Project Zomboid 42.21 Is Stable: Vanishing Zombies Fixed, Two Modding Commands Restored

Build 42.21 reached Project Zomboid's Stable branch on September 28, five days after The Indie Stone put it on Unstable for testing. The incremental update focuses on fixes and balance changes, with a few gameplay and interface improvements. It fixes zombies that disappeared when a player left and re-entered a chunk of the world, tackles multiplayer zombie duplication, changes how the XXL trees cut away around vehicles, and restores two Lua commands the studio had disabled in a security hotfix.

What the five-day gap says about the release process

The Indie Stone put 42.21 on Unstable on September 23 and moved it to Stable on September 28. The Stable announcement says the community reported no major issues, so the go button was pressed. It also says this should now be the standard procedure for every release: a build goes to Unstable, players test it, the studio may make more changes, and the result eventually reaches Stable.

The gap between those branches will vary with the complexity of each update, and the studio says it is trying to move faster. Unstable is not meant to act as an unofficial Stable branch that people settle on; it is a test branch with a defined job. For anyone deciding whether to opt in, the five days are a result of how this particular update went rather than a schedule the studio has committed to. Players on the Unstable branch need to select it themselves in Steam under Properties, then Game Versions and Betas, and the studio asks for a manual save backup before testing an existing world there.

The zombie fixes and the tree changes

The headline fix is the one hardcore players had been reporting: zombies that disappeared after a player left and re-entered a "chunk" of the game world. That is fixed in both single player and multiplayer. The studio describes it as a difficult bug to pin down at its root, and adds that a smaller number of instances are still on its radar and will be fixed in the next update.

Multiplayer zombie duplication is the second fix in the same area. The studio groups both under the worst offending bugs reported since Build 42 went stable, and asks players to report anything they still see.

The XXL trees added in Build 42 have been a common complaint since the build went Stable, partly because they can block the view while driving. In 42.21 they cut away better for players in vehicles, they no longer hide the houses and furniture they overhang, and their transparency has been adjusted. The studio calls this work in progress and says the trees will get more attention later.

The two Lua commands that came back

In the 42.20.4 hotfix the studio disabled the "loadstring" and "loadstream" Lua methods to address security vulnerabilities. In 42.21 it re-enabled both after investigating the issue further, and apologised to modders and server admins for the disruption. The Stable post also thanks Scribl (Boris) and Rasmus Moorats (nnsee) for helping flag the vulnerabilities that 42.20.4 fixed. The disable and re-enable came out of the same security investigation; the 42.21 notes announce their return without promising permanence.

What changes in an ordinary run

The balance list is short and touches habits from the early game onward. Characters with the Welder occupation now start with Welding recipes instead of Blacksmithing recipes. Washing machines clean dirty rags, strips and bandages. Fridges and freezers warm up gradually on the day the power goes out instead of losing cold at once, refrigeration now applies correctly to food inside a bag placed in a fridge or freezer, and antibiotics can be packed into a box with the crafting recipe. Explosives work in basements, which they previously did not, and 86 more fluid containers can purify water in the right kind of oven.

One entry pairs a change with a clarification. Pathfinding was improved so characters avoid walking over farming plants, and the studio edited the notes to state that player characters never damaged crops by stepping on them, so the change is cosmetic.

Split-screen received its own set of fixes, including a crash when both players shared a moving vehicle, read book status and XP boosts no longer being shared incorrectly between the two characters, and controls for both players after a gamepad disconnects.

Multiplayer, servers and what is still open

Multiplayer has the longest list. The anti-cheat system was expanded and safehouse exploits were remedied. The server browser now shows the last wipe rather than the last restart, and Connect is disabled until a server is selected. A Steam authentication exploit was closed: players had been able to enter dedicated servers without authenticating correctly through Steam, which also stopped SteamID bans from working. Fixes for driving at ping around 150 milliseconds or higher are intended to improve map loading in front of the car, passenger teleportation and multiplayer juddering, and a Z-level desync issue affecting player coordinates was fixed.

Saves and mods are the practical question. The studio says existing savegames on Build 42.20.4 should not be affected, and it recommends a manual backup before testing a save on the Unstable branch. Bug reports should reproduce the problem on a fresh save with no mods installed.

Two things remain open. The Indie Stone says some instances of its zombie issues remain on its radar for a later update. A forum member asked about driving stutter; a staff reply pointed to this build's high-ping driving fixes and invited further testing rather than claiming every stutter is gone. The next build will follow the same route through Unstable, so the length of that gap is the part to watch.