---
url: 'https://vixl.app/customize/language-servers.md'
description: >-
  Language servers drive hover and completion in the Vixl workbench. Settings >
  LSP is personal and requires the desktop app.
---
# Language servers

Language servers power hover, completion, and diagnostics in the workbench editor, and they back the agent's `lsp` and `diagnostics` tools. Settings > LSP is personal: enable/disable and install state live in `~/.vixl/lsp.json`, auto-download in `settings.json` (`lsp.autoDownload`, default on). A project folder cannot override `lsp.*`. Language servers require the desktop app.

![Editor tab with the language servers menu open, listing TypeScript, Vue, Markdown, and a config diagnostic](/features/editor.png)

## Which languages

Vixl can download servers for TypeScript / JavaScript, JSON, YAML, Markdown, Vue / Nuxt, Python, Rust, Go, Bash, HTML, CSS, Tailwind CSS, Svelte, Astro, Prisma, GraphQL, Dockerfile, Lua, C / C++, Terraform, TOML, Zig, PHP, Kotlin, XML, Postgres, Clojure, and Java.

These catalog rows are not downloaded. They use a binary already on PATH: Deno, Ruby, C# (`csharp-ls`), Swift, Elixir, Haskell, OCaml, Dart, Gleam, Nix, R, and Scala.

ESLint, Oxlint, and Biome are project-local. Vixl does not install them. They need [workspace trust](/concepts/permissions-and-approvals) for the active project.

Vue / Nuxt also installs a TypeScript hybrid helper, shown as TypeScript (Vue / Nuxt Hybrid): an install-only row with no disable toggle.

Package names, versions, and download sources are on [Managed components](/reference/managed-components).

## Download

When you activate a project, Vixl prefetches the default set (TypeScript / JavaScript, JSON, YAML, Markdown) if `lsp.autoDownload` is on. Settings > LSP has the same action. Turn auto-download off for airgapped machines.

You can still install or uninstall an individual downloadable server from its row. Uninstall applies to managed installs only.

## Where they are stored

Install and disable state: personal `~/.vixl/lsp.json` (see [`.vixl` layout](/reference/vixl-layout)). Managed downloads: `~/.vixl/lsp/<server-id>/<version>/`. PATH toolchains are not copied there.

## Use your own

Resolution order for a server: a personal absolute `command` in `lsp.json`, then the managed download, then an allowlisted basename on PATH, then (if the workspace is trusted) a project-relative path or `node_modules/.bin`.

To prefer a binary you installed:

* Put an allowlisted name on PATH, and uninstall the managed copy if one is present (managed wins over PATH).
* Or set `command` in `lsp.json` to an absolute path.

To add a language that is not in the catalog, add an id in `lsp.json` with `command` (argv array) and `extensions`. The program must be an absolute path or an allowlisted basename. Project-relative commands and `node_modules/.bin` require workspace trust. There is no Settings control to add a custom server; edit the file.

For toolchain rows (Deno, Ruby, and the rest above), install that toolchain so the binary is on PATH. Vixl will not download it.

## What the agent uses

The workbench uses language servers for hover, completion, and diagnostics. The agent calls `lsp` for go-to-definition, find-references, hover, document symbols, workspace symbols, and per-file diagnostics, and `diagnostics` for file or workspace issue summaries. Prefer those over grep when you need precise symbols.

See [Use the workbench](/using/use-the-workbench) for the editor status chip, and [Managed components](/reference/managed-components) for upstream sources.