internal-dev-workbench

A development setup for the Workflow SDK that opens a three-pane tmux session. tmux is a terminal workspace that lets several running programs share one window, while portless provides stable local URLs for separate git worktrees.

In plain words
What is it for?
Use it to start the workflow workbench, observability interface, and related status display in parallel, especially when developing across multiple worktrees.
Why use it?
It keeps each worktree’s development servers isolated and makes the workbench and observability URLs easy to find.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/vercel/workflow/internal-dev-workbench
Any agent
npx skills add vercel/workflow --skill internal-dev-workbench
Clone the repo
git clone --depth 1 https://github.com/vercel/workflow

Made for: Claude Code, Codex.

Per session 122 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,766 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 2 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00122 $0.02766
Opus 5 $0.00061 $0.01383
Sonnet 5 $0.00024 $0.00553
Haiku 4.5 $0.00012 $0.00277

Measured yesterday against content hash 4135589af160, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade B, and why

internal-dev-workbench scanned grade B with 2 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

The scan reads SKILL.md. This mod also ships 1 executable file (statusline.sh), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Reads agent configuration directoriesmediumAgent snooping

.claude/, .codex/, .gemini/ hold keys, settings and other credentials a mod has no legitimate need for.

Wire it into `~/.claude/settings.json` so it works across all sessions and worktrees. **Point the path at your primary checkout, not at a worktree**. Worktrees get deleted, so any path like `~/github/vercel/workflow--<br

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

/usr/bin/curl -s "$(portless get turbopack)/.well-known/workflow/v1/manifest.json" \
skills/internal-dev-workbench/SKILL.md · 167 lines

How it starts

The opening of the file, as written. The whole thing — 167 lines — stays where its author put it; the contents beside it link to each section on GitHub.

internal-dev-workbench

Bootstraps an opinionated 3-pane tmux session for end-to-end Workflow SDK development. Each pane is launched through portless so URLs are stable and worktree-scoped (e.g. https://<branch>.turbopack.localhost), letting multiple worktrees run concurrently without port conflicts. A companion statusline script surfaces the active URLs in Claude Code's prompt.

This is opt-in contributor tooling. The repo's standard dev path (pnpm dev from a workbench, no portless) is unaffected.

Prerequisites

  • tmux installed
  • portless installed globally (npm i -g portless or via Homebrew). Verify with portless --version.
  • Repo bootstrapped: pnpm install && pnpm build. The first run on a fresh worktree must complete both before any dev server can start (the workbench apps depend on built workspace packages; without pnpm build you get MODULE_NOT_FOUND for workflow).
  • WORKFLOW_PUBLIC_MANIFEST=1 is required on the dev server when running e2e tests against it (otherwise /.well-known/workflow/v1/manifest.json is gated).

Layout

With main-vertical, the dev server takes the left column; the right column stacks the observability UI on top of a scratchpad shell:

+----------------------+--------------------------+
|                      |  PANE_OBS: workflow web  |
|                      |  (observability UI       |
|  PANE_DEV: turbopack |   scoped to the          |
|  (Next.js dev)       |   workbench app)         |
|                      +--------------------------+
|                      |  PANE_SH: zsh scratchpad |
|                      |  (repo root, for build, |
|                      |   tests, e2e, git, etc.) |
+----------------------+--------------------------+

Setup

The session name must match the worktree's portless prefix (the basename of the current branch) so the statusline and any other tooling that derives the prefix from the branch can locate it. Always run tmux ls first to confirm there's no pre-existing session with that name; never kill an existing one.

Read the full file on GitHub · 167 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 167 lines · 122 tokens per session scan B 4135589af160

Subscribe to this mod's changes

internal-dev-workbench is a skill published in the GitHub repository vercel/workflow (2,363 stars, last pushed 3d ago), licensed Apache-2.0. It adds 122 tokens to every session and 2,766 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it B with 2 findings (reads agent configuration directories, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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