sallyport MCP Server

Sallyport

A secure browser-automation bridge between Claude Code (or any MCP client) and your Chrome. An alternative to Kimi WebBridge with explicit security boundaries instead of implicit ones.

Claude Code ── MCP/stdio ──▶ daemon ── WS+HMAC ──▶ extension ── CDP ──▶ Chrome

Status	Number
Daemon tests (pytest)	439
Extension tests (vitest)	594
Lint / typecheck (ruff, mypy, eslint, prettier, tsc)	all green

What's in the box

Path	What it is
extension/	MV3 Chrome extension (TypeScript, esbuild, vitest). Loads as an unpacked extension.
daemon/	Python MCP server. Speaks MCP on stdio to Claude Code, hosts a WS server on 127.0.0.1:10086 for the extension.
fixtures/	Cross-language canonical-JSON / HMAC vectors shared by both test suites.
.pre-commit-config.yaml	Fast lint/format checks before commit.
.github/workflows/ci.yml	Same checks plus full tests on push/PR.

Security model

A deeper threat model + known limitations lives in SECURITY.md. The short version: the original Kimi extension trusts any process that can reach 127.0.0.1:10086, which on a shared/compromised machine means everything. Sallyport changes the default in five places:

1. HMAC-SHA256 on every frame. A 32-byte random secret lives in ~/.config/sallyport/secret (chmod 600) and is generated on first run. Both sides sign every WS frame and verify timestamp drift (≤ 30 s) and nonce freshness (rolling cache of 4096 nonces — replay-protected). A cross-language test pin in pytest + vitest guarantees the canonical-JSON and MAC bytes stay byte-for-byte compatible.
2. Domain allowlist enforced in the extension. Tools refuse to run on any URL whose host isn't in chrome.storage.local.sallyport_allowlist. Patterns are example.com, *.example.com, or https://x.com/path/*. Bare * is rejected by the validator.
3. evaluate is opt-in per domain. Even on an allow-listed domain, arbitrary JS is refused unless that entry has allowEvaluate: true. Other tools (click, fill, read_text, …) use structured CDP calls only.
4. Defense-in-depth on inputs. fill refuses <input type=password> unless allowPassword=true. The daemon refuses to bind to anything that isn't a loopback address. WS frames over 16 MiB are dropped (1009).
5. Operational visibility. Every tool call (and its outcome — ok or error) is appended to chrome.storage.local.sallyport_audit (last 500 entries), browsable and JSON-exportable from the popup. One-click Pause in the popup stops the WS connection and rejects all tool calls.

Other deliberate choices:

• No content-script injection, no <all_urls> content scripts. Permissions are only what the debugger API needs (tabs, activeTab, debugger, storage, alarms).
• Per-tab accessibility refs (@e1, @e2). Snapshotting tab A cannot invalidate refs for tab B, and a ref scoped to A cannot resolve to a node in B.
• MCP-side tool calls are serialised by a daemon-side lock so Claude can't accidentally race state on the extension.
• The daemon shuts down cleanly on stdin EOF (Claude Code closing) or SIGINT/SIGTERM: pending calls fail with ExtensionNotConnected, the client gets a 1001 close, no orphan tasks.

What the extension still trusts: anyone with read access to ~/.config/sallyport/secret. The browser debugger is, ultimately, the browser debugger — this bridge limits which domains it operates on and who can drive it.

Setup

1. Build the extension

The extension is not on PyPI — pip install sallyport (step 2) gives you only the daemon. The extension lives in this repo's extension/ directory, so you need a checkout to build it:

git clone https://github.com/ginkida/sallyport
cd sallyport/extension
npm install
npm run build

The output lands in extension/dist/. Load it as an unpacked extension:

1. chrome://extensions
2. Enable Developer mode
3. Load unpacked → pick extension/dist

Pin the toolbar icon.

2. Install the daemon

Sallyport needs Python ≥ 3.10 (it uses match statements and X | Y type syntax). Check with python --version first.

pip install --user sallyport

Or from source (for development): cd daemon && pip install --user -e .

This installs the sallyport-daemon command on your PATH. Verify it landed there:

which sallyport-daemon   # should print a path; if not, add your Python
                      # user-scripts dir (e.g. ~/.local/bin) to PATH

The first time something runs it, the daemon will:

• Generate a 32-byte secret in ~/.config/sallyport/secret (chmod 600).
• Print the base64 secret to stderr — paste it into the extension popup.
• Start listening on 127.0.0.1:10086 and speak MCP on stdio.

Then run the built-in setup check, which validates the install and prints the exact block to paste into the popup:

sallyport-daemon doctor

It checks your Python version, the secret file and its permissions, and that the port is free — then prints the pairing secret and the remaining steps. Run it any time a connection won't come up. To just re-print the secret:

sallyport-daemon --show-secret

3. Register with Claude Code

Add an MCP server entry — either edit ~/.claude/mcp.json directly, or:

# Use the ABSOLUTE path. A GUI-launched Claude Code often doesn't inherit your
# shell PATH, so a bare "sallyport-daemon" command silently fails to spawn.
claude mcp add sallyport "$(which sallyport-daemon)"

sallyport-daemon doctor prints this exact line with the path already resolved (and falls back to python -m sallyport_daemon if the console script isn't on PATH) — copy it from there if you're unsure. The result:

{
  "mcpServers": {
    "sallyport": {
      "command": "/Users/you/.local/bin/sallyport-daemon",
      "args": []
    }
  }
}

Restart Claude Code. The tools appear as mcp__sallyport__navigate, mcp__sallyport__click, etc.

4. Pair the extension

1. Open the popup. It will show a one-card Pair onboarding view.
2. Get the secret. Run sallyport-daemon doctor (or --show-secret) in a terminal and copy the printed block. Note: when Claude Code spawns the daemon for you (step 3), the first-run banner goes to the daemon's stderr, which Claude Code does not display — so doctor/--show-secret is the reliable way to see it.
3. Paste into the popup textarea — you can paste the whole banner; the popup auto-extracts the base64 secret and shows "✓ secret detected (32 bytes)".
4. Click Pair. Status flips to connected with a pulsing green indicator and an at-a-glance summary of allowed sites / recent calls.

5. Add the first domain to the allowlist

The allowlist starts empty — every tool rejects every URL by default. In the popup's Allowlist tab, add an entry like example.com or *.github.com. Tick allow evaluate() only if you actually need arbitrary JS on that host.

Running a shared broker (multiple sessions)

By default each Claude Code session spawns its own daemon, and only one can own the browser at a time (they'd fight over 127.0.0.1:10086). Broker mode lets several sessions — and you, working in the same browser — share one extension:

# Start one long-lived broker (owns the extension; stays up until Ctrl-C).
sallyport-daemon broker

Now register and use Sallyport exactly as above (absolute-path claude mcp add, step 3) from as many project folders as you like. Each plain sallyport-daemon session auto-detects the running broker and attaches to it as a thin relay over a 0600 Unix-domain socket (broker-10086.sock, next to the secret); with no broker running, a session falls back to standalone, exactly as before. Pair the extension once, against the broker.

You can leave the broker running in the background (sallyport-daemon broker &, nohup, or your own service manager); it's meant to be long-lived. doctor recognises it as an intentional broker rather than a stale daemon: its port check reports the busy port as OK (a broker holding it is the intended setup, not a conflict), and sallyport-daemon doctor --kill-stale reports it and leaves it running — stop it explicitly with kill <pid> (or Ctrl-C) when you're done.

What you get:

• Many sessions at once. N agents drive the one browser concurrently; calls are serialised so they never corrupt each other's state.
• Each agent stays in its own tabs. An agent can only see and act on tabs it created (navigate with no tab opens a fresh one); it cannot touch — or even list — your tabs or another agent's. list_tabs shows a session only its own tabs.
• It won't steal your focus. Agent tabs open in a separate, un-focused window and never foreground themselves, so you can keep working while agents do.
• You're logged in. It's your real browser profile, so agents operate on the sites you're already signed into — scoped, as always, to the allowlist.

Broker mode is a software partition of one shared profile, not an OS-level sandbox: the security floor is still "any process running as you" (it can read the secret and drive the browser within the allowlist). See SECURITY.md for the full model, including the new tab-ownership and MCP-client-auth invariants.

