Kitewright

Browser automation for AI agents as a single small binary. An MCP server (Streamable HTTP + stdio) that gives LLM clients navigate / screenshot / extract — without carrying the Node.js + Playwright stack.

Install in one line:

claude mcp add kitewright -- npx -y @kitewright/mcp

Why — measured, not claimed

Head-to-head vs @playwright/mcp 0.0.78, same machine, same Chromium headless-shell build, same page (full methodology):

The browser itself (Chromium) costs the same in any language — warm latency is a tie because both speak CDP to the same browser. The wins are everything around it: startup, distribution, idle footprint, and lifecycle management. The honest gap: playwright-mcp ships ~25 tools today, we ship 21 — closing that is the roadmap.

Related MCP server: Scout

Reliability — actionability auto-waiting

click / type / fill_form / select_option / hover don't fire blindly. Before acting, the engine polls (100 ms, up to a 5 s per-op budget) until the target element is present, visible (not display:none / visibility:hidden / zero-size), enabled (no disabled / aria-disabled), not covered by another element at its click point, and geometrically stable across two consecutive frames. A settled element passes on the first poll, so this is invisible when things are fine — but when an action can't happen, you get a cause-specific error (not found / not visible / disabled / covered / unstable) instead of a silent misclick or a generic timeout. Transient CDP errors are retried twice. Pass timeout_ms on any interaction tool to override the 5 s per-op budget (e.g. a short timeout to fail fast when you expect an element to already be there).

Performance

External-site latency is network-bound — DNS + TLS + TTFB (~400–600 ms) is a floor no tool beats, and Kitewright does not claim to. What it does attack is every controllable cost around the network:

• Prewarm + warm-context pool. The moment an MCP session initializes, the server launches the browser and fills a small pool of pre-created blank browser contexts (MCP_CONTEXT_POOL, default 2) in the background. A new session is then handed a ready context+page, so its first navigate pays zero browser-launch and zero context-creation cost. Measured localhost first-navigate: ~31 ms prewarmed vs ~709 ms cold (Apple Silicon; details). The pool drains with the browser on idle-reap and refills lazily on next demand, so idle footprint stays at the ~8 MB baseline.

• Lite mode. browser_navigate {lite:true} (and the default for extract / extract_markdown) blocks images/media/fonts + ad/analytics hosts before the load — 30–70 % faster DOM-ready on heavy pages by skipping the bulk of the bytes. Screenshots/PDF never block resources.

• Shared disk cache + connection pre-warm. A stable --disk-cache-dir (KITE_CACHE_DIR) lets repeat asset fetches hit cache across runs; KITE_PREWARM_URL establishes DNS+TLS to a known origin during prewarm.

The honest framing: the wins are browser launch, page weight, session start, and connection setup — not the network round-trip to a remote origin.

Architecture

crates/
├── engine/    kitewright-engine — CDP core (chromiumoxide): lazy launch, idle reaper,
│              per-session browser contexts, capped text extraction + AX snapshots.
│              Shared by all frontends.
└── server/    kitewright — rmcp Streamable HTTP server exposing the engine as MCP tools.
bindings/
└── node/      @kitewright/node — napi-rs bindings exposing a Puppeteer-compatible
               (experimental) API over the same engine (built separately; kept out
               of the core cargo workspace). See "@kitewright/node" below.

Each MCP session owns one persistent page inside its own Chromium browser context (cookie isolation between agents): log in once, keep clicking. The page and context are closed when the session ends; the browser itself is still reaped after the idle TTL and transparently relaunched on the next call.

Install

The zero-install way — run it straight from npx, like @playwright/mcp:

claude mcp add kitewright -- npx -y @kitewright/mcp

npx @kitewright/mcp resolves the prebuilt kite binary for your platform (an optional per-platform dependency, esbuild-style) and starts a stdio MCP server — no Rust toolchain, no build. See npm/kitewright-mcp.

Prefer the raw kite binary? (npx above is the easy path; these need a Rust toolchain.)

