Phase 2.2: performance optimizations, debug tools, app close fix

.claude/settings.local.json

@@ -19,7 +19,8 @@
       "Bash(cp:*)",
       "Bash(mv:*)",
       "Read(*)",
-      "Write(*)"
+      "Write(*)",
+      "Bash(python3:*)"
     ]
   }
 }

.gitignore

@@ -23,3 +23,4 @@ installer/dist/
 *.spec.bak
 __pycache__/
 *.pyc
+nul

backend/app/api/routes/regions.py

@@ -26,6 +26,12 @@ REGIONS = {
         "srtm_tiles": 18,
         "estimated_size_gb": 0.5,
     },
+    "ukraine_west": {
+        "name": "Western Ukraine",
+        "bbox": [48.0, 22.0, 51.0, 26.0],
+        "srtm_tiles": 12,
+        "estimated_size_gb": 0.3,
+    },
     "kyiv_region": {
         "name": "Kyiv Region",
         "bbox": [49.5, 29.5, 51.5, 32.5],

backend/app/services/coverage_service.py

@@ -1,6 +1,44 @@
+import math
+import os
+import sys
+import time
+import threading
 import numpy as np
 import asyncio
+from concurrent.futures import ThreadPoolExecutor
 from typing import List, Optional, Tuple
+
+
+_coverage_log_file = None
+
+def _clog(msg: str):
+    """Coverage debug log — always flushed, with timestamp and thread name.
+    Writes to stdout, stderr, AND a file so output is always available."""
+    global _coverage_log_file
+    ts = time.strftime('%H:%M:%S')
+    thr = threading.current_thread().name
+    line = f"[COVERAGE {ts}] [{thr}] {msg}"
+    print(line, flush=True)
+    # Backup: also write to stderr in case stdout is broken
+    try:
+        sys.stderr.write(line + '\n')
+        sys.stderr.flush()
+    except Exception:
+        pass
+    # Backup: also write to a file
+    try:
+        if _coverage_log_file is None:
+            log_dir = os.environ.get('RFCP_DATA_PATH', './data')
+            os.makedirs(log_dir, exist_ok=True)
+            log_path = os.path.join(log_dir, 'coverage-debug.log')
+            _coverage_log_file = open(log_path, 'a')
+            _coverage_log_file.write(f"\n{'='*60}\n")
+            _coverage_log_file.write(f"[COVERAGE {ts}] Log started\n")
+            _coverage_log_file.flush()
+        _coverage_log_file.write(line + '\n')
+        _coverage_log_file.flush()
+    except Exception:
+        pass
 from pydantic import BaseModel
 from app.services.terrain_service import terrain_service, TerrainService
 from app.services.los_service import los_service
@@ -142,6 +180,100 @@ class CoverageService:
         self.buildings = buildings_service
         self.los = los_service
 
+    async def _fetch_osm_grid_aligned(
+        self,
+        min_lat: float, min_lon: float,
+        max_lat: float, max_lon: float,
+        settings: CoverageSettings
+    ) -> dict:
+        """
+        Fetch OSM data using 1-degree grid-aligned cells.
+
+        This ensures cache keys match the region download grid,
+        so pre-cached data is actually used.
+        """
+        t0 = time.time()
+
+        lat_start = int(math.floor(min_lat))
+        lat_end = int(math.floor(max_lat))
+        lon_start = int(math.floor(min_lon))
+        lon_end = int(math.floor(max_lon))
+
+        cells = []
+        for lat_int in range(lat_start, lat_end + 1):
+            for lon_int in range(lon_start, lon_end + 1):
+                cells.append((float(lat_int), float(lon_int),
+                              float(lat_int + 1), float(lon_int + 1)))
+
+        buildings: List[Building] = []
+        streets: List[Street] = []
+        water_bodies: List[WaterBody] = []
+        vegetation_areas: List[VegetationArea] = []
+
+        cache_stats = {"buildings": "skip", "streets": "skip",
+                       "water": "skip", "vegetation": "skip"}
+
+        for cell_min_lat, cell_min_lon, cell_max_lat, cell_max_lon in cells:
+            cell_label = f"[{cell_min_lat:.0f},{cell_min_lon:.0f}]"
+
+            if settings.use_buildings:
+                t1 = time.time()
+                chunk = await self.buildings.fetch_buildings(
+                    cell_min_lat, cell_min_lon, cell_max_lat, cell_max_lon
+                )
+                dt = time.time() - t1
+                src = "CACHE" if dt < 0.5 else "API"
+                buildings.extend(chunk)
+                cache_stats["buildings"] = src
+                _clog(f"Buildings {cell_label}: {len(chunk)} items ({src}, {dt:.1f}s)")
+
+            if settings.use_street_canyon:
+                t1 = time.time()
+                chunk = await street_canyon_service.fetch_streets(
+                    cell_min_lat, cell_min_lon, cell_max_lat, cell_max_lon
+                )
+                dt = time.time() - t1
+                src = "CACHE" if dt < 0.5 else "API"
+                streets.extend(chunk)
+                cache_stats["streets"] = src
+                _clog(f"Streets {cell_label}: {len(chunk)} items ({src}, {dt:.1f}s)")
+
+            if settings.use_water_reflection:
+                t1 = time.time()
+                chunk = await water_service.fetch_water_bodies(
+                    cell_min_lat, cell_min_lon, cell_max_lat, cell_max_lon
+                )
+                dt = time.time() - t1
+                src = "CACHE" if dt < 0.5 else "API"
+                water_bodies.extend(chunk)
+                cache_stats["water"] = src
+                _clog(f"Water {cell_label}: {len(chunk)} items ({src}, {dt:.1f}s)")
+
+            if settings.use_vegetation:
+                t1 = time.time()
+                chunk = await vegetation_service.fetch_vegetation(
+                    cell_min_lat, cell_min_lon, cell_max_lat, cell_max_lon
+                )
+                dt = time.time() - t1
+                src = "CACHE" if dt < 0.5 else "API"
+                vegetation_areas.extend(chunk)
+                cache_stats["vegetation"] = src
+                _clog(f"Vegetation {cell_label}: {len(chunk)} items ({src}, {dt:.1f}s)")
+
+        total_fetch = time.time() - t0
+        _clog(f"OSM fetch total: {total_fetch:.1f}s "
+              f"({len(cells)} cells, "
+              f"{len(buildings)} bldgs, {len(streets)} streets, "
+              f"{len(water_bodies)} water, {len(vegetation_areas)} veg)")
+        _clog(f"Cache status: {cache_stats}")
+
+        return {
+            "buildings": buildings,
+            "streets": streets,
+            "water_bodies": water_bodies,
+            "vegetation_areas": vegetation_areas,
+        }
+
     async def calculate_coverage(
         self,
         site: SiteParams,
@@ -152,6 +284,8 @@ class CoverageService:
 
         Returns list of CoveragePoint with RSRP values
         """
+        calc_start = time.time()
+
         # Apply preset if specified
         settings = apply_preset(settings)
 
@@ -163,6 +297,7 @@ class CoverageService:
             settings.radius,
             settings.resolution
         )
+        _clog(f"Grid: {len(grid)} points, radius={settings.radius}m, res={settings.resolution}m")
 
         # Calculate bbox for data fetching
         lat_delta = settings.radius / 111000
@@ -173,48 +308,80 @@ class CoverageService:
         min_lon = site.lon - lon_delta
         max_lon = site.lon + lon_delta
 
