Herdr Vercel Sandbox Plugin — Development skill for Claude Code

Vercel Sandbox for Herdr

Run one coding-agent CLI per persistent Vercel Sandbox while keeping Herdr as the local terminal and attention-management surface. Codex, OpenCode, and Claude Code ship as built-in adapters. Claude Code `2.1.220`, Codex `0.146.0`, and OpenCode `1.18.9` are lifecycle-verified and normally selectable; each pinned version has a repository-verifiable lifecycle receipt.

mental model

Herdr remains the local control room. The agent pane is a local terminal connected through `vercel sandbox exec --interactive` to a coding-agent CLI running inside an isolated Linux Sandbox. Your keystrokes go into the Sandbox and the agent's terminal output comes back into the Herdr pane.

Herdr does not inspect the microVM directly. The local wrapper sets `HERDR_AGENT=`, which lets Herdr use that agent's screen definitions to classify the visible terminal as working, waiting, or finished. The plugin separately records which Herdr pane maps to which named Sandbox.

You can start a Sandbox at any point in an existing Herdr session. Focus a pane whose current directory is inside a Git worktree and invoke **Start configured agent in a new Sandbox**. The plugin splits that pane, prepares a new Sandbox, and launches the configured agent there.

Starting is an explicit Herdr action. Typing "start a Sandbox" into an unrelated agent does not call the action; that would require exposing the action to the agent as a tool in a later integration.

requirements

• macOS or Linux
• Herdr 0.7.5 or newer
• Node.js 20 or newer
• Git
• Vercel CLI 58.7.1 or newer (managed-image creation and the full lifecycle command surface were verified against 58.7.1)
• A Vercel account with access to the team and project that should own the Sandbox
• A Vercel-linked Git worktree, or explicit scope and project configuration

Vercel account and project setup

The plugin uses the official Vercel CLI on your local machine. It does not collect Vercel credentials or copy the