# How to Make a Multiplayer Game with AI

> Make a multiplayer game with AI in Summer Engine. One prompt sets up the client and server, and Summer runs a server for every match. Nothing to host.

- URL: https://www.summerengine.com/blog/make-a-multiplayer-game-with-ai
- Published: 2026-10-09T00:00:00.000Z
- Author: Summer Team
- Tags: Multiplayer, AI Game Engine, Tutorial, Summer Engine, AI Game Dev

Multiplayer used to be the part you saved for later. It meant netcode, servers, matchmaking and a monthly hosting bill before a single friend could join. Summer changes that.

Summer Engine is the game engine built for AI. Your game can be multiplayer from day one. You describe what you want, your coding agent builds it, and Summer runs the servers. Summer Engine 0.7.0 shipped on 7 October 2026 with one line in the [0.7.0 release notes](https://www.summerengine.com/changelog/0.7.0): "You can now build multiplayer games."

This guide shows how to make a multiplayer game with AI, step by step, with the real prompts from the docs.

## What does Summer do for a multiplayer game?

Summer runs the pieces a multiplayer game needs, so your agent writes the game and not the plumbing. According to the [multiplayer quickstart](https://docs.summerengine.com/quickstarts/multiplayer-game), that includes:

- **A server for every match.** Summer starts it when the match starts. No player hosts.
- **Matchmaking.** Quick play, ranked and fixed teams. Players press Play and land in a match.
- **Parties.** Friends queue together and play on the same team.
- **Worlds that keep running.** Long-lived worlds that save and wake up when players return.
- **Player progress.** Saves that follow each player to every match and device.
- **Ratings and leaderboards.** Skill ratings and score boards with a public top 50.
- **Chat and friends.** Text chat in your game, plus each player's Summer friends.
- **Instant movement and fair hits.** Movement that feels instant and hit checks that are fair to everyone.

You do not rent or manage any machines.

## Why does this matter for AI game development?

An AI agent is good at writing game code. It is bad at things it cannot see, such as a server you forgot to start or a port your router blocks. When the hard infrastructure is part of the engine, the agent has a clear target: two scenes, a queue and a test run.

The same code runs on your machine and once the game is published. There is no separate server version to keep in sync and no local shortcuts to remove later. What your agent tests is what players get.

If you want the bigger picture on why an engine built for agents works this way, read [what an AI game engine is](/blog/ai-game-engine) and [how the engine-native agent harness works](/blog/engine-native-ai-agent-harness).

## How do I make a multiplayer game with AI, step by step?

You need Summer Engine and a coding agent connected to it. Then follow these steps.

1. **Install Summer Engine.** Tell your agent:

   ```text
   Install Summer Engine and let's make a game.
   ```

2. **Open your Summer game and make it multiplayer.** Copy this prompt into your coding agent. It sets up your server and runs a test with several players on your own computer.

   ```text
   Make my game multiplayer. A client and a server, joining a match, and a first test with several players.
   ```

3. **Not sure how it fits your game yet?** Ask for a plan first. No code is written.

   ```text
   Explain how multiplayer would fit my game. No code, just a plan.
   ```

4. **Add a way to find a match.** For a casual game, start with quick play.

   ```text
   Add quick play. A Play button, a searching screen with Cancel, and joining the match.
   ```

5. **Make movement multiplayer.**

   ```text
   Make my character move in multiplayer. Instant for the player, checked by the server, smooth for everyone else.
   ```

6. **Share the game world.**

   ```text
   Share the score, doors and timer. The server owns them; every player sees the same values.
   ```

7. **Test with Local Play.** Press Play with several players, or let your agent start it. More on this below.

8. **Publish on summer.games** when it plays well.

Every guide in the docs has a "Not sure which fits?" prompt that plans the feature without code. Use it whenever you are unsure. For more ready-made prompts, see our [Summer Engine MCP prompt templates](/blog/summer-engine-mcp-prompt-templates).

## How is a Summer multiplayer game built?

A Summer multiplayer game is one project with two starting scenes, as the guide to [making your game multiplayer](https://docs.summerengine.com/build/multiplayer) explains.

- The **client scene** is what every player runs: input, camera, visuals and menus.
- The **server scene** runs without a screen and owns the rules: the score, the doors, who won.

Three words come up everywhere:

- **World.** One running match or shared place, run by one server. A 10-minute round is a World, and so is a server that stays up for weeks.
- **Session.** One player's seat in a World. Summer checks who the player is before they get one, so your server always knows exactly who did what.
- **Queue.** How players find a World, such as "casual" or "ranked 2v2".

Players sign in once with their Summer account, and your game sees their name in every match.

## How does matchmaking work?

You describe your game modes as queues. Summer groups the players who are searching, starts a server for each match and sends every player to it. A game can declare several queues, for example casual and ranked. The [matchmaking guide](https://docs.summerengine.com/build/matchmaking) covers four setups.

### Quick play

Players are matched in the order they started searching, with no skill check. It suits casual modes, party games and any game that is starting out with few players.

### Ranked

Summer keeps a rating for every player in the queue and matches similar ratings first. If a player waits a while, the range widens. Ratings move with Elo after every ranked match, and new players start at 1200 or a value you choose.

```text
Add a ranked queue. Skill-based matching with a rating that moves after every match.
```

### Fixed teams

2v2, 3v3 or 5v5. Summer splits players into teams, keeps parties together on one team, and in a ranked queue picks the most even split it can find.

```text
Add a team queue. Fixed teams, parties kept together, teams known to the server.
```

### Accept prompt

Every player must accept before the server starts. Use it when a match is a commitment and one away player would ruin it for everyone else.

