diff --git a/tizen/README.md b/tizen/README.md
index 522b984..ddc3800 100644
--- a/tizen/README.md
+++ b/tizen/README.md
@@ -31,6 +31,7 @@ config.xml          Tizen TV web-app manifest (privileges, profile, icon)
 index.html          setup / pairing / stage screens
 css/style.css
 js/app.js           device protocol client (register, pair, heartbeat, state)
+js/device-control.js Samsung B2B/system fleet control (device:command) — #125
 js/player.js        fullscreen playlist renderer
 js/socket.io.min.js socket.io-client v4.7.5 (bundled)
 icon.png
@@ -87,20 +88,31 @@ lives in `~/tizen-studio-data`, password `screentinker`).
 - **Runtime**: loads + renders in Chromium with no JS errors (setup screen verified).
 - Not yet on real Tizen hardware — needs signing + a TV (or URL Launcher).
 
-## Remote control & preview (#120 / #121)
-The Tizen player now listens for the same dashboard events as the web/Android player.
-What it can actually do depends on what a **sideloaded web app** is allowed to do on
-the TV runtime:
+## Remote control & preview (#120 / #121 / #125)
+The Tizen player listens for the same dashboard events as the web/Android player.
+`device:command` is handled by `js/device-control.js`, which drives the real Samsung
+fleet-control surface (`webapis.systemcontrol` on Tizen 6.5/7, else `b2bapis.b2bcontrol`
+on SSSP/Tizen 4) and reports each outcome back via `device:log` (tag `command`, shown
+live on the device-detail screen) plus a structured `device:command-result`:
 
-| Command (`device:command` type)   | Tizen behaviour                                            |
-|-----------------------------------|-----------------------------------------------------------|
-| `refresh`                         | `location.reload()`                                       |
-| `launch` / `screen_on`            | clears the screen-off overlay + re-requests screen-awake  |
-| `screen_off`                      | black full-screen overlay (content keeps running behind)  |
-| `update`                          | toast: must re-install the `.wgt` (see **Updates** below) |
-| `reboot` / `shutdown`             | MDM-only — not reachable from a sideloaded app (toast)    |
-| `device:screenshot-request`       | best-effort capture (see note)                            |
-| `device:remote-start` / `-stop`   | start/stop ~1 fps preview streaming                       |
+| Command (`device:command` type)   | Tizen behaviour                                                        |
+|-----------------------------------|------------------------------------------------------------------------|
+| `refresh` / `reload`              | `location.reload()`                                                    |
+| `launch` / `screen_on`            | clears the screen-off overlay + re-asserts wake; `setPanelMute("OFF")` when the B2B surface is present |
+| `screen_off`                      | `setPanelMute("ON")` (backlight off) on a B2B panel; **black overlay fallback** otherwise |
+| `update`                          | reload to re-pull URL-Launcher content (no in-app OTA — see **Updates**) |
+| `reboot`                          | `rebootDevice()` on a B2B panel; `unsupported` otherwise               |
+| `shutdown`                        | `setPanelMute("ON")` + note (SSSP web API has no true power-off)        |
+| _unknown_                         | reported as `unsupported`                                              |
+| `device:screenshot-request`       | best-effort capture (see note)                                         |
+| `device:remote-start` / `-stop`   | start/stop ~1 fps preview streaming                                    |
+
+> **Partner-signing caveat (#125):** the `b2bcontrol` / `systemcontrol` privileges in
+> `config.xml` only take effect on a **partner-signed `.wgt` on a real SSSP panel**. On
+> the dev/URL-Launcher/web build (or a consumer TV) those surfaces are absent, so reboot
+> returns `unsupported`, `screen_off` uses the black overlay, and the startup capability
+> log reports `backend=none`. Only a partner-signed build on real hardware fully
+> validates reboot / panel power.
 
 > **Screenshot/preview note:** the TV decodes `<video>` onto a hardware overlay plane
 > and plays YouTube in a cross-origin `<iframe>`, neither of which can be read back into
@@ -108,10 +120,6 @@ the TV runtime:
 > (device + timestamp). The dashboard preview shows a truthful frame rather than a dead
 > button. Full-fidelity video preview isn't feasible on the sideloaded Tizen runtime.
 
