🧠 pi-lsp — Configurable Language Server Tools for Pi

@narumitw/pi-lsp is a native Pi coding agent extension that exposes diagnostics and source-fix tools through configurable Language Server Protocol routes.

The extension is language-agnostic: servers are selected by config and file extension instead of hard-coded language families.

✨ Features

• Configure LSP servers with simple JSON keyed by server name.
• Routes diagnostics and source fixes by configured file extensions.
• Supports multiple servers for the same extension, for example ty and ruff for .py/.pyi diagnostics.
• Uses one internal LSP runner for JSON-RPC framing, subprocess lifecycle, diagnostics, code actions, and workspace edit application.
• Supports workspace roots, file limits, recursive file discovery, server overrides, and write-or-preview edits.
• Starts language servers only for tool calls, then shuts them down.
• Shows statusline activity only while LSP tools are running.

🎯 When to use pi-lsp

Use pi-lsp when an LSP can answer a targeted question about the files being edited faster than the project's authoritative validation commands. It is most useful when:

• a full-project lint or typecheck is slow, but only a few files need intermediate feedback;
• structured diagnostics with exact ranges and severity are easier to act on than CLI output;
• a language server provides a useful source action such as source.fixAll or source.organizeImports;
• a multi-language repository benefits from one configurable interface for targeted diagnostics.

For most repositories, first document the authoritative format, lint, typecheck, build, and test commands in AGENTS.md, then enforce them with pre-commit hooks or CI where appropriate. If those commands are already fast and reliable, pi-lsp may add little value.

A practical workflow is:

1. Use lsp_diagnostics during an edit only when targeted feedback is useful.
2. Optionally use lsp_fix for a supported server-provided source action.
3. Before considering the task complete, run the repository's authoritative validation commands.
4. Treat pre-commit hooks and CI as the final enforcement layer.

Current limitations

• Diagnostics are not continuously injected into the conversation; the agent must call lsp_diagnostics.
• Language servers start and stop for each tool call, so pi-lsp does not retain an editor-like incremental session.
• The current tools expose diagnostics and source code actions, not symbol navigation, references, or semantic rename.
• A clean LSP result does not replace the project's formatter, linter, type checker, build, or tests.
• This project has not yet demonstrated through benchmarks that LSP improves agent task success, latency, or tool usage.

This outcome-first framing is informed by Eric Traut's comment on LSP integration for coding agents: the protocol was not designed specifically for coding agents, and repository-native checks may already provide much of the desired verification value.

📦 Install

pi install npm:@narumitw/pi-lsp

Try without installing permanently:

pi -e npm:@narumitw/pi-lsp

Try this package locally from the repository root:

pi -e ./extensions/pi-lsp

⚙️ Configuration

If no config is provided, pi-lsp ships a broad catalog of direct-command defaults. Servers are started only when matching files are requested. pi-lsp does not download language servers, so install the commands you need and make them available on PATH. During no-config diagnostics, unavailable default commands are filtered before workspace discovery. If none can run, diagnostics completes successfully and reports the skipped servers. Explicitly selected or custom-configured missing commands still report an error.

Language or format	Default server	Startup command	Extensions
JavaScript, TypeScript, JSON, CSS, GraphQL, HTML, Vue, Astro, Svelte	biome	biome lsp-proxy	.js, .jsx, .ts, .tsx, .json, .jsonc, .css, .graphql, .gql, .html, .vue, .astro, .svelte, and module variants
Python typing	ty	ty server	.py, .pyi
Python linting and fixes	ruff	ruff server	.py, .pyi
Rust	rust-analyzer	rust-analyzer	.rs
Go	gopls	gopls	.go
Ruby	rubocop	rubocop --lsp	.rb, .rake, .gemspec, .ru
Elixir	elixir-ls	language_server.sh (language_server.bat on Windows)	.ex, .exs
Zig	zls	zls	.zig, .zon
C#	csharp	roslyn-language-server --stdio --autoLoadProjects	.cs, .csx
F#	fsharp	fsautocomplete	.fs, .fsi, .fsx, .fsscript
Swift and Objective-C++	sourcekit-lsp	sourcekit-lsp	.swift, .mm
C and C++	clangd	clangd --background-index --clang-tidy	C/C++ source and header extensions
Java	jdtls	jdtls	.java
Kotlin	kotlin-lsp	kotlin-lsp --stdio	.kt, .kts
YAML	yaml-language-server	yaml-language-server --stdio	.yaml, .yml
Lua	lua-language-server	lua-language-server	.lua
PHP	intelephense	intelephense --stdio	.php
Prisma	prisma	prisma-language-server --stdio	.prisma
Dart	dart	dart language-server	.dart
OCaml	ocaml-lsp	ocamllsp	.ml, .mli
Bash	bash-language-server	bash-language-server start	.sh, .bash
Terraform	terraform-ls	terraform-ls serve	.tf, .tfvars
LaTeX and BibTeX	texlab	texlab	.tex, .bib
Gleam	gleam	gleam lsp	.gleam
Clojure	clojure-lsp	clojure-lsp listen	.clj, .cljs, .cljc, .edn
Nix	nixd	nixd	.nix
Typst	tinymist	tinymist	.typ, .typc
Haskell	haskell-language-server	haskell-language-server-wrapper --lsp	.hs, .lhs

For example, install the Rust and Go servers with their official toolchains:

rustup component add rust-analyzer rust-src
go install golang.org/x/tools/gopls@latest

Ensure the Go install directory ($GOBIN or $(go env GOPATH)/bin) is also on PATH.

