diff --git a/README.md b/README.md
index 4ea3dbf..abd3909 100644
--- a/README.md
+++ b/README.md
@@ -53,6 +53,7 @@ This starts:
 
 - `db` (`postgis/postgis`) on `5432` inside the container, exposed as **`7721`** on the host for remote access
 - `api` on `8122` — uses PostgreSQL via `DATABASE_URL` (migrations run on startup)
+- `minio` (S3-compatible storage) with admin UI on `8774` and internal S3 API on `9000`
 
 **Remote DB access** (e.g. `postgres://momswap:momswap@HOST_IP:7721/momswap?sslmode=disable`): The init script `etc/pg-init-remote.sh` configures `pg_hba.conf` for remote connections on fresh installs. If the DB was initialized before that was added, run once: `./bin/fix-pg-remote.sh`
 
@@ -74,6 +75,7 @@ Notes:
 - `api` service uses the production `runtime` image target.
 - `api-dev` profile uses the `dev` image target and Docker Compose watch.
 - DB defaults can be overridden via `POSTGRES_DB`, `POSTGRES_USER`, `POSTGRES_PASSWORD`.
+- S3 defaults can be overridden via `S3_ENDPOINT`, `S3_BUCKET`, `S3_REGION`, `S3_ACCESS_KEY`, `S3_SECRET_KEY`, `S3_USE_PATH_STYLE`, `S3_USE_TLS`.
 
 ## Frontend
 
@@ -89,6 +91,7 @@ Then visit:
 
 - Production: `https://momswap.produktor.duckdns.org/web/`
 - Local: `http://localhost:8122/web/`
+- Local Leaflet demo: `http://localhost:8122/web/leaflet-demo.html`
 
 ## Documentation
 
@@ -98,6 +101,8 @@ Then visit:
 | [docs/typescript-frontend-integration.md](docs/typescript-frontend-integration.md) | TypeScript client API, integration flow, examples |
 | [docs/ed25519-security-use-cases.md](docs/ed25519-security-use-cases.md) | Ed25519 auth flows, registration, signatures |
 | [docs/geo-auth-backend-plan.md](docs/geo-auth-backend-plan.md) | Architecture and planning |
+| [docs/assets-storage-and-sharing.md](docs/assets-storage-and-sharing.md) | Asset metadata, dedup, visibility rules, and `properties.assets` contract |
+| [docs/docker-minio-local-dev.md](docs/docker-minio-local-dev.md) | MinIO compose topology, bucket bootstrap, and local verification |
 
 ## API client library
 
diff --git a/cmd/api/main.go b/cmd/api/main.go
index 1347300..0f76d62 100644
--- a/cmd/api/main.go
+++ b/cmd/api/main.go
@@ -4,11 +4,13 @@ import (
 	"log"
 	"net/http"
 	"os"
+	"strconv"
 	"strings"
 	"time"
 
 	"momswap/backend/internal/app"
 	httpapi "momswap/backend/internal/http"
+	"momswap/backend/internal/storage"
 	"momswap/backend/internal/store"
 )
 
@@ -47,6 +49,11 @@ func main() {
 		SessionTTL:   24 * time.Hour,
 	}, servicePublicKey)
 	service.BootstrapAdmin(adminPublicKey)
+	if signer, err := newAssetSignerFromEnv(); err != nil {
+		log.Printf("asset storage disabled: %v", err)
+	} else if signer != nil {
+		service.ConfigureAssetStorage(signer)
+	}
 
 	api := httpapi.NewAPI(service)
 	h := api.Routes()
@@ -63,6 +70,35 @@ func main() {
 	}
 }
 
+func newAssetSignerFromEnv() (app.AssetURLSigner, error) {
+	endpoint := os.Getenv("S3_ENDPOINT")
+	bucket := os.Getenv("S3_BUCKET")
+	if endpoint == "" || bucket == "" {
+		return nil, nil
+	}
+	useTLS, err := strconv.ParseBool(getEnv("S3_USE_TLS", "false"))
+	if err != nil {
+		return nil, err
+	}
+	usePathStyle, err := strconv.ParseBool(getEnv("S3_USE_PATH_STYLE", "true"))
+	if err != nil {
+		return nil, err
+	}
+	signer, err := storage.NewS3Signer(storage.S3Config{
+		Endpoint:  endpoint,
+		Region:    getEnv("S3_REGION", "us-east-1"),
+		Bucket:    bucket,
+		AccessKey: getEnv("S3_ACCESS_KEY", ""),
+		SecretKey: getEnv("S3_SECRET_KEY", ""),
+		UseTLS:    useTLS,
+		PathStyle: usePathStyle,
+	})
+	if err != nil {
+		return nil, err
+	}
+	return signer, nil
+}
+
 func getEnv(key, fallback string) string {
 	v := os.Getenv(key)
 	if v == "" {
diff --git a/docker-compose.yml b/docker-compose.yml
index 8b5fe9c..c084d04 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -19,6 +19,42 @@ services:
       start_period: 10s
     restart: unless-stopped
 
+  minio:
+    image: minio/minio:latest
+    container_name: momswap-backend-minio
+    environment:
+      MINIO_ROOT_USER: "${S3_ACCESS_KEY:-momswap}"
+      MINIO_ROOT_PASSWORD: "${S3_SECRET_KEY:-momswap-secret}"
+    command: server /data --console-address ":9001"
+    volumes:
+      - ./var/minio:/data
+    ports:
+      - "8774:9001"
+    healthcheck:
+      test: ["CMD", "curl", "-f", "http://localhost:9000/minio/health/live"]
+      interval: 10s
+      timeout: 5s
+      retries: 10
+      start_period: 10s
+    restart: unless-stopped
+
+  minio-init:
+    image: minio/mc:latest
+    container_name: momswap-backend-minio-init
+    environment:
+      S3_ACCESS_KEY: "${S3_ACCESS_KEY:-momswap}"
+      S3_SECRET_KEY: "${S3_SECRET_KEY:-momswap-secret}"
+      S3_BUCKET: "${S3_BUCKET:-momswap-assets}"
+    depends_on:
+      minio:
+        condition: service_healthy
+    entrypoint: >
+      /bin/sh -c "
+      mc alias set local http://minio:9000 $$S3_ACCESS_KEY $$S3_SECRET_KEY &&
+      mc mb --ignore-existing local/$$S3_BUCKET
+      "
+    restart: "no"
+
   api:
     build:
       context: .
@@ -32,12 +68,23 @@ services:
       ADDR: ":8122"
       ADMIN_PUBLIC_KEY: "${ADMIN_PUBLIC_KEY:-}"
       DATABASE_URL: "postgres://${POSTGRES_USER:-momswap}:${POSTGRES_PASSWORD:-momswap}@db:5432/${POSTGRES_DB:-momswap}?sslmode=disable"
+      S3_ENDPOINT: "${S3_ENDPOINT:-minio:9000}"
+      S3_BUCKET: "${S3_BUCKET:-momswap-assets}"
+      S3_REGION: "${S3_REGION:-us-east-1}"
+      S3_ACCESS_KEY: "${S3_ACCESS_KEY:-momswap}"
+      S3_SECRET_KEY: "${S3_SECRET_KEY:-momswap-secret}"
+      S3_USE_PATH_STYLE: "${S3_USE_PATH_STYLE:-true}"
+      S3_USE_TLS: "${S3_USE_TLS:-false}"
     volumes:
       - ./etc:/app/etc:ro
       - ./var/logs:/app/var/logs
     depends_on:
       db:
         condition: service_healthy
+      minio:
+        condition: service_healthy
+      minio-init:
+        condition: service_completed_successfully
     ports:
       - "8122:8122"
     restart: unless-stopped
@@ -56,12 +103,23 @@ services:
       ADDR: ":8122"
       ADMIN_PUBLIC_KEY: "${ADMIN_PUBLIC_KEY:-}"
       DATABASE_URL: "postgres://${POSTGRES_USER:-momswap}:${POSTGRES_PASSWORD:-momswap}@db:5432/${POSTGRES_DB:-momswap}?sslmode=disable"
+      S3_ENDPOINT: "${S3_ENDPOINT:-minio:9000}"
+      S3_BUCKET: "${S3_BUCKET:-momswap-assets}"
+      S3_REGION: "${S3_REGION:-us-east-1}"
+      S3_ACCESS_KEY: "${S3_ACCESS_KEY:-momswap}"
+      S3_SECRET_KEY: "${S3_SECRET_KEY:-momswap-secret}"
+      S3_USE_PATH_STYLE: "${S3_USE_PATH_STYLE:-true}"
+      S3_USE_TLS: "${S3_USE_TLS:-false}"
     volumes:
       - ./etc:/src/etc:ro
       - ./var/logs:/src/var/logs
     depends_on:
       db:
         condition: service_healthy
+      minio:
+        condition: service_healthy
+      minio-init:
+        condition: service_completed_successfully
     ports:
       - "8122:8122"
     restart: unless-stopped
diff --git a/docs/assets-storage-and-sharing.md b/docs/assets-storage-and-sharing.md
new file mode 100644
index 0000000..0b1c970
--- /dev/null
+++ b/docs/assets-storage-and-sharing.md
@@ -0,0 +1,83 @@
+# Assets Storage and Sharing
+
+This backend stores metadata for user-owned image and 3D assets and keeps the binary files in S3-compatible object storage.
+
+## Supported asset types
+
+- Images: `jpg`, `jpeg`, `png`, `webp`
+- 3D objects: `gltf`, `glb`
+
+## Data model
+
+- Assets are deduplicated per user by `(owner_key, checksum, ext)`.
+- Canonical object key: `<publicKey>/<checksum>.<ext>`.
+- A single asset can be linked to many features.
+- Feature payloads include linked assets under `properties.assets`.
+
+Each `properties.assets` item includes:
+
+- `id`
+- `kind`
+- `name`
+- `description`
+- `checksum`
+- `ext`
+- `isPublic`
+- `link` (service-relative path, for example `/v1/assets/{id}/download`)
+
+## API flow
+
+1. Create or reuse an asset record and link it to a feature:
+   - `POST /v1/assets`
+2. Upload the binary to object storage:
+   - `POST /v1/assets/{id}/signed-upload` (returns signed PUT URL)
+3. Read linked assets from feature responses:
+   - `GET /v1/collections/{id}/features` (`properties.assets`)
+4. Download via service-relative link:
+   - `GET /v1/assets/{id}/download`
+5. Change visibility:
+   - `PATCH /v1/assets/{id}` with `{"isPublic": false|true}`
+
+## Example asset payload inside a feature
+
+```json
+{
+  "id": "feature-id",
+  "type": "Feature",
+  "properties": {
+    "name": "Palm Tree Spot",
+    "assets": [
+      {
+        "id": "asset-id",
+        "kind": "3d",
+        "name": "Palm Tree",
+        "description": "Low-poly tree",
+        "checksum": "abc123...",
+        "ext": "glb",
+        "isPublic": true,
+        "link": "/v1/assets/asset-id/download"
+      }
+    ]
+  }
+}
+```
+
+## Visibility rules
+
+- Owner can always download their own asset.
+- Other authenticated users can download only when `isPublic=true`.
+- Owner can toggle `isPublic` at any time.
+
+## Deduplication behavior
+
+- Deduplication is per owner and file identity (`owner_key + checksum + ext`).
+- If the same user submits the same checksum/extension again, backend reuses existing asset metadata.
+- One asset can be linked to multiple features without duplicating object storage files.
+
+## Spatial readiness for 3D search
+
+Feature storage is prepared for future spatial search:
+
+- Features keep GeoJSON `geometry` JSON.
+- Postgres migration also maintains a 3D-capable PostGIS column (`geom geometry(PointZ, 4326)`).
+- This enables future cube/sphere search without breaking existing API contracts.
diff --git a/docs/docker-minio-local-dev.md b/docs/docker-minio-local-dev.md
new file mode 100644
index 0000000..d38d79b
--- /dev/null
+++ b/docs/docker-minio-local-dev.md
@@ -0,0 +1,72 @@
+# Docker MinIO Local Development
+
+Local object storage is provided by MinIO in `docker-compose.yml`.
+
+## Port policy
+
+- MinIO S3 API (`9000`) is internal-only (not published on host).
+- MinIO admin UI is exposed on `8774`.
+
+## Services
+
+- `minio`: object storage
+- `minio-init`: one-shot bucket bootstrap using `mc`
+- `api` / `api-dev`: use MinIO via internal DNS endpoint `minio:9000`
+
+## Environment variables
+
+- `S3_ENDPOINT` (default `minio:9000`)
+- `S3_BUCKET` (default `momswap-assets`)
+- `S3_REGION` (default `us-east-1`)
+- `S3_ACCESS_KEY` (default `momswap`)
+- `S3_SECRET_KEY` (default `momswap-secret`)
+- `S3_USE_PATH_STYLE` (default `true`)
+- `S3_USE_TLS` (default `false`)
+
+## Start stack
+
+```bash
+./bin/gen-server-keys.sh
+docker compose up --build -d
+```
+
+## Verify storage setup
+
+1. Confirm only MinIO UI is published:
+   ```bash
+   docker compose ps
+   ```
+2. Open MinIO admin console:
+   - `http://localhost:8774`
+3. Confirm bucket exists (`momswap-assets` by default).
+4. Use API flow:
+   - create asset and get signed upload URL
+   - upload file with PUT
+   - request `/v1/assets/{id}/download`
+
+## Quick verification script
+
+Use this as a smoke-check after startup:
+
+```bash
+# 1) check API and MinIO UI reachability
+curl -fsS http://localhost:8122/healthz
+curl -I http://localhost:8774
+
+# 2) ensure MinIO S3 API is not exposed on host
+if curl -fsS http://localhost:9000/minio/health/live >/dev/null 2>&1; then
+  echo "Unexpected: MinIO S3 API is exposed on host"
+else
+  echo "OK: MinIO S3 API is internal-only"
+fi
+```
+
+## Troubleshooting
+
+- If `api` fails with storage config errors, verify `S3_*` variables in compose environment.
+- If bucket bootstrap fails, inspect:
+  - `docker compose logs minio`
+  - `docker compose logs minio-init`
+- If signed URLs are generated but upload fails, check:
+  - object key path style (`S3_USE_PATH_STYLE=true` for MinIO)
+  - MinIO credentials (`S3_ACCESS_KEY`, `S3_SECRET_KEY`)
diff --git a/docs/frontend-development.md b/docs/frontend-development.md
index 6c5ee87..9ba9f3f 100644
--- a/docs/frontend-development.md
+++ b/docs/frontend-development.md
@@ -1,60 +1,69 @@
 # Frontend Development
 
-Development guide for the Momswap Geo demo app (`web/`) and TypeScript client (`libs/geo-api-client`).
+Development guide for the demo frontend in `web/` and the reusable TypeScript client in `libs/geo-api-client`.
+
+## Architecture
+
+- `web/` is a no-bundler Vue + Vuetify app served directly by the Go backend at `/web/`.
+- `libs/geo-api-client` contains signed auth and API request logic reused by frontend code.
+- Asset binaries are stored in S3-compatible storage, while frontend works with metadata and service-relative links returned by the API.
 
