fix(windows): append compute host logs without concurrent record loss

tui_gateway/host_supervisor.py

@@ -55,14 +55,35 @@ _LATE_CONTROL_MAX = 64
 
 
 def append_log_record(path: str | Path, record: str) -> None:
-    """Append one log record using O_APPEND and exactly one os.write call."""
+    """Append a record with one native write and kernel-owned EOF placement."""
     p = Path(path)
     p.parent.mkdir(parents=True, exist_ok=True)
     text = record if record.endswith("\n") else f"{record}\n"
     data = text.encode("utf-8", errors="replace")
+    if sys.platform == "win32":
+        import ntsecuritycon
+        import win32con
+        import win32file
+
+        # The Windows CRT's O_APPEND seeks before writing, so independent file
+        # descriptors can choose the same offset. Append-only access delegates
+        # EOF placement to the kernel, without granting overwrite permission.
+        handle = win32file.CreateFile(
+            str(p), ntsecuritycon.FILE_APPEND_DATA,
+            win32con.FILE_SHARE_READ | win32con.FILE_SHARE_WRITE | win32con.FILE_SHARE_DELETE,
+            None, win32con.OPEN_ALWAYS, win32con.FILE_ATTRIBUTE_NORMAL, None,
+        )
+        try:
+            _, written = win32file.WriteFile(handle, data)
+            if written != len(data):
+                raise OSError("Incomplete log record write")
+        finally:
+            handle.Close()
+        return
     fd = os.open(str(p), os.O_WRONLY | os.O_CREAT | os.O_APPEND, 0o600)
     try:
-        os.write(fd, data)
+        if os.write(fd, data) != len(data):
+            raise OSError("Incomplete log record write")
     finally:
         os.close(fd)