Summer 4.0, the Game Engine for AI Agents

Your AI agent can now reach every part of Summer. Summer 4.0 is the game engine for AI agents. Any agent, from Claude Code, Codex and Cursor to Claude and ChatGPT, can use it. Your coding agent builds a full multiplayer game in Summer Engine, makes its art and sound, publishes it on Summer Games and then reads how it does. One link connects Summer's cloud. One Summer account covers every app. Publishing a game, live changes, deleting for good and contacting people ask you first.

Summer was always the game engine built for AI. Agents drove the engine well, but the rest of Summer reached them as a long list of tools that grew one feature at a time. 4.0 replaces that list with one catalog of operations. An agent finds the right action, knows what it will use from your credits, and knows when to ask you.

What is new in Summer 4.0?

• One catalog for everything. Assets, publishing, analytics, plans, Summer Apps, the Studio and the engine are operations with plain names, such as assets.generate_3d, store.publish and analytics.summary. The operations reference lists every one.
• One link and one Summer account for every agent app.
• A short list of everyday tools, including search and call for everything else.
• The same commands in your terminal, as summer <area> <action>.
• Agent permissions. Building and generating run on their own. Publishing a game, live changes, deletes and invites ask you first.
• Approval cards in your Studio tab when your agent needs you.
• Agent activity with Undo, so you see what your agent changed and undo the changes that support it.
• Auto top-up, so agents keep going when credits run low.
• Versions for the ChatGPT and Claude app directories.

What does a game engine for AI agents need?

An agent that makes games does more than edit scenes. It makes art, uploads a build, fills in a store page, checks the numbers and changes what players see. Each step touches a different service and carries a different risk. A wrong scene edit is undone with one key. A wrong store page reaches every player.

So every operation in 4.0 follows the same rules:

• Names in plain words. Each operation is area.action, like assets.search or jobs.wait. The area is a word you would use yourself.
• Typed input and one answer shape. One flat input, and the same kind of answer every time, so the agent never guesses.
• A dry run for every change. The agent can ask what would happen before anything changes. For asset generation, the dry run shows the most credits it will use.
• Jobs for long work. A 3D model or a video answers at once with a job, and the agent waits on it with jobs.wait. Nothing in the cloud blocks for minutes.
• One error shape. Out of credits or signed out, the answer has a stable code, a plain message and the next step to take. How Summer answers lists the codes.
• A clear risk level. Each operation is marked by the strongest thing it can do: read, change your own drafts, spend credits, publish, change what players see, or delete for good. Your agent permissions decide which of those run without asking.

How do you connect any agent with one link?

The Summer address works in every agent app that can add an MCP server by its address:

https://mcp.summerengine.com/mcp

In Claude Code, run this in your terminal, then type /mcp and sign in:

claude mcp add --transport http summer https://mcp.summerengine.com/mcp

In Codex, run codex mcp add summer --url https://mcp.summerengine.com/mcp, then codex mcp login summer. Cursor and VS Code take the address in their MCP config. Claude and ChatGPT take it as a custom connector. The Summer MCP page has the exact line for every app. The connect your agent guide covers Claude and ChatGPT step by step.

The first time, a Summer sign-in page opens in your browser. Every app you connect after that uses the same Summer account and the same agent permissions.

The link reaches everything that runs in Summer's cloud. To let your agent build and play the game in Summer Engine on your computer, add the local server too:

npx -y summer-engine@latest setup claude-code --yes

Replace claude-code with your agent, or just tell your agent "Install Summer Engine and let's make a game." Already use Summer? Run npx -y summer-engine@latest login once after you update.

How does your agent find the right operation?

The Summer link starts your agent with 20 tools for the everyday jobs: your account, Summer's docs, your games and projects, searching and generating assets, the store page and publishing, a game's numbers, and waiting on jobs. A short list keeps the agent fast and its context small.

Everything else is two tools away. summer_search takes plain words, like "set a new trailer on my store page", and returns the matching operation with its exact input. summer_call runs it by name. The rules hold either way. Dry runs, permissions and approvals are checked on Summer's side, not in the prompt.

Can you run the same commands in the terminal?

