MegaMek, MegaMekLab, and MekHQ 0.50.12 Release Notes

Hi Everyone!

Welcome to version 0.50.12! It’s been about three months since the 0.50.11 Milestone release, and there’s a lot to cover.

First, a heads-up for those still on 0.50.11: after declaring it a Milestone, we discovered a nasty bug involving ECM and C3 interactions. That bug is fixed in this release. However, we don’t anticipate 0.50.12 achieving Milestone status. There are too many big-ticket items in MegaMek that will need time to settle and stabilize.

A Farewell to a Warrior

For those who haven’t been following, early in the new year Illiani left the projects. She was the primary MekHQ developer and a driving force behind MekHQ’s improvements over the last couple of years. As we announced on Discord:

It is with a heavy heart that I announce Illiani has departed the MegaMek project. Like Kerensky leading the Exodus Fleet beyond the Periphery, sometimes the most dedicated warriors reach a point where they must step away from the front lines. After years of tireless service, Illiani has made the difficult decision to leave. We wish her peace, rest, and fair winds wherever her JumpShip takes her next.

For those who don’t know the scope of what she accomplished: Illiani was a change agent in every sense of the word. She didn’t just contribute to MekHQ. She transformed it. Every system bears her fingerprints. Nearly 9,000 commits. The #1 contributor to the MekHQ codebase. The numbers alone don’t capture it. She elevated this program in ways that will benefit players for years to come.

I need the community to understand what this means going forward. Illiani was MekHQ’s primary developer. The pace of development, particularly major new features, will slow significantly for the foreseeable future. Our remaining developers will continue to address bugs and issues as they arise, but remember: this is a volunteer project, and developers work on what they choose to work on. The programs will continue. MekHQ will continue. But this is a significant loss.

On a personal note, I’m going to miss her. Her impact on this community was phenomenal. The door remains open should she ever choose to return.

BattleTech Core Rules: What’s Our Plan?

Catalyst has announced the new Core Rule Book, and we’ve been getting questions about how MegaMek will handle the transition. If you’ve been following along, you know we implemented the relevant Playtest rules in MegaMek as they were released. So what happens now?

The simple answer: we will be supporting the Core Rules. But we can’t start coding them until we have final versions in hand. That means we won’t likely have Core Rules support in any release until after GenCon, and it will take us a few months after that to implement everything.

As part of this effort, we’ll also be doing a general cleanup. If you’re not familiar with the concept of technical debt: it’s the accumulated cost of shortcuts, workarounds, and outdated code that builds up over time in any software project. Think of it like deferred maintenance on a DropShip. Skip enough scheduled overhauls and eventually systems start interfering with each other. MegaMek has this in spades. You can’t be a 23-year-old project and not have it.

So as we look at each new rule, our approach will be: implement the new rule, and keep the legacy rule as an option where we can. If we can’t keep both, the legacy option gets removed. I know this is going to upset some players, but we don’t have a lot of choice. There are limits to what a small volunteer dev team can support. We would love to support everything. We just can’t, and we have to take that into account with everything we do.

The good news is that a lot of the Playtest rules are already implemented, and in many cases we just need to reorganize things to convert them into the final rules. But there are also a lot of new rules and corrections to existing rules that we’ll need to incorporate. As we do releases, we’ll call out Core Rules changes as we go.

Note: These release notes highlight key changes in this version. This is not an exhaustive list. For a full breakdown, see history.txt in the docs folder for each project or the change log section at the bottom.

MegaMek

New Features

Advanced Buildings: Now Witness the Firepower

In 0.50.11 we laid the foundation for a multi-stage rework of how MegaMek handles buildings. Proper fortresses, functional turrets, gun emplacements done the right way. This release delivers on that promise. TO:AR Advanced Buildings have arrived in MegaMek, and they bring a complete rethink of how defensive structures work across the suite. If you’ve ever been frustrated in MekHQ base attack missions where the game expects you to either ignore or crew-kill those old legacy Gun Emplacements, this is the fix we’ve been working toward.