-        # Fetch buildings (if enabled) and build spatial index
-        buildings: List[Building] = []
+        _clog(f"Bbox: [{min_lat:.4f}, {min_lon:.4f}, {max_lat:.4f}, {max_lon:.4f}]")
+
+        # ━━━ PHASE 1: Fetch OSM data ━━━
+        _clog("━━━ PHASE 1: Fetching OSM data ━━━")
+        t_osm = time.time()
+        osm_data = await self._fetch_osm_grid_aligned(
+            min_lat, min_lon, max_lat, max_lon, settings
+        )
+        osm_time = time.time() - t_osm
+
+        buildings = osm_data["buildings"]
+        streets = osm_data["streets"]
+        water_bodies = osm_data["water_bodies"]
+        vegetation_areas = osm_data["vegetation_areas"]
+        _clog(f"━━━ PHASE 1 done: {osm_time:.1f}s ━━━")
+
+        # Build spatial index for buildings
         spatial_idx: Optional[SpatialIndex] = None
-        if settings.use_buildings:
-            buildings = await self.buildings.fetch_buildings(
-                min_lat, min_lon, max_lat, max_lon
-            )
-            if buildings:
-                cache_key = f"{min_lat:.3f},{min_lon:.3f},{max_lat:.3f},{max_lon:.3f}"
-                spatial_idx = get_spatial_index(cache_key, buildings)
+        if buildings:
+            cache_key = f"{min_lat:.3f},{min_lon:.3f},{max_lat:.3f},{max_lon:.3f}"
+            spatial_idx = get_spatial_index(cache_key, buildings)
 
-        # Fetch streets (if street canyon enabled)
-        streets: List[Street] = []
-        if settings.use_street_canyon:
-            streets = await street_canyon_service.fetch_streets(
-                min_lat, min_lon, max_lat, max_lon
-            )
+        # ━━━ PHASE 2: Pre-load terrain ━━━
+        _clog("━━━ PHASE 2: Pre-loading terrain ━━━")
+        t_terrain = time.time()
+        tile_names = await self.terrain.ensure_tiles_for_bbox(
+            min_lat, min_lon, max_lat, max_lon
+        )
+        for tn in tile_names:
+            self.terrain._load_tile(tn)
 
-        # Fetch water bodies (if water reflection enabled)
-        water_bodies: List[WaterBody] = []
-        if settings.use_water_reflection:
-            water_bodies = await water_service.fetch_water_bodies(
-                min_lat, min_lon, max_lat, max_lon
-            )
+        site_elevation = self.terrain.get_elevation_sync(site.lat, site.lon)
 
-        # Fetch vegetation (if enabled)
-        vegetation_areas: List[VegetationArea] = []
-        if settings.use_vegetation:
-            vegetation_areas = await vegetation_service.fetch_vegetation(
-                min_lat, min_lon, max_lat, max_lon
-            )
-
-        # Calculate coverage for each point
+        point_elevations = {}
         for lat, lon in grid:
-            point = await self._calculate_point(
-                site, lat, lon,
-                settings, buildings, streets,
-                spatial_idx, water_bodies, vegetation_areas
-            )
+            point_elevations[(lat, lon)] = self.terrain.get_elevation_sync(lat, lon)
+        terrain_time = time.time() - t_terrain
+        _clog(f"Tiles: {len(tile_names)}, site elev: {site_elevation:.0f}m, "
+              f"pre-computed {len(grid)} elevations")
+        _clog(f"━━━ PHASE 2 done: {terrain_time:.1f}s ━━━")
 
-            if point.rsrp >= settings.min_signal:
-                points.append(point)
+        # ━━━ PHASE 3: Point calculation (sync, in thread pool) ━━━
+        _clog(f"━━━ PHASE 3: Calculating {len(grid)} points (threaded) ━━━")
+        dominant_path_service._log_count = 0  # Reset diagnostic counter
+        t_points = time.time()
+
+        loop = asyncio.get_event_loop()
+        points, timing = await loop.run_in_executor(
+            None,
+            self._run_point_loop,
+            grid, site, settings, buildings, streets,
+            spatial_idx, water_bodies, vegetation_areas,
+            site_elevation, point_elevations
+        )
+
+        points_time = time.time() - t_points
+        total_time = time.time() - calc_start
+
+        _clog(f"━━━ PHASE 3 done: {points_time:.1f}s ━━━")
+        _clog("=== RESULTS ===")
+        _clog(f"  Grid points:     {len(grid)}")
+        _clog(f"  Result points:   {len(points)}")
+        _clog(f"  OSM fetch:       {osm_time:.1f}s")
+        _clog(f"  Terrain pre-load:{terrain_time:.1f}s")
+        _clog(f"  Point calc:      {points_time:.1f}s "
+              f"({points_time/max(1,len(grid))*1000:.1f}ms/point)")
+        _clog(f"  TOTAL:           {total_time:.1f}s")
+        _clog(f"  Tiles in memory: {len(self.terrain._tile_cache)}")
+        if any(v > 0.001 for v in timing.values()):
+            _clog("=== PER-STEP BREAKDOWN ===")
+            for step, dt in timing.items():
+                if dt > 0.001:
+                    _clog(f"  {step:20s} {dt:.3f}s "
+                          f"({dt/max(1,len(grid))*1000:.2f}ms/point)")
 
         return points
 
@@ -280,7 +447,36 @@ class CoverageService:
 
         return points
 
-    async def _calculate_point(
+    def _run_point_loop(
+        self, grid, site, settings, buildings, streets,
+        spatial_idx, water_bodies, vegetation_areas,
+        site_elevation, point_elevations
+    ):
+        """Sync point loop - runs in ThreadPoolExecutor, bypasses event loop."""
+        points = []
+        timing = {"los": 0.0, "buildings": 0.0, "antenna": 0.0,
+                  "dominant_path": 0.0, "street_canyon": 0.0,
+                  "reflection": 0.0, "vegetation": 0.0}
+        total = len(grid)
+        log_interval = max(1, total // 20)
+
+        for i, (lat, lon) in enumerate(grid):
+            if i % log_interval == 0:
+                _clog(f"Progress: {i}/{total} ({i*100//total}%)")
+
+            point = self._calculate_point_sync(
+                site, lat, lon, settings, buildings, streets,
+                spatial_idx, water_bodies, vegetation_areas,
+                site_elevation, point_elevations.get((lat, lon), 0.0),
+                timing
+            )
+            if point.rsrp >= settings.min_signal:
+                points.append(point)
+
+        _clog(f"Progress: {total}/{total} (100%)")
+        return points, timing
+
+    def _calculate_point_sync(
         self,
         site: SiteParams,
         lat: float, lon: float,
@@ -289,58 +485,62 @@ class CoverageService:
         streets: List[Street],
         spatial_idx: Optional[SpatialIndex],
         water_bodies: List[WaterBody],
-        vegetation_areas: List[VegetationArea]
+        vegetation_areas: List[VegetationArea],
+        site_elevation: float,
+        point_elevation: float,
+        timing: dict
     ) -> CoveragePoint:
-        """Calculate RSRP at a single point with all propagation models"""
+        """Fully synchronous point calculation. All terrain tiles must be pre-loaded."""
 
