diff --git a/PLAN.md b/PLAN.md
index 21155bd..022b1b5 100644
--- a/PLAN.md
+++ b/PLAN.md
@@ -1482,44 +1482,44 @@ must be fixed, redeployed uncommitted, and the affected in-car test repeated bef
 and **ready-to-install** sign-off. Afterward, the owner handles permanent installation outside the
 phase roadmap.
 
-### Phase 25.5: Device profile & configuration sync — 🚧 PLANNED (local config mgmt)
-**Unstarted.** Replace hardcoded `account.name`, `car.model`, and avatar with managed configuration editable on the server and synced to the Pi. Enables multi-device/multi-user scenarios and eliminates manual code edits.
+### Phase 25.5: Device profile & configuration sync — 🚧 IN PROGRESS (config file + server sync planning)
+**Config file implemented; server sync planned.** Replace hardcoded values with `config/device.json`, editable by users without code changes. Server sync is eventual-consistency, connection-driven (not time-driven) to handle offline-first car scenarios.
 
-#### Scope
+#### Current state (implemented)
+- **`config/device.json`** (new): stores device identity fields:
+  - `owner_name`: "quoije" (displayed in topbar, replaces `account.name` hardcode)
+  - `car_model`: "Yaris 2013" (displayed in sidebar, replaces `car.model` hardcode)
+  - `device_name`: "Yaris OBD" (displayed on portal, not yet used on Pi)
+  - `avatar_path`: "img/yaris.png" (sourced by template, replaces hardcoded path)
+- **Code changes**:
+  - `modules/app_account.py`: loads `owner_name`, `avatar_path` from JSON on startup with fallback to hardcoded defaults
+  - `modules/app_car.py`: loads `car_model`, `device_name` from JSON on startup with fallback to hardcoded defaults
+  - `templates/base.html`: avatar image now sources from `account.avatar_path` (loaded from config) instead of hardcoded path
+- **Offline-first design**: All values loaded from local JSON at startup; no network required to boot with customized identity. Server sync is *eventual*, not critical.
+
+#### Future scope (Phase 25.5a+)
 - **Server-side config editor**: add a simple "Device Settings" page on the remote portal (login-protected, device-scoped) with editable fields:
-  - Device nickname (device_name, for display on the portal and Pi topbar)
-  - Car model/year (already in DB via Phase 24's `device_id` + `car_model`, but allow user override)
-  - Profile picture upload (stored server-side, served to both portal and Pi via API endpoint)
-  - Owner name / username (replaces hardcoded `account.name`)
-- **Pi-side config sync**: 
-  - Add a new `device_config` table to local SQLite (device_name, owner_name, car_model, avatar_url, sync_timestamp, hash)
-  - On Pi startup and every 30 minutes, fetch the latest config from the remote server via a new `/api/device-config` endpoint (authenticated with device_key, not user login)
-  - If hash differs, update local config table and restart the web app (or hot-reload via settings API)
-  - Fall back gracefully to hardcoded defaults if server is unreachable
-- **UI updates**:
-  - Pi topbar shows the synced `device_name` instead of hardcoded car model (or car model from synced config)
-  - Pi sidebar shows the synced owner_name instead of hardcoded `account.name`
-  - Avatar image sourced from synced `avatar_url` (served from server, fallback to local placeholder)
-  - All trip/tracking records use synced values at capture time (no retroactive changes to history)
-- **Device authentication**: use an existing `device_key` (generated on first Pi provisioning, stored in `/home/yaris/app/yaris-obd/.device-key` or env var) to authenticate the `/api/device-config` request. Server validates device_key against the Postgres `devices` table.
-
-#### Implementation phases
-1. **Server (Phase 25.5a)**: add `device_name`, `owner_name`, `avatar_blob` columns to Postgres `devices` table; create `/api/device-config` read endpoint and `/api/device-config` POST endpoint for edits; add Settings UI to portal for these fields.
-2. **Pi config table & sync (Phase 25.5b)**: add `device_config` SQLite table; implement 30-min sync fetch on Pi; hot-update app globals if config changes.
-3. **UI updates (Phase 25.5c)**: update topbar, sidebar, avatar rendering to use synced config; test full cycle (edit on server → Pi syncs → UI reflects change).
-4. **Acceptance (Phase 25.5d)**: multi-sync cycle test, network loss recovery, avatar upload/display, retroactive trip behavior.
+  - Device nickname (device_name)
+  - Car model/year (car_model)
+  - Profile picture upload (avatar stored on server)
+  - Owner name / username (owner_name)
+- **Pi-side sync** (connectivity-driven, not time-driven):
+  - Pi syncs config from server **only when internet is available** (when cellular/WiFi connects), not on a fixed 30-min timer
+  - Server-side changes → Pi receives on next connectivity event → updates `config/device.json` → restarts web app or hot-reloads globals
+  - If server unreachable, Pi continues with last-synced config from local JSON (already loaded at startup)
+- **Device authentication**: use an existing `device_key` to authenticate `/api/device-config` requests, validated server-side against Postgres `devices` table.
 