What’s New in MegaMek:

Full Gameplay Support: Advanced Buildings are playable with BV calculations, toHit modifier display on the map, and integration into the force generator
Princess Support: Princess can attack Advanced Buildings, deploy units to them, and use them tactically. No more hiding behind fortifications from the AI
Building Sizes: Only single-hex buildings are currently shipped with MM-Data, but the underlying code technically supports multi-hex buildings
No MML Support Yet: Advanced Buildings cannot be constructed in MegaMekLab at this time. That’s a future goal

Infantry vs Infantry Building Combat:

Breaching! While digging through TO:AR, we came across rules for “Infantry vs Infantry Combat” (TO:AR p.169-174), specifically the special case for inside buildings. This is now fully implemented.

If you (or Princess) move an Infantry unit (CI or BA) into a hex with a hostile Advanced Building, you’ll see a new action during the “Pre-End” phase to initiate infantry-vs-infantry combat. If there are any ongoing combats, a new “Infantry vs Infantry Combat” phase appears where players and Princess can order units to “Reinforce” or “Withdraw” following the rules in TO:AR.

Notably, your Advanced Building’s crew will NOT participate in combat unless you order them to “Reinforce” — the rules describe crew participation as optional. They’re taken prisoner if they don’t join the defense and lose. This lets you garrison your own emplacements and choose to use only the garrison for defense so your building doesn’t take hits. Damage is applied and reported during the end phase report.

What’s New in MekHQ:

Campaign Option: A new campaign option lets you generate Advanced Buildings instead of legacy Gun Emplacements for base defense missions
Scenario Objective Resolution: “Preserve” and “Capture” objectives now properly handle Advanced Buildings. A “Crew Killed” building counts as “Alive” for these objectives, which the legacy Gun Emplacements never handled correctly

Bug Fixes for Buildings & Infantry Combat:

Victory Report: Advanced Buildings now display correctly in the victory report
Crew Kill Tracking: Buildings with killed crews properly count as crew killed in after-action reports
Dead Crew Targeting: Buildings with dead crews can no longer be targeted for new infantry-vs-infantry actions
Reinforce Logic: Fixed reinforcement logic for infantry-vs-infantry building combat
Casualty Calculations: Fixed incorrect casualty counts for infantry-vs-infantry combat
Building Power Generators: Fixed cost, BV, and tonnage issues for building power generators

Prosthetics & Augmentations: The Word Made Flesh, Continued

The Manei Domini’s work continues. Building on the significant cybernetic implant implementation in 0.50.11, we’ve expanded the Interstellar Operations augmentation catalog further, this time focusing on prosthetics for conventional infantry:

Prosthetic Limbs Enhanced (Includes Improved): Full implementation of enhanced prosthetic limbs, giving your augmented personnel meaningful mechanical benefits
Extraneous Prosthetic Limbs for Conventional Infantry: Enhanced prosthetic limbs are now available for conventional infantry per IO p.84 — because sometimes two arms just aren’t enough
Prosthetic Tail, Enhanced: Conventional infantry can now sport enhanced prosthetic tails per IO p.85
Prosthetic Wings (Glider): Glider-type prosthetic wings are now functional
Prosthetic Wings, Powered Flight: Infantry with powered flight prosthetic wings can now take to the skies. It’s not a Cheap Trick, but your infantry can have Mighty Wings
Suicide Implants: Implemented per Interstellar Operations. Dark, but canonical

There is still additional work needed on the MekHQ side to fully integrate these prosthetics and augmentations into campaign play. With Iliani’s departure from the project, there’s no ETA on when that work will land. The MegaMek and MegaMekLab sides are functional now.