Tools

Name	Notes
list_tabs	No allowlist check — listing is free.
navigate	Checks the destination URL against allowlist. waitFor={selector?,text?,absent?,timeoutMs?} polls after the load until the page is actually usable (SPAs render long after "loaded").
reload	Hard reload via bypassCache=true. Allowlist-gated; refs invalidate.
close_tab	tabId required — no implicit fallback (closing the wrong tab loses work).
snapshot	Accessibility tree with stable @eN refs (per-tab), pruned of layout noise. Cross-checks against a DOM walk (same refs) when the a11y tree looks suspiciously sparse — Telegram Web K and similar SPAs. mode=auto|a11y|dom; compact=true → flat list of actionable elements only; selector scopes to one subtree.
read_text	Whole-page or by ref. No raw JS. Capped at 20 000 chars by default (maxChars overrides; cut results carry truncated/totalChars).
get_state	Cheap one-element probe (CSS or @eN) — {exists, visible, tag, text, box?, inViewport?} without a full snapshot. Verify an action's effect or re-check a ref in one round-trip. Never errors on a missing node: returns {exists:false, reason} (not_found/unknown_ref/detached), so it is safe to poll. Does not read input .value (no password readback). Structured CDP only.
console_tail	Recent page console errors/warnings + uncaught exceptions for a tab ({enabled, entries:[{ts,level,text,origin}]}) — tell "the handler threw and the page is wedged" from "merely slow". Opt-in (popup setting, off by default; returns {enabled:false} when off). Capture starts at first attach (no replay); entries are origin-filtered to the allowlist. Pure CDP event capture, no evaluate.
network_tail	Recent XHR/fetch responses for a tab ({enabled, entries:[{ts,method,url,status,type,contentType,size,body?}]}) — the data behind canvas dashboards (Metrika, Chart.js, WebGL) that have no readable DOM. Pull exact JSON instead of screenshot + vision. Opt-in (popup "capture API responses", off by default). Bodies only for textual content-types, capped; no auth headers captured; entries origin-filtered to the allowlist; filter narrows by URL substring. Pure CDP event capture, no evaluate.
click	DOM .click(). CSS selector or @eN ref. Optional waitFor polls for the click's effect in the same call.
mouse_click	Real Input.dispatchMouseEvent as a full hover→press→release sequence. Auto-aims around partial overlays; a fully covered target reports covered/hitTarget/hitTargetRef. Explicit x/y (viewport CSS px) as manual aim. button left/middle/right, clickCount 1–3, optional waitFor.
hover	Hover the pointer over an element/point without clicking (the mouseMoved preamble only). For CSS :hover-only menus, tooltips, row-action UIs. selector/@eN (auto-aimed, reports covered/hitTargetRef) or viewport x/y; optional waitFor to hover→wait-for-menu. Strictly weaker than mouse_click; the :hover state is transient.
fill	Blocks password fields without allowPassword=true. method=insertText clears the field and types via CDP with real input events (for SPA editors that ignore programmatic values). Optional waitFor.
select_option	Choose an option in a native <select> (the OS popup can't be driven via CDP). Sets the value in the DOM and fires input/change instead of opening the menu. One of value/label/index; array for <select multiple>. wrong_element for non-<select> targets — custom JS comboboxes (react-select, MUI) stay on click/find/reveal. Optional waitFor.
key_type	Raw text input via CDP. Blocks when focus is on a password field without allowPassword=true.
send_keys	Mod+A, Shift+Tab, etc. Mod = Cmd on macOS, Ctrl elsewhere. Same password-field gate as key_type.
screenshot	PNG/JPEG as a native MCP image block. maxWidth downscales, region={x,y,width,height} crops (viewport-relative CSS px). Hidden tabs fail fast with tab_not_visible; bringToFront=true activates the tab first (steals focus).
wait_for	Poll (250 ms) until a selector/@eN ref is visible and/or page text contains a substring; absent=true waits until it is GONE. timeoutMs ≤ 30 s; timeout returns {found:false}, not an error. Replaces blind sleeps. Prefer the embedded waitFor on the preceding action when there is one.
scroll	Deterministic scrolling — the predicate-less companion to reveal. selector → scrollIntoView; or scroll the page (or a selector container) by dx/dy (negatives = up/left) or to='top'|'bottom'. Returns {x, y, scrollHeight, atBottom} so a lazy-load loop knows when to stop. Fixed scroll probe, no evaluate.
evaluate	Per-domain opt-in. Returns {type, value}.
fetch_in_page	fetch() with page cookies/auth. Returns {status, contentType, headers, mode, data}. Allowlist-gated.
upload	Attach local files to <input type=file> via DOM.setFileInputFiles. Paths must be absolute, ..-free, and resolve under ~/Downloads/sallyport/ (override via SALLYPORT_DOWNLOAD_DIR) — same sandbox as save_to_file, with symlink escapes blocked by Path.resolve(). Target must really be a file input. Allowlist-gated.
save_to_file	Daemon-local — writes base64 to ~/Downloads/sallyport/<filename> (override via SALLYPORT_DOWNLOAD_DIR). Sandboxed: no path separators or ...
status	Daemon-answered health check: {connected, mode, version, port, pendingCalls, uptimeS, lastCalls, lastError, lastHandshakeError}. mode is broker (explicit owned tabId required per call) or standalone (active-tab fallback). lastCalls is a ring of recent tool outcomes ({tool, ok, ms, code?} — never the args) and lastError the latest failure, so a loop can attribute a stall to a specific tool/code; when connected is false, lastHandshakeError says why the extension leg failed to attach (wrong secret, clock skew, no hello). No browser round-trip and never queues behind a running call — use it as preflight before browser work.

