Plugin-created extended collection is empty, while manually created one works

Question

We’re seeing a difference between extending a published variable collection through the Plugin API and through Figma’s UI.

Our test library contains one number variable with a value of 8. In a second file:
Using Extend collection manually works: the inherited variable appears and is included in the mode’s JSON export.

Using await figma.variables.extendLibraryCollectionByKeyAsync(collectionKey, name) creates the extension, but it shows “No variables in this collection.” Its JSON export contains only parent/mode metadata—no token.

Interestingly, the Plugin API reports the inherited variable and correctly resolves its value to 8. We also successfully wrote an explicit override of 8 to the extension’s mode, but the collection still appeared empty.

We reproduced this with a minimal plugin, without logging, storage, or post-creation reads. Reopening the file and recreating the extension didn’t help.
Is there an additional initialization step required, or is this a bug in how API-created extensions are populated?

Environment: Figma desktop 126.9.10, macOS 26.7.0.

Many thanks in advance
R

Rómulo Lazarde Delgado · Accepted Answer

Quick update: we found a workaround.After creating the extended collection through the Plugin API, we open Manage libraries → Updates and enable “Show updates for all pages.” Only then does an update from the parent library appear. Accepting it makes the inherited variable appear correctly in both the Variables editor and the JSON export.The parent library hasn’t changed or been republished. Deleting and recreating the extension through the API reproduces this behavior. Creating it manually through Figma’s UI works without this extra step.Is this expected behavior or a bug? If expected, is there a supported Plugin API method to complete this synchronization, or must users accept the library update manually after creating an extension?CheersR

adamsmasher · Answer

Hi, ​@Rómulo Lazarde Delgado- thanks for your post andfor detailed description of what you are seeing. Thank you for also including the solution you discovered. I marked it as a best answer for now so it’s easy for others to find.I’m not sure what’s expected here with the Plugin API as far as whether it should do that additional initialization automatically or not, so I’m checking with the team for more information. I will let you know what I find out. Thanks for your patience in the meantime!

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