@@ -23,6 +23,9 @@ Git executable and safety
   option/protocol checks remain, and operands and stdin records receive additional
   validation. NUL-delimited ``cat-file`` requests prevent newline injection.
   Previously accepted option-like revision/ref arguments can now be rejected.
+  ``Head.checkout()`` rejects every branch name starting with a dash, including
+  when ``allow_unsafe_options=True``. This setting permits explicit keyword
+  options while branch names remain operands.
 * New plumbing calls suppress implicit hooks, filesystem monitors, automatic
   maintenance, and lazy network fetches. Index staging continues to store raw
   content rather than introduce clean filters. Diffs disable external diff and
 
@@ -279,6 +279,7 @@ def checkout(
         :param allow_unsafe_options:
             Allow unsafe options such as ``--pathspec-from-file`` to be passed to
             :manpage:`git-checkout(1)`.
+            Branch names are validated regardless of this setting.
 
         :param kwargs:
             Additional keyword arguments to be passed to git checkout, e.g.
@@ -290,6 +291,9 @@ def checkout(
             If there is no active branch, as the HEAD is now detached, the HEAD
             reference will be returned instead.
 
+        :raise git.exc.UnsafeOptionError:
+            If the branch name starts with a dash or contains NUL, CR, or LF.
+
         :note:
             By default it is only allowed to checkout heads - everything else will leave
             the HEAD detached which is allowed and possible, but remains a special state
 
@@ -73,7 +73,9 @@ def test_rename_head_cannot_select_current_branch(repo, tmp_path):
 
 
 @pytest.mark.parametrize("allow_unsafe_options", [False, True])
-@pytest.mark.parametrize("name", ["--force", "--detach", "--ours"])
+@pytest.mark.parametrize(
+    "name", ["-f", "-Bcheckout-target", "--orphan=checkout-target", "--force", "--detach", "--ours", "-", "--"]
+)
 def test_checkout_rejects_option_shaped_branch_names(repo, tmp_path, name, allow_unsafe_options):
     branch = Head(repo, "refs/heads/" + name)
     with mock.patch.object(Git, "_call_process_safe", side_effect=AssertionError("Git must not run")) as run:
 
@@ -43,6 +43,30 @@
 from test.lib.fixtures import fixture_repo, read_only_fixture, writable_fixture
 
 
+@pytest.mark.parametrize(
+    "branch_name", ["--pathspec-from-file=pathspecs", "-f", "--orphan=checkout-target", "-Bcheckout-target"]
+)
+def test_cloned_head_checkout_rejects_option_shaped_branch_names(branch_name):
+    with fixture_repo("refs.sh", "unsafe-branch", "sha1", branch_name, write=True, subdir="clone") as cloned:
+        branch = cloned.active_branch
+        assert branch.name == branch_name
+        commit = cloned.head.commit
+        path = Path(cloned.working_tree_dir) / "file.txt"
+        content = path.read_bytes()
+        status = cloned.git.status("--porcelain")
+        assert status.startswith(" M file.txt")
+        for allow_unsafe_options in (False, True):
+            with patch.object(Git, "execute", autospec=True, side_effect=Git.execute) as run:
+                with pytest.raises(UnsafeOptionError) as error:
+                    branch.checkout(force=False, allow_unsafe_options=allow_unsafe_options)
+                run.assert_not_called()
+            assert "unmatched-private-content" not in str(error.value)
+            assert cloned.active_branch == branch
+            assert cloned.head.commit == commit
+            assert path.read_bytes() == content
+            assert cloned.git.status("--porcelain") == status
+
+
 @pytest.mark.parametrize("object_format", ["sha1", "sha256"])
 def test_reference_names_preserve_unicode_line_separators(object_format):
     names = [
@@ -658,16 +682,6 @@ def test_head_checkout_rejects_pathspec_from_file(self, rw_repo):
             with self.assertRaises(UnsafeOptionError):
                 branch.checkout()
 
-    def test_cloned_head_checkout_rejects_pathspec_from_file(self):
-        with fixture_repo("refs.sh", "unsafe-branch", write=True, subdir="clone") as cloned:
-            branch_name = "--pathspec-from-file=pathspecs"
-            assert cloned.active_branch.name == branch_name
-            for allow_unsafe_options in (False, True):
-                with self.assertRaises(UnsafeOptionError) as error:
-                    cloned.active_branch.checkout(allow_unsafe_options=allow_unsafe_options)
-                assert "unmatched-private-content" not in str(error.exception)
-            assert cloned.active_branch.name == branch_name
-
     @with_rw_repo("HEAD")
     def test_head_reset_rejects_pathspec_from_file(self, rw_repo):
         pathspecs = read_only_fixture("refs-input.sh") / "pathspecs"
 
@@ -39,10 +39,12 @@ case "$1" in
         git rev-parse HEAD > ../outside-ref
         ;;
     unsafe-branch)
-        git update-ref 'refs/heads/--pathspec-from-file=pathspecs' HEAD
-        git symbolic-ref HEAD 'refs/heads/--pathspec-from-file=pathspecs'
+        branch_name="$3"
+        git update-ref "refs/heads/$branch_name" HEAD
+        git symbolic-ref HEAD "refs/heads/$branch_name"
         cd ..
         git clone repo clone
         printf 'unmatched-private-content\n' > clone/pathspecs
+        printf 'uncommitted\n' >> clone/file.txt
         ;;
 esac