-> **`screen_off`** uses an overlay, not a real panel power-off — a sideloaded app has no
-> clean panel-power API. On B2B/MDM (SSSP) firmware, true power and `reboot`/`shutdown`
-> go through Samsung's device-management channel, not this app.
-
 ## Updates (#122)
 There is **no in-app OTA** for a sideloaded, signed `.wgt`. Updating a screen means
 **re-building and re-sideloading** the `.wgt` (path B above), or — on Samsung B2B
diff --git a/tizen/config.xml b/tizen/config.xml
index c1f1918..b108f8f 100644
--- a/tizen/config.xml
+++ b/tizen/config.xml
@@ -24,4 +24,13 @@
     <tizen:privilege name="http://tizen.org/privilege/application.launch"/>
     <tizen:privilege name="http://tizen.org/privilege/display"/>
     <tizen:privilege name="http://developer.samsung.com/privilege/network.public"/>
+
+    <!-- #125: Samsung B2B fleet control (reboot / panel power via b2bcontrol /
+         systemcontrol). These are PARTNER-level privileges: they only take effect
+         when the .wgt is signed with a Samsung Partner distributor certificate on a
+         real SSSP panel. On unsigned / URL-Launcher / web / consumer-TV builds they
+         are ignored (not fatal) — the APIs are simply absent and device-control.js
+         reports "unsupported". -->
+    <tizen:privilege name="http://developer.samsung.com/privilege/b2bcontrol"/>
+    <tizen:privilege name="http://developer.samsung.com/privilege/systemcontrol"/>
 </widget>
diff --git a/tizen/index.html b/tizen/index.html
index 1885fb7..6c18194 100644
--- a/tizen/index.html
+++ b/tizen/index.html
@@ -38,9 +38,15 @@
     <!-- Tiny on-screen status (offline / errors), auto-hides -->
     <div id="toast" class="toast hidden"></div>
 
+    <!-- #125: Samsung device-API bridges. $WEBAPIS / $B2BAPIS are resolved by the
+         Tizen platform at runtime; off-hardware (browser / URL Launcher) these 404
+         harmlessly and the surfaces are simply absent. -->
+    <script src="$WEBAPIS/webapis/webapis.js"></script>
+    <script src="$B2BAPIS/b2bapis/b2bapis.js"></script>
     <script src="js/socket.io.min.js"></script>
     <script src="js/schedule-eval.js"></script>
     <script src="js/player.js"></script>
+    <script src="js/device-control.js"></script>
     <script src="js/app.js"></script>
 </body>
 </html>
diff --git a/tizen/js/app.js b/tizen/js/app.js
index 6b2088d..c48e685 100644
--- a/tizen/js/app.js
+++ b/tizen/js/app.js
@@ -167,6 +167,7 @@
       authenticated = true; // #118: this socket may now send post-register events
       clearToast();         // #118: drop any stale "Not authenticated…" banner
       startHeartbeat();
+      reportCapabilities(); // #125: surface the fleet-control backend to the dashboard
       if (data.status === 'provisioning') showPairing();
     });
 
@@ -195,36 +196,41 @@
 
     socket.on('device:playlist-update', onPlaylist);
 
