diff --git a/libraries/session/src/main/java/androidx/media3/session/MediaControllerImplBase.java b/libraries/session/src/main/java/androidx/media3/session/MediaControllerImplBase.java
index c856873c1e..0a79cb07a3 100644
--- a/libraries/session/src/main/java/androidx/media3/session/MediaControllerImplBase.java
+++ b/libraries/session/src/main/java/androidx/media3/session/MediaControllerImplBase.java
@@ -2211,8 +2211,8 @@ import org.checkerframework.checker.nullness.qual.NonNull;
     try {
       MediaUtils.getFutureResult(future, /* timeoutMs= */ 3_000);
     } catch (ExecutionException e) {
-      // It never happens because future.setException will not be called anywhere
-      throw new AssertionError(e);
+      // Never happens because future.setException will not be called.
+      throw new IllegalStateException(e);
     } catch (TimeoutException e) {
       Log.w(TAG, "set/clearVideoSurface takes too long on the session side.", e);
       // TODO(b/188888693): Let developers know the failure in their code.
@@ -2247,10 +2247,7 @@ import org.checkerframework.checker.nullness.qual.NonNull;
   /** Returns session interface if the controller can send the predefined command. */
   @Nullable
   IMediaSession getSessionInterfaceWithSessionCommandIfAble(@CommandCode int commandCode) {
-    if (commandCode == COMMAND_CODE_CUSTOM) {
-      throw new AssertionError(
-          "Use getSessionInterfaceWithSessionCommandIfAble(SessionCommand) for custom commands");
-    }
+    checkArgument(commandCode != COMMAND_CODE_CUSTOM);
     if (!sessionCommands.contains(commandCode)) {
       Log.w(TAG, "Controller isn't allowed to call command, commandCode=" + commandCode);
       return null;
@@ -2261,10 +2258,7 @@ import org.checkerframework.checker.nullness.qual.NonNull;
   /** Returns session interface if the controller can send the custom command. */
   @Nullable
   IMediaSession getSessionInterfaceWithSessionCommandIfAble(SessionCommand command) {
-    if (command.commandCode != COMMAND_CODE_CUSTOM) {
-      throw new AssertionError(
-          "Use getSessionInterfaceWithSessionCommandIfAble(int) for predefined commands");
-    }
+    checkArgument(command.commandCode == COMMAND_CODE_CUSTOM);
     if (!sessionCommands.contains(command)) {
       Log.w(TAG, "Controller isn't allowed to call session command:" + command);
       return null;
diff --git a/libraries/session/src/main/java/androidx/media3/session/MediaControllerImplLegacy.java b/libraries/session/src/main/java/androidx/media3/session/MediaControllerImplLegacy.java
index aec3f925f5..2839d46101 100644
--- a/libraries/session/src/main/java/androidx/media3/session/MediaControllerImplLegacy.java
+++ b/libraries/session/src/main/java/androidx/media3/session/MediaControllerImplLegacy.java
@@ -280,7 +280,7 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
                   Uri.parse(pendingSetMediaUriRequest.value), pendingSetMediaUriRequest.extras);
           break;
         default:
-          throw new AssertionError("Unexpected type " + pendingSetMediaUriRequest.type);
+          throw new IllegalStateException("Unexpected type " + pendingSetMediaUriRequest.type);
       }
       pendingSetMediaUriRequest.result.set(new SessionResult(RESULT_SUCCESS));
       pendingSetMediaUriRequest = null;
@@ -345,7 +345,7 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
                   Uri.parse(pendingSetMediaUriRequest.value), pendingSetMediaUriRequest.extras);
           break;
         default:
-          throw new AssertionError("Unexpected type " + pendingSetMediaUriRequest.type);
+          throw new IllegalStateException("Unexpected type " + pendingSetMediaUriRequest.type);
       }
       pendingSetMediaUriRequest.result.set(new SessionResult(RESULT_SUCCESS));
       pendingSetMediaUriRequest = null;
diff --git a/libraries/session/src/main/java/androidx/media3/session/MediaLibrarySessionImpl.java b/libraries/session/src/main/java/androidx/media3/session/MediaLibrarySessionImpl.java
index 0a13eb48cb..f33347f961 100644
--- a/libraries/session/src/main/java/androidx/media3/session/MediaLibrarySessionImpl.java
+++ b/libraries/session/src/main/java/androidx/media3/session/MediaLibrarySessionImpl.java
@@ -292,12 +292,7 @@ import java.util.concurrent.Future;
     if (result.resultCode == RESULT_SUCCESS) {
       List<MediaItem> items = checkNotNull(result.value);
       if (items.size() > pageSize) {
-        throw new AssertionError(
-            "The number of items must be less than or equal to the pageSize"
-                + ", size="
-                + items.size()
-                + ", pageSize="
-                + pageSize);
+        throw new IllegalStateException("Invalid size=" + items.size() + ", pageSize=" + pageSize);
       }
     }
   }
diff --git a/libraries/session/src/main/java/androidx/media3/session/MediaUtils.java b/libraries/session/src/main/java/androidx/media3/session/MediaUtils.java
index 46dc427e5e..6fac95e8ec 100644
--- a/libraries/session/src/main/java/androidx/media3/session/MediaUtils.java
+++ b/libraries/session/src/main/java/androidx/media3/session/MediaUtils.java
@@ -646,7 +646,7 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
         return MediaDescriptionCompat.BT_FOLDER_TYPE_YEARS;
       case MediaMetadata.FOLDER_TYPE_NONE:
       default:
-        throw new AssertionError("Unsupported folder type " + folderType);
+        throw new IllegalArgumentException("Unrecognized FolderType: " + folderType);
     }
   }
 