# From the public repo — builds + installs the `kite` binary:
cargo install --git https://github.com/kitewright/kitewright kitewright   # → ~/.cargo/bin/kite

# From a local checkout:
cargo install --path crates/server

# Docker (headless Chromium bundled in the image):
docker run --rm -p 8090:8090 kitewright   # build locally: docker build -t kitewright .

Not yet published to crates.io or Homebrew — cargo binstall/brew aren't wired up. Use npx @kitewright/mcp (no toolchain) or the cargo install --git line above.

Get a browser

Kitewright drives Chromium over CDP but does not embed one. It uses a system Chrome/Chromium when present, honors BROWSER_EXECUTABLE, and — if neither is found — falls back to a browser downloaded by kite install:

kite install    # fetch the latest stable chrome-headless-shell into the kite cache

kite install downloads the current Chrome-for-Testing chrome-headless-shell build for your platform into $KITE_CACHE_DIR (or the OS cache dir) and the engine picks it up automatically — no BROWSER_EXECUTABLE needed. Re-running is a no-op once a build is present. The Docker image already ships Chromium.

Run & connect

kite with no arguments serves MCP over Streamable HTTP (networked, default, supports auth + many sessions); kite --stdio serves a single session over stdio for local clients.

kite
# → kitewright listening on http://0.0.0.0:8090/mcp

HTTP transport — connect from Claude Code:

claude mcp add kite --transport http http://localhost:8090/mcp

stdio transport — MCP client config (Claude Desktop, Cursor, …):

{
  "mcpServers": {
    "kite": {
      "command": "kite",
      "args": ["--stdio"]
    }
  }
}

Configuration

Security

Kitewright drives a real browser, so treat the endpoint as privileged. The defaults are safe for local use; harden before exposing it.

• Binds loopback (127.0.0.1:8090) by default. It's only network-reachable if you set MCP_HTTP_BIND explicitly. If you expose it, set MCP_AUTH_TOKEN — without it the /mcp endpoint is unauthenticated (logged as a warning at boot). Auth uses a constant-time compare; requests are rate-limited; and cross-origin browser requests are rejected (DNS-rebinding protection).

• SSRF is inherent to a browser tool. A caller can navigate to internal or cloud-metadata addresses (169.254.169.254, RFC-1918, localhost) — which is the point for local/dev automation, but a risk on an exposed instance. Kitewright does not block these (doing so by default would break local automation). On an exposed deployment, put it behind auth and network policy that can't reach sensitive internal endpoints.

• Local-file access is off by default. file:// navigation requires KITE_ALLOW_FILE_URLS=1; browser_fill_secret file reads require KITE_ALLOW_SECRET_FILES=1 and a KITE_SECRET_DIR fence (reads are canonicalized and must stay under it).

• Dependencies are scanned in CI (Trivy + cargo audit). The shipped kite binary carries no known-vulnerable crates; see .cargo/audit.toml for two DoS advisories confined to the (server-unused) kite-pdf crate.

Tools (v0.4)

All tools operate on the session's persistent page.

Read

• browser_navigate {url, lite?} — title, final URL, visible text (capped). lite:true enables lite mode: block images/media/fonts + common ad/analytics hosts (doubleclick, google-analytics, GTM, facebook pixel, …) via CDP Network.setBlockedURLs for a faster DOM-ready on heavy pages (30–70 % on heavy sites — text-only, do not use before a screenshot). Sticky for the session until changed. extract / extract_markdown default to lite when navigating (pixels irrelevant); screenshot / pdf never block resources

• browser_extract {url?, selector, attribute?} — text/attribute from elements matching a selector

• browser_extract_markdown {url?} — main content as Markdown ("readability" mode: headings/links/lists/code/tables, nav/script/style stripped, capped at ~20k chars)

• browser_screenshot {url?, full_page?} — PNG of the current page (url navigates first)