 #### Benefits
-- No code edit needed to rebrand a deployed Pi
-- Server becomes the source of truth for device identity (enables future multi-Pi/multi-car scenarios)
-- Avatar management centralized
-- Graceful fallback if server unavailable (Pi uses last-synced config)
-- Enables future features: device rename, device status on portal, bulk config across devices
+- ✅ No code edit needed to customize deployed Pi (today: edit JSON file manually)
+- ✅ Offline-first: Pi boots with identity immediately, no network dependency
+- ✅ Connection-driven sync: sync happens when internet available, not wasting resources on offline car
+- 🚧 Server becomes source of truth (after Phase 25.5a)
+- 🚧 Enables multi-Pi/multi-car scenarios (after Phase 25.5a)
 
 #### Trade-offs
-- Adds config sync complexity and latency (eventual consistency)
-- Requires device authentication key rotation strategy (future)
-- Metadata storage (avatar blob) requires server-side image handling
+- Sync is eventual-consistency (changes on server may take hours to reach offline car)
+- Manual JSON edit required today (before Phase 25.5a server UI is built)
+- Avatar must be placed in `static/img/` directory (no upload yet)
 
 ---
 
diff --git a/config/device.json b/config/device.json
new file mode 100644
index 0000000..03b728c
--- /dev/null
+++ b/config/device.json
@@ -0,0 +1,6 @@
+{
+  "owner_name": "quoije",
+  "car_model": "Yaris 2013",
+  "device_name": "Yaris OBD",
+  "avatar_path": "img/yaris.png"
+}
diff --git a/deploy/readme.md b/deploy/readme.md
index 23a87d4..23495ed 100644
--- a/deploy/readme.md
+++ b/deploy/readme.md
@@ -179,6 +179,40 @@ Then test from another device:
 - `http://yaris.local`
 - if mDNS is not available on that client, try `http://10.42.0.1`
 
+## Customizing device identity
+
+The Pi displays a username, car model, device name, and avatar image. Instead of editing Python code, edit `config/device.json`:
+
+```bash
+nano /home/yaris/app/yaris-obd/config/device.json
+```
+
+**Example `config/device.json`:**
+
+```json
+{
+  "owner_name": "Your Name",
+  "car_model": "Toyota Yaris 2013",
+  "device_name": "My Yaris OBD",
+  "avatar_path": "img/yaris.png"
+}
+```
+
+- **`owner_name`**: Displayed in topbar (top-right corner of the web UI)
+- **`car_model`**: Displayed in sidebar (left panel, appears next to car icon)
+- **`device_name`**: Reserved for server-side display (Phase 25.5 feature, not yet used)
+- **`avatar_path`**: Avatar image shown in topbar; must exist in `static/img/` (replace `static/img/yaris.png` with your own image, or point to a different file)
+
+After editing, restart the app:
+
+```bash
+sudo systemctl restart yaris-obd.service
+```
+
+**Important**: The SQLite database filename is based on the username. If you change `owner_name` and restart, a new database will be created and the old data will be orphaned at `db/sql/quoije_Yaris2013.db`. Either:
+- Rename the old database file to match the new username, or
+- Delete the old database if you want a fresh start
+
 ## 7) Updating later
 
 ```bash
diff --git a/modules/app_account.py b/modules/app_account.py
index 3c83d51..0ccb15d 100644
--- a/modules/app_account.py
+++ b/modules/app_account.py
@@ -1,5 +1,22 @@
+import json
+import os
+
 class Account:
     def __init__(self):
-        self.name = "quoije"
+        # Load from config/device.json if available, else use defaults
+        config = self._load_config()
+        self.name = config.get("owner_name", "quoije")
+        self.avatar_path = config.get("avatar_path", "img/yaris.png")
         self.pp_image = None
-        self.car = None 
\ No newline at end of file
+        self.car = None
+    
+    def _load_config(self):
+        """Load device config from JSON file, return dict with defaults."""
+        config_path = os.path.join(os.path.dirname(os.path.dirname(__file__)), "config", "device.json")
+        try:
+            if os.path.exists(config_path):
+                with open(config_path, 'r') as f:
+                    return json.load(f)
+        except (IOError, json.JSONDecodeError):
+            pass
+        return {}
\ No newline at end of file
diff --git a/modules/app_car.py b/modules/app_car.py
index 892f8fe..e8b9dfd 100644
--- a/modules/app_car.py
+++ b/modules/app_car.py
@@ -1,4 +1,21 @@
+import json
+import os
+
 class Car:
     def __init__(self):
-        self.model = "Yaris 2013"
-        self.obd = None
\ No newline at end of file
+        # Load from config/device.json if available, else use defaults
+        config = self._load_config()
+        self.model = config.get("car_model", "Yaris 2013")
+        self.device_name = config.get("device_name", "Yaris OBD")
+        self.obd = None
+    
+    def _load_config(self):
+        """Load device config from JSON file, return dict with defaults."""
+        config_path = os.path.join(os.path.dirname(os.path.dirname(__file__)), "config", "device.json")
+        try:
+            if os.path.exists(config_path):
+                with open(config_path, 'r') as f:
+                    return json.load(f)
+        except (IOError, json.JSONDecodeError):
+            pass
+        return {}
\ No newline at end of file
diff --git a/readme.md b/readme.md
index ce2f27f..c4b0608 100644
--- a/readme.md
+++ b/readme.md
@@ -114,33 +114,70 @@ in [deploy/](./deploy). For a clean-install walkthrough on a fresh Pi, use
 
 For the remote server (receives trip logs + dashcam uploads), see [server/README.md](./server/README.md).
 
-## Customizing username and profile picture
+## Customizing device identity
 
-The top-right username and avatar in the local app are currently code-configured.
+The Pi displays a username, car model, and avatar image. All customizable values are stored in `config/device.json` (no code edits needed).
 
-### Change username
+### Edit device configuration
 
-Edit [modules/app_account.py](./modules/app_account.py):
+Edit [config/device.json](./config/device.json):
 
-```python
-self.name = "quoije"
+```json
+{
+  "owner_name": "quoije",
+  "car_model": "Yaris 2013",
+  "device_name": "Yaris OBD",
+  "avatar_path": "img/yaris.png"
+}
 ```
 
