Before I start, I'd like to point out that this is a bug with the current Launcher and not any particular version of Minecraft. This issue has been raised before but got dismissed on 'unsupported version' grounds.

The workaround for it dissuades players from using the official launcher.

The Issue

When using the Minecraft Launcher to start a Minecraft client of version 1.6.4 or earlier the user's Session ID is not passed to the client.

If the client then attempts to connect to a server it will be rejected with the on-screen error:

• Failed to Login: bad Login

Attached is an image of the startup log when launching Minecraft 1.6.4. You can see where the client (game) is reporting a Session ID of '-'. Starting Minecraft 1.7.2 from the same Launcher session will pass the Session ID to the client.

The issue affects versions of Minecraft 1.6.4 and earlier. I can only assume that from version 1.7.x onward a different argument name is being used for the Session ID.

Workaround

The current workaround is to use a 3rd party launcher that you can run Minecraft from. The following launchers can all be used:

• Legacy Launcher
• ATLauncher
• Technic Launcher
• MultiMC 5