__(self, alive=True, login_error=None):
+        self.login_calls = 0
+        self.close_calls = 0
+        self.alive = alive
+        self.login_error = login_error
+        self._api = types.SimpleNamespace(_is_login=False, ptt_id=None)
+
+    def call(self, api, args=None):
+        if api == "login":
+            self.login_calls += 1
+            if self.login_error is not None:
+                raise self.login_error
+            self._api._is_login = True
+            self._api.ptt_id = (args or {}).get("ptt_id")
+            return None
+        if api == "get_time":
+            if not self.alive:
+                raise RuntimeError("dead connection")
+            return "12:34"
+        if api == "logout":
+            self._api._is_login = False
+            return None
+        return None
+
+    def close(self):
+        self.close_calls += 1
+
+
+class _FakeMCP:
+    # Minimal stand-in for FastMCP that just records registered tools.
+    def __init__(self):
+        self.tools = {}
+
+    def tool(self):
+        def decorator(func):
+            self.tools[func.__name__] = func
+            return func
+
+        return decorator
+
+
+def _load_api_ptt():
+    # Allow running from the repo root: `python src/test_switch_account.py`.
+    src_dir = os.path.dirname(os.path.abspath(__file__))
+    if src_dir not in sys.path:
+        sys.path.insert(0, src_dir)
+
+    # api_ptt (and utils) import PyPtt and fastmcp at module load time. Those
+    # are heavy runtime deps that may not be installed in a test environment,
+    # so stub them out before importing.
+    sys.modules.setdefault("PyPtt", types.ModuleType("PyPtt"))
+    if "fastmcp" not in sys.modules:
+        fastmcp_stub = types.ModuleType("fastmcp")
+        setattr(fastmcp_stub, "FastMCP", object)
+        sys.modules["fastmcp"] = fastmcp_stub
+
+    import api_ptt
+
+    return api_ptt
+
+
+def _register_tools(api_ptt):
+    mcp = _FakeMCP()
+    memory_storage = {
+        "ptt_bot": None,
+        "pool": {},
+        "ptt_id": "acc1",
+        "ptt_pw": "pw1",
+        "accounts": {
+            "default": {"id": "acc1", "pw": "pw1"},
+            "alt": {"id": "acc2", "pw": "pw2"},
+        },
+        "current_account": "default",
+    }
+    api_ptt.register_tools(mcp, memory_storage, "0.0.0")
+    return mcp.tools, memory_storage
+
+
+def test_switch_account_unknown_name():
+    api_ptt = _load_api_ptt()
+    tools, memory_storage = _register_tools(api_ptt)
+
+    # 找不到帳號時提前返回，不進 _activate，故無需 stub 登入。
+    result = tools["switch_account"]("nope")
+
+    assert result["success"] is False
+    assert sorted(result["available"]) == ["alt", "default"]
+    # 找不到帳號時不得改動現有帳密與登入狀態
+    assert memory_storage["ptt_id"] == "acc1"
+    assert memory_storage["ptt_pw"] == "pw1"
+    assert memory_storage["current_account"] == "default"
+
+
+def test_switch_account_success():
+    api_ptt = _load_api_ptt()
+    tools, memory_storage = _register_tools(api_ptt)
+
+    original = api_ptt._login_new_service
+    setattr(
+        api_ptt,
+        "_login_new_service",
+        lambda ptt_id, ptt_pw: (_FakeService(), {"success": True, "message": "登入成功"}),
+    )
+    try:
+        result = tools["switch_account"]("alt")
+    finally:
+        setattr(api_ptt, "_login_new_service", original)
+
+    assert result["success"] is True
+    assert result["current"] == "alt"
+    assert result["message"] == "已切換到帳號 'alt' 並登入成功"
+    assert memory_storage["ptt_id"] == "acc2"
+    assert memory_storage["ptt_pw"] == "pw2"
+    assert memory_storage["current_account"] == "alt"
+    # active svc 進池、ptt_bot 指到它
+    assert memory_storage["pool"]["alt"] is memory_storage["ptt_bot"]
+
+
+def test_list_accounts():
+    api_ptt = _load_api_ptt()
+    tools, memory_storage = _register_tools(api_ptt)
+
+    result = tools["list_accounts"]()
+    assert result["success"] is True
+    assert sorted(result["accounts"]) == ["alt", "default"]
+    # 未登入（ptt_bot=None）不得謊報 current
