Wire NiceGUI UI into FastAPI server (Task 9)

Replace welcome HTML route with redirect to /ui, call setup_ui() to
register NiceGUI pages, and mount NiceGUI on the existing FastAPI app
via ui.run_with(). Update test to expect 307 redirect at /.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: aksOps

src/osscodeiq/server/app.py

@@ -1,11 +1,11 @@
-"""FastAPI application assembly — mounts REST API, MCP server, and welcome page."""
+"""FastAPI application assembly — mounts REST API, MCP server, and NiceGUI UI."""
 
 from __future__ import annotations
 
 from pathlib import Path
 
 from fastapi import FastAPI
-from fastapi.responses import HTMLResponse
+from fastapi.responses import RedirectResponse
 
 from osscodeiq.server.middleware import AuthMiddleware
 from osscodeiq.server.mcp_server import get_mcp_app, set_service
@@ -44,10 +44,21 @@ def create_app(
     router = create_router(service)
     app.include_router(router)
 
-    # Welcome page at /
-    @app.get("/", response_class=HTMLResponse, include_in_schema=False)
-    async def welcome():
-        template_path = Path(__file__).parent / "templates" / "welcome.html"
-        return HTMLResponse(template_path.read_text(encoding="utf-8"))
+    # Redirect / to NiceGUI UI
+    @app.get("/", include_in_schema=False)
+    async def root_redirect():
+        return RedirectResponse(url="/ui")
+
+    # NiceGUI UI (explorer, flow, MCP console)
+    from osscodeiq.server.ui import setup_ui
+    from nicegui import ui
+
+    setup_ui(service)
+    ui.run_with(
+        app,
+        dark=None,
+        title="OSSCodeIQ",
+        storage_secret="osscodeiq-ui",
+    )
 
     return app

src/osscodeiq/server/ui/__init__.py

@@ -1 +1,51 @@
 """NiceGUI-based web UI for OSSCodeIQ."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from nicegui import ui
+
+from osscodeiq.server.ui.theme import BRAND_COLOR
+
+if TYPE_CHECKING:
+    from osscodeiq.server.service import CodeIQService
+
+
+def setup_ui(service: CodeIQService) -> None:
+    """Register NiceGUI pages on the existing FastAPI app."""
+
+    @ui.page("/ui")
+    def index():
+        dark = ui.dark_mode(value=None)
+
+        with ui.header().classes("items-center justify-between px-4 py-2"):
+            with ui.row().classes("items-center gap-3"):
+                ui.icon("hub").style(f"color: {BRAND_COLOR}; font-size: 28px")
+                ui.label("OSSCodeIQ").classes("text-lg font-bold")
+            with ui.row().classes("items-center gap-2"):
+                try:
+                    stats = service.get_stats()
+                    ui.badge(f"{stats.get('total_nodes', 0):,} nodes").props("color=primary outline")
+                    ui.badge(f"{stats.get('total_edges', 0):,} edges").props("color=positive outline")
+                except Exception:
+                    pass
+                ui.button(icon="light_mode", on_click=lambda: dark.set_value(False)).props("flat dense round").tooltip("Light theme")
+                ui.button(icon="dark_mode", on_click=lambda: dark.set_value(True)).props("flat dense round").tooltip("Dark theme")
+                ui.button(icon="contrast", on_click=lambda: dark.set_value(None)).props("flat dense round").tooltip("System theme")
+
+        with ui.tabs().classes("w-full") as tabs:
+            explorer_tab = ui.tab("Explorer", icon="explore")
+            flow_tab = ui.tab("Flow", icon="account_tree")
+            console_tab = ui.tab("MCP Console", icon="terminal")
+
+        with ui.tab_panels(tabs, value=explorer_tab).classes("w-full flex-grow"):
+            with ui.tab_panel(explorer_tab):
+                from osscodeiq.server.ui.explorer import create_explorer_page
+                create_explorer_page(service)
+            with ui.tab_panel(flow_tab):
+                from osscodeiq.server.ui.flow_view import create_flow_page
+                create_flow_page(service)
+            with ui.tab_panel(console_tab):
+                from osscodeiq.server.ui.mcp_console import create_mcp_console
+                create_mcp_console(service)

tests/server/test_app.py

@@ -24,10 +24,10 @@ def test_create_app_returns_fastapi(app):
     assert isinstance(app, FastAPI)
 
 
-def test_welcome_page(client):
-    resp = client.get("/")
-    assert resp.status_code == 200
-    assert "OSSCodeIQ" in resp.text
+def test_root_redirects_to_ui(client):
+    resp = client.get("/", follow_redirects=False)
+    assert resp.status_code == 307
+    assert resp.headers["location"] == "/ui"
 
 
 def test_api_stats_route(client):