What is Bungie Marathon CAT error?

CAT is an authentication failure during Marathon login or session handshake. Fix: restart the game and Steam as Administrator on PC.

How do I fix Marathon CAT error?

Restart Marathon completely. On PC, restart Steam as Administrator. Check Bungie.net account status.

Why does CAT error happen in Marathon?

CAT occurs when the client cannot authenticate with Bungie's identity services — often due to expired tokens or auth server restarts.

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Marathon CAT Error (Bungie)

CAT is an authentication error during login or session handshake in Marathon. Often appears at launch or after a Bungie server restart.

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← Check Live Server Status

Quick Fix

Restart Marathon completely. On PC, restart Steam as Administrator.

Step-by-Step Fixes

Fully quit Marathon and relaunch
[PC] Restart Steam as Administrator (right-click Steam → Run as administrator), then launch Marathon
Check Bungie.net to confirm your account is in good standing
If repeated: clear Steam download cache (Steam → Settings → Downloads → Clear download cache) and restart

What Causes CAT?

CAT occurs when the Marathon client fails to authenticate with Bungie's identity services. This can happen if your session token expired, Bungie's auth servers restarted, or Steam's local cache is corrupted. A full restart refreshes the token and usually fixes it.

Related Errors

Still Not Fixed?

Submit a ticket or check official status:

→ Marathon Help — Submit a ticket
→ @BungieHelp — Official status updates
→ Live server status — MarathonStatus.com