Deno Runtime Guide

tywrap works with Deno 1.46+ using the same NodeBridge as Node.js. Deno requires the npm: prefix for npm imports.

⚠️ Deno Deploy Limitation

Deno Deploy does NOT support subprocess execution. Because NodeBridge spawns a Python subprocess, it cannot run in Deno Deploy.

Alternatives for Deno Deploy:

• Use PyodideBridge — runs Python in-browser via WebAssembly (no subprocess)
• Use HttpBridge — connects to a remote Python server over HTTP

Installation

deno add npm:tywrap
pip install tywrap-ir

Basic Setup

import { NodeBridge } from 'npm:tywrap';
import { setRuntimeBridge } from 'npm:tywrap/runtime';

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

Required Permissions

Deno requires explicit permission flags for subprocess execution:

deno run \
  --allow-run=python3 \
  --allow-read \
  --allow-env \
  your-script.ts

Flag	Reason
--allow-run=python3	Spawn the Python subprocess
--allow-read	Read Python scripts and config files
--allow-env	Read TYWRAP_* and PATH environment variables

Type Checking

deno check src/index.ts

Configuration Options

See the Node.js guide for the full NodeBridgeOptions reference — all options work identically in Deno.

When to Use Each Bridge in Deno

Scenario	Bridge	Notes
Local Deno script	NodeBridge	Needs --allow-run
Deno Deploy	PyodideBridge	WebAssembly, no subprocess
Deno Deploy + heavy Python libs	HttpBridge	Python runs on a separate server

Environment Variables

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

Troubleshooting

PermissionDenied: Requires run access to "python3" — Add --allow-run=python3 to your deno run command.

NotSupported: Subprocess access is not allowed — You are running in Deno Deploy. Switch to PyodideBridge or HttpBridge.

See the Node.js troubleshooting guide for additional patterns.