Agent skill

Cmux

Manage cloud development sandboxes with cmux. An agent skill from manaflow-ai/manaflow.

MITAuto-check passedProductivity & Automation

Install Cmux

skills CLI

$ npx skills add manaflow-ai/manaflow --skill cmux -a claude-code

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

GitHub CLI

$ gh skill install manaflow-ai/manaflow cmux --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/manaflow-ai/manaflow.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/cmux .claude/skills/cmux && 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 "cmux" agent skill from https://github.com/manaflow-ai/manaflow/tree/main/skills/cmux into .claude/skills/cmux/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cmux", 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/manaflow-ai/manaflow/tree/main/skills/cmux

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 manaflow-ai/manaflow --skill cmux -a codex

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

GitHub CLI

$ gh skill install manaflow-ai/manaflow cmux --agent codex

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

Manual copy

$ git clone --depth 1 https://github.com/manaflow-ai/manaflow.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/cmux .agents/skills/cmux && 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 "cmux" agent skill from https://github.com/manaflow-ai/manaflow/tree/main/skills/cmux into .agents/skills/cmux/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cmux", 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 manaflow-ai/manaflow --skill cmux -a cursor

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

GitHub CLI

$ gh skill install manaflow-ai/manaflow cmux --agent cursor

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

Manual copy

$ git clone --depth 1 https://github.com/manaflow-ai/manaflow.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/cmux .cursor/skills/cmux && 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 "cmux" agent skill from https://github.com/manaflow-ai/manaflow/tree/main/skills/cmux into .cursor/skills/cmux/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cmux", 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/manaflow-ai/manaflow.git --path skills/cmux

--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 manaflow-ai/manaflow --skill cmux -a gemini-cli

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

GitHub CLI

$ gh skill install manaflow-ai/manaflow cmux --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/manaflow-ai/manaflow.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/cmux .gemini/skills/cmux && 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 "cmux" agent skill from https://github.com/manaflow-ai/manaflow/tree/main/skills/cmux into .gemini/skills/cmux/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cmux", 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 manaflow-ai/manaflow cmux

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 manaflow-ai/manaflow --skill cmux -a github-copilot

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

Manual copy

$ git clone --depth 1 https://github.com/manaflow-ai/manaflow.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/cmux .github/skills/cmux && 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 "cmux" agent skill from https://github.com/manaflow-ai/manaflow/tree/main/skills/cmux into .github/skills/cmux/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cmux", 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 manaflow-ai/manaflow --skill cmux -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 manaflow-ai/manaflow cmux --agent opencode

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

Manual copy

$ git clone --depth 1 https://github.com/manaflow-ai/manaflow.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/cmux .opencode/skills/cmux && 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 "cmux" agent skill from https://github.com/manaflow-ai/manaflow/tree/main/skills/cmux into .opencode/skills/cmux/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cmux", 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: cmux
GitHub stars: 1.1k
Token cost: ~2k tokens
SKILL.md length: 360 words
Files: 1
Skills in repo: 2
Repo updated: Oct 6, 2026
First seen: Oct 7, 2026
Licence: MIT

At a glance

Manage cloud development sandboxes with cmux. An agent skill from manaflow-ai/manaflow.

Tasks that involve Browser automation
SKILL.md covers Installation, Quick Start, Commands and Sandbox IDs, plus 3 more sections
Calls npm; reaches 5173-xxx.e2b.app and 3000-xxx.e2b.app
Tasks that involve Web scraping

What it does

Cmux is an agent skill from manaflow-ai/manaflow. Manage cloud development sandboxes with cmux. Create, sync, and access remote VMs. Includes browser automation via Chrome CDP for scraping, testing, and web interaction.

Its SKILL.md is about 2k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Productivity & Automation, covering Browser automation and Web scraping. The repository describes itself as: Open source Claude Code web/Codex Cloud/Devin/Ramp Inspect alternative. The licence is MIT.

