feat: enhance sandbox api

src/langbot/pkg/box/service.py

@@ -208,6 +208,7 @@ class BoxService:
         return {
             'session_id': spec.session_id,
             'workdir': spec.workdir,
+            'mount_path': spec.mount_path,
             'timeout_sec': spec.timeout_sec,
             'network': spec.network.value,
             'image': spec.image,

src/langbot/pkg/provider/tools/loaders/native.py

@@ -55,7 +55,18 @@ class NativeToolLoader(loader.ToolLoader):
                     },
                     'workdir': {
                         'type': 'string',
-                        'description': 'Absolute working directory path inside the sandbox. Defaults to /workspace.',
+                        'description': (
+                            'Absolute working directory path inside the sandbox. '
+                            'Defaults to mount_path, or /workspace when mount_path is omitted.'
+                        ),
+                        'default': '/workspace',
+                    },
+                    'mount_path': {
+                        'type': 'string',
+                        'description': (
+                            'Absolute sandbox path where host_path is mounted. '
+                            'Defaults to /workspace. When omitted, workdir defaults to the same path.'
+                        ),
                         'default': '/workspace',
                     },
                     'timeout_sec': {

tests/unit_tests/box/test_box_service.py

@@ -99,6 +99,7 @@ class FakeBackend(BaseSandboxBackend):
             network=spec.network,
             host_path=spec.host_path,
             host_path_mode=spec.host_path_mode,
+            mount_path=spec.mount_path,
             cpus=spec.cpus,
             memory_mb=spec.memory_mb,
             pids_limit=spec.pids_limit,
@@ -1017,7 +1018,7 @@ class TestBoxHostMountModeNone:
         assert spec.workdir == '/opt/custom'
 
     def test_spec_with_rw_mode_requires_workspace_workdir(self):
-        """When host_path_mode is RW, workdir must be under /workspace."""
+        """When host_path_mode is RW, workdir must be under mount_path."""
         with pytest.raises(Exception):
             BoxSpec(
                 session_id='test',
@@ -1028,7 +1029,7 @@ class TestBoxHostMountModeNone:
             )
 
     def test_spec_with_ro_mode_requires_workspace_workdir(self):
-        """When host_path_mode is RO, workdir must be under /workspace."""
+        """When host_path_mode is RO, workdir must be under mount_path."""
         with pytest.raises(Exception):
             BoxSpec(
                 session_id='test',
@@ -1037,3 +1038,26 @@ class TestBoxHostMountModeNone:
                 host_path_mode=BoxHostMountMode.READ_ONLY,
                 workdir='/opt/custom',
             )
+
+    def test_spec_with_custom_mount_path_allows_matching_workdir(self):
+        spec = BoxSpec(
+            session_id='test',
+            cmd='echo hi',
+            host_path='/home/user/data',
+            host_path_mode=BoxHostMountMode.READ_WRITE,
+            mount_path='/project',
+            workdir='/project/src',
+        )
+        assert spec.mount_path == '/project'
+        assert spec.workdir == '/project/src'
+
+    def test_spec_with_custom_mount_path_rejects_outside_workdir(self):
+        with pytest.raises(Exception):
+            BoxSpec(
+                session_id='test',
+                cmd='echo hi',
+                host_path='/home/user/data',
+                host_path_mode=BoxHostMountMode.READ_WRITE,
+                mount_path='/project',
+                workdir='/workspace',
+            )