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Summer’s AI-agent layer is MIT open source. The Summer Engine desktop app is free to download and use, but its source code is not public right now. This page is also the single canonical status source for Summercraft capabilities: reference pages describe contracts, while this page says whether the supporting production path is live.

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What is open today?

The public repo is the agent layer:
  • CLI
  • MCP server
  • Agent skills
  • Hooks
  • Plugin manifests
Repo: github.com/SummerEngine/summer-engine-agent

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What is free?

The Summer Engine desktop app is free to download and use. Local MCP workflows are free too, including workflows where you bring your existing Claude Code, Cursor, Codex, Gemini, Devin Desktop, or other agent subscription.

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What is paid?

Live hosted Summer services are paid because they run cloud infrastructure and model calls:
  • Hosted Summer AI
  • Asset generation
  • Cloud storage
  • Orchestration
Managed multiplayer is planned as a paid hosted service; it is not production-live today.

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Platform capability status

Status words are deliberate:
  • Live means the production path is deployed and documented.
  • Scaffold means a contract, adapter, or tested local surface exists without a complete production path.
  • Planned means creators and agents must not promise the capability.
See Summer SDK for contracts and Submit Your Summer Game for Review for the currently deployed submission flow.

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Native multiplayer development

The production table above describes the public Summercraft submission and playback path. It is not a statement that multiplayer engine development or restricted staging testing cannot exist. A staging test does not establish general creator access or production availability. Before implementing an online game, identify the environment your installed tools actually support. The public SDK examples on this site describe the scaffolded SummerGame / SummerPlayer contract and game-only .pck submission. They are not an installation or integration guide for a separate native multiplayer development build. Do not copy those stubs into a native runtime and assume the APIs are interchangeable.

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If you have a native development environment

Use the documentation shipped with that exact build. Record its version and the target environment before writing integration code. A usable environment must supply:
  1. A compatible editor/client and an accessible native API reference or starter project.
  2. Creator authentication and a documented publication command for that environment.
  3. A matching hosted build policy, resulting build/release identity, and game configuration.
  4. An authenticated player launcher for each supported device and a documented join flow.
These are setup requirements for an online test, not tasks to solve inside gameplay scripts. This public documentation does not currently provide a self-service native staging installer, credentials, or player launcher. Do not invent their URLs, substitute public PCK submission for a different publication protocol, or require access to an internal expert assistant. Missing setup must be reported as a specific missing input.

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Work that can proceed

An agent can inspect installed tools, verify their versions, read the matching API reference, and build the requested gameplay when that integration contract is available. A missing hosted launch prerequisite does not require abandoning all game development. Keep any unfinished online requirement explicit; a local prototype does not complete a request to play with friends on separate devices. Do not silently replace that request with browser gameplay or a shared keyboard. For online acceptance, launch the same recorded release on two authenticated devices, join the same session, and verify shared gameplay and reconnection. Record any lobby capacity limit from the actual configuration; do not promise an unlimited lobby. Until this succeeds, report what was built and the exact remaining launch gate.

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Is the engine app open source?

No. The desktop app is free proprietary software right now. If Summer publishes engine source later under a no-competing-engine license, the honest term would be source-available, not open source. For the public canonical page, see summerengine.com/source-status.