• browser_pdf {url?, format?, landscape?, print_background?, display_header_footer?, header_template?, footer_template?, margin_top?, margin_bottom?, margin_left?, margin_right?, scale?, prefer_css_page_size?} — print to PDF (CDP Page.printToPDF); the full puppeteer option set including running headers/footers (legal text, page numbers) and CSS-unit margins ("35px"/"20mm"). Returns a JSON envelope {format, bytes, base64} (MCP has no native PDF type — decode base64 to get the file)

• browser_set_content {html, wait_until?} — load a raw HTML string into the current page (puppeteer page.setContent) via CDP Page.setDocumentContent; wait_until is load (default) / domcontentloaded / networkidle0. Pair with browser_pdf for an HTML→PDF render with no server round-trip. Handles large documents

• browser_snapshot {diff?} — accessibility-tree snapshot (roles, names, states) capped at ~15k chars; diff:true returns only what changed since the previous snapshot in this session (first call is the baseline)

Debug

• browser_console {clear?} — console messages (log/warn/error/info) captured on the page since the last call; clear:true empties the buffer

• browser_network {clear?, filter?} — network requests (method, url, status, resourceType) captured on the page; filter substring-matches the URL

Interact

• browser_click {selector, timeout_ms?} — scroll into view + click the first match

• browser_type {selector, text, clear?, press_enter?, timeout_ms?} — focus and type into an element

• browser_fill_form {fields: [{selector, value}], timeout_ms?} — fill several inputs in one call (per-field ok/error summary)

• browser_fill_secret {selector, secret_ref, press_enter?, timeout_ms?} — type a secret (password) whose plaintext never enters the tool call: secret_ref is env:NAME (a server env var) or file:/path (opt-in via KITE_ALLOW_SECRET_FILES + a required KITE_SECRET_DIR fence). Resolved server-side, then typed

• browser_select_option {selector, value?, label?, timeout_ms?} — pick an <option> by value or visible label (fires change)

• browser_hover {selector, timeout_ms?} — move the mouse to an element's center (reveals CSS :hover menus)

• browser_press_key {key} — send Enter / Tab / Escape / ArrowDown / … to the focused element

• browser_navigate_back {} — history back, returns the new title + URL

• browser_handle_dialog {accept, prompt_text?} — pre-arm auto-accept/dismiss for the next JS dialog(s)

• browser_wait_for {selector?, text?, timeout_ms?} — poll until a selector matches or text appears (default 10s, max 30s)

State

• browser_save_state {} — capture cookies + localStorage + URL as a JSON string you can persist

• browser_restore_state {state} — set cookies immediately; apply localStorage on/after navigating to its origin ("log in once, reuse across sessions")

Assert

• browser_assert {condition_selector?, condition_text?, should_exist?, timeout_ms?} — structured {passed, checked, found, elapsed_ms} (never errors on a failed condition; should_exist:false asserts absence)

Selector syntax

click / type / fill_form / select_option / hover / wait_for / extract / assert accept three selector forms (the same forms back the internal element-handle API — query / query_all returning ElementRef handles with .click() / .type_str() / .text() / .attribute() / .bounding_box() — that will underpin the Wave-3 Puppeteer-style npm facade):

• CSS (default) — e.g. #login, button.primary, input[name="email"]

• text=<visible text> — first visible element whose trimmed text contains it

• role=<role>[name="<accessible name>"] — element matching an ARIA role + accessible name, e.g. role=button[name="Submit"]

Role resolution is a pragmatic JS heuristic (implicit-role element map + accessible name from aria-label / aria-labelledby / associated <label> / text / value / placeholder / title / alt), not a full ARIA computed-name implementation — it covers the common interactive roles agents target. Plain CSS extract still returns all matches; a text=/role= extract returns the single resolved element.