Custom config is resolved in this order:

1. <workspace>/.pi/pi-lsp.json, only when Pi trusts the current project
2. ~/.pi/agent/pi-lsp.json
3. the built-in server catalog

An untrusted project's canonical and legacy files are ignored. A root passed to an LSP tool selects files and the server working directory; it does not grant that directory authority to provide project settings. Project settings always come from the trusted Pi session workspace.

Compatibility: user-scoped lsp.json and trusted project-scoped .pi/lsp.json remain readable with a warning and are never modified automatically; rename them to their canonical pi-lsp.json names. New paths take precedence when both names exist.

pi-lsp-specific environment settings have been removed. Move their values into canonical JSON:

Removed setting	JSON replacement
PI_LSP_CONFIG inline JSON	Save the same object as user pi-lsp.json or trusted project .pi/pi-lsp.json
PI_LSP_CONFIG=/path/to/file.json	Move or copy that configuration to one of the canonical paths above
PI_<SERVER>_LSP_COMMAND	Set the server's command to an argv array, with one string per executable or argument

servers[].env remains supported because it configures the launched LSP child process rather than pi-lsp itself.

Providing custom config replaces the default server map. The following pi-lsp.json example intentionally keeps five selected servers:

{
  "ty": {
    "command": ["ty", "server"],
    "extensions": [".py", ".pyi"]
  },
  "ruff": {
    "command": ["ruff", "server"],
    "extensions": [".py", ".pyi"]
  },
  "biome": {
    "command": ["biome", "lsp-proxy"],
    "extensions": [
      ".astro",
      ".css",
      ".graphql",
      ".gql",
      ".html",
      ".js",
      ".jsx",
      ".json",
      ".jsonc",
      ".ts",
      ".tsx",
      ".vue"
    ]
  },
  "rust-analyzer": {
    "command": ["rust-analyzer"],
    "extensions": [".rs"],
    "pullDiagnosticsGraceMs": 5000
  },
  "gopls": {
    "command": ["gopls"],
    "extensions": [".go"]
  }
}

Use servers when you need global pi-lsp options such as timeout:

{
  "timeout": 30000,
  "servers": {
    "ty": {
      "command": ["ty", "server"],
      "extensions": [".py", ".pyi"],
      "env": {
        "LSP_LOG": "debug"
      },
      "initialization": {
        "settings": {}
      },
      "skipDirectories": ["generated"]
    }
  }
}

Each server entry supports:

• command: argv array used to start the LSP server.
• extensions: file extensions that should route to this server.
• env: environment overrides for the LSP server process. The child inherits Pi's environment, then applies these values; an env.PATH value is also used to resolve command[0].
• initialization: LSP initialization options and workspace configuration values.
• skipDirectories: additional directory names to exclude from recursive discovery. Explicitly requested paths remain available.
• diagnosticsSettleMs: positive number of milliseconds without another push-diagnostics publication before using the latest result. Defaults to 800; the built-in intelephense route uses 4000. The global timeout remains the upper bound.
• pushDiagnosticsGraceMs: positive number of milliseconds to wait for the first publication from a push-only server. It is unset by default, so a silent push-only server waits for the global timeout. The built-in Lua and Haskell routes use 3000; Dart, Terraform, Gleam, and Tinymist use 2000. This lets clean files finish after bounded silence without returning before a late error publication.
• pullDiagnosticsGraceMs: positive number of milliseconds to wait for a newer push publication after a server returns an empty pull-diagnostics result. It is unset by default; the built-in rust-analyzer route uses 5000 because initial workspace analysis can finish after an early empty pull response.

Global options:

• timeout: request timeout in milliseconds. Defaults to 20000.

pi-lsp infers languageId from common extensions and falls back to the extension without the leading dot.

For example, run the configured Ruff server through the project's uv environment without shell-string parsing:

{
  "servers": {
    "ruff": {
      "command": ["uv", "run", "--no-sync", "ruff", "server"],
      "extensions": [".py", ".pyi"]
    }
  }
}

⚠️ Tool changes

lsp_format is no longer provided. pi-lsp now focuses on LSP diagnostics and source code actions:

• lsp_diagnostics
• lsp_fix

Use project formatters or shell commands for formatting workflows.

🛠️ Pi tools

lsp_diagnostics

Run diagnostics through configured servers.

Parameters:

• paths?: files or directories to check. Defaults to the workspace root.
• root?: workspace root. Defaults to cwd.
• limit?: maximum files to open per selected server.
• server?: configured server name, or an array of names. Defaults to all matching servers.

lsp_fix

Apply source fixes or import organization through a configured server that matches its extension. If multiple servers match, pass server explicitly.

Parameters:

• path: file to fix.
• root?: workspace root. Defaults to cwd.
• kind?: source action kind. Defaults to source.fixAll.
• write?: write fixed text back to the file. Defaults to false.
• server?: optional configured server name.

💬 Command

/lsp

Shows configured LSP commands and whether each command is available on PATH.

🗂️ Package layout

extensions/pi-lsp/
├── src/
│   ├── index.ts
│   ├── adapters.ts
│   ├── command.ts
│   ├── files.ts
│   ├── lsp-client.ts
│   ├── pi-lsp.ts
│   ├── routes.ts
│   ├── runner.ts
│   ├── text-edits.ts
│   └── types.ts
├── README.md
├── LICENSE
├── tsconfig.json
└── package.json

🔎 Keywords

Pi extension, Pi Coding Agent, Language Server Protocol, LSP diagnostics, code actions, source fixes, configurable language servers, TypeScript Pi package.

📄 License

MIT. See LICENSE.