@langchain/node-vfs

Node.js Virtual File System backend for DeepAgents.

This package provides an in-memory VFS implementation that enables agents to work with files in an isolated environment without touching the real filesystem. It uses node-vfs-polyfill which implements the upcoming Node.js VFS feature (nodejs/node#61478).

Installation

``bash
npm install @langchain/node-vfs deepagents


or


pnpm add @langchain/node-vfs deepagents
`

Quick Start

`typescript
import { VfsSandbox } from "@langchain/node-vfs";
import { createDeepAgent } from "deepagents";
import { ChatAnthropic } from "@langchain/anthropic";

// Create and initialize a VFS sandbox
const sandbox = await VfsSandbox.create({
initialFiles: {
"/src/index.js": "console.log('Hello from VFS!')",
},
});

try {
const agent = createDeepAgent({
model: new ChatAnthropic({ model: "claude-sonnet-4-20250514" }),
systemPrompt: "You are a coding assistant with VFS access.",
backend: sandbox,
});

const result = await agent.invoke({
messages: [{ role: "user", content: "Run the index.js file" }],
});
} finally {
await sandbox.stop();
}
`

Features

- In-Memory File Storage - Files are stored in a virtual file system using node-vfs-polyfill
- Zero Setup - No Docker, cloud services, or external dependencies required
- Full Command Execution - Execute shell commands with automatic file syncing
- Automatic Cleanup - All resources are cleaned up when sandbox stops
- Initial Files - Pre-populate the sandbox with files at creation time
- Fallback Mode - Automatically falls back to temp directory if VFS is unavailable

API Reference

$3

The main class for creating and managing VFS sandboxes.

#### Static Methods

##### VfsSandbox.create(options?)

Create and initialize a new VFS sandbox in one step.

`typescript
const sandbox = await VfsSandbox.create({
mountPath: "/vfs", // Mount path for the VFS (default: "/vfs")
timeout: 30000, // Command timeout in ms (default: 30000)
initialFiles: {
// Initial files to populate
"/README.md": "# Hello",
"/src/index.js": "console.log('Hello')",
},
});
`

#### Instance Methods

##### sandbox.execute(command)

Execute a shell command in the sandbox.

`typescript
const result = await sandbox.execute("node src/index.js");
console.log(result.output); // Command output
console.log(result.exitCode); // Exit code (0 = success)
`

##### sandbox.uploadFiles(files)

Upload files to the sandbox.

`typescript
const encoder = new TextEncoder();
await sandbox.uploadFiles([
["src/app.js", encoder.encode("console.log('Hi')")],
["package.json", encoder.encode('{"name": "test"}')],
]);
`

##### sandbox.downloadFiles(paths)

Download files from the sandbox.

`typescript
const results = await sandbox.downloadFiles(["src/app.js"]);
for (const result of results) {
if (result.content) {
console.log(new TextDecoder().decode(result.content));
}
}
`

##### sandbox.stop()

Stop the sandbox and clean up resources.

`typescript
await sandbox.stop();
`

$3

#### createVfsSandboxFactory(options?)

Create an async factory that creates new sandboxes per invocation.

`typescript
const factory = createVfsSandboxFactory({
initialFiles: { "/README.md": "# Hello" },
});

const sandbox = await factory();
`

#### createVfsSandboxFactoryFromSandbox(sandbox)

Create a factory that reuses an existing sandbox.

`typescript
const sandbox = await VfsSandbox.create();
const factory = createVfsSandboxFactoryFromSandbox(sandbox);
`

Configuration Options

| Option | Type | Default | Description |
| -------------- | -------------------------------------- | ----------- | ----------------------------------------- |
| mountPath | string | "/vfs" | Mount path for the virtual file system |
| timeout | number | 30000 | Command execution timeout in milliseconds |
| initialFiles | Record | undefined | Initial files to populate the VFS |

Error Handling

The package exports a VfsSandboxError class for typed error handling:

`typescript
import { VfsSandboxError } from "@langchain/node-vfs";

try {
await sandbox.execute("some-command");
} catch (error) {
if (error instanceof VfsSandboxError) {
switch (error.code) {
case "NOT_INITIALIZED":
// Handle uninitialized sandbox
break;
case "COMMAND_TIMEOUT":
// Handle timeout
break;
}
}
}
`

$3

- NOT_INITIALIZED - Sandbox not initialized
- ALREADY_INITIALIZED - Sandbox already initialized
- INITIALIZATION_FAILED - Failed to initialize VFS
- COMMAND_TIMEOUT - Command execution timed out
- COMMAND_FAILED - Command execution failed
- FILE_OPERATION_FAILED - File operation failed
- NOT_SUPPORTED - VFS not supported in environment

How It Works

The VFS sandbox uses a hybrid approach for maximum compatibility:

1. File Storage - Files are stored in-memory using the VirtualFileSystem from node-vfs-polyfill
2. Command Execution - When executing commands, files are synced to a temp directory, the command runs, and changes are synced back to VFS
3. Fallback Mode - If node-vfs-polyfill is unavailable, falls back to using a temp directory for both storage and execution

This approach provides the benefits of in-memory storage (isolation, speed) while maintaining full shell command execution support.

Future: Native Node.js VFS

This package uses node-vfs-polyfill which implements the upcoming Node.js VFS feature being developed in nodejs/node#61478.

When the official node:vfs` module lands in Node.js, this package will be updated to use the native implementation for better performance and compatibility.

License

MIT