 ## Demo app (`web/`)
 
-Vue 3 + Vuetify 3 single-page app, no bundler. Served by the backend at `/web/`.
+### File map
 
-### Structure
-
-```
+```text
 web/
-├── index.html    # Entry page, Vue/Vuetify from CDN
-├── app.js        # Vue app, state, handlers
-├── api.js        # GeoApiClient wrapper for browser
-├── qr.js         # QR code generation (pk/pb keys)
-└── scanner.js    # QR scanner from camera (Import pk)
+├── index.html    # Entry page, loads Vue/Vuetify from CDN
+├── app.js        # Main app state and handlers
+├── api.js        # GeoApiClient wrapper for browser usage
+├── qr.js         # QR code generation for key sharing/backup
+└── scanner.js    # Camera QR scanner for key import
 ```
 
-### Running locally
+### Local run
 
-1. Start the API:
+1. Start backend:
    ```bash
    go run ./cmd/api
-   # or: docker compose up -d
+   # or
+   docker compose up -d
    ```
-2. Open `http://localhost:8122/web/`
+2. Open:
+   - `http://localhost:8122/web/`
+   - `http://localhost:8122/web/leaflet-demo.html` (Leaflet map demo for 3D/image placement + sharing)
 
-### Dependencies
+### Runtime dependencies
 
-- Vue 3 and Vuetify 3 from CDN (no npm install in `web/`)
-- `libs/geo-api-client/dist/index.js` — built ESM client
-- `qr.js` — imports `qrcode` from esm.sh
-- `scanner.js` — imports `jsQR` from esm.sh for camera scan
+- Vue 3 and Vuetify 3 from CDN (no package manager in `web/`)
+- `libs/geo-api-client/dist/index.js` (ESM build artifact)
+- `qrcode` via `esm.sh` in `qr.js`
+- `jsQR` via `esm.sh` in `scanner.js`
 
-### Build step for client
+### Supported UI flows
 
-The demo app uses the pre-built client. After changing `libs/geo-api-client`:
-
-```bash
-cd libs/geo-api-client
-bun run build
-```
-
-With Docker, the image build runs this automatically.
-
-### Features (use-cases test)
-
-- Connection & Identity: API URL, key generation, pk/pb display, QR codes (pk shown by default, pb behind toggle), restore pb from pk, **Import pk from camera** (scan QR → restore pb → auto login → refresh collections), register, login
-- Collections: create, select, rename, remove
-- Features: add point (lon/lat validation -180..180, -90..90), remove, list
+- Connection and identity:
+  - API URL configuration
+  - key generation
+  - pk/pb display and QR export
+  - restore/import keypair from QR
+  - register and login
+- Collection management:
+  - create, select, rename, delete
+- Feature management:
+  - add/list/delete points
+  - lon/lat validation (`-180..180`, `-90..90`)
+- Asset-ready feature rendering:
+  - read linked media from `feature.properties.assets`
+  - use relative `link` value (for example `/v1/assets/{id}/download`) for fetch/open
+- Leaflet map example:
+  - click map to place object coordinates
+  - create feature + upload/link `gltf`/`glb`/image asset
+  - copy/open share link and toggle public/private visibility
 
 ## TypeScript client (`libs/geo-api-client`)
 
-Reusable API client with Ed25519 signing. See [TypeScript Frontend Integration](typescript-frontend-integration.md) for full API and integration flow.
-
-### Build & test
+The TypeScript client centralizes auth signatures and API requests.
 
