# Serein: questions and answers

## What is Serein?

Serein is a free, native macOS browser for coding agents. It runs the agent command-line tools that are already on your Mac in visible browser tabs. You can watch, take over or stop each task, and an agent gets only the access that you grant.

## Why is Serein called an agentic harness for the browser?

A harness gives an agent its tools and its limits. Serein does that for the web. It has no agent or assistant of its own. It gives the agent tools that are already on your Mac a set of tabs to work in, the access that you grant for each task, and a Stop control.

## How much does Serein cost?

Serein is free to download and use on your own Macs.

## Which Macs can run Serein?

Serein needs macOS 14 or later. The file https://serein.pro/release.json gives the processor type (`arch`) and the lowest macOS version (`minimumMacOS`) of the current build.

## Which agents does Serein work with?

Claude Code, Codex, Cursor Agent, OpenCode, Command Code, Grok, Hermes Agent, and Pi or Oh My Pi, when they are installed on the Mac. Serein offers an agent for a task only when it can enforce the limits of that task on the agent's tool. Settings → Agents gives the reason when it cannot.

## Do I need an API key?

No. Each agent tool runs with its own sign-in. Serein never asks for your password and never types, stores or reads a credential of a provider.

## Does Serein run a model on my Mac?

No. Serein starts the agent's command-line tool on your Mac, and that tool sends the task and its context to its provider under your account. Serein does not get a copy.

## What can an agent do without my permission?

It can read pages in its own tabs. Clicks and typing, your sign-ins, project edits and Mac actions are off until you grant them. See https://serein.pro/llms/permissions.md.

## Can an agent see my passwords or card numbers?

No. Agents never get the contents of password or payment fields. On a password, payment or verification-code page, the task gives the tab back to you.

## Can an agent use the sites where I am signed in?

Only when you grant "Use my sign-ins" for that task. Without the grant, agent tabs have their own cookies. You can take the grant back.

## Can an agent see my private windows?

No. Private windows are never shared with agents.

## How do I stop an agent?

Press Stop. It takes that task's browser access away at once. You can also take an agent tab over at any moment.

## How many tasks can run at the same time?

Up to three. Each task has its own process group and its own permissions.

## Can an agent change files on my Mac?

Only in a project, and only after you grant edits. Each edit needs your approval. Serein keeps a snapshot of each turn, so you can read the diff and undo the turn.

## Where is my data?

On your Mac, in `~/Library/Application Support/Serein`. Serein has no accounts, and the app sends no analytics, telemetry or crash reports. Saved passwords are in the macOS Keychain.

## Is Serein a full browser?

Yes. It has tabs (vertical or horizontal), tab groups, private windows, downloads, permissions for each site, content blocking, saved passwords, and import of bookmarks, history and chosen sign-ins from Safari, Chrome, Comet, Arc, other Chromium browsers and Firefox. It does not support passkeys.

## Is Serein open source?

No. Serein's own code is not open source. The third-party parts and their licenses are listed at https://serein.pro/licenses.

## Does Serein work on Windows, Linux or iPhone?

No. Serein is a macOS app.

## Where do I download Serein?

At https://serein.pro/#download.

More: https://serein.pro/agents.md, https://serein.pro/llms/compare.md, https://serein.pro/llms.txt