diff --git a/backend/packages/harness/deerflow/sandbox/local/local_sandbox.py b/backend/packages/harness/deerflow/sandbox/local/local_sandbox.py
index 116a62159..62577abb9 100644
--- a/backend/packages/harness/deerflow/sandbox/local/local_sandbox.py
+++ b/backend/packages/harness/deerflow/sandbox/local/local_sandbox.py
@@ -42,6 +42,13 @@ class LocalSandbox(Sandbox):
         """Return whether the selected shell is cmd.exe."""
         return LocalSandbox._shell_name(shell) in {"cmd", "cmd.exe"}
 
+    @staticmethod
+    def _is_msys_shell(shell: str) -> bool:
+        """Return whether the selected shell is a Git Bash/MSYS shell."""
+        normalized = shell.replace("\\", "/").lower()
+        shell_name = LocalSandbox._shell_name(shell)
+        return shell_name in {"sh.exe", "bash.exe"} and any(part in normalized for part in ("/git/", "/mingw", "/msys"))
+
     @staticmethod
     def _find_first_available_shell(candidates: tuple[str, ...]) -> str | None:
         """Return the first executable shell path or command found from candidates."""
@@ -303,12 +310,19 @@ class LocalSandbox(Sandbox):
         shell = self._get_shell()
 
         if os.name == "nt":
+            env = None
             if self._is_powershell(shell):
                 args = [shell, "-NoProfile", "-Command", resolved_command]
             elif self._is_cmd_shell(shell):
                 args = [shell, "/c", resolved_command]
             else:
                 args = [shell, "-c", resolved_command]
+                if self._is_msys_shell(shell):
+                    env = {
+                        **os.environ,
+                        "MSYS_NO_PATHCONV": "1",
+                        "MSYS2_ARG_CONV_EXCL": "*",
+                    }
 
             result = subprocess.run(
                 args,
@@ -316,6 +330,7 @@ class LocalSandbox(Sandbox):
                 capture_output=True,
                 text=True,
                 timeout=600,
+                env=env,
             )
         else:
             args = [shell, "-c", resolved_command]
diff --git a/backend/tests/test_local_sandbox_encoding.py b/backend/tests/test_local_sandbox_encoding.py
index f1d237379..76a5f187c 100644
--- a/backend/tests/test_local_sandbox_encoding.py
+++ b/backend/tests/test_local_sandbox_encoding.py
@@ -105,6 +105,7 @@ def test_execute_command_uses_powershell_command_mode_on_windows(monkeypatch):
                 "capture_output": True,
                 "text": True,
                 "timeout": 600,
+                "env": None,
             },
         )
     ]
@@ -118,6 +119,7 @@ def test_execute_command_uses_posix_shell_command_mode_on_windows(monkeypatch):
         return SimpleNamespace(stdout="ok", stderr="", returncode=0)
 
     monkeypatch.setattr(local_sandbox.os, "name", "nt")
+    monkeypatch.setattr(local_sandbox.os, "environ", {"PATH": r"C:\Program Files\Git\bin"})
     monkeypatch.setattr(LocalSandbox, "_get_shell", staticmethod(lambda: r"C:\Program Files\Git\bin\sh.exe"))
     monkeypatch.setattr(local_sandbox.subprocess, "run", fake_run)
 
@@ -132,11 +134,33 @@ def test_execute_command_uses_posix_shell_command_mode_on_windows(monkeypatch):
                 "capture_output": True,
                 "text": True,
                 "timeout": 600,
+                "env": {
+                    "PATH": r"C:\Program Files\Git\bin",
+                    "MSYS_NO_PATHCONV": "1",
+                    "MSYS2_ARG_CONV_EXCL": "*",
+                },
             },
         )
     ]
 
 
+def test_execute_command_does_not_set_msys_env_for_non_msys_posix_shell_on_windows(monkeypatch):
+    calls: list[tuple[object, dict]] = []
+
+    def fake_run(*args, **kwargs):
+        calls.append((args[0], kwargs))
+        return SimpleNamespace(stdout="ok", stderr="", returncode=0)
+
+    monkeypatch.setattr(local_sandbox.os, "name", "nt")
+    monkeypatch.setattr(LocalSandbox, "_get_shell", staticmethod(lambda: r"C:\tools\busybox\sh.exe"))
+    monkeypatch.setattr(local_sandbox.subprocess, "run", fake_run)
+
+    output = LocalSandbox("t").execute_command("echo /mnt/skills/demo")
+
+    assert output == "ok"
+    assert calls[0][1]["env"] is None
+
+
 def test_execute_command_uses_cmd_command_mode_on_windows(monkeypatch):
     calls: list[tuple[object, dict]] = []
 
@@ -159,6 +183,7 @@ def test_execute_command_uses_cmd_command_mode_on_windows(monkeypatch):
                 "capture_output": True,
                 "text": True,
                 "timeout": 600,
+                "env": None,
             },
         )
     ]