+    assert result["current"] is None
+
+    # 有 active 登入時，current 反映真實登入帳號
+    memory_storage["current_account"] = "alt"
+    memory_storage["ptt_bot"] = types.SimpleNamespace(
+        _api=types.SimpleNamespace(_is_login=True, ptt_id="acc2")
+    )
+    assert tools["list_accounts"]()["current"] == "alt"
+
+
+if __name__ == "__main__":
+    test_switch_account_unknown_name()
+    test_switch_account_success()
+    test_list_accounts()
+    print("OK")
diff --git a/src/test_switch_account_pool.py b/src/test_switch_account_pool.py
new file mode 100644
index 0000000..a5e57f7
--- /dev/null
+++ b/src/test_switch_account_pool.py
@@ -0,0 +1,177 @@
+"""Service 池行為測試：原子切換、死連線汰換、洩漏防護（close）、真實登入狀態。
+
+沿用 test_switch_account 的 _load_api_ptt/_register_tools 與假 Service。
+以「工廠依預排順序發假 Service」驅動 _login_new_service 的真實路徑，
+藉此連 close-on-failed-login 一併驗到。
+"""
+
+from test_switch_account import _FakeService, _load_api_ptt, _register_tools
+
+# _handle_ptt_exception 會參照這些 PyPtt 例外類別，stub 需補上才不會 AttributeError。
+_PTT_EXCEPTIONS = [
+    "RequireLogin", "UnregisteredUser", "NoSuchBoard", "NoSuchPost",
+    "NoPermission", "LoginError", "WrongIDorPassword", "CantResponse",
+    "NoFastComment", "NoSuchUser", "NoSuchMail", "MailboxFull", "NoMoney",
+    "SetContactMailFirst", "WrongPassword", "NeedModeratorPermission",
+]
+
+
+class _ServiceFactory:
+    # 取代 PyPtt.Service：依測試預排順序把假 Service 發給 _login_new_service。
+    def __init__(self):
+        self.handed_out = []
+        self._queue = []
+
+    def prepare(self, *svcs):
+        self._queue.extend(svcs)
+
+    def __call__(self, config=None):
+        svc = self._queue.pop(0)
+        self.handed_out.append(svc)
+        return svc
+
+    @property
+    def login_total(self):
+        return sum(s.login_calls for s in self.handed_out)
+
+
+def _setup(api_ptt):
+    ptt = api_ptt.PyPtt
+    for name in _PTT_EXCEPTIONS:
+        if not hasattr(ptt, name):
+            setattr(ptt, name, type(name, (Exception,), {}))
+    factory = _ServiceFactory()
+    setattr(ptt, "Service", factory)
+    return factory
+
+
+def test_atomic_on_failed_switch():
+    # (a)(e) 切到密碼錯的帳號後，active session 與 current 維持不變；失敗的 svc 被 close。
+    api_ptt = _load_api_ptt()
+    factory = _setup(api_ptt)
+    tools, ms = _register_tools(api_ptt)
+    ms["accounts"]["bad"] = {"id": "accX", "pw": "wrong"}
+
+    svc_default = _FakeService()
+    wrong = api_ptt.PyPtt.WrongIDorPassword("bad pw")
+    svc_bad = _FakeService(login_error=wrong)
+    factory.prepare(svc_default, svc_bad)
+
+    assert tools["switch_account"]("default")["success"] is True
+    assert ms["ptt_bot"] is svc_default
+    assert ms["current_account"] == "default"
+
+    result = tools["switch_account"]("bad")
+    assert result["success"] is False
+    assert ms["ptt_bot"] is svc_default          # 原子性：active 不變
+    assert ms["current_account"] == "default"
+    assert ms["ptt_id"] == "acc1"
+    assert svc_bad.close_calls == 1              # 洩漏防護
+    assert "bad" not in ms["pool"]
+
+
+def test_switch_to_new_account():
+    # (b) 成功切到新帳號：池多一筆、ptt_bot 指到新 svc、current 更新。
+    api_ptt = _load_api_ptt()
+    factory = _setup(api_ptt)
+    tools, ms = _register_tools(api_ptt)
+
+    svc_default = _FakeService()
+    svc_alt = _FakeService()
+    factory.prepare(svc_default, svc_alt)
+
+    tools["switch_account"]("default")
+    result = tools["switch_account"]("alt")
+
+    assert result["success"] is True
+    assert set(ms["pool"]) == {"default", "alt"}
+    assert ms["ptt_bot"] is svc_alt
+    assert ms["current_account"] == "alt"
+
+
+def test_switch_back_to_alive_reuses():
+    # (c) 切回池中活著的帳號：不觸發新 login，ptt_bot 重指到既有 svc。
+    api_ptt = _load_api_ptt()
+    factory = _setup(api_ptt)
+    tools, ms = _register_tools(api_ptt)
+
+    svc_default = _FakeService(alive=True)
+    svc_alt = _FakeService(alive=True)
+    factory.prepare(svc_default, svc_alt)
+
+    tools["switch_account"]("default")
+    tools["switch_account"]("alt")