 ```bash
 cd libs/geo-api-client
@@ -63,10 +72,20 @@ bun test
 bun run build
 ```
 
+After client changes, rebuild before loading the demo app. Docker image builds handle this automatically.
+
+## Frontend implementation notes for assets
+
+- Treat `properties.assets` as backend-owned metadata. Do not derive URLs in frontend from S3 config.
+- Always use backend-provided relative `link` for downloads so permission checks remain server-side.
+- When asset visibility changes (`isPublic`), refresh affected feature list to keep UI in sync.
+
 ## Related docs
 
 | Document | Description |
 |----------|-------------|
-| [TypeScript Frontend Integration](typescript-frontend-integration.md) | API client usage, integration flow, examples |
-| [Ed25519 Security Use Cases](ed25519-security-use-cases.md) | Auth flows, registration, signatures |
-| [Geo Auth Backend Plan](geo-auth-backend-plan.md) | Architecture and planning |
+| [TypeScript Frontend Integration](typescript-frontend-integration.md) | API client usage and integration flow |
+| [Assets Storage and Sharing](assets-storage-and-sharing.md) | Asset lifecycle, deduplication, visibility, API endpoints |
+| [Docker MinIO Local Development](docker-minio-local-dev.md) | Local object storage topology and verification |
+| [Ed25519 Security Use Cases](ed25519-security-use-cases.md) | Auth and signature behavior |
+| [Geo Auth Backend Plan](geo-auth-backend-plan.md) | Architecture and planning history |
diff --git a/docs/typescript-frontend-integration.md b/docs/typescript-frontend-integration.md
index 34f6f1e..f1abd96 100644
--- a/docs/typescript-frontend-integration.md
+++ b/docs/typescript-frontend-integration.md
@@ -3,6 +3,8 @@
 This document explains how frontend developers should integrate with the backend through the reusable TypeScript client at `libs/geo-api-client`.
 
 > **See also:** [Frontend Development](frontend-development.md) — demo app (`web/`), local dev, build steps.
+>
+> **Asset docs:** [Assets Storage and Sharing](assets-storage-and-sharing.md) and [Docker MinIO Local Development](docker-minio-local-dev.md).
 
 Primary backend URL for integration:
 
@@ -76,6 +78,16 @@ Key methods:
 - [`createPointFeature(collectionId, lon, lat, properties)`](https://git.produktor.io/momswap/backend/src/branch/main/libs/geo-api-client/src/GeoApiClient.ts#L156) — Add a Point. lon ∈ [-180,180], lat ∈ [-90,90]. Returns feature id.
 - [`deleteFeature(featureId)`](https://git.produktor.io/momswap/backend/src/branch/main/libs/geo-api-client/src/GeoApiClient.ts#L172) — Delete a feature.
 
+## Asset API integration note
+
+Asset endpoints are currently available at backend API level (`/v1/assets...`) and can be called from frontend apps directly with authenticated `fetch` requests.
+
+Current frontend contract points:
+
+- Feature list responses include linked media under `feature.properties.assets`.
+- Each asset includes a backend-relative download path (`link`) like `/v1/assets/{id}/download`.
+- Frontend should use this relative path and avoid constructing direct S3 URLs.
+
 ## Recommended integration flow
 
 1. Create one `GeoApiClient` instance per backend base URL.
diff --git a/go.mod b/go.mod
index 72c1962..fd7c9ee 100644
--- a/go.mod
+++ b/go.mod
@@ -3,10 +3,31 @@ module momswap/backend
 go 1.25
 
 require (
+	github.com/jackc/pgx/v5 v5.8.0
+	github.com/minio/minio-go/v7 v7.0.98
+)
+
+require (
+	github.com/dustin/go-humanize v1.0.1 // indirect
+	github.com/go-ini/ini v1.67.0 // indirect
+	github.com/google/uuid v1.6.0 // indirect
 	github.com/jackc/pgpassfile v1.0.0 // indirect
 	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
-	github.com/jackc/pgx/v5 v5.8.0 // indirect
 	github.com/jackc/puddle/v2 v2.2.2 // indirect
-	golang.org/x/sync v0.17.0 // indirect
-	golang.org/x/text v0.29.0 // indirect
+	github.com/klauspost/compress v1.18.2 // indirect
+	github.com/klauspost/cpuid/v2 v2.2.11 // indirect
+	github.com/klauspost/crc32 v1.3.0 // indirect
+	github.com/kr/text v0.2.0 // indirect
+	github.com/minio/crc64nvme v1.1.1 // indirect
+	github.com/minio/md5-simd v1.1.2 // indirect
+	github.com/philhofer/fwd v1.2.0 // indirect
+	github.com/rogpeppe/go-internal v1.14.1 // indirect
+	github.com/rs/xid v1.6.0 // indirect
+	github.com/tinylib/msgp v1.6.1 // indirect
+	go.yaml.in/yaml/v3 v3.0.4 // indirect
+	golang.org/x/crypto v0.46.0 // indirect
+	golang.org/x/net v0.48.0 // indirect
+	golang.org/x/sync v0.19.0 // indirect
+	golang.org/x/sys v0.39.0 // indirect
+	golang.org/x/text v0.32.0 // indirect
 )
diff --git a/go.sum b/go.sum
index 2aca163..fff9c02 100644
--- a/go.sum
+++ b/go.sum
@@ -1,4 +1,13 @@
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/dustin/go-humanize v1.0.1 h1:GzkhY7T5VNhEkwH0PVJgjz+fX1rhBrR7pRT3mDkpeCY=
+github.com/dustin/go-humanize v1.0.1/go.mod h1:Mu1zIs6XwVuF/gI1OepvI0qD18qycQx+mFykh5fBlto=
+github.com/go-ini/ini v1.67.0 h1:z6ZrTEZqSWOTyH2FlglNbNgARyHG8oLW9gMELqKr06A=
+github.com/go-ini/ini v1.67.0/go.mod h1:ByCAeIL28uOIIG0E3PJtZPDL8WnHpFKFOtgjp+3Ies8=
+github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
+github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsIM=
 github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
 github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 h1:iCEnooe7UlwOQYpKFhBabPMi4aNAfoODPEFNiAnClxo=
@@ -7,13 +16,53 @@ github.com/jackc/pgx/v5 v5.8.0 h1:TYPDoleBBme0xGSAX3/+NujXXtpZn9HBONkQC7IEZSo=
 github.com/jackc/pgx/v5 v5.8.0/go.mod h1:QVeDInX2m9VyzvNeiCJVjCkNFqzsNb43204HshNSZKw=
 github.com/jackc/puddle/v2 v2.2.2 h1:PR8nw+E/1w0GLuRFSmiioY6UooMp6KJv0/61nB7icHo=
 github.com/jackc/puddle/v2 v2.2.2/go.mod h1:vriiEXHvEE654aYKXXjOvZM39qJ0q+azkZFrfEOc3H4=
+github.com/klauspost/compress v1.18.2 h1:iiPHWW0YrcFgpBYhsA6D1+fqHssJscY/Tm/y2Uqnapk=
+github.com/klauspost/compress v1.18.2/go.mod h1:R0h/fSBs8DE4ENlcrlib3PsXS61voFxhIs2DeRhCvJ4=
+github.com/klauspost/cpuid/v2 v2.0.1/go.mod h1:FInQzS24/EEf25PyTYn52gqo7WaD8xa0213Md/qVLRg=
+github.com/klauspost/cpuid/v2 v2.2.11 h1:0OwqZRYI2rFrjS4kvkDnqJkKHdHaRnCm68/DY4OxRzU=
+github.com/klauspost/cpuid/v2 v2.2.11/go.mod h1:hqwkgyIinND0mEev00jJYCxPNVRVXFQeu1XKlok6oO0=
+github.com/klauspost/crc32 v1.3.0 h1:sSmTt3gUt81RP655XGZPElI0PelVTZ6YwCRnPSupoFM=
+github.com/klauspost/crc32 v1.3.0/go.mod h1:D7kQaZhnkX/Y0tstFGf8VUzv2UofNGqCjnC3zdHB0Hw=
+github.com/kr/pretty v0.3.0 h1:WgNl7dwNpEZ6jJ9k1snq4pZsg7DOEN8hP9Xw0Tsjwk0=
+github.com/kr/pretty v0.3.0/go.mod h1:640gp4NfQd8pI5XOwp5fnNeVWj67G7CFk/SaSQn7NBk=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/minio/crc64nvme v1.1.1 h1:8dwx/Pz49suywbO+auHCBpCtlW1OfpcLN7wYgVR6wAI=
+github.com/minio/crc64nvme v1.1.1/go.mod h1:eVfm2fAzLlxMdUGc0EEBGSMmPwmXD5XiNRpnu9J3bvg=
+github.com/minio/md5-simd v1.1.2 h1:Gdi1DZK69+ZVMoNHRXJyNcxrMA4dSxoYHZSQbirFg34=
+github.com/minio/md5-simd v1.1.2/go.mod h1:MzdKDxYpY2BT9XQFocsiZf/NKVtR7nkE4RoEpN+20RM=
+github.com/minio/minio-go/v7 v7.0.98 h1:MeAVKjLVz+XJ28zFcuYyImNSAh8Mq725uNW4beRisi0=
+github.com/minio/minio-go/v7 v7.0.98/go.mod h1:cY0Y+W7yozf0mdIclrttzo1Iiu7mEf9y7nk2uXqMOvM=
+github.com/philhofer/fwd v1.2.0 h1:e6DnBTl7vGY+Gz322/ASL4Gyp1FspeMvx1RNDoToZuM=
+github.com/philhofer/fwd v1.2.0/go.mod h1:RqIHx9QI14HlwKwm98g9Re5prTQ6LdeRQn+gXJFxsJM=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/rogpeppe/go-internal v1.14.1 h1:UQB4HGPB6osV0SQTLymcB4TgvyWu6ZyliaW0tI/otEQ=
+github.com/rogpeppe/go-internal v1.14.1/go.mod h1:MaRKkUm5W0goXpeCfT7UZI6fk/L7L7so1lCWt35ZSgc=
+github.com/rs/xid v1.6.0 h1:fV591PaemRlL6JfRxGDEPl69wICngIQ3shQtzfy2gxU=
+github.com/rs/xid v1.6.0/go.mod h1:7XoLgs4eV+QndskICGsho+ADou8ySMSjJKDIan90Nz0=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-golang.org/x/sync v0.17.0 h1:l60nONMj9l5drqw6jlhIELNv9I0A4OFgRsG9k2oT9Ug=
-golang.org/x/sync v0.17.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
-golang.org/x/text v0.29.0 h1:1neNs90w9YzJ9BocxfsQNHKuAT4pkghyXc4nhZ6sJvk=
-golang.org/x/text v0.29.0/go.mod h1:7MhJOA9CD2qZyOKYazxdYMF85OwPdEr9jTtBpO7ydH4=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+github.com/tinylib/msgp v1.6.1 h1:ESRv8eL3u+DNHUoSAAQRE50Hm162zqAnBoGv9PzScPY=
+github.com/tinylib/msgp v1.6.1/go.mod h1:RSp0LW9oSxFut3KzESt5Voq4GVWyS+PSulT77roAqEA=
+go.yaml.in/yaml/v3 v3.0.4 h1:tfq32ie2Jv2UxXFdLJdh3jXuOzWiL1fo0bu/FbuKpbc=
+go.yaml.in/yaml/v3 v3.0.4/go.mod h1:DhzuOOF2ATzADvBadXxruRBLzYTpT36CKvDb3+aBEFg=
+golang.org/x/crypto v0.46.0 h1:cKRW/pmt1pKAfetfu+RCEvjvZkA9RimPbh7bhFjGVBU=
+golang.org/x/crypto v0.46.0/go.mod h1:Evb/oLKmMraqjZ2iQTwDwvCtJkczlDuTmdJXoZVzqU0=
+golang.org/x/net v0.48.0 h1:zyQRTTrjc33Lhh0fBgT/H3oZq9WuvRR5gPC70xpDiQU=
+golang.org/x/net v0.48.0/go.mod h1:+ndRgGjkh8FGtu1w1FGbEC31if4VrNVMuKTgcAAnQRY=
+golang.org/x/sync v0.19.0 h1:vV+1eWNmZ5geRlYjzm2adRgW2/mcpevXNg50YZtPCE4=
+golang.org/x/sync v0.19.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
+golang.org/x/sys v0.39.0 h1:CvCKL8MeisomCi6qNZ+wbb0DN9E5AATixKsvNtMoMFk=
+golang.org/x/sys v0.39.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/text v0.32.0 h1:ZD01bjUt1FQ9WJ0ClOL5vxgxOI/sVCNgX1YtKwcY0mU=
+golang.org/x/text v0.32.0/go.mod h1:o/rUWzghvpD5TXrTIBuJU77MTaN0ljMWE47kxGJQ7jY=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/internal/app/service.go b/internal/app/service.go
index 70e685e..84ec6e4 100644
--- a/internal/app/service.go
+++ b/internal/app/service.go
@@ -1,10 +1,12 @@
 package app
 
 import (
+	"context"
 	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"fmt"
+	"strings"
 	"time"
 
 	"momswap/backend/internal/auth"
@@ -22,23 +24,43 @@ var (
 	ErrAlreadyUser               = errors.New("user already registered")
 	ErrCollectionMiss            = errors.New("collection missing")
 	ErrFeatureMiss               = errors.New("feature missing")
+	ErrAssetMiss                 = errors.New("asset missing")
+	ErrStorageNotConfigured      = errors.New("storage not configured")
 )
 
 type Config struct {
 	ChallengeTTL time.Duration
 	SessionTTL   time.Duration
+	UploadURLTTL time.Duration
+	ReadURLTTL   time.Duration
+}
+
+type AssetURLSigner interface {
+	SignedPutObjectURL(ctx context.Context, objectKey string, expiry time.Duration, contentType string) (string, error)
+	SignedGetObjectURL(ctx context.Context, objectKey string, expiry time.Duration) (string, error)
 }
 
 type Service struct {
 	store            store.Store
 	config           Config
 	servicePublicKey string
+	assetSigner      AssetURLSigner
 }
 
 func NewService(st store.Store, cfg Config, servicePublicKey string) *Service {
+	if cfg.UploadURLTTL <= 0 {
+		cfg.UploadURLTTL = 15 * time.Minute
+	}
+	if cfg.ReadURLTTL <= 0 {
+		cfg.ReadURLTTL = 10 * time.Minute
+	}
 	return &Service{store: st, config: cfg, servicePublicKey: servicePublicKey}
 }
 
+func (s *Service) ConfigureAssetStorage(signer AssetURLSigner) {
+	s.assetSigner = signer
+}
+
 type InvitationPayload struct {
 	JTI              string `json:"jti"`
 	InviterPublicKey string `json:"inviterPublicKey"`
@@ -246,8 +268,8 @@ func validatePoint(point store.Point) error {
 	if point.Type != "Point" {
 		return fmt.Errorf("%w: geometry type must be Point", ErrBadRequest)
 	}
-	if len(point.Coordinates) != 2 {
-		return fmt.Errorf("%w: coordinates must have lon/lat", ErrBadRequest)
+	if len(point.Coordinates) != 2 && len(point.Coordinates) != 3 {
+		return fmt.Errorf("%w: coordinates must have lon/lat[/alt]", ErrBadRequest)
 	}
 	lon, lat := point.Coordinates[0], point.Coordinates[1]
 	if lon < -180 || lon > 180 {
@@ -347,7 +369,28 @@ func (s *Service) ListFeatures(ownerKey, collectionID string) ([]store.Feature,
 	if collection.OwnerKey != ownerKey {
 		return nil, ErrForbidden
 	}
-	return s.store.ListFeaturesByCollection(collectionID), nil
+	features := s.store.ListFeaturesByCollection(collectionID)
+	for idx := range features {
+		featureAssets := s.store.ListAssetsByFeature(features[idx].ID)
+		assets := make([]map[string]interface{}, 0, len(featureAssets))
+		for _, linkedAsset := range featureAssets {
+			assets = append(assets, map[string]interface{}{
+				"id":          linkedAsset.ID,
+				"kind":        linkedAsset.Kind,
+				"name":        linkedAsset.Name,
+				"description": linkedAsset.Description,
+				"checksum":    linkedAsset.Checksum,
+				"ext":         linkedAsset.Ext,
+				"isPublic":    linkedAsset.IsPublic,
+				"link":        "/v1/assets/" + linkedAsset.ID + "/download",
+			})
+		}
+		if features[idx].Properties == nil {
+			features[idx].Properties = map[string]interface{}{}
+		}
+		features[idx].Properties["assets"] = assets
+	}
+	return features, nil
 }
 
 func (s *Service) DeleteFeature(ownerKey, featureID string) error {
@@ -360,3 +403,137 @@ func (s *Service) DeleteFeature(ownerKey, featureID string) error {
 	}
 	return s.store.DeleteFeature(featureID)
 }
+
+type CreateAssetInput struct {
+	FeatureID   string
+	Checksum    string
+	Ext         string
+	Kind        string
+	MimeType    string
+	SizeBytes   int64
+	Name        string
+	Description string
+	Visibility  *bool
+}
+
+func normalizeExt(ext string) string {
+	return strings.TrimPrefix(strings.ToLower(strings.TrimSpace(ext)), ".")
+}
+
+func normalizeChecksum(checksum string) string {
+	return strings.ToLower(strings.TrimSpace(checksum))
+}
+
+func (s *Service) CreateOrLinkAsset(ownerKey string, in CreateAssetInput) (store.Asset, bool, error) {
+	feature, err := s.store.GetFeature(in.FeatureID)
+	if err != nil {
+		return store.Asset{}, false, ErrFeatureMiss
+	}
+	if feature.OwnerKey != ownerKey {
+		return store.Asset{}, false, ErrForbidden
+	}
+
+	checksum := normalizeChecksum(in.Checksum)
+	ext := normalizeExt(in.Ext)
+	if checksum == "" || ext == "" {
+		return store.Asset{}, false, fmt.Errorf("%w: checksum and ext required", ErrBadRequest)
+	}
+	switch ext {
+	case "jpg", "jpeg", "png", "webp", "gltf", "glb":
+	default:
+		return store.Asset{}, false, fmt.Errorf("%w: unsupported extension", ErrBadRequest)
+	}
+	if in.Kind != "image" && in.Kind != "3d" {
