Agent skill

Webext Core

Utilities for browser extensions - proxy services for cross-context RPC, type-safe messaging, URL match patterns, fake browser for testing, job scheduling, and shadow DOM isolation.

GPL-3.0Auto-check passedDevelopment

Install Webext Core

skills CLI

$ npx skills add mengxi-ream/read-frog --skill webext-core -a claude-code

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

GitHub CLI

$ gh skill install mengxi-ream/read-frog webext-core --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/mengxi-ream/read-frog.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/webext-core .claude/skills/webext-core && 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/

Paste into Claude Code

Install the "webext-core" agent skill from https://github.com/mengxi-ream/read-frog/tree/main/.agents/skills/webext-core into .claude/skills/webext-core/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "webext-core", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/mengxi-ream/read-frog/tree/main/.agents/skills/webext-core

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add mengxi-ream/read-frog --skill webext-core -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install mengxi-ream/read-frog webext-core --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/mengxi-ream/read-frog.git skills-src && mkdir -p .agents/skills && cp -r skills-src/.agents/skills/webext-core .agents/skills/webext-core && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "webext-core" agent skill from https://github.com/mengxi-ream/read-frog/tree/main/.agents/skills/webext-core into .agents/skills/webext-core/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "webext-core", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add mengxi-ream/read-frog --skill webext-core -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install mengxi-ream/read-frog webext-core --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/mengxi-ream/read-frog.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/.agents/skills/webext-core .cursor/skills/webext-core && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "webext-core" agent skill from https://github.com/mengxi-ream/read-frog/tree/main/.agents/skills/webext-core into .cursor/skills/webext-core/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "webext-core", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/mengxi-ream/read-frog.git --path .agents/skills/webext-core

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add mengxi-ream/read-frog --skill webext-core -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install mengxi-ream/read-frog webext-core --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/mengxi-ream/read-frog.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/.agents/skills/webext-core .gemini/skills/webext-core && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "webext-core" agent skill from https://github.com/mengxi-ream/read-frog/tree/main/.agents/skills/webext-core into .gemini/skills/webext-core/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "webext-core", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install mengxi-ream/read-frog webext-core

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add mengxi-ream/read-frog --skill webext-core -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/mengxi-ream/read-frog.git skills-src && mkdir -p .github/skills && cp -r skills-src/.agents/skills/webext-core .github/skills/webext-core && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "webext-core" agent skill from https://github.com/mengxi-ream/read-frog/tree/main/.agents/skills/webext-core into .github/skills/webext-core/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "webext-core", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add mengxi-ream/read-frog --skill webext-core -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install mengxi-ream/read-frog webext-core --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/mengxi-ream/read-frog.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/.agents/skills/webext-core .opencode/skills/webext-core && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "webext-core" agent skill from https://github.com/mengxi-ream/read-frog/tree/main/.agents/skills/webext-core into .opencode/skills/webext-core/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "webext-core", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: webext-core
GitHub stars: 10k
Token cost: ~633 tokens
SKILL.md length: 117 words
Files: 10 (incl. references)
Skills in repo: 9
Repo updated: Oct 8, 2026
First seen: Oct 7, 2026
Licence: GPL-3.0

At a glance

Utilities for browser extensions - proxy services for cross-context RPC, type-safe messaging, URL match patterns, fake browser for testing, job scheduling, and shadow DOM isolation.

Tasks that involve Browser extensions
SKILL.md covers When to Use, Quick Reference and Most Common Pattern
Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
Tasks that involve Type safety

What it does

Webext Core is an agent skill from mengxi-ream/read-frog. Utilities for browser extensions - proxy services for cross-context RPC, type-safe messaging, URL match patterns, fake browser for testing, job scheduling, and shadow DOM isolation.

Its SKILL.md is about 630 tokens, which your agent loads only when the skill is triggered. The skill folder holds 10 other files, including reference files (for example `GENERATION.md`, `references/fake-browser.md` and `references/isolated-element.md`).

