sncro

scottconfusedgorilla/sncro-relay

Bridges Claude directly into your live browser during development. Once you install the FastAPI or Flask middleware, Claude can call tools like query_element, get_page_snapshot, and read console logs from the actual DOM while you're debugging. The relay at relay.sncro.net sits between your MCP client and a browser-injected agent script that long-polls for commands. Designed for debug mode only, so there's zero overhead in production. Reach for this when you're pair programming with Claude on frontend bugs or layout issues and want it to see exactly what's rendering, not just your source code. The repo includes the relay server, agent.js, and drop-in plugins for both frameworks.

tools: 9
transport: HTTP
last updated: Apr 18, 2026

View on GitHub

Tools

9 tools

Public tool metadata for what this MCP can expose to an agent.

create_sessionCreate a new sncro session. Returns a session key and secret. Args: project_key: The project key from CLAUDE.md (registered at sncro.net) git_user: The current git username (for guest access control). If omitted or empty, the call is treated as a guest session — allowed only w...3 params

Create a new sncro session. Returns a session key and secret. Args: project_key: The project key from CLAUDE.md (registered at sncro.net) git_user: The current git username (for guest access control). If omitted or empty, the call is treated as a guest session — allowed only w...

Parameters* required

briefboolean

default: false

git_userstring

default:

project_keystring

get_console_logsGet recent console logs and errors from the browser. Returns the latest console output and any JavaScript errors, including unhandled exceptions and promise rejections. This reads from baseline data that the browser pushes every 5 seconds, so it works even if the browser tab i...2 params

Get recent console logs and errors from the browser. Returns the latest console output and any JavaScript errors, including unhandled exceptions and promise rejections. This reads from baseline data that the browser pushes every 5 seconds, so it works even if the browser tab i...

Parameters* required

keystring

secretstring

query_elementQuery a DOM element by CSS selector. Returns bounding rect, attributes, computed styles, inner text, and child count. Use this to debug layout, positioning, and visibility issues. Requires a connected browser session. If you get BROWSER_NOT_CONNECTED, call check_session first...4 params

Query a DOM element by CSS selector. Returns bounding rect, attributes, computed styles, inner text, and child count. Use this to debug layout, positioning, and visibility issues. Requires a connected browser session. If you get BROWSER_NOT_CONNECTED, call check_session first...

Parameters* required

keystring

secretstring

selectorstring

stylesvalue

query_allQuery all matching DOM elements by CSS selector. Returns a summary of each matching element (tag, id, class, bounding rect, inner text). Useful for checking lists, grids, or multiple instances of a component. Requires a connected browser session. If you get BROWSER_NOT_CONNECT...4 params

Query all matching DOM elements by CSS selector. Returns a summary of each matching element (tag, id, class, bounding rect, inner text). Useful for checking lists, grids, or multiple instances of a component. Requires a connected browser session. If you get BROWSER_NOT_CONNECT...

Parameters* required

keystring

limitinteger

default: 20

secretstring

selectorstring

get_network_logGet network performance data from the browser. Returns resource timing entries (URLs, durations, sizes) sorted by duration (slowest first), plus page navigation timing. Use this to find slow API calls, large assets, or overall page load performance. Requires a connected browse...4 params

Get network performance data from the browser. Returns resource timing entries (URLs, durations, sizes) sorted by duration (slowest first), plus page navigation timing. Use this to find slow API calls, large assets, or overall page load performance. Requires a connected browse...

Parameters* required

keystring

limitinteger

default: 50

secretstring

typevalue

get_page_snapshotGet a high-level snapshot of the current page. Returns URL, title, viewport dimensions, scroll position, top-level DOM structure, recent console logs, and recent errors. Requires a connected browser session. If you get BROWSER_NOT_CONNECTED, call check_session first and wait f...2 params

Get a high-level snapshot of the current page. Returns URL, title, viewport dimensions, scroll position, top-level DOM structure, recent console logs, and recent errors. Requires a connected browser session. If you get BROWSER_NOT_CONNECTED, call check_session first and wait f...

Parameters* required

keystring

secretstring

check_sessionCheck the connection status of a sncro session. Call this after create_session to confirm the browser has connected before using other tools. If status is "waiting", the user hasn't enabled sncro yet — remind them to click/paste the enable URL, wait a few seconds, and call che...2 params

Check the connection status of a sncro session. Call this after create_session to confirm the browser has connected before using other tools. If status is "waiting", the user hasn't enabled sncro yet — remind them to click/paste the enable URL, wait a few seconds, and call che...

Parameters* required

keystring

secretstring

end_sessionExplicitly close a sncro session — "Finished With Engines". Call this when you are done debugging and will not need the sncro tools again in this conversation. After this returns, all sncro tool calls on this key will refuse with a SESSION_CLOSED message — that is your signal...2 params

Explicitly close a sncro session — "Finished With Engines". Call this when you are done debugging and will not need the sncro tools again in this conversation. After this returns, all sncro tool calls on this key will refuse with a SESSION_CLOSED message — that is your signal...

Parameters* required

keystring

secretstring

report_issueReport an issue, feature request, or success story for sncro. IMPORTANT: ALWAYS ask the user before submitting ANY feedback. Show them exactly what you plan to send and get explicit approval. Never submit feedback without the user's knowledge and consent. For ALL categories: -...4 params

Report an issue, feature request, or success story for sncro. IMPORTANT: ALWAYS ask the user before submitting ANY feedback. Show them exactly what you plan to send and get explicit approval. Never submit feedback without the user's knowledge and consent. For ALL categories: -...

Parameters* required

categorystring

descriptionstring

git_userstring

default:

project_keystring

Readme

sncro-relay

Open-source components of sncro — the MCP relay, the browser-side agent, and the framework plugins that let AI coding assistants inspect a live browser.

What this repo contains

Path	What
`relay/`	FastAPI app that exposes an MCP server plus long-poll endpoints for agent.js
`relay/static/agent.js`	Browser-side script injected by the middleware; pushes console + DOM data to the relay
`middleware/sncro_middleware.py`	FastAPI / Starlette plugin — drop-in middleware for FastAPI apps
`middleware/sncro_flask.py`	Flask plugin — drop-in middleware for Flask apps
`trysncro/`	`try.sncro.net` — a deliberately-broken demo app for exercising sncro end-to-end

How it works

View the full README on GitHub

Details

Repository: github.com/scottconfusedgorilla/sncro-relay
Website: sncro.net
Category: Web & Browser Automation
Transport: HTTP
Registry: MCP registry, active

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