Typed Python interfaces for the Language Server Protocol, with async sessions and process pooling for Python language servers. Built on Sublime LSP’s generated types. Python 3.12+; one runtime dependency, tomlkit.

• 🛡️ Pyright — the sentinel. Broad typing support and configurable execution environments. Choose basedpyright for extra diagnostics, baselines and semantic highlighting.
• 🔧 Pyrefly — the artificer. Framework-aware analysis with opt-in regex and mock.patch checks.
• 🏹 ty — the scout. Incremental analysis, explanatory diagnostics and precise type narrowing.
• 🤝 Zuban — the diplomat. Mypy-compatible configuration and editor inference for untyped code.

pip install "lsp-types[pyrefly]"  # Or [ty] / [zuban]

import asyncio
from pathlib import Path
from tempfile import TemporaryDirectory

from lsp_types import Session
from lsp_types.pyrefly.backend import PyreflyBackend

async def main():
    with TemporaryDirectory() as workspace:
        session = await Session.create(
            PyreflyBackend(),
            base_path=Path(workspace),
            initial_code='answer: int = "oops"',
        )
        try:
            print(await session.get_diagnostics())
            await session.update_code("answer: int = 42")
            print(await session.get_diagnostics())  # []
        finally:
            await session.shutdown()

asyncio.run(main())

Swap in TyBackend, ZubanBackend, or PyrightBackend. For Pyright, install Node.js and npm install -g pyright (or basedpyright) separately. Sessions write backend configuration into base_path; use a dedicated workspace as above. For types alone, import lsp_types; no server is needed.

All four backends support diagnostics, hover, completion, signature help and rename.

Pyrefly returns completion items unchanged on resolve; ty does not support the request. ty hover returns the type without the symbol name.

📖 API & lifecycle · 🎨 Semantic tokens · 🧭 Backend guide · 🎮 Browser playground

uv sync --all-extras --locked
npm install -g basedpyright
uv run pytest tests
uvx pyright --pythonpath .venv/bin/python
uvx ruff check .
make generate-latest-types