diff --git a/.gitignore b/.gitignore
index 56a2445..4d7fd6c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -19,6 +19,7 @@ archive/
 .claude.json
 .port_sessions/
 tasks/
+router_session_parquet/
 
 # Environment files
 .env
diff --git a/PARITY_CHECKLIST.md b/PARITY_CHECKLIST.md
index d115823..1277af4 100644
--- a/PARITY_CHECKLIST.md
+++ b/PARITY_CHECKLIST.md
@@ -822,7 +822,7 @@ Mirrored / scaffold areas needing real implementation:
 - [ ] Token budget calculations
 
 ### Tier 3 — Nice-to-Have Features
-- [x] Local web GUI (FastAPI + vanilla JS SPA) → `src/gui/__main__.py`, `src/gui/server.py`, `src/gui/static/*`; launch with `python -m src.gui` or `claw-code-gui`
+- [x] Local web GUI (FastAPI + vanilla JS SPA) → `src/gui/__main__.py`, `backend/api/server.py`, `frontend/legacy-static/*`; launch with `python -m src.gui` or `claw-code-gui`
 - [ ] TUI/Ink component library
 - [ ] Voice mode
 - [ ] VIM mode and keybinding system
diff --git a/README.md b/README.md
index 9fffe25..a010c0d 100644
--- a/README.md
+++ b/README.md
@@ -545,7 +545,7 @@ workspace 可以通过 `.claw-policy.json` / `.codex-policy.json` / `.claw-hooks
 有，但只对 bundled skill 生效：
 
 - `format_skills_for_system_prompt()` 把 skill 列表渲染进系统提示，帮助模型“知道”有哪些 skill，见 `src/bundled_skills.py:268-289`
-- GUI 也有 `/api/skills` 列表，见 `src/gui/server.py`
+- GUI 也有 `/api/skills` 列表，见 `backend/api/server.py`
 
 但它没有：
 
diff --git a/backend/__init__.py b/backend/__init__.py
new file mode 100644
index 0000000..5ff838a
--- /dev/null
+++ b/backend/__init__.py
@@ -0,0 +1 @@
+"""Backend API package for the claw-code agent workbench."""
diff --git a/backend/api/__init__.py b/backend/api/__init__.py
new file mode 100644
index 0000000..d2052ad
--- /dev/null
+++ b/backend/api/__init__.py
@@ -0,0 +1 @@
+"""HTTP API layer for the claw-code agent workbench."""
diff --git a/src/gui/server.py b/backend/api/server.py
similarity index 97%
rename from src/gui/server.py
rename to backend/api/server.py
index 2745435..4bd6bf2 100644
--- a/src/gui/server.py
+++ b/backend/api/server.py
@@ -17,22 +17,22 @@ from fastapi.responses import FileResponse, JSONResponse
 from fastapi.staticfiles import StaticFiles
 from pydantic import BaseModel, Field
 
-from ..agent_runtime import LocalCodingAgent
-from ..agent_slash_commands import get_slash_command_specs
-from ..agent_types import (
+from src.agent_runtime import LocalCodingAgent
+from src.agent_slash_commands import get_slash_command_specs
+from src.agent_types import (
     AgentPermissions,
     AgentRuntimeConfig,
     ModelConfig,
 )
-from ..bundled_skills import get_bundled_skills
-from ..session_store import (
+from src.bundled_skills import get_bundled_skills
+from src.session_store import (
     DEFAULT_AGENT_SESSION_DIR,
     StoredAgentSession,
     load_agent_session,
 )
 
 
-STATIC_DIR = Path(__file__).parent / 'static'
+STATIC_DIR = Path(__file__).resolve().parents[2] / 'frontend' / 'legacy-static'
 
 
 # ---------------------------------------------------------------------------
diff --git a/src/gui/static/app.css b/frontend/legacy-static/app.css
similarity index 100%
rename from src/gui/static/app.css
rename to frontend/legacy-static/app.css
diff --git a/src/gui/static/app.js b/frontend/legacy-static/app.js
similarity index 100%
rename from src/gui/static/app.js
rename to frontend/legacy-static/app.js
diff --git a/src/gui/static/index.html b/frontend/legacy-static/index.html
similarity index 100%
rename from src/gui/static/index.html
rename to frontend/legacy-static/index.html
diff --git a/pyproject.toml b/pyproject.toml
index 0b6ddf0..8057d02 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -36,6 +36,13 @@ dependencies = [
   "fastapi>=0.110",
   "uvicorn>=0.27",
   "pydantic>=2.5",
+  "openpyxl>=3.1",
+  "pyarrow>=15",
+]
+
+[project.optional-dependencies]
+dev = [
+  "httpx>=0.28",
 ]
 
 [project.urls]
@@ -51,11 +58,10 @@ include-package-data = true
 
 [tool.setuptools.packages.find]
 where = ["."]
-include = ["src*"]
+include = ["src*", "backend*"]
 
 [tool.setuptools.package-data]
 src = [
   "reference_data/*.json",
-  "gui/static/*",
   "skills/bundled/*/SKILL.md",
 ]
diff --git a/src/gui/__main__.py b/src/gui/__main__.py
index 5840ef0..f0b7d71 100644
--- a/src/gui/__main__.py
+++ b/src/gui/__main__.py
@@ -9,8 +9,9 @@ from pathlib import Path
 
 import uvicorn
 
+from backend.api.server import AgentState, create_app
+
 from ..session_store import DEFAULT_AGENT_SESSION_DIR
-from .server import AgentState, create_app
 
 
 def main() -> None:
diff --git a/tests/test_gui_server.py b/tests/test_gui_server.py
index e52bd89..87eb36b 100644
--- a/tests/test_gui_server.py
+++ b/tests/test_gui_server.py
@@ -15,7 +15,7 @@ from pathlib import Path
 
 from fastapi.testclient import TestClient
 
-from src.gui.server import AgentState, create_app
+from backend.api.server import AgentState, create_app
 
 
 def _build_client(tmp: Path) -> tuple[TestClient, AgentState]: