Take the reins of your real browser from any coding agent.
reins.tech · docs · changelog
reins gives your coding agent (Claude Code, Cursor, Codex, Copilot — anything with a shell) control of the real, logged-in Chromium browser you already use, through a CLI and a Manifest V3 extension. No MCP server to register, no debug profile, no launch flags, no tokens.
npm i -g @karnstack/reins # the CLI (daemon included, starts on demand)
npx skills add karnstack/reins # the skill, into your agent(s) of choiceThen install the extension in every Chromium browser you want agents to reach — Chrome, Brave, Edge, Arc, Dia:
Add reins from the Chrome Web Store — it finds the local daemon and connects on its own.
No store access? reins extension installs it via Load unpacked instead — see
docs/SIDELOAD.md. That's the whole setup; reins status
shows what's connected.
reins snapshot # list interactive elements with refs → e5: button "Submit"
reins click --ref e5 # act by ref
reins text # verify (or: reins screenshot → prints an image path)Every command takes --tab <id> (default: active tab), --browser <id> (only
when several are connected), and --json. reins help is self-describing;
reins cdp is the escape hatch to the full Chrome DevTools Protocol.
The full story lives on the site:
- Docs — getting started, architecture, and the complete command reference
- How it compares — vs agent-browser, dev3000, and playwright-mcp
- Security — per-site permissions,
127.0.0.1-only binding, and the threat model - Site permissions — the
deny/read/fulltiers and how to tighten them
Report vulnerabilities privately via GitHub security advisories.
mise install # Node 24.18.0 + pnpm 11.9.0 (exact, via mise)
pnpm install
pnpm dev # watch-build all packages (extension → dist/)
pnpm test # protocol + cli + extension unit/integration tests
pnpm lint && pnpm typecheck && pnpm build
pnpm reins tabs # build + run any CLI commandLocal walkthrough (load unpacked, allow the dev ID, drive tabs): docs/RUNNING.md. Releasing: docs/RELEASING.md.
Packages: protocol (shared zod frames), cli (@karnstack/reins, bin reins), extension (MV3), web (reins.tech), and skills/reins (the agent skill).