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Clip an extension onto a tool to produce a wrapped or transformed variant. An extension is a clip-on power that wraps or transforms a tool into a new variant. Applying one branches the tool: the original stays bound, and a new <tool>_<extension> variant appears alongside it. You load the extension’s module, then attach it to a tool — from the manifest or at runtime.

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Load the extension module

Name each extension module under extensions_modules. Importing the module runs its registration, adding the extension to the global catalog.
manifest.yml
List the registered extensions to confirm the catalog:

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Attach it to a tool

Attach an extension in the manifest with the extensions map on a tools entry. The map is keyed by tool name; a value is one combo ([cache]) or a list of combos. A stacked combo [[a, b]] layers both onto one branch.
manifest.yml
The extensions map only attaches — it never selects a tool. A mapped tool that is absent from the selected set raises loudly.

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Or attach at runtime

Apply a tool’s full combo list at runtime. Each --combo is one combo, written as a JSON array of extension elements; repeat it to author several combos at once. An element is a bare extension name or a {"name", "config"} object binding author config. Passing no --combo clears the tool’s extensions.
A wrapper presents the wrapped tool’s input schema unchanged apart from its own control kwargs; a transformer presents its own composed schema. Stacked extensions apply left to right, so [cache, batch] produces batch(cache(tool)).

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See also