LSP Tools

Two CLI tools for debugging Language Server Protocol (LSP) servers.

100% slop-generated

Install

npm i -g lsp-tools

lsp-debugger

Interactive web UI for sending and inspecting LSP messages.

lsp-debugger -- <lsp-command> [args...]

Example:

lsp-debugger -- greycat-lang server --stdio

Opens a browser UI at http://localhost:3000 with:

• Editor panel — compose JSON-RPC requests/notifications with method autocomplete (LSP 3.17 catalog)
• Message log — live stream of all sent/received messages, filterable by direction and text
• Latest response viewer — collapsible JSON tree (3 levels expanded by default)
• History — sent messages persisted to localStorage (per LSP command), with replay support
• Resizable panels — drag handles between sidebar, editor, and log
• Theme — dark by default, respects prefers-color-scheme, manual toggle in header
• Paste detection — paste a full JSON-RPC message and it auto-extracts method, type, and params

Keyboard shortcuts

• Ctrl+Enter — send message

lsp-trace

Transparent man-in-the-middle proxy that logs all LSP traffic to a file without altering communication. Unlike a raw tee, it parses the Content-Length framing, pretty-prints JSON-RPC bodies, and labels each message with a timestamp, direction (>>> client, <<< server), method name, and request ID — all interleaved in a single readable log.

lsp-trace [--log <file>] -- <lsp-command> [args...]

Example:

lsp-trace --log session.log -- greycat-lang server --stdio

Use it in place of the real LSP server command in your editor config. Forwards stdin/stdout byte-for-byte while writing to the log file (default: lsp-trace.log).

Requirements

• Node.js >= 18