When your agent uses it

Tasks that involve Browser automation
Tasks that involve Web scraping

Example prompts

“/cmux”

Requirements

Node.js
Docker

What it can do on your machine

Read from SKILL.md and the folder at commit ab4858e. 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:
- npm
From the folder's file list and the shell code blocks in SKILL.md.
Network
Hosts in commands or code, which the agent is likely to contact:
- 5173-xxx.e2b.app
- 3000-xxx.e2b.app
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

Cmux loads about 2k tokens when it runs. Until then it costs about 44 tokens; SKILL.md has 360 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~44
When it runs · the whole SKILL.md, loaded when a task matches: ~2k

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 manaflow-ai/manaflow at commit ab4858e, republished under its MIT licence (© manaflow-ai). 360 words, ~2,021 tokens.

Download SKILL.mdSave it as .claude/skills/cmux/SKILL.md (or your agent's skills folder).

name: cmux
description: Manage cloud development sandboxes with cmux. Create, sync, and access remote VMs. Includes browser automation via Chrome CDP for scraping, testing, and web interaction.

cmux - Cloud Sandboxes for Development

cmux manages cloud sandboxes for development. Use these commands to create, manage, and access remote development environments with built-in browser automation.

Installation

bash

npm install -g cmux

Quick Start

bash

cmux login                      # Authenticate (opens browser)
cmux start ./my-project         # Create sandbox, upload directory → returns ID
cmux start .                    # Or use current directory
cmux code <id>                  # Open VS Code
cmux pty <id>                   # Open terminal session
cmux upload <id> ./my-project   # Upload files/directories to sandbox
cmux download <id> ./output     # Download files from sandbox
cmux computer screenshot <id>   # Take browser screenshot
cmux stop <id>                  # Stop sandbox
cmux delete <id>                # Delete sandbox
cmux ls                         # List all sandboxes

Preferred: Always use cmux start . or cmux start <local-path> to sync your local directory to a cloud sandbox. This is the recommended workflow over cloning from a git repo.

Commands

Authentication

bash

cmux login               # Login (opens browser)
cmux logout              # Logout and clear credentials
cmux whoami              # Show current user and team

Sandbox Lifecycle

bash

# Preferred: local-to-cloud (syncs your local directory to the sandbox)
cmux start .             # Create sandbox from current directory (recommended)
cmux start ./my-project  # Create sandbox from a specific local directory
cmux start -o .          # Create from local dir and open VS Code immediately

# Alternative: clone from git
cmux start --git user/repo  # Clone a git repo into sandbox

cmux start --docker      # Create sandbox with Docker support
cmux ls                  # List all sandboxes
cmux status <id>         # Show sandbox details and URLs
cmux stop <id>           # Stop sandbox
cmux extend <id>         # Extend sandbox timeout
cmux delete <id>         # Delete sandbox permanently
cmux templates           # List available templates

Access Sandbox

bash

cmux code <id>           # Open VS Code in browser
cmux vnc <id>            # Open VNC desktop in browser
cmux pty <id>            # Interactive terminal session

Work with Sandbox

bash

cmux pty <id>                  # Interactive terminal session (use this to run commands)
cmux exec <id> <command>       # Execute a one-off command

Important: Prefer cmux pty for interactive work. Use cmux exec only for quick one-off commands.

File Transfer

Upload and download files or directories between local machine and sandbox.

bash

# Upload (local → sandbox)
cmux upload <id>                            # Upload current dir to /home/user/workspace
cmux upload <id> ./my-project               # Upload directory to workspace
cmux upload <id> ./config.json              # Upload single file to workspace
cmux upload <id> . -r /home/user/app        # Upload to specific remote path
cmux upload <id> . --watch                  # Watch and re-upload on changes
cmux upload <id> . --delete                 # Delete remote files not present locally
cmux upload <id> . -e "*.log"              # Exclude patterns