+		return store.Asset{}, false, fmt.Errorf("%w: kind must be image or 3d", ErrBadRequest)
+	}
+	if in.SizeBytes < 0 {
+		return store.Asset{}, false, fmt.Errorf("%w: sizeBytes must be >= 0", ErrBadRequest)
+	}
+
+	if existing, getErr := s.store.GetAssetByOwnerChecksumExt(ownerKey, checksum, ext); getErr == nil {
+		if err := s.store.LinkAssetToFeature(in.FeatureID, existing.ID, in.Name, in.Description); err != nil {
+			return store.Asset{}, false, err
+		}
+		return existing, false, nil
+	}
+
+	id, err := auth.NewRandomToken(12)
+	if err != nil {
+		return store.Asset{}, false, err
+	}
+	now := time.Now().UTC()
+	isPublic := true
+	if in.Visibility != nil {
+		isPublic = *in.Visibility
+	}
+	asset := store.Asset{
+		ID:        id,
+		OwnerKey:  ownerKey,
+		Checksum:  checksum,
+		Ext:       ext,
+		Kind:      in.Kind,
+		MimeType:  in.MimeType,
+		SizeBytes: in.SizeBytes,
+		ObjectKey: ownerKey + "/" + checksum + "." + ext,
+		IsPublic:  isPublic,
+		CreatedAt: now,
+		UpdatedAt: now,
+	}
+	s.store.SaveAsset(asset)
+	if err := s.store.LinkAssetToFeature(in.FeatureID, asset.ID, in.Name, in.Description); err != nil {
+		return store.Asset{}, false, err
+	}
+	return asset, true, nil
+}
+
+func (s *Service) SetAssetPublic(ownerKey, assetID string, isPublic bool) (store.Asset, error) {
+	asset, err := s.store.GetAsset(assetID)
+	if err != nil {
+		return store.Asset{}, ErrAssetMiss
+	}
+	if asset.OwnerKey != ownerKey {
+		return store.Asset{}, ErrForbidden
+	}
+	if err := s.store.SetAssetPublic(assetID, isPublic); err != nil {
+		return store.Asset{}, err
+	}
+	asset.IsPublic = isPublic
+	asset.UpdatedAt = time.Now().UTC()
+	return asset, nil
+}
+
+func (s *Service) SignedUploadURL(ownerKey, assetID, contentType string) (string, error) {
+	if s.assetSigner == nil {
+		return "", ErrStorageNotConfigured
+	}
+	asset, err := s.store.GetAsset(assetID)
+	if err != nil {
+		return "", ErrAssetMiss
+	}
+	if asset.OwnerKey != ownerKey {
+		return "", ErrForbidden
+	}
+	url, err := s.assetSigner.SignedPutObjectURL(context.Background(), asset.ObjectKey, s.config.UploadURLTTL, contentType)
+	if err != nil {
+		return "", err
+	}
+	return url, nil
+}
+
+func (s *Service) SignedDownloadURL(requesterKey, assetID string) (string, error) {
+	if s.assetSigner == nil {
+		return "", ErrStorageNotConfigured
+	}
+	asset, err := s.store.GetAsset(assetID)
+	if err != nil {
+		return "", ErrAssetMiss
+	}
+	if asset.OwnerKey != requesterKey && !asset.IsPublic {
+		return "", ErrForbidden
+	}
+	url, err := s.assetSigner.SignedGetObjectURL(context.Background(), asset.ObjectKey, s.config.ReadURLTTL)
+	if err != nil {
+		return "", err
+	}
+	return url, nil
+}
diff --git a/internal/http/api_test.go b/internal/http/api_test.go
index c8c4b7e..528ff15 100644
--- a/internal/http/api_test.go
+++ b/internal/http/api_test.go
@@ -2,10 +2,12 @@ package httpapi_test
 
 import (
 	"bytes"
+	"context"
 	"crypto/ed25519"
 	"crypto/rand"
 	"encoding/base64"
 	"encoding/json"
+	"fmt"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -23,10 +25,21 @@ func newTestServer(adminPublicKey string) *httptest.Server {
 		SessionTTL:   24 * time.Hour,
 	}, adminPublicKey)
 	svc.BootstrapAdmin(adminPublicKey)
+	svc.ConfigureAssetStorage(fakeSigner{})
 	api := httpapi.NewAPI(svc)
 	return httptest.NewServer(api.Routes())
 }
 
+type fakeSigner struct{}
+
+func (fakeSigner) SignedPutObjectURL(_ context.Context, objectKey string, _ time.Duration, _ string) (string, error) {
+	return "http://files.local/upload/" + objectKey, nil
+}
+
+func (fakeSigner) SignedGetObjectURL(_ context.Context, objectKey string, _ time.Duration) (string, error) {
+	return "http://files.local/download/" + objectKey, nil
+}
+
 func mustJSON(t *testing.T, value interface{}) []byte {
 	t.Helper()
 	b, err := json.Marshal(value)
@@ -72,6 +85,26 @@ func postJSON(t *testing.T, client *http.Client, url string, body interface{}, t
 	return resp, out
 }
 
+func patchJSON(t *testing.T, client *http.Client, url string, body interface{}, token string) (*http.Response, map[string]interface{}) {
+	t.Helper()
+	req, err := http.NewRequest(http.MethodPatch, url, bytes.NewReader(mustJSON(t, body)))
+	if err != nil {
+		t.Fatalf("new request: %v", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+	if token != "" {
+		req.Header.Set("Authorization", "Bearer "+token)
+	}
+	resp, err := client.Do(req)
+	if err != nil {
+		t.Fatalf("do request: %v", err)
+	}
+	defer resp.Body.Close()
+	out := map[string]interface{}{}
+	_ = json.NewDecoder(resp.Body).Decode(&out)
+	return resp, out
+}
+
 func loginUser(t *testing.T, client *http.Client, baseURL, pubB64 string, priv ed25519.PrivateKey) string {
 	t.Helper()
 	chResp, chData := postJSON(t, client, baseURL+"/v1/auth/challenge", map[string]string{"publicKey": pubB64}, "")
@@ -251,3 +284,135 @@ func TestCollectionOwnershipIsolation(t *testing.T) {
 		t.Fatalf("expected 403, got %d", resp.StatusCode)
 	}
 }
+
+func TestAssetLifecycleAndVisibility(t *testing.T) {
+	adminPub, adminPriv, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		t.Fatalf("generate admin key: %v", err)
+	}
+	adminPubB64 := base64.RawURLEncoding.EncodeToString(adminPub)
+	server := newTestServer(adminPubB64)
+	defer server.Close()
+	client := server.Client()
+	client.CheckRedirect = func(_ *http.Request, _ []*http.Request) error { return http.ErrUseLastResponse }
+
+	adminToken := loginUser(t, client, server.URL, adminPubB64, adminPriv)
+
+	user1Pub, user1Priv, _ := ed25519.GenerateKey(rand.Reader)
+	user1PubB64 := base64.RawURLEncoding.EncodeToString(user1Pub)
+	registerUserViaAdmin(t, client, server.URL, adminPubB64, adminPriv, adminToken, user1PubB64, user1Priv, "invite-asset-u1")
+	user1Token := loginUser(t, client, server.URL, user1PubB64, user1Priv)
+
+	user2Pub, user2Priv, _ := ed25519.GenerateKey(rand.Reader)
+	user2PubB64 := base64.RawURLEncoding.EncodeToString(user2Pub)
+	registerUserViaAdmin(t, client, server.URL, adminPubB64, adminPriv, adminToken, user2PubB64, user2Priv, "invite-asset-u2")
+	user2Token := loginUser(t, client, server.URL, user2PubB64, user2Priv)
+
+	createCollectionResp, createCollectionData := postJSON(t, client, server.URL+"/v1/collections", map[string]string{
+		"name": "assets",
+	}, user1Token)
+	if createCollectionResp.StatusCode != http.StatusCreated {
+		t.Fatalf("create collection status=%d body=%v", createCollectionResp.StatusCode, createCollectionData)
+	}
+	collectionID := createCollectionData["id"].(string)
+
+	createFeatureResp, createFeatureData := postJSON(t, client, server.URL+"/v1/collections/"+collectionID+"/features", map[string]interface{}{
+		"geometry": map[string]interface{}{
+			"type":        "Point",
+			"coordinates": []float64{-16.6291, 28.4636, 22},
+		},
+		"properties": map[string]interface{}{
+			"name": "feature-a",
+		},
+	}, user1Token)
+	if createFeatureResp.StatusCode != http.StatusCreated {
+		t.Fatalf("create feature status=%d body=%v", createFeatureResp.StatusCode, createFeatureData)
+	}
+	featureID := createFeatureData["id"].(string)
+
+	createAssetResp, createAssetData := postJSON(t, client, server.URL+"/v1/assets", map[string]interface{}{
+		"featureId":   featureID,
+		"checksum":    "ABCDEF1234",
+		"ext":         "glb",
+		"kind":        "3d",
+		"mimeType":    "model/gltf-binary",
+		"sizeBytes":   100,
+		"name":        "Tree",
+		"description": "Public tree",
+		"isPublic":    true,
+	}, user1Token)
+	if createAssetResp.StatusCode != http.StatusCreated {
+		t.Fatalf("create asset status=%d body=%v", createAssetResp.StatusCode, createAssetData)
+	}
+	asset := createAssetData["asset"].(map[string]interface{})
+	assetID := asset["id"].(string)
+
+	createAssetResp2, createAssetData2 := postJSON(t, client, server.URL+"/v1/assets", map[string]interface{}{
+		"featureId": featureID,
+		"checksum":  "abcdef1234",
+		"ext":       "glb",
+		"kind":      "3d",
+		"name":      "Tree v2",
+	}, user1Token)
+	if createAssetResp2.StatusCode != http.StatusOK {
+		t.Fatalf("dedup create asset status=%d body=%v", createAssetResp2.StatusCode, createAssetData2)
+	}
+	asset2 := createAssetData2["asset"].(map[string]interface{})
+	if asset2["id"].(string) != assetID {
+		t.Fatalf("expected dedup asset id=%s got=%s", assetID, asset2["id"].(string))
+	}
+
+	uploadResp, uploadData := postJSON(t, client, server.URL+"/v1/assets/"+assetID+"/signed-upload", map[string]interface{}{
+		"contentType": "model/gltf-binary",
+	}, user1Token)
+	if uploadResp.StatusCode != http.StatusOK {
+		t.Fatalf("signed upload status=%d body=%v", uploadResp.StatusCode, uploadData)
+	}
+
+	featuresResp, featuresData := getJSON(t, client, server.URL+"/v1/collections/"+collectionID+"/features", user1Token)
+	if featuresResp.StatusCode != http.StatusOK {
+		t.Fatalf("list features status=%d body=%v", featuresResp.StatusCode, featuresData)
+	}
+	features := featuresData["features"].([]interface{})
+	firstFeature := features[0].(map[string]interface{})
+	properties := firstFeature["properties"].(map[string]interface{})
+	assets := properties["assets"].([]interface{})
+	if len(assets) != 1 {
+		t.Fatalf("expected 1 linked asset, got %d", len(assets))
+	}
+	assetView := assets[0].(map[string]interface{})
+	if assetView["link"] != "/v1/assets/"+assetID+"/download" {
+		t.Fatalf("unexpected asset link: %v", assetView["link"])
+	}
+
+	reqDownloadPublic, _ := http.NewRequest(http.MethodGet, server.URL+"/v1/assets/"+assetID+"/download", nil)
+	reqDownloadPublic.Header.Set("Authorization", "Bearer "+user2Token)
+	downloadPublicResp, err := client.Do(reqDownloadPublic)
+	if err != nil {
+		t.Fatalf("download public request failed: %v", err)
+	}
+	if downloadPublicResp.StatusCode != http.StatusFound {
+		t.Fatalf("expected public asset redirect status, got %d", downloadPublicResp.StatusCode)
+	}
+	expectedLocation := fmt.Sprintf("http://files.local/download/%s/%s.%s", user1PubB64, "abcdef1234", "glb")
+	if downloadPublicResp.Header.Get("Location") != expectedLocation {
+		t.Fatalf("unexpected redirect location: %s", downloadPublicResp.Header.Get("Location"))
+	}
+
+	patchResp, patchData := patchJSON(t, client, server.URL+"/v1/assets/"+assetID, map[string]interface{}{
+		"isPublic": false,
+	}, user1Token)
+	if patchResp.StatusCode != http.StatusOK {
+		t.Fatalf("patch asset status=%d body=%v", patchResp.StatusCode, patchData)
+	}
+
+	reqDownloadPrivate, _ := http.NewRequest(http.MethodGet, server.URL+"/v1/assets/"+assetID+"/download", nil)
+	reqDownloadPrivate.Header.Set("Authorization", "Bearer "+user2Token)
+	downloadPrivateResp, err := client.Do(reqDownloadPrivate)
+	if err != nil {
+		t.Fatalf("download private request failed: %v", err)
+	}
+	if downloadPrivateResp.StatusCode != http.StatusForbidden {
+		t.Fatalf("expected 403 for private asset, got %d", downloadPrivateResp.StatusCode)
+	}
+}
diff --git a/internal/http/handlers.go b/internal/http/handlers.go
index 496651a..3f79c52 100644
--- a/internal/http/handlers.go
+++ b/internal/http/handlers.go
@@ -40,6 +40,10 @@ func (a *API) Routes() http.Handler {
 	mux.HandleFunc("POST /v1/collections/{id}/features", a.createFeature)
 	mux.HandleFunc("GET /v1/collections/{id}/features", a.listFeatures)
 	mux.HandleFunc("DELETE /v1/features/{id}", a.deleteFeature)
+	mux.HandleFunc("POST /v1/assets", a.createAsset)
+	mux.HandleFunc("PATCH /v1/assets/{id}", a.patchAsset)
+	mux.HandleFunc("POST /v1/assets/{id}/signed-upload", a.signedUpload)
+	mux.HandleFunc("GET /v1/assets/{id}/download", a.downloadAsset)
 
 	mux.Handle("/web/", http.StripPrefix("/web/", staticFiles))
 	mux.Handle("/libs/", http.StripPrefix("/libs/", libsFiles))
@@ -97,8 +101,11 @@ func statusFromErr(err error) int {
 		errors.Is(err, app.ErrInviteExhaust):
 		return http.StatusBadRequest
 	case errors.Is(err, app.ErrCollectionMiss), errors.Is(err, app.ErrFeatureMiss),
+		errors.Is(err, app.ErrAssetMiss),
 		errors.Is(err, store.ErrNotFound):
 		return http.StatusNotFound
+	case errors.Is(err, app.ErrStorageNotConfigured):
+		return http.StatusServiceUnavailable
 	default:
 		return http.StatusInternalServerError
 	}
@@ -361,3 +368,108 @@ func (a *API) deleteFeature(w http.ResponseWriter, r *http.Request) {
 	}
 	w.WriteHeader(http.StatusNoContent)
 }
+
+func (a *API) createAsset(w http.ResponseWriter, r *http.Request) {
+	user, err := a.authUser(r)
+	if err != nil {
+		writeErr(w, err)
+		return
+	}
+	var req struct {
+		FeatureID   string `json:"featureId"`
+		Checksum    string `json:"checksum"`
+		Ext         string `json:"ext"`
+		Kind        string `json:"kind"`
+		MimeType    string `json:"mimeType"`
+		SizeBytes   int64  `json:"sizeBytes"`
+		Name        string `json:"name"`
+		Description string `json:"description"`
+		IsPublic    *bool  `json:"isPublic"`
+	}
+	if err := readJSON(r, &req); err != nil {
+		writeErr(w, app.ErrBadRequest)
+		return
+	}
+	asset, created, err := a.service.CreateOrLinkAsset(user, app.CreateAssetInput{
+		FeatureID:   req.FeatureID,
+		Checksum:    req.Checksum,
+		Ext:         req.Ext,
+		Kind:        req.Kind,
+		MimeType:    req.MimeType,
+		SizeBytes:   req.SizeBytes,
+		Name:        req.Name,
+		Description: req.Description,
+		Visibility:  req.IsPublic,
+	})
+	if err != nil {
+		writeErr(w, err)
+		return
+	}
+	status := http.StatusOK
+	if created {
+		status = http.StatusCreated
+	}
+	writeJSON(w, status, map[string]interface{}{
+		"asset": asset,
+		"link":  "/v1/assets/" + asset.ID + "/download",
+	})
+}
+
+func (a *API) patchAsset(w http.ResponseWriter, r *http.Request) {
+	user, err := a.authUser(r)
+	if err != nil {
+		writeErr(w, err)
+		return
+	}
+	assetID := r.PathValue("id")
+	var req struct {
+		IsPublic bool `json:"isPublic"`
+	}
+	if err := readJSON(r, &req); err != nil {
+		writeErr(w, app.ErrBadRequest)
+		return
+	}
+	asset, err := a.service.SetAssetPublic(user, assetID, req.IsPublic)
+	if err != nil {