It sits in Development, covering Browser extensions and Type safety. It works with Chrome Extensions. The repository describes itself as: 🐸 Read Frog - Language Learning & Translate | 🐸 陪读蛙 - 语言学习与翻译. The licence is GPL-3.0.

When your agent uses it

Tasks that involve Browser extensions
Tasks that involve Type safety

Example prompts

“Use the webext-core skill to utility for browser extensions - proxy services for cross-context RPC, type-safe messaging, URL match patterns, fake…”
“/webext-core”

What it can do on your machine

Read from SKILL.md and the folder at commit 56f29ed. 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
No scripts in the folder and no shell commands in SKILL.md (its code samples are typescript).
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
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

Webext Core loads about 633 tokens when it runs, and up to ~10k if it reads all its reference files. Until then it costs about 48 tokens; SKILL.md has 117 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~48
When it runs · the whole SKILL.md, loaded when a task matches: ~633
With references · SKILL.md plus every file in references/, read only if the agent opens them: ~10k

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 passed

The automated check found no risky patterns in SKILL.md.

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 mengxi-ream/read-frog at commit 56f29ed, republished under its GPL-3.0 licence (© mengxi-ream). 117 words, ~633 tokens.

Download SKILL.mdSave it as .claude/skills/webext-core/SKILL.md (or your agent's skills folder). This skill also uses 9 other files; get the full folder from GitHub.

name: webext-core
description: Utilities for browser extensions - proxy services for cross-context RPC, type-safe messaging, URL match patterns, fake browser for testing, job scheduling, and shadow DOM isolation.

webext-core - Browser Extension Utilities

When to Use

Apply this skill when:

package.json has any @webext-core/* dependency
Code imports defineProxyService, flattenPromise from @webext-core/proxy-service
Code imports defineExtensionMessaging, defineWindowMessaging from @webext-core/messaging
Code uses MatchPattern from @webext-core/match-patterns
Tests use fakeBrowser from @webext-core/fake-browser
Code uses defineJobScheduler from @webext-core/job-scheduler
Code uses createIsolatedElement from @webext-core/isolated-element

Quick Reference

Package	Purpose	Reference
`@webext-core/proxy-service`	Cross-context RPC — call background services from anywhere	references/proxy-service.md
`@webext-core/messaging`	Type-safe extension/window/custom event messaging	references/messaging.md
`@webext-core/match-patterns`	URL pattern matching utilities	references/match-patterns.md
`@webext-core/fake-browser`	In-memory browser API for unit testing	references/fake-browser.md
`@webext-core/job-scheduler`	Background job scheduling via Alarms API	references/job-scheduler.md
`@webext-core/isolated-element`	Shadow DOM containers for content script UIs	references/isolated-element.md
`@webext-core/storage`	localStorage-like wrapper (prefer WXT storage if using WXT)	references/storage.md
Cross-package patterns and anti-patterns	—	references/patterns.md

Most Common Pattern

// services/counter.ts
import { defineProxyService } from '@webext-core/proxy-service';

const [registerCounter, getCounter] = defineProxyService('CounterService', () => {
  let count = 0;
  return {
    increment: () => ++count,
    getCount: () => count,
  };
});

export { registerCounter, getCounter };

// background.ts — register the real implementation
registerCounter();

// popup or content script — call via proxy (all methods return Promise)
const counter = getCounter();
const newCount = await counter.increment();

Files

SKILL.md and 9 other files (references) in .agents/skills/webext-core of mengxi-ream/read-frog.

SKILL.md
GENERATION.md
references/fake-browser.md
references/isolated-element.md
references/job-scheduler.md
references/match-patterns.md
references/messaging.md
references/patterns.md
references/proxy-service.md
references/storage.md

Open the folder on GitHubat commit 56f29ed

Compare with similar skills

Webext Core 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.

