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IDProjectCategoryView StatusDate SubmittedLast Update
0004595Zandronum[All Projects] Bugpublic2026-03-30 10:082026-04-14 00:12
Reporterunknownna 
Assigned To 
PriorityurgentSeveritymajorReproducibilityalways
StatusconfirmedResolutionopen 
PlatformOSOS Version
Product Version3.2.1 
Target VersionFixed in Version 
Summary0004595: Unlagged allows player to hit players behind them if facing away from them while moving in the same direction
DescriptionWhile testing the new fixes for issue 0003334, I came across a bug with the unlagged where you're able to hit a player behind you that is moving away from you on a scrolling floor. I wonder if this is the cause of some ancient Skulltag bug where you could hit a player in thin air as they moved away from you up close.
Steps To Reproduce1. zandronum -file unlagged_debug_03.wad -host +sv_cheats 1 +deathmatch 1 +sv_unlagged_debugactors 1
2. Connect 2 clients to the server with an emulated ping of 160.
3. Position the clients the way as depicted in the attached screenshot and attack. The attacking player will hit the player body of the client located behind it.

Link to wad: unlagged_debug_03.wad
Additional InformationIt's probably related to the issue in'https://zandronum.com/tracker/view.php?id=4202 [^]'
Attached Filespng file icon Screenshot_Doom_20260330_114106.png [^] (45,825 bytes) 2026-03-30 10:08

- Relationships

-  Notes
User avatar (0024694)
unknownna (updater)
2026-04-01 16:24
edited on: 2026-04-01 20:35

 I can confirm that it happens on regular floors too from testing.

It also seems to be unrelated to the tick sync, as 2 clients with a very good raw sync still causes it to happen. "cl_buffercommands 1" doesn't fix the issue, so it seems to be separate from it.

It's caused by the unlagged 100%, as turning it off with "cl_unlagged 0" removes the bug.

To get the bug to occur, you have to travel in the same direction as the other client while being behind its path of travel. It does not occur if you travel in the same direction while being in front of the other client's path.
And you can actually fire in any direction behind the client while facing away from it and still hit the client 100%, so this is actually a rather serious issue in close quarters, and is probably indeed the cause of the ancient Skulltag bug.
User avatar (0024696)
unknownna (updater)
2026-04-14 00:12

 It's not really related to 0004202, as the client prediction being on or off doesn't affect the issue here.
When unlagged is enabled, the client will hit the other player behind it regardless.

If you want to reproduce the issue for yourself on regular floors, set cl_run to 0 with one client, then tell it to move backwards with +back in the console, and then use a 2nd client with cl_run set to 1 to catch up with it and fire while facing the opposite direction of the moving client.
Make sure to use some emulated ping on the client that is firing, at around 160 to make it consistent.

Under these circumstances, the unlagged consistently over-reconciles the higher the ping is.

Turns out many "lucky kills" over the years weren't so lucky after all, and were actually the result of bugged unlagged behavior.

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- Issue History
Date Modified Username Field Change
2026-03-30 10:08 unknownna New Issue
2026-03-30 10:08 unknownna File Added: Screenshot_Doom_20260330_114106.png
2026-03-30 10:09 unknownna Relationship added related to 0004202
2026-03-30 10:09 unknownna Relationship added related to 0003334
2026-04-01 16:24 unknownna Note Added: 0024694
2026-04-01 16:24 unknownna Priority high => urgent
2026-04-01 16:24 unknownna Status new => confirmed
2026-04-01 16:25 unknownna Summary Unlagged allows player to hit player behind them on scrolling floors. => Unlagged allows player to hit players behind them if facing away from them while moving in the same direction
2026-04-01 16:32 unknownna Relationship deleted related to 0003334
2026-04-01 20:35 unknownna Note Edited: 0024694 View Revisions
2026-04-13 23:44 unknownna Relationship deleted related to 0004202
2026-04-14 00:12 unknownna Note Added: 0024696




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