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docs/06_offline_strategy.md

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+# Offline Strategy
+
+## Offline requirement
+
+Offline use must cover riding-critical information, not only maps.
+
+## Offline pack contents
+
+A trip offline pack should include:
+
+- route geometry,
+- route alternatives,
+- daily stages,
+- elevation profile,
+- selected vector/raster map area,
+- route-corridor POIs,
+- emergency/bailout POIs,
+- local rule cards,
+- cached weather forecast at departure,
+- saved bookings/deep links/addresses,
+- user notes,
+- GPX/TCX/FIT exports,
+- report queue for later upload.
+
+## Pack scope
+
+Use a corridor-based pack:
+
+```text
+primary corridor: 5 km on either side of route
+logistics corridor: 20 km around stage endpoints and bailout towns
+map context: bounding box with simplification by zoom level
+```
+
+## Offline modes
+
+### MVP offline mode
+
+- Download planned route, POIs, stage plan, rules, and GPX.
+- Allow map viewing if tile pack is present.
+- Allow report capture and sync later.
+- Allow basic distance-to-next-critical-thing calculation from cached data.
+
+### Production offline mode
+
+- Offline rerouting using a compact regional routing graph.
+- Offline POI search.
+- Offline rule lookup.
+- Offline elevation sampling.
+- Offline exports.
+
+## Storage model
+
+Mobile app storage:
+
+- SQLite for structured trip data and POIs.
+- File storage for tile packs and exports.
+- Key-value storage for user preferences and sync state.
+
+## Pack versioning
+
+Each offline pack should include:
+
+```json
+{
+  "pack_id": "pack_123",
+  "trip_id": "trip_123",
+  "created_at": "2026-06-30T00:00:00Z",
+  "data_versions": {
+    "osm_extract": "geofabrik-europe-germany-2026-06-29",
+    "poi_index": "2026-06-29",
+    "rules": "2026-06-01",
+    "weather_cached_at": "2026-06-30T06:00:00Z"
+  },
+  "bbox": [6.0, 47.0, 15.0, 55.0],
+  "route_buffer_km": 5,
+  "expires_at": "2026-07-14T00:00:00Z"
+}
+```
+
+## User-facing warnings
+
+Before departure, show:
+
+- which items are available offline,
+- which items are stale,
+- which route sections lack cached POIs,
+- whether offline rerouting is available,
+- which exports are saved.