snapshot fixes

server/src/services/turnService/index.js

@@ -196,6 +196,26 @@ function canDrive(roverId, socket) {
   return activeDrivers.get(roverId) === socket.id;
 }
 
+function canRequestLiveVideo(roverId, socket) {
+  if (!socket) return false;
+  if (canDrive(roverId, socket)) return true;
+
+  const queue = driverQueues.get(roverId);
+  if (!queue || getMode() !== MODES.TURNS) {
+    return false;
+  }
+
+  /*
+    This helper is intentionally broader than canDrive(). Bandwidth saving is a
+    presentation/subscription decision for normal driver clients: the UI keeps
+    non-current drivers on snapshots, and only asks for live video when it wants
+    to warm or show the stream. The server should still verify that the socket is
+    actually attached to this rover, but it should not reject a legitimate queued
+    driver because the browser and turn timer are a few milliseconds out of sync.
+  */
+  return queue.queue.includes(socket.id);
+}
+
 function isQueuedDriver(roverId, socketId) {
   if (!socketId) return false;
   const queue = driverQueues.get(roverId);
@@ -410,6 +430,7 @@ module.exports = {
   driverRemoved,
   cleanupRover,
   canDrive,
+  canRequestLiveVideo,
   isQueuedDriver,
   getActiveDrivers,
   turnEvents,

server/src/services/videoAuthService/policy.js

@@ -104,12 +104,12 @@ function createVideoAuthPolicy(deps) {
       if (
         !isAudio &&
         shouldUseSnapshotsForNonTurnVideo({ controllableUserCount: countControllableUsers() }) &&
-        !turnService.canDrive(roverId, socket)
+        !turnService.canRequestLiveVideo(roverId, socket)
       ) {
         /*
           This mirrors videoSocketService's token gate. MediaMTX can ask auth
-          after a token has been issued, so the active-turn bandwidth rule must
-          be evaluated here too instead of trusting an older browser decision.
+          after a token has been issued, so the same "must belong to this rover's
+          driver queue" rule has to be evaluated here too.
         */
         return false;
       }

server/src/services/videoSocketService/index.js

@@ -153,15 +153,15 @@ io.on('connection', (socket) => {
           role !== 'spectator' &&
           !isAdmin(socket) &&
           shouldUseSnapshotsForNonTurnVideo({ controllableUserCount: countControllableUsers() }) &&
-          !turnService.canDrive(baseId, socket)
+          !turnService.canRequestLiveVideo(baseId, socket)
         ) {
           /*
-            The browser also forces snapshots for non-active turn holders, but
-            the socket token path must enforce the same rule. Otherwise a stale
-            component or direct socket caller could still mint a MediaMTX token
-            while the UI is showing snapshots.
+            The browser owns the snapshot-vs-live presentation for queued rover
+            drivers. The server side only verifies that the socket belongs to
+            this rover's driver queue so legitimate warm-up/switch requests are
+            not rejected by small turn-timer timing differences.
           */
-          throw new Error('Live video is limited to the active turn');
+          throw new Error('Live video is limited to this rover queue');
         }
       } else if (target.type === 'room') {
         throw new Error('Room cameras now use the snapshot feed');