All tools accept tabId to target a specific tab; otherwise they use the active tab in the current window. There is no implicit "last touched tab" memo — explicit IDs win, the active tab is the only fallback.

For agents running on a schedule, the cheap iteration shape is: status (skip everything if the extension is detached) → scoped reads (snapshot selector=… compact=true, read_text ref=…) → actions with embedded waitFor instead of separate wait_for calls → verify with get_state ref=… (one element) instead of re-snapshotting the whole page. Driven tabs are kept awake automatically, so the loop keeps working while the browser window sits in the background (see Troubleshooting for the trade-offs).

Compared to Kimi WebBridge

Sallyport implements the everyday Kimi tools (navigate, click, fill, snapshot, screenshot, evaluate, mouse_click, upload, …) and adds a few of its own (fetch_in_page, save_to_file, reload). Three Kimi features are deliberately not here:

Kimi feature	Why Sallyport omits it	If you need the behaviour
network (start/stop/list/detail HTTP capture via Network.enable)	Kimi's version captures auth headers, cookies, and every request body with no per-domain gate — that ungated shape is what Sallyport omits.	Use network_tail: a gated subset — opt-in per popup, response bodies only (no headers/cookies), origin-filtered to the allowlist. Or fetch_in_page against a specific URL.
save_as_pdf (Page.printToPDF)	Niche — screenshot (full-page PNG/JPEG) already covers "preserve what's on screen" for the agent tasks we've seen.	Speak up if you hit a case where selectable PDF text matters; trivial to add.
_session (per-agent Chrome tab groups, coloured)	Cosmetic flair that complicates tab handling without solving a real problem at current scale.	Use list_tabs to find what you opened.

find_tab is also intentionally absent: Sallyport's list_tabs returns the full set and the agent filters client-side — one round trip instead of two.

Testing it locally

Three layers, from fastest to most realistic:

A. Wire only — no MCP, no Claude Code

Confirms HMAC pairing, allowlist, audit log without any tools firing.

# terminal: run the daemon in WS-only mode. Stays up until Ctrl-C —
# no stdin / no MCP client needed.
sallyport-daemon serve

Default sallyport-daemon (no subcommand) expects an MCP client on stdin and exits immediately on EOF — fine for Claude Code, awkward for local testing. Use serve whenever you want a stable long-running daemon.

Open the popup → Pair → paste secret → status flips to connected. That alone proves: WS reach, HMAC handshake, perms.

