Summer Engine MCP guide
How to make games in Codex with Summer Engine
Set up Codex CLI with the Summer Engine MCP server so it can operate a running desktop game engine instead of only editing files. Summer Engine is the desktop game engine; Codex CLI is the agent that drives it through MCP.
Summer is free for MCP use
Download the desktop engine and connect it to your agent. You are not paying Summer for the AI calls your existing subscription already covers.
Open Codex CLI
Use the AI editor you already have. The setup command writes the MCP config and installs the Summer game-dev skills.
Run a Summer game
The agent writes code. Summer Engine shows the Summer game, runs Play mode, and helps inspect errors. Export still requires the target templates and toolchains.
Install
Connect Summer to Codex CLI
- 1
Install Summer Engine
Downloads the desktop engine app, about 1 GB. Skip it if Summer Engine is already installed, or if you only need assets and video for a game built in another engine.
- 2
Sign in
Opens your browser once. The CLI and the engine share the session.
- 3
Connect Codex CLI
Writes the summer-engine MCP config and installs the Summer game-dev skills.
- 4
Restart and build
Restart Codex or run /mcp in a new session.
Setup notes
The 2026 specifics.
Summer Games comes too
Setup also adds summer-games, so Codex can see your Summer Games friends, message them and invite them to a party, as you. Sign in once: run `codex mcp login summer-games` and sign in on summer.games in the browser it opens.
Why this matters
Codex CLI writes with your subscription. Summer Engine shows the game.
A chat agent alone can write files. With MCP, Codex CLI gets tools for the running game engine, so it can inspect the project, run commands, and make changes that become playable inside Summer.