clef

What is this?

It's a Common Lisp Language server built against the LSP spec, initially built for use with Zed and Helix. Being built as a hobby project and still a WIP, largely functional (I use clef when building clef!). Currently supports::

• Symbol map generation
• Go to defintion
• Find references
• Document symbols (file outline) and workspace symbols
• Call hierarchy (incoming and outgoing calls)
• Diagnostics (error/warning) highlighting w/ correct location for common issues
• Symbol hover doc tooltips
• Mismatched bracket error highlighting
• Function signature assistance

⚠️ SBCL only

This is a deliberate decision, not an oversight, and it will not change.

Much of what makes this project worth doing depends on implementation internals — SBCL's compiler error contexts for real diagnostics, its arena allocator for manual memory, its derived types for type surfacing. CL's portability culture treats that as improper, with the result that the useful implementation-specific thing never gets published at all.

We would rather ship something genuinely good on one implementation than something mediocre everywhere. If you need CCL, ECL, ABCL or LispWorks, this is not for you, and you should know that before adopting it rather than after.

Why the name 'clef'?

It's a cute and short name that starts with 'cl' as is common in the Common Lisp ecosystem. I've lazily backronymed it as the (C)ommon (L)isp (E)ditor (F)acilitator 🤓, but suggestions are welcome!

More

The repo has grown a couple of sibling components alongside the language server — a structured condition extraction/rendering library, and a runner that gives a program legible errors and a meaningful exit code. See docs/motivation.md for why any of this exists and docs/roadmap.md for what's planned in what order. Both are living documents and deliberately keep their open disagreements visible.

{
  "$schema": "https://anthropic.com/claude-code/marketplace.schema.json",
  "name": "clef-marketplace",
  "description": "Local marketplace for CLEF Common Lisp LSP server",
  "owner": {
    "name": "Nathan"
  },
  "plugins": [
    {
      "name": "clef",
      "description": "Common Lisp language server (CLEF) for code intelligence - diagnostics, go-to-definition, references, hover, and completion",
      "version": "1.0.0",
      "author": {
        "name": "Nathan"
      },
      "source": "./",
      "lspServers": {
        "lisp": {
          "command": "clef",
          "extensionToLanguage": {
            ".lisp": "lisp",
            ".cl": "lisp",
            ".asd": "lisp"
          }
        }
      }
    }
  ]
}