B. Fire individual tools from the shell — no Claude Code

sallyport-daemon exec <tool> key=value... spins up the daemon, waits for the extension, calls one tool, prints JSON, exits. Values are JSON when parseable, otherwise strings.

# Catalogue of tools (works offline, no extension needed):
sallyport-daemon list-tools

# Open a tab (the host must already be in the popup's allowlist):
sallyport-daemon exec navigate url=https://example.com newTab=true

# Read the page:
sallyport-daemon exec read_text

# Get the accessibility tree + refs:
sallyport-daemon exec snapshot

# Click something from snapshot (use a ref):
sallyport-daemon exec click selector=@e3

# Targeted screenshot:
sallyport-daemon exec screenshot format=jpeg quality=70

Notes:

• exec mode is mutually exclusive with the Claude Code MCP session (single-client invariant in the WS server). Stop Claude Code first, or pass a different --port here and update the popup's daemon URL.
• The first exec waits up to 10s (--wait 30 to bump it) for the popup to connect. Once paired, the extension reconnects on its own.
• Screenshot blobs are truncated in the printout — they're still passed in full to a real MCP client.

C. End-to-end with Claude Code

Once A and B work, register the MCP server (see Setup → step 3), restart Claude Code, and ask it to do anything web-shaped. Watch the popup's Audit tab — every call lands there with ok/error and target URL.

Troubleshooting

Symptom	Fix
Anything in setup feels off	Run sallyport-daemon doctor — it checks Python version, secret + perms, and port, and reprints the pairing block.
Popup stuck on "Connecting to daemon…"	The daemon isn't reachable at the popup's URL. Confirm it's running (sallyport-daemon serve in another shell), that the Advanced → daemon URL matches (default ws://127.0.0.1:10086/ws), and that the port is free (sallyport-daemon doctor). The single-client rule means a live Claude Code session already holds the port — that's expected; the extension connects to it.
Popup says "extension is not connected"	Daemon isn't running, or the popup says paused — open and hit Resume/Reconnect.
domain_not_allowed	Add the host to the Allowlist tab.
evaluate_not_allowed	Edit the allowlist entry and re-add with allow evaluate() checked.
password_field (from fill)	fill refuses <input type=password> by default. Pass allowPassword=true if you really mean it.
wrong_element (from upload)	Selector resolved to something other than <input type=file>. Re-snapshot and pick a real file-input ref.
wrong_element (from select_option)	Target isn't a native <select> — it's a custom JS combobox (react-select, MUI, Radix). Those live in the DOM: click/mouse_click to open, then click the option (use find/reveal to locate it).
unsafe_path (from upload)	Path contains .., isn't absolute, or resolves outside the sandbox (default ~/Downloads/sallyport/). Stage the file via save_to_file first (writes to the sandbox), then upload. Widen the sandbox via SALLYPORT_DOWNLOAD_DIR if you really need to upload from elsewhere.
not_visible (from mouse_click)	Element has zero size — likely display:none or detached. Snapshot again; if it's hidden by design, drive the toggle that reveals it.
mouse_click reports covered: true	Another node sits on top of the target at every probe point. The result includes hitTarget (what ate the click) and hitTargetRef — an @eN for that node; click it directly, or aim manually with mouse_click x= y=.
Automation stalls when the browser window is in the background	Chrome freezes background tabs and fully-occluded windows. The bridge keeps driven tabs awake automatically (popup → Advanced → keep automated tabs awake, default on; note the page then believes it is focused — e.g. Telegram sends read receipts). If a page must stay alive before the bridge attaches, add its site under chrome://settings/performance → "Always keep these sites active", or run a dedicated automation profile with --disable-backgrounding-occluded-windows --disable-renderer-backgrounding --disable-background-timer-throttling.
tab_not_visible (from screenshot)	Hidden tabs render no frames — keep-awake can't help with pixels. Pass bringToFront=true (steals focus), activate the tab yourself, or keep a sliver of the window visible: macOS occlusion only kicks in when it's fully covered.
bad_ref	An @eN ref is stale (snapshot expired) or addressed at the wrong tab. Re-snapshot the right tab. Refs are per-tab and per-snapshot.
mac mismatch (in popup)	Secret in ~/.config/sallyport/secret no longer matches the one paired in the popup. Run sallyport-daemon --show-secret, copy, Unpair → paste → Pair.
timestamp skew	Clocks are >30 s apart. Check NTP.
Daemon warns about loose permissions on startup	chmod 600 ~/.config/sallyport/secret.
WS frame >16 MiB	The extension is silently dropped with a 1009 close. Lower screenshot quality or take a region screenshot.