# Download (sandbox → local)
cmux download <id>                          # Download workspace to current dir
cmux download <id> ./output                 # Download workspace to ./output
cmux download <id> . -r /home/user/app      # Download from specific remote path

Browser Automation (cmux computer)

Control Chrome browser via CDP in the sandbox's VNC desktop.

bash

cmux computer open <id> <url>    # Navigate to URL
cmux computer back <id>          # Navigate back
cmux computer forward <id>       # Navigate forward
cmux computer reload <id>        # Reload page
cmux computer url <id>           # Get current URL
cmux computer title <id>         # Get page title

Inspect Page

bash

cmux computer snapshot <id>             # Get accessibility tree with element refs (@e1, @e2...)
cmux computer screenshot <id>           # Take screenshot (base64 to stdout)
cmux computer screenshot <id> out.png   # Save screenshot to file

Interact with Elements

bash

cmux computer click <id> <selector>      # Click element (@e1 or CSS selector)
cmux computer type <id> "text"           # Type into focused element
cmux computer fill <id> <sel> "value"    # Clear input and fill with value
cmux computer press <id> <key>           # Press key (Enter, Tab, Escape, etc.)
cmux computer hover <id> <selector>      # Hover over element
cmux computer scroll <id> [direction]    # Scroll page (up/down/left/right)
cmux computer wait <id> <selector>       # Wait for element to appear

Element Selectors

Two ways to select elements:

Element refs from snapshot: @e1, @e2, @e3...
CSS selectors: #id, .class, button[type="submit"]

Sandbox IDs

Sandbox IDs look like cmux_abc12345. Use the full ID when running commands. Get IDs from cmux ls or cmux start output.

Common Workflows

Create and develop in a sandbox (preferred: local-to-cloud)

bash

cmux start ./my-project        # Creates sandbox, uploads files
cmux code cmux_abc123          # Open VS Code
cmux pty cmux_abc123           # Open terminal to run commands (e.g. npm install && npm run dev)

File transfer workflow

bash

cmux upload cmux_abc123 ./my-project     # Push local files to sandbox
# ... do work in sandbox ...
cmux download cmux_abc123 ./output       # Pull files from sandbox to local

bash

cmux computer open cmux_abc123 "https://example.com/login"
cmux computer snapshot cmux_abc123
# Output: @e1 [input] Email, @e2 [input] Password, @e3 [button] Sign In

cmux computer fill cmux_abc123 @e1 "user@example.com"
cmux computer fill cmux_abc123 @e2 "password123"
cmux computer click cmux_abc123 @e3
cmux computer screenshot cmux_abc123 result.png

Browser automation: Scrape data

bash

cmux computer open cmux_abc123 "https://example.com/data"
cmux computer snapshot cmux_abc123   # Get structured accessibility tree
cmux computer screenshot cmux_abc123 # Visual capture

Clean up

bash

cmux stop cmux_abc123      # Stop (can restart later)
cmux delete cmux_abc123    # Delete permanently

Show full SKILL.md (178 more words)Show less

Security: Dev Server URLs

CRITICAL: NEVER share or output raw E2B port-forwarded URLs.

When a dev server runs in the sandbox (e.g., Vite on port 5173, Next.js on port 3000), E2B creates publicly accessible URLs like https://5173-xxx.e2b.app. These URLs have NO authentication — anyone with the link can access the running application.

Rules:

NEVER output URLs like https://5173-xxx.e2b.app, https://3000-xxx.e2b.app, or any https://<port>-xxx.e2b.app URL
NEVER construct or guess E2B port URLs from sandbox metadata
ALWAYS tell the user to view dev servers through VNC: cmux vnc <id>
VNC is protected by token authentication (?tkn=) and is the only safe way to view dev server output
Only VSCode URLs (cmux code <id>) and VNC URLs (cmux vnc <id>) should be shared — these have proper token auth

When a dev server is started:

✓ Dev server running on port 5173
  View it in your sandbox's VNC desktop: cmux vnc <id>
  (The browser inside VNC can access http://localhost:5173)

NEVER do this:

Frontend: https://5173-xxx.e2b.app   ← WRONG: publicly accessible, no auth

Tips

Run cmux login first if not authenticated
Use --json flag for machine-readable output
Use -t <team> to override default team
Use -v for verbose output
Always run snapshot first to see available elements before browser automation
Use element refs (@e1) for reliability over CSS selectors

Files

Just SKILL.md in skills/cmux of manaflow-ai/manaflow.

