Docs / Extend
Rescriptum Tab
The browser companion: cited research, element picking, and live page inspection.
Rescriptum Tab is a browser extension that gives the agent eyes and a research assistant inside your real browser. It links to the IDE over a local connection, so the agent can read pages, look at what is broken in the running app, and look things up with sources, without you copying and pasting between windows.
It works in Chrome, Edge, and Brave (Chrome 116 or newer). The extension is Manifest V3 and is currently version 2.0.6.
What it does
Ask Tab: research with sources
The agent, or you from the Tab panel, can ask the browser a question. Tab searches the web, reads up to three of the most relevant pages, and answers with numbered citations like [1] and [2], each linked to its source. It runs in two modes: Research (default) and Chat. Turn on use active tab to include the page you are looking at.
In the IDE the agent calls this as ask_tab. It is only offered to the agent while a Tab that supports it is connected, and a call times out after about 150 seconds.
Element picker
Press Alt+Shift+C on any page, then click an element to pin it. The pin carries the CSS selector, outer HTML, computed styles, design tokens, and bounding box. On pages served by a development build of a React app, it also carries the component hierarchy and, where React exposes it, the source file and line of the component.
The agent reads the pin with browser_get_pinned_element. "Make this card's padding match the others" now points at a specific component, not a screenshot.
Source file and line appear only when the page is a dev build that includes React's debug source information. Production bundles do not have it. The pin still includes the DOM and styles.
Live page inspection
With Tab linked, the agent can look at and drive the running app:
| Tool | Does |
|---|---|
browser_get_active_tab, browser_list_tabs | Which pages are open |
tab_read_content | Page text, selection, and console and network errors |
browser_qa_inspect | DOM mount state, React tree, console output, optional selector checks |
browser_interact | Click, type, scroll, wait for an element, screenshot, read a tab |
browser_navigate | Go to a URL |
browser_eval | Run JavaScript in the page |
This is how the agent confirms a UI fix by loading the page, not by trusting the code diff.
On-page companion and side panel
A small dock on web pages shows console and network telemetry from the page, and a side panel (Ctrl+Shift+S) gives you an AI companion beside any site, with web grounding and quick actions such as Inspect Tab Errors.
The new tab page
The extension replaces the new tab page with a workspace: chat, notes, research, and shortcuts to your IDE projects when linked. It works on its own as a standalone page.
Install
- Download the extension zip from the Tab panel in the IDE or from the download page.
- Unzip it somewhere permanent. Chrome loads it from that folder.
- Open
chrome://extensions(oredge://extensions,brave://extensions) and turn on Developer mode. - Choose Load unpacked and select the unzipped folder that contains
manifest.json. - Start Rescriptum. The Tab panel shows Linked and the extension connects automatically, reconnecting if the IDE restarts.
How it connects
The IDE runs a local service, the Neuro-Bridge, on 127.0.0.1:49281. The extension connects to it over a WebSocket. Nothing is routed through a Rescriptum server.
Permissions and privacy
The extension asks for broad access because it has to work on any page you point it at.
| Permission | Why |
|---|---|
tabs, activeTab, scripting | Read the current page and run the picker and inspection |
storage | Keep settings and the new tab workspace locally |
sidePanel | The side panel |
notifications | Status notices |
declarativeNetRequest | Page inspection features |
Access to http:// and https:// pages | Run the companion and sensors on any site |
What stays local and what leaves:
- The link to the IDE stays on your machine. It is bound to the loopback address and only accepts connections from the extension, the IDE, and local development origins.
- Ask Tab and chat use models and web search. Questions and the page text they depend on are sent to the model and search providers configured for Tab. Do not point it at pages you would not paste into an AI model.
- Key sharing. While linked, the IDE can pass your OpenRouter key to the extension over the local connection so Tab can use models without asking you again. It stays on your device.
- Page reading is explicit. Pages are read when you pin an element, ask using the active tab, or when the agent calls a browser tool during a turn you started.
Internal pages (chrome://, extension pages) are never tracked as active pages.
Without the IDE
Tab still gives you the new tab page, local notes, and side panel chat if models are configured in the extension. Everything that touches your project, such as file access, terminal commands, and agent tasks, needs the IDE running.
Limits
- The bridge has no pairing token. It relies on loopback binding and origin checks, so any software running as you on the same machine and presenting a trusted origin is trusted. Keep the usual machine hygiene.
- Firefox is not a supported browser today.
ask_tabneeds a Tab build that announces research support. If it does not appear in the agent's tools, update the extension.
See also Security and privacy.