kakoune-lsp doesn’t manage installation of language servers, please install them by yourself. To see the default set of servers, that work out of the box once installed, see rc/servers.kak or run this command

To enable LSP support for configured languages (see Configuration) add the following commands to your kakrc:

Alternatively, enable LSP only for specific filetypes you need via lsp-enable-window, e.g.:

Below snippet adds useful info to the modeline and creates recommended mappings.

Many servers accept configuration options that are not part of the LSP spec. The TOML table [<server_name>.settings] holds those configuration options. It has the same structure as the corresponding fragments from VSCode’s settings.json. For example:

kakoune-lsp sends the section specified by settings_section, in this case {"formatting.gofumpt":true} as part of initializationOptions and workspace/didChangeConfiguration. Additionally, kakoune-lsp will send any sections requested by the server in workspace/configuration.

The current buffer’s lsp_language_id option value is sent to the language server as languageId. It should usually be the same as Kakoune’s filetype option but depending on the language server it may need to be different. See rc/servers.kak for the default set of exceptions.

It is possible to map more than one language server to a filetype. For example, if you want to set up TSServer and TailwindCSS to use in React projects:

Snippets are completions that come with placeholders ("tabstops") in the places you likely want to insert text (for example as arguments in a function call). The placeholders are highlighted with the two faces SnippetsNextPlaceholders and SnippetsOtherPlaceholders.

The lsp-snippets-select-next-placeholders command allows to jump to the next tabstop (like function call arguments). The suggested mapping uses <tab> (see [Configure key mappings]). Here’s a way to bind it to <c-n> instead (might need to hide the completion menu with Kakoune’s <c-o> command):

Snippet support can be disabled via set-option global lsp_snippet_support false before starting kak-lsp.

kakoune-lsp declares the following Kakoune options:

Inlay hints are used to show inferred types, parameter names in function calls, and the types of chained calls inline in the code. To enable support for it, add the following to your kakrc:

You can change the hints' face with set-face global InlayHint <face>.

Some language servers support "applying" inlay hints: inserting them as text into your document. For example, when using basedpyright to write Python, inlay hints which represent type hints can be explicitly inserted into your code.

We provide two commands for applying inlay hints: lsp-inlay-hint-apply-nearest and lsp-inlay-hint-apply-selected. They both operate per selection. nearest applies whichever hint is closest to the cursor, on the same line. selected applies all hints that fall inside the selection.

kakoune-lsp supports the semanticTokens feature for semantic highlighting. If the language server supports it, you can enable it with:

The faces used for semantic tokens and modifiers are defined via the lsp_semantic_tokens option, for example:

where face is the face that will be applied in Kakoune (you’ll want to define these in your theme/config), token is the token’s name as reported by the language server (see lsp-capabilities) and modifiers is an array of modifier names (also reported by the language server). modifiers may be omitted, but token and face are required.

You may create any arbitrary number of definitions with permutations between the token names and modifiers reported by the server. For an entry to match a token, all the entry’s modifiers must exist on the token. However, the token may have additional modifiers not assigned in the config entry.
kakoune-lsp will find the most specific matching configuration to apply, where specificity is defined as the number of matching modifiers. If multiple matching entries have the same number of modifiers, the one that was defined last in the configuration wins.

Example:

Assuming the following configuration,

kakoune-lsp will perform these mappings:

kakoune-lsp supports showing diagnostics inline after their respective line, but this behavior can be somewhat buggy and must be enabled explicitly:

kakoune-lsp shows some additional information provided by the language server in an info box. This information includes documentation for the token under the cursor (lsp-hover) and documentation for completion candidates. In both cases, the Language Server Protocol allows for both plain text and Markdown, and most servers do implement Markdown.

To make use of Markdown, kakoune-lsp transpiles it into Kakoune’s markup language, utilizing various faces for styling. These faces all default to the Information face, to ensure that the text in the info box works with any color scheme.

To enable Markdown highlighting, define some of the following faces in your theme or kakrc:

For convenience, here is a snippet to paste into your theme/config:

Current limitations of this feature are:

kakoune-lsp works best with UTF-8 documents.

The LSP spec says that column offsets (Position.character) are to be interpreted as UTF-16 code units. Many servers violate the spec. Please refer to https://github.com/Microsoft/language-server-protocol/issues/376 for some background.

kakoune-lsp adheres to the spec but will prefer UTF-8 offsets if the server advertises support for UTF-8 offsets via client capabilities general.positionEncodings or clangd protocol extension.