-    // ---- remote control from the dashboard (#120 / #121) ----
+    // ---- remote control from the dashboard (#120 / #121 / #125) ----
     // Mirror the web/Android player. The server emits device:command with the set in
     // server/routes/device-groups.js (ALLOWED_COMMANDS) plus 'refresh', and the
     // screenshot/remote events below. (The old device:reload listener was dead — the
     // server never emits it — so 'refresh' replaces it.)
+    //
+    // #125: reboot / screen power / shutdown now go through STDeviceControl, which
+    // drives the real Samsung b2bcontrol/systemcontrol surface on a partner-signed
+    // panel. Where that surface is absent (web / URL-Launcher / consumer TV), it
+    // resolves { supported:false } and we fall back to the local black overlay for
+    // screen_off so the command still does something visible.
     socket.on('device:command', function (data) {
-      switch (data && data.type) {
-        case 'refresh':
-          location.reload();
-          break;
-        case 'launch':
-        case 'screen_on':
-          clearScreenOff();
-          keepAwake();
-          break;
-        case 'screen_off':
+      var type = (data && data.type) ? String(data.type).toLowerCase() : '';
+      var payload = (data && data.payload) ? data.payload : null;
+      if (!type) return;
+
+      // "Wake" intents always clear any black overlay and re-assert screen-awake,
+      // independent of (and in addition to) the panel API.
+      if (type === 'screen_on' || type === 'launch') { clearScreenOff(); keepAwake(); }
+
+      if (!window.STDeviceControl) { reportCmd('error', type, 'device-control unavailable'); return; }
+      STDeviceControl.run(type, payload).then(function (res) {
+        var note = res.note;
+        // No real panel-power surface: keep the pre-#125 behaviour — a black overlay
+        // (content keeps running behind it) — so screen_off isn't a silent no-op.
+        if (type === 'screen_off' && res.supported === false) {
           showScreenOff();
-          break;
-        case 'update':
-          // #122: a sideloaded, signed .wgt has no in-app OTA path. Surface it rather
-          // than dropping it silently — real updates are a re-sideload / B2B-MDM push.
-          toast('Update must be re-installed (.wgt sideload / MDM)', false);
-          break;
-        case 'reboot':
-        case 'shutdown':
-          tryPowerControl(data.type);
-          break;
-        default:
-          break;
-      }
+          res = { ok: true, supported: true, reload: false };
+          note = 'no panel API — black overlay fallback';
+        }
+        var level = res.ok ? 'info' : (res.supported === false ? 'warn' : 'error');
+        reportCmd(level, type, note || (res.ok ? 'ok' : 'failed'));
+        // Delay the reload so the log/result emit reaches the server first.
+        if (res.reload) setTimeout(function () { location.reload(); }, 1200);
+      });
     });
 
     // #120: dashboard preview — single shot and start/stop streaming.
@@ -279,11 +285,28 @@
     var o = document.getElementById('screenOffOverlay');
     if (o && o.parentNode) o.parentNode.removeChild(o);
   }
-  // #121: reboot/shutdown need privileged B2B/MDM control that a sideloaded web app
-  // does not have. Signage firmware exposes these via the Samsung B2B (b2bapis) API,
-  // whose methods vary by firmware — so document it rather than failing silently.
-  function tryPowerControl(type) {
-    toast(type + ' is MDM-only on Tizen (see tizen/README.md)', false);
+  // #125: report a command outcome to the dashboard. device:log surfaces live as
+  // dashboard:device-log on the open device-detail screen; device:command-result is
+  // a structured echo (harmless if the server doesn't handle it).
+  function reportCmd(level, type, msg) {
+    var message = '[' + type + '] ' + msg;
+    try {
+      if (socket && deviceId) {
+        socket.emit('device:log', { device_id: deviceId, tag: 'command', level: level, message: message });
+        socket.emit('device:command-result', { device_id: deviceId, type: type, level: level, message: msg });
+      }
+    } catch (e) {}
+  }
+
+  // #125: log the panel's control surface at startup so the dashboard shows whether
+  // fleet control is actually wired (backend "none" on web / consumer TV / unsigned).
+  function reportCapabilities() {
+    try {
+      var caps = (window.STDeviceControl && STDeviceControl.capabilities)
+        ? STDeviceControl.capabilities() : { backend: 'none', reboot: false, panel: false };
+      reportCmd('info', 'capabilities',
+        'fleet control backend=' + caps.backend + ' reboot=' + caps.reboot + ' panel=' + caps.panel);
+    } catch (e) {}
   }
 
