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Official agent skill

D3k

by vercel-labs in vercel-labs/dev3000

A skill your agent uses when the user asks to use d3k, run/dev/test/debug a web project with d3k, or reproduce a browser issue.

OfficialMITAuto-check: warnings

Install D3k

The automated check flagged lines worth reading first. See the safety section below.

skills CLI
$ npx skills add vercel-labs/dev3000 --skill d3k -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install vercel-labs/dev3000 d3k --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/vercel-labs/dev3000.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/d3k .claude/skills/d3k && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
d3k
GitHub stars
1.6k
Token cost
~1.5k tokens
SKILL.md length
748 words
Files
3
Skills in repo
3
Repo updated
First seen
Licence
MIT

At a glance

A skill your agent uses when the user asks to use d3k, run/dev/test/debug a web project with d3k, or reproduce a browser issue.

  • Works in 4 steps: Confirm the status response includes the… → Tell the user the monitored browser is… → Keep the d3k process running and wait… → …
  • The user asks to use d3k
  • SKILL.md covers Interpret the Request, Start or Reuse d3k, User-Driven Testing and Agent-Driven Testing, plus 3 more sections
  • Calls bun and npm

What it does

D3k is an agent skill from vercel-labs/dev3000, published by the product's own GitHub organization. Use when the user asks to use d3k, run/dev/test/debug a web project with d3k, or reproduce a browser issue. Own the runtime: reuse or background-start d3k non-interactively, wait for readiness, use its project-stable managed Chrome profile, and inspect unified browser/server evidence.

Its SKILL.md is about 1.5k tokens, which your agent loads only when the skill is triggered. The skill folder holds 3 other files (for example `PUBLISH.md` and `agents/openai.yaml`).

The repository describes itself as: Captures your web app's complete development timeline - server logs, browser events, console messages, network requests, and automatic screenshots - in a unified, timestamped… The licence is MIT.

When your agent uses it

  • The user asks to use d3k
  • Run/dev/test/debug a web project with d3k
  • Reproduce a browser issue

Example prompts

  • “/d3k”

Requirements

  • Node.js

Workflow steps

4 steps, taken from the first numbered list in SKILL.md.

  1. Confirm the status response includes the app URL and "browserConnected": true.
  2. Tell the user the monitored browser is ready.
  3. Keep the d3k process running and wait for the user to reproduce the behavior.
  4. When they report that it happened, begin with

What it can do on your machine

Read from SKILL.md and the folder at commit 3b945d7. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • bun
    • npm

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md. Its commands use npm, which can reach the network depending on how they are called.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

D3k loads about 1.5k tokens when it runs. Until then it costs about 72 tokens; SKILL.md has 748 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~72
When it runs · the whole SKILL.md, loaded when a task matches
~1.5k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check: warnings

The automated check found patterns that need a careful read before installing.

  • WarningMentions a credentials file (SSH keys, cloud or package-manager tokens)SKILL.md:127
    ser startup by default. Its per-project Chrome profile preserves login state, cookies, and local storage.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from vercel-labs/dev3000 at commit 3b945d7, republished under its MIT licence (© vercel-labs). 748 words, ~1,472 tokens.

Download SKILL.mdSave it as .claude/skills/d3k/SKILL.md (or your agent's skills folder). This skill also uses 2 other files; get the full folder from GitHub.
name
d3k
description
Use when the user asks to use d3k, run/dev/test/debug a web project with d3k, or reproduce a browser issue. Own the runtime: reuse or background-start d3k non-interactively, wait for readiness, use its project-stable managed Chrome profile, and inspect unified browser/server evidence.

d3k Agent Runtime

d3k is the local web runtime for this task. It starts the dev server behind a stable Portless URL, owns a project-stable Chrome profile, and records server logs, browser console output, network activity, interactions, and screenshots in one timeline.

When this skill triggers, operate d3k. Do not merely tell the user how to run it.