-Set it to your preferred name, then restart the app/service.
+| Field | Location | Purpose |
+|-------|----------|---------|
+| `owner_name` | Top-right of app topbar | Your name/username |
+| `car_model` | Left sidebar (next to car icon) | Vehicle model/year |
+| `device_name` | (Reserved) | Future server-side use in Phase 25.5 |
+| `avatar_path` | Top-right avatar circle | Profile picture (relative to `static/`) |
 
-> Important: `account.name` is also used in the local SQLite filename (`db/sql/<name>_<car>.db` via [modules/app_sql.py](./modules/app_sql.py)).  
-> If you already have trip data and change the name, the app will create a new DB file unless you rename/migrate the existing one.
+After editing, restart the app:
 
-### Change profile picture
+```bash
+# If running as a systemd service:
+sudo systemctl restart yaris-obd.service
 
-Current avatar is hardcoded in [templates/base.html](./templates/base.html) to:
-
-```html
-src="{{ url_for('static', filename='img/yaris.png') }}"
+# If running manually:
+# Ctrl+C and python3 app.py
 ```
 
-Simplest option: replace [static/img/yaris.png](./static/img/yaris.png) with your image (same filename/path).  
-Alternative: edit the `filename='img/yaris.png'` value in [templates/base.html](./templates/base.html).
+### Changing the profile picture
+
+Option 1: Replace the default image file:
+```bash
+cp /path/to/your/image.png static/img/yaris.png
+```
+
+Option 2: Add your image to `static/img/` and update `avatar_path`:
+```json
+{
+  "avatar_path": "img/my-avatar.png"
+}
+```
+
+### Important: Username and database filename
+
+The local SQLite database filename is based on `owner_name`: `db/sql/<owner_name>_<car_model>.db` (via [modules/app_sql.py](./modules/app_sql.py)).
+
+If you **change `owner_name`** and already have trip data:
+- The app will create a **new database** with the new name
+- Your old database remains at `db/sql/quoije_Yaris2013.db` (orphaned)
+
+To preserve your data:
+```bash
+# Option 1: Rename the database file
+mv db/sql/quoije_Yaris2013.db "db/sql/YourName_YourCar.db"
+
+# Option 2: Start fresh
+rm db/sql/quoije_Yaris2013.db
+```
 
 ## Project status
 
diff --git a/templates/base.html b/templates/base.html
index 376d92d..ef35c15 100644
--- a/templates/base.html
+++ b/templates/base.html
@@ -79,7 +79,7 @@
                     </div>
                     <span class="text-muted small d-none d-sm-inline">{{ account.name }}</span>
                     <img class="rounded-circle border" style="width:2rem;height:2rem;object-fit:cover;"
-                         src="{{ url_for('static', filename='img/yaris.png') }}" alt="">
+                         src="{{ url_for('static', filename=account.avatar_path) }}" alt="">
                 </div>
             </div>
         </nav>