+		writeErr(w, err)
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]interface{}{"asset": asset, "link": "/v1/assets/" + asset.ID + "/download"})
+}
+
+func (a *API) signedUpload(w http.ResponseWriter, r *http.Request) {
+	user, err := a.authUser(r)
+	if err != nil {
+		writeErr(w, err)
+		return
+	}
+	assetID := r.PathValue("id")
+	var req struct {
+		ContentType string `json:"contentType"`
+	}
+	if err := readJSON(r, &req); err != nil {
+		writeErr(w, app.ErrBadRequest)
+		return
+	}
+	url, err := a.service.SignedUploadURL(user, assetID, req.ContentType)
+	if err != nil {
+		writeErr(w, err)
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]string{"url": url, "method": http.MethodPut})
+}
+
+func (a *API) downloadAsset(w http.ResponseWriter, r *http.Request) {
+	user, err := a.authUser(r)
+	if err != nil {
+		writeErr(w, err)
+		return
+	}
+	assetID := r.PathValue("id")
+	url, err := a.service.SignedDownloadURL(user, assetID)
+	if err != nil {
+		writeErr(w, err)
+		return
+	}
+	http.Redirect(w, r, url, http.StatusFound)
+}
diff --git a/internal/storage/s3_signer.go b/internal/storage/s3_signer.go
new file mode 100644
index 0000000..30c3b06
--- /dev/null
+++ b/internal/storage/s3_signer.go
@@ -0,0 +1,64 @@
+package storage
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	"github.com/minio/minio-go/v7"
+	"github.com/minio/minio-go/v7/pkg/credentials"
+)
+
+type S3Config struct {
+	Endpoint  string
+	Region    string
+	Bucket    string
+	AccessKey string
+	SecretKey string
+	UseTLS    bool
+	PathStyle bool
+}
+
+type S3Signer struct {
+	client *minio.Client
+	bucket string
+}
+
+func NewS3Signer(cfg S3Config) (*S3Signer, error) {
+	if cfg.Endpoint == "" || cfg.Bucket == "" {
+		return nil, errors.New("s3 endpoint and bucket are required")
+	}
+	client, err := minio.New(cfg.Endpoint, &minio.Options{
+		Creds:        credentials.NewStaticV4(cfg.AccessKey, cfg.SecretKey, ""),
+		Secure:       cfg.UseTLS,
+		Region:       cfg.Region,
+		BucketLookup: bucketLookup(cfg.PathStyle),
+	})
+	if err != nil {
+		return nil, err
+	}
+	return &S3Signer{client: client, bucket: cfg.Bucket}, nil
+}
+
+func bucketLookup(pathStyle bool) minio.BucketLookupType {
+	if pathStyle {
+		return minio.BucketLookupPath
+	}
+	return minio.BucketLookupAuto
+}
+
+func (s *S3Signer) SignedPutObjectURL(ctx context.Context, objectKey string, expiry time.Duration, _ string) (string, error) {
+	u, err := s.client.PresignedPutObject(ctx, s.bucket, objectKey, expiry)
+	if err != nil {
+		return "", err
+	}
+	return u.String(), nil
+}
+
+func (s *S3Signer) SignedGetObjectURL(ctx context.Context, objectKey string, expiry time.Duration) (string, error) {
+	u, err := s.client.PresignedGetObject(ctx, s.bucket, objectKey, expiry, nil)
+	if err != nil {
+		return "", err
+	}
+	return u.String(), nil
+}
diff --git a/internal/store/interface.go b/internal/store/interface.go
index f34353f..7c64956 100644
--- a/internal/store/interface.go
+++ b/internal/store/interface.go
@@ -22,5 +22,12 @@ type Store interface {
 	ListFeaturesByCollection(collectionID string) []Feature
 	GetFeature(featureID string) (Feature, error)
 	DeleteFeature(featureID string) error
+	SaveAsset(a Asset)
+	GetAsset(assetID string) (Asset, error)
+	GetAssetByOwnerChecksumExt(ownerKey, checksum, ext string) (Asset, error)
+	SetAssetPublic(assetID string, isPublic bool) error
+	LinkAssetToFeature(featureID, assetID, name, description string) error
+	UnlinkAssetFromFeature(featureID, assetID string) error
+	ListAssetsByFeature(featureID string) []FeatureAsset
 	PruneExpired(now time.Time)
 }
diff --git a/internal/store/memory.go b/internal/store/memory.go
index b0d4624..7321961 100644
--- a/internal/store/memory.go
+++ b/internal/store/memory.go
@@ -20,6 +20,8 @@ type MemoryStore struct {
 	invitations map[string]Invitation
 	collections map[string]Collection
 	features    map[string]Feature
+	assets      map[string]Asset
+	featureRefs map[string]map[string]FeatureAsset
 }
 
 func NewMemoryStore() *MemoryStore {
@@ -30,6 +32,8 @@ func NewMemoryStore() *MemoryStore {
 		invitations: make(map[string]Invitation),
 		collections: make(map[string]Collection),
 		features:    make(map[string]Feature),
+		assets:      make(map[string]Asset),
+		featureRefs: make(map[string]map[string]FeatureAsset),
 	}
 }
 
@@ -166,6 +170,7 @@ func (s *MemoryStore) DeleteCollection(id string) error {
 	for fid, f := range s.features {
 		if f.CollectionID == id {
 			delete(s.features, fid)
+			delete(s.featureRefs, fid)
 		}
 	}
 	delete(s.collections, id)
@@ -207,9 +212,110 @@ func (s *MemoryStore) DeleteFeature(featureID string) error {
 		return ErrNotFound
 	}
 	delete(s.features, featureID)
+	delete(s.featureRefs, featureID)
 	return nil
 }
 
+func (s *MemoryStore) SaveAsset(a Asset) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.assets[a.ID] = a
+}
+
+func (s *MemoryStore) GetAsset(assetID string) (Asset, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	a, ok := s.assets[assetID]
+	if !ok {
+		return Asset{}, ErrNotFound
+	}
+	return a, nil
+}
+
+func (s *MemoryStore) GetAssetByOwnerChecksumExt(ownerKey, checksum, ext string) (Asset, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	for _, a := range s.assets {
+		if a.OwnerKey == ownerKey && a.Checksum == checksum && a.Ext == ext {
+			return a, nil
+		}
+	}
+	return Asset{}, ErrNotFound
+}
+
+func (s *MemoryStore) SetAssetPublic(assetID string, isPublic bool) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	a, ok := s.assets[assetID]
+	if !ok {
+		return ErrNotFound
+	}
+	a.IsPublic = isPublic
+	a.UpdatedAt = time.Now().UTC()
+	s.assets[assetID] = a
+	return nil
+}
+
+func (s *MemoryStore) LinkAssetToFeature(featureID, assetID, name, description string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if _, ok := s.features[featureID]; !ok {
+		return ErrNotFound
+	}
+	a, ok := s.assets[assetID]
+	if !ok {
+		return ErrNotFound
+	}
+	if _, ok := s.featureRefs[featureID]; !ok {
+		s.featureRefs[featureID] = make(map[string]FeatureAsset)
+	}
+	if existing, exists := s.featureRefs[featureID][assetID]; exists {
+		existing.Name = name
+		existing.Description = description
+		s.featureRefs[featureID][assetID] = existing
+		return nil
+	}
+	s.featureRefs[featureID][assetID] = FeatureAsset{
+		Asset:       a,
+		FeatureID:   featureID,
+		Name:        name,
+		Description: description,
+		LinkedAt:    time.Now().UTC(),
+	}
+	return nil
+}
+
+func (s *MemoryStore) UnlinkAssetFromFeature(featureID, assetID string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	links, ok := s.featureRefs[featureID]
+	if !ok {
+		return ErrNotFound
+	}
+	if _, exists := links[assetID]; !exists {
+		return ErrNotFound
+	}
+	delete(links, assetID)
+	return nil
+}
+
+func (s *MemoryStore) ListAssetsByFeature(featureID string) []FeatureAsset {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	links, ok := s.featureRefs[featureID]
+	if !ok {
+		return []FeatureAsset{}
+	}
+	result := make([]FeatureAsset, 0, len(links))
+	for assetID, fa := range links {
+		if updated, exists := s.assets[assetID]; exists {
+			fa.Asset = updated
+		}
+		result = append(result, fa)
+	}
+	return result
+}
+
 func (s *MemoryStore) PruneExpired(now time.Time) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
diff --git a/internal/store/migrate.go b/internal/store/migrate.go
index 4886086..0fac953 100644
--- a/internal/store/migrate.go
+++ b/internal/store/migrate.go
@@ -3,8 +3,10 @@ package store
 import (
 	"database/sql"
 	"embed"
+	"fmt"
 	"io/fs"
 	"log"
+	"path/filepath"
 	"sort"
 
 	_ "github.com/jackc/pgx/v5/stdlib"
@@ -19,19 +21,25 @@ func Migrate(databaseURL string) error {
 		return err
 	}
 	defer db.Close()
-
-	entries, err := fs.Glob(migrationsFS, "migrations/*.sql")
+	files, err := fs.ReadDir(migrationsFS, "migrations")
 	if err != nil {
 		return err
 	}
-	sort.Strings(entries)
-	for _, name := range entries {
-		sql, err := migrationsFS.ReadFile(name)
-		if err != nil {
-			return err
+	paths := make([]string, 0, len(files))
+	for _, entry := range files {
+		if entry.IsDir() || filepath.Ext(entry.Name()) != ".sql" {
+			continue
 		}
-		if _, err := db.Exec(string(sql)); err != nil {
-			return err
+		paths = append(paths, "migrations/"+entry.Name())
+	}
+	sort.Strings(paths)
+	for _, path := range paths {
+		sqlBytes, readErr := migrationsFS.ReadFile(path)
+		if readErr != nil {
+			return readErr
+		}
+		if _, execErr := db.Exec(string(sqlBytes)); execErr != nil {
+			return fmt.Errorf("%s: %w", path, execErr)
 		}
 	}
 	log.Printf("migrations applied")
diff --git a/internal/store/migrations/0002_assets.sql b/internal/store/migrations/0002_assets.sql
new file mode 100644
index 0000000..6490540
--- /dev/null
+++ b/internal/store/migrations/0002_assets.sql
@@ -0,0 +1,28 @@
+CREATE TABLE IF NOT EXISTS assets (
+  id TEXT PRIMARY KEY,
+  owner_key TEXT NOT NULL,
+  checksum TEXT NOT NULL,
+  ext TEXT NOT NULL,
+  kind TEXT NOT NULL,
+  mime_type TEXT,
+  size_bytes BIGINT NOT NULL DEFAULT 0,
+  object_key TEXT NOT NULL,
+  is_public BOOLEAN NOT NULL DEFAULT TRUE,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  UNIQUE (owner_key, checksum, ext),
+  UNIQUE (owner_key, object_key)
+);
+
+CREATE TABLE IF NOT EXISTS feature_asset_links (
+  feature_id TEXT NOT NULL REFERENCES features(id) ON DELETE CASCADE,
+  asset_id TEXT NOT NULL REFERENCES assets(id) ON DELETE CASCADE,
+  name TEXT,
+  description TEXT,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  PRIMARY KEY (feature_id, asset_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_assets_owner ON assets(owner_key);
+CREATE INDEX IF NOT EXISTS idx_assets_owner_public ON assets(owner_key, is_public);
+CREATE INDEX IF NOT EXISTS idx_feature_asset_links_asset ON feature_asset_links(asset_id);
diff --git a/internal/store/migrations/0003_features_spatial.sql b/internal/store/migrations/0003_features_spatial.sql
new file mode 100644
index 0000000..ff1ce20
--- /dev/null
+++ b/internal/store/migrations/0003_features_spatial.sql
@@ -0,0 +1,21 @@
+CREATE EXTENSION IF NOT EXISTS postgis;
+
+ALTER TABLE features
+  ADD COLUMN IF NOT EXISTS geom geometry(PointZ, 4326);
+
+UPDATE features
+SET geom = ST_SetSRID(
+  ST_MakePoint(
+    (geometry->'coordinates'->>0)::double precision,
+    (geometry->'coordinates'->>1)::double precision,
+    CASE
+      WHEN jsonb_array_length(geometry->'coordinates') >= 3 THEN (geometry->'coordinates'->>2)::double precision
+      ELSE 0
+    END
+  ),
+  4326
+)
+WHERE geom IS NULL
+  AND geometry ? 'coordinates';
+
+CREATE INDEX IF NOT EXISTS idx_features_geom_gist ON features USING GIST (geom);
diff --git a/internal/store/postgres.go b/internal/store/postgres.go
index 5f9b763..4d79d44 100644
--- a/internal/store/postgres.go
+++ b/internal/store/postgres.go
@@ -219,11 +219,20 @@ func (s *PostgresStore) DeleteCollection(id string) error {
 func (s *PostgresStore) SaveFeature(f Feature) {
 	geom, _ := json.Marshal(f.Geometry)
 	props, _ := json.Marshal(f.Properties)
+	z := 0.0
+	if len(f.Geometry.Coordinates) >= 3 {
+		z = f.Geometry.Coordinates[2]
+	}
 	_, _ = s.db.Exec(
-		`INSERT INTO features (id, collection_id, owner_key, type, geometry, properties, created_at, updated_at)
-		 VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
-		 ON CONFLICT (id) DO UPDATE SET geometry = EXCLUDED.geometry, properties = EXCLUDED.properties, updated_at = EXCLUDED.updated_at`,
+		`INSERT INTO features (id, collection_id, owner_key, type, geometry, properties, created_at, updated_at, geom)
+		 VALUES ($1, $2, $3, $4, $5, $6, $7, $8, ST_SetSRID(ST_MakePoint($9, $10, $11), 4326))
+		 ON CONFLICT (id) DO UPDATE
+		 SET geometry = EXCLUDED.geometry,
+		     properties = EXCLUDED.properties,
+		     updated_at = EXCLUDED.updated_at,
+		     geom = EXCLUDED.geom`,
 		f.ID, f.CollectionID, f.OwnerKey, f.Type, geom, props, f.CreatedAt, f.UpdatedAt,
+		f.Geometry.Coordinates[0], f.Geometry.Coordinates[1], z,
 	)
 }
 
@@ -289,6 +298,118 @@ func (s *PostgresStore) SaveUserLogin(ul UserLogin) {
 	)
 }
 
+func (s *PostgresStore) SaveAsset(a Asset) {
+	_, _ = s.db.Exec(
+		`INSERT INTO assets (id, owner_key, checksum, ext, kind, mime_type, size_bytes, object_key, is_public, created_at, updated_at)
+		 VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11)
+		 ON CONFLICT (id) DO UPDATE
+		 SET kind = EXCLUDED.kind,
+		     mime_type = EXCLUDED.mime_type,
+		     size_bytes = EXCLUDED.size_bytes,
+		     is_public = EXCLUDED.is_public,
+		     updated_at = EXCLUDED.updated_at`,
+		a.ID, a.OwnerKey, a.Checksum, a.Ext, a.Kind, nullStr(a.MimeType), a.SizeBytes, a.ObjectKey, a.IsPublic, a.CreatedAt, a.UpdatedAt,
+	)
+}
+
+func (s *PostgresStore) GetAsset(assetID string) (Asset, error) {
+	var a Asset
+	var mimeType sql.NullString
+	err := s.db.QueryRow(
+		`SELECT id, owner_key, checksum, ext, kind, mime_type, size_bytes, object_key, is_public, created_at, updated_at
+		 FROM assets WHERE id = $1`,
+		assetID,
+	).Scan(&a.ID, &a.OwnerKey, &a.Checksum, &a.Ext, &a.Kind, &mimeType, &a.SizeBytes, &a.ObjectKey, &a.IsPublic, &a.CreatedAt, &a.UpdatedAt)
+	if errors.Is(err, sql.ErrNoRows) {
+		return Asset{}, ErrNotFound
+	}
+	if err != nil {
+		return Asset{}, err
+	}
+	a.MimeType = mimeType.String
+	return a, nil
+}
+
+func (s *PostgresStore) GetAssetByOwnerChecksumExt(ownerKey, checksum, ext string) (Asset, error) {
+	var a Asset
+	var mimeType sql.NullString
+	err := s.db.QueryRow(
+		`SELECT id, owner_key, checksum, ext, kind, mime_type, size_bytes, object_key, is_public, created_at, updated_at
+		 FROM assets WHERE owner_key = $1 AND checksum = $2 AND ext = $3`,
+		ownerKey, checksum, ext,
+	).Scan(&a.ID, &a.OwnerKey, &a.Checksum, &a.Ext, &a.Kind, &mimeType, &a.SizeBytes, &a.ObjectKey, &a.IsPublic, &a.CreatedAt, &a.UpdatedAt)
+	if errors.Is(err, sql.ErrNoRows) {
+		return Asset{}, ErrNotFound
+	}