   // #120: best-effort dashboard preview. The Tizen TV runtime decodes <video> onto a
diff --git a/tizen/js/device-control.js b/tizen/js/device-control.js
new file mode 100644
index 0000000..6c06c23
--- /dev/null
+++ b/tizen/js/device-control.js
@@ -0,0 +1,192 @@
+/* ScreenTinker — Tizen/Samsung fleet control (#125).
+ *
+ * Wraps the two Samsung panel-control surfaces behind one Promise-based API so the
+ * player can act on device:command (reboot / screen_off / screen_on / shutdown /
+ * update / launch) at parity with the Android player.
+ *
+ * Surfaces, newest first:
+ *   - Tizen 6.5/7  webapis.systemcontrol.*   — synchronous, throws on error
+ *   - SSSP/Tizen 4 b2bapis.b2bcontrol.*      — async onSuccess/onError callbacks
+ * Both are normalised to Promises. Each surface is re-probed on every call because
+ * the platform can inject these objects late (after the page's first script pass).
+ *
+ * IMPORTANT: these B2B/system APIs only take effect on a Samsung panel running a
+ * .wgt signed with a Samsung *Partner* distributor cert (see config.xml + README).
+ * On the unsigned dev build, the URL-Launcher/web build, or a consumer TV, the
+ * surfaces are absent and run() resolves { supported:false } — never throws.
+ *
+ * Exposes: window.STDeviceControl = { run, capabilities, backend }.
+ */
+(function () {
+  'use strict';
+
+  var TAG = 'STDeviceControl';
+  function log(msg) { try { console.log('[' + TAG + '] ' + msg); } catch (e) {} }
+
+  // ---- surface probes (fresh each call; APIs can be injected late) ----
+  function sysctl() {
+    try { return (window.webapis && webapis.systemcontrol) ? webapis.systemcontrol : null; }
+    catch (e) { return null; }
+  }
+  function b2b() {
+    try { return (window.b2bapis && b2bapis.b2bcontrol) ? b2bapis.b2bcontrol : null; }
+    catch (e) { return null; }
+  }
+
+  // Active backend, newest first; 'none' on web / consumer TV / unsigned build.
+  function backend() {
+    if (sysctl()) return 'systemcontrol';
+    if (b2b()) return 'b2bcontrol';
+    return 'none';
+  }
+
+  function errMsg(e) {
+    if (!e) return 'unknown error';
+    if (typeof e === 'string') return e;
+    return e.message || e.name || (e.code != null ? ('code ' + e.code) : 'error');
+  }
+
+  // Is `method` present on either surface (systemcontrol checked first)?
+  function methodExists(method) {
+    var sc = sysctl(); if (sc && typeof sc[method] === 'function') return true;
+    var bb = b2b(); if (bb && typeof bb[method] === 'function') return true;
+    return false;
+  }
+
+  // Call `method` with `args` on whichever surface exposes it, normalised to a
+  // Promise. systemcontrol is synchronous (resolve on return / reject on throw);
+  // b2bcontrol appends (onSuccess, onError) callbacks.
+  function call(method, args) {
+    args = args || [];
+    return new Promise(function (resolve, reject) {
+      var sc = sysctl();
+      if (sc && typeof sc[method] === 'function') {
+        try { resolve(sc[method].apply(sc, args)); }
+        catch (e) { reject(e); }
+        return;
+      }
+      var bb = b2b();
+      if (bb && typeof bb[method] === 'function') {
+        try {
+          bb[method].apply(bb, args.concat([
+            function (res) { resolve(res); },
+            function (err) { reject(err); }
+          ]));
+        } catch (e) { reject(e); }
+        return;
+      }
+      reject(new Error('method ' + method + ' not available on backend ' + backend()));
+    });
+  }
+
+  // Panel power across firmware variants. setPanelMute is the modern surface
+  // (mute ON == backlight OFF — inverted vs `on`); older firmware exposes
+  // setDisplayPanel / setPanelStatus instead. Picks the first method that EXISTS
+  // (a present-but-failing method is a real error, surfaced as-is); if none of
+  // them exist the returned promise rejects with { unsupported:true }.
+  function panelPower(on) {
+    var candidates = [
+      ['setPanelMute', [on ? 'OFF' : 'ON']],
+      ['setDisplayPanel', [!!on]],
+      ['setPanelStatus', [!!on]]
+    ];
+    for (var i = 0; i < candidates.length; i++) {
+      var method = candidates[i][0];
+      if (methodExists(method)) {
+        return call(method, candidates[i][1]).then((function (m) {
