Yab for developers

Your agent’s browser, already signed in.

Claude Code, Codex, Cursor and Zed drive Yab with your sessions, in tabs of their own. And when it’s your turn, it knows your localhost.

Download for Mac$ yab setup

Free, for macOS 15.4 or later. Version 0.0.18

that’s Claude Code, testing your checkout

~/tern claude
> check the checkout on :3000 with a test card
⏺ yab.open localhost:3000/cart
⏺ yab.type “4242 4242 4242 4242”
⏺ yab.click e14 “Place order”
✓ order #1043 · 0 console errors

Part one

A browser for your agent.

No Playwright, no debugging port, no test profile to sign in to again. Your agent gets the browser you already use, and asks you before anything that matters.

Set up in one click.

Settings › Developers puts Yab’s MCP server and its skill into Claude Code and Codex. Copy Config gives Cursor, Zed, Windsurf or Claude Desktop the entry they need.

The skill tells the agent to use Yab for anything on the web, so you don’t have to ask.
Remove takes back only what Yab added.
From a terminal: yab setup.

one click per agent

Signed in where you are.

Your agent opens pages in the space where you’re already signed in. Staging, Vercel, AWS, Linear, GitHub: it reads them as you, without you exporting a cookie or minting a token.

Passwords stay with Yab. It fills a saved one; the agent never sees it.
2FA and captchas come to you as a line at the page’s foot. Done, and it carries on.
fetch reads a URL with your cookies and no tab at all.

your sessions, its tabs

Tools made for agents.

Every tool answers so the agent needs fewer round trips.

snapshotThe page as an accessibility tree with refs like e12, and which sign-ins it offers.

click · typeReal trusted events. Says what changed, and when a modal covers the target.

runJavaScript that calls the tools as functions: up to 200 steps in one call.

fetchA URL read with your cookies, no tab. A .diff, a JSON endpoint, a dashboard.

screenshot · pdfWhat you’d see, or the page as a PDF.

upload · downloadFiles in and out, asked first, a folder per task.

history · memoryWhere you’ve been, in Yab and your other browsers, and what Yab knows about your projects.

native_*Yab itself: spaces, pins, folders, settings.

It asks before it sends.

Send, pay, delete and upload wait for your yes on a card. Matched in seven languages; any form that takes a card counts as paying.

Ask, Auto or Bypass, and Never Here per site.
Your own tabs: Yes, Ask First, or Read Only.
Private tabs don’t exist for agents.

nothing goes out without you

It works beside you.

Agent tabs never jump in front of you and never land in your history. They render off screen as if visible, so React apps behave, and close 15 minutes after the task.

A face on its folder: reading, typing, needs you, done.
Take over . or just click. Hand back and it picks up where you left off.
Steer it while it runs: yab session steer.

Claude’s in there, you’re here

Hand off a whole job.

The task tool gives a job to an agent Yab runs. Only the answer comes back, so your Claude Code session stays small; up to eight helpers browse at once.

The answer page with sources stays in the folder.
Steer or queue with task_steer and task_queue.

412 tokens back, not 11 pages

> compare pricing for Linear, Height and Plane, 12 seats
⏺ yab.task access=browser model=sonnet
3 helpers · 11 pages · 2m 40s
⏺ answer (412 tokens)
Plane $864, Height $1,224, Linear $1,440 a year

Or never open it.

Keep Chrome as your browser. yab "…" and yab mcp wake Yab hidden, with no window and no Dock icon, and it quits after 30 idle minutes.

Exit codes for scripts: 0 done, 3 needs you with a resume line, 130 stopped.
yab every "weekdays 9:00" "…" makes a routine.
yab serve turns a spare Mac into an agent box over ssh.
yab import chrome brings your sign-ins.

$ yab "is staging green? check Vercel and Sentry"
⏺ vercel.com/tern · signed in
⏺ sentry.io/tern · signed in
Green. Last deploy 14:02, no new issues in the last hour.
$ echo $?
0
$ yab every "weekdays 9:00" "anything failing in CI on my PRs?"
✓ routine “anything failing” · weekdays 9:00

Part two

And for your own day.

Your localhost, your pull requests, your reviews. Tools that know what a dev server is.

Developer Mode, per port.

Yab knows localhost, *.localhost, *.test and 127.0.0.1, and asks once for each server.

The port on the tab: three localhost tabs stop looking alike.
“2 errors” right on the page’s band, before you open anything.
Local HTTPS with a self-signed certificate just loads.

asked once per port

Errors, packed for your agent.

K lists errors, warnings and failed requests. Copy for Agent makes one Markdown pack: stacks with your frames first, repeat counts, request and response bodies.

Keys, JWTs and cookies are taken out before it’s copied.
Copy as cURL for any failed request.

one key, everything Claude needs

Measure, change it live.

U puts rulers on your page. Pin a box, hover another for the distance. The page’s own CSS rules show with their files; click a value to change it.

Copy for Agent lists every value you changed: rule, file, old and new. Claude Code applies it.
Guides stay for that server and path.

22, not 24. tweak it, hand it over

The inspector beside the page.

I docks WebKit’s inspector in a card beside, under or left of the page, and the page makes room. Tabs in Chrome’s order, Chrome’s keys.

Device mode: iPhone, Pixel and iPad widths, real layout.
Recorder: record a repro, copy it as Puppeteer JSON or for your agent to write a test.

Safari’s engine, Chrome’s keys

Your pull requests, in a folder that keeps itself.

Open a pull request in Yab once and a Pull Requests folder appears. Every few minutes it reads GitHub with your sign-in: new ones come in at the top, merged and closed ones go.

Words at the row’s end: Review, Changes, Failing, Ready, New. Nothing when nothing needs you.
Shut, it still tells you: one that turns to Review or Failing comes out under it.
GitHub issues and searches, Linear, Figma work the same. Rows sleep until opened.

merged ones leave by themselves

`J` on a pull request.

Review this pull request writes the review on the page as a draft. Edit it, then Post; nothing is submitted without you.

Sum it up on a long thread.
Capture 2 frames a part of the page for the PR description, emails and keys hidden.

written, waiting for you

	Yab	Playwright MCP	Claude in Chrome
Your signed-in sites	Yes, per space	Its own profile, or an extension	Yes
Works in its own tabs while you browse	Yes	A separate window	Its own tab group
Claude Code, Codex, Cursor, Zed	Yes	Yes	Claude apps only
Sends helpers to work many tabs at once for you	Up to 8 subagents	One browser	One agent, many tabs
Holds Send, Pay and Delete for your yes	Yes	No	Asks
Ports on tabs, rulers and live CSS on localhost	Built in	No	No

One line, then ask for anything on the web.