Extending Summer

Summer is a fork of Godot 4.6.1-stable with an unmodified core/. Everything Godot’s extension system does, Summer does, and the extension points are the same ones you already know. There are three of them. They differ in what they can reach, what they cost to build, and whether you can use them at all. If you are an agent, or you are automating Summer, the answer is almost always the first row. An editor plugin is a text file you write and a line you add to project.godot. It needs no build step, no signing, and no engine source, and it hands you the entire EditorInterface — which is the only way to reach a large set of engine capability that is simply not exposed to ordinary scripts.

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Editor plugins

A @tool script extending EditorPlugin, declared by a plugin.cfg in addons/<name>/, enabled through project.godot. It runs inside the editor process with full editor context. This is the path that turns “the API is not exposed to scripting” into “the API is reachable”. Occluder baking, forcing the import of a file an agent just wrote, saving a scene from code, registering an autoload — none of those are available to a plain script, and all of them are available from inside an editor plugin. It also works without a window. Summer --headless --editor boots the editor, loads enabled plugins, and gives you a live EditorInterface from a shell — with one sharp hazard around your running editor that the deep page documents in full.

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GDExtension

Native shared libraries loaded from a .gdextension file. No engine recompile, no custom binary — the same mechanism stock Godot uses. Summer branches from the 4.6.1-stable tag, so the GDExtension ABI is the stock 4.6.1 ABI. A library built against godot-cpp for 4.6 loads in Summer.

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Engine modules

C++ compiled directly into the binary. This requires building the engine from source, and Summer’s engine source is not public, so modules are not an option for external developers today. The page exists because the distinction matters when you are reading Godot documentation and deciding which extension mechanism a tutorial is describing.

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Using community Godot addons

Most Godot 4 addons work in Summer unchanged. Judge one by these rules rather than by whether it names Summer anywhere:

• Godot 4.6 or 4.x, pure GDScript, @tool + EditorPlugin — the safe case. No ABI, no compilation, no signing. Install into addons/ and enable it like any plugin you wrote yourself.
• Godot 4.x with a GDExtension binary — depends on the addon shipping a build for 4.6 and for your platform. The ABI is stock, so if it loads in Godot 4.6 it loads in Summer. Check GDExtension before assuming.
• Godot 3.x — dead. The 3.x plugin API does not exist in 4.x. This is not a Summer limitation; the same addon fails on stock Godot 4.
• Anything shipped as an engine module or a custom engine build — cannot be used. There is no way to compile it into Summer.

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Next steps

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