#!/usr/bin/env python3
"""Open the NexusOS UI in a native window.
Uses pywebview, which renders via the WebView2 runtime on Windows (already
present on Win10/11) -- a real app window with no browser chrome and none of the
Edge --app profile cold-start. Blocks until the window is closed; the launcher
waits on this process and stops the services when it exits.
The window opens IMMEDIATELY on a loading page and navigates to the app once the
backend answers, rather than waiting up to 40s with nothing on screen and then
appearing. One window the whole time: nothing pops up and vanishes, and there is
no moment where the user is left wondering whether the command did anything.
Falls back to the default browser if pywebview/WebView2 is unavailable, staying
alive so the launcher doesn't tear the services down underneath it.
"""
import sys
import time
import urllib.request
URL = "http://localhost:8000"
# Inline so it renders with no server and no asset files - the whole point is
# that it shows before anything is listening. Colours match the app's dark UI so
# the swap to the real page is not a flash of a different-looking window.
LOADING_HTML = """
NexusOS
Loading Nexus core services
Starting the memory service and backend...
"""
FAILED_HTML = LOADING_HTML.replace(
"", ""
).replace(
"Loading Nexus core services", "Backend did not start"
).replace(
"Starting the memory service and backend...",
"Nothing answered on :8000 after 40s. Check: ncp logs -b"
)
def _wait_for_backend(timeout: float = 40.0) -> bool:
"""Poll /status until the backend answers, so the window never loads before
the server is up (which shows a localhost error the webview won't retry)."""
status_url = URL.rstrip("/") + "/status"
deadline = time.time() + timeout
while time.time() < deadline:
try:
# 5s, not 2: /status probes Ollama, and a wedged Ollama made it
# slower than a 2s ceiling - the backend was up and answering 200
# while this loop timed out on every attempt and declared it dead.
# The server side is fixed too; this is the margin.
with urllib.request.urlopen(status_url, timeout=5) as r:
if r.status == 200:
return True
except Exception:
time.sleep(1)
return False
def main() -> int:
try:
import webview
except Exception as e: # pywebview not installed
return _browser_fallback(f"pywebview unavailable ({e})")
try:
window = webview.create_window(
"NexusOS",
html=LOADING_HTML,
width=1200,
height=800,
min_size=(900, 600),
)
def _swap_in_app(win):
"""Runs once the GUI loop is up, so the spinner is already on screen
while we wait. load_url replaces the loading page in place - there is
never a second window to close."""
if _wait_for_backend():
win.load_url(URL)
else:
print("[nexus] backend not reachable on :8000 after 40s.",
file=sys.stderr)
win.load_html(FAILED_HTML)
webview.start(_swap_in_app, window) # blocks until the window is closed
return 0
except Exception as e: # no WebView2 runtime / backend failure
return _browser_fallback(f"native window failed ({e})")
def _browser_fallback(reason: str) -> int:
import webbrowser
print(f"[nexus] {reason}; opening default browser instead.", file=sys.stderr)
webbrowser.open(URL)
# Stay alive so the launcher keeps the services up. The user stops NexusOS
# by closing the launcher (or the browser tab, then the services idle out).
try:
while True:
time.sleep(3600)
except KeyboardInterrupt:
return 0
if __name__ == "__main__":
sys.exit(main())