Lately, when I open the Minecraft launcher my username (“kpreid”) is sometimes replaced with “O” (just the one letter). The password is remembered correctly — if I retype the username I can log in. If I retype the username, log in, quit, and relaunch, then it remembers correctly for a while. I have not found how to reproduce the problem.

Has anyone seen this problem and figured out how to avoid or fix it?

Mac OS X 10.7.2
“New” (shows mcupdate site) Minecraft launcher, patched for 64-bit Java
Launched through Steam

Troubleshooting log:

2012-01-24: I launched MC through Steam and noticed the “O”. I immediately quit and relaunched it directly and saw “kpreid”, trying both several times to confirm the correlation. I then tried changing the Steam shortcut launch options to add a command-line argument, and that argument showed up as the login name (persistently), which suggests that perhaps Steam is generating a bogus “O” argument some of the time, or the way in which Steam launches MC results in it accessing files differently. The lastlogin file had identical contents before and after I logged in correctly.

2010-01-25: I saw a few occurrences of garbage including Steam-ish pathnames appearing in the login field.

  • 2
    I don't know about the cause, but maybe write-protecting .minecraft/lastlogin could solve this (chmod -w on MaxOS I guess)
    – Zommuter
    Jan 21, 2012 at 14:46
  • Interesting thought; protecting, reverting, or comparing that file might help with troubleshooting too. I'll see if I can get around to that.
    – Kevin Reid
    Jan 21, 2012 at 18:35

1 Answer 1


Based on my observations (see log in question), I am reasonably confident that this is a Steam bug where it adds garbage to the arguments of the shortcut-launched program.

On Jan 26, I added my username explicitly to the arguments in the shortcut properties; this has prevented the problem from occurring so far as I've noticed, so it apparently only happens if no explicit arguments are provided.

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