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SSH into a running Kernel browser VM for debugging, running commands, or setting up port forwarding.

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Forward local dev server to browser

A common use case is exposing a local development server to the remote Kernel browser. This lets the browser access localhost URLs that point to your local machine: 
# 1. Start your local dev server (e.g., on port 3000)
npm run dev

# 2. Create a browser with extended timeout
kernel browsers create --timeout 600

# 3. Forward your local server to the VM
#    This exposes localhost:3000 on your machine as localhost:3000 inside the VM
kernel browsers ssh <session-id> -R 3000:localhost:3000

# 4. In the browser's live view, navigate to:
#    http://localhost:3000
Kernel detects browser activity via WebRTC (live view) or CDP connections. SSH connections alone don’t count as activity, so without --timeout, your browser may be cleaned up while you’re connected via SSH. Either set a timeout or keep the live view open.

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Prerequisites

The kernel browsers ssh command requires websocat to be installed locally: 
brew install websocat

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Basic usage

Open an interactive SSH shell to a browser VM: 
kernel browsers ssh <session-id>
By default, this generates an ephemeral ed25519 SSH keypair for the session. The keypair is automatically cleaned up when the session ends.

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Using an existing SSH key

Specify an existing SSH private key instead of generating an ephemeral one: 
kernel browsers ssh <session-id> -i ~/.ssh/id_ed25519
The corresponding .pub file must exist alongside the private key (e.g., ~/.ssh/id_ed25519.pub).

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Port forwarding

Port forwarding uses standard SSH syntax.

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Local forwarding (-L)

Forward a local port to a port on the VM. Useful for accessing services running inside the VM from your local machine: 
# Access VM's port 5432 (e.g., a database) on local port 5432
kernel browsers ssh <session-id> -L 5432:localhost:5432

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Remote forwarding (-R)

Forward a VM port to a port on your local machine. Useful for exposing a local development server to the browser: 
# Expose local dev server (port 3000) on VM port 8080
kernel browsers ssh <session-id> -R 8080:localhost:3000
This allows code running in the browser to access localhost:8080 and reach your local development server.

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Setup only

Configure SSH on the VM without opening a connection: 
kernel browsers ssh <session-id> --setup-only
This installs and configures the SSH server on the VM, then prints the manual connection command. Useful if you want to connect with your own SSH client or configuration.

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Flags

FlagDescription
-i, --identity <path>Path to SSH private key (generates ephemeral if not provided).
-L, --local-forward <spec>Local port forwarding (localport:host:remoteport).
-R, --remote-forward <spec>Remote port forwarding (remoteport:host:localport).
--setup-onlySetup SSH on VM without connecting.