Open the folder on GitHubat commit ab4858e

Compare with similar skills

Cmux 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.

Cmux compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
Cmux this skillmanaflow-ai/manaflow	1.1k	—	~2k	Automated safety check: Pass	MIT	5 days ago
Dev-Browser CLI AutomationSawyerHood/dev-browser	6.7k	1 repos	~455	Automated safety check: Pass	MIT	1 mo ago
Browser Useletta-ai/letta-code	3.6k	—	~3.3k	Automated safety check: Pass	Apache-2.0	today
Browser Usedavidondrej/skills	4.1k	1 repos	~2.6k	Automated safety check: Pass	MIT	today
Puppeteer Skillsickn33/agentic-awesome-skills	47k	1 repos	~1.2k	Automated safety check: Pass	MIT	2 days ago
Use Tinyfishtinyfish-io/tinyfish-cookbook	2.2k	—	~2.1k	Automated safety check: Pass	MIT	2 days ago

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Questions about Cmux

What does Cmux do?

Manage cloud development sandboxes with cmux. An agent skill from manaflow-ai/manaflow. Cmux is an agent skill from manaflow-ai/manaflow. Manage cloud development sandboxes with cmux.

When should I use Cmux?

Cmux fits situations like: tasks that involve Browser automation; tasks that involve Web scraping.

How do I install Cmux in Claude Code?

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

How do I install Cmux in Codex?

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

Can I use Cmux 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 manaflow-ai/manaflow --skill cmux -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/cmux, .gemini/skills/cmux, .github/skills/cmux and .opencode/skills/cmux in your project.

What does Cmux need to run?

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

Does Cmux access the network?

SKILL.md names 2 domains. In commands or code: 5173-xxx.e2b.app and 3000-xxx.e2b.app; the agent is likely to contact these when it follows the instructions. This is read from the text; nothing was executed.

Is Cmux 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 Cmux use?

Cmux 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 Cmux use?

About 2k tokens (SKILL.md is roughly 8.1k 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 Cmux?

Skills that share tags, products or a category with Cmux: Dev-Browser CLI Automation (SawyerHood/dev-browser, 6.7k stars), Browser Use (letta-ai/letta-code, 3.6k stars), Browser Use (davidondrej/skills, 4.1k stars) and Puppeteer Skill (sickn33/agentic-awesome-skills, 47k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Cmux?

manaflow-ai (a GitHub organization) maintains it in manaflow-ai/manaflow, which has 1,115 GitHub stars. The repository holds 2 skills in this directory. The repository was last updated on October 6, 2026.

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

Install Cmux

Facts

At a glance

What it does

When your agent uses it

Example prompts

Requirements

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

cmux - Cloud Sandboxes for Development

Installation

Quick Start

Commands

Authentication

Sandbox Lifecycle

Access Sandbox

Work with Sandbox

File Transfer

Browser Automation (cmux computer)

Navigation

Inspect Page

Interact with Elements

Element Selectors

Sandbox IDs

Common Workflows

Create and develop in a sandbox (preferred: local-to-cloud)

File transfer workflow

Browser automation: Login to a website

Browser automation: Scrape data

Clean up

Security: Dev Server URLs

Tips

Files

Compare with similar skills

Similar skills

Dev-Browser CLI Automation

Browser Use

Browser Use

Puppeteer Skill

Use Tinyfish

Workflow Automator

More from manaflow-ai/manaflow

Cloudrouter

Related

Questions about Cmux