LSP Extension

Language Server Protocol integration for pi-coding-agent.

Highlights

• Hook (lsp.ts): Auto-diagnostics (default at agent end; optional per write/edit)
• Tool (lsp-tool.ts): On-demand LSP queries (definitions, references, hover, symbols, diagnostics, signatures)
• Manages one LSP server per project root and reuses them across turns
• Efficient: Bounded memory usage via LRU cache and idle file cleanup
• Supports TypeScript/JavaScript, Vue, Svelte, Dart/Flutter, Python, Go, Kotlin, Swift, and Rust

Supported Languages

| Language | Server | Detection | |----------|--------|-----------| | TypeScript/JavaScript | typescript-language-server | package.json, tsconfig.json | | Vue | vue-language-server | package.json, vite.config.ts | | Svelte | svelteserver | svelte.config.js | | Dart/Flutter | dart language-server | pubspec.yaml | | Python | pyright-langserver | pyproject.toml, requirements.txt | | Go | gopls | go.mod | | Kotlin | kotlin-ls | settings.gradle(.kts), build.gradle(.kts), pom.xml | | Swift | sourcekit-lsp | Package.swift, Xcode (*.xcodeproj / *.xcworkspace) | | Rust | rust-analyzer | Cargo.toml |

Known Limitations

rust-analyzer: Very slow to initialize (30-60+ seconds) because it compiles the entire Rust project before returning diagnostics. This is a known rust-analyzer behavior, not a bug in this extension. For quick feedback, consider using cargo check directly.

Usage

Installation

Install the package and enable extensions:

pi install npm:lsp-pi
pi config

Dependencies are installed automatically during pi install.

Prerequisites

Install the language servers you need:

# TypeScript/JavaScript
npm i -g typescript-language-server typescript

# Vue
npm i -g @vue/language-server

# Svelte
npm i -g svelte-language-server

# Python
npm i -g pyright

# Go (install gopls via go install)
go install golang.org/x/tools/gopls@latest

# Kotlin (kotlin-ls)
brew install JetBrains/utils/kotlin-lsp

# Swift (sourcekit-lsp; macOS)
# Usually available via Xcode / Command Line Tools
xcrun sourcekit-lsp --help

# Rust (install via rustup)
rustup component add rust-analyzer

The extension spawns binaries from your PATH.

How It Works

Hook (auto-diagnostics)

1. On session_start, warms up LSP for detected project type
2. Tracks files touched by write/edit
3. Default (agent_end): at agent end, sends touched files to LSP and posts a diagnostics message
4. Optional (edit_write): per write/edit, appends diagnostics to the tool result
5. Shows notification with diagnostic summary
6. Memory Management: Keeps up to 30 files open per LSP server (LRU eviction), automatically closes idle files (> 60s), and shuts down all LSP servers after 2 minutes of post-agent inactivity (servers restart lazily when files are read again).
7. Robustness: Reuses cached diagnostics if a server doesn't re-publish them for unchanged files, avoiding false timeouts on re-analysis.

Tool (on-demand queries)

The lsp tool provides these actions:

| Action | Description | Requires | |--------|-------------|----------| | definition | Jump to definition | file + (line/column or query) | | references | Find all references | file + (line/column or query) | | hover | Get type/docs info | file + (line/column or query) | | symbols | List symbols in file | file, optional query filter | | diagnostics | Get single file diagnostics | file, optional severity filter | | workspace-diagnostics | Get diagnostics for multiple files | files array, optional severity filter | | signature | Get function signature | file + (line/column or query) | | rename | Rename symbol across files | file + (line/column or query) + newName | | codeAction | Get available quick fixes/refactors | file + line/column, optional endLine/endColumn |

Query resolution: For position-based actions, you can provide a query (symbol name) instead of line/column. The tool will find the symbol in the file and use its position.

Severity filtering: For diagnostics and workspace-diagnostics actions, use the severity parameter to filter results:

• all (default): Show all diagnostics
• error: Only errors
• warning: Errors and warnings
• info: Errors, warnings, and info
• hint: All including hints

Workspace diagnostics: The workspace-diagnostics action analyzes multiple files at once. Pass an array of file paths in the files parameter. Each file will be opened, analyzed by the appropriate LSP server, and diagnostics returned. Files are cleaned up after analysis to prevent memory bloat.

# Find all TypeScript files and check for errors
find src -name "*.ts" -type f | xargs ...

# Example tool call
lsp action=workspace-diagnostics files=["src/index.ts", "src/utils.ts"] severity=error

Example questions the LLM can answer using this tool:

• "Where is handleSessionStart defined in lsp-hook.ts?"
• "Find all references to getManager"
• "What type does getDefinition return?"
• "List symbols in lsp-core.ts"
• "Check all TypeScript files in src/ for errors"
• "Get only errors from index.ts"
• "Rename oldFunction to newFunction"
• "What quick fixes are available at line 10?"

Settings

Use /lsp to configure the auto diagnostics hook:

• Mode: default at agent end; can run after each edit/write or be disabled
• Scope: session-only or global (~/.pi/agent/settings.json)

To disable auto diagnostics, choose "Disabled" in /lsp or set in ~/.pi/agent/settings.json:

{
  "lsp": {
    "hookMode": "disabled"
  }
}

Other values: "agent_end" (default) and "edit_write".

Agent-end mode analyzes files touched during the full agent response (after all tool calls complete) and posts a diagnostics message only once. Disabling the hook does not disable the /lsp tool.

File Structure

| File | Purpose | |------|---------| | lsp.ts | Hook extension (auto-diagnostics; default at agent end) | | lsp-tool.ts | Tool extension (on-demand LSP queries) | | lsp-core.ts | LSPManager class, server configs, singleton manager | | package.json | Declares both extensions via "pi" field |

Testing

# Unit tests (root detection, configuration)
npm test

# Tool tests
npm run test:tool

# Integration tests (spawns real language servers)
npm run test:integration

# Run rust-analyzer tests (slow, disabled by default)
RUST_LSP_TEST=1 npm run test:integration

License

MIT