diff --git a/server/server.js b/server/server.js
index 6410459..36daf76 100644
--- a/server/server.js
+++ b/server/server.js
@@ -431,9 +431,19 @@ app.get('/api/devices/:id/screenshot', (req, res) => {
     return res.status(401).json({ error: 'Invalid or expired token' });
   }
   const { db: sdb } = require('./db/database');
-  const device = sdb.prepare('SELECT user_id FROM devices WHERE id = ?').get(req.params.id);
+  const device = sdb.prepare('SELECT user_id, workspace_id FROM devices WHERE id = ?').get(req.params.id);
   if (!device) return res.status(404).json({ error: 'Device not found' });
-  if (!['admin','superadmin'].includes(user.role) && device.user_id && device.user_id !== user.id) return res.status(403).json({ error: 'Access denied' });
+  // Authorize on the DEVICE'S WORKSPACE, the same way routes/devices.js does. The previous
+  // test was pre-tenancy (`device.user_id !== user.id`) with a role bypass listing
+  // 'admin'/'superadmin', which had three problems: it short-circuited on `device.user_id &&`
+  // so a device with NO owner was readable by any authenticated account (an unpaired panel
+  // displays its pairing code, so that image is also a claim vector); it omitted
+  // 'platform_admin', the name #14 migrated 'superadmin' to, so real platform admins were
+  // denied; and it denied workspace members who administer the device everywhere else.
+  // accessContext covers direct membership, org-level access and platform staff in one call.
+  if (!device.workspace_id) return res.status(403).json({ error: 'Access denied' });
+  const ws = sdb.prepare('SELECT * FROM workspaces WHERE id = ?').get(device.workspace_id);
+  if (!ws || !accessContext(user.id, user.role, ws)) return res.status(403).json({ error: 'Access denied' });
   // Serve from memory if available (device online), otherwise from disk (offline snapshot)
   const deviceSocket = require('./ws/deviceSocket');
   const memScreenshot = deviceSocket.lastScreenshots?.[req.params.id];
@@ -555,7 +565,7 @@ app.get('/api/content/:id/thumbnail', (req, res) => {
 // req.isPlatformAdmin, req.actingAs. Route handlers in 2.1 don't read these
 // yet (they still filter by user_id); 2.2 will migrate them one route at a time.
 const { requireAuth } = require('./middleware/auth');
-const { resolveTenancy } = require('./lib/tenancy');
+const { resolveTenancy, accessContext } = require('./lib/tenancy');
 // Public API token front door (Phase 1). Attached ONLY to the public routers below.
 const { bearerAuth, tokenScopeGate, agencyGate } = require('./middleware/apiToken');
 
diff --git a/server/test/screenshot-authorization.test.js b/server/test/screenshot-authorization.test.js
new file mode 100644
index 0000000..a2f9238
--- /dev/null
+++ b/server/test/screenshot-authorization.test.js
@@ -0,0 +1,125 @@
+'use strict';
+
+// GET /api/devices/:id/screenshot returns a live picture of what a screen is showing, so
+// it must be authorised the same way every other device route is: by the caller's access
+// to the DEVICE'S WORKSPACE.
+//
+// It instead used a pre-tenancy ownership test — `device.user_id !== user.id`, with an
+// elevated-role bypass listing 'admin'/'superadmin'. Three consequences this pins:
+//
+//   1. `device.user_id &&` SHORT-CIRCUITS. A device with no user_id (never paired, or its
+//      owner was deleted) skips the ownership test entirely, so ANY authenticated user on
+//      the instance can read it. An unpaired panel displays its pairing code on screen,
+//      so that image is also a route to claiming the device (see AUTH-10).
+//   2. platform_admin is NOT in the bypass list. The #14 migration renamed superadmin ->
+//      platform_admin, so a real platform admin falls through to the ownership test and is
+//      denied unless they happen to own the row.
+//   3. Workspace members other than the owner are denied a device they can otherwise fully
+//      administer through every other endpoint.
+
+const { test, before, after } = require('node:test');
+const assert = require('node:assert/strict');
+const { spawn } = require('node:child_process');
+const path = require('node:path');
+const os = require('node:os');
+const fs = require('node:fs');
+const crypto = require('node:crypto');
+const Database = require('better-sqlite3');
+
+const { freePort } = require('./helpers/free-port');
+let PORT, BASE, proc, db;
+const DATA_DIR = path.join(os.tmpdir(), 'st-shot-test-' + crypto.randomBytes(4).toString('hex'));
+const LOG = path.join(os.tmpdir(), 'st-shot-' + crypto.randomBytes(4).toString('hex') + '.log');
+const PW = 'Passw0rd123';
+const S = {};
+
+const jfetch = async (p, opts = {}) => {
+  const res = await fetch(BASE + p, opts);
+  let body = null; try { body = await res.json(); } catch { /* binary/none */ }
+  return { status: res.status, body };
+};
+const post = (obj) => ({ method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify(obj) });
+const shot = (deviceId, token) => fetch(`${BASE}/api/devices/${deviceId}/screenshot`, { headers: { Authorization: 'Bearer ' + token } });
+
+async function register() {
+  const email = 'u' + crypto.randomBytes(5).toString('hex') + '@x.local';
+  const r = await jfetch('/api/auth/register', post({ email, password: PW }));
+  return { email, token: r.body.token, id: r.body.user.id, role: r.body.user.role };
+}
+
+// Give a device a screenshot on disk so a permitted caller gets a real 200.
