The possibility to add custom language servers in configuration only

[eproxus]

When trying to understand the documentation regarding language server configuration, I kind of guessed that something like this should be possible:

    "languages": {
        "SQL": {
            "language_servers": [
                "sql-language-server"
            ],
        }
    },
    "lsp": {
        "sql-language-server": {
            "binary": {
                "path": "sql-language-server",
                "arguments": [
                    "--method",
                    "stdio"
                ]
            },
            "filetypes": [
                "sql"
            ],
        }
    },

However, Zed just reports this in the log:

[WARN] no language server found matching 'sql-language-server'

There are also some documentation and a lot of comments suggesting custom language servers has to have an extension for them to work.

Why is it not possible to add a custom LSP configuration that uses an external binary? Isn't that the promise of LSP, that you don't have to implement custom support in each and every editor?

Is it simply because Zed doesn't have any support for this (e.g. in contrast to Sublime LSP or other editors) and only has a model where it requires extensions?

[SomeoneToIgnore]

Is it simply because Zed doesn't have any support for this (e.g. in contrast to Sublime LSP or other editors) and only has a model where it requires extensions?

Precisely.

[henrybarreto]

Zed is a really great tool, but that feature is blocking my fully migration to it. I hope they have plans for it.

[hmemcpy]

Sorry for the "me too" message, but it would be great if it were possible to add/extend Zed with a custom LSP server from configuration only, without having to add a custom extension.
In particular, I wanted to add support for RustOwl - an LSP server that highlights lifetime and ownership in Rust, to work alongside the existing rust-analyzer. And it seems that it's not possible to add just from the config.

It would be great to have support for that!

[owlx56]

@hmemcpy It seems Zed extension lacks the necessary API to support RustOwl.

[AbhinavPalacharla]

Has there been any improvement on this?

[eproxus]

Not that I'm aware of. Funnily enough you can add external MCP servers as Docker containers (why not CLI commands?) but not language servers.

[iwinux]

This forced extension thing seems really unnecessary. All I want are some TreeSitter definitions + LSP JSON blocks copied from nvim-lspconfig.

[Askath]

Oh cool. Was wondering why I can not get the Sonarlint lsp to work.. Is there a template that one can use to append an LSP to an existing language/extension?

[shish]

Gah, this is frustrating D:

Does anybody happen to have a "just hook an existing LSP server into zed" extension that I could copy-paste and tweak for my own LSP server?

[Askath]

I Started to Build https://github.com/Askath/zed-sonarlint

Does not fully work because he cannot find the lsp but maybe it helps as a starting point

[SephReed]

I'm also stuck here. Thank you all for making me feel like maybe I'm not so alone or crazy

Further, development is very stilted even when I tried to make an extension. Claude had this to say:

Zed extensions are compiled to WebAssembly, so:

  1. Every LSP code change = Rust rebuild (30-40 seconds)
  2. Every extension change = Rust rebuild
  3. No hot reload for extension development

  This is terrible for rapid development compared to:

  - VS Code: Edit JSON, restart editor (5 seconds)
  - Neovim: Edit Lua config, reload (instant)
  - Emacs: Edit elisp, eval (instant)

  Zed's design choice:
  - WebAssembly for "security" and "performance"
  - But kills developer experience
  - Even simple config changes need compilation

  Your options:
  1. Accept the pain - 40 second rebuild cycle
  2. Switch editors - VS Code has simple JSON-based language extensions
  3. External tooling - Build your own JSDX tools outside any editor

  The Zed team prioritized sandboxing over developer ergonomics. It's a philosophical choice that makes custom language development incredibly
  painful.

[phwhite]

While I agree that a JSON-form of LSP configuration would be really helpful and agree with the ask of this thread, I just wanted to comment that WebAssembly doesn't block rapid development, as highlighted by another user.

I just recently finished a language extension for Zed, and the most complicated part was getting the tree-sitter logic right. I was able to do the rest with help from Zed Agentic AI. There is a "Rebuild" button within the Zed UI to rebuild and reload the extension after a change has been made, and this took less than 10 seconds for me, rebuilding tree-sitter & other components each time I needed to tune/change something.

[SephReed]

Good to know. 10s is not so bad.

I've decided that for rapid development, I'll write my LSP in Zed but test it in VSCode. Once it's working, I'll port it to a Zed extension.

[Jaakkonen]

It'd be super great if there was an ability to add external LSPs into the config. For example testing the tsgo --lsp --stdio for faster Typescript checks and go-to-definitions instead of relying on the Javascript based LSP.

[alinnow]

If one LSP is strictly better than the default, then an alternative action could be to use the key of a language server used in the default configuration (e.g. typescript-language-server (disabled by default) or vstls). I just had the idea to "steal" an unused LSP key for a completely different language even and that works:

    "typescript-language-server": {
      "binary": {
        "arguments": [
          "start"
        ],
        "path": "fish-lsp"
      }
    }

Of course you'll need to install the LSP manually

[iwinux]

All we need is an built-in "extension" that loads any language server defined in settings.

[shish]

I tried that and hit a roadblock already - extensions are hard-coded to be associated with specific file-types, so while you can create a configurable extension like "use whichever LSP server you have configured when you open a .txt file", it won't work for anything except .txt files

[iwinux]

That's a sad news to hear.

[SephReed]

That’s a super clever strategy. Thank you for suggesting this. I might attempt this route later. For now, I switched to developing in VS code that has this ability built in. I plan to port to Zed once all the testing is done. But I would really rather just live in Zed.

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