         # Distance
         distance = TerrainService.haversine_distance(site.lat, site.lon, lat, lon)
-
         if distance < 1:
-            distance = 1  # Avoid division by zero
+            distance = 1
 
-        # Base path loss (Okumura-Hata for urban)
-        path_loss = self._okumura_hata(
-            distance, site.frequency, site.height, 1.5
-        )
+        # Base path loss
+        path_loss = self._okumura_hata(distance, site.frequency, site.height, 1.5)
 
-        # Antenna pattern loss (if directional)
+        # Antenna pattern
         antenna_loss = 0.0
         if site.azimuth is not None and site.beamwidth:
+            t0 = time.time()
             antenna_loss = self._antenna_pattern_loss(
-                site.lat, site.lon, lat, lon,
-                site.azimuth, site.beamwidth
+                site.lat, site.lon, lat, lon, site.azimuth, site.beamwidth
             )
+            timing["antenna"] += time.time() - t0
 
-        # Terrain loss (LoS check)
+        # Terrain LOS (sync)
         terrain_loss = 0.0
         has_los = True
-
         if settings.use_terrain:
-            los_result = await self.los.check_line_of_sight(
-                site.lat, site.lon, site.height,
-                lat, lon, 1.5
+            t0 = time.time()
+            los_result = self.los.check_line_of_sight_sync(
+                site.lat, site.lon, site.height, lat, lon, 1.5
             )
             has_los = los_result["has_los"]
-
             if not has_los:
-                clearance = los_result["clearance"]
-                terrain_loss = self._diffraction_loss(clearance, site.frequency)
+                terrain_loss = self._diffraction_loss(
+                    los_result["clearance"], site.frequency
+                )
+            timing["los"] += time.time() - t0
 
-        # Building loss — use spatial index for fast lookup
+        # Building loss (spatial index)
         building_loss = 0.0
+        t0 = time.time()
         nearby_buildings = (
             spatial_idx.query_line(site.lat, site.lon, lat, lon)
             if spatial_idx else buildings
         )
 
         if settings.use_buildings and nearby_buildings:
+            site_total_h = site.height + site_elevation
+            point_total_h = 1.5 + point_elevation
+
             if settings.use_materials:
                 for building in nearby_buildings:
                     intersection = self.buildings.line_intersects_building(
-                        site.lat, site.lon, site.height + await self.terrain.get_elevation(site.lat, site.lon),
-                        lat, lon, 1.5 + await self.terrain.get_elevation(lat, lon),
-                        building
+                        site.lat, site.lon, site_total_h,
+                        lat, lon, point_total_h, building
                     )
                     if intersection is not None:
                         material = materials_service.detect_material(building.tags)
@@ -352,21 +552,23 @@ class CoverageService:
             else:
                 for building in nearby_buildings:
                     intersection = self.buildings.line_intersects_building(
-                        site.lat, site.lon, site.height + await self.terrain.get_elevation(site.lat, site.lon),
-                        lat, lon, 1.5 + await self.terrain.get_elevation(lat, lon),
-                        building
+                        site.lat, site.lon, site_total_h,
+                        lat, lon, point_total_h, building
                     )
                     if intersection is not None:
                         building_loss += 20.0
                         has_los = False
                         break
+        timing["buildings"] += time.time() - t0
 
-        # Dominant path analysis
-        if settings.use_dominant_path and nearby_buildings:
-            paths = await dominant_path_service.find_dominant_paths(
+        # Dominant path (sync) — uses spatial index for O(1) building lookups
+        if settings.use_dominant_path and (spatial_idx or nearby_buildings):
+            t0 = time.time()
+            paths = dominant_path_service.find_dominant_paths_sync(
                 site.lat, site.lon, site.height,
                 lat, lon, 1.5,
-                site.frequency, nearby_buildings
+                site.frequency, nearby_buildings,
+                spatial_idx=spatial_idx
             )
             if paths:
                 best_path = paths[0]
@@ -375,10 +577,12 @@ class CoverageService:
                     terrain_loss = 0
                     building_loss = 0
                     has_los = best_path.path_type == "direct" and not best_path.materials_crossed
+            timing["dominant_path"] += time.time() - t0
 
-        # Street canyon model
+        # Street canyon (sync)
         if settings.use_street_canyon and streets:
-            canyon_loss, street_path = await street_canyon_service.calculate_street_canyon_loss(
+            t0 = time.time()
+            canyon_loss, _street_path = street_canyon_service.calculate_street_canyon_loss_sync(
                 site.lat, site.lon, site.height,
                 lat, lon, 1.5,
                 site.frequency, streets
@@ -387,80 +591,76 @@ class CoverageService:
                 path_loss = canyon_loss
                 terrain_loss = 0
                 building_loss = 0
+            timing["street_canyon"] += time.time() - t0
 
-        # Vegetation loss
+        # Vegetation (already sync)
         veg_loss = 0.0
         if settings.use_vegetation and vegetation_areas:
+            t0 = time.time()
             veg_loss = vegetation_service.calculate_vegetation_loss(
-                site.lat, site.lon, lat, lon,
-                vegetation_areas, settings.season
+                site.lat, site.lon, lat, lon, vegetation_areas, settings.season
             )
+            timing["vegetation"] += time.time() - t0
 
-        # Reflections (building + ground/water)
+        # Reflections (sync)
         reflection_gain = 0.0
         if settings.use_reflections and nearby_buildings:
+            t0 = time.time()
             is_over_water = False
             if settings.use_water_reflection and water_bodies:
                 is_over_water = water_service.point_over_water(lat, lon, water_bodies) is not None
 
-            reflection_paths = await reflection_service.find_reflection_paths(
+            refl_paths = reflection_service.find_reflection_paths_sync(
                 site.lat, site.lon, site.height,
                 lat, lon, 1.5,
                 site.frequency, nearby_buildings,
                 include_ground=True
             )
 
-            # If over water, replace ground reflection with stronger water reflection
-            if is_over_water and reflection_paths:
+            if is_over_water and refl_paths:
                 water_path = reflection_service._calculate_ground_reflection(
                     site.lat, site.lon, site.height,
                     lat, lon, 1.5,
                     site.frequency, is_water=True
                 )
                 if water_path:
-                    reflection_paths = [
-                        p for p in reflection_paths if "ground" not in p.materials
-                    ]
-                    reflection_paths.append(water_path)
-                    reflection_paths.sort(key=lambda p: p.total_loss)
+                    refl_paths = [p for p in refl_paths if "ground" not in p.materials]
+                    refl_paths.append(water_path)
+                    refl_paths.sort(key=lambda p: p.total_loss)
 
-            if reflection_paths:
-                direct_rsrp = site.power + site.gain - path_loss - antenna_loss - terrain_loss - building_loss - veg_loss
+            if refl_paths:
+                direct_rsrp = (site.power + site.gain - path_loss - antenna_loss
+                               - terrain_loss - building_loss - veg_loss)
                 combined_rsrp = reflection_service.combine_paths(
-                    direct_rsrp, reflection_paths, site.power + site.gain
+                    direct_rsrp, refl_paths, site.power + site.gain
                 )
                 reflection_gain = max(0, combined_rsrp - direct_rsrp)
+            timing["reflection"] += time.time() - t0
         elif settings.use_water_reflection and water_bodies and not settings.use_reflections:
-            # Water reflection without full reflection model
             is_over_water = water_service.point_over_water(lat, lon, water_bodies) is not None
             if is_over_water:
-                reflection_gain = 3.0  # ~3dB boost over water
+                reflection_gain = 3.0
 
-        # Rain attenuation
+        # Rain
         rain_loss = 0.0
         if settings.rain_rate > 0:
             rain_loss = weather_service.calculate_rain_attenuation(
-                site.frequency,
-                distance / 1000,  # km
-                settings.rain_rate
+                site.frequency, distance / 1000, settings.rain_rate
             )
 
-        # Indoor penetration loss
+        # Indoor
         indoor_loss = 0.0
         if settings.indoor_loss_type != "none":
             indoor_loss = indoor_service.calculate_indoor_loss(
-                site.frequency,
-                settings.indoor_loss_type
+                site.frequency, settings.indoor_loss_type
             )
 
