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CatPaw v0.1.0

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@github-actions github-actions released this 10 Oct 16:45
· 15 commits to main since this release
v0.1.0
2473a38

The first preview: a browser an agent drives over MCP, with the user
asked before anything is sent on their behalf. The tools and their
results may still change before 1.0. What does not work as a browser's
would yet is listed in Known gaps.

Binaries for Linux (x86_64, aarch64), macOS on Apple silicon and Windows
(x86_64); Intel Macs build from source.

For agents

  • catpaw mcp --stdio serves fifteen tools: navigate, snapshot,
    click, type, fill, press, select, act, wait, read,
    screenshot, evaluate, tabs, logs and handoff (and, on
    request, session for checkpoints). catpaw setup claude-code,
    codex or cursor registers it with a host.
  • Snapshots in a compact text form with refs that are never reused; an
    action answers with what happened and what changed, once the page has
    settled, and a page that did not settle says what it waits on.
  • Confirmations: a form posted, a file uploaded (and, under --policy strict, script sending data to another site, and evaluate) waits
    for the user. A host with MCP elicitation asks in its own prompt;
    otherwise CatPaw opens an approval page in the user's browser.
  • Hand-off: the user takes over a tab in their own browser (a login, a
    check meant for people), and the agent gets it back with what they
    typed masked.
  • A flight journal of every call, profiles that keep cookies and
    storage between sessions, checkpoints, and traffic recorded to HAR and
    replayed byte for byte.

The engine

  • HTTP/1.1 and HTTP/2 over rustls, cookies, proxies, private addresses
    refused by default, and Web Bot Auth request signing for deployers with
    their own key.
  • HTML parsing, style by Stylo, JavaScript by Boa with bindings generated
    from Web IDL, an event loop with virtual time, frames, popups, workers,
    WebSocket, storage, Web Crypto and Canvas 2D.
  • Shadow trees styled and shown as they render: their own and adopted
    style sheets, slots, and document rules kept out of them.
  • Media elements that play nothing and say so, no plugins and no PDF
    viewer; :has() and :nth-child(… of …) selectors; RegExp.$1 and the
    other legacy static properties of RegExp; Intl.DateTimeFormat
    formatToParts, and dates with the whole year and 2-digit padding as
    asked for.
  • Date.parse takes 2026/10/10 15:51:46+00:00, 2026-10-10 15:51:46 UTC
    and its own toString() back; a stack overflow is a RangeError script
    can catch, as in browsers.
  • The modules a module imports load side by side, as a browser loads a
    module graph: x.com's 590 modules took 100 seconds one by one, now 10.
  • Layout by Taffy and Parley when something asks for geometry, and
    screenshots by tiny-skia.
  • web-platform-tests run in CI against recorded expectations.

Identity

CatPaw says what it is: its User-Agent is CatPaw/0.1.0 (+https://catpaw.sh/bot), and it ships no fingerprint impersonation and
no CAPTCHA solving.

Install

macOS (Apple silicon) and Linux (x86_64, aarch64):

curl -fsSL https://catpaw.sh/install.sh | sh

Windows (PowerShell):

irm https://catpaw.sh/install.ps1 | iex

The scripts download the archive for your system from this release and
check it against SHA256SUMS. Or download an archive below, check it
(sha256sum -c SHA256SUMS --ignore-missing), and put catpaw on your
PATH. Then connect it to your agent:

catpaw setup claude-code

Intel Macs and other systems build from source: see the README.

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