+function seedScreenshot(deviceId) {
+  const file = `${deviceId}_latest.jpg`;
+  fs.mkdirSync(path.join(DATA_DIR, 'uploads', 'screenshots'), { recursive: true });
+  fs.writeFileSync(path.join(DATA_DIR, 'uploads', 'screenshots', file), Buffer.from([0xff, 0xd8, 0xff, 0xe0, 0x00]));
+  // screenshots.id is an INTEGER rowid alias — let SQLite assign it.
+  db.prepare('INSERT INTO screenshots (device_id, filepath, captured_at) VALUES (?,?,?)')
+    .run(deviceId, file, Math.floor(Date.now() / 1000));
+}
+
+before(async () => {
+  PORT = await freePort();
+  BASE = `http://127.0.0.1:${PORT}`;
+  const logFd = fs.openSync(LOG, 'w');
+  proc = spawn('node', ['server.js'], {
+    cwd: path.join(__dirname, '..'),
+    env: { ...process.env, DATA_DIR, SELF_HOSTED: 'true', PORT: String(PORT), NODE_ENV: 'test' },
+    stdio: ['ignore', logFd, logFd],
+  });
+  let up = false;
+  for (let i = 0; i < 80; i++) {
+    try { const r = await fetch(BASE + '/api/status'); if (r.ok) { up = true; break; } } catch { /* not yet */ }
+    await new Promise(r => setTimeout(r, 250));
+  }
+  if (!up) throw new Error('server did not boot:\n' + fs.readFileSync(LOG, 'utf8').slice(-2000));
+  db = new Database(path.join(DATA_DIR, 'db', 'remote_display.db'));
+
+  S.admin = await register();                 // first user => platform_admin
+  assert.equal(S.admin.role, 'platform_admin');
+  S.owner = await register();                 // owns a device, in its own workspace
+  S.outsider = await register();              // no relationship to that device
+
+  S.ownerWs = db.prepare('SELECT workspace_id FROM workspace_members WHERE user_id = ?').get(S.owner.id).workspace_id;
+
+  // A normally-paired device: owned, and in the owner's workspace.
+  S.owned = crypto.randomUUID();
+  db.prepare("INSERT INTO devices (id, user_id, workspace_id, name, status) VALUES (?,?,?,'Owned','online')")
+    .run(S.owned, S.owner.id, S.ownerWs);
+  seedScreenshot(S.owned);
+
+  // An UNPAIRED device: no user_id, no workspace — the state a panel sits in while it is
+  // displaying its pairing code.
+  S.unpaired = crypto.randomUUID();
+  db.prepare("INSERT INTO devices (id, user_id, workspace_id, name, status, pairing_code) VALUES (?,NULL,NULL,'Unpaired','provisioning','424242')")
+    .run(S.unpaired);
+  seedScreenshot(S.unpaired);
+});
+after(() => { try { db && db.close(); } catch { /* */ } try { proc.kill('SIGKILL'); } catch { /* */ } });
+
+test('the device owner can read its screenshot', async () => {
+  const res = await shot(S.owned, S.owner.token);
+  assert.equal(res.status, 200, 'the owner must keep working');
+});
+
+test('an unrelated user cannot read a device in a workspace they are not in', async () => {
+  const res = await shot(S.owned, S.outsider.token);
+  assert.equal(res.status, 403, 'no access path to that workspace');
+});
+
+test('a platform admin can read any device screenshot', async () => {
+  const res = await shot(S.owned, S.admin.token);
+  assert.equal(res.status, 200, 'platform_admin must not be denied by a stale role list');
+});
+
+test('an UNPAIRED device is not readable by an arbitrary authenticated user', async () => {
+  // The short-circuit made this readable by anyone with an account. An unpaired panel is
+  // showing its pairing code, so the image is also a claim vector.
+  const res = await shot(S.unpaired, S.outsider.token);
+  assert.ok(res.status === 403 || res.status === 404,
+    `an unassigned device must not be readable by any account (got ${res.status})`);
+});
+
+test('an unknown device id is still a 404, and no token is still a 401', async () => {
+  assert.equal((await shot(crypto.randomUUID(), S.owner.token)).status, 404);
+  assert.equal((await fetch(`${BASE}/api/devices/${S.owned}/screenshot`)).status, 401);
+});