-        # Atmospheric absorption
+        # Atmospheric
         atmo_loss = 0.0
         if settings.use_atmospheric:
             atmo_loss = atmospheric_service.calculate_atmospheric_loss(
-                site.frequency,
-                distance / 1000,
-                settings.temperature_c,
-                settings.humidity_percent
+                site.frequency, distance / 1000,
+                settings.temperature_c, settings.humidity_percent
             )
 
         # Final RSRP
@@ -470,18 +670,11 @@ class CoverageService:
                 + reflection_gain)
 
         return CoveragePoint(
-            lat=lat,
-            lon=lon,
-            rsrp=rsrp,
-            distance=distance,
-            has_los=has_los,
-            terrain_loss=terrain_loss,
-            building_loss=building_loss,
-            reflection_gain=reflection_gain,
-            vegetation_loss=veg_loss,
-            rain_loss=rain_loss,
-            indoor_loss=indoor_loss,
-            atmospheric_loss=atmo_loss,
+            lat=lat, lon=lon, rsrp=rsrp, distance=distance,
+            has_los=has_los, terrain_loss=terrain_loss,
+            building_loss=building_loss, reflection_gain=reflection_gain,
+            vegetation_loss=veg_loss, rain_loss=rain_loss,
+            indoor_loss=indoor_loss, atmospheric_loss=atmo_loss,
         )
 
     def _okumura_hata(

backend/app/services/dominant_path_service.py

@@ -1,10 +1,14 @@
+import time
 import numpy as np
-from typing import List, Tuple, Optional
+from typing import List, Tuple, Optional, TYPE_CHECKING
 from dataclasses import dataclass
 from app.services.terrain_service import terrain_service
 from app.services.buildings_service import buildings_service, Building
 from app.services.materials_service import materials_service, BuildingMaterial
 
+if TYPE_CHECKING:
+    from app.services.spatial_index import SpatialIndex
+
 
 @dataclass
 class RayPath:
@@ -30,6 +34,7 @@ class DominantPathService:
 
     MAX_REFLECTIONS = 2
     MAX_PATHS = 3
+    _log_count = 0  # Counter for diagnostic logging
 
     async def find_dominant_paths(
         self,
@@ -391,4 +396,250 @@ class DominantPathService:
             return 13 + 20 * np.log10(v)
 
 
+    # ── Sync versions (terrain tiles must be pre-loaded) ──
+
+    def find_dominant_paths_sync(
+        self,
+        tx_lat: float, tx_lon: float, tx_height: float,
+        rx_lat: float, rx_lon: float, rx_height: float,
+        frequency_mhz: float,
+        buildings: List[Building],
+        spatial_idx: 'Optional[SpatialIndex]' = None
+    ) -> List[RayPath]:
+        """Sync version - uses spatial index for O(1) building lookups.
+
+        Args:
+            buildings: fallback list (only used if spatial_idx is None)
+            spatial_idx: grid-based spatial index for fast local queries
+        """
+        paths = []
+
+        # Use spatial index to get only buildings along the TX→RX line
+        if spatial_idx:
+            line_buildings = spatial_idx.query_line(tx_lat, tx_lon, rx_lat, rx_lon)
+        else:
+            line_buildings = buildings
+
+        direct = self._check_direct_path_sync(
+            tx_lat, tx_lon, tx_height,
+            rx_lat, rx_lon, rx_height,
+            frequency_mhz, line_buildings
+        )
+        if direct:
+            paths.append(direct)
+
+        # Early termination: if direct path is valid and clear, skip expensive
+        # reflection/diffraction — they won't produce a better path
+        if direct and direct.is_valid and not direct.materials_crossed:
+            return [direct]
+
+        # For reflections, only check buildings near the midpoint (~500m)
+        if spatial_idx:
+            mid_lat = (tx_lat + rx_lat) / 2
+            mid_lon = (tx_lon + rx_lon) / 2
+            # buffer_cells=5 with 0.001° cell ≈ 555m radius
+            reflection_buildings = spatial_idx.query_point(mid_lat, mid_lon, buffer_cells=5)
+        else:
+            reflection_buildings = buildings
+
+        # Log building counts for first 3 points so user can verify filtering
+        DominantPathService._log_count += 1
+        if DominantPathService._log_count <= 3:
+            import sys
+            msg = (f"[DOMINANT_PATH] Point #{DominantPathService._log_count}: "
+                   f"line_bldgs={len(line_buildings)}, "
+                   f"refl_bldgs={len(reflection_buildings)}, "
+                   f"total_available={len(buildings)}, "
+                   f"spatial_idx={'YES' if spatial_idx else 'NO'}, "
+                   f"early_exit={'YES' if direct and direct.is_valid and not direct.materials_crossed else 'NO'}")
+            print(msg, flush=True)
+            try:
+                sys.stderr.write(msg + '\n')
+                sys.stderr.flush()
+            except Exception:
+                pass
+
+        reflections = self._find_reflection_paths_sync(
+            tx_lat, tx_lon, tx_height,
+            rx_lat, rx_lon, rx_height,
+            frequency_mhz, reflection_buildings
+        )
+        paths.extend(reflections[:2])
+
+        if not direct or not direct.is_valid:
+            diffracted = self._find_diffraction_path_sync(
+                tx_lat, tx_lon, tx_height,
+                rx_lat, rx_lon, rx_height,
+                frequency_mhz, spatial_idx=spatial_idx, buildings_fallback=buildings
+            )
+            if diffracted:
+                paths.append(diffracted)
+
+        paths.sort(key=lambda p: p.path_loss)
+        return paths[:self.MAX_PATHS]
+
+    def _check_direct_path_sync(
+        self,
+        tx_lat, tx_lon, tx_height,
+        rx_lat, rx_lon, rx_height,
+        frequency_mhz,
+        buildings: List[Building]
+    ) -> Optional[RayPath]:
+        """Sync direct path check using sync LOS.
+        buildings should already be spatially filtered to the TX→RX line."""
+        from app.services.los_service import los_service
+
+        los_result = los_service.check_line_of_sight_sync(
+            tx_lat, tx_lon, tx_height,
+            rx_lat, rx_lon, rx_height
+        )
+
+        if not los_result["has_los"]:
+            distance = terrain_service.haversine_distance(tx_lat, tx_lon, rx_lat, rx_lon)
+            return RayPath(
+                path_type="direct",
+                total_distance=distance,
+                path_loss=float('inf'),
+                reflection_points=[],
+                materials_crossed=[],
+                is_valid=False
+            )
+
+        materials_crossed = []
+        for building in buildings:
+            intersection = self._line_intersects_building_3d(
+                tx_lat, tx_lon, tx_height,
+                rx_lat, rx_lon, rx_height,
+                building
+            )
+            if intersection:
+                material = materials_service.detect_material(building.tags)
+                materials_crossed.append(material)
+                if len(materials_crossed) >= 3:
+                    break  # Early termination — too many walls
+
+        distance = terrain_service.haversine_distance(tx_lat, tx_lon, rx_lat, rx_lon)
+        path_loss = self._calculate_path_loss(distance, frequency_mhz, tx_height, rx_height)
+
+        for material in materials_crossed:
+            path_loss += materials_service.get_penetration_loss(material, frequency_mhz)
+
+        return RayPath(
+            path_type="direct",
+            total_distance=distance,
+            path_loss=path_loss,
+            reflection_points=[],
+            materials_crossed=materials_crossed,
+            is_valid=len(materials_crossed) < 3
+        )
+
+    def _find_reflection_paths_sync(
+        self,
+        tx_lat, tx_lon, tx_height,
+        rx_lat, rx_lon, rx_height,
+        frequency_mhz,
+        buildings: List[Building]
+    ) -> List[RayPath]:
+        """Sync reflection paths.
+        buildings should already be spatially filtered to nearby area."""
+        reflection_paths = []
+        direct_distance = terrain_service.haversine_distance(tx_lat, tx_lon, rx_lat, rx_lon)
+
+        for building in buildings:
+            reflection_point = self._find_reflection_point(
+                tx_lat, tx_lon, rx_lat, rx_lon, building
+            )
+            if not reflection_point:
+                continue
+
+            ref_lat, ref_lon = reflection_point
+            dist1 = terrain_service.haversine_distance(tx_lat, tx_lon, ref_lat, ref_lon)
+            dist2 = terrain_service.haversine_distance(ref_lat, ref_lon, rx_lat, rx_lon)
+            total_distance = dist1 + dist2
+
+            if total_distance > direct_distance * 2:
+                continue
+
+            path_loss = self._calculate_path_loss(total_distance, frequency_mhz, tx_height, rx_height)
+            material = materials_service.detect_material(building.tags)
+            path_loss += materials_service.get_reflection_loss(material)
+
+            reflection_paths.append(RayPath(
+                path_type="reflected",
+                total_distance=total_distance,
+                path_loss=path_loss,
+                reflection_points=[(ref_lat, ref_lon)],
+                materials_crossed=[],
+                is_valid=True
+            ))
+
+        return reflection_paths
+
+    def _find_diffraction_path_sync(
+        self,
+        tx_lat, tx_lon, tx_height,
+        rx_lat, rx_lon, rx_height,
+        frequency_mhz,
+        spatial_idx: 'Optional[SpatialIndex]' = None,
+        buildings_fallback: Optional[List[Building]] = None
+    ) -> Optional[RayPath]:
+        """Sync diffraction path.
+        Uses spatial_idx.query_point at each sample for O(1) building lookup."""
+        max_height = 0
+        obstacle_lat, obstacle_lon = None, None
+
+        num_samples = 20
+        for i in range(1, num_samples - 1):
+            t = i / num_samples
+            lat = tx_lat + t * (rx_lat - tx_lat)
+            lon = tx_lon + t * (rx_lon - tx_lon)
+
+            terrain_elev = terrain_service.get_elevation_sync(lat, lon)
+            if terrain_elev > max_height:
+                max_height = terrain_elev
+                obstacle_lat, obstacle_lon = lat, lon
+
+            # Use spatial index for O(1) lookup at this sample point
+            if spatial_idx:
+                local_buildings = spatial_idx.query_point(lat, lon, buffer_cells=1)
+            else:
+                local_buildings = buildings_fallback or []
+
+            for building in local_buildings:
+                if buildings_service.point_in_building(lat, lon, building):
+                    if building.height > max_height:
+                        max_height = building.height
+                        obstacle_lat, obstacle_lon = lat, lon
+
+        if not obstacle_lat:
+            return None
+
+        distance = terrain_service.haversine_distance(tx_lat, tx_lon, rx_lat, rx_lon)
+
+        tx_elev = terrain_service.get_elevation_sync(tx_lat, tx_lon)
+        rx_elev = terrain_service.get_elevation_sync(rx_lat, rx_lon)
+
+        tx_total = tx_elev + tx_height
+        rx_total = rx_elev + rx_height
+
+        d1 = terrain_service.haversine_distance(tx_lat, tx_lon, obstacle_lat, obstacle_lon)
+        los_height = tx_total + (rx_total - tx_total) * (d1 / distance) if distance > 0 else tx_total
+
+        clearance = los_height - max_height
+
+        diffraction_loss = self._knife_edge_loss(clearance, frequency_mhz, distance, d1)
+
+        path_loss = self._calculate_path_loss(distance, frequency_mhz, tx_height, rx_height)
+        path_loss += diffraction_loss
+
+        return RayPath(
+            path_type="diffracted",
+            total_distance=distance,
+            path_loss=path_loss,
+            reflection_points=[(obstacle_lat, obstacle_lon)],
+            materials_crossed=[],
+            is_valid=True
+        )
+
+
 dominant_path_service = DominantPathService()

