setup-multiplayer

setup-multiplayer is a skill for Claude Code, Codex from SummerEngine/summer-engine-agent. It costs 125 tokens per session (3,670 once invoked), scanned A, original, MIT.

A workflow for adding multiplayer features to an existing Summer Engine game, such as cooperative play, online play, player-versus-player matches, or lobbies. It helps choose how game state is controlled and shared between players.

In plain words
What is it for?
Use it to plan host-based, server-based, or peer-to-peer multiplayer; configure MultiplayerAPI, MultiplayerSpawner, MultiplayerSynchronizer, and ENet; and choose suitable remote procedure call patterns.
Why use it?
Multiplayer architecture decisions are difficult to change later. This workflow makes you decide the game type, player count, network, and authority model before writing networking code.

Skill for Claude CodeCodex

Part of the summer plugin — 80 skills, 2 commands, 2 hooks, 1 MCP server shipped together

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/summerengine/summer-engine-agent/setup-multiplayer
Any agent
npx skills add SummerEngine/summer-engine-agent --skill setup-multiplayer
Clone the repo
git clone --depth 1 https://github.com/SummerEngine/summer-engine-agent

Made for: Claude Code, Codex.

Or install summer, the plugin that ships this one along with the rest of its 80 skills, 2 commands, 2 hooks, 1 MCP server.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for setup-multiplayer

README.md
[![agentmods](https://agentmods.dev/badge/skills/summerengine/summer-engine-agent/setup-multiplayer.svg)](https://agentmods.dev/skills/summerengine/summer-engine-agent/setup-multiplayer)
Your own site
<a href="https://agentmods.dev/skills/summerengine/summer-engine-agent/setup-multiplayer"><img src="https://agentmods.dev/badge/skills/summerengine/summer-engine-agent/setup-multiplayer.svg" alt="Measured on agentmods" height="20"></a>
Per session 125 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,670 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found 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 $0.00125 $0.03670
Opus 5 $0.00063 $0.01835
Sonnet 5 $0.00025 $0.00734
Haiku 4.5 $0.00013 $0.00367

Measured yesterday against content hash 80d1a10ab8cc, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

setup-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.

skills/multiplayer-and-networking/setup-multiplayer/SKILL.md · 337 lines

How it starts

The opening of the file, as written. The whole thing — 337 lines — stays where its author put it; the contents beside it link to each section on GitHub.

/setup-multiplayer — Add Multiplayer Without Repainting the Project

Overview

Multiplayer is a one-way door. Pick the wrong authority model and refactoring later is brutal. Start with Summer Engine's high-level MultiplayerAPI + MultiplayerSpawner + MultiplayerSynchronizer + ENet. Do not roll custom networking without a measured reason.

Core principle: the architecture decision (peer authority vs server authority) is harder than the code. Lock it before touching a single RPC.

Steps

1. Ask the four blocking questions

Before any code:

  1. What kind of multiplayer? co-op LAN / co-op online / competitive PvP / lobbies + matchmaking
  2. How many players? 2 / 2–4 / 8+
  3. Who runs the simulation? host (one of the players) / dedicated server / authoritative peer-to-peer
  4. What's the network you're targeting? same Wi-Fi / public internet with ~80ms RTT / mobile

Wait. Each answer flips an irreversible knob.

2. Pick the authority model — irreversible decision

Lock it now. Refactoring authority is a project-killer.

Model Best for Pros Cons
Host authority (one player runs the sim) Co-op (2–4 players), casual PvP, friends-only Cheapest. No server bill. Host migration possible. Host advantage (no lag for them). Cheating possible.
Dedicated server authority Competitive PvP, matchmaking, > 4 players Fair. Anti-cheat possible. Stable. Server bill. Need a deploy story. Higher complexity.
Peer-to-peer with shared authority Lock-step strategy / RTS, fighting games (rollback) Symmetric latency. No "host advantage". Determinism is a project on its own. Hard to debug.

Default recommendation: host authority for co-op (2–4 players), dedicated server for everything else. If user says "competitive PvP" + "lobbies": dedicated.

State the choice explicitly:

Going with host authority for 2–4 player co-op. The first player to start a game is the host. Their scene tree is the source of truth; clients receive replicated state and send input RPCs. Host migration is hard with this model — if the host quits, the game ends. Confirm?

Read the full file on GitHub · 337 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 Changed · +125 tokens per session 80d1a10ab8cc
  2. 5d ago First seen · 337 lines · 0 tokens per session scan A 984008009c48

Subscribe to this mod's changes

setup-multiplayer is a skill published in the GitHub repository SummerEngine/summer-engine-agent (57 stars, last pushed yesterday), licensed MIT. It adds 125 tokens to every session and 3,670 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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