diff --git a/openviking/parse/gitignore.py b/openviking/parse/gitignore.py
index 3351cdb30..e3a107054 100644
--- a/openviking/parse/gitignore.py
+++ b/openviking/parse/gitignore.py
@@ -41,13 +41,19 @@ def _transform_gitignore_line(line: str, base_rel: str) -> str:
         return raw
 
     scoped = pattern
-    if scoped.startswith("/"):
-        scoped = scoped.lstrip("/")
-        scoped = f"{base_rel}/{scoped}" if scoped else base_rel
-    elif "/" in scoped:
-        scoped = f"{base_rel}/{scoped}"
+    is_dir_only = scoped.endswith("/")
+    body = scoped.rstrip("/") if is_dir_only else scoped
+
+    if body.startswith("/"):
+        body = body.lstrip("/")
+        scoped = f"{base_rel}/{body}" if body else base_rel
+    elif "/" in body:
+        scoped = f"{base_rel}/{body}"
     else:
-        scoped = f"{base_rel}/**/{scoped}" if scoped else base_rel
+        scoped = f"{base_rel}/**/{body}" if body else base_rel
+
+    if is_dir_only and scoped:
+        scoped = f"{scoped}/"
 
     return f"!{scoped}" if negated else scoped
 
diff --git a/tests/parse/test_gitignore_dir_anchoring.py b/tests/parse/test_gitignore_dir_anchoring.py
new file mode 100644
index 000000000..1358e079e
--- /dev/null
+++ b/tests/parse/test_gitignore_dir_anchoring.py
@@ -0,0 +1,34 @@
+# Copyright (c) 2026 Beijing Volcano Engine Technology Co., Ltd.
+# SPDX-License-Identifier: AGPL-3.0
+"""Tests for _transform_gitignore_line directory-pattern anchoring.
+
+A trailing-slash directory pattern (e.g. ``build/``) from a nested .gitignore
+must remain unanchored (match anywhere under base_rel) instead of being scoped
+directly to base_rel because the trailing ``/`` made it look like a path with
+a separator.
+"""
+
+from openviking.parse.gitignore import _transform_gitignore_line
+
+
+class TestTransformGitignoreDirAnchoring:
+    def test_dir_only_pattern_stays_unanchored(self):
+        """``build/`` must expand to ``src/**/build/`` (match anywhere), not ``src/build/``."""
+        result = _transform_gitignore_line("build/", "src")
+        assert result == "src/**/build/"
+
+    def test_plain_pattern_without_slash_is_unanchored(self):
+        """``build`` (no slash) matches anywhere under base_rel."""
+        assert _transform_gitignore_line("build", "src") == "src/**/build"
+
+    def test_leading_slash_pattern_is_anchored(self):
+        """``/build`` is anchored directly to base_rel."""
+        assert _transform_gitignore_line("/build", "src") == "src/build"
+
+    def test_dir_only_with_leading_slash_stays_anchored(self):
+        """``/build/`` stays anchored to base_rel but preserves the dir-only slash."""
+        assert _transform_gitignore_line("/build/", "src") == "src/build/"
+
+    def test_negated_dir_only_pattern_preserves_bang(self):
+        """Negation prefix is preserved through the unanchored transform."""
+        assert _transform_gitignore_line("!build/", "src") == "!src/**/build/"