agentmods.dev

dev-browser

A fallback skill for controlling a persistent Chrome browser through dev-browser when the primary browser automation tool is unavailable or blocked.

In plain words
What is it for?
For browser-based tasks that require an existing Chrome session, but only when the primary browser automation option cannot be used.
Why use it?
It preserves a signed-in browser session and avoids setting up a new disposable browser for each task.

Skill for Claude CodeCodex

59 2mo ago A scan 21 tokens copy · 100% MIT
View the source file udecode/plate-template
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/udecode/plate-template/dev-browser
Any agent
npx skills add udecode/plate-template --skill dev-browser
Clone the repo
git clone --depth 1 https://github.com/udecode/plate-template

Made for: Claude Code, Codex.

Per session 21 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,373 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin 100% copy Near-identical to another mod 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 $0.00021 $0.01373
Opus 5 $0.00010 $0.00687
Sonnet 5 $0.00004 $0.00275
Haiku 4.5 $0.00002 $0.00137

Measured 2d ago against content hash 27539c3ce0d3, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

dev-browser scanned grade A with 1 finding 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 2d ago.

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.

Makes network callslowCapability

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

curl -sS http://127.0.0.1:9222/json/version
Origin

This is a copy

100% identical to dev-browser — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.agents/skills/dev-browser/SKILL.md · 135 lines

How it starts

The opening of the file, as written. The whole thing — 135 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Dev Browser

Use this only as the fallback browser path when [@browser-use](plugin://browser-use@openai-bundled) is unavailable or blocked.

Do not substitute Puppeteer, standalone Playwright, or raw Chrome DevTools for this fallback path.

Installation

npm install -g dev-browser
dev-browser install

Run dev-browser --help to learn more.

Plate Defaults

  • Use dev-browser --connect http://127.0.0.1:9222 by default. Do not preflight 9222 first.
  • Only inspect 9222 after a direct dev-browser --connect http://127.0.0.1:9222 attempt fails.
  • Reuse one persistent debug Chrome on 127.0.0.1:9222. Do not spin up disposable browser instances unless the user asks.
  • Use a dedicated Chrome --user-data-dir for that debug browser, not the user's normal daily Chrome data dir.
  • Clone the signed-in Chrome profile into the dedicated debug dir, then launch the debug browser from that clone.
  • On macOS, launch the debug browser with open -na "Google Chrome" --args ... --remote-debugging-port=9222 so it opens as a separate Chrome instance without hijacking the user's normal window.
  • Do not close or stop the user's connected debug browser. Leave that debug window open and reuse it. Close named pages only when needed.
  • Keep scripts small and direct. Prefer browser.getPage("persistent-main") for the main app.
  • Use dev-browser instead of agent-browser or next-devtools browser_eval.
  • For Plate registry/browser proof, prefer /blocks/[id]-demo over docs wrappers when that standalone demo route exists.
  • If dev-browser gets blocked by a human prompt or loops on the same step, stop and ask the user to unblock.

Fallback Setup

Use this only after dev-browser --connect http://127.0.0.1:9222 fails because no reusable debug Chrome is available or the CDP endpoint is broken.

Rules

  • Prefer one permanent debug browser/profile over disposable automation browsers.
  • Treat a custom --user-data-dir as mandatory, not optional. Chrome 136+ expects remote debugging to happen from a dedicated profile.
  • Keep auth in that profile. Do not fall back to cookie dumps or state files unless the user asks.
  • Use a separate signed-in Chrome profile for browser work, like dev. Do not use the user's normal daily Default profile as the source profile.
  • Clone that separate signed-in Chrome profile into the dedicated debug --user-data-dir; do not point 9222 straight at the user's daily Chrome data dir.
  • On macOS, use open -na "Google Chrome" --args ... for the debug browser. That starts a separate Chrome instance with the dedicated debug profile without touching the user's normal Chrome window.

Read the full file on GitHub · 135 lines

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. 2d ago First seen · 135 lines · 21 tokens per session scan A 27539c3ce0d3

Subscribe to this mod's changes

dev-browser is a skill published in the GitHub repository udecode/plate-template (59 stars, last pushed 2mo ago), licensed MIT. It adds 21 tokens to every session and 1,373 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). It is 100% identical to dev-browser, differing in 0 lines, and is treated as a copy.

Browser automationFrontendProductivityeditornextjsplateradix-uishadcn-uislate
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