+    logins_before = factory.login_total
+    services_before = len(factory.handed_out)
+
+    result = tools["switch_account"]("default")
+    assert result["success"] is True
+    assert factory.login_total == logins_before          # 沒有新 login
+    assert len(factory.handed_out) == services_before     # 沒有新 Service
+    assert ms["ptt_bot"] is svc_default
+    assert ms["current_account"] == "default"
+
+
+def test_switch_to_dead_relogs():
+    # (d)(e) 切到池中死掉的帳號：舊 svc 被 close，且發生一次重登。
+    api_ptt = _load_api_ptt()
+    factory = _setup(api_ptt)
+    tools, ms = _register_tools(api_ptt)
+
+    svc_default = _FakeService(alive=True)
+    svc_alt = _FakeService(alive=True)
+    svc_default2 = _FakeService(alive=True)
+    factory.prepare(svc_default, svc_alt, svc_default2)
+
+    tools["switch_account"]("default")
+    tools["switch_account"]("alt")
+    svc_default.alive = False                     # 模擬 server 端閒置斷線
+
+    result = tools["switch_account"]("default")
+    assert result["success"] is True
+    assert svc_default.close_calls == 1           # 死連線被汰換並 close
+    assert svc_default2.login_calls == 1          # 一次重登
+    assert ms["ptt_bot"] is svc_default2
+    assert ms["pool"]["default"] is svc_default2
+
+
+def test_logout_closes_active_only():
+    # logout 只登出/close/移除 active 帳號，其他池內帳號不動。
+    api_ptt = _load_api_ptt()
+    factory = _setup(api_ptt)
+    tools, ms = _register_tools(api_ptt)
+
+    svc_default = _FakeService()
+    svc_alt = _FakeService()
+    factory.prepare(svc_default, svc_alt)
+
+    tools["switch_account"]("default")
+    tools["switch_account"]("alt")                # active = alt
+
+    result = tools["logout"]()
+    assert result["success"] is True
+    assert svc_alt.close_calls == 1
+    assert "alt" not in ms["pool"]
+    assert ms["ptt_bot"] is None
+    assert ms["pool"]["default"] is svc_default    # 其他池內帳號不動
+    assert svc_default.close_calls == 0
+
+
+def test_list_accounts_current_none_when_not_logged_in():
+    # (f) 未登入時 current 為 None。
+    api_ptt = _load_api_ptt()
+    _setup(api_ptt)
+    tools, ms = _register_tools(api_ptt)
+
+    assert ms["ptt_bot"] is None
+    assert tools["list_accounts"]()["current"] is None
+
+
+if __name__ == "__main__":
+    test_atomic_on_failed_switch()
+    test_switch_to_new_account()
+    test_switch_back_to_alive_reuses()
+    test_switch_to_dead_relogs()
+    test_logout_closes_active_only()
+    test_list_accounts_current_none_when_not_logged_in()
+    print("OK")
diff --git a/src/test_whoami.py b/src/test_whoami.py
new file mode 100644
index 0000000..67042f8
--- /dev/null
+++ b/src/test_whoami.py
@@ -0,0 +1,45 @@
+import types
+
+from test_switch_account import _load_api_ptt, _register_tools
+
+
+def test_whoami_not_logged_in():
+    tools, memory_storage = _register_tools(_load_api_ptt())
+
+    result = tools["whoami"]()
+    assert result["success"] is True
+    assert result["account"] == "default"
+    assert result["ptt_id"] is None
+    assert result["logged_in"] is False
+
+
+def test_whoami_logged_in():
+    tools, memory_storage = _register_tools(_load_api_ptt())
+    memory_storage["ptt_bot"] = types.SimpleNamespace(
+        _api=types.SimpleNamespace(_is_login=True, ptt_id="CodingMan")
+    )
+    memory_storage["current_account"] = "alt"
+
+    result = tools["whoami"]()
+    assert result["account"] == "alt"
+    assert result["ptt_id"] == "CodingMan"
+    assert result["logged_in"] is True
+
+
+def test_whoami_stale_ptt_id_after_logout():
+    # PyPtt 登出後不會清 ptt_id，whoami 不得回報殘留值
+    tools, memory_storage = _register_tools(_load_api_ptt())
+    memory_storage["ptt_bot"] = types.SimpleNamespace(
+        _api=types.SimpleNamespace(_is_login=False, ptt_id="stale")
+    )
+
+    result = tools["whoami"]()
+    assert result["logged_in"] is False
+    assert result["ptt_id"] is None
+
+
+if __name__ == "__main__":
+    test_whoami_not_logged_in()
+    test_whoami_logged_in()
+    test_whoami_stale_ptt_id_after_logout()
+    print("OK")