Roblox crashes or won't launch
The client starts and immediately closes, or never opens at all.
The client opens and closes straight away
This is almost always a bad Fast Flag. A flag that Roblox's client can't handle will take the process down immediately.
- Turn off Fast Flag management. Settings → Engine Settings → uncheck Allow Agentstrap to manage Fast Flags, then press Save.
- Restart Roblox. If it launches cleanly, one of your flags is the culprit.
- Add your flags back one at a time. Use the Fast Flag Editor's Validate action to catch malformed ones.
Your flags aren't deleted. Turning off management only stops Agentstrap copying them into the Roblox
install. Your configuration is still there, and you can turn management back on once you've found the problem.
The client never opens at all
- Check the launch status. Command Center → Last launch tells you whether the launch was cancelled, failed, or never completed.
- Check the Roblox install. If
RobloxPlayerBeta.exeis missing from the version folder, see Repairing a broken Roblox install. - Check for the Media Feature Pack. Roblox needs
mfplat.dll. - Check for a pending configuration migration. A stale configuration can stop the client from starting. Updates → Configuration → Check.
The client crashes after a while
- Turn off exclusive fullscreen. Some graphics drivers handle it badly. Don't use Alt+Enter to go fullscreen.
- Turn off custom window attributes. A fixed window size can exceed your display's usable area.
- Disable mods. Set every preset back to Default on the Mods page and confirm the game is stable before re-adding them.
- Update your graphics driver. Roblox is far more stable on current drivers.
The client crashes on a specific game only
That's usually the game's own content, not Agentstrap. But if the crash happens before the game even loads its assets, check the same list as above — especially Fast Flags.
Getting the actual error
Agentstrap's log records the exit and the reason. On the Advanced page, use Clear logs and then reproduce the crash, so the log contains only that attempt.
Roblox keeps its own logs too, in %LOCALAPPDATA%\Roblox\logs. The Deployment page has an
Open Roblox logs shortcut.
Check the Roblox server status.
If nothing you change makes a difference, Roblox's own status page may be the answer. A client that can't reach
Roblox's servers looks exactly like a crash.