+	if err != nil {
+		return Asset{}, err
+	}
+	a.MimeType = mimeType.String
+	return a, nil
+}
+
+func (s *PostgresStore) SetAssetPublic(assetID string, isPublic bool) error {
+	res, err := s.db.Exec(`UPDATE assets SET is_public = $2, updated_at = NOW() WHERE id = $1`, assetID, isPublic)
+	if err != nil {
+		return err
+	}
+	n, _ := res.RowsAffected()
+	if n == 0 {
+		return ErrNotFound
+	}
+	return nil
+}
+
+func (s *PostgresStore) LinkAssetToFeature(featureID, assetID, name, description string) error {
+	_, err := s.db.Exec(
+		`INSERT INTO feature_asset_links (feature_id, asset_id, name, description)
+		 VALUES ($1, $2, $3, $4)
+		 ON CONFLICT (feature_id, asset_id) DO UPDATE SET name = EXCLUDED.name, description = EXCLUDED.description`,
+		featureID, assetID, nullStr(name), nullStr(description),
+	)
+	return err
+}
+
+func (s *PostgresStore) UnlinkAssetFromFeature(featureID, assetID string) error {
+	res, err := s.db.Exec(`DELETE FROM feature_asset_links WHERE feature_id = $1 AND asset_id = $2`, featureID, assetID)
+	if err != nil {
+		return err
+	}
+	n, _ := res.RowsAffected()
+	if n == 0 {
+		return ErrNotFound
+	}
+	return nil
+}
+
+func (s *PostgresStore) ListAssetsByFeature(featureID string) []FeatureAsset {
+	rows, err := s.db.Query(
+		`SELECT a.id, a.owner_key, a.checksum, a.ext, a.kind, COALESCE(a.mime_type, ''), a.size_bytes, a.object_key,
+		        a.is_public, a.created_at, a.updated_at,
+		        l.feature_id, COALESCE(l.name, ''), COALESCE(l.description, ''), l.created_at
+		 FROM feature_asset_links l
+		 JOIN assets a ON a.id = l.asset_id
+		 WHERE l.feature_id = $1
+		 ORDER BY l.created_at`,
+		featureID,
+	)
+	if err != nil {
+		return nil
+	}
+	defer rows.Close()
+	result := make([]FeatureAsset, 0)
+	for rows.Next() {
+		var fa FeatureAsset
+		if err := rows.Scan(
+			&fa.ID, &fa.OwnerKey, &fa.Checksum, &fa.Ext, &fa.Kind, &fa.MimeType, &fa.SizeBytes, &fa.ObjectKey,
+			&fa.IsPublic, &fa.CreatedAt, &fa.UpdatedAt, &fa.FeatureID, &fa.Name, &fa.Description, &fa.LinkedAt,
+		); err != nil {
+			return result
+		}
+		result = append(result, fa)
+	}
+	return result
+}
 func (s *PostgresStore) PruneExpired(now time.Time) {
 	_, _ = s.db.Exec(`DELETE FROM challenges WHERE expires_at < $1`, now)
 	_, _ = s.db.Exec(`DELETE FROM sessions WHERE expires_at < $1`, now)
diff --git a/internal/store/types.go b/internal/store/types.go
index bbb4392..89d548b 100644
--- a/internal/store/types.go
+++ b/internal/store/types.go
@@ -60,3 +60,25 @@ type Feature struct {
 	CreatedAt    time.Time              `json:"createdAt"`
 	UpdatedAt    time.Time              `json:"updatedAt"`
 }
+
+type Asset struct {
+	ID        string    `json:"id"`
+	OwnerKey  string    `json:"ownerKey"`
+	Checksum  string    `json:"checksum"`
+	Ext       string    `json:"ext"`
+	Kind      string    `json:"kind"`
+	MimeType  string    `json:"mimeType,omitempty"`
+	SizeBytes int64     `json:"sizeBytes"`
+	ObjectKey string    `json:"objectKey"`
+	IsPublic  bool      `json:"isPublic"`
+	CreatedAt time.Time `json:"createdAt"`
+	UpdatedAt time.Time `json:"updatedAt"`
+}
+
+type FeatureAsset struct {
+	Asset
+	FeatureID   string    `json:"featureId"`
+	Name        string    `json:"name,omitempty"`
+	Description string    `json:"description,omitempty"`
+	LinkedAt    time.Time `json:"linkedAt"`
+}
diff --git a/libs/geo-api-client/dist/index.js b/libs/geo-api-client/dist/index.js
index 7bb9ae4..54fecb9 100644
--- a/libs/geo-api-client/dist/index.js
+++ b/libs/geo-api-client/dist/index.js
@@ -638,6 +638,26 @@ class GeoApiClient {
   async deleteFeature(featureId) {
     return this.request(`/v1/features/${featureId}`, { method: "DELETE" });
   }
+  async createOrLinkAsset(input) {
+    return this.request("/v1/assets", { method: "POST", body: input });
+  }
+  async getAssetSignedUploadUrl(assetId, contentType) {
+    return this.request(`/v1/assets/${assetId}/signed-upload`, {
+      method: "POST",
+      body: { contentType: contentType ?? "application/octet-stream" }
+    });
+  }
+  async setAssetVisibility(assetId, isPublic) {
+    return this.request(`/v1/assets/${assetId}`, {
+      method: "PATCH",
+      body: { isPublic }
+    });
+  }
+  resolveRelativeLink(path) {
+    if (!path.startsWith("/"))
+      return `${this.baseUrl}/${path}`;
+    return `${this.baseUrl}${path}`;
+  }
 }
 export {
   signMessage,
diff --git a/libs/geo-api-client/src/GeoApiClient.ts b/libs/geo-api-client/src/GeoApiClient.ts
index 4bf024c..830a35d 100644
--- a/libs/geo-api-client/src/GeoApiClient.ts
+++ b/libs/geo-api-client/src/GeoApiClient.ts
@@ -1,10 +1,23 @@
 import { generateKeyPair, signMessage, getPublicKeyFromPrivate } from "./keys";
 import { bytesToBase64Url, textToBytes } from "./encoding";
 import { DEFAULT_KEYS_STORAGE_KEY, loadKeys, saveKeys } from "./storage";
-import type { InvitationPayload, StorageLike, StoredKeys } from "./types";
+import type { AssetKind, AssetRecord, FeatureAsset, InvitationPayload, StorageLike, StoredKeys } from "./types";
 
 type RequestInitLike = Omit<RequestInit, "body"> & { body?: unknown };
 
+type FeatureProperties = {
+  assets?: FeatureAsset[];
+  [key: string]: unknown;
+};
+
+type GeoFeature = {
+  id: string;
+  geometry?: {
+    coordinates?: number[];
+  };
+  properties?: FeatureProperties;
+};
+
 /**
  * TypeScript API client for Momswap Geo backend.
  * Handles Ed25519 key storage, auth flows, and GeoJSON collection/feature CRUD.
@@ -201,7 +214,7 @@ export class GeoApiClient {
   }
 
   /** List GeoJSON features in a collection. Must own the collection. */
-  async listFeatures(collectionId: string): Promise<{ features: unknown[] }> {
+  async listFeatures(collectionId: string): Promise<{ features: GeoFeature[] }> {
     return this.request(`/v1/collections/${collectionId}/features`, { method: "GET" });
   }
 
@@ -228,4 +241,47 @@ export class GeoApiClient {
   async deleteFeature(featureId: string): Promise<void> {
     return this.request(`/v1/features/${featureId}`, { method: "DELETE" });
   }
+
+  /**
+   * Create or reuse an asset by checksum+ext for the authenticated owner and link it to a feature.
+   * If checksum/ext already exists for this owner, backend returns existing asset and refreshes link metadata.
+   */
+  async createOrLinkAsset(input: {
+    featureId: string;
+    checksum: string;
+    ext: string;
+    kind: AssetKind;
+    mimeType?: string;
+    sizeBytes?: number;
+    name?: string;
+    description?: string;
+    isPublic?: boolean;
+  }): Promise<{ asset: AssetRecord; link: string }> {
+    return this.request("/v1/assets", { method: "POST", body: input });
+  }
+
+  /** Request a signed upload URL for an existing asset. */
+  async getAssetSignedUploadUrl(
+    assetId: string,
+    contentType?: string
+  ): Promise<{ url: string; method: string }> {
+    return this.request(`/v1/assets/${assetId}/signed-upload`, {
+      method: "POST",
+      body: { contentType: contentType ?? "application/octet-stream" },
+    });
+  }
+
+  /** Update asset visibility (owner only). */
+  async setAssetVisibility(assetId: string, isPublic: boolean): Promise<{ asset: AssetRecord; link: string }> {
+    return this.request(`/v1/assets/${assetId}`, {
+      method: "PATCH",
+      body: { isPublic },
+    });
+  }
+
+  /** Build absolute download URL from service-relative link returned in feature assets. */
+  resolveRelativeLink(path: string): string {
+    if (!path.startsWith("/")) return `${this.baseUrl}/${path}`;
+    return `${this.baseUrl}${path}`;
+  }
 }
diff --git a/libs/geo-api-client/src/index.ts b/libs/geo-api-client/src/index.ts
index 0abfdeb..ee74127 100644
--- a/libs/geo-api-client/src/index.ts
+++ b/libs/geo-api-client/src/index.ts
@@ -1,4 +1,12 @@
 export { GeoApiClient } from "./GeoApiClient";
 export { generateKeyPair, signMessage, getPublicKeyFromPrivate } from "./keys";
 export { clearKeys, loadKeys, saveKeys, DEFAULT_KEYS_STORAGE_KEY } from "./storage";
-export type { InvitationPayload, StorageLike, StoredKeys } from "./types";
+export type {
+  AssetKind,
+  AssetRecord,
+  AssetVisibility,
+  FeatureAsset,
+  InvitationPayload,
+  StorageLike,
+  StoredKeys,
+} from "./types";
diff --git a/libs/geo-api-client/src/types.ts b/libs/geo-api-client/src/types.ts
index f3d2500..0e47bc3 100644
--- a/libs/geo-api-client/src/types.ts
+++ b/libs/geo-api-client/src/types.ts
@@ -16,3 +16,34 @@ export type StorageLike = {
   setItem(key: string, value: string): void;
   removeItem(key: string): void;
 };
+
+export type AssetKind = "image" | "3d";
+
+export type AssetVisibility = {
+  isPublic: boolean;
+};
+
+export type AssetRecord = {
+  id: string;
+  ownerKey: string;
+  checksum: string;
+  ext: string;
+  kind: AssetKind;
+  mimeType?: string;
+  sizeBytes: number;
+  objectKey: string;
+  isPublic: boolean;
+  createdAt: string;
+  updatedAt: string;
+};
+
+export type FeatureAsset = {
+  id: string;
+  kind: AssetKind;
+  name?: string;
+  description?: string;
+  checksum: string;
+  ext: string;
+  isPublic: boolean;
+  link: string;
+};
diff --git a/libs/geo-api-client/test/integration.test.ts b/libs/geo-api-client/test/integration.test.ts
index 27f4631..0dd74fd 100644
--- a/libs/geo-api-client/test/integration.test.ts
+++ b/libs/geo-api-client/test/integration.test.ts
@@ -27,6 +27,22 @@ async function createMockServer(): Promise<{ url: string; server: ReturnType<typ
   const sessions = new Map<string, string>();
   let collectionId = 0;
   let featureId = 0;
+  let assetId = 0;
+  const collectionsByUser = new Map<string, Array<{ id: string; name: string }>>();
+  const featuresByCollection = new Map<string, Array<{ id: string; geometry: unknown; properties: Record<string, unknown> }>>();
+  const assetsByOwner = new Map<string, Array<{
+    id: string;
+    ownerKey: string;
+    checksum: string;
+    ext: string;
+    kind: "image" | "3d";
+    mimeType?: string;
+    sizeBytes: number;
+    objectKey: string;
+    isPublic: boolean;
+    createdAt: string;
+    updatedAt: string;
+  }>>();
 
   const server = Bun.serve({
     port: 0,
@@ -98,35 +114,138 @@ async function createMockServer(): Promise<{ url: string; server: ReturnType<typ
       if (!user && path.startsWith("/v1/collections") && method !== "GET") {
         return Response.json({ error: "unauthorized" }, { status: 401 });
       }
+      if (!user && path.startsWith("/v1/assets")) {
+        return Response.json({ error: "unauthorized" }, { status: 401 });
+      }
 
       // POST /v1/collections
       if (method === "POST" && path === "/v1/collections") {
         const body = (await req.json()) as { name?: string };
         collectionId++;
         const c = { id: `col-${collectionId}`, name: body?.name ?? "Unnamed" };
+        const list = collectionsByUser.get(user!) ?? [];
+        list.push(c);
+        collectionsByUser.set(user!, list);
         return Response.json(c, { status: 201 });
       }
 
       // GET /v1/collections
       if (method === "GET" && path === "/v1/collections") {
-        return Response.json({ collections: [] });
+        return Response.json({ collections: collectionsByUser.get(user ?? "") ?? [] });
       }
 
       // POST /v1/collections/:id/features
       if (method === "POST" && path.match(/^\/v1\/collections\/[^/]+\/features$/)) {
+        const colId = path.split("/")[3]!;
+        const owned = (collectionsByUser.get(user!) ?? []).some((c) => c.id === colId);
+        if (!owned) {
+          return Response.json({ error: "forbidden" }, { status: 403 });
+        }
         const body = (await req.json()) as { geometry?: unknown; properties?: unknown };
         featureId++;
         const f = {
           id: `feat-${featureId}`,
           geometry: body?.geometry ?? { type: "Point", coordinates: [0, 0] },
-          properties: body?.properties ?? {},
+          properties: (body?.properties as Record<string, unknown>) ?? {},
         };
+        const list = featuresByCollection.get(colId) ?? [];
+        list.push(f);
+        featuresByCollection.set(colId, list);
         return Response.json(f, { status: 201 });
       }
 
       // GET /v1/collections/:id/features
       if (method === "GET" && path.match(/^\/v1\/collections\/[^/]+\/features$/)) {
-        return Response.json({ features: [] });
+        const colId = path.split("/")[3]!;
+        const features = featuresByCollection.get(colId) ?? [];
+        const ownerAssets = assetsByOwner.get(user ?? "") ?? [];
+        const withAssets = features.map((f) => {
+          const assets = ownerAssets
+            .filter((a) => (f.properties.assets as Array<{ id: string }> | undefined)?.some((x) => x.id === a.id))
+            .map((a) => ({
+              id: a.id,
+              kind: a.kind,
+              checksum: a.checksum,
+              ext: a.ext,
+              isPublic: a.isPublic,
+              link: `/v1/assets/${a.id}/download`,
+            }));
+          return { ...f, properties: { ...f.properties, assets } };
+        });
+        return Response.json({ features: withAssets });
+      }
+
+      // POST /v1/assets
+      if (method === "POST" && path === "/v1/assets") {
+        const body = (await req.json()) as {
+          featureId?: string;
+          checksum?: string;
+          ext?: string;
+          kind?: "image" | "3d";
+          mimeType?: string;
+          sizeBytes?: number;
+          name?: string;
+          description?: string;
+          isPublic?: boolean;
+        };
+        if (!body.featureId || !body.checksum || !body.ext || !body.kind) {
+          return Response.json({ error: "missing fields" }, { status: 400 });
+        }
+        const ownerAssets = assetsByOwner.get(user!) ?? [];
+        const existing = ownerAssets.find(
+          (a) => a.checksum === body.checksum.toLowerCase() && a.ext === body.ext.toLowerCase()
+        );
