A guide to building games where multiple players share the same game session over a network. It covers how servers, players, game state, and delayed connections can work together.

It supports decisions about dedicated servers, host-based games, peer-to-peer networking, turn-based games, large online games, state syncing, input syncing, prediction, interpolation, and reconciliation.

It helps choose a network design suited to the game, keep players' views synchronised, and handle lag or limited bandwidth.

multiplayer — Skill by diillson

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/diillson/chatcli/multiplayer

Any agent

npx skills add diillson/chatcli --skill multiplayer

Clone the repo

git clone --depth 1 https://github.com/diillson/chatcli

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 659 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. Scan, not verified.

Origin 100% 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.

Model	Per session	Once invoked
Fable 5	$0.00015	$0.00659
Opus 5	$0.00008	$0.00329
Sonnet 5	$0.00003	$0.00132
Haiku 4.5	$0.00002	$0.00066

Measured 2d ago against content hash 79ee8d6f2e04, 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 2d ago.

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

100% identical to multiplayer — 0 lines 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.

.agent/skills/game-development/multiplayer/SKILL.md · 133 lines

How it starts

The opening of the file, as written. The whole thing — 133 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 · 133 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.

2d ago First seen · 133 lines · 15 tokens per session scan A 79ee8d6f2e04

Subscribe to this mod's changes

multiplayer is a skill published in the GitHub repository diillson/chatcli (89 stars, last pushed 3d ago), licensed Apache-2.0. It adds 15 tokens to every session and 659 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to multiplayer, differing in 0 lines, and is treated as a copy.

Game development Memory and context Planning agent ai aiops compression context-engineering context-window

multiplayer