multiplayer

A guide to designing multiplayer games, covering server architecture, keeping players’ game states in sync, handling lag, and reducing network traffic. Multiplayer games let several players share the same game session.

In plain words
What is it for?
Use it when planning dedicated-server, host-based, peer-to-peer, or turn-based games, and when designing prediction, interpolation, reconciliation, and compression.
Why use it?
It helps developers choose how game clients and servers should communicate and avoid common problems such as conflicting state, delay, and excessive data use.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/felipeslo/opencode-kit/multiplayer
Any agent
npx skills add felipeslo/opencode-kit --skill multiplayer
Clone the repo
git clone --depth 1 https://github.com/felipeslo/opencode-kit

Made for: Claude Code, Codex.

Per session 15 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 643 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 94% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00015 $0.00643
Opus 5 $0.00008 $0.00321
Sonnet 5 $0.00003 $0.00129
Haiku 4.5 $0.00002 $0.00064

Measured yesterday against content hash e7c1482ab9a2, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

multiplayer scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

94% identical to multiplayer — 1 line differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.opencode/skills/game-development/multiplayer/SKILL.md · 132 lines

How it starts

The opening of the file, as written. The whole thing — 132 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Multiplayer Game Development

Networking architecture and synchronization principles.


1. Architecture Selection

Decision Tree

What type of multiplayer?
│
├── Competitive / Real-time
│   └── Dedicated Server (authoritative)
│
├── Cooperative / Casual
│   └── Host-based (one player is server)
│
├── Turn-based
│   └── Client-server (simple)
│
└── Massive (MMO)
    └── Distributed servers

Comparison

Architecture Latency Cost Security
Dedicated Low High Strong
P2P Variable Low Weak
Host-based Medium Low Medium

2. Synchronization Principles

State vs Input

Approach Sync What Best For
State Sync Game state Simple, few objects
Input Sync Player inputs Action games
Hybrid Both Most games

Lag Compensation

Technique Purpose
Prediction Client predicts server
Interpolation Smooth remote players
Reconciliation Fix mispredictions
Lag compensation Rewind for hit detection

3. Network Optimization

Bandwidth Reduction

Technique Savings
Delta compression Send only changes
Quantization Reduce precision
Priority Important data first
Area of interest Only nearby entities

Update Rates

Type Rate
Position 20-60 Hz
Health On change
Inventory On change
Chat On send

4. Security Principles

Server Authority

Client: "I hit the enemy"
Server: Validate → did projectile actually hit?
         → was player in valid state?
         → was timing possible?

Anti-Cheat

Cheat Prevention
Speed hack Server validates movement
Aimbot Server validates sight line
Item dupe Server owns inventory
Wall hack Don't send hidden data

Read the full file on GitHub · 132 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 132 lines · 15 tokens per session scan A e7c1482ab9a2

Subscribe to this mod's changes

multiplayer is a skill published in the GitHub repository felipeslo/opencode-kit (2 stars, last pushed 5mo ago), licensed MIT. It adds 15 tokens to every session and 643 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 94% identical to multiplayer, differing in 1 line, and is treated as a copy.

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