CoopParryFix

Valheim 1.0 plugin. One DLL for clients and the dedicated server.

The problem

Vanilla perfect parry is 250ms, timed on your PC when you raise the shield.

In co-op the mob is often simulated on someone else’s PC (the owner), not yours. Their attack has to travel owner → server → you before your client can count the parry. That extra hop is why a parry that would have worked in solo can miss online.

Steam ping only measures you ↔ server. It does not include the owner’s hop, and on a Steam dedicated server it is often 0. That is not “no delay.”

What this mod does

If you own the attacker, nothing changes: still 250ms.

If you do not, CoopParryFix pings the owner on the same round trip as combat (you → server → owner → server → you), takes half of that as the one-way delay, adds hitch if the owner’s frame time is above 33ms, and widens the window by that amount. A shield raise timed like vanilla still lands when the hit RPC is late.

Install on the dedicated server and every client for best results. If CoopParryFix is missing on a client and/or the server, pings time out and the parrying client falls back (GetNetStats if ping > 0, otherwise a 40ms floor). Blocking still works; the window is just a coarser guess.

Compatible with SmoothServer. Does not use SS_Ping. Owner-path delay uses CPF_Ping / CPF_Pong.

Details

Vanilla check: m_blockTimer < 0.25.

• If attacker.IsOwner(): 250ms, same as solo.
• If not: + (owner-path RTT × 0.5) + hitch above 33ms, using the max sample in the last 5 seconds.
• Crowd extra is off by default (Milliseconds Per Player = 0).

Co-op check on dedicated: the owner kept 250ms; the other client widened by measured owner-path RTT (~20ms on LAN) while Steam ping stayed 0.

Install

Requires BepInExPack Valheim.

Drop CoopParryFix.dll from the GitHub release zip into BepInEx/plugins on the dedicated server and every client. One file, not two. Restart after replacing the DLL.

Combat / ping debug lines go to BepInEx/plugins/Ageous27-CoopParryFix/CoopParryFix.log (and are also copied into BepInEx/LogOutput.log).

Config

BepInEx/config/Ageous.CoopParryFix.cfg after first launch.

• Latency.Compensate Latency — default on. Skipped when you own the attacker.
• Latency.Ping Scale — default 0.5 (combat one-way).
• Latency.Window Seconds — default 5.
• Latency.Rtt Stat — default Max (also P90, Ema).
• Latency.Hitch Budget Milliseconds — default 33 (30 FPS). Only frame time above this counts as hitch.
• Latency.Min Remote Owner Milliseconds — default 40 when no ping sample is available.
• Parry.Milliseconds Per Player — default 0.
• General.Debug Logs — default on.

Changelog

0.4.1

• CoopParryFix writes BepInEx/plugins/Ageous27-CoopParryFix/CoopParryFix.log (next to the DLL), and still mirrors lines into BepInEx LogOutput.log.

0.4.0

• Same DLL on dedicated server and clients. Routed CPF_Ping / CPF_Pong to attacker.GetOwner() measures you→server→owner→server→you.
• Remote-owned parry window uses max RTT in a 5s window (half, plus hitch above 33ms). Debug Logs default on.
• Missing CoopParryFix on a client or the server: ping times out and falls back to GetNetStats or a 40ms floor. Does not break blocking.

0.3.0

• Latency bonus is 0 when this client owns the attacker (Character.IsOwner()). Remote-owned hits still use ZNet.GetNetStats.
• Crowd extra defaults to 0ms so nearby players do not make parries easier than solo. Set Milliseconds Per Player to 50 for the old behavior.
• Soft-detects SmoothServer (Nosferatu.SmoothServer) and does not duplicate its net/ownership work.
• Debug Logs default on for new config files.

0.2.2

• Renamed the mod to CoopParryFix (was ZoneParry). New GUID Ageous.CoopParryFix; remove the old ZoneParry.dll.
• Debug BlockAttack prefix no longer calls private Humanoid.GetCurrentBlocker() (MethodAccessException on the live assembly).

0.2.1

• Fix FieldAccessException spam on Character.m_nview (publicized-at-compile, private-at-runtime). That Update exception was breaking combat.
• Latency now uses only public ZNet.GetNetStats ping/quality. No private Character fields.
• Clamp the parry window so it cannot become NaN/infinite.

0.2.0

• Client-side latency compensation: samples Steam/PlayFab connection ping, jitter, and quality.
• Adds one-way ping plus jitter to the 250ms vanilla window so a locally timed parry still counts when the hit RPC is late.
• Crowd bonus is unchanged (50ms per extra player in the zone).

0.1.1

• Debug now logs every blocked hit, not only when the nearby player count changes.
• Stopped using is Player (could skip the bonus/log). Player check is Character.IsPlayer().

0.1.0

• Initial release for Valheim 1.0.
• Harmony transpile of Humanoid.BlockAttack replaces the hardcoded 0.25s perfect-parry window.
• Adds 50ms per extra player in the same 64m world zone. Optional WorldChunk (512m) or radius grouping.