refactor(box): run Box Runtime as subprocess inside LangBot container

Remove the separate langbot_box_runtime Docker service. Box Runtime
  now always launches as a local stdio subprocess, regardless of whether
  LangBot runs in Docker or not. The WebSocket transport path is kept
  only for explicit runtime_url configuration (remote deployment).

  This simplifies deployment by eliminating cross-container path mapping
  and network hops. Box Runtime is a pure scheduling process (talks to
  Docker socket / nsjail), it does not execute user code or touch the
  filesystem, so container isolation is unnecessary — unlike Plugin
  Runtime.

docker/docker-compose.yaml

@@ -4,24 +4,6 @@ version: "3"
 
 services:
 
-  langbot_box_runtime:
-    image: rockchin/langbot:latest
-    container_name: langbot_box_runtime
-    command: ["uv", "run", "--no-sync", "-m", "langbot_plugin.box.server"]
-    volumes:
-      # Mount the container runtime socket from the host.
-      # Uncomment the one that matches your container runtime:
-      # - /var/run/podman/podman.sock:/var/run/podman/podman.sock   # Podman
-      - /var/run/docker.sock:/var/run/docker.sock                   # Docker
-      - ./data/box:/workspaces
-    ports:
-      - 5410:5410
-    restart: on-failure
-    environment:
-      - TZ=Asia/Shanghai
-    networks:
-      - langbot_network
-
   langbot_plugin_runtime:
     image: rockchin/langbot:latest
     container_name: langbot_plugin_runtime
@@ -42,6 +24,10 @@ services:
     volumes:
       - ./data:/app/data
       - ./data/box:/workspaces
+      # Mount container runtime socket for Box sandbox (Docker backend).
+      # Uncomment the one that matches your container runtime:
+      # - /var/run/podman/podman.sock:/var/run/podman/podman.sock   # Podman
+      - /var/run/docker.sock:/var/run/docker.sock                   # Docker
     restart: on-failure
     environment:
       - TZ=Asia/Shanghai

src/langbot/pkg/box/connector.py

@@ -12,7 +12,6 @@ from langbot_plugin.runtime.io.connection import Connection
 
 from langbot_plugin.box.client import ActionRPCBoxClient
 from langbot_plugin.box.errors import BoxRuntimeUnavailableError
-from ..utils import platform
 
 if TYPE_CHECKING:
     from ..core import app as core_app
@@ -31,8 +30,6 @@ def resolve_box_ws_relay_url(ap: core_app.Application) -> str:
     if runtime_url:
         return runtime_url
 
-    if platform.get_platform() == 'docker':
-        return 'http://langbot_box_runtime:5410'
     return 'http://127.0.0.1:5410'
 
 
@@ -160,4 +157,4 @@ class BoxRuntimeConnector:
         return str(_get_box_config(self.ap).get('runtime_url', '')).strip()
 
     def _should_manage_local_runtime(self) -> bool:
-        return not self.configured_runtime_url and platform.get_platform() != 'docker'
+        return not self.configured_runtime_url

src/langbot/templates/config.yaml

@@ -89,7 +89,7 @@ monitoring:
         check_interval_hours: 1
 box:
     profile: 'default'
-    runtime_url: ''  # Leave empty to use defaults: http://127.0.0.1:5410 locally, http://langbot_box_runtime:5410 in Docker
+    runtime_url: ''  # Leave empty to auto-launch local Box Runtime subprocess. Set to a URL only for remote/external deployment.
     shared_host_root: './data/box'  # For Docker deployment, use '/workspaces'
     default_host_workspace: ''  # Defaults to '<shared_host_root>/default'
     allowed_host_mount_roots:  # Defaults to ['<shared_host_root>'] when left empty

tests/unit_tests/box/test_box_connector.py

@@ -25,12 +25,7 @@ def make_app(logger: Mock, runtime_url: str = ''):
     )
 
 
-def patch_platform(monkeypatch: pytest.MonkeyPatch, value: str):
-    monkeypatch.setattr('langbot.pkg.box.connector.platform.get_platform', lambda: value)
-
-
-def test_box_runtime_connector_manages_local_when_no_url(monkeypatch: pytest.MonkeyPatch):
-    patch_platform(monkeypatch, 'linux')
+def test_box_runtime_connector_manages_local_when_no_url():
     connector = BoxRuntimeConnector(make_app(Mock()))
 
     assert connector.manages_local_runtime is True
@@ -45,16 +40,15 @@ def test_box_runtime_connector_remote_when_url_configured():
     assert isinstance(connector.client, ActionRPCBoxClient)
 
 
-def test_box_runtime_connector_remote_when_docker(monkeypatch: pytest.MonkeyPatch):
-    patch_platform(monkeypatch, 'docker')
+def test_box_runtime_connector_manages_local_in_docker(monkeypatch: pytest.MonkeyPatch):
+    monkeypatch.setattr('langbot.pkg.utils.platform.get_platform', lambda: 'docker')
     connector = BoxRuntimeConnector(make_app(Mock()))
 
-    assert connector.manages_local_runtime is False
-    assert connector.ws_relay_base_url == 'http://langbot_box_runtime:5410'
+    assert connector.manages_local_runtime is True
+    assert connector.ws_relay_base_url == 'http://127.0.0.1:5410'
 
 
-def test_box_runtime_connector_ws_relay_url_default(monkeypatch: pytest.MonkeyPatch):
-    patch_platform(monkeypatch, 'linux')
+def test_box_runtime_connector_ws_relay_url_default():
     connector = BoxRuntimeConnector(make_app(Mock()))
 
     assert connector.ws_relay_base_url == 'http://127.0.0.1:5410'