+        const now = new Date().toISOString();
+        const asset =
+          existing ??
+          {
+            id: `asset-${++assetId}`,
+            ownerKey: user!,
+            checksum: body.checksum.toLowerCase(),
+            ext: body.ext.toLowerCase(),
+            kind: body.kind,
+            mimeType: body.mimeType,
+            sizeBytes: body.sizeBytes ?? 0,
+            objectKey: `${user!}/${body.checksum.toLowerCase()}.${body.ext.toLowerCase()}`,
+            isPublic: body.isPublic ?? true,
+            createdAt: now,
+            updatedAt: now,
+          };
+        if (!existing) {
+          ownerAssets.push(asset);
+          assetsByOwner.set(user!, ownerAssets);
+        }
+        for (const featureList of featuresByCollection.values()) {
+          for (const f of featureList) {
+            if (f.id === body.featureId) {
+              const oldAssets = Array.isArray(f.properties.assets) ? (f.properties.assets as Array<{ id: string }>) : [];
+              if (!oldAssets.some((x) => x.id === asset.id)) {
+                f.properties.assets = [...oldAssets, { id: asset.id, name: body.name, description: body.description }];
+              }
+            }
+          }
+        }
+        return Response.json({ asset, link: `/v1/assets/${asset.id}/download` }, { status: existing ? 200 : 201 });
+      }
+
+      // POST /v1/assets/:id/signed-upload
+      if (method === "POST" && path.match(/^\/v1\/assets\/[^/]+\/signed-upload$/)) {
+        const id = path.split("/")[3]!;
+        return Response.json({ url: `http://upload.local/${id}`, method: "PUT" });
+      }
+
+      // PATCH /v1/assets/:id
+      if (method === "PATCH" && path.match(/^\/v1\/assets\/[^/]+$/)) {
+        const id = path.split("/")[3]!;
+        const body = (await req.json()) as { isPublic?: boolean };
+        const ownerAssets = assetsByOwner.get(user!) ?? [];
+        const asset = ownerAssets.find((a) => a.id === id);
+        if (!asset) {
+          return Response.json({ error: "not found" }, { status: 404 });
+        }
+        asset.isPublic = Boolean(body.isPublic);
+        asset.updatedAt = new Date().toISOString();
+        return Response.json({ asset, link: `/v1/assets/${asset.id}/download` });
       }
 
       return new Response("Not Found", { status: 404 });
@@ -180,4 +299,41 @@ describe("GeoApiClient integration (docs flow)", () => {
     const { features } = await client.listFeatures(created.id);
     expect(Array.isArray(features)).toBe(true);
   });
+
+  test("asset flow: create/link -> signed upload -> toggle visibility", async () => {
+    const keys = await client.ensureKeysInStorage();
+    await client.registerBySigningServiceKey(keys.publicKey, keys.privateKey);
+    await client.loginWithSignature(keys.publicKey, keys.privateKey);
+
+    const created = await client.createCollection("3D");
+    const feature = await client.createPointFeature(created.id, -16.6291, 28.4636, { name: "Palm Tree Point" });
+
+    const createdAsset = await client.createOrLinkAsset({
+      featureId: feature.id,
+      checksum: "ABCDEF0123",
+      ext: "glb",
+      kind: "3d",
+      mimeType: "model/gltf-binary",
+      sizeBytes: 1024,
+      name: "Palm Tree",
+      description: "Low poly",
+      isPublic: true,
+    });
+    expect(createdAsset.asset.id).toBeDefined();
+    expect(createdAsset.link).toBe(`/v1/assets/${createdAsset.asset.id}/download`);
+    expect(client.resolveRelativeLink(createdAsset.link)).toContain(`/v1/assets/${createdAsset.asset.id}/download`);
+
+    const upload = await client.getAssetSignedUploadUrl(createdAsset.asset.id, "model/gltf-binary");
+    expect(upload.method).toBe("PUT");
+    expect(upload.url).toContain(createdAsset.asset.id);
+
+    const toggled = await client.setAssetVisibility(createdAsset.asset.id, false);
+    expect(toggled.asset.isPublic).toBe(false);
+
+    const listed = await client.listFeatures(created.id);
+    const first = listed.features[0];
+    const assets = first.properties?.assets ?? [];
+    expect(assets.length).toBeGreaterThan(0);
+    expect(assets[0]?.id).toBe(createdAsset.asset.id);
+  });
 });
diff --git a/web/app.js b/web/app.js
index 185176f..cd9c7cb 100644
--- a/web/app.js
+++ b/web/app.js
@@ -16,9 +16,13 @@ createApp({
       selectedCollectionId: "",
       editingCollectionName: "",
       featuresByCollection: {},
+      selectedFeatureId: "",
       newFeatureLon: "",
       newFeatureLat: "",
       newFeatureName: "",
+      newAssetName: "",
+      newAssetDescription: "",
+      selectedAssetFileName: "",
       status: "Ready",
       qrPk: "",
       qrPb: "",
@@ -28,6 +32,7 @@ createApp({
       cameraError: "",
       cameraAbortController: null,
     });
+    const selectedAssetFile = ref(null);
 
     let client = createApiClient(apiBase.value);
 
@@ -207,6 +212,12 @@ createApp({
         client.setAccessToken(state.accessToken);
         const data = await client.listFeatures(collectionId);
         state.featuresByCollection[collectionId] = data.features || [];
+        if (
+          state.selectedFeatureId &&
+          !(state.featuresByCollection[collectionId] || []).some((f) => f.id === state.selectedFeatureId)
+        ) {
+          state.selectedFeatureId = "";
+        }
       } catch (err) {
         state.status = err.message;
       }
@@ -259,7 +270,108 @@ createApp({
       const lon = coords?.[0] ?? "—";
       const lat = coords?.[1] ?? "—";
       const name = f.properties?.name ?? f.id ?? "—";
-      return { id: f.id, name, lon, lat };
+      const assets = Array.isArray(f.properties?.assets) ? f.properties.assets : [];
+      return { id: f.id, name, lon, lat, assets };
+    };
+
+    const selectFeature = (featureId) => {
+      state.selectedFeatureId = featureId;
+    };
+
+    const selectedFeature = () => {
+      const collectionId = state.selectedCollectionId;
+      if (!collectionId || !state.selectedFeatureId) return null;
+      return (state.featuresByCollection[collectionId] || []).find((f) => f.id === state.selectedFeatureId) ?? null;
+    };
+
+    const fileExtension = (name) => {
+      const idx = name.lastIndexOf(".");
+      if (idx <= 0) return "";
+      return name.slice(idx + 1).toLowerCase();
+    };
+
+    const kindFromExtension = (ext) => (ext === "gltf" || ext === "glb" ? "3d" : "image");
+
+    const hashFileSha256 = async (file) => {
+      const buffer = await file.arrayBuffer();
+      const digest = await crypto.subtle.digest("SHA-256", buffer);
+      return Array.from(new Uint8Array(digest))
+        .map((b) => b.toString(16).padStart(2, "0"))
+        .join("");
+    };
+
+    const onAssetFileChange = (event) => {
+      const target = event?.target;
+      const file = target?.files?.[0] ?? null;
+      selectedAssetFile.value = file;
+      state.selectedAssetFileName = file ? file.name : "";
+    };
+
+    const createAndUploadAsset = async () => {
+      const feature = selectedFeature();
+      if (!feature) {
+        state.status = "Select a feature first.";
+        return;
+      }
+      if (!selectedAssetFile.value) {
+        state.status = "Select a file first.";
+        return;
+      }
+      const file = selectedAssetFile.value;
+      const ext = fileExtension(file.name);
+      if (!ext) {
+        state.status = "File extension is required.";
+        return;
+      }
+      try {
+        client.setAccessToken(state.accessToken);
+        const checksum = await hashFileSha256(file);
+        const kind = kindFromExtension(ext);
+        const created = await client.createOrLinkAsset({
+          featureId: feature.id,
+          checksum,
+          ext,
+          kind,
+          mimeType: file.type || "application/octet-stream",
+          sizeBytes: file.size,
+          name: state.newAssetName || file.name,
+          description: state.newAssetDescription,
+          isPublic: true,
+        });
+        const upload = await client.getAssetSignedUploadUrl(created.asset.id, file.type || "application/octet-stream");
+        const putRes = await fetch(upload.url, {
+          method: upload.method || "PUT",
+          headers: file.type ? { "Content-Type": file.type } : undefined,
+          body: file,
+        });
+        if (!putRes.ok) {
+          throw new Error(`Upload failed with status ${putRes.status}`);
+        }
+        state.newAssetName = "";
+        state.newAssetDescription = "";
+        state.selectedAssetFileName = "";
+        selectedAssetFile.value = null;
+        await listFeatures(state.selectedCollectionId);
+        state.status = "Asset uploaded and linked to feature.";
+      } catch (err) {
+        state.status = err.message;
+      }
+    };
+
+    const toggleAssetVisibility = async (asset) => {
+      try {
+        client.setAccessToken(state.accessToken);
+        await client.setAssetVisibility(asset.id, !asset.isPublic);
+        await listFeatures(state.selectedCollectionId);
+        state.status = `Asset visibility updated: ${asset.id}`;
+      } catch (err) {
+        state.status = err.message;
+      }
+    };
+
+    const openAssetLink = (asset) => {
+      const absolute = client.resolveRelativeLink(asset.link);
+      window.open(absolute, "_blank", "noopener,noreferrer");
     };
 
     watch(
@@ -277,6 +389,7 @@ createApp({
 
     const selectCollection = (id) => {
       state.selectedCollectionId = id;
+      state.selectedFeatureId = "";
       const c = state.collections.find((x) => x.id === id);
       state.editingCollectionName = c ? c.name : "";
     };
@@ -338,6 +451,12 @@ createApp({
       removeFeature,
       formatFeature,
       featuresFor,
+      selectFeature,
+      selectedFeature,
+      onAssetFileChange,
+      createAndUploadAsset,
+      toggleAssetVisibility,
+      openAssetLink,
       togglePrivateQR,
       togglePublicQR,
     };
diff --git a/web/index.html b/web/index.html
index aa9687c..0360e4f 100644
--- a/web/index.html
+++ b/web/index.html
@@ -130,9 +130,65 @@
                   </v-row>
                   <div v-for="f in featuresFor(selectedCollection().id)" :key="f.id" class="d-flex align-center py-2 mb-1 rounded px-2" style="background: rgba(255,255,255,0.05)">
                     <span class="flex-grow-1">{{ formatFeature(f).name }} ({{ formatFeature(f).lon }}, {{ formatFeature(f).lat }})</span>
+                    <v-btn
+                      variant="tonal"
+                      size="small"
+                      class="mr-2"
+                      :color="state.selectedFeatureId === f.id ? 'primary' : undefined"
+                      @click="selectFeature(f.id)"
+                    >
+                      {{ state.selectedFeatureId === f.id ? 'Selected' : 'Select' }}
+                    </v-btn>
                     <v-btn variant="outlined" color="error" size="small" @click="removeFeature(selectedCollection().id, f.id)">Remove</v-btn>
                   </div>
                   <div v-if="featuresFor(selectedCollection().id).length === 0" class="text-medium-emphasis text-caption py-2">No features. Add a point above.</div>
+
+                  <v-divider class="my-4"></v-divider>
+                  <v-card variant="tonal" class="pa-3">
+                    <v-card-subtitle class="mb-2">Asset example flow (images + 3D)</v-card-subtitle>
+                    <div class="text-caption mb-2">
+                      Select a feature, choose a file, then upload. The backend stores metadata and links it under
+                      <code>feature.properties.assets</code>.
+                    </div>
+                    <v-alert v-if="!selectedFeature()" type="info" variant="tonal" density="compact" class="mb-2">
+                      Select a feature to enable asset actions.
+                    </v-alert>
+                    <div v-else class="text-caption mb-2">
+                      Target feature: <strong>{{ formatFeature(selectedFeature()).name }}</strong> ({{ selectedFeature().id }})
+                    </div>
+                    <input type="file" @change="onAssetFileChange" :disabled="!selectedFeature()" />
+                    <div class="text-caption mt-1 mb-2" v-if="state.selectedAssetFileName">Selected: {{ state.selectedAssetFileName }}</div>
+                    <v-row dense>
+                      <v-col cols="12" sm="4">
+                        <v-text-field v-model="state.newAssetName" label="Asset name" density="compact" hide-details></v-text-field>
+                      </v-col>
+                      <v-col cols="12" sm="6">
+                        <v-text-field v-model="state.newAssetDescription" label="Asset description" density="compact" hide-details></v-text-field>
+                      </v-col>
+                      <v-col cols="12" sm="2">
+                        <v-btn color="primary" size="small" :disabled="!selectedFeature()" @click="createAndUploadAsset">Upload</v-btn>
+                      </v-col>
+                    </v-row>
+
+                    <div v-if="selectedFeature() && formatFeature(selectedFeature()).assets.length > 0" class="mt-3">
+                      <div class="text-caption mb-2">Linked assets:</div>
+                      <div
+                        v-for="asset in formatFeature(selectedFeature()).assets"
+                        :key="asset.id"
+                        class="d-flex align-center py-2 px-2 mb-1 rounded"
+                        style="background: rgba(255,255,255,0.05)"
+                      >
+                        <div class="flex-grow-1 text-caption">
+                          <div><strong>{{ asset.kind }}</strong> • {{ asset.ext }} • {{ asset.id }}</div>
+                          <div>Visibility: {{ asset.isPublic ? "public" : "private" }}</div>
+                        </div>