+          return function (res) { return { method: m, result: res }; };
+        })(method));
+      }
+    }
+    return Promise.reject({ unsupported: true });
+  }
+
+  // Uniform result shape — run() always resolves to one of these.
+  function result(o) {
+    return {
+      ok: !!o.ok,
+      supported: o.supported !== false,
+      action: o.action || null,
+      note: o.note || null,
+      reload: !!o.reload
+    };
+  }
+
+  function panelUnsupportedOr(e, action, unsupportedNote) {
+    if (e && e.unsupported) {
+      return result({ ok: false, supported: false, action: action,
+        note: unsupportedNote || ('no panel-power API on this surface (' + backend() + ')') });
+    }
+    return result({ ok: false, action: action, note: action + ' failed: ' + errMsg(e) });
+  }
+
+  // run(type, payload): lowercases type, NEVER rejects, always resolves to a result.
+  function run(type, payload) {
+    type = String(type || '').toLowerCase();
+    try {
+      switch (type) {
+        case 'reboot':
+          if (!methodExists('rebootDevice')) {
+            log('reboot: no rebootDevice on backend ' + backend());
+            return Promise.resolve(result({ ok: false, supported: false, action: 'reboot',
+              note: 'no reboot API on this surface (' + backend() + ')' }));
+          }
+          return call('rebootDevice', [])
+            .then(function () { return result({ ok: true, action: 'reboot', note: 'rebootDevice() issued' }); })
+            .catch(function (e) { return result({ ok: false, action: 'reboot', note: 'rebootDevice failed: ' + errMsg(e) }); });
+
+        case 'screen_off':
+          return panelPower(false)
+            .then(function (r) { return result({ ok: true, action: 'screen_off', note: 'panel backlight off via ' + r.method }); })
+            .catch(function (e) { return panelUnsupportedOr(e, 'screen_off'); });
+
+        case 'screen_on':
+          return panelPower(true)
+            .then(function (r) { return result({ ok: true, action: 'screen_on', note: 'panel backlight on via ' + r.method }); })
+            .catch(function (e) { return panelUnsupportedOr(e, 'screen_on'); });
+
+        case 'shutdown':
+          // SSSP/Tizen web APIs have no true power-off; the closest honest action is
+          // muting the panel (backlight off). Report that it's not a real shutdown.
+          return panelPower(false)
+            .then(function (r) { return result({ ok: true, action: 'shutdown',
+              note: 'no true power-off on SSSP web API — panel backlight off via ' + r.method }); })
+            .catch(function (e) { return panelUnsupportedOr(e, 'shutdown',
+              'no true power-off on SSSP web API and no panel-mute surface available'); });
+
+        case 'update':
+          // No in-app OTA for a sideloaded / URL-Launcher build; reloading re-pulls
+          // the latest URL-Launcher content (app.js performs the reload).
+          return Promise.resolve(result({ ok: true, action: 'update', reload: true,
+            note: 'reloading to re-pull URL-Launcher content (no in-app OTA)' }));
+
+        case 'launch':
+          // Already the foreground app — nothing to launch.
+          log('launch: no-op (already foreground)');
+          return Promise.resolve(result({ ok: true, action: 'launch', note: 'already foreground (no-op)' }));
+
+        case 'reload':
+        case 'refresh':
+          return Promise.resolve(result({ ok: true, action: type, reload: true, note: 'reload requested' }));
+
+        default:
+          log('unknown command: ' + type);
+          return Promise.resolve(result({ ok: false, supported: false, action: type, note: 'unknown command' }));
+      }
+    } catch (e) {
+      return Promise.resolve(result({ ok: false, action: type, note: 'exception: ' + errMsg(e) }));
+    }
+  }
+
+  // Snapshot for a startup log: which surface, and whether reboot/panel are present.
+  function capabilities() {
+    return {
+      backend: backend(),
+      reboot: methodExists('rebootDevice'),
+      panel: methodExists('setPanelMute') || methodExists('setDisplayPanel') || methodExists('setPanelStatus')
+    };
+  }
+
+  window.STDeviceControl = { run: run, capabilities: capabilities, backend: backend };
+  log('loaded (backend=' + backend() + ')');
+})();