Cockpit Modifications & Neural Interfaces

We’ve implemented several cockpit modifications from Interstellar Operations. The Direct Neural Interface and Damage Interrupt Circuit (IO p.39) are now fully functional, with DNI providing direct neural control and the DIC giving pilots a buffer against cockpit damage feedback. Enhanced Imaging has been updated to properly follow IO p.69/p.77 rules, and all three systems (DNI, EI Interface, and DIC) now have full integration across applicable unit types.

Quick Reference: What Do I Enable?

I want to...	Toggle/Set
Use DNI/EI implants without worrying about equipment	Leave "Track Neural Interface Hardware" OFF
Enforce realistic hardware requirements	Turn "Track Neural Interface Hardware" ON, then add cockpit mods to units
Protect my pilot from ammo explosions	Add DIC to a BattleMek (works independently, no game option needed)
Get aimed shots with EI	Give pilot EI Implant, add EI Interface to unit (if tracking ON)
Get initiative bonus	Give pilot VDNI/BVDNI + TCP augmentation

Note: If you enable “Track Neural Interface Hardware,” ProtoMeks will become Experimental tech level, as EI is classified as Experimental. If you’re running a campaign or game at Standard or Advanced rules levels, leave this option off to keep ProtoMeks available.

Munitions & Ordnance

Some players just want to watch the world burn. Incendiary LRM munitions are now available and properly included in autoconfig selections. We’ve also added EMP Mines, which can now be deployed on the battlefield.

Combat Systems

MekWarriors can now abandon their ‘Meks under specific conditions per TacOps:AR p.165, with the ejection options reorganized for clarity. Vehicle crews also gain new survival options with the Combat Vehicle Escape Pod (CVEP) implemented per TO:AUE p.121.

Handheld Weapons

Handheld Weapons continue to receive stability fixes from their 0.50.10 debut (see Bug Fixes below).

Quality of Life

Save Advanced Searches: Your custom search filters are now preserved between sessions
Elevation Cross-Section Diagram: The Ruler/LOS Tool now includes an elevation cross-section diagram and consolidates the separate rulers into one, making LOS determination more intuitive

Network Information Dialog: New dialog displays network connection details for multiplayer sessions
Bot Priority Targeting by Range: You can now set bot priority target IDs by range, giving you finer control over Princess’s targeting behavior
Board Editor Tagger: New board tagger menu item added to the Board Editor

Improvements

Princess / Bot

EMP Mine Deployment: Princess can now deploy EMP mines just like other minefields
Hidden Unit Detection: Fixed Princess incorrectly detecting hidden units through expected damage calculations. No more psychic Princess
DropShip Pathfinding: Princess will no longer crash DropShips through buildings. She’s reckless, but not that reckless
Performance: Weapon attack expected damage calculations are now cached, improving Princess’s decision-making speed

Board & Map

Several board and map improvements landed this release. BoardView drawing code has been unified for better consistency, and board files now support copyright header information. Custom deployment settings are clearer and less confusing, fortified hex indicators have been improved to reduce confusion, and the map now properly adapts to new entity types.

Display & Data

Unit readout tables have been improved, and the spotting field of view now correctly shows the Mast Mount elevation bonus. Quirks received proper tooltips with word wrapping and typo corrections, and display issues with the Static Ammo Feed weapon quirk have been resolved. Squadron support has been added for the MUL file format.

Bug Fixes

Combat & Damage

Artillery Cluster Munitions: Fixed cluster munitions using incorrect hit tables. Above table for ‘Meks and front table for tanks now applied correctly
Swarm LRMs: Fixed swarm LRMs incorrectly transferring immobile status to secondary targets
Semi-Guided LRMs: Spotter movement modifiers now correctly applied when using Semi-guided LRMs against spotted (but not TAGged) targets
AMS Double Engagement: Anti-Missile Systems no longer engage the same incoming attack twice
Sprinting and Buildings: Sprinting units can no longer automatically hit adjacent buildings
Sprinting and Clubs: ‘Meks can no longer pick up clubs while sprinting
LRM Smoke Drift: Smoke from LRM rounds now drifts correctly
Planted Fields LOS: Line of sight calculations through planted fields now work properly

