[Cursor] Unable to activate extension in Cursor (`Cannot find package 'vscode'`) - possibly related to ESM build

[paulmelero]

Describe the bug

Activation error

The extension is not working in Cursor.

• I noticed the icons were not visible (whereas the same config in VS Code works fine).
• Then I saw that running the commands result in an error (command 'iconify.clear-cache' not found).
• And then I discovered in Output > Extension Host's log that the extension is not activated:

026-01-16 00:14:09.292 [error] Activating extension antfu.iconify failed due to an error:
2026-01-16 00:14:09.292 [error] Error [ERR_MODULE_NOT_FOUND]: Cannot find package 'vscode' imported from /Users/paul.melero/.cursor/extensions/antfu.iconify-1.0.0-universal/dist/index.js
    at Object.getPackageJSONURL (node:internal/modules/package_json_reader:266:9)
    at packageResolve (node:internal/modules/esm/resolve:779:81)

> Cannot find package 'vscode'

I wonder why, though. At first I thought that it was because the extension is being packed with --no-dependencies, but I guess it's not a good lead, since most extensions depend on vscode (i.e, https://github.com/slidevjs/slidev/blob/main/packages/vscode does the same and it is activated correctly).

vscode as external

Then, comparing both extensions, I saw that both declare 'vscode' as external dependency. So, this might not be an issue either.

Previous versions

I could verify that the activation issue is present in versions >0.12.0, but not in 0.3.4. For some reason, I cannot test the versions in between (were they not published?).

Cursor limitation

Anyway, if this is just a limitation of Curor' plugin API, I understand. In that case, there's not much we can do.

Edit: I found that Prettier v12 had a similar issue, and it was because Cursor does not fully support ESM (wow): prettier/prettier-vscode#3887

Reproduction

Install the extension in VS Code on a project with icons and properly configured (it works), run the same project in Cursor (it does not work). Inspect the Extension Host output to see

System Info

## Extension version
1.0.0

## Cursor info

Version: 2.3.34 (Universal)
VSCode Version: 1.105.1
Chromium: 138.0.7204.251
Node.js: 22.20.0
V8: 13.8.258.32-electron.0
OS: Darwin arm64 25.1.0

## VSCode

Version: 1.108.0 (Universal)

Used Package Manager

npm

Validations

• Follow our Code of Conduct
• Read the Contributing Guide.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A, please open a GitHub Discussion instead.
• The provided reproduction is a minimal reproducible of the bug.

Contributions

• I am willing to submit a PR to fix this issue
• I am willing to submit a PR with failing tests (actually just go ahead and do it, thanks!)

[yeonjulee1005]

Me too..!
So, I changed version 0.3.4..