+                        <v-btn variant="outlined" size="small" class="mr-2" @click="openAssetLink(asset)">Open</v-btn>
+                        <v-btn variant="tonal" size="small" @click="toggleAssetVisibility(asset)">
+                          Set {{ asset.isPublic ? "Private" : "Public" }}
+                        </v-btn>
+                      </div>
+                    </div>
+                  </v-card>
                 </v-card>
               </v-card>
             </v-col>
diff --git a/web/leaflet-demo.html b/web/leaflet-demo.html
new file mode 100644
index 0000000..eecc096
--- /dev/null
+++ b/web/leaflet-demo.html
@@ -0,0 +1,153 @@
+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>Momswap Leaflet 3D Assets Demo</title>
+    <link
+      rel="stylesheet"
+      href="https://unpkg.com/leaflet@1.9.4/dist/leaflet.css"
+      integrity="sha256-p4NxAoJBhIIN+hmNHrzRCf9tD/miZyoHS5obTRR9BMY="
+      crossorigin=""
+    />
+    <style>
+      :root {
+        color-scheme: dark;
+      }
+      body {
+        margin: 0;
+        font-family: Inter, system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
+        background: #0b1220;
+        color: #dbe5f6;
+      }
+      .layout {
+        display: grid;
+        grid-template-columns: 360px 1fr;
+        gap: 12px;
+        height: 100vh;
+        padding: 12px;
+        box-sizing: border-box;
+      }
+      .panel {
+        background: #10192c;
+        border: 1px solid #24344f;
+        border-radius: 12px;
+        padding: 12px;
+        overflow: auto;
+      }
+      h1 {
+        font-size: 18px;
+        margin: 0 0 10px;
+      }
+      h2 {
+        font-size: 14px;
+        margin: 14px 0 8px;
+      }
+      label {
+        display: block;
+        font-size: 12px;
+        margin-bottom: 4px;
+        color: #9eb0ce;
+      }
+      input,
+      button,
+      select {
+        width: 100%;
+        box-sizing: border-box;
+        margin-bottom: 8px;
+        border-radius: 8px;
+        border: 1px solid #33496a;
+        background: #0d1525;
+        color: #e4ecfa;
+        padding: 8px 10px;
+      }
+      button {
+        cursor: pointer;
+      }
+      .row {
+        display: grid;
+        grid-template-columns: 1fr 1fr;
+        gap: 8px;
+      }
+      .muted {
+        font-size: 12px;
+        color: #9eb0ce;
+      }
+      .status {
+        font-size: 12px;
+        color: #8ee3a1;
+        min-height: 18px;
+      }
+      #map {
+        border-radius: 12px;
+        border: 1px solid #24344f;
+      }
+      .asset-card {
+        border: 1px solid #314869;
+        border-radius: 8px;
+        padding: 8px;
+        margin-bottom: 8px;
+      }
+      .asset-actions {
+        display: grid;
+        grid-template-columns: 1fr 1fr;
+        gap: 8px;
+        margin-top: 8px;
+      }
+      @media (max-width: 980px) {
+        .layout {
+          grid-template-columns: 1fr;
+          grid-template-rows: auto 1fr;
+        }
+      }
+    </style>
+  </head>
+  <body>
+    <div class="layout">
+      <div class="panel">
+        <h1>Leaflet 3D Asset Sharing Demo</h1>
+        <div class="muted">Click map to place an object, upload asset, then share via backend link.</div>
+
+        <h2>Connection</h2>
+        <label for="apiBase">API Base URL</label>
+        <input id="apiBase" value="http://localhost:8122" />
+        <button id="applyApi">Apply API URL</button>
+
+        <h2>Auth</h2>
+        <button id="ensureKeys">Ensure Keys</button>
+        <button id="register">Register</button>
+        <button id="login">Login</button>
+        <div class="muted" id="publicKeyPreview"></div>
+
+        <h2>Collection</h2>
+        <label for="collectionName">Name</label>
+        <input id="collectionName" placeholder="3D objects" value="3D objects demo" />
+        <button id="createCollection">Create Collection</button>
+        <div class="muted">Current: <span id="collectionInfo">none</span></div>
+
+        <h2>Place + Upload Asset</h2>
+        <div class="muted">1) Click map to choose location. 2) Select file. 3) Upload and link.</div>
+        <label for="assetFile">3D/Image file</label>
+        <input id="assetFile" type="file" accept=".gltf,.glb,.jpg,.jpeg,.png,.webp" />
+        <label for="assetName">Asset name</label>
+        <input id="assetName" placeholder="Palm Tree" />
+        <label for="assetDesc">Description</label>
+        <input id="assetDesc" placeholder="Low-poly palm tree" />
+        <button id="uploadAsset">Create Feature + Upload + Link</button>
+
+        <h2>Stored Assets</h2>
+        <div id="assetsList"></div>
+
+        <div class="status" id="status"></div>
+      </div>
+      <div id="map"></div>
+    </div>
+
+    <script
+      src="https://unpkg.com/leaflet@1.9.4/dist/leaflet.js"
+      integrity="sha256-20nQCchB9co0qIjJZRGuk2/Z9VM+kNiyxNV1lvTlZBo="
+      crossorigin=""
+    ></script>
+    <script type="module" src="./leaflet-demo.js"></script>
+  </body>
+</html>
diff --git a/web/leaflet-demo.js b/web/leaflet-demo.js
new file mode 100644
index 0000000..00304b7
--- /dev/null
+++ b/web/leaflet-demo.js
@@ -0,0 +1,274 @@
+import { GeoApiClient } from "../libs/geo-api-client/dist/index.js";
+
+class BrowserStorage {
+  getItem(key) {
+    return localStorage.getItem(key);
+  }
+  setItem(key, value) {
+    localStorage.setItem(key, value);
+  }
+  removeItem(key) {
+    localStorage.removeItem(key);
+  }
+}
+
+const statusEl = document.getElementById("status");
+const apiBaseEl = document.getElementById("apiBase");
+const publicKeyPreviewEl = document.getElementById("publicKeyPreview");
+const collectionInfoEl = document.getElementById("collectionInfo");
+const collectionNameEl = document.getElementById("collectionName");
+const assetFileEl = document.getElementById("assetFile");
+const assetNameEl = document.getElementById("assetName");
+const assetDescEl = document.getElementById("assetDesc");
+const assetsListEl = document.getElementById("assetsList");
+
+let client = new GeoApiClient(apiBaseEl.value.trim(), new BrowserStorage());
+let keys = null;
+let accessToken = "";
+let collectionId = "";
+let selectedLatLng = null;
+const markers = new Map();
+
+const map = L.map("map").setView([28.4636, -16.2518], 10);
+L.tileLayer("https://tile.openstreetmap.org/{z}/{x}/{y}.png", {
+  maxZoom: 19,
+  attribution: "&copy; OpenStreetMap",
+}).addTo(map);
+
+let pendingMarker = null;
+map.on("click", (event) => {
+  selectedLatLng = event.latlng;
+  if (pendingMarker) map.removeLayer(pendingMarker);
+  pendingMarker = L.marker(event.latlng, { title: "Pending feature position" }).addTo(map);
+  setStatus(`Selected location: ${event.latlng.lat.toFixed(5)}, ${event.latlng.lng.toFixed(5)}`);
+});
+
+function setStatus(message) {
+  statusEl.textContent = message;
+}
+
+function extFromFilename(name) {
+  const idx = name.lastIndexOf(".");
+  if (idx <= 0) return "";
+  return name.slice(idx + 1).toLowerCase();
+}
+
+function kindFromExt(ext) {
+  return ext === "gltf" || ext === "glb" ? "3d" : "image";
+}
+
+async function sha256Hex(file) {
+  const buffer = await file.arrayBuffer();
+  const digest = await crypto.subtle.digest("SHA-256", buffer);
+  return Array.from(new Uint8Array(digest))
+    .map((b) => b.toString(16).padStart(2, "0"))
+    .join("");
+}
+
+function setClientBase(baseUrl) {
+  const normalized = baseUrl.trim().replace(/\/+$/g, "");
+  client = new GeoApiClient(normalized, new BrowserStorage());
+  if (accessToken) client.setAccessToken(accessToken);
+  localStorage.setItem("geo_api_base", normalized);
+  setStatus(`API base updated: ${normalized}`);
+}
+
+async function ensureKeys() {
+  keys = await client.ensureKeysInStorage();
+  publicKeyPreviewEl.textContent = `Public key: ${keys.publicKey.slice(0, 24)}...`;
+}
+
+async function register() {
+  if (!keys) await ensureKeys();
+  await client.registerBySigningServiceKey(keys.publicKey, keys.privateKey);
+}
+
+async function login() {
+  if (!keys) await ensureKeys();
+  accessToken = await client.loginWithSignature(keys.publicKey, keys.privateKey);
+  client.setAccessToken(accessToken);
+}
+
+async function ensureCollection() {
+  if (collectionId) return collectionId;
+  const created = await client.createCollection(collectionNameEl.value.trim() || "3D objects demo");
+  collectionId = created.id;
+  collectionInfoEl.textContent = `${created.name} (${created.id})`;
+  return collectionId;
+}
+
+function renderAssets(features) {
+  assetsListEl.innerHTML = "";
+  for (const feature of features) {
+    const assets = Array.isArray(feature.properties?.assets) ? feature.properties.assets : [];
+    for (const asset of assets) {
+      const card = document.createElement("div");
+      card.className = "asset-card";
+      const absoluteLink = client.resolveRelativeLink(asset.link);
+      card.innerHTML = `
+        <div><strong>${asset.kind}</strong> • ${asset.ext}</div>
+        <div class="muted">Feature: ${feature.id}</div>
+        <div class="muted">Visibility: ${asset.isPublic ? "public" : "private"}</div>
+        <div class="muted">Link: ${asset.link}</div>
+      `;
+      const actions = document.createElement("div");
+      actions.className = "asset-actions";
+
+      const openBtn = document.createElement("button");
+      openBtn.textContent = "Open";
+      openBtn.onclick = () => window.open(absoluteLink, "_blank", "noopener,noreferrer");
+      actions.appendChild(openBtn);
+
+      const toggleBtn = document.createElement("button");
+      toggleBtn.textContent = asset.isPublic ? "Set Private" : "Set Public";
+      toggleBtn.onclick = async () => {
+        try {
+          await client.setAssetVisibility(asset.id, !asset.isPublic);
+          await refreshFeatures();
+          setStatus(`Updated visibility for ${asset.id}`);
+        } catch (error) {
+          setStatus(error.message);
+        }
+      };
+      actions.appendChild(toggleBtn);
+
+      const copyBtn = document.createElement("button");
+      copyBtn.textContent = "Copy Share Link";
+      copyBtn.onclick = async () => {
+        await navigator.clipboard.writeText(absoluteLink);
+        setStatus("Share link copied to clipboard.");
+      };
+      actions.appendChild(copyBtn);
+
+      card.appendChild(actions);
+      assetsListEl.appendChild(card);
+    }
+  }
+  if (!assetsListEl.children.length) {
+    assetsListEl.innerHTML = `<div class="muted">No assets linked yet.</div>`;
+  }
+}
+
+async function refreshFeatures() {
+  if (!collectionId) return;
+  const { features } = await client.listFeatures(collectionId);
+  for (const feature of features) {
+    const coords = feature.geometry?.coordinates;
+    if (!coords || coords.length < 2) continue;
+    const lat = coords[1];
+    const lon = coords[0];
+    if (!markers.has(feature.id)) {
+      const marker = L.marker([lat, lon]).addTo(map);
+      marker.bindPopup(`Feature ${feature.id}`);
+      markers.set(feature.id, marker);
+    }
+  }
+  renderAssets(features);
+}
+
+async function createFeatureAndUpload() {
+  if (!selectedLatLng) {
+    throw new Error("Click the map to choose object location first.");
+  }
+  const file = assetFileEl.files?.[0];
+  if (!file) {
+    throw new Error("Select a 3D/image file first.");
+  }
+  const ext = extFromFilename(file.name);
+  if (!ext) {
+    throw new Error("File extension is required.");
+  }
+
+  await ensureCollection();
+  const featureName = assetNameEl.value.trim() || file.name;
+  const feature = await client.createPointFeature(
+    collectionId,
+    selectedLatLng.lng,
+    selectedLatLng.lat,
+    { name: featureName, placement: "leaflet-demo" }
+  );
+
+  const checksum = await sha256Hex(file);
+  const kind = kindFromExt(ext);
+  const created = await client.createOrLinkAsset({
+    featureId: feature.id,
+    checksum,
+    ext,
+    kind,
+    mimeType: file.type || "application/octet-stream",
+    sizeBytes: file.size,
+    name: featureName,
+    description: assetDescEl.value.trim(),
+    isPublic: true,
+  });
+  const signedUpload = await client.getAssetSignedUploadUrl(created.asset.id, file.type || "application/octet-stream");
+  const uploadRes = await fetch(signedUpload.url, {
+    method: signedUpload.method || "PUT",
+    headers: file.type ? { "Content-Type": file.type } : undefined,
+    body: file,
+  });
+  if (!uploadRes.ok) {
+    throw new Error(`Upload failed with status ${uploadRes.status}`);
+  }
+
+  await refreshFeatures();
+  assetNameEl.value = "";
+  assetDescEl.value = "";
+  assetFileEl.value = "";
+  setStatus("3D/image object stored and linked. Share link available in Stored Assets.");
+}
+
+document.getElementById("applyApi").onclick = () => {
+  setClientBase(apiBaseEl.value);
+};
+
+document.getElementById("ensureKeys").onclick = async () => {
+  try {
+    await ensureKeys();
+    setStatus("Keys are ready.");
+  } catch (error) {
+    setStatus(error.message);
+  }
+};
+
+document.getElementById("register").onclick = async () => {
+  try {
+    await register();
+    setStatus("Registered.");
+  } catch (error) {
+    setStatus(error.message);
+  }
+};
+
+document.getElementById("login").onclick = async () => {
+  try {
+    await login();
+    setStatus("Logged in.");
+  } catch (error) {
+    setStatus(error.message);
+  }
+};
+
+document.getElementById("createCollection").onclick = async () => {
+  try {
+    await ensureCollection();
+    setStatus("Collection is ready.");
+  } catch (error) {
+    setStatus(error.message);
+  }
+};
+
+document.getElementById("uploadAsset").onclick = async () => {
+  try {
+    if (!accessToken) throw new Error("Login first.");
+    await createFeatureAndUpload();
+  } catch (error) {
+    setStatus(error.message);
+  }
+};
+
+const savedBase = localStorage.getItem("geo_api_base");
+if (savedBase) {
+  apiBaseEl.value = savedBase;
+  setClientBase(savedBase);
+}