KCL extension for Zed

[bcorey]

I had codex write a Zed extension wrapper around the KCL LSP. Jon pointed out we could better organize the directories associated with the LSP and clients, so that's been rolled into this PR as well.

Testing

Zed
I installed this extension in Zed as a "dev extension". At first it was reporting all errors twice. This has been fixed by preventing the lsp server from reporting errors on both push and pull interactions with the server. VSCode client had to be tested as well to validate this didn't break things over there.

1. Used "Install dev extension" on the extensions page.
2. selected the modeling-app/rust/kcl-lsp-zed-client folder
3. Normally the extension pulls the latest LSP release. Overrode with the local build to get the error reporting fix included.
4. tested "format buffer" command
5. tested syntax error detection

VSCode

1. built lsp client & server
2. installed from VSIX
3. configured extension to point at the lsp server binary
4. tested "format document"
5. tested syntax error detection

Questions

• Zed extension works without configuring an API key. is it reading my ZOO_API_KEY env variable automatically or is no key needed?
• does anything here look dissimilar to how we do things for our vscode extension?

After Merging

This extension needs to be added to the official extension library once, after which it seems hands-off on our end. The extension will pull the latest KCL LSP release automatically.

1. fork https://github.com/zed-industries/extensions
2. add this repo as an HTTPS submodule

git submodule add \
  https://github.com/KittyCAD/modeling-app.git \
  extensions/zoo-kcl

11. Add this to the registry's extensions.toml

[zoo-kcl]
submodule = "extensions/zoo-kcl"
path = "rust/kcl-language-server/zed"
version = "0.1.3"

12. run pnpm sort-extensions
13. open a PR

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Project	Deployment	Actions	Updated
modeling-app	Ready	Preview	Sep 1, 2026 7:59pm UTC

[codspeed-hq]

Merging this PR will not alter performance

✅ 151 untouched benchmarks
⏩ 126 skipped benchmarks¹

---

_{Comparing bcorey/zed-extension (21ae5e1) with main (8ba70e6)²}

Footnotes

1. 126 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (30c939d) during the generation of this report, so 8ba70e6 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[adamchalmers]

KCL lib will indeed read your API key from $ZOO_API_TOKEN, if it's set. Might want to let the extension take some sort of configuration to read the API key from somewhere else too.

[bcorey]

Updated the main comment to note the folder reorganization effort and the test process for both vscode and zed clients. Includes a fix to keep the LSP server from reporting errors on both push and pull interactions.

[bcorey]

/modeling-app/rust/kcl-lsp-server/benches/lsp_semantic_tokens_benchmark_criterion.rs got rolled into my diff during refactors. It seems to have been recently introduced on main, but let me know if it looks out of place after the folder reorg. @adamchalmers