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Harper LS (Grammar & Spelling)

Harper LS (harper-ls) is an offline, privacy-first grammar and spelling checker exposed as a Language Server. It works well for prose-heavy formats such as TeX, LaTeX, Typst, BibTeX, Markdown, and plain text.

TeXlyre connects to Harper LS via WebSocket using lsp-ws-proxy.

1. Install the server​

Harper LS is distributed via Cargo and requires the Rust toolchain.

Install harper-ls:

cargo install harper-ls --locked

2. Install the WebSocket proxy​

TeXlyre requires a WebSocket transport. lsp-ws-proxy bridges WebSocket to stdio.

Install lsp-ws-proxy:

cargo install lsp-ws-proxy --locked

3. Run the server​

Start the proxy and launch Harper LS over stdio:

lsp-ws-proxy -l 127.0.0.1:7000 -- harper-ls --stdio
  • The proxy listens on ws://localhost:7000
  • Keep this process running while using TeXlyre

4. TeXlyre configuration​

You can use more than one LSP at the same time. To do this, simply add another config block below this one in the same list. Keep everything inside the square brackets [ ] and separate each { } block with a comma.

Paste the following JSON into Settings ⚙️ → LSP → Generic LSP → LSP Configurations.

This configuration maps all supported file types to the markdown language ID so Harper LS treats them consistently as prose.

[
  {
    "id": "harper-ls",
    "name": "Harper LS",
    "enabled": true,
    "fileExtensions": ["tex", "latex", "typ", "bib", "md", "txt"],
    "languageIdMap": {
      "tex": "markdown",
      "latex": "markdown",
      "typ": "markdown",
      "bib": "markdown",
      "md": "markdown",
      "txt": "markdown"
    },
    "transportConfig": {
      "type": "websocket",
      "url": "ws://localhost:7000",
      "contentLength": false
    },
    "clientConfig": "{\"rootUri\":\"file:///\",\"workspaceFolders\":[]}"
  }
]

Notes​

  • If you change the proxy port, update transportConfig.url accordingly.
  • Harper LS provides diagnostics and code actions such as ignoring rules or adding words to a dictionary (currently, adding new words to the dictionary is functional but NOT stable in TeXlyre).