diff --git a/CHANGELOG.md b/CHANGELOG.md
index c8ec94654..f331ac518 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,11 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Windows native runs now skip the POSIX-only turn-journal directory fsync instead of raising `AttributeError` for missing `os.O_DIRECTORY` on every submitted turn (#3170).
+- `/api/media` now treats Windows cross-drive `commonpath()` comparisons as non-matches instead of 500ing when media paths and allowed roots live on different drives (#3171).
+
 ## [v0.51.171] — 2026-05-30 — Release EQ (stage-batch53 — tool-output card badge + Neon opt-in skin)
 
 ### Added
diff --git a/api/routes.py b/api/routes.py
index d448a382d..4d536bd5a 100644
--- a/api/routes.py
+++ b/api/routes.py
@@ -7887,6 +7887,14 @@ def _session_media_token_allows_image_path(sid: str, target: Path, image_mimes:
     return False
 
 
+def _path_is_within_root(child: Path, root: Path) -> bool:
+    """Return True when ``child`` is inside ``root`` without crashing on Windows drives."""
+    try:
+        return os.path.commonpath([str(child), str(root)]) == str(root)
+    except ValueError:
+        return False
+
+
 def _handle_media(handler, parsed):
     """Serve a local file by absolute path for inline display in the chat.
 
@@ -7963,7 +7971,7 @@ def _handle_media(handler, parsed):
         "image/x-icon", "image/bmp",
     }
     within_allowed = any(
-        _os.path.commonpath([str(target), str(root)]) == str(root)
+        _path_is_within_root(target, root)
         for root in allowed_roots
         if root.exists()
     )
diff --git a/api/turn_journal.py b/api/turn_journal.py
index 58369be58..3dba35bdf 100644
--- a/api/turn_journal.py
+++ b/api/turn_journal.py
@@ -94,14 +94,16 @@ def append_turn_journal_event(
             fh.write(line)
             fh.flush()
             os.fsync(fh.fileno())
-    try:
-        dir_fd = os.open(path.parent, os.O_DIRECTORY)
+    o_directory = getattr(os, "O_DIRECTORY", None)
+    if o_directory is not None:
         try:
-            os.fsync(dir_fd)
-        finally:
-            os.close(dir_fd)
-    except OSError:
-        pass
+            dir_fd = os.open(path.parent, o_directory)
+            try:
+                os.fsync(dir_fd)
+            finally:
+                os.close(dir_fd)
+        except OSError:
+            pass
     return payload
 
 
diff --git a/tests/test_media_inline.py b/tests/test_media_inline.py
index 41e84dc4c..621da1205 100644
--- a/tests/test_media_inline.py
+++ b/tests/test_media_inline.py
@@ -255,6 +255,32 @@ class TestMediaEndpointUnit(unittest.TestCase):
         self.assertIn(".split(_os.pathsep)", block)
         self.assertNotIn('.split(":")', block)
 
+    def test_path_is_within_root_treats_commonpath_valueerror_as_not_within(self):
+        """Windows cross-drive commonpath() errors must not crash /api/media."""
+        from api import routes
+
+        with mock.patch.object(
+            routes.os.path,
+            "commonpath",
+            side_effect=ValueError("Paths don't have the same drive"),
+        ):
+            self.assertFalse(
+                routes._path_is_within_root(
+                    pathlib.Path("D:/outputs/card.png"),
+                    pathlib.Path("C:/Users/agent/.hermes"),
+                )
+            )
+
+    def test_path_is_within_root_accepts_child_path(self):
+        from api import routes
+
+        with tempfile.TemporaryDirectory() as tmpd:
+            root = pathlib.Path(tmpd).resolve()
+            child = root / "media" / "card.png"
+            child.parent.mkdir()
+            child.write_bytes(b"png")
+            self.assertTrue(routes._path_is_within_root(child.resolve(), root))
+
     def test_media_endpoints_advertise_byte_range_support(self):
         routes_src = (REPO_ROOT / "api" / "routes.py").read_text(encoding="utf-8")
         self.assertIn("Accept-Ranges", routes_src)
diff --git a/tests/test_turn_journal_lifecycle.py b/tests/test_turn_journal_lifecycle.py
index 3f5a317ad..656714d83 100644
--- a/tests/test_turn_journal_lifecycle.py
+++ b/tests/test_turn_journal_lifecycle.py
@@ -1,3 +1,5 @@
+import os
+
 from api.turn_journal import (
     append_turn_journal_event,
     append_turn_journal_event_for_stream,
@@ -36,3 +38,16 @@ def test_append_turn_journal_event_for_stream_falls_back_to_new_turn_for_missing
     assert event["stream_id"] == "stream-missing"
     assert event["turn_id"]
     assert event["event"] == "interrupted"
+
+
+def test_append_turn_journal_event_skips_directory_fsync_without_o_directory(tmp_path, monkeypatch):
+    monkeypatch.delattr(os, "O_DIRECTORY", raising=False)
+
+    event = append_turn_journal_event(
+        "sid-windows",
+        {"event": "submitted", "content": "hello"},
+        session_dir=tmp_path,
+    )
+
+    assert event["event"] == "submitted"
+    assert (tmp_path / "_turn_journal" / "sid-windows.jsonl").is_file()