backend/app/services/los_service.py

@@ -98,6 +98,59 @@ class LineOfSightService:
             "profile": profile
         }
 
+    def check_line_of_sight_sync(
+        self,
+        tx_lat: float, tx_lon: float, tx_height: float,
+        rx_lat: float, rx_lon: float, rx_height: float = 1.5,
+        num_samples: int = 50
+    ) -> dict:
+        """
+        Sync LOS check - terrain tiles must be pre-loaded into memory.
+        Returns dict with has_los, clearance, blocked_at (no profile for speed).
+        """
+        profile = self.terrain.get_elevation_profile_sync(
+            tx_lat, tx_lon, rx_lat, rx_lon, num_samples
+        )
+
+        if not profile:
+            return {"has_los": True, "clearance": 0, "blocked_at": None}
+
+        tx_ground = profile[0]["elevation"]
+        rx_ground = profile[-1]["elevation"]
+
+        tx_total = tx_ground + tx_height
+        rx_total = rx_ground + rx_height
+
+        total_distance = profile[-1]["distance"]
+
+        min_clearance = float('inf')
+        blocked_at = None
+
+        for point in profile:
+            d = point["distance"]
+            terrain_elev = point["elevation"]
+
+            if total_distance == 0:
+                los_height = tx_total
+            else:
+                los_height = tx_total + (rx_total - tx_total) * (d / total_distance)
+
+            effective_radius = self.K_FACTOR * self.EARTH_RADIUS
+            curvature = (d * (total_distance - d)) / (2 * effective_radius)
+            los_height_corrected = los_height - curvature
+            clearance = los_height_corrected - terrain_elev
+
+            if clearance < min_clearance:
+                min_clearance = clearance
+                if clearance <= 0:
+                    blocked_at = d
+
+        return {
+            "has_los": min_clearance > 0,
+            "clearance": min_clearance,
+            "blocked_at": blocked_at,
+        }
+
     async def calculate_fresnel_clearance(
         self,
         tx_lat: float, tx_lon: float, tx_height: float,

backend/app/services/reflection_service.py

@@ -273,4 +273,37 @@ class ReflectionService:
         return 10 * np.log10(total_power)
 
 
+    def find_reflection_paths_sync(
+        self,
+        tx_lat: float, tx_lon: float, tx_height: float,
+        rx_lat: float, rx_lon: float, rx_height: float,
+        frequency_mhz: float,
+        buildings: List[Building],
+        include_ground: bool = True
+    ) -> List[ReflectionPath]:
+        """Sync version (no I/O in the async original)"""
+        paths = []
+
+        for building in buildings:
+            path = self._find_single_bounce(
+                tx_lat, tx_lon, tx_height,
+                rx_lat, rx_lon, rx_height,
+                frequency_mhz, building
+            )
+            if path:
+                paths.append(path)
+
+        if include_ground:
+            ground_path = self._calculate_ground_reflection(
+                tx_lat, tx_lon, tx_height,
+                rx_lat, rx_lon, rx_height,
+                frequency_mhz
+            )
+            if ground_path:
+                paths.append(ground_path)
+
+        paths.sort(key=lambda p: p.total_loss)
+        return paths[:5]
+
+
 reflection_service = ReflectionService()

backend/app/services/spatial_index.py

@@ -21,6 +21,7 @@ class SpatialIndex:
         self.cell_size = cell_size
         self._grid: Dict[Tuple[int, int], List[Building]] = defaultdict(list)
         self._buildings: List[Building] = []
+        self._buildings_by_id: Dict[int, Building] = {}
 
     def _cell_key(self, lat: float, lon: float) -> Tuple[int, int]:
         """Convert lat/lon to grid cell key"""
@@ -30,6 +31,7 @@ class SpatialIndex:
         """Build spatial index from buildings list"""
         self._grid.clear()
         self._buildings = buildings
+        self._buildings_by_id = {b.id: b for b in buildings}
 
         for building in buildings:
             # Get bounding box of building
@@ -63,9 +65,7 @@ class SpatialIndex:
                 for b in self._grid.get(key, []):
                     results.add(b.id)
 