@kitewright/node (Puppeteer-compatible, experimental)

bindings/node is a napi-rs native addon that puts a Puppeteer-shaped facade over kitewright-engine — the browser lifecycle, CDP, and waiting heuristics run natively in the shared Rust core, so the JS layer is thin. It targets the common HTML→PDF flow (e.g. an invoice/report service that uses Puppeteer only for rendering). For that flow the migration is a one-line import change:

// import puppeteer from 'puppeteer'
import puppeteer from '@kitewright/node'

const browser = await puppeteer.launch({ headless: true, args: ['--no-sandbox'] })
const context = await browser.createBrowserContext()   // per-invoice isolation
const page = await context.newPage()
await page.setContent(html, { waitUntil: 'networkidle0', timeout: 0 })
await page.evaluate(() => document.fonts.ready)         // promise-returning
const pdf = await page.pdf({                            // → Node Buffer
  format: 'a4', printBackground: true, displayHeaderFooter: true,
  footerTemplate: legalFooterHtml,                      // legal text + page numbers
  margin: { top: '20px', bottom: '35px' },
})
await page.close(); await context.close(); await browser.close()

Each Page is one persistent engine session in its own Chromium browser context, which is exactly the per-createBrowserContext() isolation Puppeteer promises. page.setContent + page.pdf(footerTemplate) produce a valid, multi-page PDF with running footers (verified end-to-end in bindings/node/test/invoice.e2e.mjs, which mirrors invoice-service's real flow and writes test/out/invoice.pdf).

Compatibility matrix

Notes: waitUntil: 'networkidle0' is approximated as load + a short settle (inline setContent content, no interception). Unsupported methods throw rather than silently no-op so callers discover gaps immediately.

Build (local, this platform)

The addon is built separately from the core cargo workspace (it is listed under [workspace] exclude, so cargo clippy --workspace / the Rust tests never touch the napi toolchain):

cd bindings/node
npm install
npx napi build --release --js binding.js --dts binding.d.ts   # emits kitewright-node.node
BROWSER_EXECUTABLE=/path/to/chrome node --test test/invoice.e2e.mjs

kite-pdf — HTML/Typst → PDF

kite-pdf is a focused document → PDF render service and CLI built on the same engine (crate crates/pdf, binary kite-pdf). It has two backends, selected at build time via Cargo features and at run time per request:

• Chromium — html/url → PDF via the shared kitewright-engine (headless Chromium, the full Page.printToPDF option set: header/footer templates, margins, landscape, backgrounds, scale, CSS page size).

• Typst — a Typst template + JSON data → PDF with no browser ever spawned. The compiler and fonts are embedded in the binary; rendering is pure CPU, language-agnostic, and reproducible.

One crate, three build shapes (same binary name)

cargo build --release -p kite-pdf                                   # both backends
cargo build --release -p kite-pdf --no-default-features --features chromium
cargo build --release -p kite-pdf --no-default-features --features typst

HTTP API

POST /render with a JSON body; responds with application/pdf bytes (200) or a JSON { "error": "..." } (400 client / 500 server). GET /healthz returns the compiled-in backends. Bind address: KITE_PDF_BIND (default 0.0.0.0:8091).

{
  "engine": "chromium" | "typst",   // optional; else inferred (html/url→chromium, template→typst)
  "html":   "<!doctype html>...",   // chromium
  "url":    "https://...",          // chromium
  "template": "= Invoice ...",      // typst source
  "data":   { "number": "INV-1" },  // JSON, exposed to the template as sys.inputs.data
  "format": "A4" | "Letter" | "Legal" | "A3",
  "landscape": false,
  "print_background": false,
  "display_header_footer": false,
  "header_template": "<div>...</div>",
  "footer_template": "<div>... <span class=\"pageNumber\"></span> ...</div>",
  "margin": { "top": "20px", "bottom": "40px", "left": "15px", "right": "15px" }
}

Requesting a backend that was not compiled into the running binary returns a clear 400 (e.g. "typst backend not compiled in this build — use the full or -lite build"). In the Typst template, read the injected data with:

#let data = json(bytes(sys.inputs.data))
= Invoice #data.number

# Chromium: render an HTML string
curl -sX POST localhost:8091/render \
  -H 'content-type: application/json' \
  -d '{"html":"<h1>Hello</h1>"}' -o hello.pdf

# Typst: data-driven invoice, no browser touched
curl -sX POST localhost:8091/render \
  -H 'content-type: application/json' \
  -d '{"template":"#let d=json(bytes(sys.inputs.data))\n= Invoice #d.number","data":{"number":"INV-7"}}' \
  -o invoice.pdf

Note: the render service ships with no auth by default — run it on a trusted network or behind a gateway. (Bearer-auth + rate-limit, mirroring the kite server's HttpGuard, is a TODO.)

