Bun Runtime Guide

tywrap works with Bun 1.1+ using the same NodeBridge as Node.js. No separate bridge is needed.

Installation

bun add tywrap
pip install tywrap-ir

Basic Setup

import { NodeBridge } from 'tywrap/node';
import { setRuntimeBridge } from 'tywrap/runtime';

setRuntimeBridge(new NodeBridge({
  pythonPath: 'python3',
  virtualEnv: '.venv',
  timeoutMs: 30000,
}));

Note: Both 'tywrap/node' and 'tywrap' work on Bun. Use 'tywrap/node' for smaller bundles via tree-shaking.

Configuration Options

NodeBridge accepts the same options under Bun as under Node.js. See the Node.js guide for the full option reference.

Key options:

Option	Default	Description
pythonPath	auto-detect	Path to python3 executable
virtualEnv	—	Path to virtual environment directory
timeoutMs	30000	Request timeout in milliseconds
inheritProcessEnv	false	Set true to pass full process.env to subprocess

bunfig.toml

tywrap ships with a bunfig.toml for build and run settings:

[build]
target = "bun"
format = "esm"
splitting = true
sourcemap = "external"
external = ["pyodide"]

[dev]
hot = true

Running Bun-Specific Tests

npm run test:bun

Or directly:

LC_ALL=C LANG=C bun run vitest --run test/runtime_bun.test.ts

Virtual Environments

setRuntimeBridge(new NodeBridge({
  pythonPath: '.venv/bin/python',
  virtualEnv: '.venv',
}));

Environment Variables

The same TYWRAP_* env vars work under Bun. See the environment variables reference.

Troubleshooting

python3: command not found — Set pythonPath explicitly or ensure Python is on PATH.

Subprocess times out — Increase timeoutMs. Verify pip install tywrap-ir ran in the correct environment.

See the Node.js troubleshooting guide for additional patterns — all apply equally to Bun.