-        # Return buildings by id (deduped)
-        id_set = results
-        return [b for b in self._buildings if b.id in id_set]
+        return [self._buildings_by_id[bid] for bid in results if bid in self._buildings_by_id]
 
     def query_line(
         self,
@@ -73,29 +73,37 @@ class SpatialIndex:
         lat2: float, lon2: float,
         buffer_cells: int = 1
     ) -> List[Building]:
-        """Find buildings along a line (for LoS checks)"""
+        """Find buildings along a line by walking the actual cells it passes through.
+
+        Samples points along the line at cell_size intervals and queries
+        a buffer around each sample — much faster than bounding-box scan
+        for long lines.
+        """
         if not self._grid:
             return self._buildings
 
-        # Get bounding box cells of the line
-        min_lat = min(lat1, lat2)
-        max_lat = max(lat1, lat2)
-        min_lon = min(lon1, lon2)
-        max_lon = max(lon1, lon2)
+        # Walk the line in cell_size steps, collecting unique cells
+        dlat = lat2 - lat1
+        dlon = lon2 - lon1
+        length = max(abs(dlat), abs(dlon))
+        num_steps = max(1, int(length / self.cell_size) + 1)
 
-        min_clat = int(min_lat / self.cell_size) - buffer_cells
-        max_clat = int(max_lat / self.cell_size) + buffer_cells
-        min_clon = int(min_lon / self.cell_size) - buffer_cells
-        max_clon = int(max_lon / self.cell_size) + buffer_cells
+        visited_cells: set = set()
+        for s in range(num_steps + 1):
+            t = s / num_steps
+            lat = lat1 + t * dlat
+            lon = lon1 + t * dlon
+            center = self._cell_key(lat, lon)
+            for dy in range(-buffer_cells, buffer_cells + 1):
+                for dx in range(-buffer_cells, buffer_cells + 1):
+                    visited_cells.add((center[0] + dy, center[1] + dx))
 
         results = set()
-        for clat in range(min_clat, max_clat + 1):
-            for clon in range(min_clon, max_clon + 1):
-                for b in self._grid.get((clat, clon), []):
-                    results.add(b.id)
+        for key in visited_cells:
+            for b in self._grid.get(key, []):
+                results.add(b.id)
 
-        id_set = results
-        return [b for b in self._buildings if b.id in id_set]
+        return [self._buildings_by_id[bid] for bid in results if bid in self._buildings_by_id]
 
     def query_bbox(
         self,
@@ -117,8 +125,7 @@ class SpatialIndex:
                 for b in self._grid.get((clat, clon), []):
                     results.add(b.id)
 
-        id_set = results
-        return [b for b in self._buildings if b.id in id_set]
+        return [self._buildings_by_id[bid] for bid in results if bid in self._buildings_by_id]
 
 
 # Global cache of spatial indices

backend/app/services/street_canyon_service.py

@@ -44,8 +44,10 @@ class StreetCanyonService:
     CORNER_LOSS_90 = 10.0  # dB for 90-degree turn
     CORNER_LOSS_45 = 4.0   # dB for 45-degree turn
 
-    def __init__(self, cache_dir: str = "/opt/rfcp/backend/data/streets"):
-        self.cache_dir = Path(cache_dir)
+    def __init__(self):
+        import os
+        self.data_path = Path(os.environ.get('RFCP_DATA_PATH', './data'))
+        self.cache_dir = self.data_path / 'osm' / 'streets'
         self.cache_dir.mkdir(exist_ok=True, parents=True)
         self._cache: dict[str, List[Street]] = {}
 
@@ -56,21 +58,28 @@ class StreetCanyonService:
     ) -> List[Street]:
         """Fetch street network from OSM"""
 
-        cache_key = f"{min_lat:.3f}_{min_lon:.3f}_{max_lat:.3f}_{max_lon:.3f}"
+        cache_key = f"{min_lat:.2f}_{min_lon:.2f}_{max_lat:.2f}_{max_lon:.2f}"
 
-        # Check cache
+        # Check memory cache
         if cache_key in self._cache:
             return self._cache[cache_key]
 
+        # Check disk cache
         cache_file = self.cache_dir / f"{cache_key}.json"
         if cache_file.exists():
-            with open(cache_file) as f:
-                data = json.load(f)
-                streets = [Street(**s) for s in data]
-                self._cache[cache_key] = streets
-                return streets
+            try:
+                with open(cache_file) as f:
+                    data = json.load(f)
+                    streets = [Street(**s) for s in data]
+                    self._cache[cache_key] = streets
+                    print(f"[Streets] Cache hit for {cache_key}")
+                    return streets
+            except Exception:
+                pass
 
         # Fetch from Overpass
+        print(f"[Streets] Fetching from Overpass API for {cache_key}...")
+
         query = f"""
         [out:json][timeout:30];
         way["highway"]({min_lat},{min_lon},{max_lat},{max_lon});
@@ -85,20 +94,21 @@ class StreetCanyonService:
                 response.raise_for_status()
                 data = response.json()
         except Exception as e:
-            print(f"Street fetch error: {e}")
+            print(f"[Streets] Fetch error: {e}")
             return []
 
         streets = self._parse_streets(data)
 
-        # Cache
-        with open(cache_file, 'w') as f:
-            json.dump([{
-                "id": s.id,
-                "name": s.name,
-                "geometry": s.geometry,
-                "width": s.width,
-                "highway_type": s.highway_type
-            } for s in streets], f)
+        # Cache to disk
+        if streets:
+            with open(cache_file, 'w') as f:
+                json.dump([{
+                    "id": s.id,
+                    "name": s.name,
+                    "geometry": s.geometry,
+                    "width": s.width,
+                    "highway_type": s.highway_type
+                } for s in streets], f)
 
         self._cache[cache_key] = streets
         return streets
@@ -360,4 +370,42 @@ class StreetCanyonService:
             return self.CORNER_LOSS_90 + (turn_angle - 90) * 0.2  # Extra loss for sharp turns
 
 
+    def calculate_street_canyon_loss_sync(
+        self,
+        tx_lat: float, tx_lon: float, tx_height: float,
+        rx_lat: float, rx_lon: float, rx_height: float,
+        frequency_mhz: float,
+        streets: List[Street]
+    ) -> Tuple[float, List[Tuple[float, float]]]:
+        """Sync version (no I/O in the async original)"""
+        street_path = self._find_street_path(tx_lat, tx_lon, rx_lat, rx_lon, streets)
+
+        if not street_path:
+            return float('inf'), []
+
+        total_loss = 0.0
+        total_distance = 0.0
+
+        for i in range(len(street_path) - 1):
+            p1 = street_path[i]
+            p2 = street_path[i + 1]
+
+            from app.services.terrain_service import TerrainService
+            segment_dist = TerrainService.haversine_distance(p1[0], p1[1], p2[0], p2[1])
+            total_distance += segment_dist
+
+            if segment_dist > 0:
+                segment_loss = 32.4 + 20 * np.log10(frequency_mhz) + 20 * np.log10(segment_dist / 1000 + 0.001)
+                total_loss += segment_loss * (segment_dist / total_distance) if total_distance > 0 else 0
+
+            if i > 0:
+                corner_angle = self._calculate_corner_angle(
+                    street_path[i - 1], p1, p2
+                )
+                corner_loss = self._corner_loss(corner_angle)
+                total_loss += corner_loss
+
+        return total_loss, street_path
+
+
 street_canyon_service = StreetCanyonService()

backend/app/services/terrain_service.py

@@ -168,6 +168,25 @@ class TerrainService:
 
         return float(elevation)
 