Rotating the secret

1. rm ~/.config/sallyport/secret
2. Restart whatever runs sallyport-daemon (Claude Code will respawn it on next call). A new secret prints to stderr.
3. In the popup: Unpair → paste new secret → Pair.

Development

# Extension
cd extension
npm install
npm run watch         # esbuild rebuild on save — reload extension in chrome://extensions to pick up
npm run typecheck     # tsc --noEmit
npm test              # vitest run
npm run lint          # eslint
npm run format        # prettier --write
npm run format:check  # prettier --check (CI gate)

# Daemon
cd daemon
pip install -e '.[dev]'
ruff check .
mypy
pytest -q
sallyport-daemon --verbose < <(sleep 99999)   # smoke-test a long-running daemon

Pre-commit

pip install --user pre-commit
pre-commit install

This runs trailing-whitespace/json/yaml/merge-conflict checks plus ruff, mypy, prettier, eslint, and tsc on each commit. Heavy test suites stay in CI because they're too slow for a commit gate.

CI

.github/workflows/ci.yml matrices over Python 3.10/3.11/3.12 (daemon) and Node 20/22 (extension), runs lint + typecheck + tests + build for both, and uploads extension/dist as an artefact on main.

Adding a new tool

Five files, same order both for an extension-side tool and a daemon-local one — keep tool names byte-identical on both sides since routing is a dict lookup.

1. Implement. Extension-side: a new extension/src/tools/<name>.ts exporting a Tool. Pure validators (path / arg shape) belong in a chrome-free sibling module like upload-path.ts so vitest can cover them without a chrome harness. Daemon-only: a coroutine in daemon/src/sallyport_daemon/local_tools.py registered in LOCAL_TOOLS.
2. Register on the extension side. Add an import + entry to the tools map in extension/src/tools.ts.
3. Declare the MCP schema. Append a Tool(name=..., description=..., inputSchema=...) to TOOLS in daemon/src/sallyport_daemon/mcp_server.py. Mark fields required whenever the implementation throws without them — schema and behaviour should agree (see the close_tab regression captured by test_close_tab_requires_tab_id).
4. Pin the catalogue. Add the new name to the expected set in daemon/tests/test_mcp_server.py::test_tools_catalogue_covers_extension. Mismatches between the daemon and extension registries fail the build immediately rather than at the wire.
5. Document. A row in the Tools table in README.md, and an entry in CHANGELOG.md under [Unreleased] / Added describing the user-visible shape (args, gates, error codes worth knowing).

Then cd extension && npm test && npm run lint && npm run typecheck and cd daemon && ruff check . && mypy && pytest -q — all green before calling it done.

Versioning & releases

CHANGELOG.md tracks every notable change; the project uses Semantic Versioning. The wire protocol version is 1 — bump only on incompatible changes and update the cross-language vector tests in the same commit.

License

MIT — see LICENSE.

Wire protocol

Documented in extension/src/protocol.ts and daemon/src/sallyport_daemon/protocol.py. Envelope shape:

{ v, ts, nonce, type, id?, body, mac }

mac = HMAC-SHA256(secret, canonical_json({v, ts, nonce, type, id?, body})), base64. Canonical JSON: keys sorted by Unicode code point, no whitespace, unicode passthrough, cross-language number formatting.

The exact bytes are pinned to 49 cross-language vectors in fixtures/canonical-vectors.json — both daemon/tests/test_vectors.py and extension/test/vectors.test.ts read that file and assert byte-by-byte agreement. If you change the canonicalisation rules, regenerate via python3 fixtures/generate.py and update both implementations in the same commit.

There is no version negotiation — both sides expect v: 1. Bump it on breaking changes and update both vector tests in the same commit.