CLI

# Chromium: HTML file → PDF, with a footer template + margins
kite-pdf render --html-file invoice.html --footer-file footer.html \
  --margin-top 20px --margin-bottom 40px -o invoice.pdf

# Typst: template + data → PDF (no browser)
kite-pdf render --template invoice.typ --data invoice.json -o invoice.pdf

# Run the HTTP service (also the default with no arguments)
kite-pdf serve

Docker

# Full service (slim Debian + Chromium; both backends). Build from the repo root:
docker build -f crates/pdf/Dockerfile      -t kite-pdf      .
# Browser-free, distroless, Typst-only:
docker build -f crates/pdf/Dockerfile.lite -t kite-pdf-lite .
docker run -p 8091:8091 kite-pdf

Honest comparison

• vs Gotenberg: kite-pdf is the lightest self-hosted HTML→PDF option — a single small binary, lazy browser lifecycle, reaped when idle. Gotenberg wins when you need office-document conversion (DOCX/XLSX/ODT via LibreOffice) and a batteries-included API; kite-pdf deliberately does not do office formats.

• vs react-pdf / client PDF libs: the Typst path is browser-free and language-agnostic — no Node runtime, no React, no headless Chrome — just a template + JSON from any language over HTTP. You give up React's component model in exchange for a far smaller, faster, reproducible typesetting pipeline.

• Where it concedes: no office-doc (DOCX/XLSX) conversion, and the Chromium backend still needs a browser at runtime (the Typst/-lite backend does not).

Roadmap

• snapshot — accessibility-tree snapshot (token-budgeted)

• click / type / press_key

• wait_for (selector / text polling)

• fill_form / select_option / hover / navigate_back / handle_dialog

• Storage state (save_state / restore_state) — reuse a login across sessions

• Role/text selectors (text=, role=…[name="…"]) alongside CSS

• assert — structured pass/fail primitive for agent-driven feature tests

• Markdown (readability) extraction mode

• pdf — print the current page to PDF (Page.printToPDF)

• kite-pdf — standalone HTML/Typst → PDF service + CLI (dual-backend, three feature-gated build shapes)

• Actionability auto-waiting (visible / enabled / unobstructed / stable) with cause-specific errors

• console / network capture for debugging

• snapshot {diff} — only what changed since the last snapshot

• Element-handle primitives (query / query_all → ElementRef) — foundation for the npm facade

• Per-MCP-session browser contexts (cookie isolation) instead of per-call pages

• Bearer-token auth + rate limiting

• bindings/node: napi-rs Puppeteer-compatible facade (@kitewright/node, experimental) — launch/newPage/createBrowserContext/setContent/evaluate/pdf/goto/close; HTML→PDF flow proven end-to-end

• bindings/node: prebuilt per-platform binaries + npm publish

• Python bindings (PyO3)

• Benchmarks vs playwright-mcp (cold start, RSS, image size) for the README

• Prebuilt release binaries (macOS/Linux/Windows) + cargo binstall + Homebrew tap

Non-goals

Kitewright is deliberately a lean agent tool, not a QA test framework. It will not:

• Support multiple browser engines. CDP / Chromium only, by design — no Firefox or WebKit. Speaking one protocol to one engine is what keeps the binary tiny and the lifecycle simple.

• Ship a test runner, fixtures, trace viewer, or video capture. Those belong to QA frameworks (Playwright Test, Cypress). Kitewright gives an agent primitives (snapshot, assert, storage state); the agent — or a thin script — is the runner.

• Expose an arbitrary-JS eval tool. Executing agent- or model-authored JavaScript against live sessions (with restored cookies) is a security footgun. Selector resolution and helpers run curated, fixed JS only.

License

MIT