diff --git a/launch/core/platforms/linux.py b/launch/core/platforms/linux.py
index bd87786..9706370 100644
--- a/launch/core/platforms/linux.py
+++ b/launch/core/platforms/linux.py
@@ -16,7 +16,9 @@
     BaseRuntime
 )
 
-import os, json
+import json
+import os
+import posixpath
 from typing import Any, Optional
 import queue
 import threading
@@ -26,6 +28,12 @@
 import docker
 from docker.models.containers import Container
 
+
+def _container_mount_path(mount_path: str, filename: str) -> str:
+    """Build a path for a Linux container regardless of the host platform."""
+    return posixpath.join(mount_path, filename)
+
+
 class LinuxRuntime(BaseRuntime):
 
     def __init__(
@@ -207,7 +215,7 @@ def apply_patch(self, patch: str, verbose: bool = False) -> bool:
         hostpath = os.path.join(self.mnt_host, filename)
         with open(hostpath, "w") as f:
             f.write(patch)
-        containerpath =  os.path.join(self.mnt_container, filename)
+        containerpath = _container_mount_path(self.mnt_container, filename)
         
         cmd = f"""git apply --reject  --whitespace=nowarn  {containerpath} """
         res = self.send_command(cmd)
diff --git a/tests/runtime_test.py b/tests/runtime_test.py
index 809ec3d..f291e54 100644
--- a/tests/runtime_test.py
+++ b/tests/runtime_test.py
@@ -41,6 +41,7 @@
 
 import os
 import platform as host_platform
+from types import SimpleNamespace
 import warnings
 
 import docker
@@ -170,6 +171,25 @@ def test_runtime_constructor_attributes(runtime_cls, expected_attrs, patch_runti
 
 
 
+def test_linux_runtime_uses_posix_path_for_mounted_patch(monkeypatch, tmp_path):
+    runtime = LinuxRuntime.__new__(LinuxRuntime)
+    runtime.stopped = True
+    runtime.mnt_host = str(tmp_path)
+    runtime.mnt_container = "/mnt_tmp"
+    commands = []
+
+    def send_command(command, timeout=None):
+        commands.append(command)
+        return SimpleNamespace(metadata=SimpleNamespace(exit_code=0), output="")
+
+    monkeypatch.setattr(runtime, "send_command", send_command)
+    assert runtime.apply_patch("diff --git a/a b/a\n") is True
+    assert commands[0].startswith("git apply")
+    assert "/mnt_tmp/" in commands[0]
+    assert "\\" not in commands[0]
+    assert commands[1].startswith("rm /mnt_tmp/")
+
+
 def supported_integration_platforms() -> set[str]:
     system = host_platform.system().lower()
     if system == "windows":