diff --git a/pyproject.toml b/pyproject.toml
index 846165c..63c9023 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "mcp-synology-filestation"
-version = "0.2.4"
+version = "0.2.5"
 description = "MCP server for Synology FileStation"
 requires-python = ">=3.12"
 dependencies = [
diff --git a/src/mcp_synology_filestation/__init__.py b/src/mcp_synology_filestation/__init__.py
index 4646ba6..a334bba 100644
--- a/src/mcp_synology_filestation/__init__.py
+++ b/src/mcp_synology_filestation/__init__.py
@@ -1,3 +1,3 @@
 """MCP server for Synology FileStation."""
 
-__version__ = "0.2.4"
+__version__ = "0.2.5"
diff --git a/src/mcp_synology_filestation/client.py b/src/mcp_synology_filestation/client.py
index 10ea729..2c06f6c 100644
--- a/src/mcp_synology_filestation/client.py
+++ b/src/mcp_synology_filestation/client.py
@@ -247,8 +247,6 @@ class FileStationClient:
         Raises:
             SynologyError: On API errors.
         """
-        sys.stderr.write(f"[dsm] request: {api}/{method}\n")
-        sys.stderr.flush()
         if not self._initializing:
             await self._ensure_initialized()
         http = self._get_http()
diff --git a/src/mcp_synology_filestation/tools/filestation.py b/src/mcp_synology_filestation/tools/filestation.py
index aab94b1..14b9666 100644
--- a/src/mcp_synology_filestation/tools/filestation.py
+++ b/src/mcp_synology_filestation/tools/filestation.py
@@ -66,6 +66,7 @@ def register_filestation(
         version: int,
         taskid: str,
         initial_delay: float = 0.2,
+        window_timeout: float | None = None,
     ) -> tuple[bool, dict[str, Any] | str]:
         """Poll a DSM async task until finished or timeout.
 
@@ -76,6 +77,11 @@ def register_filestation(
             initial_delay: Seconds to wait before the first status poll.
                 Set to 0.0 for tasks that may finish before the first poll
                 interval (e.g. DirSize on small directories, MD5 on small files).
+            window_timeout: For one-shot tasks (DirSize, MD5) whose result is
+                available exactly once: if we receive nothing but 599 errors for
+                this many seconds without ever seeing the task running
+                (``finished=False``), the result window was missed — return an
+                error immediately instead of waiting for the full 60 s timeout.
 
         Returns:
             ``(True, status_dict)`` on success, or ``(False, "Error: …")`` on
@@ -86,6 +92,7 @@ def register_filestation(
         delay = 0.2
         elapsed = initial_delay
         timeout = 60.0
+        seen_task_alive = False  # True once we receive any non-599 status response
 
         if initial_delay > 0:
             await asyncio.sleep(initial_delay)
@@ -100,13 +107,25 @@ def register_filestation(
                 )
             except _SynologyError as e:
                 if e.code == 599:
-                    # DSM returns 599 while the async task is still initialising
-                    # or running (task-not-yet-available). Treat it the same as
-                    # finished=False and keep polling until the 60 s timeout.
-                    pass
+                    # DSM 599 = task not found. For one-shot tasks (DirSize, MD5)
+                    # this means either the task hasn't started yet or the result
+                    # window has already closed. If we've never seen the task
+                    # running and window_timeout has elapsed, the window is gone —
+                    # fail fast so the caller can retry rather than wait 60 s.
+                    if (
+                        window_timeout is not None
+                        and not seen_task_alive
+                        and elapsed >= window_timeout
+                    ):
+                        return (
+                            False,
+                            "Error: Could not read task result — the operation finished"
+                            " before the first successful poll. Please retry.",
+                        )
                 else:
                     return False, f"Error: {e}"
             else:
+                seen_task_alive = True
                 if status_data.get("finished"):
                     return True, status_data
 
@@ -821,7 +840,9 @@ def register_filestation(
         if not taskid:
             return "Error: DSM did not return a task ID."
 
-        ok, result = await _poll_task("SYNO.FileStation.DirSize", 1, taskid, initial_delay=0.0)
+        ok, result = await _poll_task(
+            "SYNO.FileStation.DirSize", 1, taskid, initial_delay=0.0, window_timeout=3.0
+        )
         if not ok:
             return result  # type: ignore[return-value]
 
@@ -882,7 +903,9 @@ def register_filestation(
         if not taskid:
             return "Error: DSM did not return a task ID."
 
-        ok, result = await _poll_task("SYNO.FileStation.MD5", 1, taskid, initial_delay=0.0)
+        ok, result = await _poll_task(
+            "SYNO.FileStation.MD5", 1, taskid, initial_delay=0.0, window_timeout=3.0
+        )
         if not ok:
             return result  # type: ignore[return-value]
 
diff --git a/tests/test_tools_filestation.py b/tests/test_tools_filestation.py
index c88e355..8cb8d55 100644
--- a/tests/test_tools_filestation.py
+++ b/tests/test_tools_filestation.py
@@ -1635,8 +1635,13 @@ async def test_dir_size_retries_on_transient_599(config: AppConfig) -> None:
 
 
 @pytest.mark.asyncio
-async def test_dir_size_times_out_on_persistent_599(config: AppConfig) -> None:
-    """dir_size returns Error: after 60 s timeout when DSM keeps returning 599."""
+async def test_dir_size_window_timeout_on_persistent_599(config: AppConfig) -> None:
+    """dir_size fails fast (window_timeout=3 s) when DSM returns only 599s.
+
+    Once the window_timeout elapses without ever seeing the task running
+    (finished=False), _poll_task returns the "result window missed" error
+    rather than waiting the full 60 s.
+    """
     client = MagicMock()
 
     async def _request(api, method, version=None, params=None, **kwargs):
@@ -1651,7 +1656,7 @@ async def test_dir_size_times_out_on_persistent_599(config: AppConfig) -> None:
         result = await tools["dir_size"](path="/dead")
 
     assert result.startswith("Error:")
-    assert "timed out" in result.lower() or "60 seconds" in result
+    assert "retry" in result.lower() or "window" in result.lower() or "poll" in result.lower()
 
 
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