refactor(webui): replace real-time polling with click-to-check version updates

- Remove background PyPI polling loop and WebSocket broadcast
- Remove UpdateBanner from ThreadHeader (keep main page clean)
- Add on-demand version check endpoint (GET /api/settings/version-check)
- Add 'About' section in Settings > Overview with check-for-updates button
- Design: no auto-fetch, user initiates check explicitly via button click

nanobot/webui/settings_api.py

@@ -34,9 +34,18 @@ from nanobot.webui.workspaces import (
     write_webui_default_access_mode,
 )
 
+from nanobot import __version__
+
 QueryParams = dict[str, list[str]]
 RuntimeSurface = Literal["browser", "native"]
 
+
+def _version_payload() -> dict[str, Any]:
+    """Return version info for the settings payload."""
+    return {
+        "current": __version__,
+    }
+
 _RUNTIME_CAPABILITIES = {
     "can_restart_engine": False,
     "can_pick_folder": False,
@@ -805,6 +814,7 @@ def settings_payload(
             "exec_path_append_set": bool(exec_config.path_append),
         },
         "requires_restart": requires_restart,
+        "version": _version_payload(),
     }
     return decorate_settings_payload(
         payload,

nanobot/webui/settings_routes.py

@@ -36,6 +36,7 @@ from nanobot.webui.settings_api import (
     update_transcription_settings,
     update_web_search_settings,
 )
+from nanobot.webui.version_check import check_for_update
 
 QueryParams = dict[str, list[str]]
 
@@ -117,6 +118,8 @@ class WebUISettingsRouter:
             return await self._handle_settings_cli_apps_action(request, "test")
         if path == "/api/settings/mcp-presets":
             return await self._handle_settings_mcp_presets(request)
+        if path == "/api/settings/version-check":
+            return await self._handle_settings_version_check(request)
         mcp_action = _MCP_PRESET_ACTIONS_BY_PATH.get(path)
         if mcp_action is not None:
             return await self._handle_settings_mcp_presets(request, mcp_action)
@@ -347,3 +350,15 @@ class WebUISettingsRouter:
         if action is None:
             return self._json_response(payload)
         return self._json_response(self._with_restart_state(payload, section="runtime"))
+
+    async def _handle_settings_version_check(self, request: WsRequest) -> Response:
+        if not self._authorized(request):
+            return self._unauthorized()
+        try:
+            update_info = await asyncio.to_thread(check_for_update)
+        except Exception:
+            self.logger.exception("version check failed")
+            return self._error_response(500, "version check failed")
+        return self._json_response({
+            "updateAvailable": update_info,
+        })

nanobot/webui/version_check.py

@@ -0,0 +1,51 @@
+"""On-demand version checker for nanobot-ai releases.
+
+Checks PyPI for newer versions when explicitly requested (no background polling).
+"""
+
+from __future__ import annotations
+
+import logging
+import time
+from typing import Any
+
+import httpx
+
+from nanobot import __version__
+
+logger = logging.getLogger(__name__)
+
+_PYPI_URL = "https://pypi.org/pypi/nanobot-ai/json"
+_CACHE_TTL_S = 300  # 5 minutes cache to avoid hammering PyPI
+
+_cache: tuple[float, str | None] = (0.0, None)
+
+
+def check_for_update() -> dict[str, Any] | None:
+    """Check PyPI for a newer version. Returns update info dict or None if up-to-date.
+
+    Uses a short cache to avoid repeated requests within the TTL window.
+    This is a blocking call — invoke from a thread or background task.
+    """
+    global _cache
+    now = time.monotonic()
+    cached_at, cached_val = _cache
+    if now - cached_at < _CACHE_TTL_S and cached_val is not None:
+        latest = cached_val
+    else:
+        try:
+            resp = httpx.get(_PYPI_URL, timeout=5.0, follow_redirects=True)
+            resp.raise_for_status()
+            latest = resp.json().get("info", {}).get("version")
+        except Exception:
+            logger.debug("PyPI version check failed", exc_info=True)
+            return None
+        _cache = (now, latest)
+
+    if not latest or latest == __version__:
+        return None
+    return {
+        "currentVersion": __version__,
+        "latestVersion": latest,
+        "pypiUrl": "https://pypi.org/project/nanobot-ai/",
+    }