webctl 0.3.0

Browser automation via CLI — for humans and agents

webctl

Browser automation for AI agents and humans, built on the command line.

# 1. Install
pip install webctl

# 2. Auto-configure your agent (creates skills/prompts for all supported agents)
webctl init

# 3. Start browsing
webctl start
webctl navigate "https://google.com"
webctl snapshot --interactive-only

webctl init automatically generates the skills and prompts your agents need to drive the browser.

Why CLI Instead of MCP?

MCP browser tools have a fundamental problem: the server controls what enters your context. With Playwright MCP, every response includes the full accessibility tree plus console messages. After a few page queries, your context window is full.

CLI flips this around: you control what enters context.

# Filter before context
webctl snapshot --interactive-only --limit 30      # Only buttons, links, inputs
webctl snapshot --within "role=main"               # Skip nav, footer, ads

# Pipe through Unix tools
webctl snapshot | grep -i "submit"                 # Find specific elements
webctl --format jsonl snapshot | jq '.data.role'   # Extract with jq

Beyond filtering, CLI gives you:

Capability	CLI	MCP
Filter output	Built-in flags + grep/jq/head	Server decides
Debug	Run same command as agent	Opaque
Cache & Cost	webctl snapshot > cache.txt	Every call hits server
Script	Save to .sh, version control	Ephemeral
Human takeover	Same commands	Different interface

---

Agent Integration

Step 1: Install

pip install webctl
webctl setup  # Downloads Chromium

Step 2: Generate Skills/Prompts

webctl init              # Project-level (recommended)
webctl init --global     # Global (works across all projects)

This creates:

• Skills for Claude Code and Goose (loaded on-demand when doing web tasks)
• Lean prompts for Gemini, Copilot, and Codex (always in context)

Supported agents:

Agent	Format	Location (project)	Location (global)
claude	Skill	.claude/skills/webctl/SKILL.md	~/.claude/skills/webctl/SKILL.md
goose	Skill	.agents/skills/webctl/SKILL.md	~/.config/agents/skills/webctl/SKILL.md
gemini	Prompt	GEMINI.md	~/.gemini/GEMINI.md
copilot	Prompt	.github/copilot-instructions.md	-
codex	Prompt	AGENTS.md	~/.codex/AGENTS.md
claude-noskill	Prompt	CLAUDE.md (legacy)	~/.claude/CLAUDE.md

Why skills? Skills are loaded on-demand - your agent only reads webctl instructions when actually doing web automation. This keeps your context clean for other tasks.

Select specific agents:

webctl init --agents claude,gemini    # Only Claude and Gemini
webctl init --agents claude-noskill   # Legacy CLAUDE.md format

Step 3: Add to Config (optional)

If your agent doesn't auto-detect the generated files, add this to your system prompt:

For web browsing, use webctl CLI. Run webctl agent-prompt for instructions.

Note: If a browser MCP is already configured, disable it to avoid conflicts.

---

Quick Start (Human Usage)

Verify the installation works by driving it yourself:

webctl start                    # Opens visible browser window
webctl navigate "https://example.com"
webctl snapshot --interactive-only
webctl stop --daemon            # Closes browser and daemon

Global installation with `uv`

uv tool install webctl
uv tool run webctl

Linux system dependencies

playwright install-deps chromium
# Or manually install libraries listed in Playwright documentation

---

Core Concepts

Sessions

Browser stays open across commands. Cookies persist to disk.

webctl start                    # Visible browser
webctl start --mode unattended  # Headless (invisible)
webctl -s work start            # Named profile (separate cookies)

Element Queries

Semantic targeting based on ARIA roles - stable across CSS refactors:

role=button                     # Any button
role=button name="Submit"       # Exact match
role=button name~="Submit"      # Contains text (preferred)

Output Control

webctl snapshot                                    # Human-readable
webctl --quiet navigate "..."                      # Suppress events
webctl --result-only --format jsonl navigate "..." # Pure JSON

---

Commands

Navigation & Observation

webctl navigate "https://..."
webctl back / forward / reload
webctl snapshot --interactive-only        # Buttons, links, inputs only
webctl snapshot --within "role=main"      # Scope to container
webctl query "role=button name~=Submit"   # Debug query
webctl screenshot --path shot.png

Interaction

webctl click 'role=button name~="Submit"'
webctl type 'role=textbox name~="Email"' "[e-mail]"
webctl type 'role=textbox name~="Search"' "query" --submit
webctl select 'role=combobox name~="Country"' --label "Germany"
webctl check 'role=checkbox name~="Remember"'
webctl press Enter
webctl scroll down

Wait Conditions

webctl wait network-idle
webctl wait 'exists:role=button name~="Continue"'
webctl wait 'url-contains:"/dashboard"'

Session & Console

webctl status                   # Current state & error counts
webctl save                     # Persist cookies now
webctl console --count          # Just counts by level (LLM-friendly)
webctl console --level error    # Filter to errors only

---

Architecture

┌─────────────┐  Unix Socket   ┌─────────────┐
│   CLI       │ ◄────────────► │   Daemon    │
│  (webctl)   │   JSON-RPC     │  (browser)  │
└─────────────┘                └─────────────┘
      │                               │
      ▼                               ▼
  Agent/User                   Chromium + Playwright

• CLI: Stateless, sends commands to daemon
• Daemon: Manages browser, auto-starts on first command
• Socket: $WEBCTL_SOCKET_DIR or OS default (see below)
• Profiles: ~/.local/share/webctl/profiles/

Socket Paths

Platform	Default
Linux	/run/user/<uid>/webctl-<session>.sock
macOS	/tmp/webctl-<session>.sock
Windows	%TEMP%\webctl-<session>.sock

Override directory with WEBCTL_SOCKET_DIR environment variable.

---

Container Deployment

Set WEBCTL_SOCKET_DIR to share the Unix socket between host and container (or between containers).

Daemon in Container, Client on Host

mkdir -p /tmp/webctl-ipc

docker run -d --name webctl-daemon \
  -u $(id -u):$(id -g) \
  -v /tmp/webctl-ipc:/ipc \
  -e WEBCTL_SOCKET_DIR=/ipc \
  my-webctl-image python -m webctl.daemon.server

export WEBCTL_SOCKET_DIR=/tmp/webctl-ipc
webctl start && webctl navigate "https://example.com"

-u $(id -u):$(id -g) ensures the socket file is owned by your host user.

Daemon and Client in Separate Containers

docker volume create webctl-ipc

docker run -d --name webctl-daemon \
  -v webctl-ipc:/ipc \
  -e WEBCTL_SOCKET_DIR=/ipc \
  my-webctl-image python -m webctl.daemon.server

docker run --rm \
  -v webctl-ipc:/ipc \
  -e WEBCTL_SOCKET_DIR=/ipc \
  my-webctl-image webctl navigate "https://example.com"

No UID matching needed - both containers run as the same user.

---

Security

IPC Authentication

webctl verifies that CLI commands come from the same user as the daemon:

Platform	Mechanism	Strength
Linux	SO_PEERCRED	Kernel-enforced UID check
macOS	LOCAL_PEERCRED	Kernel-enforced UID check
Windows	SIO_AF_UNIX_GETPEERPID + process token	Kernel-enforced SID check

All platforms use kernel-level credential verification. This prevents other users from controlling your browser session.

Note: Root/Administrator can still access any user's session (OS limitation).

---

License

MIT