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.