## How does movement stay fast and fair?

Each player's own device moves their character. A key press moves the character that same frame, and the camera follows at once, on any connection. The server checks each position a player sends. A move that is too fast or out of bounds is refused, and that player snaps back to the last allowed spot. Everyone else sees other players glide smoothly. The [movement guide](https://docs.summerengine.com/build/movement) has the details, including respawns and teleports set by the server.

## How do players share the game world?

Apart from movement, your server owns every fact in the game. Players ask, and the server checks the request first. The [shared state guide](https://docs.summerengine.com/build/shared-state) splits this into four parts:

- **Shared facts.** The score, the timer, a door. Everyone sees the same value, including players who join late.
- **Private facts.** A hand of cards, a wallet, a secret role. Only the owner's device gets it.
- **Requests.** Collect, buy, open, ready. The server accepts or refuses with a reason your game can show.
- **One-off effects.** Sparkles, sounds and hit flashes, sent once as they happen.

This is also what stops a modified client from giving itself points, speed or items.

## What happens when a player leaves or drops out?

No player is the host, so nobody ends the match by leaving. If someone quits or drops out, everyone else keeps playing. A player whose connection drops keeps their seat for a short time, and gets it back if they reconnect in time. A player who leaves for good is recorded as abandoned when the match ends, so the result always covers everyone who played. See [ending a match and showing results](https://docs.summerengine.com/build/match-results).

## Can friends play together?

Yes. Players make parties in the Summer app. When the leader presses Play, every member who has your game open follows into the same search and the same match. Your game can open Summer's invite screen from its own menu. Read [how parties work](https://docs.summerengine.com/build/parties).

```text
Let parties play together. The leader presses Play and every member follows into the same match.
```

## Can a world keep running between sessions?

Yes. A persistent World is a place players come back to, such as a base, a farm or a realm. Your server saves it while people play. When nobody plays, Summer can let it sleep, and it wakes up from its last save when someone joins. Players find their Worlds under My Worlds in Summer Games. Publishing a new version does not touch existing private Worlds. See [persistent worlds](https://docs.summerengine.com/build/persistent-worlds).

```text
Make my World persistent. It saves while people play, sleeps when empty, and players come back to it.
```

## How is player progress saved?

Coins, unlocks, level and settings belong to the player's Summer account, so they follow the player to every match and device. Your server saves them, so nobody can edit a save file to cheat. Only the player's newest match can save, so an old match cannot undo what they earned. See [saving player progress](https://docs.summerengine.com/build/player-progress).

```text
Save player progress. Coins, unlocks and level come back in every match.
```

## How many players can a match hold?

Each kind of World sets the most players it admits, from 1 up to 1,024. Separately, you pick a server size from Small up to 8XL. Turn-based games can start on Small, real-time matches with physics on Standard, and big worlds on Large or bigger. Start small and move up only when your game needs it. See [server size and player count](https://docs.summerengine.com/build/server-size).

## How do I test multiplayer on my own computer?

Local Play runs your whole multiplayer game on one computer. Press Play and Summer starts the server scene in the background plus one game window per player, side by side, each signed in as a test player. Choose the number of players in **Debug > Local Multiplayer**. No account, server or extra tools are needed, and your agent can start it for you.

Check that every window shows the same shared facts, that private facts only appear for their owner, and that your own character never stutters while moving.

## How do I publish a multiplayer game?

The [publishing guide](https://docs.summerengine.com/build/publish) walks through it:

1. In the editor, open **Project > Export**, pick the summer.games preset and click **Export Project**. You get one .zip with your game and its server.
2. Go to summerengine.com/publish, enter your title and click **Create store page**.
3. Upload your export, give it a version and wait for **Checks passed**.
4. Click **Submit for review**. Once approved, click **Go live**.

Your agent can prepare the project first:

```text
Get my multiplayer game ready to publish. Server preset, platform checks and one summer.games export.
```

A multiplayer game goes to the Summer Games apps for Mac and Windows, with iPhone in beta, and Summer runs its server for you. Players get the [Summer Games desktop apps for Mac and Windows](https://summer.games/download). Star Weavers is already live on summer.games as a multiplayer game for iOS (beta), Mac and Windows. For store art, see [store art from your agent](/blog/introducing-store-art-from-your-agent). For more detail, read [how to publish on Summer Games](https://docs.summerengine.com/publishing/summer-games).

## What are the limits today?

- **Local Play is not the hosted game.** Players are placed straight away with no real search, the accept prompt never appears, and players are not grouped by rating.
- **No parties or friends in Local Play.** Every test window plays solo. Friends features report that they are not available, so build the solo path first.
- **Leaderboards show real data only when hosted.** Your server can still end a match and get test rating changes back.
- **Persistent Worlds start empty in Local Play.** Saves are kept in memory for the run only.
- **Local Play does not pick your server size.** Publish and play with as many players as you expect.
- **Multiplayer runs in the Summer Games apps.** It is not available in a web browser.

## What should I do next?

Pick the guide closest to your game, such as [co-op games](https://docs.summerengine.com/build/games-like/co-op) or [party games](https://docs.summerengine.com/build/games-like/party-games), and paste its "Plan my game" prompt. After launch, learn how to [grow your game in Summer Studio](/blog/grow-your-game-in-summer-studio) and [record game analytics and events](/blog/game-analytics-and-events) so you see what players do.

Tell your agent "Install Summer Engine and let's make a game." Start at [summerengine.com](https://www.summerengine.com).

---

## Machine-readable resources

- Site index for agents: https://www.summerengine.com/llms.txt
- Full inlined content: https://www.summerengine.com/llms-full.txt
- Porting catalog: https://www.summerengine.com/llms-porting.txt
- Structured catalog: https://www.summerengine.com/agent-catalog.json
- Sitemap: https://www.summerengine.com/sitemap.xml
- Developer resources: https://www.summerengine.com/docs