@@ -743,15 +743,14 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
       case Player.STATE_IDLE:
         return PlaybackStateCompat.STATE_NONE;
       case Player.STATE_READY:
+      case Player.STATE_ENDED:
         return PlaybackStateCompat.STATE_PAUSED;
       case Player.STATE_BUFFERING:
         return playWhenReady
             ? PlaybackStateCompat.STATE_BUFFERING
             : PlaybackStateCompat.STATE_PAUSED;
-      case Player.STATE_ENDED:
-        return PlaybackStateCompat.STATE_PAUSED;
       default:
-        throw new AssertionError("Playback state shouldn't be " + playbackState);
+        throw new IllegalArgumentException("Unrecognized State: " + playbackState);
     }
   }
 
@@ -820,8 +819,8 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
             convertToCurrentPositionMs(playbackStateCompat, currentMediaMetadata, timeDiffMs);
         return (currentPosition < duration) ? Player.STATE_READY : Player.STATE_ENDED;
       default:
-        throw new AssertionError(
-            "PlaybackStateCompat.State shouldn't be " + playbackStateCompat.getState());
+        throw new IllegalStateException(
+            "Unrecognized PlaybackStateCompat: " + playbackStateCompat.getState());
     }
   }
 
@@ -947,8 +946,8 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
       case PlaybackStateCompat.REPEAT_MODE_GROUP:
         return Player.REPEAT_MODE_ALL;
       default:
-        throw new AssertionError(
-            "PlaybackStateCompat repeat mode shouldn't be " + playbackStateCompatRepeatMode);
+        throw new IllegalArgumentException(
+            "Unrecognized PlaybackStateCompat.RepeatMode: " + playbackStateCompatRepeatMode);
     }
   }
 
@@ -963,7 +962,7 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
       case Player.REPEAT_MODE_ALL:
         return PlaybackStateCompat.REPEAT_MODE_ALL;
       default:
-        throw new AssertionError("Player.RepeatMode shouldn't be " + repeatMode);
+        throw new IllegalArgumentException("Unrecognized RepeatMode: " + repeatMode);
     }
   }
 
@@ -978,8 +977,8 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
       case PlaybackStateCompat.SHUFFLE_MODE_GROUP:
         return true;
       default:
-        throw new AssertionError(
-            "PlaybackStateCompat.ShuffleMode shouldn't be " + playbackStateCompatShuffleMode);
+        throw new IllegalArgumentException(
+            "Unrecognized ShuffleMode: " + playbackStateCompatShuffleMode);
     }
   }