pi-lsp-extension

A pi coding agent extension that integrates Language Server Protocol (LSP) servers, giving the LLM access to the same language intelligence that powers your IDE.

Tools

| Tool | Description | |------|-------------| | lsp_diagnostics | Compilation errors and warnings for a file | | lsp_hover | Type information and documentation at a position | | lsp_definition | Go to definition of a symbol | | lsp_references | Find all references to a symbol | | lsp_symbols | List file symbols or search workspace symbols | | lsp_rename | Preview rename refactoring (returns planned edits) |

LSP servers start lazily — they only spin up when a tool is first used on a file of that language.

Auto-diagnostics

After a successful write or edit, if an LSP server is already running for that file type, the extension automatically appends compilation errors to the tool result. This gives the LLM immediate feedback without requiring a separate lsp_diagnostics call.

• Scoped to the single changed file (no workspace-wide noise)
• Only errors, max 10 lines — keeps context lean
• Only fires when a server is already running (no lazy startup)

Installation

git clone https://github.com/samfoy/pi-lsp-extension.git
cd pi-lsp-extension
npm install

Add to your pi settings.json:

{
  "extensions": ["/path/to/pi-lsp-extension/src/index.ts"]
}

Or run directly:

pi -e /path/to/pi-lsp-extension/src/index.ts

Supported Languages

Install the language server you need, then it works automatically:

| Language | Server | Install | |----------|--------|---------| | TypeScript/JavaScript | typescript-language-server | npm i -g typescript-language-server typescript | | Python | pyright-langserver | pip install pyright | | Rust | rust-analyzer | rustup | | Go | gopls | go install golang.org/x/tools/gopls@latest | | Java | jdtls | Eclipse JDT.LS |

Add more at runtime:

/lsp-config ruby solargraph stdio
/lsp-config lua lua-language-server

Commands

| Command | Description | |---------|-------------| | /lsp | Show status of running LSP servers | | /lsp-config <lang> <cmd> [args] | Configure a language server | | /lsp-lombok [path] | Set Lombok jar path for Java (or show current) | | /bemol [run\|watch\|stop\|status] | Manage bemol (Brazil workspaces) |

How it Works

1. Lazy startup — servers start on first tool use for a file type
2. File sync — pi's read/write/edit operations are automatically synced to the LSP via didOpen/didChange
3. Diagnostics cache — the server pushes diagnostics asynchronously; tools read from a local cache
4. Auto-diagnostics — errors are appended to write/edit results when a server is running
5. Shared daemons — in supported workspaces, LSP servers run as background daemons shared across pi sessions

Lombok Support (Java)

If your Java project uses Lombok, jdtls needs the Lombok agent jar to understand generated code. The extension resolves the jar in this order:

1. /lsp-lombok command — set the path at runtime:

   /lsp-lombok /path/to/lombok.jar

2. LOMBOK_JAR environment variable — set before starting pi:

   export LOMBOK_JAR=/path/to/lombok.jar
   pi

3. Auto-detection — in Brazil workspaces, the extension searches env/Lombok-*/runtime/lib/ and env/gradle-cache-2/ automatically.

Run /lsp-lombok with no arguments to see which jar is currently configured.

Architecture

src/
├── index.ts              # Extension entry point
├── lsp-client.ts         # JSON-RPC client (stdio + socket modes)
├── lsp-manager.ts        # Server lifecycle, per-language instances
├── file-sync.ts          # didOpen/didChange tracking
├── lsp-daemon.ts         # Background daemon for shared servers
├── lsp-daemon-launcher.cjs
├── bemol.ts              # Brazil workspace support
├── locks.ts              # File-based locking for daemon coordination
└── tools/
    ├── diagnostics.ts
    ├── hover.ts
    ├── definition.ts
    ├── references.ts
    ├── symbols.ts
    └── rename.ts

Tips

• Position parameters are 1-indexed (line 1, column 1 = first character)
• lsp_rename returns a preview — the LLM uses edit/write to apply changes
• The extension adds a system prompt guideline nudging the LLM to check diagnostics after edits

License

MIT