Interpret the Request

  • "Let me test/dev my project with d3k": prepare the runtime and headed browser, confirm it is ready, then hand control to the user. Wait for them to reproduce the issue before inspecting evidence.
  • "Test/debug/fix this with d3k": prepare the runtime, then drive the managed browser and investigate autonomously.
  • If ambiguous, start the runtime and browser first. That action is safe and useful for either path.

Start or Reuse d3k

Run from the project root.

  1. Check canonical Portless readiness before starting any app process:
bash
d3k portless status --json

If "setupRequired": true, run:

bash
d3k portless setup

On macOS this opens the system administrator authorization dialog. Wait for the user to approve it, then rerun d3k portless status --json. Do not start d3k until "canonical": true, "serviceInstalled": true, and "setupRequired": false. If authorization is declined or unavailable, stop and explain the blocker. Never silently substitute direct localhost.

  1. Check for an existing project runtime:
bash
d3k status --json

Reuse it only if it reports "running": true, "ready": true, "routing": "portless", "browserConnected": true, and a genuinely port-free https://...localhost appUrl. If an active session reports "routing": "direct", stop that retained d3k session and restart after Portless is ready. Do not start a second dev server or browser.

  1. If d3k is not installed, install it:
bash
bun install -g dev3000

Use npm install -g dev3000 only when Bun is unavailable.

  1. Start d3k with the agent's shell/process tool as a retained background or yielded session (non-TUI by default):
bash
d3k -t

Do not wait for this long-running command to exit. Keep its process/session handle so you can monitor or stop it later. Prefer the execution tool's background/session support over shelling with &.

If the target URL is already known, pass it so the managed browser opens there:

bash
d3k -t --app-url "<url>"

Let d3k auto-detect the package manager, dev command, and port. Add --command, --script, or --port only when detection is wrong or the user specified them.

  1. Poll until the runtime is ready:
bash
d3k status --json

A successful status response is the readiness boundary only when it reports "ready": true, "routing": "portless", "browserConnected": true, and a port-free https://...localhost appUrl. The underlying app port may change between runs. If startup fails, inspect the retained process output and d3k logs --type server; do not launch a separate dev server.

Show full SKILL.md (331 more words)Show less

User-Driven Testing

When the user says "let me test":

  1. Confirm the status response includes the app URL and "browserConnected": true.
  2. Tell the user the monitored browser is ready.
  3. Keep the d3k process running and wait for the user to reproduce the behavior.
  4. When they report that it happened, begin with:
bash
d3k errors --context
d3k logs -n 200

Do not replace the headed browser with automation while the user is testing.

Agent-Driven Testing

Drive the exact browser d3k is monitoring:

bash
d3k agent-browser snapshot -i
d3k agent-browser click @e2
d3k agent-browser fill @e3 "text"
d3k errors --context

Use --require-d3k-browser when opening a URL so failure cannot silently create another browser:

bash
d3k agent-browser --require-d3k-browser open "<url>"

After every reproduction or code change, replay the relevant interaction and check d3k errors --context again.

Evidence Commands

Prefer these over ad-hoc log scraping:

bash
d3k status --json
d3k errors --context
d3k logs -n 200
d3k logs --type browser
d3k logs --type server

Artifacts live under ~/.d3k/<project>/, including session.json, logs, screenshots, and the Chrome profile.

Browser and Auth Safety

d3k must own browser startup by default. Its per-project Chrome profile preserves login state, cookies, and local storage.

For Google OAuth, Supabase auth, and other auth-sensitive flows, never substitute raw Chrome, Playwright, a browser MCP session, manual CDP attachment, or agent-browser --profile. Those paths use a different browser/profile and can trigger "This browser or app may not be secure."

If the managed browser is unavailable, stop or interrupt the retained d3k process and restart d3k cleanly. Do not work around it by creating another browser.

Use --headless only for CI or when explicitly requested. Use --servers-only only when browser monitoring is intentionally unwanted.

