MegaMek: Game Freeze With Immobilized Infantry Transport

Hey guys! It looks like there's a pretty serious issue popping up in the nightly builds of MegaMek. Specifically, the game can get completely stuck during the movement phase if you have a vehicle that's carrying infantry and that vehicle becomes immobilized. Let's dive into the details and see what's going on.

Brief Description of the Issue

So, here’s the deal. The game hits a snag and refuses to continue the movement phase when a vehicle loaded with infantry finds itself immobilized the previous turn. It’s like the game gets caught in a loop and can’t figure out what to do next. This can be super frustrating, especially if you're in the middle of a heated battle.

Digging into the logs, it seems like the problem might stem from a NullPointerException. Here’s the snippet from the log that seems to be causing the trouble:

10:52:24,306 ERROR [megamek.common.net.connections.AbstractConnection] {Connection 0}
megamek.common.net.connections.AbstractConnection.update(AbstractConnection.java:320) - Server had an error receiving a packet
java.lang.NullPointerException: Cannot invoke "megamek.common.Hex.terrainLevel(int)" because "startingHex" is null
   at megamek.server.totalWarfare.MovePathHandler.processMovement(MovePathHandler.java:359)
   at megamek.server.totalWarfare.TWGameManager.skipCurrentTurn(TWGameManager.java:2268)
   at megamek.server.commands.SkipCommand.run(SkipCommand.java:71)
   at megamek.server.Server.processCommand(Server.java:1241)
   at megamek.server.Server.handle(Server.java:1297)
   at megamek.server.Server$1.packetReceived(Server.java:269)
   at megamek.common.net.connections.AbstractConnection.processConnectionEvent(AbstractConnection.java:398)
   at megamek.common.net.connections.AbstractConnection.processPacket(AbstractConnection.java:357)
   at megamek.common.net.connections.AbstractConnection.update(AbstractConnection.java:311)
   at megamek.server.ConnectionHandler.run(ConnectionHandler.java:67)
   at java.base/java.lang.Thread.run(Thread.java:840)

It looks like the startingHex is coming up as null, which is causing the game to freak out when it tries to figure out the terrain level. This is a classic case of something the developers probably didn't account for when they were coding the movement logic. When a vehicle is immobilized while carrying infantry, the game's pathfinding or movement processing logic hits an unexpected state, leading to the dreaded NullPointerException. This is a critical issue because it completely halts gameplay, preventing players from continuing their scenarios or campaigns. Understanding this error message can give you, as a player, a hint as to why the game might be failing. For the developers, it pinpoints exactly where the bug lies in the code, making it easier to target and fix. The MovePathHandler and TWGameManager classes are central to unit movement, so any bug within them can have far-reaching consequences. Knowing this allows the development team to focus their debugging efforts efficiently.

Steps to Reproduce the Error

Okay, so how can you make this happen yourself? Follow these steps:

1. Load Up: Start a game and add a vehicle that has the capacity to carry infantry.
2. Get Passengers: Load some infantry units into the vehicle.
3. Immobilize: Find a way to immobilize that vehicle while the infantry is still on board. This could be through enemy fire, terrain, or any other means that causes the vehicle to become stuck.
4. Observe: On the next turn, the game should hang right at the beginning of the movement phase. Boom, you’ve reproduced the error!

By following these steps, you can reliably reproduce the bug and confirm that it’s indeed the same issue. This is incredibly valuable for developers, as it allows them to see the problem firsthand and test their fixes effectively. The more players who can reproduce the issue, the faster it can be resolved.

Additional Information

The included screenshot and log file provide a clear picture of the error in action. The log file contains detailed information about the game state and the errors that occurred, while the screenshot visually confirms the game freeze. Analyzing these resources will help developers understand the context in which the error occurs and identify potential causes.

Severity

This is definitely a Critical issue. When the game crashes or a core feature becomes unusable, it completely disrupts the gameplay experience. Imagine being in the middle of an intense campaign, only to have the game freeze up because of this bug! That's why it's marked as critical – it needs to be addressed ASAP.

MegaMek Suite Version

This bug was found in: MekHQ-0.50.07-nightly-2025-10-09

Knowing the exact version helps the developers narrow down the scope of the issue. Nightly builds are constantly evolving, so it's important to specify which version is affected. This allows the team to focus on the changes made in that specific build and identify any potential regressions or newly introduced bugs. The more specific you are, the easier it is for the developers to track down and fix the problem.

Operating System and Java Version

• Operating System: Windows 11 10.0
• Java Version: Adoptium 17.0.011

Providing the operating system and Java version can also be helpful, as these factors can sometimes influence how the game behaves. While the bug is likely in the MegaMek code itself, knowing the environment in which it occurs can rule out any compatibility issues or platform-specific problems. For example, certain Java versions might have quirks that affect the game's performance or stability. This information helps the developers ensure that the fix is effective across different platforms and configurations.

Final Verification Checklist

• [x] I confirm this is a single, unique issue that hasn't been reported before
• [x] I have included all necessary information and files to help reproduce this issue
• [x] I have asked on MegaMek Discord about this issue
• [x] I have confirmed this issue is being opened on the correct repository: MegaMek, MegaMekLab, or MekHQ

Conclusion

Alright, that’s the scoop on this annoying game-breaking bug. Hopefully, the MegaMek developers can squash it soon so we can all get back to enjoying our games without interruption! Thanks for reading, and happy gaming!

For more information about MegaMek and its development, you can check out the official MegaMek website. This will give you access to the latest news, downloads, and community forums.