Webext Core compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
Webext Core this skillmengxi-ream/read-frog	10k	—	~633	Automated safety check: Pass	GPL-3.0	today
Crxjssamber/cc-skills	228	—	~2.6k	Automated safety check: Pass	MIT	7 days ago
Wxt Browser Extensionsvantezzen/skip-silence	468	2 repos	~1.9k	Automated safety check: Pass	MIT	3 mo ago
Kimi WebbridgeMoonshotAI/kimi-code	7.8k	—	~3.6k	Automated safety check: Pass	MIT	today
Repomix Browser Extension Developeryamadashy/repomix	29k	1 repos	~288	Automated safety check: Pass	MIT	5 days ago
Deepseek Automationzhu1090093659/deepseek-pp	1.9k	—	~2.1k	Automated safety check: Notes	Apache-2.0	1 mo ago

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Questions about Webext Core

What does Webext Core do?

Utilities for browser extensions - proxy services for cross-context RPC, type-safe messaging, URL match patterns, fake browser for testing, job scheduling, and shadow DOM isolation. Webext Core is an agent skill from mengxi-ream/read-frog. Utilities for browser extensions - proxy services for cross-context RPC, type-safe messaging, URL match patterns, fake browser for testing, job scheduling, and shadow DOM isolation.

When should I use Webext Core?

Webext Core fits situations like: tasks that involve Browser extensions; tasks that involve Type safety.

How do I install Webext Core in Claude Code?

Run `npx skills add mengxi-ream/read-frog --skill webext-core -a claude-code`. Or copy the skill folder (.agents/skills/webext-core in mengxi-ream/read-frog) into .claude/skills/webext-core in your project. Claude Code loads it when a task matches its description.

How do I install Webext Core in Codex?

Run `npx skills add mengxi-ream/read-frog --skill webext-core -a codex`. Or copy the skill folder (.agents/skills/webext-core in mengxi-ream/read-frog) into .agents/skills/webext-core in your project. Codex loads it when a task matches its description.

Can I use Webext Core 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 mengxi-ream/read-frog --skill webext-core -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/webext-core, .gemini/skills/webext-core, .github/skills/webext-core and .opencode/skills/webext-core in your project.

What does Webext Core need to run?

SKILL.md names no scripts, command-line tools or credentials: Webext Core is instructions for the agent only.

Does Webext Core access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Webext Core safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Webext Core use?

Webext Core is published under the GPL-3.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Webext Core use?

About 633 tokens (SKILL.md is roughly 2.5k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 9.4k tokens, read only when the agent opens those files.

What are the alternatives to Webext Core?

Skills that share tags, products or a category with Webext Core: Crxjs (samber/cc-skills, 228 stars), Wxt Browser Extensions (vantezzen/skip-silence, 468 stars), Kimi Webbridge (MoonshotAI/kimi-code, 7.8k stars) and Repomix Browser Extension Developer (yamadashy/repomix, 29k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Webext Core?

mengxi-ream (a GitHub user) maintains it in mengxi-ream/read-frog, which has 9,993 GitHub stars. The repository holds 9 skills in this directory. The repository was last updated on October 8, 2026.

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

Webext Core

Install Webext Core

Facts

At a glance

What it does

When your agent uses it

Example prompts

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

webext-core - Browser Extension Utilities

When to Use

Quick Reference

Most Common Pattern

Files

Compare with similar skills

Similar skills

Crxjs

Wxt Browser Extensions

Kimi Webbridge

Repomix Browser Extension Developer

Deepseek Automation

Live Extension UI Automation

More from mengxi-ream/read-frog

Adversarial Review

Record Extension Demo

Extension Puppeteer Debugging

Wxt

Create PR

Migration Scripts

Questions about Webext Core

Install Webext Core

Facts

At a glance

What it does

When your agent uses it

Example prompts

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

webext-core - Browser Extension Utilities

When to Use

Quick Reference

Most Common Pattern

Files

Compare with similar skills

Similar skills

More from mengxi-ream/read-frog

Related

Questions about Webext Core