Operating Rules

  • Do not run npm run dev, bun run dev, or another dev server alongside d3k.
  • Do not start a second d3k when d3k status --json reports an active one.
  • Keep d3k alive across edits and retests.
  • Preserve the project-stable Chrome profile unless the user explicitly asks for a fresh profile.
  • Leave the runtime running when handing a headed browser to the user; stop it only when asked or when the task requires a clean restart.
  • Canonical Portless HTTPS routing is required by default. Never add --no-portless or set PORTLESS=0 unless the user explicitly requests direct localhost routing.

© vercel-labs, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 2 other files in skills/d3k of vercel-labs/dev3000.

  • SKILL.md
  • PUBLISH.md
  • agents/openai.yaml

Open the folder on GitHubat commit 3b945d7

Compare with similar skills

D3k next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

D3k compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
D3k this skillvercel-labs/dev30001.6k—~1.5kAutomated safety check: WarnMIT
Debugasgeirtj/system_prompts_leaks69k—~439Automated safety check: PassCC0-1.0
Openclaw Debuggingopenclaw/openclaw392k—~1.9kAutomated safety check: PassMIT
Debugging Executionsn8n-io/n8n207k—~2.6kAutomated safety check: PassCustom licence
DebuggingJetBrains/intellij-community21k—~422Automated safety check: PassCustom licence
Debugging Toolkitsickn33/agentic-awesome-skills47k1 repos~344Automated safety check: PassMIT

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Questions about D3k

What does D3k do?

A skill your agent uses when the user asks to use d3k, run/dev/test/debug a web project with d3k, or reproduce a browser issue. D3k is an agent skill from vercel-labs/dev3000, published by the product's own GitHub organization. Use when the user asks to use d3k, run/dev/test/debug a web project with d3k, or reproduce a browser issue.

When should I use D3k?

D3k fits situations like: the user asks to use d3k; run/dev/test/debug a web project with d3k; reproduce a browser issue.

How do I install D3k in Claude Code?

Run `npx skills add vercel-labs/dev3000 --skill d3k -a claude-code`. Or copy the skill folder (skills/d3k in vercel-labs/dev3000) into .claude/skills/d3k in your project. Claude Code loads it when a task matches its description.

How do I install D3k in Codex?

Run `npx skills add vercel-labs/dev3000 --skill d3k -a codex`. Or copy the skill folder (skills/d3k in vercel-labs/dev3000) into .agents/skills/d3k in your project. Codex loads it when a task matches its description.

Can I use D3k in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add vercel-labs/dev3000 --skill d3k -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/d3k, .gemini/skills/d3k, .github/skills/d3k and .opencode/skills/d3k in your project.

What does D3k need to run?

Going by SKILL.md and its folder, D3k needs the command-line tools its instructions call (bun and npm). Our summary lists: Node.js.

Does D3k access the network?

SKILL.md contains no URLs. Its commands use npm, which can reach the network depending on how they are called. This is read from the text; nothing was executed.

Is D3k safe to install?

Our automated static check of SKILL.md flagged 1 warning(s): mentions a credentials file (ssh keys, cloud or package-manager tokens). Read the flagged lines before installing; the check is not a guarantee either way.

What licence does D3k use?

D3k is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does D3k use?

About 1.5k tokens (SKILL.md is roughly 5.9k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to D3k?

Skills that share tags, products or a category with D3k: Debug (asgeirtj/system_prompts_leaks, 69k stars), Openclaw Debugging (openclaw/openclaw, 392k stars), Debugging Executions (n8n-io/n8n, 207k stars) and Debugging (JetBrains/intellij-community, 21k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains D3k?

vercel-labs (a GitHub organization, an official publisher) maintains it in vercel-labs/dev3000, which has 1,582 GitHub stars. The repository holds 3 skills in this directory. The repository was last updated on October 7, 2026.

Source: vercel-labs/dev3000 on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.