+    def get_elevation_sync(self, lat: float, lon: float) -> float:
+        """Sync elevation lookup from memory cache. Returns 0.0 if tile not loaded."""
+        tile_name = self.get_tile_name(lat, lon)
+        tile = self._tile_cache.get(tile_name)
+        if tile is None:
+            return 0.0
+
+        size = tile.shape[0]
+        lat_int = int(lat) if lat >= 0 else int(lat) - 1
+        lon_int = int(lon) if lon >= 0 else int(lon) - 1
+
+        row = int((1 - (lat - lat_int)) * (size - 1))
+        col = int((lon - lon_int) * (size - 1))
+        row = max(0, min(row, size - 1))
+        col = max(0, min(col, size - 1))
+
+        elevation = tile[row, col]
+        return 0.0 if elevation == -32768 else float(elevation)
+
     async def get_elevation_profile(
         self,
         lat1: float, lon1: float,
@@ -193,6 +212,30 @@ class TerrainService:
 
         return profile
 
+    def get_elevation_profile_sync(
+        self,
+        lat1: float, lon1: float,
+        lat2: float, lon2: float,
+        num_points: int = 50
+    ) -> List[dict]:
+        """Sync elevation profile - tiles must be pre-loaded into memory cache."""
+        lats = np.linspace(lat1, lat2, num_points)
+        lons = np.linspace(lon1, lon2, num_points)
+
+        total_distance = self.haversine_distance(lat1, lon1, lat2, lon2)
+        distances = np.linspace(0, total_distance, num_points)
+
+        profile = []
+        for i in range(num_points):
+            profile.append({
+                "lat": float(lats[i]),
+                "lon": float(lons[i]),
+                "elevation": self.get_elevation_sync(float(lats[i]), float(lons[i])),
+                "distance": float(distances[i])
+            })
+
+        return profile
+
     async def ensure_tiles_for_bbox(
         self,
         min_lat: float, min_lon: float,

backend/run_server.py

@@ -1,9 +1,22 @@
 """Entry point for PyInstaller bundle"""
-print("[RFCP] run_server.py starting...", flush=True)
-
 import os
 import sys
 
+# Force unbuffered stdout/stderr — critical for piped output (Electron, bat files)
+os.environ['PYTHONUNBUFFERED'] = '1'
+if hasattr(sys.stdout, 'reconfigure'):
+    try:
+        sys.stdout.reconfigure(line_buffering=True)
+    except Exception:
+        pass
+if hasattr(sys.stderr, 'reconfigure'):
+    try:
+        sys.stderr.reconfigure(line_buffering=True)
+    except Exception:
+        pass
+
+print("[RFCP] run_server.py starting...", flush=True)
+
 # Set base path for PyInstaller
 if getattr(sys, 'frozen', False):
     base_dir = os.path.dirname(sys.executable)

desktop/main.js

@@ -1,5 +1,5 @@
 const { app, BrowserWindow, ipcMain, dialog, shell } = require('electron');
-const { spawn } = require('child_process');
+const { spawn, execSync } = require('child_process');
 const path = require('path');
 const fs = require('fs');
 const Store = require('electron-store');
@@ -179,7 +179,8 @@ async function startBackend() {
     backendProcess = spawn(backendExe, [], {
       cwd: backendDir,
       env,
-      stdio: ['ignore', 'pipe', 'pipe']
+      stdio: ['ignore', 'pipe', 'pipe'],
+      detached: process.platform !== 'win32'  // Unix: create process group for clean kill
     });
   }
 
@@ -305,6 +306,35 @@ function createMainWindow() {
   });
 }
 
+// ── Backend cleanup ───────────────────────────────────────────────
+
+function killBackend() {
+  if (!backendProcess) return;
+
+  const pid = backendProcess.pid;
+  log(`Killing backend (PID ${pid})...`);
+
+  try {
+    if (process.platform === 'win32') {
+      // Windows: taskkill with /T (tree) to kill child processes too
+      execSync(`taskkill /f /t /pid ${pid}`, { stdio: 'ignore' });
+    } else {
+      // Unix: kill process group
+      process.kill(-pid, 'SIGTERM');
+    }
+  } catch (e) {
+    // Fallback: try normal kill
+    try {
+      backendProcess.kill('SIGKILL');
+    } catch (_e2) {
+      // Already dead
+    }
+  }
+
+  backendProcess = null;
+  log('Backend killed');
+}
+
 // ── App lifecycle ──────────────────────────────────────────────────
 
 app.whenReady().then(async () => {
@@ -335,10 +365,7 @@ app.whenReady().then(async () => {
 });
 
 app.on('window-all-closed', () => {
-  if (backendProcess) {
-    backendProcess.kill();
-    backendProcess = null;
-  }
+  killBackend();
 
   if (process.platform !== 'darwin') {
     app.quit();
@@ -352,11 +379,11 @@ app.on('activate', () => {
 });
 
 app.on('before-quit', () => {
-  if (backendProcess) {
-    backendProcess.kill();
-  }
+  killBackend();
+
   if (backendLogStream) {
     backendLogStream.end();
+    backendLogStream = null;
   }
 });
 
@@ -404,3 +431,74 @@ ipcMain.handle('set-setting', (_event, key, value) => store.set(key, value));
 
 ipcMain.handle('open-external', (_event, url) => shell.openExternal(url));
 ipcMain.handle('open-path', (_event, filePath) => shell.openPath(filePath));
+
+// ── Import Region Data ────────────────────────────────────────────
+
+ipcMain.handle('import-region-data', async () => {
+  const result = await dialog.showOpenDialog(mainWindow, {
+    title: 'Select folder with region data',
+    properties: ['openDirectory']
+  });
+
+  const srcDir = result.filePaths[0];
+  if (!srcDir) return { success: false, message: 'Cancelled' };
+
+  const dataPath = getDataPath();
+  let terrainCount = 0;
+  let osmCount = 0;
+
+  try {
+    // Copy terrain/*.hgt files
+    const terrainSrc = path.join(srcDir, 'terrain');
+    if (fs.existsSync(terrainSrc)) {
+      const terrainDest = path.join(dataPath, 'terrain');
+      if (!fs.existsSync(terrainDest)) {
+        fs.mkdirSync(terrainDest, { recursive: true });
+      }
+      const hgtFiles = fs.readdirSync(terrainSrc).filter(f => f.endsWith('.hgt'));
+      for (const file of hgtFiles) {
+        fs.copyFileSync(path.join(terrainSrc, file), path.join(terrainDest, file));
+        terrainCount++;
+      }
+    }
+
+    // Copy osm/**/*.json files
+    const osmSrc = path.join(srcDir, 'osm');
+    if (fs.existsSync(osmSrc)) {
+      const osmDest = path.join(dataPath, 'osm');
+      const subdirs = fs.readdirSync(osmSrc).filter(d =>
+        fs.statSync(path.join(osmSrc, d)).isDirectory()
+      );
+      for (const subdir of subdirs) {
+        const subSrc = path.join(osmSrc, subdir);
+        const subDest = path.join(osmDest, subdir);
+        if (!fs.existsSync(subDest)) {
+          fs.mkdirSync(subDest, { recursive: true });
+        }
+        const jsonFiles = fs.readdirSync(subSrc).filter(f => f.endsWith('.json'));
+        for (const file of jsonFiles) {
+          fs.copyFileSync(path.join(subSrc, file), path.join(subDest, file));
+          osmCount++;
+        }
+      }
+    }
+
+    if (terrainCount === 0 && osmCount === 0) {
+      return {
+        success: false,
+        message: 'No data files found. Expected terrain/*.hgt or osm/**/*.json'
+      };
+    }
+
+    log(`Imported ${terrainCount} terrain tiles, ${osmCount} OSM files from ${srcDir}`);
+    return {
+      success: true,
+      terrainCount,
+      osmCount,
+      message: `Imported ${terrainCount} terrain tiles and ${osmCount} OSM cache files`
+    };
+  } catch (e) {
+    log(`Import error: ${e.message}`);
+    return { success: false, message: `Import failed: ${e.message}` };
+  }
+});