Yes. Every operation is also a command, summer <area> <action>, with its input as flags:

summer whoami
summer ops search set a new trailer
summer assets generate-image --prompt "a cozy pixel-art tavern at night" --dry-run
summer analytics summary --game-id g_123 --days 7

Without a global install, run them as npx -y summer-engine <area> <action>. Add --dry-run to see what would happen, --wait to follow a job until it ends, and --json to print the exact answer an agent gets. An agent with a terminal can script a hundred calls this way instead of making them one by one. The CLI reference has every flag.

What can your agent do without asking?

In Studio, Settings > Agent permissions shows six switches and their defaults. Publish and Prices and live changes show On, but today Summer Games still asks you first for those:

Permission	What it covers	Today
Make and build	Edit drafts, plans and uploads, and start builds	Runs on its own
Spend credits	Generate assets and run paid builds, within your credits and auto top-up limit	Runs on its own
Publish	Publish store pages, versions and releases. Summer's store review still runs first	Asks you once, as the game's owner
Prices and live changes	Change prices and sales, start or stop A/B tests, change member roles	Asks you
Delete for good	Delete or remove things for good	Asks you
Contact people	Send invites and other emails to real people	Asks you

Reading never asks. Changing these switches yourself is coming soon, and only you will be able to turn one on. The permissions guide explains each group. A few things always ask: changing these permissions or auto top-up, entering a game jam (it agrees to the jam's rules) and changing your event limit.

What happens when your agent needs your approval?

When something needs you, the agent does not fail. It asks. If Summer Studio is open in your browser, a card appears in that tab. It starts with "Your agent wants to", says exactly what would change, before and after, and which agent asked. Owner requests show Approve and Decline. Other requests show the action's own word, such as Invite or Remove, and Cancel. With no Studio tab open, the agent gives you the link instead.

Nothing changes until you press it. If what the request would change has changed since, it stops instead of overwriting.

Publishing to Summer Games asks you once today. Your agent uploads the build, fills in the store page and sends you one link to publish. After you approve, Summer's store review runs before anything goes live. Our guide to store art from your agent covers the store page itself, and the publishing docs cover the review.

How do you see and undo what your agent did?

Under the switches, Agent activity lists what your agents changed or asked for through the Summer link, newest first, each marked Done, Waiting for you, Started or Undone. Changes to prices, sales, member roles, team names and the event limit have an Undo button. Only you can press it, and it runs once. For prices, roles and the event limit, it refuses if the value changed again since.

How do agents keep going when credits run low?

Generation and paid builds use your Summer credits. Before an asset generation runs, the agent can see the most credits it will use. When you run out, the answer says so and gives one link to add more.

Auto top-up can keep your agents going. Turn it on in Studio on the Billing page or in the Add credits step. You set when credits fall below an amount, how much to add, and a monthly limit. Summer charges your saved card only by that rule, emails a receipt for every charge, and turns the rule off if a charge fails. Your agent never buys credits on its own.

Is Summer in ChatGPT and Claude?

Summer has versions made for the ChatGPT and Claude app directories. Each follows its store's rules. Every action is its own tool, with no search-and-run tool, and the ChatGPT version never shows checkout or billing links. Until the listings are live, add the Summer address as a custom connector in either app. The ChatGPT and Claude guide shows how.

What does a full session look like?

Each line is one ask to your agent.

1. "Make a two-player co-op game about frogs racing on lily pads." The agent builds it in Summer Engine and tests it with two players on your computer. Read how to add multiplayer to your game for that step.
2. "Make the frog model and a jump sound." The model runs as a job, and the sound comes back at once. Our post on game audio with your AI agent goes deeper.
3. "Publish it on Summer Games." The agent fills in the store page and sends you the publish link.
4. "How did it do this week?" The agent reads page views, launches, sessions and play time, with one reading of what to fix. It is the same data you see in Grow in Summer Studio.
5. "Invite sam@example.com to the team." Contacting people asks you first, so a card appears, and the invite goes out when you press Invite.

What are the limits today?

• The engine runs on your computer. The hosted link cannot edit scenes. Add the local server for that. Scene edits show in the editor, where undo works, not in Agent activity.
• Publishing still asks you once, and Summer's store review runs before a game goes live.
• Game numbers come from Summer Games. Games launched in other stores are not counted. The analytics guide explains what is tracked.
• Some Grow tools are still rolling out, such as store page A/B tests.

What should you do next?

Connect one agent with the link above and ask it what it can do for your game. Then let it make something.

Tell your agent "Install Summer Engine and let's make a game."