LSP extension for pi coding agent. Provides LSP tools that the LLM can use to query language servers, plus automatic diagnostics after edit/write operations.

Features

LSP Tools (callable by LLM)

lsp_hover - Get hover documentation for a symbol
lsp_definition - Find the definition of a symbol
lsp_references - Find all references to a symbol
lsp_completion - Get completion suggestions
lsp_documentSymbol - Get the symbol outline of a file
lsp_diagnostics - Get lint/type-check diagnostics

Auto-Check

Automatically runs LSP diagnostics after edit or write tool calls. If issues are found, sends a message with the diagnostics to the LLM.

Enable/disable:

pi --lsp-auto-check=false  # Disable auto-check
pi --lsp-auto-check=true   # Enable (default)

Manual Check Command

Run diagnostics manually on specific files:

/lsp-check main.go utils.go

Install

cd ~/.pi/extensions/lsp
npm install

CLI Usage (for development/testing)

tsx ./cli.ts <file> <lsp_command> <req_data_json> [--no-daemon]
tsx ./cli.ts daemon <status|stop>

Requests use a long-lived background daemon by default. The daemon is autospawned on first use, keeps one language server alive per (server.id, project root), and evicts idle servers after ServerConfig.idleTtlMs (default: 5 minutes). Pass --no-daemon to use the legacy one-shot path for debugging.

req_data_json is the raw LSP params for the command, minus textDocument.uri (we inject that from <file>).

Commands

hover
definition
references
completion
documentSymbol
diagnostics (waits briefly for the first publishDiagnostics)

Examples

# Hover at line 224, col 23 (LSP is 0-indexed, so subtract 1)
npm run lsp -- backend/api/server.go hover \
  '{"position":{"line":223,"character":22}}'

# Go to definition
npm run lsp -- backend/api/server.go definition \
  '{"position":{"line":223,"character":22}}'

# Document symbols (no params needed)
npm run lsp -- backend/api/server.go documentSymbol '{}'

# Diagnostics
npm run lsp -- backend/api/server.go diagnostics '{}'

# Inspect/stop the background daemon
npm run lsp -- daemon status
npm run lsp -- daemon stop

Set LSP_DEBUG=1 to forward server stderr to the daemon log. The daemon socket is $XDG_RUNTIME_DIR/pi-lsp-$UID.sock (tmpdir fallback); logs are in /tmp/pi-lsp-daemon.log.

Adding A Server

Edit server.ts:

{
  id: "rust-analyzer",
  match: ["rs"],
  command: "rust-analyzer",
  args: [],
  rootMarkers: ["Cargo.toml"],
  languageId: "rust",
}

Adding A Command

Add to the LspCommand union in src/types.ts.
Add a handler in src/commands.ts.

Future

Daemon hardening - persistent metrics, health checks, and richer status output.
Build output - ship compiled JS entrypoints instead of relying on tsx for development.