Movement & Deployment

Aerodyne Reverse Flight: Aerodyne aircraft can no longer fly backwards in atmosphere. Physics wins
LAM Fly-Off: Fixed a crash when LAMs attempt to fly off the map
Bridge Height: Units can once again move on height 0 bridges
Tripod Turns: Tripod turn handling now works correctly
Environmental Sealing: Environmental sealing checks now properly applied during movement and deployment
ACAR Deployment: Fixed formations scheduled for round 0 that were never deploying

C3 / Networking

C3M BV Bonus: Fixed incorrect BV bonus calculation when C3 Master is connected to C3 Master Master
Nova Link: Fixed a crash in the /nova link command. As a reminder, players should be using the Nova CEWS GUI during the end phase rather than the command line
Boosted C3 and AECM: Prevented infinite loop when a boosted C3 master is affected by Angel ECM
ARAD and ECM: Anti-Radiation missiles are no longer incorrectly affected by ECM

Handheld Weapons

Lobby Configuration: Fixed crash when configuring a ‘Mek carrying a handheld weapon in the lobby
Impossible Shots: Fixed HHWs incorrectly flagging valid shots as impossible
Weapon Drop: Fixed HHWs not properly dropping and remaining available in ‘Mek arms after being discarded
RAC Ammo Source: Rotary Autocannons in handheld weapons now correctly draw ammo from the weapon entity

Units & Loading

Command Console Head Hits: ‘Meks with Command Console cockpits and only one crew member no longer apply head hit damage twice to the single pilot
Zero-Armor Aero Display: Aero units with zero armor no longer incorrectly show as damaged
Single Fighters Option: Fixed lobby loading for fighters when “Single Fighters Not Capital” option is enabled
Support Vehicle Loading: Fixed a crash from misinterpreted armor_tech field when loading support vehicles
TSM Implant Damage Divisor: Fixed TSM implant incorrectly reducing damage divisor when the armor kit already has a divisor of 1.0
Industrial Mek Heat: Industrial ‘Meks no longer assigned incorrect movement heat
Silver Bullet Gauss: Hit modifier moved from ammo to weapon where it belongs
MD Augmentation Availability: Fixed MD Augmentation tech availability checks

Interface & Display

Cockpit Validation: Interface cockpit validation now works correctly
Mission Equipment Storage: Removed incorrect validation that limited Mission Equipment Storage to one per unit
Dazzle Mode: Dazzle mode no longer persists when the option is disabled
Unit Overview: Fixed unit overview frame thickness display issues
Bridge Collapse Warning: Bridge collapse warnings now display correctly
Deployment Weapon Selection: Fixed crash when selecting an un-deployed unit’s weapons during the deployment phase
Individual Initiative: Initiative bonuses for “Individual Initiative” now correctly come from the team, not the individual

MekHQ Integration

Fixed aerospace units returning to battle after being told not to, along with a related MekHQ POW capture bug. Also fixed a MekHQ save loading failure.

Additional Fixes

Hand Actuator: Missing hand actuator penalty is no longer cumulative where it shouldn’t be
Alpha Strike Conversions: Fixed Rail movement, MFB, and Conventional Infantry heat conversions for Alpha Strike
Ammo Serialization: Fixed ammo mutator shortName and serialization issues
Faction Advancement: Fixed setFactionsAdvancement and fallbackFactions ordering issues
RAT Generator: Fixed RAT generator loading failures due to invalid unit type
Modular Armor Cost: Corrected modular armor cost calculations
Stealth Armor Validation: Stealth armor now properly validated on superheavy ‘Meks
MASH on Small Craft: MASH now correctly displays on Small Craft record sheets
Infantry Armor Panel: Custom armors only shown when rules level is set to Advanced or higher