sctl

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sctl puts the browser you are using under the control of the command line, AI clients, and scripts. One cross-platform binary runs a local bridge daemon that reaches ScriptCat for userscript management and its own sctl Browser extension for tabs, browser data, page automation, and debugging.

sctl <command> ───────────────┐
AI client ── MCP ── sctl mcp ──┴─ control API ─▶ sctl serve ─┬─ WebSocket ─▶ ScriptCat      userscripts
Playwright / Puppeteer ────── CDP endpoint ────▶             └─ WebSocket ─▶ sctl Browser   tabs, data, pages, debugging

Who decides: ScriptCat stays the authority for its scripts, so reading source and every write wait for approval in the browser. Browser control, page automation, debugging, and raw CDP run immediately, by design; only deleting bookmarks and uninstalling an extension wait for approval, and other destructive commands need --yes. Read docs/threat-model.md before exposing sctl to anything you do not trust.

• ScriptCat userscripts — list, read metadata and source (line windows, search), install, edit by content anchors, enable, disable, delete.
• Tabs and windows — list, open, close, activate, move, pin, mute, reload, duplicate, and group tabs across one or more paired browsers.
• Browser data — bookmarks, reading list, history, recently closed tabs, downloads, cookies, browsing data, and extensions.
• Page automation — accessibility snapshots with element refs, click, hover, fill, type, select, upload, scroll, navigate, wait, screenshot, and run JavaScript, in background tabs without switching the one you are on.
• Debugging — console messages, uncaught exceptions, browser messages, and network requests with headers and bodies.
• Raw CDP — send one Chrome DevTools Protocol command, or open an endpoint that Playwright connectOverCDP and Puppeteer connect attach to.
• One binary — JSON-RPC 2.0 over a mutually authenticated WebSocket, loopback by default; no Native Messaging host.

macOS and Linux:

curl -fsSL https://raw.githubusercontent.com/scriptscat/sctl/main/scripts/install.sh | sh

Windows PowerShell:

irm https://raw.githubusercontent.com/scriptscat/sctl/main/scripts/install.ps1 | iex

The installer verifies the release archive's sha256 and installs sctl into ~/.local/bin (macOS/Linux) or %LOCALAPPDATA%\sctl\bin (Windows). Pinning a version, manual downloads, and building from source are covered in docs/mcp.md.

1. Start the daemon and leave it running:

   sctl serve

2. Pair the extensions. sctl connect prints a one-time code; each code pairs one extension, so run it once per extension.

   • ScriptCat: enable External Access in its options and enter the code.
   • sctl Browser: download sctl-browser-extension-<version>.zip from GitHub Releases, unzip it, load the folder as an unpacked extension, and enter a code in its popup. It needs Chrome 125 or newer (or a Chromium browser of that version).

3. Check the connection:

   sctl status      # daemon and ScriptCat
   sctl browsers    # paired sctl Browser instances

Every sctl process must use the same data directory and listener address; the defaults work when they all run as the same user. The step-by-step guide, including SCTL_DATA_DIR, --listen-address, and the debugging infobar Chrome shows while a page is being driven, is docs/mcp.md.

Command line. Every capability is a command; add -o json for scripts.

sctl tabs list
sctl page snapshot --tab 123
sctl debug console --tab 123 --level error
sctl get                      # ScriptCat scripts

Behavior, exit codes, and confirmations are in docs/cli.md.

AI clients over MCP. Configure the client to launch /absolute/path/to/sctl mcp --name my-ai-client. sctl mcp does not start the daemon. Client configuration, the tool reference, and troubleshooting are in docs/mcp.md.

Agent skill. To have an agent drive the command line instead of MCP, install the skill in skills/sctl/. For Claude Code, link it from a clone of this repository:

ln -s "$PWD/skills/sctl" ~/.claude/skills/sctl

Playwright and Puppeteer. sctl cdp endpoint prints addresses that existing scripts connect to, keeping the browser's logins; see docs/cli.md.

sctl <command> --help lists every subcommand and flag; docs/cli.md is the full reference.

• docs/cli.md — command-line reference.
• docs/mcp.md — installation, pairing, MCP client setup, and the MCP tool reference.
• docs/threat-model.md — what sctl protects and what it deliberately does not.
• docs/README.md — index of the contributor docs (architecture, protocol, development).

GPL-3.0, the same license as ScriptCat. See LICENSE.