Frequently asked questions

Tencil is an open-source browser review tool for coding agents. Press C on your running dev site, click any element and type what should change. Tencil pins the comment to that element, hands your agent the component, source file and markup, and streams its progress onto the pin while your dev server hot-reloads the result.

Node 22 or newer, and T3 Code (the desktop app) or Claude Code (installed and logged in). Run npx tencil in your project. The first time, it sets up your machine: it picks your agent, pairs with T3 Code if you use it, and starts the daemon, at login if you like. Then it adds the integration. Start your dev server as usual and press C on the page.

One line in one file: <Tencil /> in your Next.js root layout, or tencil() in the plugins of your vite.config. It shows the diff and asks before it writes anything, and npx tencil init --dry-run only shows it. It also adds tencil to your dev dependencies.

Run npx tencil@latest setup again. Setup, start and npx tencil also tell you when a newer version is out.

No. Tencil runs on your machine, with the agent and the login you already have. There is nothing to sign up for.

Yes. Run npx tencil in the app you want, or in the root, where it lists the apps it finds. One daemon serves every project on your machine, each with its own pins and agent.

T3 Code and Claude Code. Setup uses the one you have, or asks once if you have both. Each project can switch in the overlay: the gear on the toolbar opens its settings. Pins keep the agent they started with.

Yes. A new element starts a new thread by default; in the composer, switch New thread to any thread of the project, and the element you picked becomes its next message. The inbox opens any of those threads next to the page, so you can read what your agent did and reply while you look at the result. It works the other way too: with T3 Code, every pin is a real thread you can open there, and with Claude Code a session you can pick up with claude --resume.

Your prompt, plus the element's component, source file and markup, and a screenshot if you attach one. Every provider gets exactly the same input, rendered by the daemon.

Yes. Pick the agent and model of a new pin in the comment box; the choice is saved per project. On the command line, --model takes a Claude Code model such as claude-opus-5-5, or a T3 Code instance and model such as claudeAgent:claude-fable-5-1.

Nobody sits at a terminal to approve tool calls, so --runtime-mode decides up front. full-access (the default) lets the agent run anything; with approval-required, auto-accept-edits or auto, tools that would need approval are refused and the agent is told why.

Not directly yet: Tencil talks to T3 Code and Claude Code. T3 Code runs the providers you set up in it, so the models you use there work with Tencil too.

Next.js (app and pages router) through the <Tencil /> component, and every Vite app (React, Vue, Svelte, TanStack Start, Astro and others) through the Vite plugin. Anything else works with one script tag in your development HTML. In React apps, Tencil also finds the component and source file of what you click.

Yes. For Next.js, Tencil doesn't hook into the bundler: <Tencil /> loads the overlay from the daemon in the browser, whatever builds your app.

Load one script in your development HTML only: <script src="http://localhost:4747/tencil.js" async></script>. Without the daemon running, it does nothing.

Yes. Tencil matches a page to its project through the port it is served on. When that does not work, the overlay asks which project the page belongs to and remembers your answer.

Tencil itself has no server and no account: the daemon runs on localhost and only talks to your agent on the same machine. That agent talks to its model provider, exactly like it does without Tencil.

No. The overlay is loaded from the daemon on your machine, only in development. Production builds don't include it, and for anyone without the daemon running, the script doesn't load and nothing appears.

No. The daemon listens on 127.0.0.1 and only accepts connections from loopback origins such as localhost, unless you pass --allow-origin. Requests for any other host name are refused, which blocks DNS rebinding.

Pins live per project in ~/.config/tencil/projects/, never inside your repository. Credentials live in ~/.config/tencil/credentials.json, readable only by you, and never reach the page.

No. The software sends nothing to us: no telemetry, no analytics, no crash reports. The source code is public, so you can check.

Privately, through the Security tab of the GitHub repository: Report a vulnerability. Please not in a public issue. SECURITY.md says what is in scope.

Yes, under the Apache License 2.0. The CLI, the daemon, the overlay and the integrations are on GitHub at github.com/tencildev/tencil, where issues and pull requests are welcome; CONTRIBUTING.md explains how to get started.

Yes. Tencil is free and open source. You use your own agent and its subscription or API key, as you do without Tencil.