lsp-mcp

LSP intelligence through a persistent daemon. It can run as an MCP server (Claude Code, Codex, any MCP client) or as a Pi package.

One LSP setup, every harness

Coding agents each ship their own LSP story: some have built-in language-server integrations, some rely on shelling out to tsc/eslint/prettier, some have nothing. That means the same edit gets verified differently depending on which harness you happen to be using.

lsp-mcp moves LSP out of the harness and behind MCP. Any MCP-capable agent gets the same lsp_* tools backed by the same warm daemon, the same project config (.lsp-mcp.json), and the same diagnostics/format/autofix behavior:

• Switch harnesses freely — Claude Code, Codex, Pi, opencode, or anything else that speaks MCP: no reconfiguration, no relearning a different LSP integration.

• One daemon per project root — language servers stay warm and are shared across harnesses and sessions, so checks are fast.

• Consistent verification flow — pair it with the lsp-verification skill so every harness checks edits the same way instead of falling back to CLI tools.

• Config lives with the project — .lsp-mcp.json defines servers and formatters once, for every agent that works in the repo.

bun and the language server you select (such as tsgo, typescript-language-server, vscode-eslint-language-server, or gopls) must be available on PATH.

Related MCP server: ACE-MCP

Pi

From npm (not published yet — substitute your scope once it is):

pi install @your-scope/lsp-mcp

From a local checkout:

pi install /absolute/path/to/lsp-mcp
# or for one run
pi -e /absolute/path/to/lsp-mcp/extensions/lsp-mcp.ts

The extension registers the lsp_* tools (diagnostics, definitions, references, hover, symbols, code actions, formatting, rename, and sync) directly in Pi. It starts the bundled MCP server with bun on first use and closes that client when the Pi session ends.

Claude Code (via npm)

claude mcp add lsp-mcp -- bunx @your-scope/lsp-mcp

Or add it to a project .mcp.json (or your user-level MCP config):

{
  "mcpServers": {
    "lsp-mcp": {
      "command": "bunx",
      "args": ["@your-scope/lsp-mcp"]
    }
  }
}

Codex CLI (via npm)

codex mcp add lsp-mcp -- bunx @your-scope/lsp-mcp

Or add it to ~/.codex/config.toml:

[mcp_servers.lsp-mcp]
command = "bunx"
args = ["@your-scope/lsp-mcp"]

Any other MCP client

The server speaks newline-delimited JSON-RPC over standard input/output. Point the client at:

bunx @your-scope/lsp-mcp

Run it directly from a checkout with:

bun run bin/lsp-mcp.ts

Project config

Configure project servers in .lsp-mcp.json at the project root:

{ "servers": ["tsserver"] }

lsp_diagnostics automatically starts matching configured servers — no need to call lsp_start first.

Multiple files per call

The file-based tools accept file as a single path or an array of paths, so a batch of files needs one call:

• lsp_diagnostics — flat list of diagnostics for all files

• lsp_document_symbols — { "results": [{ "file": ..., "symbols": [...] }] }

• lsp_format_document — { "results": [{ "file": ..., "changed": ..., "edits": ... }] }

• lsp_sync_file — { "results": [{ "file": ..., "version": ... }] }

• lsp_autofix — aggregate appliedActions / changedFiles / totalEdits plus per-file results

• lsp_pull_changes — diffs for the given files

Passing a single string keeps the original response shape.

Make your agent verify with LSP

The skill in skills/lsp-verification/ teaches agents to check edits with lsp-mcp — lsp_sync_file → lsp_diagnostics → lsp_autofix — before falling back to tsc, eslint, prettier, or similar CLI tools, whenever a language server covers the file.

Claude Code / opencode (SKILL.md)

# user-level
mkdir -p ~/.claude/skills && cp -R skills/lsp-verification ~/.claude/skills/
mkdir -p ~/.config/opencode/skills && cp -R skills/lsp-verification ~/.config/opencode/skills/
# or project-level
mkdir -p .claude/skills && cp -R skills/lsp-verification .claude/skills/

Codex, Pi, and other AGENTS.md harnesses

Append skills/lsp-verification/AGENTS.md to your project's AGENTS.md.

Releasing

The unscoped lsp-mcp name on npm is a security-holding package, so publish under a scope:

1. Set "name": "@your-scope/lsp-mcp" in package.json (scope must match your npm user or org).

2. npm login (or set NPM_TOKEN for CI).

3. npm publish — the prepublishOnly script runs bun test and tsc --noEmit first.

publishConfig.access is already public (required for scoped packages). The tarball ships bin/, src/, extensions/, plus README/LICENSE/package.json — no tests, lockfile, or local config.