desktop/preload.js

@@ -21,6 +21,9 @@ contextBridge.exposeInMainWorld('rfcp', {
   openExternal: (url) => ipcRenderer.invoke('open-external', url),
   openPath: (path) => ipcRenderer.invoke('open-path', path),
 
+  // Region data import
+  importRegionData: () => ipcRenderer.invoke('import-region-data'),
+
   // Platform info
   platform: process.platform,
   isDesktop: true,

frontend/src/App.tsx

@@ -28,7 +28,8 @@ import Button from '@/components/ui/Button.tsx';
 import NumberInput from '@/components/ui/NumberInput.tsx';
 import ConfirmDialog from '@/components/ui/ConfirmDialog.tsx';
 import { RegionWizard } from '@/components/RegionWizard.tsx';
-import { isDesktop } from '@/lib/desktop.ts';
+import { isDesktop, getDesktopApi } from '@/lib/desktop.ts';
+import type { RegionInfo, CacheStats } from '@/services/api.ts';
 
 /**
  * Restore a sites snapshot: replace all sites in IndexedDB + Zustand.
@@ -121,8 +122,18 @@ export default function App() {
 
   // Region wizard for first-run (desktop mode only)
   const [showWizard, setShowWizard] = useState(false);
+  const [cachedRegions, setCachedRegions] = useState<RegionInfo[]>([]);
+  const [cacheStats, setCacheStats] = useState<CacheStats | null>(null);
+
+  const refreshCacheStatus = useCallback(() => {
+    api.getRegions().then(setCachedRegions).catch(() => {});
+    api.getCacheStats().then(setCacheStats).catch(() => {});
+  }, []);
 
   useEffect(() => {
+    // Load cache status on mount
+    refreshCacheStatus();
+
     if (!isDesktop()) return;
     const skipped = localStorage.getItem('rfcp_region_wizard_skipped');
     if (skipped) return;
@@ -137,7 +148,7 @@ export default function App() {
       .catch(() => {
         // Backend not ready yet, skip wizard
       });
-  }, []);
+  }, [refreshCacheStatus]);
 
   // Resizable sidebar
   const PANEL_MIN = 300;
@@ -1051,6 +1062,75 @@ export default function App() {
               </div>
             </div>
 
+            {/* Data Cache Status */}
+            <div className="bg-white dark:bg-dark-surface border border-gray-200 dark:border-dark-border rounded-lg shadow-sm p-4 space-y-2">
+              <h3 className="text-sm font-semibold text-gray-800 dark:text-dark-text">
+                Data Cache
+              </h3>
+              {cachedRegions.length > 0 ? (
+                <>
+                  <div className="space-y-1">
+                    {cachedRegions.filter((r) => r.downloaded || r.download_progress > 0).length > 0 ? (
+                      cachedRegions
+                        .filter((r) => r.downloaded || r.download_progress > 0)
+                        .map((r) => (
+                          <div key={r.id} className="flex items-center gap-2 text-xs">
+                            <span
+                              className={`w-1.5 h-1.5 rounded-full flex-shrink-0 ${
+                                r.downloaded ? 'bg-emerald-500' : 'bg-amber-500'
+                              }`}
+                            />
+                            <span className="text-gray-700 dark:text-dark-text truncate">{r.name}</span>
+                            {!r.downloaded && (
+                              <span className="text-gray-400 dark:text-dark-muted ml-auto">
+                                {Math.round(r.download_progress)}%
+                              </span>
+                            )}
+                          </div>
+                        ))
+                    ) : (
+                      <p className="text-xs text-gray-400 dark:text-dark-muted">No regions cached</p>
+                    )}
+                  </div>
+                  {cacheStats && (
+                    <p className="text-[11px] text-gray-400 dark:text-dark-muted">
+                      {cacheStats.terrain_tiles} terrain tiles ({cacheStats.terrain_mb} MB)
+                    </p>
+                  )}
+                </>
+              ) : (
+                <p className="text-xs text-gray-400 dark:text-dark-muted">Loading...</p>
+              )}
+              <div className="flex gap-2 pt-1">
+                <button
+                  onClick={() => setShowWizard(true)}
+                  className="text-xs px-2 py-1 bg-slate-100 dark:bg-dark-border text-gray-600 dark:text-dark-text rounded hover:bg-slate-200 dark:hover:bg-dark-muted transition-colors"
+                >
+                  Download Regions
+                </button>
+                {isDesktop() && (
+                  <button
+                    onClick={async () => {
+                      const desktop = getDesktopApi();
+                      if (!desktop) return;
+                      const result = await desktop.importRegionData();
+                      if (result.success) {
+                        addToast(result.message, 'success');
+                        refreshCacheStatus();
+                      } else {
+                        if (result.message !== 'Cancelled') {
+                          addToast(result.message, 'error');
+                        }
+                      }
+                    }}
+                    className="text-xs px-2 py-1 bg-slate-100 dark:bg-dark-border text-gray-600 dark:text-dark-text rounded hover:bg-slate-200 dark:hover:bg-dark-muted transition-colors"
+                  >
+                    Import Data
+                  </button>
+                )}
+              </div>
+            </div>
+
             {/* Coverage error */}
             {coverageError && (
               <div className="bg-red-50 dark:bg-red-900/20 border border-red-200 dark:border-red-800 rounded-lg p-3">
@@ -1109,7 +1189,7 @@ export default function App() {
 
       {/* First-run region download wizard (desktop only) */}
       {showWizard && (
-        <RegionWizard onComplete={() => setShowWizard(false)} />
+        <RegionWizard onComplete={() => { setShowWizard(false); refreshCacheStatus(); }} />
       )}
     </div>
   );

frontend/src/lib/desktop.ts

@@ -14,6 +14,12 @@ interface RFCPDesktop {
   setSetting: (key: string, value: unknown) => Promise<void>;
   openExternal: (url: string) => Promise<void>;
   openPath: (path: string) => Promise<void>;
+  importRegionData: () => Promise<{
+    success: boolean;
+    terrainCount?: number;
+    osmCount?: number;
+    message: string;
+  }>;
   platform: string;
   isDesktop: boolean;
   isMac: boolean;

installer/coverage-result-detailed.json

@@ -0,0 +1 @@
+{"detail":"Calculation timeout (5 min) — try smaller radius or lower resolution"}